Liquid ejection head and liquid ejection apparatus

Abstract

To provide a liquid ejection head and a liquid ejection apparatus capable of improving accuracy of fluid resistance.SOLUTION: According to one embodiment, the liquid ejection head includes a plurality of flow path substrates. The plurality of flow path substrates are each provided with an opening for forming a flow path and are stacked in a stacking direction. At least one of the flow path substrates includes a slit. A flow path formed by the slit has a flow path cross section in which a dimension in a longitudinal direction orthogonal to an extending direction of the slit and the stacking direction is three times or more a dimension in a short side direction along the stacking direction of the flow path substrates.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a liquid ejection head and a liquid ejection device.

Background Art

[0002] In a liquid ejection head such as an inkjet head, a diaphragm is deformed by using an actuator made of a piezoelectric material such as PZT (lead zirconate titanate), and a pressure chamber facing the diaphragm is deformed to eject ink from a nozzle communicating with the pressure chamber. The liquid ejection head includes a plurality of actuators joined to the diaphragm, and a flow path portion that forms a plurality of pressure chambers facing the diaphragm and a flow path having a larger fluid resistance than the pressure chambers communicating with the pressure chambers. In the flow path portion of such an inkjet head, there is one in which a plurality of flow path plates having slits of a predetermined shape are laminated to form the flow path portion. The accuracy of the fluid resistance portion in the flow path portion greatly affects the performance. That is, if the cross-sectional area is large, the meniscus vibration of the nozzle portion after ejection becomes large, and if it is small, the refilling becomes slow, both of which cause hindrance to high-speed followability. Particularly in the circulation method in which ink circulates in the pressure chamber, if the fluid resistance between the upstream and downstream varies, the negative pressure in the pressure chamber varies, which causes variation in ejection performance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem to be solved by the present invention is to provide a liquid ejection head and a liquid ejection device capable of improving the accuracy of fluid resistance.

Means for Solving the Problems

[0005] A liquid ejection head according to one embodiment includes a plurality of flow path substrates. The plurality of flow path substrates are laminated in a stacking direction while having openings for forming flow paths. At least one of the flow path substrates has a slit. The flow path formed by the slit has a flow path cross section in which a longitudinal dimension orthogonal to the extending direction of the slit and the stacking direction is three times or more the short-side dimension along the stacking direction of the flow path substrate.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0007] Next, the inkjet head 1 which is a liquid ejection head according to the first embodiment and the inkjet recording apparatus 100 which is a liquid ejection apparatus will be described with reference to FIGS. 1 to 8. FIG. 1 is a cross-sectional view showing a partial configuration of the inkjet head according to the first embodiment, and FIG. 2 is a cross-sectional view showing a partial configuration of the inkjet head. FIG. 3 is a cross-sectional view showing a partial configuration of the flow path substrates 401 and 402 of the inkjet head, and FIG. 4 is a cross-sectional view showing a partial configuration of the flow path substrate 403. FIG. 5 is a table showing the pipe friction coefficient ratio of a rectangular pipe, and FIG. 6 is a graph showing the relationship between the pipe friction coefficient ratio and the aspect ratio of a rectangular pipe. FIG. 7 is a graph showing the correspondence between the longitudinal and lateral dimensions of the flow path of the inkjet head according to the first embodiment and the fluid resistance ratio. FIG. 8 is an explanatory view showing a schematic configuration of the inkjet recording apparatus. Arrows X, Y, and Z in the figures respectively indicate three mutually orthogonal directions. In the present embodiment, X is the parallel direction of the nozzles 51 and the pressure chambers 31, Y is the extending direction, and Z is along the axial direction of the nozzles. For the sake of explanation in each figure, the configuration is appropriately enlarged, reduced, or omitted.

[0008] As shown in FIGS. 1 and 2, the inkjet head 1 includes an actuator unit 20, a diaphragm 30, a flow path unit 40 as a flow path unit having a plurality of flow path substrates 401, 402, and 403, a nozzle plate 50 as a nozzle unit having a plurality of nozzles 51, a frame unit 45 as a structural unit, and a drive circuit 70. As an example, in the present embodiment, the inkjet head 1 shows an example in which the stacking direction of the piezoelectric layer 211, the vibration direction of the piezoelectric element 21, and the vibration direction of the diaphragm 30 are respectively along the Z direction. In the present embodiment, on the back side of the nozzle plate 50, a flow path structure unit that forms an ink flow path 35 in the head 1 is configured by the diaphragm 30 and the flow path unit 40. The inkjet head 1 is a circulation type that circulates liquid in a predetermined flow path.

[0009] The actuator unit 20 is composed of, for example, piezoelectric members, and includes a plurality of driving piezoelectric elements 21 as actuators arranged alternately along the column direction, a plurality of non-driving piezoelectric elements 22, and a piezoelectric structure unit 26 that integrally connects these plurality of piezoelectric elements 21 and 22. In the present embodiment, a nozzle 51 is provided at the center of the extending direction of the actuator unit 20, and the actuator unit 20 has a symmetric structure with one side and the other side centered on the nozzle 51. For example, the actuator unit 20 is joined to a rectangular base. Note that the actuator unit 20 may be individually divided such that the piezoelectric structure unit 26 does not connect between the plurality of driving piezoelectric elements 21 and non-driving piezoelectric elements 22 continuously.

[0010] In the actuator unit 20, the plurality of driving piezoelectric elements 21 and the plurality of non-driving piezoelectric elements 22 are arranged in parallel in the row direction at a certain interval. As an example, both the plurality of driving piezoelectric elements 21 and the plurality of non-driving piezoelectric elements 22 are configured in the shape of a rectangular parallelepiped column with the same outer shape. The actuator unit 20 is divided into a plurality by a plurality of groove portions 23, and the plurality of driving piezoelectric elements 21 and non-driving piezoelectric elements 22 are arranged in the column direction at the same pitch by groove portions 23 having, for example, the same width. For example, the number of driving piezoelectric elements 21 arranged in the column direction in the actuator unit 20 corresponds to the number of nozzles 51 and pressure chambers 31.

[0011] For example, each of the plurality of driving piezoelectric elements 21 and the plurality of non-driving piezoelectric elements 22 is configured in a rectangular shape such that, in a plan view seen from the Z direction, which is the axial direction of the nozzle 51, the short side direction is along the column direction of the element row, and the long side direction is along the extending direction orthogonal to the column direction and the Z direction.

[0012] The driving piezoelectric elements 21 are arranged at positions respectively facing a plurality of pressure chambers 31 formed in the flow path portion 40 in the Z direction. As an example, the center positions of the driving piezoelectric elements 21 in the column direction and the extending direction and the center positions of the pressure chambers 31 in the column direction and the extending direction are arranged side by side in the Z direction.

[0013] The non-driven piezoelectric elements 22 are arranged at positions facing the partition walls 42 formed in the flow path portion 40 in the Z direction, respectively. As an example, the central positions of the non-driven piezoelectric elements 22 in the column direction and the extending direction are arranged side by side in the Z direction with the central positions of the partition walls 42 in the column direction and the extending direction.

[0014] For example, the laminated piezoelectric member constituting the actuator portion 20 is formed by laminating and sintering sheet-like piezoelectric materials. The actuator portion 20 forms a plurality of piezoelectric elements formed in a rectangular columnar shape at predetermined intervals by dicing the laminated piezoelectric member from one end face to form a groove portion 23. Then, electrodes and the like are provided on the formed plurality of columnar elements, and a plurality of driving piezoelectric elements 21 and a plurality of non-driven piezoelectric elements 22 arranged alternately are formed. The plurality of driving piezoelectric elements 21 and the plurality of non-driven piezoelectric elements 22 are arranged alternately in parallel with the groove portion 23 interposed therebetween in the column direction.

[0015] The piezoelectric members constituting the driving piezoelectric element 21 and the non-driven piezoelectric element 22 are, for example, laminated piezoelectric bodies. The driving piezoelectric element 21 and the non-driven piezoelectric element 22 include a plurality of laminated piezoelectric layers 211 and internal electrodes 221 and 222 formed on the main surfaces of the respective piezoelectric layers 211. As an example, the driving piezoelectric element 21 and the non-driven piezoelectric element 22 have the same laminated structure. The driving piezoelectric element 21 and the non-driven piezoelectric element 22 are provided with external electrodes 223 and 224 formed on the surface.

[0016] The piezoelectric layer 211 is composed of a piezoelectric material such as a PZT (lead zirconate titanate) - based material or a lead-free KNN (sodium potassium niobate) - based material. The plurality of piezoelectric layers 211 are laminated with the thickness direction along the lamination direction. For example, in the present embodiment, the thickness direction and the lamination direction of the piezoelectric layer 211 are arranged along the vibration direction (Z direction).

[0017] The internal electrodes 221 and 222 are conductive films formed of a sinterable conductive material such as silver palladium into a predetermined shape. The internal electrodes 221 and 222 are formed in a predetermined region on the main surface of each piezoelectric layer 211. The internal electrodes 221 and 222 have different polarities. For example, one of the internal electrodes 221 is formed in a region that reaches one end of the piezoelectric layer 211 but does not reach the other end of the piezoelectric layer 211 in the extending direction (Y direction), which is a direction orthogonal to both the column direction (X direction), which is the arrangement direction of the plurality of drive piezoelectric elements 21 and the plurality of non-drive piezoelectric elements 22, and the vibration direction (Z direction). The other internal electrode 222 is formed in a region that does not reach one end of the piezoelectric layer 211 but reaches the other end of the piezoelectric layer 211 in the extending direction. The internal electrodes 221 and 222 are respectively connected to external electrodes 223 and 224 formed on the side surfaces of the piezoelectric elements 21 and 22.

[0018] Further, the laminated piezoelectric members constituting the drive piezoelectric elements 21 and the non-drive piezoelectric elements 22 may further include dummy layers on either or both of the ends on the nozzle plate 50 side or the opposite side. For example, the dummy layer is made of the same material as the piezoelectric layer 211, has electrodes only on one side, and does not deform because no electric field is applied. For example, the dummy layer does not function as a piezoelectric body, fixes the actuator portion 20 to the base, or serves as a polishing allowance for polishing to achieve accuracy during or after assembly.

[0019] The external electrodes 223 and 224 are formed on the surfaces of the plurality of drive piezoelectric elements 21 and the plurality of non-drive piezoelectric elements 22, and are configured by collecting the ends of the internal electrodes 221 and 222. For example, the external electrodes 223 and 224 are respectively formed on one end face and the other end face of the piezoelectric layer 211 in the extending direction. The external electrodes 223 and 224 are formed of Ni, Cr, Au, etc. by a method such as plating or sputtering. The external electrode 223 and the external electrode 224 have different polarities. The external electrode 223 and the external electrode 224 are respectively arranged on different side faces of the plurality of drive piezoelectric elements 21 and the plurality of non-drive piezoelectric elements 22. Note that the external electrodes 223 and 224 may be routed in different regions of the same side face of the plurality of drive piezoelectric elements 21 and the plurality of non-drive piezoelectric elements 22.

[0020] In this embodiment, as an example, the external electrode 223 is an individual electrode and the external electrode 224 is a common electrode. The external electrodes 223, which are the individual electrodes of the plurality of driving piezoelectric elements 21 and the plurality of non-driving piezoelectric elements 22, have electrode layers divided by the groove portions 23 and are arranged independently of each other. The external electrode 224 serving as a common electrode has electrode layers connected to each other, for example, on the side surface of the piezoelectric structure portion 26 and is grounded, for example. The external electrodes 223 and 224 are connected to the driving circuit 70 via a wiring film, for example. For example, the individual external electrodes 223 and 224 are connected to the control unit 150 via the driving IC 72 of the driving circuit 70 and are configured to be drive-controllable. Note that the arrangement of the common electrode and the individual electrodes may be reversed.

[0021] Also, the vibration directions of the piezoelectric elements 21 and 22 are along the stacking direction, and by applying an electric field, they are displaced in the d33 direction. Each of the piezoelectric elements 21 and 22 has three or more layers of the piezoelectric layer 211 and the internal electrodes 221 and 222. As an example, each of the piezoelectric elements 21 and 22 has three or more and 50 or less layers, the thickness of each layer is 10 μm or more and 40 μm or less, and the product of the thickness and the total number of stacked layers is less than 1000 μm.

[0022] In the inkjet head 1, when a voltage is applied to the internal electrodes 221 and 222 via the external electrodes 223 and 224, the driving piezoelectric element 21 vibrates. In this embodiment, the driving piezoelectric element 21 vibrates longitudinally along the stacking direction of the piezoelectric layer 211. The longitudinal vibration mentioned here is, for example, "vibration in the thickness direction defined by the piezoelectric constant d33". The driving piezoelectric element 21 displaces the diaphragm 30 and deforms the pressure chamber 31 by longitudinal vibration.

[0023] The diaphragm 30 extends along a plane orthogonal to the Z direction which is the vibration direction, and is joined to one side of the piezoelectric layer 211 of the plurality of piezoelectric elements 21 and 22 in the vibration direction, that is, the surface on the nozzle plate 50 side. In the Z direction which is the vibration direction, the diaphragm 30 faces the plurality of nozzles 51 through the pressure chamber 31. The diaphragm 30 is configured to be deformable, for example. The diaphragm 30 is joined to the drive piezoelectric element 21 and the non-drive piezoelectric element 22 of the actuator unit 20, and the frame portion 45. For example, the diaphragm 30 has a vibration region 301 facing the piezoelectric elements 21 and 22, and a support region 302 facing the frame portion 45. The diaphragm 30 is provided between the flow path substrate 401 and the actuator unit 20 in the vibration direction. The diaphragm 30 is arranged to overlap the plurality of flow path substrates 401, 402, and 403, and constitutes a part of the ink flow path 35.

[0024] The vibration region 301 is, for example, in a flat plate shape arranged such that the thickness direction is the vibration direction of the piezoelectric layer 211. The plane direction of the diaphragm 30 extends in the arrangement direction of the plurality of drive piezoelectric elements 21 and the plurality of non-drive piezoelectric elements 22. The diaphragm 30 is, for example, a metal plate. The diaphragm 30 has a plurality of vibration sites facing each pressure chamber 31 and displaceable individually. The plurality of vibration sites of the diaphragm 30 are integrally formed continuously.

[0025] As an example, the diaphragm 30 is composed of nickel or a SUS plate, and the thickness dimension along the vibration direction is configured to be about 5 μm to 15 μm. Note that in the vibration region 301, folds or steps may be formed between the vibration sites and the adjacent sites or between the vibration sites adjacent to each other so that the plurality of vibration sites are easily displaceable. The vibration region 301 is deformed by the displacement of the portion facing the drive piezoelectric element 21 due to the elongation and compression of the drive piezoelectric element 21. For example, since the diaphragm 30 is very thin and requires a complicated shape, it is formed by an electroforming method or the like. The diaphragm 30 is joined to the upper end surface of the actuator unit 20 by adhesion or the like.

[0026] The support area 302 is a plate-like member disposed between the frame portion 45 and the flow path substrate 401. The diaphragm 30 has a symmetrical structure with one side and the other side in the Y direction centered on the nozzle 51.

[0027] The flow path portion 40 is joined to one side of the diaphragm 30.

[0028] The flow path portion 40 includes a plurality of flat plate-like flow path substrates 401, 402, 403 that are laminated. As an example, the flow path portion 40 includes the flow path substrate 401 and the flow path substrate 402 as the first flow path substrates having the same shape, and the flow path substrate 403 as the second flow path substrate, which are laminated. For example, according to the viscosity of the ink, the volume to be discharged, etc., a plurality of flow path substrates 401, 402, 403, the nozzle plate 50, and the diaphragm 30 are combined and joined to form a desired ink flow path 35. The plurality of flow path substrates 401, 402, 403 are arranged overlappingly in the lamination direction, and a plurality of pressure chambers 31 communicating with the plurality of nozzles 51, a plurality of throttle flow paths 34 as individual flow paths, and individual liquid chambers 33 communicating with the common chamber 32 are formed by openings and grooves formed in each of the flow path substrates 401, 402, 403, constituting a predetermined ink flow path 35.

[0029] The flow path portion 40 is disposed between the nozzle plate 50 and the diaphragm 30. The flow path portion 40 has a plurality of flow path substrates 401, 402, 403 laminated and joined to each other, thereby forming, inside, a plurality of pressure chambers 31, a plurality of individual liquid chambers 33 communicating with the common chamber 32, and throttle flow paths 34 as a plurality of resistance flow paths from the individual liquid chambers 33 to the pressure chambers 31, to form a predetermined ink flow path 35 (liquid chamber). In other words, the flow path portion 40 is surrounded by a peripheral wall portion 41 that forms an ink flow path 35 (liquid chamber) composed of a plurality of pressure chambers 31, a plurality of throttle flow paths 34, and individual liquid chambers 33 by a plurality of laminated flow path substrates 401, 402, 403, a plurality of partition wall portions 42 that separate the rows of the plurality of pressure chambers 31, and side wall portions 43 that separate the plurality of throttle flow paths 34.

[0030] As shown in FIGS. 1 to 4, the flow path substrate 401, which is the first flow path substrate, is joined to the diaphragm 30. The flow path substrate 401 is a plate-like member having the same shape as the diaphragm 30, and is made of a metal material including SUS430 as an example, or a resin material such as silicon. In FIGS. 3 and 4, a region corresponding to three rows of the ink flow paths 35 formed in a plurality of rows in the parallel direction is shown.

[0031] The flow path substrate 401 has a first opening 4011 that forms a part of the pressure chamber 31 and a second opening 4012 that constitutes a part of the individual liquid chamber 33. For example, the first opening 4011 is disposed at the center in the extending direction in which the ink flow path 35 extends, and the second openings 4012 are respectively disposed at both ends. In the arrangement direction, the openings 4011 and 4012 are arranged in a plurality of rows corresponding to the number of arrays of the nozzles 51, respectively. A beam-like portion 461 is formed between the openings 4011 adjacent in the arrangement direction, and a beam-like portion 462 is formed between the openings 4012 adjacent in the arrangement direction. The beam-like portions 461 and 462 have the same length as the lengths of the openings 4011 and 4012, respectively.

[0032] The flow path substrate 402, which is the second flow path substrate, is laminated on the flow path substrate 401 and joined to the flow path substrate 401. The flow path substrate 402 is a plate-like member having the same outer shape as the diaphragm 30, and is made of a metal material including SUS430 as an example, or a resin material such as silicon. The flow path substrate 402 has an elongated hole portion 4024 integrally having a first opening 4021 that forms a part of the pressure chamber 31, a second opening 4022 that constitutes a part of the individual liquid chamber 33, and a slit 4023 that communicates the first opening 4021 and the second opening 4022 and constitutes a throttle flow path 34 that is an individual flow path. For example, the first opening 4021 is disposed at the center in the extending direction in which the ink flow path 35 extends, the second openings 4022 are respectively disposed at both ends, and these are continuous by the slit 4023 to form an elongated groove-shaped hole portion 4024.

[0033] The hole portions 4024 are arranged in a plurality of rows in the arrangement direction, and a beam-like portion 463 is formed between the hole portions 4024 adjacent in the arrangement direction. The beam-like portion 463 has the same length as the length of the hole portion 4024.

[0034] That is, the flow path substrate 402 has a long hole portion 4024 whose opening length in the extending direction is longer than that of the other flow path substrates, namely the flow path substrate 401 and the flow path substrate 403. For example, the long hole portion 4024 of the flow path substrate 402 is a slit that spans the entire length of the ink flow path 35 in one direction, and extends from one end to the other end of the ink flow path 35 in the extending direction (Y direction).

[0035] The thickness dimension HA of the second flow path substrate 402 is 1 / 3 or less of the width dimension WA of the slit 4023 formed in the second flow path substrate 402. In this embodiment, the flow path cross section of the throttle flow path 34 that is orthogonal to the extending direction that is the flow direction has the width direction of the slit 4023 configured to be longer than the thickness direction. Therefore, the longitudinal direction of the flow path cross section of the throttle flow path 34 is the width direction of the slit 4023, and the short direction of the flow path cross section is the thickness direction of the substrate 402. In this embodiment, the width dimension WA in the width direction of the slit 4023, which is the longitudinal direction of the flow path cross section of the slit 4023 that is a part of the opening formed in the second flow path substrate 402, is 3 times or more the thickness dimension HA of the flow path substrate 402 in the short direction of the flow path cross section.

[0036] For example, the second flow path substrate 402 is configured to have a thickness of 20 μm to 100 μm. For example, in the case of 300 dpi, the pitch of the arrangement of the pressure chambers 31 in the parallel direction is 169 μm, the width of the pressure chambers 31 is about 100 μm to 150 μm, and for example, the width of the beam-like portion 463 is about 20 μm to 70 μm.

[0037] The flow path substrate 403 serving as the first flow path substrate is joined to the flow path substrate 402. The flow path substrate 403 is a plate-shaped member having the same shape as the flow path substrate 401, and is made of a metal material including SUS430 as an example, or a resin material such as silicon. The flow path substrate 403 has a first opening 4031 that forms part of the pressure chamber 31 and a second opening 4032 that constitutes part of the individual liquid chamber 33. For example, the first opening 4031 is disposed at the center in the extending direction in which the ink flow path 35 extends, and the second openings 4032 are disposed at both ends respectively. In the arrangement direction, a plurality of each of the openings 4031 and 4032 are arranged, and a beam-shaped portion 461 is formed between the openings 4021 adjacent in the arrangement direction, and a beam-shaped portion 462 is formed between the openings 4012 adjacent in the arrangement direction. The beam-shaped portions 461 and 462 have the same length as the lengths of the openings 4021 and 4022 respectively in the longitudinal direction.

[0038] For example, the flow path substrates 401 and 403 which are the first flow path substrates are configured to have a thickness of 20 μm to 100 μm. For example, in the case of 300 dpi, the pitch of the arrangement of the pressure chambers 31 in the parallel direction is 169 μm, the width of the pressure chamber 31 is about 100 μm to 150 μm, and the width of the beam-shaped portion 461 is about 20 μm to 70 μm.

[0039] For example, the flow path substrates 401, 402, and 403 are created by forming openings at predetermined locations on a metal plate processed into a plate shape of a predetermined thickness with SUS or the like by an etching process.

[0040] In the flow path portion 40, a plurality of pressure chambers 31 are formed by the first openings 4011, 4021, and 4031 of the plurality of flow path substrates 401, 402, and 403 that are arranged and communicate in the stacking direction. The plurality of pressure chambers 31 are spaces formed on one side of the vibration region 301 of the diaphragm 30, and each pressure chamber 31 communicates with a nozzle 51 formed in a nozzle plate 50 (nozzle member). Also, the opposite side of the nozzle plate 50 is blocked by the diaphragm 30.

[0041] The plurality of pressure chambers 31 communicate with the common chamber 32 through the throttle flow paths 34 and the individual liquid chambers 33 via the openings 303. The pressure chambers 31 hold the liquid supplied from the common chamber 32, and by deforming due to the vibration of the diaphragm 30 that forms part of the pressure chamber 31, the liquid is discharged from the nozzles 51.

[0042] In the flow path portion 40, the individual liquid chambers 33 on both sides of the pressure chamber in the Y direction are formed by the second openings 4012, 4022, and 4032 of the plurality of flow path substrates 401, 402, and 403 that are arranged in the stacking direction and communicate with each other.

[0043] The individual liquid chambers 33 are flow paths that communicate with the ends of the plurality of throttle flow paths 34 in the flow direction. The individual liquid chambers 33 are formed, for example, between the diaphragm 30 and the nozzle plate 50 and communicate with the common chamber 32 of the frame portion 45. Here, each of the flow path substrates 401, 402, and 403 has a symmetrical structure with one side and the other side in the Y direction centered on the nozzle 51, and the flow path lengths of the individual liquid chambers 33 arranged on both sides in the Y direction centered on the central pressure chamber 31 and the cross-sectional shape of the flow path orthogonal to the Y direction are configured to be equal.

[0044] Also, in the flow path portion 40, the throttle flow paths 34 are formed by the slits 4023. The throttle flow paths 34 communicate the respective pressure chambers 31 with the individual liquid chambers 33 and extend in the Y direction which is the flow direction. The throttle flow paths 34 on both sides are configured to have a smaller dimension in the width direction orthogonal to the extending direction which is the flow direction than the individual liquid chambers 33 and the pressure chambers 31, and the flow path cross-section is configured to be narrow. That is, the throttle flow paths 34 are narrow portions where the flow path is reduced in the width direction that intersects the stacking direction and the extending direction of the flow path.

[0045] Here, each of the flow path substrates 401, 402, and 403 has a symmetrical structure with one side and the other side in the Y direction centered on the nozzle 51, and the flow path lengths of the throttle flow paths 34 arranged on both sides in the Y direction centered on the central pressure chamber 31 and the cross-sectional shape of the flow path orthogonal to the Y direction are configured to be equal. In the flow path portion 40, a partition wall portion 42 that separates between a plurality of pressure chambers 31 is formed by the central portions of the beam-like portions 461 of the flow path substrates 401 and 402 to be laminated and the beam-like portion 463 of the flow path substrate 403.

[0046] The partition wall portion 42 is a wall-like member that separates between a plurality of pressure chambers 31 in the arrangement direction. The partition wall portion 42 is disposed opposite to the non-driven piezoelectric element 22 via the diaphragm 30 and is supported by the non-driven piezoelectric element 22. A plurality of partition wall portions 42 are provided at the same pitch as the pitch at which the plurality of pressure chambers 31 are arranged.

[0047] In the flow path portion 40, a side wall portion 43 that separates between a plurality of throttle flow paths 34 is formed by the portion between the slits 4023 of the beam-like portion 463 of the flow path substrate 403.

[0048] The side wall portion 43 is a wall-like member that separates between a plurality of throttle flow paths 34 in the arrangement direction. For example, the side wall portion 43 is provided at the inlet of the pressure chamber 31. The side wall portion 43 is configured such that the flow path resistance of the throttle flow path 34 is larger than that inside the pressure chamber 31 and the flow path cross-sectional area of the throttle flow path 34 is smaller than that inside the pressure chamber 31. A plurality of side wall portions 43 are provided at the same pitch as the pitch at which the plurality of pressure chambers 31 are arranged.

[0049] That is, in the flow path portion 40, a throttle flow path 34 is formed in a space sandwiched between the flow path substrate 401 and the flow path substrate 403 in the stacking direction and sandwiched between the side wall portions 43 and 43 in the width direction and extending along the extending direction. The flow path cross-section, which is a cross-section of the throttle flow path 34 orthogonal to the extending direction, has a short-side dimension in the short-side direction equal to the thickness dimension HA of the flow path substrate 402, which is the dimension between the flow path substrate 401 and the flow path substrate 403, and a long-side dimension in the long-side direction equal to the widthwise dimension of the slit 4023.

[0050] Therefore, on both sides of the pressure chamber 31, the throttle flow path 34 extending along the extending direction has a rectangular flow path cross-section in which the longitudinal dimension along the width direction of the slit 4023 is three times or more the short-side dimension along the thickness direction of the flow path substrate 402.

[0051] Figure 5 is a table showing the relationship between the pipe friction coefficient ratio k of a rectangular pipe and the aspect ratio (from the technical data of the Japan Society of Mechanical Engineers, "Fluid Resistance of Pipelines and Ducts"). Figure 6 is a graph showing the relationship between the pipe friction coefficient ratio k of a rectangular pipe and the aspect ratio, where the horizontal axis is the aspect ratio ε and the vertical axis is the pipe friction coefficient ratio k.

[0052] As shown in Figure 5, in a rectangular cross-section flow path, when the Reynolds number is small and the pipeline length L is sufficiently long (for example, more than one order of magnitude longer than the sides of the cross-section), the flow path resistance R of a pipeline with a cross-sectional area A (m²), wetted perimeter length S (m), and pipeline length L (m) is, with the viscosity of the ink being μ (Pa·s), R(Pa·s / m^3)=2k(S^2 / A^3)·L·μ (Equation 1) is expressed as.

[0053] At this time, k is the pipe friction coefficient ratio of the rectangular pipe, and as shown in Figures 5 and 6, it increases rapidly when the aspect ratio is less than 0.3. The pipeline length L is the length in the extending direction of the flow path.

[0054] Figure 7 is a table comparing the magnitudes of fluid resistance by substituting values of ±10% for the long side of 100 μm and the short side of 30 μm in the flow path cross-section orthogonal to the extending direction of the throttle flow path 34, which is the fluid resistance portion. Note that for calculating the fluid resistance ratio, the units were not changed to m but remained in μm, and k was calculated from the approximate formula of the graph. L and μ were the same.

[0055] According to Figure 7, the change in the resistance value due to a 3-μm change in the short side is greater than the change in the resistance value due to a 10-μm change in the long side. That is, in Figure 7, when the short side is fixed at 30 μm and the length of the long side is changed by 10 μm in the upper three rows of the table, and when the length of the long side is fixed and the length of the short side is changed by 3 μm in the lower two rows of the table, it can be seen that the change in fluid resistance is greater when the length of the short side is changed. Therefore, it can be said that the fluid resistance value is dominated by the accuracy of the short side, and improving the accuracy of the short side leads to an improvement in the accuracy of the fluid resistance.

[0056] For example, the flow path substrate 402 is formed by forming an opening in a metal plate such as a thin SUS plate by etching or the like. Although it depends on the method and cost, generally, since the plate thickness accuracy is higher than the etching accuracy, by setting the plate thickness as the short side and the etching opening as the long side, the accuracy of the fluid resistance is improved. Particularly, the smaller the viscosity of the ink, the greater the factors other than the ink viscosity in the fluid resistance, so the accuracy of the flow path shape becomes important.

[0057] The nozzle plate 50 is formed of a rectangular plate shape with a thickness of about 10 μm to 100 μm made of a metal such as SUS or Ni or a resin material such as polyimide. The nozzle plate 50 is disposed on one side of the flow path portion 40 so as to cover the opening on one side of the pressure chamber 31. The nozzle plate 50 has a plurality of nozzles 51 for discharging droplets. The plurality of nozzles 51 are holes penetrating the nozzle plate 50 in the thickness direction. A plurality of nozzles 51 are arranged in the same first direction as the arrangement direction of the pressure chambers 31 to form a nozzle row. Each nozzle 51 is provided at a position corresponding to a plurality of pressure chambers 31.

[0058] The frame portion 45 is a structure joined to the diaphragm 30 together with the piezoelectric elements 21 and 22. The frame portion 45 is provided on the side of the piezoelectric elements 21 and 22 opposite to the flow path portion 40 of the diaphragm 30, and is disposed adjacent to the actuator portion 20 in the present embodiment, for example. The frame portion 45 constitutes the outer shell of the inkjet head 1. Further, the frame portion 45 may form a liquid flow path inside. In the present embodiment, the frame portion 45 is joined to the other side of the diaphragm 30 and forms a common chamber 32 between the frame portion 45 and the diaphragm 30.

[0059] The common chamber 32 is formed inside the frame portion 45 and communicates with the pressure chamber 31 through the opening 303 provided in the diaphragm 30, the individual liquid chambers 33, and the throttle flow path 34.

[0060] The drive circuit 70 includes a wiring film having one end connected to the external electrodes 223 and 224, a driver IC mounted on the wiring film, and a printed wiring board mounted on the other end of the wiring film.

[0061] The drive circuit 70 drives the piezoelectric element 21 by applying a drive voltage to the external electrodes 223 and 224 with a driver IC, increases or decreases the volume of the pressure chamber 31, and discharges droplets from the nozzle 51.

[0062] The wiring film is connected to a plurality of external electrodes 223 and 224. For example, the wiring film is an ACF (anisotropic conductive film) fixed to the connection portions of the external electrodes 223 and 224 by thermocompression bonding or the like. The wiring film is, for example, a COF (Chip on Film) on which a driver IC is mounted.

[0063] The driver IC is connected to the external electrodes 223 and 224 via the wiring film. Note that the driver IC may be connected to the external electrodes 223 and 224 by other means such as ACP (anisotropic conductive paste), NCF (non-conductive film), and NCP (non-conductive paste) instead of the wiring film.

[0064] The driver IC generates a control signal and a drive signal for operating each piezoelectric element 21. The driver IC generates a control signal for control such as selecting the timing of discharging ink and the piezoelectric element 21 for discharging ink according to the image signal input from the control unit 150 of the inkjet recording apparatus 100. Further, the driver IC generates a voltage to be applied to the piezoelectric element 21 according to the control signal, that is, a drive signal (electrical signal). When the driver IC applies a drive signal to the piezoelectric element 21, the piezoelectric element 21 drives the diaphragm 30 to be displaced to change the volume of the pressure chamber 31. As a result, the ink filled in the pressure chamber 31 generates a pressure vibration. Due to the pressure vibration, the ink is discharged from the nozzle 51 provided in the pressure chamber 31. Note that the inkjet head 1 may be configured to be able to realize gradation expression by changing the amount of ink droplets landing on one pixel. Further, the inkjet head 1 may be configured to be able to change the amount of ink droplets landing on one pixel by changing the number of times of discharging ink. In this way, the driver IC is an example of an application unit that applies a drive signal to the piezoelectric element 21.

[0065] For example, the driver IC includes a data buffer, a decoder, and a driver. The data buffer stores the printing data in time series for each piezoelectric element 21. The decoder controls the driver based on the printing data stored in the data buffer for each piezoelectric element 21. The driver outputs a drive signal for operating each piezoelectric element 21 based on the control of the decoder. The drive signal is, for example, a voltage applied to each piezoelectric element 21.

[0066] The printed wiring board is a PWA (Printing Wiring Assembly) on which various electronic components and connectors are mounted. The printed wiring board is connected to the control unit 150 of the inkjet recording apparatus 100.

[0067] In the inkjet head 1 configured as described above, a plurality of pressure chambers 31 communicating with the nozzles 51, an individual flow path composed of throttle flow paths 34 communicating with the plurality of pressure chambers 31, an individual liquid chamber 33 serving as a common flow path, and a common chamber 32 are formed by the nozzle plate 50, the frame portion 45, the flow path portion 40, and the diaphragm 30. An ink flow path 35 is formed. For example, the common chamber 32 communicates with the cartridge, and ink is supplied to each pressure chamber 31 through the common chamber 32. All the piezoelectric elements 21 are connected by wiring so that a voltage can be applied. In the inkjet head 1, when the control unit 150 applies a drive voltage to the electrodes 221 and 222 by the driver IC, the piezoelectric element 21 to be driven vibrates in the stacking direction, that is, in the thickness direction of each piezoelectric layer 211. That is, the piezoelectric element 21 vibrates longitudinally.

[0068] Specifically, the control unit 150 applies a drive voltage to the internal electrodes 221 and 222 of the piezoelectric element 21 to be driven, and selectively drives the piezoelectric element 21 to be driven. Then, by combining the deformation in the tensile direction and the deformation in the compression direction by the piezoelectric element 21 to be driven, the diaphragm 30 is deformed, and the volume of the pressure chamber 31 is changed, so that the liquid is guided from the common chamber 32 and ejected from the nozzle 51.

[0069] Hereinafter, an example of an inkjet recording apparatus 100 including an inkjet head 1 will be described with reference to FIG. 8. The inkjet recording apparatus 100 includes a housing 111, a medium supply unit 112, an image forming unit 113, a medium discharge unit 114, a transport device 115, and a control unit 150.

[0070] The inkjet recording apparatus 100 is a liquid ejection apparatus that performs an image forming process on a sheet of paper P by ejecting a liquid such as ink while transporting the sheet of paper P as a printing medium to be ejected along a predetermined transport path RA that extends from the medium supply unit 112 through the image forming unit 113 to the medium discharge unit 114.

[0071] The housing 111 constitutes the outer shell of the inkjet recording apparatus 100. A discharge port for discharging the sheet of paper P to the outside is provided at a predetermined location on the housing 111.

[0072] The medium supply unit 112 includes a plurality of paper feed cassettes and is configured to be able to stack and hold a plurality of sheets of paper P of various sizes.

[0073] The medium discharge unit 114 includes a paper discharge tray configured to be able to hold the sheet of paper P discharged from the discharge port.

[0074] The image forming unit 113 includes a support unit 117 that supports the sheet of paper P and a plurality of head units 130 that are disposed opposite to the upper side of the support unit 117.

[0075] The support unit 117 includes a transport belt 118 that is provided in a loop shape in a predetermined area where image formation is performed, a support plate 119 that supports the transport belt 118 from the back side, and a plurality of belt rollers 120 that are provided on the back side of the transport belt 118.

[0076] During image formation, the support unit 117 supports the sheet of paper P on the holding surface that is the upper surface of the transport belt 118 and transports the sheet of paper P to the downstream side by sending the transport belt 118 at a predetermined timing by the rotation of the belt rollers 120.

[0077] The head unit 130 includes a plurality (4 colors) of inkjet heads 1, ink tanks 132 as liquid tanks respectively mounted on each inkjet head 1, connection channels 133 connecting the inkjet heads 1 and the ink tanks 132, and a supply pump 134.

[0078] In this embodiment, it includes four-color inkjet heads 1 of cyan, magenta, yellow, and black, and ink tanks 132 for storing the inks of these respective colors. The ink tanks 132 are connected to the inkjet heads 1 by the connection channels 133.

[0079] Also, a negative pressure control device such as a pump (not shown) is connected to the ink tank 132. Then, corresponding to the water head values of the inkjet head 1 and the ink tank 132, the inside of the ink tank 132 is controlled to be under negative pressure by the negative pressure control device, so as to form an ink supplied to each nozzle 51 of the inkjet head 1 into a meniscus of a predetermined shape.

[0080] The supply pump 134 is a liquid delivery pump composed of, for example, a piezoelectric pump. The supply pump 134 is provided in a supply channel. The supply pump 134 is connected to the drive circuit of the control unit 150 by wiring and is configured to be controllable under the control of a CPU (Central Processing Unit). The supply pump 134 supplies liquid to the inkjet head 1.

[0081] The conveyance device 115 conveys the paper P along a conveyance path RA extending from the medium supply unit 112 through the image forming unit 113 to the medium discharge unit 114. The conveyance device 115 includes a plurality of pairs of guide plates 121 arranged along the conveyance path RA and a plurality of conveyance rollers 122.

[0082] Each of the plurality of pairs of guide plates 121 includes a pair of plate members arranged opposite to each other with the conveyed paper P sandwiched therebetween, and guides the paper P along the conveyance path RA.

[0083] The conveyance roller 122 is driven to rotate under the control of the control unit 150, and thereby feeds the sheet P downstream along the conveyance path RA. Sensors for detecting the conveyance state of the sheet are arranged at various positions in the conveyance path RA.

[0084] The control unit 150 includes a control circuit 151 such as a CPU which is a controller, a ROM (Read Only Memory) that stores various programs and the like, a RAM (Random Access Memory) that temporarily stores various variable data, image data, and the like, and an interface unit that inputs data from the outside and outputs data to the outside.

[0085] In the inkjet recording apparatus 100 configured as described above, when the control unit 150 detects a print instruction by the user's operation input on the interface, for example, it drives the conveyance device 115 to convey the sheet P, and outputs a print signal to the head unit 130 at a predetermined timing, thereby driving the inkjet head 1. As a discharge operation, the inkjet head 1 sends a drive signal to the driver IC according to an image signal corresponding to the image data, applies a drive voltage to the internal electrodes 221 and 222 to selectively drive the piezoelectric element 21 to be discharged to vibrate vertically in the stacking direction, changes the volume of the pressure chamber 31, and discharges ink from the nozzle 51 to form an image on the sheet P held on the conveyance belt 118. Also, as a liquid discharge operation, the control unit 150 drives the supply pump 134 to supply ink from the ink tank 132 to the common chamber 32 of the inkjet head 1.

[0086] Here, the driving operation for driving the inkjet head 1 will be described. The inkjet head 1 according to the present embodiment includes a piezoelectric element 21 disposed opposite to the pressure chamber 31, and these piezoelectric elements 21 are connected by wiring so that a voltage can be applied. The control unit 150 sends a driving signal to the driver IC according to an image signal corresponding to the image data, applies a driving voltage to the internal electrodes 221 and 222 of the piezoelectric element 21 to be driven, and selectively deforms the piezoelectric element 21 to be driven. Then, by combining the deformation in the tensile direction and the deformation in the compression direction of the diaphragm 30 to change the volume of the pressure chamber 31, the liquid is discharged.

[0087] For example, the control unit 150 alternately performs a pulling operation and a compressing operation. In the inkjet head 1, during the pulling when the internal volume of the target pressure chamber 31 is increased, the piezoelectric element 21 to be driven is contracted, and the driving piezoelectric elements other than the one to be driven are not deformed. Also, in the inkjet head 1, during the compression when the internal volume of the target pressure chamber 31 is decreased, the target driving piezoelectric element 21 is extended, and the non-driving piezoelectric element 22 is not deformed.

[0088] According to the inkjet head 1 and the inkjet recording apparatus 100 according to the above-described embodiment, the accuracy of the fluid resistance can be improved, and the variation in the ejection performance for each nozzle of the inkjet head can be suppressed. In the inkjet head 1 according to the above embodiment, on both sides of the pressure chamber 31, the throttle flow path 34 along the extending direction has a flow path cross section in which the longitudinal dimension of the flow path cross section along the width direction of the slit 4023 is three times or more the transverse dimension of the flow path cross section along the thickness direction of the flow path substrate 402. That is, when the flow path substrate 402 is formed by processing a metal such as SUS and the thickness dimension is defined, and an opening is formed by etching, generally, it is easier to ensure dimensional accuracy with a higher dimensional accuracy in the processing accuracy of the plate thickness than the etching accuracy. Therefore, the thickness direction, which is easy to ensure dimensional accuracy, is set as the short side of the flow path cross section, the opening width direction, which is difficult to ensure dimensional accuracy, is set as the long side of the flow path cross section, and the aspect ratio is set to three times or more, so that it is easy to ensure dimensional accuracy and the accuracy of the fluid resistance can be improved. For this reason, the variation in the ejection performance for each nozzle of the inkjet head can be suppressed. In particular, the smaller the viscosity of the ink, the greater the factor other than the ink viscosity in the fluid resistance, so the accuracy of the flow path shape becomes important. However, according to the above embodiment, the ejection performance can be improved by ensuring the accuracy of the flow path shape.

[0089] Note that the present invention is not limited to the above embodiment as it is, and at the implementation stage, the components can be modified and embodied without departing from the gist thereof.

[0090] For example, the specific configuration of the flow path portion 40 is not limited to the above. For example, although an example formed by three flow path substrates 401, 402, and 403 is shown, it may be two or four or more. Also, the shape of the opening in each of the flow path substrates 401, 402, and 403 is not limited to the above embodiment.

[0091] Further, for example, in the above-described embodiment, although an example in which the second openings 4012, 4022, and 4032 are divided into a plurality in the column direction to constitute a plurality of individual liquid chambers 33 connected by the common chamber 32 has been shown, the present invention is not limited thereto. For example, a plurality of second openings 4012, 4022, and 4032 may be continuous in the arrangement direction to form a common flow path. Also, the positions in the stacking direction of the first flow path substrates 401 and 403 and the second flow path substrate 402 and the shapes of the respective openings are not limited to those in the above-described embodiment, and can be appropriately changed. For example, the flow path substrates 401 and 403, which are the first flow path substrates, may be on the nozzle plate 50 side, and the flow path substrate 402, which is the second flow path substrate, may be on the actuator unit 20 side.

[0092] For example, in the above-described embodiment, a configuration in which a plurality of layers of piezoelectric members are stacked and the piezoelectric element 21 is driven using longitudinal vibration (d33) in the stacking direction has been adopted, but the present invention is not limited thereto. For example, the present invention is applicable also to a form in which the piezoelectric element 21 is constituted by a single-layer piezoelectric member, and is also applicable to a form in which the piezoelectric element 21 is driven by transverse vibration (d31).

[0093] Also, the specific configurations of the piezoelectric elements 21 and 22, the shape of the flow path, and the configurations and positional relationships of various components including the flow path portion 40, the nozzle plate 50, and the frame portion 45 are not limited to the examples described above, and can be appropriately changed. Also, the arrangement of the nozzles 51 and the pressure chambers 31 is not limited to the above. For example, two or more rows of nozzles 51 may be arranged. Also, a dummy chamber may be formed between a plurality of pressure chambers 31.

[0094] Also, the liquid to be ejected is not limited to ink for printing, and for example, an apparatus that ejects a liquid containing conductive particles for forming a wiring pattern of a printed wiring board may be used.

[0095] Also, in the above-described embodiment, although an example in which the inkjet head 1 is used in a liquid ejection apparatus such as an inkjet recording apparatus has been shown, the present invention is not limited thereto. For example, the inkjet head 1 can also be used in a 3D printer, an industrial manufacturing machine, or for medical purposes, and can be made smaller and lighter and less costly.

[0096] According to at least one embodiment described above, the accuracy of fluid resistance can be improved, and the variation in ejection performance for each nozzle of the inkjet head can be suppressed.

[0097] In addition, although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

Explanation of Reference Numerals

[0098] 1... Inkjet head, 20... Actuator section, 21... Driving piezoelectric element, 22... Non-driving piezoelectric element, 23... Groove section, 26... Piezoelectric structure section, 30... Diaphragm, 31... Pressure chamber, 32... Common chamber, 33... Individual liquid chamber, 34... Throttle flow path (resistance flow path), 35... Ink flow path, 40... Flow path section, 41... Peripheral wall section, 42... Partition section, 43... Side wall section, 45... Frame section, 50... Nozzle plate, 51... Nozzle, 70... Driving circuit, 100... Inkjet recording apparatus, 111... Housing, 112... Medium supply section, 113... Image forming section, 114... Medium discharge section, 115... Conveying device, 117... Support section, 118... Conveying belt, 119... Support plate, 120... Belt roller, 121... Pair of guide plates, 122... Conveying roller, 130... Head unit, 132... Ink tank, 133... Connection flow path, 134... Supply pump, 150... Control section, 151... Control circuit, 211... Piezoelectric layer, 221... Internal electrode, 222... Internal electrode, 223... External electrode, 224... External electrode, 301... Vibration region, 302... Support region, 303... Opening, 401... Flow path substrate, 402... Flow path substrate, 403... Flow path substrate, 461, 462, 463... Beam-like sections, 4011... First opening, 4012... Second opening, 4021... First opening, 4022... Second opening, 4023... Slit, 4024... Long hole section, 4031... First opening, 4032... Second opening, Driving IC... 72, d33... Piezoelectric constant.

Claims

1. A liquid ejection head comprising a plurality of flow path substrates that are stacked in a stacking direction and in which openings for forming flow paths are formed. At least one of the flow path substrates has a slit, and the flow path formed by the slit has a flow path cross-section in which a longitudinal dimension orthogonal to the extending direction of the slit and the stacking direction is three times or more the short-side dimension along the stacking direction.

2. By communicating the plurality of openings formed in the plurality of flow path substrates, a plurality of pressure chambers, a plurality of resistance flow paths that communicate with the plurality of pressure chambers respectively and have a cross-section orthogonal to one direction smaller than that of the pressure chambers, and a common chamber that communicates with the plurality of resistance flow paths are formed. The liquid ejection head according to claim 1, wherein the slit constitutes the resistance flow path.

3. The liquid ejection head according to claim 1, wherein the flow path substrate is made of metal.

4. A nozzle member having a plurality of nozzles in an arrangement direction. A flow path portion that is disposed opposite to one side of the nozzle member in the stacking direction, is configured by stacking a plurality of the flow path substrates, and has a plurality of the pressure chambers and the resistance flow paths in the arrangement direction. A plurality of vibration portions disposed opposite to one side of the pressure chamber in the stacking direction. An actuator portion having a plurality of actuators disposed opposite to one side of the vibration portion in the stacking direction. The liquid ejection head according to claim 2, comprising:

5. A liquid ejection device comprising the liquid ejection head according to any one of claims 1 to 4.

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