Liquid dispensing head

Abstract

To provide a liquid discharge head capable of securing stable discharge characteristics.SOLUTION: A liquid discharge head includes an actuator part, and a cover part. The actuator part has a plurality of pressure chambers and a plurality of air chambers which are composed of piezoelectric materials and are alternately aligned. The cover part has a plurality of wall members, and blocks the air chamber.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] Embodiments of the present invention relate to a liquid ejection head.

Background Art

[0002] In recent years, in inkjet heads, high productivity has been demanded, and speeding up and increasing the droplet volume have become problems. For example, a share mode shared wall type inkjet head has high rigidity of a pressure chamber formed of a piezoelectric body, so it becomes high power and is suitable for discharging high viscosity ink and large droplets. A share mode shared wall type inkjet head. The same drive column is shared by two pressure chambers, and so-called three-cycle driving is generally used in which one-third of a plurality of arranged chambers are simultaneously driven as pressure chambers. In addition, an independent drive head has been developed in which both sides of a pressure chamber to be driven are air chambers and one pressure chamber is driven by two independent drive columns. For example, a structure has been developed in which a large number of grooves are formed in a piezoelectric member, every other groove is blocked at an entrance and exit, for example, with a resin wall to form an air chamber, and a groove whose entrance and exit are not blocked is used as a pressure chamber for independent driving.

[0003] In such an inkjet head, if the formation of the resin wall blocking the air chamber is insufficient, ink enters the air chamber, the AL (Acoustic Length) of the adjacent pressure chamber is displaced, and the in-plane AL variation becomes large. AL is half of the acoustic resonance period of the pressure wave in the pressure chamber. Further, when the air chamber is filled with ink, a so-called crosstalk phenomenon occurs in which vibration is transmitted to an adjacent pressure chamber.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem that this invention aims to solve is to provide a liquid dispensing head that can ensure stable dispensing characteristics. [Means for solving the problem]

[0006] A liquid discharge head according to one embodiment comprises an actuator section and a cover section. The actuator section is composed of a piezoelectric member and has a plurality of alternately arranged pressure chambers and a plurality of air chambers. The cover section has a plurality of wall members that close the air chambers. The pressure chambers and air chambers are arranged alternately in the direction of alignment. The ends of the multiple pressure chambers in the extension direction intersecting the direction of alignment communicate with a common chamber. The cover portions are positioned at both ends of the air chambers in the extension direction and close the communication portions with the common chamber. Each of the cover portions at both ends is formed into a triple-wall structure having three wall members aligned in the extension direction, with gaps formed between the three wall members. [Brief explanation of the drawing]

[0007] [Figure 1] A perspective view showing an inkjet head according to an embodiment. [Figure 2] An exploded perspective view showing a partial configuration of an inkjet head according to an embodiment. [Figure 3] Figure 2 is a perspective view showing a portion of the inkjet head. [Figure 4] A cross-sectional view showing a magnified view of a part of the inkjet head's components. [Figure 5] Figure 4 shows a cross-sectional view of the inkjet head cut at the pressure chamber. [Figure 6] Figure 4 shows a cross-sectional view of the inkjet head cut at the location of the air chamber. [Figure 7] Figure 2 is a partially enlarged cross-sectional view showing a portion of the cross-section obtained by cutting the inkjet head along line VII-VII. [Figure 8] An explanatory diagram showing the relationship between AL and the printing state of the inkjet head according to the embodiment. [Figure 9] This diagram illustrates the relationship between the flow path length and AL (Acid Alt) of the inkjet head. [Figure 10] A schematic diagram showing an inkjet printer according to this embodiment. [Figure 11] A cross-sectional view showing a part of an inkjet head according to another embodiment. [Modes for carrying out the invention]

[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 Figures 1 to 8. Figure 1 is a perspective view showing the inkjet head according to the first embodiment, and Figure 2 is an exploded perspective view of a part of the inkjet head. Figure 3 is an enlarged perspective view showing a part of the configuration of the inkjet head, and Figures 4 to 7 are enlarged cross-sectional views showing a part of the configuration of the inkjet head. Figure 8 is an explanatory diagram showing the relationship between AL of the inkjet head and the printing state, and Figure 9 is an explanatory diagram showing the relationship between the flow path length of the inkjet head and AL. In the figures, X, Y, and Z indicate the first, second, and third directions, respectively, which are orthogonal to each other. In this embodiment, the directions are described based on the orientation in which the alignment direction of the grooves constituting the nozzle, pressure chamber 31 and air chamber 32 is along the X axis, the extension direction of the pressure chamber 31 and air chamber 32 is along the Y axis, and the liquid ejection direction is along the Z axis, but the description of directions is not limited to this.

[0009] The inkjet head 10 shown in Figures 1 to 7 is a so-called side-shooter type shear mode shared wall inkjet head. The inkjet head 10 is a device for ejecting ink and is mounted, for example, inside an inkjet printer. For example, the inkjet head 10 is an independently driven inkjet head in which pressure chambers 31 and air chambers 32 are arranged alternately. The air chambers 32 are air chambers to which ink is not supplied and do not have nozzles 28.

[0010] The inkjet head 10 comprises 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, into which ink, 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 the path between the inkjet head 10 and the ink tank.

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

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

[0014] As shown in FIGS. 2 and 3, a pattern wiring 211 is formed on the substrate 21 of the actuator base 11. The pattern wiring 211 is formed from, for example, a nickel thin film. The pattern wiring 211 has a common pattern and individual patterns, and is configured in a predetermined pattern shape that is connected to an electrode layer 34 formed in the actuator portion 22. For example, the pattern wiring 211 is formed at a position avoiding the supply holes 25 and the discharge holes 26.

[0015] The supply holes 25 are provided side by side in the longitudinal direction of the actuator portion 22 at the central portion of the substrate 21 and between the pair of actuator portions 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 the ink in the ink tank to the ink chamber 27.

[0016] The discharge holes 26 are arranged in two rows, flanking the supply holes 25 and a pair of actuator units 22. The discharge holes 26 communicate with the ink discharge section of the manifold 18. The discharge holes 26 are connected to the ink tank via the ink discharge section. The discharge holes 26 discharge the ink from the ink chamber 27 to the ink tank. In this configuration, the inkjet head 10 is a circulating type, and ink flows to each pressure chamber 31 from one side where the supply holes 25 are located to the other side where the discharge holes 26 are located. Alternatively, the ink discharge section may be configured to be opened only during maintenance, for example, and to communicate with the ink supply section during printing. In this configuration, the inkjet head 10 is a non-circulating type, and ink flows into each pressure chamber 31 from both sides.

[0017] A pair of actuator units 22 are bonded to the mounting surface of the substrate 21. The pair of actuator units 22 are arranged in two rows on the substrate 21, with the supply hole 25 in between. Each actuator unit 22 is formed by two plate-shaped piezoelectric elements 201 and 202, each made of, for example, lead zirconate titanate (PZT). For example, the two piezoelectric elements 201 and 202 are polarized such that their polarization directions are opposite to each other in the thickness direction. That is, the actuator unit 22 is formed by stacking a pair of piezoelectric elements 201 and 202 and polarizing them in opposite directions in the stacking direction. The actuator units 22 are bonded to the mounting surface of the substrate 21 by, for example, a thermosetting epoxy adhesive. As shown in Figure 2, the actuator units 22 are arranged in parallel within the ink chamber 27, corresponding to the two rows of nozzles 28. The actuator unit 22 divides the ink chamber 27 into a first common chamber 271 through which the supply hole 25 opens, and two second common chambers 272 through which the discharge holes 26 open. The top of the actuator unit 22 is bonded to the nozzle plate 12.

[0018] The actuator unit 22 is composed of a laminated piezoelectric member in which a plurality of piezoelectric bodies 201 and 202 are laminated, and includes a plurality of side walls 33 serving as drive elements. The plurality of piezoelectric bodies 201 and 202 are laminated along the third direction which is the thickness direction, and are bonded to each other. Note that the laminated piezoelectric member is polarized in the manufacturing process.

[0019] On one side surface in the third direction which is the depth direction of the actuator unit 22, that is, on one side surface facing the nozzle plate 12, a plurality of grooves forming the pressure chamber 31 and the air chamber 32 are formed side by side in the first direction which is the parallel direction. The actuator unit 22 is configured such that the laminated piezoelectric member is divided into a plurality of parts on one side by a plurality of grooves, and the bottom sides of the plurality of grooves are integrally connected in a comb shape. The actuator unit 22 is divided into a plurality of parts by forming grooves on one side surface, for example, by dicing, and the other end sides are connected, and a plurality of side walls 33 are arranged in parallel with the grooves interposed therebetween along the first direction indicated by X in the figure.

[0020] The actuator unit 22 has a plurality of side walls 33, and between the side walls 33, there are grooves forming the pressure chamber 31 and the air chamber 32. In other words, the side walls 33 are formed as drive elements between the grooves forming the pressure chamber 31 and the air chamber 32. The side walls 33 are formed between the pressure chamber 31 and the air chamber 32, and by deforming according to a drive signal, the volume of the pressure chamber 31 is changed.

[0021] The width of the actuator unit 22 in the short side direction gradually increases from the top side toward the substrate side. The cross-sectional shape along the direction (short side direction) orthogonal to the longitudinal direction of the actuator unit 22 is formed in a trapezoidal shape. The side surface portion 221 of the actuator unit 22 has an inclined surface inclined with respect to the second direction and the third direction.

[0022] FIG. 4 is a partially enlarged cross-sectional view of one of the actuator units 22 of the inkjet head 10 shown in FIG. 2. FIG. 5 is a cross-sectional view of the inkjet head 10 shown in FIG. 4 with the groove forming the pressure chamber 31 cut. FIG. 6 is a cross-sectional view of the inkjet head 10 shown in FIG. 4 with the groove forming the air chamber 32 cut.

[0023] As shown in Figures 2, 5, and 6, the bottom surface of the groove and the main surface of the substrate 21 are connected by an inclined side surface 221. Multiple pressure chambers 31 and air chambers 32 are arranged alternately. The pressure chambers 31 and air chambers 32 extend in directions intersecting the longitudinal direction of the actuator section 22, and multiple of them are arranged in parallel in the first direction (X-axis in the figure), which is the longitudinal direction of the actuator section 22. In this embodiment, for example, the multiple grooves constituting the pressure chambers 31 and air chambers 32 have a width dimension in the X direction that is constant in the depth direction along the Z direction, and the cross-section perpendicular to the Y direction, which is the extension direction of the grooves, is rectangular.

[0024] The bottom of the pressure chamber 31, the bottom of the air chamber 32, and the side walls 33 are made of laminated piezoelectric material. Specifically, the inner walls of the pressure chamber 31 and the air chamber 32, including their bottoms, are made of piezoelectric material, and a nozzle plate 12, which is a non-piezoelectric material, is placed at the opening on one side, while the openings at both ends of the air chamber 32 in the extending direction are closed by cover portions 23, which are non-piezoelectric material.

[0025] Electrode layers 34 are provided on the inner walls of the pressure chamber 31 and air chamber 32 of the actuator section 22, as well as on the side surface 221. The electrode layers 34 are formed of a conductive film, such as a nickel thin film. The electrode layers 34 extend from the inner surface of the groove through the side surface 221 to the substrate 21 and are connected to the pattern wiring 211. For example, the electrode layers 34 are formed on the inner surface of the groove, including the bottom surface of the side wall 33. As an example, the electrode layers 34 formed in the pressure chamber 31 constitute individual electrodes, and the electrode layers 34 formed in the air chamber 32 constitute a common electrode. The electrode layers 34 constituting individual electrodes are formed on the inner surface including the bottom of the pressure chamber 31, are led out from one side in the extending direction of the pressure chamber 31 to one side surface 221, and are connected to the pattern wiring 211. The electrode layers 34 constituting a common electrode are formed on the inner surface including the bottom of the air chamber 32, are led out from the other side to the other side surface 221, and are connected to the pattern wiring 211.

[0026] Multiple pressure chambers 31 communicate with multiple nozzles 28 of a 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 the first common chamber 271 of the ink chambers 27, and the other end opens into the second common chamber 272 of the ink chambers 27. Therefore, ink flows in from the communicating end of one end of the pressure chamber 31, and ink flows out from the communicating end of the other end. Alternatively, ink may flow in from both ends of the pressure chambers 31.

[0027] As shown in Figures 3 and 6, the air chamber 32 is sealed on one side in the third direction (Z direction) by a nozzle plate 12 which is joined to the top. In addition, multiple air chambers 32 are sealed at both ends in the second direction by cover portions 23. Specifically, cover portions 23 are placed in the communication portions between the first common chamber 271 and the air chamber 32 of the ink chamber 27, and between the air chamber 32 and the second common chamber 272, and both ends of the air chamber 32 are separated from the ink chamber 27. Therefore, the air chamber 32 constitutes an air chamber into which ink does not flow.

[0028] For example, the cover portion 23 is provided at both ends in the Y direction, which is the extension direction of each air chamber 32. The cover portion 23 connects the ends of the side walls 33 and separates the common chambers 271 and 272 from the air chambers 32.

[0029] The cover portion 23 has a plurality of wall members 231, 232, and 233 arranged in the extending direction. In this embodiment, the cover portion 23 is formed in a triple-wall structure by the three wall members 231, 232, and 233, and gaps 2311 are formed between the plurality of wall members 231, 232, and 233. The plurality of wall members 231, 232, and 233 connect the ends of a pair of side walls 33 that constitute both sides of the air chamber 32. The plurality of wall members 231, 232, and 233 are made of a photosensitive resin material, and for example, their thickness, which is a dimension in the extending direction, is formed to be constant. For example, the plurality of wall members 231, 232, and 233 are formed by applying a photosensitive resin to both ends of the air chamber 32, and then exposing them from the top side in a predetermined exposure pattern, thereby curing the areas corresponding to the wall members 231, 232, and 233. For example, the plurality of wall members 231, 232, and 233 are arranged inside the air chamber 32.

[0030] In each air chamber 32, the structure of the cover portion 23 at one end and the other end is symmetrical with respect to the nozzle 28. That is, it is symmetrical in the extension direction, and specifically, the dimensions and number of wall members 231, 232, and 233 at one end and the other end are the same. Furthermore, the multiple cover portions 23 that are each configured in the multiple air chambers 32 in the actuator portion 22 are uniform. For example, the multiple cover portions 23 formed in two rows of air chambers 32 arranged in a parallel direction are configured to be the same in shape, position, and size.

[0031] The cover portion 23 is formed at a position where the range of change of AL is within 0.4 μs. That is, in the air chamber 32, the distance between the pair of inner wall members 233, which is the length in the extension direction of the movable range of the side wall 33, is set to a distance where the range of change of AL is within 0.4 μs with respect to a reference state where the entire length of the side wall 33 is the movable range. Here, AL (Acoustic Length) is the duration for which the volume of the pressure chamber is expanded or contracted, and is half the acoustic resonance period of the pressure wave in the pressure chamber 31. AL is the pulse width at which the flight velocity of the liquid is maximized when the voltage value of the drive electrode is kept constant and the pulse width is changed. For example, the velocity of ink droplets ejected when a rectangular wave drive pulse is applied can be measured, and the pulse width at which the velocity is maximized can be defined as AL.

[0032] AL changes according to the range of motion in which the side wall 33 deforms; for example, AL decreases as the range of motion decreases. For example, in a reference state where the extension length LB (flow path length) of the air chamber 32 in the range of motion not blocked by the cover portion 23 is the same as the flow path length LA of the pressure chamber 31, that is, a state in which the range of motion of the side wall 33 is secured to the length of the flow path of the pressure chamber 31, the range of motion of the side wall 33 decreases due to the presence of the cover portion 23, and the further inward the region in the extension direction the deformation of the side wall 33 is suppressed, the smaller AL becomes.

[0033] For example, AL changes with changes in flow path length, and depending on the value of AL, non-discharge may occur. Figure 8 shows the printing state when the pulse width is changed with respect to AL. As shown in Figure 8, a discharge failure occurs when AL is -0.3μs. On the other hand, a discharge failure also occurs when AL is +0.3μs or higher. For example, it can be seen that good discharge performance can be obtained within the range of AL ±0.2μs (0.4μs in the range).

[0034] Figure 9 shows the calculation results of AL when the flow path length LB of the air chamber 32 is changed. As shown in Figure 9, when the flow path length LB of the air chamber 32, which is the length in the extension direction (second direction) of the movable range of the side wall 33, is in the range of 1 mm to 1.5 mm, the amount of change (range) of AL is 0.37 μs. That is, when the length in the extension direction of the side wall 33 that defines the flow path length LA of the pressure chamber 31 is 1.5 mm, when the end of the air chamber 32 is closed by the cover part 23, if the length of the unclosed area (movable range) of the air chamber 32, i.e., the flow path length LB of the air chamber 32, is in the range of 1 to 1.5 mm, then even if liquid leaks from any of the wall members 231, 232, or 233, as long as none of the liquid leaks, the range of change of AL can be kept within 0.4 μs. For this reason, by providing the wall members 231, 232, and 233 of the cover part 23 in the flow path length range of 1 to 1.5 mm, discharge performance can be ensured. Therefore, in this embodiment, the cover portion 23 is configured under the condition that the range of change of AL is within 0.4 μs. For example, in this embodiment, the wall members 231, 232, and 233 of the cover portion 23 are arranged within a range of 1 / 6 of the total length from both ends in the extending direction of the air chamber 32, and a range of 2 / 3 or more of the total length functions as a movable range.

[0035] The nozzle plate 12 is a non-piezoelectric material and is formed, for example, from a rectangular film made of polyimide. The nozzle plate 12 faces the mounting surface of the actuator base 11. Multiple nozzles 28 are formed on the nozzle plate 12, penetrating the nozzle plate 12 in the thickness direction.

[0036] Multiple nozzles 28 are provided in the same number as the pressure chambers 31, and are positioned opposite each other to the pressure chambers 31. Multiple nozzles 28 are arranged in a row along the first direction (X direction), corresponding to a pair of actuator parts 22, and are arranged in two rows. Each nozzle 28 is configured as a cylindrical shape with its axis extending in a third direction. For example, the nozzle 28 may have a constant diameter, or it may have a shape that narrows in diameter towards the center or tip. The nozzles 28 are positioned opposite each other at the midpoint in the extension direction of the pressure chambers 31 formed in the pair of actuator parts 22, and each nozzle communicates with the pressure chambers 31. Multiple nozzles 28 are positioned one by one at positions corresponding to the space between the ends of each pressure chamber 31, for example, at the center in the longitudinal direction.

[0037] The frame 13 is formed in 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 the mounting surface of the actuator base 11 and the nozzle plate 12, respectively. In other words, the nozzle plate 12 is attached to the actuator base 11 via the frame 13.

[0038] The manifold 18 is joined to the actuator base 11 on the side opposite to the nozzle plate 12. Inside the manifold 18, an ink supply section is formed, which is a flow path communicating with the supply hole 25, and an ink discharge section is formed, which is a flow path communicating with the discharge hole 26.

[0039] The circuit board 17 shown in Figure 1 is a film carrier package (FCP). The circuit board 17 has a flexible resin film 51 on which multiple wirings are formed, and a drive IC 52 connected to the multiple wirings of the film 51. The drive IC 52 is electrically connected to the electrode layer 34 via the wirings and pattern wirings 211 of the film 51.

[0040] Within the inkjet head 10 configured as described 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 divided into three sections in the second direction (Y direction) by two actuator sections 22, and has two second common chambers 272 as a common chamber through which the discharge holes 26 open, and a first common chamber 271 as a common chamber through which the supply holes 25 open. The first common chamber 271 and the second common chambers 272 are in communication with a plurality of pressure chambers 31.

[0041] In the inkjet head 10 configured as described above, ink circulates between the ink tank and the ink chamber 27 through the supply hole 25, the pressure chamber 31, and the discharge hole 26. For example, a signal input from the control unit of the inkjet printer causes the drive IC 52 to apply a drive voltage to the electrode layer 34 of the pressure chamber 31 via the wiring of the film 51, thereby creating a potential difference between the electrode layer 34 of the pressure chamber 31 and the electrode layer 34 of the air chamber 32, and selectively causing the side wall 33 to undergo shear mode deformation. The side wall 33 undergoes shear deformation so that the cross-sectional shape of the laminated piezoelectric material bends into a V-shape. By deforming the side wall 33 formed between the pressure chamber 31 and the air chamber 32 in accordance with the drive signal, the volume of the pressure chamber 31 is changed.

[0042] As the side wall 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. This causes the ink from the ink chamber 27 to flow into the pressure chamber 31.

[0043] When the volume of the pressure chamber 31 increases, the drive IC 52 applies a drive voltage with a reverse potential to the electrode layer 34 of the pressure chamber 31. This causes the side wall 33 to deform in shear mode, reducing the volume of the pressure chamber 31 where the electrode layer 34 is located and increasing the pressure. As a result, the ink inside the pressure chamber 31 is pressurized and ejected from the nozzle 28.

[0044] A method for manufacturing the inkjet head 10 will now be described. First, a piezoelectric member that forms multiple grooves is attached to a plate-shaped substrate 21 with an adhesive or the like, and an actuator base 11 having a predetermined outer shape is formed by machining using a dicing saw or slicer. Alternatively, for example, a block-shaped base member with the thickness of multiple sheets may be formed in advance and then divided to manufacture multiple actuator bases 11 of the predetermined shape.

[0045] Next, electrode layers 34 and pattern wiring 211 are formed on the inner surfaces of the grooves constituting the pressure chamber 31 and air chamber 32, and on the surface of the substrate 21. As a result, electrode layers 34 and pattern wiring 211 are formed at predetermined locations on the surface of the actuator base 11.

[0046] Next, the ends of the air chamber 32 are sealed by forming a cover portion 23 at the end of the air chamber 32. For example, a photosensitive resin is filled into the grooves that make up the air chamber 32, and masks corresponding to the patterns of the multiple wall members 231, 232, and 233 are placed on top of it and exposed from the top side to harden the target area and form the cover portion 23.

[0047] Then, the actuator base 11 is assembled to the manifold 18, and the frame 13 is attached to one side of the substrate 21 of the actuator base 11 using a thermoplastic resin adhesive sheet.

[0048] Next, the assembled frame 13 and the side wall 33 of the actuator section 22 are polished so that the top surface facing the nozzle plate 12 is flush with the surface. Then, the nozzle plate 12 is attached by bonding it to the top surface of the side wall 33 and the polished surface of the frame 13. At this time, the nozzle 28 is positioned to face the pressure chamber 31. Furthermore, as shown in Figure 1, the inkjet head 10 is completed by connecting the drive IC 52 and the circuit board 17 to the pattern wiring 211 formed on the main surface of the substrate 21 via a flexible printed circuit board.

[0049] An example of an inkjet printer 100 equipped with an inkjet head 10 will be described below with reference to Figure 10. The inkjet printer 100 comprises a housing 111, a media supply unit 112, an image forming unit 113, a media discharge unit 114, a transport device 115, and a control unit 116.

[0050] The inkjet printer 100 is a liquid ejection device that performs image formation processing on paper P by ejecting a liquid such as ink while transporting paper P, for example, as a recording medium to be ejected, along a predetermined transport path A from the media supply unit 112 through the image forming unit 113 to the media ejection unit 114.

[0051] The housing 111 constitutes the outer casing of the inkjet printer 100. The housing 111 is provided with an outlet at a predetermined location for ejecting paper P to the outside.

[0052] The media supply unit 112 is equipped with multiple paper feed cassettes and is configured to hold multiple sheets of paper P of various sizes stacked on top of each other.

[0053] The media discharge unit 114 includes a paper output tray configured to hold the paper P discharged from the discharge port.

[0054] The image forming unit 113 includes a support unit 117 that supports the paper P, and a plurality of head units 130 that are positioned opposite each other above the support unit 117.

[0055] The support unit 117 includes a conveyor belt 118 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, and a plurality of belt rollers 120 provided on the back of the conveyor belt 118.

[0056] During image formation, the support unit 117 supports the paper P on the holding surface, which is the upper surface of the conveyor belt 118, and conveys the paper P downstream by moving the conveyor belt 118 at a predetermined timing by the rotation of the belt roller 120.

[0057] The head unit 130 comprises multiple (four-color) inkjet heads 10, ink tanks 132 acting as liquid tanks mounted on each inkjet head 10, a connecting channel 133 connecting the inkjet heads 10 and the ink tanks 132, and a circulation pump 134 which is a circulation unit. The head unit 130 is a circulating type head unit that constantly circulates liquid in the ink tanks 132 and in the pressure chamber 31, air chamber 32, and ink chamber 27 built inside the inkjet heads 10.

[0058] In this embodiment, the system includes four inkjet heads 10 for cyan, magenta, yellow, and black, and ink tanks 132 each containing ink for one of these colors. The ink tanks 132 are connected to the inkjet heads 10 by a connecting channel 133. The connecting channel 133 includes a supply channel connected to the supply port of the inkjet head 10 and a recovery channel connected to the discharge port of the inkjet head 10.

[0059] Furthermore, a negative pressure control device, such as a pump (not shown), is connected to the ink tank 132. The negative pressure control device controls the negative pressure inside the ink tank 132 in accordance with the head value between the inkjet head 10 and the ink tank 132, thereby forming a meniscus of a predetermined shape with the ink supplied to each nozzle 28 of the inkjet head 10.

[0060] The circulation pump 134 is a liquid transfer pump, for example, a piezoelectric pump. The circulation pump 134 is installed in the supply channel. The circulation pump 134 is connected to the drive circuit of the control unit 116 by wiring and is configured to be controllable by the CPU (Central Processing Unit). The circulation pump 134 circulates the liquid in the circulation channel, which includes the inkjet head 10 and the ink tank 132.

[0061] The transport device 115 transports the paper P along a transport path A, which runs from the media supply unit 112 through the image forming unit 113 to the media discharge unit 114. The transport device 115 comprises a plurality of guide plate pairs 121 and a plurality of transport rollers 122 arranged along the transport path A.

[0062] Each of the multiple guide plate pairs 121 comprises a pair of plate members positioned opposite each other with the paper being transported P in between, and guides the paper P along the transport path A.

[0063] The transport roller 122 is driven and rotated by the control unit 116 to feed the paper P downstream along the transport path A. Sensors for detecting the paper transport status are placed at various points along the transport path A.

[0064] The control unit 116 includes a control circuit such as a CPU which acts as a controller, a ROM (Read Only Memory) for storing various programs, a RAM (Random Access Memory) for temporarily storing various variable data and image data, and an interface unit for inputting data from the outside and outputting data to the outside.

[0065] In the inkjet printer 100 configured as described above, when the control unit 116 detects a print command from a user operating the operation input unit in the interface unit, for example, it drives the transport device 115 to transport the paper P and drives the inkjet head 10 by outputting a print signal to the head unit 130 at a predetermined timing. In its ejection operation, the inkjet head 10 sends a drive signal to the drive IC 52 using an image signal corresponding to the image data, applies a drive voltage to the electrode layer 34 of the pressure chamber 31 via wiring, selectively drives the side wall 33 of the actuator unit 22 to eject ink as droplets from the nozzle 28, and forms an image on the paper P held on the transport belt 118. In addition, in its liquid ejection operation, the control unit 116 drives the circulation pump 134 to circulate liquid through a circulation channel that passes between the ink tank 132 and the inkjet head 10. Through the circulation mechanism, the ink in the ink tank 132 is supplied from the supply hole 25 to the first common chamber 271 of the ink chamber 27 via the ink supply section of the manifold 18, when the circulation pump 134 is driven. This ink is supplied to multiple pressure chambers 31 of a pair of actuator sections 22. The ink flows through the pressure chambers 31 to the second common chamber 272 of the ink chamber 27. This ink is then discharged from the discharge hole 26 through the ink discharge section of the manifold 18 back into the ink tank 132.

[0066] According to the inkjet head 10 of the above embodiment, so-called crosstalk can be suppressed, making it easier to ensure stable ejection performance. For example, generally, if the cover portion that seals the air chamber is not formed properly, ink will enter the air chamber, causing the AL of the adjacent pressure chamber to shift and increasing the variation in AL within the plane. Also, when the air chamber is filled with ink, vibrations are transmitted to the adjacent pressure chamber (crosstalk). These can lead to a deterioration in the accuracy of the ink droplets or even cause them to fall out. In contrast, according to the inkjet head 10 of the above embodiment, the cover portion 23 is configured to have multiple wall members 231, 232, and 233. For example, even if one of the multiple wall members 231, 232, and 233 is damaged, the other wall members 231, 232, and 233 can prevent ink from flowing in. Therefore, the possibility of the air chamber 32 being filled with ink can be reduced, and so-called crosstalk, where vibrations of the side wall 33 when the actuator unit 22 drives the pressure chamber 31 are transmitted to the ink in another adjacent pressure chamber 31 and affect the ink pressure in the pressure chamber, can be suppressed, making it easier to maintain ejection performance.

[0067] Furthermore, by forming a gap 2311 between the multiple wall members 231, 232, and 233, the adhesive can escape into the gap 2311 when bonding the nozzle plate 12. Therefore, when joining the nozzle plate 12, the adhesive does not flow into the pressure chamber 31, and deterioration of print quality can be suppressed.

[0068] Furthermore, by making the structure of the cover portion 23 symmetrical and ensuring uniformity in the actuator portion 22, uniformity of AL and uniformity of the degree of adhesive relief groove can be ensured.

[0069] Furthermore, by configuring the cover portion 23 under conditions where the change range of AL is within 0.4 μs, it is possible to ensure good discharge performance.

[0070] It should be noted that the present invention is not limited to the embodiments described above, and the components can be modified and implemented in practice without departing from the spirit of the invention.

[0071] For example, the shape of the cover portion 23 is not limited to the above embodiment and can be changed as appropriate. For example, in the above embodiment, a wall structure with three layers of the same thickness was exemplified, but it is not limited to this. For example, it may have two or four layers, or the thickness of each layer may be different. As another embodiment, the inkjet head 1010 shown in Figure 11 has two wall members 234 and 235, and the thickness of one wall member 234 is configured to be thicker than the other wall member 235. The same effects as in the above embodiment can be obtained in this configuration as well.

[0072] In the above embodiment, the cover portion 23 is shown as being located inside the air chamber 32, but it is not limited to this, and for example, part or all of it may be located outside the air chamber 32.

[0073] In the above embodiment, an example was shown in which an actuator section 22 having multiple grooves is arranged on the main surface portion of the substrate 21, but the embodiment is not limited to this. For example, the actuator may be provided on the end face of the substrate 21. Also, the number of nozzle rows is not limited to the above embodiment, and a configuration with one row or three or more rows may be used.

[0074] Furthermore, while the above embodiment illustrates an actuator base 11 equipped with a laminated piezoelectric member consisting of multiple piezoelectric elements on a substrate 21, the embodiment is not limited to this. For example, the actuator base 11 may be formed using only piezoelectric elements without a substrate. Also, the supply side and discharge side may be reversed, or they may be configured to be switchable.

[0075] Furthermore, in the above embodiment, as an example, a circulating inkjet head is provided in which one side of the pressure chamber 31 is the supply side and the other side is the discharge side, and ink flows in from one side of the pressure chamber and flows out from the other side. However, the invention is not limited to this. For example, a non-circulating type may be used. Alternatively, for example, the common chambers on both sides of the pressure chamber 31 may be the supply side, and ink may flow in from both sides. That is, ink may flow in from both sides of the pressure chamber 31 and flow out from a nozzle 28 located in the center of the pressure chamber 31.

[0076] Furthermore, in the above embodiment, a side-shooter type inkjet head was exemplified in which the nozzle 28 is positioned opposite the pressure chamber 31 midway and both sides communicate with a common chamber, but the invention is not limited to this. For example, the pressure chamber 31 and the air chamber 32 may be closed at one end in the extending direction, and only the other end of the air chamber 32 may be closed by the cover portion 23, which may be an end-shooter type. Even in this case, the same effects as in the above embodiment can be obtained by making the cover portion 23 of the air chamber 32 a double-wall structure or a multi-wall structure of three or more layers.

[0077] Furthermore, the liquid to be dispensed is not limited to printing ink; for example, it could be a device that dispenses a liquid containing conductive particles for forming wiring patterns on a printed circuit board.

[0078] Furthermore, while the above embodiment shows an example of the inkjet head being used in a liquid ejection device such as an inkjet printer, it is not limited to this, and can also be used in 3D printers, industrial manufacturing machinery, and medical applications, enabling miniaturization, weight reduction, and cost reduction.

[0079] According to at least one embodiment described above, a liquid dispensing head that can ensure stable dispensing characteristics can be provided.

[0080] In addition, several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be carried out 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 variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. The following is an appended description equivalent to the invention described in the claims of the original application. (1) An actuator section composed of piezoelectric material, having multiple pressure chambers and multiple air chambers arranged alternately, A cover portion having multiple wall members that closes the air chamber, A shared-mode, shared-wall type liquid dispensing head. (2) The pressure chamber and the air chamber are arranged alternately in the direction of alignment. The multiple pressure chambers have ends in the extension direction intersecting the alignment direction that communicate with a common chamber. The cover portion is positioned at the end of the air chamber in the extending direction and closes the communication portion with the common chamber. The multiple wall members are arranged in the direction of extension. The liquid discharge head according to (1), further comprising a nozzle plate having a nozzle that communicates with the pressure chamber and is arranged opposite to the actuator portion in a direction intersecting the alignment direction and the extension direction. (3) The liquid discharge head according to (2), wherein at least a portion of the cover portion is located inside the air chamber and is formed in a region where the range of change of AL is within 0.4 μs. (4) The common chambers are arranged on both sides of the air chamber in the direction of extension. The cover portion is provided at both ends of the air chamber in the extension direction. The liquid dispensing head according to (2), wherein the cover portions provided at both ends of the air chamber are symmetrical. (5) The liquid dispensing head according to (2), wherein the cover portion provided in each of the multiple air chambers is uniform. [Explanation of Symbols]

[0081] 10, 1010…Inkjet head, 11…Actuator base, 12…Nozzle plate, 13…Frame, 17…Circuit board, 18…Manifold, 21…Substrate, 22…Actuator section, 23…Cover section, 231~235…Wall members, 2311…Gap, 25…Supply hole, 26…Discharge hole, 27…Ink chamber, 31…Pressure chamber, 32…Air chamber, 33…Side wall, 34…Electrode layer, 51…Film, 52…Drive IC, 100…Inkjet printer, 1 11...Housing, 112...Media supply unit, 113...Image forming unit, 114...Media discharge unit, 115...Conveyor device, 116...Control unit, 117...Support unit, 118...Conveyor belt, 119...Support plate, 120...Belt roller, 121...Guide plate pair, 122...Conveyor roller, 130...Head unit, 132...Ink tank, 133...Connection channel, 134...Circulation pump, 211...Pattern wiring, 221...Side section, 271...First common room, 272...Second common room.

Claims

1. An actuator section composed of piezoelectric material, having multiple pressure chambers and multiple air chambers arranged alternately, A cover portion having multiple wall members that closes the air chamber, Equipped with, The pressure chamber and the air chamber are arranged alternately in the direction of alignment. The multiple pressure chambers have ends in the extension direction intersecting the alignment direction that communicate with a common chamber. The cover portion is positioned at both ends of the air chamber in the extending direction and closes the communication portion with the common chamber. The cover portions at both ends are each formed into a triple-wall structure having three wall members aligned in the extending direction, and gaps are formed between the three wall members. Shared-mode shared-wall type liquid dispensing head.

2. The three wall members of the cover portion are arranged within a range of 1 / 6 of the total length from both ends in the extending direction of the air chamber, and the range of motion is 2 / 3 or more of the total length of the air chamber. The liquid discharge head according to claim 1, further comprising a nozzle plate having a nozzle that communicates with the pressure chamber, which is arranged opposite to the actuator portion in a direction intersecting the alignment direction and the extension direction.

3. The liquid discharge head according to claim 2, wherein at least a portion of the cover portion is located inside the air chamber and is formed in a region where the range of change of AL is within 0.4 μs.

4. The common chambers are arranged on both sides of the air chamber in the direction of extension. The cover portion is provided at both ends of the air chamber in the extension direction. The liquid dispensing head according to claim 2, wherein the cover portions provided at both ends of the air chamber are symmetrical.

5. The liquid dispensing head according to claim 2, wherein the cover portion provided in each of the multiple air chambers is uniform.

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