Printing device

Abstract

To improve printing quality in a printing device using a robot.SOLUTION: A printing device has a head and a robot that changes a position and a posture of the head to a workpiece. The head includes a first nozzle array on which a plurality of nozzles discharging a first ink are aligned, and a second nozzle array on which a plurality of nozzles discharging a second ink are aligned. The robot has an arm portion that has a tip end, a base end, and a plurality of joints, and a base portion connected to the base end. At the tip end, the head is supported. The brightness of the second ink is lower than the brightness of the first ink. If setting a timing for discharging the first ink to a predetermined position on the workpiece from the first nozzle array as a first timing, and a timing for discharging the second ink to the predetermined position from the second nozzle array as a second timing, a distance between the tip end and the base end at the second timing is smaller than a distance between the tip end and the base end at the first timing.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to printing devices. [Background technology]

[0002] Inkjet printing devices that use robots such as articulated robots are known. For example, the device described in Patent Document 1 includes an inkjet head and a robot that holds the head. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-215438 Summary of the Invention [Problem to be solved by the invention]

[0004] When printing using multiple colors of ink, the head is generally provided with multiple nozzle rows, one for each color of ink. Patent Document 1 does not disclose anything about the arrangement of multiple nozzle rows when ejecting multiple colors of ink. In a printing device that uses a robot to move the head, when printing using multiple colors of ink, it is desirable to achieve an appropriate arrangement of the multiple nozzle rows to obtain good print quality. [Means for solving the problem]

[0005] In order to solve the above problems, one aspect of the printing device according to the present disclosure is a robot having 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, an arm having a tip end, a base end, and a plurality of joints, and a base connected to the base end, the head being supported at the tip end, and the robot changing the position and attitude of the head relative to a workpiece, wherein the brightness of the second ink is lower than the brightness of the first ink, and when a first timing is defined as a timing for ejecting the first ink from the first nozzle row to a predetermined position on the workpiece and a second timing is defined as a timing for ejecting the second ink from the second nozzle row to the predetermined position, the distance between the tip end and the base end at the second timing is smaller than the distance between the tip end and the base end at the first timing.

[0006] Another aspect of the printing device according to the present disclosure is a robot having 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, an arm having a tip end, a base end, and a plurality of joints, and a base connected to the base end, the head being supported at the tip end, and changing the position and attitude of the head relative to a workpiece, wherein the brightness of the second ink is lower than the brightness of the first ink, and the distance between the second nozzle row and the base end is longer than the distance between the first nozzle row and the base end. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a perspective view showing an outline of a printing device according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the printing device according to the first embodiment. [Figure 3] FIG. 2 is a perspective view showing a schematic configuration of a head unit used in the first embodiment. [Figure 4] FIG. 2 is a diagram illustrating a printing operation of the printing device according to the first embodiment. [Figure 5]FIG. 10 is a diagram showing the state of the robot at a first timing. [Figure 6] FIG. 10 is a diagram for explaining the distance between the tip and base ends of the arm of the robot at a first timing. [Figure 7] FIG. 10 is a diagram showing the state of the robot at a second timing. [Figure 8] FIG. 10 is a diagram for explaining the distance between the tip and base ends of the arm of the robot at a second timing. [Figure 9] 10 is a graph showing the relationship between the distance between the tip and base ends of the arm and the rotation angle of the joint of the robot. [Figure 10] FIG. 10 is a diagram for explaining a printing operation in the second embodiment. [Figure 11] FIG. 10 is a block diagram showing the electrical configuration of a printing device according to a third embodiment. [Figure 12] FIG. 11 is a perspective view showing a schematic configuration of a head unit used in a third embodiment. [Figure 13] FIG. 10 is a diagram illustrating a printing operation of a printing device according to a third embodiment. [Figure 14] FIG. 10 is a perspective view showing a schematic configuration of a head unit used in a fourth embodiment. [Figure 15] FIG. 10 is a diagram for explaining a movement path of a head in a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that the dimensions and scale of each part in the drawings may differ from the actual dimensions and are shown schematically to facilitate understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description to the effect that the present disclosure is limited.

[0009] For convenience, the following description will use the mutually intersecting X-axis, Y-axis, and Z-axis as appropriate. In the following description, one direction along the X-axis is the X1 direction, and the direction opposite the X1 direction is the X2 direction. Similarly, the opposite directions along the Y-axis are the Y1 direction and the Y2 direction. Furthermore, the opposite directions along the Z-axis are the Z1 direction and the Z2 direction.

[0010] Here, the X-axis, Y-axis, and Z-axis correspond to the coordinate axes of a world coordinate system set in a space in which the robot 2 (described later) is installed. Typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to the downward vertical direction. A base coordinate system based on the position of a base 210 (described later) of the robot 2 is associated with the world coordinate system by calibration. For convenience, the following describes an example in which the operation of the robot 2 is controlled using the world coordinate system as the robot coordinate system.

[0011] The Z axis does not have to be a vertical axis. Furthermore, the X axis, Y axis, and Z axis are typically perpendicular to one another, but this is not a limitation and they may not be perpendicular. For example, the X axis, Y axis, and Z axis may intersect each other at an angle between 80° and 100°.

[0012] 1. First embodiment 1-1.Outline of the printing device 1 is a perspective view showing an outline of a printing apparatus 1 according to a first embodiment. The printing apparatus 1 is an apparatus that performs printing on the surface of a workpiece W by an inkjet method.

[0013] The workpiece W has a surface WF to be printed. In the example shown in FIG. 1, the workpiece W is a rectangular parallelepiped, and the surface WF is flat. During printing, the workpiece W is supported as needed by a structure such as a predetermined installation table, robot hand, or conveyor. The shape, size, etc. of the workpiece W or the surface WF are not limited to the example shown in FIG. 1 and are arbitrary. For example, the surface WF may have a curved or bent portion, or the workpiece W may be a sheet material such as paper or cloth. Furthermore, the position or posture of the workpiece W or the surface WF during printing may be arbitrary as long as it is printable and is not limited to the example shown in FIG. 1.

[0014] 1, the printing device 1 has a robot 2, a head unit 3, a controller 5, a piping section 10, and a wiring section 11. First, these will be briefly described in order below.

[0015] The robot 2 is a robot that changes the position and posture of the head unit 3 in the world coordinate system. In the example shown in Fig. 1, the robot 2 is a so-called six-axis vertical articulated robot.

[0016] As shown in FIG. 1, the robot 2 has a base 210 and an arm 220.

[0017] Base 210 is a platform that supports arm 220. In the example shown in Fig. 1, base 210 is fixed by screws or the like to an installation surface such as a floor surface or a base facing in the Z1 direction. The installation surface to which base 210 is fixed may be a surface facing any direction and is not limited to the example shown in Fig. 1, and may be, for example, a wall, a ceiling, a surface of a movable cart, or the like.

[0018] Arm 220 is a six-axis robot arm having a base end EB attached to base 210 and a tip end ET that changes its position and posture three-dimensionally relative to base end EB. Specifically, arm 220 has arms 221, 222, 223, 224, 225, and 226, which are also called links. These are connected in this order: arms 221, 222, 223, 224, 225, and 226.

[0019] The arm 221 is connected to the base 210 via a joint 230_1 so as to be rotatable around a rotation axis O1. The arm 222 is connected to the arm 221 via a joint 230_2 so as to be rotatable around a rotation axis O2. The arm 223 is connected to the arm 222 via a joint 230_3 so as to be rotatable around a rotation axis O3. The arm 224 is connected to the arm 223 via a joint 230_4 so as to be rotatable around a rotation axis O4. The arm 225 is connected to the arm 224 via a joint 230_5 so as to be rotatable around a rotation axis O5. The arm 226 is connected to the arm 225 via a joint 230_6 so as to be rotatable around a rotation axis O6.

[0020] Each of the joints 230_1 to 230_6 is a mechanism that rotatably connects one of two adjacent members among the base 210 and the arms 221 to 226 to the other. Note that hereinafter, each of the joints 230_1 to 230_6 may be referred to as a "joint 230." Here, the base end EB is one end of the arm 220 whose position in the base coordinate system does not change even when the joint 230 rotates, and the tip ET is the other end of the arm 220 whose position in the base coordinate system changes with the rotation of the joint 230_6. The base end EB can be defined, for example, as the intersection of the boundary between the base 210 and the arm 221 and the rotation axis O1. The tip ET can be defined, for example, as the intersection of the end face of the arm 226 that is farthest from the arm 225 or a plane extending from that end face and the rotation axis O6.

[0021] Although not shown in Fig. 1, each of the joints 230_1 to 230_6 is provided with a drive mechanism that rotates one of the two corresponding members relative to the other. The drive mechanism includes, for example, a motor that generates a drive force for the rotation, a reducer that reduces and outputs the drive force, and an encoder such as a rotary encoder that detects the amount of movement, such as the angle of the rotation. The assembly of the drive mechanisms of the joints 230_1 to 230_6 corresponds to an arm drive mechanism 2a shown in Fig. 2, which will be described later.

[0022] The rotation axis O1 is an axis perpendicular to an installation surface (not shown) to which the base 210 is fixed. The rotation axis O2 is an axis perpendicular to the rotation axis O1. The rotation axis O3 is an axis parallel to the rotation axis O2. The rotation axis O4 is an axis perpendicular to the rotation axis O3. The rotation axis O5 is an axis perpendicular to the rotation axis O4. The rotation axis O6 is an axis perpendicular to the rotation axis O5.

[0023] Regarding these rotation axes, "perpendicular" refers not only to the case where the angle between the two rotation axes is exactly 90°, but also to the case where the angle between the two rotation axes is deviated from 90° within a range of about ±5°. Similarly, "parallel" refers not only to the case where the two rotation axes are strictly parallel, but also to the case where one of the two rotation axes is inclined relative to the other within a range of about ±5°.

[0024] A head unit 3 is attached as an end effector to the tip ET of the arm 220 of the robot 2 in a state fixed by screws or the like.

[0025] The head unit 3 is an assembly having a head 3a that ejects a plurality of types of ink with different brightness toward the workpiece W. In this embodiment, the head unit 3 has a pressure adjustment valve 3b and an energy emission unit 3c in addition to the head 3a. Details of the head unit 3 will be described later with reference to FIG. 3.

[0026] In this embodiment, four types of inks are used, consisting of a first ink, a second ink, a third ink, and a fourth ink, each having a different lightness. The order of lightness of these inks, from highest to lowest, is the first ink, the third ink, the fourth ink, and the second ink. When full-color printing is performed, the four types of inks are typically 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 ink and the fourth ink is magenta ink and the other is cyan ink. Here, lightness is, for example, determined based on the CIE L standard defined by the International Commission on Illumination (CIE). * a* b * In this embodiment, it can be defined as the brightness of the CIE L color space. * a * b * The lightness in the color space is 83 for yellow ink, 54 for magenta ink, 56 for cyan ink, and 11 for black ink. Note that the lightness value of the ink is obtained, for example, by applying the ink to a medium such as printing paper to create a predetermined color patch, and then measuring the color patch with a colorimeter. Here, the comparison of the magnitude of the lightness of multiple types of ink is performed by creating a color patch for each of the multiple types of ink using the same amount of ink on the same medium, and comparing the colorimetric values ​​of the color patches of the multiple types of ink.

[0027] Each of these inks is a liquid medium in which a coloring material such as a dye or pigment is dissolved or dispersed in a solvent. The inks may be any of water-based inks in which a coloring material such as a dye or pigment is dissolved in a water-based solvent, curable inks using a curable resin such as a UV-curable ink, and solvent-based inks in which a coloring material such as a dye or pigment is dissolved in an organic solvent, but curable inks are preferred. The curable inks are not particularly limited and may be, for example, heat-curable, photo-curable, radiation-curable, or electron beam-curable, but photo-curable inks such as UV-curable inks are preferred. Furthermore, inks containing coloring materials are not limited to yellow ink, magenta ink, cyan ink, and black ink, but may also be, for example, white ink, gray ink, light cyan ink, or light magenta ink.

[0028] A piping section 10 and a wiring section 11 are connected to the head unit 3. The piping section 10 is a group of pipes that supplies ink from an ink tank (not shown) to the head unit 3. The wiring section 11 is a wire or a group of wires that supplies an electrical signal that drives the head 3a.

[0029] The controller 5 is a robot controller that controls the driving of the robot 2. Below, the electrical configuration of the printing device 1 will be described with reference to FIG.

[0030] 1-2. Electrical configuration of the printing device Fig. 2 is a block diagram showing the electrical configuration of the printing device 1 according to the first embodiment. Fig. 2 shows the electrical components of the printing device 1. As shown in Fig. 2, in addition to the components shown in Fig. 1, the printing device 1 also has a control module 6 communicatively connected to the controller 5, and a computer 7 communicatively connected to the controller 5 and the control module 6.

[0031] 2 may be divided appropriately, some may be included in other components, or may be integrated with other components. For example, some or all of the functions of the controller 5 or control module 6 may be implemented by a computer 7, or may be implemented by another external device such as a PC (personal computer) connected to the controller 5 via a network such as a LAN (Local Area Network) or the Internet.

[0032] The controller 5 has a function of controlling the driving of the robot 2 and a function of generating a signal D3 for synchronizing the ink ejection operation of the head unit 3 with the operation of the robot 2.

[0033] The controller 5 includes a memory circuit 5a and a processing circuit 5b.

[0034] 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 includes, for example, one or both of semiconductor memories: a volatile memory such as a random access memory (RAM) and a nonvolatile memory such as a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), or a programmable read-only memory (PROM). Note that part or all of the storage circuit 5a may be included in the processing circuit 5b.

[0035] Path information Da is stored in the memory circuit 5a. The path information Da is information indicating the path along which the head unit 3 should move and the attitude of the head unit 3 on that path. The path information Da is generated using, for example, information acquired by direct teaching or offline teaching, and information such as CAD (computer-aided design) data indicating the shape of the workpiece W. The path information Da is expressed using, for example, coordinate values ​​in a base coordinate system or a world coordinate system. The above path information Da is input from the computer 7 to the memory circuit 5a.

[0036] The processing circuit 5b controls the operation of the arm driving mechanism 2a of the robot 2 based on the path information Da and generates a signal D3. The processing circuit 5b includes, for example, one or more processors such as a CPU (Central Processing Unit). Note that the processing circuit 5b may include a programmable logic device such as an FPGA (Field-Programmable Gate Array) instead of or in addition to a CPU.

[0037] Here, the arm driving mechanism 2a is an assembly of driving mechanisms for the above-mentioned joints 230_1 to 230_6, and each joint 230 has a motor for driving the joint 230 and an encoder for detecting the rotation angle of the joint 230.

[0038] The processing circuit 5b performs inverse kinematics calculations, which are calculations that convert the path information Da into movement quantities such as the rotation angle and rotation speed of each joint 230 of the robot 2. The processing circuit 5b then outputs a control signal Sk1 based on the output D1 from each encoder of the arm driving mechanism 2a so that the movement quantities such as the actual rotation angle and rotation speed of each joint 230 match the aforementioned calculation results based on the path information Da. The control signal Sk1 is a signal for controlling the driving of the motor of the arm driving mechanism 2a. Here, the control signal Sk1 is corrected by the processing circuit 5b as necessary based on the output from a distance sensor (not shown).

[0039] Furthermore, the processing circuit 5b generates a signal D3 based on an output D1 from at least one of the multiple encoders of the arm drive mechanism 2a. For example, the processing circuit 5b generates, as the signal D3, a trigger signal including a pulse at the timing when the output D1 from one of the multiple encoders reaches a predetermined value.

[0040] The control module 6 is a circuit that controls the ink ejection operation from each nozzle N of the head unit 3 based on a signal D3 output from the controller 5 and print data Img from the computer 7. The control module 6 has a timing signal generation circuit 6a, a power supply circuit 6b, a control circuit 6c, and a drive signal generation circuit 6d.

[0041] The timing signal generating circuit 6a generates a timing signal PTS based on the signal D3. The timing signal generating circuit 6a is configured, for example, with a timer that starts generating the timing signal PTS in response to detection of the signal D3. The timing signal PTS includes, for example, a pulse that is determined based on the output D1.

[0042] The power supply circuit 6b receives power from a commercial power supply (not shown) and generates various predetermined potentials. The generated potentials are supplied appropriately to the control module 6 and each component of the head unit 3. For example, the power supply circuit 6b generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the head unit 3. The power supply potential VHV is also supplied to the drive signal generation circuit 6d.

[0043] The control circuit 6c generates a print data signal SI, a waveform designation signal dCom, a latch signal LAT, a clock signal CLK, and a change signal CNG based on the timing signal PTS. These signals are synchronized with the timing signal PTS. Of these signals, the waveform designation signal dCom is input to the drive signal generation circuit 6d, and the other signals are input to the switch circuit 3e of the head unit 3.

[0044] The print data signal SI is a digital signal that specifies the operating state of the drive elements of the head 3a of the head unit 3. Specifically, the print data signal SI specifies whether or not to supply a drive signal Com (described below) to the drive element based on the print data. This specification, for example, specifies whether or not to eject ink from the nozzle corresponding to the drive element, or specifies the amount of ink to be ejected from the nozzle. The waveform specification signal dCom is a digital signal that defines the waveform of the drive signal Com. The latch signal LAT and change signal CNG are used in conjunction with the print data signal SI to specify the drive timing of the drive element, thereby specifying the timing of ink ejection from the nozzle. The clock signal CLK is a reference clock signal synchronized with the timing signal PTS.

[0045] The control circuit 6c described above includes, for example, one or more processors such as CPUs, etc. Note that the control circuit 6c may include a programmable logic device such as an FPGA instead of or in addition to a CPU.

[0046] The drive signal generation circuit 6d is a circuit that generates a drive signal Com for driving each drive element 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 amplifier circuit. In the drive signal generation circuit 6d, the DA conversion circuit converts the waveform designation signal dCom from the control circuit 6c from a digital signal to an analog signal, and the amplifier circuit amplifies the analog signal using the power supply potential VHV from the power supply circuit 6b to generate the drive signal Com. Here, of the waveforms included in the drive signal Com, the signal with the waveform actually supplied to the drive element is the drive pulse PD. The drive pulse PD is supplied from the drive signal generation circuit 6d to the drive element via the switch circuit 3e of the head unit 3.

[0047] Here, the switch circuit 3e is a circuit including a switching element that switches whether or not at least a part of the waveform included in the drive signal Com is to be supplied as the drive pulse PD based on the print data signal SI.

[0048] The computer 7 has a function of supplying information such as path information Da to the controller 5, and a function of supplying information such as print data Img to the control module 6. In addition to these functions, the computer 7 of this embodiment also has a function of controlling the driving of the energy emitter 3c. The computer 7 is, for example, a desktop or notebook computer on which programs that realize these functions are installed.

[0049] 1-3.Head unit configuration FIG. 3 is a perspective view showing a schematic configuration of the head unit 3 used in the first embodiment. For convenience, the following description will be made using the mutually intersecting a-axis, b-axis, and c-axis as appropriate. In the following description, one direction along the a-axis is the a1 direction, and the direction opposite 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.

[0050] 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, and the relative position and posture relationship with the world coordinate system or robot coordinate system changes depending on the operation of the robot 2. In the example shown in FIG. 3, the c-axis is an axis parallel to the rotation axis O6. The a-axis, b-axis, and c-axis are typically perpendicular to each other, but are not limited to this. For example, they may intersect at an angle between 80° and 100°. The tool coordinate system and the base coordinate system or the robot coordinate system are associated by calibration. The tool coordinate system is set, for example, so that the center of the ejection surface FN (described later) serves as the reference (TCP: tool center point).

[0051] As described above, the head unit 3 has a head 3a, a pressure adjustment valve 3b, and an energy emission unit 3c. These are supported by a support 3f indicated by a two-dot chain line in FIG. 3. In the example shown in FIG. 3, the head unit 3 has one head 3a and one pressure adjustment valve 3b, but the numbers are not limited to those shown in FIG. 3 and may be two or more. In addition, the installation position of the pressure adjustment valve 3b is not limited to the head unit 3 and may be, for example, on the arm 226 or in a fixed position relative to the base 210.

[0052] The support 3f is made of, for example, a metal material and is substantially rigid. In the example shown in FIG. 3, the support 3f has a flat plate shape extending in a direction perpendicular to the a-axis. In this embodiment, the head 3a is attached to the surface of the support 3f facing the a1 direction. Meanwhile, the energy emitter 3c is attached to the surface of the support 3f facing the a2 direction. The shape of the support 3f is not limited to the example shown in FIG. 3 and may be any shape, such as a box shape.

[0053] The support 3f is attached to the arm 226. Therefore, the head 3a, the pressure adjustment valve 3b, and the energy output unit 3c are collectively supported on the arm 226 by the support 3f. Therefore, the relative positions of the head 3a, the pressure adjustment valve 3b, and the energy output unit 3c with respect to the arm 226 are fixed. In the example shown in FIG. 3, the pressure adjustment valve 3b is disposed at a position in the c1 direction with respect to the head 3a. The energy output unit 3c is disposed at a position in the a2 direction with respect to the head 3a.

[0054] The head 3a has a discharge surface FN and a plurality of nozzles N opening on the discharge surface FN. The discharge surface FN is a nozzle surface on which the nozzles N open, and is configured, for example, by the surface of a nozzle plate in which the nozzles N are provided as through-holes in a plate-like member made of a material such as silicon (Si) or metal.

[0055] 3, the normal direction of the ejection surface FN is the c2 direction, and the multiple nozzles N are divided into a first nozzle row L1, a second nozzle row L2, a third nozzle row L3, and a fourth nozzle row L4. These nozzle rows are arranged in the a1 direction at intervals from one another in the order of first nozzle row L1, third nozzle row L3, fourth nozzle row L4, and second nozzle row L2.

[0056] Each of the first nozzle row L1, the second nozzle row L2, the third nozzle row L3, and the fourth nozzle row L4 is a collection of multiple nozzles N linearly arranged in the direction along the b-axis. In this embodiment, the nozzle density of the individual nozzles N included in each nozzle row in the direction along the b-axis is 300 npi (nozzles per inch). However, the present invention is not limited to this, and a lower nozzle density may be used. However, from the viewpoint of print quality and efficiency, a nozzle density of 25 npi or more is preferable. To achieve such a nozzle density, the nozzles N may be arranged in a staggered pattern in each nozzle row. Here, the first nozzle row L1, the second nozzle row L2, the third nozzle row L3, and the fourth nozzle row L4 eject different types of ink. Specifically, the first nozzle row L1 ejects a first ink. The second nozzle row L2 ejects a second ink. The third nozzle row L3 ejects a third ink. The fourth nozzle row L4 ejects a fourth ink. Since both inks are ejected in the c2 direction under ideal conditions, the c2 direction can also be expressed as the ejection direction.

[0057] Although not shown, the head 3a has a piezoelectric element serving as a drive element and a cavity for containing ink for each nozzle N. The piezoelectric element changes the pressure in the cavity corresponding to the piezoelectric element, thereby ejecting ink from the nozzle corresponding to the cavity. This type of head 3a can be obtained, for example, by bonding together with an adhesive multiple substrates, such as silicon substrates, that have been appropriately processed by etching or the like. Note that instead of the piezoelectric element, a heater for heating the ink in the cavity may be used as the drive element for ejecting ink from the nozzle. With the head 3a configured as described above, the control module 6 can individually control the presence or absence of ink ejection and the amount of ink ejection for each nozzle N, making it possible to form an ink image.

[0058] As described above, ink is supplied to the head 3a from an ink tank (not shown) via the supply pipe 10a. A pressure adjustment valve 3b is interposed between the supply pipe 10a and the head 3a.

[0059] The pressure regulation valve 3b is a valve mechanism that opens and closes in response to the pressure of the ink in the head 3a. This opening and closing maintains the ink pressure in the head 3a at a negative pressure within a predetermined range, even if the relative position of the head 3a and the ink tank (not shown) changes. This stabilizes the ink meniscus formed in the nozzle N of the head 3a. This prevents air bubbles from entering the nozzle N and ink from overflowing from the nozzle N. Furthermore, ink from the pressure regulation valve 3b is appropriately distributed to multiple locations in the head 3a via branch flow paths (not shown). Here, ink from an ink tank (not shown) is transported into the supply pipe 10a at a predetermined pressure using a pump, a hydraulic head difference, or the like. Although not shown, the pressure regulation valve 3b has ink flow paths and pressure regulation configurations for each type of ink, allowing the pressure of each of the four types of ink to be individually adjusted.

[0060] The energy emitter 3c emits energy such as light, heat, electron beams, or radiation to harden or solidify the ink on the workpiece W. For example, if the ink is ultraviolet-curable, the energy emitter 3c is configured with a light-emitting element such as an LED (light emitting diode) that emits ultraviolet light. The energy emitter 3c may also include optical components such as lenses for adjusting the energy emission direction or emission range, as appropriate.

[0061] Here, the energy emitter 3c includes an emission surface FL that emits the energy, and is disposed so that the emission surface FL faces in the c2 direction. Furthermore, as described above, since the energy emitter 3c is disposed in the a2 direction relative to the head 3a, the distance DL2 between the second nozzle row L2 and the emission surface FL is greater than the distance DL1 between the first nozzle row L1 and the emission surface FL.

[0062] The energy emitter 3c does not have to completely cure or completely solidify the ink on the workpiece W. In this case, for example, the ink may be completely cured or completely solidified after being irradiated with energy from the energy emitter 3c using energy from a curing light source that is separately installed on the installation surface of the base 210 of the robot 2.

[0063] 1-4. Printing operation of the printing device Fig. 4 is a diagram for explaining the printing operation of the printing device 1 according to the first embodiment. Fig. 4 illustrates an example in which printing is performed on a predetermined area RP on the surface WF of the workpiece W, which is placed at a position in the Y2 direction from the base 210 of the robot 2 when viewed along the Z axis. The predetermined area RP is located at a position in the X2 direction from the base 210 of the robot 2 when viewed along the Y axis.

[0064] During the printing operation, the robot 2 changes the position and orientation of the head 3a, causing the head 3a to eject ink. The position and orientation of the head 3a are changed based on the path information Da. As a result, the head 3a moves along the movement path RU while maintaining a predetermined orientation with respect to the surface WF. Note that the head 3a may move along the movement path RU multiple times for each color of ink ejection, or all inks may be ejected in parallel during a single movement of the head 3a along the movement path RU.

[0065] The movement path RU is the path from position PS to position PE. Position PS is a position further in the X1 direction than the predetermined area RP when viewed in the Z2 direction. Position PE is a position further in the X2 direction than the predetermined area RP when viewed in the Z2 direction. During the period from position PS until head 3a reaches the predetermined area RP, head 3a accelerates to a predetermined speed. During the period while head 3a is positioned above the predetermined area RP, head 3a moves at a constant speed at that predetermined speed. During the period from above the predetermined area RP until head 3a reaches position PE, head 3a decelerates so that it can stop at position PE. Here, the predetermined area RP is the area along the movement path RU from position PR1 to position PR2.

[0066] In the example shown in FIG. 4, the movement path RU is linear when viewed in the Z2 direction. In this embodiment, during a printing operation, the robot 2 operates four or more of the six joints 230, including joints 230_2, 230_3, and 230_5, to move the head 3a linearly along the movement path RU. The robot 2 also moves the head 3a in a direction away from the base 210. Here, the aforementioned a1 direction faces forward in the movement direction of the head 3a. Therefore, the energy emitter 3c is located behind the head 3a in the movement direction of the head 3a. This allows energy from the energy emitter 3c to be irradiated onto the ink immediately after it has landed on the surface WF from the head 3a.

[0067] The workpiece W may be placed at a position further in the X2 direction than the base 210 of the robot 2 so that its position in the direction along the Y axis coincides with the position of the base 210. In this case, the movement path RU forms a straight line along the X axis when viewed in the Z2 direction. In this case, the robot 2 performs a printing operation by operating three of the six joints 230 during the printing operation. More specifically, during the printing operation, the robot 2 operates the joints 230_2, 230_3, and 230_5 while aligning the rotation axes of these joints 230_2, 230_3, and 230_5 in a state parallel to the Y axis. Such operation of the three joints 230 allows the head 3a to move stably along the movement path RU.

[0068] Furthermore, during the printing operation, the a1 direction mentioned above faces forward in the movement direction of the head 3a, and therefore the first nozzle row L1, the third nozzle row L3, the fourth nozzle row L4, and the second nozzle row L2 are arranged in this order from the closest to the farthest from the base 210. Therefore, when the first ink, the second ink, the third ink, and the fourth ink are ejected at the same position on the surface WF, the posture of the robot 2 at the ejection timing of each ink is different from one another.

[0069] Here, with regard to the timings for ejecting the first ink, second ink, third ink, and fourth ink at the same position on the surface WF, the ejection timing of the first ink is the “first timing,” the ejection timing of the second ink is the “second timing,” the ejection timing of the third ink is the “third timing,” and the ejection timing of the fourth ink is the “fourth timing.” Below, the first timing and second timing will be described as representative examples.

[0070] Fig. 5 is a diagram showing the state of the robot 2 at the first timing. Fig. 6 is a diagram for explaining the distance DA between the tip ET and base end EB of the arm 220 of the robot 2 at the first timing. Figs. 5 and 6 illustrate a state in which the timing at which the first nozzle row L1 ejects the first ink at position PR2 is the first timing. Note that for ease of explanation, Figs. 5 and 6 schematically illustrate each part of the robot 2 and head unit 3.

[0071] As shown in FIGS. 5 and 6 , at the first timing, the first nozzle row L1, the third nozzle row L3, the fourth nozzle row L4, and the second nozzle row L2 are arranged in this order from closest to farthest from the base 210. Therefore, the distances between these nozzle rows and the base end EB are, from smallest to largest, the distance DN1 between the first nozzle row L1 and the base end EB, the distance DN3 between the third nozzle row L3 and the base end EB, the distance DN4 between the fourth nozzle row L4 and the base end EB, and the distance DN2 between the second nozzle row L2 and the base end EB. In this embodiment, the distance DN1 is defined as the shortest horizontal distance between the center of the first nozzle row L1 and the center of the base end EB. Similarly, the distances DN2, DN3, and DN4 are defined as the shortest horizontal distance between the center of the corresponding nozzle row and the center of the base end EB. However, the distances DN1, DN2, DN3, and DN4 may simply be the linear distance between the center of each nozzle row and the center of the base end EB, regardless of the direction.

[0072] It is preferable that this arrangement order of the nozzle rows be maintained during the execution of the printing operation for the predetermined region RP.

[0073] In this embodiment, since the head 3a moves in a direction away from the base 210, the angle θ1 formed between the extending direction of the arm 224 and the extending direction of the arm 222 increases as the head 3a moves during the printing operation. In contrast, the angle θ2 formed between the extending direction of the arm 222 and the rotation axis O1 decreases as the head 3a moves during the printing operation.

[0074] Fig. 7 is a diagram showing the state of the robot 2 at the second timing. Fig. 8 is a diagram for explaining the distance between the tip ET and base end EB of the arm 220 of the robot 2 at the second timing. Figs. 7 and 8 illustrate a state in which the second timing is the timing at which the second nozzle row L2 ejects the second ink at position PR2. Note that for ease of explanation, Figs. 7 and 8 schematically illustrate each part of the robot 2 and head unit 3.

[0075] 7 and 8, at the second timing, similarly to the first timing, the first nozzle row L1, the third nozzle row L3, the fourth nozzle row L4, and the second nozzle row L2 are arranged in this order from closest to farthest from the base 210. Therefore, the distances between these nozzle rows and the base end EB are, from smallest to largest, the distance DN1 between the first nozzle row L1 and the base end EB, the distance DN3 between the third nozzle row L3 and the base end EB, the distance DN4 between the fourth nozzle row L4 and the base end EB, and the distance DN2 between the second nozzle row L2 and the base end EB.

[0076] However, the distance DN1 at the second timing is smaller than the distance DN1 at the first timing. The difference between these distances DN1 corresponds to the distance between the first nozzle row L1 and the second nozzle row L2. Similarly, the distance DN2 at the second timing is smaller than the distance DN2 at the first timing. The distance DN3 at the second timing is smaller than the distance DN3 at the first timing. The distance DN4 at the second timing is smaller than the distance DN4 at the first timing.

[0077] Due to the relationship between the distances DN1, DN2, DN3, and DN4 at the second timing and the distances DN1, DN2, DN3, and DN4 at the first timing, the distance DA between the tip ET and base end EB of the arm portion 220 at the second timing is smaller than the distance DA at the first timing.

[0078] Here, the arm 220 at the second timing is in a contracted state compared to the arm 220 at the first timing. Therefore, the angle θ1 at the second timing is smaller than the angle θ1 at the first timing. Also, the angle θ2 at the second timing is larger than the angle θ2 at the first timing.

[0079] FIG. 9 is a graph showing the relationship between the distance DA between the tip ET and base EB of the arm 220 and the rotation angle θ of the joint 230 of the robot 2. The rotation angle θ in FIG. 9 is the angle θ1 or θ2 described above. FIG. 9 shows the relationship between the distance DA and the rotation angle θ when the rotation axes O2, O3, and O5 are maintained parallel to one another and the rotation axes O1 and O6 are maintained parallel to the Z axis and the joint 230 is operated. Here, the example shows a case where the distance between the rotation axis O3 and the tip ET is equal to the distance between the rotation axis O3 and the base EB. The distance DA in FIG. 9 is set to 0 when the arm 220 is fully retracted, and 1 when the arm 220 is fully extended. For simplicity, FIG. 9 does not take into account the limits of the range of motion of the joint 230.

[0080] The joint 230 can be a source of vibration in the arm 220. Generally, the joint 230 is more likely to vibrate when the rotation speed changes (increases or decreases) than when the rotation motion is stopped or the rotation speed is constant. Furthermore, once vibration of the joint 230 occurs, it is difficult to suppress the vibration. The vibration generated in the joint 230 propagates to the head 3a via the arm 220. As a result, the head 3a vibrates. When the head 3a vibrates, the actual movement path of the head 3a deviates from the ideal movement path, resulting in a decrease in print quality.

[0081] 9, the angle θ1 increases as the distance DA increases. Conversely, the angle θ2 decreases as the distance DA increases. Here, the amount of change in each of the angles θ1 and θ2 per unit length of the distance DA is roughly constant when the distance DA is within a range of 0 to 0.8, but increases as the distance DA increases when the distance DA exceeds 0.8.

[0082] Therefore, when a continuous movement is made from a state in which the arm 220 is retracted with a relatively small distance DA to a state in which the arm 220 is extended with a relatively large distance DA, and the distance DA changes at a constant speed, the rotational speed of the joint 230 is initially almost constant, but as the arm 220 approaches the extended state, the change in the rotational speed of the joint 230 becomes greater. Therefore, when the arm 220 is extended with a relatively large distance DA, vibration of the joint 230 is more likely to occur than when the arm 220 is retracted with a relatively small distance DA. Therefore, at the second timing when the distance DA is small, vibration of the head 3a is more easily suppressed than at the first timing.

[0083] Here, the first period refers to a period during which the head 3a ejects the first ink from the first nozzle row L1 onto the predetermined region RP while scanning the predetermined region RP along the movement path RU. The second period refers to a period during which the head 3a ejects the second ink from the second nozzle row L2 onto the predetermined region RP while scanning the predetermined region RP along the movement path RU. The first period includes a first timing, and the second period includes a second timing. As described above, the distance DA at the second timing is smaller than the distance DA at the first timing, and as can be seen from the graph in FIG. 9 , when ink is ejected onto the same predetermined region RP during the first and second periods, the total amount of rotation of the multiple joints 230 during the second period is smaller than the total amount of rotation of the multiple joints 230 during the first period. The first period and the second period may or may not overlap each other. In other words, the ejection of the first ink from the first nozzle row and the ejection of the second ink from the second nozzle row may be performed simultaneously in one scan of the head 3a, or may be performed separately so that the ejection of the first ink from the first nozzle row is performed in the first scan of the head 3a and the ejection of the second ink from the second nozzle row is performed in the second scan of the head 3a.

[0084] As described above, the printing device 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 row L1 in which a plurality of nozzles N that eject a first ink are arranged, and a second nozzle row L2 in which a plurality of nozzles N that eject a second ink are arranged. The robot 2 includes an arm 220 having a tip end ET, a base end EB, and a plurality of joints 230, and a base 210 connected to the base end EB, and the head 3a is supported on the tip end ET. The brightness of the second ink is lower than that of the first ink.

[0085] Furthermore, when the timing at which the first ink is ejected from the first nozzle row L1 onto a predetermined position PR2 on the workpiece W is defined as the first timing, and the timing at which the second ink is ejected from the second nozzle row L2 onto the predetermined position PR2 is defined as the second timing, the distance DA between the tip ET and the base end EB at the second timing is smaller than the distance DA between the tip ET and the base end EB at the first timing.

[0086] In the printing device 1 described above, because the brightness of the second ink is lower than the brightness of the first ink, landing errors of the second ink on the workpiece W are more noticeable than landing errors of the first ink on the workpiece W. In other words, the second ink is more likely to cause a decrease in print quality due to landing errors on the workpiece W than the first ink. Therefore, in order to improve print quality, the distance DA at the second timing is made smaller than the distance DA at the first timing.

[0087] More specifically, by making the distance DA at the second timing shorter than the distance DA at the first timing, the moment around the base end EB of the arm portion 220 at the second timing can be made smaller than the moment around the base end EB of the arm portion 220 at the first timing. Therefore, vibration is less likely to occur in the tip end ET of the arm portion 220, and ultimately in the head 3a, at the second timing compared to the first timing. As a result, the landing error of the second ink on the workpiece W can be reduced at the second timing compared to the first timing.

[0088] Furthermore, the greater the distance DA, the greater the amount of rotation of the joint 230 per unit moving distance of the head 3a. Therefore, the greater the distance DA, the more likely vibration of the head 3a occurs due to driving of the joint 230. Therefore, making the distance DA at the second timing shorter than the distance DA at the first timing also brings about the effect of reducing vibration of the head 3a due to driving of the joint 230.

[0089] On the other hand, at the first timing, vibrations are more likely to occur in the head 3a than at the second timing, but the first ink is used, which causes less noticeable landing errors than the second ink.

[0090] As described above, by improving the landing accuracy of the second ink, which has more noticeable landing errors, compared to the landing accuracy of the first ink, which has less noticeable landing errors, of the first and second inks having different brightnesses, it is possible to reduce the overall degradation of print quality due to ink landing errors on the workpiece W. Therefore, it is possible to improve print quality compared to a configuration in which the distance DA at the second timing is equal to or greater than the distance DA at the first timing.

[0091] Furthermore, as described above, at both the first timing and the second timing, the distance DN2 between the second nozzle row L2 and the base end EB is greater than the distance DN1 between the first nozzle row L1 and the base end EB. Therefore, the distance DA at the second timing can be made shorter than the distance DA at the first timing. Note that, regardless of the first timing or the second timing, by making the distance DN2 longer than the distance DN1, the distance DA when printing with the second nozzle row L2 can be made shorter than the distance DA when printing with the first nozzle row L1.

[0092] Furthermore, as described above, the distance DN2 between the second nozzle row L2 and the base end EB is maintained greater than the distance DN1 between the first nozzle row L1 and the base end EB during both the period in which the robot 2 ejects the first ink from the first nozzle row L1 while scanning the head 3a along the predetermined region RP that includes the predetermined position PR2 on the workpiece W, and the period in which the robot 2 ejects the second ink from the second nozzle row L2 while scanning the head 3a along the predetermined region RP. Therefore, the distance DA at the second timing can be made shorter than the distance DA at the first timing throughout the entire printing period.

[0093] As described above, the head 3a further includes a third nozzle row L3 in which multiple nozzles N are arranged to eject the third ink. The brightness of the third ink is lower than that of the first ink and higher than that of the second ink. Furthermore, at each of the first and second timings, the distance DN3 between the third nozzle row L3 and the base end EB is greater than the distance DN1 between the first nozzle row L1 and the base end EB and is smaller than the distance DN2 between the second nozzle row L2 and the base end EB. Therefore, even when the third ink is used in addition to the first and second inks, it is possible to reduce degradation of print quality due to ink landing errors on the workpiece W.

[0094] In this embodiment, as described above, the head 3a includes 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 that eject ink. Of any two nozzle rows selected from the multiple nozzle rows, the brightness of the ink ejected from the nozzle row that is farther from the base end EB is lower than the brightness of the ink ejected from the nozzle row that is closer to the base end EB. In other words, the multiple nozzle rows are arranged such that the brightness of the ink ejected from a nozzle row that is farther from the base end EB is lower. Therefore, when multiple types of ink are used, degradation of print quality due to ink landing errors on the workpiece W can be effectively reduced.

[0095] As described above, the printing apparatus 1 further includes the energy emitter 3c. The energy emitter 3c is supported by the tip ET and includes an emission surface FL that emits energy to cure each of the first ink and the second ink.

[0096] Furthermore, the distance DL2 between the second nozzle row L2 and the exit surface FL is greater than the distance DL1 between the first nozzle row L1 and the exit surface FL. This allows the amount of second ink adhering to the exit surface FL to be smaller than the amount of first ink. Because the second ink has a lower brightness than the first ink, the second ink more easily absorbs energy from the exit surface FL than the first ink. Therefore, reducing the amount of second ink adhering to the exit surface FL has the effect of suppressing a decrease in the efficiency of energy irradiation from the exit surface FL to each ink and reducing the frequency of maintenance, such as cleaning, of the exit surface FL. Because the first ink absorbs energy from the exit surface FL less easily than the second ink, even if the amount of first ink adhering to the exit surface FL is large, problems such as a decrease in the efficiency of energy irradiation from the exit surface FL to each ink and an increase in the frequency of maintenance, such as cleaning, of the exit surface FL are less likely to occur compared to when the second ink is adhering to the exit surface FL.

[0097] As described above, a first period and a second period are defined for the period during which the head 3a scans along a predetermined region RP including a predetermined position PR2 on the workpiece W. The first period is a period during which the first nozzle row L1 ejects a first ink onto the predetermined region RP. The second period is a period during which the second nozzle row L2 ejects a second ink onto the predetermined region RP. Furthermore, the total amount of rotation of the multiple joints 230 during the second period is smaller than the total amount of rotation of the multiple joints 230 during the first period. Therefore, the vibration of the head 3a during the second period can be smaller than the vibration of the head 3a during the first period.

[0098] Furthermore, as mentioned above, the first ink is the ink with the highest lightness among the inks ejected from the head 3a, which makes it possible to suitably improve print quality.

[0099] In this embodiment, as described above, the first ink is yellow ink. Generally, among the multiple colors of ink used in full-color printing, the ink with the highest brightness is yellow ink. Therefore, by using yellow ink as the first ink, the print quality in full-color printing can be suitably improved. Note that in configurations using five or more types of ink, white ink may be used as the ink with the highest brightness. In this case, the first ink may be white ink.

[0100] Furthermore, as mentioned above, the second ink is the ink with the lowest lightness among the inks ejected from the head 3a, which can favorably improve print quality.

[0101] In this embodiment, as described above, the second ink is black ink. Generally, among the inks of multiple colors used in full-color printing, etc., black ink has the lowest lightness. Therefore, by using black ink as the second ink, the print quality of full-color printing, etc. can be suitably improved.

[0102] Furthermore, as described above, the head 3a includes a plurality of nozzle rows that eject ink: a first nozzle row L1, a second nozzle row L2, a third nozzle row L3, and a fourth nozzle row L4. Here, the first nozzle row L1 and the second nozzle row L2 are preferably the two nozzle rows that are arranged furthest apart from each other among the plurality of nozzle rows. In this case, print quality can be improved compared to a configuration in which the other nozzle rows are the first nozzle row L1 and the second nozzle row L2.

[0103] 2. Second embodiment A second embodiment of the present invention will be described below. In the following exemplary embodiment, for elements whose actions and functions are similar to those of the first embodiment, the reference numerals used in the description of the first embodiment will be used and detailed descriptions of each element will be omitted as appropriate.

[0104] FIG. 10 is a diagram for explaining the printing operation in the second embodiment. This embodiment is the same as the aforementioned first embodiment except that the predetermined region RP is different. In the first embodiment, an example is illustrated in which the magnitude relationship of the distances DN1 to DN4 between each nozzle row and the proximal end EB does not change during the execution of the printing operation, but the magnitude relationship may change.

[0105] In this embodiment, the printing region PR is expanded in the X1 direction compared to the first embodiment. Here, the predetermined region RP is divided into a region RP1 and a region RP2 by a virtual straight line YB that passes through the proximal end EB and is orthogonal to the scanning direction of the head 3a along the movement path RU when viewed in the direction along the Z axis.

[0106] In the example shown in FIG. 10, since the movement path RU is parallel to the X axis when viewed in the direction along the Z axis, the straight line YB is parallel to the Y axis. The region RP1 is located in the X1 direction with respect to the straight line YB when viewed in the direction along the Z axis. On the other hand, the region RP2 is located in the X2 direction with respect to the straight line YB when viewed in the direction along the Z axis.

[0107] When printing is performed during the period in which the head 3a is moved from the position PS to the position PE in the X2 direction along the movement path RU with respect to such a predetermined region RP, the ejection of ink from the first nozzle row L1 starts at the position PR1 within the region RP1 and stops at the position PR2 within the region RP2. Here, the arrangement order of the nozzle rows in the direction along the X axis is maintained throughout the printing period. For this reason, the magnitude relationship of the distances DN1 to DN4 changes during the printing period.

[0108] More specifically, in a state where the tip ET is located in the region RP2, similar to the first embodiment, the magnitude relationship of the distances between each nozzle row and the proximal end EB satisfies DN2 > DN1. On the other hand, in a state where the tip ET is located in the region RP1, the magnitude relationship of the distances between each nozzle row and the proximal end EB satisfies DN2 < DN1. Thus, when the tip ET passes over the straight line YB, the magnitude relationship of the distances DN1 to DN4 changes during the printing period.

[0109] From the perspective of improving printing quality, it is not preferable to perform printing in a state where DN2 < DN1. Therefore, in the predetermined region RP, it is preferable that there is no region RP1 where DN2 < DN1. Alternatively, even if the predetermined region RP includes the region RP1, it is preferable to control the operation of the robot 2 so that DN2 > DN1.

[0110] However, printing may be performed in a state where DN2 < DN1. That is, there may be cases where printing in a state where DN2 < DN1 is allowed. Here, when the predetermined region RP includes the region RP1, from the perspective of the balance between printing quality and productivity, the length of the region RP1 along the movement path RU is preferably shorter than the length of the region RP2 along the movement path RU. More preferably, the length of the region RP1 along the movement path RU is 1 / 2 or less with respect to the length of the region RP2 along the movement path RU. Thus, if the length of the region RP1 along the movement path RU is short enough, even if there is a period of printing in a state where DN2 < DN1, there is a period of printing in a state where DN2 > DN1, so that printing with an excellent balance between printing quality and productivity can be performed.

[0111] 3. Third Embodiment Hereinafter, the third embodiment of the present invention will be described. For elements whose actions and functions are the same as those in the first embodiment in the forms exemplified below, the reference numerals used in the description of the first embodiment are reused and the detailed description of each is appropriately omitted.

[0112] FIG. 11 is a block diagram showing the electrical configuration of the printing apparatus 1A according to the third embodiment. The printing apparatus 1A is configured in the same manner as the printing apparatus 1 of the first embodiment, except that it includes a head unit 3A instead of the head unit 3. The head unit 3A is configured in the same manner as the head unit 3, except that the arrangement of the energy emitting unit 3c is different and an optical sensor 3g is added.

[0113] Fig. 12 is a perspective view showing a schematic configuration of a head unit 3A used in the third embodiment. As shown in Fig. 12, in the head unit 3A, an energy emitter 3c is arranged at a position in the a1 direction relative to the head 3a, while an optical sensor 3g is arranged at a position in the a2 direction. Here, the energy emitter 3c is attached to a support 3f via a member (not shown). The optical sensor 3g is attached by screwing or the like to the surface of the support f facing the a2 direction.

[0114] The optical sensor 3g is a sensor such as an optical displacement meter or an imaging device that includes a light receiving unit FS. The light receiving unit FS has a surface facing the c2 direction and is an optical component for introducing light into, for example, a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary MOS) image sensor.

[0115] For example, the controller 5 corrects the actual movement path of the head 3a based on the output from the optical sensor 3g. The optical sensor 3g may be connected to the computer 7. If the optical sensor 3g is an imaging device, the output from the optical sensor 3g may be used for other purposes, such as teaching the robot 2.

[0116] Fig. 13 is a diagram for explaining the printing operation of the printing device 1A according to the third embodiment. As with Fig. 4, Fig. 13 illustrates a case where printing is performed on a predetermined area RP on the surface WF of the workpiece W placed at a position in the X2 direction further from the base 210 of the robot 2 as viewed in the direction along the Y axis.

[0117] In this embodiment, the robot 2 moves the head 3a in a direction approaching the base 210. Here, the a2 direction faces forward in the movement direction of the head 3a. Therefore, similar to the first embodiment, the first nozzle row L1, the third nozzle row L3, the fourth nozzle row L4, and the second nozzle row L2 are arranged in this order from closer to farther from the base 210.

[0118] The energy emitter 3c is located behind the head 3a in the direction of movement of the head 3a. This allows the energy emitter 3c to irradiate the ink immediately after it lands on the surface WF from the head 3a. The optical sensor 3g is located ahead of the head 3a in the direction of movement of the head 3a.

[0119] The third embodiment described above also improves print quality. In this embodiment, the printing device 1A has an energy emission unit 3c. However, unlike the first embodiment, the distance DL2 between the second nozzle row L2 and the emission surface FL is shorter than the distance DL1 between the first nozzle row L1 and the emission surface FL. Therefore, the period from the time when the second ink lands on the workpiece W to the time when energy is applied to the second ink can be shorter than the period from the time when the first ink lands on the workpiece W to the time when energy is applied to the first ink. Here, because the brightness of the second ink is lower than that of the first ink, bleeding of the second ink on the workpiece W is more noticeable than that of the first ink. Therefore, shortening the period from the time when the second ink lands on the workpiece W to the time when energy is applied to the second ink has the effect of improving print quality. Furthermore, since bleeding of the first ink on the workpiece W is less noticeable than that of the second ink, even if the period between the time when the first ink lands on the workpiece W and the time when energy is applied to the first ink is long, the problem of reduced print quality is less likely to occur.

[0120] The relationship between the distances DL1 and DL2, whether that relationship is the first or third embodiment, is determined taking into consideration factors such as the tendency of the second ink to bleed. For example, if the second ink bleeds easily, a configuration in which the distance DL2 is smaller than the distance DL1 is adopted, as in this embodiment. On the other hand, if the second ink bleeds less easily, a configuration in which the distance DL2 is larger than the distance DL1 is adopted, as in the first embodiment.

[0121] In this embodiment, as described above, the printing apparatus 1A further includes an optical sensor 3g, which is supported at the tip ET and includes a light receiving portion FS.

[0122] Furthermore, the distance DS2 between the second nozzle row L2 and the light receiving unit FS is greater than the distance DS1 between the first nozzle row L1 and the light receiving unit FS. Therefore, the amount of second ink adhering to the light receiving unit FS can be made smaller than the amount of first ink. Here, because the lightness of the second ink is lower than that of the first ink, the second ink is more likely to absorb light that reaches the light receiving unit FS than the first ink. Therefore, reducing the amount of second ink adhering to the light receiving unit FS has the effect of increasing the light receiving efficiency at the light receiving unit FS. Furthermore, because the first ink is less likely to absorb light that reaches the light receiving unit FS than the second ink, even if the amount of first ink adhering to the light receiving unit FS is increased, the problem of reduced light receiving efficiency at the light receiving unit FS is unlikely to occur.

[0123] 4. Fourth embodiment A fourth embodiment of the present invention will be described below. In the following exemplary embodiments, elements whose actions and functions are similar to those of the first embodiment will be designated by the same reference numerals as those used in the description of the first embodiment, and detailed descriptions of each element will be omitted where appropriate.

[0124] FIG. 14 is a perspective view showing a schematic configuration of a head unit 3B used in the fourth embodiment. The printing device 1B has the same configuration as the printing device 1 of the first embodiment, except that it includes a head unit B instead of the head unit 3. As shown in Fig. 14, the head unit 3B has two energy emitters 3c. Of the two energy emitters 3c, one energy emitter 3c is positioned in the a1 direction relative to the head 3a, and the other energy emitter 3c is positioned in the a2 direction relative to the head 3a.

[0125] FIG. 15 is a diagram illustrating movement paths RU1 and RU2 of the head 3a in the fourth embodiment. Movement path RU1 is a path from position PS1 to position PE1. The robot 2 moves the head 3a along movement path RU1 in a direction away from the base 210. At this time, the a1 direction faces forward in the movement direction of the head 3a. Movement path RU2 is a path from position PS2 to position PE2. The robot 2 moves the head 3a along movement path RU2 in a direction approaching the base 210. At this time, the a2 direction faces forward in the movement direction of the head 3a.

[0126] Although not shown, positions PS1 and PE2 are located in the X1 direction from the predetermined region RP when viewed in the Z2 direction. Although not shown, positions PE1 and PS2 are located in the X2 direction from the predetermined region RP when viewed in the Z2 direction.

[0127] The fourth embodiment described above can also improve print quality. In this embodiment, as described above, two energy emitters 3c are arranged via the head 3a. Therefore, whether printing is performed in a direction in which the head 3a moves away from or toward the base 210, energy can be irradiated onto the ink immediately after it lands on the workpiece W while maintaining the relationship between the distance DN1 and the distance DN2, as in the first and third embodiments.

[0128] 5. Variations Each of the above-mentioned exemplary embodiments can be modified in various ways. Specific modified embodiments that can be applied to each of the above-mentioned embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be appropriately combined within the scope of not contradicting each other.

[0129] 5-1. Variation 1 In the above-described embodiment, the first nozzle row L1, the third nozzle row L3, the fourth nozzle row L4, and the second nozzle row L2 are arranged in this order from closest to farthest from the base 210, but the arrangement is not limited to that of the above-described embodiment as long as the second nozzle row L2 is arranged in a position farther from the base 210 than the first nozzle row L1. For example, the nozzle rows may be arranged in the order of the first nozzle row L1, the fourth nozzle row L4, the third nozzle row L3, and the second nozzle row L2 from closest to the base 210.

[0130] 5-2. Variation 2 In the above embodiment, a configuration in which printing is performed using four types of ink is exemplified, but the present disclosure is not limited to this configuration as long as a first ink and a second ink are used, and can also be applied to a configuration in which printing is performed using two, three, or five or more types of ink. Furthermore, the first ink may be an ink with a higher brightness than the second ink, and is not limited to yellow ink. Furthermore, the second ink may be an ink with a lower brightness than the first ink, and is not limited to black ink.

[0131] 5-3. Variation 3 In the above-described embodiment, a configuration using the energy emitter 3c is exemplified, but the present invention is not limited to this configuration, and the energy emitter 3c may be omitted. In this case, for example, a separate means for emitting light to harden or solidify the ink on the workpiece may be arranged outside the robot 2.

[0132] 5-4. Variation 4 In the above-described embodiment, a configuration using a six-axis vertical multi-axis robot is exemplified as the movement mechanism, but the movement mechanism is not limited to this configuration. The movement mechanism may be, for example, a vertical multi-axis robot other than a six-axis robot, or a horizontal multi-axis robot. Furthermore, the arm of the robot may have an extension mechanism or a linear motion mechanism in addition to a rotation unit configured with a rotation mechanism. However, from the viewpoint of balancing the print quality during printing operations and the degree of freedom of the robot's movement during non-printing operations, it is preferable that the robot be a multi-axis robot with six or more axes.

[0133] 5-5. Variation 5 In the above-described embodiment, the head is fixed to the robot using screws or the like, but is not limited to this. For example, the head may be fixed to the robot by gripping it with a gripping mechanism such as a hand attached as an end effector of the robot. [Explanation of symbols]

[0134] 1...printing device, 1A...printing device, 1B...printing device, 2...robot, 2a...arm drive mechanism, 3...head unit, 3A...head unit, 3B...head unit, 3a...head, 3b...pressure regulating valve, 3c...energy output unit, 3e...switch circuit, 3f...support, 3g...optical sensor, 5...controller, 5a...memory circuit, 5b...processing circuit, 6...control module, 6a...timing signal generating circuit, 6b...power supply circuit, 6c...control circuit, 6d...drive signal generating circuit composition circuit, 7...computer, 10...piping section, 10a...supply pipe, 11...wiring section, 210...base section, 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, 230_6...joint, CLK...clock signal, CNG...change signal, Com...drive signal, D1...output, D3...signal, DA ...distance, DL1...distance, DL2...distance, DN1...distance, DN2...distance, DN3...distance, DN4...distance, DS1...distance, DS2...distance, Da...path information, EB...base end, ET...tip end, FL...emission surface, FN...ejection surface, FS...light receiving unit, Img...print 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, O 6...rotation axis, PD...drive pulse, PE...position, PE1...position, PE2...position, PR1...position, PR2...position, PS...position, PS1...position, PS2...position, PTS...timing signal, RP...predetermined area, RU...movement path, RU1...movement path, RU2...movement path, SI...print data signal, Sk1...control signal, VBS...offset potential, VHV...power supply potential, W...workpiece, WF...surface, dCom...waveform designation signal, f...support, θ...rotation angle, θ1...angle, θ2...angle.

Claims

1. 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; a robot having an arm having a tip end, a base end, and a plurality of joints, and a base connected to the base end, the head being supported at the tip end, and changing the position and orientation of the head relative to a workpiece; the brightness of the second ink is lower than the brightness of the first ink; a timing at which the first ink is ejected from the first nozzle row onto a predetermined position on the workpiece is defined as a first timing; When the timing at which the second ink is ejected from the second nozzle row to the predetermined position is set as a second timing, The distance between the distal end and the proximal end at the second timing is smaller than the distance between the distal end and the proximal end at the first timing. Printing device.

2. At each of the first timing and the second timing, the distance between the second nozzle row and the base end is greater than the distance between the first nozzle row and the base end. The printing device of claim 1 .

3. a period in which the robot ejects the first ink from the first nozzle row while scanning the head along a predetermined area including the predetermined position on the workpiece; a period during which the robot ejects the second ink from the second nozzle row while scanning the head along the predetermined area; In both cases, a state in which the distance between the second nozzle row and the base end is greater than the distance between the first nozzle row and the base end is maintained.

3. The printing device according to claim 1.

4. the head further includes a third nozzle row in which a plurality of nozzles that eject a third ink are arranged, the brightness of the third ink is lower than the brightness of the first ink and higher than the brightness of the second ink; At each of the first timing and the second timing, a distance between the third nozzle row and the base end is greater than a distance between the first nozzle row and the base end and is smaller than a distance between the second nozzle row and the base end; The printing device according to any one of claims 1 to 3.

5. The head includes a plurality of nozzle rows that eject ink, the plurality of nozzle rows include the first nozzle row and the second nozzle row, of any two nozzle rows selected from the plurality of nozzle rows, the lightness of ink ejected from the nozzle row that is farther from the base end is lower than the lightness of ink ejected from the nozzle row that is closer to the base end; The printing device according to any one of claims 1 to 4.

6. an energy emitting unit supported by the tip and including an emitting surface that emits energy to cure each of the first ink and the second ink; a distance between the second nozzle row and the emission surface is greater than a distance between the first nozzle row and the emission surface; The printing device according to any one of claims 1 to 5.

7. an energy emitting unit supported by the tip and including an emitting surface that emits energy to cure each of the first ink and the second ink; a distance between the second nozzle row and the emission surface is smaller than a distance between the first nozzle row and the emission surface; The printing device according to any one of claims 1 to 5.

8. an optical sensor supported on the tip and including a light receiving portion; a distance between the second nozzle row and the light receiving unit is greater than a distance between the first nozzle row and the light receiving unit; The printing device according to any one of claims 1 to 7.

9. During a period in which the head scans along an area including the predetermined position on the workpiece, a period during which the first ink is ejected from the first nozzle row onto the region is defined as a first period; When a period during which the second ink is ejected from the second nozzle row onto the region is defined as a second period, a sum of the rotation amounts of the plurality of joints in the second time period is smaller than a sum of the rotation amounts of the plurality of joints in the first time period; The printing device according to any one of claims 1 to 8.

10. the first ink is the ink with the highest lightness among the inks ejected from the head; The printing device according to any one of claims 1 to 9.

11. the first ink is a yellow ink or a white ink; The printing device according to any one of claims 1 to 10.

12. the second ink is the ink with the lowest lightness among the inks ejected from the head; The printing device according to any one of claims 1 to 11.

13. The second ink is a black ink. The printing device according to any one of claims 1 to 12.

14. The head includes a plurality of nozzle rows that eject ink, the first nozzle row and the second nozzle row are two nozzle rows that are arranged farthest from each other among the plurality of nozzle rows; The printing device according to any one of claims 1 to 13.

15. 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; a robot having an arm having a tip end, a base end, and a plurality of joints, and a base connected to the base end, the head being supported at the tip end, and changing the position and orientation of the head relative to a workpiece; the brightness of the second ink is lower than the brightness of the first ink; when the head faces a predetermined region of the workpiece including a predetermined position to which the first ink is ejected from the first nozzle row, and the first ink is ejected from the first nozzle row to the predetermined position, the distance between the second nozzle row and the base end is longer than the distance between the first nozzle row and the base end; Printing device.

16. 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 that is lower in brightness than the first ink are arranged; A printing method for a printing device having a robot including an arm having a tip end, a base end, and a plurality of joints, and a base connected to the base end, the head being supported at the tip end, and changing the position and orientation of the head relative to a workpiece, a printing operation in which the head ejects the first ink and the second ink while the robot moves the head away from the base; When a timing at which the first ink is ejected from the first nozzle row to a predetermined position on the workpiece during the printing operation is defined as a first timing, and a timing at which the second ink is ejected from the second nozzle row to the predetermined position is defined as a second timing, The distance between the distal end and the proximal end at the second timing is smaller than the distance between the distal end and the proximal end at the first timing. Printing method.

17. 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 that is lower in brightness than the first ink are arranged; A printing method for a printing device having a robot including an arm having a tip end, a base end, and a plurality of joints, and a base connected to the base end, the head being supported at the tip end, and changing the position and orientation of the head relative to a workpiece, a printing operation in which the head ejects the first ink and the second ink while the robot moves the head so as to approach the base, When a timing at which the first ink is ejected from the first nozzle row to a predetermined position on the workpiece during the printing operation is defined as a first timing, and a timing at which the second ink is ejected from the second nozzle row to the predetermined position is defined as a second timing, The distance between the distal end and the proximal end at the second timing is smaller than the distance between the distal end and the proximal end at the first timing. Printing method.

Images