Printing apparatus

Abstract

To operate a head at desired timing.SOLUTION: A printer comprises: a head which discharges liquid to a workpiece; a robot which changes the relative positions of the workpiece and the head; a position information output unit which outputs position information about the position of the robot; and a timing adjustment unit which adjusts discharge timing of the liquid from the head on the basis of the position information. When the timing adjustment unit sets the timing of acquiring first position information as the position information as first acquisition timing, sets the timing of acquiring second position information as the position information as second acquisition timing after the first acquisition timing and sets discharge timing after the second acquisition timing as first discharge timing, the timing adjustment unit adjusts the first discharge timing on the basis of the first position information and the second position information.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a printing apparatus.

Background Art

[0002] An inkjet printing apparatus using a robot such as an articulated robot is known. For example, the apparatus described in Patent Document 1 includes a head which is an inkjet head, a robot that holds the head, a head control unit that controls the driving of the head, and a robot control unit that controls the driving of the robot. The robot control unit calculates the moving speed of the head by synthesizing the speeds of a plurality of axes of the robot, and outputs a speed signal including the calculated moving speed information to the head control unit. The head driving unit controls the driving of the head based on the information from the robot control unit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the apparatus described in Patent Document 1, there are cases where the operation of the head control unit cannot operate the head at a desired timing due to the constraint of the control cycle of the robot control unit.

Means for Solving the Problems

[0005] To solve the above problems, one embodiment of the printing apparatus according to the present invention comprises a head for ejecting liquid onto a workpiece, a robot for changing the relative position of the workpiece and the head, a position information output unit for outputting position information relating to the position of the robot, and a timing adjustment unit for adjusting the timing of liquid ejection from the head based on the position information. The timing adjustment unit adjusts the first ejection timing based on the first and second position information. The timing adjustment unit adjusts the first ejection timing based on the first and second position information. [Brief explanation of the drawing]

[0006] [Figure 1] This is a schematic perspective view showing the printing apparatus according to the first embodiment. [Figure 2] This block diagram shows the electrical configuration of the printing apparatus according to the first embodiment. [Figure 3] This is a perspective view showing the schematic configuration of the head unit in the first embodiment. [Figure 4] This is a diagram illustrating the printing operation of a printing device. [Figure 5] This diagram illustrates the discharge timing based on position information when no adjustment is made by the timing adjustment unit. [Figure 6] This figure illustrates the discharge timing based on the predicted position by the timing adjustment unit in the first embodiment. [Figure 7] This is a timing chart used to explain the operation of a switch circuit. [Figure 8] This figure illustrates the discharge position based on the predicted position by the timing adjustment unit in the second embodiment. [Figure 9] This is a block diagram showing the electrical configuration of a printing apparatus according to the third embodiment. [Figure 10] This block diagram shows the electrical configuration of the printing apparatus according to the fourth embodiment. [Figure 11] This is a block diagram showing the electrical configuration of the printing apparatus according to the fifth embodiment. [Figure 12] This figure shows an example of the signals output from each encoder. [Figure 13] This figure shows an example of correspondence information for converting signals from an encoder into positional information. [Modes for carrying out the invention]

[0007] Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. Note that the dimensions and scale of the parts in the drawings differ from those of the actual parts as appropriate, and some parts are shown schematically for ease of understanding. Furthermore, the scope of the present invention is not limited to these embodiments unless otherwise stated in the following description.

[0008] For convenience, the following explanation will use the X, Y, and Z axes intersecting each other as appropriate. In the following, one direction along the X axis is the X1 direction, and the direction opposite to the X1 direction is the X2 direction. Similarly, opposite directions along the Y axis are the Y1 and Y2 directions. Also, opposite directions along the Z axis are the Z1 and Z2 directions.

[0009] Here, the X, Y, and Z axes correspond to the coordinate axes of the world coordinate system set in the space where the robot 200 (described later) is installed. Typically, the Z axis is the vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. A base coordinate system, based on the position of the robot 200's base 210 (described later), is calibrated to this world coordinate system. In the following examples, for convenience, the case in which the robot's movement is controlled using the world coordinate system as the robot coordinate system is illustrated.

[0010] Note that the Z-axis does not have to be a vertical axis. Also, the X-axis, Y-axis, and Z-axis typically intersect orthogonally with each other, but are not limited to this, and may not intersect orthogonally. For example, the X-axis, Y-axis, and Z-axis may intersect at an angle within the range of 80° or more and 100° or less with each other.

[0011] 1. First Embodiment 1-1. Outline of Printing Device FIG. 1 is a perspective view showing an outline of a printing device 100 according to the first embodiment. The printing device 100 is a device that performs printing on the surface of a work W by an inkjet method.

[0012] The work W has a surface WF to be printed. In the example shown in FIG. 1, the work W is a rectangular parallelepiped, and the surface WF is a plane facing in the Z1 direction. Note that the printing target may be a surface other than the surface WF among the plurality of surfaces of the work W. Also, the size, shape, or installation posture of the work W is not limited to the example shown in FIG. 1 and is arbitrary.

[0013] In the example shown in FIG. 1, the printing device 100 is an inkjet printer using a vertically articulated robot. Specifically, as shown in FIG. 1, the printing device 100 includes a robot 200, a head unit 300, and a controller 600 which is an example of a "robot controller". Hereinafter, first, each part of the printing device 100 shown in FIG. 1 will be sequentially and briefly described.

[0014] The robot 200 is a moving mechanism that changes the position and posture of the head unit 300 with respect to the work W. In the example shown in FIG. 1, the robot 200 is a so-called 6-axis vertically articulated robot. Specifically, the robot 200 includes a base 210 and an arm 220.

[0015] The base 210 is a base that supports the arm 220. In the example shown in FIG. 1, the base 210 is fixed to an installation surface such as a floor surface facing in the Z1 direction by screwing or the like. Note that the installation surface to which the base 210 is fixed may be a surface facing any direction and is not limited to the example shown in FIG. 1. For example, it may be a surface of a wall, a ceiling, a movable cart, or the like.

[0016] The arm 220 is a six-axis robotic arm having a base end attached to the base 210 and a tip end that changes its position and orientation three-dimensionally with respect to the base end. Specifically, the arm 220 has arms 221, 222, 223, 224, 225, and 226, which are connected in this order.

[0017] The arm 221 is connected to the base 210 via a joint portion 230_1 so as to be rotatable about a first rotation axis O1. The arm 222 is connected to the arm 221 via a joint portion 230_2 so as to be rotatable about a second rotation axis O2. The arm 223 is connected to the arm 222 via a joint portion 230_3 so as to be rotatable about a third rotation axis O3. The arm 224 is connected to the arm 223 via a joint portion 230_4 so as to be rotatable about a fourth rotation axis O4. The arm 225 is connected to the arm 224 via a joint portion 230_5 so as to be rotatable about a fifth rotation axis O5. The arm 226 is connected to the arm 225 via a joint portion 230_6 so as to be rotatable about a sixth rotation axis O6. Hereinafter, each of the joint portions 230_1 to 230_6 may be referred to as the joint portion 230.

[0018] Each of the joint portions 230_1 to 230_6 is an example of a "movable part". In FIG. 1, a case where the number N of the joint portions 230 is six is illustrated. In the example shown in FIG. 1, each of the joint portions 230_1 to 230_6 is a mechanism that rotatably connects one of two adjacent arms to the other. Although not shown in FIG. 1, each of the joint portions 2S0_1 to 230_6 is provided with a drive mechanism for rotating one of two adjacent arms with respect to the other. The drive mechanism has, for example, a motor that generates a driving force for the rotation, a speed reducer that decelerates and outputs the driving force, and an encoder such as a rotary encoder that detects an operation amount such as the angle of the rotation. The assembly of the drive mechanisms corresponds to the arm drive mechanism 240 shown in FIG. 2 described later. Further, the encoder corresponds to the encoder 241 shown in FIG. 2 and the like described later.

[0019] The first rotation axis O1 is an axis perpendicular to the mounting surface (not shown) to which the base 210 is fixed. The second rotation axis O2 is an axis perpendicular to the first rotation axis O1. The third rotation axis O3 is an axis parallel to the second rotation axis O2. The fourth rotation axis O4 is an axis perpendicular to the third rotation axis O3. The fifth rotation axis O5 is an axis perpendicular to the fourth rotation axis O4. The sixth rotation axis O6 is an axis perpendicular to the fifth rotation axis O5.

[0020] Furthermore, regarding these pivot axes, "perpendicular" includes not only cases where the angle between the two pivot axes is exactly 90°, but also cases where the angle between the two pivot axes deviates from 90° by approximately ±5°. Similarly, "parallel" includes not only cases where the two pivot axes are exactly parallel, but also cases where one of the two pivot axes is tilted relative to the other by approximately ±5°.

[0021] The head unit 300 is mounted as an end effector at the tip of the arm 220, i.e., the arm 226.

[0022] The head unit 300 is a mechanism having a head 310 that ejects ink, which is an example of a liquid, toward the workpiece W. In this embodiment, in addition to the head 310, the head unit 300 has a pressure regulating valve 320 that adjusts the pressure of the ink supplied to the head 310. Since both are fixed to the arm 226, the relative positions and orientations of these components are fixed. In addition to the head 310 and the pressure regulating valve 320, the head unit 300 may also have, for example, a sensor that detects the relative position of the head 310 with respect to the workpiece W, a light source for curing or solidifying the ink, etc.

[0023] Although not shown in Figure 1, the print head 310 comprises a plurality of piezoelectric elements, a plurality of cavities for containing ink, and a plurality of nozzles. Here, each nozzle is provided for each cavity and communicates with the cavity. Each piezoelectric element is provided for each cavity and, by changing the pressure in the cavity, causes ink to be ejected from the nozzle corresponding to the cavity. Such a print head 310 can be obtained, for example, by bonding together a plurality of substrates, such as silicon substrates, which have been appropriately processed by etching or the like, using an adhesive. The piezoelectric elements correspond to the piezoelectric elements 311 shown in Figure 2, which will be described later. Alternatively, instead of the piezoelectric elements, heaters that heat the ink in the cavities may be used as driving elements for ejecting ink from the nozzles.

[0024] The pressure regulating valve 320 is a valve mechanism that opens and closes in accordance with the ink pressure in the print head 310. This opening and closing maintains the ink pressure in the print head 310 at a negative pressure within a predetermined range. This stabilizes the ink meniscus formed in the nozzle N of the print head 310. As a result, it prevents air bubbles from entering the nozzle N and prevents ink from overflowing from the nozzle N.

[0025] In the example shown in Figure 1, the head unit 300 has one head 310 and one pressure regulating valve 320, but this number is not limited to the example shown in Figure 1 and may be two or more. Also, the installation position of the pressure regulating valve 320 is not limited to the arm 226, but may be on other arms, for example, or in a fixed position relative to the base 210.

[0026] The head 310 and a liquid supply unit (not shown) are connected via the pressure regulating valve 320 described above. This liquid supply unit has a liquid reservoir and a supply channel. The liquid reservoir is a container for storing ink. The ink stored in the liquid reservoir is, for example, an ink containing a colorant, or an ink containing a conductive material such as a powder. The ink may also have curability, such as UV curability. The supply channel consists of a pipe that supplies ink from the liquid reservoir to the pressure regulating valve 320. The pipe is made of an elastic material such as rubber or elastomer and is flexible.

[0027] The controller 600 is a robot controller that controls the drive of the robot 200. Although not shown in Figure 1, a control module that controls the discharge operation of the head unit 300 is electrically connected to the controller 600. A computer is communicated to both the controller 600 and the control module. This control module is an example of a "head drive unit" and corresponds to the control module 500 shown in Figure 2 below. This computer corresponds to the computer 700 shown in Figure 2 below.

[0028] 1-2. Electrical configuration of the printing apparatus Figure 2 is a block diagram showing the electrical configuration of the printing apparatus 100 according to the first embodiment. Figure 2 shows the electrical components of the printing apparatus 100. Figure 2 also shows the arm drive mechanism 240, which includes encoders 241_1 to 241_6. The arm drive mechanism 240 is an assembly of the aforementioned drive mechanisms that operate the joints 230_1 to 230_6. Encoders 241_1 to 241_6 are rotary encoders provided corresponding to the joints 230_1 to 230_6, and measure the amount of movement such as the rotation angle of the joints 230_1 to 230_6. Hereafter, encoders 241_1 to 241_6 may each be referred to as encoder 241.

[0029] As shown in Figure 2, the printing apparatus 100 includes the aforementioned robot 200, head unit 300, and controller 600, as well as a control module 500, which is an example of a "head drive unit," and a computer 700. Note that the electrical components described below may be divided as appropriate, some of which may be included in other components, or may be integrated with other components. For example, some or all of the functions of the control module 500 or the controller 600 may be implemented by the computer 700 connected to the controller 600, or by other external devices such as a PC (personal computer) connected to the controller 600 via a network such as a LAN (Local Area Network) or the Internet. Alternatively, some or all of the functions of the control module 500 may be implemented by the controller 600.

[0030] The controller 600 has the function of controlling the drive of the robot 200 and the function of generating position information D2 related to the position of the head 310. The controller 600 includes a first memory circuit 610, a second memory circuit 620, a first processing circuit 630, and a second processing circuit 640.

[0031] The first storage circuit 610 stores various programs executed by the first processing circuit 630 and various data processed by the first processing circuit 630. The first storage circuit 610 includes, for example, one or both of semiconductor memories: a volatile memory such as RAM (Random Access Memory) and a non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable ROM). Part or all of the first storage circuit 610 may be included in the first processing circuit 630.

[0032] The first memory circuit 610 stores path information Da. Path information Da indicates the path that the head 310 should take. For example, path information Da is represented using coordinate values ​​from the base coordinate system. Path information Da is determined based on work information indicating the position and shape of the workpiece W. This work information is obtained by associating information such as CAD (computer-aided design) data showing the three-dimensional shape of the workpiece W with the aforementioned base coordinate system. The above path information Da is input from the computer 700 to the first memory circuit 610.

[0033] The second memory circuit 620 stores various programs executed by the second processing circuit 640 and various data processed by the second processing circuit 640. The second memory circuit 620 includes, for example, one or both of semiconductor memories: a volatile memory such as RAM (Random Access Memory) and a non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable ROM). Part or all of the second memory circuit 620 may be included in the second processing circuit 640, or it may be configured as an integral part of the first memory circuit 610.

[0034] The second memory circuit 620 stores correspondence information Db. Correspondence information Db is information regarding the correspondence between the output from one of the encoders 241_1 to 241_6 (encoder 241) and time or position. This correspondence information Db is input to the second memory circuit 620 from the computer 700. Correspondence information Db will be described in detail later.

[0035] The first processing circuit 630 calculates the amount of motion of each joint 230_1 to 230_6 based on the path information Da. Specifically, the first processing circuit 630 performs inverse kinematics calculations, which are calculations that convert the path information Da into amounts of motion such as the rotation angle and rotation speed of each joint 230_1 to 230_6.

[0036] In this embodiment, the first processing circuit 630 calculates coordinates indicating the position of the head 310 based on signals from encoders 241_1 to 241_6, and generates position information D2 indicating the calculation result. Here, this calculation is performed by forward kinematics calculation, for example, by converting the motion amounts such as rotation angle and rotation speed indicated by signals D1_1 to D1_6 from encoders 241_1 to 241_6 into coordinate values ​​of the head 310. Position information D2 is information about the position of the head 310, and is information about the coordinates indicating the position of the head 310. These coordinates are expressed, for example, as coordinate values ​​in the robot coordinate system described above.

[0037] Furthermore, the first processing circuit 630 functions as a position information output unit 631 that outputs position information D2 generated by the first processing circuit 630. In this embodiment, the position information D2 output from the position information output unit 631 is input to the control module 500.

[0038] The first processing circuit 630 described above includes, for example, one or more processors such as CPUs (Central Processing Units). The first processing circuit 630 may also include a programmable logic device such as an FPGA (field-programmable gate array) instead of a CPU, or in addition to a CPU.

[0039] The second processing circuit 640 controls the operation of the joints 230_1 to 230_6 based on the calculation results of the first processing circuit 630. Specifically, the second processing circuit 640 performs feedback control, outputting control signals Sk_1 to Sk_6 to each joint 230_1 to 230_6 based on signals D1_1 to D1_6 from encoders 241_1 to 241_6 included in the arm drive mechanism 240 of the robot 200, so that the actual rotation angle and rotation speed of each joint 230_1 to 230_6 match the calculation results of the first processing circuit 630. The control signals Sk_1 to Sk_6 correspond to the joints 230_1 to 230_6 and control the drive of the motors provided in the corresponding joints 230. In other words, the controller 600 controls the operation of the robot 200 based on signals D1_1 to D1_6 from encoders 241_1 to 241_6 included in the arm drive mechanism 240. Signals D1_1 to D1_6 correspond to encoders 241_1 to 241_6. In the following, each of signals D1_1 to D1_6 may be referred to simply as signal D1.

[0040] The second processing circuit 640 described above is composed of a separate circuit from the first processing circuit 630 described above. Therefore, the processing load of the first processing circuit 630 does not affect the processing load of the second processing circuit 640. Here, the second processing circuit 640 may include one or more processors such as CPUs (Central Processing Units), similar to the first processing circuit 630, but it is preferable that it is a circuit with a shorter control period than the first processing circuit 630. By shortening the control period of the second processing circuit 640, the period of feedback control for each joint 230_1 to 230_6 can be shortened, and the operating accuracy of the robot 200 can be improved. From the viewpoint of shortening the control period of the second processing circuit 640 compared to the control period of the first processing circuit 630, it is preferable that the second processing circuit 640 includes a computing device such as an FPGA (Field-Programmable Gate Array) or a DSP (Digital Signal Processor).

[0041] Here, as mentioned above, the controller 600 may have two different control cycles for the first processing circuit 630 and the second processing circuit 640. However, in the following, these control cycles will not be distinguished and will be referred to as control cycle C2.

[0042] The control module 500 is a circuit that controls the ejection operation of the head 310 based on position information D2 output from the controller 600 and print data from the computer 700. The control module 500 includes a timing signal generation circuit 510, a power supply circuit 520, a control circuit 530, and a drive signal generation circuit 540.

[0043] The timing signal generation circuit 510 generates a timing signal PTS based on position information D2. In particular, the timing signal generation circuit 510 functions as a timing adjustment unit 511 that adjusts the ink ejection timing from the head 310 based on position information D2. The timing signal generation circuit 510 is composed of a computing device such as an FPGA (Field-Programmable Gate Array) or a DSP (Digital Signal Processor). As will be described in detail later, the timing signal PTS is a signal that defines the timing of the operation of the head 310, a so-called Pulse Timing Signal.

[0044] The power supply circuit 520 receives power from a commercial power source (not shown) and generates various predetermined potentials. The generated potentials are supplied to various parts of the printing device 100 as appropriate. For example, the power supply circuit 520 generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the head unit 300. The power supply potential VHV is supplied to the drive signal generation circuit 540.

[0045] The control circuit 530 generates a control signal SI, a waveform specification 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 specification signal dCom is input to the drive signal generation circuit 540, and the other signals are input to the switch circuit 340 of the head unit 300.

[0046] The control signal SI is a digital signal used to specify the operating state of the piezoelectric element 311 of the head 310. Specifically, the control signal SI specifies whether or not to supply the drive signal Com, described later, to the piezoelectric element 311. This specification, for example, specifies whether or not to eject ink from the nozzle corresponding to the piezoelectric element 311, and specifies the amount of ink ejected from the nozzle. The waveform specification signal dCom is a digital signal used to define the waveform of the drive signal Com. The latch signal LAT and the change signal CNG are used in conjunction with the control signal SI to define the timing of ink ejection from the nozzle by defining the driving timing of the piezoelectric element 311. Here, as mentioned above, since the latch signal LAT and the change signal CNG are synchronized with the timing signal PTS, it can be said that the timing signal PTS defines the ejection timing. The clock signal CLK is a reference clock signal synchronized with the timing signal PTS. Of the above signals, the signals input to the switch circuit 340 of the head unit 300 will be described in detail later.

[0047] The drive signal generation circuit 540 is a circuit that generates a drive signal Com for driving each piezoelectric element 311 of the head 310. Specifically, the drive signal generation circuit 540 includes, for example, a DA conversion circuit and an amplification circuit. In the drive signal generation circuit 540, the DA conversion circuit converts the waveform specification signal dCom from the control circuit 530 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 520 to generate the drive signal Com. Here, the signal of the waveform included in the drive signal Com that is actually supplied to the piezoelectric element 311 is the drive pulse PD. The drive pulse PD is supplied from the drive signal generation circuit 540 to the piezoelectric element 311 via the switch circuit 340. The switch circuit 340 switches whether or not to supply at least a part of the waveform included in the drive signal Com as the drive pulse PD based on the control signal SI.

[0048] The computer 700 has the function of supplying route information Da to the controller 600 and the function of supplying print data to the control module 500.

[0049] 1-3. Head Unit Figure 3 is a perspective view showing the schematic configuration of the head unit 300 in the first embodiment. For convenience, the following description will use the a-axis, b-axis, and c-axis, which intersect with each other, as appropriate. 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. Also, the opposite directions along the c-axis are the c1 direction and the c2 direction.

[0050] Here, axes a, b, and c correspond to the coordinate axes of the tool coordinate system set on the head unit 300, and the relative position and orientation relationship with the world coordinate system or robot coordinate system changes as the robot 200 moves. In the example shown in Figure 3, axis c is the axis parallel to the sixth rotation axis O6. While axes a, b, and c are typically orthogonal to each other, they are not limited to this and may intersect at angles within the range of 80° to 100°.

[0051] The tool coordinate system and the base coordinate system or robot coordinate system are mapped through calibration. Furthermore, the tool coordinate system is set such that, for example, the center of the nozzle surface F (described later) becomes the reference point (TCP: Tool Center Point). This reference point indicates the position of the head 310 in the base coordinate system or robot coordinate system.

[0052] As described above, the head unit 300 includes a head 310 and a pressure regulating valve 320. These are supported by a support 350, which is shown by the dashed line in Figure 3.

[0053] The support 350 is made of, for example, a metal material and is essentially a rigid body. In Figure 3, the support 350 is shown as a flattened box shape, but the shape of the support 350 is not particularly limited and can be arbitrary.

[0054] The support 350 described above is attached to the tip of the arm 220, i.e., the arm 226. Therefore, the head 310 and the pressure regulating valve 320 are fixed to the arm 226. In the example shown in Figure 3, the pressure regulating valve 320 is located in the c1 direction relative to the head 310.

[0055] A supply channel 400 (not shown) is connected to the pressure regulating valve 320. The supply channel 400 supplies ink from a liquid reservoir (not shown) to the pressure regulating valve 320. The pressure regulating valve 320 is also connected to the head 310 via a flow channel member 330. The flow channel member 330 is a tube that supplies ink from the pressure regulating valve 320 to the head 310. The flow channel member 330 is made of, for example, resin.

[0056] The head 310 has a nozzle surface F and a plurality of nozzles N that open into the nozzle surface F. In the example shown in Figure 3, the normal direction of the nozzle surface F is the c2 direction, and the plurality of nozzles N are divided into a first nozzle row L1 and a second nozzle row L2 that are spaced apart from each other in the direction along the a axis. Each of the first nozzle row L1 and the second nozzle row L2 is an example of a "nozzle row," and is a collection of a plurality of nozzles N arranged linearly in the direction along the b axis. Here, the elements related to each nozzle N in the first nozzle row L1 and the elements related to each nozzle N in the second nozzle row L2 of the head 310 are configured to be approximately symmetrical with respect to each other in the direction along the a axis.

[0057] However, the positions of the multiple nozzles N in the first nozzle row L1 and the multiple nozzles N in the second nozzle row L2 along the b-axis may coincide or differ. Also, elements related to each nozzle N in either the first nozzle row L1 or the second nozzle row L2 may be omitted. Below, an example is given in which the positions of the multiple nozzles N in the first nozzle row L1 and the multiple nozzles N in the second nozzle row L2 along the b-axis coincide.

[0058] 1_4. Operation of the Printing Device Figure 4 is a diagram illustrating the printing operation of the printing device 100. Figure 4 illustrates a state in which the printing device 100 prints on the surface WF of the workpiece W. As shown in Figure 4, the printing device 100 prints on the surface WF by having the robot 200 move the head 310 in a predetermined scanning direction DS and ejecting ink from the head 310.

[0059] The scanning direction DS is the direction along the path indicated by the aforementioned path information Da. In the example shown in Figure 4, the scanning direction DS is the X1 direction. Also, the a1 direction in the tool coordinate system points towards the scanning direction DS. Note that the scanning direction DS is not limited to the example shown in Figure 4 and can be arbitrary. Similarly, the shape of the path indicated by the path information Da is not limited to the example shown in Figure 4 and can be arbitrary.

[0060] In this printing operation, the control module 500 controls the timing of ink ejection from the head 310 based on the position information D2.

[0061] Figure 5 is a diagram illustrating the discharge timing based on position information D2 when no adjustment is made by the timing adjustment unit 511, as a comparative example. In Figure 5, the horizontal axis represents time and the vertical axis represents position.

[0062] The position information D2 is updated with each control cycle C2 of the position information output unit 631. Therefore, the position indicated by the position information D2 output from the position information output unit 631 changes in a stepwise manner with each control cycle C2, as shown in Figure 5. As a result, there is an error between the position indicated by the position information D2 and the actual position RP of the head 310.

[0063] In Figure 5, timings t1 to t5 are typically shown as the update timings for location information D2. In the example shown in Figure 5, during the period between timing t1 and timing t2, location information D2 indicates location p1. During the period between timing t2 and timing t3, location information D2 indicates location p2. During the period between timing t3 and timing t4, location information D2 indicates location p3. During the period between timing t4 and timing t5, location information D2 indicates location p4.

[0064] While the system determines whether the ink has reached the ejection position based on the position information D2, if the timing adjustment unit 511 does not perform adjustments, it becomes impossible to accurately determine the ink ejection timing, and as a result, the ink cannot be ejected to the desired ejection position. For example, as shown in Figure 5, even if the system attempts to eject ink to two different ejection positions TP1 and TP2 between positions p2 and p3, the ejection timing for both will be timing t3. As a result, the actual ejection position will be position p3 in both cases.

[0065] In other words, the timing signal generation circuit 510 in the comparative example generates the timing signal PTS using the position information D2 directly. Therefore, the timing of the timing signal PTS reflects the position error indicated by the aforementioned position information D2. As a result, errors occur in the discharge timing, leading to variations in the discharge position.

[0066] Figure 6 is a diagram illustrating the discharge timing based on the predicted position PP by the timing adjustment unit 511 in the first embodiment. In Figure 6, the horizontal axis represents time and the vertical axis represents position.

[0067] The timing adjustment unit 511 acquires the first position information D2_1 as position information D2 at the first acquisition timing ST1. After the first acquisition timing ST1, the timing adjustment unit 511 acquires the second position information D2_2 as position information D2 at the second acquisition timing ST2. After the second acquisition timing ST2, the timing adjustment unit 511 acquires the third position information D2_3 as position information D2 at the third acquisition timing ST3. After the third acquisition timing ST3, the timing adjustment unit 511 acquires the fourth position information D2_4 as position information D2 at the fourth acquisition timing ST4.

[0068] Here, the first acquisition timing ST1 corresponds to the timing t1 shown in Figure 5 above. The position P1 indicated by the first position information D2_1 corresponds to the position p1 shown in Figure 5 above. Similarly, the second acquisition timing ST2, the third acquisition timing ST3, and the fourth acquisition timing ST4 correspond to the timings t2, t3, and t4 shown in Figure 5 above, respectively. The positions P2, P3, and P4 indicated by the second position information D2_2, the third position information D2_3, and the fourth position information D2_4 correspond to the positions p2, p3, and p4 shown in Figure 5 above, respectively.

[0069] Therefore, the interval between the first acquisition timing ST1 and the second acquisition timing ST2 is equal to the control period C2 of the position information output unit 631. Similarly, the interval between the second acquisition timing ST2 and the third acquisition timing ST3 is equal to the control period C2. The interval between the third acquisition timing ST3 and the fourth acquisition timing ST4 is equal to the control period C2. Here, "equal" includes not only cases where they are exactly equal, but also cases where there is a difference of 1 / 10 or less of the control period C2.

[0070] The timing adjustment unit 511 adjusts the ink ejection timing from the head 310 based on the position information D2. This adjustment is performed every control cycle C2. The following explanation will describe this adjustment using the example of ejecting ink to two different ejection positions TP1 and TP2 between positions P2 and P3.

[0071] Here, the timing at which ink is ejected to ejection position TP1 is the first ejection timing TT1, and the timing at which ink is ejected to ejection position TP2 is the second ejection timing TT2. Furthermore, the interval between the second acquisition timing ST2 and the first ejection timing TT1 is shorter than the control cycle C2, and the interval between the second acquisition timing ST2 and the second ejection timing TT2 is shorter than the control cycle C2. Therefore, the first ejection timing TT1 and the second ejection timing TT2 are each the timing between the second acquisition timing ST2 and the third acquisition timing ST3. Note that the interval between the first ejection timing TT1 and the second ejection timing TT2 corresponds to the ejection cycle C1.

[0072] The timing adjustment unit 511 adjusts the first discharge timing TT1, which is the discharge timing after the second acquisition timing ST2, based on the first position information D2_1 and the second position information D2_2.

[0073] Specifically, first, the timing adjustment unit 511 calculates the predicted position PP of the head 310 after the second acquisition timing ST2 based on the first position information D2_1 and the second position information D2_2. Next, the timing adjustment unit 511 determines whether or not the discharge position TP1 has been reached based on the predicted position PP, and if it determines that the discharge position TP1 has been reached, it determines that it is the first discharge timing TT1. Then, the timing adjustment unit 511 outputs a timing signal PTS synchronized with the first discharge timing TT1.

[0074] In the example shown in Figure 6, the predicted position PP is expressed as a linear function representing the relationship between timing and position after the second acquisition timing ST2. This linear function is determined based on the first acquisition timing ST1, the second acquisition timing ST2, position P1, and position P2. The predicted position PP may also be determined using position information D2 prior to the first position information D2_1, in addition to the first position information D2_1 and the second position information D2_2. Furthermore, the predicted position PP is not limited to being expressed as a linear function; for example, it may be expressed as a quadratic function, and known prediction methods can be used as appropriate.

[0075] Similarly, the timing adjustment unit 511 adjusts the second discharge timing TT2, which is the discharge timing that follows the first discharge timing TT1, based on the first position information D2_1 and the second position information D2_2.

[0076] Specifically, the timing adjustment unit 511 determines whether or not the discharge position TP2 has been reached based on the predicted position PP mentioned above. If it determines that the discharge position TP2 has been reached, it determines that it is the second discharge timing TT2. The timing adjustment unit 511 then outputs a timing signal PTS synchronized with the second discharge timing TT2.

[0077] Figure 7 is a timing chart illustrating the operation of the switch circuit 340. As shown in Figure 7, the timing signal PTS contains n pulses PlsP for each unit period Tu, where n is a natural number greater than or equal to 1. In the example shown in Figure 7, the case where n is 7 is shown. In Figure 7, the n pulses PlsP are denoted as pulses PlsP_1 to PlsP_n. Note that n is not limited to the example shown in Figure 7, and for example, is preferably in the range of 1 to 20, and more preferably in the range of 5 to 10.

[0078] The unit period Tu corresponds, for example, to the discharge period C1 described above. However, the pulse PlsP may be at a timing shifted from the pulse PlsL of the latch signal LAT described later. When the number of pulses PlsP in the unit period Tu is 1, the control circuit 530 described above may output the timing signal PTS as the latch signal LAT as is, or it may output the timing signal PTS as the latch signal LAT at a shifted timing. Also, as an example different from Figure 7, multiple pulses PlsL of the latch signal LAT described later may be output for one pulse PlsP of the timing signal PTS.

[0079] The latch signal LAT includes a pulse PlsL to define a unit period Tu. The unit period Tu is defined, for example, as the period from the rising edge of pulse PlsL to the rising edge of the next pulse PlsL. The change signal CNG includes a pulse PlsC to divide the unit period Tu into a control period Tu1 and a control period Tu2. The control period Tu1 is, for example, the period from the rising edge of pulse PlsL to the rising edge of pulse PlsC. The control period Tu2 is, for example, the period from the rising edge of pulse PlsC to the rising edge of pulse PlsL.

[0080] Furthermore, the control signal SI includes individual designation signals Sd[1] to Sd[M] that specify the type of operation of the piezoelectric elements 311[1] to 311[M] in each unit period Tu. The individual designation signals Sd[1] to Sd[M] are supplied to the switch circuit 340 in synchronization with the clock signal CLK prior to the unit period Tu. The switch circuit 340 switches on and off based on the individual designation signal Sd[m] in the unit period Tu. Hereinafter, M is the number of piezoelectric elements 311, and m is a natural number between 1 and M. The subscripts [M] or [m] are notations used to distinguish the M piezoelectric elements 311. In the following, the subscript [m] may also be used to indicate the correspondence with the piezoelectric elements 311[m] for the other M elements.

[0081] The drive signal Com has a waveform PX provided during the control period Tu1 and a waveform PY provided during the control period Tu2. In the example shown in Figure 7, the potential difference between the highest potential VHX and the lowest potential VLX in waveform PX is greater than the potential difference between the highest potential VHY and the lowest potential VLY in waveform PY. Note that the waveform of the drive signal Com is not limited to the example shown in Figure 7, and for example, waveform PY may be omitted.

[0082] If the individual designation signal Sd[m] is a value that specifies the formation of a medium dot, the switch circuit 340 turns on during control period Tu1 and turns off during control period Tu2. Therefore, only the waveform PX of the drive signal Com is supplied to the piezoelectric element 311 as the drive pulse PD. As a result, an amount of ink corresponding to a medium dot is ejected from the nozzle corresponding to the piezoelectric element 311.

[0083] If the individual designation signal Sd[m] is a value that specifies the formation of a small dot, the switch circuit 340 is turned off during the control period Tu1 and turned on during the control period Tu2. As a result, only the waveform PY of the drive signal Com is supplied to the piezoelectric element 311 as the drive pulse PD. Consequently, an amount of ink corresponding to a small dot is ejected from the nozzle corresponding to the piezoelectric element 311.

[0084] If the individual designation signal Sd[m] is a value that specifies the formation of a large dot, the switch circuit 340 is turned on during both control periods Tu1 and Tu2. As a result, the waveforms PX and PY in the drive signal Com are supplied to the piezoelectric element 311 as drive pulses PD. Consequently, an amount of ink equivalent to a large dot is ejected from the nozzle corresponding to the piezoelectric element 311.

[0085] If the individual designation signal Sd[m] is a value that specifies no ink ejection, the switch circuit 340 is turned off during both control periods Tu1 and Tu2. As a result, neither the waveforms PX and PY of the drive signal Com are supplied to the piezoelectric element 311. Consequently, no ink is ejected from the nozzle corresponding to that piezoelectric element 311.

[0086] As described above, ink is ejected from the nozzle at a timing based on the timing signal PTS.

[0087] As described above, the printing apparatus 100 comprises a head 310, a robot 200, a position information output unit 631, and a timing adjustment unit 511. The head 310 ejects ink, which is an example of a "liquid," onto the workpiece W. The robot 200 changes the relative position of the workpiece W and the head 310. The position information output unit 631 outputs position information D2 related to the position of the robot 200. The timing adjustment unit 511 adjusts the timing of ink ejection from the head 310 based on the position information D2.

[0088] Here, the timing adjustment unit 511 adjusts the first discharge timing TT1 based on the first position information D2_1 and the second position information D2_2. The first acquisition timing ST1 is the timing at which the timing adjustment unit 511 acquires the first position information D2_1 as position information D2. The second acquisition timing ST2 is the timing at which the timing adjustment unit 511 acquires the second position information D2_2 as position information D2 after the first acquisition timing ST1. The first discharge timing TT1 is the discharge timing after the second acquisition timing ST2.

[0089] In the printing apparatus 100 described above, the first ejection timing TT1 can be predicted based on the first position information D2_1 and the second position information D2_2. Therefore, by adjusting the first ejection timing TT1 based on the first position information D2_1 and the second position information D2_2, a first ejection timing TT1 that allows ink to be ejected at a desired timing can be obtained, regardless of the acquisition timing. In other words, the ink ejection timing by the head 310 is not limited by the control cycle C2 of the controller 600. In this way, by operating the head 310 at a desired timing, ink can be landed at an accurate position on the surface WF of the workpiece W, and the print quality of the printing apparatus 100 can be improved.

[0090] As mentioned above, the printing apparatus 100 further includes a controller 600, which is an example of a "robot controller". The controller 600 has a position information output unit 631 and controls the operation of the robot 200. Therefore, the position information output unit 631 can be implemented using an existing controller 600.

[0091] As mentioned above, the robot 200 has N (where N is a natural number greater than or equal to 2) "movable parts," which are joints 230, and N encoders 241. The joints 230 are provided in correspondence to each of the N joints 230, and measure the amount of movement of each joint 230. In this embodiment, N is 6. The controller 600 calculates coordinates indicating the position of the head 310 based on signals from the N encoders 241. The position information output unit 631 then outputs information regarding these coordinates as position information D2. Therefore, the position information output unit 631 can be implemented using an existing controller 600. Here, the output from the controller 600 can be used directly as position information D2.

[0092] Furthermore, as mentioned above, the printing apparatus 100 further includes a control module 500, which is an example of a "head drive unit". The control module 500 drives the head 310. Here, the timing adjustment unit 511 outputs a timing signal PTS that defines the ejection timing. The control module 500 then drives the head 310 at the timing based on the timing signal PTS. Therefore, the head 310 can be driven at the ejection timing adjusted by the timing adjustment unit 511.

[0093] Furthermore, as mentioned above, if the interval between the first acquisition timing ST1 and the second acquisition timing ST2 is equal to the control cycle C2 of the position information output unit 631, the acquisition timing of position information D2 in the timing adjustment unit 511 can be matched to the control cycle C2 of the existing controller 600. As a result, the acquisition of position information D2 in the timing adjustment unit 511 can be performed efficiently.

[0094] In this embodiment, as described above, the interval between the second acquisition timing ST2 and the first ejection timing TT1 is shorter than the control cycle C2. Therefore, ink can be ejected within the control cycle C2 from the acquisition of position information D2 by the timing adjustment unit 511. In other words, ink can be ejected at the ejection timing using the most recent position information D2.

[0095] Furthermore, as mentioned above, when the ejection timing following the first ejection timing TT1 is set to the second ejection timing TT2, the timing adjustment unit 511 adjusts the second ejection timing TT2 based on the first position information D2_1 and the second position information D2_2. Therefore, even if the position information D2 is not updated within the control cycle C2 after the second acquisition timing ST2, ink can be ejected at the second ejection timing TT2 after ink has been ejected at the first ejection timing TT1.

[0096] As mentioned above, the interval between the second acquisition timing ST2 and the second ejection timing TT2 is shorter than the control cycle C2. Therefore, ink ejection at the second ejection timing TT2 can be performed within the control cycle C2 after the second acquisition timing ST2.

[0097] Furthermore, as mentioned above, when the timing adjustment unit 511 acquires the third position information D2_3 as position information D2 after the second acquisition timing ST2, and this timing is defined as the third acquisition timing ST3, the first ejection timing TT1 and the second ejection timing TT2 are each between the second acquisition timing ST2 and the third acquisition timing ST3. Therefore, the ink ejection cycle C1 can be made shorter than the control cycle C2. As a result, even when using a controller with a long control cycle due to low specifications, or when using a signal line with a long control cycle, high-speed printing can be performed with highly accurate ejection timing.

[0098] Furthermore, as mentioned above, if the interval between the second acquisition timing ST2 and the third acquisition timing ST3 is equal to the control cycle C2 of the position information output unit 631, the acquisition timing of position information D2 by the timing adjustment unit 511 can be adjusted to match the control cycle C2 of the position information output unit 631. As a result, the acquisition of position information D2 by the timing adjustment unit 511 can be performed efficiently.

[0099] 2. Second Embodiment A second embodiment of the present invention will now be described. For elements whose operation and function are the same as those in the first embodiment in the embodiments described below, the reference numerals used in the description of the first embodiment will be reused, and detailed descriptions of each will be omitted as appropriate.

[0100] Figure 8 is a diagram illustrating the discharge positions TP1 and TP2 based on the predicted positions PP1 and PP2 by the timing adjustment unit 511 in the second embodiment. This embodiment is the same as the first embodiment described above, except that the discharge position TP2 is between position P2 and position P3.

[0101] To explain in more detail, first, the timing adjustment unit 511 calculates the predicted position PP1 of the head 310 after the second acquisition timing ST2 based on the first position information D2_1 and the second position information D2_2. The predicted position PP1 is the same as the predicted position PP described above. Next, the timing adjustment unit 511 determines whether or not the discharge position TP1 has been reached based on the predicted position PP1, and if it determines that the discharge position TP1 has been reached, it determines that it is the first discharge timing TT1. Then, the timing adjustment unit 511 outputs a timing signal PTS synchronized with the first discharge timing TT1.

[0102] Subsequently, the timing adjustment unit 511 calculates the predicted position PP2 of the head 310 after the third acquisition timing ST3 based on the second position information D2_2 and the third position information D2_3. Next, the timing adjustment unit 511 determines whether or not the discharge position TP2 has been reached based on the predicted position PP2, and if it determines that the discharge position TP2 has been reached, it determines that it is the second discharge timing TT2. Then, the timing adjustment unit 511 outputs a timing signal PTS synchronized with the second discharge timing TT2.

[0103] In the example shown in Figure 8, the predicted position PP2 is expressed as a linear function representing the relationship between timing and position after the third acquisition timing ST3. This linear function is determined based on the second acquisition timing ST2, the third acquisition timing ST3, position P2, and position P3. Note that the predicted position PP2 may also be determined using position information D2, such as the first position information D2_1, which precedes the second position information D2_2, in addition to the second position information D2_2 and the third position information D2_3. Furthermore, the predicted position PP2 is not limited to being expressed as a linear function; for example, it may be expressed as a quadratic function, and known prediction methods can be used as appropriate.

[0104] The head 310 can also be operated at a desired timing according to the second embodiment described above. In this embodiment, as described above, the timing at which the timing adjustment unit 511 acquires the third position information D2_3 as position information D2 after the second acquisition timing ST2 is defined as the third acquisition timing ST3, and the discharge timing that follows the first discharge timing TT1 is defined as the second discharge timing TT2. Then, the third acquisition timing ST3 is after the first discharge timing TT1 and before the second discharge timing TT2. The timing adjustment unit 511 then adjusts the second discharge timing TT2 based on the second position information D2_2 and the third position information D2_3. Therefore, the timing adjustment unit 511 can adjust the discharge timing each time the position information D2 is updated.

[0105] Furthermore, as mentioned above, the interval between the second acquisition timing ST2 and the third acquisition timing ST3 is equal to the control cycle C2 of the position information output unit 631. Therefore, the acquisition timing of position information D2 in the timing adjustment unit 511 can be matched to the control cycle C2 of the existing controller 600. As a result, the acquisition of position information D2 in the timing adjustment unit 511 can be performed efficiently.

[0106] Furthermore, as mentioned above, if the interval between the first ejection timing TT1 and the second ejection timing TT2 is greater than or equal to the control cycle C2 of the position information output unit 631, the ink ejection cycle C1 can be made longer than the control cycle. As a result, the ejection timing can be adjusted with high precision.

[0107] 3. Third Embodiment A third embodiment of the present invention will now be described. For elements whose operation and function are the same as in the first embodiment in the embodiments described below, the reference numerals used in the description of the first or second embodiment will be reused, and detailed descriptions of each will be omitted as appropriate.

[0108] Figure 9 is a block diagram showing the electrical configuration of the printing apparatus 100A according to the third embodiment. The printing apparatus 100A is configured similarly to the printing apparatus 100 of the first embodiment described above, except that it includes a control module 500A and a controller 600A instead of the control module 500 and controller 600. The control module 500A is an example of a "head drive unit" and is configured similarly to the control module 500, except that the timing signal generation circuit 510 is omitted. The controller 600A is an example of a "robot controller" and is configured similarly to the controller 600, except that a timing adjustment circuit 650 is added.

[0109] The timing adjustment circuit 650 is an example of a "timing adjustment unit" and is configured similarly to the timing signal generation circuit 510 of the first embodiment. Here, the timing adjustment circuit 650 is configured as a separate circuit from the second processing circuit 640. Therefore, the control period of the timing adjustment circuit 650 can be made shorter than the control period of the second processing circuit 640.

[0110] The head 310 can also be operated at a desired timing according to the third embodiment described above. The timing adjustment circuit 650 may adjust the second discharge timing TT2 based on the second position information D2_2 and the third position information D2_3, similar to the second embodiment described above.

[0111] 4. Fourth Embodiment A fourth embodiment of the present invention will now be described. For elements whose operation and function are the same as in the first embodiment in the embodiments described below, the reference numerals used in the descriptions of the first to third embodiments will be reused, and detailed descriptions of each will be omitted as appropriate.

[0112] Figure 10 is a block diagram showing the electrical configuration of the printing apparatus 100B according to the fourth embodiment. The printing apparatus 100B is configured similarly to the printing apparatus 100 of the first embodiment described above, except that it includes a control module 500A in place of the control module 500 and adds a timing adjustment circuit 800. In other words, the printing apparatus 100B is configured similarly to the printing apparatus 100A of the third embodiment described above, except that it includes a controller 600 in place of the controller 600A and adds a timing adjustment circuit 800.

[0113] The timing adjustment circuit 800 is an example of a "timing adjustment unit" and is provided independently of the controller 600 and the control module 500A. On the other hand, the function of the timing adjustment circuit 800 itself is the same as that of the timing signal generation circuit 510 in the first embodiment, or the same as that of the timing adjustment circuit 650 in the third embodiment.

[0114] The head 310 can also be operated at a desired timing according to the fourth embodiment described above. The timing adjustment circuit 800 may adjust the second discharge timing TT2 based on the second position information D2_2 and the third position information D2_3, similar to the second embodiment described above.

[0115] 5. Fifth Embodiment A fifth embodiment of the present invention will now be described. For elements whose operation and function are the same as those in the first embodiment in the embodiments described below, the reference numerals used in the description of the first embodiment will be reused, and detailed descriptions of each will be omitted as appropriate.

[0116] Figure 11 is a block diagram showing the electrical configuration of the printing apparatus 100C according to the fifth embodiment. The printing apparatus 100C is configured similarly to the printing apparatus 100 of the first embodiment described above, except that it includes a control module 500C and a controller 600C instead of the control module 500 and controller 600. The control module 500C is an example of a "head drive unit" and is configured similarly to the control module 500, except that it includes a timing signal generation circuit 510C instead of the timing signal generation circuit 510. The controller 600C is an example of a "robot controller" and is configured similarly to the controller 600, except that the second processing circuit 640 functions as a position information output unit 641.

[0117] The second processing circuit 640 generates position information D3 based on a signal D1 from one of the encoders 241_1 to 241_6, specifically from encoder 241. The second processing circuit 640 also functions as a position information output unit 641 that outputs the position information D3. In this embodiment, the position information D3 output from the position information output unit 641 is input to the control module 500C.

[0118] Figure 12 shows an example of a signal output from each encoder 241. Although not shown, the encoder 241 includes, for example, a scale, a light-emitting element, and a light-receiving element. Here, the light-emitting element emits light toward the scale. The light-receiving element receives the reflected or transmitted light from the scale and outputs signals ENC_A and ENC_B as signals output from the encoder 241, as shown in Figure 12. Note that the encoder 241 may be an absolute type or an incremental type. Also, the waveform of the signal is not limited to the example shown in Figure 12.

[0119] Each of signals ENC_A and ENC_B includes a pulse PE that appears as the joint rotates. The time interval Td at which pulse PE appears decreases as the rotation speed of the joint increases. Therefore, the rotation speed of the joint can be measured based on the time interval Td. The time intervals Td of signals ENC_A and ENC_B are equal. However, the phases of signals ENC_A and ENC_B are shifted by 90 degrees, with a phase difference ΔT. Here, the direction of the phase shift of signals ENC_A and ENC_B differs depending on the direction of rotation of the joint. Therefore, the direction of rotation of the joint can be identified based on this direction.

[0120] The second processing circuit 640 has the function of cumulatively counting pulses PE. The position information output unit 641 outputs the cumulative value as position information D3, which is information about the position of the head 310, at each control cycle C2. The cumulative value changes according to the rotation angle of the corresponding joint, as indicated by the signal D1 from the encoder 241.

[0121] Normally, during printing, the position indicated by position information D3 does not have a linear relationship with the position of the head 310 in the scanning direction. Therefore, the timing adjustment unit 512 uses the corresponding information Db to convert position information D3 into position information D2 as in the first embodiment, and then performs the same processing as the timing adjustment unit 511 in the first embodiment.

[0122] Here, the timing signal generation circuit 510C stores correspondence information Db. Correspondence information Db is information relating to the correspondence between the rotation angle indicated by the position information D3 and time or position. The above correspondence information Db is input to the timing signal generation circuit 510C from the computer 700. In this embodiment, the timing signal generation circuit 510C is provided as one of the components of the control module 500C, but it may also be provided as one of the components of the controller 600C. Furthermore, the timing signal generation circuit 510C may be provided independently of the timing signal generation circuit 510C and the controller 600C. Correspondence information Db will be described below.

[0123] Figure 13 shows an example of correspondence information Db for converting the signal from encoder 241 into position information D3. The upper part of Figure 13 shows the change in the rotation angle indicated by position information D3 when the robot 200 moves the head 310 along the path indicated by path information Da during the printing operation, and the lower part of Figure 13 shows the change in the position where printing by the head 310 is possible in the X-axis direction on the surface WF of the workpiece W, B. This printing operation is the same as the printing operation shown in Figure 4 above.

[0124] As the head unit 300 passes along the scanning direction DS on the surface WF of the workpiece W, the position of the head unit 300 where the first print should be made is defined as the print start position Xs. The time from when the robot 200 starts moving until it reaches a position appropriate for the head unit 300 to begin ejecting liquid in order to print at the print start position Xs is defined as the ejection start time Ts. In other words, in order to properly print from the print start position Xs on the surface WF of the workpiece W, the head unit 300 must start ejecting ink at the timing of the ejection start time Ts.

[0125] In this embodiment, a preliminary operation is performed before the printing operation. In this preliminary operation, the robot 200 moves the head 310 along the path indicated by the path information Da, and acquires output information related to the output from the encoder 241_1 and position information related to the relative position of the head 310 with respect to the workpiece W. This acquisition is performed by the computer 700. The computer 700 then generates corresponding information Db based on the acquired output information and position information.

[0126] Here, the position information may be obtained using measurement results from a distance meter (not shown) during the preliminary operation, or it may be obtained by calculation in the first processing circuit 630 using the outputs from encoders 241_1 to 241_6 during the preliminary operation. Alternatively, the position information may be obtained by printing a test pattern on the workpiece W during the preliminary operation and imaging the test pattern with a camera (not shown). In this case, for example, by fixing the camera to the arm 226, the relative positions and orientations of the head unit 300 and the camera are fixed, and the position information is obtained based on the imaging information from the camera. Alternatively, the test pattern may not be printed using the workpiece W, and an object whose test pattern printing area has the same shape as the workpiece W may be used.

[0127] The head 310 can also be operated at a desired timing according to the fifth embodiment described above. In this embodiment, as described above, the position information output unit 641 outputs information regarding the rotation angle indicated by the signal D1 from at least one of the N encoders 241 as position information D3. Generally, the control period of each joint 230 based on the signal D1 from the encoder 241 is shorter than the control period for calculating the coordinates of the tip of the robot 200 by forward kinematics based on the signal D1 from the N encoders 241. In other words, generally, the control period of the second processing circuit 640 is shorter than the control period of the first processing circuit 630. Therefore, by outputting information regarding the cumulative value of the number of pulses PE included in the signal D1 from the encoder 241 from the position information output unit 641 provided in the second processing circuit 640 and using it as position information D3, the ejection timing can be adjusted with high precision.

[0128] 6. Variations Each of the above examples can be modified in various ways. Specific examples of modifications that can be applied to each of the aforementioned examples are given below. Note that two or more of the following examples can be arbitrarily selected and combined as appropriate, provided they do not contradict each other.

[0129] 6-1. Variation 1 In the aforementioned configuration, a 6-axis vertical multi-axis robot is used as the moving mechanism, but the system is not limited to this configuration. The moving mechanism only needs to be able to change the relative position and orientation of the head to the workpiece in three dimensions. Therefore, the moving mechanism may be a vertical multi-axis robot other than a 6-axis robot, or a horizontal multi-axis robot. Furthermore, the movable parts of the robot arm are not limited to rotational mechanisms, but may also include, for example, telescopic mechanisms.

[0130] 6-2. Variation 2 In the above-described embodiment, a configuration in which the head is fixed to the tip of the robot arm using screws or the like is exemplified, but the configuration is not limited to this. For example, the head may be fixed to the tip of the robot arm by gripping it with a gripping mechanism such as a hand attached to the tip of the robot arm.

[0131] 6-3. Variation 3 Furthermore, while the above-described embodiment exemplifies a moving mechanism that moves the head, the invention is not limited to this configuration. For example, the head may be fixed in position, and the moving mechanism may move the workpiece, thereby changing the workpiece's relative position and orientation to the head in three dimensions. In this case, for example, the workpiece may be gripped by a gripping mechanism such as a hand attached to the tip of a robot arm.

[0132] 6-4. Variation 4 The above-described embodiment exemplifies a configuration in which printing is performed using one type of ink, but the present invention is not limited to this configuration and can also be applied to configurations in which printing is performed using two or more types of ink.

[0133] 6-5. Variation 5 The applications of the printing apparatus of the present invention are not limited to printing. For example, a printing apparatus that dispenses a colorant solution can be used as a manufacturing apparatus for forming color filters for liquid crystal display devices. A printing apparatus that dispenses a conductive material solution can be used as a manufacturing apparatus for forming wiring and electrodes on a wiring board. Furthermore, the printing apparatus can also be used as a jet dispenser for applying liquids such as adhesives to a workpiece. [Explanation of symbols]

[0134] 100...Printing device, 100A...Printing device, 100B...Printing device, 100C...Printing device, 200...Robot, 210...Base, 220...Arm, 221...Arm, 222...Arm, 223...Arm, 224...Arm, 225...Arm, 226...Arm, 230...Joint (movable part), 230_1...Joint (movable part), 230_2...Joint (movable part), 230_3...Joint (movable part), 230_4...Joint (movable part), 230_5...Joint (movable part), 230_6...Joint (movable part), 240...Arm drive mechanism, 241...Encoder, 241_1~241_6...E 300... Head unit, 310... Head, 311... Piezoelectric element, 320... Pressure regulating valve, 330... Flow channel member, 340... Switch circuit, 350... Support, 400... Supply flow channel, 500... Control module (head drive unit), 500A... Control module (head drive unit), 500C... Control module (head drive unit), 510... Timing signal generation circuit, 510C... Timing signal generation circuit, 511... Timing adjustment unit, 512... Timing adjustment unit, 520... Power supply circuit, 530... Control circuit, 540... Drive signal generation circuit, 600... Controller (robot) Controller), 600A... Controller (Robot Controller), 600C... Controller (Robot Controller), 610... First Memory Circuit, 620... Second Memory Circuit, 630... First Processing Circuit, 640... Second Processing Circuit, 631... Position Information Output Unit, 641... Position Information Output Unit, 650... Timing Adjustment Circuit, 700... Computer, 800... Timing Adjustment Circuit (Timing Adjustment Unit), A... Transition, B... Transition, C1... Discharge Cycle, C2... Control Cycle, CLK... Clock Signal, CNG... Change Signal, Com... Drive Signal, D1... Signal, D1_1... Signal D2...Position information, D2_1...First position information, D2_2...Second position information, D2_3...Third position information, D2_4...Fourth position information, D3...Position information, DS...Scanning direction, Da...Path information, Db...Correspondence information, ENC_A...Signal, ENC_B...Signal, F...Nozzle surface, L1...First nozzle row, L2...Second nozzle row, LAT...Latch signal, N...Nozzle, O1...First rotation axis, O2...Second rotation axis, O3...Third rotation axis, O4...Fourth rotation axis, O5...Fifth rotation axis, O6...Sixth rotation axis, P1...Position, P2...Position, P3...Position, P4...Position, PD...Drive pulse, PE...Pulse, PP...Predicted positionPP1…Predicted position, PP2…Predicted position, PTS…Timing signal, PX…Waveform, PY…Waveform, PlsC…Pulse, PlsL…Pulse, PlsP…Pulse, PlsP_1…Pulse, RP…Position, SI…Control signal, ST1…First acquisition timing, ST2…Second acquisition timing, ST3…Third acquisition timing, ST4…Fourth acquisition timing, Sd…Individually specified signal, Sk_1~Sk_6…Control signals, TP1…Discharge position, TP2…Discharge position, TT1…First discharge timing, TT2…Second discharge Timing, Td...time interval, Ts...discharge start time, Tu...unit period, Tu1...control period, Tu2...control period, VBS...offset potential, VHV...power supply potential, VHX...highest potential, VHY...highest potential, VLX...lowest potential, VLY...lowest potential, W...workpiece, WF...surface, Xs...print start position, dCom...waveform specification signal, p1...position, p2...position, p3...position, p4...position, t1...timing, t2...timing, t3...timing, t4...timing, t5...timing, ΔT...shift amount.

Claims

1. A head that dispenses liquid onto the workpiece, A robot that changes the relative position of the workpiece and the head, A position information output unit that outputs position information relating to the position of the head, The system includes a timing adjustment unit that adjusts the timing of liquid discharge from the head based on the position information, The timing at which the timing adjustment unit acquires the first position information as the position information is defined as the first acquisition timing. The timing at which the timing adjustment unit acquires the second position information as the position information after the first acquisition timing is defined as the second acquisition timing. When the discharge timing after the second acquisition timing is defined as the first discharge timing, The timing adjustment unit calculates the predicted position of the head after the second acquisition timing based on the first position information and the second position information, and adjusts the first discharge timing based on the predicted position. A printing apparatus characterized by the following features.

2. The robot controller further comprises the position information output unit and controls the operation of the robot. The printing apparatus according to feature 1.

3. The head drive unit further comprises a head drive unit that drives the head. The timing adjustment unit outputs a timing signal that defines the discharge timing. The head drive unit drives the head at a timing based on the timing signal. The printing apparatus according to claim 1 or 2.

4. The interval between the first acquisition timing and the second acquisition timing is equal to the control cycle in which the position information output unit updates the position information. The printing apparatus according to any one of claims 1 to 3.

5. The interval between the second acquisition timing and the first discharge timing is shorter than the control cycle. The printing apparatus according to feature 4.

6. When the discharge timing that follows the first discharge timing is defined as the second discharge timing, The timing adjustment unit adjusts the second discharge timing based on the first position information and the second position information. The printing apparatus according to feature 5.

7. The interval between the second acquisition timing and the second discharge timing is shorter than the control cycle. The printing apparatus according to feature 6.

8. When the timing adjustment unit acquires the third position information as the position information after the second acquisition timing is defined as the third acquisition timing, The first discharge timing and the second discharge timing are each timings between the second acquisition timing and the third acquisition timing. The printing apparatus according to claim 6 or 7.

9. The interval between the second acquisition timing and the third acquisition timing is equal to the control cycle in which the position information output unit updates the position information. The printing apparatus according to feature 8.

10. The timing at which the timing adjustment unit acquires the third position information as position information after the second acquisition timing is defined as the third acquisition timing. When the discharge timing that follows the first discharge timing is defined as the second discharge timing, The third acquisition timing is after the first discharge timing and before the second discharge timing. The timing adjustment unit adjusts the second discharge timing based on the second position information and the third position information. The printing apparatus according to feature 5.

11. The interval between the second acquisition timing and the third acquisition timing is equal to the control cycle in which the position information output unit updates the position information. The printing apparatus according to feature 10.

12. The interval between the first discharge timing and the second discharge timing is greater than or equal to the control cycle for which the position information output unit updates the position information. The printing apparatus according to feature 11.

13. The robot controller further comprises a robot controller that controls the operation of the robot, The aforementioned robot, N (where N is a natural number greater than or equal to 2) movable parts, The system includes N encoders provided for each of the N movable parts, each corresponding to a movable part, for measuring the amount of movement of each movable part. The robot controller calculates coordinates indicating the position of the head based on signals from the N encoders, The position information output unit outputs the coordinate information as the position information. A printing apparatus according to any one of claims 1 to 12.

14. The aforementioned robot, N (where N is a natural number greater than or equal to 2) movable parts, The system includes N encoders provided for each of the N movable parts, each corresponding to a movable part, for measuring the amount of movement of each movable part. The position information output unit outputs information regarding the rotation angle indicated by the signal from at least one of the N encoders as the position information. A printing apparatus according to any one of claims 1 to 12.

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