Liquid ejection head

Abstract

To provide a liquid discharge head capable of securing stable discharge characteristics.SOLUTION: A liquid discharge head includes an actuator, a common chamber, and a diaphragm member. The actuator has a plurality of grooves constituting a plurality of pressure chambers which are arranged side by side in a first direction and communicate with nozzles for discharging a liquid and a plurality of dummy chambers arranged among the plurality of pressure chambers, and a plurality of side walls formed among the grooves constituting the pressure chambers and the dummy chambers. The common chamber communicates with both ends of the pressure chambers of the actuator. The diaphragm member has a strip part which is constituted in a plate shape extending in the first direction, is joined to the side face of the actuator among both ends of the pressure chambers and the dummy chambers and the common chamber, and blocks a part of a communication port communicating with the common chamber of the pressure chamber.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] An embodiment of the present invention relates to 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 that can ensure stable ejection characteristics. [Means for solving the problem]

[0006] A liquid ejection head according to one embodiment includes an actuator, a common chamber, and a throttle member. The actuator has a plurality of pressure chambers arranged in a line in a first direction and communicating with nozzles that eject liquid, a plurality of grooves that constitute a plurality of dummy chambers arranged between the pressure chambers, and a plurality of side walls formed between the pressure chambers and the grooves that constitute the dummy chambers. The common chamber communicates with both ends of the pressure chambers of the actuator. The throttle member is configured in a plate shape extending in the first direction, and is arranged to extend between the common chamber and both ends of the pressure chambers and the dummy chambers of the actuator. Both sides On the side each The pressure chamber has a rectangular portion that is joined to the common chamber and blocks a portion of the communication port that communicates with the common chamber. The pressure chamber extends in a second direction intersecting the first direction. The fluid resistance of the communication holes on both sides of the pressure chamber in the second direction, which are partially blocked by the throttle member, is configured to be greater than the flow path resistance inside the pressure chamber and the common chamber. The nozzle is disposed at a position corresponding to a midway point of the pressure chamber in the second direction, and a liquid ejection direction is different from the first direction and the second direction. [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 perspective view showing a configuration of a portion of the inkjet head. [Diagram 5] FIG. 2 is an enlarged side view showing a configuration of a portion of the inkjet head. [Figure 6] FIG. 2 is an enlarged cross-sectional view showing a configuration of a portion of the inkjet head. [Figure 7] FIG. 2 is an enlarged cross-sectional view showing a configuration of a portion of the inkjet head. [Figure 8]3A to 3C are explanatory diagrams of a method for manufacturing the inkjet head. [Figure 9] 3A to 3C are explanatory diagrams of a method for manufacturing the inkjet head. [Figure 10] FIG. 4 is an explanatory diagram of an inkjet head according to Test Example 1 and Test Example 2. [Figure 11] 13 is a graph showing the ejection speed of the inkjet head in Test Example 1. [Figure 12] 13 is a graph showing the ejection speed of an inkjet head according to Test Example 2. [Figure 13] 13 is a graph showing meniscus recovery characteristics of the inkjet heads according to Test Examples 1 and 2. [Figure 14] FIG. 13 is an explanatory diagram of an inkjet head of an end shooter according to Test Example 1 and Test Example 3. [Figure 15] 13 is a graph showing driving waveforms of the inkjet heads according to Test Examples 1 and 3. [Figure 16] 13 is a graph showing nozzle flow velocity vibration of the inkjet heads according to Test Examples 1 and 3. [Figure 17] 13 is a graph showing the ejection volume of the inkjet heads according to Test Examples 1 and 3. [Figure 18] 13 is a graph showing meniscus recovery characteristics of the inkjet heads according to Test Examples 1 and 3. [Figure 19] FIG. 1 is a schematic diagram showing an inkjet printer according to an embodiment. [Figure 20] FIG. 11 is an enlarged perspective view showing a configuration of a portion of an inkjet head according to another 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 7. 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. FIG. 3 is a cross-sectional view showing an enlarged part of the inkjet head, and FIG. 4 is a cross-sectional view showing an enlarged part of the inkjet head. FIG. 5 is a side view showing an enlarged part of the configuration of the inkjet head. FIGS. 6 and 7 are cross-sectional views of the actuator 22, and FIG. 6 shows a cross-sectional view at a position passing through the pressure chamber, and FIG. 7 shows a cross-sectional view at a position passing through the dummy chamber. FIGS. 8 and 9 are explanatory diagrams of the manufacturing process of the inkjet head. In the drawings, X, Y, and Z respectively indicate a first direction, a second direction, and a third direction that are orthogonal to each other. In this embodiment, the directions will be described based on the orientation in which the parallel direction of the nozzles 28 and the 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] As shown in Fig. 1, 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, a cover portion 23, and a throttle 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. 1, 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] 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 figure) 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 multiple pressure chambers 31 communicate with multiple 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 into a first common chamber 271 of the ink chambers 27, and the other end opens into 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 throttling member 24, increasing the flow path resistance.

[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 portion 23.

[0023] The cover portion 23 is provided at both ends in the second direction of the groove constituting the dummy chamber 32, and closes the opening of the dummy chamber 32. For example, the cover portion 23 is formed by applying a photosensitive resin to the entrance of the dummy chamber 32 and hardening the resin. Alternatively, the cover portion 23 may be formed of a plate adhered to the side wall portion 33. Note that the groove constituting the pressure chamber 31 is not completely covered by the cover portion 23, and a part of the groove opens to the first common chamber 271 and the second common chamber 272. The cover portion 23 is formed, for example, from a photosensitive resin material. For example, the cover portion 23 is formed by filling the groove constituting the dummy chamber 32 with photosensitive resin and hardening the resin.

[0024] The throttle members 24 are provided at both ends of the pressure chamber 31. The throttle members 24 are formed in a plate shape with a predetermined width. For example, the throttle members 24 are made of a film member made of a resin material such as PI (polyimide) or PET (polyethylene terephthalate), a molded part made of a ceramic material such as zirconia-alumina, or are formed by cutting machinable ceramics. The throttle members 24 form throttle sections 240 that reduce the cross-sectional area of ​​the flow path perpendicular to the second direction of the pressure chamber 31 and increase the fluid resistance by blocking a part of the communication port with the first common chamber 271 and the second common chamber 272 that are common chambers at both ends of the pressure chamber 31. The throttle members 24 are formed in a plate shape with a predetermined width and thickness in advance, and are attached to a position where they open a part of the communication port. For example, the throttle sections 240 have rectangular plate-like strip parts 241 that extend in the first direction at the communication ports that serve as inlets and outlets on both sides of the pressure chamber 31 and block the area on the nozzle plate 12 side in the depth direction of the pressure chamber 31 and the dummy chamber.

[0025] The strip portion 241 is disposed opposite the inclined side surface portion 221 of the actuator 22 and is joined to the side surface portion 221. For example, the strip portion 241 has a predetermined length in the first direction that is longer than the region in which the pressure chambers 31 and the dummy chambers 32 are lined up, and has a certain width dimension that extends from the top of the side surface portion 221 of the actuator 22 to a predetermined position on the top side of the bottom surface of the pressure chamber 31. For example, the thickness of the strip portion 241 is configured to be 0.5 mm or less. The strip portion 241 is located in a region on the nozzle plate 12 side in the third direction, which is the depth direction of the groove that constitutes the pressure chamber 31, and is formed over the entire length in the first direction. The edge of the strip portion 241 opposite to the top side of the actuator 22 is located at a position on the nozzle plate 12 side of the bottom of the pressure chamber 31. That is, in the third direction, the rectangular portion 241 closes the portion of the pressure chamber 31 on the nozzle plate 12 side, while leaving a predetermined width open on the bottom side of the pressure chamber 31. That is, the rectangular portion 241 partially closes the communication port which serves as the entrance and exit of the pressure chamber 31, thereby forming a throttling portion 240 having a throttling port 242 where the flow path narrows.

[0026] If the fluid resistance of the throttle section 240 is too large, the replenishment after ink droplet ejection will be slow, hindering high-speed operation. The meniscus rise will vary depending on the ink viscosity, ejection volume, drive frequency, etc. Therefore, the width and position of the strip section 241 of the throttle section 240 are set to provide a flow path resistance that corresponds to the ink replenishment conditions and the characteristics of the meniscus rise.

[0027] Both ends of the multiple dummy chambers 32 are closed, for example, by the cover portion 23. That is, the cover portions 23 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 with reference to Figures 8 to 10. First, a piezoelectric member having a plurality of grooves is attached to a plate-like substrate 21 with an adhesive or the like, and then machining is performed using a dicing saw, slicer, or the like to form an actuator base 11 having a predetermined outer shape. Note that, for example, a block-shaped base member having a thickness equivalent to that of multiple sheets may be formed in advance, and then divided to manufacture multiple actuator bases 11 having the predetermined shape.

[0039] Next, the electrode layer 34 and the pattern wiring 211 are formed on the inner surface of the grooves constituting the pressure chamber 31 and the dummy chamber 32 and on the surface of the substrate 21. As a result, as shown in FIG. 8, the electrode layer 34 and the pattern wiring 211 are formed at predetermined locations on the surface of the actuator base 11. In addition, the cover portion 23 is formed at predetermined locations to close both ends of the dummy chamber 32. For example, the cover portion 23 is formed by filling the grooves constituting the dummy chamber 32 with a photosensitive resin and curing it. Furthermore, the diaphragm member 24 formed in a predetermined shape is bonded to the side portion 221 of the actuator 22. The diaphragm member 24 is formed of a film member made of a resin material such as PI or PET, or a mold part made of a ceramic material such as zirconia or alumina, or is formed in advance in a strip shape by cutting machinable ceramics. As a result, the strip portions 241 are arranged on both side portions 221 of the actuator 22, and the diaphragm portion 240 with the diaphragm opening 242 is formed.

[0040] 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.

[0041] Then, the assembled frame 13, the top 222 of the side wall portion 33 of the actuator 22, and the surfaces of the cover portion 23 and the throttle 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 portion 33, the frame 13, the cover portion 23, and the throttle 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.

[0042] An example of an inkjet printer 100 including an inkjet head 10 will be described below with reference to Fig. 19. 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] The medium discharge unit 114 includes a paper discharge tray configured to be able to hold the paper P discharged from the discharge opening.

[0047] 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.

[0048] The support section 117 includes a conveyor belt 118 that is provided in a loop shape in a predetermined area where image formation is performed, a support plate 119 that supports the conveyor belt 118 from the back side, and a plurality of belt rollers 120 that are provided on the back side of the conveyor belt 118.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] According to the above-mentioned embodiment, it is possible to provide a liquid ejection head that can ensure stable ejection characteristics. That is, in the inkjet head 10 according to the above-mentioned embodiment, by providing the throttle member 24 in the pressure chamber 31, the inlet and outlet of the pressure chamber 31 have a larger 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 into 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, reducing the effect on the next droplet, and improving ejection stability.

[0060] Fig. 10 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. 11 shows the frequency characteristics of inkjet head 110 equipped with a throttling according to Test Example 1, and Fig. 12 shows the frequency characteristics of inkjet head 1010 equipped with no throttling as Comparative Example 2. Figs. 11 and 12 each show the relationship between nozzle discharge speed and frequency for 1 drop and 3 drops, respectively.

[0061] Here, the inkjet head 110 in test example 1 is a side shooter type in which both sides in the second direction, which is the extension direction of the pressure chamber 31, are connected to a common chamber, forming a flow path through which fluid flows from one side to the other in the second direction, and the nozzle 28 opens halfway through the extension direction of the pressure chamber 31.

[0062] As shown in FIG. 12, 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.

[0063] On the other hand, in the inkjet head 110 having a throttle portion, the ejection speed tends to be flat for both 1 drop and 3 drops as shown in Fig. 11. This is because the fluid resistance between the nozzles increases from the common liquid, and the rise of the meniscus becomes smaller.

[0064] FIG. 13 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. 13, 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. Therefore, 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.

[0065] FIG. 14 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.

[0066] 15 to 18 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. 15 shows the drive waveform, Fig. 16 shows the nozzle flow velocity vibration, Fig. 17 shows the ejection volume, and Fig. 18 shows the meniscus return characteristics.

[0067] 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.

[0068] 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.

[0069] Generally, 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 throttle member 24 has a simple shape having a thin plate-like strip portion 241 and can be produced at low cost. In addition, the production process is few, making joining and alignment easy.

[0070] Moreover, since fine processing is not required to form the throttle member 24, it is possible to easily form the throttle section 240. Moreover, the throttle member 24 can be made lightweight by forming it into a thin plate shape with a thickness of 0.5 mm or less, and therefore the throttle member 24 can be easily joined and its position can be easily controlled, making it easy to control the discharge performance.

[0071] Furthermore, in the inkjet head 10 according to the above embodiment, a restriction is formed partially in the communication port serving as the inlet and outlet of the pressure chamber 31, so it is easier to ensure the volume of the pressure chamber 31 than if the pressure chamber 31 were narrowed overall. Therefore, there are fewer restrictions on the size of the nozzle and droplets compared to a configuration in which the pressure chamber is narrowed overall, making it easier to maintain ejection performance.

[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 aperture member 24 is shaped like a strip extending in the first direction, but the shape is not limited to this and can be changed as appropriate. For example, in an inkjet head 3010 shown in FIG. 20 as another embodiment, the aperture member 24 is configured to be U-shaped and has a support portion 245 that is continuous with both ends of the strip portion 241. The support portion 245 is disposed at both ends of the actuator 22 in the first direction. The support portion 245 extends along the inclined surface of the side wall portion 33 and is joined to the side wall portion 33, and the tip surface is joined to, for example, a flat portion of the substrate 21 that does not have wiring or the like. According to this embodiment, the aperture member 24 is supported on a flat surface of the substrate 21 of the inkjet head that does not have wiring or the like, thereby improving the positional accuracy of the aperture member 24 and the accuracy of the size of the aperture.

[0074] In the above embodiment, an example was shown in which actuator 22 having a plurality of grooves was disposed on the main surface portion 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.

[0075] 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.

[0076] 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 non-circulation type may be used. Also, 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 communication ports on 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.

[0077] 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.

[0078] 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.

[0079] According to at least one of the embodiments described above, stable ejection characteristics can be ensured.

[0080] 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 including: a plurality of pressure chambers arranged side by side in a first direction and communicating with nozzles that eject liquid; a plurality of grooves that constitute a plurality of dummy chambers arranged between the plurality of pressure chambers; and a plurality of side walls formed between the pressure chambers and the grooves that constitute the dummy chambers; a common chamber communicating with both ends of the pressure chamber of the actuator; a throttle member having a plate shape extending in the first direction, the throttle member being joined to a side surface of the actuator between both ends of the pressure chambers and the dummy chamber and the common chamber, the throttle member having a rectangular portion that closes a part of a communication port of the pressure chamber that communicates with the common chamber; A liquid ejection head comprising: (2) the pressure chambers and the dummy chambers are arranged in a plurality of rows along the first direction, a nozzle plate having a plurality of the nozzles arranged side by side in the first direction and communicating with the pressure chambers; a base on which the actuator is disposed, A bottom surface of the groove is joined to the base, Each of the pressure chambers extends in a second direction intersecting the first direction, The liquid ejection head according to (1), wherein the nozzle is disposed at a position corresponding to a midway portion of the pressure chamber in the second direction. (3) The liquid ejection head described in (2), wherein the throttle member is arranged opposite an area of ​​the nozzle plate side opposite the bottom side of the groove in a third direction which is a depth direction of the groove which intersects with the first direction and the second direction which intersects with the first direction, and closes the area of ​​the nozzle plate side of the groove and opens the area of ​​the bottom side. (4) The liquid ejection head according to any one of (1) to (3), wherein the strip portion is made of a film member made of a resin material or ceramics. [Explanation of symbols]

[0081] 10...inkjet head, 11...actuator base, 12...nozzle plate, 13...frame, 17...circuit board, 18...manifold, 21...substrate, 22...actuator, 23...cover portion, 24...throttling 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 portion, 113...image forming portion, 114...medium discharge portion, 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, 24241...wall portion, 242...throttling port, 243...dry film resist material, 271...first common chamber, 272...second common chamber, 245...support portion, 246...hole portion.

Claims

1. an actuator including: a plurality of pressure chambers arranged side by side in a first direction and communicating with nozzles that eject liquid; a plurality of grooves that constitute a plurality of dummy chambers arranged between the plurality of pressure chambers; and a plurality of side walls formed between the pressure chambers and the grooves that constitute the dummy chambers; a common chamber communicating with both ends of the pressure chamber of the actuator; a throttle member having a plate shape extending in the first direction, the throttle member being joined to both side surfaces of the actuator between both ends of the pressure chambers and the common chamber and the common chamber, the throttle member having a rectangular portion that closes a part of a communication port of the pressure chamber that communicates with the common chamber; Equipped with The pressure chamber extends in a second direction intersecting the first direction, a fluid resistance of the communication port on both sides of the pressure chamber in the second direction, the communication port being partially blocked by the throttle member, is configured to be larger than a flow path resistance of the inside of the pressure chamber and the common chamber, the nozzle is disposed at a position corresponding to a midpoint of the pressure chamber in the second direction, A liquid ejection head, wherein a liquid ejection direction is different from the first direction and the second direction.

2. the pressure chambers and the dummy chambers are arranged in a plurality of rows along the first direction, a nozzle plate having a plurality of the nozzles arranged side by side in the first direction and communicating with the pressure chambers; a base on which the actuator is disposed, The liquid ejection head according to claim 1 , wherein a surface on a bottom side of the groove is bonded to the base.

3. An actuator having a plurality of pressure chambers arranged in a first direction and communicating with a nozzle that ejects liquid, a plurality of grooves constituting a plurality of dummy chambers arranged between the pressure chambers, and a plurality of side walls formed between the pressure chambers and the grooves constituting the dummy chambers; a common chamber communicating with both ends of the pressure chamber of the actuator; a throttle member having a plate shape extending in the first direction, the throttle member being joined to a side surface of the actuator between both ends of the pressure chambers and the dummy chamber and the common chamber, the throttle member having a rectangular portion that closes a part of a communication port of the pressure chamber that communicates with the common chamber; a nozzle plate having a plurality of the nozzles arranged side by side in the first direction and communicating with the pressure chambers; a base on which the actuator is disposed, the pressure chambers and the dummy chambers are arranged in a plurality of rows along the first direction, A bottom surface of the groove is joined to the base, 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 head, wherein the throttle member is arranged opposite an area of ​​the nozzle plate side opposite a bottom side of the groove in a third direction which is a depth direction of the groove which intersects with the first direction and the second direction which intersects with the first direction, and closes the area of ​​the nozzle plate side of the groove and opens the area of ​​the bottom side.

4. 4. The liquid ejection head according to claim 1, wherein the strip portion is made of a film member made of a resin material or a ceramic material.

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