Liquid ejection head and liquid ejection apparatus

Abstract

To provide a desirable configuration of a piezoelectric element when a detection part for detecting residual vibration and a pressure part for discharging liquid are separately provided.SOLUTION: The liquid discharge head includes a pressure chamber for discharging liquid from a nozzle by driving a first piezoelectric element, and a detection chamber for detecting residual vibration of the liquid to which pressure is applied in the pressure chamber by a second piezoelectric element. The first piezoelectric element includes a first piezoelectric body, a first upper electrode, a first lower electrode, and a first vibration plate provided below the first lower electrode, the second piezoelectric element includes a second piezoelectric body, a second upper electrode, a second lower electrode, and a second vibration plate provided below the second lower electrode, and a neutral axis of the second piezoelectric element is located below a neutral axis of the first piezoelectric element.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection head and a liquid ejection apparatus. [Background technology]

[0002] There are known liquid ejection heads that use actuators such as piezoelectric elements to apply pressure to liquid such as ink in a pressure chamber, causing the liquid to be ejected from a nozzle, and liquid ejection devices that use such heads, such as printers. In this way, the liquid ejection head can determine whether the nozzle is clogged with foreign matter or whether the liquid has become viscous by detecting residual vibrations that occur in the liquid in the pressure chamber after the liquid is ejected (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-147363 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology of Patent Document 1 is excellent in that it uses the same piezoelectric element and the same pressure chamber to drive the liquid ejection and detect residual vibration, but because the piezoelectric element and the pressure chamber are both used, there is a problem in that when attempting to detect residual vibration in real time while ejecting ink, the drive frequency for ejection is limited, and sufficient throughput may not be achieved.It is possible to provide a pressure chamber and piezoelectric element that detects residual vibration separately from the pressure chamber and piezoelectric element that ejects liquid, but it cannot be said that sufficient consideration has been given to the structure of the piezoelectric element in such a case. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms or application examples. One form of the present disclosure is a liquid ejection head. The liquid ejection head includes a pressure chamber that applies liquid pressure for ejecting liquid from the nozzle by driving a first piezoelectric element, a second piezoelectric element, and a detection chamber that detects residual vibration of the liquid pressure applied in the pressure chamber using the second piezoelectric element. In this liquid ejection head, the first piezoelectric element includes a first piezoelectric body, a first upper electrode provided on the first piezoelectric body, a first lower electrode provided below the first piezoelectric body, and a first diaphragm provided below the first lower electrode. The second piezoelectric element includes a second piezoelectric body, a second upper electrode provided on the second piezoelectric body, a second lower electrode provided below the second piezoelectric body, and a second diaphragm provided below the second lower electrode. The neutral axis of the second piezoelectric element is located below the neutral axis of the first piezoelectric element.

[0006] Another aspect of the present disclosure is a liquid ejection head as described below, which includes a nozzle, a first piezoelectric element, a pressure chamber that applies pressure to eject liquid from the nozzle when the first piezoelectric element is driven, a second piezoelectric element, and a detection chamber that detects residual vibrations of the pressure applied in the pressure chamber by the second piezoelectric element. In this liquid ejection head, the first piezoelectric element includes a first piezoelectric body, a first upper electrode provided on the first piezoelectric body, a first lower electrode provided below the first piezoelectric body, and a first vibration plate provided below the first lower electrode, the second piezoelectric element includes a second piezoelectric body, a second upper electrode provided on the second piezoelectric body, a second lower electrode provided below the second piezoelectric body, and a second vibration plate provided below the second lower electrode, the first vibration plate includes a first insulating layer and a first elastic layer provided below the first insulating layer, and the second vibration plate includes a second insulating layer and a second elastic layer provided below the second insulating layer, where a first ratio is a ratio of the sum of the thicknesses of the first piezoelectric body and the first insulating layer to the thickness of the first elastic layer, and a second ratio is a ratio of the sum of the thicknesses of the second piezoelectric body and the second insulating layer to the thickness of the second elastic layer, the second ratio being smaller than the first ratio. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is an exploded perspective view showing a liquid ejection head according to an embodiment. [Figure 2] FIG. 2 is an explanatory diagram showing a cross section of the liquid ejection head taken along line II-II in FIG. 1, together with other members that constitute the liquid ejection device. [Figure 3] FIG. 3 is a plan view showing a portion of the communication plate according to the first embodiment. [Figure 4] FIG. 2 is a plan view showing a part of a pressure chamber substrate according to the first embodiment. [Figure 5] FIG. 3 is an explanatory diagram showing a schematic configuration of a vibration absorbing section and a pressure applying section. [Figure 6] FIG. 4 is an explanatory diagram showing an enlarged view of a lead-out wiring portion of the pressure unit. [Figure 7] FIG. 2 is an explanatory diagram showing a schematic configuration of a vibration detection unit. [Figure 8] FIG. 4 is an explanatory diagram showing an example of wiring from a flexible wiring board to each piezoelectric element. [Figure 9] 3A and 3B are explanatory diagrams showing a comparison of the form of a piezoelectric element in a pressure unit and the form of a piezoelectric element in a vibration detection unit in the first embodiment. [Figure 10A] FIG. 4 is an explanatory diagram schematically showing the position of the neutral axis of the piezoelectric element of the pressure applying section. [Figure 10B] FIG. 4 is an explanatory diagram schematically showing the position of the neutral axis of a piezoelectric element of a vibration detection unit. [Figure 11] 6 is a graph showing an example of a drive signal applied to a first piezoelectric element and a detection signal corresponding to residual vibrations generated in ink by the drive signal. [Figure 12] FIG. 10 is an explanatory diagram illustrating a modified example of the first embodiment. [Figure 13] 10A and 10B are explanatory diagrams showing a comparison between the form of a piezoelectric element in a pressure unit and the form of a piezoelectric element in a vibration detection unit of the second embodiment. [Figure 14] 10A and 10B are explanatory diagrams showing a comparison between the form of a piezoelectric element in a pressure unit and the form of a piezoelectric element in a vibration detection unit of the third embodiment. [Figure 15] 10A and 10B are explanatory diagrams showing a comparison between the form of a piezoelectric element in a pressure unit and the form of a piezoelectric element in a vibration detection unit of the fourth embodiment. [Figure 16] FIG. 1 is an explanatory diagram showing an example of a liquid ejection device. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. Schematic configuration of the liquid ejection head: (A1) Overall structure: Prior to describing each embodiment described below, the configuration of each part common to the liquid ejection head 10 of the embodiments will be described with reference to Figures 1 to 8. In each figure, the dimensions and scale of each part are given priority for ease of understanding and may differ from the actual ones. The embodiments described below are preferred specific examples of the present disclosure, and therefore various technically preferable limitations are applied, but the scope of the present disclosure is not limited to these forms unless otherwise specified in the following description to the effect that these limitations are present.

[0009] FIG. 1 is an exploded perspective view of a liquid ejection head 10, and FIG. 2 is a cross-sectional view taken along the XZ plane including line II-II shown in FIG. 1, passing through one nozzle N. In this embodiment, the liquid ejection head 10 is configured as an ink ejection head in a printer. Ink is introduced into the liquid ejection head 10, and a portion of the ink is ejected from the nozzle N toward the outside, for example, toward a printing medium. Because the ink is circulated, ink not ejected from the nozzle N is discharged from the liquid ejection head 10. For this reason, the terms "supply side" and "discharge side" are sometimes used in this specification. The "supply side" refers to the upstream side of a pressure chamber CC, which will be described later, in terms of the liquid flow path. Also, the term "supply side" may refer to the upstream side of the pressure chamber CC. The "discharge side" refers to the downstream side of the pressure chamber CC in terms of the liquid flow path. Note that the "discharge side" does not include the nozzle N, which will be described later. Also, the term "discharge side" may refer to the downstream side of the pressure chamber CC. Note that the liquid is not limited to ink; the liquid ejection head 10 can be configured to eject other liquids.

[0010] In the following description, the three intersecting directions may be referred to as the X-axis direction, the Y-axis direction, and the Z-axis direction. The X-axis direction includes the X1 and X2 directions, which are opposite to each other. The Y-axis direction includes the Y1 and Y2 directions, which are opposite to each other. As illustrated in FIG. 1, the Y-axis direction is the arrangement direction of multiple nozzles N in the liquid ejection head. The arrangement and function of the nozzles N will be described later. The Z-axis direction includes the Z1 and Z2 directions, which are opposite to each other. The Z1 direction is the direction in which liquid is ejected from the nozzles N. In this embodiment, it is the direction along the direction of gravity, and the downward direction according to gravity coincides with the Z1 direction. In this case, the Z2 direction may be referred to as the "upper side" or "upward direction," and the Z1 direction may be referred to as the "lower side" or "downward direction." The X-axis direction is a direction perpendicular to both the Y-axis direction and the Z-axis direction. Note that in this embodiment, the Z-axis direction coincides with the up-down direction according to the direction of gravity, but it does not necessarily have to coincide with the direction of gravity and may be set at a predetermined angle with respect to the direction of gravity.

[0011] First, the configuration of the liquid ejection head as a whole, in which multiple substrates are stacked, will be described with reference to the drawings. As shown in Figures 1 and 2, the liquid ejection head 10 includes, in order from the bottom in the Z1 direction along the Z axis, a nozzle substrate 21, a communication plate 24, a pressure chamber substrate 25, a sealing plate 27, and a case 28. The thickness directions of the nozzle substrate 21, the communication plate 24, the pressure chamber substrate 25, the sealing plate 27, and the case 28 are aligned with the Z axis direction. Sealed spaces S1 to S3 are formed in the sealing plate 27, spaced apart in the X axis direction. Sealed spaces S1 and S2 house multiple first and second piezoelectric elements 51 and 72, respectively, and sealed space S3 houses a single third piezoelectric element 73. The structures of the first to third piezoelectric elements 51, 72, 73 will be explained in detail later, but the first piezoelectric element 51 includes a first vibration plate 26 that is integrally provided at a position that seals the sealed space S1, the second piezoelectric element 72 includes a second vibration plate 29 that is integrally provided at a position that seals the sealed space S2, and the third piezoelectric element 73 includes a third vibration plate 23 that is integrally provided at a position that seals the sealed space S3.

[0012] In addition, the liquid ejection head 10 includes a COF 60. COF is an abbreviation for Chip on Film. By laminating substrates such as the nozzle substrate 21 described above, the liquid ejection head 10 includes, from the supply side, a supply-side common liquid chamber RA, a vibration absorbing section 70A, a pressurizing section 70C, a wiring introduction section RC, a vibration detecting section 70B, and a discharge-side common liquid chamber RB, as shown in FIG. 2. In the vibration absorbing section 70A, a third diaphragm 23 is sandwiched between a sealing plate 27 and a pressure chamber substrate 25. In the pressurizing section 70C, a first diaphragm 26 is sandwiched between the sealing plate 27 and a pressure chamber substrate 25, and in the vibration detecting section 70B, a second diaphragm 29 is sandwiched between the sealing plate 27 and a pressure chamber substrate 25.

[0013] A sealing plate 27 is disposed in the Z2 direction from the first diaphragm 26 and the third diaphragm 23. The sealing plate 27 includes a portion that is outer than the third diaphragm 23 in the X-axis direction. The outer portion of the sealing plate 27 in the X-axis direction is located in the Z2 direction from the pressure chamber substrate 25. The sealing plate 27 covers the third diaphragm 23, the first diaphragm 26, the second diaphragm 29, the plurality of first piezoelectric elements 51, and the pressure chamber substrate 25. A case 28 is disposed on the sealing plate 27. The first piezoelectric elements 51 are provided corresponding to the pressure chambers CC. Note that although the third diaphragm 23, the first diaphragm 26, and the second diaphragm 29 are depicted as a single continuous plate in FIGS. 1 and 2, the plate thicknesses of these components differ, as will be described later. This point will be discussed later.

[0014] Next, the structures of the sealing plate 27 and the case 28 will be described. The sealing plate 27 has a rectangular shape when viewed in the Z-axis direction. The sealing plate 27 protects the multiple first piezoelectric elements 51, the multiple second piezoelectric elements 72, and the single third piezoelectric element 73, and also reinforces the mechanical strength of the pressure chamber substrate 25, the first diaphragm 26, the second diaphragm 29, and the third diaphragm 23. The sealing plate 27 is adhered to the first diaphragm 26, etc., by, for example, an adhesive. The sealing plate 27 is fixed to the pressure chamber substrate 25 via the first diaphragm 26, the second diaphragm 29, and the third diaphragm 23.

[0015] The sealing plate 27 has sealed spaces S1 to S3 formed therein. A recess is formed in the lower surface of the sealing plate 27. The spaces formed by this recess are the sealed spaces S1 to S3. The sealed spaces S1 to S3 are each formed to be continuous in the Y-axis direction. The sealed space S1 is formed to overlap with a plurality of pressure chambers CC when viewed in the Z-axis direction. The sealed space S1 houses a plurality of first piezoelectric elements 51. The sealed space S2 is formed to overlap with a plurality of detection chambers (hereinafter referred to as vibration detection chambers) DB for detecting vibrations of the liquid when viewed in the Z-axis direction. The sealed space S2 houses a plurality of second piezoelectric elements 72. The sealed space S3 is formed to overlap with an absorption chamber DA for absorbing vibrations of the liquid when viewed in the Z-axis direction. In this embodiment, the sealed space S3 houses one third piezoelectric element 73.

[0016] The sealing plate 27 is further formed with a flow path 44A included in the common liquid chamber RA and a flow path 44B included in the common liquid chamber RB. The flow paths 44A and 44B are formed to penetrate the sealing plate 27 in the Z-axis direction. The flow path 44A is located in the X1 direction of the sealed space S3. The flow path 44B is located in the X2 direction of the sealed space S2.

[0017] The case 28 is located in the Z2 direction of the sealing plate 27. A supply port 42A, a discharge port 42B, and flow paths 43A and 43B are formed in the case 28. The flow path 43A is included in the common liquid chamber RA. The flow path 43A is formed so as to overlap with the flow path 44A of the sealing plate 27 when viewed in the Z-axis direction. The supply port 42A communicates with the flow path 43A. The flow path 43B is included in the common liquid chamber RB. The flow path 43B is formed so as to overlap with the flow path 44B of the sealing plate 27 when viewed in the Z-axis direction. The discharge port 42B communicates with the flow path 43B.

[0018] Compliance substrates 77A and 77B are fixed to the case 28. As shown in FIG. 2, the compliance substrates 77A and 77B are provided in the common liquid chambers RA and RB. The compliance substrates 77A and 77B are different from the third diaphragm 23 provided in correspondence with the damper chamber DA. Note that, although FIG. 2 shows a configuration in which the compliance substrates 77A and 77B are not exposed to the outside of the liquid ejection head 10, the compliance substrates 77A and 77B may be exposed to the outside of the liquid ejection head 10.

[0019] The compliance substrate 77A is provided corresponding to the flow path 43A of the common liquid chamber RA. The compliance substrate 77A is located in the X1 direction of the flow path 43A. The compliance substrate 77A is arranged so as to cover the opening that forms the flow path 43A. The thickness direction of the compliance substrate 77A is along the X-axis direction. The compliance substrate 77A extends in the Y-axis direction.

[0020] The compliance substrate 77B is provided corresponding to the flow path 43B of the common liquid chamber RB. The compliance substrate 77B is located in the X2 direction of the flow path 43B. The compliance substrate 77B is arranged so as to cover the opening that forms the flow path 43B. The thickness direction of the compliance substrate 77B is along the X-axis direction. The compliance substrate 77B extends in the Y-axis direction.

[0021] Compliance substrates 77A and 77B are preferably made of a material that is more flexible than third diaphragm 23, but may have the same configuration as third diaphragm 23. Compliance substrates 77A and 77B include an elastic layer and an insulating layer. The elastic layer is made of, for example, silicon dioxide (SiO2). The insulating layer is made of, for example, zirconium dioxide (ZrO2).

[0022] The compliance substrate 77A is deformable in response to the pressure of ink in the flow path 43A of the common liquid chamber RA. The compliance substrate 77A deforms in response to the pressure of ink, absorbing pressure fluctuations in the flow path 43A of the common liquid chamber RA. Similarly, the compliance substrate 77B is deformable in response to the pressure of ink in the flow path 43B of the common liquid chamber RB. The compliance substrate 77B is deformable in response to the pressure of ink, absorbing pressure fluctuations in the flow path 43B of the common liquid chamber RB.

[0023] (A2) Ink flow path: Next, the configuration of the flow channels 40 through which ink flows will be described. The flow channels 40 through which ink flows are formed in the liquid ejection head 10. The flow channels 40 include a supply port 42A, an outlet 42B, common liquid chambers RA and RB, a damper chamber DA, a pressure chamber CC, a vibration detection chamber DB, communicating flow channels 47A to 47C, and a nozzle N. The flow channels 40 include a plurality of individual flow channels provided individually corresponding to the nozzles N, and a common flow channel provided in common to the individual flow channels. In order to understand the distinction between these, reference will be made as appropriate to FIG. 3, which is a plan view showing a portion of the communicating plate 24, and FIG. 4, which is a plan view showing a portion of the pressure chamber substrate 25.

[0024] The flow path 40 has a supply flow path 41A and a discharge flow path 41B. The supply flow path 41A is a flow path upstream of the pressure chamber CC and is a flow path within the communicating plate 24 and the pressure chamber substrate 25. The supply flow path 41A includes a flow path 45A, a flow path 46A, and a damper chamber DA. The discharge flow path 41B is a flow path downstream of the pressure chamber CC and is a flow path within the communicating plate 24 and the pressure chamber substrate 25. The discharge flow path 41B includes a communicating flow path 47C, a communicating flow path 47B, a vibration detection chamber DB, a flow path 46B, and a flow path 45B. Note that the supply flow path 41A does not include the flow path 44A in the sealing plate 27 or the flow path 43A in the case 28. The discharge flow path 41B does not include the flow path 44B in the sealing plate 27 or the flow path 43B in the case 28.

[0025] The common liquid chamber RA is provided in common to the multiple pressure chambers CC. The common liquid chamber RA is continuous in the Y-axis direction. The common liquid chamber RA includes a flow path 43A provided in the case 28, a flow path 44A provided in the sealing plate 27, a flow path 45A provided in the pressure chamber substrate 25, and a flow path 46A provided in the communication plate 24. These flow paths 43A, 44A, 45A, and 46A are continuous in the Z-axis direction.

[0026] In the communicating plate 24, a communicating flow path 47A continuing from the supply flow path 41A is disposed downstream of the common liquid chamber RA, and is connected to the common liquid chamber RA via a flow path 46A. As shown in FIG. 3, the communicating flow path 47A is a common flow path commonly connected to the flow path 46A. The communicating flow path 47A is a common flow path commonly connected to multiple pressure chambers CC. In this embodiment, the communicating flow path 47A is provided in common to multiple pressure chambers CC, but it may have other shapes, such as individual flow paths corresponding to the pressure chambers CC, or a common flow path shared by several pressure chambers CC, as long as it can absorb pressure fluctuations upstream of the pressure chambers CC.

[0027] The damper chamber DA is provided in common to the multiple vibration absorbing units 70A. The damper chamber DA is located in the Z2 direction of the communication flow path 47A and communicates with the pressure chamber CC downstream of the communication flow path 47A. The damper chamber DA is located in the X1 direction when viewed from the pressure chamber CC. A nozzle N communicates with each of the multiple pressure chambers CC. The nozzle N is an opening that penetrates the communication plate 24 and the nozzle substrate 21 at the same position toward the Z1 direction of the pressure chamber CC. The position of the nozzle N in the X axis direction is approximately the center of the pressurizing unit 70C.

[0028] A plurality of nozzles N are formed in the nozzle substrate 21. The plurality of nozzles N constitute a nozzle row N1. The nozzle row N1 includes a plurality of nozzles N lined up in the Y-axis direction. The nozzles N are through-holes that penetrate the nozzle substrate 21 in the Z-axis direction.

[0029] As shown in Figures 3 and 4, the multiple communication channels 47C are provided for the multiple pressure chambers CC, respectively. In other words, the communication channels 47C are individual channels that individually connect to the multiple pressure chambers CC. The multiple communication channels 47C communicate with the downstream of the pressure chambers CC. As shown in Figure 2, the downstream end of the pressure chamber CC, that is, the end in the X2 direction, and the upstream end of the communication channel 47C, that is, the end in the X1 direction, overlap when viewed in the Z-axis direction. A communication channel 47B is disposed downstream of each of the multiple communication channels 47C. The ends of the multiple communication channels 47C opposite the pressure chamber CC are directly connected to the communication channel 47B.

[0030] The vibration detection chambers DB are provided corresponding to the pressure chambers CC, respectively. The vibration detection chambers DB are located in the Z2 direction of the communication flow path 47B. The vibration detection chambers DB are respectively connected to the communication flow paths 47B. The vibration detection chambers DB are connected to the pressure chambers CC via the communication flow paths 47B and 47C. The vibration detection chambers DB are provided to detect residual vibrations that occur in the liquid when the liquid is ejected from the nozzle N by pressurizing the liquid in the pressurizing unit 70C using the pressurizing unit 70C.

[0031] The common liquid chamber RB is provided downstream of the pressure chambers CC and is shared by the pressure chambers CC via the communication flow paths 47C and 47B. The common liquid chamber RB is commonly connected to the communication flow paths 47B. The common liquid chamber RB is connected to the pressure chambers CC via the communication flow paths 47B and 47C. The common liquid chamber RB is disposed downstream of

[0032] The common liquid chamber RB is continuous in the Y-axis direction. The common liquid chamber RB includes a flow path 43B provided in the case 28, a flow path 44B provided in the sealing plate 27, a flow path 45B provided in the pressure chamber substrate 25, and a flow path 46B provided in the communication plate 24. These flow paths 43B, 44B, 45B, and 46B are continuous in the Z-axis direction.

[0033] In this embodiment, as described above, the liquid ejection head 10 employs a circulation system in which ink that has flowed through the pressure chambers CC is circulated. A circulation mechanism 18 that circulates the ink is connected to the liquid ejection head 10. The circulation mechanism 18 includes a pump, and supplies ink from a liquid container to the liquid ejection head 10 by pump operation. The ink passes through a supply port 42A of the liquid ejection head 10 and is supplied to a common liquid chamber RA. Furthermore, ink discharged from the liquid ejection head 10 is collected from the common liquid chamber RB through a discharge port 42B.

[0034] The ink in the liquid container 2 is transported by the pump 83, flows through the supply flow path 81, and passes through the supply port 42A shown in FIG. 2 and flows into the common liquid chamber RA. The ink in the common liquid chamber RA passes through the communication flow path 47A and the damper chamber DA and is supplied to the pressure chamber CC. A portion of the ink in the pressure chamber CC is ejected from the nozzle N.

[0035] Ink that is not ejected from the nozzle N passes through the communication flow path 47C and the communication flow path 47B and flows into the common liquid chamber RB. A portion of the ink that flows through the communication flow path 47C flows into the vibration detection chamber DB. The ink in the common liquid chamber RB flows into the recovery flow path 82 through the outlet 42B and is recovered by the circulation mechanism 18. In the liquid ejection head 10 of this embodiment, the ink is circulated in this manner.

[0036] As shown in FIGS. 2 and 3, the communicating plate 24 is formed with flow paths 46A, 47A, 47C, and 47B, which are part of the common liquid chamber RA, and a flow path 46B, which is part of the common liquid chamber RB. That is, the communicating plate 24 is provided with supply flow paths and part of the discharge flow paths. The communicating plate 24 is formed with through-holes, grooves, recesses, and the like. These through-holes, grooves, recesses, and the like form part of the common liquid chambers RA and RB and the communicating flow paths 47A, 47B, and 47C. In the illustrated embodiment, the damper chamber DA and the communicating flow path 47A are common flow paths corresponding to each pressure chamber CC, but at least one of them can also be formed as an individual flow path. Furthermore, if a common flow path is used, a configuration is also possible in which the damper chamber DA and the communicating flow path 47A are provided as a common flow path corresponding to multiple pressure chambers CC. The size (volume) of the vibrating region of the vibration absorbing unit 70A changes depending on whether the damper chamber DA and the communicating flow path 47A are configured as individual flow paths or a common flow path. Therefore, the configuration of the damper chamber DA and the communicating flow path 47A, i.e., whether they are individual flow paths or a common flow path, can be set according to the absorption efficiency required for the liquid ejection head 10. When at least a portion of the flow paths are configured as individual flow paths, the third piezoelectric element 73 of the vibration absorbing unit 70A may also be provided individually corresponding to the individual flow paths.

[0037] 2 and 4, the pressure chamber substrate 25 is formed with a flow path 45A which is part of the common liquid chamber RA, a damper chamber DA, multiple pressure chambers CC, multiple vibration detection chambers DB, and a flow path 45B which is part of the common liquid chamber RA. In FIG. 4, the arrangement of the nozzles N is indicated by dashed lines to clarify the positional relationship between the nozzles N and the pressure chambers CC. The pressure chamber substrate 25 can be manufactured from a silicon single crystal substrate, for example. The pressure chamber substrate 25 may also be manufactured from other materials.

[0038] As shown in FIG. 4, the damper chamber DA extends in the X-axis direction, and the damper chamber DA and the common liquid chamber RA are spaced apart from each other in the X-axis direction. The damper chamber DA and the pressure chamber CC are formed as a common space that is continuous in the X-axis direction. The damper chamber DA penetrates the pressure chamber substrate 25 in the Z-axis direction. The damper chamber DA has a predetermined volume. The damper chamber DA has a shape that is continuous in the Y-axis direction. A relay flow path may be formed between the damper chamber DA and the pressure chamber CC.

[0039] The pressure chambers CC extend in the X-axis direction. The pressure chambers CC penetrate the pressure chamber substrate 25 in the Z-axis direction. The pressure chambers CC have a predetermined volume. The multiple pressure chambers CC are arranged at predetermined intervals in the Y-axis direction. The multiple pressure chambers CC are connected to a common damper chamber DA in the Y-axis direction. The multiple pressure chambers CC form a pressure chamber array CL aligned in the Y-axis direction. The pressure chamber array CL includes multiple pressure chambers CC. In Figure 4, imaginary lines L1 and L2 indicating the boundaries of the pressure chambers CC are shown by two-dot chain lines. The imaginary line L1 indicates the end of the pressure chamber CC in the X1 direction. The imaginary line L2 indicates the end of the pressure chamber CC in the X2 direction.

[0040] The multiple vibration detection chambers DB extend in the X-axis direction. The vibration detection chambers DB and the pressure chambers CC are spaced apart in the X-axis direction. As shown in FIG. 2, a communication flow path 47C is formed between the vibration detection chambers DB and the pressure chambers CC. The vibration detection chambers DB and the common liquid chamber RB are spaced apart from each other in the X-axis direction. When viewed in the Z-axis direction, the vibration detection chambers DB are formed to overlap with the communication flow path 47B. The vibration detection chambers DB penetrate the pressure chamber substrate 25 in the Z-axis direction. The vibration detection chambers DB and the communication flow path 47B are in communication with each other in the Z-axis direction. The vibration detection chambers DB have a predetermined volume. The multiple vibration detection chambers DB are arranged at predetermined intervals in the Y-axis direction.

[0041] As described above, the liquid ejection head 10 includes, in order from the upstream side of the ink supply, the vibration absorbing unit 70A, the pressure applying unit 70C, and the vibration detecting unit 70B, and the wiring introduction portion RC is provided between the pressure applying unit 70C and the vibration detecting unit 70B. As shown in FIG. 1, this wiring introduction portion RC is formed from the opening 27a of the sealing plate 27 that is connected to the opening of the case 28, and the COF 60 is introduced here. The COF 60 and the wiring from the COF 60 will be described later.

[0042] (A3) Configuration and Function of Vibration Absorbing Unit 70A, Pressurizing Unit 70C, and Vibration Detecting Unit 70B: Next, the configurations of the vibration absorbing unit 70A, the pressure applying unit 70C, and the vibration detecting unit 70B will be described with reference to FIGS. 5 to 7, focusing on the piezoelectric elements of each unit. FIG. 6 is an enlarged cross-sectional view of a portion of the first vibration plate 26, the first piezoelectric element 51, and the first wiring unit 54 in the pressure applying unit 70C shown in FIG. 5. As shown in FIGS. 5 to 7, the first piezoelectric element 51, the second piezoelectric element 72, and the third piezoelectric element 73 each have electrodes on the top surface (the end surface in the Z2 direction) and the bottom surface (the end surface in the Z1 direction) of the piezoelectric body. The piezoelectric body sandwiched between the two electrodes deforms due to the electrostrictive effect when a voltage is applied between the upper and lower electrodes. On the other hand, when an external force is applied to deform the piezoelectric body, a voltage is generated between the electrodes due to the piezoelectric effect. In this embodiment, the first piezoelectric element 51, second piezoelectric element 72, and third piezoelectric element 73 have roughly the same configuration, but the first piezoelectric element 51 is used as a piezoelectric element that generates vibrations in the first diaphragm 26 by applying a voltage between the electrodes, and the second piezoelectric element 72 is used as a piezoelectric element that generates pressure when vibrations are applied from outside to the second diaphragm 29, thereby detecting the vibrations. The third piezoelectric element 73 has the same configuration as the other piezoelectric elements, but the upper and lower electrodes are not electrically connected, and it is used as a mass to absorb pressure changes in the liquid in the damper chamber DA.

[0043] The first piezoelectric element 51, the second piezoelectric element 72, and the third piezoelectric element 73 have the same configuration, so the general configuration will be described first using the first piezoelectric element 51 as an example. The first piezoelectric element 51 has a first lower electrode 51a, a first upper electrode 51b, and a first piezoelectric body 51c, and further has a first vibration plate 26 below the first lower electrode 51a in the Z1 direction. The first lower electrode 51a, the first piezoelectric body 51c, and the first upper electrode 51b are layered in this order on the first vibration plate 26. The first piezoelectric body 51c is sandwiched between the first lower electrode 51a and the first upper electrode 51b. Here, the first lower electrode 51a is an individual electrode that applies a potential to the plurality of first piezoelectric elements 51 individually, and the first upper electrode 51b is a common electrode that applies a potential to the plurality of first piezoelectric elements 51 in common, but the first lower electrode 51a may be a common electrode and the first upper electrode 51b may be an individual electrode. This also applies to the second piezoelectric element 72 and the third piezoelectric element 73, which will be described later in order.

[0044] The first diaphragm 26 includes a first elastic layer 26a and a first insulating layer 26b. The first elastic layer 26a is made of, for example, silicon dioxide (SiO2). The first insulating layer 26b is made of, for example, zirconium dioxide (ZrO2).

[0045] A plurality of first piezoelectric elements 51 are formed on the first vibration plate 26 provided below the first lower electrode 51a in the Z1 direction. The first piezoelectric elements 51 are arranged at positions overlapping with the pressure chambers CC when viewed in the Z-axis direction. The first piezoelectric elements 51 are provided for each of the plurality of pressure chambers CC.

[0046] The first diaphragm 26 is driven by the first piezoelectric element 51 and vibrates in the Z-axis direction. The first diaphragm 26, which forms the upper wall surface of the pressure chamber CC, is driven by the first piezoelectric element 51 above the pressure chamber CC. The specific configuration, material, and thickness of the first diaphragm 26, as well as differences from the second diaphragm 29, will be described in detail in the sections on each embodiment described below. As an example, the total thickness of the first diaphragm 26 is, for example, 2 μm or less. The total thickness of the first diaphragm 26 may be 15 μm or less, 40 μm or less, or 100 μm or less. For example, if the total thickness of the first diaphragm 26 is 15 μm or less, it may include a resin layer. The first diaphragm 26 may be made of metal. Examples of metal include stainless steel and nickel. If the first diaphragm 26 is made of metal, the thickness of the first diaphragm 26 may be 15 μm or more and 100 μm or less.

[0047] The configuration of the first piezoelectric element 51 will be described in detail below. The first lower electrode 51a provided on the upper surface of the first piezoelectric element 51 in the Z2 direction is elongated along the X-axis direction. The multiple first lower electrodes 51a are arranged at intervals from each other in the Y-axis direction. The multiple first lower electrodes 51a are arranged for each of the multiple pressure chambers CC. The first lower electrodes 51a are arranged at positions overlapping with the multiple pressure chambers CC when viewed in the Z-axis direction. The first upper electrode 51b is strip-shaped and extends in the Y-axis direction. The first upper electrode 51b is continuous so as to cover the multiple first lower electrodes 51a.

[0048] The first lower electrode 51a includes an underlayer and an electrode layer. The underlayer includes, for example, titanium (Ti). The electrode layer includes, for example, a low-resistance conductive material such as platinum (Pt) or iridium (Ir). The electrode layer may be formed of an oxide such as strontium ruthenate (SrRuO) or lanthanum nickelate (LaNiO). The first piezoelectric element 51c is formed of a known piezoelectric material such as lead zirconate titanate (Pb(Zr,Ti)O) or ceramic.

[0049] The first upper electrode 51b includes a base layer and an electrode layer. The base layer includes, for example, titanium. The electrode layer includes, for example, a low-resistance conductive material such as platinum or iridium. The electrode layer may be formed of an oxide such as strontium ruthenate or lanthanum nickelate. Of the first piezoelectric body 51c, the region between the first lower electrode 51a and the first upper electrode 51b serves as a driving region. Driving regions are formed on each of the multiple pressure chambers CC.

[0050] A predetermined reference voltage is applied to the first upper electrode 51b. The reference voltage is a constant voltage, and is set to, for example, a voltage higher than the ground voltage. For example, a holding signal having a constant voltage is applied to the first upper electrode 51b. A drive signal having a fluctuating voltage is applied to the first lower electrode 51a. A voltage corresponding to the difference between the reference voltage applied to the first upper electrode 51b and the drive signal supplied to the first lower electrode 51a is applied to the first piezoelectric element 51c. The drive signal corresponds to the amount of liquid ejected from the nozzle N.

[0051] When a voltage is applied between the first lower electrode 51a and the first upper electrode 51b, the first piezoelectric body 51c is deformed, and the first piezoelectric element 51 generates energy that flexes and deforms the first diaphragm 26. The energy generated by the first piezoelectric element 51 causes the first diaphragm 26 to vibrate, changing the pressure of the liquid in the pressure chamber CC, and the liquid in the pressure chamber CC is ejected from the nozzle N.

[0052] As shown in FIG. 6, which is an enlarged view of the lead-out wiring portion, which is the connection portion between the pressure applying portion 70C and the first wiring portion 54, the first wiring portion 54 is connected to the Y-direction end portion of the first piezoelectric element 51. The first wiring portion 54 has an electrode layer 54a, a first adhesion layer 54b, and a first wiring layer 54c. The electrode layer 54a covers the X2-direction end face of the first piezoelectric body 51c. The X2-direction end face forms a plane intersecting with the X-axis direction. The first adhesion layer 54b covers the electrode layer 54a and the first lower electrode 51a. The first adhesion layer 54b is in close contact with the electrode layer 54a and the first lower electrode 51a. The first wiring layer 54c covers the first adhesion layer 54b. The first wiring layer 54c is electrically connected to the first lower electrode 51a via the first adhesion layer 54b.

[0053] The first piezoelectric element 51 is provided with a VBS wiring 55. The VBS wiring 55 is disposed on the first upper electrode 51b and extends in the Y-axis direction. The VBS wiring is strip-shaped when viewed from the Z-axis direction and is formed to cover the first upper electrode 51b. The VBS wiring 55 connects the first upper electrode 51b of the first piezoelectric element 51 to the flexible wiring substrate 61. The VBS wiring 55 is electrically connected to the COF 60 at the end of the liquid ejection head 10 in the Y-axis direction. The VBS wiring 55 is provided as an auxiliary wiring that substantially reduces the electrical resistance of the first upper electrode 51.

[0054] An insulating adhesive layer 59 made of an insulating adhesive is formed between the first piezoelectric element 51 and the sealing plate 27. The insulating adhesive layer 59 bonds the first piezoelectric element 51 to the sealing plate 27 and also insulates the end face of the first wiring layer 54c from the end face of the VBS wiring 55. The latter prevents electrical conduction that may occur due to ion migration.

[0055] The first wiring portions 54 of the liquid ejection head 10 are connected to the first lower electrodes 51a, respectively. The first wiring portions 54 extend in the X-axis direction and are drawn out into the openings 27a of the wiring introduction portions RC. The openings 27a penetrate the sealing plate 27 in the Z-axis direction. The first wiring portions 54 are electrically connected to the COF 60 at positions corresponding to the openings 27a when viewed in the Z-axis direction. The first wiring portions 54 are formed of a conductive material with lower resistance than the first lower electrodes 51a. For example, the first wiring portions 54 are a conductive pattern having a structure in which a conductive film of gold (Au) is laminated on the surface of a conductive film made of nichrome (NiCr).

[0056] Next, the vibration absorbing section 70A will be briefly described. The supply-side vibration absorbing section 70A is provided for the supply-side damper chamber DA. As shown in FIG. 5, the vibration absorbing section 70A includes a third piezoelectric element 73. The third piezoelectric element 73 includes a third diaphragm (hereinafter also referred to as a compliance substrate) 23. The compliance substrate 23 is located in the X1 direction of the first diaphragm 26. The compliance substrate 23 is disposed on the upper surface of the pressure chamber substrate 25. The compliance substrate 23 covers the portion of the opening of the pressure chamber substrate 25 that corresponds to the damper chamber DA. The compliance substrate 23 forms the upper wall surface of the damper chamber DA. The compliance substrate 23 is disposed in a position that corresponds to the sealed space S3 formed in the sealing plate 27 when viewed in the Z-axis direction.

[0057] The compliance substrate 23 includes a flexible film. The compliance substrate 23 includes a third elastic layer 23a and a third insulating layer 23b. The third elastic layer 23a is made of, for example, silicon dioxide (SiO2). The third insulating layer 23b is made of, for example, zirconium dioxide (ZrO2). The third elastic layer 23a is formed on the pressure chamber substrate 25, and the third insulating layer 23b is formed on the third elastic layer 23a. The third elastic layer 23a is formed continuously with the first elastic layer 26a of the first diaphragm 26 that covers the pressure chamber CC. The third insulating layer 23b is formed continuously with the first insulating layer 26b of the first diaphragm 26. The compliance substrate 23 is deformable when subjected to ink pressure. The compliance substrate 23 deforms due to the ink pressure and absorbs pressure fluctuations of the ink in the damper chambers DA. The multiple compliance substrates 23 individually deform in accordance with the damper chambers DA.

[0058] As shown in FIG. 5 , the vibration absorbing unit 70A includes a third piezoelectric element 73. The third piezoelectric element 73 is disposed at a position overlapping the damper chamber DA when viewed in the Z-axis direction. The third piezoelectric element 73 is provided relative to the damper chamber DA. Similar to the first piezoelectric element 51, the third piezoelectric element 73 includes a third lower electrode 73a, a third upper electrode 73b, a third piezoelectric body 73c, and a compliance substrate 23. The third lower electrode 73a, the third upper electrode 73b, and the third piezoelectric body 73c are layered in this order on the compliance substrate 23. The third piezoelectric body 73c is sandwiched between the third lower electrode 73a and the third upper electrode 73b. The electrode arrangement, structure, and materials are similar to those of the first piezoelectric element 51, and therefore detailed description thereof will be omitted.

[0059] Finally, the configuration of the vibration detection unit 70B will be described using FIG. 7. As shown in the figure, the vibration detection unit 70B includes a second piezoelectric element 72. The second piezoelectric element 72 includes a second diaphragm 29. The second diaphragm 29 is located in the X2 direction of the first diaphragm 26. The second diaphragm 29 is located on the opposite side of the compliance substrate 23 from the first diaphragm 26 in the X-axis direction. As shown in the figure, the second diaphragm 29 is disposed on the upper surface of the pressure chamber substrate 25. The second diaphragm 29 covers the portion of the opening of the pressure chamber substrate 25 that corresponds to the vibration detection chamber DB. The second diaphragm 29 forms the upper wall surface of the vibration detection chamber DB. The second diaphragm 29 is disposed at a position corresponding to the sealed space S2 formed in the sealing plate 27 when viewed in the Z-axis direction.

[0060] The second diaphragm 29 includes a flexible film. The second diaphragm 29 includes a second elastic layer 29a and a second insulating layer 29b. The second elastic layer 29a is made of, for example, silicon dioxide (SiO2). The second insulating layer 29b is made of, for example, zirconium dioxide (ZrO2). The second elastic layer 29a is formed on the pressure chamber substrate 25, and the second insulating layer 29b is formed on the second elastic layer 29a. The second elastic layer 29a may be formed continuously with the first elastic layer 26a of the first diaphragm 26, or may be formed separately. The second insulating layer 29b may be formed continuously with the first insulating layer 26b of the first diaphragm 26, or may be formed separately.

[0061] The multiple second vibration plates 29 are provided corresponding to the multiple vibration detection chambers DB aligned in the Y-axis direction. The second vibration plates 29 are deformable when subjected to ink pressure. The second vibration plates 29 deform in response to fluctuations in ink pressure within the vibration detection chambers DB. The multiple second vibration plates 29 move individually in correspondence with the multiple vibration detection chambers DB. A multiple number of second piezoelectric elements 72 are formed on the second vibration plate 29. The second piezoelectric elements 72 are arranged at positions overlapping the vibration detection chambers DB when viewed in the Z-axis direction. The second piezoelectric elements 72 are provided corresponding to the multiple vibration detection chambers DB respectively.

[0062] Similar to the first piezoelectric element 51, the second piezoelectric element 72 has a second lower electrode 72a, a second upper electrode 72b, a second piezoelectric body 72c, and a second vibration plate 29. The second lower electrode 72a, the second upper electrode 72b, and the second piezoelectric body 72c are layered in this order on the second vibration plate 29. The second piezoelectric body 72c is sandwiched between the second lower electrode 72a and the second upper electrode 72b. The second lower electrode 72a is elongated along the X-axis direction. The multiple second lower electrodes 72a are arranged at intervals in the Y-axis direction. The multiple second lower electrodes 72a are arranged for each of the multiple vibration detection chambers DB. The second lower electrodes 72a are arranged at positions overlapping the multiple vibration detection chambers DB when viewed in the Z-axis direction. The second upper electrode 72b is strip-shaped and extends in the Y-axis direction. The second upper electrode 72b is continuous and covers the plurality of second lower electrodes 72a.

[0063] The structure and material of the second lower electrode 72a are the same as those of the first lower electrode 51a of the first piezoelectric element 51. The structure and material of the second upper electrode 72b are the same as those of the first upper electrode 51b of the first piezoelectric element 51. The structure and material of the second piezoelectric body 72c are the same as those of the first piezoelectric body 51c of the first piezoelectric element 51. The second piezoelectric element 72 can be formed in the same manner as the first piezoelectric element 51 and the third piezoelectric element 73. Although not shown in detail, the second lower electrode 72a and the second upper electrode 72b of the second piezoelectric element 72 are connected to the flexible wiring substrate 61, similar to the first lower electrode 51a and the first upper electrode 51b of the first piezoelectric element 51. In the drawing, the wiring from the flexible wiring substrate 61 to the second piezoelectric element 72 is shown as a second wiring portion 74. The configuration of the connection portion between the second piezoelectric element 72 and the second wiring portion 74 is similar to the configuration using the electrode layer 54a, first adhesion layer 54b, and first wiring layer 54c of the first wiring portion 54 in the first piezoelectric element 51 shown in Figure 6, so illustration and description of these are omitted.

[0064] A drive signal output to the first piezoelectric element 51 of the pressure applying unit 70C and a detection signal detected by the second piezoelectric element 72 of the vibration detecting unit 70B are exchanged with the control circuit 62 via a flexible wiring board 61. The flexible wiring board 61 is a flexible wiring board. The flexible wiring board 61 is, for example, an FPC. The flexible wiring board 61 may also be, for example, an FFC. FPC is an abbreviation for Flexible Printed Circuit. FFC is an abbreviation for Flexible Flat Cable.

[0065] 6, the flexible wiring board 61 is electrically connected to the first lower electrode 51a and the first upper electrode 51b of the first piezoelectric element 51 of the pressure applying unit 70C and the second lower electrode 72a and the second upper electrode 72b of the vibration detecting unit 70B via the first wiring part 54 described below. The flexible wiring board 61 is electrically connected to the control unit 20, and exchanges signals, such as signals for driving the first piezoelectric element 51 of the pressure applying unit 70C and detection signals corresponding to residual vibrations generated in the second piezoelectric element 72 of the vibration detecting unit 70B, with the control unit 20 via the control circuit 62.

[0066] The control circuit 62 is mounted on the flexible wiring board 61. The control circuit 62 includes a switching element for driving the first piezoelectric element 51. The control circuit 62 receives a drive signal Com for the first piezoelectric element 51 output from the control unit 20. The switching element of the control circuit 62 switches whether or not to supply the drive signal Com to the first piezoelectric element 51. The control circuit 62 supplies a drive voltage or current to the first piezoelectric element 51 to vibrate the first diaphragm 26. The control circuit 62 also receives a voltage signal generated in the second piezoelectric element 72 due to vibration of the second diaphragm 29 caused by residual vibration in the ink, extracts information such as the magnitude and frequency of the residual vibration, and outputs the information to the control unit 20.

[0067] The wiring from the flexible wiring board 61 to the first piezoelectric element 51 and the second piezoelectric element 72 is shown schematically in FIG. 8. In the figure, the flexible wiring board 61 does not represent a single wire but a collection of multiple wires. A drive signal output from the control circuit 62 to the first piezoelectric element 51 via the flexible wiring board 61 is transmitted to the first upper electrode 51b and the first lower electrode 51a via the first wiring section 54. A detection signal from the second piezoelectric element 72 is transmitted to the second upper electrode 72b and the second lower electrode 72a via the second wiring section 74 to the second piezoelectric element 72.

[0068] (A4) Configuration as the first embodiment: The above has described the basic configuration of the liquid ejection head 10. Based on the above basic configuration, the pressure applying unit 70C and the vibration detecting unit 70B of each embodiment have their own unique configurations, as will be explained below. These will be explained in order.

[0069] 9 is an explanatory diagram comparing the shapes of the first piezoelectric element 51 in the pressure applying unit 70C and the second piezoelectric element 72 in the vibration detecting unit 70B of the first embodiment. The upper part of the diagram schematically illustrates the cross-sections of both elements in the XZ plane as viewed in the Y direction, and the lower part of the diagram schematically illustrates the cross-sections taken along the arrows JJ and KK of the upper diagram. For convenience of illustration, the first diaphragm 26 and the second diaphragm 29 are labeled separately from the first piezoelectric element 51 and the second piezoelectric element 72. However, as already explained, the first diaphragm 26 is included in the first piezoelectric element 51, and the second diaphragm 29 is included in the second piezoelectric element 72. In illustrations of other embodiments, the two may also be labeled separately for convenience of illustration.

[0070] As shown in the figure comparing the first piezoelectric element 51 and the second piezoelectric element 72 of the first embodiment, comparing the first vibration plate 26 of the first piezoelectric element 51 of the pressure applying unit 70C with the second vibration plate 29 of the second piezoelectric element 72 of the vibration detecting unit 70B, the thickness K1 of the first insulating layer 26b constituting the first vibration plate 26 is greater than the thickness J1 of the second insulating layer 29b constituting the second vibration plate 29. The first piezoelectric element 51 and the second piezoelectric element 72 are substantially identical in dimensions at least in the X direction, except for the thicknesses of the first insulating layers 26b and 29b. As a result, the Z-direction position (also referred to as the first height) of the neutral axis of the first piezoelectric element 51 of the pressure applying unit 70C is different from the Z-direction position (also referred to as the second height) of the neutral axis of the second piezoelectric element 72 of the pressure applying unit 70B.

[0071] The neutral axis of a piezoelectric element refers to the position within a cross section where tensile and compressive forces balance when a piezoelectric body deforms and a bending moment is generated in the component. The position where symmetrical tensile and compressive forces balance due to the deformation of the piezoelectric body is the fulcrum of the deformation. The force generated by the deformation is applied to one side of the fulcrum (the point of force) and acts on the other side of the fulcrum (the point of action). Figure 10A shows a schematic example of a pressure applying unit 70C. In this case, a first piezoelectric element 51 is attached to approximately the center of the first diaphragm 26 in the X direction. The first piezoelectric body 51c and first insulating layer 26b of the attached first piezoelectric element 51 have tensile stress, and the first elastic layer 26a has compressive stress. Because the first elastic layer 26a has compressive stress (stress against compression), it tends to stretch as a film alone, which generates an outward force as indicated by the lower arrows in Figures 10A and 10B. Conversely, because the piezoelectric body and insulating layer have tensile stress (stress against tension), they tend to shrink as films. This results in an inward force, as indicated by the upper arrows in FIGS. 10A and 10B. The position where this force, i.e., the compressive stress and the tensile stress, are balanced corresponds to the position of the neutral axis NA. In this state, when a voltage is applied between the first lower electrode 51a and the first upper electrode 51b of the first piezoelectric element 51, the deformation force generated in the first piezoelectric body 51c acts on the first insulating layer 26b with the neutral axis NS as the fulcrum. This also applies to the relationship between compressive stress and tensile stress in the initial state of the vibration detection unit 70B, which will be described below, and when a force acts on the piezoelectric body due to an external force.

[0072] When a predetermined voltage due to the power supply EMF is applied between the first lower electrode 51a and the first upper electrode 51b of the first piezoelectric element 51, the first piezoelectric body 51c is deformed. At this time, as shown in Fig. 10A, the point of force ep where stress due to deformation of the first piezoelectric body 51c is applied and the point of action lp where stress that deforms the first elastic layer 26a of the first diaphragm 26 acts are on opposite sides of the fulcrum fp, which is the position of the neutral axis NA. According to the principle of leverage, the force F1e applied to the point of force ep is a force F2e according to the ratio (Lee / Lle) of the distance Lee from the point of force ep to the fulcrum fp and the distance Lle from the fulcrum fp to the point of action lp, as shown in the following equation (1): F2e = (Lee / Lle) × F1e …(1) As a result, it acts on the first elastic layer 26a at the action point lp. As shown in the figure, if Lee < Lle, the force of the first piezoelectric element 51 is so-called reduced, and the first elastic layer 26a is deformed, and it is possible to suppress an excessive force from being applied to the first elastic layer 26a. As a result, it is possible to suppress the possibility of failure of the first elastic layer 26a or the like. Further, if Lee < Lle, an appropriate reaction force is applied to the first piezoelectric element 51, so that deformation of the first piezoelectric element 51 can be suppressed, and the possibility that cracks occur in the first piezoelectric element 51 due to excessive deformation can be reduced. Therefore, it is also possible to reduce the possibility of failure of the first piezoelectric element 51 or the like, and to improve reliability and achieve a long life.

[0073] On the other hand, in the vibration detection unit 70B, the second piezoelectric element 72 is provided to detect residual vibration applied to the second diaphragm 29. In the second piezoelectric element 72, as shown in FIG. 10B, when residual vibration in the ink is applied to the second diaphragm 29 and the second piezoelectric body 72c is deformed, the potential of the second lower electrode 72a with respect to the second upper electrode 72b changes due to the electromotive force generated by the piezoelectric effect. If this change in potential is detected by the voltage detector MQ, the force applied to the second diaphragm 29, that is, the magnitude of the residual vibration can be detected. In the vibration detection unit 70B, as shown in comparison with FIG. 9, the thickness J1 of the second insulating layer 29b of the second diaphragm 29 to which the second piezoelectric element 72 is attached is smaller than the thickness K1 of the corresponding first insulating layer 26b of the pressurizing unit 70C. Therefore, the Z-direction position (second position) of the neutral axis NA is lower than the Z-direction position (first height) of the neutral axis NA of the first piezoelectric element 51 in the pressurizing unit 70C, as shown in FIG. 10B.

[0074] As a result, in the vibration detection unit 70B, although the positions of the force point and the action point are opposite to those of the pressurizing unit 70C, the distance Lev from the force point ep, where the force due to the deformation of the second diaphragm 29 is applied, to the fulcrum point fp, which is the position of the neutral axis NA, is relatively smaller than the distance Llv from the fulcrum point fp to the action point lp. That is, as shown by the following equation (2), the force F2v obtained by multiplying the force F1v that the second diaphragm 29 receives due to residual vibration by the ratio of the two distances (Lev / Llv), that is, F2v=(Lev / Llv)×F1v …(2) acts on the second piezoelectric element 72 at the action point lp. As shown in the figure, if Lev < Llv, the force applied to the second diaphragm 29 due to residual vibration is reduced, and the second piezoelectric element 72 is deformed, so that the electromotive force generated by the piezoelectric effect can be suppressed. As a result, it is possible to suppress the possibility that an overcurrent is applied to the wiring for detecting the electromotive force of the second piezoelectric element 72, and it is possible to suppress the possibility that damage such as burnout occurs in the wiring.

[0075] In FIGS. 10A and 10B, due to the difference in the thickness K1 of the first insulating layer 26b and the thickness J1 of the second insulating layer 29b, the position of the neutral axis NA (the first height and the second height) is Lee<Lle and Lev<Llv is drawn as such, but if the value of Lev / Llv in the vibration detection unit 70B becomes smaller than the value of Lev / Llv in the case of J1 = K1 by setting J1 < K1, it does not matter even if Lev < Llv is not satisfied.

[0076] FIG. 11 shows an example of the drive signal applied between the electrodes of the first piezoelectric element 51 of the pressure applying unit 70C in the above embodiment, and the residual vibrations that occur in the ink when ink is ejected in response to the drive signal. When ink is to be ejected from nozzle N, as shown in the upper part of the figure, a first drive signal VinA is applied between the electrodes of the first piezoelectric element 51 of the ejection unit 70C. The first drive signal VinA is a signal with a waveform change that drives the meniscus of nozzle N in a pull-push-pull manner. The first piezoelectric element 51 is driven by the first drive signal VinA, which causes a pressure change in the pressure chamber CC, causing an ink droplet to be ejected from the nozzle N. The pull-push-pull drive generates pressure fluctuations in the ink in the pressure chamber CC. These pressure fluctuations remain for a certain period of time even after the ink droplet is ejected. This is called residual vibration.

[0077] The vibration detection unit 70B detects this pressure fluctuation by the second piezoelectric element 72. The pressure fluctuation generated in the pressure chamber CC propagates to the vibration detection chamber DB, where it is detected by the second piezoelectric element 72 and output as a residual vibration signal Vout. Specifically, the second piezoelectric element 72 detects the ink pressure change during the period Td from the point at which the drive signal VinA returns to the predetermined potential V3 as residual vibration, and outputs the residual vibration signal Vout. From the residual vibration signal VoutA, the control circuit 62 obtains the period NTc, phase time TF, and amplitude Vmax of the residual vibration. Furthermore, the control unit 20, which obtains this information from the control circuit 62, detects events such as nozzle clogging and increased ink viscosity.

[0078] In the liquid ejection head 10 of the first embodiment described above, while the first piezoelectric element 51 used in the vibration detection unit 70B and the second piezoelectric element 72 used in the pressurization unit 70C have substantially the same configuration, the thickness J1 of the second insulating layer 29b of the second diaphragm 29 to which the second piezoelectric element 72 of the vibration detection unit 70B is bonded is made thinner than the thickness K1 of the first insulating layer 26b of the first diaphragm 26 to which the first piezoelectric element 51 of the pressurization unit 70C is bonded. By doing so, the position of the neutral axis NA in the vibration detection unit 70B can be made lower in the Z direction than the position of the neutral axis NA in the pressurization unit 70C, and the characteristics required for both the pressurization unit 70C and the vibration detection unit 70B can be satisfied. Specifically, a force F2e that weakens the force F1e by the first piezoelectric element 51 itself is extracted in the pressurization unit 70C, and it is possible to suppress an excessive force from being applied to the first elastic layer 26a. As a result, the possibility of failure of the first elastic layer 26a and the like can be suppressed. Also, if Lee < Lle, an appropriate reaction force is applied to the first piezoelectric element 51, so that the deformation of the first piezoelectric element 51 can be suppressed, and the possibility of cracks occurring in the first piezoelectric element 51 due to excessive deformation can be reduced. Therefore, the possibility of failure of the first piezoelectric element 51 and the like can be reduced, and it is also possible to improve reliability and extend the service life. Moreover, since the second piezoelectric element 72 in the vibration detection unit 70B is deformed by a force F2v that weakens the force F1v due to the residual vibration of the ink in the vibration detection chamber DB, the electromotive force generated by the piezoelectric effect can be suppressed. As a result, the possibility of an overcurrent being applied to the wiring or the like for detecting the electromotive force of the second piezoelectric element 72 can be suppressed, and the possibility of damage such as burnout occurring in the wiring can be suppressed. Since the first piezoelectric element 51 used in the vibration detection unit 70B and the second piezoelectric element 72 used in the pressurization unit 70C can have substantially the same configuration, the manufacturing of the liquid ejection head 10 becomes easy. Also, by doing so, the throughput of ink ejection in the liquid ejection head 10 can be sufficiently increased.

[0079] (A5) Modification example: In the first embodiment, the thicknesses of the first and second insulating layers 26b and 29b are different from each other, but the thicknesses of the other components are the same. In this case, the height of the neutral axis NA can be understood as the height from the lower surface (the end surface in the Z1 direction) of the first diaphragm 26 or the second diaphragm 29, so it is easy to understand that the neutral axis NA in the vibration detection unit 70B is located lower than the neutral axis in the pressure application unit 70C. When the thicknesses of the layers other than the first and second insulating layers 26b and 29b are different from each other, the height of the neutral axis can be defined as follows, and the height of the neutral axis in the vibration detection unit 70B can be compared with the height of the neutral axis in the pressure application unit 70C.

[0080] FIG. 12 is an explanatory diagram illustrating the definition of the height of the neutral axis NA. Here, the height of the neutral axis NA of the first piezoelectric element 51 in the pressure applying unit 70C is defined as t1 / T1. Here, T1 is the thickness (dimension in the Z direction) of the first piezoelectric element 51, specifically the distance from the upper surface of the first upper electrode 51b at the top of the first piezoelectric element 51 to the lower surface of the first vibration plate 26. Also, t1 is the distance from the lower surface of the first vibration plate 26 to the neutral axis NA. Similarly, with regard to the second piezoelectric element 72 in the vibration detecting unit 70B, the height of its neutral axis NA is defined as t2 / T2. Here, T2 is the thickness (dimension in the Z direction) of the second piezoelectric element 72, specifically the distance from the upper surface of the second upper electrode 72b at the top of the second piezoelectric element 72 to the lower surface of the second vibration plate 29. Also, t2 is the distance from the lower surface of the second vibration plate 29 to the neutral axis NA.

[0081] In the first embodiment, it has been explained that the position of the neutral axis NA of the second piezoelectric element 72 is lower than the position of the neutral axis NA of the first piezoelectric element 51, that is, located on the lower side, by making the thickness of the first insulating layer 26b of the first diaphragm 26 and the thickness of the second insulating layer 29b of the second diaphragm 29 different. However, in accordance with the above definition, this can be expressed as follows, as shown in the following inequality (3): t2 / T2 <t1 / T1 …(3) This definition is equivalent to saying that, for example, even if there is a slight difference in thickness between the first elastic layer 26a and the second elastic layer 29a, the difference in height of the neutral axis NA can be determined.

[0082] B. Second embodiment: Next, a liquid ejection head 10 according to a second embodiment will be described. FIG. 13 is an explanatory diagram comparing the configurations of a vibration detection unit 70B2 and a pressure application unit 70C2 in the liquid ejection head 10 according to the second embodiment. The upper part of the diagram schematically illustrates the cross-sections of both units in the XZ plane as viewed in the Y direction, and the lower part of the diagram schematically illustrates the cross-sections as viewed along the MM and NN arrows of the upper diagram. As shown in the diagram, the pressure application unit 70C2 includes a first piezoelectric element 512. The first piezoelectric element 512 includes a first vibration plate 262 at its lowermost portion in the Z direction. The first vibration plate 262 is configured by laminating a first elastic layer 262a and a first insulating layer 262b, as in the first embodiment. On the other hand, the vibration detection unit 70B2 includes a second piezoelectric element 722. The second piezoelectric element 722 includes a second vibration plate 292 at its lowermost portion in the Z direction. Similar to the first embodiment, the second diaphragm 292 is configured by laminating a second elastic layer 292a and a second insulating layer 292b.

[0083] The liquid ejection head 10 of the second embodiment has the same overall configuration as the first embodiment, but differs in the method for making the height of the neutral axis NA of the second piezoelectric element 722 lower than the neutral axis NA of the first piezoelectric element 512. In the first embodiment, the heights of the neutral axes of the two elements were adjusted by making the thicknesses of the second insulating layer 29b and the first insulating layer 26b different, but in the second embodiment, the thickness of the second insulating layer 292b of the second piezoelectric element 722 and the thickness of the first diaphragm 262 of the first piezoelectric element 512 are the same, and the heights of the neutral axes of the two elements are adjusted by making the thicknesses of the second piezoelectric body 722c and the first piezoelectric body 512c different.

[0084] As shown in the figure, the first piezoelectric element 512 includes a first lower electrode 51a, a first upper electrode 512b, a first piezoelectric body 512c, and a first vibration plate 262. The first vibration plate 262 includes a first elastic layer 262a and a first insulating layer 262b bonded together. The materials and other components of the first piezoelectric element 512 are the same as those in the first embodiment. The second piezoelectric element 722 includes a second lower electrode 722a, a second upper electrode 722b, a second piezoelectric body 722c, and a second vibration plate 292. The second vibration plate 292 includes a second elastic layer 292a and a second insulating layer 292b bonded together. The materials and other components of the second piezoelectric element 722 are the same as those in the first embodiment.

[0085] In the second embodiment, the thickness J2 of the second piezoelectric body 722c is smaller than the thickness K2 of the first piezoelectric body 512c. The thicknesses of all other layers are substantially the same. The thicknesses of each component in the second embodiment are determined so that inequality (3) described in the modified example of the first embodiment holds. Because the thickness J2 of the second piezoelectric body 722c is smaller than the thickness K2 of the first piezoelectric body 512c, the neutral axis NA of the second piezoelectric element 722 is positioned lower than the neutral axis NA of the first piezoelectric element 512. As a result, similar to the first embodiment, the pressure applying unit 70C2 does not apply excessive force to the first piezoelectric element 512, and the vibration detecting unit 70B2 prevents the second piezoelectric element 722 from generating excessive electromotive force. This simultaneously satisfies the requirements of preventing failure of the first piezoelectric element 512 and preventing damage to wiring and the like due to electromotive force generated in the second piezoelectric element 722. As a result, the reliability and life of the liquid ejection head 10 can be improved.

[0086] C. Third embodiment: Next, a liquid ejection head 10 according to a third embodiment will be described. FIG. 14 is an explanatory diagram comparing the configurations of a vibration detection unit 70B3 and a pressure application unit 70C3 in the liquid ejection head 10 according to the third embodiment. The upper part of the diagram schematically illustrates the cross-sections of both units in the XZ plane as viewed in the Y direction, while the lower part of the diagram schematically illustrates the cross-sections of the upper diagram as viewed along the arrows PP and QQ. As shown in the diagram, the pressure application unit 70C3 includes a first piezoelectric element 513. The configuration of the first piezoelectric element 513, including its thickness, is the same as that of the first embodiment, and therefore a detailed description thereof will be omitted. The first piezoelectric element 513 includes a first vibration plate 263 at its lowermost position in the Z direction. The first vibration plate 263 is configured by laminating a first elastic layer 263a and a first insulating layer 263b, as in the first embodiment. On the other hand, the vibration detection unit 70B3 includes a second piezoelectric element 723. The configuration of the second piezoelectric element 723, including its thickness, is the same as that of the first embodiment, so a detailed description thereof will be omitted. The second piezoelectric element 723 includes a second vibration plate 293 at its lowermost portion in the Z direction. As in the first embodiment, the second vibration plate 293 is configured by laminating a second elastic layer 293a and a second insulating layer 293b.

[0087] The liquid ejection head 10 of the third embodiment has the same overall configuration as the first embodiment, but differs in the method for making the height of the neutral axis NA of the second piezoelectric element 723 lower than the neutral axis NA of the first piezoelectric element 513. In the first embodiment, the heights of the neutral axes of the two elements were adjusted by making the thicknesses of the second insulating layer 29b and the first insulating layer 26b different, but in the third embodiment, the thickness of the second insulating layer 293b of the second piezoelectric element 723 and the thickness of the first diaphragm 263 of the first piezoelectric element 513 are the same, and the heights of the neutral axes of the two elements are adjusted by making the thicknesses of the second elastic layer 293a and the first elastic layer 263a different.

[0088] The first vibration plate 263 of the first piezoelectric element 513 is formed by bonding a first elastic layer 263a and a first insulating layer 263b together. The materials and the like of each part of the first piezoelectric element 513 are the same as those in the first embodiment. The second vibration plate 293 of the second piezoelectric element 723 is formed by bonding a second elastic layer 293a and a second insulating layer 293b together. The materials and the like of each part of the second piezoelectric element 723 are the same as those in the first embodiment.

[0089] In the third embodiment, the thickness K3 of the first piezoelectric body 513c is greater than the thickness J3 of the second piezoelectric body 723c. The thicknesses of all other layers are substantially the same. The thicknesses of each component in the third embodiment are determined so that inequality (3) described in the modified example of the first embodiment holds. Because the thickness J3 of the second piezoelectric body 723c is greater than the thickness K3 of the first piezoelectric body 513c, the neutral axis NA of the second piezoelectric element 723 is positioned higher than the neutral axis NA of the first piezoelectric element 513. As a result, similar to the first embodiment, the pressure applying unit 70C3 does not apply excessive force to the first piezoelectric element 513, and the vibration detecting unit 70B3 prevents the second piezoelectric element 723 from generating excessive electromotive force. This simultaneously satisfies the requirements of preventing failure of the first piezoelectric element 513 and preventing damage to wiring and other components due to the electromotive force generated in the second piezoelectric element 723. As a result, the reliability and life of the liquid ejection head 10 can be improved.

[0090] D. Fourth embodiment: Next, a liquid ejection head 10 according to a fourth embodiment will be described. FIG. 15 is an explanatory diagram illustrating the configurations of a vibration detection unit 70B4 and a pressure application unit 70C4 in the liquid ejection head 10 according to the fourth embodiment. As shown in the figure, the pressure application unit 70C4 includes a first piezoelectric element 514. The first piezoelectric element 514 includes a first vibration plate 264 at its lowermost portion in the Z direction. Similar to the first embodiment, the first vibration plate 264 is configured by laminating a first elastic layer 264a and a first insulating layer 264b. On the other hand, the vibration detection unit 70B4 includes a second piezoelectric element 724. The second piezoelectric element 724 includes a second vibration plate 294 at its lowermost portion in the Z direction. Similar to the first embodiment, the second vibration plate 294 is configured by laminating a second elastic layer 294a and an insulating layer 294b.

[0091] The liquid ejection head 10 of the fourth embodiment has the same overall configuration as the first embodiment, but differs in the method for making the height of the neutral axis NA of the second piezoelectric element 724 higher than the neutral axis NA of the first piezoelectric element 514. In the first embodiment, the heights of the neutral axes of both elements were adjusted by differentiating the thicknesses of the second insulating layer 29b and the first insulating layer 26b, but in the fourth embodiment, the heights of the neutral axes of both elements are adjusted by differentiating the shapes of the first diaphragm 264 and the second diaphragm 294.

[0092] As shown in the figure, the first piezoelectric element 514 includes a first lower electrode 51a, a first upper electrode 514b, a first piezoelectric body 514c, and a first vibration plate 264. The first vibration plate 264 is formed by bonding a first elastic layer 264a and a first insulating layer 264b together. The materials and other components of the first piezoelectric element 514 are the same as those in the first embodiment. The second piezoelectric element 724 includes a second lower electrode 724a, a second upper electrode 724b, a second piezoelectric body 724c, and a second vibration plate 294. The second vibration plate 294 is formed by bonding a second elastic layer 294a and an insulating layer 294b together. The materials and other components of the second piezoelectric element 724 are the same as those in the first embodiment.

[0093] In the fourth embodiment, unlike the first to third embodiments, the first vibration plate 264 of the pressure applying unit 70C4 and the second vibration plate 294 of the vibration detecting unit 70B4 are not flat, but rather, as shown in the figure, are convex in the Z1 direction at the position of the first piezoelectric element 514c and concave in the Z1 direction (convex in the Z2 direction) at the position of the second piezoelectric element 724c. Except for this point, the pressure applying unit 70C4 and the vibration detecting unit 70B4 all have substantially the same configuration. In the fourth embodiment, since the first vibration plate 264 and the second vibration plate 294 have the shapes shown in the figure, the neutral axis NA of the second piezoelectric element 724 is lower than the neutral axis NA of the first piezoelectric element 514. As a result, similar to the first embodiment, in the pressure applying unit 70C4, the first piezoelectric element 514 does not deform excessively, and in the vibration detecting unit 70B4, the electromotive force generated in the second piezoelectric element 724 due to the residual vibration received by the second diaphragm 294 from the ink does not become excessive. This makes it possible to simultaneously satisfy the requirements of suppressing the occurrence of failures, etc. of the first piezoelectric element 514 and suppressing damage to wiring, etc. due to the electromotive force generated in the second piezoelectric element 724. As a result, the reliability and lifespan of the liquid ejection head 10 can be improved.

[0094] E. Other Embodiments: (1) In the first to third embodiments described above, the thickness of the insulating layer or second piezoelectric element of the second diaphragm in the pressure applying unit and the vibration detecting unit is made smaller than the thickness of the insulating layer or first piezoelectric element of the first diaphragm, or the thickness of the elastic layer of the second diaphragm is made thicker than the thickness of the elastic layer of the first diaphragm, thereby making the Z-direction position of the neutral axis of the second piezoelectric element of the vibration detecting unit lower than the Z-direction position of the neutral axis of the first piezoelectric element of the pressure applying unit. As a result, in these embodiments, excessive deformation of the first piezoelectric element of the pressure applying unit is prevented, and excessive electromotive force is prevented from being generated in the second piezoelectric element due to residual vibrations that the second diaphragm of the vibration detecting unit receives from the ink. Similar effects can be obtained in the following embodiments.

[0095] 9, 13, and 14, the liquid ejection head 10 of this embodiment will be described using the thicknesses K1 to K3 and J1 to J3 of the various portions. When the ratio of the total thickness (K2+K1) of the first piezoelectric element and the first insulating layer to the thickness K3 of the first elastic layer is defined as a first ratio RK, and the ratio of the total thickness (J2+J1) of the second piezoelectric element and the second insulating layer to the thickness J3 of the second elastic layer is defined as a second ratio RJ, the second ratio RJ is smaller than the first ratio RK as shown in the following formula (4): RJ <RK … (4) Here, RJ=(J2+J1) / J3, RK=(K2+K1) / K3 This makes it possible to simultaneously satisfy the requirements of suppressing the occurrence of failures in the first piezoelectric element and suppressing damage to the wiring and the like due to electromotive force generated in the second piezoelectric element.

[0096] (2) In the first embodiment described above, the thickness of the first insulating layer 26b in the first diaphragm 26 is made different from the thickness of the second insulating layer 29b in the second diaphragm 29, and in the third embodiment, the thickness of the first elastic layer 263a in the first diaphragm 263 is made different from the thickness of the second elastic layer 293a in the second diaphragm 293. In these cases, if the thicknesses of the first piezoelectric bodies 51c, 513c and the second piezoelectric bodies 72c, 723c are substantially the same, it is only necessary to make the ratio ja / jb of the thickness ja of the second elastic layer 29a, 293a to the thickness jb of the second insulating layer 29b, 293b in the vibration detection units 70B, 70B3 larger than the ratio ka / kb of the thickness ka of the first elastic layer 26a, 263a to the thickness kb of the first insulating layer 26b, 263b in the pressure application units 70C, 70C3, without needing to determine the position of the neutral axis NS. This makes it possible to simultaneously satisfy the requirements of suppressing the occurrence of failures in the first piezoelectric element and suppressing damage to the wiring and the like due to electromotive force generated in the second piezoelectric element.

[0097] Furthermore, in the second embodiment described above, the thickness of the first piezoelectric body 512c in the first piezoelectric element 512 is made different from the thickness of the second piezoelectric body 722c in the second piezoelectric element 722. In this case, if the thicknesses of the first insulating layer 262b and the second insulating layer 292b and the thicknesses of the first elastic layers 262a and 292a are substantially the same, it is not necessary to determine the position of the neutral axis NS; all that is necessary is to make the ratio jc / jd of the thickness jc of the second piezoelectric body 722c to the thickness jd of the second diaphragm 292 in the vibration detection unit 70B2 smaller than the ratio kc / kd of the thickness kc of the first piezoelectric body 512c to the thickness kd of the first diaphragm 262 in the pressure application unit 70C2. This makes it possible to simultaneously satisfy the requirements of suppressing the occurrence of failures, etc. of the first piezoelectric element and suppressing damage to wiring, etc. due to electromotive force generated in the second piezoelectric element.

[0098] (3) In the liquid ejection head 10 of the first embodiment, the thickness K1 of the first insulating layer 26b of the first diaphragm 26 and the thickness J1 of the second insulating layer 29b of the second diaphragm 29 are different, but they are manufactured by forming them as a single insulating layer having a thickness of J1 or more and then thinning them to the thicknesses K1 and J1 by a method such as etching. Alternatively, the first insulating layer 26b and the second insulating layer 29b may be formed as separate layers having the respective thicknesses K1 and J1 and then bonded together, or may be left separate and have the joints sealed before being sandwiched between the pressure chamber substrate 25 and the sealing plate 27. The first elastic layer 263a and the second elastic layer 293a of the third embodiment can be manufactured in a similar manner.

[0099] (4) In the first to fourth embodiments, the thickness and shape of each layer were different. However, the height of the neutral axis NA may be different by making the thickness and shape of each layer the same but varying the material or physical properties. For example, if the first insulating layer 26b is made of zirconium dioxide (ZrO2), changing the sintering temperature or sintering time of the zirconium dioxide to make its hardness higher than that of the second insulating layer 29b will be equivalent to the thickness of the first insulating layer 26b being thicker than the second insulating layer 29b, even if the two layers have the same thickness, and the height of the neutral axis NA of the second piezoelectric element can be lowered. Alternatively, the hardness may be similarly changed by changing the binder or additive to achieve the desired characteristics.

[0100] (5) As shown in Fig. 8, the above configuration may further include a wiring board 61 electrically connected to the outside of the liquid ejection head 10, for example, to the control unit 20 of the liquid ejection device, a first wiring section 54 electrically connecting the first piezoelectric element 51 to the wiring board 61, and a second wiring section 74 electrically connecting the second piezoelectric element 72 to the wiring board 61. In this way, wiring to the first piezoelectric element 51 and wiring to the second piezoelectric element 72 can be performed using a single wiring board 61.

[0101] (6) In this configuration, the wiring substrate 61 may be located between the first piezoelectric element 51 and the second piezoelectric element 72 in the extension direction of the pressure chamber CC. In the first embodiment, the wiring substrate 61 is provided in a wiring lead-in portion RC provided between the pressure chamber CC and the vibration detection chamber DB, thereby achieving this configuration. In this case, the first wiring portion 54 extending from the wiring substrate 61 to the first piezoelectric element 51 and the second wiring portion 74 extending from the wiring substrate 61 to the second piezoelectric element 72 are in opposite directions across the wiring substrate 61, making it difficult for crosstalk to occur between them. This prevents or suppresses the generation of induced noise in the second wiring portion 74 when a drive voltage for driving the first piezoelectric element 51 is applied to the first wiring portion 54. This improves the accuracy of residual vibration detection by the vibration detection unit 70B.

[0102] (7) The above configuration may further include a third piezoelectric element 73 that is not electrically connected to the wiring substrate 61, and an absorption chamber (damper chamber) DA that absorbs residual vibrations of the pressure applied in the pressure chamber CC using the third piezoelectric element 73. This makes it difficult for residual vibrations to propagate upstream from the pressure chamber CC, thereby suppressing pressure fluctuations on the upstream side. As a result, pressure fluctuations of ink flowing from the upstream side toward the pressure chamber CC can be suppressed, and the pressure applied to the nozzle N in the pressurizing unit 70C can be controlled with high precision. It is preferable that the neutral axis NA of such a third piezoelectric element 73 be at a height intermediate between the height (first height) of the neutral axis NA of the first piezoelectric element 51 and the height (second height) of the neutral axis NA of the second piezoelectric element 72.

[0103] (8) In the above configuration, the third piezoelectric element 73 may include a third piezoelectric body 73c, a third upper electrode 73b provided on the third piezoelectric body 73c, a third lower electrode 73a provided below the third piezoelectric body 73c, and a third diaphragm (compliance substrate) 23 that is a third diaphragm provided below the third lower electrode 73a. This allows the vibration absorbing unit 70A to be configured with the same components and have the same assembly relationship as the vibration detecting unit 70B and the pressure applying unit 70C, thereby facilitating manufacturing and maintenance.

[0104] Furthermore, in the liquid ejection head 10 of each embodiment, the third piezoelectric element 73 is provided on the third diaphragm 23, and therefore the vibration of the ink in the damper chamber DA can be absorbed by deforming the third piezoelectric element 73 in accordance with the deformation of the third diaphragm 23. Furthermore, by providing the third piezoelectric element 73 on the third diaphragm 23, the third diaphragm 23 can be reinforced.

[0105] (9) In the above configuration, the second piezoelectric element 72, wiring board 61, first piezoelectric element 51, and third piezoelectric element 73 may be arranged in this order along the extension direction of the pressure chamber CC (the X1 direction in each embodiment). This not only provides the effect of reducing crosstalk described in (6) above, but also allows the first piezoelectric element 51 and the third piezoelectric element 73 to be arranged close to each other, thereby enabling the pressure generated in the pressure chamber CC by the vibration absorbing section 70A to be efficiently absorbed, thereby providing superior effects and advantages in terms of electrical wiring and absorption of pressure fluctuations compared to other arrangements.

[0106] (10) The above configuration may further include a common liquid chamber RA, which is a supply reservoir for supplying liquid to the pressure chamber CC, and a common liquid chamber RB, which is a discharge reservoir for discharging liquid from the pressure chamber CC, and the liquid may flow in the order of the common liquid chamber RA, absorption chamber DA, pressure chamber CC, vibration detection chamber DB, which is a detection chamber, and common liquid chamber RB, which is a discharge reservoir. This eliminates unnecessary branches and stagnation points in the liquid flow, making the liquid flow smooth. The nozzle N may be provided between the pressure chamber CC and the vibration detection chamber DB.

[0107] (11) The above configuration may further include a common liquid chamber RA, which is a supply reservoir for supplying liquid to the pressure chamber CC, and a common liquid chamber RB, which is a discharge reservoir for discharging liquid from the pressure chamber CC, so that the liquid flows in the order of the common liquid chamber RA, the vibration detection chamber DB, which is a detection chamber, the pressure chamber CC, the absorption chamber DA, and the common liquid chamber RB. This allows pressure fluctuations propagating downstream of the liquid flow from the pressure chamber CC to be quickly absorbed.

[0108] (12) A liquid ejection device 11 can be easily realized by using the various liquid ejection heads 10 described above and combining them with a control unit 20 that controls the ejection operation from the liquid ejection heads 10. FIG. 16 shows an example of the configuration of the liquid ejection device 11 as a printer that ejects ink to perform printing. The liquid ejection device 11 receives image data, etc., from an image output device (not shown) and prints the image data using the liquid ejection head 10 on printing paper P, which serves as a printing medium, attached to a platen 17. The liquid ejection device 11 is configured as a line printer. The platen 17 is transported by a paper transport mechanism 15. The ECU 12, which controls the entire liquid ejection device 11, ejects ink from the liquid ejection head 10 while transporting the printing paper P via the paper transport mechanism 15 and the control unit 20, thereby printing an image, etc., on the printing paper P. Other components constituting the printer are well known, and therefore illustrations and descriptions thereof are omitted. Such a liquid ejection device can handle various liquids, such as ink, water, alcohol, liquid fuel, and chemicals.

[0109] In each of the above embodiments, some of the configurations implemented by hardware may be replaced with software. At least a portion of the configurations implemented by software may also be implemented by a discrete circuit configuration. Furthermore, when some or all of the functions of the present disclosure are implemented by software, the software (computer program) may be provided in a form stored on a computer-readable recording medium. The term "computer-readable recording medium" is not limited to portable recording media such as floppy disks and CD-ROMs, but also includes internal storage devices within a computer, such as various RAMs and ROMs, and external storage devices fixed to a computer, such as a hard disk. In other words, the term "computer-readable recording medium" has a broad meaning, including any recording medium capable of fixing data packets, not just temporarily.

[0110] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0111] 10...liquid ejection head, 11...liquid ejection device, 18...circulation mechanism, 20...controller, 21...nozzle substrate, 23...third diaphragm (compliance substrate), 23a...third elastic layer, 23b...third insulating layer, 24...communicating plate, 25...pressure chamber substrate, 26...first diaphragm, 26a...first elastic layer, 26b...first insulating layer, 27...sealing plate, 27a...opening, 28...case, 29...second diaphragm, 29a...second elastic layer, 29b...second insulating layer, 40...flow path, 41A...supply flow path, 41B...discharge flow path, 42A...supply port, 42B...discharge port, 43A, 43B, 44A, 44B, 45A, 45B, 46A, 46B...flow paths, 47A to 47C...communicating flow paths, 51...first piezoelectric element , 51a...first lower electrode, 51b...first upper electrode, 51c...first piezoelectric element, 54...first wiring portion, 54a...electrode layer, 54b...first adhesion layer, 54c...first wiring layer, 55...VBS wiring, 59...insulating adhesive layer, 61...flexible wiring substrate, 62...control circuit, 70A...vibration absorbing portion, 70B, 70B2, 70B3, 70B4...vibration detecting portion, 70C, 70C2, 70C3, 70C4...pressure portion, 72...second piezoelectric element, 72a...second lower electrode, 72b...second upper electrode, 72c...second piezoelectric element, 73...third piezoelectric element, 73a...third lower electrode, 73b...third upper electrode, 73c...third piezoelectric element, 74...second wiring portion, 77A, 77B...compliance substrate

Claims

1. A nozzle; a first piezoelectric element; a pressure chamber that applies pressure to the liquid to eject the liquid from the nozzle when the first piezoelectric element is driven; A second piezoelectric element; a detection chamber that detects residual vibration of the pressure of the liquid applied in the pressure chamber by the second piezoelectric element, the first piezoelectric element has a first piezoelectric body, a first upper electrode provided on the first piezoelectric body, a first lower electrode provided below the first piezoelectric body, and a first vibration plate provided below the first lower electrode; the second piezoelectric element has a second piezoelectric body, a second upper electrode provided on the second piezoelectric body, a second lower electrode provided below the second piezoelectric body, and a second vibration plate provided below the second lower electrode, A liquid ejection head, wherein a neutral axis of the second piezoelectric element is located below a neutral axis of the first piezoelectric element.

2. the first diaphragm has a first insulating layer and a first elastic layer provided below the first insulating layer, the second diaphragm has a second insulating layer and a second elastic layer provided below the second insulating layer, a ratio of the total thickness of the first piezoelectric body and the first insulating layer to the thickness of the first elastic layer is a first ratio; When the ratio of the total thickness of the second piezoelectric body and the second insulating layer to the thickness of the second elastic layer is defined as a second ratio, The second ratio is smaller than the first ratio. The liquid ejection head according to claim 1 .

3. A nozzle; a first piezoelectric element; a pressure chamber that applies pressure to eject liquid from the nozzle when the first piezoelectric element is driven; A second piezoelectric element; a detection chamber that detects residual vibration of the pressure applied in the pressure chamber by the second piezoelectric element, the first piezoelectric element has a first piezoelectric body, a first upper electrode provided on the first piezoelectric body, a first lower electrode provided below the first piezoelectric body, and a first vibration plate provided below the first lower electrode; the second piezoelectric element has a second piezoelectric body, a second upper electrode provided on the second piezoelectric body, a second lower electrode provided below the second piezoelectric body, and a second vibration plate provided below the second lower electrode, the first diaphragm has a first insulating layer and a first elastic layer provided below the first insulating layer, the second diaphragm has a second insulating layer and a second elastic layer provided below the second insulating layer, a ratio of the total thickness of the first piezoelectric body and the first insulating layer to the thickness of the first elastic layer is a first ratio; When the ratio of the total thickness of the second piezoelectric body and the second insulating layer to the thickness of the second elastic layer is defined as a second ratio, The second ratio is smaller than the first ratio. Liquid ejection head.

4. 4. The liquid ejection head according to claim 2, wherein the second insulating layer is thinner than the first insulating layer.

5. 4. The liquid ejection head according to claim 2, wherein the second piezoelectric element is thinner than the first piezoelectric element.

6. 4. The liquid ejection head according to claim 2, wherein the second elastic layer is thicker than the first elastic layer.

7. each of the first piezoelectric body, the second piezoelectric body, the first insulating layer, and the second insulating layer has a tensile stress; 4. The liquid ejection head according to claim 2, wherein the first elastic layer and the second elastic layer each have a compressive stress.

8. a wiring board electrically connected to the outside of the liquid ejection head; a first wiring portion that electrically connects the first piezoelectric element and the wiring substrate; 4. The liquid ejection head according to claim 2, further comprising a second wiring portion that electrically connects the second piezoelectric element and the wiring substrate.

9. The liquid ejection head according to claim 8 , wherein the wiring substrate is located between the first piezoelectric element and the second piezoelectric element in the extension direction of the pressure chamber.

10. a third piezoelectric element that is not electrically connected to the wiring board; 9. The liquid ejection head according to claim 8, further comprising an absorption chamber that absorbs residual vibrations of the pressure applied in the pressure chamber by the third piezoelectric element.

11. A liquid ejection head as described in claim 10, wherein the third piezoelectric element has a third piezoelectric body, a third upper electrode provided on the third piezoelectric body, a third lower electrode provided below the third piezoelectric body, and a third vibration plate provided below the third lower electrode.

12. The liquid ejection head according to claim 11 , wherein the neutral axis of the third piezoelectric element is located below the neutral axis of the first piezoelectric element and above the neutral axis of the second piezoelectric element.

13. The liquid ejection head according to claim 10 , wherein the second piezoelectric element, the wiring substrate, the first piezoelectric element, and the third piezoelectric element are arranged in this order in the extension direction of the pressure chamber.

14. a supply reservoir for supplying liquid to the pressure chamber; a drain reservoir for draining liquid from the pressure chamber; The liquid ejection head according to claim 10 , wherein the liquid flows in the order of the supply reservoir, the absorption chamber, the pressure chamber, the detection chamber, and the discharge reservoir.

15. a supply reservoir for supplying liquid to the pressure chamber; a drain reservoir for draining liquid from the pressure chamber; The liquid flows in the order of the supply reservoir, the detection chamber, the pressure chamber, the absorption chamber, and the discharge reservoir. The liquid ejection head according to claim 10.

16. The liquid ejection head according to any one of claims 1 to 3, a control unit for controlling a discharge operation from the liquid discharge head, Liquid discharge device.

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