Liquid discharge head and liquid discharge device

Abstract

To provide a liquid discharge head and a liquid discharge device capable of ensuring good discharge performance.SOLUTION: A liquid discharge head according to one embodiment comprises: a plurality of pressure chambers; a common liquid chamber communicating with the plurality of pressure chambers; an inflow channel that connects an inflow side of the pressure chamber to the common liquid chamber and includes a resistance channel having a smaller cross-sectional area than the pressure chamber; and an outflow channel that connects an outflow side of the pressure chamber to the common liquid chamber and includes a resistance channel having a smaller cross-sectional area than the pressure chamber. The flow channel resistance of the inflow channel is greater than the flow channel resistance of the outflow channel.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a liquid ejection head and a liquid ejection apparatus. [Background technology]

[0002] In a liquid ejection head such as an inkjet head, a method is used in which a vibration plate is deformed using an actuator made of a piezoelectric material such as PZT (lead zirconate titanate), thereby deforming pressure chambers facing the vibration plate and ejecting ink from nozzles communicating with the pressure chambers. The liquid ejection head includes a plurality of actuators joined to the vibration plate, and a flow path portion that forms a plurality of pressure chambers facing the vibration plate and flow paths communicating with the pressure chambers.

[0003] In such an inkjet head, if the fluid resistance is high when circulating ink, it becomes difficult to maintain negative pressure in the nozzles, which can lead to ink leakage from the nozzles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5943292 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a liquid ejection head and a liquid ejection apparatus that can ensure good ejection performance. [Means for solving the problem]

[0006] A liquid ejection head according to one embodiment includes a plurality of pressure chambers, a common liquid chamber communicating with the plurality of pressure chambers, inflow channels communicating the inflow sides of the pressure chambers with the common liquid chamber and having a resistance channel with a cross-sectional area smaller than that of the pressure chambers, and outflow channels communicating the outflow sides of the pressure chambers with the common liquid chamber and having a resistance channel with a cross-sectional area smaller than that of the pressure chambers, wherein the channel resistance of the inflow channels is greater than the channel resistance of the outflow channels. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view showing the configuration of a portion of an inkjet head according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing a configuration of a part of the inkjet head. [Figure 3] FIG. 3 is a cross-sectional view showing the configuration of a first flow path substrate of the inkjet head. [Figure 4] FIG. 3 is a cross-sectional view showing the configuration of a second flow path substrate of the inkjet head. [Figure 5] FIG. 2 is an explanatory diagram showing the shape of a flow path of the inkjet head. [Figure 6] 10 is a table showing the change in viscous resistance when the cross-sectional area of ​​the resistance flow path is changed. [Figure 7] 10 is a graph showing the relationship between the circulation flow rate and the variation in the nozzle negative pressure. [Figure 8] FIG. 1 is an explanatory diagram showing a schematic configuration of an inkjet recording apparatus according to a first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] An inkjet head 1, which is a liquid ejection head, and an inkjet recording apparatus 100, which is a liquid ejection apparatus, according to a first embodiment will be described below 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 plan view showing a partial configuration of the inkjet head. FIG. 3 is a cross-sectional view showing a flow path substrate 401, and FIG. 4 is a cross-sectional view showing a flow path substrate 402. FIG. 5 is an explanatory diagram showing the shape of the flow path. FIG. 6 is a table showing the change in viscous resistance when the cross-sectional area of ​​the resistance flow path is changed. FIG. 7 is a graph showing the relationship between the circulation flow rate and the variation in nozzle negative pressure. FIG. 8 is an explanatory diagram showing the schematic configuration of an inkjet recording apparatus. In the diagram, arrows X, Y, and Z indicate three mutually orthogonal directions. In this embodiment, X indicates the arrangement direction of the nozzles 51 and pressure chambers 31, Y indicates the extension direction, and Z indicates the opposing direction and the axial direction of the nozzles. In each diagram, the configuration is enlarged, reduced, or omitted as appropriate for ease of explanation.

[0009] 1 and 2, the inkjet head 1 includes an actuator unit 20, a diaphragm 30, a manifold 40 as a flow path member having a plurality of flow path substrates 401, 402, a nozzle plate 50 as a nozzle member having a plurality of nozzles 51, a frame unit 45 as a structural unit, and a drive circuit 70. As an example, in this 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 all along the Z direction. In this embodiment, on the back side of the nozzle plate 50, the diaphragm 30 and the manifold 40 form a flow path structure unit that forms an ink flow path 35 (flow path unit) within the inkjet head 1. The inkjet head 1 is a circulation type that circulates liquid in a predetermined flow path.

[0010] The actuator section 20 is made of, for example, a piezoelectric member and includes a plurality of drive piezoelectric elements 21 (piezoelectric sections) as actuators arranged alternately along the column direction, and a plurality of non-drive piezoelectric elements 22. In this embodiment, a nozzle 51 is provided at the center of the extension direction of the actuator section 20, and the actuator section 20 has a structure in which one side and the other side are symmetrical with respect to the nozzle 51. For example, the actuator section 20 is joined to a rectangular base.

[0011] In the actuator section 20, the plurality of drive piezoelectric elements 21 and the plurality of non-drive piezoelectric elements 22 are arranged in parallel at regular intervals. As an example, the plurality of drive piezoelectric elements 21 and the plurality of non-drive piezoelectric elements 22 are all configured in the shape of a rectangular parallelepiped column with the same external shape. The actuator section 20 is divided into a plurality of sections by, for example, a plurality of grooves 23, and the plurality of drive piezoelectric elements 21 and non-drive piezoelectric elements 22 are arranged in a column direction at the same pitch by, for example, grooves 23 of the same width.

[0012] For example, the plurality of driving piezoelectric elements 21 and the plurality of non-driving piezoelectric elements 22 are each configured in a rectangular shape when viewed in a plan view from the Z direction, which is the axial direction of the nozzle 51, with the short side direction aligned with the row direction of the element row and the long side direction aligned with an extension direction perpendicular to the row direction and the Z direction.

[0013] The driving piezoelectric elements 21 are arranged in positions in the Z direction opposite to the plurality of pressure chambers 31 formed in the manifold 40. As an example, the center positions in the column direction and extension direction of the driving piezoelectric elements 21 and the center positions in the column direction and extension direction of the pressure chambers 31 are arranged side by side in the Z direction.

[0014] The non-driven piezoelectric elements 22 are arranged in positions in the Z direction facing the partition walls 42 formed in the manifold 40. As an example, the center positions in the column direction and extension direction of the non-driven piezoelectric elements 22 and the center positions in the column direction and extension direction of the partition walls 42 are arranged side by side in the Z direction.

[0015] For example, the laminated piezoelectric member that constitutes the actuator section 20 is formed by stacking and sintering sheet-like piezoelectric materials. The actuator section 20 is formed by dicing the laminated piezoelectric member from one end face to form grooves 23, thereby forming a plurality of rectangular columnar piezoelectric elements at predetermined intervals. Electrodes and the like are then provided on the formed columnar elements, forming a plurality of drive piezoelectric elements 21 and a plurality of non-drive piezoelectric elements 22 that are alternately arranged. The plurality of drive piezoelectric elements 21 and the plurality of non-drive piezoelectric elements 22 are alternately arranged in parallel in the column direction, with the grooves 23 sandwiched between them.

[0016] The piezoelectric members constituting the driving piezoelectric element 21 and the non-driven piezoelectric element 22 are, for example, laminated piezoelectric elements. The driving piezoelectric element 21 and the non-driven piezoelectric element 22 each include a plurality of laminated piezoelectric layers 211 and internal electrodes 221, 222 formed on the main surface of each piezoelectric layer 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 each include external electrodes 223, 224 formed on the surface.

[0017] The piezoelectric layers 211 are made of a piezoelectric material such as PZT (lead zirconate titanate) or lead-free KNN (potassium sodium niobate). The thickness direction of the multiple piezoelectric layers 211 is stacked along the stacking direction. For example, in this embodiment, the thickness direction and stacking direction of the piezoelectric layers 211 are arranged along the vibration direction (Z direction).

[0018] The internal electrodes 221, 222 are conductive films formed into a predetermined shape using a sinterable conductive material such as silver-palladium. The internal electrodes 221, 222 are formed in predetermined regions on the main surface of each piezoelectric layer 211. The internal electrodes 221, 222 have opposite polarities. For example, one internal electrode 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 extension direction (Y direction), which is a direction perpendicular to both the row direction (X direction) in which the multiple drive piezoelectric elements 21 and the multiple non-drive piezoelectric elements 22 are arranged 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 extension direction. The internal electrodes 221, 222 are connected to external electrodes 223, 224 formed on the side surfaces of the piezoelectric elements 21, 22, respectively.

[0019] Furthermore, the laminated piezoelectric members constituting the drive piezoelectric elements 21 and the non-drive piezoelectric elements 22 may further include a dummy layer on either or both of the nozzle plate 50 side and the opposite end. For example, the dummy layer is made of the same material as the piezoelectric layer 211, has an electrode on only one side, and is not deformed because no electric field is applied. For example, the dummy layer does not function as a piezoelectric body, but serves to secure the actuator unit 20 to the base or as a polishing allowance when polishing to achieve precision during or after assembly.

[0020] The external electrodes 223, 224 are formed on the surfaces of the plurality of drive piezoelectric elements 21 and the plurality of non-driven piezoelectric elements 22, and are formed by collecting the ends of the internal electrodes 221, 222. For example, the external electrodes 223, 224 are formed on one end face and the other end face in the extension direction of the piezoelectric layer 211, respectively. The external electrodes 223, 224 are formed by depositing Ni, Cr, Au, or the like by a known method such as plating or sputtering. The external electrodes 223 and 224 have opposite polarities. The external electrodes 223 and 224 are disposed on different side surfaces of the plurality of drive piezoelectric elements 21 and the plurality of non-driven piezoelectric elements 22, respectively. Note that the external electrodes 223 and 224 may be routed to different regions of the same side surfaces of the plurality of drive piezoelectric elements 21 and the plurality of non-driven piezoelectric elements 22.

[0021] 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 serve as individual electrodes for the multiple driving piezoelectric elements 21 and the multiple non-driving piezoelectric elements 22, have their electrode layers divided by grooves 23 and are arranged independently of each other. The external electrode 224, which serves as a common electrode, has its electrode layers connected to each other, for example, on the side surface of the actuator section 20, and is, for example, grounded. The external electrodes 223, 224 are connected to the drive circuit 70, for example, via a wiring film. For example, each of the external electrodes 223, 224 is connected to the control section 150 via a drive IC 72 of the drive circuit 70, and is configured to be drive-controllable. The arrangement of the common electrode and the individual electrodes may be reversed.

[0022] The vibration direction of each piezoelectric element 21, 22 is along the stacking direction, and when an electric field is applied, it is displaced in the d33 direction. Each piezoelectric element 21, 22 has three or more stacked layers of piezoelectric layers 211 and internal electrodes 221, 222. As an example, each piezoelectric element 21, 22 has three or more and 50 or less layers, each layer is 10 μm or more and 40 μm or less in thickness, and the product of the thickness and the total number of stacked layers is less than 1000 μm.

[0023] In the inkjet head 1, the driving piezoelectric element 21 vibrates when a voltage is applied to the internal electrodes 221 and 222 via the external electrodes 223 and 224. In this embodiment, the driving piezoelectric element 21 vibrates longitudinally along the stacking direction of the piezoelectric layer 211. The longitudinal vibration here refers to, for example, "vibration in the thickness direction defined by the piezoelectric constant d33." The driving piezoelectric element 21 displaces the vibration plate 30 and deforms the pressure chamber 31 by the longitudinal vibration.

[0024] The vibration plate 30 extends along a plane perpendicular to the Z direction, which is the vibration direction, and is bonded to one side of the vibration direction of the piezoelectric layer 211 of the plurality of piezoelectric elements 21, 22, i.e., the surface on the nozzle plate 50 side. The vibration plate 30 faces the plurality of nozzles 51 in the Z direction, which is the vibration direction, via pressure chambers 31. The vibration plate 30 is configured to be deformable, for example. The vibration plate 30 is bonded to the drive piezoelectric elements 21 and non-drive piezoelectric elements 22 of the actuator section 20 and to the frame section 45. For example, the vibration plate 30 has a vibration region 301 facing the piezoelectric elements 21, 22 and a support region 302 facing the frame section 45. The vibration plate 30 is provided between a flow path substrate 401 and the actuator section 20 in the vibration direction. The vibration plate 30 is arranged overlapping the plurality of flow path substrates 401, 402 and forms part of the ink flow path 35.

[0025] The vibration region 301 is, for example, in the form of a flat plate arranged such that the thickness direction coincides with the vibration direction of the piezoelectric layer 211. The vibration plate 30 has a surface extending in the direction in which the multiple drive piezoelectric elements 21 and the multiple non-drive piezoelectric elements 22 are arranged. The vibration plate 30 is, for example, a metal plate. The vibration plate 30 has multiple vibration parts that face each pressure chamber 31 and can be displaced individually. The vibration plate 30 is formed by integrally connecting the multiple vibration parts.

[0026] As an example, the vibration plate 30 is made of a nickel or SUS plate, and is configured to have a thickness dimension along the vibration direction of approximately 5 μm to 15 μm. Note that the vibration region 301 may have folds or steps formed in areas adjacent to a vibration region or between adjacent vibration regions to facilitate displacement of multiple vibration regions. The vibration region 301 is deformed when the area opposite the drive piezoelectric element 21 is displaced due to expansion and compression of the drive piezoelectric element 21. For example, since the vibration plate 30 needs to be very thin and have a complex shape, it is formed by electroforming or the like. The vibration plate 30 is joined to the upper end surface of the actuator section 20 by adhesive or the like.

[0027] The support region 302 is a plate-like member disposed between the frame portion 45 and the flow path substrate 401. The vibration plate 30 has a structure in which one side and the other side in the Y direction are symmetrical with respect to the nozzle 51 as the center. For example, the support region 302 of the vibration plate 30 is disposed between the common liquid chamber 32 and the second common liquid chamber 33. For example, the support region 302 of the vibration plate 30 has an opening 303 formed therein that connects the second common liquid chamber 33 and the common liquid chamber 32.

[0028] The manifold 40 is bonded to one side of the vibration plate 30. As shown in FIGS. 1 to 3, the manifold 40 includes a plurality of stacked flow path substrates 401, 402. For example, the plurality of flow path substrates 401, 402 having openings or grooves according to the viscosity of the ink, the volume to be ejected, and the nozzle plate 50 and vibration plate 30 are combined and bonded to form a desired ink flow path 35. The plurality of flow path substrates 401, 402 are stacked in the stacking direction, and the openings or grooves formed in each of the flow path substrates 401, 402 form a predetermined ink flow path 35 including a second common liquid chamber 33, a resistance flow path 34 serving as a flow path resistance portion that is a throttle flow path, and a pressure chamber 31. As an example, the flow path substrate 401, which is a first flow path substrate, and the flow path substrate 402, which is a second flow path substrate, are stacked in this order from the vibration plate 30 side, and the flow path substrate 402 is disposed opposite the nozzle plate 50.

[0029] In this embodiment, the ink flow path 35 has an inflow flow path formed on the inflow side, which is one side in the extension direction of the pressure chamber 31, and an outflow flow path formed on the other side in the extension direction. Specifically, the resistance flow path 341 arranged on one side of the pressure chamber 31 and the common liquid chambers 32 and 33 form an inflow flow path 351, and the resistance flow path 342 arranged on the other side of the pressure chamber 31 and the common liquid chambers 32 and 33 form an outflow flow path 352.

[0030] The manifold 40 is disposed between the nozzle plate 50 and the vibration plate 30. The manifold 40 is formed by stacking and bonding a plurality of flow path substrates 401, 402 together to form predetermined ink flow paths 35 (liquid chambers) therein, each of which includes a plurality of pressure chambers 31, a second common liquid chamber 33 communicating with a first common liquid chamber 32, and a plurality of resistance flow paths 34 extending from the second common liquid chamber 33 to the pressure chambers 31. In other words, the manifold 40 is formed by the stacked flow path substrates 401, 402 to form a peripheral wall portion 41 surrounding the ink flow path 35 (liquid chamber) made up of the plurality of pressure chambers 31, the plurality of resistance flow paths 34, the first common liquid chamber 32, and the second common liquid chamber 33, a plurality of partition wall portions 42 separating the rows of the plurality of pressure chambers 31, and a side wall portion 43 separating the plurality of resistance flow paths 34. For example, in this embodiment, FIGS. 3 to 5 show an area of ​​the manifold 40 corresponding to one row of pressure chambers.

[0031] 1 and 2, the flow path substrate 401 is bonded to the diaphragm 30. The flow path substrate 401 is a plate-like member having the same outer shape as the diaphragm 30, and is made of a metal material such as SUS430, or a resin material such as silicone, for example. The flow path substrate 401 has a first opening 4011 that forms part of the pressure chamber 31, and a second opening 4012 that forms part of the second common liquid chamber 33. For example, the first opening 4011 is disposed in the center of the extension direction of the ink flow path 35, and the second openings 4012 are disposed at both ends.

[0032] The flow path substrate 402 is bonded to the flow path substrate 401. The flow path substrate 402 is a plate-like member having the same shape as the flow path substrate 401, and is made of, for example, a metal material such as SUS430, or a resin material such as silicone. The flow path substrate 402 has a first opening 4021 that forms part of the pressure chamber 31, a second opening 4022 that forms part of the second common liquid chamber 33, and a long, thin slit opening 4023 that forms the resistance flow path 34, which is an individual flow path. For example, the first opening 4021 is disposed in the center of the extension direction of the ink flow path 35, the slit openings 4023 are disposed at both ends of the first opening 4021, and the second openings 4022 are disposed at the outer ends of the slit openings 4023 on both sides. In the arrangement direction, the openings 4021, 4022, and 4023 are each arranged in multiple rows.

[0033] For example, the flow path substrates 401, 402 are configured to have a thickness of 20 μm to 100 μm. For example, in the case of 300 dpi, the arrangement pitch of the pressure chambers 31 in the parallel direction is 169 μm, the width WA of the pressure chambers 31 is approximately 100 μm to 150 μm, and the widths WB, WC of the slit openings 4023 that form the resistance flow paths 34 are smaller than the width WA of the first openings 4021 that form the pressure chambers 31 and the second openings 4022 that form the common liquid chamber 32. Note that the widths WA, WB, and WC are width dimensions in the X direction, which is a width dimension that intersects one direction and the stacking direction. In other words, the resistance flow paths 34 form a flow path resistance portion with a smaller cross-sectional area than the pressure chambers 31. As an example, in this embodiment, the resistance flow paths 34 have a constant flow path cross section over the entire length in the extension direction, and the entire length of the resistance flow paths 34 forms a flow path resistance portion.

[0034] In the manifold 40, a plurality of pressure chambers 31 are formed by first openings 4011, 4021 of a plurality of flow path substrates 401, 402 that are aligned in the stacking direction and communicate with each other. The plurality of pressure chambers 31 are spaces formed on one side of the vibration region 301 of the vibration plate 30, and each pressure chamber 31 communicates with a nozzle 51 formed in the nozzle plate 50. In addition, the pressure chamber 31 is closed on the side opposite to the nozzle plate 50 by the vibration plate 30.

[0035] The plurality of pressure chambers 31 are connected to the first common liquid chamber 32 via the resistance flow path 34 and the second common liquid chamber 33 and the opening 303. The pressure chambers 31 hold liquid supplied from the first common liquid chamber 32 via the second common liquid chamber 33 and the resistance flow path 34, and are deformed by vibration of the vibration plate 30 that forms part of the pressure chambers 31, thereby ejecting the liquid from the nozzles 51.

[0036] In the manifold 40, the second common liquid chambers 33 on both sides of the pressure chamber in the Y direction are formed by the second openings 4012, 4022 of the plurality of flow path substrates 401, 402 that are aligned in the stacking direction and communicate with each other.

[0037] The second common liquid chamber 33 is a flow path that communicates with the ends in the flow direction of the multiple resistance flow paths 34. The second common liquid chamber 33 is formed, for example, between the vibration plate 30 and the nozzle plate 50, and communicates with the first common liquid chamber 32 of the frame portion 45. Here, each flow path substrate 401, 402 has a structure that is symmetrical on one side and the other side in the Y direction with the nozzle 51 at the center, and the flow path lengths and flow path cross-sectional shapes perpendicular to the Y direction of the second common liquid chambers 33 arranged on both sides in the Y direction with the central pressure chamber 31 at the center are configured to be equal.

[0038] Furthermore, in the manifold 40, resistance flow paths 34 are formed by slit openings 4023 in the flow path substrate 402. The resistance flow paths 34 communicate with each pressure chamber 31 and the second common liquid chamber 33, and extend in the Y direction, which is the flow direction. The resistance flow paths 34 on both sides are configured to have smaller dimensions in the width direction perpendicular to the extension direction, which is the flow direction, than the second common liquid chamber 33 and the pressure chamber 31, and are configured to have narrower flow path cross sections.

[0039] Here, the flow path substrates 401, 402 are configured so that the flow path lengths and heights of the resistance flow paths 34 arranged on both sides in the Y direction centered on the central pressure chamber 31 are equal. In the manifold 40, the partition wall portions 42 that separate the multiple pressure chambers 31 are formed by the areas around the first openings 4011, 4021 of the stacked flow path substrates 401, 402.

[0040] The partition wall portions 42 are wall-shaped members that separate the multiple pressure chambers 31 in the arrangement direction. The partition wall portions 42 are disposed opposite the non-driven piezoelectric elements 22 via the vibration plate 30, and are supported by the non-driven piezoelectric elements 22. A plurality of partition wall portions 42 are provided at the same pitch as the arrangement of the multiple pressure chambers 31.

[0041] In the manifold 40, the portions on both sides of the slit opening 4023 of the flow path substrate 402 form sidewall portions 43 that separate the plurality of resistance flow paths .

[0042] The side wall portions 43 are wall-shaped members that separate the multiple resistance flow paths 34 in the arrangement direction. For example, the side wall portions 43 are provided so as to communicate with both sides of the pressure chamber 31. The side wall portions 43 are configured so that the flow path resistance of the resistance flow path 34 is greater than that inside the pressure chamber 31, and the flow path cross-sectional area of ​​the resistance 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 multiple pressure chambers 31 are arranged.

[0043] Here, the resistance flow path 34, which is a fluid resistance portion, is configured to have a smaller cross-sectional area perpendicular to the second direction, which is the flow direction of ink, than the pressure chamber 31. Here, in this embodiment, the flow direction is set from one side to the other in the extension direction. As an example in this embodiment, of the resistance flow paths 34, 34 on both sides, one resistance flow path 34 on the primary side in the flow direction is designated as a supply-side resistance flow path 341, and the other resistance flow path 34 on the secondary side in the flow direction is designated as a discharge-side resistance flow path 342. For example, the supply-side resistance flow path 341, the pressure chamber 31, and the outflow-side resistance flow path 342 are arranged in order along the extension direction.

[0044] In this embodiment, the cross-sectional area of ​​the discharge-side resistance flow path 342 on the OUT side is larger than the cross-sectional area of ​​the supply-side resistance flow path 341 on the IN side. For example, the cross-sectional areas are set so that the difference in viscous resistance is -17 to +17%. As an example, the height and length directions are the same, and the width direction is narrower.

[0045] Figure 6 is a table showing the change in viscous resistance when the cross-sectional area of ​​the resistance flow path is changed. Figure 6 shows the correspondence between the resistance flow path width WB on the supply side (IN side), the resistance flow path width WC on the discharge side (OUT side), the dimensional difference between the width WB and WC, the viscous resistance on the IN side, the viscous resistance on the OUT side, the viscous resistance ratio between the IN and OUT sides, the width dimension ratio of the resistance flow paths 341 and 342 on the IN and OUT sides, the circulation flow rate, the nozzle negative pressure variation, and the nozzle negative pressure variation range. Figure 7 is a graph showing the relationship between the circulation flow rate and the nozzle negative pressure variation. As a reference example, Figure 7 shows the circulation flow rate and the nozzle negative pressure variation when the resistance flow path height is 30 μm and the IN and OUT flow path widths are both 70 μm, with a maximum dimensional variation of ±5.4.3 μm.

[0046] The maintenance of nozzle negative pressure is due to viscous resistance, and can be calculated from the viscous resistance values ​​of the resistance flow path 34 and the common liquid chambers 32 and 33. Note that here, the viscous resistance of the common liquid chambers 32 and 33 is approximately 1 / 100 of that of the resistance flow path 34, and is therefore at a virtually negligible level, so the calculation is based on the viscous resistance value of the resistance flow path 34 without taking this into consideration. Note that it is also possible to calculate the resistance of the common liquid chambers 32 and 33 as well.

[0047] According to FIG. 6, when the cross-sectional area ratio of the resistance flow paths 341, 342 changes by -15% to +13%, the viscous resistance changes by -17% to +17%. Therefore, in this embodiment, the viscous resistance of the IN-side and OUT-side resistance flow paths 341, 342 is smaller on the OUT side than on the IN side, and the difference in viscous resistance is, for example, within 17% of the viscous resistance of the IN side. Furthermore, the cross-sectional area of ​​the IN-side and OUT-side resistance flow paths 341, 342 is larger on the OUT side than on the IN side, and the difference in cross-sectional area is within 15% of the cross-sectional area of ​​the IN side. That is, in this embodiment, since the heights are equal, the difference WB-WC between the flow path widths WB and WC is within 15% of the width WB. Note that when the cross-sectional area and width of the OUT side are used as references, the difference in cross-sectional area is within 13% of the cross-sectional area of ​​the OUT side, and the difference in flow path width WB-WC is within 13% of the flow path width WC.

[0048] Here, the nozzle negative pressure variation is expressed as ΔP = R × Q, which is the relationship between resistance and circulation flow rate. R: resistance [kg / m^4 / s] (resistance flow path dimension), Q: circulation flow rate [mL / min]. Also, as shown in Figure 7, nozzle negative pressure variation generally tends to increase depending on the circulation flow rate. In other words, nozzle negative pressure variation ΔP is determined by resistance R and circulation flow rate Q, and resistance R is determined by the flow path resistance dimension. Therefore, nozzle negative pressure variation ΔP can be determined by the cross-sectional area and circulation flow rate Q. In this embodiment, nozzle negative pressure variation ΔP can be determined by specifying the width dimension WB.WC and the circulation flow rate Q. Based on these relationships, in this embodiment, the nozzle negative pressure variation should be set to 500 Pa or less, and the allowable circulation flow rate at that time is 5 mL / min. A circulation flow rate of 5 mL / min can ensure a sufficient circulation flow rate.

[0049] The nozzle plate 50 is configured as a rectangular plate with a thickness of approximately 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 arranged on one side of the manifold 40 so as to cover the openings on one side of the pressure chambers 31. The nozzle plate 50 has a plurality of nozzles 51 that eject droplets. The plurality of nozzles 51 are holes that penetrate the nozzle plate 50 in the thickness direction. The nozzles 51 are arranged in a first direction, which is the same as the arrangement direction of the pressure chambers 31, to form a nozzle row. Each nozzle 51 is provided at a position corresponding to one of the plurality of pressure chambers 31.

[0050] The frame portion 45 is a structure that is bonded to the vibration plate 30 together with the piezoelectric elements 21 and 22. The frame portion 45 is provided on the side of the vibration plate 30 opposite the manifold 40 from the piezoelectric elements 21 and 22, and is disposed adjacent to the actuator portion 20 in this embodiment, for example. The frame portion 45 forms the outer shell of the inkjet head 1. The frame portion 45 may also have a liquid flow path formed therein. In this embodiment, the frame portion 45 is bonded to the other side of the vibration plate 30, and forms a first common liquid chamber 32 between itself and the vibration plate 30.

[0051] The first common liquid chamber 32 is formed inside the frame portion 45, and communicates with the pressure chamber 31 through an opening 303 provided in the vibration plate 30, the second common liquid chamber 33, and the resistance flow path .

[0052] 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.

[0053] The drive circuit 70 applies a drive voltage to the external electrodes 223 and 224 using a driver IC, thereby driving the piezoelectric element 21 and increasing or decreasing the volume of the pressure chamber 31 , thereby causing droplets to be ejected from the nozzle 51 .

[0054] The wiring film is connected to the plurality of external electrodes 223, 224. For example, the wiring film is an ACF (anisotropic conductive film) that is fixed by thermocompression bonding or the like to the connection portions of the external electrodes 223, 224. The wiring film is, for example, a COF (chip on film) on which a driver IC is mounted.

[0055] The driver IC is connected to the external electrodes 223, 224 via a wiring film. The driver IC may be connected to the external electrodes 223, 224 by other means such as ACP (anisotropic conductive paste), NCF (non-conductive film), and NCP (non-conductive paste) instead of the wiring film.

[0056] The driver IC generates control signals and drive signals for operating each piezoelectric element 21. The driver IC generates control signals for controlling the timing of ink ejection and the selection of the piezoelectric elements 21 to eject ink, in accordance with an image signal input from the control unit 150 of the inkjet recording apparatus 100. The driver IC also generates a voltage, i.e., a drive signal (electrical signal), to be applied to the piezoelectric elements 21 in accordance with the control signal. When the driver IC applies the drive signal to the piezoelectric elements 21, the piezoelectric elements 21 are driven to displace the diaphragm 30 and change the volume of the pressure chambers 31. This causes pressure vibrations in the ink filled in the pressure chambers 31. The pressure vibrations cause ink to be ejected from the nozzles 51 provided in the pressure chambers 31. The inkjet head 1 may be configured to achieve gradation expression by changing the amount of ink droplets that land on one pixel. The inkjet head 1 may also be configured to change the amount of ink droplets that land on one pixel by changing the number of ink ejections. Thus, the driver IC is an example of an application unit that applies drive signals to the piezoelectric elements 21.

[0057] For example, the driver IC includes a data buffer, a decoder, and a driver. The data buffer stores print data for each piezoelectric element 21 in chronological order. The decoder controls the driver for each piezoelectric element 21 based on the print data stored in the data buffer. The driver outputs a drive signal that operates each piezoelectric element 21 under the control of the decoder. The drive signal is, for example, a voltage applied to each piezoelectric element 21.

[0058] 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 a control unit 150 of the inkjet recording apparatus 100.

[0059] In the inkjet head 1 configured as described above, the nozzle plate 50, frame portion 45, manifold 40, and vibration plate 30 form an ink flow path 35 having a plurality of pressure chambers 31 communicating with the nozzles 51, connection flow paths made up of resistance flow paths 34 communicating with each of the plurality of pressure chambers 31 in the extension direction, and a second common liquid chamber 33 and a first common liquid chamber 32 that serve as a common flow path. The resistance flow paths 34 are arranged on both sides of the pressure chambers 31 in the extension direction, and further, a common chamber made up of the common liquid chambers 33, 32 is arranged continuous with the ends of the resistance flow paths 34 on both sides in the extension direction.

[0060] The inkjet head 1 is of a circulation type, and for example, the first common liquid chamber 32 communicates with a cartridge, and ink is supplied to each pressure chamber 31 through the first common liquid chamber 32 on the inlet side. All of 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, 222 using a driver IC, the piezoelectric element 21 to be driven vibrates in the stacking direction, i.e., in the thickness direction of each piezoelectric layer 211. In other words, the piezoelectric element 21 vibrates vertically.

[0061] Specifically, the control unit 150 applies a drive voltage to the internal electrodes 221, 222 of the piezoelectric element 21 to be driven, thereby selectively driving the piezoelectric element 21 to be driven. Then, the vibration plate 30 is deformed by a combination of tensile deformation and compressive deformation caused by the piezoelectric element 21 to be driven, and the volume of the pressure chamber 31 is changed, thereby guiding liquid from the first common liquid chamber 32 and ejecting it from the nozzle 51.

[0062] The ink supplied to the pressure chamber 31 is ejected from the nozzle 51, and also passes through the other resistance flow path 34 on the recovery side, the second common liquid chamber 33, and the first common liquid chamber, and is then recovered into the cartridge.

[0063] In the inkjet head 1, one side in the extension direction is the inflow side (supply side), and the other side is the outflow side (recovery side), and ink circulates in the ink flow path .

[0064] An example of an inkjet recording apparatus 100 equipped with the inkjet head 1 will be described below 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 conveying device 115, and a control unit 150.

[0065] The inkjet recording device 100 is a liquid ejection device that performs an image formation process on paper P by ejecting a liquid such as ink while transporting the paper P as a printing medium, which is the ejection target, along a predetermined transport path A that runs from a medium supply section 112 through an image forming section 113 to a medium ejection section 114.

[0066] The housing 111 constitutes the outer shell of the inkjet recording apparatus 100. The housing 111 is provided at a predetermined location with an outlet for discharging the paper P to the outside.

[0067] The medium supply unit 112 includes a plurality of paper feed cassettes, and is configured to be able to hold a stack of multiple sheets of paper P of various sizes.

[0068] The medium discharge unit 114 includes a paper discharge tray configured to be able to hold the paper P discharged from the discharge port.

[0069] The image forming section 113 includes a support section 117 that supports the paper P, and a plurality of head units 130 that are disposed above the support section 117 and face each other.

[0070] The support section 117 includes a conveyor belt 118 that is looped in a predetermined area where image formation is performed, a support plate 119 that supports the conveyor belt 118 from the back side, and a plurality of belt rollers 120 that are provided on the back side of the conveyor belt 118.

[0071] During image formation, the support unit 117 supports the paper P on a holding surface, which is the upper surface of the conveyor belt 118, and conveys the paper P downstream by moving the conveyor belt 118 at a predetermined timing by the rotation of the belt roller 120.

[0072] The head unit 130 includes multiple (four color) inkjet heads 1, ink tanks 132 as liquid tanks mounted on each inkjet head 1, a connection path 133 connecting the inkjet heads 1 and the ink tanks 132, and a supply pump 134.

[0073] In this embodiment, the inkjet heads 1 are provided with four colors, cyan, magenta, yellow, and black, and ink tanks 132 that contain ink of each color. The ink tanks 132 are connected to the inkjet heads 1 by connection paths 133.

[0074] A negative pressure control device such as a pump (not shown) is connected to the ink tank 132. The negative pressure control device controls the negative pressure inside the ink tank 132 in accordance with the head value between the inkjet head 1 and the ink tank 132, thereby causing the ink supplied to each nozzle 51 of the inkjet head 1 to form a meniscus of a predetermined shape.

[0075] The supply pump 134 is a liquid transfer pump formed, for example, by a piezoelectric pump. The supply pump 134 is provided in a supply flow path. The supply pump 134 is connected to a drive circuit of the control unit 150 by wiring, and is configured to be controllable by a CPU (Central Processing Unit). The supply pump 134 supplies liquid to the inkjet head 1.

[0076] The conveying device 115 conveys the paper P along a conveying path A that runs from the medium supply unit 112 through the image forming unit 113 to the medium discharge unit 114. The conveying device 115 includes a plurality of guide plate pairs 121 and a plurality of conveying rollers 122 that are arranged along the conveying path A.

[0077] Each of the guide plate pairs 121 includes a pair of plate members arranged opposite each other with the paper P being conveyed therebetween, and guides the paper P along the conveying path A.

[0078] The conveying rollers 122 are driven to rotate under the control of the control unit 150, thereby sending the paper P downstream along the conveying path A. Note that sensors for detecting the conveying status of the paper are arranged at various points along the conveying path A.

[0079] The control unit 150 includes a control circuit 151 such as a CPU which is a controller, a ROM (Read Only Memory) which stores various programs, a RAM (Random Access Memory) which temporarily stores various variable data, image data, etc., and an interface unit which inputs data from the outside and outputs data to the outside.

[0080] In the inkjet recording apparatus 100 configured as described above, when the control unit 150 detects a print instruction entered by a user operating the operation input unit via an interface, for example, the control unit 150 drives the transport device 115 to transport the paper P and outputs a print signal to the head unit 130 at a predetermined timing, thereby driving the inkjet head 1. In the inkjet head 1, an image signal corresponding to image data is used to send a drive signal to the driver IC, which applies a drive voltage to the internal electrodes 221 and 222 to selectively drive the piezoelectric elements 21 to be ejected, causing them to vibrate longitudinally in the stacking direction, thereby changing the volume of the pressure chambers 31 and ejecting ink from the nozzles 51, thereby forming an image on the paper P held on the conveyor belt 118. In addition, in the liquid ejection operation, the control unit 150 drives the supply pump 134 to supply ink from the ink tank 132 to the first common liquid chamber 32 of the inkjet head 1.

[0081] Here, a driving operation for driving the inkjet head 1 will be described. The inkjet head 1 according to this embodiment includes piezoelectric elements 21 arranged opposite the pressure chambers 31, and these piezoelectric elements 21 are connected by wiring so that a voltage can be applied to them. The control unit 150 sends a driving signal to the driver IC in response to an image signal corresponding to image data, and applies a driving voltage to the internal electrodes 221, 222 of the piezoelectric elements 21 to be driven, thereby selectively deforming the piezoelectric elements 21 to be driven. Then, the volume of the pressure chambers 31 is changed by combining the deformation in the tensile direction and the deformation in the compressive direction of the vibration plate 30, thereby ejecting liquid.

[0082] For example, the control unit 150 alternately performs a tension operation and a compression operation. In the inkjet head 1, when tension is performed to increase the internal volume of the target pressure chamber 31, the piezoelectric element 21 to be driven is contracted, and the driving piezoelectric elements 22 that are not the driving target are not deformed. Also, in the inkjet head 1, when compression is performed to decrease the internal volume of the target pressure chamber 31, the driving piezoelectric element 21 to be driven is expanded, and the non-driven piezoelectric elements 22 are not deformed.

[0083] According to the inkjet head 1 and inkjet recording apparatus 100 of the above-described embodiment, the flow path resistance of the OUT-side resistance flow path can be made smaller than the flow path resistance of the IN-side resistance flow path, thereby maintaining the nozzle negative pressure. For example, when the cross-sectional area of ​​the OUT-side is smaller than the cross-sectional area of ​​the IN-side during ink circulation, ink leakage tends to occur, making it difficult to remove air bubbles remaining in the head, which affects the nozzle negative pressure. However, in the above-described embodiment, by making the flow path resistance on the OUT-side smaller than that on the IN-side, it is possible to suppress ink leakage and facilitate the removal of air bubbles. Furthermore, since the resistance flow path 341, pressure chamber 31, and resistance flow path 342 are arranged side by side from one side to the other in the extension direction and the flow direction is formed straight along the extension direction, it is easy to manage the flow path resistance.

[0084] The present invention is not limited to the above-described embodiment, and in the implementation stage, the components can be modified and embodied without departing from the spirit of the invention.

[0085] In this embodiment, an example has been shown in which the cross-sectional area of ​​the resistance flow path 34 is constant over the entire length, and the flow path resistance portion is formed over the entire length of the resistance flow path 34, but this is not limited to this. For example, a flow path resistance portion having a narrower cross-sectional area than other regions may be arranged in a partial region of the middle of the flow path connecting the pressure chamber and the common liquid chamber. Also, the cross-sectional area of ​​the resistance flow path does not have to be constant. In this case, too, the same effect as in the above embodiment can be obtained by making the flow path resistance on the OUT side smaller than that on the IN side.

[0086] For example, the specific configuration of the manifold 40 is not limited to that described above. For example, although an example has been shown in which the manifold 40 is formed from two flow path substrates 401 and 402, it may be formed from three or more substrates. Furthermore, the shape of the openings in each of the flow path substrates 401 and 402 is not limited to that in the above embodiment.

[0087] Furthermore, for example, in the above embodiment, an example was shown in which the second openings 4012, 4022 are divided into rows of pressure chambers 31 in the alignment direction to form the second common liquid chamber 33, but this is not limited to this, and for example, multiple second openings 4012, 4022 may be continuous in the alignment direction to form a common flow path.

[0088] For example, in the above embodiment, multiple layers of piezoelectric members are stacked and the piezoelectric element 21 is driven using longitudinal vibration (d33) in the stacking direction, but the present invention is not limited to this. For example, the present invention is applicable to a configuration in which the piezoelectric element 21 is composed of a single layer of piezoelectric member, and also applicable to a configuration in which the piezoelectric element 21 is driven by lateral vibration (d31).

[0089] Furthermore, the specific configuration of the piezoelectric elements 21 and 22, the shape of the flow paths, and the configuration and positional relationship of various components including the manifold 40, nozzle plate 50, and frame portion 45 are not limited to the above examples and can be modified as appropriate. Furthermore, the arrangement of the nozzles 51 and pressure chambers 31 is not limited to the above examples. For example, the nozzles 51 may be arranged in two or more rows. Furthermore, dummy chambers may be formed between multiple pressure chambers 31.

[0090] Furthermore, the liquid to be ejected is not limited to ink for printing, but may be, for example, a device that ejects liquid containing conductive particles for forming a wiring pattern on a printed wiring board.

[0091] Furthermore, in the above embodiment, the inkjet head 1 is used in a liquid ejection device such as an inkjet recording device, but the invention is not limited to this and can also be used in, for example, 3D printers, industrial manufacturing machines, and medical applications, and can be made smaller, lighter, and less expensive.

[0092] According to at least one of the embodiments described above, a desired flow path shape can be easily set.

[0093] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0094] 1...inkjet head, 20...actuator section, 21...driving piezoelectric element, 22...non-driving piezoelectric element, 23...groove, 30...diaphragm, 31...pressure chamber, 32...first common liquid chamber, 33...second common liquid chamber, 34 (341, 342)...resistance flow path, 35...ink flow path, 40...manifold, 41...peripheral wall section, 42...partition wall section, 43...side wall section, 45...frame section, 50...nozzle plate, 51...nozzle, 70...driving circuit, 100...inkjet recording device, 111...casing, 112...medium supply section, 113...image forming section, 114...medium discharge section, 115...transport device, 117...support section, 118...transport Belt, 119...support plate, 120...belt roller, 121...pair of guide plates, 122...conveyor roller, 130...head unit, 132...ink tank, 133...connecting path, 134...supply pump, 150...control unit, 151...control circuit, 211...piezoelectric layer, 221...internal electrode, 222...internal electrode, 223...external electrode, 224...external electrode, 301...vibration area, 302...support area, 303...opening, 401...flow path substrate, 402...flow path substrate, 4011...first opening, 4012...second opening, 4021...first opening, 4022...second opening, 4023...slit opening.

Claims

1. A plurality of pressure chambers; a common liquid chamber communicating with the plurality of pressure chambers; an inflow flow path that connects the inflow side of the pressure chamber with the common liquid chamber and has a resistance flow path with a cross-sectional area smaller than that of the pressure chamber; an outflow flow path that connects the outflow side of the pressure chamber with the common liquid chamber and has a resistance flow path with a cross-sectional area smaller than that of the pressure chamber; A liquid ejection head, wherein the flow path resistance of the inflow flow path is greater than the flow path resistance of the outflow flow path.

2. 2. The liquid ejection head according to claim 1, wherein a cross-sectional area of ​​the inflow channel perpendicular to the direction in which the resistance channel extends is smaller than a cross-sectional area of ​​the outflow channel perpendicular to the direction in which the resistance channel extends.

3. 2. The liquid ejection head according to claim 1, wherein a difference in viscous resistance between the resistance flow path of the inflow flow path and the resistance flow path of the outflow flow path is within 17%.

4. the common liquid chambers are disposed on one side and the other side in the extension direction of the pressure chambers, the inflow channel and the outflow channel are arranged along the extension direction on one side and the other side of the extension direction of the pressure chamber, respectively; The pressure chambers are arranged in a direction intersecting the extension direction, The liquid ejection head according to claim 1 , which is a circulation type, in which the inflow resistance flow path, the pressure chamber, and the outflow resistance flow path are aligned in order along the extension direction.

5. A liquid ejection apparatus comprising the liquid ejection head according to claim 1 .

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