Pressure detection element, liquid ejection head, and liquid ejection apparatus

Abstract

The invention provides a pressure detection element with high detection sensitivity, a liquid ejection head, and a liquid ejection apparatus. The pressure detection element is provided with: a pressure detection chamber for detecting the internal pressure; a first electrode; a second electrode; and a first piezoelectric body that is disposed between the first electrode and the second electrode, the capacitance of the first piezoelectric body being changed in accordance with the pressure of the pressure detection chamber, the first piezoelectric body including a first piezoelectric body layer located on the first electrode side and a second piezoelectric body layer located on the second electrode side, the second piezoelectric layer is any one of a tetragonal system, a cubic system and a monoclinic system, the first piezoelectric layer is a rhombohedral system, and the thickness of the second piezoelectric layer is smaller than that of the first piezoelectric layer.

Description

Technical Field

[0001] The present invention relates to a pressure detection element, a liquid ejection head and a liquid ejection device. Background Art

[0002] A sensor used for measuring physical quantities such as pressure and acceleration is known. Patent document 1 discloses a ceramic sensor constructed in the following manner, that is, a piezoelectric ceramic single crystal thin film is formed on a metal foil, and an electrode is attached to the surface thereof, and a circuit is formed by separating the metal foil and the electrode with a detection unit. In addition, a circuit is formed between the electrode and the metal foil. In the ceramic sensor involved, when a mechanical stimulus is applied to the piezoelectric ceramic, a change in current or voltage occurs. By inserting an ammeter and a voltmeter in the circuit, it functions as a sensor.

[0003] However, the piezoelectric ceramic described in Patent Document 1 is a single layer. Even if a large stress is applied to the piezoelectric ceramic, its deformation is small. Therefore, the change in the dielectric constant is small, making it difficult to improve the detection sensitivity. Therefore, in a single-layer piezoelectric ceramic as described in Patent Document 1, it is difficult to improve the detection sensitivity.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2002-55116 Summary of the invention

[0005] The pressure detection element involved in a preferred embodiment of the present invention comprises: a pressure detection chamber, which is used to detect internal pressure; a first electrode; a second electrode; a first piezoelectric body, which is arranged between the first electrode and the second electrode, and the electrostatic capacitance of the first piezoelectric body changes according to the pressure in the pressure detection chamber, the first piezoelectric body includes a first piezoelectric body layer located on the first electrode side, and a second piezoelectric body layer located on the second electrode side, the second piezoelectric body layer is any one of a tetragonal crystal system, a cubic crystal system, and a monoclinic crystal system, the first piezoelectric body layer is a rhombohedral crystal system, and the thickness of the second piezoelectric body layer is thinner than the thickness of the first piezoelectric body layer.

[0006] The pressure detection element involved in a preferred embodiment of the present invention comprises: a pressure detection chamber, which is used to detect internal pressure; a first electrode; a second electrode; a first piezoelectric body, which is arranged between the first electrode and the second electrode, and the electrostatic capacitance of the first piezoelectric body changes according to the pressure in the pressure detection chamber, the first piezoelectric body includes a first piezoelectric body layer located on the first electrode side, and a second piezoelectric body layer located on the second electrode side, the Young's modulus of the second piezoelectric body layer is smaller than that of the first piezoelectric body layer, and the thickness of the second piezoelectric body layer is thinner than that of the first piezoelectric body layer.

[0007] The liquid ejection head involved in a preferred embodiment of the present invention comprises: a pressure detecting element; a nozzle substrate, which is provided with a nozzle for ejecting liquid; a pressure chamber substrate, which has a pressure chamber for applying pressure to the liquid for ejecting the liquid from the nozzle, and the pressure detection chamber adjacent to the pressure chamber; a second piezoelectric body, which is arranged corresponding to the pressure chamber and applies pressure to the pressure chamber by applying voltage, and the pressure detecting element and the pressure detection chamber are arranged correspondingly.

[0008] A liquid ejection device according to a preferred embodiment of the present invention includes: a liquid ejection head; and a control unit that controls an ejection operation performed from the liquid ejection head. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a schematic diagram illustrating the structure of the liquid ejecting device according to the first embodiment.

[0010] Figure 2 for Figure 1 Block diagram of a liquid ejection device.

[0011] Figure 3 for Figure 1 A cross-sectional view of a portion of a liquid ejection head is shown.

[0012] Figure 4 To express Figure 3 Figure 2. A diagram of a portion of the pressure chamber substrate.

[0013] Figure 5 To express Figure 3 FIG. 1 is a diagram of a portion of a sealing substrate.

[0014] Figure 6 for Figure 3 A cross-sectional view of a pressure sensing element.

[0015] Figure 7 This is a graph showing an example of the relationship between the electrostatic capacitance of the first piezoelectric body and the pressure.

[0016] Figure 8 To express Figure 2 FIG. 5 is a diagram of a pressure sensing element and a third piezoelectric element.

[0017] Fig. 9 A cross-sectional view of a pressure sensing element according to a modified example.

[0018] Fig.10 It is a top view of a pressure detection element showing a modified example.

[0019] Fig.11 It is a top view of a pressure detection element showing a modified example.

[0020] Fig.12 It is a cross-sectional view of a second piezoelectric element and a pressure sensing element according to a modified example.

[0021] Fig.13 It is a cross-sectional view of a second piezoelectric element and a pressure sensing element according to a modified example.

[0022] Fig.14 This is a block diagram of a liquid ejection device according to a modified example.

[0023] Fig.15 This is a diagram showing an example of the relationship between voltage and charge.

[0024] Fig.16 A diagram showing an example of the relationship between voltage and capacitance. DETAILED DESCRIPTION

[0025] Hereinafter, the preferred embodiments of the present invention will be described with reference to the accompanying drawings. In addition, in the accompanying drawings, the size or scale of each part is appropriately different from the actual situation, and there are also parts schematically shown for easy understanding. In addition, as long as there is no record of the meaning of the present invention being particularly limited in the following description, the scope of the present invention is not limited to these modes. In addition, the so-called "element β on element α" is not limited to a structure in which element α and element β are in direct contact, but also includes a structure in which element α and element β are not in direct contact. In addition, the so-called "element α and element β are approximately equal" includes, in addition to the case of being strictly equal, a case in which there is a difference in the degree of manufacturing error and measurement error.

[0026] 1. First Implementation

[0027] 1-1. Overall Structure of Liquid Dispensing Device 100

[0028] Figure 1 This is a schematic diagram illustrating the structure of the liquid ejection device 100 involved in the first embodiment. In the following, for the convenience of explanation, the X-axis, Y-axis and Z-axis that are orthogonal to each other are appropriately used for appropriate explanation. In addition, a direction along the X-axis is recorded as the X1 direction, and the direction opposite to the X1 direction is recorded as the X2 direction. Similarly, a direction along the Y-axis is recorded as the Y1 direction, and the direction opposite to the Y1 direction is recorded as the Y2 direction. A direction along the Z-axis is recorded as the Z1 direction, and the direction opposite to the Z1 direction is recorded as the Z2 direction.

[0029] Figure 1The liquid ejection device 100 is an inkjet printing device that ejects ink, which is an example of liquid, onto a medium 90. Although the medium 90 is typically printing paper, a printing object made of any material such as a resin film or cloth can also be used as the medium 90. Figure 1 As shown in the example, the liquid ejection device 100 is provided with a liquid container 9 for storing ink. For example, a cartridge detachable from the liquid ejection device 100, a bag-shaped ink pack formed of a flexible film, or an ink tank capable of replenishing ink can be used as the liquid container 9.

[0030] The liquid ejection device 100 includes a control unit 20, a medium conveying mechanism 22, a moving mechanism 24, and a liquid ejection head 1. The control unit 20 includes, for example, one or more processing circuits such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and one or more storage circuits such as a semiconductor memory, and comprehensively controls various elements of the liquid ejection device 100.

[0031] The medium conveying mechanism 22 conveys the medium 90 in the direction along the Y axis under the control of the control unit 20. In addition, the moving mechanism 24 moves the liquid ejecting head 1 back and forth along the X axis under the control of the control unit 20. The moving mechanism 24 includes a substantially box-shaped conveying body 242 for accommodating the liquid ejecting head 1, and a conveying belt 244 to which the conveying body 242 is fixed. In addition, a structure in which a plurality of liquid ejecting heads 1 are mounted on the conveying body 242, or a structure in which the liquid container 9 is mounted on the conveying body 242 together with the liquid ejecting head 1, may be adopted.

[0032] The liquid ejection head 1 ejects ink supplied from the liquid container 9 from a plurality of nozzles toward the medium 90 under the control of the control unit 20. Each liquid ejection head 1 ejects ink toward the medium 90 in parallel with the transport of the medium 90 by the medium transport mechanism 22 and the repeated reciprocating movement of the transport body 242, thereby forming an image on the surface of the medium 90.

[0033] Figure 2 for Figure 1 A block diagram of a liquid ejection device 100 is shown. Figure 2As shown, the liquid ejection device 100 includes a control unit 20, a medium conveying mechanism 22, a moving mechanism 24, and a liquid ejection head 1. The control unit 20 includes a control unit 21, a storage unit 23, and a drive signal generating circuit 25. The liquid ejection head 1 includes a drive circuit 40, a plurality of second piezoelectric elements 3, a voltage applying unit 41, a pressure acquiring unit 42, one or more pressure detecting elements 5, and one or more third piezoelectric elements 6.

[0034] The control unit 21 includes one or more processing circuits such as a CPU or an FPGA. The control unit 21 generates signals for controlling the operation of each part of the liquid ejection device 100. The control unit 21 controls the ink ejection operation performed by the liquid ejection head 1.

[0035] The control unit 21 generates a printing signal SI, a waveform designation signal dCom, and a timing signal PTS. The printing signal SI is a digital signal for designating the type of action of the liquid ejection head 1. The printing signal SI designates whether to supply the drive signal Com to the second piezoelectric element 3. The waveform designation signal dCom is a digital signal that specifies the waveform of the drive signal Com. The drive signal Com is an analog signal for driving the second piezoelectric element 3. The timing signal PTS is a signal that specifies the timing of generating the drive signal Com.

[0036] The storage unit 23 includes one or more storage circuits such as semiconductor memories. The storage unit 23 stores the print data Img supplied from the host computer. The storage unit 23 stores the control program of the liquid ejecting device 100.

[0037] The drive signal generation circuit 25 includes a DA conversion circuit. The drive signal generation circuit 25 generates a drive signal Com having a waveform specified by the waveform designation signal dCom. The drive signal generation circuit 25 outputs the drive signal Com every time it receives the timing signal PTS.

[0038] The drive circuit 40 switches whether to supply the drive signal Com to each second piezoelectric element 3 based on the print signal SI. The drive circuit 40 selects the second piezoelectric element 3 to which the drive signal Com is supplied based on the print signal SI, the latch signal LAT, and the exchange signal CH supplied from the control unit 20. The latch signal LAT specifies the latch timing of the print data Img. The exchange signal CH specifies the selection timing of the drive pulse included in the drive signal Com.

[0039] The voltage applying unit 41 applies a predetermined voltage to one or more pressure detecting elements 5 and one or more third piezoelectric elements 6. The voltage applying unit 41 includes, for example, a power supply circuit. The pressure acquiring unit 42 acquires the pressure of a pressure detecting chamber S2 described later in the liquid ejection head 1 based on the voltage applied to the pressure detecting element 5. The pressure acquiring unit 42 outputs, for example, a detection signal as a voltage value.

[0040] The liquid ejection device 100 includes a liquid ejection head 1 and a control unit 20, wherein the control unit 20 includes a control unit 21 for controlling the ejection action ejected from the liquid ejection head 1. The liquid ejection head 1 includes a pressure detection element 5 which can exert a detection sensitivity which is better than that of the conventional one, which will be described later. Therefore, according to the present embodiment, a liquid ejection device 100 including a liquid ejection head 1 which can detect the pressure of the pressure detection chamber S2 with high sensitivity can be provided.

[0041] 1-2. Liquid ejection head 1

[0042] Figure 3 for Figure 1 The cross-sectional view of a portion of the liquid ejection head 1 is shown, and is a cross-sectional view parallel to the XZ plane. The Z axis is an axis along the ejection direction of the ink ejected from the liquid ejection head 1. In addition, the situation observed from the direction along the Z axis is referred to as "top view".

[0043] Figure 3 The liquid ejection head 1 is a structure that is substantially plane-symmetrical with respect to the imaginary plane a along the YZ plane. Figure 3 The structure on the right side of the middle part, and the part close to the imaginary surface a is appropriately omitted. Figure 3 Description of the structure on the left.

[0044] The liquid ejection head 1 has a nozzle substrate 11, a pressure chamber substrate 12, a vibration plate 13, a sealing substrate 14, a wiring substrate 49, a second piezoelectric element 3, and a pressure detection element 5. The second piezoelectric element 3 includes a second piezoelectric body 31, a third electrode 32, and a fourth electrode 33. The pressure detection element 5 includes a first piezoelectric body 51, a first electrode 52, and a second electrode 53. In addition, although not shown in detail, the nozzle substrate 11, the pressure chamber substrate 12, the vibration plate 13, and the sealing substrate 14 are in the shape of a long strip along the Y axis.

[0045] The nozzle substrate 11 is a plate-shaped member provided with a plurality of nozzles N for ejecting ink as an example of liquid. Each of the plurality of nozzles N is a circular through hole for ejecting ink. The plurality of nozzles N are arranged in a straight line along the Y axis. The nozzle substrate 11 is manufactured by processing a semiconductor substrate such as a single crystal substrate of silicon, for example.

[0046] The pressure chamber substrate 12 is a flow channel structure having a flow channel for supplying ink to each of the plurality of nozzles N formed therein. The pressure chamber substrate 12 is a laminate of a first substrate 121 and a second substrate 122. The first substrate 121 and the second substrate 122 are manufactured by processing semiconductor substrates such as a single crystal substrate of silicon, for example. In addition, the first substrate 121 and the second substrate 122 may each be formed integrally. In addition, the pressure chamber substrate 12 may also include components other than the first substrate 121 and the second substrate 122.

[0047] The flow path of ink is formed on the pressure chamber substrate 12. Specifically, a plurality of pressure chambers S1, a pressure detection chamber S2, a plurality of first communication flow paths R1, and a second communication flow path R2 are formed on the pressure chamber substrate 12. The first substrate 121 and the second substrate 122 each have a recess or a through hole, and the plurality of pressure chambers S1, the pressure detection chamber S2, a plurality of first communication flow paths R1, and a second communication flow path R2 are formed through these recesses or through holes.

[0048] Figure 4 To express Figure 3 FIG. 1 is a diagram of a portion of a pressure chamber substrate 12. Figure 4 As shown, each pressure chamber S1 is a narrow and long shape extending in the X2 direction. The plurality of pressure chambers S1 are separated from each other and arranged along the Y2 direction. In addition, the plurality of pressure chambers S1 are arranged on the plurality of nozzles N in a one-to-one manner. Each pressure chamber S1 is a space for applying pressure to the ink for ejecting the ink from the nozzle N.

[0049] The plurality of first communication channels R1 are separated from each other and arranged along the Y2 direction. The plurality of first communication channels R1 are arranged on the plurality of pressure chambers S1 in a one-to-one manner. Each first communication channel R1 connects the corresponding pressure chamber S1 and the nozzle N. Each first communication channel R1 overlaps the corresponding pressure chamber S1 and the nozzle N when viewed from above.

[0050] The pressure detection chamber S2 is arranged on the upstream side relative to the multiple pressure chambers S1. The direction in which the pressure chambers S1 and the pressure detection chamber S2 are arranged is the X2 direction. The pressure detection chamber S2 is a long and narrow shape extending in the Y2 direction. The volume of the pressure detection chamber S2 is very large compared to the volume of each pressure chamber S1. The pressure detection chamber S2 is provided on the multiple pressure chambers S1 in a shared manner and is connected to the multiple pressure chambers S1. The pressure detection chamber S2 is adjacent to the pressure chamber S1 and absorbs the vibration of the ink generated when pressure is applied to the ink in the pressure chamber S1. By providing the pressure detection chamber S2, the ink ejection performance can be stabilized. In addition, by making the pressure detection chamber S2 adjacent to the pressure chamber S1, the absorption efficiency of the vibration of the ink can be improved compared to the case of phase separation. Therefore, the stability of the ink ejection performance can be improved.

[0051] The second communication flow path R2 is provided at the upstream side of the pressure detection chamber S2 and is connected to the pressure detection chamber S2. The second communication flow path R2 has a long and narrow shape extending in the Y2 direction.

[0052] like Figure 3 As shown, a vibration plate 13 is arranged on the surface of the pressure chamber substrate 12 in the Z2 direction. The thickness of the vibration plate 13 is very thin compared with the thickness of each of the first substrate 121 and the second substrate 122 of the pressure chamber substrate 12. The thickness is the length in the Z1 direction. The vibration plate 13 can be elastically deformed. The vibration plate 13 includes a plurality of second vibration plates 132 and a first vibration plate 131. The plurality of second vibration plates 132 and the first vibration plate 131 are formed by one component.

[0053] A plurality of second vibration plates 132 are arranged on a plurality of pressure chambers S1 in a one-to-one manner. Each second vibration plate 132 is a portion of the vibration plate 13 that overlaps with the plurality of pressure chambers S1 when viewed from above. Each second vibration plate 132 forms a portion of the pressure chamber S1. Each second vibration plate 132 vibrates by applying a voltage to the second piezoelectric body 31 of the second piezoelectric element 3, thereby applying pressure to the pressure chamber S1. By providing the second vibration plate 132, the second piezoelectric element 3 can be provided on the pressure chamber S1, and the pressure formed by the vibration generated by applying a voltage to the second piezoelectric body 31 through the second vibration plate 132 can be efficiently applied to the pressure chamber S1.

[0054] The first vibration plate 131 is a portion of the vibration plate 13 that overlaps with the pressure detection chamber S2 when viewed from above. The first vibration plate 131 forms a portion of the pressure detection chamber S2. The first vibration plate 131 is driven by the pressure applied from the pressure detection chamber S2, and applies pressure to the first piezoelectric body 51 of the pressure detection element 5. By providing the first vibration plate 131, the pressure detection element 5 can be provided on the pressure detection chamber S2, and pressure can be applied to the first piezoelectric body 51 efficiently.

[0055] In addition, the plurality of second vibration plates 132 and the first vibration plate 131 are not separated but formed by a continuous component. Therefore, it is easy to make each second vibration plate 132 adjacent to the first vibration plate 131. Therefore, it is easy to make the plurality of pressure chambers S1 adjacent to the pressure detection chamber S2. Since the plurality of pressure chambers S1 can be adjacent to the pressure detection chamber S2, the absorption efficiency of the vibration of the ink can be improved.

[0056] The vibration plate 13 is manufactured, for example, by processing a semiconductor substrate such as a single crystal substrate of silicon. In addition, the vibration plate 13 may be formed by a portion of the pressure chamber substrate 12. For example, the vibration plate 13 may be formed by thinning a portion of the second substrate 122. In addition, the vibration plate 13 may also be composed of a multi-layer laminate. For example, the vibration plate 13 is formed by a laminate of a silicon oxide film formed by thermally oxidizing a single crystal substrate of silicon and a zirconium oxide film.

[0057] A sealing substrate 14 is disposed on the surface in the Z2 direction of the vibration plate 13. The sealing substrate 14 is a structure that protects a plurality of second piezoelectric elements 3 and pressure detection elements 5 described later and reinforces the mechanical strength of the pressure chamber substrate 12.

[0058] The third communication channel R3, the first space H1, the second space H2, and the wiring space H0 are formed on the sealing substrate 14. The sealing substrate 14 has a recess or a through hole, and each channel or space is formed through these recesses or through holes. The third communication channel R3 and the wiring space H0 are holes that penetrate the sealing substrate 14. The first space H1 and the second space H2 are spaces surrounded by the recess formed on the sealing substrate 14.

[0059] The third communication flow channel R3 overlaps with the second communication flow channel R2 in a plan view and is connected to the second communication flow channel R2. The third communication flow channel R3 and the second communication flow channel R2 form a common ink chamber R. The common ink chamber R functions as a liquid reservoir. In addition, a filter 141 for removing bubbles and foreign matter mixed in the ink is provided on the portion overlapping with the common ink chamber R in a plan view. The filter 141 may also be omitted.

[0060] Figure 5 To express Figure 3 A top view of a portion of the sealing substrate 14 is shown. Figure 5 In the figure, dots are marked on the fourth electrode 33 of the second piezoelectric element 3 and the second electrode 53 of the pressure detection element 5 for convenience of explanation.

[0061] like Figure 5 As shown, the first space H1, the second space H2, the third communication channel R3 and the wiring space H0 are each long and narrow and extend in the Y2 direction. The wiring space H0, the first space H1, the second space H2 and the third communication channel R3 are arranged in this order in the X2 direction.

[0062] like Figure 3 As shown, a plurality of second piezoelectric elements 3 are arranged in the first space H1. A pressure detection element 5 is arranged in the second space H2. A wiring substrate 49 is arranged in the wiring space H0. The wiring substrate 49 is bonded to the pressure chamber substrate 12. The wiring substrate 49 is a mounting component formed with a plurality of wirings for electrically connecting the control unit 20 and the liquid ejection head 1. As the wiring substrate 49, for example, TCP (Tape Carrier Package) or FPC (Flexible Printed Circuit) is used.

[0063] Each second piezoelectric element 3 is in a long and narrow shape extending in the X2 direction. The plurality of second piezoelectric elements 3 are separated from each other and arranged in the Y2 direction. The plurality of second piezoelectric elements 3 are arranged in a one-to-one manner on the plurality of pressure chambers S1. In addition, the pressure detection element 5 is in a long and narrow shape extending in the Y2 direction, and extends in a direction intersecting the plurality of second piezoelectric elements 3. The pressure detection element 5 is arranged corresponding to the pressure detection chamber S2, and overlaps with the pressure detection chamber S2 when viewed from above.

[0064] The second piezoelectric element 3 is provided corresponding to the pressure chamber S1. Specifically, the second piezoelectric element 3 is arranged on the surface of the second vibration plate 132 on the opposite side of the pressure chamber S1 for each pressure chamber S1. The second piezoelectric element 3 is an energy generating element that generates energy for ejecting ink by applying a driving signal Com. In addition, the second piezoelectric element 3 is also a driving element that is driven by applying a driving signal Com. The second piezoelectric element 3 contracts when a voltage is applied, and the second vibration plate 132 is bent to pressurize the pressure chamber S1.

[0065] In brief, the second piezoelectric element 3 includes a fourth electrode 33, a second piezoelectric body 31, and a third electrode 32. The fourth electrode 33, the second piezoelectric body 31, and the third electrode 32 are stacked in order from the second vibration plate 132. Therefore, the third electrode 32 is located closer to the Z2 direction than the second piezoelectric body 31. The fourth electrode 33 is located closer to the Z1 direction than the second piezoelectric body 31. In addition, the fourth electrode 33 may be in contact with the second vibration plate 132, or another component may be present between the fourth electrode 33 and the second vibration plate 132.

[0066] The second piezoelectric body 31 is a dielectric body that is individually provided for each of the plurality of second piezoelectric elements 3. In addition, the plurality of second piezoelectric bodies 31 may be connected to each other. For example, the plurality of second piezoelectric bodies 31 may be separated by forming a plurality of cuts in a strip-shaped dielectric film extending along the Y2 direction. Therefore, the plurality of second piezoelectric bodies 31 may also be formed by one dielectric film. The second piezoelectric body 31 may be formed by, for example, lead zirconate titanate (Pb(Zr,Ti)O 3 ) and other piezoelectric materials.

[0067] The third electrode 32 is a common electrode provided in common with respect to the plurality of second piezoelectric bodies 31. The third electrode 32 is in the shape of a strip extending in the Y2 direction in a continuous manner across the plurality of second piezoelectric elements 3. The fourth electrode 33 is provided in common with respect to the plurality of pressure chambers S1. By providing in common, it is easy to achieve miniaturization of the second piezoelectric elements 3 compared with the case of providing separately. The third electrode 32 is formed by using a low-resistance conductive material such as platinum (Pt) or iridium (Ir) in the same manner as the fourth electrode 33.

[0068] like Figure 5 As shown in FIG. 1 , the fourth electrode 33 is long and narrow along the X-axis. A plurality of fourth electrodes 33 are arranged along the Y-axis. The fourth electrode 33 is a separate electrode formed for each second piezoelectric element 3 in a mutually separated manner. The fourth electrode 33 is provided separately with respect to the plurality of pressure chambers S1. By being provided separately, even when the plurality of second piezoelectric bodies 31 are formed by one dielectric film, one dielectric film can be divided into a plurality of second piezoelectric bodies 31. The fourth electrode 33 is formed of a conductive material such as platinum or iridium.

[0069] The second piezoelectric element 3 is a piezoelectric element related to the ejection of ink. A reference voltage as a fixed voltage is applied to the third electrode 32. The reference voltage may be, for example, a ground voltage or a voltage higher than the ground voltage. A drive signal Com is supplied to the fourth electrode 33. Therefore, a drive voltage whose voltage changes with time is applied to the fourth electrode 33.

[0070] A voltage corresponding to the difference between the reference voltage applied to the third electrode 32 and the driving voltage supplied to the fourth electrode 33 is applied to the second piezoelectric body 31. Figure 2 The driving circuit 40 applies a driving voltage that changes with time to the second piezoelectric body 31. A voltage equivalent to the difference between the reference voltage applied to the third electrode 32 and the driving voltage supplied to the fourth electrode 33 is applied to the second piezoelectric body 31, causing the second piezoelectric body 31 to deform, so that the second piezoelectric element 3 generates energy that causes the second vibration plate 132 to bend and deform. Therefore, the second piezoelectric element 3 applies pressure to the pressure chamber S1 by applying this voltage. By using the energy generated by the second piezoelectric element 3 to bend and deform the second vibration plate 132, the pressure in the pressure chamber S1 changes, and the ink in the pressure chamber S1 is moved from the pressure chamber S1 to the pressure chamber S1. Figure 3 The nozzle N shown sprays out.

[0071] Figure 3 The pressure detection element 5 shown is provided corresponding to the pressure detection chamber S2. Specifically, the pressure detection element 5 is arranged on the surface of the first vibration plate 131 on the side opposite to the pressure detection chamber S2. The pressure detection element 5 is used to detect the pressure of the pressure detection chamber S2. The pressure detection element 5 is deformed according to the first vibration plate 131 that is bent based on the pressure of the pressure detection chamber S2.

[0072] The pressure detection element 5 includes a second electrode 53, a first piezoelectric body 51, and a first electrode 52. The second electrode 53, the first piezoelectric body 51, and the first electrode 52 are stacked in this order from the first vibration plate 131. In addition, the second electrode 53 and the first vibration plate 131 may be in contact, or another component may be present between the second electrode 53 and the first vibration plate 131.

[0073] The first piezoelectric body 51 is a strip-shaped dielectric film extending in the Y2 direction. The first piezoelectric body 51 is formed of a known piezoelectric material such as lead zirconate titanate. The thickness of the first piezoelectric body 51 is the same as that of the second piezoelectric body 31. The thickness is the length in the Z1 direction.

[0074] The first electrode 52 and the second electrode 53 are respectively long and narrow along the Y axis. The first electrode 52 and the second electrode 53 are respectively formed of conductive materials such as platinum or iridium. For example, the second electrode 53 is stacked in sequence from the first vibration plate 131 with a first layer containing titanium, a second layer containing platinum, a third layer containing iridium, and a fourth layer containing titanium. The thickness of the first layer is thinner than the thickness of the fourth layer. The first layer is used for the close contact between the first vibration plate 131 and the second electrode 53. The fourth layer is a seed layer for improving the orientation of the first piezoelectric body 51. By providing the fourth layer, when the first piezoelectric body 51 is formed, the island-shaped titanium becomes a crystal nucleus and improves the orientation of the first piezoelectric body 51. In addition, the aforementioned fourth electrode 33 can also be the same structure as the second electrode 53.

[0075] Although in Figure 5 Only the second electrode 53 is shown in the figure, but the planar areas of the first electrode 52 and the first piezoelectric body 51 are substantially the same as the planar areas of the second electrode 53, and the first electrode 52 and the first piezoelectric body 51 overlap with the second electrode 53 when viewed from above. In addition, the first piezoelectric body 51, the first electrode 52, and the second electrode 53 overlap with substantially the entire area of ​​the pressure detection chamber S2 when viewed from above.

[0076] The electrostatic capacitance of the first piezoelectric body 51 changes according to the pressure of the pressure detection chamber S2. Since the electrostatic capacitance of the first piezoelectric body 51 is correlated with the pressure P, the pressure of the pressure detection chamber S2 can be detected based on the electrostatic capacitance by using the first piezoelectric body 51. Specifically, when the pressure in the pressure detection chamber S2 changes, the first vibration plate 131 deforms according to the change in pressure. The first vibration plate 131 deforms in a manner that bends in the Z1 direction or the Z2 direction. When the first vibration plate 131 deforms, stress is applied to the first piezoelectric body 51 on the first vibration plate 131, thereby causing deformation on the first piezoelectric body 51. By applying stress to the first piezoelectric body 51, the polarization state of the first piezoelectric body 51 changes. The change in the state of the polarization is expressed as a change in the dielectric constant ε of the first piezoelectric body 51, thereby causing a change in the electrostatic capacitance. Therefore, according to the change in the pressure of the pressure detection chamber S2, the electrostatic capacitance changes.

[0077] Electrostatic capacitance is expressed by equation [1].

[0078] C = ε(S / d)…[1]

[0079] C is the electrostatic capacitance. S is the electrode area. d is the distance between the first electrode 52 and the second electrode 53.

[0080] Figure 6 for Figure 3A cross-sectional view of the pressure sensing element 5. Figure 6 As shown, the first piezoelectric body 51 is arranged between the first electrode 52 and the second electrode 53. The electrostatic capacitance of the first piezoelectric body 51 changes according to the pressure of the pressure detection chamber S2. The first electrode 52 is located on the side of the first piezoelectric body 51 opposite to the pressure detection chamber S2. The second electrode 53 is located on the pressure detection chamber S2 side of the first piezoelectric body 51.

[0081] The first piezoelectric body 51 includes a first piezoelectric layer 511 and a second piezoelectric layer 512. The first piezoelectric layer 511 is located on the side of the first electrode 52 and is in contact with the first electrode 52. In addition, the second piezoelectric layer 512 is located on the side of the second electrode 53 and is in contact with the second electrode 53. The second piezoelectric layer 512 is in contact with the first piezoelectric layer 511. In addition, in the present embodiment, the planar area of ​​the first piezoelectric layer 511 is substantially equal to the planar area of ​​the second piezoelectric layer 512. Similarly, the cross-sectional area of ​​the first piezoelectric body 51 when viewed from the thickness direction is substantially equal to the cross-sectional area of ​​the second piezoelectric body 31 when viewed from the thickness direction.

[0082] The crystal systems of the first piezoelectric layer 511 and the second piezoelectric layer 512 are different. Specifically, the second piezoelectric layer 512 is any one of a tetragonal system, a cubic system, and a monoclinic system. The first piezoelectric layer 511 is a rhombohedral crystal system. In the tetragonal system, the three crystal axes a, b, and c are orthogonal to each other, and the lengths of the two axes are equal, and only the length of one axis is different. In the cubic system, the three crystal axes a, b, and c are orthogonal to each other, and the lengths of the axes are equal to each other. In the monoclinic system, the three crystal axes a, b, and c are orthogonal to each other, and the lengths of the axes are different from each other. In the rhombohedral crystal system, although the lengths of the three crystal axes a, b, and c are equal to each other, two of the three angles α, β, and γ formed by the axes are 90°, and the remaining angle is 120°.

[0083] The rhombohedral system has a larger degree of strain than the tetragonal system, the cubic system and the monoclinic system. For example, the lengths of two of the three crystal axes of the tetragonal crystal are equal to each other, and the length of the remaining one axis is different from the lengths of the other two axes. In addition, the three crystal axes of the monoclinic crystal are different from each other. On the other hand, the lengths of the three crystal axes of the rhombohedral crystal are equal to each other. Therefore, the rhombohedral crystal has a larger deformation than the tetragonal crystal and the monoclinic crystal.

[0084] Therefore, the degree of deformation relative to stress in the first piezoelectric layer 511 and the second piezoelectric layer 512 is different from each other. When the same stress is applied, the second piezoelectric layer 512 is deformed more than the first piezoelectric layer 511. Therefore, a phenomenon called flexoelectricity occurs in the first piezoelectric body 51, and the flexoelectric effect is a phenomenon in which an electrical deviation is generated and the dielectric constant changes. Due to the flexoelectric effect, there is a difference in the degree of deformation on the first electrode 52 side and the second electrode 53 side of the first piezoelectric body 51, which results in a large change in the dielectric constant. Therefore, a large change in electrostatic capacitance occurs. Since electrostatic capacitance is correlated with pressure, by using the first piezoelectric body 51, the pressure of the pressure detection chamber S2 can be detected with good sensitivity.

[0085] Even if a large stress is applied to the piezoelectric body, its deformation is small. Assuming that the first piezoelectric body 51 is composed of only one layer of the first piezoelectric layer 511 and the second piezoelectric layer 512, even if a large pressure is applied, it is difficult to produce a difference in deformation on the first electrode 52 side and the second electrode 53 side of the first piezoelectric body 51. Therefore, the change in dielectric constant is small, and it is difficult to obtain the detection accuracy of pressure. In contrast, in the present embodiment, as described above, the first piezoelectric body 51 is formed by two layers, the first piezoelectric layer 511 and the second piezoelectric layer 512, which have different degrees of deformation. Therefore, pressure can be detected with good sensitivity.

[0086] In addition, the thickness D2 of the second piezoelectric layer 512 is thinner than the thickness D1 of the first piezoelectric layer 511. The thinner the thickness D2 of the second piezoelectric layer 512, the greater the deformation of the second piezoelectric layer 512, and therefore, the greater the dielectric constant. In other words, the thickness is inversely proportional to the dielectric constant. Therefore, by making the thickness D2 of the second piezoelectric layer 512, which is more deformed than the first piezoelectric layer 511, thinner than the thickness D1 of the first piezoelectric layer 511, the difference in the deformation between the first piezoelectric layer 511 and the second piezoelectric layer 512 can be increased. Therefore, a large change in the dielectric constant will occur on the first electrode 52 side and the second electrode 53 side of the first piezoelectric body 51. Therefore, the pressure of the pressure detection chamber S2 can be detected with high sensitivity.

[0087] The thickness D2 of the second piezoelectric layer 512 is preferably thicker than 1 / 14 of the thickness D1 of the first piezoelectric layer 511. Since the thickness D2 of the second piezoelectric layer 512 is thicker than the above value, the second piezoelectric layer 512 is easier to form than when it is thinner. In addition, from the above viewpoint, the thickness D2 is more preferably thicker than 1 / 13 of the thickness D1, and further preferably thicker than 1 / 12 of the thickness D1.

[0088] The thickness D2 of the second piezoelectric layer 512 is preferably thinner than 1 / 8 of the thickness D1 of the first piezoelectric layer 511. Since the thickness D2 of the second piezoelectric layer 512 is thinner than the above value, the pressure of the pressure detection chamber S2 can be detected with particularly good sensitivity compared to the case where it is thicker. In addition, from the viewpoint of improving the detection sensitivity of the pressure, the thickness D2 is more preferably thinner than 1 / 9 of the thickness D1, and further preferably thinner than 1 / 10 of the thickness D2.

[0089] The Young's modulus of the second piezoelectric layer 512 is smaller than that of the first piezoelectric layer 511. Therefore, the degree of deformation of the first piezoelectric layer 511 and the second piezoelectric layer 512 relative to the stress is different from each other. When the same stress is applied to the first piezoelectric layer 511 and the second piezoelectric layer 512, the second piezoelectric layer 512 is deformed to a greater extent than the first piezoelectric layer 511. Therefore, as mentioned above, a phenomenon called flexoelectric effect occurs inside the first piezoelectric body 51, and the flexoelectric effect is a phenomenon in which an electrical deviation is generated and the dielectric constant changes. Due to the flexoelectric effect, there is a difference in the degree of deformation on the first electrode 52 side and the second electrode 53 side of the first piezoelectric body 51, resulting in a large change in the dielectric constant. Therefore, a large change in electrostatic capacitance occurs. Therefore, since electrostatic capacitance is correlated with pressure, by using the first piezoelectric body 51, the pressure of the pressure detection chamber S2 can be detected with good sensitivity.

[0090] Fig.15 This is a diagram showing an example of the relationship between voltage and charge. Fig.16 This is a diagram showing an example of the relationship between voltage and capacity. Fig.15 as well as Fig.16 The example shown is a result of measuring the charge or capacitance per unit electrode area of ​​the first piezoelectric body 51 by applying a triangular waveform voltage between the first electrode 52 and the second electrode 53. This measurement is performed while applying pressure.

[0091] The first piezoelectric body 51 has Fig.15 The hysteresis characteristic shown. Fig.15 The magnitude of the electric field at the voltage where the charge is zero is the coercive electric field. In this example, the voltage corresponding to the coercive electric field is about ±4V. Fig.16 As can be seen, in this example, a large capacitance change occurs near ±4 V. Therefore, in this example, by applying a sine wave centered at ±4 V to the first electrode 52 of the pressure detection element 5, for example, the rate of change of the electrostatic capacitance with respect to the pressure can be maximized.

[0092] Figure 7 : is a graph showing an example of the relationship between the electrostatic capacitance C of the first piezoelectric body 51 and the pressure P. Figure 7 The horizontal axis is pressure P [kPa], and the vertical axis is the rate of change of electrostatic capacitance. Fig.16 The peak value of the capacitance at the pressure of 0 [kPa] is used as a reference, and the peak values ​​of the capacitance at each pressure relative to the reference are shown. Figure 7 In the example shown, the rate of change of the electrostatic capacitance of the first piezoelectric body 51 decreases as the pressure P increases. For example, it is known that the electrostatic capacitance changes by about 2.5% at 100 [kPa].

[0093] As from Figure 7 as well as Fig.14 As can be seen, by using a voltage corresponding to the coercive electric field of the first piezoelectric body 51, the rate of change of the electrostatic capacitance with respect to the pressure can be maximized. Therefore, it is preferable to detect the pressure of the pressure detection chamber S2 based on the change of the electrostatic capacitance when the voltage corresponding to the coercive electric field of the first piezoelectric body 51 is applied. By using a voltage corresponding to the coercive electric field, the pressure of the pressure detection chamber S2 can be detected with high sensitivity. For example, according to Figure 7 as well as Fig.16 In the example shown, it is preferable to apply a sine wave in the range of ±0.1 V centered at 4 V, for example, to the first electrode 52 of the pressure detection element 5. Alternatively, a voltage other than the voltage corresponding to the coercive electric field may be used.

[0094] In addition, as mentioned above, the pressure detection element 5 is provided corresponding to the pressure detection chamber S2. The pressure chamber S1 and the pressure detection chamber S2 are provided on the pressure chamber substrate 12, and the pressure chamber S1 and the pressure detection chamber S2 are adjacent. In the manner in which the pressure chamber S1 and the pressure detection chamber S2 are adjacent, the pressure detection element 5 is provided corresponding to the pressure detection chamber S2. Therefore, since the pressure of the pressure detection chamber S2 adjacent to the pressure chamber S1 can be obtained through the pressure detection element 5, the movement of the ink corresponding to the pressure of the pressure chamber S1 can be detected. Therefore, for example, it is possible to detect whether various adverse conditions such as insufficient supply of ink to multiple pressure chambers S1 and the pressure detection chamber S2 have not occurred. Therefore, since the pressure of the pressure detection chamber S2 near the pressure chamber S1 can be obtained, it can contribute to the improvement of the quality of the liquid ejection head 1.

[0095] Furthermore, the pressure detection chamber S2 is not directly related to the discharge of ink like the pressure chamber S1. Therefore, the pressure of the pressure detection chamber S2 can be detected based on the voltage applied to the first piezoelectric body 51 regardless of the discharge of ink and can be always performed.

[0096] In addition, as mentioned above, the pressure detection chamber S2 has a function of absorbing the vibration of the ink generated when pressure is applied to the ink in the pressure chamber S1. Therefore, by providing the pressure detection chamber S2, the ink ejection performance can be stabilized. In the present embodiment, a pressure detection element 5 is provided corresponding to the pressure detection chamber S2. Therefore, the pressure near the pressure chamber S1 can be detected by using the pressure detection chamber S2. Therefore, the pressure near the pressure chamber S1 can be detected with a simple structure without separately forming a space for detecting the pressure near the pressure chamber S1.

[0097] Figure 8 To express Figure 2 FIG. 5 is a diagram of the pressure detection element 5 and the third piezoelectric element 6. Figure 8 The third piezoelectric element 6 is a reference piezoelectric element. The third piezoelectric element 6 is connected in series with the pressure detection element 5. The third piezoelectric element 6 is not disposed on the aforementioned vibration plate 13, but is provided at a location that does not deform according to the pressure in the flow channel.

[0098] The third piezoelectric element 6 has the same structure as the pressure detection element 5. The third piezoelectric element 6 includes a third piezoelectric body 61, a fifth electrode 62, and a sixth electrode 63. The third piezoelectric body 61 is sandwiched by the fifth electrode 62 and the sixth electrode 63. The third piezoelectric body 61 is a dielectric body and is formed using a known piezoelectric material such as lead zirconate titanate. The electrostatic capacitance of the third piezoelectric body 61 is a known electrostatic capacitance.

[0099] The fifth electrode 62 and the sixth electrode 63 are formed of conductive materials such as platinum or iridium, respectively. The fifth electrode 62 is electrically connected to the second electrode 53 of the pressure detection element 5. A fixed predetermined voltage is applied to the sixth electrode 63. In the illustrated example, the predetermined voltage is a ground voltage, and the sixth electrode 63 is grounded. In addition, preferably, a voltage corresponding to the aforementioned coercive electric field is applied to the first electrode 52 of the aforementioned pressure detection element 5, for example, as a predetermined voltage Vx. Therefore, Figure 2 The voltage applying unit 41 applies a predetermined voltage Vx to the first piezoelectric body 51 and the third piezoelectric body 61 .

[0100] As described in [4] below, the capacitance C2 of the first piezoelectric body 51 can be obtained based on the voltage V2 applied to the first piezoelectric body 51 , the voltage V3 applied to the third piezoelectric body 61 , and the capacitance C3 of the third piezoelectric body 61 .

[0101] V2=C2×Q2 …[2]

[0102] V3=C3×Q3 …[3]

[0103] C2=(V2 / V3)×C3 …[4]

[0104] Formula [4] is derived from Formula [2] and Formula [3]. Q2 is the charge generated on the pressure detection element 5, and Q3 is the charge generated on the third piezoelectric element 6. Voltage V2 is the voltage applied to the first piezoelectric body 51 when the predetermined voltage Vx is applied by the voltage application unit 41. Voltage V3 is the voltage applied to the third piezoelectric body 61 when the predetermined voltage Vx is applied by the voltage application unit 41.

[0105] When stress is applied to the first piezoelectric body 51 and the electrostatic capacitance C of the first piezoelectric body 51 changes, the voltage V2 across the first piezoelectric body 51 changes. Figure 2 The pressure acquisition unit 42 acquires the signal of the voltage V2. The voltage V2, the voltage V3, and the known electrostatic capacitance C3 are used to obtain the electrostatic capacitance C2 of the first piezoelectric body 51 by using the formula [4]. Therefore, the pressure acquisition unit 42 acquires the electrostatic capacitance C2 based on the voltage V2, the voltage V3, and the electrostatic capacitance C3. Figure 7 The pressure P of the first piezoelectric body 51 is obtained by looking at the correlation between the electrostatic capacitance and the pressure shown in FIG. In this way, the pressure acquisition unit 42 acquires the pressure of the pressure detection chamber S2 based on the electrostatic capacitance.

[0106] In this embodiment, as described above, the pressure acquisition unit 42 uses the third piezoelectric body 61 whose electrostatic capacitance C3 is known to obtain the electrostatic capacitance C2 of the first piezoelectric body 51, and detects the pressure of the pressure detection chamber S2 through the electrostatic capacitance C2. According to the detection method using the third piezoelectric body 61, the pressure of the pressure detection chamber S2 near the pressure chamber S1 can be detected with a simple structure. In addition, the method of detecting the pressure of the pressure detection chamber S2 is not limited to the detection method using the third piezoelectric body 61, and the third piezoelectric element 6 can also be omitted according to the detection method.

[0107] Furthermore, as described above, at least a plurality of pressure chambers S1 and one pressure detection chamber S2 connected to the plurality of pressure chambers S1 in a shared manner are provided on the pressure chamber substrate 12. Since the volume of the pressure detection chamber S2 is larger than the volume of each pressure chamber S1, the plane area of ​​the first vibration plate 131 forming the pressure detection chamber S2 can be made larger than the plane area of ​​each second vibration plate 132 forming each pressure chamber S1. Therefore, the displacement of the first vibration plate 131 can be made larger than the displacement of the second vibration plate 132.

[0108] By being able to detect the pressure of one pressure detection chamber S2 connected to a plurality of pressure chambers S1 in a shared manner, it is possible to detect the pressure of the pressure detection chamber S2 generated by the influence of the plurality of pressure chambers S1, rather than the pressure of each pressure chamber S1. Therefore, the pressure can be used to detect whether various adverse conditions such as insufficient ink supply have occurred, etc.

[0109] Since a pressure detection chamber S2 is provided which is connected to a plurality of pressure chambers S1 in a shared manner, the planar surface area of ​​the first piezoelectric body 51 is larger than the planar surface area of ​​the second piezoelectric body 31. Similarly, the cross-sectional area of ​​the first piezoelectric body 51 when viewed from the thickness direction is larger than the cross-sectional area of ​​the second piezoelectric body 31 when viewed from the thickness direction. The larger the cross-sectional area of ​​the first piezoelectric body 51, the greater the electrostatic capacitance of the first piezoelectric body 51. Therefore, the accuracy of pressure detection can be improved. On the other hand, if the cross-sectional area of ​​the second piezoelectric body 31 is made too large, there is a possibility that the deducted volume becomes too much and the ejection amount becomes too much.

[0110] In addition, the second piezoelectric body 31 and the first piezoelectric body 51 have different directions of easy bending. The pressure chamber S1, the second piezoelectric body 31 and the fourth electrode 33 are long and narrow along the X2 direction. If the pressure chamber S1 increases the exclusion volume as much as possible during the extension process in the X2 direction, the second piezoelectric body 31 and the fourth electrode 33 are also easy to extend in the X2 direction. Therefore, the second piezoelectric body 31 and the fourth electrode 33 are easy to bend with the center near the center of the X2 direction as the center. Therefore, by arranging the second piezoelectric body 31 along the extension direction of the pressure chamber S1, the ejection accuracy can be improved.

[0111] On the other hand, the pressure detection chamber S2, the first piezoelectric body 51, and the second electrode 53 are long and narrow along the Y2 direction. Therefore, the first piezoelectric body 51 and the second electrode 53 are respectively easy to bend around the center of the Y2 direction. In addition, the pressure detection chamber S2 is provided in a common manner relative to the plurality of pressure chambers S1, and the pressure detection chamber S2 is commonly given pressure from the plurality of pressure chambers S1. It is difficult to imagine a situation in which pressure is concentrated only from a specific pressure chamber S1. From this point of view, the first piezoelectric body 51 and the second electrode 53 are also respectively easy to bend around the center of the Y2 direction. Therefore, by providing the first piezoelectric body 51 along the extension direction of the pressure detection chamber S2, the pressure detection sensitivity can be improved.

[0112] Alternatively, for example, the first piezoelectric body 51 and the second electrode 53 may be arranged along the X2 direction. However, in this case, the deflection amount of the first piezoelectric body 51 and the second electrode 53 is smaller than that when the first piezoelectric body 51 and the second electrode 53 are arranged along the X2 direction.

[0113] In addition, if Figure 5 As shown, the second electrode 53 overlaps with the center of the pressure detection chamber S2 in the X2 direction. Similarly, the first electrode 52 and the first piezoelectric body 51 overlap with the center of the pressure detection chamber S2 in the X2 direction. Therefore, the pressure detection element 5 overlaps with the center of the first vibration plate 131 in the X2 direction. The center of the first vibration plate 131 in the X2 direction is the part with the largest displacement. Therefore, by overlapping the pressure detection element 5 with the center of the pressure detection chamber S2 in the X2 direction, the detection accuracy of the pressure of the pressure detection chamber S2 can be improved. In addition, the pressure detection element 5 may not overlap with the center in the X2 direction.

[0114] 2. Modifications

[0115] The embodiments illustrated above can be modified in various ways. In the following, specific modified modes that can be applied to the aforementioned embodiments are illustrated. Two or more modes arbitrarily selected from the following examples can be appropriately combined within the scope of non-contradiction.

[0116] Fig. 9 It is a cross-sectional view of a pressure sensing element 5A of a modified example. The planar area of ​​the first piezoelectric layer 511 and the planar area of ​​the second piezoelectric layer 512 of the pressure sensing element 5A are different from each other. The planar area of ​​the second piezoelectric layer 512 is larger than the planar area of ​​the first piezoelectric layer 511. Similarly, the cross-sectional area of ​​the first piezoelectric layer 511 when viewed from the thickness direction and the cross-sectional area of ​​the second piezoelectric layer 512 when viewed from the thickness direction are different from each other. The cross-sectional area of ​​the second piezoelectric layer 512 when viewed from the thickness direction is larger than the cross-sectional area of ​​the first piezoelectric layer 511 when viewed from the thickness direction. Therefore, in the illustrated example, the length of the second piezoelectric layer 512 in the X2 direction, i.e., the width W2, is smaller than the length of the first piezoelectric layer 511 in the X2 direction, i.e., the width W1.

[0117] The dielectric constant change can be increased by making the cross-sectional area of ​​the second piezoelectric layer 512 larger than the cross-sectional area of ​​the first piezoelectric layer 511 when viewed from the thickness direction. In addition, the cross-sectional area of ​​the first piezoelectric layer 511 can also be larger than the cross-sectional area of ​​the second piezoelectric layer 512.

[0118] Fig.10 1 is a plan view showing a pressure detection element 5B according to a modified example. Fig.10 The pressure sensing element 5B shown does not overlap the entire area of ​​the pressure sensing chamber S2 when viewed from above, but overlaps the center of the pressure sensing chamber S2 in the X2 direction. For example, the length of the first piezoelectric body 51 in the X2 direction is less than half of the length of the pressure sensing chamber S2 and the first vibration plate 131 in the X2 direction.

[0119] Since the first piezoelectric body 51 is not disposed over the entire area of ​​the pressure detection chamber S2 in a plan view, it is easier to deform the first vibration plate 131 than when it is disposed over the entire area. The first piezoelectric body 51 is disposed so as to overlap the center of the first vibration plate 131 in the X2 direction, which is most easily displaced, so that the detection accuracy of the pressure of the pressure detection chamber S2 can be improved.

[0120] Fig.11 1 is a plan view showing a pressure sensing element 5C according to a modified example. Fig.11 The pressure sensing element 5C shown has a corrugated shape that extends along the X2 direction and is sequentially folded back toward the Y2 direction.

[0121] The pressure sensing element 5C includes a plurality of first parts 501 and a plurality of second parts 502. The plurality of first parts 501 are parts extending in the X2 direction, and are separated from each other and arranged in the Y2 direction. The plurality of second parts 502 are parts extending in the Y2 direction. Each second part 502 is arranged between two adjacent first parts 501 and connects the two adjacent first parts 501. The plurality of second parts 502 are alternately arranged at the end edge in the X1 direction and the end edge in the X2 direction of the first part 501. The second part 502 located closest to the Y1 direction among the plurality of second parts 502 is set as the first, and the plurality of second parts 502 are counted toward the Y2 direction. In this case, for example, the odd-numbered second part 502 among the plurality of second parts 502 is connected to the end of the first part 501 in the X2 direction. The even-numbered second part 502 among the plurality of second parts 502 is connected to the end of the first part 501 in the X1 direction.

[0122] The first piezoelectric body 51, the first electrode 52, and the second electrode 53 of the pressure detection element 5C are configured to have a pleated shape that extends along the X2 direction and folds back in sequence. By setting the pressure detection element 5C to a pleated shape, the pressure detection element 5C is more susceptible to the stress generated by the deformation of the first vibration plate 131 than the case of a narrow and long shape along the Y2 direction as in the pressure detection element 5 of the first embodiment. In addition, since the pressure detection element 5C is in a pleated shape, the flat area is reduced compared to the pressure detection element 5 of the first embodiment. Therefore, the volume of the pressure detection element 5C on the first vibration plate 131 can be reduced. Therefore, the first vibration plate 131 becomes easy to deform. Therefore, the detection accuracy of the pressure of the pressure detection chamber S2 can be improved.

[0123] In addition, the shape of the pressure sensing element 5C is preferably a shape that is easily subjected to stress caused by deformation of the first vibration plate 131 , and is not limited to the illustrated corrugated shape.

[0124] Fig.12 as well as Fig.13 The following are cross-sectional views of the second piezoelectric element 3 and the pressure sensing element 5 of the modified example. The thickness D5 of the first piezoelectric body 51 of the pressure sensing element 5 may be different from the thickness D3 of the second piezoelectric body 31 of the second piezoelectric element 3 .

[0125] For example, in Fig.12, the thickness D5 of the first piezoelectric body 51 is thinner than the thickness D3 of the second piezoelectric body 31. By making it thinner, the first piezoelectric body 51 is easier to deform than the second piezoelectric body 31. Since the thickness D5 is thinner than the thickness D3, the detection accuracy of the pressure of the pressure detection chamber S2 can be improved compared with the case where it is thicker. On the other hand, the second piezoelectric body 31 is a part that contributes to the ejection. Therefore, since the thickness D5 is thicker than the thickness D3, cracks and the like can be reduced.

[0126] For example, in Fig.13 In the embodiment, the thickness D5 of the first piezoelectric body 51 is thicker than the thickness D3 of the second piezoelectric body 31. Since the thickness D5 is thicker than the thickness D3, that is, the thickness D3 is thinner than the thickness D5, the second piezoelectric body 31 is more easily deformed than the first piezoelectric body 51. Therefore, the ink ejection performance can be improved.

[0127] Fig.14 1 is a block diagram of a liquid ejection device 100a of a modified example. The liquid ejection device 100a includes a liquid ejection head 1a and a control unit 20a. The drive circuit 40, the voltage application unit 41 and the pressure acquisition unit 42 are provided on the control unit 20a. The voltage application unit 41 and the pressure acquisition unit 42 are not provided on the liquid ejection head 1a.

[0128] like Fig.14 As shown, each of the driving circuit 40, the voltage applying unit 41, and the pressure acquiring unit 42 may be partially or entirely provided on the control unit 20. With the liquid ejecting device 100a, the pressure near the pressure chamber S1 can be acquired by using the pressure detecting chamber S2 as a space for absorbing the vibration of the ink, as in the respective embodiments.

[0129] In addition, the "liquid ejection head" may also be a circulation type head having a so-called circulation flow path. In addition, although in the embodiment, the third electrode 32 is a common electrode and the fourth electrode 33 is a separate electrode, the third electrode 32 may be a separate electrode and the fourth electrode 33 may be a common electrode.

[0130] The "pressure detection element" is not limited to the element used in the "liquid ejection head" and can also be used in other devices. As other devices, for example, a pressure-electric converter, a piezoelectric transformer, etc. can be listed. In addition, the "pressure detection element" can be used as a sensor such as a pressure sensor.

[0131] In addition to equipment dedicated to printing, "liquid ejection devices" can also be used in various equipment such as fax machines or copiers. The use of liquid ejection devices is not limited to printing. For example, a liquid ejection device that ejects a solution of a color material is used as a color filter manufacturing device for forming a display device such as a liquid crystal display panel. In addition, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring or electrodes of a wiring substrate. In addition, a liquid ejection device that ejects a solution of an organic substance related to a living body is used, for example, as a manufacturing device for manufacturing a biochip.

[0132] Although the present invention has been described above based on preferred embodiments, the present invention is not limited to the aforementioned embodiments. In addition, the structure of each part of the present invention can be replaced with any structure that performs the same function as the aforementioned embodiments, and any structure can be added.

[0133] Explanation of symbols

[0134] 1…liquid ejection head; 1a…liquid ejection head; 3…second piezoelectric element; 5…pressure detection element; 5A…pressure detection element; 5B…pressure detection element; 5C…pressure detection element; 6…third piezoelectric element; 9…liquid container; 11…nozzle substrate; 12…pressure chamber substrate; 13…vibration plate; 14…sealing substrate; 20…control unit; 20a…control unit; 21…control unit; 22…medium conveying mechanism; 23…storage unit; 24…moving mechanism; 25…driving signal generating circuit; 31…second piezoelectric body; 32…third electrode; 33…fourth electrode; 40…driving circuit; 41…voltage applying unit; 42…pressure acquiring unit; 49…wiring substrate; 51…first piezoelectric body; 52…first electrode; 53…second electrode; 61…the third piezoelectric body; 62…the fifth electrode; 63…the sixth electrode; 90…the medium; 100…the liquid ejecting device; 100a…the liquid ejecting device; 121…the first substrate; 122…the second substrate; 131…the first vibration plate; 132…the second vibration plate; 141…the filter; 242…the conveying body; 244…the conveying belt; 501…the first part; 502…the second part; 511…the first piezoelectric layer; 512…the second piezoelectric layer; D1…the thickness; D2…the thickness; H0…the wiring space; H1…the first space; H2…the second space; N…the nozzle; R…the common ink chamber; R1…the first connecting flow channel; R2…the second connecting flow channel; R3…the third connecting flow channel; S1…the pressure chamber; S2…the pressure detection chamber; a…the imaginary surface.

Claims

1. A pressure detection element, characterized in that: have: A pressure detection chamber, which is used to detect the internal pressure; a first electrode; a second electrode; a first piezoelectric body disposed between the first electrode and the second electrode, wherein the electrostatic capacitance of the first piezoelectric body changes according to the pressure of the pressure detection chamber, The first piezoelectric body includes a first piezoelectric body layer located on the first electrode side and a second piezoelectric body layer located on the second electrode side. The second piezoelectric layer is any one of a tetragonal system, a cubic system and a monoclinic system, The first piezoelectric layer is a rhombohedral crystal system, The thickness of the second piezoelectric layer is thinner than the thickness of the first piezoelectric layer.

2. The pressure sensing element according to claim 1, wherein: The Young's modulus of the second piezoelectric layer is smaller than the Young's modulus of the first piezoelectric layer.

3. The pressure sensing element according to claim 1, wherein: The thickness of the second piezoelectric layer is thicker than 1 / 14 of the thickness of the first piezoelectric layer.

4. The pressure sensing element according to claim 1, wherein: The thickness of the second piezoelectric layer is thinner than 1 / 8 of the thickness of the first piezoelectric layer.

5. The pressure sensing element according to claim 1, wherein: A cross-sectional area of ​​the second piezoelectric layer when viewed in the thickness direction is larger than a cross-sectional area of ​​the first piezoelectric layer when viewed in the thickness direction.

6. The pressure sensing element according to claim 1, wherein: The first electrode is located on a side of the first piezoelectric body opposite to the pressure detection chamber. The second electrode is located on the pressure detection chamber side of the first piezoelectric body.

7. The pressure sensing element according to claim 1, wherein: The pressure of the pressure detection chamber is detected based on a change in electrostatic capacitance when a voltage corresponding to the coercive electric field of the first piezoelectric body is applied.

8. A pressure detection element, characterized in that: have: A pressure detection chamber, which is used to detect the internal pressure; a first electrode; a second electrode; a first piezoelectric body disposed between the first electrode and the second electrode, wherein the electrostatic capacitance of the first piezoelectric body changes according to the pressure of the pressure detection chamber, The first piezoelectric body includes a first piezoelectric body layer located on the first electrode side and a second piezoelectric body layer located on the second electrode side. The Young's modulus of the second piezoelectric layer is smaller than the Young's modulus of the first piezoelectric layer. The thickness of the second piezoelectric layer is thinner than the thickness of the first piezoelectric layer.

9. A liquid ejection head, characterized in that: have: The pressure sensing element according to any one of claims 1 to 8; a nozzle substrate provided with a nozzle for ejecting liquid; a pressure chamber substrate having a pressure chamber for applying pressure to liquid for ejecting the liquid from the nozzle, and the pressure detection chamber adjacent to the pressure chamber; a second piezoelectric body which is provided corresponding to the pressure chamber and applies pressure to the pressure chamber by applying a voltage thereto; The pressure detection element is provided corresponding to the pressure detection chamber.

10. The liquid ejection head according to claim 9, wherein: The pressure detection chamber has a function of absorbing vibration of the liquid generated when pressure is applied to the liquid in the pressure chamber.

11. The liquid ejection head according to claim 9, wherein The thickness of the first piezoelectric body is thinner than the thickness of the second piezoelectric body.

12. The liquid ejection head according to claim 9, wherein: A cross-sectional area of ​​the first piezoelectric body when viewed in the thickness direction is larger than a cross-sectional area of ​​the second piezoelectric body when viewed in the thickness direction.

13. A liquid ejection device, characterized in that: have: The liquid ejection head according to claim 9; A control unit controls the discharge operation performed from the liquid discharge head.

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