Liquid dispensing device and liquid dispensing method

Abstract

Reduces uneven application of liquid to the target object. [Solution] A liquid dispensing device according to one aspect of the present disclosure comprises a head having a plurality of nozzles for dispensing liquid onto the surface of an object, a variable mechanism for changing the relative position of the head with respect to the object, and a control unit for controlling the operation of at least the head, wherein the plurality of nozzles include at least one of three or more nozzles with different nozzle diameters arranged at the same pitch, and three or more nozzles with the same nozzle diameter arranged at different pitches, and the control unit selects two nozzles from the three or more nozzles to dispense the liquid at adjacent positions on the surface of the object, according to the radius of curvature of the surface of the object.

Description

[[Technical Field]]

[0001] The present disclosure relates to a liquid ejection apparatus and a liquid ejection method. [[Background Art]]

[0002] Conventionally, there has been known a liquid ejection apparatus that ejects liquid from a plurality of nozzles provided in a head and applies the liquid to a target object.

[0003] For example, Patent Document 1 discloses a liquid ejection apparatus that changes the amount of liquid ejected from a plurality of nozzles in accordance with the ratio of the total length of a first curved surface directly below the plurality of nozzles at a reference position to the total length of a second curved surface directly below the plurality of nozzles at a position of a curved surface from which liquid is to be ejected. [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] However, in the apparatus described in Patent Document 1, since the pitch of the plurality of nozzles is constant, an increase in the amount of ejected liquid is required, for example, when the target object has a curved surface shape with a small radius of curvature. Due to the large amount of ejected liquid, when the liquid lands on the target object, it scatters to generate mist, which may cause uneven application of the liquid to the target object.

[0005] An object of the present disclosure is to reduce uneven application of liquid to a target object. [[Means for Solving the Problem]]

[0006] A liquid dispensing device according to one aspect of the present disclosure comprises a head having a plurality of nozzles for dispensing liquid onto the surface of an object, a variable mechanism for changing the relative position of the head with respect to the object, and a control unit for controlling the operation of at least the head, wherein the plurality of nozzles include at least one of three or more nozzles with different nozzle diameters arranged at the same pitch, and three or more nozzles with the same nozzle diameter arranged at different pitches, and the control unit selects two nozzles from the three or more nozzles to dispense the liquid at adjacent positions on the surface of the object, according to the radius of curvature of the surface of the object. [Effects of the Invention]

[0007] According to this disclosure, uneven application of liquid to the target object can be reduced. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing the overall configuration of the liquid dispensing device according to the first embodiment. [Figure 2] This is a block diagram showing the overall configuration of the liquid dispensing device according to the first embodiment. [Figure 3] This is a schematic perspective view showing the head of the liquid dispensing device according to the first embodiment. [Figure 4] This is a schematic cross-sectional view traversing the liquid flow path of a head in a liquid dispensing device according to the first embodiment. [Figure 5] This is a schematic enlarged perspective view showing the lower end of the head of the liquid dispensing device according to the first embodiment, with the lower housing removed. [Figure 6A] This is a schematic bottom view showing the nozzle plate of the head of the liquid dispensing device according to the first embodiment. [Figure 6B] This is a schematic bottom view showing the nozzle plate of a head related to a reference example. [Figure 7A] This is a schematic diagram showing the first example of how liquid discharged from a head related to a reference example lands on the surface of an object. [Figure 7B]This is a schematic diagram showing a second example of how liquid discharged from a head related to the reference example lands on the surface of an object. [Figure 8A] This is a schematic bottom view showing a first example of a head of a liquid dispensing device according to the first embodiment. [Figure 8B] This is a schematic bottom view showing a second example of a head in a liquid dispensing device according to the first embodiment. [Figure 9] This figure shows the hardware configuration of the control unit of the liquid dispensing device according to the first embodiment. [Figure 10] This figure shows the functional configuration of the control unit of the liquid dispensing device according to the first embodiment. [Figure 11A] This figure shows a first example of a method for determining the nozzle to be discharged in a liquid dispensing device according to the first embodiment. [Figure 11B] This figure shows a second example of a method for determining the nozzle to be discharged in a liquid dispensing device according to the first embodiment. [Figure 11C] This figure illustrates a method for calculating the droplet radius by the nozzle selection unit of the control unit of the liquid dispensing device according to the first embodiment. [Figure 12] This figure shows the processing performed by the control unit of the liquid dispensing device according to the first embodiment. [Figure 13] This is a schematic cross-sectional view of the nozzle plate in the head of the liquid dispensing device according to the second embodiment, along the dispensing direction. [Figure 14A] This is a schematic bottom view showing a first example of a head in a liquid dispensing device according to the third embodiment. [Figure 14B] This is a schematic bottom view showing a second example of a head in a liquid dispensing device according to the third embodiment. [Figure 15] This is a schematic perspective view showing a liquid dispensing device according to the fourth embodiment. [Modes for carrying out the invention]

[0009] A liquid ejection apparatus according to an embodiment of the present disclosure will be described in detail with reference to the drawings. However, the form shown below is an example of a liquid ejection apparatus for embodying the technical idea of the embodiment, and is not limited to the following. In addition, unless specifically stated, the dimensions, materials, shapes, relative arrangements, and the like of components described in the embodiments are not intended to limit the scope of the present disclosure only thereto, but are merely illustrative examples. Note that the sizes, positional relationships, and the like of members shown in the respective drawings may be exaggerated for clarity of explanation. In the following description, the same names and reference numerals denote the same or homogeneous members, and detailed descriptions thereof will be omitted as appropriate.

[0010] Terms indicating a specific direction or position (for example, "upper", "lower", and other terms including these terms) may be used. However, these terms are only used for easy understanding of the relative direction or position in the referenced drawings.

[0011] In the description of the embodiments below, "along the direction" includes that the object has an inclination within a range of ±10° with respect to the direction. In addition, "disposed" is not limited to the case where two objects are in contact with each other, but also includes the case where one object is disposed indirectly on another object via another member, for example.

[0012] [First Embodiment] (Overall Configuration) With reference to FIGS. 1 and 2, the overall configuration of a liquid ejection apparatus according to a first embodiment of the present disclosure will be described. FIG. 1 is a schematic diagram illustrating an example of the overall configuration of a liquid ejection apparatus 201 according to the first embodiment of the present disclosure. FIG. 2 is a block diagram showing the overall configuration of the liquid ejection apparatus 201.

[0013] As shown in Figures 1 and 2, the liquid ejection device 201 includes a head 1 having multiple nozzles for ejecting liquid onto the surface of an object 300, a variable mechanism 250 for changing the relative position of the head 1 with respect to the object 300, and a control unit 200 for controlling the operation of at least the head 1. In the example shown in Figures 1 and 2, the control unit 200 can control the operation of the head 1 and the variable mechanism 250, respectively. The liquid ejection device 201 is a device that paints an object 300 by applying liquid ejected from the head 1 to the surface of the object 300 using an inkjet method. The liquid ejected by the head 1 is paint. However, the liquid may be ink.

[0014] Object 300 is a car body with an impermeable surface. However, object 300 may also be a truck or aircraft body, etc., as long as it has an impermeable surface. Here, impermeability refers to the property that a liquid applied to the surface does not penetrate into the interior. However, the surface of object 300 is not limited to an impermeable surface; it may also be a permeable surface. The surface of object 300 shown in Figure 1 is a curved surface with a radius of curvature. However, the surface of object 300 may also be a flat surface.

[0015] The control unit 200 is connected to the variable mechanism 250 and the head 1 via wired or wireless means, enabling communication between them. Based on shape information Od and painting area information Pd, the control unit 200 outputs a drive command Rc to the variable mechanism 250 to move the head 1 to the variable mechanism 250. The control unit 200 also outputs a drive signal Hc to the head 1 to discharge liquid from the head 1. Shape information Od is shape information of the object 300 input from an external device such as an external PC (Personal Computer). Painting area information Pd is information corresponding to the area of ​​the object 300 surface to be painted.

[0016] The variable mechanism 250 is, for example, a multi-axis driveable robot arm. The variable mechanism 250 moves the held head 1 to a desired position in three-dimensional space. The liquid dispensing device 201 can apply the liquid dispensed from the head 1 to a desired position on the object 300 by driving the variable mechanism 250. The drive mechanism is not limited to a robot arm and can also be configured with a stage that can move linearly in three axes. Alternatively, the object 300 may be moved without moving the head 1, or both the head 1 and the object 300 may be moved.

[0017] (Head 1) The configuration of the head 1 of the liquid dispensing device 201 will be described with reference to Figures 3, 4, 5, 6A, 6B, 7A, 7B, 8A, and 8B. Figure 3 is a schematic perspective view showing the head 1. Figure 4 is a schematic cross-sectional view across the liquid flow path of the head 1. Figure 5 is a schematic enlarged perspective view showing the lower end of the head 1 with the lower housing removed. Figure 6A is a schematic bottom view showing the nozzle plate 101 of the head 1 of the liquid dispensing device 201. Figure 6B is a schematic bottom view showing the nozzle plate 101 of a head according to a reference example.

[0018] Figure 7A is a schematic diagram showing the first example of how liquid discharged from the head according to the reference example lands on the surface of an object. Figure 7B is a schematic diagram showing the second example of how liquid discharged from the head according to the reference example lands on the surface of an object. Figure 8A is a schematic bottom view showing the first example of head 1. Figure 8B is a schematic bottom view showing the second example of head 1.

[0019] Figure 3 shows the head 1 viewed from a diagonal downward angle. The housing 10 of the head 1 has an upper housing 10a and a lower housing 10b. The upper housing 10a and the lower housing 10b can also be formed integrally. A cover 20 is mounted on top of the upper housing 10a, and electrical components are provided inside this cover 20. A connector portion 2 for the electrical components is provided at the upper end of the cover 20.

[0020] A nozzle plate 101 made of a corrosion-resistant metal such as stainless steel (SUS) is provided on the lower surface of the lower housing 10b. Liquid is discharged from fine nozzles 111 formed on the nozzle plate 101.

[0021] As shown in Figure 4, a liquid flow path 112 is formed inside the lower housing 10b. As shown in Figure 3, one end of this flow path 112 is in communication with the supply port 11, and the other end is in communication with the recovery port 12.

[0022] The supply port 11 and the recovery port 12 are connected via a circulation passage. Pressurized liquid, pressurized by the pump in the circulation passage, is supplied to the supply port 11. Pressurized liquid that is not discharged from the nozzle 111 is recovered from the recovery port 12 and then supplied back to the supply port 11 via the circulation passage and the pump.

[0023] When the lower housing 10b is removed, as shown in Figure 5, the tip of the needle valve 113, which is a axial member, is exposed from the bearing 121 on the lower surface of the upper housing 10a. The needle valve 113 is made of corrosion-resistant SUS metal. The needle valve 113 is very thin. The diameter of the thin part of the needle valve 113 is 1 mm or less, and the diameter of the thicker part is about 2 mm. The needle valve 113 is exposed from the bearing 121 of the upper housing 10a for a length of, for example, 1 mm to 20 mm.

[0024] The tip of the needle valve 113 is provided with a valve body 113a that opens and closes the nozzle 111. Above the valve body 113a is provided an elastic O-ring 113b that acts as a sealing member, and a washer 113c for fixing the O-ring 113b to the needle valve 113. The peripheral edge of the nozzle plate 101 is joined to the housing 10 with a thermosetting resin or the like.

[0025] The design of the flow path of head 1 or the driving method of head 1 needs to be adjusted according to the viscosity of the liquid to be discharged. By configuring the liquid discharge unit with multiple heads 1, it is possible to combine heads 1 designed to suit the viscosity of the liquid to be discharged. This makes it possible to appropriately discharge multiple types of liquids with different viscosities from a single liquid discharge unit.

[0026] As shown in Figure 4, a needle valve 113 and a piezoelectric element 114 that drives the needle valve 113 are provided in the upper housing 10a. The piezoelectric element 114 is held in the central space 115a of the holding member 115.

[0027] Spring portions are formed at both the upper and lower ends of the retaining member 115. These spring portions hold the piezoelectric element 114 in a compressed state in the axial direction (along the Z-axis). The tip portion 115b of the retaining member 115 and the rear end of the needle valve 113 are connected coaxially to the piezoelectric element 114 and the needle valve 113. As a result, when the piezoelectric element 114 contracts in the longitudinal direction (along the Z-axis), the retaining member 115 also contracts in the longitudinal direction (along the Z-axis), allowing a biasing force to be applied to the needle valve 113 in the direction that opens the nozzle 111 (opposite to the direction in which the Z-axis arrow points).

[0028] The piezoelectric element 114 operates in d31 mode when a voltage is applied by the voltage application means, driving the needle valve 113 in the direction that opens the nozzle 111. In other words, the needle valve 113 is driven in the direction that opens the nozzle 111 when a voltage is applied to the piezoelectric element 114. Therefore, when no voltage is applied to the piezoelectric element 114, the needle valve 113 closes the nozzle 111. For this reason, even if pressurized liquid is supplied to the flow path 112, no liquid is discharged from the nozzle 111.

[0029] By applying a voltage to the piezoelectric element 114, the piezoelectric element 114 contracts, pulling the needle valve 113 via the holding member 115. This causes the valve body 113a of the needle valve 113 to separate from the nozzle 111, opening the nozzle 111. As a result, the pressurized liquid supplied to the flow path 112 is discharged from the nozzle 111, and the discharged liquid lands on the surface of the object 300 as droplets. Note that droplets refer to liquid that has been droplet-formed from the discharged head 1.

[0030] The piezoelectric element 114 can also be operated in d33 mode, which extends in the direction that closes the needle valve 113 (in the direction indicated by the Z-axis arrow) when a voltage is applied. When the piezoelectric element operates in d33 mode, the valve body 113a of the needle valve 113 is pressed against the nozzle 111 side when a voltage is applied, thereby closing the nozzle 111.

[0031] When discharging liquid, the voltage applied to the piezoelectric element 114 is stopped or reduced, causing the valve body 113a of the needle valve 113 to move in the opening direction and open the nozzle 111. The d33 mode of the piezoelectric element 114 has high responsiveness and a large displacement. Therefore, the d33 mode is suitable when it is desired to improve the responsiveness of the opening and closing operation of the needle valve 113 and reduce variations in the droplet speed and liquid volume of the liquid discharged from the nozzle 111.

[0032] The retaining member 115 is positioned within the upper housing 10a so as to be adjustable in the vertical direction (along the Z-axis) as shown in Figure 4. The rear end portion 115c of the retaining member 115 can be positioned and fixed to the upper housing 10a by a fixing screw 124. Female screw holes 115d are formed in the rear end portion 115c of the retaining member 115 in the axial direction (along the Z-axis) and in the direction perpendicular to the X-axis, and the tip of the fixing screw 124 is screwed into these female screw holes 115d.

[0033] As shown in Figure 4, an elongated hole 30 is formed at the upper end of the upper housing 10a in the axial direction (along the Z-axis), and a fixing screw 124 is inserted through this elongated hole 30. When the fixing screw 124 is loosened, the retaining member 115 becomes movable up and down.

[0034] The fixing screw 124 is tightened and fixed into the elongated hole 30 at a position where a predetermined gap δ is formed between the valve body 113a and the nozzle 111, as shown in Figure 3. The head 1 is delivered as a product in this state.

[0035] Now, with reference to Figures 6A and 6B, the arrangement of nozzles in the head 1 of the liquid dispensing device according to the first embodiment of this disclosure will be described.

[0036] Conventionally, the nozzles 111 of the nozzle plate 101 were often formed in a single row, as shown in Figure 6B. In contrast, in the first embodiment of this disclosure, in order to improve image quality, make the liquid discharge device more compact, etc., as shown in Figure 6A, a single nozzle plate 101 in the head 1 is provided with two or more rows of nozzles. In the example shown in Figure 6A, the nozzle plate 101 is provided with two rows of nozzles. In the two rows of nozzles, multiple nozzles 111 are arranged in a staggered pattern. Note that in Figure 6B, for the sake of clarity, in the head relating to the reference example, components having the same function as the head 1 shown in Figure 6A are denoted by the same reference numerals as the head 1.

[0037] For example, when a liquid is ejected from a head to form (print) an image on a recording medium such as paper, in order to obtain the desired image quality, it is necessary to shorten the pitch between the nozzles 111 in the direction perpendicular to the printing direction X. In the reference example shown in Figure 6B, the nozzle plate 101 is arranged at a considerable angle with respect to the printing direction X, thereby shortening the pitch between the nozzles 111 in the direction perpendicular to the printing direction X. As a result, as shown by the shaded area in Figure 6B, there are areas where image formation is restricted in a single image formation operation. This may lead to decreased productivity due to an increase in the number of image formation operations required to form an image in these restricted areas, inconvenience during image formation, or a decrease in the image quality of the formed image.

[0038] As shown in Figure 6A, by providing multiple nozzle rows on the nozzle plate 101 of the head 1, in the first embodiment of this disclosure, the pitch between nozzles 111 in a direction perpendicular to the printing direction X can be shortened without arranging the nozzle plate 101 at an angle with respect to the printing direction X. As a result, the number of areas where image formation is constrained can be reduced, enabling higher image quality, a more compact device, and improved production efficiency through an increased painting area.

[0039] Figure 6A shows a configuration in which six nozzle plates 101 are joined to a housing 10. However, a liquid discharge unit can also be formed by arranging six heads 1, each with a housing joined to a nozzle plate 101. By configuring a liquid discharge unit with multiple heads 1 in this way, a liquid supply channel can be provided for each nozzle plate 101. This makes it possible to supply and discharge different liquids to each nozzle plate 101.

[0040] For example, if a different colored liquid is supplied to the head 1 for each of the six nozzle plates 101 shown in Figure 6A, an image can be formed using six different colored liquids with a single liquid dispensing unit. Alternatively, by supplying liquids of different viscosities to each of the six nozzle plates 101 that make up the head 1, liquids of different viscosities can be dispensed with a single liquid dispensing unit.

[0041] Next, with reference to Figures 7A and 7B, concerns regarding the application of liquid to an object 300 having a three-dimensional curved shape using the head 1X according to the reference example will be explained. The head 1X according to the reference example differs from the head 1 in the first embodiment of this disclosure in that the nozzle diameters of the multiple nozzles provided on the head 1X are the same, and the pitch between adjacent nozzles is constant.

[0042] In Figures 7A and 7B, the trajectories of the liquid ejected from the four nozzles of head 1X are represented by four arrows. Furthermore, the application surface 300-1 shown in Figure 7A represents a portion of the surface of the object 300 to which the liquid was applied in the first example shown in Figure 7A, viewed from a direction opposite to that surface. The application surface 300-2 shown in Figure 7B represents a portion of the surface of the object 300 to which the liquid was applied in the second example shown in Figure 7B, viewed from a direction opposite to that surface.

[0043] In order to apply liquid to a three-dimensional curved surface, it is necessary to increase the gap between the object 300 and the head, or to adjust the relative angle of the head so that it faces the surface of the object 300, compared to when applying liquid to a flat surface, in order to avoid contact between the object 300 and the head. In this case, when the radius of curvature of the curved surface of the object 300 is small (in other words, the curvature is large), the distance to the surface of the object 300 may differ for each of the multiple nozzles on the head.

[0044] In the examples shown in Figures 7A and 7B, the small radius of curvature of the curved surface of the object 300 causes the arrival timing of two of the liquids discharged from the four nozzles to the object 300 to differ from that of the other two liquids. As a result, two of the four arrows reach the surface of the object 300, while the other two do not. Such differences in arrival timing can lead to uneven application of the liquid to the object 300.

[0045] In the first example shown in Figure 7A, on the surface of the object 300, liquids applied to adjacent positions come closer together and overlap according to the radius of curvature of the curved surface of the object 300, resulting in uneven liquid application, specifically uneven liquid concentration 301a, on the application surface 300-1. In the second example shown in Figure 7B, liquids applied to adjacent positions move further apart from each other according to the radius of curvature of the curved surface of the object 300, resulting in streaks 301b (white spots) on the application surface 300-2, also as uneven liquid application. Such uneven application of liquid to the object 300 reduces the quality of liquid application to the object 300, for example, reducing the quality of the coating applied to the object 300. Furthermore, if the relative movement between the head and the object 300 by the variable mechanism 250 is performed multiple times to fill the streaks on the object 300 with liquid in order to reduce the streaks, productivity may decrease.

[0046] To reduce uneven liquid distribution, it is conceivable to adjust the amount of liquid applied to adjacent positions according to the radius of curvature of the curved surface of the object 300. For example, to increase the amount of liquid discharged from a specific nozzle 111, it is conceivable to increase the time a specific needle valve 113 is open. However, in this method of increasing the amount of liquid by increasing the time the needle valve 113 is open, the flight speed of the liquid increases in proportion to the amount of liquid. When liquid lands on the surface of the object 300 at high speed, a milk crown phenomenon may occur. The milk crown phenomenon refers to the phenomenon in which, when liquid lands on the surface of the object 300, the liquid bounces back and scatters in an unintended direction. As the liquid scatters, it is applied to unintended areas on the surface of the object 300, resulting in uneven liquid distribution on the surface of the object 300.

[0047] As shown in Figures 8A and 8B, in the first embodiment of the present disclosure, the plurality of nozzles 111 include at least one of three or more nozzles 111 with different nozzle diameters arranged at the same pitch, and three or more nozzles 111 with the same nozzle diameter arranged at different pitches. The control unit 200 selects two nozzles 111 from the three or more nozzles 111 that discharge liquid at adjacent positions on the surface of the object 300, according to the radius of curvature of the surface of the object 300.

[0048] The example shown in Figure 8A shows five nozzles 111 with different nozzle diameters, arranged at the same pitch. The five nozzles 111 shown in Figure 8 are arranged in order of decreasing nozzle diameter along the first direction D1. Note that "multiple nozzles 111 are arranged in order of decreasing nozzle diameter" means that the nozzle diameter increases as you move toward a predetermined direction. In the example shown in Figure 8A, the predetermined direction corresponds to the opposite direction of the arrow indicating the first direction D1. The control unit 200 selects two nozzles 111 from these five nozzles 111 that will discharge liquid at adjacent positions on the surface of the object 300, according to the radius of curvature of the surface of the object 300. The process of selecting two nozzles 111 by the control unit 200 will be described in detail separately with reference to Figures 10, 11A, 11B, and 12.

[0049] With the needle valve 113 open for a constant amount of time, the larger the nozzle diameter of the nozzle 111, the greater the amount of liquid discharged from the nozzle 111. Therefore, by selecting a nozzle 111 to discharge liquid from three or more nozzles 111 with different diameters, the amount of liquid discharged from the nozzle 111 can be adjusted without changing the time the needle valve 113 is open. By not changing the time the needle valve 113 is open, changes in the flight speed of the liquid discharged from the nozzle 111 can be reduced, and the occurrence of the milk crown phenomenon can be reduced. This reduces liquid splashing and makes it easier to reduce uneven liquid application. Furthermore, by selecting two nozzles 111 to discharge liquid at adjacent positions on the object 300 from three or more nozzles 111 with different diameters, the amount of liquid applied to adjacent positions on the object 300 can be adjusted. This reduces the overlapping or separation of adjacent liquids on the surface of the object 300 according to the radius of curvature of the surface of the object 300, making it easier to reduce uneven liquid application. As described above, the first embodiment of this disclosure can reduce uneven application of liquid. Furthermore, in the first embodiment of this disclosure, the relative movement between the head and the object 300 by the variable mechanism 250 is not performed multiple times in order to reduce streaks. Therefore, uneven application of liquid to the object 300 can be reduced without reducing productivity.

[0050] The number of nozzles 111 is not limited to five, as long as there are three or more. Furthermore, three or more nozzles 111 may be arranged in order of increasing nozzle diameter along the first direction D1. "Arrangement of multiple nozzles 111 in order of increasing nozzle diameter" means that the nozzle diameter decreases as you move toward a predetermined direction. In the example shown in Figure 8A, "arrangement of multiple nozzles 111 in order of increasing nozzle diameter" means that the nozzle diameter decreases as you move toward the direction opposite to the direction indicated by the arrow representing the first direction D1. The control unit 200 can also select two nozzles 111 based on the "curvature," which is the reciprocal of the radius of curvature, rather than the "radius of curvature" of the surface of the object 300.

[0051] In the first embodiment of this disclosure, as shown in Figure 8B, five nozzles 111 with different nozzle diameters, arranged at the same pitch, may be arranged in a line along a first direction D1 and a second direction D2 intersecting the first direction D1. In the second example shown in Figure 8B, three of the five nozzles 111 are arranged along the first direction D1, and three of the five nozzles 111 are arranged along the second direction D2. The control unit 200 can obtain the same effect as in the first example shown in Figure 8A by selecting two nozzles 111 from the five nozzles 111 that discharge liquid at adjacent positions on the surface of the object 300, according to the radius of curvature of the surface of the object 300.

[0052] Furthermore, in the second example shown in Figure 8B, the control unit 200 can also select the central nozzle 111 from the five nozzles 111 as the reference nozzle, and, depending on the radius of curvature of the surface of the object 300, select the reference nozzle and another nozzle 111 to discharge from in addition to the reference nozzle. This makes it possible to bring the distance of the liquid discharged from the two selected nozzles 111 closer to the surface of the object 300, further reducing unevenness in liquid application.

[0053] In the first embodiment of this disclosure, depending on the shape of the object 300, liquid can be applied to the object 300 by using at least one of the arrangement of nozzles 111 according to the first example shown in Figure 8A and the arrangement of nozzles 111 according to the second example shown in Figure 8B.

[0054] (Configuration of the control unit 200) (Hardware configuration) Figure 9 is a block diagram showing the hardware configuration of the control unit 200. The control unit 200 includes a CPU (Central Processing Unit) 211, a ROM (Read Only Memory) 212, a RAM (Random Access Memory) 213, an HDD (Hard Disk Drive) / SSD (Solid State Drive) 214, a connection I / F (Interface) 215, and a communication I / F 216. These are electrically connected to each other via the system bus B. The control unit 200 is built using, for example, a PC.

[0055] The CPU 211 uses the RAM 213 as a workspace and controls the operation of the entire control unit 200 by executing programs stored in the ROM 212. The ROM 212 is a non-volatile memory that stores programs for controlling operations such as recording to the CPU 211, as well as other fixed data. The RAM 213 is a volatile memory that temporarily stores various types of data.

[0056] The HDD / SSD214 is a non-volatile memory capable of storing information such as painting area information Pd and shape information Od of the object 300's body. The information stored in the HDD / SSD214 can be read by the CPU211 and may be used during program execution. The connection I / F215 is an interface for controlling communication between the control unit 200 and other devices. Examples of external devices include the variable mechanism 250 and the head 1. The communication I / F216 is an interface for connecting to external devices such as an external PC for communication.

[0057] (Functional Configuration) The functional configuration of the control unit 200 will be described with reference to Figures 10, 11A, and 11B. Figure 10 is a block diagram showing the functional configuration of the control unit 200. Figure 11A is a diagram showing a first example of a method for determining the nozzle 111 that discharges liquid. Figure 11B is a diagram showing a second example of a method for determining the nozzle 111 that discharges liquid.

[0058] As shown in Figure 10, the control unit 200 includes a communication unit 221, an input / output unit 222, a drive command unit 223, a radius of curvature / angle acquisition unit 224, and a nozzle selection unit 225. The control unit 200 also includes a pulse signal generation unit 226, a relative movement trajectory acquisition unit 227, a discharge timing determination unit 228, a discharge control unit 229, and a storage unit 231.

[0059] The functions of the communication unit 221 are realized by the communication interface 216, etc. The functions of the input / output unit 222 are realized by the connection interface 215, etc. The functions of the drive command unit 223, the radius of curvature / angle acquisition unit 224, the nozzle selection unit 225, the pulse signal generation unit 226, the relative movement trajectory acquisition unit 227, the discharge timing determination unit 228, and the discharge control unit 229 are realized by executing various processes by executing instruction codes stored in memory using electronic circuits. Alternatively, each of the above functions may be realized by executing various processes using electronic circuits designed for special applications. The electronic circuit is, for example, the CPU 211. However, FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), etc. may be used as the electronic circuit. The functions of the storage unit 231 are realized by RAM 213, HDD / SSD 214, etc.

[0060] The control unit 200 may have a functional configuration other than those described above. Furthermore, devices or equipment other than the control unit 200 may have some of the functions of the control unit 200. These other devices may include an external PC, for example. Other equipment may include the variable mechanism 250 or the head 1, for example. Some of the functions of the control unit 200 may be realized through distributed processing between the control unit 200 and the other devices or equipment.

[0061] The communication unit 221 controls communication with external devices such as external PCs, thereby enabling the communication of signals and data with external devices. The input / output unit 222 controls communication with the variable mechanism 250 and the head 1, thereby enabling the input and output of signals and data between the variable mechanism 250 and the head 1.

[0062] The drive command unit 223 outputs a drive command Rc to the variable mechanism 250 via the input / output unit 222, and drives the variable mechanism 250 to move the head 1 relative to it.

[0063] The radius of curvature / angle acquisition unit 224 calculates and acquires the radius of curvature R at each discharge position on the surface of the object 300, based on the shape information Od of the object 300 which has a curved surface. The radius of curvature / angle acquisition unit 224 also calculates and acquires information on the flight angle, which is the angle between the flight direction of the liquid discharged from each of the multiple nozzles 111 and the normal direction of the surface of the object 300. For example, the radius of curvature / angle acquisition unit 224 calculates and acquires information on the normal direction at each position on the surface of the object 300, based on the shape information Od of the object 300 which has a curved surface. The radius of curvature / angle acquisition unit 224 can acquire information on the flight angle by calculating the angle between the flight direction of the liquid and the normal direction of the surface of the object 300.

[0064] The nozzle selection unit 225 determines the droplet radius r to be discharged from multiple nozzles 111 and land on the surface of the object 300, as well as the two nozzles to be used for painting, based on the radius of curvature R and flight angle acquired by the radius of curvature / angle acquisition unit 224. For example, the nozzle selection unit 225 can determine the droplet radius r to land on the surface of the object 300 and the two nozzles to be used for painting by referring to the correspondence information 233 stored in the storage unit 231. The nozzle selection unit 225 passes information regarding the droplet radius r and the two nozzles to be used for painting to the discharge control unit 229.

[0065] In the examples shown in Figures 11A and 11B, the correspondence information 233 is a table showing the correspondence between the radius of curvature R of the surface of the object 300 and the nozzle 111 that discharges the liquid. In Figures 11A and 11B, "〇" indicates a nozzle that is selected as the nozzle for discharging the liquid. Also, in the examples shown in Figures 11A and 11B, the number of nozzles 111 included in the head 1 is n in each case. The correspondence information 233 can be determined in advance through preliminary experiments, etc.

[0066] For example, in the first example shown in Figure 11A, when the radius of curvature R of the surface of the object 300 is 1 mm, the nozzle selection unit 225 selects "Nozzle 1" and "Nozzle 2" as the nozzles 111 that will discharge the liquid. In the example shown in Figure 11B, the nozzle selection unit 225 uses "Nozzle 3" as the reference nozzle and selects the reference nozzle and one other nozzle as the two nozzles 111 that will discharge the liquid.

[0067] The nozzle selection unit 225 can also select the nozzle 111 to be used for discharge by calculating the respective droplet radii r1 and r2 of two droplets d1 and d2 that land adjacent to the surface of the object 300 using the following equation (1), without using the correspondence information 233. r² = R × sinθ - r¹···(1)

[0068] Here, Figure 11C illustrates the method for calculating droplet radii r1 and r2 using the above formula (1) by the nozzle selection unit 225. In Figure 11C, the radius of curvature R is the radius of curvature of the surface of the object 300. The droplet radius r1 is the radius of droplet d1 discharged from one adjacent nozzle. The droplet radius r2 is the radius of droplet d2 discharged from the other adjacent nozzle. The flight angle θ is the angle between the direction L3 in which droplet d2 flies and the normal L2 of the surface of the object 300 at the point where droplet d2 lands, assuming that droplet d1 flies and lands along the normal L1 passing through the landing position on the surface of the object 300. The center position OR is the position of the center of curvature of the surface of the object 300.

[0069] The liquid dispensing device 201 uses a nozzle selection unit 225 to select the nozzle diameters of two adjacent nozzles such that the droplet radius r1 of droplet d1 and the droplet radius r2 of droplet d2 satisfy the relationship given by equation (1). This allows the liquid dispensing device 201 to bring droplets d1 and d2 into contact when they land on the surface of the object 300.

[0070] In equation (1), the flight angle θ is preferably small, for example, 30° or less, from the viewpoint of coating quality. When the flight angle θ is small, the distance on the curved surface and the distance on the plane are almost the same. For this reason, the nozzle selection unit 225 can select two nozzles suitable for discharge with simple calculations by applying a plane approximation. From the viewpoint of obtaining the flight angle θ and the relationship between adjacent liquids on the surface of the object 300 more accurately, it is preferable for the nozzle selection unit 225 to select two nozzles by performing calculations using the law of cosines or the like.

[0071] The pulse signal generation unit 226 generates a pulse signal k, which serves as a reference for the timing of liquid discharge from each of the multiple nozzles 111, according to the relative movement distance between the head 1 and the object 300 by the variable mechanism 250, and outputs it to the discharge timing determination unit 228 and the discharge control unit 229.

[0072] For example, the pulse signal generation unit 226 generates a pulse signal k based on a detection signal output by a detection unit such as a rotary encoder or acceleration sensor of the variable mechanism 250 in accordance with the operation of the variable mechanism 250. The timing for generating the pulse signal k may be predetermined based on an operation simulation of the variable mechanism 250.

[0073] The relative movement trajectory acquisition unit 227 acquires information on the relative movement trajectory between the object 300 and the head 1 by calculation, based on the painting area information Pd.

[0074] The discharge timing determination unit 228 determines the liquid discharge timing Δt based on the target distance, which is the distance between each of the multiple nozzles 111 and the object 300, and outputs it to the discharge control unit 229. For example, the discharge timing determination unit 228 calculates the target distance information for each division point obtained by dividing the relative movement trajectory by the discharge interval, which is the distance between discharge positions along the relative movement direction of the multiple nozzles 111 and the object 300. The discharge timing determination unit 228 can determine the liquid discharge timing Δt based on this target distance.

[0075] The discharge control unit 229 acquires a drive signal Hc based on the painting area information Pd, the pulse signal k, the droplet radius r, the two nozzles used for painting, and the liquid discharge timing Δt, and outputs the drive signal Hc to the head 1 via the input / output unit 222. Upon receiving the drive signal Hc, the head 1 discharges liquid from the multiple nozzles 111.

[0076] The storage unit 231 stores correspondence information 233, which is information indicating the correspondence between the size of each nozzle 111 and the droplet radius r and radius of curvature R corresponding to each nozzle 111, or information related to the correspondence.

[0077] <Processing by the control unit 200> Figure 12 is a flowchart illustrating the operation of the control unit 200. For example, the control unit 200 starts the process shown in Figure 12 when it receives shape information Od and painting area information Pd from an external PC or the like via the communication unit 221.

[0078] First, in step S111, the control unit 200 uses the radius of curvature / angle acquisition unit 224 to calculate and acquire the radius of curvature R based on the shape information Od of the object 300. The radius of curvature / angle acquisition unit 224 also calculates and acquires information regarding the normal direction of the surface of the object 300, and calculates the angle between the direction of liquid flight and the normal direction to acquire the flight angle.

[0079] Next, in step S112, the control unit 200, using the nozzle selection unit 225, selects, or calculates, the droplet radius r of the droplets that land on the surface of the object 300 from each of the multiple nozzles 111, and the two nozzles 111 from which to discharge the liquid, based on the radius of curvature R and flight angle acquired by the radius of curvature and angle acquisition unit 224, by referring to the correspondence information 233. The nozzle selection unit 225 then passes the information regarding the two selected or determined nozzles 111 to the discharge control unit 229.

[0080] Next, in step S113, the control unit 200 uses the pulse signal generation unit 226 to generate a pulse signal k, which serves as a reference for the timing of liquid discharge from each of the multiple nozzles 111, according to the relative movement distance L between the head 1 and the object 300 by the variable mechanism 250. The pulse signal generation unit 226 outputs the pulse signal k to the discharge timing determination unit 228 and the discharge control unit 229.

[0081] Next, in step S114, the control unit 200 uses the relative movement trajectory acquisition unit 227 to calculate and acquire information on the relative movement trajectory between the object 300 and the head 1 based on the painting area information Pd.

[0082] Next, in step S115, the control unit 200, using the discharge timing determination unit 228, calculates and obtains information on the target distance d at each division point obtained by dividing the relative movement trajectory according to the discharge interval of each of the multiple nozzles 111.

[0083] Next, in step S116, the control unit 200 determines the liquid discharge timing Δt based on the target distance d using the discharge timing determination unit 228.

[0084] Next, in step S117, the control unit 200, via the discharge control unit 229, outputs a drive signal Hc to the head 1 to discharge liquid, based on the coating area information Pd, the pulse signal k, the droplet radius r that lands on the surface of the object 300, and the liquid discharge timing Δt. The head 1 discharges liquid from each of the multiple nozzles 111 in response to the drive signal Hc.

[0085] Next, in step S118, the control unit 200 determines whether or not to terminate the process. For example, the control unit 200 can determine whether or not to terminate the process based on all the information in the shape information Od or the painted area information Pd.

[0086] If it is determined in step S118 that the process should not be terminated (step S118, NO), the control unit 200 repeats the process from step S111 onwards until it is determined in step S118 that the process should be terminated. On the other hand, if it is determined in step S118 that the process should be terminated (step S118, YES), The control unit 200 terminates the process.

[0087] In this way, the control unit 200 can control the discharge of the liquid based on the shape information Od and the coating area information Pd, and apply the liquid to the target object 300.

[0088] [Second Embodiment] Next, a second embodiment of this disclosure will be described. Note that names and reference numerals identical to those used in the previously described embodiments indicate the same or identical components or configurations, and detailed explanations will be omitted as appropriate. This also applies to the embodiments described hereafter.

[0089] Figure 13 is a schematic cross-sectional view of the nozzle plate 101 in the head of a liquid dispensing device according to the second embodiment of this disclosure, along the dispensing direction D3.

[0090] The nozzle 111 is a hole that penetrates the nozzle plate 101. As shown in Figure 13, in the second embodiment of this disclosure, the nozzle 111 includes an outlet portion 101a from which liquid is discharged and an inlet portion 101b located on the opposite side of the outlet portion 101a. The nozzle diameter Nb at the inlet portion 101b is greater than the nozzle diameter Na at the outlet portion 101a. The liquid dispensing device according to the second embodiment of this disclosure differs from the liquid dispensing device according to the first embodiment of this disclosure in this respect. Note that nozzle diameter refers to the diameter of the nozzle.

[0091] In the example shown in Figure 13, the nozzle 111 includes an outlet-side straight hole 111a located on the outlet-side 101a and an inlet-side straight hole 111b located on the inlet-side 101b. The diameter φb of the inlet-side straight hole 111b is larger than the diameter φa of the outlet-side straight hole 111a.

[0092] In a second embodiment of this disclosure, the fluid resistance of the nozzle 111 can be reduced by making the diameter φb of the inlet-side straight hole 111b larger than the diameter φa of the outlet-side straight hole 111a. This makes it possible to make the amount of liquid discharged from multiple nozzles 111 differ more significantly than the difference in the amount of liquid discharged from multiple nozzles 111 when the diameter φb is less than or equal to the diameter φa.

[0093] In a second embodiment of this disclosure, the diameter φb of the inlet-side straight hole 111b can be made larger than the diameter φa of the outlet-side straight hole 111a, and the depth hb of the inlet-side straight hole 111b can be made deeper than the depth ha of the outlet-side straight hole 111a. This further reduces the fluid resistance of the nozzle 111. As a result, the amount of liquid discharged between the multiple nozzles 111 can be made to differ even more significantly compared to the difference in the amount of liquid discharged between the multiple nozzles 111 when the depth hb is less than or equal to the depth ha.

[0094] Note that the tapered portion 110 in Figure 13 is formed when the nozzle 111 is machined using a drill. This tapered portion 110 is not necessarily required. However, from the viewpoint of facilitating the flow of liquid inside the nozzle 111, it is preferable to have the tapered portion 110.

[0095] The configuration in which the nozzle diameter Nb at the inlet portion 101b is larger than the nozzle diameter Na at the outlet portion 101a is not limited to one consisting of two straight holes of different diameters. For example, in a second embodiment of the present disclosure, the nozzle 111 may have a tapered shape in which the diameter gradually decreases from the inlet portion 101b to the outlet portion 101a.

[0096] The effects of the second embodiment of this disclosure, other than those described above, are the same as those described in the first embodiment of this disclosure.

[0097] [Third Embodiment] Next, a third embodiment of the present disclosure will be described with reference to Figures 14A and 14B. Figure 14A is a schematic bottom view showing a first example of a head of a liquid dispensing device according to the third embodiment of the present disclosure. Figure 14B is a schematic bottom view showing a second example of a head of a liquid dispensing device according to the third embodiment of the present disclosure.

[0098] In the second embodiment of the present disclosure, the head differs from the head in the first embodiment of the present disclosure in that the plurality of nozzles 111 include three or more nozzles 111 having the same nozzle diameter and arranged at different pitches. In Figures 14A and 14B, five nozzles 111 are arranged at different pitches P1, P2, P3, and P4. In the first example shown in Figure 14A, three or more nozzles 111 are arranged in a line along a first direction. In the second example shown in Figure 14B, three or more nozzles 111 are arranged in a line along a first direction D1 and a second direction D2 intersecting the first direction D1.

[0099] The larger the pitch between adjacent nozzles 111 among the multiple nozzles 111, and the smaller the radius of curvature R of the surface of the object 300, in other words, the sharper the curved surface, the more likely it is that the liquid discharged from the multiple nozzles 111 will be applied unevenly to the object 300. For example, the liquid discharged from the multiple nozzles 111 may not be applied evenly to the surface of the object 300, resulting in streaks (white spots). Furthermore, if the relative movement between the head and the object 300 by the variable mechanism 250 is performed multiple times to fill the streaks on the object 300 with liquid in order to reduce the streaks, productivity may decrease.

[0100] In the second embodiment of this disclosure, the control unit 200 selects two nozzles 111 that discharge liquid at adjacent positions on the surface of the object 300 from among three or more nozzles 111 arranged as shown in Figures 14A and 14B, according to the radius of curvature of the surface of the object 300. This makes it possible to apply liquid discharged from two nozzles arranged at the same pitch to the surface of the object 300 at equal intervals, even if it is not possible to apply liquid discharged from two nozzles at equal intervals to the surface of the object 300, by making the pitch between the two nozzles different. As a result, liquid discharged from multiple nozzles 111 can be applied to the surface of the object 300 at equal intervals according to the radius of curvature of the surface of the object 300, and unevenness in liquid application to the object 300 can be reduced. Furthermore, since the relative movement between the head and the object 300 by the variable mechanism 250 is not performed many times to reduce streaks, unevenness in liquid application to the object 300 can be reduced without reducing productivity.

[0101] The number of nozzles 111 is not limited to five, as long as there are three or more. Furthermore, the control unit 200 can also select two nozzles 111 based on the "curvature," which is the reciprocal of the radius of curvature, rather than the "radius of curvature" of the surface of the object 300.

[0102] The effects of the third embodiment of this disclosure, other than those described above, are the same as those described in the first embodiment of this disclosure.

[0103] [Fourth Embodiment] Next, a liquid dispensing device according to the fourth embodiment of this disclosure will be described. Figure 15 is a schematic perspective view showing a liquid dispensing device 201a according to the fourth embodiment of this disclosure. The liquid dispensing device 201a has a painting robot 8000 and is a device for painting the body of an automobile.

[0104] The painting robot 8000 is equipped with a robotic arm 810 that has multiple joints to enable free movement like a human arm, and a head 820 that ejects ink at the tip of the robotic arm 810. The robotic arm 810 is also equipped with a 3D sensor 830 near the head 820.

[0105] As the painting robot 8000, a multi-joint robot with an appropriate number of axes, such as 5, 6, or 7 axes, can be used. The painting robot 8000 detects the position of the head 820 relative to the object 300 using the 3D sensor 830, and moves the robot arm 810 to paint the object 300 based on the detection result. In this case, the head 1 according to the embodiment can be used as the head 820.

[0106] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims.

[0107] The ordinal numbers, quantities, and other figures used in the description of the embodiments are all illustrative to specifically illustrate the technology of the present invention, and the present invention is not limited to these illustrative figures. Furthermore, the connection relationships between the components are illustrative to specifically illustrate the technology of the present invention, and do not limit the connection relationships that realize the functions of the present invention.

[0108] The division of blocks in the functional block diagram is just one example; multiple blocks may be implemented as a single block, one block may be divided into multiple parts, or some functions may be moved to other blocks. Furthermore, the functions of multiple blocks with similar functions may be processed in parallel or time-sharing by a single piece of hardware or software. Also, some or all of the functions may be distributed across multiple computers. [Explanation of Symbols]

[0109] 1 head 2 Connector section 10 Housing 10a Upper housing 10b Lower housing 11 supply ports 12 Collection Ports 20 Covers 30 long hole 101 Nozzle Plate 101a Exit section 101b Entrance 110 Tapered section 111 Nozzles 111a Straight hole on the outlet side 111b Inlet side straight hole 112 channels 113 Needle valve 113a Valve body 113b O-ring 113c washer 114 Piezoelectric element 115 Retaining member 115a Central space 115b Tip 115c rear end 115d Female threaded hole 121 Bearing 124 Fixing screws 200 Control Unit 201, 201a Liquid discharge device 211 CPU 212 ROM 213 RAM 214 HDD / SSD 215 Connection I / F 216 Communication I / F 221 Communications Department 222 Input / output section 223 Drive command unit 224 Curvature radius / angle acquisition part 225 Nozzle Selection Section 226 Pulse signal generation unit 227 Relative movement trajectory acquisition unit 228 Discharge timing determination unit 229 Discharge control unit 231 Storage Unit 233 Correspondence Information 250 Variable Mechanism 300 objects 300-1, 300-2 Applied surface 301a Concentration unevenness 301b Suji 810 Robot Arm 820 head 830 3D Sensor 8000 Painting Robots B System Bathroom D1 1st direction D2 2nd direction D3 Discharge direction ha, hb depth k pulse signal Na, Nb Nozzle Diameter Od Shape Information P, P1, P2, P3, P4 pitch Pd Painting Area Information R radius of curvature r1, r2 droplet radius Rc drive command Hc drive signal δ gap Δt Liquid dispensing timing φa, φb diameter [Prior art documents] [Patent Documents]

[0110] [Patent Document 1] Japanese Patent Publication No. 2016-123942

Claims

1. A head having multiple nozzles for dispensing liquid onto the surface of an object, A variable mechanism for changing the relative position of the head with respect to the object, It includes at least a control unit that controls the movement of the head, The plurality of nozzles include at least one of three or more nozzles with different diameters arranged at the same pitch, and three or more nozzles with the same diameter arranged at different pitches. The control unit is a liquid dispensing device that selects two nozzles from among the three or more nozzles to dispense the liquid at adjacent positions on the surface of the object, according to the radius of curvature of the surface of the object.

2. The plurality of nozzles include three or more nozzles with different nozzle diameters that are arranged at the same pitch. The liquid dispensing device according to claim 1, wherein the three or more nozzles are arranged in a line along the first direction in order of increasing nozzle diameter or decreasing nozzle diameter.

3. The plurality of nozzles include three or more nozzles with different nozzle diameters that are arranged at the same pitch. The liquid dispensing device according to claim 1, wherein the three or more nozzles are arranged in a line along a first direction and a second direction intersecting the first direction.

4. The plurality of nozzles includes three or more nozzles having the same nozzle diameter and arranged at different pitches. The liquid dispensing device according to claim 1, wherein the three or more nozzles are arranged in a line along the first direction.

5. The plurality of nozzles includes three or more nozzles having the same nozzle diameter and arranged at different pitches. The liquid dispensing device according to claim 1, wherein the three or more nozzles are arranged in a line along a first direction and a second direction intersecting the first direction.

6. The nozzle is a hole that penetrates the nozzle plate and includes an outlet portion from which the liquid is discharged and an inlet portion located on the opposite side of the outlet portion of the nozzle. The liquid dispensing device according to claim 1, wherein the nozzle diameter at the inlet is larger than the nozzle diameter at the outlet.

7. The nozzle includes an outlet-side straight hole located on the outlet side and an inlet-side straight hole located on the inlet side, The liquid dispensing device according to claim 6, wherein the diameter of the inlet-side straight hole is larger than the diameter of the outlet-side straight hole.

8. The liquid dispensing device according to claim 7, wherein the depth of the inlet-side straight hole is greater than the depth of the outlet-side straight hole.

9. A method for dispensing liquid using a liquid dispensing device, wherein the liquid dispensing device is A head with multiple nozzles dispenses liquid onto the surface of an object. The variable mechanism changes the relative position of the head with respect to the object, The control unit controls at least the movement of the head, The plurality of nozzles include at least one of three or more nozzles with different diameters arranged at the same pitch, and three or more nozzles with the same diameter arranged at different pitches. The control unit, Information relating to the radius of curvature of the surface of the object is obtained, Of the three or more nozzles mentioned above, two nozzles that discharge the liquid at adjacent positions on the surface of the object are selected based on the information relating to the radius of curvature. A liquid discharge method comprising discharging a liquid from the two nozzles onto the surface of the object.

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