Pressure detection element, liquid discharge head and liquid discharge device

Abstract

To provide a pressure detection element with high detection sensitivity, a liquid discharge head, and a liquid discharge device.SOLUTION: A pressure detection element has: a pressure detection chamber for detecting an internal pressure; a first electrode; a second electrode; and a first piezoelectric body which is located between the first electrode and the second electrode, and has electrostatic capacity changing according to a pressure in the pressure detection chamber. The first piezoelectric body includes a first piezoelectric layer positioned on the first electrode side, and a second piezoelectric layer on the second electrode side. The second piezoelectric layer is any one of tetragonal system, cubic system and monoclinic system, and the first piezoelectric layer is rhombohedral crystal system. A thickness of the second piezoelectric layer is thinner than a thickness of the first piezoelectric layer.SELECTED DRAWING: Figure 6

Description

[Technical field]

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

[0002] Sensors used to measure physical quantities such as pressure and acceleration are known. Patent Document 1 discloses a ceramic sensor in which a piezoelectric ceramic single crystal thin film is formed on a metal foil, electrodes are attached to the surface, and an electric circuit is formed between the metal foil and the electrodes via a detection means. An electric circuit is also formed between the electrodes and the metal foil. In such a ceramic sensor, a change in current or voltage occurs when a mechanical stimulus is applied to the piezoelectric ceramic. By inserting an ammeter or voltmeter into the electric circuit, it functions as a sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-55116 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the piezoelectric ceramic described in Patent Document 1 is a single layer. Piezoelectric ceramics are only slightly deformed even when a large stress is applied. Therefore, the change in dielectric constant is small, making it difficult to increase the detection sensitivity. Therefore, with a single-layer piezoelectric ceramic as described in Patent Document 1, it is difficult to increase the detection sensitivity. [Means for solving the problem]

[0005] A pressure detection element according to a preferred embodiment of the present invention has a pressure detection chamber for detecting internal pressure, a first electrode, a second electrode, and a first piezoelectric body arranged between the first electrode and the second electrode, the capacitance of which changes depending on the pressure in the pressure detection chamber, wherein the first piezoelectric body includes a first piezoelectric layer located on the first electrode side and a second piezoelectric layer located on the second electrode side, the second piezoelectric layer being of a tetragonal, cubic, or monoclinic crystal system, the first piezoelectric layer being of a rhombohedral crystal system, and the thickness of the second piezoelectric layer being thinner than the thickness of the first piezoelectric layer.

[0006] A pressure detection element according to a preferred embodiment of the present invention is a pressure detection element having a pressure detection chamber for detecting internal pressure, a first electrode, a second electrode, and a first piezoelectric body arranged between the first electrode and the second electrode and having a capacitance that changes depending on the pressure in the pressure detection chamber, wherein the first piezoelectric body includes a first piezoelectric layer located on the first electrode side and a second piezoelectric layer located on the second electrode side, the Young's modulus of the second piezoelectric layer being smaller than the Young's modulus of the first piezoelectric layer, and the thickness of the second piezoelectric layer being thinner than the thickness of the first piezoelectric layer.

[0007] A liquid ejection head according to a preferred embodiment of the present invention is a liquid ejection head comprising: a pressure detection element; a nozzle substrate having a nozzle for ejecting liquid; a pressure chamber substrate having a pressure chamber in which pressure is applied to the liquid to eject the liquid from the nozzle and the pressure detection chamber adjacent to the pressure chamber; and a second piezoelectric element provided corresponding to the pressure chamber and applying pressure to the pressure chamber when a voltage is applied thereto, wherein the pressure detection element is provided corresponding to the pressure detection chamber.

[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 from the liquid ejection head. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration of a liquid ejection device according to a first embodiment. [Diagram 2] FIG. 2 is a block diagram of the liquid ejection device of FIG. [Diagram 3] 2 is a cross-sectional view of a portion of the liquid ejection head shown in FIG. [Figure 4] 4 is a diagram showing a part of the pressure chamber substrate in FIG. 3. [Diagram 5] FIG. 4 is a diagram showing a part of the sealing substrate in FIG. [Figure 6] FIG. 4 is a cross-sectional view of the pressure detection element of FIG. [Figure 7] 4 is a graph showing an example of the relationship between the capacitance of the first piezoelectric body and pressure. [Figure 8] 3 is a diagram showing the pressure detection element and a third piezoelectric element in FIG. 2. [Figure 9] FIG. 11 is a cross-sectional view of a pressure detection element according to a modified example. [Figure 10] FIG. 11 is a plan view showing a pressure detection element according to a modified example. [Figure 11] FIG. 11 is a plan view showing a pressure detection element according to a modified example. [Figure 12] 13 is a cross-sectional view of a second piezoelectric element and a pressure detection element of a modified example. FIG. [Figure 13] 13 is a cross-sectional view of a second piezoelectric element and a pressure detection element of a modified example. FIG. [Figure 14] FIG. 11 is a block diagram of a liquid ejection device according to a modified example. [Figure 15] FIG. 1 is a diagram illustrating an example of a relationship between voltage and charge. [Figure 16] FIG. 13 is a diagram illustrating an example of a relationship between voltage and capacitance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. Note that the dimensions or scale of each part in the drawings may differ from the actual dimensions, and some parts are shown diagrammatically to facilitate understanding. The scope of the present invention is not limited to these forms unless otherwise specified in the following description to the effect that the present invention is limited. Furthermore, "element β on element α" is not limited to a configuration in which element α and element β are in direct contact with each other, but also includes a configuration in which element α and element β are not in direct contact with each other. Furthermore, "element α and element β are substantially equal" includes cases in which they are strictly equal, as well as cases in which there is a difference on the order of manufacturing error and measurement error.

[0011] 1. First embodiment 1-1. Overall configuration of the liquid ejection device 100 1 is a schematic diagram illustrating the configuration of a liquid ejection device 100 according to a first embodiment. In the following, for convenience of explanation, an X-axis, a Y-axis, and a Z-axis that are orthogonal to each other will be appropriately used. Moreover, one direction along the X-axis will be referred to as the X1 direction, and the direction opposite to the X1 direction will be referred to as the X2 direction. Similarly, one direction along the Y-axis will be referred to as the Y1 direction, and the direction opposite to the Y1 direction will be referred to as the Y2 direction. One direction along the Z-axis will be referred to as the Z1 direction, and the direction opposite to the Z1 direction will be referred to as the Z2 direction.

[0012] The liquid ejection device 100 in Fig. 1 is an inkjet printing device that ejects ink, which is an example of a liquid, onto a medium 90. The medium 90 is typically printing paper, but any printing target made of any material, such as a resin film or fabric, can be used as the medium 90. As illustrated in Fig. 1, the liquid ejection device 100 is provided with a liquid container 9 that stores ink. For example, a cartridge that can be detachably attached to the liquid ejection device 100, a bag-shaped ink pack made of a flexible film, or an ink tank that can be refilled with ink can be used as the liquid container 9.

[0013] The liquid ejection device 100 includes a control unit 20, a medium transport mechanism 22, a moving mechanism 24, and a liquid ejection head 1. The control unit 20 includes one or more processing circuits, such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and one or more storage circuits, such as a semiconductor memory, and performs overall control of each element of the liquid ejection device 100.

[0014] The medium transport mechanism 22 transports the medium 90 in a direction along the Y axis under the control of the control unit 20. The movement mechanism 24 reciprocates the liquid ejection head 1 along the X axis under the control of the control unit 20. The movement mechanism 24 includes a substantially box-shaped transport body 242 that houses the liquid ejection head 1, and a transport belt 244 to which the transport body 242 is fixed. Note that a configuration in which a plurality of liquid ejection heads 1 are mounted on the transport body 242, or a configuration in which the liquid container 9 is mounted on the transport body 242 together with the liquid ejection head 1, may also be employed.

[0015] The liquid ejection head 1 ejects ink supplied from a liquid container 9 from multiple nozzles onto a medium 90 under the control of a control unit 20. An image is formed on the surface of the medium 90 by each liquid ejection head 1 ejecting ink onto the medium 90 in parallel with the transport of the medium 90 by the medium transport mechanism 22 and the repeated reciprocating motion of the transport body 242.

[0016] Fig. 2 is a block diagram of the liquid ejection device 100 of Fig. 1. As shown in Fig. 2, the liquid ejection device 100 includes a control unit 20, a medium transport 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 generation circuit 25. The liquid ejection head 1 includes a drive circuit 40, a plurality of second piezoelectric elements 3, a voltage application unit 41, a pressure acquisition unit 42, one or more pressure detection elements 5, and one or more third piezoelectric elements 6.

[0017] The control unit 21 includes one or more processing circuits, such as a CPU or an FPGA, etc. 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 of the liquid ejection head 1.

[0018] The control unit 21 generates a print signal SI, a waveform designation signal dCom, and a timing signal PTS. The print signal SI is a digital signal for designating the type of operation of the liquid ejection head 1. The print signal SI designates whether or not to supply the drive signal Com to the second piezoelectric element 3. The waveform designation signal dCom is a digital signal that defines the waveform of the drive signal Com. The drive signal Com is an analog signal for driving the second piezoelectric element 3. The timing signal PTS is a signal that defines the generation timing of the drive signal Com.

[0019] The storage unit 23 includes one or more storage circuits such as semiconductor memories. The storage unit 23 stores print data Img supplied from the host computer. The storage unit 23 stores a control program for the liquid ejection device 100.

[0020] The drive signal generating circuit 25 includes a DA conversion circuit. The drive signal generating circuit 25 generates a drive signal Com having a waveform defined by a waveform designation signal dCom. The drive signal generating circuit 25 outputs the drive signal Com every time it receives a timing signal PTS.

[0021] The drive circuit 40 switches whether or not 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, latch signal LAT, and change signal CH supplied from the control unit 20. The latch signal LAT defines the latch timing of the print data Img. The change signal CH defines the selection timing of the drive pulse included in the drive signal Com.

[0022] The voltage application unit 41 applies a predetermined voltage to the one or more pressure detection elements 5 and the one or more third piezoelectric elements 6. The voltage application unit 41 includes, for example, a power supply circuit. The pressure acquisition unit 42 acquires the pressure of a pressure detection chamber S2 (described below) of the liquid ejection head 1 based on the voltage applied to the pressure detection element 5. The pressure acquisition unit 42 outputs, for example, a detection signal as a voltage value.

[0023] The liquid ejection device 100 includes a liquid ejection head 1 and a control unit 20 including a control unit 21 that controls the ejection operation from the liquid ejection head 1. The liquid ejection head 1 includes a pressure detection element 5 that can exhibit detection sensitivity superior to conventional pressure detection elements, which will be described later. Therefore, according to this embodiment, it is possible to provide a liquid ejection device 100 that includes a liquid ejection head 1 that can detect the pressure in the pressure detection chamber S2 with high sensitivity.

[0024] 1-2. Liquid ejection head 1 Fig. 3 is a cross-sectional view of a portion of the liquid ejection head 1 shown in Fig. 1, and is a cross-sectional view parallel to the XZ plane. The Z axis is an axis line along the direction in which ink is ejected by the liquid ejection head 1. Also, a view from a direction along the Z axis is referred to as a "planar view."

[0025] The liquid ejection head 1 in Fig. 3 has a structure that is nearly symmetrical with respect to an imaginary plane a along the YZ plane. In the following explanation, the configuration on the right side of the imaginary plane a in Fig. 3 will be mainly explained, and the explanation of the configuration on the left side of the imaginary plane a in Fig. 3 will be omitted as appropriate.

[0026] 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. Although not shown in detail, the nozzle substrate 11, the pressure chamber substrate 12, the vibration plate 13, and the sealing substrate 14 are elongated plates aligned along the Y axis.

[0027] The nozzle substrate 11 is a plate-like member provided with a plurality of nozzles N that eject ink, which is an example of a liquid. Each of the plurality of nozzles N is a circular through-hole that ejects ink. The plurality of nozzles N are linearly arranged along the Y axis. The nozzle substrate 11 is manufactured by processing a semiconductor substrate, such as a silicon single crystal substrate.

[0028] The pressure chamber substrate 12 is a flow path structure in which a flow path for supplying ink to each of the multiple nozzles N is formed. The pressure chamber substrate 12 is a laminate of a first substrate 121 and a second substrate 122. Each of the first substrate 121 and the second substrate 122 is manufactured by processing a semiconductor substrate such as a silicon single crystal substrate. The first substrate 121 and the second substrate 122 may be formed integrally. The pressure chamber substrate 12 may also include members other than the first substrate 121 and the second substrate 122.

[0029] Ink flow paths are formed in the pressure chamber substrate 12. Specifically, a plurality of pressure chambers S1, a pressure detection chamber S2, a plurality of first communication paths R1, and a second communication path R2 are formed in the pressure chamber substrate 12. Each of the first substrate 121 and the second substrate 122 has a recess or a through hole, and these recesses or through holes form the plurality of pressure chambers S1, the pressure detection chambers S2, the plurality of first communication paths R1, and the second communication paths R2.

[0030] Fig. 4 is a diagram showing a part of the pressure chamber substrate 12 of Fig. 3. As shown in Fig. 4, each pressure chamber S1 has a longitudinal shape extending in the X2 direction. The multiple pressure chambers S1 are spaced apart from one another and lined up in the Y2 direction. The multiple pressure chambers S1 are provided in a one-to-one correspondence with the multiple nozzles N. Each pressure chamber S1 is a space in which pressure is applied to ink to eject the ink from the nozzle N.

[0031] The multiple first communication channels R1 are spaced apart from each other and lined up in the Y2 direction. The multiple first communication channels R1 are provided in a one-to-one correspondence with the multiple pressure chambers S1. Each first communication channel R1 communicates the corresponding pressure chamber S1 with the nozzle N. Each first communication channel R1 overlaps with the corresponding pressure chamber S1 and nozzle N in a plan view.

[0032] The pressure detection chamber S2 is provided upstream of the multiple pressure chambers S1. The pressure chamber S1 and the pressure detection chamber S2 are aligned in the X2 direction. The pressure detection chamber S2 has a longitudinal shape extending in the Y2 direction. The volume of the pressure detection chamber S2 is much larger than the volume of each pressure chamber S1. The pressure detection chamber S2 is provided in common to the multiple pressure chambers S1 and is connected to the multiple pressure chambers S1. The pressure detection chamber S2 is adjacent to the pressure chamber S1 and absorbs ink vibrations that occur when pressure is applied to the ink in the pressure chamber S1. By providing the pressure detection chamber S2, it is possible to stabilize the ink ejection performance. In addition, by having the pressure detection chamber S2 adjacent to the pressure chamber S1, it is possible to increase the efficiency of absorbing ink vibrations compared to when the pressure detection chambers S2 are separated from each other. Therefore, it is possible to increase the stability of the ink ejection performance.

[0033] The second communication flow path R2 is provided upstream of the pressure detection chamber S2 and is connected to the pressure detection chamber S2. The second communication flow path R2 has an elongated shape extending in the Y2 direction.

[0034] As shown in Fig. 3, a vibration plate 13 is disposed on the surface in the Z2 direction of the pressure chamber substrate 12. The thickness of the vibration plate 13 is much thinner than the thicknesses 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 is elastically deformable. 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 from a single member.

[0035] The second vibration plates 132 are provided in a one-to-one correspondence with the pressure chambers S1. Each of the second vibration plates 132 is a portion of the vibration plate 13 that overlaps with the pressure chambers S1 in a plan view. Each of the second vibration plates 132 forms a part of the pressure chamber S1. When a voltage is applied to the second piezoelectric body 31 of the second piezoelectric element 3, the second vibration plates 132 vibrate and apply pressure to the pressure chamber S1. By providing the second vibration plate 132, the second piezoelectric element 3 can be provided above the pressure chamber S1, and pressure due to vibration caused by application of a voltage to the second piezoelectric body 31 via the second vibration plate 132 can be efficiently applied to the pressure chamber S1.

[0036] The first diaphragm 131 is a portion of the diaphragm 13 that overlaps with the pressure detection chamber S2 in a plan view. The first diaphragm 131 forms a part of the pressure detection chamber S2. The first diaphragm 131 is driven by pressure being 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 diaphragm 131, the pressure detection element 5 can be provided above the pressure detection chamber S2, and pressure can be applied to the first piezoelectric body 51 efficiently.

[0037] Furthermore, the multiple second diaphragms 132 and the first diaphragm 131 are not separated, but are formed from a continuous member. This makes it easy to arrange the second diaphragms 132 and the first diaphragm 131 adjacent to each other. This also makes it easy to arrange the multiple pressure chambers S1 and the pressure detection chambers S2 adjacent to each other. Because the multiple pressure chambers S1 and the pressure detection chambers S2 can be arranged adjacent to each other, the efficiency of absorbing ink vibrations can be improved.

[0038] The diaphragm 13 is manufactured by processing a semiconductor substrate such as a silicon single crystal substrate. The diaphragm 13 may be formed from a part of the pressure chamber substrate 12. For example, the diaphragm 13 may be formed by thinning a part of the second substrate 122. The diaphragm 13 may also be composed of a laminate of multiple layers. For example, the diaphragm 13 is formed from a laminate of a silicon oxide film formed by thermally oxidizing a silicon single crystal substrate and a zirconium oxide film.

[0039] A sealing substrate 14 is disposed on the Z2 direction surface of the diaphragm 13. The sealing substrate 14 is a structure that protects the multiple second piezoelectric elements 3 and pressure detection elements 5 described below and reinforces the mechanical strength of the pressure chamber substrate 12.

[0040] The sealing substrate 14 is formed with a third communication flow path R3, a first space H1, a second space H2, and a space for wiring H0. The sealing substrate 14 has a recess or a through hole, and each of the flow paths or spaces is formed by the recess or the through hole. The third communication flow path R3 and the space for wiring H0 are holes penetrating the sealing substrate 14. The first space H1 and the second space H2 are spaces surrounded by recesses formed in the sealing substrate 14.

[0041] The third communication flow path R3 overlaps with the second communication flow path R2 in plan view and is connected to the second communication flow path R2. The third communication flow path R3 and the second communication flow path R2 form a common ink chamber R. The common ink chamber R functions as a reservoir. A filter 141 is provided in the portion overlapping with the common ink chamber R in plan view to remove air bubbles and foreign matter that may get mixed in with the ink. The filter 141 may be omitted.

[0042] Fig. 5 is a plan view showing a part of the sealing substrate 14 of Fig. 3. For convenience, the fourth electrode 33 of the second piezoelectric element 3 and the second electrode 53 of the pressure detection element 5 are indicated by dots in Fig. 5.

[0043] 5, the first space H1, the second space H2, the third communication channel R3, and the wiring space H0 each have a longitudinal shape extending 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.

[0044] As shown in Fig. 3, 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 board 49 is arranged in the wiring space H0. The wiring board 49 is joined to the pressure chamber substrate 12. The wiring board 49 is a mounting component on which a plurality of wiring lines are formed for electrically connecting the control unit 20 and the liquid ejection head 1. For example, a TCP (Tape Carrier Package) or an FPC (Flexible Printed Circuit) is used as the wiring board 49.

[0045] Each second piezoelectric element 3 has an elongated shape extending in the X2 direction. The multiple second piezoelectric elements 3 are spaced apart from each other and lined up in the Y2 direction. The multiple second piezoelectric elements 3 are provided in a one-to-one correspondence with the multiple pressure chambers S1. The pressure detection element 5 has an elongated shape extending in the Y2 direction and extends in a direction intersecting with the multiple second piezoelectric elements 3. The pressure detection element 5 is provided corresponding to the pressure detection chamber S2 and overlaps with the pressure detection chamber S2 in a plan view.

[0046] The second piezoelectric element 3 is provided corresponding to the pressure chamber S1. Specifically, the second piezoelectric element 3 is arranged for each pressure chamber S1 on the surface of the second vibration plate 132 opposite to the pressure chamber S1. The second piezoelectric element 3 is an energy generating element that generates energy for ejecting ink when a drive signal Com is applied to it. The second piezoelectric element 3 is also a driving element that is driven when the drive signal Com is applied to it. The second piezoelectric element 3 contracts when a voltage is applied to it, bending the second vibration plate 132 and pressurizing the pressure chamber S1.

[0047] The second piezoelectric element 3 generally has 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 laminated in this order from the second vibration plate 132. Therefore, the third electrode 32 is located further in the Z2 direction than the second piezoelectric body 31. The fourth electrode 33 is located further in the Z1 direction than the second piezoelectric body 31. The fourth electrode 33 and the second vibration plate 132 may be in contact with each other, or another member may be interposed between the fourth electrode 33 and the second vibration plate 132.

[0048] The second piezoelectric body 31 is a dielectric body provided for each of the second piezoelectric elements 3. The second piezoelectric bodies 31 may be connected to each other. For example, the second piezoelectric bodies 31 may be separated by forming a plurality of notches in a strip-shaped dielectric film extending along the Y2 direction. Therefore, the second piezoelectric bodies 31 may be formed of a single dielectric film. The second piezoelectric body 31 is formed of a piezoelectric material such as lead zirconate titanate (Pb(Zr,Ti)O3).

[0049] The third electrode 32 is a common electrode provided in common to the multiple second piezoelectric bodies 31. The third electrode 32 is strip-shaped extending in the Y2 direction so as to be continuous across the multiple second piezoelectric elements 3. The fourth electrode 33 is provided in common to the multiple pressure chambers S1. By providing them in common, it is easier to miniaturize the second piezoelectric elements 3 compared to when they are individual. The third electrode 32, like the fourth electrode 33, is formed of a low-resistance conductive material such as platinum (Pt) or iridium (Ir).

[0050] As shown in FIG. 5, the fourth electrode 33 is elongated along the X-axis. The multiple fourth electrodes 33 are arranged along the Y-axis. The fourth electrodes 33 are individual electrodes formed at a distance from each other for each second piezoelectric element 3. The fourth electrodes 33 are provided individually for the multiple pressure chambers S1. By providing the fourth electrodes individually, even if the multiple second piezoelectric bodies 31 are formed of a single dielectric film, it is possible to divide the single dielectric film into the multiple second piezoelectric bodies 31. The fourth electrode 33 is formed of a conductive material such as platinum or iridium.

[0051] The second piezoelectric element 3 is a piezoelectric element involved in the ejection of ink. A reference voltage, which is a constant 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. Thus, a drive voltage, the voltage of which changes with time, is applied to the fourth electrode 33.

[0052] A voltage corresponding to the difference between the reference voltage applied to the third electrode 32 and the drive voltage supplied to the fourth electrode 33 is applied to the second piezoelectric body 31. Therefore, the drive circuit 40 of FIG. 2 applies a drive voltage whose voltage changes with time to the second piezoelectric body 31. The second piezoelectric body 31 is deformed by applying a voltage corresponding to the difference between the reference voltage applied to the third electrode 32 and the drive voltage supplied to the fourth electrode 33 to the second piezoelectric body 31, and the second piezoelectric element 3 generates energy that flexes and deforms the second vibration plate 132. Therefore, the second piezoelectric element 3 applies pressure to the pressure chamber S1 by applying the voltage. The second vibration plate 132 is flexibly deformed by the energy generated by the second piezoelectric element 3, so that the pressure in the pressure chamber S1 changes, and the ink in the pressure chamber S1 is ejected from the nozzle N shown in FIG. 3.

[0053] 3 is provided corresponding to the pressure detection chamber S2. Specifically, the pressure detection element 5 is disposed on the surface of the first diaphragm 131 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 deforms in response to the first diaphragm 131, which bends in response to the pressure of the pressure detection chamber S2.

[0054] The pressure detection element 5 has 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 laminated in this order from the first diaphragm 131. The second electrode 53 and the first diaphragm 131 may be in contact with each other, or another member may be interposed between the second electrode 53 and the first diaphragm 131.

[0055] The first piezoelectric body 51 is a strip-shaped dielectric film extending in the Y2 direction. The first piezoelectric body 51 is made of a known piezoelectric material such as lead zirconate titanate. The thickness of the first piezoelectric body 51 is the same as the thickness of the second piezoelectric body 31. The thickness is the length in the Z1 direction.

[0056] Each of the first electrode 52 and the second electrode 53 is elongated along the Y-axis. Each of the first electrode 52 and the second electrode 53 is formed of a conductive material such as platinum or iridium. For example, the second electrode 53 is formed by stacking a first layer containing titanium, a second layer containing platinum, a third layer containing iridium, and a fourth layer containing titanium in this order from the first vibration plate 131. The thickness of the first layer is thinner than the thickness of the fourth layer. The first layer is used for adhesion 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 forming the first piezoelectric body 51, the island-shaped titanium becomes a crystal nucleus, improving the orientation of the first piezoelectric body 51. The fourth electrode 33 described above may also have a similar configuration to the second electrode 53.

[0057] 5, only the second electrode 53 is shown, but the planar areas of the first electrode 52 and the first piezoelectric body 51 are almost the same as the planar area of ​​the second electrode 53, and the first electrode 52 and the first piezoelectric body 51 overlap the second electrode 53 in a planar view. Moreover, the first piezoelectric body 51, the first electrode 52, and the second electrode 53 overlap almost the entire area of ​​the pressure detection chamber S2 in a planar view.

[0058] The capacitance of the first piezoelectric body 51 changes according to the pressure in the pressure detection chamber S2. Since there is a correlation between the capacitance of the first piezoelectric body 51 and the pressure P, the pressure in the pressure detection chamber S2 can be detected based on the 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 so as to bend in the Z1 direction or the Z2 direction. When the first vibration plate 131 deforms, a stress is applied to the first piezoelectric body 51 on the first vibration plate 131, and distortion occurs in the first piezoelectric body 51. When the stress is applied to the first piezoelectric body 51, the polarization state of the first piezoelectric body 51 changes. This change in the polarization state appears as a change in the dielectric constant ε of the first piezoelectric body 51, and a change occurs in the capacitance. Therefore, the capacitance changes according to the change in pressure in the pressure detection chamber S2.

[0059] Capacitance is expressed by equation [1]: C=ε(S / d) …[1] C is the capacitance. S is the electrode area. d is the distance between the first electrode 52 and the second electrode 53.

[0060] Fig. 6 is a cross-sectional view of the pressure detection element 5 of Fig. 3. As shown in Fig. 6, a first piezoelectric body 51 is disposed between a first electrode 52 and a second electrode 53. The capacitance of the first piezoelectric body 51 changes in response to the pressure in the pressure detection chamber S2. The first electrode 52 is located on the side of the first piezoelectric body 51 opposite the pressure detection chamber S2. The second electrode 53 is located on the side of the first piezoelectric body 51 facing the pressure detection chamber S2.

[0061] 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 first electrode 52 side and in contact with the first electrode 52. The second piezoelectric layer 512 is located on the second electrode 53 side and in contact with the second electrode 53. The second piezoelectric layer 512 and the first piezoelectric layer 511 are in contact with each other. In this embodiment, the plane area of ​​the first piezoelectric layer 511 is approximately equal to the plane area of ​​the second piezoelectric layer 512. Similarly, the cross-sectional area of ​​the first piezoelectric body 51 as viewed in the thickness direction is approximately equal to the cross-sectional area of ​​the second piezoelectric body 31 as viewed in the thickness direction.

[0062] The first piezoelectric layer 511 and the second piezoelectric layer 512 have different crystal systems. Specifically, the second piezoelectric layer 512 is either a tetragonal system, a cubic system, or a monoclinic system. The first piezoelectric layer 511 is a rhombohedral system. In the tetragonal system, three crystal axes a, b, and c are mutually perpendicular, and two of the axes have the same length, with only one axis having a different length. In the cubic system, three crystal axes a, b, and c are mutually perpendicular, and each axis has the same length. In the monoclinic system, three crystal axes a, b, and c are mutually perpendicular, and each axis has a different length. In the rhombohedral system, the three crystal axes a, b, and c have the same length, but two of the three angles α, β, and γ between the axes are 90°, and the remaining angle is 120°.

[0063] The rhombohedral system has a greater degree of distortion than the tetragonal, cubic, and monoclinic systems. For example, of the three crystal axes of a tetragonal crystal, two of them are equal in length, and the remaining axis is different from the other two. The three crystal axes of a monoclinic crystal are different from each other. On the other hand, the lengths of the three crystal axes of a rhombohedral crystal are equal. For this reason, the rhombohedral crystal has a greater degree of crystal deformation than the tetragonal and monoclinic crystals.

[0064] Therefore, the first piezoelectric layer 511 and the second piezoelectric layer 512 have different degrees of distortion in response to stress. When the same stress is applied, the second piezoelectric layer 512 has a larger distortion than the first piezoelectric layer 511. Therefore, a phenomenon called flexoelectricity occurs in the first piezoelectric 51, in which an electrical bias occurs and the dielectric constant changes. Due to the flexoelectricity, a difference occurs in the degree of distortion between the first electrode 52 side and the second electrode 53 side of the first piezoelectric 51, causing a large change in the dielectric constant. Therefore, a large change in capacitance occurs. Since there is a correlation between capacitance and pressure, the pressure in the pressure detection chamber S2 can be detected with high sensitivity by using such a first piezoelectric 51.

[0065] Piezoelectric bodies are only slightly deformed even when a large stress is applied. If the first piezoelectric body 51 is composed of only one of the first piezoelectric layer 511 and the second piezoelectric layer 512, a difference in strain is unlikely to occur between the first electrode 52 side and the second electrode 53 side of the first piezoelectric body 51 even when a large pressure is applied. Therefore, the change in dielectric constant is small, and therefore it is difficult to achieve high pressure detection accuracy. In contrast, in this embodiment, as described above, the first piezoelectric body 51 is formed of two layers, the first piezoelectric layer 511 and the second piezoelectric layer 512, which have different degrees of strain. Therefore, pressure can be detected with high sensitivity.

[0066] Also, 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 amount of distortion of the second piezoelectric layer 512, and therefore the greater the dielectric constant. That is, the thickness and the dielectric constant are inversely proportional. Therefore, by making the thickness D2 of the second piezoelectric layer 512, which has a greater degree of distortion than the first piezoelectric layer 511, thinner than the thickness D1 of the first piezoelectric layer 511, the difference in the amount of distortion between the first piezoelectric layer 511 and the second piezoelectric layer 512 can be increased. Thus, a large change in dielectric constant occurs between the first electrode 52 side and the second electrode 53 side of the first piezoelectric 51. Therefore, the pressure in the pressure detection chamber S2 can be detected with high sensitivity.

[0067] 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. When the thickness D2 of the second piezoelectric layer 512 is thicker than the above numerical value, the second piezoelectric layer 512 is easier to form than when it is thinner. From this 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.

[0068] 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. When the thickness D2 of the second piezoelectric layer 512 is thinner than the above-mentioned numerical value, the pressure in the pressure detection chamber S2 can be detected with particularly high sensitivity compared to when the thickness D2 is thicker. From the viewpoint of increasing the pressure detection sensitivity, the thickness D2 is more preferably thinner than 1 / 9 of the thickness D1, and even more preferably thinner than 1 / 10 of the thickness D2.

[0069] The Young's modulus of the second piezoelectric layer 512 is smaller than that of the first piezoelectric layer 511. Therefore, the first piezoelectric layer 511 and the second piezoelectric layer 512 have different degrees of distortion with respect to stress. When the same stress is applied to the first piezoelectric layer 511 and the second piezoelectric layer 512, the second piezoelectric layer 512 has a greater degree of distortion than the first piezoelectric layer 511. Therefore, as described above, a phenomenon called flexoelectricity occurs inside the first piezoelectric body 51, in which an electrical bias occurs and the dielectric constant changes. Due to the flexoelectricity, a difference occurs in the degree of distortion between the first electrode 52 side and the second electrode 53 side of the first piezoelectric body 51, causing a large change in the dielectric constant. Therefore, a large change in capacitance occurs. Therefore, since there is a correlation between the capacitance and the pressure, the pressure in the pressure detection chamber S2 can be detected with high sensitivity by using such a first piezoelectric body 51.

[0070] Fig. 15 is a diagram showing an example of the relationship between voltage and charge. Fig. 16 is a diagram showing an example of the relationship between voltage and capacitance. The examples shown in Fig. 15 and Fig. 16 are results of measuring the charge or capacitance per unit electrode area of ​​the first piezoelectric body 51 by applying, for example, a triangular waveform voltage between the first electrode 52 and the second electrode 53. The measurement is performed while applying pressure.

[0071] The first piezoelectric body 51 has a hysteresis characteristic as shown in FIG. 15. The magnitude of the electric field at the voltage where the charge shown in FIG. 15 is zero is the coercive electric field. In this example, the voltage corresponding to the coercive electric field is about ±4V. As can be seen from FIG. 16, in this example, a large capacitance change occurs near ±4V. Therefore, in this example, for example, by applying a sine wave centered on ±4V to the first electrode 52 of the pressure detection element 5, the rate of change in capacitance with respect to pressure can be maximized.

[0072] FIG. 7 is a graph showing an example of the relationship between the capacitance C of the first piezoelectric body 51 and the pressure P. The horizontal axis of FIG. 7 is pressure P [kPa], and the vertical axis is the rate of change of the capacitance. The rate of change is shown as the peak value of the capacitance at a pressure of 0 [kPa] shown in FIG. 16 as a reference, and the peak value of the capacitance at each pressure is shown with respect to the reference. In the example shown in FIG. 7, the rate of change of the capacitance of the first piezoelectric body 51 decreases as the pressure P increases. For example, it can be seen that the capacitance changes by about 2.5% at 100 [kPa].

[0073] As can be seen from FIG. 7 and FIG. 14, the rate of change in capacitance with respect to pressure can be maximized by using a voltage corresponding to the coercive electric field of the first piezoelectric body 51. For this reason, it is preferable to detect the pressure in the pressure detection chamber S2 based on the change in capacitance when a 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 in the pressure detection chamber S2 can be detected with high sensitivity. For example, according to the example shown in FIG. 7 and FIG. 16, it is preferable to apply a sine wave in the range of ±0.1 V centered on 4 V to the first electrode 52 of the pressure detection element 5. Note that a voltage other than the voltage corresponding to the coercive electric field may be used.

[0074] As described 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 in the pressure chamber substrate 12, and the pressure chamber S1 and the pressure detection chamber S2 are adjacent to each other. In a configuration in which the pressure chamber S1 and the pressure detection chamber S2 are adjacent to each other, the pressure detection element 5 is provided corresponding to the pressure detection chamber S2. Therefore, the pressure of the pressure detection chamber S2 adjacent to the pressure chamber S1 can be obtained by the pressure detection element 5, so that the behavior of the ink according to the pressure of the pressure chamber S1 can be detected. Therefore, for example, it can be detected whether or not various malfunctions such as insufficient supply of ink to the multiple pressure chambers S1 and the pressure detection chamber S2 occur. Therefore, by being able to obtain the pressure of the pressure detection chamber S2 near the pressure chamber S1, it is possible to contribute to improving the quality of the liquid ejection head 1.

[0075] Moreover, unlike the pressure chamber S1, the pressure detection chamber S2 is not directly related to the ejection of ink. For this reason, it is always possible to detect the pressure in the pressure detection chamber S2 based on the voltage applied to the first piezoelectric body 51, regardless of the ejection of ink.

[0076] As described above, the pressure detection chamber S2 has a function of absorbing ink vibrations that occur when pressure is applied to the ink in the pressure chamber S1. Therefore, by providing this pressure detection chamber S2, it is possible to stabilize the ink ejection performance. In this embodiment, a pressure detection element 5 is provided corresponding to this pressure detection chamber S2. Therefore, it is possible to detect the pressure in the vicinity of the pressure chamber S1 using the pressure detection chamber S2. Therefore, it is possible to detect the pressure in the vicinity of the pressure chamber S1 with a simple configuration without forming a separate space or the like for detecting the pressure in the vicinity of the pressure chamber S1.

[0077] Fig. 8 is a diagram showing the pressure detection element 5 and the third piezoelectric element 6 of Fig. 2. The third piezoelectric element 6 shown in Fig. 8 is a reference piezoelectric element. The third piezoelectric element 6 is connected in series to the pressure detection element 5. Note that the third piezoelectric element 6 is not disposed on the above-mentioned vibration plate 13, but is provided in a location that is not deformed by the pressure in the flow path.

[0078] The third piezoelectric element 6 has the same configuration 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 between the fifth electrode 62 and the sixth electrode 63. The third piezoelectric body 61 is a dielectric material, and is formed of a known piezoelectric material such as lead zirconate titanate. The capacitance of the third piezoelectric body 61 is known.

[0079] Each of the fifth electrode 62 and the sixth electrode 63 is formed of a conductive material such as platinum or iridium. The fifth electrode 62 is electrically connected to the second electrode 53 of the pressure detection element 5. A constant 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, it is preferable that a voltage corresponding to the coercive electric field described above is applied to the first electrode 52 of the pressure detection element 5 as the predetermined voltage Vx. Therefore, the voltage application unit 41 in FIG. 2 applies the predetermined voltage Vx to the first piezoelectric body 51 and the third piezoelectric body 61.

[0080] 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, the capacitance C2 of the first piezoelectric body 51 can be obtained as shown in [4] below.

[0081] V2 = C2 × Q2 …[2] V3 = C3 × Q3 …[3] C2 = (V2 / V3) × C3 …[4] Equation [4] is derived from equation [2] and equation [3]. Q2 is the charge generated in the pressure detection element 5, and Q3 is the charge generated in the third piezoelectric element 6. Voltage V2 is the voltage applied to the first piezoelectric body 51 when a predetermined voltage Vx is applied by the voltage application unit 41. Voltage V3 is the voltage applied to the third piezoelectric body 61 when a predetermined voltage Vx is applied by the voltage application unit 41.

[0082] When stress is applied to the first piezoelectric body 51 and the capacitance C of the first piezoelectric body 51 changes, the voltage V2 applied to the first piezoelectric body 51 changes. The signal of this voltage V2 is acquired by the pressure acquisition unit 42 in FIG. 2. The capacitance C2 of the first piezoelectric body 51 is calculated by equation [4] using the voltages V2 and V3 and the known capacitance C3. Therefore, the pressure acquisition unit 42 acquires the capacitance C2 based on the voltages V2 and V3 and the capacitance C3. Then, the pressure P of the first piezoelectric body 51 is calculated from the capacitance C2 and the correlation between the capacitance and the pressure shown in FIG. 7. In this way, the pressure acquisition unit 42 acquires the pressure in the pressure detection chamber S2 based on the capacitance.

[0083] In this embodiment, as described above, the pressure acquisition unit 42 obtains the capacitance C2 of the first piezoelectric body 51 using the third piezoelectric body 61, whose capacitance C3 is known, and detects the pressure in the pressure detection chamber S2 using the capacitance C2. According to the detection method using the third piezoelectric body 61, it is possible to detect the pressure in the pressure detection chamber S2 near the pressure chamber S1 with a simple configuration. Note that the method of detecting the pressure in the pressure detection chamber S2 is not limited to the detection method using the third piezoelectric body 61, and the third piezoelectric element 6 may be omitted depending on the detection method.

[0084] As described above, the pressure chamber substrate 12 is provided with at least a plurality of pressure chambers S1 and one pressure detection chamber S2 commonly connected to the plurality of pressure chambers S1. 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 diaphragm 131 forming the pressure detection chamber S2 can be made larger than the plane area of ​​each second diaphragm 132 forming each pressure chamber S1. Therefore, the displacement of the first diaphragm 131 can be made larger than the displacement of the second diaphragm 132.

[0085] By detecting the pressure in one pressure detection chamber S2 commonly connected to multiple pressure chambers S1, it is possible to detect the pressure in the pressure detection chamber S2 affected by the multiple pressure chambers S1, rather than the pressure in each pressure chamber S1, and thus the pressure can be used to detect malfunctions such as a shortage of ink supply.

[0086] Since one pressure detection chamber S2 is provided which is commonly connected to the multiple pressure chambers S1, the plane area of ​​the first piezoelectric body 51 is larger than the plane area of ​​the second piezoelectric body 31. Similarly, the cross-sectional area of ​​the first piezoelectric body 51 when viewed in the thickness direction is larger than the cross-sectional area of ​​the second piezoelectric body 31 when viewed in the thickness direction. The larger the cross-sectional area of ​​the first piezoelectric body 51 is, the larger the capacitance of the first piezoelectric body 51 can be. This makes it possible to improve the pressure detection accuracy. On the other hand, if the cross-sectional area of ​​the second piezoelectric body 31 is made too large, the deduction volume becomes too large, which may result in an excessive discharge amount.

[0087] In addition, the second piezoelectric body 31 and the first piezoelectric body 51 have different directions in which they tend to bend. The pressure chamber S1, the second piezoelectric body 31, and the fourth electrode 33 are elongated along the X2 direction. When the pressure chamber S1 extends in the X2 direction and the excluded volume is to be made as large as possible, the second piezoelectric body 31 and the fourth electrode 33 also tend to extend in the X2 direction. Therefore, each of the second piezoelectric body 31 and the fourth electrode 33 tends to bend around the center in the X2 direction. Therefore, by providing the second piezoelectric body 31 along the extension direction of the pressure chamber S1, the ejection accuracy can be improved.

[0088] On the other hand, the pressure detection chamber S2, the first piezoelectric body 51, and the second electrode 53 are elongated along the Y2 direction. Therefore, each of the first piezoelectric body 51 and the second electrode 53 is easily deflected around the center in the Y2 direction. In addition, the pressure detection chamber S2 is provided in common with respect to the multiple pressure chambers S1, and pressure is commonly applied to the pressure detection chamber S2 from the multiple pressure chambers S1. It is difficult to imagine that pressure is applied in a concentrated manner only from a specific pressure chamber S1. From this perspective, each of the first piezoelectric body 51 and the second electrode 53 is easily deflected around the center in 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.

[0089] For example, the first piezoelectric body 51 and the second electrode 53 may be arranged along the X2 direction. In this case, however, the amount of bending of the first piezoelectric body 51 and the second electrode 53 will be smaller than the amount of bending when the first piezoelectric body 51 and the second electrode 53 are arranged along the X2 direction.

[0090] 5, 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 that is most displaced. Therefore, by having the pressure detection element 5 overlap 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. Note that the pressure detection element 5 does not have to overlap with the center in the X2 direction.

[0091] 2. Variations The above-described embodiment may be modified in various ways. Specific modified aspects that may be applied to the above-described embodiment are illustrated below. Two or more aspects selected from the following examples may be combined as appropriate to the extent that they are not mutually contradictory.

[0092] 9 is a cross-sectional view of a pressure detection element 5A of a modified example. In the pressure detection element 5A, the plane area of ​​the first piezoelectric layer 511 and the plane area of ​​the second piezoelectric layer 512 are different from each other. The plane area of ​​the second piezoelectric layer 512 is larger than the plane 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 width W2, which is the length in the X2 direction of the second piezoelectric layer 512, is larger than the width W1, which is the length in the X2 direction of the first piezoelectric layer 511.

[0093] The change in dielectric constant can be increased by making the cross-sectional area of ​​the second piezoelectric layer 512 larger when viewed in the thickness direction than the cross-sectional area of ​​the first piezoelectric layer 511 when viewed in the thickness direction. The cross-sectional area of ​​the first piezoelectric layer 511 may be larger than the cross-sectional area of ​​the second piezoelectric layer 512.

[0094] Fig. 10 is a plan view showing a pressure detection element 5B of a modified example. In plan view, the pressure detection element 5B shown in Fig. 10 does not overlap the entire pressure detection chamber S2, but overlaps with the center of the pressure detection chamber S2 in the X2 direction. For example, the length of the first piezoelectric body 51 in the X2 direction is half or less of the length of the pressure detection chamber S2 and the first vibration plate 131 in the X2 direction.

[0095] Since the first piezoelectric body 51 is not provided over the entire area of ​​the pressure detection chamber S2 in a plan view, the first diaphragm 131 is more easily deformed than when the first piezoelectric body 51 is provided over the entire area. By providing the first piezoelectric body 51 overlapping the center of the first diaphragm 131 in the X2 direction, which is the part most susceptible to deformation, the detection accuracy of the pressure in the pressure detection chamber S2 can be improved.

[0096] Fig. 11 is a plan view showing a modified pressure detection element 5C. The pressure detection element 5C shown in Fig. 11 has a bellows shape that extends in the X2 direction and is folded back in the Y2 direction.

[0097] The pressure detection element 5C includes a plurality of first portions 501 and a plurality of second portions 502. The plurality of first portions 501 are portions extending in the X2 direction, spaced apart from each other and arranged in the Y2 direction. The plurality of second portions 502 are portions extending in the Y2 direction. Each second portion 502 is disposed between two adjacent first portions 501 and connects the two adjacent first portions 501. The plurality of second portions 502 are disposed alternately at the ends of the first portions 501 in the X1 direction and the ends of the first portions 501 in the X2 direction. The second portion 502 located furthest in the Y1 direction among the plurality of second portions 502 is counted in the Y2 direction. In this case, for example, the odd-numbered second portions 502 among the plurality of second portions 502 are connected to the ends of the first portions 501 in the X2 direction. Among the multiple second portions 502, the even-numbered second portions 502 are connected to the ends of the first portions 501 in the X1 direction.

[0098] 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 bellows shape that extends along the X2 direction and is folded back in sequence. Since the pressure detection element 5C has a bellows shape, the pressure detection element 5C is more susceptible to stress due to deformation of the first vibration plate 131 than the pressure detection element 5 of the first embodiment, which is elongated along the Y2 direction. Furthermore, since the pressure detection element 5C has a bellows shape, the plane 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 is reduced. Therefore, the first vibration plate 131 is more likely to deform. This can improve the detection accuracy of the pressure in the pressure detection chamber S2.

[0099] The shape of pressure detection element 5C is preferably a shape that is easily subjected to stress due to deformation of first diaphragm 131, and is not limited to the bellows shape shown in the figure.

[0100] 12 and 13 are cross-sectional views of modified examples of the second piezoelectric element 3 and the pressure detection element 5. A thickness D5 of the first piezoelectric body 51 of the pressure detection element 5 may be different from a thickness D3 of the second piezoelectric body 31 of the second piezoelectric element 3.

[0101] 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 the thickness thinner, the first piezoelectric body 51 is easier to deform than the second piezoelectric body 31. By making the thickness D5 thinner than the thickness D3, it is possible to improve the detection accuracy of the pressure in the pressure detection chamber S2 compared to when the thickness D5 is thicker. On the other hand, the second piezoelectric body 31 is a part that contributes to ejection. Therefore, by making the thickness D5 thicker than the thickness D3, it is possible to reduce cracks and the like.

[0102] 13, for example, the thickness D5 of the first piezoelectric body 51 is thicker than the thickness D3 of the second piezoelectric body 31. When the thickness D5 is thicker than the thickness D3, that is, when the thickness D3 is thinner than the thickness D5, the second piezoelectric body 31 is easier to deform than the first piezoelectric body 51. This can improve the ink ejection performance.

[0103] 14 is a block diagram of a liquid ejection device 100a according to a modified example. The liquid ejection device 100a includes a liquid ejection head 1a and a control unit 20a. A drive circuit 40, a voltage application unit 41, and a pressure acquisition unit 42 are provided in the control unit 20a. The liquid ejection head 1a is not provided with the voltage application unit 41 or the pressure acquisition unit 42.

[0104] 14, the drive circuit 40, the voltage application unit 41, and the pressure acquisition unit 42 may be provided in part or in whole in the control unit 20. With this liquid ejection device 100a, as in each of the embodiments, the pressure in the vicinity of the pressure chamber S1 can be acquired by utilizing the pressure detection chamber S2, which is a space that absorbs vibrations of the ink.

[0105] The "liquid ejection head" may be a circulation type head having a so-called circulation flow path. In the embodiment, the third electrode 32 is a common electrode and the fourth electrode 33 is an individual electrode, but the third electrode 32 may be an individual electrode and the fourth electrode 33 may be a common electrode.

[0106] The "pressure detection element" is not limited to an element used in a "liquid ejection head", but can also be used in other devices. Examples of other devices include a pressure-electrical converter and a piezoelectric transformer. The "pressure detection element" can also be used as a sensor such as a pressure sensor.

[0107] The "liquid ejection device" can be used in various devices such as facsimile machines and copy machines, as well as devices dedicated to printing. The uses of the liquid ejection device are not limited to printing. For example, a liquid ejection device that ejects a solution of a color material is used as a manufacturing device for forming a color filter of a display device such as a liquid crystal display panel. A liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes of a wiring board. A liquid ejection device that ejects a solution of an organic substance related to a living body is used as a manufacturing device for manufacturing a biochip, for example.

[0108] Although the present invention has been described based on the preferred embodiment, the present invention is not limited to the above-mentioned embodiment. Furthermore, the configuration of each part of the present invention can be replaced with any configuration that exhibits the same function as the above-mentioned embodiment, and any configuration can be added. [Explanation of symbols]

[0109] 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...diaphragm, 14...sealing substrate, 20...control unit, 20a...control unit, 21...control section, 22...medium transport mechanism, 23...storage section, 24...movement mechanism, 25...driving signal generating circuit, 31...second piezoelectric body, 32...third electrode, 33...fourth electrode, 40...driving circuit, 41...voltage application section, 42...pressure acquisition section, 49...wiring substrate, 51...first piezoelectric body, 52...first electrode, 53...second electrode electrode, 61...third piezoelectric element, 62...fifth electrode, 63...sixth electrode, 90...medium, 100...liquid ejection device, 100a...liquid ejection device, 121...first substrate, 122...second substrate, 131...first diaphragm, 132...second diaphragm, 141...filter, 242...transport body, 244...transport belt, 501...first portion, 502...second portion, 511...first piezoelectric layer, 512...second piezoelectric layer, D1...thickness, D2...thickness, H0...wiring space, H1...first space, H2...second space, N...nozzle, R...common ink chamber, R1...first communicating flow path, R2...second communicating flow path, R3...third communicating flow path, S1...pressure chamber, S2...pressure detection chamber, a...virtual surface.

Claims

1. a pressure detection chamber for detecting an internal pressure; A first electrode; A second electrode; a first piezoelectric body disposed between the first electrode and the second electrode, the first piezoelectric body having a capacitance that changes in response to a pressure in the pressure detection chamber, the first piezoelectric body includes a first piezoelectric layer located on the first electrode side and a second piezoelectric 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, A pressure detection element, wherein the second piezoelectric layer is thinner than the first piezoelectric layer.

2. 2. The pressure detection 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. 2. The pressure detection element according to claim 1, wherein the thickness of the second piezoelectric layer is greater than 1 / 14 of the thickness of the first piezoelectric layer.

4. 2. The pressure detection element according to claim 1, wherein the thickness of the second piezoelectric layer is less than 1 / 8 of the thickness of the first piezoelectric layer.

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

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

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

8. a pressure detection chamber for detecting an internal pressure; A first electrode; A second electrode; a first piezoelectric body disposed between the first electrode and the second electrode, the first piezoelectric body having a capacitance that changes in response to the pressure in the pressure detection chamber; A pressure detection element having the first piezoelectric body includes a first piezoelectric layer located on the first electrode side and a second piezoelectric 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; A pressure detection element, wherein the second piezoelectric layer is thinner than the first piezoelectric layer.

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

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

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

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

13. A liquid ejection head according to claim 9, a control unit for controlling a discharge operation from the liquid discharge head.

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