Liquid ejection head and liquid ejection apparatus

Abstract

The invention provides a liquid ejection head and a liquid ejection apparatus capable of ensuring good ejection performance. A liquid ejection head according to one embodiment includes: a plurality of pressure chambers; the common liquid chamber is communicated with the plurality of pressure chambers; and connection flow paths that are respectively disposed on one side and the other side of the pressure chambers, constitute flow paths that connect the pressure chambers and the common liquid chamber, and have flow path resistance parts. The cross-sectional area of the pressure chamber, which is orthogonal to the direction in which the pressure chamber extends from the one side toward the other side, is 0.01 mm2 or less. The cross-sectional area of the flow path resistance portion orthogonal to the extension direction is less than 1 / 4 of the cross-sectional area of the pressure chamber orthogonal to the extension direction.

Description

Technical Field

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

[0002] In a liquid ejection head such as an inkjet head, the following method is used: a diaphragm is deformed by an actuator made of a piezoelectric material such as PZT (lead zirconate titanate), and a pressure chamber facing the diaphragm is deformed, and ink is ejected from a nozzle communicating with the pressure chamber. The liquid ejection head includes: a plurality of actuators joined to the diaphragm; and a flow path portion that forms a plurality of pressure chambers facing the diaphragm and flow paths communicating with the pressure chambers. The accuracy of the fluid resistance portion in the flow path portion of such an inkjet head greatly affects the performance. That is, when the cross-sectional area is large, the meniscus vibration of the nozzle portion after ejection becomes large, and when it is small, the refilling becomes slow, both of which become reasons for hindering high-speed followability.

[0003] On the other hand, when there is not enough difference in size between the pressure chamber and the fluid resistance portion, parasitic vibration occurs in the pressure chamber, and when it is large, ejection abnormalities occur. For example, in the case of a circulation type, when the pressure chamber is too large, the flow velocity in the pressure chamber becomes small, and the circulation effect cannot be exerted. However, when the size of the pressure chamber is suppressed, the difference from the fluid resistance portion becomes small, and parasitic vibration is likely to occur.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Publication 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 capable of ensuring good ejection performance.

[0009] Technical Solution for Solving the Problem

[0010] A liquid ejection head according to one aspect includes: a plurality of pressure chambers; a common liquid chamber communicating with the plurality of pressure chambers; and connecting flow paths respectively disposed on one side and the other side of the pressure chamber, forming flow paths connecting the pressure chamber and the common liquid chamber, and having flow path resistance portions. The cross-sectional area of the pressure chamber orthogonal to the extending direction from the one side to the other side is 0.01 mm 2 or less. The cross-sectional area of the flow path resistance portion orthogonal to the extending direction is less than 1 / 4 of the cross-sectional area of the pressure chamber orthogonal to the extending direction. Brief Description of the Drawings

[0011] Figure 1 It is a cross-sectional view showing a partial structure of an inkjet head according to the first embodiment.

[0012] Figure 2 It is a cross-sectional view showing a partial structure of the same inkjet head.

[0013] Figure 3 It is a top view showing a partial structure of a flow path portion of the same inkjet head.

[0014] Figure 4 It is a graph showing a flow path shape and vibration characteristics.

[0015] Figure 5 It is a graph showing ejection states under different driving conditions.

[0016] Figure 6 It is a table showing ejection characteristics under different driving conditions.

[0017] Figure 7 It is an explanatory view showing a schematic structure of an inkjet recording apparatus according to the first embodiment.

[0018] Explanation of Reference Numerals

[0019] 1: Inkjet head; 20: Actuator portion; 21: Driving piezoelectric element; 22: Non-driving piezoelectric element; 23: Groove; 30: Vibration plate; 31: Pressure chamber; 32: First common liquid chamber; 33: Second common liquid chamber; 34: Connecting flow path; 341: Flow path resistance portion; 35: Ink flow path; 40: Manifold; 41: Peripheral wall portion; 42: Partition portion; 43: Side wall portion; 45: Frame portion; 50: Nozzle plate; 51: Nozzle; 70: Driving circuit; 100: Inkjet recording apparatus; 111: Housing; 112: Medium supply portion; 113: Image forming portion; 114: Medium discharge portion; 115: Conveying device; 117: Support portion; 118: Conveyor belt; 119: Support plate; 120: Belt roller; 121: Pair of guide plates; 122: Conveying roller; 130: Head unit; 132: Ink tank; 133: Connecting path; 134: Supply pump; 150: Control portion; 151: Control circuit; 211: Piezoelectric layer; 221: Internal electrode; 222: Internal electrode; 223: External electrode; 224: External electrode; 301: Vibration region; 302: Support region; 303: Opening; 401: Flow path substrate; 402: Flow path substrate; 403: Flow path substrate; 4011: First opening; 4012: Second opening; 4021: First opening; 4022: Second opening; 4023: Slit; 4031: First opening; 4032: Second opening. Detailed Description of the Embodiment

[0020] Hereinafter, with reference to Figures 1 to 7The liquid ejection head, i.e., the inkjet head 1, and the liquid ejection device, i.e., the inkjet recording device 100, of the first embodiment will be described. Figure 1 It is a cross-sectional view showing a partial structure of the inkjet head of the first embodiment, Figure 2 It is a cross-sectional view showing a partial structure of the inkjet head. Figure 3 It is a top view showing a partial structure of the flow channel portion of the inkjet head. Figure 4 It is a chart showing the flow channel shape and vibration characteristics. Figure 5 It is an explanatory diagram showing the ejection states under different conditions. Figure 6 It is a table showing the driving conditions and ejection characteristics. Figure 7 It is an explanatory diagram showing the schematic structure of the inkjet recording device. Arrows X, Y, and Z in the figure respectively show three mutually orthogonal directions. In the present embodiment, X is along the juxtaposed direction of the nozzles 51 and the pressure chambers 31, Y is along the extending direction, and Z is along the opposing direction and the axial direction of the nozzles. In each figure, for the sake of explanation, the structure is shown with appropriate enlargement, reduction, or omission.

[0021] As Figure 1 and Figure 2 shown, the inkjet head 1 includes an actuator portion 20, a vibration plate 30, a manifold 40 as a flow channel member having a plurality of flow channel substrates 401, 402, 403, a nozzle plate 50 as a nozzle member having a plurality of nozzles 51, a frame portion 45 as a structural portion, and a drive circuit 70. As an example, in the present embodiment, the inkjet head 1 shows an example in which the stacking direction of the piezoelectric layer 211, the vibration direction of the piezoelectric element 21, and the vibration direction of the vibration plate 30 are respectively along the Z direction. In the present embodiment, inside the nozzle plate 50, a flow channel structure portion for forming an ink flow channel 35 (flow channel portion) in the inkjet head 1 is constituted by the vibration plate 30 and the manifold 40. The inkjet head 1 is a circulation type in which the liquid circulates in a prescribed flow channel.

[0022] The actuator portion 20 includes, for example, drive piezoelectric elements 21 (piezoelectric portions) constituted by piezoelectric members and arranged alternately along the column direction as a plurality of actuators, and a plurality of non-drive piezoelectric elements 22. In the present embodiment, a nozzle 51 is provided at the center of the extending direction of the actuator portion 20, and the actuator portion 20 has a structure symmetric on one side and the other side with the nozzle 51 as the center. For example, the actuator portion 20 is joined 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 side by side in the juxtaposition direction at a certain interval. As an example, both the plurality of driving piezoelectric elements 21 and the plurality of non-driving piezoelectric elements 22 are configured as columnar bodies in the shape of a rectangular parallelepiped with the same outer shape. The actuator unit 20 is divided into a plurality of parts by a plurality of grooves 23, for example. The plurality of driving piezoelectric elements 21 and non-driving piezoelectric elements 22 are arranged side by side in the column direction at the same pitch through the grooves 23 with the same width, for example.

[0024] 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 such that, in a plan view observed from the axial direction of the nozzle 51, i.e., the Z direction, the short side direction is along the column direction of the element columns and the long side direction is along the extending direction orthogonal to the column direction and the Z direction.

[0025] The driving piezoelectric elements 21 are arranged in the Z direction at positions respectively opposed to the plurality of pressure chambers 31 formed in the manifold 40. As an example, the central positions in the column direction and the extending direction of the driving piezoelectric elements 21 are arranged side by side in the Z direction with the central positions in the column direction and the extending direction of the pressure chambers 31.

[0026] The non-driving piezoelectric elements 22 are arranged in the Z direction at positions respectively opposed to the partition wall portions 42 formed in the manifold 40. As an example, the central positions in the column direction and the extending direction of the non-driving piezoelectric elements 22 are arranged side by side in the Z direction with the central positions in the column direction and the extending direction of the partition wall portions 42.

[0027] For example, the laminated piezoelectric member constituting the actuator unit 20 is formed by laminating and sintering sheet-like piezoelectric materials. The actuator unit 20 forms the grooves 23 by cutting the laminated piezoelectric member from one end face, thereby forming a plurality of piezoelectric elements formed in a rectangular columnar shape at a prescribed interval. Then, electrodes and the like are provided on the formed plurality of columnar elements to form a plurality of driving piezoelectric elements 21 and a plurality of non-driving piezoelectric elements 22 which are alternately arranged. The plurality of driving piezoelectric elements 21 and the plurality of non-driving piezoelectric elements 22 are alternately arranged side by side with the grooves 23 interposed therebetween in the column direction.

[0028] The piezoelectric members constituting the driving piezoelectric elements 21 and the non-driving piezoelectric elements 22 are, for example, laminated piezoelectric bodies. The driving piezoelectric elements 21 and the non-driving piezoelectric elements 22 include a plurality of piezoelectric body layers 211 laminated together and internal electrodes 221, 222 formed on the main surfaces of the respective piezoelectric body layers 211. In addition, as an example, the driving piezoelectric elements 21 and the non-driving piezoelectric elements 22 have the same laminated structure. Moreover, the driving piezoelectric elements 21 and the non-driving piezoelectric elements 22 include external electrodes 223, 224 formed on the surfaces.

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

[0030] The internal electrodes 221 and 222 are conductive films made of a firing - capable conductive material such as silver - palladium and formed into a prescribed shape. The internal electrodes 221 and 222 are formed in prescribed regions on the main surfaces of the respective piezoelectric layers 211. The internal electrodes 221 and 222 are different poles. For example, one of the internal electrodes 221 is formed in a region that reaches one end of the piezoelectric layer 211 but does not reach the other end of the piezoelectric layer 211 in the direction (Y - direction) that is orthogonal to both the row direction (X - direction), which is the side - by - side direction of the plurality of driving piezoelectric elements 21 and the plurality of non - driving piezoelectric elements 22, and the vibration direction (Z - direction). The other internal electrode 222 is formed in a region that does not reach one end of the piezoelectric layer 211 but reaches the other end of the piezoelectric layer 211 in the extending direction. The internal electrodes 221 and 222 are respectively connected to the external electrodes 223 and 224 formed on the side surfaces of the piezoelectric elements 21 and 22.

[0031] In addition, the laminated piezoelectric members constituting the driving piezoelectric elements 21 and the non - driving piezoelectric elements 22 may further include dummy layers on either one or both of the ends on the nozzle plate 50 side or the opposite side. For example, the dummy layer is made of the same material as the piezoelectric layer 211. Since it has an electrode only on one side and no electric field is applied, it does not deform. For example, the dummy layer does not function as a piezoelectric body but fixes the actuator portion 20 to the base, or serves as a polishing margin for polishing in order to obtain accuracy during and after assembly.

[0032] The external electrodes 223 and 224 are formed on the surfaces of the plurality of driving piezoelectric elements 21 and the plurality of non - driving piezoelectric elements 22, and are formed by gathering 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 extending direction of the piezoelectric layer 211. The external electrodes 223 and 224 are formed by known methods such as electroplating and sputtering with Ni, Cr, Au, etc. The external electrode 223 and the external electrode 224 are different poles. The external electrode 223 and the external electrode 224 are respectively arranged on different side faces of the plurality of driving piezoelectric elements 21 and the plurality of non - driving piezoelectric elements 22. In addition, the external electrodes 223 and 224 may also surround different regions on the same side face of the plurality of driving piezoelectric elements 21 and the plurality of non - driving piezoelectric elements 22.

[0033] In the present embodiment, as an example, the external electrode 223 is set as a single electrode, and the external electrode 224 is set as a common electrode. The external electrode 223, which is a single electrode for a plurality of driving piezoelectric elements 21 and a plurality of non-driving piezoelectric elements 22, has its electrode layer divided by the groove 23 and is arranged independently of each other. The external electrode 224, which is a common electrode, has its electrode layers connected to each other on the side surface of the actuator portion 20, for example, and is grounded. The external electrodes 223 and 224 are connected to the drive circuit 70 via a wiring film, for example. For example, each of the external electrodes 223 and 224 is connected to the control unit 150 via the drive IC 72 of the drive circuit 70 and is configured to enable drive control. In addition, the arrangement of the common electrode and the single electrode may be reversed.

[0034] In addition, the vibration directions of the piezoelectric elements 21 and 22 are along the stacking direction, and they are displaced in the d33 direction by applying an electric field. The number of stacked layers of the piezoelectric body layers 211 and the internal electrodes 221 and 222 of each of the piezoelectric elements 21 and 22 is three or more. As an example, each of the piezoelectric elements 21 and 22 has three or more and fifty or less layers, the thickness of each layer is set to be 10 μm or more and 40 μm or less, and the product of the thickness and the total number of stacked layers is less than 1000 μm.

[0035] In the inkjet head 1, a voltage is applied to the internal electrodes 221 and 222 via the external electrodes 223 and 224, thereby driving the piezoelectric element 21 to vibrate. In the present embodiment, the driving piezoelectric element 21 performs longitudinal vibration along the stacking direction of the piezoelectric body layer 211. The longitudinal vibration mentioned here is, for example, "vibration in the thickness direction defined by the piezoelectric constant d33". The driving piezoelectric element 21 displaces the vibration plate 30 by longitudinal vibration and deforms the pressure chamber 31.

[0036] The vibration plate 30 extends along a plane orthogonal to the vibration direction, i.e., the Z direction, and is joined to the surface on the vibration direction side of the piezoelectric body layers 211 of the plurality of piezoelectric elements 21 and 22, i.e., the side of the nozzle plate 50. The vibration plate 30 faces a plurality of nozzles 51 across the pressure chamber 31 in the vibration direction, i.e., the Z direction. The vibration plate 30 is configured to be deformable, for example. The vibration plate 30 is joined to the driving piezoelectric element 21 and the non-driving piezoelectric element 22 of the actuator portion 20 and the frame portion 45. For example, the vibration plate 30 has a vibration region 301 facing the piezoelectric elements 21 and 22 and a support region 302 facing the frame portion 45. The vibration plate 30 is disposed between the flow channel substrate 401 and the actuator portion 20 in the vibration direction. The vibration plate 30 is arranged overlapping with a plurality of flow channel substrates 401, 402, and 403 and constitutes a part of the ink flow channel 35.

[0037] The vibration region 301 is arranged in a flat plate shape with, for example, the thickness direction being the vibration direction of the piezoelectric layer 211. The plane direction of the vibration plate 30 extends in the side-by-side direction of the plurality of drive piezoelectric elements 21 and the plurality of non-drive piezoelectric elements 22. The vibration plate 30 is, for example, a metal plate. The vibration plate 30 has a plurality of vibration parts that face each pressure chamber 31 and can be displaced individually. The plurality of vibration parts are integrally connected to form the vibration plate 30.

[0038] As an example, the vibration plate 30 is made of nickel or a SUS plate, and the thickness dimension along the vibration direction is configured to be about 5 μm to 15 μm. In addition, the vibration region 301 may form a folding portion or a step difference at a portion adjacent to the vibration part or between adjacent vibration components in a manner that facilitates the displacement of the plurality of vibration parts. By the elongation and compression of the drive piezoelectric element 21, the portion disposed opposite to the drive piezoelectric element 21 is displaced, thereby deforming the vibration region 301. 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 portion 20 by bonding or the like.

[0039] The support region 302 is a plate-like member disposed between the frame portion 45 and the flow channel substrate 401. The vibration plate 30 has a structure that is symmetric on 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 first common liquid chamber 32 and the second common liquid chamber 33. For example, the support region 302 of the vibration plate 30 forms an opening 303 that communicates the second common liquid chamber 33 with the first common liquid chamber 32.

[0041] The manifold 40 is joined to one side of the vibration plate 30.

[0042] As Figures 1 to 3 shown, the manifold 40 includes a plurality of stacked flow channel substrates 401, 402, 403. For example, according to the viscosity of the ink, the ejected volume, etc., the plurality of flow channel substrates 401, 402, 403, the nozzle plate 50 having openings or grooves, and the vibration plate 30 are combined and joined to form a desired ink flow channel 35. The plurality of flow channel substrates 401, 402, 403 are overlapped and arranged in the stacking direction, and a predetermined ink flow channel 35 including the second common liquid chamber 33, the connecting flow channel 34 as a throttling flow channel, and the pressure chamber 31 is constituted by the openings or grooves formed in each of the flow channel substrates 401, 402, 403. As an example, the flow channel substrates 401, 402, 403 are sequentially stacked and arranged from the vibration plate 30 side, and the flow channel substrate 403 is disposed opposite to the nozzle plate 50.

[0043] The manifold 40 is disposed between the nozzle plate 50 and the vibration plate 30. The manifold 40 internally forms a prescribed ink flow path 35 (liquid chamber) having a plurality of pressure chambers 31, a second common liquid chamber 33 communicating with the first common liquid chamber 32, and a plurality of connecting flow paths 34 reaching the pressure chambers 31 from the second common liquid chamber 33 by laminating and mutually joining a plurality of flow path substrates 401, 402, 403. In other words, the manifold 40 is constituted by the laminated plurality of flow path substrates 401, 402, 403 to form a peripheral wall portion 41, a plurality of partition portions 42, and a side wall portion 43. The peripheral wall portion 41 surrounds the ink flow path 35 (liquid chamber) constituted by the plurality of pressure chambers 31, the plurality of connecting flow paths 34, the first common liquid chamber 32, and the second common liquid chamber 33. The plurality of partition portions 42 separate between columns of the plurality of pressure chambers 31, and the side wall portion 43 separates the plurality of connecting flow paths 34. For example, in the present embodiment, in Figure 3 the region corresponding to three columns of pressure chambers in the manifold 40 is shown.

[0044] As Figure 1 well as Figure 2 shown, the flow path substrate 401 is joined to the vibration plate 30. The flow path substrate 401 is a plate-like member having the same outer shape as the vibration plate 30 and is constituted by, as an example, a metal material including SUS430 or a resin material such as silicon. The flow path substrate 401 has a first opening 4011 forming a part of the pressure chamber 31 and a second opening 4012 constituting a part of the second common liquid chamber 33. For example, the first opening 4011 is disposed at the center in the extending direction in which the ink flow path 35 extends, and the second openings 4012 are disposed at both ends respectively.

[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 is constituted by, as an example, a metal material including SUS430 or a resin material such as silicon. The flow path substrate 402 has a first opening 4021 forming a part of the pressure chamber 31, a second opening 4022 constituting a part of the second common liquid chamber 33, and a long and narrow slit opening 4023 constituting a single flow path, i.e., the connecting flow path 34. For example, the first opening 4021 is disposed at the center in the extending direction in which the ink flow path 35 extends, the slit openings 4023 are disposed at both ends of the first opening 4021, and the second openings 4022 are disposed at the outer end portions on both sides of the slit openings 4023. In the side-by-side direction, the respective openings 4021, 4022, 4023 are arranged in multiple columns.

[0046] As Figures 1 to 3As shown, the flow channel substrate 403 is laminated on the flow channel substrate 402 and joined to the flow channel substrate 402. The flow channel substrate 403 is a plate-like member having the same shape as the diaphragm 30 and is made of, for example, a metal material including SUS430 or a resin material such as silicon. The flow channel substrate 403 has a first opening 4031 that forms a part of the pressure chamber 31 and a second opening 4032 that constitutes a part of the second common liquid chamber 33. For example, the first opening 4031 is disposed at the center in the extending direction in which the ink flow channel 35 extends, and the second openings 4032 are disposed at both ends, respectively.

[0047] For example, the flow channel substrates 401, 402, and 403 are configured to have a thickness of about 20 μm to 100 μm. For example, in the case of 300 dpi, the pitch of the arrangement of the pressure chambers 31 in the juxtaposed direction is 169 μm, the width WA of the pressure chamber 31 is about 100 μm to 150 μm, and the width WB of the slit opening 4023 that forms the connecting flow channel 34 is smaller than the widths of the first opening 4021 and the second opening 4022. In addition, the widths WA and WB are width dimensions in the X direction, which is a width dimension intersecting with one direction and the lamination direction. That is, the connecting flow channel 34 has a flow channel resistance portion 341 having a cross-sectional area smaller than that of the pressure chamber 31. As an example, in the present embodiment, the flow channel cross-section of the connecting flow channel 34 is constant over the entire length in the extending direction, and the entire length of the connecting flow channel 34 constitutes the flow channel resistance portion 341.

[0048] In the manifold 40, a plurality of pressure chambers 31 are formed by the first openings 4011, 4021, and 4031 of the plurality of flow channel substrates 401, 402, and 403 that are connected in parallel in the lamination direction. The plurality of pressure chambers 31 are spaces formed on one side of the vibration region 301 of the diaphragm 30, and each pressure chamber 31 communicates with a nozzle 51 formed in the nozzle plate 50. In addition, the pressure chamber 31 blocks the opposite side of the nozzle plate 50 by the diaphragm 30.

[0049] The plurality of pressure chambers 31 communicate with the first common liquid chamber 32 via the connecting flow channel 34 and the second common liquid chamber 33 and via the opening 303. The pressure chamber 31 holds the liquid supplied from the first common liquid chamber 32 through the second common liquid chamber 33 and the connecting flow channel 34, and the liquid is ejected from the nozzle 51 by the vibration of the diaphragm 30 that forms a part of the pressure chamber 31. The pressure chamber 31 is configured such that the cross-sectional area orthogonal to the flow direction, i.e., the Y direction, is 0.01 mm 2 The following.

[0050] In the manifold 40, the second common liquid chambers 33 on both sides in the Y direction of the pressure chamber are formed by the second openings 4012, 4022, and 4032 of the plurality of flow channel substrates 401, 402, and 403 that are connected in parallel in the lamination direction.

[0051] The second common liquid chamber 33 is a flow channel that communicates with the end portions in the flow direction of the plurality of connection flow channels 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 channel substrates 401, 402, and 403 has a structure that is symmetric on one side and the other side in the Y direction with the nozzle 51 as the center. The flow channel lengths of the second common liquid chambers 33 arranged on both sides in the Y direction with the central pressure chamber 31 as the center and the cross-sectional shape of the flow channel orthogonal to the Y direction are configured to be equal.

[0052] In addition, in the manifold 40, the connection flow channels 34 are formed through the slit openings 4023 of the flow channel substrate 402. The connection flow channels 34 connect the respective pressure chambers 31 and the second common liquid chamber 33 and extend in the Y direction which is the flow direction. Compared with the second common liquid chamber 33 and the pressure chambers 31, the connection flow channels 34 on both sides are configured to have a smaller dimension in the width direction orthogonal to the flow direction, that is, the extending direction, and are configured to have a narrower flow channel cross-section.

[0053] Here, each of the flow channel substrates 401, 402, and 403 has a structure that is symmetric on one side and the other side in the Y direction with the nozzle 51 as the center. The flow channel lengths of the connection flow channels 34 arranged on both sides in the Y direction with the central pressure chamber 31 as the center and the cross-sectional shape of the flow channel orthogonal to the Y direction are configured to be equal. In addition, in the manifold 40, through the portions around the first openings 4011, 4021, and 4031 of the stacked flow channel substrates 401, 402, and 403, a partition portion 42 that separates between the plurality of pressure chambers 31 is formed.

[0054] The partition portion 42 is a wall-like member that separates between the plurality of pressure chambers 31 in the side-by-side direction. The partition portion 42 is disposed opposite to the non-driven piezoelectric element 22 with the vibration plate 30 interposed therebetween and is supported by the non-driven piezoelectric element 22. A plurality of partition portions 42 are provided at the same pitch as the pitch of the plurality of pressure chambers 31 arranged side by side.

[0055] In the manifold 40, side wall portions 43 that separate between the plurality of connection flow channels 34 are formed through the portions on both sides of the slit openings 4023 of the flow channel substrate 402.

[0056] The side wall portions 43 are wall-like members that separate between the plurality of connection flow channels 34 in the side-by-side direction. For example, the side wall portions 43 are provided in communication with both sides of the pressure chamber 31. The side wall portions 43 are configured such that the flow resistance of the connection flow channels 34 is larger than that inside the pressure chamber 31 and the cross-sectional area of the connection flow channels 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 of the plurality of pressure chambers 31 arranged side by side.

[0057] Here, the fluid resistance portion, i.e., the connecting flow path 34, is configured such that the cross-sectional area orthogonal to the flow direction of the ink, i.e., the second direction, is smaller than that of the pressure chamber 31. For example, the cross-sectional area of the pressure chamber 31 / the cross-sectional area of the connecting flow path 34 is 4 or more. In other words, the cross-sectional area of the pressure chamber 31 is four times or more that of the connecting flow path 34.

[0058] That is, the connecting flow path 34 is configured such that the dimension in the X direction, i.e., the width dimension, or the dimension in the Z direction, i.e., the height dimension, or both are smaller than those of the pressure chamber 31.

[0059] In the present embodiment, it is assumed that the width WB of the connecting flow path 34 is 70 μm and the width WA of the pressure chamber 31 is 130 μm. In addition, it is assumed that the height HB of the connecting flow path 34 in the third direction (Z direction) as the opposing direction is 25 μm and the height HA of the pressure chamber 31 is 75 μm. Therefore, the cross-sectional area of the pressure chamber 31 / the cross-sectional area of the connecting flow path 34 is 4 or more.

[0060] In addition, as an example, the length dimension in the extending direction (Y direction) is LB = 0.9 mm for the extending direction of the connecting flow path 34 and LA = 1.35 mm for the extending direction of the pressure chamber 31.

[0061] The nozzle plate 50 is configured as a square plate-like member with a thickness of about 10 μm to 100 μm, made of a metal such as SUS / Ni or a resin material such as polyimide, for example. The nozzle plate 50 is disposed on one side of the manifold 40 so as to cover the opening on one side of the pressure chamber 31. The nozzle plate 50 has a plurality of nozzles 51 for ejecting droplets. The plurality of nozzles 51 are hole portions that penetrate the nozzle plate 50 in the thickness direction. The plurality of nozzles 51 are arranged side by side in the first direction same as the side-by-side direction of the pressure chambers 31 to form a nozzle row. Each nozzle 51 is provided at a position corresponding to the plurality of pressure chambers 31.

[0062] The frame portion 45 is a structure that is joined to the diaphragm 30 together with the piezoelectric elements 21 and 22. The frame portion 45 is provided on the side of the diaphragm 30 opposite to the manifold 40 with respect to the piezoelectric elements 21 and 22, and is disposed adjacent to the actuator portion 20 in the present embodiment, for example. The frame portion 45 constitutes the outer contour of the inkjet head 1. In addition, the frame portion 45 may form a flow path for the liquid inside. In the present embodiment, the frame portion 45 is joined to the other side of the diaphragm 30 and forms a first common liquid chamber 32 between the frame portion 45 and the diaphragm 30.

[0063] 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 diaphragm 30, the second common liquid chamber 33, and the connecting flow path 34.

[0064] 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.

[0065] The drive circuit 70 applies a drive voltage to the external electrodes 223 and 224 through the driver IC, thereby driving the piezoelectric element 21, increasing or decreasing the volume of the pressure chamber 31, and ejecting droplets from the nozzle 51.

[0066] The wiring film is connected to a plurality of external electrodes 223 and 224. For example, the wiring film is an ACF (anisotropic conductive film) fixed to the connection portions of the external electrodes 223 and 224 by thermocompression bonding or the like. The wiring film is, for example, a COF (Chip on Film) on which a driver IC is mounted.

[0067] The driver IC is connected to the external electrodes 223 and 224 via the wiring film. In addition, the driver IC may be connected to the external electrodes 223 and 224 by other means such as ACP (anisotropic conductive paste), NCF (non-conductive film), and NCP (non-conductive paste) without passing through the wiring film.

[0068] The driver IC generates a control signal and a drive signal for operating each piezoelectric element 21. The driver IC generates a control signal for controlling the timing of ejecting ink and selecting the piezoelectric element 21 for ejecting ink, etc., in accordance with the image signal input from the control unit 150 of the inkjet recording apparatus 100. In addition, the driver IC generates a voltage applied to the piezoelectric element 21, that is, a drive signal (electrical signal), in accordance with the control signal. When the driver IC applies a drive signal to the piezoelectric element 21, the piezoelectric element 21 drives in such a manner that the diaphragm 30 is displaced and the volume of the pressure chamber 31 is changed. As a result, pressure vibration is generated in the ink filled in the pressure chamber 31. The ink is ejected from the nozzle 51 provided in the pressure chamber 31 by the pressure vibration. In addition, the inkjet head 1 can also achieve gray-scale representation by changing the amount of ink droplets landing on one pixel. In addition, the inkjet head 1 can also change the amount of ink droplets landing on one pixel by changing the number of times of ink ejection. In this way, the driver IC is an example of an application unit that applies a drive signal to the piezoelectric element 21.

[0069] 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 time series. The decoder controls the driver based on the print data stored in the data buffer for each piezoelectric element 21. The driver outputs a drive signal for operating each piezoelectric element 21 based on the control of the decoder. The drive signal is, for example, a voltage applied to each piezoelectric element 21.

[0070] A 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 device 100.

[0071] In the inkjet head 1 configured as described above, an ink flow path 35 having a plurality of pressure chambers 31, connecting flow paths, and a second common liquid chamber 33 and a first common liquid chamber 32 serving as common flow paths is formed by a nozzle plate 50, a frame portion 45, a manifold 40, and a vibration plate 30. Among them, the plurality of pressure chambers 31 communicate with nozzles 51, and the connecting flow paths are constituted by connecting flow paths 34 that communicate with each other in the extending direction of the plurality of pressure chambers 31. In the extending direction, the connecting flow paths 34 are arranged on both sides of the pressure chamber 31, and further, common chambers based on the common liquid chambers 33 and 32 are continuously arranged at the end portions in the extending direction of the connecting flow paths 34 on both sides.

[0072] The inkjet head 1 is a circulation type. For example, the first common liquid chamber 32 communicates with an ink cartridge, and ink is supplied to each pressure chamber 31 through the first common liquid chamber 32 on the inflow side. All the piezoelectric elements 21 are connected by wiring so that a voltage can be applied. In the inkjet head 1, when the control unit 150 applies a driving voltage to the internal electrodes 221 and 222 through the driver IC, the driven piezoelectric element 21 vibrates in the stacking direction, that is, in the thickness direction of each piezoelectric layer 211. That is, the piezoelectric element 21 performs longitudinal vibration.

[0073] Specifically, the control unit 150 applies a driving voltage to the internal electrodes 221 and 222 of the driven piezoelectric element 21, and selectively drives the driven piezoelectric element 21. Moreover, by combining the deformation in the stretching direction and the deformation in the compression direction of the driven piezoelectric element 21, the vibration plate 30 is deformed, the volume of the pressure chamber 31 is changed, so that liquid is derived from the first common liquid chamber 32 and ejected from the nozzle 51.

[0074] The ink supplied to the pressure chamber 31 is not only ejected from the nozzle 51 but also recovered into the ink cartridge through the connecting flow path 34 on the other side serving as the recovery side, the second common liquid chamber 33, and the first common liquid chamber.

[0075] In the inkjet head 1, one side in the extending direction is used as the inflow side (supply side), and the other side is used as the outflow side (recovery side), and the ink circulates in the ink flow path 35.

[0076] Hereinafter, with reference to Figure 7 An example of the inkjet recording device 100 including the inkjet head 1 will be described. The inkjet recording device 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.

[0077] The inkjet recording apparatus 100 is a liquid ejection apparatus that ejects a liquid such as ink while conveying a sheet P, which is an object to be ejected, i.e., a printing medium, along a predetermined conveyance path A that extends from a medium supply unit 112 through an image forming unit 113 to a medium discharge unit 114, thereby performing an image forming process on the sheet P.

[0078] A housing 111 forms an outer contour of the inkjet recording apparatus 100. A discharge port for discharging the sheet P to the outside is provided at a predetermined position of the housing 111.

[0079] The medium supply unit 112 includes a plurality of paper feed cassettes and is configured to stack and hold a plurality of sheets P of various sizes.

[0080] The medium discharge unit 114 includes a paper discharge tray configured to hold the sheet P discharged from the discharge port.

[0081] The image forming unit 113 includes a support unit 117 that supports the sheet P and a plurality of head units 130 disposed opposite to the upper side of the support unit 117.

[0082] The support unit 117 includes a conveyor belt 118 provided in a ring shape in a predetermined area where image formation is performed, a support plate 119 that supports the conveyor belt 118 from the inside, and a plurality of belt rollers 120 provided on the inside of the conveyor belt 118.

[0083] The support unit 117 supports the sheet P on the upper surface, i.e., the support surface, of the conveyor belt 118 during image formation, and conveys the conveyor belt 118 at a predetermined timing by the rotation of the belt rollers 120, thereby conveying the sheet P toward the downstream side.

[0084] The head unit 130 includes a plurality of (four colors) inkjet heads 1, ink tanks 132 that are liquid tanks respectively mounted on the respective inkjet heads 1, connection paths 133 that connect the inkjet heads 1 and the ink tanks 132, and supply pumps 134.

[0085] In the present embodiment, there are provided inkjet heads 1 of four colors, i.e., cyan, magenta, yellow, and black, and ink tanks 132 that respectively contain inks of these colors. The ink tanks 132 are connected to the inkjet heads 1 through the connection paths 133.

[0086] In addition, a negative pressure control device such as a pump (not shown) is connected to the ink tank 132. Moreover, in correspondence with the head height values of the inkjet heads 1 and the ink tanks 132, the inside of the ink tank 132 is subjected to negative pressure control by the negative pressure control device, thereby forming a meniscus of a predetermined shape in the ink supplied to each nozzle 51 of the inkjet head 1.

[0087] The supply pump 134 is a liquid supply pump constituted by a piezoelectric pump, for example. The supply pump 134 is provided in the supply flow path. The supply pump 134 is connected to the drive circuit of the control unit 150 via wiring, and is configured to be controllable under the control of a CPU (Central Processing Unit). The supply pump 134 supplies liquid to the inkjet head 1.

[0088] The conveying device 115 conveys the paper P along a conveyance path A that extends from the medium supply unit 112, passes through the image forming unit 113, and reaches 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 conveyance path A.

[0089] Each of the plurality of guide plate pairs 121 includes a pair of plate members that are opposed to each other with the conveyed paper P therebetween, and guides the paper P along the conveyance path A.

[0090] The conveying rollers 122 are driven to rotate under the control of the control unit 150, and thereby convey the paper P downstream along the conveyance path A. In addition, sensors for detecting the conveyance state of the paper are arranged at various positions in the conveyance path A.

[0091] The control unit 150 includes a control circuit 151 such as a controller (i.e., a CPU), a ROM (Read Only Memory) that stores various programs, etc., a RAM (Random Access Memory) that temporarily stores various variable data, image data, etc., and an interface unit that performs input of data from the outside and output of data to the outside.

[0092] In the inkjet recording apparatus 100 configured as described above, when the control unit 150 detects, for example, a print instruction based on an operation of the operation input unit in the interface by the user, it drives the conveying device 115 to convey the paper P, and outputs a print signal to the head unit 130 at a predetermined timing, thereby driving the inkjet head 1. As a discharging operation, the inkjet head 1 transmits a drive signal to the driver IC via an image signal corresponding to the image data, applies a drive voltage to the internal electrodes 221 and 222, selectively drives the piezoelectric elements 21 to be discharged to vibrate longitudinally in the stacking direction, changes the volume of the pressure chamber 31, and thereby ejects ink from the nozzle 51 to form an image on the paper P held on the conveyor belt 118. In addition, as a liquid ejection operation, the control unit 150 supplies ink from the ink tank 132 to the first common liquid chamber 32 of the inkjet head 1 by driving the supply pump 134.

[0093] Here, the driving operation of the inkjet head 1 will be described. The inkjet head 1 of the present embodiment includes piezoelectric elements 21 disposed opposite to the pressure chambers 31, and these piezoelectric elements 21 are connected by wirings so that a voltage can be applied. The control unit 150 transmits a driving signal to the driver IC through an image signal corresponding to the image data, applies a driving voltage to the internal electrodes 221 and 222 of the piezoelectric element 21 to be driven, and selectively deforms the piezoelectric element 21 to be driven. Moreover, by combining the deformation in the stretching direction and the deformation in the compression direction of the diaphragm 30, the volume of the pressure chamber 31 is changed, thereby ejecting the liquid.

[0094] For example, the control unit 150 alternately performs a stretching operation and a compression operation. In the inkjet head 1, when stretching 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 outside the driving target are not deformed. Further, in the inkjet head 1, when compressing to decrease the internal volume of the target pressure chamber 31, the piezoelectric element 21 to be driven of the target is elongated, and the non-driving piezoelectric element 22 is not deformed.

[0095] According to the inkjet head 1 and the inkjet recording apparatus 100 of the above-described embodiment, the influence of parasitic vibration can be suppressed, and good ejection performance can be ensured.

[0096] That is, in the above-described embodiment, the connection flow paths 34 and the common liquid chambers 32 and 33 serving as fluid resistance portions are provided on both sides of the pressure chamber 31 to circulate the ink, and by setting the cross-sectional area orthogonal to the ink flow in the pressure chamber 31 to 0.01 mm 2 Hereinafter, by setting the cross-sectional area ratio of the pressure chamber 31 to the cross-sectional area of the connection flow path 34 to 4 or more, the circulation effect can be maintained, and good printing can be performed without being affected by parasitic vibration.

[0097] Figure 4 It is a graph showing vibration characteristics at different cross-sectional area ratios, and shows the results of an experiment in which the cross-sectional areas of the pressure chamber 31 and the connection flow path 34 are changed and ink is ejected. Figure 4 It is the case where the cross-sectional area ratio of the pressure chamber to the connection flow path is set to 4 or more and the case where it is set to less than 4. The vibration of the meniscus of the nozzle portion is measured by a vibrometer and FFT analysis is performed. In Figure 4 it, the vibration characteristics with a cross-sectional area ratio of 4 or more are shown as a solid line, and the vibration characteristics with a cross-sectional area ratio set to less than 4 are shown by a dashed line. As Figure 4 shown, the circulation performance and the influence of parasitic vibration are different according to the cross-sectional area of the pressure chamber 31 orthogonal to the ink flow and the cross-sectional area of the connection flow path 34. For example, parasitic vibration refers to vibration having peaks P2 and P3 different from the main vibration P1 as shown by the dashed line in Figure 4 it, Figure 5Shows the flying state of the ink with and without parasitic vibration. It can be seen that, for example, the size of the first droplet D1 is smaller and the size of the subsequent second droplet D2 becomes larger in the case of parasitic vibration, while the size of the first droplet D1 and the size of the second droplet D2 can be maintained the same in the case of no parasitic vibration. That is, when the parasitic vibration is large (ratio to the peak value of the main vibration), as Figure 5 shown, the first droplet becomes smaller and the printing quality deteriorates. The larger the cross-sectional area ratio of the pressure chamber 31 / connection flow path 34, the smaller the parasitic vibration and the fewer the parasitic vibrations.

[0098] Figure 6 Shows the results of an experiment in which the cross-sectional areas of the pressure chamber 31 and the connection flow path 34 were changed and ink was ejected. The cycle was evaluated entirely based on the flow rate flowing under the same pressure. In Figure 6 , three items, namely the cycle effect, high-speed followability, and ejection failure caused by parasitic vibration, were evaluated. Here, the cycle effect means that ink ejection can be performed as usual from the start when left for a certain period of time. If ink can be ejected from the start after being left for a certain period of time (for example, several hours), the cycle effect is obtained. If ink cannot be ejected from the start after being left for a certain period of time, the cycle effect is not obtained and it is judged as ×. In addition, as for high-speed followability, the upper limit of the frequency band in which the deviation of the ejection speed is within a certain range and becomes a stable state is shown. As can be seen from Figure 6 , when the pressure chamber 31 is large, the cycle flow rate becomes small and the cycle effect cannot be obtained. On the other hand, it can be seen that the high-speed followability is determined by the cross-sectional area of the connection flow path 34. In addition, it can be seen that if the cross-sectional area of the pressure chamber 31 / cross-sectional area of the connection flow path 34 is set to 4 or more, the influence of parasitic vibration will not occur. Therefore, according to the present embodiment, by setting the cross-sectional area of the pressure chamber 31 orthogonal to the ink flow to 0.01 mm 2 or less and setting the cross-sectional area of the pressure chamber 31 / cross-sectional area of the connection flow path 34 to 4 or more, the cycle effect can be maintained and good printing can be performed without being affected by parasitic vibration.

[0099] In addition, the present invention is not limited to the above-described embodiments, and structural elements can be deformed and embodied within the scope not departing from the gist thereof at the implementation stage.

[0100] In addition, in the present embodiment, an example is shown in which the cross-sectional area is constant over the entire length of the connection flow path and a flow path resistance portion is formed over the entire length of the connection flow path, but it is not limited thereto. For example, a structure may be adopted in which a flow path resistance portion having a narrower cross-sectional area than other regions is arranged in a part of the middle portion of the connection flow path. In addition, the cross-sectional area of the flow path resistance portion may not be constant. In this case, it is only necessary to configure such that, based on the portion having the smallest cross-sectional area in the connection flow path 34, the minimum cross-sectional area is less than 1 / 4 of the cross-sectional area of the pressure chamber 31.

[0101] For example, the specific structure of the manifold 40 is not limited to the above. For example, an example in which it is formed by three flow path substrates 401, 402, and 403 is shown, but it may also be two or four or more. In addition, the shape of the opening portions in each of the flow path substrates 401 and 402 is not limited to the above embodiment.

[0102] In addition, for example, in the above embodiment, an example is shown in which the second opening portions 4012, 4022, and 4032 are divided by each column of the pressure chamber 31 in the side-by-side direction to form the second common liquid chamber 33, but it is not limited thereto. For example, a plurality of second opening portions 4012, 4022, and 4032 may also continuously form a common flow path in the side-by-side direction.

[0103] For example, in the above embodiment, it is configured such that a multilayer piezoelectric member is laminated and the longitudinal vibration (d33) in the lamination direction is used to drive the piezoelectric element 21, but it is not limited thereto. For example, it can be applied to a method in which the piezoelectric element 21 is composed of a single-layer piezoelectric member, or a method in which it is driven by lateral vibration (d31).

[0104] In addition, the specific structures of the piezoelectric elements 21 and 22, the shape of the flow path, the structures of various components including the manifold 40, the nozzle plate 50, and the frame portion 45, and the positional relationship are not limited to the above examples and can be appropriately changed. In addition, the arrangement of the nozzles 51 and the pressure chambers 31 is not limited to the above. For example, two or more columns of nozzles 51 may be arranged. In addition, a virtual chamber may be formed between a plurality of pressure chambers 31.

[0105] In addition, the ejected liquid is not limited to ink for printing. For example, it may also be a device that ejects a liquid including conductive particles for forming a wiring pattern of a printed wiring board.

[0106] In addition, in the above embodiment, an example is shown in which the inkjet head 1 is used in a liquid ejection device such as an inkjet recording device, but it is not limited thereto. For example, it can also be used in a 3D printer, an industrial manufacturing device, and a medical application, and can achieve miniaturization, light weight, and low cost.

[0107] According to at least one embodiment described above, a desired runner shape can be easily set.

[0108] In addition, several embodiments of the present invention have been described, but these embodiments are presented only as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention and are included in the invention described in the claims and its equivalents.

Claims

1. A liquid ejection head, characterized in that: have: Multiple pressure chambers; a common liquid chamber communicating with the plurality of pressure chambers; and The connecting flow channel is respectively arranged at one side and the other side of the pressure chamber, constitutes a flow channel connecting the pressure chamber and the common liquid chamber, and has a flow channel resistance part. The cross-sectional area of ​​the pressure chamber orthogonal to the extending direction from the one side toward the other side is within 0.01 mm 2 the following, A cross-sectional area of ​​the flow path resistance portion perpendicular to the extending direction is smaller than 1 / 4 of a cross-sectional area of ​​the pressure chamber perpendicular to the extending direction.

2. The liquid ejection head according to claim 1, wherein: The connecting flow channel extends along the extending direction, The plurality of pressure chambers are arranged in a parallel direction intersecting the extending direction.

3. The liquid ejection head according to claim 1, wherein: The pressure chamber and the pair of connecting channels are arranged in a circulation manner side by side along the extending direction.

4. The liquid ejection head according to claim 1, wherein: The liquid ejection head comprises: A nozzle member having a plurality of nozzles in a side-by-side direction; A flow channel member is disposed opposite to one side of an opposing direction intersecting the parallel direction and the extending direction of the nozzle member, and forms a plurality of the pressure chambers and the connecting flow channels in the parallel direction; A plurality of vibration parts are arranged opposite to one side of the pressure chamber in the opposite direction; as well as The actuator portion includes a plurality of piezoelectric portions arranged to face one side of the vibrating portion in the facing direction.

5. The liquid ejection head according to claim 4, wherein: The plurality of vibration parts are integrally connected to form a vibration plate.

6. The liquid ejection head according to claim 1, wherein: The connecting flow channel has a constant flow channel cross section over the entire length of the extending direction, and the entire length of the connecting flow channel constitutes the flow channel resistance portion.

7. A liquid ejection device, characterized in that: have: The liquid ejection head according to any one of claims 1 to 4.

8. The liquid ejection device according to claim 7, characterized in that: The connecting flow channel has a constant flow channel cross section over the entire length of the extending direction, and the entire length of the connecting flow channel constitutes the flow channel resistance portion.

9. The liquid ejection device according to claim 7, characterized in that: The liquid ejecting device ejects liquid while conveying a printing medium as an ejection object, thereby performing an image forming process on the printing medium.

10. The liquid ejection device according to claim 9, characterized in that: The liquid is printing ink or a liquid containing conductive particles for forming a wiring pattern of a printed wiring board.

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