Liquid ejection apparatus, liquid ejection method, and program

Abstract

The present disclosure is to provide a liquid ejection apparatus capable of reducing coating unevenness. A liquid ejection apparatus according to one aspect of the present disclosure is configured to eject a liquid to apply the liquid to an object, the liquid ejection apparatus comprising: a head including a nozzle row in which a plurality of nozzles, each configured to eject the liquid, are arranged at a predetermined nozzle pitch along a sub-scanning direction; and a variable mechanism configured to change a relative position between the head and the object in a main scanning direction orthogonal to the sub-scanning direction, wherein an ejection amount of the liquid ejected from the head periodically changes according to a position in the sub-scanning direction, and wherein a wavelength of the periodic change in the ejection amount according to the position in the sub-scanning direction is shorter than the nozzle pitch.

Description

LIQUID EJECTION APPARATUS, LIQUID EJECTION METHOD, AND PROGRAM

[0001] The present disclosure relates to a liquid ejection apparatus, a liquid ejection method, and a program.

[0002] Conventionally, a liquid ejection apparatus that ejects liquid from a head and applies the liquid to an object has been known.

[0003] For example, Patent Document 1 discloses a liquid ejection apparatus that ejects liquid droplets from a head having a nozzle array in which a plurality of nozzles for ejecting liquid droplets are arranged, and forms an image including dot rows constituted by dots arranged continuously. The liquid ejection apparatus combines dots of a predetermined size and dots smaller than the predetermined size to form a constriction in the dot rows in a direction orthogonal to the nozzle array of the head.

[0004] [PTL 1] Japanese Unexamined Patent Application Publication No. 2008-213427

[0005] An object of the present disclosure is to provide a liquid ejection apparatus capable of reducing coating unevenness.

[0006] A liquid ejection apparatus according to one aspect of the present disclosure is a liquid ejection apparatus that ejects liquid and applies the liquid to an object, the liquid ejection apparatus including:

[0007] a head including a nozzle array in which a plurality of nozzles, each of which ejects the liquid, are arranged at a predetermined nozzle pitch along a sub-scanning direction; and

[0008] a variable mechanism that changes a relative position between the head and the object in a main scanning direction orthogonal to the sub-scanning direction,

[0009] wherein an ejection amount of the liquid ejected from the head periodically varies according to a position in the sub-scanning direction, and

[0010] wherein a wavelength of the periodic variation of the ejection amount according to the position in the sub-scanning direction is shorter than the nozzle pitch.Advantageous Effect of Invention

[0011] According to the present disclosure, it is possible to provide a liquid ejection apparatus capable of reducing coating unevenness.

[0012] FIG. 1 is a schematic diagram illustrating an overall configuration of a liquid ejection apparatus according to a first embodiment.FIG. 2 is a schematic perspective view illustrating a configuration of a head included in the liquid ejection apparatus according to the first embodiment.FIG. 3 is a schematic cross-sectional view illustrating the configuration of the head included in the liquid ejection apparatus according to the first embodiment.FIG. 4 is a schematic plan view illustrating the configuration of the head included in the liquid ejection apparatus according to the first embodiment.FIG. 5 is a schematic diagram illustrating a configuration of a supply unit included in the liquid ejection apparatus according to the first embodiment.FIG. 6 is a block diagram illustrating a hardware configuration of the liquid ejection apparatus according to the first embodiment.FIG. 7 is a block diagram illustrating a functional configuration of a controller included in the liquid ejection apparatus according to the first embodiment.FIG. 8A is a diagram illustrating a state in which the head included in the liquid ejection apparatus according to the first embodiment is not rotating, and a shape of a coating film surface.FIG. 8B is a diagram illustrating a state in which the head included in the liquid ejection apparatus according to the first embodiment is rotating, and the shape of the coating film surface.FIG. 9A is a diagram illustrating a relationship between shear rate applied to a liquid that has landed on an object and viscosity.FIG. 9B is a diagram illustrating a relationship between elapsed time after landing of the liquid on the object and viscosity.FIG. 10 is a diagram illustrating a model of shear stress applied when the liquid that has landed on the object is leveling.FIG. 11A is a diagram illustrating a relationship between a rotational wavelength and a half-amplitude period in periodic changes of the coating film surface shape with respect to positions in a sub-scanning direction.FIG. 11B is a diagram illustrating a relationship between the rotational wavelength and shear stress applied to the liquid in the periodic changes of the coating film surface shape according to positions in the sub-scanning direction.FIG. 12 is a diagram illustrating a state in which the head included in the liquid ejection apparatus according to the first embodiment is rotating, droplets formed by liquid ejected from the head, and the shape of the coating film surface.FIG. 13A is a diagram illustrating a change in an ejection amount of liquid by a frequency-based method in the liquid ejection apparatus according to the first embodiment.FIG. 13B is a diagram illustrating a change in an ejection amount of liquid by a ratio-based method in the liquid ejection apparatus according to the first embodiment.FIG. 14 is a flowchart illustrating a method of generating coating command data by the liquid ejection apparatus according to the first embodiment.FIG. 15 is a schematic diagram illustrating a configuration of a liquid ejection apparatus according to a second embodiment.

[0013] Hereinafter, a liquid ejection apparatus, a liquid ejection method, and a program according to embodiments of the present disclosure will be described in detail with reference to the drawings. However, the embodiments described below are examples of a liquid ejection apparatus, a liquid ejection method, and a program that embody the technical idea of the embodiments of the present disclosure, and the present disclosure is not limited thereto. In addition, the sizes, positional relationships, and the like of members shown in the drawings may be exaggerated for clarity of explanation. Further, in the following description, members having the same names and reference numerals indicate the same or similar members, and detailed descriptions thereof will be omitted as appropriate.

[0014] In each drawing, an orthogonal coordinate system having an X-axis, a Y-axis, and a Z-axis is used as directional expressions. The X-axis, the Y-axis, and the Z-axis are orthogonal to each other. An X-direction along the X-axis corresponds to a sub-scanning direction. A Y-direction along the Y-axis corresponds to a main scanning direction. A Z-direction along the Z-axis corresponds to an ejection direction. In the present specification, the X-direction is referred to as a sub-scanning direction X, the Y-direction is referred to as a main scanning direction Y, and the Z-direction is referred to as an ejection direction Z. A direction indicated by an arrow in the X-direction is referred to as a ＋X side, and a direction opposite to the ＋X side is referred to as a －X side. A direction indicated by an arrow in the Y-direction is referred to as a ＋Y side, and a direction opposite to the ＋Y side is referred to as a －Y side. A direction indicated by an arrow in the Z-direction is referred to as a ＋Z side, and a direction opposite to the ＋Z side is referred to as a －Z side. The liquid ejection apparatus according to the embodiment ejects liquid in the ＋Z direction.

[0015] In the present specification, “along the X-axis, the Y-axis, and the Z-axis” includes a case in which an object has an inclination within a range of ±20° with respect to these axes. The term “disposed” is not limited to direct contact, and also includes indirect disposition, for example, disposition via another member.First Embodiment

[0016] Configuration of the Liquid Ejecting Device According to the First Embodiment Overall Configuration

[0017] FIG. 1 is a schematic diagram illustrating an overall configuration of a liquid ejection apparatus 100 according to a first embodiment.

[0018] The liquid ejection apparatus 100 is an apparatus that ejects liquid and applies the liquid to an object 200. As illustrated in FIG. 1, the liquid ejection apparatus 100 includes four liquid ejection units 10 (10-1, 10-2, 10-3, and 10-4) that eject liquid toward the object 200, and a control unit 20 that controls operations of the liquid ejection units 10. The four liquid ejection units 10 are disposed around the object 200. Each of the four liquid ejection units 10 includes a head 11 having nozzle arrays in which a plurality of nozzles are arranged, a detector 12 that detects a relative position between the liquid ejection unit 10 and the object 200, and a robot arm 13 that changes the relative position between the liquid ejection unit 10 and the object 200.

[0019] A coating surface 210 is a surface of the object 200 that is coated by the liquid ejection apparatus 100. The coating surface 210 illustrated in FIG. 1 includes a three-dimensional curved surface. The head 11 ejects liquid from nozzles provided on a nozzle surface toward the coating surface 210. The control unit 20 controls operations of each of the head 11 and the robot arm 13.

[0020] The liquid ejection apparatus 100 can coat the coating surface 210 by applying liquid ejected from the head 11 to the coating surface 210. The object 200 is a body of a vehicle, an aircraft, a ship, or the like. The vehicle includes an automobile, a truck, a train, and the like. In the example illustrated in FIG. 1, the object 200 is an automobile body.

[0021] The heads 11 (11-1, 11-2, 11-3, and 11-4) are attached to distal ends of the robot arms 13. Each head 11 is moved relative to the object 200 by the robot arm 13, and applies liquid ejected from the nozzles to the object 200.

[0022] The robot arm 13 moves the head 11 relative to the object 200. In the example illustrated in FIG. 1, the robot arm 13 moves the head 11 along a surface of the object 200, thereby moving the head 11 relative to the object 200. The robot arm 13 is an example of a variable mechanism that changes a relative position between the head 11 and the object 200 in the main scanning direction Y orthogonal to the sub-scanning direction X. In the example illustrated in FIG. 1, the robot arm 13 is capable of changing the relative position between the head 11 and the object 200 in each of the main scanning direction Y and the sub-scanning direction X.

[0023] The detectors 12 (12-1, 12-2, 12-3, and 12-4) are attached to the distal ends of the robot arms 13. Each detector 12 detects three or more feature points on the object 200 and outputs feature point information relating to three-dimensional positions of the feature points. Each detector 12 includes a stereo camera. However, the detector 12 is not limited to a stereo camera, and may include a three-dimensional sensor other than a stereo camera, a laser displacement meter, or the like.

[0024] In the example illustrated in FIG. 1, the detector 12 can measure a position of the head 11 or an inclination of the coating surface 210, and detect a coating start position on the coating surface 210 or a size of the object 200, by using a stereo camera. The stereo camera includes a plurality of cameras. The stereo camera acquires a distance image of the object 200 by a triangulation method based on parallax between images captured by the plurality of cameras. The distance image is an image in which luminance values of pixels constituting the image represent distances at positions of the respective pixels. The stereo camera outputs the distance image to the control unit 20 as feature point information.

[0025] The robot arms 13 (13-1, 13-2, 13-3, and 13-4) include links and joints. The robot arms 13 rotate or displace the links and joints to change a relative position and a relative inclination between the head 11 and the object 200, thereby allowing a nozzle surface of the head 11 to face the object 200.

[0026] The control unit 20 drives the robot arms 13 holding the four heads 11 based on predetermined shape data of the object 200 and feature point information relating to three-dimensional positions of three or more feature points output from each of the four detectors 12. The liquid ejection apparatus 100 applies liquid ejected from the four heads 11 to the object 200.

[0027] The liquid ejection apparatus 100 may further include a supply unit and a maintenance unit, in addition to the configuration illustrated in FIG. 1. The supply unit supplies liquid to be ejected toward the object 200 to each of the four heads 11. The maintenance unit removes thickened liquid or foreign matter adhering to the nozzle surfaces of the heads 11, or thickened liquid or foreign matter present inside the heads 11. By removing thickened liquid or foreign matter by the maintenance unit, the liquid ejection apparatus 100 can reduce ejection abnormalities such as non-ejection, ejection deviation, and variation in ejection speed at the heads 11, and can maintain normal ejection states of the heads 11.

[0028] The object 200 is conveyed by a conveying unit such as a belt conveyor and is placed at a predetermined coating position. The liquid ejection apparatus 100 coats the object 200 placed and stopped at the coating position by relatively moving the head 11 by the robot arm 13. After completion of coating, the liquid ejection apparatus 100 stops the coating operation. The object 200 after completion of coating is conveyed from the coating position to the outside by the conveying unit. After the coated object 200 is conveyed away, a next object 200 is conveyed to the coating position by the conveying unit. The liquid ejection apparatus 100 coats the next object 200 placed and stopped at the coating position. In this manner, the liquid ejection apparatus 100 can repeatedly coat objects 200 placed at the coating position. Head 11

[0029] With reference to FIGS. 2 to 4, a configuration of the head 11 included in the liquid ejection apparatus 100 will be described. FIG. 2 is a schematic perspective view illustrating a configuration of the head 11. FIG. 3 is a schematic cross-sectional view illustrating the configuration of the head 11. FIG. 4 is a schematic plan view illustrating the configuration of the head 11.

[0030] As illustrated in FIGS. 2 and 3, the head 11 includes a supply port 111, a collection port 112, and an ejection module 340. FIG. 3 illustrates a cross section of the head 11 taken along a plane S1 illustrated in FIG. 2.

[0031] The supply port 111 supplies externally pressurized liquid to the ejection module 340. The collection port 112 discharges, to the outside, liquid that is not ejected when a valve of the nozzle 311, which will be described later, is opened.

[0032] The ejection module 340 includes a housing 110, a nozzle plate 321 including nozzles 311, a liquid flow path 322, a valve 310, and a piezoelectric element 324.

[0033] The nozzle plate 321 is joined to the housing 110 and ejects liquid supplied from the supply port 111 through the nozzles 311. A nozzle surface 320 is a surface of the nozzle plate 321 that faces the object 200 during coating. The liquid flow path 322 is a common flow path for a plurality of ejection modules 340 (eight ejection modules in FIG. 3) provided in the housing 110.

[0034] The valve 310 is a needle-shaped valve body. The valve 310 is driven by the piezoelectric element 324 and reciprocates within the housing 110 in the liquid ejection direction Z, thereby opening and closing the nozzle 311. The head 11 supplies pressurized liquid from the supply port 111 through the liquid flow path 322 in a state in which a valve of the collection port 112 is closed. When the valve 310 is located at a position at which the nozzle 311 is closed, the nozzle 311 does not eject liquid. On the other hand, when the piezoelectric element 324 is driven to raise the valve 310, the valve of the nozzle 311 is opened, and liquid is ejected from the nozzle 311.

[0035] FIG. 4 illustrates the head 11 as viewed from the ＋Z direction. As illustrated in FIG. 4, in the present embodiment, the head 11 includes a nozzle array 315 in which a plurality of nozzles 311, each of which ejects liquid, are arranged at a predetermined nozzle pitch P along the sub-scanning direction X.

[0036] In the example illustrated in FIG. 4, four heads 11 arranged in the main scanning direction Y are illustrated. Each of the four heads 11 includes the nozzle surface 320 and the nozzle array 315 including four nozzles 311 provided at the nozzle surface 320. The four nozzles 311 included in the nozzle array are arranged along the sub-scanning direction X.

[0037] The four heads 11 are disposed with their positions slightly different from each other in the sub-scanning direction X such that, when the heads 11 move relative to the object 200 in the main scanning direction Y, liquid can be ejected in the sub-scanning direction X at intervals shorter than the nozzle pitch P. However, the number of heads 11 is not limited to four. The number of nozzles 311 included in the nozzle array 315 is not limited to four. The head 11 may include one nozzle array 315 or two or more nozzle arrays 315. Further, the four heads 11 do not necessarily have to be disposed at mutually different positions in the sub-scanning direction X. Supply Unit 14

[0038] FIG. 5 is a diagram illustrating one configuration example of a supply unit 14 included in the liquid ejection apparatus 100. In FIG. 5, the supply unit 14 includes liquid tanks 330 (330-1, 330-2, 330-3, and 330-4) as sealed containers that store liquid 325 to be ejected from the heads 11. Each liquid tank 330 and an inlet (supply port 111) of a corresponding head 11 are connected so that liquid can flow therebetween via a tube 333.

[0039] Each liquid tank 330 is connected to a compressor 230 via a pipe 331 including an air regulator 332, and the compressor 230 supplies pressurized air. Accordingly, the pressurized liquid 325 is supplied to the inlet of the head 11, and the liquid ejection apparatus 100 ejects the liquid 325 from the nozzles of the head 11.

[0040] The liquid tanks 330 do not necessarily have to be provided for each head 11, and liquid may be supplied to all of the heads 11 from a single liquid tank 330. Hardware Configuration

[0041] FIG. 6 is a block diagram illustrating a hardware configuration of the liquid ejection apparatus 100. As illustrated in FIG. 6, the liquid ejection apparatus 100 includes a controller 901, a head control device 902, a robot control device 904, and liquid ejection units 10. The liquid ejection apparatus 100 is communicatively connected to a PC (Personal Computer) 903. In FIG. 6, among four liquid ejection units 10, only liquid ejection units 10-1 and 10-2 are illustrated. Each of the liquid ejection units 10-1 and 10-2 includes an encoder sensor 109 and a robot drive unit 72.

[0042] The controller 901 includes a CPU (Central Processing Unit) 9001, a ROM (Read Only Memory) 9002, a RAM (Random Access Memory) 9003, and an I / F (Interface) 9004. The controller 901, the head control device 902, and the robot control device 904 constitute a control unit 20.

[0043] The controller 901 is communicatively connected to the PC 903. The CPU 9001 is a processing unit or a processor that implements various functions of the liquid ejection apparatus 100 by reading programs or data stored in the ROM 9002 or the like into the RAM 9003 and executing processing. The ROM 9002 is a nonvolatile memory capable of retaining programs or data even when power is turned off. The RAM 9003 is a volatile memory used as a work area for the CPU 9001 or the like. The I / F 9004 is an interface for inputting and outputting characters, numerical values, various instructions, and the like to and from various external devices. The I / F 9004 is an interface that enables communication between the controller 901 and external devices such as the PC 903.

[0044] The robot arm 13 is, for example, a multi-joint robot. The encoder sensor 109 optically detects slits of encoders provided at joints or the like of the robot arm 13. The encoder sensor 109 acquires position information of the head 11 based on an amount of rotation of the robot arm 13.

[0045] The head control device 902 receives an ejection cycle signal from the controller 901 and controls a liquid ejection operation of the head 11 based on the ejection cycle signal. The robot control device 904 receives a synchronization control signal from the controller 901 and controls driving of the robot drive unit 72 based on the synchronization control signal. By controlling driving of the robot drive unit 72, the robot arm 13 and the head 11 are relatively moved to desired positions.

[0046] The head 11 ejects liquid in response to a drive signal from the head control device 902. The detector 12 transmits detection results of the object 200 to the PC 903. The robot drive unit 72 moves the robot arm 13, the head 11, and the like to desired positions in response to a drive signal from the robot control device 904. In this example, the head control device 902 and the robot control device 904 are shared by the liquid ejection units 10-1 and 10-2; however, the head control device 902 and the robot control device 904 may be provided for each of the liquid ejection units 10-1 and 10-2.

[0047] The PC 903 includes an RIP (Raster Image Processor) unit 9031 as a functional configuration. The RIP unit 9031 performs image processing according to a color profile or user settings.

[0048] The PC 903 is connected to an input device 9033 for setting image data and coordinate data, selecting a coating mode, setting a coating range (a coating start position and a coating end position), and issuing coating instructions. The input device 9033 includes a keyboard, a mouse, a touch panel, and the like, and receives input from a user. The PC 903 also acquires position data from the detector 12 in each of the liquid ejection units 10-1 and 10-2, and performs processing such as creating a coating route for relatively moving the head 11 by the robot arm 13. Functional Configuration of Controller 901

[0049] FIG. 7 is a block diagram illustrating a functional configuration of the controller 901. The controller 901 includes a system control unit 9011, an ejection cycle signal generator 9014, a memory control unit 9013, a data storage unit 9012, a synchronization control unit 9015, a rendering unit 9016, a wavelength determination unit 9017, and a scheme selection unit 9018. Note that the controller 901 may include the RIP unit 9031 included in the PC 903, instead of the PC 903 illustrated in FIG. 6.

[0050] The controller 901 implements each function of the controller 901 by executing instruction codes stored in a memory by means of electronic circuitry. Alternatively, the controller 901 may implement each function included in the controller 901 by executing various processes using electronic circuitry designed for a specific purpose. The electronic circuitry is, for example, the CPU 9001 described above. The electronic circuitry may include an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or the like.

[0051] Functions of the system control unit 9011, the ejection cycle signal generator 9014, the memory control unit 9013, the synchronization control unit 9015, the rendering unit 9016, the wavelength determination unit 9017, and the scheme selection unit 9018 are implemented by, for example, the CPU 9001 executing instruction codes stored in the ROM 9002. The function of the data storage unit 9012 is implemented by the ROM 9002 and the RAM 9003. The data storage unit 9012 may be implemented by an HDD (Hard Disk Drive), an SSD (Solid State Drive), or the like.

[0052] Some of the functions of the controller 901 may be implemented by devices other than the controller 901. Further, some of the functions of the controller 901 may be implemented by distributed processing between the controller 901 and devices other than the controller 901. The devices other than the controller 901 include, for example, the PC 903 or an external server communicatively connected to the controller 901.

[0053] The system control unit 9011 controls overall operations of the liquid ejection apparatus 100 using image data or instructions received from the PC 903. The data storage unit 9012 stores image data received from the PC 903, coating range (coating target size) data, and the like. The memory control unit 9013 controls the data storage unit 9012. The ejection cycle signal generator 9014 generates an ejection cycle signal based on an output signal of the encoder sensor 109 and information indicating a resolution of image data received from the PC 903. The ejection cycle signal generator 9014 transmits the generated ejection cycle signal to the head control device 902.

[0054] The synchronization control unit 9015 synchronizes an operation of the robot arm 13 with an ejection operation of the head 11 based on image data, a coating instruction, and the like received from the PC 903. The synchronization control unit 9015 transmits a synchronization control signal to the robot control device 904. By the CPU 9001 functioning as the memory control unit 9013 executing a program recorded in advance as stored data, functions of the controller 901 are implemented. The rendering unit 9016 decomposes image data, which is information relating to coating to be applied to the object 200, into coating data for each relative movement of the head 11 in the main scanning direction, for example.

[0055] The wavelength determination unit 9017 determines a wavelength of a periodic change in an ejection amount according to a position in the sub-scanning direction X, which will be described later, according to a type of liquid ejected from the head 11. The wavelength determination unit 9017 provides information regarding the determined wavelength to the system control unit 9011.

[0056] As will be described later, the head 11 is capable of executing the following three ejection amount variation schemes for liquid. Specifically, the head 11 can execute a volume-based method in which a volume per droplet of a liquid droplet formed by liquid ejected from the nozzle 311 of the head 11 is varied according to a position in the sub-scanning direction X. The head 11 can also execute a frequency-based method in which an ejection frequency of liquid is varied according to a position in the sub-scanning direction X. Further, the head 11 can execute a ratio-based method in which a ratio of the number of nozzles 311 that eject liquid to the number of nozzles 311 that do not eject liquid among a plurality of nozzles 311 is varied according to a position in the sub-scanning direction X. The scheme selection unit 9018 selects one of the volume-based method, the frequency-based method, or the ratio-based method according to a type of liquid. The scheme selection unit 9018 provides information regarding the selected method to the system control unit 9011. Operation of Liquid Ejection Apparatus 100 Relationship Between Rotation of Head 11 and Shape of Coating Film Surface

[0057] First, with reference to FIGS. 8A and 8B, a relationship between rotation of the head 11 and a shape of a coating film surface will be described. FIG. 8A illustrates a state in which the head 11 is not rotated and a shape of a coating film surface 211a. FIG. 8B illustrates a state in which the head 11 is rotated and a shape of the coating film surface 211a.

[0058] The coating film surface 211a refers to a surface of a coating film 211 formed by liquid ejected from the head 11 and landed on the object 200. In the examples illustrated in FIGS. 8A and 8B, the coating film surface 211a is a surface on a －Z side of the coating film 211. FIG. 8A illustrates the head 11 in a non-rotated state and the coating film surface 211a of the coating film 211 formed by liquid ejected from the head 11 in this state and landed on the object 200. FIG. 8B illustrates the head 11 in a rotated state and the coating film surface 211a of the coating film 211 formed by liquid ejected from the head 11 in this state and landed on the object 200.

[0059] FIGS. 8A and 8B each illustrate the head 11 as viewed from the ＋Z direction and the coating film surface 211a as viewed from the ＋Y direction. A rotation center 11C illustrated in FIGS. 8A and 8B represents a rotation center of the head 11. The four heads 11 illustrated in FIGS. 8A and 8B can rotate integrally about the rotation center 11C, for example, in a direction indicated by arrow B1 in FIG. 8B. When the head 11 rotates, positions of the nozzles 311 deviate from desired positions.

[0060] As illustrated in FIG. 8A, when the head 11 is not rotated, the nozzles 311 do not deviate from the desired positions. Therefore, pitches in the sub-scanning direction X of four liquids ejected from the respective four nozzles 311 arranged along the sub-scanning direction X become substantially equal to the predetermined nozzle pitch P. Since the pitches in the sub-scanning direction X of the four liquids are substantially equal to the nozzle pitch P, the coating film surface 211a immediately after formation of the coating film 211 becomes substantially flat.

[0061] On the other hand, as illustrated in FIG. 8B, when the head 11 is in a rotated state, the nozzles 311 deviate from the desired positions according to a rotation angle. As a result, pitches in the sub-scanning direction X of four liquids ejected from the respective four nozzles 311 arranged along the sub-scanning direction X deviate from the nozzle pitch P. Consequently, a shape of the coating film surface 211a periodically varies in the sub-scanning direction X. A rotation wavelength λ0, which is a wavelength of periodic variation in the shape of the coating film surface 211a corresponding to rotation of the head 11, is substantially equal to the nozzle pitch P. Relationship Between Shear Rate Applied to Liquid and Viscosity of Liquid

[0062] FIG. 9A is a diagram illustrating a relationship between a shear rate applied to a liquid that has landed on an object 200 and a viscosity of the liquid. FIG. 9B is a diagram illustrating a relationship between an elapsed time after landing of the liquid on the object 200 and the viscosity of the liquid.

[0063] In coating, non-Newtonian fluids such as water-based paints are often used. FIGS. 9A and 9B illustrate, for a liquid that is a non-Newtonian fluid, a relationship between a shear rate applied to the liquid and the viscosity, and a relationship between an elapsed time after landing of the liquid and the viscosity. In FIGS. 9A and 9B, time t0 represents a time immediately after the liquid lands on the object 200.

[0064] In a non-Newtonian fluid, immediately after being ejected from the head 11, a shear stress applied to the liquid is large, and therefore the viscosity of the liquid is low. As illustrated in FIGS. 9A and 9B, as time elapses from time t0 immediately after the liquid ejected from the head 11 lands on the object 200, the viscosity increases. FIG. 9A illustrates that the shear rate changes in a direction indicated by arrow B2 from time t0 and the viscosity increases. FIG. 9B illustrates that the elapsed time increases in a direction indicated by arrow B3 from time t0 and the viscosity increases.

[0065] The non-Newtonian fluid liquid that has landed on the object 200 gradually increases in viscosity while spreading and wetting the object 200, and eventually hardens. When the liquid hardens, the shape of the coating film surface 211a is maintained. If a period during which the viscosity of the liquid remains low after landing on the object 200 is long, the liquid spreads and wets the object 200 and becomes flattened, that is, leveled, whereby a flat coating film surface 211a is obtained. On the other hand, if the viscosity of the liquid rapidly increases after landing on the object 200, the liquid hardens before spreading and wetting to be leveled on the object 200, and a flat coating film surface 211a cannot be obtained. For example, when the viscosity of the liquid rapidly increases, the coating film surface 211a may have a periodically varying shape.

[0066] FIG. 10 is a diagram illustrating a model of shear stress applied when the liquid that has landed on the object 200 is leveling. In FIG. 10, a shape wavelength λ1 represents a wavelength of a periodic change in the shape of the coating film surface 211a. A shear stress τ represents a shear stress applied to the liquid that has landed on the object 200. An average film thickness h represents an average thickness of the coating film 211 that varies according to the shape of the coating film surface 211a.

[0067] A half-amplitude period t1 / 2, which is a period during which an amplitude of a periodic change in a shape of the coating film surface 211a becomes half, can be expressed by the following equation (1):Math 1

[0068] Further, the shear stress τ can be expressed by the following equation (2):Math 2

[0069] FIG. 11A is a diagram illustrating a relationship between a shape wavelength λ1 and a half-amplitude period t1 / 2in a periodic change in a shape of the coating film surface 211a depending on a position in the sub-scanning direction X. FIG. 11B is a diagram illustrating a relationship between the shape wavelength λ1 and the shear stress τ applied to the liquid in the periodic change in the shape of the coating film surface 211a depending on the position in the sub-scanning direction X.

[0070] As illustrated in FIG. 11A, as the shape wavelength λ1 increases, the half-amplitude period t1 / 2increases exponentially. As illustrated in FIG. 11B, as the shape wavelength λ1 increases, the shear stress τ decreases exponentially. The relationships illustrated in FIGS. 11A and 11B can be explained based on the model illustrated in FIG. 10 and equations (1) and (2), respectively.

[0071] From FIGS. 11A and 11B, the following (A) and (B) can be stated. (A) As the shape wavelength λ1 becomes shorter, a higher shear stress is applied, and a period during which the viscosity remains low becomes shorter. (B) As the shape wavelength λ1 becomes longer, a lower shear stress is applied, and a period during which the viscosity remains low becomes longer.

[0072] Based on the above (A) and (B), it is considered that by ejecting the liquid from the head 11 so as to obtain a shape of the coating film surface 211a in which shapes having a long shape wavelength λ1 and shapes having a short shape wavelength λ1 are appropriately combined, an increase in viscosity over time can be reduced. Further, by reducing the increase in viscosity over time, spreading and wetting of the liquid can be promoted, thereby reducing coating unevenness. Periodic Variation in Liquid Ejection Amount from Head 11 Volume-Based Scheme

[0073] FIG. 12 is a diagram illustrating a state in which the head 11 included in the liquid ejection apparatus 100 according to the first embodiment is rotating, liquid droplets formed from liquid ejected from the head 11, and the shape of the coating film surface 211a.

[0074] The head 11 illustrated in FIG. 12 represents a view of the head 11 in a rotating state as viewed from the ＋Z direction. The liquid droplets illustrated in FIG. 12 represent views of liquid droplets ejected from a plurality of nozzles 311 of the head 11 as viewed from the ＋Z direction. Further, the coating film surface 211a illustrated in FIG. 12 represents a view, as viewed from the ＋Y direction, of the coating film surface 211a of a coating film 211 formed on a coating surface 210 of the object 200 by liquid ejected from the plurality of nozzles 311 of the head 11.

[0075] The head 11 rotates in a direction indicated by arrow B1 about a rotation center 11C. Among the liquid ejected from the head 11, a liquid droplet Q1 represents a droplet of liquid ejected from nozzle 311-1 among the plurality of nozzles 311 included in the head 11. Similarly, a liquid droplet Q2 represents a droplet of liquid ejected from nozzle 311-2, a liquid droplet Q3 represents a droplet of liquid ejected from nozzle 311-3, and a liquid droplet Q4 represents a droplet of liquid ejected from nozzle 311-4. Positions of nozzles 311-1, 311-2, 311-3, and 311-4 in the sub-scanning direction X are different from each other. Correspondingly, positions of liquid droplets Q1, Q2, Q3, and Q4 in the sub-scanning direction X are different from each other according to differences in positions of the nozzles 311.

[0076] In the present embodiment, an amount of liquid ejected from the head 11 periodically varies according to a position in the sub-scanning direction X. A wavelength λ of the periodic variation in the ejection amount according to the position in the sub-scanning direction X is shorter than the nozzle pitch P. Here, the “liquid ejection amount” refers to a total amount of liquid ejected by the nozzle 311 to apply liquid to a predetermined position on the object 200 and a region around the predetermined position. For example, the liquid ejection amount can be calculated by capturing images of liquid in flight ejected from the nozzle 311 until the liquid reaches the object 200, and calculating the ejection amount from images of the liquid appearing in the captured images.

[0077] In the example illustrated in FIG. 12, a variation in the liquid ejection amount according to the position in the sub-scanning direction X is equal to a variation, according to the position in the sub-scanning direction X, in a volume per droplet of liquid droplets formed from the liquid ejected from the nozzle 311. The volume per droplet can be calculated by capturing images of liquid droplets in flight ejected from the nozzle 311 until the droplets reach the object 200, and calculating the volume from images of the droplets appearing in the captured images.

[0078] A volume of the liquid droplet Q2 is larger than a volume of the liquid droplet Q1. Therefore, an ejection amount corresponding to the liquid droplet Q2 is larger than an ejection amount corresponding to the liquid droplet Q1. A volume of the liquid droplet Q3 is smaller than the volume of the liquid droplet Q2. Therefore, an ejection amount corresponding to the liquid droplet Q3 is smaller than the ejection amount corresponding to the liquid droplet Q2. A volume of the liquid droplet Q4 is larger than the volume of the liquid droplet Q3. Therefore, an ejection amount corresponding to the liquid droplet Q4 is larger than the ejection amount corresponding to the liquid droplet Q3. As described above, by making volumes of the liquid droplets different according to the position in the sub-scanning direction X, the liquid ejection amount from the head 11 varies according to the position in the sub-scanning direction X.

[0079] When the liquid ejection amount from the head 11 varies according to the position in the sub-scanning direction X, a shape of the coating film surface 211a of the coating film 211 formed by the liquid landing on the coating surface 210 varies according to the position in the sub-scanning direction X. As illustrated in FIG. 12, in the present embodiment, wavelengths λ of periodic variations in each of the liquid ejection amount and the shape of the coating film surface 211a according to the position in the sub-scanning direction X are shorter than the nozzle pitch P. Although the nozzle pitch when the head 11 is rotating slightly deviates from the nozzle pitch P when the head 11 is not rotating, such deviation is sufficiently small relative to the nozzle pitch P when the head 11 is not rotating. Therefore, the nozzle pitch when the head 11 is rotating can be regarded as being substantially equal to the nozzle pitch P when the head 11 is not rotating.

[0080] When the wavelength λ is shorter than the nozzle pitch P, an increase in viscosity over time can be reduced by the mechanism described above with reference to FIGS. 11A and 11B, as compared with a case where the wavelength λ is equal to the nozzle pitch P. By reducing the increase in viscosity over time, spreading and wetting of the liquid can be promoted, thereby reducing coating unevenness. As a result, the present embodiment can provide a liquid ejection apparatus 100 capable of reducing coating unevenness. The liquid ejection apparatus 100 can achieve the above effect not only when a non-Newtonian fluid is used but also when a Newtonian fluid is used. However, in the present embodiment, the above effect is particularly remarkable when the liquid is a non-Newtonian fluid.

[0081] The ejection amount variation scheme in the example illustrated in FIG. 12 corresponds to a volume-based scheme. Here, the “ejection amount variation scheme” refers to a method for varying the liquid ejection amount according to the position in the sub-scanning direction X. The “volume-based scheme” refers to a method for varying the liquid ejection amount by making a volume per droplet different for each of the plurality of nozzles 311 according to the position in the sub-scanning direction X. However, the ejection amount variation scheme in the present embodiment is not limited to the volume-based scheme. As the ejection amount variation scheme in the present embodiment, a frequency-based scheme or a ratio-based scheme described below may also be used. Frequency-Based Scheme

[0082] FIG. 13A is a diagram illustrating a variation in a liquid ejection amount by a frequency-based scheme of the liquid ejection apparatus 100.

[0083] FIG. 13A illustrates liquid droplets formed from liquid ejected from a plurality of nozzles 311 of the head 11 as viewed from the ＋Z direction. FIG. 13A also illustrates the coating film surface 211a of a coating film 211 formed on a coating surface 210 of the object 200 by liquid ejected from the plurality of nozzles 311 of the head 11, as viewed from the ＋Y direction.

[0084] The frequency-based scheme refers to a method in which the head 11 varies an ejection frequency of liquid for each of the plurality of nozzles 311 according to a position in the sub-scanning direction X, thereby varying a liquid ejection amount according to the position in the sub-scanning direction X.

[0085] In the example illustrated in FIG. 13A, liquid droplets Q1, Q2, Q3, and Q4 represent liquid droplets formed from liquid ejected from nozzles 311 located at different positions in the sub-scanning direction X.

[0086] As illustrated in FIG. 13A, the liquid droplets Q1, Q2, Q3, and Q4 have equal volumes per droplet. On the other hand, the liquid droplet Q1 is ejected more frequently than the liquid droplet Q2 and thus has a higher ejection frequency. Therefore, an ejection amount corresponding to the liquid droplet Q1 is larger than an ejection amount corresponding to the liquid droplet Q2. The liquid droplet Q2 is ejected more frequently than the liquid droplet Q3 and thus has a higher ejection frequency. Therefore, an ejection amount corresponding to the liquid droplet Q2 is larger than an ejection amount corresponding to the liquid droplet Q3. The liquid droplet Q3 is ejected less frequently than the liquid droplet Q4 and thus has a lower ejection frequency. Therefore, an ejection amount corresponding to the liquid droplet Q3 is smaller than an ejection amount corresponding to the liquid droplet Q4. As described above, the liquid ejection apparatus 100 can vary the liquid ejection amount according to the position in the sub-scanning direction X by using the frequency-based scheme. As a result, the liquid ejection apparatus 100 can promote spreading and wetting of the liquid and reduce coating unevenness. Ratio-Based Scheme

[0087] FIG. 13B is a diagram illustrating a variation in a liquid ejection amount by a ratio-based scheme of the liquid ejection apparatus 100.

[0088] FIG. 13B illustrates liquid droplets formed from liquid ejected from a plurality of nozzles 311 of the head 11 as viewed from the ＋Z direction. FIG. 13B also illustrates the coating film surface 211a of a coating film 211 formed on a coating surface 210 of the object 200 by liquid ejected from the plurality of nozzles 311 of the head 11, as viewed from the ＋Y direction.

[0089] The ratio-based scheme refers to a scheme in which the head 11 varies a ratio of the number of nozzles 311 that eject liquid to the number of nozzles 311 that do not eject liquid among the plurality of nozzles 311 according to a position in the sub-scanning direction X, thereby varying a liquid ejection amount.

[0090] In the example illustrated in FIG. 13B, liquid droplets Q1, Q2, Q3, Q5, and Q7 represent liquid droplets formed from liquid ejected from nozzles 311 located at different positions in the sub-scanning direction X.

[0091] As illustrated in FIG. 13B, the liquid droplets Q1, Q2, Q3, Q5, and Q7 have equal volumes per droplet. On the other hand, in the sub-scanning direction X, liquid droplets between the liquid droplets Q3 and Q5 are thinned out, and liquid droplets between the liquid droplets Q5 and Q7 are thinned out.

[0092] In the sub-scanning direction X, in the section from the liquid droplet Q1 to the liquid droplet Q3, liquid is ejected from each of the three nozzles 311. Therefore, the ratio of the number of the nozzles 311 that eject liquid to the number of the nozzles 311 that do not eject liquid is 100％. On the other hand, in the section from the liquid droplet Q3 to the liquid droplet Q5, liquid is ejected from two nozzles 311, and liquid is not ejected from one nozzle 311. Therefore, the above ratio is 67％. In the section from the liquid droplet Q5 to the liquid droplet Q7, liquid is ejected from two nozzles 311, and liquid is not ejected from one nozzle 311. Therefore, the above ratio is 67％.

[0093] In the section from the liquid droplet Q1 to the liquid droplet Q3, a liquid ejection amount is larger than that in the section from the liquid droplet Q3 to the liquid droplet Q5. In the section from the liquid droplet Q3 to the liquid droplet Q5, a liquid ejection amount is equal to that in the section from the liquid droplet Q5 to the liquid droplet Q7. As described above, the liquid ejection apparatus 100 can vary the liquid ejection amount according to the position in the sub-scanning direction X by using the ratio-based scheme. As a result, the liquid ejection apparatus 100 can promote spreading and wetting of the liquid and reduce coating unevenness. Generation Method of Coating Instruction Data

[0094] FIG. 14 is a flowchart illustrating a method for generating coating instruction data by the liquid ejection apparatus 100. Here, the coating instruction data refers to data for providing the robot arm 13 with instructions to change a relative position between the object 200 and the head 11 and for providing the head 11 with instructions to eject liquid. For example, the coating instruction data describes, for each relative position between the object 200 and the head 11 along a coating route, a nozzle 311 of the head 11 that ejects liquid, a volume of a liquid droplet ejected from the nozzle, an ejection frequency of liquid by the nozzle, and the like.

[0095] The coating instruction data is generated before coating of the object 200 is performed by the liquid ejection apparatus 100. For example, the liquid ejection apparatus 100 starts the operation illustrated in FIG. 14 when receiving, via an operation unit of the liquid ejection apparatus 100 or the like, an operation input for starting generation of the coating instruction data.

[0096] First, in step S11, the liquid ejection apparatus 100 determines, by the control unit 20, a wavelength λ of a periodic variation in an ejection amount according to the position in the sub-scanning direction X according to a type of liquid.

[0097] The type of liquid includes information on whether the liquid is a Newtonian fluid, information on whether the liquid is a water-based ink, information on a composition of the liquid, and the like. Physical properties such as viscosity or surface tension of the liquid differ depending on the type of liquid. Due to such differences in physical properties, an appropriate wavelength λ for reducing an increase in viscosity over time and promoting spreading and wetting of the liquid differs depending on the type of liquid. The liquid ejection apparatus 100 determines an appropriate wavelength λ for reducing an increase in viscosity over time and promoting spreading and wetting of the liquid according to a predetermined type of liquid. For example, the liquid ejection apparatus 100 can determine the wavelength λ based on information on the type of liquid by referring to a table indicating a relationship between predetermined types of liquid and wavelengths λ.

[0098] Next, in step S12, the liquid ejection apparatus 100 selects, by the control unit 20, one of a volume-based scheme, a frequency-based scheme, and a ratio-based scheme as an ejection amount variation scheme according to the type of liquid.

[0099] Since physical properties of the liquid differ, an appropriate ejection amount variation scheme for reducing an increase in viscosity over time and promoting spreading and wetting of the liquid also differs. The liquid ejection apparatus 100 selects an appropriate ejection amount variation scheme for reducing an increase in viscosity over time and promoting spreading and wetting of the liquid according to a predetermined type of liquid. For example, the liquid ejection apparatus 100 can select the ejection amount variation scheme based on the type of liquid by referring to a table indicating a relationship between predetermined types of liquid and ejection amount variation schemes.

[0100] Next, in step S13, the liquid ejection apparatus 100 describes coating instruction data by the control unit 20. For example, the control unit 20 can generate the coating instruction data based on predetermined CAD (Computer-Aided Design) data of the object 200. The control unit 20 can also associate the coating instruction data with the wavelength λ determined in step S11 and the ejection amount variation scheme selected in step S12.

[0101] Next, in step S14, the liquid ejection apparatus 100 determines, by the control unit 20, whether to end generation of the coating instruction data. For example, when generation of coating instruction data for coating an entirety of the object 200 based on the CAD data is completed, the control unit 20 determines to end generation of the coating instruction data.

[0102] When it is determined not to end the generation (step S14: NO), the liquid ejection apparatus 100 repeats the operations from step S13 onward until it is determined to end the generation in step S14. On the other hand, when it is determined to end the generation (step S14: YES), the liquid ejection apparatus 100 ends the operation.

[0103] As described above, the liquid ejection apparatus 100 can generate coating instruction data. After generating the coating instruction data, the liquid ejection apparatus 100 can coat the object 200 according to the generated coating instruction data.Second Embodiment

[0104] Next, a liquid ejection apparatus according to a second embodiment will be described. Note that components and configurations having the same names and reference numerals as those of the embodiments already described indicate the same or equivalent members or configurations, and detailed descriptions thereof will be omitted as appropriate. The same applies to the embodiments described below.

[0105] FIG. 15 is a schematic diagram illustrating a configuration of a liquid ejection apparatus 100a according to the second embodiment. The liquid ejection apparatus 100a differs from the liquid ejection apparatus 100 according to the first embodiment in that the liquid ejection apparatus 100a includes a robot arm 13a that supports an object 200, and a support member 101 that supports the head 11.

[0106] In the liquid ejection apparatus 100a, the object 200 is moved relative to the head 11, which is fixed by the support member 101, by the robot arm 13a, and liquid is ejected from the head 11 to perform coating. Even in such a liquid ejection apparatus 100a, effects similar to those of the liquid ejection apparatus 100 according to the first embodiment can be obtained. The liquid ejection apparatus 100a is suitable for a lightweight object 200 that is movable by the robot arm 13a.Third Embodiment

[0107] Next, a liquid ejection apparatus according to a third embodiment will be described.

[0108] By analyzing big data, which is an enormous amount of data that cannot be sufficiently handled by conventional databases, it becomes possible to create new value in various fields. Advantages of utilizing big data include more accurate decision-making, discovery of new business opportunities, improvement of operational efficiency, and enhancement of customer satisfaction.

[0109] Here, by performing simulations based on big data, it becomes possible to more accurately predict phenomena that have been difficult to predict in the past and to analyze the behavior of complex systems in detail.

[0110] An example of a method of performing simulations based on big data, such as shape data and correction data, in the embodiments described above is as follows.

[0111] (1) Data collection and preprocessing

[0112] Data sources capable of collecting necessary data are identified, and data is collected. As preprocessing of the collected data, data cleaning (removal of missing values, outliers, noise, etc.) is performed to improve data quality. The data formats are unified and converted into formats that are easy to analyze, and features that are effective for analysis are extracted and generated. At this stage, deeper features may also be extracted from the data using techniques such as machine learning and deep learning.

[0113] (2) Model selection

[0114] An appropriate model is selected according to the purpose of the simulation, parameters of the selected model are appropriately set, and the accuracy of the model is verified using past data.

[0115] (3) Execution of simulation

[0116] An environment for executing simulations is constructed, simulations are executed using the constructed model, and the simulation results are visualized using graphs, diagrams, or the like. By applying simulations based on big data such as shape data and correction data in the embodiments described above, it becomes possible to perform highly accurate correction with respect to rotation of the head. Digital Twin

[0117] A digital twin, which links the real world and a virtual space, is a technology that enables prediction and optimization of the real world by reproducing real-world objects in a virtual space and simulating their behavior. Simulation is the core of the digital twin and is an important tool for performing various experiments and analyses in a virtual space based on real-world data. Simulation data provides benefits such as improved prediction accuracy, optimization, risk reduction, and cost reduction by quantifying and modeling complex real-world phenomena. Digital twins are expected to become increasingly sophisticated through integration with AI and IoT; for example, it is conceivable to improve the accuracy of simulation models using machine learning and to realize real-time simulations by utilizing edge computing.

[0118] An example of a method of applying simulation data in the embodiments described above to a digital twin is as follows.

[0119] (1) Preprocessing of simulation data

[0120] “Data cleaning” is performed to improve data quality by processing noise and missing values contained in the collected simulation data, and “data transformation” is performed to convert the cleaned simulation data into a format that can be handled by simulation models.

[0121] (2) Construction of simulation models

[0122] “Construction of a physical model,” in which a model describing physical characteristics of an object to be simulated is built, is performed. “Construction of a mathematical model,” in which the constructed physical model is expressed by mathematical equations, is then performed, followed by “numerical analysis,” in which algorithms for numerically solving the constructed mathematical model are developed.

[0123] (3) Integration into a digital twin

[0124] “Visualization of simulation results,” in which simulation results are displayed in an easily understandable visual form such as 3D models or graphs, is performed. “Model accuracy verification,” in which the visualized simulation results are compared with real-world measurement data, sensor data, or the like to verify model accuracy, is then performed. Based on the simulation results, control parameters in the real world are adjusted to further improve the accuracy of the verified model.

[0125] By applying the simulation data in the embodiments described above to a digital twin, it becomes possible to simulate correction with respect to rotation of a head used when coating a coating target surface. By applying this principle, it also becomes possible to perform simulations for heads mounted on various printers.

[0126] Although preferred embodiments have been described in detail above, the present disclosure is not limited to the embodiments described above, and various modifications and substitutions may be made without departing from the scope described in the claims.

[0127] Ordinal numbers, numerical values, and the like used in the description of the embodiments are merely examples for specifically describing the technology of the present disclosure, and the present disclosure is not limited to the exemplified numerical values. Connection relationships between components are also examples for specifically describing the technology of the present disclosure and are not intended to limit the connection relationships necessary for realizing the functions of the present disclosure.

[0128] The division of blocks in the functional block diagrams is merely an example, and multiple blocks may be realized as a single block, a single block may be divided into multiple blocks, or some functions may be transferred to other blocks. In addition, functions of multiple blocks having similar functions may be processed in parallel or in a time-sharing manner by a single piece of hardware or software. Furthermore, some or all functions may be distributed among multiple computers.

[0129] In the embodiments, the liquid ejected from the head 11 may be a solution, a suspension, an emulsion, or the like containing a solvent such as water or an organic solvent, a colorant such as a dye or a pigment, a polymerizable compound, a resin, a functional additive material such as a surfactant, DNA, amino acids or proteins, biocompatible materials such as calcium, edible materials such as natural pigments, or the like. These liquids can be used, for example, as inkjet ink, coating paint, surface treatment liquid, liquid for forming components of electronic devices or light-emitting devices or electronic circuit resist patterns, material liquid for three-dimensional fabrication, and the like.

[0130] The coating surface 210 refers to an object to which a liquid adheres and is fixed, an object to which a liquid adheres and penetrates, or the like. Specific examples include recording media such as vehicle bodies, building materials, paper, recording paper, recording sheets, films, and cloth; electronic components such as electronic substrates and piezoelectric elements; powder layers (powder beds); organ models; inspection cells; and the like. Unless otherwise specified, the coating surface 210 includes any object to which a liquid can adhere.

[0131] Each function of the embodiments can be implemented by one or more processing circuits. Here, the term “processing circuit” in the present specification includes a processor programmed to execute each function by software, such as a processor implemented by an electronic circuit, and devices such as an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or a conventional circuit module designed to execute the respective functions described above.

[0132] For example, aspects of the present disclosure are as follows. <1> A liquid ejection apparatus configured to eject a liquid to apply the liquid to an object, the liquid ejection apparatus comprising: a head including a nozzle row in which a plurality of nozzles, each configured to eject the liquid, are arranged at a predetermined nozzle pitch along a sub-scanning direction; and a variable mechanism configured to change a relative position between the head and the object in a main scanning direction orthogonal to the sub-scanning direction, wherein an ejection amount of the liquid ejected from the head periodically changes according to a position in the sub-scanning direction, and wherein a wavelength of the periodic change in the ejection amount according to the position in the sub-scanning direction is shorter than the nozzle pitch. <2> The liquid ejection apparatus according to <1>, wherein the head changes the ejection amount by making a volume per droplet of liquid droplets different among the plurality of nozzles according to the position in the sub-scanning direction, the liquid droplets being formed from the liquid ejected from the nozzles. <3> The liquid ejection apparatus according to <1> or <2>, wherein the head changes the ejection amount by making an ejection frequency of the liquid different among the plurality of nozzles according to the position in the sub-scanning direction. <4> The liquid ejection apparatus according to any one of <1> to <3>, wherein the head changes the ejection amount by making a ratio of a number of nozzles that eject the liquid to a number of nozzles that do not eject the liquid different according to the position in the sub-scanning direction. <5> The liquid ejection apparatus according to any one of <1> to <4>, wherein the wavelength is determined according to a type of the liquid. <6> The liquid ejection apparatus according to any one of <1> to <5>, wherein one scheme selected according to the type of the liquid is applied, the scheme being any one of: a volume-based scheme in which a volume per droplet of liquid droplets is made different according to the position in the sub-scanning direction, the liquid droplets being formed from the liquid ejected from the nozzles; a frequency-based scheme in which an ejection frequency of the liquid is made different according to the position in the sub-scanning direction; or a ratio-based scheme in which a ratio of the number of nozzles that eject the liquid to the number of nozzles that do not eject the liquid is made different according to the position in the sub-scanning direction. <7> A liquid ejection method using a liquid ejection apparatus configured to eject a liquid to apply the liquid to an object, the liquid ejection method comprising: ejecting the liquid by a head including a nozzle row in which a plurality of nozzles, each configured to eject the liquid, are arranged at a predetermined nozzle pitch along a sub-scanning direction; and changing, by a variable mechanism, a relative position between the head and the object in a main scanning direction orthogonal to the sub-scanning direction, wherein an ejection amount of the liquid ejected from the head periodically changes according to a position in the sub-scanning direction, and wherein a wavelength of the periodic change in the ejection amount according to the position in the sub-scanning direction is shorter than the nozzle pitch. <8> The liquid ejection method according to <7>, wherein the liquid is a non-Newtonian fluid. <9> A program for causing an information processing apparatus to execute a process, the information processing apparatus being communicably connected to a liquid ejection apparatus configured to eject a liquid to apply the liquid to an object, the liquid ejection apparatus including a head including a nozzle row in which a plurality of nozzles, each configured to eject the liquid, are arranged at a predetermined nozzle pitch along a sub-scanning direction, and a variable mechanism configured to change a relative position between the head and the object in a main scanning direction orthogonal to the sub-scanning direction, wherein an ejection amount of the liquid ejected from the head periodically changes according to a position in the sub-scanning direction, and a wavelength of the periodic change in the ejection amount according to the position in the sub-scanning direction is shorter than the nozzle pitch, the process comprising: determining a wavelength according to a type of the liquid; and selecting, according to the type of the liquid, one scheme from among: a volume-based scheme in which a volume per droplet of liquid droplets is made different according to the position in the sub-scanning direction, the liquid droplets being formed from the liquid ejected from the nozzles; a frequency-based scheme in which an ejection frequency of the liquid is made different according to the position in the sub-scanning direction; or a ratio-based scheme in which a ratio of the number of nozzles that eject the liquid to the number of nozzles that do not eject the liquid is made different according to the position in the sub-scanning direction.

[0133] The present application is based on and claims the benefit of priority of Japanese Patent Application No. 2025-019108 filed on February 7, 2025. The entire content of this application is incorporated herein by reference.

[0134] 10, 10-1, 10-2, 10-3, 10-4: liquid ejection unit 11, 11-1, 11-2, 11-3, 11-4: head 11C: rotation center 12, 12-1, 12-2, 12-3, 12-4: detector 13, 13-1, 13-2, 13-3, 13-4: robot arm 13a: robot arm 14: supply unit 20: control unit 72: robot driving unit 100, 100a: liquid ejection apparatus 101: support member 109: encoder sensor 110: housing 111: supply port 112: collection port 200: object 210: coating surface 211: coating film 211a: coating film surface 230: compressor 310: valve 311, 311-1, 311-2, 311-4: nozzle 311C: central axis 320: nozzle surface 321: nozzle plate 322: flow path 324: piezoelectric element 325: liquid 330, 330-1, 330-2, 330-3, 330-4: liquid tank 331: pipe 332: air regulator 333: tube 340: ejection module 901: controller 902: head control device 903: PC 904: robot control device 9001: CPU 9002: ROM 9003: RAM 9004: I / F 9011: system control unit 9012: data storage unit 9013: memory control unit 9014: ejection cycle signal generation unit 9015: synchronization control unit 9016: rendering unit 9017: wavelength determination unit 9018: method selection unit 9031: RIP unit 9033: input device B1, B2, B3: arrows h: average film thickness P: nozzle pitch Q1, Q2, Q3, Q4, Q5, Q7: liquid droplets t0: time t1 / 2: half-amplitude period X: sub-scanning direction Y: main scanning direction Z: ejection direction λ0: rotation wavelength λ1: shape wavelength λ: wavelength τ: shear stress

Claims

1. A liquid ejection apparatus configured to eject a liquid to apply the liquid to an object, the liquid ejection apparatus comprising: a head including a nozzle row in which a plurality of nozzles, each configured to eject the liquid, are arranged at a predetermined nozzle pitch along a sub-scanning direction; and a variable mechanism configured to change a relative position between the head and the object in a main scanning direction orthogonal to the sub-scanning direction, wherein an ejection amount of the liquid ejected from the head periodically changes according to a position in the sub-scanning direction, and wherein a wavelength of the periodic change in the ejection amount according to the position in the sub-scanning direction is shorter than the nozzle pitch.

2. The liquid ejection apparatus according to claim 1, wherein the head changes the ejection amount by making a volume per droplet of liquid droplets different among the plurality of nozzles according to the position in the sub-scanning direction, the liquid droplets being formed from the liquid ejected from the nozzles.

3. The liquid ejection apparatus according to claim 1, wherein the head changes the ejection amount by making an ejection frequency of the liquid different among the plurality of nozzles according to the position in the sub-scanning direction.

4. The liquid ejection apparatus according to claim 1, wherein the head changes the ejection amount by making a ratio of a number of nozzles that eject the liquid to a number of nozzles that do not eject the liquid different according to the position in the sub-scanning direction.

5. The liquid ejection apparatus according to any one of claims 1 to 4, wherein the wavelength is determined according to a type of the liquid.

6. The liquid ejection apparatus according to any one of claims 1 to 4, wherein one scheme selected according to the type of the liquid is applied, the one scheme being any one of: a volume-based scheme in which a volume per droplet of liquid droplets is made different according to the position in the sub-scanning direction, the liquid droplets being formed from the liquid ejected from the nozzles; a frequency-based scheme in which an ejection frequency of the liquid is made different according to the position in the sub-scanning direction; or a ratio-based scheme in which a ratio of the number of nozzles that eject the liquid to the number of nozzles that do not eject the liquid is made different according to the position in the sub-scanning direction.

7. A liquid ejection method using a liquid ejection apparatus configured to eject a liquid to apply the liquid to an object, the liquid ejection method comprising: ejecting the liquid by a head including a nozzle row in which a plurality of nozzles, each configured to eject the liquid, are arranged at a predetermined nozzle pitch along a sub-scanning direction; and changing, by a variable mechanism, a relative position between the head and the object in a main scanning direction orthogonal to the sub-scanning direction, wherein an ejection amount of the liquid ejected from the head periodically changes according to a position in the sub-scanning direction, and wherein a wavelength of the periodic change in the ejection amount according to the position in the sub-scanning direction is shorter than the nozzle pitch.

8. The liquid ejection method according to claim 7, wherein the liquid is a non-Newtonian fluid.

9. A program for causing an information processing apparatus to execute a process, the information processing apparatus being communicably connected to a liquid ejection apparatus configured to eject a liquid to apply the liquid to an object, and the liquid ejection apparatus including a head including a nozzle row in which a plurality of nozzles, each configured to eject the liquid, are arranged at a predetermined nozzle pitch along a sub-scanning direction, and a variable mechanism configured to change a relative position between the head and the object in a main scanning direction orthogonal to the sub-scanning direction, wherein an ejection amount of the liquid ejected from the head periodically changes according to a position in the sub-scanning direction, and a wavelength of the periodic change in the ejection amount according to the position in the sub-scanning direction is shorter than the nozzle pitch, the process comprising: determining a wavelength according to a type of the liquid; and selecting, according to the type of the liquid, one scheme from among: a volume-based scheme in which a volume per droplet of liquid droplets is made different according to the position in the sub-scanning direction, the liquid droplets being formed from the liquid ejected from the nozzles; a frequency-based scheme in which an ejection frequency of the liquid is made different according to the position in the sub-scanning direction; or a ratio-based scheme in which a ratio of the number of nozzles that eject the liquid to the number of nozzles that do not eject the liquid is made different according to the position in the sub-scanning direction.

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