Cleaning device

Abstract

This invention relates to a cleaning apparatus, providing a technique for effectively removing foreign matter adhering to a nozzle. The cleaning apparatus includes a liquid nozzle and a cleaning unit. The liquid nozzle has a piezoelectric element, a vibrating plate, a pressure chamber, and a nozzle plate. The nozzle plate has at least one nozzle array arranged along a first direction and a spray surface with nozzle openings. The cleaning unit includes a cover covering the spray surface and an ultrasonic device disposed on the cover. The ultrasonic device includes: a first element group having a resonant frequency of a first frequency and a plurality of first ultrasonic elements arranged to transmit first ultrasonic waves at the first frequency; and a second element group having a resonant frequency of a second frequency lower than the first frequency and a plurality of second ultrasonic elements arranged to transmit second ultrasonic waves at the second frequency. The first element group and the second element group are alternately arranged along a second direction parallel to the spray surface.

Description

Technical Field

[0001] This disclosure relates to a cleaning apparatus. Background Technology

[0002] Patent Document 1 discloses a droplet ejection device in which an ultrasonic transducer is installed on the cover of the ejection head to prevent the ejected liquid from evaporating. In this device, with the ejection nozzle and the cover filled with liquid, ultrasonic waves are emitted from the ultrasonic transducer to clean the ejection nozzle and the nozzle plate while the cover is placed over the ejection nozzle.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2006-347000

[0004] When using ultrasound to remove foreign objects attached to a nozzle, the appropriate frequency of the ultrasound varies depending on the size and type of the foreign object. Therefore, in ultrasonic devices with a single resonant frequency, it is sometimes difficult to effectively remove foreign objects attached to the nozzle. Summary of the Invention

[0005] According to a first aspect of this disclosure, a cleaning apparatus is provided. The cleaning apparatus includes: a liquid nozzle; and a cleaning unit disposed below the liquid nozzle. The liquid nozzle has: a piezoelectric element; a vibrating plate that vibrates by being driven by the piezoelectric element; a pressure chamber that applies pressure to liquid stored inside by the vibration of the vibrating plate; and a nozzle plate having at least one nozzle array in which nozzles communicating with the pressure chamber and spraying the liquid are arranged along a first direction. The nozzle plate has a spray surface on its lower surface with nozzle openings formed for each of the nozzles. The cleaning unit includes: a cover disposed opposite to the spray surface and covering the spray surface; and an ultrasonic device disposed on the cover for transmitting ultrasonic waves to liquid filled within the cover. The ultrasonic device includes: a first element group having a resonant frequency of a first frequency and having a plurality of first ultrasonic elements arranged to transmit the first ultrasonic wave at the first frequency; and a second element group having a resonant frequency of a second frequency lower than the first frequency and having a plurality of second ultrasonic elements arranged to transmit the second ultrasonic wave at the second frequency. The first element group and the second element group are alternately arranged along a second direction parallel to the spray surface. Attached Figure Description

[0006] Figure 1 This is an explanatory diagram showing the general structure of a liquid injection device.

[0007] Figure 2 This is an exploded perspective view showing the structure of the liquid nozzle.

[0008] Figure 3This is an explanatory diagram showing the structure of a liquid nozzle from a top-down view.

[0009] Figure 4 It is shown Figure 3 A cross-sectional view at position IV-IV.

[0010] Figure 5 It is a schematic cross-sectional view showing the detailed structure of a piezoelectric element.

[0011] Figure 6 This is an explanatory diagram showing the general structure of the cleaning unit.

[0012] Figure 7 This is a partial cross-sectional view of the liquid nozzle and cleaning unit.

[0013] Figure 8 This is a top view of an ultrasonic device.

[0014] Figure 9 This is a top view showing the general structure of the first element group.

[0015] Figure 10 It is shown Figure 9 A cross-sectional view of position XX in the diagram.

[0016] Figure 11 It is shown Figure 9 A cross-sectional view of the XI-XI position.

[0017] Figure 12 This is a flowchart illustrating a nozzle cleaning method.

[0018] Figure 13 This is a partial cross-sectional view of the liquid nozzle and cleaning unit in the second embodiment.

[0019] Figure 14 This is a top view of the ultrasonic device in the second embodiment.

[0020] Figure 15 This is a partial cross-sectional view of the liquid nozzle and cleaning unit in the third embodiment.

[0021] Figure 16 This is a top view of the ultrasonic device in the third embodiment.

[0022] Figure 17 This is a partial cross-sectional view of the liquid nozzle and cleaning unit in the fourth embodiment.

[0023] Figure 18 This is a top view of the ultrasonic device in the fourth embodiment.

[0024] Figure 19 It is a diagram illustrating the relationship between the state of the nozzle and the waveform of the reflected wave.

[0025] Figure 20 This is a flowchart illustrating the nozzle cleaning method in the fourth embodiment.

[0026] Figure 21 This is a flowchart of the cleaning process.

[0027] Figure 22 This is a partial cross-sectional view of the liquid nozzle and cleaning unit in the fifth embodiment.

[0028] Figure 23 This is a top view of the ultrasonic device in the fifth embodiment.

[0029] Explanation of reference numerals in the attached figures

[0030] 10: Pressure chamber base plate; 12: Pressure chamber; 13: Contraction section; 14: Pressure chamber supply path; 15: Connecting plate; 16: Nozzle connecting path; 17: First manifold section; 18: Second manifold section; 19: Supply connecting path; 20, 20b, 20c, 20e: Nozzle plates; 21: Nozzle; 22: Nozzle opening; 23: Spray surface; 25: Nozzle array; 30: Sealing base plate; 30T: Top; 30W: Wall section; 31: Holding section; 32: Through hole; 40: Housing component; 41: Receiving section; 42 43: Third manifold section; 44: Connection port; 45: Supply port; 46: Moldable substrate; 47: Sealing film; 48: Fixing substrate; 49: Opening; 50: Moldable section; 50: Vibrating plate; 55: Elastic membrane; 56: Insulating film; 60: First electrode; 60b: One end; 70: Piezoelectric element; 70b: One end; 80: Second electrode; 80b: One end; 82: Protective film; 85: Wiring section; 91: First drive wiring; 92: Second drive wiring; 92a: Extension setting section; 92b: Extension unit; 100: Manifold; 120: Wiring board; 121: Integrated circuit; 300: Piezoelectric element; 500: Liquid jetting device; 510: Liquid nozzle; 550: Ink cartridge; 552: Tube; 560: Conveying mechanism; 562: Conveying roller; 564: Conveying rod; 566: Conveying motor; 570: Moving mechanism; 572: Carriage; 574: Conveying belt; 576: Moving motor; 577: Pulley; 580: Control unit; 600: Cleaning unit; 610: Cover; 611: Recess Part; 612: Inner surface; 613: Side wall; 620, 620b, 620c, 620d, 620e: Ultrasonic device; 621: First element group; 622: Third electrode; 623: Piezoelectric element; 624: Fourth electrode; 625: Insulating layer; 626: First ultrasonic element; 631: Second element group; 640: Cleaning fluid supply device; 645: Connecting pipe; 650: Suction device; 655: Connecting pipe; L1: First pressure chamber row; L2: Second pressure chamber row; P: Printing paper. Detailed Implementation

[0031] A. First implementation method: Figure 1 This is an explanatory diagram showing the schematic structure of the liquid jetting device 500. In this embodiment, the liquid jetting device 500 is an inkjet printer that jets ink, an example of a liquid, onto printing paper P to form an image. Alternatively, the liquid jetting device 500 can use any type of medium, such as resin film or fabric, instead of printing paper P as the ink jetting target. Figure 1 The diagram shows arrows indicating the mutually orthogonal X, Y, and Z directions. The X and Y directions are parallel to the horizontal plane. The Z direction is parallel to the vertical direction. Figure 1 The X, Y, and Z directions in this diagram indicate the same direction as those in other diagrams. When a direction is defined, the positive direction indicated by the arrow is designated as "+", and the negative direction, the opposite direction, is designated as "-". Positive and negative signs are used in the direction representation. In this specification, +Z indicates vertically downward, and -Z indicates vertically upward.

[0032] The liquid jetting device 500 includes a liquid nozzle 510, an ink cartridge 550, a transport mechanism 560, a moving mechanism 570, a cleaning unit 600, and a control unit 580. The liquid nozzle 510 has multiple nozzles that jet four colors of ink—black, cyan, magenta, and yellow—into the +Z direction to form an image on printing paper P. The liquid nozzle 510 is mounted on a carriage 572 and reciprocates in the main scanning direction as the carriage 572 moves. In this embodiment, the main scanning direction is the +X and -X directions.

[0033] The ink cartridge 550 contains ink for ejecting from the liquid printhead 510. The ink cartridge 550 is connected to the liquid printhead 510 via a resin tube 552. The ink from the ink cartridge 550 is supplied to the liquid printhead 510 via the tube 552. Alternatively, a pouch-shaped liquid bag made of flexible membrane can be used instead of the ink cartridge 550.

[0034] The conveying mechanism 560 conveys the printing paper P in the secondary scanning direction. The secondary scanning direction is the direction that intersects with the X direction, which is the primary scanning direction; in this embodiment, it is the +Y and -Y directions. The conveying mechanism 560 includes a conveying rod 564 on which three conveying rollers 562 are mounted and a conveying motor 566 that drives the conveying rod 564 to rotate. By driving the conveying rod 564 to rotate via the conveying motor 566, the printing paper P is conveyed in the +Y direction, which is the secondary scanning direction. The number of conveying rollers 562 is not limited to three and can be any number.

[0035] The moving mechanism 570 includes a carriage 572, a conveyor belt 574, a moving motor 576, and pulleys 577. The carriage 572 is equipped with a liquid nozzle 510 capable of spraying ink. The carriage 572 is fixed to the conveyor belt 574. The conveyor belt 574 is positioned between the moving motor 576 and the pulleys 577. Driven by the rotation of the moving motor 576, the conveyor belt 574 reciprocates in the main scanning direction. Consequently, the carriage 572, fixed to the conveyor belt 574, also reciprocates in the main scanning direction.

[0036] The cleaning unit 600 cleans the nozzles of the liquid spray head 510. Details of the cleaning unit 600 are described below. In this disclosure, the cleaning unit 600 and the liquid spray head 510 are collectively referred to as a cleaning apparatus.

[0037] The control unit 580 is configured as a microcomputer with a CPU and a storage unit. The storage unit may be, for example, a non-volatile memory that can be erased by electrical signals, such as an EEPROM; a non-volatile memory that can be erased by ultraviolet light, such as a One-Time-PROM or EPROM; or a non-erasable non-volatile memory, such as a PROM. Various programs for the functions provided in this embodiment are stored in the storage unit. The CPU controls all parts of the liquid jetting device 500 by unfolding and executing the programs stored in the storage unit. The control unit 580 controls the reciprocating motion of the carriage 572 along the main scanning direction, the conveying motion of the printing paper P along the sub-scanning direction, and the jetting motion of liquid from the liquid nozzle 510.

[0038] Reference Figures 2 to 4 The details of the liquid nozzle 510 are explained below. Figure 2 This is an exploded perspective view showing the structure of the liquid nozzle 510. Figure 3 This is an explanatory diagram showing the structure of the liquid nozzle 510 from a top-down view. In this disclosure, "top-down view" refers to observing the state of an object along a vertical direction. Figure 3 The diagram shows the structure around the pressure chamber substrate 10 and the vibrating plate 50 in the liquid nozzle 510. For ease of understanding, the protective film 82, sealing substrate 30, housing component 40, etc., are omitted from the illustration. Figure 4 It is shown Figure 3 A cross-sectional view at position IV-IV.

[0039] Liquid nozzle 510 has Figure 2 The pressure chamber base plate 10, connecting plate 15, nozzle plate 20, malleable base plate 45, vibrating plate 50, sealing base plate 30, housing component 40, wiring base plate 120, and other components shown are described. Figure 3The piezoelectric element 300 is shown. A liquid nozzle 510 is formed by stacking these stacked components. In this disclosure, the direction in which the stacked components forming the liquid nozzle 510 are stacked is also referred to as the "stack direction". In this embodiment, the stack direction is aligned with the Z-direction.

[0040] The pressure chamber substrate 10 is formed, for example, using a silicon substrate, glass substrate, SOI substrate, or various ceramic substrates. Figure 3 As shown, a plurality of pressure chambers 12 are formed on the pressure chamber substrate 10. The pressure chambers 12 extend along the X direction. Specifically, the pressure chambers 12 are formed in a generally rectangular shape in which the length in the X direction is longer than the length in the Y direction when viewed from above. However, the shape of the pressure chambers 12 is not limited to a rectangular shape, and may also be a parallelogram shape, a polygon shape, etc. In this specification, the X direction is also referred to as the "extension direction".

[0041] like Figure 3 As shown, a plurality of pressure chambers 12 are arranged in the pressure chamber substrate 10 along a direction intersecting the extending direction. In this specification, the direction in which the plurality of pressure chambers 12 are arranged is also referred to as the "arrangement direction" when viewed from above. In this embodiment, the plurality of pressure chambers 12 are arranged in two parallel columns, each with the Y-direction as its arrangement direction. Figure 3 In the example, the pressure chamber substrate 10 has two pressure chamber rows: a first pressure chamber row L1 having a first arrangement direction parallel to the Y direction and a second pressure chamber row L2 having a second arrangement direction parallel to the Y direction.

[0042] like Figure 2 As shown, a connecting plate 15, a nozzle plate 20, and a malleable substrate 45 are stacked on the +Z direction side of the pressure chamber substrate 10. The connecting plate 15 is, for example, a flat plate made of a silicon substrate, glass substrate, SOI substrate, various ceramic substrates, metal substrates, etc. A nozzle connecting passage 16 and a first manifold section 17 are provided on the connecting plate 15. Figure 4 The second manifold 18 and the supply connection path 19 are shown.

[0043] like Figure 4 As shown, the nozzle connection path 16 is a flow path connecting the pressure chamber 12 and the nozzle 21. The first manifold section 17 and the second manifold section 18 function as part of a manifold 100 that connects the multiple pressure chambers 12 to a common liquid chamber. The first manifold section 17 is arranged to pass through the connecting plate 15 in the Z direction. Furthermore, as... Figure 4 As shown, the second manifold portion 18 does not penetrate the connecting plate 15 in the Z direction, but is provided on the surface of the connecting plate 15 in the +Z direction.

[0044] like Figure 4As shown, the supply connection 19 is a flow path connected to the pressure chamber supply path 14 provided on the pressure chamber substrate 10. The pressure chamber supply path 14 is a flow path connected to one end of the pressure chamber 12 in the X direction via a contraction portion 13. The contraction portion 13 is a flow path provided between the pressure chamber 12 and the pressure chamber supply path 14. The contraction portion 13 is a flow path whose inner wall protrudes more than the pressure chamber 12 or the pressure chamber supply path 14, and is formed to be narrower than the pressure chamber 12 or the pressure chamber supply path 14. As a result, the flow resistance of the contraction portion 13 is higher than that of the pressure chamber 12 or the pressure chamber supply path 14. With this configuration, even when pressure is applied to the pressure chamber 12 by the piezoelectric element 300 during ink ejection, it is possible to suppress or prevent the backflow of ink in the pressure chamber 12 to the pressure chamber supply path 14. There are multiple supply connection paths 19, arranged along the Y direction, i.e., the arrangement direction, and each is individually provided relative to each of the pressure chambers 12. The supply connection path 19 and the pressure chamber supply path 14 connect the second manifold section 18 and each pressure chamber 12, supplying the ink in the manifold 100 to each pressure chamber 12.

[0045] The nozzle plate 20 is disposed on the side opposite to the pressure chamber substrate 10, i.e., on the +Z direction side of the connecting plate 15, separated by the connecting plate 15. The material of the nozzle plate 20 is not particularly limited; for example, silicon substrates, glass substrates, SOI substrates, various ceramic substrates, and metal substrates can be used. For example, stainless steel substrates can be used as metal substrates. Organic materials such as polyimide resin can also be used as the material of the nozzle plate 20.

[0046] A plurality of nozzles 21 are formed on the nozzle plate 20. Each nozzle 21 is connected to a pressure chamber 12 via a nozzle connecting passage 16. Figure 2 As shown, a plurality of nozzles 21 are arranged along the arrangement direction of the pressure chamber 12, i.e., the Y direction. In this disclosure, the direction in which the plurality of nozzles 21 are arranged is also referred to as the "first direction". In this embodiment, the first direction is the Y direction. That is, the nozzles 21 are arranged along the first direction. Two rows of nozzles 25 are provided on the nozzle plate 20, and the nozzle rows 25 are formed by arranging these plurality of nozzles 21 along the first direction. The two nozzle rows 25 correspond to the first pressure chamber row L1 and the second pressure chamber row L2, respectively. Figure 4 As shown, the nozzle plate 20 has a spray surface 23 on which a nozzle opening 22 is formed, and a nozzle 21 is formed. The spray surface 23 is the lower surface of the nozzle plate 20, that is, the surface of the nozzle plate 20 in the +Z direction.

[0047] like Figure 4As shown, the malleable substrate 45, together with the nozzle plate 20, is disposed on the side opposite to the pressure chamber substrate 10, i.e., on the +Z direction side of the connecting plate 15, separated by the connecting plate 15. The malleable substrate 45 is disposed around the nozzle plate 20, covering the openings of the first manifold portion 17 and the second manifold portion 18 disposed on the connecting plate 15. The malleable substrate 45 may include, for example, a sealing film 46 made of a flexible thin film and a fixing substrate 47 made of a rigid material such as metal. Figure 4 As shown, the region in the fixed substrate 47 opposite to the manifold 100 is defined by completely removing it in the thickness direction to form an opening 48. Therefore, one side of the manifold 100 becomes a malleable portion 49 sealed only by the sealing film 46.

[0048] like Figure 4 As shown, a vibrating plate 50 and a piezoelectric element 300 are stacked on the side opposite to the pressure chamber substrate 10 and the connecting plate 15, i.e., on the -Z direction side of the pressure chamber substrate 10. The piezoelectric element 300 causes the vibrating plate 50 to flexibly deform, causing pressure changes in the ink within the pressure chamber 12. Figure 4 The diagram of the piezoelectric element 300 has been simplified.

[0049] A vibrating plate 50 is disposed between the piezoelectric element 300 and the pressure chamber substrate 10. The vibrating plate 50 is positioned closer to the pressure chamber substrate 10 than the piezoelectric element 300 and includes: an elastic film 55 having silicon oxide (SiO2); and an insulating film 56 disposed on the elastic film 55, having a zirconium oxide film (ZrO2). The elastic film 55 forms the -Z direction side of the flow path such as the pressure chamber 12. Furthermore, the vibrating plate 50 can be composed of either the elastic film 55 or the insulating film 56, or it can include other films besides the elastic film 55 and the insulating film 56. Examples of other film materials include organosilicon and silicon nitride.

[0050] like Figure 2 As shown, a sealing substrate 30, which has approximately the same size as the pressure chamber substrate 10 when viewed from above, is also bonded to the -Z direction side of the pressure chamber substrate 10 by an adhesive or the like. Figure 4 As shown, the sealing substrate 30 includes a top 30T, a wall portion 30W, a holding portion 31, and a through hole 32. The holding portion 31, defined by the top 30T and the wall portion 30W, protects the active part of the piezoelectric element 300 by accommodating it. In this embodiment, the holding portions 31 are arranged in each row of the piezoelectric elements 300; more specifically, two holding portions 31 corresponding to the first pressure chamber row L1 and the second pressure chamber row L2 are formed adjacent to each other. The through hole 32 penetrates the sealing substrate 30 along the Z direction. When viewed from above, the through hole 32 is positioned between two holding portions 31 and is formed into a long rectangular shape along the Y direction.

[0051] like Figure 4 As shown, a housing component 40 is fixed on the sealing base plate 30. The housing component 40, together with the connecting plate 15, forms a manifold 100 communicating with a plurality of pressure chambers 12. The housing component 40 has a substantially the same external shape as the connecting plate 15 when viewed from above, and is engaged in a manner that covers the sealing base plate 30 and the connecting plate 15.

[0052] The housing component 40 has a receiving portion 41, a supply port 44, a third manifold portion 42, and a connection port 43. The receiving portion 41 is a space with a depth capable of accommodating the pressure chamber substrate 10, the vibrating plate 50, and the sealing substrate 30. The third manifold portion 42 is a space formed in the housing component 40 near both ends of the receiving portion 41 in the X direction. A manifold 100 is formed by connecting the third manifold portion 42 and the first manifold portion 17 and the second manifold portion 18 provided on the connecting plate 15. The manifold 100 has an elongated shape in the Y direction. The supply port 44 communicates with the manifold 100 and supplies ink to each manifold 100. The connection port 43 is a through hole communicating with the through hole 32 of the sealing substrate 30, through which the wiring substrate 120 is inserted.

[0053] Liquid nozzle 510 from Figure 4 The supply port 44 shown is used to take in from Figure 1 The ink supplied by the ink cartridge 550, after filling the internal flow path from the manifold 100 to the nozzle 21, applies a voltage based on a drive signal to each piezoelectric element 300 corresponding to the plurality of pressure chambers 12. As a result, the vibrating plate 50 and the piezoelectric elements 300 flex and deform together, the volume of each pressure chamber 12 changes, the internal pressure increases, and ink droplets are ejected from each nozzle 21.

[0054] and Figure 3 , Figure 4 Together, refer to appropriately Figure 5 The structure of the piezoelectric element 300 is described. Figure 5 This is a schematic cross-sectional view showing the detailed structure of the piezoelectric element 300. (See diagram below.) Figure 5 As shown, the piezoelectric element 300 has a first electrode 60, a piezoelectric body 70, and a second electrode 80. The first electrode 60, the piezoelectric body 70, and the second electrode 80 are stacked in this order toward the -Z direction of the stacking direction. The piezoelectric body 70 is disposed between the first electrode 60 and the second electrode 80 in the stacking direction.

[0055] The first electrode 60 and the second electrode 80 are connected via drive wiring. Figure 3 as well as Figure 4The wiring substrate 120 shown is electrically connected. The driving wiring includes a first driving wiring 91 electrically connecting the wiring substrate 120 and the first electrode 60, and a second driving wiring 92 electrically connecting the wiring substrate 120 and the second electrode 80. The first electrode 60 and the second electrode 80 apply a voltage corresponding to the driving signal to the piezoelectric element 70. The driving voltage is the voltage applied to the piezoelectric element 300 from the first electrode 60 and the second electrode 80 by the control unit 580 for driving the piezoelectric element 300. In the piezoelectric element 300, the portion that generates piezoelectric strain in the piezoelectric element 70 when a voltage is applied between the first electrode 60 and the second electrode 80 is also referred to as the active portion, and the portion that does not generate piezoelectric strain in the piezoelectric element 70 is also referred to as the passive portion.

[0056] A driving voltage varying according to the amount of ink ejected is applied to the first electrode 60, while a predetermined reference voltage, independent of the amount of ink ejected, is applied to the second electrode 80. If a voltage difference is generated between the first electrode 60 and the second electrode 80 by applying the driving voltage and the reference voltage, the piezoelectric element 70 of the piezoelectric element 300 deforms. This deformation of the piezoelectric element 70 causes the vibrating plate 50 to deform or vibrate, resulting in a change in the volume of the pressure chamber 12. This change in the volume of the pressure chamber 12 applies pressure to the ink contained within it, causing the ink to be ejected from the nozzle 21 via the nozzle connection 16.

[0057] The first electrode 60 is a separate electrode disposed independently relative to the plurality of pressure chambers 12. For example... Figure 5 As shown, the first electrode 60 is a lower electrode disposed on the opposite side of the second electrode 80, separated from it by the piezoelectric element 70, i.e., below the piezoelectric element 70. The first electrode 60 is formed, for example, from conductive materials such as metals like platinum (Pt), iridium (Ir), gold (Au), and titanium (Ti), or conductive metal oxides such as indium tin oxide (ITO). The first electrode 60 can also be formed by stacking various materials such as platinum (Pt), iridium (Ir), gold (Au), and titanium (Ti).

[0058] like Figure 3As shown, the piezoelectric element 70 has a predetermined width in the X direction and a long rectangular shape along the Y direction, which is the arrangement direction of the pressure chambers 12. Examples of the piezoelectric element 70 include a perovskite-structured crystalline film formed on the first electrode 60, composed of a highly dielectric ceramic material exhibiting electromechanical conversion, or a so-called perovskite-type crystal. Materials for the piezoelectric element 70 can include, for example, highly dielectric piezoelectric materials such as lead zirconate titanate (PZT), or materials formed by adding metal oxides such as niobium oxide, nickel oxide, or magnesium oxide. Specifically, lead titanate (PbTiO3), lead zirconate titanate (Pb(Zr,Ti)O3), lead zirconate (PbZrO3), lanthanum lead titanate ((Pb,La),TiO3), lanthanum lead zirconate titanate ((Pb,La)(Zr,Ti)O3), or lead zirconate titanate magnesium niobate (Pb(Zr,Ti)(Mg,Nb)O3) can be used.

[0059] The material used for the piezoelectric element 70 is not limited to lead-based piezoelectric materials containing lead; lead-free non-lead piezoelectric materials can also be used. Examples of lead-free piezoelectric materials include bismuth ferrite (BiFeO3, abbreviated as "BFO"), barium titanate (BaTiO3, abbreviated as "BT"), potassium sodium lithium niobate (K,Na,Li)(NbO3), potassium sodium lithium niobate tantalate (K,Na,Li)(Nb,Ta)O3, and bismuth potassium titanate (Bi1 / 2K). 1 / 2 TiO3, abbreviated as "BKT"), sodium bismuth titanate (Bi1 / 2Na) 1 / 2 TiO3 (abbreviated as "BNT"), bismuth manganate (BiMnO3, abbreviated as "BM"), and composite oxides with a perovskite structure containing bismuth, potassium, titanium, and iron (x[(Bi x K 1-x (1-x)[BiFeO3]-(1-x)[BiFeO3], abbreviated as "BKT-BF"), composite oxides with a perovskite structure containing bismuth, iron, barium and titanium ((1-x)[BiFeO3]-x[BaTiO3], abbreviated as "BFO-BT"), and materials made by adding metals such as manganese, cobalt and chromium ((1-x)[Bi(FeO3]-(1-x)[BiFeO3]-(1-x)[BiFeO3], abbreviated as "BKT-BF"), composite oxides with a perovskite structure containing bismuth, iron, barium and titanium, and materials made by adding metals such as manganese, cobalt and chromium ((1-x)[Bi(FeO3]-(1-x)[BiFeO3]-(1-x)[BiFeO3]-(1-x)[ 1-y M y [O3]-x[BaTiO3] (M is Mn, Co or Cr) etc.

[0060] like Figure 3 As shown, the second electrode 80 is a common electrode shared by the plurality of pressure chambers 12. The second electrode 80 has a predetermined width in the X direction and extends along the arrangement direction of the pressure chambers 12, i.e., the Y direction. Figure 5As shown, the second electrode 80 is an upper electrode disposed on the opposite side of the first electrode 60, separated by the piezoelectric element 70, i.e., above the piezoelectric element 70. The second electrode 80 is formed, for example, from conductive materials such as metals like platinum (Pt), iridium (Ir), gold (Au), and titanium (Ti), or conductive metal oxides such as indium tin oxide (ITO). The second electrode 80 can also be formed by stacking multiple materials such as platinum (Pt), iridium (Ir), gold (Au), and titanium (Ti).

[0061] like Figure 5 As shown, a protective film 82 is formed at the end of the second electrode 80 on the -X direction side. The protective film 82 is made of a material that has electrical insulation and moisture-blocking properties. For example, the protective film 82 can be an oxide insulating film such as alumina or hafnium oxide, or a polymer film such as polyimide. The protective film 82 is formed in such a way that it covers one end 80b of the second electrode 80 and the surface of the piezoelectric body 70.

[0062] like Figure 5 As shown, a wiring portion 85 is provided on the -X direction side further than the -X direction end of the second electrode 80. Additionally, in Figure 3 The wiring portion 85 is omitted from the illustration. The wiring portion 85 is on the same layer as the second electrode 80, but is electrically discontinuous with it. The wiring portion 85 is formed from one end 70b of the piezoelectric body 70 in the -X direction to one end 60b of the first electrode 60 in the -X direction, spaced apart from one end 80b of the second electrode 80. The end 60b of the first electrode 60 in the -X direction is extended to a position further outward than the end 70b of the piezoelectric body 70. Multiple wiring portions 85 are provided for each piezoelectric element 300, and are arranged at predetermined intervals along the Y direction. Alternatively, the wiring portion 85 may be formed on a different layer than the second electrode 80.

[0063] like Figure 5 As shown, the first driving wiring 91 is electrically connected to the first electrode 60, which is a separate electrode, and the extension portions 92a and 92b of the second driving wiring 92 are electrically connected to the second electrode 80, which is a common electrode. The first driving wiring 91 and the second driving wiring 92 function as driving wiring for applying a voltage from the wiring substrate 120 to drive the piezoelectric element 70.

[0064] The first drive wiring 91 is configured individually for each first electrode 60. For example... Figure 5As shown, the first drive wiring 91 is connected to a portion 85 near one end 60b of the first electrode 60 and is led out in the -X direction to the vibrating plate 50. The first drive wiring 91 is electrically connected to the end 60b of the first electrode 60 in the -X direction, which is further outward than the end 70b of the piezoelectric element 70. Alternatively, the wiring portion 85 can be omitted, and the first drive wiring 91 can be directly connected to one end 60b of the first electrode 60.

[0065] like Figure 3 As shown, the second drive wiring 92 extends along the Y direction, bends at both ends in the Y direction, and extends out along the X direction. The second drive wiring 92 has an extension portion 92a and an extension portion 92b extending along the Y direction. Figure 3 as well as Figure 4 As shown, the ends of the first drive wiring 91 and the second drive wiring 92 extend in such a way that they are exposed in the through hole 32 of the sealing substrate 30 and are electrically connected to the wiring substrate 120 in the through hole 32.

[0066] The first drive wiring 91 and the second drive wiring 92 are formed on the same layer in a state that is electrically discontinuous with each other. Alternatively, the first drive wiring 91 and the second drive wiring 92 may be formed on different layers. The materials of the first drive wiring 91 and the second drive wiring 92 are conductive materials, such as gold (Au), copper (Cu), titanium (Ti), tungsten (W), nickel (Ni), chromium (Cr), platinum (Pt), aluminum (Al), etc.

[0067] The wiring substrate 120 is, for example, made of a flexible substrate (FPC: Flexible Printed Circuit). The wiring substrate 120 has multiple wirings for connection to the control unit 580 and a power supply circuit (not shown). Alternatively, it can be made of any flexible substrate such as an FFC (Flexible Flat Cable) instead of an FPC. An integrated circuit 121 having switching elements is mounted on the wiring substrate 120. Command signals for driving the piezoelectric element 300 are input to the integrated circuit 121. Based on the command signals, the integrated circuit 121 controls the timing of supplying the drive signal for driving the piezoelectric element 300 to the first electrode 60.

[0068] Figure 6 This is an explanatory diagram showing the schematic structure of the cleaning unit 600. The cleaning unit 600 includes a cover 610, an ultrasonic device 620, a cleaning fluid supply device 640, and a suction device 650. The cover 610 is configured to be installed on the liquid nozzle 510 during the cleaning of the nozzle 21.

[0069] Figure 7This is a partial cross-sectional view of the liquid nozzle 510 and the cleaning unit 600 with the cover 610 installed. Figure 7 The diagram shows a cross-sectional view of the nozzle plate 20 and a portion of the cleaning unit 600, cut by a plane including the nozzle 21 and orthogonal to the Y direction, which is the first direction. Figure 7 As shown, the cover 610 is positioned below the liquid nozzle 510 when it is installed on the liquid nozzle 510. The cover 610 is positioned opposite the spray surface 23 of the nozzle plate 20 and covers the spray surface 23 when installed on the liquid nozzle 510. Specifically, the cover 610 covers all the nozzles 21 when installed on the liquid nozzle 510. The cover 610 is formed, for example, of a metal such as stainless steel or a plastic resin.

[0070] like Figure 6 As shown, the cover 610 has a recess 611 capable of storing liquid. The recess 611 is composed of an inner surface 612 opposite to the spray surface 23 and a sidewall 613 protruding upwards from the inner surface 612. The inner surface 612 is the surface of the cover 610 in the -Z direction. In this embodiment, the inner surface 612 is a plane parallel to the horizontal plane. Alternatively, the inner surface 612 may also be a curved surface. The sidewall 613 is provided on the outer periphery of the cover 610 and contacts the spray surface 23 when the cover 610 is mounted on the liquid nozzle 510. By contacting the spray surface 23 with the sidewall 613, leakage of liquid supplied to the recess 611 to the outside of the cover 610 is prevented when cleaning the nozzle 21. The sidewall 613 is preferably formed of an elastic material. A gasket made of an elastic material may also be provided at the upper end of the sidewall 613. An ultrasonic device 620 is provided on the inner surface 612 of the cover 610. Details of the ultrasonic device 620 are described below.

[0071] The cleaning fluid supply device 640 supplies cleaning fluid to the recess 611 of the cover 610. The cleaning fluid can be, for example, a solvent suitable for dissolving foreign matter adhering to the nozzle 21, the ink itself, or the main solvent of the ink. The cleaning fluid supply device 640 is connected to the cover 610 via a connecting pipe 645. The connecting pipe 645 is, for example, a flexible hose. The cleaning fluid supply device 640 supplies cleaning fluid from the bottom of the cover 610 using the pressure of the water level difference. Alternatively, the cleaning fluid supply device 640 can supply cleaning fluid from the opening of the cover 610 to the recess 611, or a pump or the like can be used to supply cleaning fluid to the recess 611.

[0072] The suction device 650 draws liquid from the recess 611 of the cap 610. The suction device 650 is connected to the cap 610 via a connecting pipe 655. The connecting pipe 655 is, for example, a flexible hose. The suction device 650 has a suction pump (not shown) that recovers the cleaning fluid via the connecting pipe 655. The suction device 650 preferably applies sufficient negative pressure to the recess 611 of the cap 610 and the interior of the nozzle 21.

[0073] Figure 8 This is a top view of the ultrasonic device 620. Figure 8 In the diagram, the dotted line indicates the position of the nozzle opening 22 when the cover 610 is installed on the liquid nozzle 510. An ultrasonic device 620 is disposed on the cover 610 and transmits ultrasonic waves to the liquid filled within the cover 610. (Example...) Figure 7 as well as Figure 8 As shown, the ultrasonic device 620 has a first element group 621 and a second element group 631. The first element group 621 is an element group in which a plurality of first ultrasonic elements 626 with a resonant frequency of a first frequency are arranged. The second element group 631 is an element group in which a plurality of second ultrasonic elements with a resonant frequency of a second frequency lower than the first frequency are arranged.

[0074] Figure 9 This is a top view showing the schematic structure of the first element group 621. Figure 10 It is shown Figure 9 A cross-sectional view of position XX in the diagram. Figure 11 It is shown Figure 9 A cross-sectional view at position XI-XI. In this embodiment, the first element group 621 is a piezoelectric element. The first element group 621 has a third electrode 622, a piezoelectric body 623, a fourth electrode 624, and an insulating layer 625. Furthermore, in... Figure 9 The insulation layer 625 is omitted in the text.

[0075] The third electrode 622, piezoelectric element 623, and fourth electrode 624 are stacked in this order, facing the -Z direction. The piezoelectric element 623 is positioned between the third electrode 622 and the fourth electrode 624 in the Z direction. The third electrode 622 is the lower electrode of the piezoelectric element 623, located on the +Z side, i.e., below the piezoelectric element 623. The fourth electrode 624 is the upper electrode of the piezoelectric element 623, located on the -Z side, i.e., above the piezoelectric element 623. Multiple third electrodes 622 extend in the Y direction and are arranged along the X direction. Multiple fourth electrodes 624 extend in the X direction and are arranged along the Y direction. The overlapping portions of the piezoelectric element 623 in the Z direction between the third electrode 622 and the fourth electrode 624 are arranged in a matrix shape in both the X and Y directions.

[0076] The third electrode 622 and the fourth electrode 624 are formed, for example, by conductive materials such as metals like platinum (Pt), iridium (Ir), gold (Au), and titanium (Ti), or conductive metal oxides such as indium tin oxide (ITO). The third electrode 622 and the fourth electrode 624 can also be formed by stacking multiple materials such as platinum (Pt), iridium (Ir), gold (Au), and titanium (Ti).

[0077] As a piezoelectric material 623, a so-called perovskite-type crystal can be cited as an example. Materials used as piezoelectric materials 623 include, for example, highly dielectric piezoelectric materials such as lead zirconate titanate (PZT), and materials formed by adding metal oxides such as niobium oxide, nickel oxide, or magnesium oxide. Specifically, lead titanate (PbTiO3), lead zirconate titanate (Pb(Zr,Ti)O3), lead zirconate (PbZrO3), lanthanum lead titanate ((Pb,La),TiO3), lanthanum lead zirconate titanate ((Pb,La)(Zr,Ti)O3), or lead zirconate titanate magnesium niobate (Pb(Zr,Ti)(Mg,Nb)O3) can be used.

[0078] The material used for the piezoelectric element 623 is not limited to lead-based piezoelectric materials containing lead; lead-free non-lead piezoelectric materials can also be used. Examples of lead-free piezoelectric materials include bismuth ferrite (BiFeO3, abbreviated as "BFO"), barium titanate (BaTiO3, abbreviated as "BT"), potassium sodium lithium niobate (K,Na,Li)(NbO3), potassium sodium lithium niobate tantalate (K,Na,Li)(Nb,Ta)O3, and bismuth potassium titanate (Bi1 / 2K). 1 / 2 TiO3, abbreviated as "BKT"), sodium bismuth titanate (Bi1 / 2Na) 1 / 2 TiO3 (abbreviated as "BNT"), bismuth manganate (BiMnO3, abbreviated as "BM"), and composite oxides with a perovskite structure containing bismuth, potassium, titanium, and iron (x[(Bi x K 1-x (1-x)[BiFeO3]-(1-x)[BiFeO3], abbreviated as "BKT-BF"), composite oxides with a perovskite structure containing bismuth, iron, barium and titanium ((1-x)[BiFeO3]-x[BaTiO3], abbreviated as "BFO-BT"), and materials made by adding metals such as manganese, cobalt and chromium ((1-x)[Bi(FeO3]-(1-x)[BiFeO3]-(1-x)[BiFeO3], abbreviated as "BKT-BF"), composite oxides with a perovskite structure containing bismuth, iron, barium and titanium, and materials made by adding metals such as manganese, cobalt and chromium ((1-x)[Bi(FeO3]-(1-x)[BiFeO3]-(1-x)[BiFeO3]-(1-x)[ 1-y M y [O3]-x[BaTiO3] (M is Mn, Co or Cr) etc.

[0079] The first ultrasonic element 626 corresponds to the region where the third electrode 622, piezoelectric element 623, and fourth electrode 624 overlap in the Z direction. That is, the first ultrasonic element 626 is the active part of the piezoelectric element constituting the first element group 621. One first ultrasonic element 626 corresponds to one active part of the piezoelectric element constituting the first element group 621. Figure 9 As shown, the first ultrasonic element 626 is arranged in a matrix along the X and Y directions. Additionally, in Figure 9The diagram shows 12 first ultrasonic elements 626, and the first element group 621 preferably has hundreds of first ultrasonic elements 626 arranged in a matrix. By applying a voltage between the third electrode 622 and the fourth electrode 624, each first ultrasonic element 626 vibrates in the Z direction, transmitting a first ultrasonic wave of a first frequency. The first frequency is a frequency in the range of 1 MHz to 1000 MHz. The first frequency is preferably a frequency in the range of 1 MHz to 10 MHz. In this embodiment, the first frequency is 5 MHz. Furthermore, in... Figures 9 to 11 The wiring for applying voltage to the third electrode 622 and the fourth electrode 624 is omitted.

[0080] An insulating layer 625 is formed on the upper surface of the piezoelectric element, which is composed of a third electrode 622, a piezoelectric body 623, and a fourth electrode 624. The insulating layer 625 is formed, for example, from aluminum oxide or zirconium oxide.

[0081] In this embodiment, the second element group 631 is a piezoelectric element. The structure of the second element group 631 is the same as that of the first element group 621. Therefore, the description of the second element group 631 is omitted. The second ultrasonic element of the second element group 631 corresponds to the first ultrasonic element 626 of the first element group 621. By applying a voltage to the second element group 631 in the same manner as the first element group 621, the second ultrasonic element vibrates in the Z direction, and a second ultrasonic wave of a second frequency is emitted from the second ultrasonic element. The second frequency is lower than the first frequency and is a frequency in the range of 1MHz to 1000MHz. The second frequency is preferably a frequency in the range of 1MHz to 10MHz. In this embodiment, the second frequency is 1MHz.

[0082] like Figure 7 as well as Figure 8As shown, the first element group 621 and the second element group 631 extend along the Y direction, which is the first direction. The first element group 621 and the second element group 631 are alternately arranged along a second direction parallel to the spray surface 23, that is, orthogonal to the first direction. In this embodiment, the second direction is the X direction. In this embodiment, the ultrasonic device 620 has one first element group 621 and two second element groups 631. The first element group 621 and the second element group 631 are arranged in the +X direction in the order of second element group 631, first element group 621, and second element group 631. Alternatively, the first element group 621 and the second element group 631 may also be arranged in the +X direction in the order of first element group 621, second element group 631, and first element group 621. When the liquid nozzle 510 is covered with the cover 610, the first element group 621 and the second element group 631 are arranged on the inner surface 612 of the cover 610 such that the boundaries of the first element group 621 and the second element group 631 overlap with the nozzle array 25 when viewed from the Z direction. In other words, with the cover 610 covering the spray surface 23, when viewed from a direction orthogonal to the spray surface 23, the boundaries of the first element group 621 and the second element group 631 overlap with the nozzle array 25. The boundaries of the first element group 621 and the second element group 631 are straight lines along the first direction.

[0083] Figure 12 This is a flowchart illustrating a cleaning method for nozzle 21. First, in step S10, the ink inside nozzle 21 is discharged.

[0084] In step S20, cleaning fluid is supplied to the interior of nozzle 21. The cleaning fluid is supplied from cleaning fluid supply device 640 to the interior of nozzle 21 via piping (not shown). In step S20, preferably, the interior of nozzle 21 is filled with cleaning fluid.

[0085] In step S30, cleaning fluid is supplied from the cleaning fluid supply device 640 to the recess 611 of the cover 610. The cleaning fluid supply device 640 supplies cleaning fluid to the recess 611 of the cover 610 in such a way that the recess 611 is filled with cleaning fluid. At this time, it is preferable that the cleaning fluid supplied to the recess 611 forms a mountain shape due to surface tension. This is because, when the cover 610 is installed on the liquid nozzle 510, the generation of air bubbles between the cover 610 and the liquid nozzle 510 is suppressed.

[0086] In step S40, a cover 610 is installed on the liquid nozzle 510. The control unit 580 controls a cover moving mechanism (not shown) to move the cover 610, thereby installing the cover 610 on the liquid nozzle 510. Alternatively, the cover 610 can be installed on the liquid nozzle 510 by moving the liquid nozzle 510 while the cover 610 is in a fixed position.

[0087] In step S50, the control unit 580 drives the ultrasonic device 620 to transmit ultrasonic waves. Specifically, the control unit 580 drives at least one of the first element group 621 and the second element group 631. When driving the first element group 621, the control unit 580 applies a voltage based on a drive signal to the piezoelectric element 623 of the first element group 621, causing the first ultrasonic element 626 to vibrate and transmitting first ultrasonic waves from the first element group 621. When driving the second element group 631, the control unit 580 applies a voltage based on a drive signal to the piezoelectric element 623 of the second element group 631, causing the second ultrasonic element to vibrate and transmitting second ultrasonic waves from the second element group 631. Thus, the nozzle 21 is cleaned using ultrasonic waves to remove foreign matter adhering to the nozzle 21.

[0088] In this embodiment, the control unit 580 determines which of the first element group 621 and the second element group 631 to drive based on the type of ink used in the liquid nozzle 510 before cleaning the nozzle 21. For example, if UV ink or resin ink is used in the liquid nozzle 510, the control unit 580 drives the second element group 631. If water-based ink is used in the liquid nozzle 510, the control unit 580 drives the first element group 621. The control unit 580 retrieves the type of ink used in the liquid nozzle 510 before cleaning the nozzle 21 from the storage unit. Alternatively, the control unit 580 may also retrieve the type of ink input by the user to the liquid jetting device 500 as the type of ink used in the liquid nozzle 510 before cleaning the nozzle 21. The type and size of foreign matter adhering to the nozzle 21 vary depending on the type of ink used in the liquid nozzle 510. Therefore, the nozzle 21 can be effectively cleaned using ultrasonic waves of a frequency corresponding to the foreign matter adhering to the nozzle 21.

[0089] Furthermore, in step S50, the control unit 580 can drive the second element group 631 after driving the first element group 621, or drive the first element group 621 after driving the second element group 631. In this case, two different frequencies of ultrasonic waves can be used to clean the nozzle 21, thereby improving the removal performance of foreign matter adhering to the nozzle 21.

[0090] In step S60, the suction device 650 suctions the cleaning fluid in the recess 611 of the cover 610 and the nozzle 21.

[0091] In step S70, the cover 610 is removed from the liquid nozzle 510 by controlling the cover moving mechanism via the control unit 580. As described above, the nozzle 21 is cleaned.

[0092] Alternatively, during the cleaning of nozzle 21, cleaning fluid can be supplied to the interior of nozzle 21 or the recess 611 of cover 610 after cover 610 is installed on liquid nozzle 510. In this case, a unit such as a valve to release air from inside cover 610 to the outside is required. Furthermore, the cleaning unit 600 may also have a heating device for heating the cleaning fluid. The heating device may be installed on cover 610 or on cleaning fluid supply device 640.

[0093] According to the first embodiment described above, the cleaning unit 600 includes: a cover 610, disposed opposite to the spray surface 23 and covering the spray surface 23; and an ultrasonic device 620 disposed on the cover 610, which transmits ultrasonic waves to the liquid filled in the cover 610. The ultrasonic device 620 includes: a first element group 621 having a resonant frequency of a first frequency and arranging a plurality of first ultrasonic elements 626 that transmit the first ultrasonic waves at the first frequency; and a second element group 631 having a resonant frequency of a second frequency lower than the first frequency and arranging a plurality of second ultrasonic elements that transmit the second ultrasonic waves at the second frequency. The first element group 621 and the second element group 631 are alternately arranged along a second direction parallel to the spray surface 23. Therefore, even when foreign objects of different sizes or multiple foreign objects are attached to the nozzle 21, the performance of removing foreign objects attached to the nozzle 21 can be improved.

[0094] Furthermore, in this embodiment, with the cover 610 covering the spray surface 23, when viewed from a direction orthogonal to the spray surface 23, the boundaries of the first element group 621 and the second element group 631 overlap with the nozzle array 25. In this embodiment, the distance between the first element group 621 and the nozzle array 25 and the distance between the second element group 631 and the nozzle array 25 are equal, thus enabling the first ultrasonic wave and the second ultrasonic wave to reach the nozzle 21 in the same manner.

[0095] B. Second implementation method: In the second embodiment, the liquid nozzle 510 has a nozzle array 25. Furthermore, in the second embodiment, the structure of the ultrasonic device 620b differs from that in the first embodiment. The structure of the liquid jetting device 500, except for the number of nozzle arrays 25 in the liquid nozzle 510 and the structure of the ultrasonic device 620b, is the same as in the first embodiment.

[0096] Figure 13 This is a partial cross-sectional view of the liquid nozzle 510 and the cleaning unit 600 in the second embodiment, with the cover 610 installed on the liquid nozzle 510. Figure 13 The diagram shows a cross-sectional view of the nozzle plate 20b and a portion of the cleaning unit 600 cut off by a plane containing the nozzle 21 and orthogonal to the Y direction, which is the first direction. Figure 14This is a top view of the ultrasonic device 620b in the second embodiment.

[0097] In the second embodiment, the ultrasonic device 620b has a first element group 621 and a second element group 631. The first element group 621 and the second element group 631 are arranged in the +X direction in the order of first element group 621 and second element group 631. Alternatively, the first element group 621 and the second element group 631 may be arranged in the +X direction in the order of second element group 631 and first element group 621. When the liquid nozzle 510 is covered with the cover 610, the first element group 621 and the second element group 631 are arranged on the inner surface 612 of the cover 610 such that the boundaries of the first element group 621 and the second element group 631 overlap with the nozzle array 25 when viewed from the Z direction. In other words, when the cover 610 covers the spray surface 23, the boundaries of the first element group 621 and the second element group 631 overlap with the nozzle array 25 when viewed from a direction orthogonal to the spray surface 23. The boundaries of the first element group 621 and the second element group 631 are straight lines along the first direction. In this disclosure, "the first element group 621 and the second element group 631 are alternately arranged along the second direction" also includes the case where a first element group 621 and a second element group 631 are arranged along the second direction. That is, in the second embodiment, the first element group 621 and the second element group 631 are alternately arranged along the X direction, which is the second direction.

[0098] According to the second embodiment described above, the performance of removing foreign matter attached to the nozzle 21 can be improved in the same way as in the first embodiment.

[0099] C. Third implementation method: In the third embodiment, the liquid nozzle 510 has three nozzle rows 25. Furthermore, in the third embodiment, the structure of the ultrasonic device 620c differs from that of the first embodiment. The structure of each part of the liquid jetting device 500, except for the number of nozzle rows 25 in the liquid nozzle 510 and the structure of the ultrasonic device 620c, is the same as in the first embodiment.

[0100] Figure 15 This is a partial cross-sectional view of the liquid nozzle 510 and the cleaning unit 600 in the third embodiment, with the cover 610 installed on the liquid nozzle 510. Figure 15 The diagram shows a cross-sectional view of the nozzle plate 20c and a portion of the cleaning unit 600 cut off by a plane containing the nozzle 21 and orthogonal to the Y direction, which is the first direction. Figure 16 This is a top view of the ultrasonic device 620c in the third embodiment.

[0101] The first element group 621 and the second element group 631 are alternately arranged along the X direction, which is the second direction. In the third embodiment, the ultrasonic device 620b has two first element groups 621 and two second element groups 631. The first element groups 621 and the second element groups 631 are arranged in the +X direction in the order of first element group 621, second element group 631, first element group 621, second element group 631. Alternatively, the first element groups 621 and the second element groups 631 may be arranged in the +X direction in the order of second element group 631, first element group 621, second element group 631, first element group 621. When the liquid nozzle 510 is covered with the cover 610, the first element groups 621 and 631 are arranged on the inner surface 612 of the cover 610 such that the boundaries of the first element groups 621 and 631 overlap with the nozzle array 25 when viewed from the Z direction. In other words, with the cover 610 covering the spray surface 23, when viewed from a direction orthogonal to the spray surface 23, the boundaries of the first element group 621 and the second element group 631 overlap with the nozzle array 25. The boundaries of the first element group 621 and the second element group 631 are straight lines along the first direction.

[0102] According to the third embodiment described above, the performance of removing foreign matter attached to the nozzle 21 can be improved in the same way as in the first embodiment.

[0103] D. Fourth Implementation Method: In the fourth embodiment, the structure of the ultrasonic device 620d differs from that in the first embodiment. The structures of all parts of the liquid jetting device 500 other than the ultrasonic device 620d are the same as in the first embodiment.

[0104] Figure 17 This is a partial cross-sectional view of the liquid nozzle 510 and the cleaning unit 600 in the fourth embodiment, with the cover 610 installed on the liquid nozzle 510. Figure 17 The diagram shows a cross-sectional view of the nozzle plate 20 and a portion of the cleaning unit 600 cut off by a plane containing the nozzle 21 and orthogonal to the Y direction, which is the first direction. Figure 18 This is a top view of the ultrasonic device 620d in the fourth embodiment.

[0105] The first element group 621 and the second element group 631 are alternately arranged along the X direction, which is the second direction. In the fourth embodiment, the ultrasonic device 620d has two first element groups 621 and three second element groups 631. The first element groups 621 and the second element groups 631 are arranged in the +X direction in the order of second element group 631, first element group 621, second element group 631, first element group 621, and second element group 631. When the liquid nozzle 510 is covered with a cover 610, the first element group 621 is arranged on the inner surface 612 of the cover 610 in a manner that overlaps with the nozzle array 25 when viewed from the Z direction. One first element group 621 is located below one nozzle array 25. When the liquid nozzle 510 is covered with a cover 610, the second element group 631 is arranged on the inner surface 612 of the cover 610 in a manner that does not overlap with the nozzle array 25 when viewed from the Z direction. The second element group 631 is disposed between the two first element groups 621 in the X direction, at the +X direction end of the ultrasonic device 620d, and at the -X direction end of the ultrasonic device 620d. In other words, with the cover 610 covering the spray surface 23, when viewed from a direction orthogonal to the spray surface 23, the first element group 621 is disposed in the area overlapping with the nozzle array 25, and the second element group 631 is disposed in the area not overlapping with the nozzle array 25. The boundary between the first element group 621 and the second element group 631 is a straight line along the first direction.

[0106] In the fourth embodiment, the control unit 580 drives the first element group 621 in either a first driving mode or a second driving mode. In the first driving mode, the first element group 621 transmits a pulsed first ultrasonic wave, and in the second driving mode, the first element group 621 continuously transmits the first ultrasonic wave. The first driving mode is a mode in which the first element group 621 is used as a distance sensor. The first element group 621 transmits, for example, a pulse wave as a pulsed first ultrasonic wave. The first element group 621 is capable of receiving the reflected wave of the pulsed first ultrasonic wave transmitted by the first element group 621. The control unit 580 obtains information related to the reflected wave of the pulsed first ultrasonic wave from the first element group 621. The control unit 580 uses the information obtained from the first element group 621 to calculate the response time, which is the time from when the first element group 621 transmits the pulsed first ultrasonic wave to when the first element group 621 receives the reflected wave of the pulsed first ultrasonic wave. Furthermore, the control unit 580 uses the information obtained from the first element group 621 to calculate the intensity of the reflected wave of the pulsed first ultrasonic wave received by the first element group 621. Hereinafter, the reflected wave of the pulsed first ultrasonic wave transmitted by the first element group 621 will be referred to simply as the "reflected wave".

[0107] Figure 19 This is a diagram illustrating the relationship between the state of nozzle 21 and the waveform of the reflected wave. Figure 19In the above, (a) shows an example of the waveform of the reflected wave when the foreign object is not attached to the nozzle 21, (b) shows an example of the waveform of the reflected wave when the foreign object is attached to the vicinity of the nozzle opening 22, and (c) shows an example of the waveform of the reflected wave when the foreign object is attached to the inside of the nozzle 21. Figure 19 The horizontal axis represents the elapsed time since the first pulse-shaped ultrasonic wave was emitted from the first element group 621, and the vertical axis represents the intensity of the reflected wave.

[0108] As shown in (a), when no foreign matter adheres to the nozzle 21, the first element group 621 receives two reflected waves. The first reflected wave is a reflected wave generated by a first ultrasonic wave reflected from the liquid surface of the ink in standby mode inside the nozzle 21. The second reflected wave is a reflected wave generated by a first ultrasonic wave reflected from the pressure chamber 12. Hereinafter, the first reflected wave will also be referred to as the liquid surface reflected wave, and the second reflected wave will also be referred to as the pressure chamber reflected wave. Furthermore, the time from sending the pulsed first ultrasonic wave from the first element group 621 to receiving the liquid surface reflected wave is also called the response time of the liquid surface reflected wave, and the time from sending the pulsed first ultrasonic wave from the first element group 621 to receiving the pressure chamber reflected wave is also called the response time of the pressure chamber reflected wave. The response time of the pressure chamber reflected wave is longer than the response time of the liquid surface reflected wave.

[0109] When a foreign object adheres to the vicinity of the nozzle opening 22, the pulsed first ultrasonic wave transmitted from the first element group 621 is reflected near the nozzle opening 22. Therefore, as shown in (b), the response time when a foreign object adheres to the vicinity of the nozzle opening 22 is shorter than the response time of the liquid surface reflected wave. For example, a fragment of printing paper P can be cited as a foreign object adhering to the vicinity of the nozzle opening 22.

[0110] When a foreign object adheres to the inside of the nozzle 21, the pulsed first ultrasonic wave transmitted from the first element group 621 is reflected inside the nozzle 21. Therefore, as shown in (c), the response time when a foreign object adheres to the inside of the nozzle 21 is similar to the response time of the liquid surface reflection wave. Furthermore, the intensity of the reflected wave when a foreign object adheres to the inside of the nozzle 21 is greater than the intensity of the liquid surface reflection wave. Examples of foreign objects that can adhere to the inside of the nozzle 21 include, for example, cured ink.

[0111] Figure 20 This is a flowchart illustrating the cleaning method for nozzle 21 in the fourth embodiment. Furthermore, for parts that perform the same processing as the cleaning method for nozzle 21 in the first embodiment, the same reference numerals are used and descriptions are omitted.

[0112] In step S51, a cleaning process is performed. Figure 21This is a flowchart of the cleaning process in step S51. In step S110 of the cleaning process, the control unit 580 drives the first element group 621 in a first drive mode, sends a pulsed first ultrasonic wave from the first element group 621, and calculates the response time of the received reflected wave.

[0113] In step S120, the control unit 580 determines whether the response time is shorter than a predetermined first time T1. Here, as... Figure 19 As shown, the first time T1 is shorter than the response time of the reflected wave from the liquid surface. The first time T1 is pre-stored in the storage unit. Alternatively, the first time T1 can also be set by the user. If the response time is shorter than the first time T1, step S130 is executed. If the response time is longer than or equal to the first time T1, step S140 is executed.

[0114] In step S130, the control unit 580 drives the first element group 621 in a second drive mode. As described above, when the response time is shorter than the first time T1, it is predicted that foreign matter is attached near the nozzle opening 22. Fragments of printing paper P are easily attached near the nozzle opening 22. To remove fragments of printing paper P, etc., it is preferable to use ultrasonic waves with a higher frequency. Therefore, the control unit 580 drives the first element group 621 with a resonant frequency higher than that of the second element group 631. After executing step S130, the process returns to step S110.

[0115] In step S140, the control unit 580 determines whether the response time is shorter than a predetermined second time T2 and whether the intensity of the reflected wave is greater than a predetermined reference intensity. Here, as... Figure 19 As shown, the second time T2 is a time longer than the response time of the reflected wave from the liquid surface. The reference intensity is a preset value that is the same intensity as the reflected wave from the liquid surface. The second time T2 and the reference intensity are preset in the storage unit. Alternatively, the second time T2 and the reference intensity can also be set by the user. If the response time is shorter than the preset second time T2 and the intensity of the reflected wave is greater than the preset reference intensity, step S150 is executed. If the response time is greater than or equal to the preset second time T2, or the intensity of the reflected wave is less than or equal to the preset reference intensity, the cleaning process ends. The period between the first time T1 and the second time T2 is also referred to as the reference period.

[0116] In step S150, the control unit 580 drives the second element group 631. As described above, when the response time is greater than or equal to the first time T1 and shorter than the second time T2, and the intensity of the reflected wave is greater than the reference intensity, it is predicted that foreign matter is attached inside the nozzle 21. Cured ink or the like can easily adhere inside the nozzle 21. To remove the cured ink or the like, it is preferable to use ultrasound with a lower frequency. Therefore, the control unit 580 drives the second element group 631, whose resonant frequency is lower than that of the first element group 621. After executing step S150, the process returns to step S110. As explained above, a cleaning process is performed.

[0117] According to the fourth embodiment described above, with the cover 610 covering the spray surface 23, when viewed from a direction orthogonal to the spray surface 23, the first element group 621 is disposed in the area overlapping with the nozzle array 25, and the second element group 631 is disposed in the area not overlapping with the nozzle array 25. The frequency of the first ultrasonic wave is higher than the frequency of the second ultrasonic wave, and therefore it is prone to attenuation during propagation in the liquid. In this embodiment, the distance between the nozzle 21 and the first element group 621 is shorter than the distance between the nozzle 21 and the second element group 631, thus reducing the attenuation effect of the first ultrasonic wave before reaching the nozzle 21.

[0118] Furthermore, in this embodiment, the control unit 580 drives the first element group 621 in either a first drive mode or a second drive mode. In the first drive mode, the first element group 621 transmits pulsed first ultrasonic waves, and in the second drive mode, the first element group 621 continuously transmits first ultrasonic waves. Therefore, the first element group 621 can be used to estimate whether foreign objects are attached to the nozzle 21 and the location of the foreign objects attached to the nozzle 21.

[0119] Furthermore, in this embodiment, the control unit 580 drives the first element group 621 in a first drive mode, transmitting pulsed first ultrasonic waves from the first element group 621. If the response time is shorter than a predetermined first time T1, the control unit 580 drives the first element group 621 in a second mode. If the response time is greater than or equal to the first time T1 but shorter than the second time T2, and the intensity of the reflected wave is greater than a predetermined reference intensity, the control unit 580 drives the second element group 631. The second time T2 is a predetermined time longer than the first time T1. The response time and the intensity of the reflected wave vary depending on whether foreign matter is attached to the nozzle 21 and at what location on the nozzle 21. Foreign matter tends to adhere to different locations on the nozzle 21 depending on its type. Therefore, foreign matter attached to the nozzle 21 can be effectively removed.

[0120] E. Fifth implementation method: In the fifth embodiment, the liquid nozzle 510 has a nozzle array 25. Furthermore, in the fifth embodiment, the structure of the ultrasonic device 620e differs from that of the fourth embodiment. The structure of each part of the liquid jetting device 500, except for the number of nozzle arrays 25 in the liquid nozzle 510 and the structure of the ultrasonic device 620e, is the same as in the fourth embodiment. The cleaning method for the nozzle 21 in the fifth embodiment is the same as in the fourth embodiment.

[0121] Figure 22 This is a partial cross-sectional view of the liquid nozzle 510 and the cleaning unit 600 in the fifth embodiment, with the cover 610 installed on the liquid nozzle 510. Figure 22 The diagram shows a cross-sectional view of the nozzle plate 20e and a portion of the cleaning unit 600 cut off by a plane containing the nozzle 21 and orthogonal to the Y direction, which is the first direction. Figure 23 This is a top view of the ultrasonic device 620e in the fifth embodiment.

[0122] The first element group 621 and the second element group 631 are alternately arranged along the X direction, which is the second direction. In the fifth embodiment, the ultrasonic device 620d has one first element group 621 and two second element groups 631. The first element group 621 and the second element group 631 are arranged in the order of second element group 631, first element group 621, and second element group 631 facing the +X direction. When the liquid nozzle 510 is covered with the cover 610, the first element group 621 is arranged on the inner surface 612 of the cover 610 in a manner that overlaps with the nozzle array 25 when viewed from the Z direction. One first element group 621 is located below one nozzle array 25. When the liquid nozzle 510 is covered with the cover 610, the second element group 631 is arranged on the inner surface 612 of the cover 610 in a manner that does not overlap with the nozzle array 25 when viewed from the Z direction. The second element group 631 is arranged on both the +X direction side and the -X direction side of the first element group 621. In other words, with the cover 610 covering the spray surface 23, when viewed from a direction orthogonal to the spray surface 23, the first element group 621 is disposed in the area overlapping with the nozzle array 25, and the second element group 631 is disposed in the area not overlapping with the nozzle array 25. The boundary between the first element group 621 and the second element group 631 is a straight line along the first direction.

[0123] According to the fifth embodiment described above, the effect of the first ultrasonic wave attenuating before reaching the nozzle 21 can be reduced in the same way as in the fourth embodiment.

[0124] F. Other implementation methods: (F-1) In the first to third embodiments, when the cover 610 covers the spray surface 23, the boundaries of the first element group 621 and the second element group 631 overlap with the nozzle array 25 when viewed from a direction orthogonal to the spray surface 23. In the first embodiment, the liquid nozzle 510 has two nozzle arrays 25; in the second embodiment, the liquid nozzle 510 has one nozzle array 25; and in the third embodiment, the liquid nozzle 510 has three nozzle arrays 25. In contrast, when the cover 610 covers the spray surface 23, and the boundaries of the first element group 621 and the second element group 631 overlap with the nozzle array 25 when viewed from a direction orthogonal to the spray surface 23, the liquid nozzle 510 may also have four or more nozzle arrays 25.

[0125] (F-2) In the fourth and fifth embodiments, with the cover 610 covering the spray surface 23, when viewed from a direction orthogonal to the spray surface 23, the first element group 621 is disposed in the area overlapping with the nozzle array 25, and the second element group 631 is disposed in the area not overlapping with the nozzle array 25. In the fourth embodiment, the liquid nozzle 510 has two nozzle arrays 25, and in the fifth embodiment, the liquid nozzle 510 has one nozzle array 25. Conversely, in the case where, with the cover 610 covering the spray surface 23, when viewed from a direction orthogonal to the spray surface 23, the first element group 621 is disposed in the area overlapping with the nozzle array 25, and the second element group 631 is disposed in the area not overlapping with the nozzle array 25, the liquid nozzle 510 may also have three or more nozzle arrays 25.

[0126] (F-3) In the fourth and fifth embodiments, the control unit 580 drives the first component group 621 in either the first drive mode or the second drive mode. Alternatively, the control unit 580 may not drive the first component group 621 in the first drive mode. In this case, the cleaning process of the nozzle 21 is performed in the same manner as in the first embodiment.

[0127] (F-4) In the fourth and fifth embodiments, when the response time is shorter than a predetermined first time T1, the control unit 580 drives the first element group 621 in a second mode; when the response time is greater than or equal to the first time T1 but shorter than the second time T2, and the intensity of the reflected wave is greater than a predetermined reference intensity, the control unit 580 drives the second element group 631. The second time T2 is a predetermined time longer than the first time T1. Conversely, when the response time is shorter than the predetermined first time T1, the control unit 580 may not drive the first element group 621 in the second mode. Furthermore, when the response time is greater than or equal to the first time T1 but shorter than the second time T2, and the intensity of the reflected wave is greater than a predetermined reference intensity, the control unit 580 may not drive the second element group 631. The second time T2 is a predetermined time longer than the first time T1.

[0128] (F-5) In the above embodiment, the ultrasonic device 620 is a piezoelectric element. In contrast, the ultrasonic device 620 can be any device capable of generating ultrasonic waves, and is not limited to a piezoelectric element.

[0129] (F-6) In the above embodiment, the second direction is a direction parallel to the injection surface 23 and orthogonal to the first direction. In contrast, the second direction can be any direction parallel to the injection surface 23, or it can be a direction that is not orthogonal to the first direction.

[0130] G. Other methods: This disclosure is not limited to the embodiments described above, and can be implemented in various ways without departing from its spirit. For example, this disclosure can also be implemented in the following ways. In order to solve part or all of the technical problems of this disclosure, or to achieve part or all of the effects of this disclosure, the technical features in the above embodiments corresponding to the technical features in the various methods described below can be appropriately replaced or combined. In addition, if a technical feature is not described as an essential technical feature in this specification, it can be appropriately deleted.

[0131] (1) According to a first aspect of the present disclosure, a cleaning apparatus is provided. The cleaning apparatus includes: a liquid nozzle; and a cleaning unit disposed below the liquid nozzle, the liquid nozzle having: a piezoelectric element; a vibrating plate that vibrates by being driven by the piezoelectric element; a pressure chamber that applies pressure to liquid stored inside by the vibration of the vibrating plate; and a nozzle plate having at least one nozzle array, in which nozzles communicating with the pressure chamber and spraying the liquid are arranged along a first direction, the nozzle plate having a spray surface on its lower surface having nozzle openings of each of the nozzles, the cleaning unit having: a cover disposed opposite to the spray surface and covering the spray surface; and an ultrasonic device disposed on the cover and transmitting ultrasonic waves to liquid filled in the cover, the ultrasonic device having: a first element group having a resonant frequency of a first frequency and having a plurality of first ultrasonic elements arranged to transmit the first ultrasonic waves of the first frequency; and a second element group having a resonant frequency of a second frequency lower than the first frequency and having a plurality of second ultrasonic elements arranged to transmit the second ultrasonic waves of the second frequency, the first element group and the second element group being alternately arranged along a second direction parallel to the spray surface.

[0132] In this way, even when foreign objects of different sizes or multiple foreign objects are attached to the nozzle, the performance of removing foreign objects attached to the nozzle can be improved.

[0133] (2) In the above manner, the nozzle plate may also have a plurality of the nozzle rows.

[0134] (3) In the above manner, it is also possible that, when the cover covers the spray surface, the boundaries of the first element group and the second element group overlap with the nozzle array when viewed from a direction orthogonal to the spray surface.

[0135] In this manner, the distance between the first element group and the nozzle array is equal to the distance between the second element group and the nozzle array, thus enabling the first and second ultrasonic waves to reach the nozzle in the same way.

[0136] (4) In the above manner, it is also possible that, when the cover covers the spray surface, viewed from a direction orthogonal to the spray surface, the first element group is arranged in the area overlapping with the nozzle array, and the second element group is arranged in the area not overlapping with the nozzle array.

[0137] The first ultrasonic wave has a higher frequency than the second ultrasonic wave, and therefore attenuates more easily during propagation in the liquid. In this way, the attenuation of the first ultrasonic wave before it reaches the nozzle can be reduced.

[0138] (5) In the above-described manner, the cleaning device may also include a control unit that controls the ultrasonic device. The control unit drives the first element group in a first driving mode or a second driving mode. In the first driving mode, the first element group sends pulsed first ultrasonic waves. In the second driving mode, the first element group continuously sends the first ultrasonic waves.

[0139] In this way, by using the first set of elements, it is possible to estimate whether there are foreign objects attached to the nozzle and the location of the foreign objects attached to the nozzle.

[0140] (6) In the above method, the control unit may also drive the first element group in the first driving mode, such that the pulsed first ultrasonic wave is sent from the first element group. If the response time is shorter than a predetermined first time, the control unit drives the first element group in the second driving mode. The response time is the time from when the pulsed first ultrasonic wave is sent from the first element group to when the first element group receives the reflected wave of the pulsed first ultrasonic wave. If the response time is greater than the first time and shorter than the second time, and the intensity of the reflected wave is greater than a predetermined reference intensity, the control unit drives the second element group. The second time is a predetermined time longer than the first time.

[0141] The response time and the intensity of the reflected wave vary depending on whether foreign matter is attached to the nozzle and where it is located on the nozzle. Different types of foreign matter tend to adhere to different locations on the nozzle. In this way, foreign matter attached to the nozzle can be effectively removed.

Claims

1. A cleaning device, characterized in that, have: Liquid nozzles; and A cleaning unit is located below the liquid nozzle. The liquid nozzle has: piezoelectric elements; The vibrating plate vibrates under the drive of the piezoelectric element; The pressure chamber applies pressure to the liquid stored inside through the vibration of the vibrating plate. as well as A nozzle plate having at least one nozzle array, wherein nozzles communicating with the pressure chamber and ejecting the liquid are arranged along a first direction. The nozzle plate has a spray surface on its lower surface, on which nozzle openings for each of the nozzles are formed. The cleaning unit includes: A cover, configured opposite to the spray surface, covers the spray surface; and An ultrasonic device, disposed in the cover, transmits ultrasonic waves to the liquid filling the cover. The ultrasonic device comprises: A first element group, having a resonant frequency of a first frequency, and arranged with a plurality of first ultrasonic elements for transmitting a first ultrasonic wave at the first frequency; and The second element group has a resonant frequency that is lower than the first frequency, and is composed of multiple second ultrasonic elements that transmit second ultrasonic waves at the second frequency. The first element group and the second element group are alternately arranged along a second direction parallel to the jet surface.

2. The cleaning device according to claim 1, characterized in that, The nozzle plate has a plurality of the nozzle rows.

3. The cleaning device according to claim 1, characterized in that, With the cover covering the spray surface, when viewed from a direction orthogonal to the spray surface, the boundaries of the first element group and the second element group overlap with the nozzle array.

4. The cleaning device according to claim 1, characterized in that, With the cover covering the spray surface, when viewed from a direction orthogonal to the spray surface, the first element group is arranged in the area overlapping with the nozzle array, and the second element group is arranged in the area not overlapping with the nozzle array.

5. The cleaning device according to claim 4, characterized in that, The cleaning device includes a control unit for controlling the ultrasonic device. The control unit drives the first component group in a first driving mode or a second driving mode. In the first driving mode, the first component group sends pulsed first ultrasonic waves. In the second driving mode, the first component group continuously sends the first ultrasonic waves.

6. The cleaning apparatus according to claim 5, characterized in that, The control unit drives the first component group in the first driving mode, causing the pulsed first ultrasonic wave to be transmitted from the first component group. If the response time is shorter than a predetermined first time, the control unit drives the first element group in the second drive mode. The response time is the time from when the first element group sends the pulsed first ultrasonic wave to when the first element group receives the reflected wave of the pulsed first ultrasonic wave. When the response time is greater than or equal to the first time but less than the second time, and the intensity of the reflected wave is greater than a predetermined reference intensity, the control unit drives the second element group, where the second time is a predetermined time longer than the first time.

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