Liquid jet

Abstract

A liquid ejection head capable of ensuring stable ejection characteristics is provided. A liquid ejection head according to one embodiment includes an actuator member, a common electrode, a separate electrode, and a non-piezoelectric member. The actuator member has piezoelectric bodies polarized in opposite directions laminated, and has a plurality of grooves that constitute a plurality of pressure chambers and a plurality of grooves that constitute a plurality of air chambers on one side, the bottoms of the plurality of grooves being connected. The plurality of grooves that constitute the plurality of air chambers are adjacent to the plurality of pressure chambers, and have a larger size in the depth direction than the grooves that constitute the pressure chambers. The common electrode is formed on the inner surfaces of the plurality of air chambers including the bottoms. The separate electrode is formed on the inner surfaces of the plurality of pressure chambers including the bottoms. The non-piezoelectric member is disposed opposite the one side of the actuator member.

Description

TECHNICAL FIELD

[0001] An embodiment of the present application relates to a liquid ejection head. BACKGROUND

[0002] In recent years, high productivity, high speed, and an increase in the amount of droplets have been required for an inkjet head. For example, in a share mode share wall type inkjet head, a so-called three-cycle drive is generally employed, in which the same drive column is shared by two pressure chambers, and 1 / 3 of a plurality of aligned chambers are driven at the same time. In addition, a separate drive head has been developed in which both sides of a pressure chamber to be driven are used as virtual pressure chambers, and one pressure chamber is driven by two independent drive columns. For example, a configuration has been developed in which a plurality of grooves are formed in a piezoelectric member, every other groove is plugged at the outlet, and the grooves whose outlets are not plugged are used as pressure chambers, and the plugged grooves are used as air chambers, and are driven independently.

[0003] In such an inkjet head, vibration at the time of driving a pressure chamber is transmitted to ink in other pressure chambers via the piezoelectric member, and thus so-called crosstalk occurs in which the speed and volume of ink droplets change due to the influence of driving of an adjacent pressure chamber. SUMMARY

[0004] PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] An object of the present application is to provide a liquid ejection head capable of ensuring stable ejection characteristics.

[0006] MEANS FOR SOLVING THE PROBLEMS

[0007] A liquid ejection head according to an embodiment includes an actuator member, a common electrode, a separate electrode, and a non-piezoelectric member. The actuator member has a piezoelectric body polarized in opposite directions to each other, and has a plurality of grooves constituting a plurality of pressure chambers and a plurality of grooves constituting a plurality of air chambers on one side, and the bottoms of the plurality of grooves are connected. The plurality of grooves constituting the plurality of air chambers are adjacent to the plurality of pressure chambers and have a larger size in the depth direction than the grooves constituting the pressure chambers. The common electrode is formed on the inner surface of the plurality of air chambers including the bottoms. The separate electrode is formed on the inner surface of the plurality of pressure chambers including the bottoms. The non-piezoelectric member is disposed opposite to the one side of the actuator member. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a perspective view showing an inkjet head according to an embodiment.

[0009] Figure 2 is an exploded perspective view showing a configuration of a part of an inkjet head according to an embodiment.

[0010] Figure 3 It means Figure 2 A three-dimensional view of a portion of the inkjet head.

[0011] Figure 4 It is a cross-sectional view showing an enlarged portion of the structure of the inkjet head.

[0012] Figure 5 It is Figure 4 A cross-sectional view of the inkjet head cut along the VV line.

[0013] Figure 6 It is Figure 4 A cross-sectional view of the inkjet head cut along VI-VI.

[0014] Figure 7 It is Figure 2 A magnified partial cross-sectional view of a portion of the section obtained by cutting along VII-VII of the inkjet head.

[0015] Figure 8 This is an explanatory diagram showing the relationship between the depth of the air chamber of the inkjet head and the amount of crosstalk in the embodiment.

[0016] Figure 9 This is an explanatory diagram of the deformation amount of the actuator in the inkjet head and the comparative example under the driving state.

[0017] Figure 10 This is a schematic diagram illustrating an inkjet printer according to the implementation method.

[0018] Figure 11 This is a perspective view showing a portion of the inkjet head involved in other embodiments.

[0019] Figure 12 It is a cross-sectional view showing an enlarged portion of the structure of the inkjet head.

[0020] Figure 13 It is Figure 12 A cross-sectional view of the inkjet head cut along line XIII-XIII.

[0021] Figure 14 It is Figure 12 A cross-sectional view of the inkjet head cut along line XIV-XIV. Detailed Implementation

[0022] The following is for reference Figures 1 to 8 The structure of the liquid printhead, i.e., the inkjet head 10, according to the first embodiment will be described. Figure 1 This is a perspective view showing the inkjet head according to the first embodiment. Figure 2 This is an exploded 3D view of a part of the inkjet head. Figure 3is a perspective view that enlargedly shows a structure of a portion of an inkjet head, Figures 4 to 7 is a cross-sectional view that enlargedly shows a structure of a portion of an inkjet head. In the drawing, X, Y, and Z respectively represent a first direction, a second direction, and a third direction that are orthogonal to each other. Furthermore, in the present embodiment, the explanation of the directions is described based on the posture in which the arrangement direction of the nozzles, or the grooves that constitute the pressure chambers 31 and the air chambers 32 is along the X axis, the extension direction of the pressure chambers 31 and the air chambers 32 is along the Y axis, and the ejection direction of the liquid is along the Z axis, but is not limited thereto.

[0023] Figures 1 to 7 The inkjet head 10 shown is a so-called side-shooting type of shared mode type inkjet head. The inkjet head 10 is a device for ejecting ink, for example, mounted inside an inkjet printer. The inkjet head 10 is, for example, an independently driven type inkjet head in which the pressure chambers 31 and the air chambers 32 are arranged alternately. The air chamber 32 is an air chamber that is not supplied with ink, and does not have a nozzle 28.

[0024] The inkjet head 10 has an actuator base 11, a nozzle plate 12, and a frame 13. The actuator base 11 is one example of a base material. Inside the inkjet head 10, an ink chamber 27 that supplies ink, which is one example of a liquid, is formed.

[0025] Further, the inkjet head 10 has a circuit substrate 17 that controls the inkjet head 10, a manifold 18 that forms a part of a path between the inkjet head 10 and an ink tank, and the like.

[0026] As shown in Figure 2 , the actuator base 11 has a substrate 21 and a pair of actuator members 22.

[0027] The substrate 21 is formed in a rectangular plate shape, for example, from alumina or the like ceramic. The substrate 21 has a flat mounting surface. The pair of actuator members 22 is joined to the mounting surface of the substrate. A plurality of supply holes 25 and discharge holes 26 are formed in the substrate 21.

[0028] As shown in Figure 2 and Figure 3 , a pattern wiring 211 is formed in the substrate 21 of the actuator base 11. The pattern wiring 211 is formed from a nickel thin film, for example. The pattern wiring 211 has a general pattern, an individual pattern, and is configured as a prescribed pattern shape that connects to the electrode layer 34 formed in the actuator member 22. For example, the pattern wiring 211 is formed at a position that avoids the supply holes 25 and the discharge holes 26.

[0029] The supply holes 25 are arranged in the central portion of the substrate 21 and between the pair of actuator members 22 in the long edge direction of the actuator members 22. The supply holes 25 communicate with an ink supply portion of the manifold 18. The supply holes 25 are connected to the ink tank via the ink supply portion. The supply holes 25 supply the ink of the ink tank to the ink chamber 27.

[0030] The discharge holes 26 are arranged in two rows across the supply holes 25 and the pair of actuator members 22. The discharge holes 26 communicate with the ink discharge portions of the manifold 18. The discharge holes 26 are connected to the ink tank via the ink discharge portions. The discharge holes 26 discharge the ink of the ink chamber 27 toward the ink tank. In the case of being configured as such, the inkjet head 10 becomes a circulation type, and the ink flows from the side having the supply holes 25 toward the other side having the discharge holes 26 with respect to each pressure chamber 31. Alternatively, the ink discharge portions can also be configured to be opened only at the time of maintenance, for example, and communicate with the ink supply portions during printing. In the case of being configured as such, the inkjet head 10 becomes a non-circulation type, and the ink flows into each pressure chamber 31 from both sides.

[0031] The pair of actuator members 22 are adhered to the mounting surface of the substrate 21. The pair of actuator members 22 are arranged in two rows on the substrate 21 across the supply holes 25. Each actuator member 22 is formed of two plate-shaped piezoelectric bodies 201, 202 formed of lead zirconate titanate (PZT), for example. The two piezoelectric bodies 201, 202 are polarized in such a manner that the polarization directions thereof are in opposite directions in the thickness direction thereof. That is, the actuator member 22 is laminated with a pair of piezoelectric bodies 201, 202, and polarized in opposite directions with respect to each other in the lamination direction. The actuator member 22 is adhered to the mounting surface of the substrate 21 by an epoxy-based adhesive having heat-curing properties, for example. As shown in FIG. 2, the actuator member 22 is arranged in parallel with the nozzles 28 arranged in two rows within the ink chamber 27. The actuator member 22 divides the ink chamber 27 into a first common chamber 271 opened by the supply holes 25 and two second common chambers 272 opened by the discharge holes 26. The top of the actuator member 22 is adhered to the nozzle plate 12. Figure 2

[0032] The actuator member 22 is composed of a laminated piezoelectric member in which a plurality of piezoelectric bodies 201, 202 are laminated, and alternately and juxtaposedly provided with a plurality of side walls 33, a plurality of pressure chambers 31, and a plurality of air chambers 32 as driving elements. The plurality of piezoelectric bodies 201, 202 are configured to be laminated in the thickness direction along the third direction, and adhered to each other. Further, the laminated piezoelectric member is polarized in the manufacturing process.

[0033] The actuator member 22 is formed with a plurality of grooves constituting the pressure chambers 31 and the air chambers 32 in the first direction on the side surface of the third direction, that is, on the side surface of the side opposite to the nozzle plate 12. The actuator member 22 is configured to be divided into a plurality of comb-tooth shapes in which one side of the laminated piezoelectric member is divided by the plurality of grooves, and the bottom sides of the plurality of grooves are integrally connected. The actuator member 22 is divided into a plurality of pieces by forming grooves in one side surface by cutting processing or the like, and the other end sides are connected, and the plurality of side walls 33 are juxtaposedly arranged in the first direction indicated by X in the drawing across the grooves. ​

[0034] The actuator member 22 has a plurality of side walls 33, with grooves constituting the pressure chambers 31 and the air chambers 32 therebetween. In other words, the side walls 33 are formed as driving elements between the grooves forming the pressure chambers 31 and the air chambers 32. The side walls 33 are formed between the pressure chambers 31 and the air chambers 32, and are deformed in accordance with the driving signal, thereby changing the volume of the pressure chambers 31.

[0035] The width of the actuator member 22 in the short side direction gradually increases from the top side toward the substrate side. The cross-sectional shape of the actuator member 22 along a direction orthogonal to the long side direction (short side direction) is formed in a trapezoidal shape. The side surface portion 221 of the actuator member 22 has an inclined surface inclined with respect to the second direction and the third direction.

[0036] Figure 4 is a partial enlargement Figure 2 is a cross-sectional view of one of the actuator members 22 of the inkjet head 10 shown in Fig. 1. Figure 5 is a cross-sectional view of the groove constituting Figure 4 is a cross-sectional view of the groove constituting the pressure chamber 31 of the inkjet head 10 shown in Fig. 1. Then, Figure 6 is a cross-sectional view of the groove constituting Figure 4 is a cross-sectional view of the groove constituting the air chamber 32 of the inkjet head 10 shown in Fig. 1.

[0037] As shown in Figs. 1 and 2, Figure 2 , Figure 5 , Figure 6 the bottom surface portion of the groove is connected to the main surface of the substrate 21 through the inclined side surface portion 221. A plurality of the pressure chambers 31 and the air chambers 32 are alternately arranged. The pressure chambers 31 and the air chambers 32 respectively extend in a direction intersecting the long side direction of the actuator member 22, and a plurality of the pressure chambers 31 and the air chambers 32 are arranged in parallel in the long side direction of the actuator member 22, i.e., the first direction (X axis in the drawing). In the present embodiment, for example, the plurality of grooves constituting the pressure chambers 31 and the air chambers 32 are configured such that the width dimension in the X direction is constant in the depth direction along the Z direction, and the cross section orthogonal to the extension direction of the groove, i.e., the Y direction, is rectangular.

[0038] The plurality of grooves arranged in the first direction are configured such that the depth DB of the grooves constituting the air chamber 32 is deeper than the depth DA of the grooves constituting the pressure chamber 31. That is, in the pressure chamber 31 and the air chamber 32 which are open on the nozzle plate 12 side, the bottom of the grooves constituting the air chamber 32 is disposed on the side of the depth direction, i.e., the third direction, compared to the bottom of the grooves constituting the pressure chamber 31, and is disposed at a position separated from the nozzle plate 12, i.e., at a position on the inside of the actuator member 22. As one example, the depth DB of the air chamber 32 is deeper than the depth DA of the pressure chamber 31 by the amount of the thickness of the side wall 33, i.e., the interval between the pressure chamber 31 and the air chamber 32. In the present embodiment, the depth DA of the pressure chamber 31 is configured to be 150 μm, and the depth DB of the air chamber 32 is configured to be 200 μm. Further, the grooves constituting the pressure chamber 31 and the grooves constituting the air chamber 32 can be configured to have the same or different dimensions in the width direction along the long side direction, i.e., the dimension in the extending direction. The bottom of the pressure chamber 31, the bottom of the air chamber 32, and the side wall 33 are configured by laminated piezoelectric members. That is, the pressure chamber 31 and the air chamber 32 are configured to have inner wall surfaces including the bottoms thereof by piezoelectric members, and the opening on one side is provided with the nozzle plate 12 which is a non-piezoelectric member, and the openings on both ends in the extending direction of the air chamber 32 are plugged by the cap portion 23 which is a non-piezoelectric member.

[0039] An electrode layer 34 is provided on the inner wall surfaces of the pressure chamber 31 and the air chamber 32, and the side surface portion 221 of the actuator member 22. The electrode layer 34 is formed of, for example, a conductive film such as a nickel thin film. The electrode layer 34 is connected to the pattern wiring 211 on the substrate 21 from the inner surface portion of the grooves through the side surface portion 221. For example, the electrode layer 34 is formed on the inner surface of the grooves of the side wall 33 including the bottom surface portion. As one example, the electrode layer 34 formed on the pressure chamber 31 constitutes a separate electrode, and the electrode layer 34 formed on the air chamber 32 constitutes a common electrode. The electrode layer 34 constituting the separate electrode is formed on the inner surface including the bottom of the pressure chamber 31, and is led out to one side surface portion 221 from one side in the extending direction of the pressure chamber 31, and is connected to the pattern wiring 211. The electrode layer 34 constituting the common electrode is formed on the inner surface including the bottom of the air chamber 32, and is led out to the other side surface portion 221 from the other side, and is connected to the pattern wiring 211.

[0040] The plurality of pressure chambers 31 communicate with the plurality of nozzles 28 of the nozzle plate 12 joined to the top portion. The both ends of the pressure chamber 31 in the second direction communicate with the ink chamber 27. That is, one end portion is open to the first common chamber 271 of the ink chamber 27, and the other end portion is open to the second common chamber 272 of the ink chamber 27. Therefore, ink flows in from one end portion of the pressure chamber 31, and ink flows out from the other end portion. Further, ink can also flow in from both end portions of the pressure chamber 31.

[0041] As Figure 3 , Figure 6As shown, one side of the air chamber 32 in the third direction (Z direction) is plugged by the nozzle plate 12 joined to the top. In addition, both ends of the air chamber 32 in the second direction, for example, are plugged by the cover portion 23. That is, the cover portion 23 is provided between the first common chamber 271 of the ink chamber 27 and the air chamber 32 and between the air chamber 32 and the second common chamber 272, respectively, thereby separating both ends of the air chamber 32 from the ink chamber 27. Thus, the air chamber 32 constitutes an air chamber into which ink does not flow.

[0042] The cover portion 23 is provided at both ends in the Y direction, that is, the extending direction of each air chamber 32, for example. The cover portion 23 is a partition wall that connects end portions of the side walls 33 to each other while separating the common chambers 271, 272 from the air chamber 32.

[0043] The cover portion 23 is a wall-like member that plugs the end portion of the air chamber 32. The cover portion 23 connects end portions of a pair of side walls 33 that constitute both side portions of the air chamber 32 to each other, for example. The cover portion 23 is made of a photosensitive resin material. The cover portion 23 is formed into a predetermined shape by applying a photosensitive resin to both end portions of the air chamber 32 and then exposing and curing it, for example. A part of the cover portion 23 is disposed inside the air chamber 32, for example.

[0044] The nozzle plate 12 is a non-piezoelectric member, for example, a rectangular film made of polyimide. The nozzle plate 12 opposes the mounting surface of the actuator base 11. A plurality of nozzles 28 that penetrate the nozzle plate 12 in the thickness direction are formed in the nozzle plate 12.

[0045] The plurality of nozzles 28 are provided in the same number as the pressure chambers 31 and are disposed opposite the pressure chambers 31, respectively. The nozzles 28 are arranged in a plurality of rows in the first direction (X direction) and are arranged in two rows corresponding to the pair of actuator members 22. Each nozzle 28 is configured in a cylindrical shape with an axis extending in the third direction. The diameter of the nozzle 28 can be constant or can be tapered toward the central portion or the tip end portion, for example. The nozzles 28 are disposed opposite the intermediate portions in the extending direction of the pressure chambers 31 formed in the pair of actuator members 22 and communicate with the pressure chambers 31, respectively. The plurality of nozzles 28 are disposed one each at positions corresponding to the intermediate portions between both end portions in each pressure chamber 31, for example.

[0046] The frame 13 is formed in a rectangular frame shape by a nickel alloy, for example. 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. That is, the nozzle plate 12 is mounted to the actuator base 11 via the frame 13.

[0047] The manifold 18 is joined to the side of the actuator base 11 opposite the nozzle plate 12. A flow path, that is, an ink supply portion, that communicates with the supply hole 25 and a flow path, that is, an ink discharge portion, that communicates with the discharge hole 26 are formed in the inside of the manifold 18.

[0048] Figure 1 The circuit substrate 17 shown is a film carrier package (FCP). The circuit substrate 17 has a resin-made film 51 in which a plurality of wirings are formed while having flexibility, and a drive IC 52 connected to the plurality of wirings of the film 51. The drive IC 52 is electrically connected to the electrode layer 34 via the wirings of the film 51, the pattern wiring 211.

[0049] An ink chamber 27 surrounded by the actuator base 11, the nozzle plate 12, and the frame 13 is formed inside the inkjet head 10 configured as above. That is, the ink chamber 27 is formed between the actuator base 11 and the nozzle plate 12. The ink chamber 27 is divided into three sections by two actuator members 22 in the second direction (Y direction), for example, and has two second common chambers 272 that are common chambers for the discharge holes 26 and a first common chamber 271 that is a common chamber for the supply holes 25. The first common chamber 271 and the second common chambers 272 communicate with the plurality of pressure chambers 31.

[0050] In the inkjet head 10 configured as above, ink circulates between the ink tank and the ink chamber 27 through the supply holes, the pressure chambers, and the discharge holes. The drive IC 52 applies a drive voltage to the electrode layer 34 of the pressure chamber 31 via the wirings of the film 51, for example, in accordance with a signal input from a control section of an inkjet printer, thereby generating 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 deform in a shared mode. The side wall 33 is shear-deformed in a manner that bends the cross-sectional shape of the laminated piezoelectric body into a Z shape. The volume of the pressure chamber 31 changes by deforming the side wall 33 formed between the pressure chamber 31 and the air chamber 32 in accordance with the drive signal.

[0051] By deforming the side wall 33 in the shared mode, the volume of the pressure chamber 31 provided with the electrode layer 34 increases, and the pressure decreases. Thereby, the ink of the ink chamber 27 flows into the pressure chamber 31.

[0052] In a state where the volume of the pressure chamber 31 increases, when the drive IC 52 applies a drive voltage of a counter potential to the electrode layer 34 of the pressure chamber 31, the side wall 33 deforms in the shared mode, the volume of the pressure chamber 31 provided with the electrode layer 34 decreases, and the pressure increases. Thereby, the ink in the pressure chamber 31 is pressurized and ejected from the nozzle 28.

[0053] The manufacturing method of the inkjet head 10 will be described. First, a piezoelectric component with multiple grooves is bonded to a plate-shaped substrate 21 using an adhesive or the like. Then, a driver base 11 with a predetermined shape is formed by machining using a cutting saw, slicer, or the like. Alternatively, for example, multiple actuator bases 11 of a predetermined shape can be manufactured by pre-forming multiple block-shaped base components of multiple thicknesses and then dividing them.

[0054] Next, an electrode layer 34 and a pattern wiring 211 are formed on the inner surface of the groove constituting the pressure chamber 31 and the air chamber 32, and on the surface of the substrate 21. Through the above, an electrode layer 34 and a pattern wiring 211 are formed at specified locations on the surface of the actuator base 11.

[0055] Next, the two ends of the air chamber 32 are blocked by forming a cover 23 at the end of the air chamber 32. For example, the cover 23 is formed by filling the groove constituting the air chamber 32 with photosensitive resin and curing the target area. Alternatively, the cover 23 is formed by molding the photosensitive resin layer after curing the photosensitive resin.

[0056] Then, the actuator base 11 is assembled to the manifold 18, and the frame 13 is glued to one side of the substrate 21 of the actuator base 11 using a thermoplastic resin adhesive sheet.

[0057] Then, grinding is performed so that the surface of the nozzle plate 12 on the top of the side wall 33 of the assembled frame 13 and actuator component 22 is the same surface. Then, the nozzle plate 12 is bonded and installed on the top of the side wall 33 and the ground surface of the frame 13. At this time, the nozzle 28 is positioned so that it faces the pressure chamber 31. Furthermore, as... Figure 1 As shown, the inkjet head 10 is completed by connecting the driver IC 52 and the circuit board 17 via a flexible printed circuit board on the pattern wiring 211 formed on the main surface of the substrate 21.

[0058] The following is for reference Figure 10 An example of an inkjet printer 100 equipped with an inkjet head 10 will be described. The inkjet printer 100 includes 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.

[0059] The inkjet printer 100 is a liquid ejection device that ejects liquid such as ink along a predetermined transport path A from the media supply unit 112 through the image forming unit 113 to the media discharge unit 114, thereby performing image forming processing on the paper P by transporting the object to be ejected, i.e., the recording medium such as paper P.

[0060] The housing 111 forms the outer contour of the inkjet printer 100. A discharge port for discharging paper P to the outside is provided at a designated location on the housing 111.

[0061] The medium supply unit 112 has a plurality of paper cassettes and is configured to be able to stack and hold a plurality of sheets P of various sizes.

[0062] The medium discharge unit 114 has a paper tray configured to be able to hold the sheets P discharged from the discharge port.

[0063] The image forming unit 113 has a support unit 117 that supports the sheets P and a plurality of head units 130 disposed in opposition above the support unit 117.

[0064] The support unit 117 has a conveyance belt 118 provided in a prescribed region where image formation is performed in a loop shape, a support plate 119 that supports the conveyance belt 118 from the back surface side, and a plurality of belt rollers 120 provided on the back surface side of the conveyance belt 118.

[0065] The support unit 117 supports the sheets P on the upper surface, i.e., the holding surface, of the conveyance belt 118 at the time of image formation and simultaneously conveys the conveyance belt 118 at a prescribed timing by rotation of the belt rollers 120, thereby conveying the sheets P toward the downstream side.

[0066] The head unit 130 has a plurality of (4 colors) inkjet heads 10, ink tanks 132 as liquid tanks mounted on each of the inkjet heads 10, connection flow paths 133 that connect the inkjet heads 10 and the ink tanks 132, and a circulation unit, i.e., a circulation pump 134. The head unit 130 is a circulation type head unit that circulates liquid in the ink tanks 132 and the pressure chambers 31, air chambers 32, and ink chambers 27 formed inside the inkjet heads 10 at all times.

[0067] In the present embodiment, the inkjet heads 10 of four colors, i.e., cyan, magenta, yellow, and black, and the ink tanks 132 that respectively house ink of each of these colors are provided. The ink tanks 132 are connected to the inkjet heads 10 by the connection flow paths 133. The connection flow paths 133 have a supply flow path connected to the supply port of the inkjet heads 10 and a recovery flow path connected to the discharge port of the inkjet heads 10.

[0068] In addition, a negative pressure control device such as a pump, not shown, is connected to the ink tanks 132. Then, the negative pressure control device performs negative pressure control on the inside of the ink tanks 132 in correspondence with the head values of the inkjet heads 10 and the ink tanks 132, thereby causing the ink supplied to each nozzle 28 of the inkjet heads 10 to form a meniscus of a prescribed shape.

[0069] The circulation pump 134 is, for example, a liquid feeding pump constituted by 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 section 116 by wiring and is configured to be controllable by control based on a CPU (Central Processing Unit). The circulation pump 134 circulates liquid in a circulation flow path including the inkjet head 10 and the ink tank 132.

[0070] The conveyance device 115 conveys the paper sheet P along a conveyance path A from the medium supply section 112 through the image forming section 113 to the medium discharge section 114. The conveyance device 115 is provided with a plurality of pairs of guide plates 121 and a plurality of conveyance rollers 122 arranged along the conveyance path A.

[0071] The plurality of pairs of guide plates 121 each include a pair of plate members arranged in opposition across the paper sheet P being conveyed, and guide the paper sheet P along the conveyance path A.

[0072] The conveyance rollers 122 are driven and rotated by control of the control section 116, thereby conveying the paper sheet P along the conveyance path A to the downstream side. Further, sensors that detect the conveyance state of the paper sheet are arranged at various locations of the conveyance path A.

[0073] The control section 116 is provided with a controller, that is, a control circuit such as a CPU, a ROM (Read Only Memory) that stores various programs and the like, a RAM (Random Access Memory) that temporarily stores various variable data, image data, and the like, and an interface section that performs input of data from the outside and output of data to the outside.

[0074] In the inkjet printer 100 configured as above, when the control section 116 detects a print instruction by the user operating the input section, for example, in the interface section, it drives the conveyance device 115 to convey the paper sheet P, and at a prescribed timing, it outputs a printing signal to the head unit 130 to drive the inkjet head 10. As the ejection operation, the inkjet head 10 sends a drive signal to the drive IC 52 according to an image signal corresponding to the image data, applies a drive voltage to the electrode layer 34 of the pressure chamber 31 via the wiring, selectively drives the side wall 33 of the actuator member 22, and ejects ink as droplets from the nozzle 28 to form an image on the paper sheet P held on the conveyance belt 118. In addition, as the liquid ejection operation, the control section 116 circulates the liquid in the circulation flow path through the ink tank 132 and the inkjet head 10 by driving the circulation pump 134. By the circulation operation, 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 through the ink supply portion of the manifold 18 when the circulation pump 134 is driven. The ink is supplied to the plurality of pressure chambers 31 of the pair of actuator members 22. The ink flows into the second common chamber 272 of the ink chamber 27 through the pressure chamber 31. The ink is discharged from the discharge hole 26 to the ink tank 132 through the ink discharge portion of the manifold 18.

[0075] According to the inkjet head 10 related to the above-described embodiment, it is possible to suppress so-called crosstalk and easily ensure stable ejection performance. That is, according to the inkjet head 10 of the above-described embodiment, by deeply forming the air chamber 32, it is possible to suppress the vibration transmission between the plurality of pressure chambers 31. That is, by increasing the depth of the air chamber 32, it is possible to ensure the distance from the vibration site of the side wall 33 of the piezoelectric member 20 to the joint site at which the plurality of side walls 33 are joined, and thus it is possible to suppress the vibration transmission to the other side walls 33 via the joint site. Thus, it is possible to suppress the so-called crosstalk in which the vibration of the side wall 33 when driving the pressure chamber 31 in the actuator member 22 is transmitted to the ink in the adjacent other pressure chamber 31 to affect the pressure of the ink in the pressure chamber, and thus it is easy to maintain the ejection performance.

[0076] Figure 8 is a graph showing the relationship between the depth [μm] of the air chamber 32 in the inkjet head 10 and the crosstalk amount [%]. Here, the crosstalk amount indicates the ratio of the flow rate amplitude generated in the adjacent nozzle 28 when the flow rate amplitude generated in the nozzle 28 to be driven is set to 100%. In Figure 8 is shown the crosstalk amount when the depth of the air chamber 32 is changed from 150 μm to 300 μm when the depth of the pressure chamber 31 is set to 150 μm. According to Figure 8 It is known that the deeper the depth of the air chamber 32, the smaller the crosstalk amount.

[0077] Figure 9is an explanatory diagram showing the deformation state of the side wall 33 at the time of driving the inkjet head 10 according to the present embodiment and the inkjet head 1010 according to Comparative Example 1. Figure 9 The size and direction of the deformation of each part of the actuator member 22 are indicated by arrows. The direction of the arrow indicates the direction of the deformation (displacement) at that position, and the size of the arrow indicates the amount of deformation (displacement). The inkjet head 1010 according to Comparative Example 1 is configured so that the depth of the air chamber 32 is equal to the depth of the pressure chamber 31, and the other structures are configured to be the same as the inkjet head 10. Figure 9 is a diagram showing the vibration state when the pressure chamber 311 on one side in the arrangement direction of the grooves of the inkjet head 10, 1010 is driven and the pressure chamber 312 on the other side is not driven.

[0078] According to Figure 9 It is understood that, in the inkjet head 1010 according to Comparative Example 1, the side wall 33 on the other side of the air chamber 32 in the arrangement direction of the grooves, which forms the pressure chamber 312 that is not driven, deforms even though the pressure chamber 312 is not driven, and the operation of the pressure chamber 311 affects the pressure chamber 312. On the other hand, it is understood that, in the inkjet head 10 according to the present embodiment, the deformation of the side wall 33 on the other side of the air chamber 32 in the arrangement direction of the grooves, which forms the pressure chamber 312 that is not driven, is suppressed compared to the inkjet head 1010, and the operation of the pressure chamber 311 has less effect on the pressure chamber 312.

[0079] That is, the inkjet head 10 according to the present embodiment is able to suppress the transmission of vibration to the adjacent pressure chamber 31 by making the air chamber 32 deeper than the pressure chamber 31.

[0080] Furthermore, the present application is not limited to the above-described embodiments, and the constituent elements can be deformed within a range not departing from the gist thereof to be embodied in the implementation stage.

[0081] For example, the shape of the cover portion 23 is not limited to the above-described embodiments and can be appropriately changed. For example, an example is shown in which a part of the cover portion 23 is disposed inside the air chamber 32, but this is not limiting, and for example, it can be disposed entirely outside the air chamber 32. In addition, the cover portion 23 can be a plate-shaped member along the side surface of the actuator member 22.

[0082] For example, as another embodiment, Figures 11 to 14 The cover portion 230 of the inkjet head 110 shown is formed in a concave shape. Figure 11 is a perspective view showing a part of an inkjet head according to another embodiment, Figure 12 is a cross-sectional view showing the structure of a part of the inkjet head in an enlarged manner. Figure 13 is a cross-sectional view of the inkjet head of Figure 12 cut along the XIII-XIII line, Figure 14is cut along the line XIV-XIV. Figure 12 is cut along the line XIV-XIV.

[0083] The cover portion 230 according to the present embodiment is a wall-like member that is provided at an outer side in the extending direction of the air chamber 32 compared to the end portion of the side wall 33 and that blocks the end portion of the air chamber 32, and has a curved portion that is curved in a U shape or a C shape. For example, the cover portion 230 has a pair of extending walls 231 that extend along the extending direction of the air chamber 32 and a connecting wall 232 that connects the pair of extending walls 231, and is formed in a concave shape that has a slit-like air layer 321 between the pair of extending walls 231. The cover portion 230 is composed of a photosensitive resin material. For example, the cover portion 230 is formed in a predetermined shape by applying a photosensitive resin to both end portions of the air chamber 32 and then exposing and curing it. The cover portion 230 absorbs the deformation of the side wall 33 through the extending walls 231, thereby reducing crosstalk via the cover portion 230. That is, by providing the cover portion 230 in a shape in which vibration is difficult to transmit between the side walls 33, the effect of attenuating vibration can be increased.

[0084] In the above-described embodiment, an example in which the actuator member 22 having a plurality of grooves is provided at the main surface portion of the substrate 21 is shown, but the present application is not limited thereto. For example, a structure in which the actuator is provided at the end surface of the substrate 21 can also be employed. In addition, the number of nozzle rows is not limited to that of the above-described embodiment, and can be one row or three or more rows.

[0085] In the above-described embodiment, an example in which the actuator base 11 is provided with a laminated piezoelectric member composed of a plurality of piezoelectric bodies in the substrate 21 is shown, but the present application is not limited thereto. For example, the actuator base 11 can be formed of only a piezoelectric member without using a substrate. In addition, the supply side and the discharge side can be reversed, or can be configured to be switchable.

[0086] In the above-described embodiment, an example in which the one side of the pressure chamber 31 is the supply side, the other side is the discharge side, and the ink circulates so as to flow in from one side and flow out from the other side of the pressure chamber is shown, but the present application is not limited thereto. For example, a non-circulation type can also be employed. In addition, for example, a structure in which the common chambers on both sides of the pressure chamber 31 are the supply sides and the ink flows in from both sides can also be employed. That is, a structure in which the ink flows in from both sides of the pressure chamber 31 and flows out from the nozzle 28 provided at the center of the pressure chamber 31 can also be employed. In addition, the shapes of the cover portions 23 formed at both ends can be different from each other.

[0087] In addition, for example, the liquid to be ejected is not limited to ink for printing, and for example, a device that ejects a liquid containing conductive particles for forming a wiring pattern of a printed wiring board or the like can also be employed.

[0088] In addition, in the above-described embodiments, an example in which the inkjet head is used for a liquid ejecting apparatus such as an inkjet printer is shown, but the present application is not limited thereto, and can be used for a 3D printer, a manufacturing machine for industrial use, a medical use, and the like, and can achieve miniaturization, weight reduction, and cost reduction.

[0089] According to at least one of the embodiments described above, a liquid ejecting head capable of ensuring stable ejection characteristics can be provided.

[0090] Although several embodiments have been described, these embodiments are presented by way of example only, and are not intended to limit the scope of the application. These embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the spirit of the application. These embodiments and modifications thereof are included within the scope and spirit of the application, and are included within the scope of the application and equivalents thereof recited in the claims.

[0091] Explanation of Reference Numerals

[0092] 10, 110, inkjet head; 11, actuator base; 12, nozzle plate; 13, frame; 17, circuit substrate; 18, manifold; 21, substrate; 22, actuator member; 23, cover portion; 231, extension wall; 232, connection wall; 321, air layer; 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; 111, housing; 112, medium supply portion; 113, image forming portion; 114, medium discharge portion; 115, conveyance device; 116, control portion; 117, support portion; 118, conveyance belt; 119, support plate; 120, belt roller; 121, pair of guide plates; 122, conveyance roller; 130, head unit; 132, ink tank; 133, connection flow path; 134, circulation pump; 211, pattern wiring; 221, side portion; 271, first common chamber; 272, second common chamber.

Claims

1. A liquid ejection head comprising: an actuator member in which piezoelectric bodies polarized in opposite directions are stacked, and which has, on one side, a plurality of grooves constituting a plurality of pressure chambers, and a plurality of grooves constituting a plurality of air chambers adjacent to the plurality of pressure chambers and larger in size in a depth direction than the grooves constituting the pressure chambers, with the bottoms of the plurality of grooves being connected; individual electrodes formed on inner surfaces including bottoms of the plurality of pressure chambers; a common electrode formed on inner surfaces including bottoms of the plurality of air chambers; a non-piezoelectric member disposed opposite the one side of the actuator member; and a cover portion that plugs ends of the grooves constituting the air chambers in an extension direction intersecting the depth direction, the actuator member comprising a plurality of side walls disposed between the plurality of pressure chambers and the plurality of air chambers, the non-piezoelectric member being a nozzle plate comprising a plurality of nozzles communicating with the pressure chambers, the cover portion comprising a pair of extension walls extending from ends of a pair of the side walls on both sides of the air chambers in an extension direction intersecting the depth direction of the grooves and an arrangement direction of the plurality of grooves, respectively, to the outside of the grooves in the extension direction, and a connection wall connecting the extension walls at an outer side compared to the ends of the side walls, the cover portion plugging the ends of the grooves of the air chambers, the depth direction of the grooves being parallel to the direction of polarization of the piezoelectric bodies.

2. The liquid ejection head according to claim 1, wherein the plurality of piezoelectric bodies of the actuator member are stacked in the depth direction of the grooves, and polarized in opposite directions in the stacking direction.

3. The liquid ejection head according to claim 1 or 2, wherein the cover portion is composed of a photosensitive resin material.

4. The liquid ejection head according to claim 1 or 2, wherein a width of the actuator member in a short side direction gradually increases from a top side toward a substrate side. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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