Liquid ejection head and liquid ejection apparatus

Abstract

The invention provides a liquid ejection head and a liquid ejection apparatus, which can ensure good ejection performance. 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; an inflow flow path that connects the inflow side of the pressure chamber and the common liquid chamber, and that has a resistance flow path having a smaller cross-sectional area than the pressure chamber; and an outflow flow path that connects the outflow side of the pressure chamber and the common liquid chamber, and that has a resistance flow path having a smaller cross-sectional area than the pressure chamber. The flow path resistance of the inflow flow path is greater than the flow path resistance of the outflow flow path.

Description

Technical Field

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

[0002] Inkjet heads and other liquid ejection heads use a method whereby actuators made of piezoelectric materials such as PZT (lead zirconate titanate) deform a vibrating plate, thereby deforming pressure chambers facing the vibrating plate. This causes ink to be ejected from nozzles connected to the pressure chambers. The liquid ejection head comprises multiple actuators bonded to the vibrating plate and a flow path unit that forms the flow paths connecting the multiple pressure chambers facing the vibrating plate and the pressure chambers.

[0003] In such an inkjet head, when circulating ink, if the fluid resistance is high, it becomes difficult to maintain the nozzle negative pressure, which becomes a major factor causing ink leakage from the nozzle.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 5943292 Summary of the Invention

[0007] Technical problem to be solved by the invention

[0008] The technical problem to be solved by the present invention is to provide a liquid ejection head and a liquid ejection device that can ensure good ejection performance.

[0009] Technical solutions to technical problems

[0010] 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; an inlet flow path communicating the inflow side of the pressure chambers with the common liquid chamber and having a resistance flow path having a smaller cross-sectional area than that of the pressure chambers; and an outlet flow path communicating the outflow side of the pressure chambers with the common liquid chamber and having a resistance flow path having a smaller cross-sectional area than that of the pressure chambers. The flow path resistance of the inlet flow path is greater than the flow path resistance of the outlet flow path.

[0011] A liquid ejection device according to one embodiment includes the above-mentioned liquid ejection head. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a cross-sectional view showing a partial structure of the inkjet head according to the first embodiment.

[0013] Figure 2 It is a cross-sectional view showing the structure of a portion of the inkjet head.

[0014] Figure 3This is a cross-sectional view showing the structure of the first flow channel substrate of the inkjet head.

[0015] Figure 4 This is a cross-sectional view showing the structure of the second flow channel substrate of the inkjet head.

[0016] Figure 5 It is an explanatory diagram showing the shape of the flow path of the same inkjet head.

[0017] Figure 6 This is a table showing changes in viscous resistance when the cross-sectional area of ​​the resistance flow path is changed.

[0018] Figure 7 This is a graph showing the relationship between the circulation flow rate and the nozzle negative pressure deviation.

[0019] Figure 8 It is an explanatory diagram showing a schematic configuration of an inkjet recording apparatus according to the first embodiment. DETAILED DESCRIPTION

[0020] Below, refer to Figures 1 to 8 An inkjet head 1 as a liquid ejecting head and an inkjet recording apparatus 100 as a liquid ejecting device according to a first embodiment will be described. Figure 1 is a cross-sectional view showing a portion of the inkjet head according to the first embodiment. Figure 2 It is a plan view showing a part of the structure of the inkjet head. Figure 3 is a cross-sectional view showing the flow path substrate 401, Figure 4 4 is a cross-sectional view showing the fluid channel substrate 402 . Figure 5 It is an explanatory diagram showing the shape of the flow path. Figure 6 This is a table showing changes in viscous resistance when the cross-sectional area of ​​the resistance flow path is changed. Figure 7 This is a graph showing the relationship between the circulation flow rate and the nozzle negative pressure deviation. Figure 8 This is an explanatory diagram schematically illustrating the configuration of an inkjet recording device. Arrows X, Y, and Z in the figures indicate three mutually orthogonal directions. In this embodiment, X corresponds to the alignment direction of the nozzle 51 and pressure chamber 31, Y corresponds to the extension direction, and Z corresponds to the opposing direction and the nozzle axial direction. For ease of explanation, the various figures may be appropriately enlarged, reduced, or omitted.

[0021] like Figure 1 as well as Figure 2As shown, the inkjet head 1 includes an actuator unit 20, a vibration plate 30, a manifold 40 (a flow path member) having multiple flow path substrates 401 and 402, a nozzle plate 50 (a nozzle member) having multiple nozzles 51, a frame 45 (a structural component), and a drive circuit 70. As an example, this embodiment 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 vibration plate 30 of the inkjet head 1 are all along the Z direction. In this embodiment, the vibration plate 30 and the manifold 40 form a flow path structure on the back side of the nozzle plate 50, forming the ink flow path 35 (flow path portion) within the inkjet head 1. The inkjet head 1 is a circulation-type device that circulates liquid through a predetermined flow path.

[0022] The actuator unit 20 is composed, for example, of a piezoelectric member and includes a plurality of driving piezoelectric elements 21 (piezoelectric unit) and a plurality of non-driving piezoelectric elements 22, which are arranged alternately along the row direction. In this embodiment, a nozzle 51 is provided at the center of the actuator unit 20 in its extension direction. The actuator unit 20 has a symmetrical structure with one side centered on the nozzle 51. For example, the actuator unit 20 is bonded to a rectangular base.

[0023] In the actuator unit 20, a plurality of driving piezoelectric elements 21 and a plurality of non-driving piezoelectric elements 22 are arranged in a parallel direction at a certain interval. As an example, the plurality of driving piezoelectric elements 21 and the plurality of non-driving piezoelectric elements 22 are all configured as rectangular parallelepiped columns with the same outer shape. The actuator unit 20 is divided into a plurality of parts by, for example, a plurality of grooves 23, and the plurality of driving piezoelectric elements 21 and non-driving piezoelectric elements 22 are arranged in a column direction at the same intervals, for example, through grooves 23 of the same width.

[0024] For example, in a top view observed from the Z direction which is the axial direction of the nozzle 51, the multiple driving piezoelectric elements 21 and the multiple non-driving piezoelectric elements 22 are respectively configured as rectangles with the short side direction along the column direction of the element column and the long side direction along the extension direction orthogonal to the column direction and the Z direction.

[0025] The driving piezoelectric elements 21 are arranged in the Z direction at positions facing each of the plurality of pressure chambers 31 formed in the manifold 40. As an example, the center positions of the driving piezoelectric elements 21 in the row direction and the extension direction are aligned with the center positions of the pressure chambers 31 in the row direction and the extension direction in the Z direction.

[0026] The non-driven piezoelectric elements 22 are arranged in the Z direction at positions opposite to the partition walls 42 formed in the manifold 40. As an example, the center positions of the non-driven piezoelectric elements 22 in the row direction and the extension direction are aligned with the center positions of the partition walls 42 in the row direction and the extension direction in the Z direction.

[0027] For example, the stacked piezoelectric component constituting the actuator portion 20 is formed by stacking sheet-like piezoelectric materials and sintering them. In the actuator portion 20, a groove 23 is formed by cutting the stacked piezoelectric component from one end face, thereby forming a plurality of piezoelectric elements formed into a rectangular column at specified intervals. In addition, electrodes are provided in the plurality of columnar elements formed, forming a plurality of driving piezoelectric elements 21 and a plurality of non-driving piezoelectric elements 22 that are alternately configured. A plurality of driving piezoelectric elements 21 and a plurality of non-driving piezoelectric elements 22 are alternately arranged side by side with the groove 23 clamped in the column direction.

[0028] The piezoelectric components constituting the driven piezoelectric element 21 and the non-driven piezoelectric element 22 are, for example, stacked piezoelectric bodies. The driven piezoelectric element 21 and the non-driven piezoelectric element 22 include a plurality of stacked piezoelectric layers 211 and internal electrodes 221 and 222 formed on the main surfaces of each piezoelectric layer 211. It should be noted that, as an example, the driven piezoelectric element 21 and the non-driven piezoelectric element 22 have the same stacked structure. Furthermore, the driven piezoelectric element 21 and the non-driven piezoelectric element 22 include external electrodes 223 and 224 formed on their surfaces.

[0029] The piezoelectric layer 211 is composed of a piezoelectric material such as PZT (lead zirconate titanate) or a lead-free KNN (sodium potassium niobate)-based material. The piezoelectric layers 211 are stacked with their thickness aligned along the stacking direction. For example, in this embodiment, the piezoelectric layers 211 are arranged with their thickness and stacking directions aligned along the vibration direction (Z direction).

[0030] The internal electrodes 221 and 222 are conductive films formed in a predetermined shape using a sinterable conductive material such as silver palladium. The internal electrodes 221 and 222 are formed in predetermined regions on the main surface of each piezoelectric layer 211. The internal electrodes 221 and 222 have different poles. 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 orthogonal to both the column direction (X direction) and the vibration direction (Z direction) that are the directions in which the multiple driven piezoelectric elements 21 and the multiple non-driven piezoelectric elements 22 are arranged. 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 and 222 are connected to external electrodes 223 and 224 formed on the side surfaces of the piezoelectric elements 21 and 22, respectively.

[0031] Furthermore, the laminated piezoelectric components constituting the driving piezoelectric element 21 and the non-driving piezoelectric element 22 may further include a dummy layer on either or both of the ends on the nozzle plate 50 side or the opposite side. For example, the dummy layer may be made of the same material as the piezoelectric layer 211, have an electrode on only one side, and, because no electric field is applied, does not deform. For example, the dummy layer does not function as a piezoelectric element, but rather serves to secure the actuator unit 20 to the base or to provide a grinding allowance for improving precision during or after assembly.

[0032] The external electrodes 223 and 224 are formed on the surfaces of multiple driving piezoelectric elements 21 and multiple non-driving piezoelectric elements 22, and are composed of 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 in the extension direction of the piezoelectric layer 211. The external electrodes 223 and 224 are formed into films using Ni, Cr, Au, etc. using known methods such as electroplating and sputtering. The external electrodes 223 and 224 are different poles. The external electrodes 223 and 224 are respectively configured on different side surfaces of multiple driving piezoelectric elements 21 and multiple non-driving piezoelectric elements 22. It should be noted that the external electrodes 223 and 224 can also be wound around different regions in the same side surface of multiple driving piezoelectric elements 21 and multiple non-driving piezoelectric elements 22.

[0033] In this embodiment, as an example, the external electrode 223 is set as an independent electrode, and the external electrode 224 is set as a common electrode. The electrode layers of the external electrodes 223 that become independent electrodes of multiple driving piezoelectric elements 21 and multiple non-driving piezoelectric elements 22 are divided by the groove 23 and are configured independently of each other. The electrode layers of the external electrodes 224 that become common electrodes are connected to each other, for example, on the side of the actuator part 20, for example, they are grounded. The external electrodes 223 and 224 are connected to the driving circuit 70, for example, via a wiring film. For example, each external electrode 223 and 224 is connected to the control unit 150 via the driving IC 72 of the driving circuit 70, and is configured to be capable of driving control. It should be noted that the configuration of the common electrode and the independent electrode can also be reversed.

[0034] Furthermore, the vibration direction of each piezoelectric element 21, 22 is along the stacking direction, and is displaced in the d33 direction by application of an electric field. The number of stacked layers of piezoelectric layers 211 and internal electrodes 221, 22 in each piezoelectric element 21, 22 is three or more. As an example, each piezoelectric element 21, 22 has three or more layers and no more than 50 layers, with each layer having a thickness of 10 μm or more and 40 μm or less, and the product of the thickness and the total number of stacked layers being less than 1000 μm.

[0035] In the inkjet head 1, the piezoelectric element 21 is driven to vibrate by applying a voltage to the internal electrodes 221 and 222 via the external electrodes 223 and 224. In this embodiment, the piezoelectric element 21 is driven to vibrate longitudinally along the stacking direction of the piezoelectric layer 211. The longitudinal vibration referred to here refers to, for example, "vibration in the thickness direction defined by the piezoelectric constant d33." This longitudinal vibration of the piezoelectric element 21 displaces the vibration plate 30, thereby deforming the pressure chamber 31.

[0036] The vibration plate 30 extends along a surface perpendicular to the Z direction, which is the vibration direction, and is bonded to a surface on one side of the vibration direction of the piezoelectric layer 211 of the plurality of piezoelectric elements 21 and 22, that is, on the nozzle plate 50 side. The vibration plate 30 is opposite to the plurality of nozzles 51 via the pressure chamber 31 in the Z direction, which is the vibration direction. The vibration plate 30 is configured to be deformable, for example. The vibration plate 30 is bonded to the driving piezoelectric element 21 and the non-driving piezoelectric element 22 of the actuator unit 20, and the frame unit 45. For example, the vibration plate 30 has a vibration region 301 opposite to the piezoelectric elements 21 and 22, and a support region 302 opposite to the frame unit 45. The vibration plate 30 is arranged between the flow path substrate 401 and the actuator unit 20 in the vibration direction. The vibration plate 30 and the plurality of flow path substrates 401 and 402 are arranged to overlap and constitute a part of the ink flow path 35.

[0037] The vibration region 301 is, for example, a flat plate configured such that its thickness direction corresponds to the vibration direction of the piezoelectric layer 211. The surface of the vibration plate 30 extends in the direction in which the multiple driven piezoelectric elements 21 and the multiple non-driven piezoelectric elements 22 are arranged side by side. The vibration plate 30 is, for example, a metal plate. The vibration plate 30 has multiple vibration regions that are opposed to each pressure chamber 31 and can be independently displaced. The vibration plate 30 is formed by connecting the multiple vibration regions into one integral body.

[0038] As an example, the vibration plate 30 is made of nickel or SUS plate, and the thickness dimension along the vibration direction is about 5μm to 15μm. It should be noted that the vibration region 301 can also form folds and steps in the parts adjacent to the vibration parts or between the vibration parts adjacent to each other, so that multiple vibration parts are easy to displace. The vibration region 301 is deformed by the displacement of the part opposite to the driving piezoelectric element 21 through the extension and compression of the driving piezoelectric element 21. For example, the vibration plate 30 needs to be very thin and complex in shape, so it is formed by electroforming or the like. The vibration plate 30 is joined to the upper end surface of the actuator part 20 by bonding or the like.

[0039] The support region 302 is a plate-shaped member disposed between the frame portion 45 and the fluid channel substrate 401. The vibration plate 30 has a structure symmetrical between one side and the other side in the Y direction with the nozzle 51 as the center.

[0040] 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 that connects the second common liquid chamber 33 and the common liquid chamber 32.

[0041] The manifold 40 is joined to one side of the vibration plate 30. Figures 1 to 3 As shown, the manifold 40 includes a plurality of stacked flow path substrates 401 and 402. For example, depending on the viscosity of the ink, the ejection volume, and other factors, a plurality of flow path substrates 401 and 402 having openings or grooves, the nozzle plate 50, and the vibration plate 30 are combined and joined to form the desired ink flow path 35. The plurality of flow path substrates 401 and 402 are stacked in the stacking direction. The openings or grooves formed in each flow path substrate 401 and 402 define the predetermined ink flow path 35, which includes the second common liquid chamber 33, the resistance flow path 34 serving as a throttling flow path or flow path resistance portion, and the pressure chamber 31. For example, a first flow path substrate 401 and a second flow path substrate 402 are stacked in order from the vibration plate 30 side, with the flow path substrate 402 facing the nozzle plate 50.

[0042] In this embodiment, the ink flow path 35 has an inflow path formed on the inflow side, which is one side in the direction in which the pressure chamber 31 extends, and an outflow path formed on the other side in the direction in which the pressure chamber 31 extends. Specifically, the resistance flow path 341 and the common liquid chambers 32 and 33 arranged on one side of the pressure chamber 31 serve as the inflow path 351, while the resistance flow path 342 and the common liquid chambers 32 and 33 arranged on the other side of the pressure chamber 31 serve as the outflow path 352.

[0043] The manifold 40 is arranged between the nozzle plate 50 and the vibration plate 30. The manifold 40 is formed by stacking a plurality of flow path substrates 401 and 402 and bonding them to each other, and a prescribed ink flow path 35 (liquid chamber) is formed inside thereof, which has a plurality of pressure chambers 31, a second common liquid chamber 33 connected to the first common liquid chamber 32, and a plurality of resistance flow paths 34 reaching the pressure chamber 31 from the second common liquid chamber 33. In other words, the manifold 40 is formed by stacking a plurality of flow path substrates 401 and 402 to form a peripheral wall portion 41, a plurality of partition wall portions 42 separating the columns of the plurality of pressure chambers 31, and a side wall portion 43 separating the plurality of resistance flow paths 34, and the peripheral wall portion 41 surrounds the ink flow path 35 (liquid chamber) composed 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. For example, in the present embodiment, Figures 3 to 5 4 shows a region of the manifold 40 corresponding to a column of pressure chambers.

[0044] like Figure 1 as well as Figure 2As shown, the fluid path substrate 401 is bonded to the vibration plate 30. The fluid path substrate 401 is a plate-shaped member having the same outer shape as the vibration plate 30 and, for example, is made of a metal material such as SUS430 or a resin material such as silicone. The fluid 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 located in the center of the ink flow path 35 in the direction of extension, and the second openings 4012 are located at both ends.

[0045] The flow path substrate 402 is joined 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, for example, is made of 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 a portion of the pressure chamber 31, a second opening 4022 that forms a portion of the second common liquid chamber 33, and an elongated slit opening 4023 that forms the resistance flow path 34 as an independent flow path. For example, the first opening 4021 is arranged in the center of the direction in which the ink flow path 35 extends, the slit openings 4023 are arranged at both ends of the first opening 4021, and the second openings 4022 are arranged at the outer ends of the slit openings 4023 on both sides. The openings 4021, 4022, and 4023 are arranged in multiple rows in the parallel direction.

[0046] For example, the flow path substrates 401 and 402 are configured to have a thickness of 20 μm to 100 μm. For example, at 300 dpi, the 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 and WC of the slit opening 4023 forming the resistance flow path 34 are smaller than the width WA of the first opening 4021 forming the pressure chamber 31 and the second opening 4022 forming the common liquid chamber 32. It should be noted that the widths WA, WB, and WC are the width dimensions in the X direction, which are the width dimensions intersecting one direction and the stacking direction. That is, the resistance flow path 34 constitutes a flow path resistance portion having a smaller cross-sectional area than the pressure chamber 31. As an example, in this embodiment, the flow path cross-section of the resistance flow path 34 is constant over the entire length of the extension direction, and the entire length of the resistance flow path 34 constitutes the flow path resistance portion.

[0047] In the manifold 40, the first openings 4011 and 4021 of the plurality of fluid channel substrates 401 and 402 arranged and communicating with each other in the stacking direction form a plurality of pressure chambers 31. 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 on the nozzle plate 50. The side of the pressure chambers 31 opposite the nozzle plate 50 is blocked by the vibration plate 30.

[0048] The plurality of pressure chambers 31 communicate with the first common liquid chamber 32 via the resistance flow path 34 and the second common liquid chamber 33 through the opening 303. The pressure chambers 31 hold liquid supplied from the first common liquid chamber 32 through the second common liquid chamber 33 and the resistance flow path 34. The pressure chambers 31 are deformed by the vibration of the vibrating plate 30, which forms a portion of the pressure chambers 31, and the liquid is ejected from the nozzles 51.

[0049] 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 and 4022 of the plurality of fluid channel substrates 401 and 402 arranged in the stacking direction and communicating with each other.

[0050] The second common liquid chamber 33 is a flow path that communicates with the flow direction ends of the plurality of 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 of the flow path substrates 401 and 402 has a symmetrical structure with one side and the other side in the Y direction centered on the nozzle 51. The second common liquid chambers 33 arranged on both sides in the Y direction, centered on the central pressure chamber 31, are configured to have equal flow path lengths and flow path cross-sectional shapes perpendicular to the Y direction.

[0051] Furthermore, in the manifold 40, the slit openings 4023 of the fluidic channel substrate 402 form resistance channels 34. The resistance channels 34 connect the pressure chambers 31 and the second common liquid chamber 33 and extend in the Y direction, which serves as the flow direction. The resistance channels 34 on both sides are configured so that their width, perpendicular to the direction of extension serving as the flow direction, is smaller than that of the second common liquid chamber 33 and the pressure chamber 31, and thus have a narrower flow channel cross section.

[0052] Here, each fluid-channel substrate 401, 402 is configured so that the resistance channels 34, arranged on both sides of the central pressure chamber 31 in the Y direction, have equal channel lengths and heights. Furthermore, in the manifold 40, the areas surrounding the first openings 4011, 4021 of the stacked fluid-channel substrates 401, 402 form partition walls 42 that separate the multiple pressure chambers 31.

[0053] The partition wall 42 is a wall-like member that separates the plurality of pressure chambers 31 in the parallel direction. The partition wall 42 is arranged opposite the non-driven piezoelectric element 22 via the vibration plate 30 and is supported by the non-driven piezoelectric element 22. A plurality of partition walls 42 are provided at the same pitch as the pitch of the plurality of pressure chambers 31.

[0054] In the manifold 40 , sidewalls 43 that separate the plurality of resistance flow paths 34 are formed by portions on both sides of the slit opening 4023 of the flow path substrate 402 .

[0055] The sidewalls 43 are wall-like members that separate the plurality of resistance flow paths 34 in the parallel direction. For example, the sidewalls 43 are provided so as to communicate with both sides of the pressure chamber 31. The sidewalls 43 are configured so that the flow resistance of the resistance flow path 34 is greater than that within the pressure chamber 31, and the flow cross-sectional area of ​​the resistance flow path 34 is smaller than that within the pressure chamber 31. A plurality of sidewalls 43 are provided at the same pitch as the arrangement of the plurality of pressure chambers 31.

[0056] Here, the resistance flow path 34, which serves as the fluid resistance portion, is configured to have a cross-sectional area perpendicular to the second direction, which serves as the flow direction of the ink, smaller than that of the pressure chamber 31. In this embodiment, the flow direction is set from one side of the extension direction to the other side. In this embodiment, as an example, with respect to the resistance flow paths 34, 34 on both sides, the resistance flow path 34 on the one side, which will serve as the primary side of the flow direction, is set as the supply-side resistance flow path 341, and the resistance flow path 34 on the other side, which will serve as the secondary side of the flow direction, is set as the discharge-side resistance flow path 342. For example, the supply-side resistance flow path 341, the pressure chamber 31, and the discharge-side resistance flow path 342 are arranged in sequence along the extension direction.

[0057] 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 area is set so that the difference in viscous resistance is between -17% and +17%. As an example, the height and length dimensions are set to be the same, while the width dimension is narrow.

[0058] Figure 6 This is a table showing changes in viscous resistance when the cross-sectional area of ​​the resistance flow path is changed. Figure 6 The correspondence is shown among 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 size difference between the widths WB and WC, the viscous resistance on the IN side, the viscous resistance on the OUT side, the viscous resistance ratio between the IN side and the OUT side, the width size ratio of the resistance flow paths 341 and 342 on the IN side and the OUT side, the circulation flow rate, the nozzle negative pressure deviation, and the nozzle negative pressure deviation range. Figure 7 This is a graph showing the relationship between the circulation flow rate and the nozzle negative pressure deviation. Figure 7 As a reference example, the deviation of the circulation flow rate and the nozzle negative pressure when the maximum dimensional deviation is ±5, 4, and 3µm is shown when the resistance flow path height is set to 30µm and the flow path widths of IN and OUT are both set to 70µm.

[0059] Maintenance of nozzle negative pressure can be calculated based on viscous resistance using the viscous resistance values ​​of the resistance flow path 34 and the common liquid chambers 32 and 33. It should be noted that, here, since the viscous resistance of the common liquid chambers 32 and 33 is approximately 1 / 100 of that of the resistance flow path 34, which is almost negligible, it is not considered and the calculation is based on the viscous resistance value of the resistance flow path 34. It should be noted that the calculation can also include the resistance of the common liquid chambers 32 and 33.

[0060] according to Figure 6 When the cross-sectional area ratio of the resistance flow paths 341 and 342 varies between -15% and +13%, the viscous resistance varies between -17% and +17%. Therefore, in this embodiment, the viscous resistance of the resistance flow paths 341 and 342 on the IN and OUT sides is smaller on the OUT side than on the IN side, and the difference in viscous resistance is set, for example, to within 17% of the viscous resistance on the IN side. Furthermore, the cross-sectional area of ​​the resistance flow paths 341 and 342 on the IN and OUT sides is larger on the OUT side than on the IN side, and the difference in cross-sectional area is set to within 15% of the cross-sectional area on 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 set to within 15% of the width WB. It should be noted that, based on the cross-sectional area and width on the OUT side, the difference in cross-sectional area is set to within 13% of the cross-sectional area on the OUT side, and the difference (WB-WC) in the flow path width is set to within 13% of the flow path width WC.

[0061] Here, the nozzle negative pressure deviation can be expressed as ΔP = R × Q based on the relationship between resistance and circulation flow rate. R: resistance [kg / m^4 / s] (resistance flow path size) Q: circulation flow rate [mL / min]. In addition, if Figure 7 As shown, nozzle negative pressure deviation generally tends to increase with circulation flow rate. Specifically, nozzle negative pressure deviation ΔP is determined by resistance R and circulation flow rate Q, with resistance R being determined by the flow path resistance dimension. Therefore, nozzle negative pressure deviation ΔP can be specified based on the cross-sectional area and circulation flow rate Q. In this embodiment, nozzle negative pressure deviation ΔP can be specified by specifying width dimensions WB and WC and circulation flow rate Q.

[0062] Based on these relationships, in this embodiment, the nozzle negative pressure deviation is set to 500 Pa or less as an indicator, and the allowable circulation flow rate at this time is 5 mL / min. If it is 5 mL / min, a sufficient circulation flow rate can be ensured.

[0063] The nozzle plate 50 is a square plate with a thickness of approximately 10 to 100 μm, made of, for example, a metal such as SUS or Ni, or a resin material such as polyimide. The nozzle plate 50 is positioned on one side of the manifold 40 so as to cover the opening on one side of the pressure chambers 31. The nozzle plate 50 includes a plurality of nozzles 51 for ejecting droplets. The plurality of nozzles 51 are holes that penetrate the nozzle plate 50 in the thickness direction. The plurality of nozzles 51 are arranged side by side in a first direction that is the same as the direction in which the pressure chambers 31 are arranged, forming a nozzle row. Each nozzle 51 is provided at a position corresponding to each of the plurality of pressure chambers 31.

[0064] The frame portion 45 is a structure that is joined 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 to the manifold 40 of the piezoelectric elements 21 and 22, and is, for example, arranged adjacent to the actuator portion 20 in this embodiment. The frame portion 45 constitutes the outer contour of the inkjet head 1. In addition, the frame portion 45 may also form a flow path for the liquid inside. In this embodiment, the frame portion 45 is joined to the other side of the vibration plate 30 and forms a first common liquid chamber 32 between the frame portion 45 and the vibration plate 30.

[0065] The first common liquid chamber 32 is formed inside the frame portion 45 and communicates with the pressure chamber 31 through the opening 303 provided in the vibration plate 30 , the second common liquid chamber 33 , and the resistance flow path 34 .

[0066] The driving 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.

[0067] The driving circuit 70 applies a driving voltage to the external electrodes 223 and 224 using a driver IC to drive the piezoelectric element 21 , thereby increasing or decreasing the volume of the pressure chamber 31 and ejecting liquid droplets from the nozzle 51 .

[0068] The wiring film is connected to the plurality of external electrodes 223 and 224. For example, the wiring film is an ACF (anisotropic conductive film) fixed to the connection portion of the external electrodes 223 and 224 by thermocompression bonding or the like. For example, the wiring film is a COF (chip on film) on which a driver IC is mounted.

[0069] The driver IC is connected to the external electrodes 223 and 224 via a wiring film. Note that the driver IC may be connected to the external electrodes 223 and 224 using other methods such as ACP (anisotropic conductive paste), NCF (non-conductive film), or NCP (non-conductive paste) instead of the wiring film.

[0070] The driver IC generates control signals and drive signals for operating each piezoelectric element 21. Based on image signals input from the control unit 150 of the inkjet recording device 100, the driver IC generates control signals for controlling the timing of ink ejection and the selection of the piezoelectric element 21 to eject ink. Furthermore, based on the control signals, the driver IC generates a voltage applied to the piezoelectric element 21, namely a drive signal (electrical signal). When the driver IC applies the drive signal to the piezoelectric element 21, the piezoelectric element 21 is driven so that the vibration plate 30 displaces, thereby changing the volume of the pressure chamber 31. This generates pressure vibrations in the ink filling the pressure chamber 31. These pressure vibrations cause the ink to be ejected from the nozzle 51 provided in the pressure chamber 31. It should be noted that the inkjet head 1 can also be configured to achieve grayscale rendering by varying the amount of ink droplets deposited per pixel. Alternatively, the inkjet head 1 can be configured to vary the amount of ink droplets deposited per pixel by changing the number of ink ejections. Thus, the driver IC is an example of a unit that applies the drive signal to the piezoelectric element 21.

[0071] For example, the driver IC includes a data buffer, a decoder, and a driver. The data buffer stores print data in a time-series format for each piezoelectric element 21. The decoder controls the driver for each piezoelectric element 21 based on the print data stored in the data buffer. Based on the decoder's control, the driver outputs a drive signal to activate each piezoelectric element 21. The drive signal is, for example, a voltage applied to each piezoelectric element 21.

[0072] 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 .

[0073] In the inkjet head 1 constructed as described above, the nozzle plate 50, frame portion 45, manifold 40, and vibration plate 30 form an ink flow path 35. The ink flow path 35 includes a plurality of pressure chambers 31 communicating with the nozzles 51, a connecting flow path formed by resistance flow paths 34 communicating with each of the plurality of pressure chambers 31 in the extending direction, and a second common liquid chamber 33 and a first common liquid chamber 32 serving as a common flow path. The resistance flow paths 34 are disposed on either side of the pressure chambers 31 in the extending direction, and a common chamber formed by the common liquid chambers 33 and 32 is disposed continuously at the ends of the resistance flow paths 34 on both sides in the extending direction.

[0074] The inkjet head 1 is a circulation-type inkjet head. For example, the first common liquid chamber 32 is connected to the cartridge, and ink is supplied to each pressure chamber 31 through the first common liquid chamber 32 on the inflow side. All piezoelectric elements 21 are connected by wiring so that voltage can be applied. In the inkjet head 1, when the control unit 150 applies a driving voltage to the electrodes 221 and 222 via the driver IC, the piezoelectric elements 21 vibrate in the stacking direction, that is, in the thickness direction of each piezoelectric layer 211. In other words, the piezoelectric elements 21 vibrate longitudinally.

[0075] Specifically, the control unit 150 applies a driving voltage to the internal electrodes 221 and 222 of the piezoelectric element 21 to be driven, thereby selectively driving the piezoelectric element 21. The vibration plate 30 is then deformed by combining the tensile and compressive deformations of the piezoelectric element 21 to change the volume of the pressure chamber 31. This causes liquid to be drawn from the first common liquid chamber 32 and ejected from the nozzle 51.

[0076] The ink supplied to the pressure chamber 31 is discharged from the nozzle 51 and then recovered in the cartridge through the other resistance flow path 34 , the second common liquid chamber 33 , and the first common liquid chamber.

[0077] In the inkjet head 1 , ink circulates in the ink flow path 35 , with one side in the extending direction being the inflow side (supply side) and the other side being the outflow side (recovery side).

[0078] Below, refer to Figure 8 An example of an inkjet recording apparatus 100 including the inkjet head 1 will be described. 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 .

[0079] The inkjet recording device 100 is a liquid ejecting device that ejects liquid such as ink while transporting, for example, paper P as a ejection object, i.e., a printing medium, along a predetermined transport path A from a medium supply unit 112 through an image forming unit 113 to a medium discharge unit 114, thereby performing image forming processing on the paper P.

[0080] The housing 111 constitutes the outer shell of the inkjet recording apparatus 100. The housing 111 is provided with a discharge port at a predetermined position thereof for discharging the paper P to the outside.

[0081] 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.

[0082] The medium discharge unit 114 includes a paper discharge tray configured to hold the paper P discharged from the discharge port.

[0083] The image forming section 113 includes a support portion 117 that supports the paper P, and a plurality of head units 130 that are arranged to face each other above the support portion 117 .

[0084] The support portion 117 includes a conveyor belt 118 provided in an endless shape in a predetermined area where image formation is performed, a support plate 119 supporting the conveyor belt 118 from the rear side, and a plurality of belt rollers 120 provided on the rear side of the conveyor belt 118 .

[0085] During image formation, the support portion 117 supports the paper P on a holding surface serving as the upper surface of the conveyor belt 118 , and conveys the conveyor belt 118 at a predetermined timing by the rotation of the belt roller 120 , thereby conveying the paper P downstream.

[0086] The head unit 130 includes a plurality of (four colors) inkjet heads 1 , ink tanks 132 as liquid cartridges mounted on the respective inkjet heads 1 , connection paths 133 connecting the inkjet heads 1 and the ink tanks 132 , and a supply pump 134 .

[0087] In this embodiment, the inkjet heads 1 for four colors, cyan, magenta, yellow, and black, and ink tanks 132 for storing inks of these colors are provided. The ink tanks 132 are connected to the inkjet heads 1 via connection paths 133 .

[0088] Furthermore, 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 within the ink tank 132 in accordance with the hydraulic head value between the inkjet head 1 and the ink tank 132, thereby forming a meniscus of a predetermined shape into the ink supplied to each nozzle 51 of the inkjet head 1.

[0089] The supply pump 134 is a liquid delivery pump, for example, a piezoelectric pump. The supply pump 134 is disposed in the supply flow path. The supply pump 134 is connected to the drive circuit of the control unit 150 via wiring and is controlled by the CPU (Central Processing Unit). The supply pump 134 supplies liquid to the inkjet head 1 .

[0090] The transport device 115 transports the paper P along a transport path A from the medium supply unit 112 through the image forming unit 113 to the medium discharge unit 114 . The transport device 115 includes a plurality of guide plate pairs 121 arranged along the transport path A and a plurality of transport rollers 122 .

[0091] Each of the plurality of guide plate pairs 121 includes a pair of plate members disposed opposite to each other with the paper P being transported interposed therebetween, and guides the paper P along the transport path A.

[0092] The conveyance roller 122 is driven and rotated under the control of the control unit 150 , thereby conveying the paper P downstream along the conveyance path A. Note that sensors for detecting the conveyance status of the paper are disposed at various locations in the conveyance path A.

[0093] The control unit 150 includes a control circuit 151 such as a CPU serving as a controller, a ROM (Read Only Memory) for storing various programs, a RAM (Random Access Memory) for temporarily storing various variable data, image data, etc., and an interface unit for inputting and outputting data from and to the outside.

[0094] In the inkjet recording device 100 configured as described above, when, for example, the interface detects a print instruction from a user operating the operation input unit, 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. As the inkjet head 1 performs an ejection operation, a drive signal is transmitted to the driver IC based on an image signal corresponding to image data. This applies a drive voltage to the internal electrodes 221 and 222, selectively driving the piezoelectric element 21 to be ejected, causing it to vibrate longitudinally in the stacking direction, thereby changing the volume of the pressure chamber 31. This causes ink to be ejected from the nozzle 51, forming an image on the paper P held on the transport belt 118. Furthermore, as a 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.

[0095] Here, the driving operation of the inkjet head 1 is described. The inkjet head 1 involved in this embodiment includes piezoelectric elements 21 arranged opposite to the pressure chamber 31. These piezoelectric elements 21 are connected by wiring so that voltage can be applied. The control unit 150 transmits a driving signal to the driver IC based on the image signal corresponding to the image data. The driving voltage is applied to the internal electrodes 221 and 222 of the piezoelectric element 21 to be driven, causing the piezoelectric element 21 to be driven to selectively deform. Then, by combining the deformation of the vibration plate 30 in the tensile direction and the deformation in the compressive direction, the volume of the pressure chamber 31 changes, causing liquid to be ejected.

[0096] For example, the control unit 150 alternates between stretching and compressing. In the inkjet head 1, when stretching is performed to increase the internal volume of the pressure chamber 31 of the object, the piezoelectric element 21 of the driven object is contracted, and the driven piezoelectric elements outside the driven object are not deformed. In addition, when compressing is performed to reduce the internal volume of the pressure chamber 31 of the object, the driven piezoelectric element 21 of the object is extended, and the non-driven piezoelectric elements 22 are not deformed.

[0097] According to the inkjet head 1 and inkjet recording device 100 according to the above-described embodiment, nozzle negative pressure can be maintained by making the flow resistance of the resistance flow path on the OUT side smaller than that of the resistance flow path on the IN side. For example, during ink circulation, if the cross-sectional area on the OUT side is smaller than that on the IN side, ink leakage tends to occur, making it difficult to remove bubbles trapped in the head, thus affecting nozzle negative pressure. However, in the above-described embodiment, by making the flow resistance on the OUT side smaller than that on the IN side, ink leakage can be suppressed and bubbles can be easily removed. 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, flow resistance can be easily managed.

[0098] It should be noted that the present invention is not limited to the above-described embodiment as it is, and in the implementation stage, constituent elements can be modified and embodied within a scope not departing from the gist of the invention.

[0099] It should be noted that in this embodiment, an example is 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 by the entire length of the resistance flow path 34, but the present invention is not limited to this. For example, a flow path resistance portion having a narrower cross-sectional area than other areas may be provided in a portion of the flow path connecting the pressure chamber and the common liquid chamber. Furthermore, the cross-sectional area of ​​the resistance flow path does not have to be constant. In this case, by making the flow path resistance on the OUT side smaller than on the IN side, the same effects as those of the above embodiment can be achieved.

[0100] For example, the specific structure of the manifold 40 is not limited to that described above. For example, an example is shown in which the manifold 40 is formed of two flow channel substrates 401 and 402, but it can also be formed of three or more. In addition, the shape of the openings in each flow channel substrate 401 and 402 is not limited to the above embodiment.

[0101] In addition, for example, in the above-mentioned embodiment, an example is shown in which the second opening portions 4012 and 4022 are divided into each column of the pressure chamber 31 in the parallel direction to form a second common liquid chamber 33, but it is not limited to this. For example, multiple second opening portions 4012 and 4022 can also be made continuous in the parallel direction to form a common flow path.

[0102] For example, in the above embodiment, a configuration is used in which piezoelectric elements 21 are driven by longitudinal vibration (d33) in the stacking direction using multiple layers of piezoelectric components. However, the present invention is not limited to this configuration. For example, the present invention can be applied to a configuration in which the piezoelectric element 21 is composed of a single layer of piezoelectric components, or to a configuration in which the piezoelectric element 21 is driven by transverse vibration (d31).

[0103] The specific configuration of the piezoelectric elements 21 and 22, the shape of the flow paths, and the configuration and positional relationships of the various components including the manifold 40, nozzle plate 50, and frame 45 are not limited to the examples described above and can be modified as appropriate. Furthermore, the arrangement of the nozzles 51 and pressure chambers 31 is not limited to that described above. For example, the nozzles 51 may be arranged in two or more rows. Furthermore, dummy chambers may be formed between multiple pressure chambers 31.

[0104] Furthermore, the liquid to be discharged is not limited to ink for printing, and for example, a device that discharges a liquid containing conductive particles for forming a wiring pattern of a printed wiring board may also be used.

[0105] In addition, in the above embodiment, an example of the inkjet head 1 being used in a liquid ejecting device such as an inkjet recording device is shown, but it is not limited to this. For example, it can also be used in 3D printers, industrial manufacturing machinery, and medical applications, and can achieve miniaturization, lightness, and low cost.

[0106] According to at least one embodiment described above, a desired flow path shape can be easily set.

[0107] In addition, although several embodiments of the present invention have been described, these embodiments are provided as examples only and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways and can be omitted, replaced, or modified in various ways without departing from the scope of the invention. These embodiments and their variations are included in the scope and spirit of the invention and are also included in the invention described in the claims and their equivalents.

[0108] Description of Reference Numerals

[0109] 1…Inkjet head; 20…Actuator unit; 21…Driven piezoelectric element; 22…Non-driven piezoelectric element; 23…Groove; 30…Vibration plate; 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; 42…Partition wall; 43…Side wall; 45…Frame; 50…Nozzle plate; 51…Nozzle; 70…Drive circuit; 100…Inkjet recording device; 111…Casing; 112…Media supply unit; 113…Image forming unit; 114…Media discharge unit; 115…Conveyor device; 117…Supporting unit; 118…Conveyor belt ; 119…support plate; 120…belt roller; 121…guide plate pair; 122…conveyor roller; 130…head unit; 132…ink tank; 133…connection 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 region; 302…support region; 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 liquid ejection head comprising: Multiple pressure chambers; a common liquid chamber, communicating with the plurality of pressure chambers; an inflow channel that connects the inflow side of the pressure chamber to the common liquid chamber and has a resistance channel having a smaller cross-sectional area than that of the pressure chamber; and an outflow passage connecting the outflow side of the pressure chamber with the common liquid chamber and having a resistance passage with a smaller cross-sectional area than that of the pressure chamber, The flow path resistance of the inflow flow path is greater than the flow path resistance of the outflow flow path.

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

3. The liquid ejection head according to claim 1, wherein A difference in viscosity 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 liquid ejection head according to claim 1, wherein The common liquid chamber is respectively arranged on one side and the other side of the extension direction of the pressure chamber. The inflow channel and the outflow channel are respectively arranged along the extension direction on one side and the other side of the extension direction of the pressure chamber. The plurality of pressure chambers are arranged in a parallel direction intersecting the extending direction. The resistance flow path on the inflow side, the pressure chamber, and the resistance flow path on the outflow side are arranged in sequence along the extending direction. The liquid ejection head is of a circulation type. 5 . A liquid ejecting device comprising the liquid ejecting head according to claim 1 .

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