Printing device

Abstract

The present disclosure provides a printing device that improves print quality in a printing device using a robot. The printing device has a head including a first nozzle row in which a plurality of nozzles that eject a first ink are arranged, and a second nozzle row in which a plurality of nozzles that eject a second ink are arranged, and a robot that changes the position and attitude of the head with respect to a workpiece, the robot having an arm portion having a tip end at which the head is supported, a base end, and a plurality of joints, and a base portion connected to the base end, the second ink having a lower brightness than the first ink, the plurality of joints having a first joint that is the joint closest to the tip end among the plurality of joints, the first joint being a turning mechanism that turns around a first turning axis, and the distance between the second nozzle row and the first turning axis being smaller than the distance between the first nozzle row and the first turning axis when viewed in a direction along the first turning axis.

Description

Technical Field

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

[0002] A printing apparatus using an inkjet method employing a robot such as a multi-jointed robot is known. For example, the apparatus described in Patent Document 1 includes a head that serves as an inkjet head and a robot that holds the head.

[0003] When printing with multiple colors of ink, generally, the printing head is equipped with multiple nozzle rows for each color of ink. Patent Document 1 does not describe the configuration of these multiple nozzle rows when printing with multiple colors of ink. In printing apparatuses that use a robot to move the printing head, when printing with multiple colors of ink, it is desirable to achieve an appropriate configuration of the multiple nozzle rows to obtain good print quality.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2016-215438 Summary of the Invention

[0005] To address the above-mentioned issues, one aspect of the printing apparatus disclosed herein includes: a head comprising a first nozzle array with a plurality of nozzles for ejecting a first ink and a second nozzle array with a plurality of nozzles for ejecting a second ink; a robot having an arm and a base, the arm having a tip, a base end, and a plurality of joints, the base being connected to the base end, the head being supported on the tip, the robot causing the head to change position and orientation relative to a workpiece, the brightness of the second ink being lower than the brightness of the first ink, the plurality of joints having a first joint, the first joint being the joint closest to the tip among the plurality of joints, the first joint being a rotation mechanism about a first rotation axis, wherein when viewed in a direction along the first rotation axis, the distance between the second nozzle array and the first rotation axis is less than the distance between the first nozzle array and the first rotation axis. Attached Figure Description

[0006] Figure 1 A perspective view showing the outline of the printing apparatus according to the first embodiment.

[0007] Figure 2 This is a block diagram illustrating the electrical structure of the printing apparatus according to the first embodiment.

[0008] Figure 3 This is a perspective view showing the outline structure of the head unit used in the first embodiment.

[0009] Figure 4This diagram is used to explain the printing operation of the printing apparatus according to the first embodiment.

[0010] Figure 5 This is a schematic top view used to illustrate the configuration of the multiple nozzle rows in the first embodiment.

[0011] Figure 6 This is a schematic side view used to illustrate the configuration of the multiple nozzle rows in the first embodiment.

[0012] Figure 7 This is a schematic top view used to illustrate the configuration of the multiple nozzle rows in the second embodiment.

[0013] Figure 8 This is a schematic side view used to illustrate the configuration of the multiple nozzle rows in the second embodiment.

[0014] Figure 9 This is a perspective view showing the outline structure of the head unit used in the third embodiment.

[0015] Figure 10 This is a diagram used to illustrate the movement path of the head in the third embodiment.

[0016] Figure 11 This is a schematic side view used to illustrate the configuration of multiple nozzle rows in Example 1. Detailed Implementation

[0017] Hereinafter, preferred embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that the dimensions and scales of the parts in the drawings may differ appropriately from actual dimensions, and some parts may be shown schematically for ease of understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description.

[0018] For simplicity, the following description uses intersecting X-axis, Y-axis, and Z-axis as appropriate. Furthermore, in the following description, one direction along the X-axis is the X1 direction, and the opposite direction is the X2 direction. Similarly, opposite directions along the Y-axis are the Y1 and Y2 directions. Additionally, opposite directions along the Z-axis are the Z1 and Z2 directions.

[0019] Here, the X, Y, and Z axes correspond to the coordinate axes of a world coordinate system set in the space containing the robot 2 (described later). Typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. Within this world coordinate system, a base coordinate system is established based on the position of the base 210 of the robot 2 (described later) through calibration. For convenience, the following example illustrates the use of the world coordinate system as the robot coordinate system to control the movements of the robot 2.

[0020] Additionally, the Z-axis does not have to be vertical. Furthermore, while the X, Y, and Z axes are typically orthogonal, this is not a limitation, and there are cases where they are not orthogonal. For example, the X, Y, and Z axes can intersect each other at an angle between 80° and 100°.

[0021] 1. First Implementation Method

[0022] 1-1. Overview of Printing Equipment

[0023] Figure 1 The diagram shows a perspective view of the printing apparatus 1 according to the first embodiment. The printing apparatus 1 is an apparatus that performs printing on the surface of a workpiece W by inkjet printing.

[0024] The workpiece W has a surface WF that becomes the object of printing. Figure 1 In the example shown, the workpiece W is a cuboid, and surface WF is a plane. During printing, the workpiece W is supported as needed, for example by a predetermined mounting platform, robotic arm, or conveyor belt. Furthermore, the shape or size of the workpiece W or surface WF is not limited to... Figure 1 The examples shown are arbitrary. For instance, the surface WF can have curved or buckled portions, and the workpiece W can be a thin sheet material such as paper or cloth. Furthermore, the position or orientation of the workpiece W or the surface WF during printing is not limited to any particular type, as long as printing is feasible. Figure 1 The example shown is arbitrary.

[0025] like Figure 1 As shown, the printing apparatus 1 includes: a robot 2, a head unit 3, a controller 5, a piping unit 10, and a wiring unit 11. Hereinafter, these components will be briefly described in turn.

[0026] Robot 2 is the robot that changes the position and orientation of head unit 3 in the world coordinate system. Figure 1 In the example shown, robot 2 is a so-called six-axis vertical jointed robot.

[0027] like Figure 1 As shown, robot 2 has a base 210 and an arm 220.

[0028] The base 210 is a pedestal that supports the arm 220. Figure 1 In the example shown, the base 210 is fixed to a mounting surface such as a floor surface or a base facing the Z1 direction by means of threaded fastening or the like. However, the mounting surface to which the base 210 is fixed can be a surface facing any direction and is not limited to any particular direction. Figure 1 The examples shown could also be surfaces such as walls, ceilings, or movable trolleys.

[0029] Arm 220 is a six-axis robotic arm having a base end EB mounted on a base 210 and a tip ET that allows for three-dimensional changes in position and orientation relative to the base end EB. Specifically, arm 220 has arms 221, 222, 223, 224, 225, and 226, also referred to as links. These arms are connected together in the order of arms 221, 222, 223, 224, 225, and 226.

[0030] Arm 221 is connected to base 210 via joint 230_1, allowing it to rotate about rotation axis O1. Arm 222 is connected to arm 221 via joint 230_2, allowing it to rotate about rotation axis O2. Arm 223 is connected to arm 222 via joint 230_3, allowing it to rotate about rotation axis O3. Arm 224 is connected to arm 223 via joint 230_4, allowing it to rotate about rotation axis O4. Arm 225 is connected to arm 224 via joint 230_5, allowing it to rotate about rotation axis O5. Arm 226 is connected to arm 225 via joint 230_6, allowing it to rotate about rotation axis O6. Furthermore, joint 230_6 is an example of a "first joint," and rotation axis O6 is an example of a "first rotation axis." Joint 230_5 is an example of a "second joint," and rotation axis O5 is an example of a "second rotation axis."

[0031] Joints 230_1 to 230_6 are mechanisms that rotatably connect one of two adjacent components of the base 210 and arms 221 to 226 relative to the other. In the following text, joints 230_1 to 230_6 will sometimes be referred to as "joint 230". Here, the base end EB is one end of the arm 220 whose position in the basic coordinate system does not change even when joint 230 rotates, and the tip ET is the other end of the arm 220 whose position in the basic coordinate system changes due to rotation of joint 230_6. The base end EB can be defined, for example, as the intersection of the boundary between the base 210 and arm 221 and the rotation axis O1. Furthermore, the tip ET can be defined, for example, as the intersection of the end face of arm 226 furthest from arm 225 or the surface extending from that end face and the rotation axis O6.

[0032] Although Figure 1 Although not illustrated, joints 230_1 to 230_6 are each equipped with a drive mechanism that rotates one of the corresponding two components relative to the other. This drive mechanism may include, for example, a motor that generates the driving force for the rotation, a speed reducer that reduces and outputs the driving force, and a rotary encoder that detects the amount of motion, such as the angle of rotation. Furthermore, the assembly of these drive mechanisms for joints 230_1 to 230_6 corresponds to the [described later]... Figure 2 The arm drive mechanism 2a is shown. Furthermore, this motor is equivalent to... Figure 2 The motors shown are 2a1 to 2a6.

[0033] Rotation axis O1 is a perpendicular axis to a mounting surface (not shown) on which the base 210 is fixed. Rotation axis O2 is a perpendicular axis to rotation axis O1. Rotation axis O3 is a parallel axis to rotation axis O2. Rotation axis O4 is a perpendicular axis to rotation axis O3. Rotation axis O5 is a perpendicular axis to rotation axis O4. Rotation axis O6 is a perpendicular axis to rotation axis O5.

[0034] Furthermore, regarding these rotating axes, the term "perpendicular" includes not only the case where the angle between the two rotating axes is strictly 90°, but also the case where the angle between the two rotating axes deviates from 90° within a range of approximately ±5°. Similarly, the term "parallel" includes not only the case where the two rotating axes are strictly parallel, but also the case where one of the two rotating axes is tilted relative to the other within a range of approximately ±5°.

[0035] On the top end ET of the arm 220 of the robot 2 described above, a head unit 3 is installed as an end effector in a fixed state by means of thread fixing or the like.

[0036] Head unit 3 is an assembly having a head 3a that ejects multiple types of ink with different brightness levels toward the workpiece W. In this embodiment, in addition to the head 3a, head unit 3 also includes a pressure regulating valve 3b and an energy emission section 3c. Further details regarding head unit 3 will be provided later. Figure 3 Let me explain.

[0037] In this embodiment, a case is illustrated using four inks: a first ink, a second ink, a third ink, and a fourth ink, each with different brightness levels. The brightness of these inks, from highest to lowest, is listed as the first ink, the third ink, the fourth ink, and the second ink. In full-color printing, typically, these four inks are yellow ink, magenta ink, cyan ink, and black ink. In this case, the first ink is yellow ink, the second ink is black ink, and one of the third and fourth inks is magenta ink, while the other is cyan ink. Here, the brightness can, for example, conform to CIE L as specified by the International Commission on Illumination (CIE). * a * b * The color space is defined by its luminance. In this embodiment, CIE L... * a * b * The brightness values ​​for the color space are 83 for yellow ink, 54 for magenta ink, 56 for cyan ink, and 11 for black ink. Furthermore, the brightness values ​​of inks can be obtained, for example, by applying the ink to a medium such as printing paper to create a predetermined color mark, and then measuring the color mark using a colorimeter. Here, the comparison of the brightness values ​​of multiple inks can be performed by creating color marks for each of the multiple inks on the same medium using the same amount of ink, and then comparing the values ​​obtained by measuring the color marks of the multiple inks.

[0038] Such inks are, for example, liquid media in which color materials such as dyes or pigments are dissolved or dispersed in a solvent. While each ink can be any of the following: water-based inks that dissolve color materials such as dyes or pigments in water-based solvents, curable inks using curable resins such as UV-curable inks, and solvent-based inks that dissolve color materials such as dyes or pigments in organic solvents, curable inks are preferred. Although curable inks are not particularly limited, and can be, for example, any of the following: thermosetting, photocurable, radiation-curable, and electron beam-curable inks, photocurable inks such as UV-curable inks are preferred. Furthermore, inks containing color materials are not limited to yellow inks, magenta inks, blue-green inks, and black inks; for example, white inks, gray inks, light blue-green inks, and light magenta inks can also be used.

[0039] The head unit 3 is connected to a piping section 10 and a wiring section 11. The piping section 10 is a piping assembly that supplies ink from an ink tank (not shown) to the head unit 3. The wiring section 11 is a wiring or wiring assembly that supplies electrical signals for driving the head 3a.

[0040] Controller 5 is a robot controller that controls the drive of robot 2. The following is based on... Figure 2 The electrical structure of the printing apparatus 1 will be described in a manner that includes a detailed description of the controller 5.

[0041] 1-2. Electrical Structure of the Printing Equipment

[0042] Figure 2 Here is a block diagram illustrating the electrical structure of the printing apparatus 1 according to the first embodiment. Figure 2 The diagram shows the electrical structural elements within the structural elements of the printing apparatus 1. For example... Figure 2 As shown, in the printing apparatus 1, in addition to having the aforementioned Figure 1 In addition to the structural elements shown, it also includes a control module 6 that is communicatively connected to the controller 5, and a computer 7 that is communicatively connected to both the controller 5 and the control module 6.

[0043] in addition, Figure 2 The various electrical structural elements shown can be appropriately divided, partially included in other structural elements, or integrally formed with other structural elements. For example, part or all of the function of controller 5 or control module 6 can be implemented by computer 7, or by other external devices such as PC (personal computer) connected to controller 5 via a network such as LAN (Local Area Network) or the Internet.

[0044] The controller 5 has the function of controlling the drive of the robot 2 and generating a signal D3 to synchronize the ink ejection action in the head unit 3 with the action of the robot 2.

[0045] The controller 5 has a storage circuit 5a and a processing circuit 5b.

[0046] The storage circuit 5a stores various programs executed by the processing circuit 5b and various data processed by the processing circuit 5b. The storage circuit 5a may include, for example, a semiconductor memory comprising one or both of the following: volatile memory such as RAM (Random Access Memory) and non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable Read-Only Memory). Alternatively, part or all of the storage circuit 5a may be included in the processing circuit 5b.

[0047] The storage circuit 5a stores path information Da. Path information Da represents the path that the head unit 3 should move along and the orientation of the head unit 3 along that path. Path information Da is generated, for example, using information obtained through direct instruction or online instruction, and CAD (computer-aided design) data representing the shape of the workpiece W. Path information Da is represented, for example, using coordinate values ​​from a base coordinate system or a world coordinate system. The path information Da can be input from the computer 7 into the storage circuit 5a.

[0048] The processing circuit 5b controls the movement of the arm drive mechanism 2a of the robot 2 based on the path information Da, and generates a signal D3. The processing circuit 5b may include, for example, one or more processors such as CPUs (Central Processing Units). Alternatively, the processing circuit 5b may replace the CPU or include programmable logic devices such as FPGAs (Field-Programmable Gate Arrays) in addition to the CPU.

[0049] Here, the arm drive mechanism 2a is an assembly of the drive mechanisms for the aforementioned joints 230_1 to 230_6, and for each joint 230, it has motors 2a1 to 2a6 for driving the joint 230, and an encoder (not shown) for detecting the rotation angle of the joint 230. Specifically, motor 2a1 is for driving joint 230_1; motor 2a2 is for driving joint 230_2; motor 2a3 is for driving joint 230_3; motor 2a4 is for driving joint 230_4; motor 2a5 is for driving joint 230_5; and motor 2a6 is for driving joint 230_6.

[0050] The processing circuit 5b performs inverse kinematics calculations, converting the path information Da into motion quantities such as rotation angles and rotational speeds of each joint 230 of the robot 2. Then, the processing circuit 5b outputs control signals Sk1 based on the outputs D1 of each encoder from the arm drive mechanism 2a, in a manner that makes the actual rotation angles and rotational speeds of each joint 230 the motion quantities based on the aforementioned calculation results of the path information Da. The control signals Sk1 are signals used to control the drive of the motors of the arm drive mechanism 2a. Here, the control signals Sk1 are corrected by the processing circuit 5b as needed, based on the output of a distance measuring instrument (not shown). This distance measuring instrument is, for example, mounted on the head unit 3 and outputs a signal corresponding to the distance between itself and the workpiece W.

[0051] Furthermore, the processing circuit 5b generates a signal D3 based on the output D1 from at least one of the plurality of encoders from the arm drive mechanism 2a. For example, the processing circuit 5b generates a trigger signal, including a timing pulse from the output D1 of one of the plurality of encoders, which is set to a predetermined value, as signal D3.

[0052] The control module 6 is a circuit that controls the ink ejection action in the head unit 3 based on the signal D3 output from the controller 5 and the printing data Img from the computer 7. The control module 6 includes a timing signal generation circuit 6a, a power supply circuit 6b, a control circuit 6c, and a drive signal generation circuit 6d.

[0053] The timing signal generation circuit 6a generates a timing signal PTS based on signal D3. The timing signal generation circuit 6a is, for example, composed of a timer that begins generating the timing signal PTS upon detection of signal D3. The timing signal PTS, for example, includes pulses defined based on output D1.

[0054] The power supply circuit 6b receives power from a commercial power supply not shown in the diagram and generates various predetermined potentials. These potentials are appropriately supplied to the control module 6 and various parts of the head unit 3. For example, the power supply circuit 6b generates a power supply potential VHV and a bias potential VBS. The bias potential VBS is supplied to the head unit 3. Furthermore, the power supply potential VHV is supplied to the drive signal generation circuit 6d.

[0055] The control circuit 6c generates the printing data signal SI, the waveform specification signal dCom, the latch signal LAT, the clock signal CLK, and the conversion signal CNG based on the timing signal PTS. These signals are synchronized with the timing signal PTS. The waveform specification signal dCom is input to the drive signal generation circuit 6d, while the other signals are input to the switching circuit 3e of the head unit 3.

[0056] The printing data signal SI is a digital signal used to specify the operating state of the drive element of the head 3a of the head unit 3. Specifically, the printing data signal SI specifies whether to supply the drive signal Com (described later) to the drive element based on printing data. This specification specifies, for example, whether ink is ejected from the nozzle corresponding to the drive element, or the amount of ink ejected from the nozzle. The waveform specification signal dCom is a digital signal used to specify the waveform of the drive signal Com. The latch signal LAT and the conversion signal CNG are used in conjunction with the printing data signal SI and specify the timing of ink ejection from the nozzle by specifying the driving timing of the drive element. The clock signal CLK is a clock signal that is synchronized with the timing signal PTS and serves as a reference.

[0057] The control circuit 6c described above includes, for example, one or more processors such as CPUs. Alternatively, the control circuit 6c may replace a CPU or include programmable logic devices such as FPGAs in addition to a CPU.

[0058] The drive signal generation circuit 6d is a circuit that generates drive signals Com for driving the various drive elements of the head 3a of the head unit 3. Specifically, the drive signal generation circuit 6d includes, for example, a DA conversion circuit and an amplification circuit. In the drive signal generation circuit 6d, the DA conversion circuit converts the waveform specification signal dCom from the control circuit 6c from a digital signal to an analog signal, and the amplification circuit amplifies the analog signal using the power supply potential VHV from the power supply circuit 6b, thereby generating the drive signal Com. Here, the signal of the waveform actually supplied to the drive element in the waveform contained in the drive signal Com is the drive pulse PD. The drive pulse PD is supplied to the drive element from the drive signal generation circuit 6d via the switching circuit 3e of the head unit 3.

[0059] Here, the switching circuit 3e is a circuit that includes a switching element that switches whether to supply at least a portion of the waveform contained in the drive signal Com as a drive pulse PD based on the printed data signal SI.

[0060] The computer 7 has the function of supplying path information Da and other information to the controller 5, and the function of supplying printing data Img and other information to the control module 6. In addition to these functions, the computer 7 in this embodiment also has the function of controlling the drive of the energy emission unit 3c. The computer 7 is, for example, a desktop or laptop computer with programs that implement these functions installed.

[0061] 1-3. Structure of the head unit

[0062] Figure 3 Here is a perspective view showing the outline structure of the head unit 3 used in the first embodiment. For convenience, the following description will appropriately use the intersecting a-axis, b-axis, and c-axis. Furthermore, in the following description, one direction along the a-axis is the a1 direction, and the direction opposite to the a1 direction is the a2 direction. Similarly, the opposite directions along the b-axis are the b1 direction and the b2 direction. Furthermore, the opposite directions along the c-axis are the c1 direction and the c2 direction.

[0063] Here, the a-axis, b-axis, and c-axis correspond to the coordinate axes of the tool coordinate system set in the head unit 3. The robot 2's movements change its relative position and orientation with respect to the world coordinate system or robot coordinate system. Figure 3 In the example shown, the c-axis is parallel to the aforementioned rotation axis O6. Furthermore, while the a-axis, b-axis, and c-axis are typically orthogonal, this is not a limitation; they can intersect at angles between 80° and 100°. Additionally, the tool coordinate system and the base coordinate system or robot coordinate system are established through calibration. Moreover, the tool coordinate system is set, for example, with the center of the ejection surface FN (described later) as the reference (TCP: tool center point).

[0064] As described above, head unit 3 includes a head 3a, a pressure regulating valve 3b, and an energy emission section 3c. These components are all... Figure 3 The support is shown as 3f with double-dotted lines. Additionally, although in Figure 3 In the example shown, the head unit 3 has one head 3a and one pressure regulating valve 3b, but this number is not limited to one. Figure 3 The example shown can also include more than two. Furthermore, the position of the pressure regulating valve 3b is not limited to the head unit 3; for example, it can be the arm 226, or it can be a position fixed relative to the base 210.

[0065] The support 3f is made of, for example, a metallic material and is a solid rigid body. Figure 3 In the example shown, the support body 3f is a flat plate extending in a direction orthogonal to axis a. In this embodiment, a head 3a is mounted on the surface of the support body 3f facing the a1 direction. On the other hand, an energy emission part 3c is mounted on the surface of the support body 3f facing the a2 direction. Furthermore, the shape of the support body 3f is not limited to... Figure 3 The example shown is arbitrary; for example, it could also be box-shaped, etc.

[0066] The aforementioned support body 3f is mounted on the arm 226. Therefore, the head 3a, pressure regulating valve 3b, and energy emission part 3c are supported on the arm 226 in a unified manner by the support body 3f. Thus, the relative positions of the head 3a, pressure regulating valve 3b, and energy emission part 3c with respect to the arm 226 are fixed. Figure 3 In the example shown, a pressure regulating valve 3b is positioned in the c1 direction relative to the head 3a. An energy emission section 3c is positioned in the a2 direction relative to the head 3a.

[0067] The head 3a has an ejection surface FN and a plurality of nozzles N that are open on the ejection surface FN. The ejection surface FN is a nozzle surface with the nozzles N open, for example, it is formed by the surface of a nozzle plate on a plate-shaped member made of a material such as silicon (Si) or metal, in which the nozzles N are provided as through holes.

[0068] exist Figure 3 In the example shown, the normal direction of the ejection surface FN is the c2 direction. Here, the rotation axis O6 intersects the ejection surface FN. In the illustration, when viewed along the direction of the rotation axis O6, the center PC of the ejection surface FN is aligned with the rotation axis O6. However, when viewed along the direction of the rotation axis O6, the center PC of the ejection surface FN may deviate from the rotation axis O6.

[0069] Multiple nozzles N disposed on the ejection surface FN are divided into a first nozzle column L1, a second nozzle column L2, a third nozzle column L3, and a fourth nozzle column L4. These nozzle columns are arranged in a direction facing a1 and are spaced apart from each other in the order of first nozzle column L1, fourth nozzle column L4, second nozzle column L2, and third nozzle column L3.

[0070] The first nozzle array L1, the second nozzle array L2, the third nozzle array L3, and the fourth nozzle array L4 are each a collection of multiple nozzles N arranged linearly along the b-axis. In this embodiment, the nozzle density of each nozzle N in each nozzle array along the b-axis is 300 npi (number of nozzles per inch). However, the invention is not limited to this; lower nozzle densities are possible, but from the viewpoint of print quality or efficiency, a nozzle density of 25 npi or higher is preferred. Furthermore, to achieve such a nozzle density, the nozzles N can be staggered in each nozzle array. Here, the first nozzle array L1, the second nozzle array L2, the third nozzle array L3, and the fourth nozzle array L4 eject different types of ink. Specifically, the first nozzle array L1 ejects a first ink. The second nozzle array L2 ejects a second ink. The third nozzle array L3 ejects a third ink. The fourth nozzle array L4 ejects a fourth ink. Since any ink is ejected in the c2 direction under ideal conditions, the c2 direction can also be expressed as the ejection direction. Furthermore, the configuration of the first nozzle array L1, the second nozzle array L2, the third nozzle array L3, and the fourth nozzle array L4 will be discussed later based on... Figure 5 as well as Figure 6 Let me describe it in detail.

[0071] Although not illustrated, the head 3a has a piezoelectric element as a driving element and a cavity for collecting ink for each nozzle N. Here, the piezoelectric element causes a pressure change in the cavity corresponding to the piezoelectric element, thereby causing ink to be ejected from the nozzle corresponding to that cavity. Such a head 3a can be obtained, for example, by using an adhesive or the like to bond together multiple substrates, such as silicon substrates, that have been appropriately processed by etching. Alternatively, a heater that heats the ink within the cavity can be used instead of the piezoelectric element as the driving element for ejecting ink from the nozzle.

[0072] In the above-described head 3a, ink is supplied to an ink tank (not shown) via the first supply pipe 10a1, the second supply pipe 10a2, the third supply pipe 10a3, and the fourth supply pipe 10a4. Here, a pressure regulating valve 3b is located between each of the first, second, third, and fourth supply pipes 10a1 and the head 3a. The first supply pipe 10a1 is a flexible pipe that supplies the first ink to the head 3a. The second supply pipe 10a2 is a flexible pipe that supplies the second ink to the head 3a. The third supply pipe 10a3 is a flexible pipe that supplies the third ink to the head 3a. The fourth supply pipe 10a4 is a flexible pipe that supplies the fourth ink to the head 3a.

[0073] exist Figure 3In the example shown, the downstream ends of the first supply pipe 10a1, the second supply pipe 10a2, the third supply pipe 10a3, and the fourth supply pipe 10a4 face the direction a1 and are arranged in the order of the first supply pipe 10a1, the fourth supply pipe 10a4, the second supply pipe 10a2, and the third supply pipe 10a3. Here, the distance between the downstream end of the second supply pipe 10a2 or the fourth supply pipe 10a4 and the rotation shaft O6 is less than the distance between the downstream end of the first supply pipe 10a1 or the third supply pipe 10a3 and the rotation shaft O6.

[0074] The pressure regulating valve 3b is a valve mechanism that opens and closes according to the pressure of the ink in the head 3a. Through this opening and closing, even if the positional relationship between the head 3a and the aforementioned ink reservoir (not shown) changes, the pressure of the ink in the head 3a is maintained at a negative pressure within a predetermined range. Therefore, the meniscus of the ink formed in the nozzle N of the head 3a is stabilized. As a result, air bubbles entering the nozzle N or ink overflowing from the nozzle N is prevented. Furthermore, the ink from the pressure regulating valve 3b is appropriately distributed to multiple locations in the head 3a via a branched flow path (not shown). Here, the ink from the ink reservoir (not shown) is transferred at a predetermined pressure to the first supply pipe 10a1, the second supply pipe 10a2, the third supply pipe 10a3, and the fourth supply pipe 10a4 using a pump or head difference, etc. Additionally, although not shown, the pressure regulating valve 3b has an ink flow path and a pressure regulating structure for each type of ink, so that the pressure of each of the four inks can be individually adjusted.

[0075] The energy emitting unit 3c emits energy such as light, heat, electron beams, or radiation to harden or cure the ink on the workpiece W. For example, if the ink has ultraviolet curability, the energy emitting unit 3c is composed of a light-emitting element such as an LED (light emitting diode) that emits ultraviolet light. In addition, the energy emitting unit 3c may also appropriately include optical components such as lenses for adjusting the direction or range of energy emission.

[0076] Here, the energy emission section 3c includes an emission surface FL that emits the energy, and is arranged such that the emission surface FL faces the c2 direction. Furthermore, as described above, since the rotation axis O6 intersects with the ejection surface FN, the distance between each nozzle row and the rotation axis O6 is smaller than the distance between the ejection surface FL and the rotation axis O6.

[0077] Alternatively, the energy emission section 3c may not completely harden or cure the ink on the workpiece W. In this case, for example, the ink irradiated by the energy emission section 3c may be completely hardened or cured by the energy from a curing light source that is separately provided on the mounting surface of the base 210 of the robot 2.

[0078] 1-3. Printing Operation of the Printing Equipment

[0079] Figure 4 This is a diagram used to explain the printing operation of the printing apparatus 1 according to the first embodiment. Figure 4 The example illustrates printing on a predetermined area RP of the surface WF of a workpiece W positioned in the X2 direction relative to the base 210 of the robot 2 when viewed along the Y-axis. Alternatively, when viewed along the X-axis, the workpiece W can be positioned offset from the base 210 of the robot 2 in either the Y1 or Y2 direction. Furthermore, when the robot 2 is suspended from the ceiling, the workpiece W and the base 210 can be positioned to overlap when viewed along the Z-axis.

[0080] During the printing process, robot 2 causes the head 3a to change its position and orientation while simultaneously ejecting ink from the head 3a. The changes in the position and orientation of the head 3a are implemented based on path information Da. Thus, the head 3a maintains a predetermined orientation relative to the surface WF while moving along the movement path RU. Furthermore, the movement of the head 3a along the movement path RU can be performed multiple times each time different colors of ink are ejected, or all ink ejection can be performed in parallel during a single movement of the head 3a along the movement path RU.

[0081] The movement path RU is the path from position PS to position PE. Position PS is the position relative to the predetermined area RP in the X1 direction when viewed in the Z2 direction. Position PE is the position relative to the predetermined area RP in the X2 direction when viewed in the Z2 direction. During the period from position PS to the predetermined area RP, head 3a accelerates until it reaches a predetermined speed. During the period when head 3a is on the predetermined area RP, head 3a moves at a fixed speed at that predetermined speed. During the period from the predetermined area RP to position PE, head 3a decelerates in a manner that allows it to stop at position PE. Here, the predetermined area RP is the area that crosses from position PR1 to position PR2 along the movement path RU.

[0082] exist Figure 4In the example shown, the movement path RU is straight when viewed in the Z2 direction. During the execution of the printing action, the robot 2 moves the head 3a linearly along the movement path RU by manipulating three or more of the six joints 230, including joints 230_2, 230_3, and 230_5. Furthermore, the robot 2 moves the head 3a in a direction away from the base 210. Here, the aforementioned a1 direction is forward of the head 3a in the direction of movement. Therefore, the energy emission section 3c is located rearward relative to the head 3a in the direction of movement. Thus, energy from the energy emission section 3c can be applied to the ink that has just been sprayed from the head 3a onto the surface WF.

[0083] Here, when viewed along the X-axis, with the workpiece W positioned overlapping the base 210, the movement path RU appears as a straight line along the X-axis when viewed along the Z2 direction. Furthermore, in this case, the robot 2 performs the printing action by manipulating three of the six joints 230. More specifically, during the printing action, the robot 2 sets the rotation axes of joints 230_2, 230_3, and 230_5 to be parallel to the Y-axis and manipulates these joints 230. Through the manipulation of these three joints 230, the head 3a can move stably along the movement path RU. In this case, it is not necessary to manipulate joint 230_6. On the other hand, when viewed along the X-axis, if the workpiece W is positioned at a location that deviates from the base 210 in the Y1 or Y2 direction, and the movement path RU is a straight line along the X-axis when viewed in the Z2 direction, in order to maintain the posture relative to the movement direction of the head 3a, the joint 230_6 needs to move along the movement path RU. Therefore, the effect achieved by the nozzle array configuration, as described later, is more significant.

[0084] Alternatively, robot 2 can also move head 3a from position PE to position PS along the movement path RU in a direction close to base 210. In this case, the orientation of head unit 3 is adjusted so that it faces forward in the movement direction of head 3a in the direction a1. Figure 4 The printing is performed in the state shown, which is rotated 180° around the rotation axis O6.

[0085] Furthermore, since the aforementioned a1 direction is forward in the direction of movement of the head 3a during the execution of the printing action, these nozzle rows are arranged from near to far relative to the base 210 in the order of the aforementioned first nozzle row L1, fourth nozzle row L4, second nozzle row L2, and third nozzle row L3.

[0086] 1-4. Nozzle array configuration

[0087] Figure 5 This is a schematic top view used to illustrate the configuration of multiple nozzle rows in the first embodiment. Figure 5 The diagram shows the first nozzle array L1, the second nozzle array L2, the third nozzle array L3, and the fourth nozzle array L4 as viewed in the c1 direction. As described above, these nozzle arrays are arranged in the order of first nozzle array L1, fourth nozzle array L4, second nozzle array L2, and third nozzle array L3, facing the a1 direction. Figure 5 In the example shown, these nozzle rows are arranged at equal intervals. Alternatively, the intervals between these nozzle rows can be unequal. Furthermore, the lengths of these nozzle rows can also be different.

[0088] Here, when viewed along the direction of rotation axis O6, rotation axis O6 is located inside the region RN defined by the set of the first nozzle row L1, the second nozzle row L2, the third nozzle row L3, and the fourth nozzle row L4. Region RN can be represented as a quadrilateral with the smallest area enclosed by all the nozzles N set on the ejection surface FN. Figure 5 In the example shown, since the nozzle rows are of equal length and configured with their ends aligned, the region RN is rectangular in shape. However, the shape of region RN can be any quadrilateral, not limited to rectangles. For example, when the nozzle rows extend in the same direction inclined relative to the b-axis, the region RN is parallelogram-shaped. Furthermore, the ends of the nozzle rows may not be aligned. That is, at least one of the nozzle rows may be offset in the direction of extension of the nozzle rows.

[0089] exist Figure 5 In the example shown, when viewed along the direction of rotation axis O6, rotation axis O6 is located between the second nozzle row L2 and the fourth nozzle row L4. Furthermore, the position of rotation axis O6 as observed along the direction of rotation axis O6 is not limited to... Figure 5 The example shown could, for instance, be a position overlapping with the second nozzle array L2 or the fourth nozzle array L4. However, it is preferable that, among the first nozzle array L1, the second nozzle array L2, the third nozzle array L3, and the fourth nozzle array L4, the second nozzle array L2 is the nozzle array closest to the center PC of the ejection surface FN or the rotation axis O6.

[0090] As understood from the above, when viewed along the direction of rotation axis O6, the distance DN12 between the second nozzle array L2 and the rotation axis O6 is less than the distance DN11 between the first nozzle array L1 and the rotation axis O6, and less than the distance DN13 between the third nozzle array L3 and the rotation axis O6.

[0091] Similarly, the distance DN14 between the fourth nozzle array L4 and the rotation shaft O6 is less than the distance DN11 between the first nozzle array L1 and the rotation shaft O6, and less than the distance DN13 between the third nozzle array L3 and the rotation shaft O6.

[0092] exist Figure 5 In the example shown, distance DN11 is equal to distance DN13, and distance DN12 is equal to distance DN14. Alternatively, distance DN11 can be different from distance DN13. Furthermore, distance DN12 can also be different from distance DN14.

[0093] Figure 6 This is a schematic side view used to illustrate the configuration of the multiple nozzle rows in the first embodiment. Figure 6 The diagram shows the first nozzle array L1, the second nozzle array L2, the third nozzle array L3, and the fourth nozzle array L4 viewed in the b1 direction as the plurality of nozzle arrays.

[0094] Here, as Figure 6 As shown, the rotation axis O5 is orthogonal to the rotation axis O6. When viewed along the direction of the rotation axis O5, the distance DN22 between the second nozzle array L2 and the rotation axis O5 is less than the distance DN21 between the first nozzle array L1 and the rotation axis O5, and less than the distance DN23 between the third nozzle array L3 and the rotation axis O5.

[0095] Similarly, when viewed along the direction of rotation axis O5, the distance DN24 between the fourth nozzle array L4 and the rotation axis O5 is less than the distance DN21 between the first nozzle array L1 and the rotation axis O5, and less than the distance DN23 between the third nozzle array L3 and the rotation axis O5.

[0096] exist Figure 6 In the example shown, distance DN21 is equal to distance DN23, and distance DN22 is equal to distance DN24. Alternatively, distance DN21 can be different from distance DN23. Furthermore, distance DN22 can also be different from distance DN24.

[0097] 1-5. Summary of the First Implementation Method

[0098] As described above, the printing apparatus 1 includes a head 3a and a robot 2 that changes the position and orientation of the head 3a relative to the workpiece W. Here, the head 3a includes a first nozzle array L1 with multiple nozzles N emitting a first ink and a second nozzle array L2 with multiple nozzles N emitting a second ink. The robot 2 has an arm 220 having a tip ET, a base EB, and multiple joints 230; and a base 210 connected to the base EB, supporting the head 3a on the tip ET. The brightness of the second ink is lower than that of the first ink. The multiple joints 230 include a joint 230_6, which is an example of a "first joint". Joint 230_6 is the joint 230 closest to the tip ET among the multiple joints 230. Furthermore, joint 230_6 is a rotation mechanism about a rotation axis O6, which is an example of a "first rotation axis".

[0099] Based on this, when observed along the direction of rotation axis O6, the distance DN12 between the second nozzle array L2 and the rotation axis O6 is less than the distance DN11 between the first nozzle array L1 and the rotation axis O6.

[0100] In the printing apparatus 1 described above, since the brightness of the second ink is lower than that of the first ink, the spraying error of the second ink relative to the workpiece W is more noticeable compared to the spraying error of the first ink relative to the workpiece W. That is, compared to the first ink, the second ink is more likely to cause a decrease in print quality due to the spraying error relative to the workpiece W. Therefore, in order to improve print quality, the distance DN12 between the second nozzle array L2 and the rotation axis O6 is made smaller than the distance DN11 between the first nozzle array L1 and the rotation axis O6 when viewed along the rotation axis O6.

[0101] To be more specific, joint 230_6 can sometimes become a source of vibration in the arm 220 compared to other joints 230 due to insufficient holding force caused by the low rated output of the motor, backlash in the reducer, etc. Here, the greater the distance of nozzle N from the rotation axis O6, the greater the ink spraying error caused by this vibration. This is because the greater the distance of nozzle N from the rotation axis O6, the greater the torque around the rotation axis O6. Therefore, by making the distance DN12 smaller than the distance DN11, the influence of this torque on the second nozzle array L2 can be suppressed compared to the first nozzle array L1. As a result, the vibration of the second nozzle array L2 accompanying the vibration of joint 230_6 can be reduced compared to the vibration of the first nozzle array L1. Therefore, the spraying error of the second ink relative to the workpiece W can be reduced.

[0102] Furthermore, as described above, each of the plurality of joints 230 is provided with a motor 2a1 to 2a6 for driving the joint 230. Here, the rated output of the motor 2a6 for driving joint 230_6 is less than the rated output of the motors 2a1 to 2a5 for driving each of the other joints 230_1 to 230_5 in the plurality of joints 230.

[0103] On the other hand, although the vibration of the first nozzle line L1, which is accompanied by the vibration of the joint 230_6, is greater than that of the second nozzle line L2, the first nozzle line L1 uses a first ink whose spraying error is less noticeable compared to the second ink.

[0104] As described above, by improving the spraying accuracy of the second ink, whose spraying error is more noticeable, compared to the first ink, whose spraying error is less noticeable, among the first ink and the second ink with different brightness, the overall reduction in print quality caused by the spraying error of the ink relative to the workpiece W can be reduced. Therefore, compared to structures where the distance from DN12 is greater than DN11, print quality can be improved.

[0105] In this embodiment, as described above, the head 3a further includes a third nozzle array L3 with a plurality of nozzles N arranged to eject a third ink. The brightness of the third ink is lower than that of the first ink but higher than that of the second ink. Furthermore, when viewed along the rotation axis O6, the distance DN12 between the second nozzle array L2 and the rotation axis O6 is smaller than the distance DN13 between the third nozzle array L3 and the rotation axis O6. Moreover, when viewed along the rotation axis O6, the second nozzle array L2 is located between the first nozzle array L1 and the third nozzle array L3. Therefore, even when a third ink is used in addition to the first and second inks, the reduction in print quality caused by ink ejection error relative to the workpiece W can be reduced.

[0106] Furthermore, in this embodiment, as described above, the head 3a also includes a fourth nozzle array L4, in which a plurality of nozzles N for ejecting a fourth ink are arranged. The brightness of the fourth ink is higher than that of the second ink and lower than that of the third ink. Based on this, when viewed along the rotation axis O6, the distance DN14 between the fourth nozzle array L4 and the rotation axis O6 is smaller than the distance DN11 between the first nozzle array L1 and the rotation axis O6, and smaller than the distance DN13 between the third nozzle array L3 and the rotation axis O6. Moreover, when viewed along the rotation axis O6, the fourth nozzle array L4 is located between the first nozzle array L1 and the third nozzle array L3. Therefore, even when a fourth ink is used in addition to the first, second, and third inks, the reduction in print quality caused by ink ejection error relative to the workpiece W can be reduced.

[0107] Furthermore, as described above, the plurality of joints 230 includes joint 230_5 as an example of a "second joint". Joint 230_5 is the joint 230 closest to the top ET among the plurality of joints 230, second only to joint 230_6. Furthermore, joint 230_5 is a rotation mechanism about a rotation axis O5 as an example of a "second rotation axis". Rotation axis O5 is an axis that intersects rotation axis O6. Based on this, when viewed in the direction along rotation axis O5, the distance DN22 between the second nozzle array L2 and rotation axis O5 is less than the distance DN21 between the first nozzle array L1 and rotation axis O5.

[0108] Joint 230_5 is second only to joint 230_6 in its tendency to cause vibration in arm 220. Here, the greater the distance of nozzle N from the rotation axis O5, the greater the ink spraying error caused by this vibration. This is because the greater the distance of nozzle N from the rotation axis O5, the greater the torque around the rotation axis O5. Therefore, by making the distance DN22 smaller than the distance DN21, the influence of this torque on the second nozzle array L2 can be suppressed compared to the first nozzle array L1. As a result, the vibration of the second nozzle array L2, which accompanies the vibration of joint 230_5, can be less than the vibration of the first nozzle array L1. Therefore, the spraying error of the second ink relative to the workpiece W can be reduced.

[0109] On the other hand, although the vibration of the first nozzle array L1, which is accompanied by the vibration of joint 230_5, is greater than that of the second nozzle array L2, the first nozzle array L1 uses a first ink whose spray error is less noticeable compared to the second ink. As a result, overall, the reduction in print quality caused by the spray error of ink relative to the workpiece W can be reduced. Furthermore, when viewed along the direction of rotation axis O5, it is sufficient that the condition that the distance DN22 between the second nozzle array L2 and the rotation axis O5 is less than the distance DN21 between the first nozzle array L1 and the rotation axis O5 is met during the execution of the printing operation, and it is not necessarily required to be met during the period when no liquid is sprayed onto the workpiece W. For example, there may be cases where the distance between the rotation axis O5 and each nozzle array changes due to the rotation of joints like joint 230_6, which are closer to the tip ET than joint 230_5.

[0110] As described above, the printing apparatus 1 also includes a flexible first supply tube 10a1 for supplying first ink to the first nozzle array L1, and a flexible second supply tube 10a2 for supplying second ink to the second nozzle array L2. A portion of each of the first supply tube 10a1 and the second supply tube 10a2 is held by the arm 220. Preferably, the distance between the downstream end of the second supply tube 10a2 and the rotation shaft O6 is less than the distance between the downstream end of the first supply tube 10a1 and the rotation shaft O6. When the deformation of the second supply tube 10a2 increases with the movement of the robot 2, poor ejection of the second ink may occur due to changes in the flow resistance within the second supply tube 10a2. Therefore, by making the distance between the downstream end of the second supply pipe 10a2 and the rotation shaft O6 smaller than the distance between the downstream end of the first supply pipe 10a1 and the rotation shaft O6, the deformation of the second supply pipe 10a2 accompanying the movement of the joint 230_6 can be made smaller than the deformation of the first supply pipe 10a1. As a result, poor ejection of the second ink can be prevented.

[0111] Furthermore, as described above, the printing apparatus 1 also includes an energy emission section 3c. The energy emission section 3c is supported by a top end ET and includes an emission surface FL that emits energy to cure the first ink and the second ink, respectively. Here, the head 3a comprises a first nozzle row L1, a second nozzle row L2, a third nozzle row L3, and a fourth nozzle row L4 as multiple nozzle rows for ejecting ink. Based on this, when viewed along the rotation axis O6, the distances DN11, DN12, DN13, and DN14 between each of these multiple nozzle rows and the rotation axis O6 are less than the distance DL between the emission surface FL and the rotation axis O6. Therefore, compared to a structure where the distances DN11, DN12, DN13, and DN14 are greater than DL, the ink ejection accuracy relative to the workpiece W can be improved. Here, since the accuracy of the irradiation position of the energy irradiating the workpiece W from the emission surface FL may not be high compared to the ejection accuracy, no problem arises even if the distance DL is greater than the distances DN11, DN12, DN13, and DN14.

[0112] Here, as mentioned above, when viewed along the direction of rotation axis O6, rotation axis O6 is located inside the region RN defined by the collection of the plurality of nozzle rows. Therefore, compared to a structure where rotation axis O6 is located outside region RN, the influence of the torque around rotation axis O6 can be reduced, resulting in improved ink spraying accuracy relative to workpiece W.

[0113] More specifically, as described above, the head 3a has an ejection surface FN provided with four nozzle rows for ejecting ink, namely a first nozzle row L1, a second nozzle row L2, a third nozzle row L3, and a fourth nozzle row L4. The second nozzle row L2 is the nozzle row closest to the center PC of the ejection surface FN among the four nozzle rows. Therefore, in a structure where the rotation shaft O6 is close to the center PC, compared to a structure where the other nozzle rows are closest to the center PC, the ejection accuracy of the second ink relative to the workpiece W can be improved. Furthermore, the second nozzle row L2 can also be the nozzle row closest to the center of the region RN among the four nozzle rows. Moreover, when the surface WF of the workpiece W is a convex curved surface, such as... Figure 6As shown, while reducing the distance between each nozzle array and the surface WF, the distance PG2 between the second nozzle array L2 and the surface WF can be made smaller than the distance PG1 between the first nozzle array L1 and the surface WF. Therefore, even at this point, the spraying accuracy of the second ink relative to the workpiece W can be improved. Furthermore, this effect is not limited to the structure of this embodiment. For example, even in a structure where the position of the head 3a in the base coordinate system based on the position of the base 210 of the robot 2 is fixed, and the robot 2 moves the top of the arm 220 while holding the workpiece W, the same effect can be obtained. In other words, in a structure where the relative position and orientation of the workpiece W with the convex curved surface WF and the head 3a change during the execution of the printing action, as long as the second nozzle array L2 is set as the nozzle array closest to the center PC of the ejection surface FN among the other nozzle arrays, the spraying accuracy can be improved for the second ink, whose spraying error is more noticeable compared to the first ink, thereby suppressing the overall reduction in print quality.

[0114] In this embodiment, as described above, the second ink is the ink with the lowest brightness among the inks ejected from the first 3a. Therefore, the printing quality can be appropriately improved.

[0115] Furthermore, as mentioned above, the second ink is black ink. Generally speaking, black ink is the ink with the lowest brightness among the various colors of ink used in full-color printing. Therefore, by setting black ink as the second ink, the printing quality of full-color printing and the like can be appropriately improved.

[0116] In this embodiment, as described above, the first ink is the ink with the highest brightness among the inks ejected from the first 3a. Therefore, the printing quality can be appropriately improved.

[0117] Furthermore, as mentioned above, the first ink is yellow ink. Generally speaking, among the multiple colors of ink used in full-color printing, yellow ink is the brightest. Therefore, by setting yellow ink as the first ink, the print quality in full-color printing can be appropriately improved. Additionally, in structures using five or more inks, white ink is sometimes used as the brightest ink. In this case, the first ink can also be white ink.

[0118] 2. Second Implementation Method

[0119] The second embodiment of the present invention will now be described. Elements that function and operate the same as those in the first embodiment as in the embodiments illustrated below will be referred to by the same symbols used in the description of the first embodiment, and detailed descriptions of each will be omitted as appropriate.

[0120] Figure 7 This is a schematic top view used to illustrate the configuration of the multiple nozzle rows in the second embodiment. Figure 7 The diagram shows the first nozzle array L1, the second nozzle array L2, the third nozzle array L3, and the fourth nozzle array L4 viewed in the c1 direction as the plurality of nozzle arrays. In the head unit 3A of this embodiment, except for the interchangeable arrangement order of the second nozzle array L2 and the fourth nozzle array L4, it is identical to the head unit 3 of the first embodiment described above. Specifically, these nozzle arrays are arranged in the order of first nozzle array L1, second nozzle array L2, fourth nozzle array L4, and third nozzle array L3, facing the a1 direction. Figure 7 In the example shown, these nozzle rows are arranged at equal intervals. Alternatively, the intervals between these nozzle rows can also be unequal.

[0121] Even in the above-described nozzle array configuration, when viewed along the direction of rotation axis O6, the distance DN12 between the second nozzle array L2 and the rotation axis O6 is smaller than the distance DN11 between the first nozzle array L1 and the rotation axis O6, and smaller than the distance DN13 between the third nozzle array L3 and the rotation axis O6.

[0122] Similarly, the distance DN14 between the fourth nozzle array L4 and the rotation shaft O6 is less than the distance DN11 between the first nozzle array L1 and the rotation shaft O6, and less than the distance DN13 between the third nozzle array L3 and the rotation shaft O6.

[0123] exist Figure 7 In the example shown, distance DN11 is equal to distance DN13, and distance DN12 is equal to distance DN14. Alternatively, distance DN11 can be different from distance DN13. Furthermore, distance DN12 can also be different from distance DN14.

[0124] Figure 8 This is a schematic side view used to illustrate the configuration of the multiple nozzle rows in the second embodiment. Figure 8 The diagram shows the first nozzle array L1, the second nozzle array L2, the third nozzle array L3, and the fourth nozzle array L4 viewed in the b1 direction as the plurality of nozzle arrays.

[0125] Here, as Figure 8 As shown, even in this embodiment, when viewed in the direction along the rotation axis O5, the distance DN22 between the second nozzle array L2 and the rotation axis O5 is smaller than the distance DN21 between the first nozzle array L1 and the rotation axis O5, and smaller than the distance DN23 between the third nozzle array L3 and the rotation axis O5.

[0126] Similarly, when viewed along the direction of rotation axis O5, the distance DN24 between the fourth nozzle array L4 and the rotation axis O5 is less than the distance DN21 between the first nozzle array L1 and the rotation axis O5, and less than the distance DN23 between the third nozzle array L3 and the rotation axis O5.

[0127] exist Figure 8 In the example shown, distance DN21 is equal to distance DN23, and distance DN22 is equal to distance DN24. Alternatively, distance DN21 can be different from distance DN23. Furthermore, distance DN22 can also be different from distance DN24.

[0128] Even according to the second embodiment described above, printing quality can be improved.

[0129] 3. Third Implementation Method

[0130] The third embodiment of the present invention will now be described. Elements that function and operate the same as those in the first embodiment as in the embodiments illustrated below will be referred to by the same symbols used in the description of the first embodiment, and detailed descriptions of each will be omitted as appropriate.

[0131] Figure 9 This is a perspective view showing the schematic structure of the head unit 3B used in the third embodiment. In this embodiment, except that head unit 3B is used instead of head unit 3, everything else is the same as in the first embodiment. Figure 9 As shown, the head unit 3A has two energy emission sections 3c. One of the energy emission sections 3c is positioned relative to the head 3a in the a1 direction, and the other energy emission section 3c is positioned relative to the head 3a in the a2 direction.

[0132] Figure 10 This diagram illustrates the movement paths RU1 and RU2 of the head 3a in the third embodiment. Movement path RU1 is the path from position PS1 to position PE1. Robot 2 moves head 3a along movement path RU1 in a direction away from base 210. At this time, the direction a1 is forward in the direction of movement of head 3a. Movement path RU2 is the path from position PS2 to position PE2. Robot 2 moves head a along movement path RU2 in a direction closer to base 210. At this time, the direction a2 is forward in the direction of movement of head 3a.

[0133] Although not illustrated here, positions PS1 and PE2 represent the X1-direction positions relative to the predetermined area RP when viewed from the Z2 direction.

[0134] Even according to the third embodiment described above, printing quality can be improved. In this embodiment, as described above, two energy emission sections 3c are arranged via the head 3a. Therefore, even without rotating the head unit 3B 180° around the rotation axis O6, printing can be performed in either the direction away from or towards the base 210, and energy can be irradiated onto the ink immediately after it has been sprayed onto the workpiece W.

[0135] 4. Change the example

[0136] The various methods illustrated above can be modified in a wide variety of ways. The following sections illustrate specific modifications that can be applied to the aforementioned methods. Furthermore, two or more methods chosen from the following examples can be appropriately combined without contradiction.

[0137] 4-1. Modify Example 1

[0138] While the aforementioned embodiments show structures in which the rotation axis O6 is located inside region RN when viewed along the direction of rotation O6, the embodiments are not limited to these structures. Hereinafter, an example of a structure in which the rotation axis O6 is located outside region RN when viewed along the direction of rotation O6 will be described.

[0139] Figure 11 This is a schematic side view used to illustrate the configuration of multiple nozzle rows in Example 1. Figure 11 The diagram shows the first nozzle array L1, the second nozzle array L2, the third nozzle array L3, and the fourth nozzle array L4 viewed in the b1 direction as the plurality of nozzle arrays. In the head unit 3C of this modified example, when viewed in the direction along the rotation axis O6, the rotation axis O6 is located outside the region RN. Figure 11 In the example shown, region RN is positioned in the a1 direction relative to the rotation axis O6.

[0140] Here, the nozzle rows are arranged in the order of second nozzle row L2, fourth nozzle row L4, third nozzle row L3, and first nozzle row L1, facing the direction of a1. Figure 11 In the example shown, these nozzle rows are arranged at equal intervals. Alternatively, the intervals between these nozzle rows can also be unequal.

[0141] In a nozzle array configuration as described above, the distances to the rotation axis O6, observed along the direction of rotation O6, from smallest to largest, are: second nozzle array L2, fourth nozzle array L4, third nozzle array L3, and first nozzle array L1. That is, from smallest to largest, they are: distance DN12, distance DN14, distance DN13, and distance DN11.

[0142] Furthermore, the distances to the rotation axis O5 observed along the direction of rotation O5, from smallest to largest, are: second nozzle row L2, fourth nozzle row L4, third nozzle row L3, and first nozzle row L1. That is, from smallest to largest, they are: distance DN22, distance DN24, distance DN23, and distance DN21.

[0143] Even according to the above modified example 1, since the distance DN12 is smaller than the distance DN11, the print quality can still be improved. Furthermore, since the distance DN22 is smaller than the distance DN21, the print quality can also be improved at this point.

[0144] 4-2. Modify Example 2

[0145] Although the foregoing embodiment illustrates a configuration where the second nozzle row L2 is the closest to the rotation axis O5 or O6 and the first nozzle row L1 is the furthest, this configuration is not limited to that configuration. For the arrangement of multiple nozzle rows, it is sufficient that the second nozzle row L2 is positioned closer to the rotation axis O5 or O6 than the first nozzle row L1.

[0146] 4-3. Modify Example 3

[0147] Although the foregoing example illustrates a structure in which the ejection surface FN is orthogonal to the rotation axis O6, the method is not limited to this structure, as long as the aforementioned relationship between the rotation axis O6 and the distances between the nozzle rows is satisfied. For example, if such a relationship is satisfied, the ejection surface FN can be parallel to the rotation axis O6, or the ejection surface FN can be inclined relative to either the rotation axis O5 or the rotation axis O6.

[0148] 4-4. Modify Example 4

[0149] Although the foregoing description illustrates a structure for printing using four types of inks, the present disclosure is not limited to any structure using only the first and second inks. It can also be applied to structures using two, three, or five or more types of inks. Furthermore, the first ink is not limited to yellow ink, as long as it has a higher brightness compared to the second ink. Similarly, the second ink is not limited to black ink, as long as it has a lower brightness compared to the first ink.

[0150] 4-5. Modify Example 5

[0151] Although the structure using the energy emission section 3c is illustrated in the foregoing, the system is not limited to this structure, and the energy emission section 3c may be omitted. In this case, for example, another device that emits light to harden or cure ink on the workpiece may be configured outside the robot 2.

[0152] 4-6. Modify Example 6

[0153] While the foregoing description illustrates a structure using a six-axis vertical multi-axis robot as a movement mechanism, the robot is not limited to this structure. The movement mechanism can be, for example, a vertical multi-axis robot with five or fewer axes or seven or more axes, or a horizontal multi-axis robot. Furthermore, the robot's arm can have a telescopic mechanism or a linear mechanism, in addition to a rotating part composed of a rotating mechanism. However, from the viewpoint of balancing print quality during printing operations and the degrees of freedom of the robot's movements during non-printing operations, a multi-axis robot with six or more axes is preferred.

[0154] 4-7. Modify Example 7

[0155] While the foregoing examples illustrate structures such as threaded fixing for securing the head relative to the robot, the method is not limited to these structures. For instance, the head can also be secured relative to the robot by using a gripping mechanism such as a handle installed as an end effector of the robot to hold it in place.

[0156] 4-8. Modify Example 8

[0157] Although the foregoing description illustrates a structure where the ejector surface FN intersects the rotation axis O6 perpendicularly, the method is not limited to this structure. For example, the angle between the ejector surface FN and the rotation axis O6 may be less than 90°. In this case, the distance between the rotation axis O6, which serves as an example of a "first rotation axis," and the nozzle array can be defined as the distance between the intersection of the ejector surface FN and the rotation axis O6 and the nozzle array.

[0158] Symbol Explanation

[0159] 1…printing apparatus; 2…robot; 2a…arm drive mechanism; 2a1…motor; 2a2…motor; 2a3…motor; 2a4…motor; 2a5…motor; 2a6…motor; 3…head unit; 3A…head unit; 3B…head unit; 3C…head unit; 3a…head; 3b…pressure regulating valve; 3c…energy emission unit; 3e…switching circuit; 3f…support body; 5…controller; 5a…storage circuit; 5b…processing circuit; 6…control module; 6a…timing signal generation circuit; 6b…power supply circuit; 6c…control circuit; 6d…drive signal generation circuit; 7…computer; 10…equipment Pipe section; 10a1… First supply pipe; 10a2… Second supply pipe; 10a3… Third supply pipe; 10a4… Fourth supply pipe; 11… Wiring section; 210… Base; 220… Arm section; 221… Arm; 222… Arm; 223… Arm; 224… Arm; 225… Arm; 226… Arm; 230… Joint; 230_1… Joint; 230_2… Joint; 230_3… Joint; 230_4… Joint; 230_5… Joint (Second Joint); 230_6… Joint (First Joint); CLK… Clock signal; CNG… Conversion signal; Com… Drive signal; D1… Output Output; D3…signal; DL…distance; DN11…distance; DN12…distance; DN13…distance; DN14…distance; DN21…distance; DN22…distance; DN23…distance; DN24…distance; Da…path information; EB…base end; ET…top end; FL…ejection surface; FN…ejection surface; Img…printing data; L1…first nozzle row; L2…second nozzle row; L3…third nozzle row; L4…fourth nozzle row; LAT…latch signal; N…nozzle; O1…rotation axis; O2…rotation axis; O3…rotation axis; O4…rotation axis; O5…rotation axis (second…) O6… Rotation axis; O6… Rotation axis (first rotation axis); PC… Center; PD… Drive pulse; PE… Position; PE1… Position; PE2… Position; PG1… Distance; PG2… Distance; PR1… Position; PR2… Position; PS… Position; PS1… Position; PS2… Position; PTS… Timing signal; RN… Area; RP… Predetermined area; RU… Movement path; RU1… Movement path; RU2… Movement path; SI… Printing data signal; Sk1… Control signal; VBS… Bias potential; VHV… Power supply potential; W… Workpiece; WF… Surface; dCom… Waveform specification signal.

Claims

1. A printing apparatus comprising: The head includes a first nozzle array arranged with a plurality of nozzles ejecting a first ink and a second nozzle array arranged with a plurality of nozzles ejecting a second ink. A robot has an arm and a base. The arm has a tip, a base, and multiple joints. The base is connected to the base, and a head is supported on the tip. The robot can change the position and orientation of the head relative to a workpiece. The brightness of the second ink is lower than that of the first ink. The plurality of joints has a first joint, which is the joint closest to the apex among the plurality of joints. The first joint is a rotating mechanism that rotates around an axis, wherein the axis is a first rotation axis. When viewed along the direction of the first rotation axis, the distance between the second nozzle array and the first rotation axis is less than the distance between the first nozzle array and the first rotation axis.

2. The printing apparatus as claimed in claim 1, wherein, The head also includes a third nozzle array comprising a plurality of nozzles arranged to eject a third ink. The brightness of the third ink is lower than that of the first ink but higher than that of the second ink. When viewed along the direction of the first rotation axis, the distance between the second nozzle array and the first rotation axis is less than the distance between the third nozzle array and the first rotation axis. When viewed in the direction along the first rotation axis, the second nozzle array is located between the first nozzle array and the third nozzle array.

3. The printing apparatus as claimed in claim 2, wherein, The head also includes a fourth nozzle array, which consists of multiple nozzles arranged to eject a fourth ink. The brightness of the fourth ink is higher than that of the second ink but lower than that of the third ink. When viewed along the first rotation axis, the distance between the fourth nozzle array and the first rotation axis is less than the distance between the first nozzle array and the first rotation axis, and less than the distance between the third nozzle array and the first rotation axis. When viewed along the direction of the first rotation axis, the fourth nozzle array is located between the first nozzle array and the third nozzle array.

4. The printing apparatus according to any one of claims 1 to 3, wherein, The plurality of joints has a second joint, which is the joint among the plurality of joints that is second only to the first joint and closest to the apex. The second joint is a rotation mechanism surrounding a second rotation axis that intersects the first rotation axis. When viewed along the direction of the second rotation axis, the distance between the second nozzle array and the second rotation axis is less than the distance between the first nozzle array and the second rotation axis.

5. The printing apparatus as claimed in claim 1, wherein, It also has: A flexible first supply tube for supplying the first ink to the first nozzle array; A flexible second supply tube for supplying the second ink to the second nozzle array. A portion of each of the first and second supply tubes is held by the arm. The distance between the downstream end of the second supply pipe and the first rotating shaft is less than the distance between the downstream end of the first supply pipe and the first rotating shaft.

6. The printing apparatus as claimed in claim 1, wherein, It also has an energy emission section supported by the top end and includes an emission surface that emits energy to cure each of the first ink and the second ink. The head includes multiple rows of nozzles that eject ink. The plurality of nozzle columns include the first nozzle column and the second nozzle column. When viewed in a direction along the first rotation axis, the distance between each of the plurality of nozzle arrays and the first rotation axis is less than the distance between the exit surface and the first rotation axis.

7. The printing apparatus as claimed in claim 1, wherein, The head includes multiple rows of nozzles that eject ink. When viewed in the direction along the first rotation axis, the first rotation axis is located inside the area defined by the set of the plurality of nozzle arrays.

8. The printing apparatus as claimed in claim 1, wherein, The head has an ejection surface with four rows of nozzles for ejecting ink. The four nozzle rows include the first nozzle row and the second nozzle row. The second nozzle column is the nozzle column that is closest to the center of the ejection surface among the four nozzle columns.

9. The printing apparatus as claimed in claim 1, wherein, The second ink is the ink with the lowest brightness among the inks ejected from the head.

10. The printing apparatus of claim 1, wherein, The second ink is black ink.

11. The printing apparatus as claimed in claim 1, wherein, The first ink is the ink with the highest brightness among the inks ejected from the head.

12. The printing apparatus of claim 1, wherein, The first ink is either yellow or white.

13. The printing apparatus of claim 1, wherein, Each of the plurality of joints is provided with a motor for driving the joint. The rated output of the motor driving the first joint is less than the rated output of the motors driving each of the plurality of joints except the first joint.

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