LIQUID DISCHARGE HEAD AND METHOD FOR MANUFACTURING LIQUID DISCHARGE HEAD

Abstract

To provide a liquid discharge head capable of securing stable discharge characteristics, and a method for manufacturing the liquid discharge head.SOLUTION: A liquid discharge head is of a side shooter type, and includes an actuator, a common chamber, and a cover plate. The actuator has a plurality of pressure chambers which communicate with nozzles for discharging a liquid, and a plurality of dummy chambers arranged among the plurality of pressure chambers. The common chamber is arranged on both ends of the actuator and communicates with the plurality of pressure chambers. The cover plate is joined to the side face of the actuator, is constituted in a plate shape, and has an opening which communicates the common chamber and the pressure chambers and has a fluid resistance larger than the inside of the pressure chamber at a position partitioning the pressure chambers, the dummy chambers and the common chamber and facing the plurality of pressure chambers.SELECTED DRAWING: Figure 6

Description

[Technical field]

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

[0002] In recent years, high productivity is required for inkjet heads, and high speed and an increase in droplet volume are issues. For example, a share-mode shared-wall type inkjet head is high-powered and suitable for ejecting high-viscosity ink and ejecting large droplets. In a share-mode shared-wall type inkjet head, the same driving column is shared by two pressure chambers, and so-called three-cycle driving is common, in which one-third of the multiple arranged chambers are simultaneously driven as pressure chambers. In addition, an independent driving head has been developed in which both sides of the driven pressure chamber are used as dummy pressure chambers and one pressure chamber is driven by two independent driving columns. For example, a structure has been developed in which many grooves are formed in a piezoelectric body, and the entrances and exits of every other groove are blocked, and the grooves whose entrances and exits are not blocked are used as pressure chambers and the blocked grooves are used as air chambers, and the independently driven structure is used.

[0003] In such inkjet heads, after an ink droplet is ejected, ink is replenished from the common liquid chamber to the pressure chamber. At this time, a phenomenon occurs in which the ink overshoots at the nozzle, causing the meniscus to swell. The smaller the fluid resistance of the flow path from the common liquid chamber to the nozzle, the larger the overshoot becomes, and unless this overshoot subsides, ejection cannot be performed with the meniscus in a stable state. Therefore, in order to increase the speed of an inkjet head, it is necessary to quickly converge the meniscus swell and ensure stable ejection characteristics. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-94036 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a liquid ejection head capable of ensuring stable ejection characteristics, and a method for manufacturing the liquid ejection head. [Means for solving the problem]

[0006] The liquid ejection head according to the embodiment includes: The actuator includes a plurality of pressure chambers communicating with nozzles that eject liquid and a plurality of dummy chambers arranged between the pressure chambers, a common chamber arranged at both ends of the actuator and communicating with the pressure chambers, and a cover plate joined to both side surfaces of the actuator, configured in a plate shape, separating the pressure chambers and the dummy chambers from the common chamber, and having openings facing the pressure chambers that have a higher fluid resistance than the inside of the pressure chambers that communicate the common chamber with the pressure chambers. The nozzle is arranged at a position corresponding to a midway point in the extension direction of the pressure chamber. The ejection direction of the liquid from the nozzle intersects with the extension direction, and the common chambers are arranged on both sides of the pressure chambers in the extension direction. The cover plates are arranged between the common chambers at both ends of the pressure chambers. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view showing an inkjet head according to an embodiment. [Diagram 2] FIG. 2 is an exploded perspective view showing a configuration of a portion of an inkjet head according to an embodiment. [Diagram 3] FIG. 2 is an enlarged cross-sectional view showing a configuration of a portion of the inkjet head. [Figure 4] FIG. 2 is an enlarged cross-sectional view showing a configuration of a portion of the inkjet head. [Diagram 5] FIG. 2 is an enlarged cross-sectional view showing a configuration of a portion of the inkjet head. [Figure 6] FIG. 2 is an enlarged perspective view showing a configuration of a portion of the inkjet head. [Figure 7] 3A to 3C are explanatory diagrams of a method for manufacturing the inkjet head. [Figure 8] FIG. 4 is an explanatory diagram of an inkjet head according to Test Example 1 and Test Example 2. [Figure 9] 13 is a graph showing the ejection speed of the inkjet head in Test Example 1. [Figure 10] 13 is a graph showing the ejection speed of an inkjet head according to Test Example 2. [Figure 11] 13 is a graph showing meniscus recovery characteristics of the inkjet heads according to Test Examples 1 and 2. [Figure 12] FIG. 13 is an explanatory diagram of an inkjet head of an end shooter according to Test Example 1 and Test Example 3. [Figure 13]13 is a graph showing driving waveforms of the inkjet heads according to Test Examples 1 and 3. [Figure 14] 13 is a graph showing nozzle flow velocity vibration of the inkjet heads according to Test Examples 1 and 3. [Figure 15] 13 is a graph showing the ejection volume of the inkjet heads according to Test Examples 1 and 3. [Figure 16] 13 is a graph showing meniscus recovery characteristics of the inkjet heads according to Test Examples 1 and 3. [Figure 17] FIG. 1 is a schematic diagram showing an inkjet printer according to an embodiment. [Figure 18] FIG. 11 is an enlarged perspective view showing a configuration of a portion of an inkjet head according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The configuration of the inkjet head 10, which is a liquid ejection head according to the first embodiment, will be described below with reference to FIGS. 1 to 6. FIG. 1 is a perspective view showing the inkjet head according to the first embodiment, and FIG. 2 is an exploded perspective view of a part of the inkjet head. FIGS. 3, 4, and 5 are cross-sectional views showing an enlarged view of a part of the inkjet head, and FIG. 6 is a perspective view showing an enlarged view of a part of the inkjet head. FIG. 7 is an explanatory diagram of a manufacturing process of the inkjet head, and shows the internal structure with the cover member 24 omitted. In the figure, X, Y, and Z respectively indicate a first direction, a second direction, and a third direction that are perpendicular to each other. In this embodiment, the directions are described based on the orientation in which the parallel direction of the nozzles 28 and pressure chambers 31 of the inkjet head 10 is along the X axis, the extension direction of the pressure chambers 31 is along the Y axis, and the ejection direction of the liquid is along the Z axis, but the present invention is not limited to this.

[0009] 1 to 6, the inkjet head 10 is a so-called side shooter type share mode share wall type inkjet head. The inkjet head 10 is a device for ejecting ink, and is mounted inside an inkjet printer, for example. For example, the inkjet head 10 is an independently driven inkjet head in which pressure chambers 31 and dummy chambers 32 are alternately arranged. The dummy chambers 32 are air chambers to which ink is not supplied, and do not include nozzles 28.

[0010] The inkjet head 10 includes an actuator base 11, a nozzle plate 12, and a frame 13. The actuator base 11 is an example of a substrate. An ink chamber 27 is formed inside the inkjet head 10 to which ink, which is an example of a liquid, is supplied.

[0011] Furthermore, the inkjet head 10 includes components such as a circuit board 17 that controls the inkjet head 10 and a manifold 18 that forms part of a path between the inkjet head 10 and an ink tank.

[0012] As shown in FIG. 2, the actuator base 11 includes a substrate 21, a pair of actuators 22, and a cover member 24.

[0013] The substrate 21 is formed in a rectangular plate shape from ceramics such as alumina. The substrate 21 has a flat mounting surface. A pair of actuators 22 are bonded to the mounting surface of the substrate. A plurality of supply holes 25 and discharge holes 26 are formed in the substrate 21.

[0014] 2, a pattern wiring 211 is formed on the substrate 21 of the actuator base 11. The pattern wiring 211 is formed of, for example, a nickel thin film. The pattern wiring 211 has a common pattern and an individual pattern, and is configured in a predetermined pattern shape connected to the electrode layer 34 formed on the actuator 22.

[0015] The supply holes 25 are provided in the center of the substrate 21, between the pair of actuators 22, and aligned in the longitudinal direction of the actuators 22. The supply holes 25 communicate with the ink supply portion of the manifold 18. The supply holes 25 are connected to an ink tank via the ink supply portion. The supply holes 25 supply ink from the ink tank to the ink chambers 27.

[0016] The discharge holes 26 are arranged in two rows, sandwiching the supply holes 25 and the pair of actuators 22. The discharge holes 26 communicate with the ink discharge portion of the manifold 18. The discharge holes 26 are connected to the ink tank via the ink discharge portion. The discharge holes 26 discharge ink from the ink chambers 27 to the ink tank.

[0017] A pair of actuators 22 is bonded to the mounting surface of the substrate 21. The pair of actuators 22 are arranged in two rows on the substrate 21 with a supply hole 25 in between. Each actuator 22 is formed of two plate-shaped piezoelectric bodies made of, for example, lead zirconate titanate (PZT). The two piezoelectric bodies are bonded together so that their polarization directions are opposite to each other in the thickness direction. The actuators 22 are bonded to the mounting surface of the substrate 21 by, for example, a thermosetting epoxy adhesive. As shown in FIG. 2, the actuators 22 are arranged in parallel in the ink chamber 27 in correspondence with the two rows of nozzles 28. The actuators 22 divide the ink chamber 27 into a first common chamber 271 in which the supply hole 25 opens and two second common chambers 272 in which the discharge hole 26 opens.

[0018] The actuator 22 is formed to have a trapezoidal cross section. A side surface portion 221 of the actuator 22 has an inclined surface that is inclined with respect to the second direction and the third direction. That is, the actuator 22 is configured to have a trapezoidal cross section perpendicular to the second direction. The top portion of the actuator 22 is bonded to the nozzle plate 12. The actuator 22 includes a plurality of pressure chambers 31 and a plurality of dummy chambers 32. The actuator 22 has a plurality of side wall portions 33, and has grooves that form the pressure chambers 31 and the dummy chambers 32 between the side wall portions 33. In other words, the side wall portions 33 are formed as drive elements between the grooves that form the pressure chambers 31 and the dummy chambers 32.

[0019] 1 to 6, the bottom surface of the groove and the main surface of the substrate 21 are connected by an inclined side surface 221. The pressure chambers 31 and the dummy chambers 32 are arranged alternately. The pressure chambers 31 and the dummy chambers 32 each extend in a direction intersecting the longitudinal direction of the actuator 22, and are arranged in parallel in a first direction (X-axis in the drawings) which is the longitudinal direction of the actuator 22.

[0020] The pressure chamber 31 and the dummy chamber 32 may have different shapes. The side wall portion 33 is formed between the pressure chamber 31 and the dummy chamber 32, and changes the volume of the pressure chamber 31 by deforming in response to a drive signal.

[0021] The pressure chambers 31 communicate with the nozzles 28 of the nozzle plate 12 joined to the top. Both ends of the pressure chambers 31 in the second direction communicate with the ink chambers 27. That is, one end opens to a first common chamber 271 of the ink chambers 27, and the other end opens to a second common chamber 272 of the ink chambers 27. For this reason, ink flows in from one end of the pressure chambers 31, and ink flows out from the other end. The pressure chambers 31 have throttling sections 240 in which the openings at both ends in the second direction are partially blocked by the cover member 24, thereby increasing the flow path resistance. The throttling section 240 increases the fluid resistance, for example, by reducing the cross-sectional area of ​​the flow path perpendicular to the second direction of the pressure chambers 31 compared to the inside of the pressure chambers 31. The throttling section 240 is configured, for example, so that the width dimension in the direction intersecting the second direction, which is the extension direction of the pressure chambers 31, for example, the first direction or the third direction, is narrowed at the inlets and outlets at both ends of the pressure chambers 31. For example, the throttle portion 240 is provided with a cover member 24 that closes the flow path of the pressure chamber 31, so that a part of the flow path between the pressure chamber 31 and the ink chamber 27 is closed.

[0022] The dummy chamber 32 has one side in the third direction closed by the nozzle plate 12 joined to the top, and both sides in the second direction closed by the cover member 24.

[0023] The cover member 24 has a cover plate 241 having a predetermined thickness. The cover plate 241 is configured in a shape corresponding to the inclined side portion 221 of the actuator, for example, in a rectangular shape extending in the first direction. The cover plate 241 is formed with a plurality of throttling holes 242 as throttling openings penetrating in the thickness direction. The cover member 24 is provided at both ends of the actuator 22 in the second direction, and closes the opening of the dummy chamber 32 and closes a part of the opening of the pressure chamber. For example, the cover member 24 is made of a resin material such as PI (polyimide) or PET (polyethylene terephthalate). The groove constituting the pressure chamber 31 communicates with the first common chamber 271 and the second common chamber 272 through the throttling hole 242 formed in the cover member 24. The throttling hole 242 is, for example, an opening smaller than the cross-sectional area of ​​the pressure chamber, and is configured as a circular through hole as an example.

[0024] The cover member 24 closes a part of an opening communicating with a first common chamber 271 and a second common chamber 272 which are common chambers at both ends of the pressure chamber 31, thereby forming a throttle portion 240 having a larger fluid resistance than the pressure chamber 31.

[0025] The cover member 24 is joined to the inclined side surface portion 221 of the actuator 22. In addition, one edge of the cover member 24 may be joined to the substrate 21.

[0026] If the fluid resistance of the throttle section 240 is too large, the supply of ink to the pressure chamber 31 after the ink droplets are ejected will be delayed, hindering high-speed operation. The rise of the meniscus differs depending on the ink viscosity, ejection volume, drive frequency, etc. Therefore, the thickness of the cover member 24 and the dimensions and position of the throttle hole 242 of the throttle section 240 are set so as to provide a flow path resistance according to the ink supply conditions and the characteristics of the rise of the meniscus.

[0027] Both ends of the multiple dummy chambers 32 are closed, for example, by cover members 24. That is, cover members 24 are respectively disposed between the first common chamber 271 of the ink chamber 27 and the inlet of the dummy chamber 32, and between the outlet of the dummy chamber 32 and the second common chamber 272, and both ends of the dummy chamber 32 are separated from the ink chamber 27. For this reason, the dummy chamber 32 constitutes an air chamber into which ink does not flow.

[0028] An electrode layer 34 is provided in each of the pressure chambers 31 and the dummy chambers 32 of the actuator base 11. The electrode layer 34 is formed of, for example, a nickel thin film. The electrode layer 34 extends from the bottom of the groove onto the substrate 21 and is connected to the pattern wiring 211.

[0029] The nozzle plate 12 is formed of, for example, a rectangular polyimide film. The nozzle plate 12 faces the mounting surface of the actuator base 11. The nozzle plate 12 is formed with a plurality of nozzles 28 that penetrate the nozzle plate 12 in the thickness direction.

[0030] The nozzles 28 are provided in the same number as the pressure chambers 31, and are arranged opposite the pressure chambers 31, respectively. The nozzles 28 are aligned along the first direction, and are arranged in two rows corresponding to the pair of actuators 22. Each nozzle 28 is configured in a cylindrical shape with an axis extending in the third direction. For example, the nozzles 28 may have a constant diameter, or may have a shape that narrows toward the center or tip. The nozzles 28 are arranged opposite the midpoints of the pressure chambers 31 formed in the pair of actuators 22 in the extension direction, and each communicates with the pressure chambers 31. One nozzle 28 is arranged in the longitudinal center of each pressure chamber 31.

[0031] The frame 13 is formed into a rectangular frame shape, for example, from a nickel alloy. The frame 13 is interposed between the mounting surface of the actuator base 11 and the nozzle plate 12. The frame 13 is bonded to both the mounting surface of the actuator base 11 and the nozzle plate 12. In other words, the nozzle plate 12 is attached to the actuator base 11 via the frame 13.

[0032] The manifold 18 is joined to the side of the actuator base 11 opposite to the nozzle plate 12. Inside the manifold 18, an ink supply portion which is a flow path communicating with the supply hole 25 and an ink discharge portion which is a flow path communicating with the discharge hole 26 are formed.

[0033] The circuit board 17 is a film carrier package (FCP). The circuit board 17 has a flexible resin film 51 on which a plurality of wirings are formed, and an IC 52 connected to the plurality of wirings of the film 51. The IC 52 is electrically connected to the electrode layer 34 via the wirings of the film 51 and the pattern wiring 211.

[0034] In the inkjet head 10 configured as above, an ink chamber 27 is formed surrounded by the actuator base 11, the nozzle plate 12, and the frame 13. That is, the ink chamber 27 is formed between the actuator base 11 and the nozzle plate 12. For example, the ink chamber 27 is partitioned into three sections in the second direction by the two actuators 22, and has two second common chambers 272 as common chambers into which the discharge holes 26 open, and a first common chamber 271 as common chamber into which the supply hole 25 opens. The first common chamber 271 and the second common chamber 272 are in communication with a plurality of pressure chambers 31.

[0035] In the inkjet head 10 configured as above, ink circulates between the ink tank and the ink chamber 27 through the supply hole, the pressure chamber, and the discharge hole. For example, in response to a signal input from a control unit of the inkjet printer, the driving IC 52 applies a driving voltage to the electrode layer 34 of the pressure chamber 31 via the wiring of the film 51, thereby generating a potential difference between the electrode layer 34 of the pressure chamber 31 and the electrode layer 34 of the dummy chamber 32, thereby selectively deforming the side wall portion 33 in a shear mode. The volume of the pressure chamber 31 is changed by deforming the side wall portion 33 formed between the pressure chamber 31 and the dummy chamber 32 in response to the driving signal.

[0036] When the side wall portion 33 undergoes shear mode deformation, the volume of the pressure chamber 31 in which the electrode layer 34 is provided increases, and the pressure decreases. As a result, the ink in the ink chamber 27 flows into the pressure chamber 31.

[0037] With the volume of the pressure chamber 31 increased, the IC 52 applies a drive voltage of a reverse potential to the electrode layer 34 of the pressure chamber 31. This causes the side wall portion 33 to deform in a shear mode, reducing the volume of the pressure chamber 31 in which the electrode layer 34 is provided, and increasing the pressure. This causes the ink in the pressure chamber 31 to be pressurized and ejected from the nozzle 28.

[0038] A method for manufacturing the inkjet head 10 will be described. First, a piezoelectric member having a plurality of grooves is attached to a plate-shaped substrate 21 with an adhesive or the like, and machining using a dicing saw, a slicer, or the like is performed to form an actuator base 11 having an outer shape of a predetermined shape. Note that, for example, a block-shaped base member having a thickness for a plurality of sheets may be formed in advance and then divided to manufacture a plurality of actuator bases 11 having a predetermined shape.

[0039] Subsequently, an electrode layer 34 and a pattern wiring 211 are formed on the inner surface of the grooves forming the pressure chamber 31 and the dummy chamber 32 and the surface of the substrate 21. As described above, as shown in FIG. 7, the electrode layer 34 and the pattern wiring 211 are formed at predetermined positions, and the actuator 22 that forms the pressure chamber 31 and the dummy chamber 32 is formed. Then, a cover member 24 that is configured in a thin plate shape and has a plurality of throttle holes 242, which are a plurality of throttling openings, is adhered to both side surface portions 221 on both sides where the pressure chamber 31 and the dummy chamber 32 of the actuator 22 open. For example, the cover member 24 is obtained by forming a plurality of throttle holes 242 that are narrower than the inside of the pressure chamber 31 in a cover plate 241 that is configured in a plate shape from an insulating material in advance. The cover plate is a film material made of a resin material such as PI (polyimide) or PET (polyethylene terephthalate), or a mold part formed in a plate shape from a ceramic material such as zirconia alumina.

[0040] For example, when a resin film such as PI or PET is used as the cover plate 241, a plurality of throttle holes 242 are formed by forming an opening narrower than the inside of the pressure chamber by laser processing. Alternatively, when a ceramic plate is used as the cover plate 241, an opening narrower than the inside of the pressure chamber is formed by laser processing or machining to form the throttle holes 242. Alternatively, machinable ceramics may be cut and fabricated. As described above, by attaching the cover member 24 that has the throttle holes 242 in advance and is configured in a plate shape, the opening of the dummy chamber 32 is covered, a part of the opening of the pressure chamber 31 is covered, and the throttle holes 242 having a flow path cross-sectional area smaller than the inside of the pressure chamber 31 communicate with the common chambers 271 and 272.

[0041] Furthermore, the actuator base 11 is assembled to the manifold 18, and the frame 13 is attached to one surface of the substrate 21 of the actuator base 11 with an adhesive sheet made of a thermoplastic resin.

[0042] The assembled frame 13, the top 222 of the side wall 33 of the actuator 22, and the surface of the cover member 24 on the nozzle plate 12 side are polished to be flush with each other. The nozzle plate 12 is then attached by bonding to the polished surfaces of the top 222 of the side wall 33, the frame 13, and the cover member 24. At this time, the nozzles 28 are positioned so as to face the pressure chambers 31. Furthermore, the driving IC chip 52 and the circuit board 17 are connected to the pattern wiring 211 formed on the main surface of the substrate 21 via a flexible printed circuit board as shown in FIG. 1, thereby completing the inkjet head 10.

[0043] An example of an inkjet printer 100 including an inkjet head 10 will be described below with reference to Fig. 17. The inkjet printer 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 116.

[0044] The inkjet printer 100 is a liquid ejection device that performs an image formation process on a sheet of paper P by ejecting a liquid such as ink while transporting the sheet of paper P as a recording medium, which is the object of ejection, along a predetermined transport path A from a medium supply section 112 through an image forming section 113 to a medium ejection section 114.

[0045] The housing 111 constitutes the outer shell of the inkjet printer 100. A discharge port for discharging the paper P to the outside is provided at a predetermined location of the housing 111.

[0046] The medium supply unit 112 includes a plurality of paper feed cassettes, and is configured to be able to hold a plurality of sheets of paper P of various sizes in a stack.

[0047] The medium discharge unit 114 includes a paper discharge tray configured to be able to hold the paper P discharged from the discharge opening.

[0048] The image forming section 113 includes a support section 117 that supports the paper P, and a plurality of head units 130 that are disposed above the support section 117 so as to face the support section 117.

[0049] The support section 117 includes a conveyor belt 118 provided in a loop shape in a predetermined area where image formation is performed, a support plate 119 supporting the conveyor belt 118 from the back side, and a plurality of belt rollers 120 provided on the back side of the conveyor belt 118.

[0050] During image formation, the support section 117 supports the paper P on a holding surface, which is the upper surface of the conveyor belt 118, and conveys the paper P downstream by feeding the conveyor belt 118 at a predetermined timing by the rotation of the belt roller 120.

[0051] The head unit 130 includes a plurality of inkjet heads 10 (four colors), ink tanks 132 as liquid tanks mounted on each inkjet head 10, a connection flow path 133 connecting the inkjet heads 10 and the ink tanks 132, and a circulation pump 134 as a circulation unit. The head unit 130 is a circulation type head unit that constantly circulates liquid in the ink tanks 132, and the pressure chambers 31, dummy chambers 32, and ink chambers 27 built inside the inkjet heads 10.

[0052] In this embodiment, the inkjet heads 10 are provided with four colors, cyan, magenta, yellow, and black, and ink tanks 132 that respectively accommodate ink of each color. The ink tanks 132 are connected to the inkjet heads 10 by connection flow paths 133. The connection flow paths 133 include a supply flow path that is connected to a supply port of the inkjet head 10, and a recovery flow path that is connected to a discharge port of the inkjet head 10.

[0053] 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 in the ink tank 132 in accordance with the head value between the inkjet head 10 and the ink tank 132, thereby causing the ink supplied to each nozzle 28 of the inkjet head 10 to form a meniscus of a predetermined shape.

[0054] The circulation pump 134 is a liquid sending pump constituted by, for example, a piezoelectric pump. The circulation pump 134 is provided in the supply flow path. The circulation pump 134 is connected to a drive circuit of the control unit 116 by wiring, and is configured to be controllable by a CPU (Central Processing Unit). The circulation pump 134 circulates the liquid in the circulation flow path including the inkjet head 10 and the ink tank 132.

[0055] The conveying device 115 conveys the paper P along a conveying path A that extends from the medium supply unit 112 through the image forming unit 113 to the medium discharge unit 114. The conveying device 115 includes a plurality of guide plate pairs 121 and a plurality of conveying rollers 122 that are arranged along the conveying path A.

[0056] Each of the guide plate pairs 121 includes a pair of plate members disposed opposite each other with the paper P being transported therebetween, and guides the paper P along the transport path A.

[0057] The conveying rollers 122 are driven to rotate under the control of the control unit 116, thereby sending the paper P downstream along the conveying path A. Sensors for detecting the conveying status of the paper are disposed at various points along the conveying path A.

[0058] The control unit 116 includes a control circuit such as a CPU which serves as a controller, a ROM (Read Only Memory) which stores various programs, a RAM (Random Access Memory) which temporarily stores various variable data, image data, etc., and an interface unit which inputs data from the outside and outputs data to the outside.

[0059] In the inkjet printer 100 configured as above, when the control unit 116 detects a print instruction by a user operating the operation input unit, for example, via an interface, the control unit 116 drives the transport device 115 to transport the paper P and outputs a print signal to the head unit 130 at a predetermined timing to drive the inkjet head 10. As a discharge operation, the inkjet head 10 sends a drive signal to the IC by an image signal corresponding to image data, applies a drive voltage to the electrode layer 34 of the pressure chamber 31 via wiring, and selectively drives the side wall portion 33 of the actuator 22 to discharge ink from the nozzle 28, thereby forming an image on the paper P held on the transport belt 118. As a liquid discharge operation, the control unit 116 drives the circulation pump 134 to circulate the liquid in a circulation flow path passing through the ink tank 132 and the inkjet head 10. By the circulation operation, the ink in the ink tank 132 is supplied through the ink supply portion of the manifold 18 and from the supply hole 25 to the first common chamber 271 of the ink chamber 27 by driving the circulation pump 134. This ink is supplied to the multiple pressure chambers 31 and the multiple dummy chambers 32 of the pair of actuators 22. The ink flows into the second common chamber 272 of the ink chamber 27 through the pressure chambers 31 and the dummy chambers 32. This ink is discharged from the discharge hole 26 through the ink discharge portion of the manifold 18 to the ink tank 132.

[0060] According to the above-mentioned embodiment, an inkjet head with high frequency characteristics can be provided. That is, in the inkjet head 10 according to the above-mentioned embodiment, by providing the cover member 24 to the pressure chamber 31, the inlet and outlet of the pressure chamber 31 have a higher flow resistance than the inside of the pressure chamber 31, the first common chamber 271, and the second common chamber 272. As a specific example, the openings that open to the first common chamber 271 and the second common chamber 272, which are the common chambers of the pressure chamber 31, are smaller than the flow cross-sectional area of ​​the pressure chamber 31. Therefore, the meniscus does not rise as much when liquid is ejected from the inkjet head 10. Therefore, the meniscus returns quickly, the effect on the next droplet can be reduced, and ejection stability can be improved.

[0061] Fig. 8 shows Test Example 1 of inkjet head 110 equipped with a throttling (throttle section 240), and Test Example 2 of inkjet head 1010 equipped with no throttling. Fig. 9 shows the frequency characteristics of inkjet head 110 equipped with a throttling according to Test Example 1, and Fig. 10 shows the frequency characteristics of inkjet head 1010 equipped with no throttling as Comparative Example 2. Figs. 9 and 10 each show the relationship between nozzle ejection speed and frequency for 1 drop and 3 drops, respectively.

[0062] The inkjet head 110 in the first test example is a side shooter type in which both sides in the second direction, which is the extension direction of the pressure chamber 31, communicate with a common chamber, and the nozzle 28 opens halfway in the extension direction of the pressure chamber 31.

[0063] As shown in FIG. 10, in the inkjet head 1010 according to the second test example, the ejection speed is flat in the low frequency region, but the ejection speed tends to decrease as the frequency increases, and there is a difference in the ejection speed between the low frequency region and the high frequency region. In the inkjet head 1010 according to the second test example, the ejection speed is flat up to 25 kHz, but the ejection speed tends to decrease as the frequency increases above 25 kHz. In addition, in the inkjet head 1010 according to the second test example, the ejection speed is flat up to 15 kHz, but the ejection speed tends to decrease as the frequency increases above 15 kHz. Therefore, the landing position is shifted depending on the printing pattern. If the difference in the ejection speed is large, it takes time for the meniscus to settle, which causes a decrease in print quality, and therefore high-speed driving is not possible.

[0064] 9, in the inkjet head 110 having a throttle portion, the ejection speed tends to be flat for both 1 drop and 3 drops. This is because the fluid resistance between the nozzles increases from the common liquid, and the rise of the meniscus becomes smaller.

[0065] FIG. 11 shows the results of a simulation of meniscus recovery in Test Example 1, in which a throttle is provided in the pressure chamber, and Test Example 2, in which a throttle is not provided. According to FIG. 11, in the case of low frequency, the meniscus state of the nozzle has a sufficient time from when an ink droplet is discharged until the next droplet is discharged, and discharge is possible in a stable state after waiting for the meniscus to recover, regardless of whether a throttle is provided. On the other hand, in the case of high frequency, the time from when a dot (ink droplet) is discharged until the next droplet is discharged is short, so that the discharge of the next droplet begins before the meniscus recovers. For this reason, in the case of the inkjet head 1010 without a throttle, the meniscus rises large after discharge, and the meniscus cannot recover before the discharge of the next droplet, and the discharge speed decreases. In contrast, when a throttle is provided, the rise of the meniscus is small, so the meniscus returns quickly and the impact on the next droplet can be reduced. Therefore, from these simulation results, it can be said that providing a throttle between the pressure chamber 31 and the common chamber leads to improved discharge stability of the inkjet head 110.

[0066] FIG. 12 is an explanatory diagram of a side shooter type inkjet head 110 as test example 1, and a share mode shared wall end shooter type inkjet head 2010 as test example 3, in which an ink inlet / outlet is formed at one end and a nozzle is formed at the other end.

[0067] 13 to 16 are diagrams comparing the simulation characteristics when a throttle is provided in the end-shooter type inkjet head 2010 of Test Example 3 and the side-shooter type inkjet head 110 of Test Example 1. Fig. 13 shows the drive waveform, Fig. 14 shows the nozzle flow velocity vibration, Fig. 15 shows the ejection volume, and Fig. 16 shows the meniscus return characteristics.

[0068] The inkjet head 2010 according to Test Example 3 was an end shooter type in which one end in the second direction, which is the extension direction of the pressure chambers 31, communicated with the common chamber, the other end was closed, and a nozzle opened at the end of the flow path. In other words, the inkjet head 2010 forms a flow path through which ink flows from one side in the second direction toward the nozzle 28.

[0069] In the case of the end-shooter type inkjet head 2010 supplying from one side as Test Example 3 and the side-shooter type inkjet head 110 supplying from both sides as Test Example 1, the drive voltage when the ejection volume, nozzle flow velocity vibration, and meniscus return characteristics are aligned is the lowest for the side-shooter type configuration with double-sided supply, so it can be said that the double-sided supply is superior to the single-sided supply in terms of drive efficiency. In other words, the so-called side-shooter type inkjet head 110, which has a nozzle in the center of the pressure chamber and ink inlets and outlets at both ends, has better ejection efficiency than the end-shooter type inkjet head 2010.

[0070] Furthermore, in the above embodiment, by attaching the thin plate-shaped cover member 24, on which a narrowing opening has already been formed, to the actuator 22, the number of assembly steps is reduced, and since the groove is formed in advance, the precision is high and the narrowing can be easily formed.

[0071] In addition, the cover member 24 has a simple shape, can be produced inexpensively, and requires fewer production steps, making joining and alignment easy. In addition, PI, which is the material of the cover member 24, has good laser processability and excellent chemical resistance, making it suitable for use as a part that comes into contact with ink.

[0072] The present invention is not limited to the above-described embodiment, and in the implementation stage, the components can be modified and embodied without departing from the spirit of the invention.

[0073] For example, in the above embodiment, the cover member 24 in which the multiple throttling holes 242 are formed in the cover plate 241 has been exemplified, but the present invention is not limited to this. For example, the cover member 24 may be configured as a throttling section 240 having a higher fluid resistance than the pressure chamber 31. For example, as another embodiment, as shown in FIG. 18, the throttling openings may be formed by multiple grooves.

[0074] An inkjet head according to another embodiment will be described below. As shown in FIG. 18, the cover member 24 has a cover plate 241 having a predetermined thickness. The cover plate 241 is configured to have a shape corresponding to the inclined side surface portion 221 of the actuator, for example, a rectangular shape extending in the first direction. The cover plate 241 is formed with a plurality of throttle grooves 2242 as throttle openings penetrating in the thickness direction. The cover member 24 is provided at both ends of the actuator 22 in the second direction, and closes the opening of the dummy chamber 32 and closes a part of the opening of the pressure chamber. For example, the cover member 24 is made of a resin material such as PI (polyimide) or PET (polyethylene terephthalate). The grooves constituting the pressure chamber 31 communicate with the first common chamber 271 and the second common chamber 272 through the throttle groove 2242 formed in the cover member 24. The throttle groove 2242 is a slit formed at a position on the nozzle plate 12 side of the cover plate 241 and provided across both main surfaces of the cover plate 241, and is configured to have an opening area smaller than the cross-sectional area of ​​the pressure chamber. For example, the depth dimension of the throttle groove 2242 in the third direction is configured to be smaller than the depth dimension of the pressure chamber 31. The area on the bottom side of the pressure chamber 31 in the third direction is blocked by this cover member 24, thereby forming a throttle section 240 with a narrower opening area. The width dimension of the throttle groove 2242 in the first direction is set appropriately so as to provide, for example, a predetermined fluid resistance.

[0075] In other words, the cover member 24 blocks a portion of the opening that communicates with the first common chamber 271 and the second common chamber 272, which are common chambers at both ends of the pressure chamber 31, thereby forming a constriction portion 240 that reduces the cross-sectional area of ​​the flow path perpendicular to the second direction of the pressure chamber 31 and increases the fluid resistance.

[0076] The cover member 24 is joined to the inclined side surface portion 221 of the actuator 22. In addition, one edge of the cover member 24 may be joined to the substrate 21.

[0077] If the fluid resistance of the throttle section 240 is too large, the supply of ink to the pressure chamber 31 after the ink droplet is ejected slows down, hindering high-speed operation. The meniscus rise differs depending on the ink viscosity, ejection volume, drive frequency, etc. Therefore, the thickness of the cover member 24 and the dimensions and position of the throttle groove 2242 of the throttle section 240 are set to provide a flow path resistance that corresponds to the ink supply conditions and the characteristics of the meniscus rise.

[0078] Both ends of the multiple dummy chambers 32 are closed, for example, by cover members 24. That is, cover members 24 are respectively disposed between the first common chamber 271 of the ink chamber 27 and the inlet of the dummy chamber 32, and between the outlet of the dummy chamber 32 and the second common chamber 272, and both ends of the dummy chamber 32 are separated from the ink chamber 27. For this reason, the dummy chamber 32 constitutes an air chamber into which ink does not flow.

[0079] In the manufacturing method of the inkjet head 2010 according to the present embodiment, a cover member 24 formed in a thin plate shape and having a plurality of throttle grooves 2242 formed therein is bonded to the side surface portion 221 at both ends where the pressure chambers 31 and the dummy chambers 32 of the actuator 22 are opened. The cover member 24 is manufactured by forming a plurality of throttle grooves 2242, which are slits narrower than the inside of the pressure chambers, in a cover plate 241 formed in a plate shape from an insulating material. The cover plate 241 is made of a film material made of a resin material such as PI (polyimide) or PET (polyethylene terephthalate), or a mold part formed in a plate shape from a ceramic material such as zirconia-alumina. For example, when a resin film such as PI or PET is used as the cover plate 241, the plurality of throttle grooves 2242 are formed by forming an opening narrower than the inside of the pressure chamber by laser processing. Alternatively, when a ceramic plate is used as the cover plate 241, the throttle grooves 2242 are formed by forming an opening narrower than the inside of the pressure chamber by laser processing or machining. Alternatively, the cover plate 241 may be manufactured by cutting machinable ceramics. As described above, by attaching the cover member 24 which has a plate-like configuration and has a pre-defined throttling groove 2242, the opening of the dummy chamber 32 is covered, and the opening of the pressure chamber 31 is partially covered, and the throttling groove 2242, which has a flow path cross-sectional area smaller than the inside of the pressure chamber 31, communicates with the common chambers, the first common chamber 271 and the second common chamber 272.

[0080] In the inkjet head 2010 according to this embodiment, stable ejection performance can also be achieved by arranging the cover member 24 having the throttle grooves 2242 on both sides of the pressure chamber 31 to increase the fluid resistance at the entrance and exit of the pressure chamber 31. That is, when the state of the meniscus in the nozzle portion becomes high frequency, the time from when an ink droplet is ejected until the next droplet is ejected is short, so that the ejection of the next droplet begins before the meniscus returns, and the ejection speed decreases, which leads to a deterioration of the frequency characteristics, but by providing a throttle at the entrance and exit of the pressure chamber 31, the time until the meniscus returns can be shortened, and the frequency characteristics can be improved.

[0081] Furthermore, in general, in a share-mode shared-wall type inkjet head, for example, the pressure chamber is configured with a fine groove formed in a piezoelectric body by a diamond cutter, making it difficult to reduce the cross section of a portion of the pressure chamber, but according to the above embodiment, the number of assembly steps is reduced by attaching a thin plate-like cover member 24 in which the throttle groove 2242 is formed in advance to the actuator 22. Also, since the groove 2242 is formed in the cover member 24, the precision is high and the throttle can be easily formed.

[0082] In addition, the cover member 24 has a simple shape, can be produced inexpensively, and requires fewer production steps, making joining and alignment easy. In addition, PI, which is the material of the cover member 24, has good laser processability and excellent chemical resistance, making it suitable for use as a part that comes into contact with ink.

[0083] The present invention is not limited to the above-described embodiment, and in the implementation stage, the components can be modified and embodied without departing from the spirit of the invention.

[0084] In the above embodiment, an example was shown in which actuator 22 having a plurality of grooves was disposed on the main surface of substrate 21, but this is not limited to the above. For example, the actuator may be provided on an end surface of substrate 21. Furthermore, the number of nozzle rows is not limited to that in the above embodiment, and a configuration having one row, or three or more rows may be used.

[0085] In the above embodiment, the actuator base 11 is provided with a laminated piezoelectric body made of the piezoelectric member 131 on the substrate 21, but the present invention is not limited to this. For example, the actuator base 11 may be formed only with the piezoelectric member without using a substrate. Also, instead of using two piezoelectric members, one piezoelectric member may be used. The dummy chamber 32 may be connected to the first common chamber 271 and the second common chamber 272, which are common chambers. The supply side and the discharge side may be reversed, or may be configured to be switchable.

[0086] In the above embodiment, as an example, a circulation type inkjet head in which one side of the pressure chamber 31 is the supply side and the other side is the discharge side, and fluid flows in from one side of the pressure chamber and flows out from the other side, is exemplified, but is not limited to this. For example, a common chamber on both sides of the pressure chamber 31 may be the supply side, and fluid may flow in from both sides. That is, a configuration in which fluid flows in from both sides of the pressure chamber 31 and flows out from the nozzle 28 arranged in the center of the pressure chamber 31 may be used. Even in this case, by providing a throttle portion 240 at the inlet portion on both sides of the pressure chamber 31, the fluid resistance can be increased and the ejection efficiency can be improved.

[0087] For example, the liquid to be ejected is not limited to ink for printing, but may be, for example, a device that ejects liquid containing conductive particles for forming a wiring pattern on a printed wiring board.

[0088] In addition, in the above embodiment, the inkjet head is used in a liquid ejection device such as an inkjet printer, but the present invention is not limited to this and can also be used in, for example, 3D printers, industrial manufacturing machines, and medical applications, enabling reduction in size, weight, and cost.

[0089] According to at least one of the embodiments described above, it is possible to provide a liquid ejection head that is easy to manufacture.

[0090] Although several other embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. The following is a description equivalent to the invention described in the claims of the original application. (1) an actuator having a plurality of pressure chambers communicating with nozzles that eject liquid, and a plurality of dummy chambers disposed between the plurality of pressure chambers; a common chamber disposed at both ends of the actuator and communicating with the pressure chambers; a cover plate joined to a side of the actuator, configured in a plate shape, separating the pressure chambers and the dummy chambers from the common chamber, and having openings facing a plurality of the pressure chambers that connect the common chamber to the pressure chambers and have a higher fluid resistance than the inside of the pressure chambers. (2) the cover plate is a ceramic plate or a resin film; the opening is a groove or a hole; the actuator includes a plurality of side walls arranged in parallel along a first direction and defining a groove between the pressure chamber and the dummy chamber; Each of the pressure chambers extends in a second direction intersecting the first direction, the nozzle is disposed at a position corresponding to a midway portion of the pressure chamber in the second direction, a liquid ejection direction of the nozzle intersects with the first direction and the second direction, the common chambers are disposed on both sides of the pressure chamber in the second direction, The liquid ejection head according to (1), wherein the cover plates are disposed between the pressure chambers and the common chamber at both ends of the pressure chambers, and are joined to the side walls. (3) A method for manufacturing a liquid ejection head, comprising: attaching a plate-shaped cover plate to a side of an actuator facing a common chamber, the side facing the common chamber, the cover plate having an opening facing the pressure chambers and having a greater fluid resistance than the inside of the pressure chambers, the side facing the common chamber of an actuator having a plurality of pressure chambers communicating with nozzles that eject liquid, a plurality of dummy chambers arranged between the pressure chambers, and a common chamber communicating with both sides of the pressure chambers and the dummy chambers. (4) The method for manufacturing a liquid ejection head according to (3), wherein the cover plate is a resin film and the opening is formed by laser processing. (5) The method for manufacturing a liquid ejection head according to (3), wherein the cover plate is a ceramic plate and the grooves or holes are formed by machining. [Explanation of symbols]

[0091] 10...inkjet head, 11...actuator base, 12...nozzle plate, 13...frame, 17...circuit board, 18...manifold, 21...substrate, 22...actuator, 24...cover member (wall portion), 25...supply hole, 26...discharge hole, 27...ink chamber, 31...pressure chamber, 32...dummy chamber, 33...side wall portion, 34...electrode layer, 51...film, 52...driving IC chip, 100...inkjet printer, 111...housing, 112...medium supply section, 113...image forming section, 114...medium discharge section , 115...conveying device, 116...control unit, 117...support unit, 118...conveying belt, 119...support plate, 120...belt roller, 121...pair of guide plates, 122...conveying roller, 130...head unit, 132...ink tank, 133...connecting flow path, 134...circulation pump, 211...pattern wiring, 221...side portion, 222...top, 240...throttling portion, 241...cover plate, 242...throttling hole (throttling opening), 271...first common chamber, 272...second common chamber, 2242...throttling groove (throttling opening).

Claims

1. an actuator having a plurality of pressure chambers communicating with nozzles that eject liquid, and a plurality of dummy chambers disposed between the plurality of pressure chambers; a common chamber disposed at both ends of the actuator and communicating with the pressure chambers; a cover plate joined to each of both side surfaces of the actuator, configured in a plate shape, separating the pressure chambers and the dummy chambers from the common chamber, and having openings at positions facing the pressure chambers that communicate with the common chamber and have a fluid resistance greater than that of the inside of the pressure chambers, the nozzle is disposed at a position corresponding to a midway point in an extension direction of the pressure chamber, a liquid ejection direction of the nozzle intersects with the extension direction; the common chambers are disposed on both sides of the pressure chamber in the extension direction, The cover plate is disposed between the pressure chamber and the common chamber on both ends of the pressure chamber.

2. the cover plate is a ceramic plate or a resin film; the opening is a groove or a hole; the actuator includes a plurality of side walls arranged in parallel along a first direction and defining a groove between the pressure chamber and the dummy chamber; Each of the pressure chambers extends in a second direction intersecting the first direction. The liquid ejection head according to claim 1 .

3. A method for manufacturing a liquid ejection head, comprising: attaching a plate-shaped cover plate to a side of an actuator facing a common chamber, the side facing the common chamber, the cover plate having an opening facing the pressure chambers and having a greater fluid resistance than the inside of the pressure chambers, the side facing the common chamber of an actuator having a plurality of pressure chambers communicating with nozzles that eject liquid, a plurality of dummy chambers arranged between the pressure chambers, and a common chamber communicating with both sides of the pressure chambers and the dummy chambers.

4. The method for manufacturing a liquid ejection head according to claim 3 , wherein the cover plate is a resin film and the opening is formed by laser processing.

5. The method for manufacturing a liquid ejection head according to claim 3 , wherein the cover plate is a ceramic plate, and the grooves or holes are formed by machining.

Images