Liquid dispensing device, liquid dispensing method, and program

Abstract

To suppress reduction in coating quality.SOLUTION: A liquid discharge device 200 includes a liquid discharge head 10 having a nozzle hole N for discharging a liquid, an opening / closing valve 12 for opening / closing the nozzle hole N, and a valve driving mechanism 13 for driving the opening / closing valve 12, discharges the pressurized liquid and imparts the liquid to an object 3000, and includes a control part 500 for changing valve opening time of the opening / closing valve 12 on the basis of the pressure of the liquid supplied to the liquid discharge head 10.SELECTED DRAWING: Figure 12

Description

Technical Field

[0004] , , The liquid discharge head is capable of performing a first discharge operation in which liquid is discharged from the nozzle hole at a first hydraulic pressure in a first region, and a second discharge operation in which liquid is discharged from the nozzle hole at a second hydraulic pressure in a second region, and the control unit is characterized in that, when the second hydraulic pressure is lower than the first hydraulic pressure, the valve opening time in the second discharge operation is made longer than the valve opening time in the first discharge operation. , ,

[0006] , , , , , , , , , , , , ,

[0005] ,

[0007] ,

[0001] The present invention relates to a liquid ejection device, a liquid ejection method, and a program.

Background Art

[0002] Conventionally, a liquid ejection device that ejects a liquid from a liquid ejection head and applies it to an object has been known. Such a liquid ejection device is used for various applications such as painting an object and forming an image on a recording medium.

[0003] For example, the liquid ejection device described in Patent Document 1 includes a nozzle hole that ejects ink, an ink chamber that supplies the ink pressurized to the nozzle hole, a needle valve provided in the ink chamber that opens and closes the nozzle hole, and a drive mechanism that drives the needle valve.

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the configuration described in Patent Document 1, when the liquid ejection operation starts immediately or when the number of nozzle holes for ejecting the liquid fluctuates, the ejection amount of the liquid ejected from the ejection head decreases, and the quality of the liquid applied to the object may deteriorate.

[0005] The present invention provides a liquid ejection device capable of suppressing a decrease in the quality of the liquid applied to an object.

Means for Solving the Problems

[0006] The liquid ejection device of the present invention includes a liquid ejection head having a nozzle hole that ejects a liquid, an opening / closing valve that opens and closes the nozzle hole, and a valve drive mechanism that drives the opening / closing valve, and is a liquid ejection device that ejects the pressurized liquid and applies it to an object, and includes a control unit that changes the valve opening time of the opening / closing valve based on the pressure of the liquid supplied to the liquid ejection head The liquid discharge head is capable of performing a first discharge operation in which liquid is discharged from the nozzle hole at a first hydraulic pressure in a first region, and a second discharge operation in which liquid is discharged from the nozzle hole at a second hydraulic pressure in a second region, and the control unit is characterized in that, when the second hydraulic pressure is lower than the first hydraulic pressure, the valve opening time in the second discharge operation is made longer than the valve opening time in the first discharge operation. .

Effects of the Invention

[0007] This invention can suppress the deterioration of the quality of liquid application to an object. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing a painting robot equipped with a liquid dispensing device according to an embodiment. [Figure 2] This is a schematic diagram showing a liquid dispensing device according to an embodiment. [Figure 3] This is an overall perspective view showing an example of a discharge head according to the embodiment. [Figure 4] This is a block diagram showing the hardware configuration of a liquid dispensing device according to an embodiment. [Figure 5] This is a functional block diagram of a liquid dispensing device according to an embodiment. [Figure 6] This figure shows the change in hydraulic pressure inside the head over time. [Figure 7] This figure shows the change in discharge volume over time. [Figure 8] This diagram shows the time-dependent change in hydraulic pressure inside the head, and illustrates the differences depending on the number of driven nozzles. [Figure 9] This figure shows an example of a drive waveform. [Figure 10] This figure shows the relationship between valve opening time and discharge volume. [Figure 11] This figure shows an example of the hydraulic pressure inside the head, valve opening time, and discharge volume. [Figure 12] This figure shows an example of the hydraulic pressure inside the head, valve opening time, and discharge volume. [Modes for carrying out the invention]

[0009] <Overview of Liquid Dispensing Device> First, the general outline of the liquid dispensing device will be explained using Figure 1. Figure 1 is an overall schematic diagram of a liquid dispensing device according to an embodiment of the present invention. The liquid dispensing device illustrated here is a painting robot used to paint the body of an automobile or the like. In each figure, arrows indicating the three intersecting directions, the X-axis, Y-axis, and Z-axis, may be shown. The X-axis direction is, for example, along the front-to-back direction of the vehicle body to be painted. The Y-axis direction is along the width direction of the vehicle body. The Z-axis direction is along the up-and-down direction.

[0010] As shown in Figure 1, the painting robot 1000 is installed facing an object 3000, such as the side of an automobile body. The painting robot 1000 comprises a base 100, a first arm 101, a second arm 102, and a head unit 103. The first arm 101 is connected to the base 100. The second arm 102 is connected to the first arm 101. The head unit 103 is connected to the second arm 102.

[0011] The painting robot 1000 includes a first joint 104, a second joint 105, and a third joint 106. The first joint 104 connects the base 100 and the first arm 101. The second joint 105 connects the first arm 101 and the second arm 102. The third joint 106 connects the second arm 102 and the head unit 103.

[0012] The painting robot 1000 is, for example, an articulated robot. The base 100 is rotatable in the a direction with respect to an axis extending in the Z direction. The base 100 supports one end of the first arm 101 via a first joint 104.

[0013] The first arm 101 is pivotable in the b direction with respect to an axis parallel to the XY plane. The other end of the first arm 101 is supported by one end of the second arm 102 via the second joint 105. The second arm 102 is swingable in the c direction with respect to an axis parallel to the XY plane. The second arm 102 is also rotatable in the d direction with respect to an axis extending in the longitudinal direction of the second arm 102.

[0014] The other end of the second arm 102 supports the head unit 103 via the third joint 106. The head unit 103 is rotatable in the e direction about an axis extending in a direction intersecting the longitudinal direction of the second arm 102 as a rotation axis. Further, the head unit 103 is rotatable in the f direction about an axis extending in a direction in which the head unit 103 and the third joint 106 are separated from each other as a rotation axis.

[0015] The painting robot 1000 can freely move the head unit 103 with respect to the object 3000. The painting robot 1000 can accurately position the head unit 103 with respect to the object 3000. The painting robot 1000 can accurately position the head unit 103 with respect to the painting position. The painting robot 1000 discharges paint toward the object 3000 to paint the object 3000.

[0016] In this embodiment, a system configuration in which one painting robot 1000 is arranged on each side of the object 3000 is illustrated, but the painting robot 1000 is not limited to being arranged on both sides of the object 3000. The number of installation of the painting robot 1000 may be one or three or more with respect to the object 3000.

[0017] FIG. 2 is a schematic diagram showing the liquid discharge device 200. The painting robot 1000 has the liquid discharge device 200. The liquid discharge device 200 can execute a liquid discharge method. The liquid discharge device 200 includes a tank 2, a discharge head (liquid discharge head) 10, and a control device 500. The liquid discharge device 200 includes a pipe 1, a pipe 4, and a pipe 8. The liquid discharge device 200 includes a pressure sensor 5 that detects the pressure of the liquid in the discharge head 10.

[0018] Tank 2 is a container that stores the liquid to be supplied to the discharge head 10. Tank 2 stores paint 3, which is an example of a liquid. Pipe 1 is connected to Tank 2. Pipe 1 is connected to, for example, a compressor. The compressor supplies pressurized air to Tank 2. The compressor can increase the pressure inside Tank 2 via Pipe 1. Pipe 1 functions as a pressure supply path that supplies pressure to the liquid inside Tank 2.

[0019] Pipe 4 is a flow path that connects Tank 2 and the discharge head 10. The paint 3 inside Tank 2 flows through Pipe 4 and is supplied to the discharge head 10. Pipe 4 functions as a liquid supply flow path that supplies paint 3 to the discharge head 10.

[0020] The discharge head 10 has a nozzle hole N, an ink chamber 11, and an on-off valve 12. The discharge head 10 has a valve drive mechanism 13 for driving the on-off valve 12. The nozzle hole N communicates with the ink chamber 11. The ink chamber 11 stores the paint 3 supplied from Tank 2. The on-off valve 12 is disposed inside the ink chamber 11. The on-off valve 12 opens and closes the nozzle hole N. The on-off valve 12 is, for example, a needle valve. The discharge head 10 discharges the paint 3 inside the ink chamber 11 from the nozzle hole N. The discharge head 10 discharges the pressurized paint 3 and adheres it to the object 3000. The valve drive mechanism 13 drives the on-off valve 12 according to a drive signal supplied from the control device 500. The on-off valve 12 approaches the nozzle hole N and closes the nozzle hole N. The on-off valve 12 moves away from the nozzle hole N and opens the nozzle hole N.

[0021] The control device 500 and the PC 600 control the liquid discharge by the discharge head 10. The control device 500 and the PC 600 operate the on-off valve 12 to discharge the paint 3.

[0022] Pipe 8 communicates with the discharge head 10. A valve 9 is provided in Pipe 8. When filling the ink chamber 11 with the paint 3, the valve 9 is opened and the pressure inside the ink chamber 11 is released. When discharging the paint 3 from the nozzle hole N of the discharge head 10, the valve 9 is closed.

[0023] The pressure sensor 5 is installed, for example, in the piping 4. The pressure sensor 5 is installed, for example, near the ink chamber 11 of the dispensing head 10. The pressure sensor 5 outputs data regarding the detected liquid pressure to the control device 500. Based on the data input from the pressure sensor 5, the control device 500 can detect the pressure of the liquid supplied to the dispensing head 10. The control device 500 may also calculate the pressure of the liquid inside the dispensing head 10. When the pressure of the liquid inside the dispensing head 10 changes, the pressure of the liquid supplied to the dispensing head 10 also changes.

[0024] <Discharge head configuration> Next, the schematic configuration of the discharge head 10 will be explained using Figure 3. Figure 3 is an overall perspective view showing an example of a discharge head according to the embodiment.

[0025] The ejection head 10 shown in Figure 3 is a head employing a valve inkjet method. The ejection head 10 mainly comprises a nozzle surface 301, nozzle holes N, and a housing 303. The nozzle surface 301 is provided on one surface of the housing 303. The nozzle surface 301 has a plurality of nozzle holes N for ejecting liquid. The nozzle holes N are minute openings. As described above, the valve drive mechanism 13 can open and close the nozzle holes N. By opening the nozzle holes N, the ejection head 10 ejects liquid from the nozzle holes N. For example, the housing 303 incorporates the valve drive mechanism 13.

[0026] The nozzle surface 301 having the nozzle holes N may be formed on a nozzle plate which is a separate component from the housing 303. The housing 303 may also be configured to include a nozzle plate having the nozzle surface 301. The number of nozzle holes N may be, for example, 18 or more. The number of nozzle holes N is not limited to multiple, and may be just one. Alternatively, the liquid discharge device 200 may be configured to include multiple discharge heads 10, each having one nozzle hole N. For example, when performing control to change the valve opening time, a discharge head 10 with one nozzle hole N can be used. Furthermore, the nozzle row, in which multiple nozzle holes N are arranged, may be one row or multiple rows.

[0027] <Hardware Configuration> Next, with reference to Figure 4, the hardware configuration of the liquid dispensing device 200 according to the first embodiment will be described. Figure 4 is a block diagram showing the hardware configuration of the liquid dispensing device 200 according to the first embodiment. The hardware configuration shown in Figure 4 may include additional components as needed. The hardware may not include the components shown in Figure 4 as needed.

[0028] The liquid dispensing device 200 is equipped with a control device 500. The control device 500 has a CPU (Center Processing Unit) 501, a ROM (Read Only Memory) 502, a RAM (Random Access Memory) 503, an NVRAM (Random Access Memory) 504, and an HDD (Hard Disk Drive). The CPU 501 is responsible for the overall control of the liquid dispensing device 200. The ROM 502 stores various programs for the CPU 501 to execute liquid dispensing control, as well as various data necessary for painting. The ROM 502 also stores a program for scanning the dispensing head 10.

[0029] RAM 503 temporarily stores position data of the dispensing head 10, etc. NVRAM 504 is a non-volatile memory that can retain data even when the power to the liquid dispensing device 200 is cut off. The control device 500 has a main control unit 500A, which includes a CPU 501, ROM 502, and RAM 503.

[0030] The control device 500 includes an ASIC (Application Specific Integrated Circuit) 505. The ASIC 505 processes input and output signals for controlling the entire liquid dispensing device 200. The ASIC 505 can also perform various signal processing on image data. The ASIC 505 can perform image processing on image data input to the control device 500.

[0031] The control device 500 is equipped with an external interface (external I / F) 506 for sending and receiving data, etc., with an external device, the PC 600. The PC 600 has, for example, a RIP (Routing Information Protocol) unit 601. The RIP unit 601 includes a lettering unit 602.

[0032] An input device 603 is connected to PC600. Additionally, a position measuring device 15 is connected to PC600.

[0033] The ROM502, RAM503, NVRAM504, and HDD508, among other memories, store image data and data related to the painting area received from the computer 600. The data related to the painting area includes data such as the size of the object to be painted.

[0034] Furthermore, the control device 500 includes an input / output (I / O) unit 507 for receiving detection signals output from the sensors 18. The sensors 18 include the pressure sensor 5 shown in Figure 2.

[0035] The control device 500 includes a head control device 510 that drives and controls the discharge head 10. The head control device 510 can control the drive mechanism of the discharge head 10. The head control device 510 can perform liquid discharge by controlling the drive mechanism of the discharge head 10. The head control device 510 can perform drive control of the on / off valve 12 of the discharge head 10. The discharge head 10 can control the pressure in the tank 2. The discharge head 10 can perform drive control of the valve 9. The head control device 510 can perform various controls related to the discharge head 10.

[0036] The control device 500 includes a robot control device 511. The robot control device 511 controls the robot drive mechanism 31 according to commands from the CPU 501. The painting robot 1000 is equipped with a robot drive mechanism 31. The robot drive mechanism 31 includes, for example, a motor. The robot drive mechanism 31 drives the rotation axis of the base 100. Similarly, the robot drive mechanism 31 drives the rotation axis of the first arm 101, the rotation axis of the second arm 102, the rotation axis of the head unit 103, the rotation axis of the first joint 104, the rotation axis of the second joint 105, and the rotation axis of the third joint 106.

[0037] The painting robot 1000 is equipped with encoder sensors 32. The control device 500 receives signals from the encoder sensors 32 via I / O 507. The encoder sensors 32 are provided for the first joint 104, the second joint 105, and the third joint 106, respectively. These first joints 104, the second joint 105, and the third joint 106 are provided with slits that rotate together with the rotation axis. The encoder sensors 32 optically detect the slits. The encoder sensors 32 detect the rotation angles of the first joints 104, the second joint 105, and the third joint 106.

[0038] The painting robot 1000 is equipped with a position measuring device 15. The position measuring device 15 measures the position of the discharge head 10. The position measuring device 15 may be, for example, a 3D sensor or a 3D camera. The position measuring device 15 can measure the position of the discharge head 10 in the XY direction. The position measuring device can measure the inclination of the discharge head 10. The position measuring device 15 can detect the painting start position. The position measuring device 15 may also detect the size of the object to be painted.

[0039] The position measuring device 15 may include a laser displacement meter. The position measuring device 15 can measure the length of the object 3000 in the Z-axis direction. The position measuring device 15 may also measure the height position of the roof of the object 3000. The position measuring device 15 outputs the measurement results to the computer 600. The position measuring device 15 can detect the curvature of the object 3000.

[0040] The PC can acquire position data of the discharge head 10 from the position measuring device 15. The control device 500 can input position data of the discharge head 10 via the PC 600. The control device 500 may also input data from the position measuring device 15 via the I / O 507.

[0041] An input device 603 is connected to the PC600. The input device 603 can input image data and position data to the PC600. The position measuring device 15 may also input the measured position data of the discharge head 10 to the PC600.

[0042] PC600 generates a painting route for the painting robot 1000. The lettering unit 602 decomposes the painting area data into data for each scan. The painting area is, for example, the area to be painted. The lettering unit 602 determines the number of drive nozzles and whether or not to perform dry dispensing in each scan. The number of drive nozzles is the number of nozzle holes N from which liquid is discharged in the discharge head 10. Dry dispensing includes discharging liquid from the nozzle holes N before scanning. The lettering unit 602 can decide whether or not to perform dry dispensing.

[0043] The PC600 can determine the valve opening time during scanning. The valve opening time control unit 131 of the PC600 determines the valve opening time during scanning according to pre-created data on printing time for each number of drive nozzles. The data on printing time for each number of drive nozzles is predetermined based on liquid pressure fluctuations. "Liquid pressure fluctuations" refer to, for example, fluctuations in the liquid pressure inside the discharge head 10.

[0044] The computer 600 has a RIP unit 601. The RIP unit 601 can perform image processing according to the color profile and user settings.

[0045] The RIP unit 601 includes a lettering unit 602. The lettering unit 602 decomposes the data of the painted area to be applied to the object 3000 into paint (image) data for each scan (for example, each movement of the head 300 in the main scanning direction). The object 3000 is, for example, the body of an automobile. "Each scan" means, for example, each movement of the ejection head 10 along the main scanning direction. The "main scanning direction" may be, for example, the direction along the longitudinal direction of the object 3000, or any other direction.

[0046] An input device 603 is connected to the computer 600. The user can input various data into the computer 600 by operating the input device 603. The computer 600 can receive image data and coordinate data indicating the area to be painted on the object 3000 via the input device 603.

[0047] Computer 600 can receive signals from input device 603 and set the painting mode. The user can select the painting mode by operating input device 603. Computer 600 can receive signals from input device 603 and set the painting range. Computer 600 can set the painting start position and painting end position. Computer 600 can set the painting start timing. The user can change various settings by operating computer 600 via input device 603.

[0048] The input device 603 may include, for example, a keyboard, mouse, or touch panel. The computer 600 can also acquire position data of the discharge head 10 from the position measuring device 15 of the painting robot 1000. Based on the acquired position data, the computer 600 can generate a painting route for the discharge head 10. The painting route includes position data relating to the movement path of the discharge head 10. The painting route may also include other data.

[0049] The painting system 2000 is an example of a liquid dispensing system. The painting system 2000 comprises a liquid dispensing device 200 and a computer 600.

[0050] <Functional Configuration> Next, with reference to Figure 5, the functional configuration of the liquid dispensing device 200 according to the first embodiment will be described. Figure 5 is a functional block diagram of the liquid dispensing device 200 according to the first embodiment. The CPU 501 shown in Figure 3 executes programs stored in a storage unit such as a ROM 502 to realize the functions of the system control unit 221, valve opening time control unit 231, dispensing cycle signal generation unit 232, memory control unit 233, and synchronization control unit 235 shown in Figure 5.

[0051] The system control unit 221 controls the overall operation of the painting system 2000. The system control unit 221 can control the overall operation of the painting system 2000 by receiving image data of the painting area and command signals from the computer 600.

[0052] The valve opening time control unit 231 controls the valve opening time of the on-off valve 12. The valve opening time is the length of time during which the on-off valve 12 is open and liquid can be discharged.

[0053] The memory control unit 233 controls the memory such as ROM 502, RAM 503, NVRAM 504, and HDD 508.

[0054] The synchronous control unit 235 generates an ejection cycle signal based on the output signal from the encoder sensor 32 and the resolution information of the image data output from the computer 600. The ejection cycle signal is a signal that indicates the ejection cycle of the paint ejected from the nozzle hole N.

[0055] The synchronization control unit 235 synchronizes the movements of the multiple painting robots 1000 with the paint discharge operation of the discharge head 10 based on image data and painting instruction signals received from the computer 600.

[0056] The head control device 510 receives a discharge cycle signal and controls the liquid discharge operation of the discharge head 10 based on the received discharge cycle signal. The robot control device 511 receives a synchronization control signal and controls the robot drive mechanism 31 based on the received synchronization control signal. The control device 500 controls the robot drive mechanism 31 to move the first arm 101, the second arm 102, and the head unit 103 to desired positions.

[0057] The system control unit 221, valve opening time control unit 231, discharge cycle signal generation unit 232, memory control unit 233, and synchronization control unit 235 can be implemented in software by programs stored in the memory unit. Alternatively, all or part of these system control unit 221, valve opening time control unit 231, discharge cycle signal generation unit 232, memory control unit 233, and synchronization control unit 235 may be implemented in hardware such as an IC (Integrated Circuit).

[0058] Furthermore, the program may be recorded as installable or executable file information on a recording medium readable by a computer device, such as a CD-ROM or flexible disk (FD), and provided to the liquid dispensing device 200 via such a recording medium. Alternatively, the program may be recorded on a recording medium readable by a computer device, such as a CD-R, DVD (Digital Versatile Disk), Blu-ray® disc, or semiconductor memory, and provided to the liquid dispensing device 200 via such a recording medium. The program may also be provided to the liquid dispensing device 200 by installation via a network such as the Internet. Furthermore, the program may be pre-installed in ROM or the like within the liquid dispensing device 200.

[0059] Furthermore, the control device 500 may perform functions that the computer 600 performs. Similarly, the computer 600 may perform functions that the control device 500 performs.

[0060] <Challenges of conventional technology> Next, we will explain the problems of the conventional technology. The conventional liquid dispensing device has a valve-type inkjet nozzle that dispenses liquid by opening and closing an on-off valve. In the conventional liquid dispensing device, the liquid pressure drops by the amount of pressure loss due to the dispensing of the liquid paint. As a result, the amount of liquid dispensed from the dispensing head decreases immediately after the start of painting, and until the liquid pressure reaches equilibrium when the number of driven nozzles changes. A decrease in the amount of liquid dispensed from the dispensing head leads to a problem of reduced painting quality.

[0061] <Time-dependent changes in liquid pressure and discharge volume within the dispensing head> Next, with reference to Figures 6 and 7, an example of the time variation of the liquid pressure and discharge volume inside the discharge head when paint is discharged using a discharge head with a valve-type inkjet nozzle will be described. Note that "liquid pressure inside the discharge head" may be abbreviated as "internal head liquid pressure" or "liquid pressure". Figure 6 is a diagram showing the time variation of the internal head liquid pressure. Figure 7 is a diagram showing the time variation of the discharge volume. In Figure 6, the horizontal axis shows time and the vertical axis shows the internal head liquid pressure. In Figure 7, the horizontal axis shows time and the vertical axis shows the discharge volume.

[0062] Time T0 is the time before discharge begins. Time T1 is the discharge start time. In the discharge head, the paint is pressurized with a constant supply pressure, and the on / off valve is opened to discharge the liquid from the nozzle hole N. Therefore, the liquid pressure inside the head decreases at the same time as discharge begins. This is because it takes some time for the pressure of the system with the discharge head to reach a new equilibrium state. Until the system with the discharge head reaches a new equilibrium state, the liquid pressure inside the head remains low. Therefore, as shown in Figure 7, the discharge volume decreases immediately after discharge begins, resulting in uneven paint quality and a decrease in paint quality. After time T1, the liquid pressure inside the head and the discharge volume decrease immediately.

[0063] <Time-dependent change in internal head fluid pressure based on the number of drive nozzles> Next, with reference to Figure 8, we will explain the time variation of the hydraulic pressure inside the head based on the number of drive nozzles. Figure 8 is a diagram showing the time variation of the hydraulic pressure inside the head, and illustrates the differences depending on the number of drive nozzles. In Figure 8, the horizontal axis represents time, and the vertical axis represents the hydraulic pressure inside the head.

[0064] Figure 8 shows the difference in the range of fluctuation in the internal hydraulic pressure of the head when using an ejection head with multiple valve-type inkjet nozzles, depending on the increase or decrease in the number of driven nozzles. Internal hydraulic pressure PA is when there are many driven nozzles, and internal hydraulic pressure PB is when there are few driven nozzles. When there are many driven nozzles, the pressure loss due to ejection is greater compared to when there are few driven nozzles.

[0065] For example, at time T1, which is the discharge start time, the internal fluid pressures PA and PB are the same at internal fluid pressure P0, but as time progresses, the difference between internal fluid pressure PA and internal fluid pressure PB increases. At time T2, after a certain period of time has elapsed, internal fluid pressure PA becomes internal fluid pressure P21, and internal fluid pressure PB becomes internal fluid pressure P22. Internal fluid pressure P22 is a lower pressure than internal fluid pressure P21. The discharge volume at internal fluid pressure P22 is less than the discharge volume at internal fluid pressure P1. When there are many drive nozzles, the decrease in discharge volume at internal fluid pressure PA is less than the decrease in discharge volume at internal fluid pressure PB when there are few drive nozzles.

[0066] Thus, when the number of drive nozzles is different, if the number of drive nozzles switches at time T2, the paint quality becomes uneven due to the difference in discharge volume.

[0067] <Drive voltage waveform> Next, with reference to Figure 9, the drive waveform applied to the discharge head 10 will be described. Figure 9 is a diagram showing an example of a drive waveform. In Figure 9, the horizontal axis represents time, and the vertical axis represents the drive voltage. Time progresses in the order of T11, T12, T21, T22, T31, T32, and T41. The period from time T11 to time T21 is one drive cycle S1. Similarly, the period from time T21 to time T31 is one drive cycle S1. The period from time T31 to time T41 is one drive cycle S1.

[0068] The drive voltage changes between drive voltage V1 and drive voltage V2. In one drive cycle S1, the drive voltage changes between drive voltage V1 and drive voltage V2. For example, at drive voltage V1, the on-off valve 12 is closed, and at drive voltage V2, the on-off valve 12 is opened and liquid is discharged from the nozzle hole N. In one drive cycle S1, the length of time T10 during which the drive voltage V2 is maintained is the valve open time.

[0069] For example, from time T11 to time T12, the drive voltage V2 is maintained and the on-off valve 12 is opened. The length of time T10 from time T11 to time T12 is the valve open time. At time T12, the drive voltage changes from V2 to V1 and the on-off valve 12 is closed. From time T12 to time T21, the drive voltage V1 is maintained and the on-off valve 12 remains closed.

[0070] At time T21, the drive voltage changes from V1 to V2, and the on-off valve 12 opens. In this way, the on-off valve 12 is opened and closed from time T11 to time T21. The valve opening time control unit 231 of the control device 500 can set the valve opening time between a minimum of 0 seconds and a maximum of 1 drive cycle S1. The valve opening time control unit 231 can change the valve opening time for each drive cycle S1.

[0071] <Relationship between valve opening time and discharge volume> Next, the relationship between valve opening time and discharge volume will be explained with reference to Figure 10. Figure 10 is a diagram showing the relationship between valve opening time and discharge volume. In Figure 10, the horizontal axis shows the length of valve opening time, and the vertical axis shows the discharge volume of liquid discharged from the nozzle hole N.

[0072] Figure 10 shows the relationship between valve opening time and discharge volume for different hydraulic pressures PC, PD, and PE. The hydraulic pressure is highest for PC, followed by PD and then PE. Of the three hydraulic pressures, PC has the highest pressure and PE has the lowest. At the same hydraulic pressure, the discharge volume of liquid discharged from the nozzle hole N is proportional to the valve opening time. At the same hydraulic pressure, the longer the valve opening time, the greater the discharge volume. The rate of increase in discharge volume for hydraulic pressures PC, PD, and PE is greater as the hydraulic pressure increases. The rate of increase in discharge volume for hydraulic pressure PC is greater than the rate of increase in discharge volume for hydraulic pressures PD and PE. The slope of the graph shown in Figure 10 is greatest for hydraulic pressure PC and smallest for hydraulic pressure PE.

[0073] The memory of the control device 500 can store data on the change in discharge volume at different hydraulic pressures. The valve opening time control unit 231 of the control device 500 can set the valve opening time for each hydraulic pressure to make the discharge volume the same. The valve opening time control unit 231 can set different valve opening times T51, T52, and T53 for each hydraulic pressure PC, PD, and PE to set the same discharge volume Q10. Of the times T51, T52, and T53, time T51 is the shortest and time T53 is the longest.

[0074] <Example of internal fluid pressure, valve opening time, and discharge volume> Next, an example of bed fluid pressure, valve opening time, and discharge volume will be described with reference to Figures 11 and 12. Figures 11 and 12 show an example of head fluid pressure, valve opening time, and discharge volume. The example shown in Figure 11 differs from the example shown in Figure 12. The example shown in Figure 11 is when the number of drive nozzles increases, while the example shown in Figure 12 is when the number of drive nozzles decreases.

[0075] Figures 11 and 12 show the time variation of the hydraulic pressure inside the head in the upper section, the time variation of the valve opening time in the middle section, and the time variation of the discharge volume in the lower section. Time variation refers to the change over time.

[0076] In the example shown in Figure 11, discharge begins at time T61, and at time T62, the number of drive nozzles increases from the number of first drive nozzles to the number of second drive nozzles. The number of second drive nozzles is greater than the number of first drive nozzles.

[0077] The fluid pressure inside the head decreases from fluid pressure P0 immediately after discharge starts, reaching fluid pressure P62 at time T62. The valve opening time increases from valve opening time T71 immediately after discharge starts, reaching valve opening time T72 at time T62. The valve opening time control unit 231 lengthens the valve opening time as the fluid pressure inside the head decreases.

[0078] The control device 500 increases the number of drive nozzles at time T62. After the increase in the number of drive nozzles, the internal hydraulic pressure in the head decreases from internal hydraulic pressure P62 to internal hydraulic pressure P63 at time T62. Internal hydraulic pressure P63 is lower than internal hydraulic pressure P62. After the increase in the number of drive nozzles, the valve opening time increases from valve opening time T72 to valve opening time T73 at time T63. The valve opening time control unit 231 lengthens the valve opening time as the internal hydraulic pressure in the head decreases.

[0079] The control device 500 increases the valve opening time as the internal fluid pressure in the head decreases. This results in a single discharge volume, which is Q60. The liquid discharge device 200 can discharge a constant amount of liquid Q60 regardless of changes in internal fluid pressure in the head. The liquid discharge device 200 can maintain a constant discharge volume regardless of fluctuations in the number of drive nozzles. Since the liquid discharge device 200 can maintain a constant discharge volume from immediately after liquid discharge, uniformity in painting quality can be achieved.

[0080] In the example shown in Figure 12, discharge begins at time T81, and at time T82, the number of drive nozzles decreases from the number of second drive nozzles to the number of first drive nozzles. The number of first drive nozzles is smaller than the number of second drive nozzles.

[0081] The fluid pressure inside the head decreases from fluid pressure P0 immediately after discharge starts, reaching fluid pressure P83 at time T82. The valve opening time increases from valve opening time T91 immediately after discharge starts, reaching valve opening time T93 at time T82. The valve opening time control unit 231 lengthens the valve opening time as the fluid pressure inside the head decreases.

[0082] The control device 500 reduces the number of drive nozzles at time T82. After the reduction in the number of drive nozzles, the head fluid pressure increases from head fluid pressure P83 to head fluid pressure P82 at time T82. Head fluid pressure P82 is a higher value than head fluid pressure P83. After the reduction in the number of drive nozzles, the valve opening time decreases from valve opening time T93 to valve opening time T92 at time T83. The valve opening time control unit 231 shortens the valve opening time as the head fluid pressure increases.

[0083] The control device 500 increases the valve opening time as the internal hydraulic pressure in the head decreases, and decreases the valve opening time as the internal hydraulic pressure in the head increases. As a result, the discharge volume becomes a single value, which is the discharge volume Q80. The liquid discharge device 200 can discharge a constant amount of liquid Q80 regardless of changes in internal hydraulic pressure in the head. The liquid discharge device 200 can maintain a constant discharge volume regardless of fluctuations in the number of drive nozzles. Since the liquid discharge device 200 can maintain a constant discharge volume from immediately after liquid discharge, uniformity of painting quality can be achieved.

[0084] <Example of a decrease in the number of drive nozzles> Next, we will explain examples where the number of drive nozzles decreases. For example, when the target painting area decreases in the scanning direction, the number of drive nozzles decreases. For example, when painting from the roof to the pillar, the target painting area decreases in the scanning direction, and the number of drive nozzles decreases. For example, when the target painting area decreases from a large area to an area less than the scanning width, the number of drive nozzles decreases. "Scanning width" is the length of the area corresponding to the target painting area in a direction intersecting the scanning direction. Also, when the last row of the target painting area has an area less than the scanning width, the number of drive nozzles decreases. The control device 500 can scan the object 3000 and calculate the number of drive nozzles.

[0085] "Number of drive nozzles" refers to the number of nozzle holes N from which liquid is discharged when painting an object 3000. If the target painting area does not change in the scanning direction, the number of drive nozzles does not change. If the target painting area increases in the scanning direction, the number of drive nozzles increases, and if the target painting area decreases, the number of drive nozzles decreases. "Target painting area" refers to the area of ​​the object 3000 that is painted.

[0086] For example, the number of drive nozzles is limited if unusable nozzle holes N occur due to painting conditions. For example, unusable nozzle holes N may occur due to painting conditions such as gap and angle of incidence. "Gap" refers to the gap between the object 3000 and the nozzle hole N. "Angle of incidence" refers to the angle at which the droplet is incident on the painted surface of the object 3000.

[0087] For example, when painting an area with a large change in curvature, such as the body panel of a vehicle (object 3000), it is expected that gaps and incidence angles will exceed a certain value during the painting process from areas with low curvature to areas with high curvature. In such cases, the number of drive nozzles will be reduced.

[0088] <Example of increasing the number of drive nozzles> Next, we will explain an example where the number of drive nozzles increases. For example, the number of drive nozzles increases from 0ch to the initial number of drive nozzles at the start of printing. "At the start of printing" can also mean "at the start of painting" or "at the start of ejection". "0ch" means that the number of drive nozzles is "0".

[0089] For example, if certain painting conditions cause unusable nozzle holes N, a change in painting conditions may allow these previously restricted nozzle holes to become usable. In such cases, the number of drive nozzles increases because the previously restricted nozzle holes become usable.

[0090] For example, when painting areas with a large curvature, such as the body panels of a vehicle, the number of drive nozzles increases when painting from areas with a large curvature where the gap or angle of incidence exceeds a certain value towards areas with a smaller curvature. The control device 500 can change the valve opening time in accordance with the increase or decrease in the number of drive nozzles to keep the discharge volume constant.

[0091] With this type of liquid dispensing device 200, the valve opening time of the on-off valve 12 can be changed based on the liquid pressure supplied to the dispensing head 10. This suppresses fluctuations in the amount of liquid dispensed from the nozzle hole N, thereby achieving uniformity in painting quality. "Liquid pressure supplied to the dispensing head" refers to the pressure of the liquid supplied to the dispensing head.

[0092] In the liquid dispensing device 200, the valve opening time of the on-off valve 12 can be changed based on the number of drive nozzles, which is the number of nozzle holes N from which liquid is dispensed during painting (printing). This reduces the impact of fluctuations in the number of drive nozzles and suppresses fluctuations in the amount of liquid dispensed from the nozzle holes N, thereby achieving uniformity in painting quality.

[0093] The discharge head 10 of the liquid discharge device 200 can perform a first discharge operation in which liquid is discharged from the nozzle hole N at a first hydraulic pressure in a first region, and a second discharge operation in which liquid is discharged from the nozzle hole N at a second hydraulic pressure in a second region. The hydraulic pressure inside the discharge head 10 may decrease from the first hydraulic pressure to the second hydraulic pressure and increase from the second hydraulic pressure to the first hydraulic pressure. The "first hydraulic pressure" and "second hydraulic pressure" can be any values.

[0094] In the liquid dispensing device 200, when the second liquid pressure is lower than the first liquid pressure, the valve opening time in the second dispensing operation can be made longer than the valve opening time in the first dispensing operation. In the liquid dispensing device 200, the valve opening time can be adjusted according to the liquid pressure supplied to the dispensing head 10 to keep the discharge volume constant.

[0095] The liquid discharge device 200 can change the valve opening time by changing the voltage duty cycle of the drive voltage waveform applied to the valve drive mechanism 13. The liquid discharge device 200 opens and closes the on / off valve 12 by supplying the drive voltage waveform shown in Figure 8, for example, to the valve drive mechanism 13. The voltage duty cycle is the pulse width of the drive voltage V2 for one drive cycle S1. The control device 500 can change the valve opening time by changing the pulse width of the drive voltage waveform based on the liquid pressure supplied to the discharge head 10. The control device 500 can change the valve opening time by changing the pulse width of the drive voltage waveform according to the number of drive nozzles.

[0096] The liquid discharge device 200 can shorten the switching interval for valve opening time when the rate of change of liquid pressure in the discharge head 10 is greater than the rate of change of first time, compared to when the rate of change of first time is greater.

[0097] For example, as shown in Figures 11 and 12, the rate of change of the hydraulic pressure inside the head varies with time. The slope of the graph showing the change in hydraulic pressure inside the head over time indicates the magnitude of the rate of change over time. When the rate of change of hydraulic pressure over time is large, the liquid discharge device 200 can shorten the switching interval of the valve opening time compared to when the rate of change of hydraulic pressure over time is small. This allows the rate of change of the valve opening time to be matched to the rate of change of hydraulic pressure inside the head. When the rate of change of hydraulic pressure inside the head over time is large, the rate of change of the valve opening time can be increased, and when the rate of change of hydraulic pressure inside the head over time is small, the rate of change of the valve opening time can be decreased. The rate of change of the valve opening time can be adjusted by changing the length of the valve opening time T10 in the drive voltage waveform shown in Figure 8. Alternatively, the rate of change of the valve opening time can be adjusted by changing the length of one drive cycle S1 in the drive voltage waveform.

[0098] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from or altering the technical concept of the present invention.

[0099] In the above embodiment, a liquid dispensing device 200 is described that includes a dispensing head 10 having multiple nozzle holes N. However, "control of valve opening time" may be performed in a dispensing head 10 having only one nozzle hole N. [Explanation of Symbols]

[0100] 200 Liquid discharge device 10. Dispensing head (liquid dispensing head) 12. Shut-off valves 13 Valve drive mechanism 500 Control device (control unit) 3000 objects N Nozzle Hole [Prior art documents] [Patent Documents]

[0101] [Patent Document 1] Patent No. 4123897 specification

Claims

1. A nozzle hole for dispensing liquid, A valve for opening and closing the nozzle hole, A valve drive mechanism for driving the aforementioned on-off valve, A liquid dispensing device comprising a liquid dispensing head having a pressurized liquid and applying it to an object, The system includes a control unit that changes the valve opening time of the on / off valve based on the pressure of the liquid supplied to the liquid discharge head, The aforementioned liquid dispensing head is A first discharge operation in which liquid is discharged from the nozzle hole at a first hydraulic pressure to the first region, A second discharge operation is possible, in which liquid is discharged from the nozzle hole at a second hydraulic pressure to the second region. The liquid dispensing device is characterized in that, when the second liquid pressure is lower than the first liquid pressure, the valve opening time in the second dispensing operation is made longer than the valve opening time in the first dispensing operation.

2. Multiple nozzle holes for dispensing liquid, A valve for opening and closing the nozzle hole, A valve drive mechanism for driving the aforementioned on-off valve, A liquid dispensing device comprising a liquid dispensing head having a pressurized liquid and applying it to an object, A liquid dispensing device characterized by comprising a control unit that changes the valve opening time of the on / off valve based on the number of drive nozzles, which is the number of nozzle holes that discharge liquid during liquid application.

3. The aforementioned liquid dispensing head is A first discharge operation in which liquid is discharged from the nozzle hole at a first hydraulic pressure to the first region, A second discharge operation is possible, in which liquid is discharged from the nozzle hole at a second hydraulic pressure to the second region. The liquid dispensing device according to claim 2, characterized in that the control unit makes the valve opening time in the second dispensing operation longer than the valve opening time in the first dispensing operation when the second liquid pressure is lower than the first liquid pressure.

4. The liquid dispensing device according to any one of claims 1 to 3, characterized in that the control unit changes the valve opening time by changing the voltage duty cycle of the voltage waveform applied to the valve drive mechanism.

5. The liquid dispensing device according to any one of claims 1 to 3, characterized in that the control unit shortens the switching interval of the valve opening time when the rate of change of the liquid pressure inside the nozzle hole is a second rate of change which is greater than the first rate of change.

6. A nozzle hole for dispensing liquid, A valve for opening and closing the nozzle hole, A valve drive mechanism for driving the aforementioned on-off valve, A liquid dispensing method comprising using a liquid dispensing head having a pressurized liquid and applying it to an object, The aforementioned liquid dispensing head is A first discharge operation in which liquid is discharged from the nozzle hole at a first hydraulic pressure to the first region, A second discharge operation is possible, in which liquid is discharged from the nozzle hole at a second hydraulic pressure to the second region. Based on the pressure of the liquid supplied to the liquid discharge head, the valve opening time of the on / off valve is changed. A liquid discharge method characterized in that, when the second liquid pressure is lower than the first liquid pressure, the valve opening time in the second discharge operation is made longer than the valve opening time in the first discharge operation.

7. Multiple nozzle holes for dispensing liquid, A valve for opening and closing the nozzle hole, A valve drive mechanism for driving the aforementioned on-off valve, A liquid dispensing method comprising using a liquid dispensing head having a pressurized liquid and applying it to an object, A liquid dispensing method characterized by changing the valve opening time of the on-off valve based on the number of drive nozzles, which is the number of nozzle holes that discharge liquid during liquid application.

8. A nozzle hole for dispensing liquid, A valve for opening and closing the nozzle hole, A valve drive mechanism for driving the aforementioned on-off valve, A program that causes a computer to perform a process of dispensing pressurized liquid and applying it to an object using a liquid dispensing head having the following: The aforementioned liquid dispensing head is A first discharge operation in which liquid is discharged from the nozzle hole at a first hydraulic pressure to the first region, A second discharge operation is possible, in which liquid is discharged from the nozzle hole at a second hydraulic pressure to the second region. The aforementioned program, A process for changing the valve opening time of the on / off valve based on the pressure of the liquid supplied to the liquid discharge head, A program characterized in that, when the second hydraulic pressure is lower than the first hydraulic pressure, the computer is instructed to perform a process that makes the valve opening time in the second discharge operation longer than the valve opening time in the first discharge operation.

9. Multiple nozzle holes for dispensing liquid, A valve for opening and closing the nozzle hole, A valve drive mechanism for driving the aforementioned on-off valve, A program that causes a computer to perform a process of dispensing a pressurized liquid and applying it to an object using a liquid dispensing head having the following: The aforementioned program, A program characterized by causing the computer to perform a process to change the valve opening time of the on-off valve based on the number of drive nozzles, which is the number of nozzle holes that discharge liquid during liquid application.

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