Liquid ejection device, liquid ejection method, and program

Abstract

To suppress deterioration of the quality of liquid application.SOLUTION: A liquid discharge device 200 makes a plurality of nozzle holes of a liquid discharge head 10 discharge liquid and apply the liquid to an object. In the liquid discharge device 200, the liquid discharge head can execute: a first discharging operation of making a first driving nozzle number of the nozzle holes discharge liquid to a first area at the start of applying liquid to the object; a second discharging operation of making a second driving nozzle number of nozzles holes (N) which is larger than the first driving nozzle number discharge liquid to a second area at the start of scanning; a first idle-discharging operation of discharging liquid before the first discharging operation; and a second idle-discharging operation of discharging liquid before the second discharging operation, where a second total idle-discharge amount which is a total discharge amount of liquid in the second idle-discharging operation is larger than a first total idle-discharge amount which is a total discharge amount of liquid in the first idle-discharging operation.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] 2. Description of the Related Art Liquid ejection devices that eject liquid from a liquid ejection head onto a target object are known. Such liquid ejection devices are used for a variety of purposes, such as painting the target object or 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 pressurized ink to the nozzle hole, a needle valve that is provided in the ink chamber and opens and closes the nozzle hole, and a drive mechanism that drives the needle valve. Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the configuration described in Patent Document 1, the quality of liquid application may be reduced at the start of liquid application due to the thixotropy of the liquid and a drop in liquid pressure caused by ejection. [Means for solving the problem]

[0005] The liquid ejection device of the present invention is a liquid ejection device that ejects liquid from a plurality of nozzle holes of a liquid ejection head and applies the liquid to an object, and the liquid ejection head comprises: an on-off valve that opens and closes the nozzle hole, and a valve drive mechanism that drives the on-off valve; Object At the start of scanning the first region, a first ejection operation of ejecting liquid from a first number of nozzle holes driven onto a first region; For the second region of the object a second discharge operation for discharging liquid from nozzle holes of a second number of driven nozzles that is greater than the first number of driven nozzles into a second region at the start of scanning; a first dummy discharge operation for discharging liquid before the first discharge operation; and a second dummy discharge operation for discharging liquid before the second discharge operation, In the first discharge operation, liquid is discharged from the nozzle hole for a first valve opening time at the start of scanning a first region of the target, and in the first blank discharge operation, blank discharge is performed for a valve opening time longer than the first valve opening time. In the second discharge operation, liquid is discharged from the nozzle hole for a second valve opening time at the start of scanning a second region of the target, and in the second blank discharge operation, blank discharge is performed for a valve opening time longer than the second valve opening time.The second total idling discharge amount, which is the total discharge amount of liquid in the second idling discharge operation, is characterized in that it is greater than the first total idling discharge amount, which is the total discharge amount of liquid in the first idling discharge operation. [Effects of the Invention]

[0006] The present invention can suppress deterioration in the quality of liquid application at the start of liquid application. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram showing a coating robot equipped with a liquid ejection device according to an embodiment. [Figure 2] FIG. 1 is a schematic diagram illustrating a liquid ejection device according to an embodiment. [Figure 3] FIG. 2 is a block diagram showing the hardware configuration of the liquid ejection device according to the embodiment. [Figure 4] FIG. 2 is a functional block diagram of the liquid ejection device according to the embodiment. [Figure 5] 10 is a flowchart showing the procedure of a painting route generation process. [Figure 6] 10 is a graph showing the relationship between droplet ejection time and paint viscosity. [Figure 7] 10 is a graph showing the relationship between droplet ejection time and paint liquid pressure. [Figure 8] 10 is a graph showing the relationship between the droplet ejection time and the paint liquid pressure when the number of driven nozzles is different. [Figure 9] 10 is a graph showing the relationship between the droplet ejection time and the paint liquid pressure when idle ejection is performed using nozzle holes N that is greater than or equal to the number of driven nozzles used during painting. [Figure 10] 10 is a graph showing the relationship between decap time and paint viscosity. [Figure 11] FIG. 2 is a plan view showing a first region and a second region included in an object. DETAILED DESCRIPTION OF THE INVENTION

[0008] <Outline of liquid ejection device> First, an overview of a liquid ejection device will be described using Figure 1. Figure 1 is an overall schematic diagram of a liquid ejection device according to an embodiment of the present invention. The liquid ejection device illustrated here is a painting robot that paints automobile bodies and the like. Note that in each figure, arrows may be shown indicating three mutually intersecting directions: the X-axis direction, the Y-axis direction, and the Z-axis direction. The X-axis direction is, for example, along the front-rear direction of the car body, which is the object to be painted. The Y-axis direction is along the width direction of the car body. The Z-axis direction is along the up-down direction.

[0009] As shown in Fig. 1, the painting robot 1000 is installed facing an object 3000, such as the side of an automobile body. The painting robot 1000 includes 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.

[0010] 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.

[0011] The painting robot 1000 is, for example, an articulated robot. The base 100 can rotate in the a direction around an axis extending in the Z direction. The base 100 supports one end of a first arm 101 via a first joint 104.

[0012] The first arm 101 can rotate in the direction b around an axis parallel to the XY plane as a rotation axis. The other end of the first arm 101 is supported by one end of the second arm 102 via a second joint 105. The second arm 102 can swing in the direction c around an axis parallel to the XY plane as a rotation axis. In addition, the second arm 102 can rotate in the direction d around an axis extending in the longitudinal direction of the second arm 102 as a rotation axis.

[0013] The other end of second arm 102 supports head unit 103 via third joint 106. Head unit 103 is rotatable in direction e around an axis that extends in a direction intersecting the longitudinal direction of second arm 102. Head unit 103 is also rotatable in direction f around an axis that extends in a direction separating head unit 103 and third joint 106.

[0014] The painting robot 1000 can freely move the head unit 103 relative to the object 3000. The painting robot 1000 can accurately position the head unit 103 relative to the object 3000. The painting robot 1000 can accurately position the head unit 103 relative to the position where painting is to be performed. The painting robot 1000 ejects paint toward the object 3000 and paints the object 3000.

[0015] In this embodiment, a system configuration has been exemplified in which the painting robots 1000 are arranged one on each side of the object 3000, but the painting robots 1000 are not limited to being arranged on both sides of the object 3000. The number of painting robots 1000 installed may be one, three or more for each object 3000.

[0016] 2 is a schematic diagram showing a liquid ejection device 200. The painting robot 1000 has the liquid ejection device 200. The liquid ejection device 200 can perform a liquid ejection method. The liquid ejection device 200 includes a tank 2, an ejection head (liquid ejection head) 10, and a control device 500. The liquid ejection device 200 includes a pipe 1, a pipe 4, and a pipe 8.

[0017] The tank 2 is a container that stores the liquid to be supplied to the discharge head 10. The tank 2 stores paint 3, which is an example of the liquid. A pipe 1 is connected to the tank 2. A compressor, for example, is connected to the pipe 1. The compressor supplies pressurized air to the tank 2. The compressor can increase the pressure inside the tank 2 via the pipe 1. The pipe 1 functions as a pressure supply path that supplies pressure to the liquid in the tank 2.

[0018] The pipe 4 is a flow path that connects the tank 2 and the discharge head 10. The paint 3 in the tank 2 flows through the pipe 4 and is supplied to the discharge head 10. The pipe 4 functions as a liquid supply flow path that supplies the paint 3 to the discharge head 10.

[0019] The ejection head 10 has a nozzle hole N, an ink chamber 11, and an on-off valve 12. The ejection head 10 has a valve drive mechanism 13 for driving the on-off valve 12. The nozzle hole N is in communication with the ink chamber 11. The ink chamber 11 stores the paint 3 supplied from the tank 2. The on-off valve 12 is disposed within 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 ejection head 10 ejects the paint 3 in the ink chamber 11 from the nozzle hole N. The ejection head 10 ejects the pressurized paint 3 and deposits it on the target object 3000. The valve drive mechanism 13 drives the on-off valve 12 in accordance with a drive signal supplied from the control device 500. The on-off valve 12 approaches the nozzle hole N to close the nozzle hole N. The on-off valve 12 moves away from the nozzle hole N to open the nozzle hole N.

[0020] The control device 500 and the PC 600 control the liquid ejection by the ejection head 10. The control device 500 and the PC 600 operate the on-off valve 12 to eject the paint 3.

[0021] The pipe 8 communicates with the ejection head 10. The pipe 8 is provided with a valve 9. When filling the ink chamber 11 with the paint 3, the valve 9 is opened to release the pressure in the ink chamber 11. When ejecting the paint 3 from the nozzle hole N of the ejection head 10, the valve 9 is closed.

[0022] <Hardware configuration> Next, the hardware configuration of the liquid ejection device 200 according to the first embodiment will be described with reference to Fig. 3. Fig. 3 is a block diagram showing the hardware configuration of the liquid ejection device 200 according to the first embodiment. The hardware configuration shown in Fig. 3 may include additional components as needed. The hardware may not include the components shown in Fig. 3 as needed.

[0023] The liquid ejection device 200 includes a control device 500. The control device 500 includes 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 controls the entire liquid ejection device 200. The ROM 502 stores various programs for causing the CPU 501 to execute liquid ejection control, as well as various data necessary for painting. The ROM 502 also stores a program for scanning the ejection head 10.

[0024] The RAM 503 temporarily stores position data and the like of the ejection head 10. The NVRAM 504 is a non-volatile memory, and can retain data even while the power to the liquid ejection device 200 is cut off. The control device 500 has a main control unit 500A, which includes a CPU 501, a ROM 502, and a RAM 503.

[0025] The control device 500 has an ASIC (Application Specific Integrated Circuit) 505. The ASIC 505 processes input and output signals for controlling the entire liquid ejection 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.

[0026] The control device 500 includes an external interface (external I / F) 506 for transmitting and receiving data to and from an external device, such as a PC 600. The PC 600 includes, for example, a RIP unit 601. The RIP unit 601 includes a lettering unit 602.

[0027] An input device 603 is connected to the PC 600. In addition, a position measuring device 15 is connected to the PC 600.

[0028] Memories such as the ROM 502, RAM 503, NVRAM 504, and HDD 508 store image data and data relating to the area to be painted received from the computer 600. The data relating to the area to be painted includes data such as the size of the object to be painted.

[0029] The control device 500 also includes an input / output unit (I / O) 507 for receiving detection signals output from the sensors 18. Examples of the sensors 18 include a temperature sensor, a pressure sensor, and a viscosity sensor.

[0030] The control device 500 includes a head control device 510 that controls the drive of the ejection head 10. The head control device 510 can control the drive device of the ejection head 10. The head control device 510 can control the drive device of the ejection head 10 to eject liquid. The head control device 510 can control the drive of the on-off valve 12 of the ejection head 10. The ejection head 10 can control the pressure inside the tank 2. The ejection head 10 can control the drive of the valve 9. The head control device 510 can perform various controls related to the ejection head 10.

[0031] The control device 500 includes a robot control device 511. The robot control device 511 controls the robot drive mechanism 31 in accordance with commands from the CPU 501. The painting robot 1000 is equipped with the 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.

[0032] The painting robot 1000 is equipped with an encoder sensor 32. The control device 500 receives a signal from the encoder sensor 32 via an I / O 507. An encoder sensor 32 is provided for each of the first joint 104, the second joint 105, and the third joint 106. The first joint 104, the second joint 105, and the third joint 106 are provided with slits that rotate together with the rotation shafts. The encoder sensor 32 optically detects the slits. The encoder sensor 32 detects the rotation angles of the first joint 104, the second joint 105, and the third joint 106.

[0033] 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 X and Y directions. 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.

[0034] 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.

[0035] The PC can acquire position data of the ejection head 10 from the position measuring device 15. The control device 500 can input the position data of the ejection head 10 via the PC 600. The control device 500 may input data from the position measuring device 15 via the I / O 507.

[0036] An input device 603 is connected to the PC 600. The input device 603 can input image data and position data to the PC 600. The position measuring device 15 may input the measured position data of the ejection head 10 to the PC 600.

[0037] The PC 600 generates a painting route for the painting robot 1000. The lettering unit 602 breaks down the data of the painting area into data for each scan. The painting area is, for example, the area where painting is to be performed. The lettering unit 602 determines the number of nozzles to be driven in each scan and whether or not to perform blank discharge. The number of driven nozzles is the number of nozzle holes N that discharge liquid in the discharge head 10. Blank discharge includes discharging liquid from the nozzle hole N before a scan. The lettering unit 602 can determine whether or not to perform blank discharge.

[0038] The PC 600 can determine the valve open time during scanning. The valve open time control unit 131 of the PC 600 determines the valve open time during scanning in accordance with pre-created data relating to the printing time for each number of driven nozzles. The data relating to the printing time for each number of driven nozzles is determined in advance based on liquid pressure fluctuations. "Liquid pressure fluctuations" refers to, for example, pressure fluctuations of the liquid inside the ejection head 10.

[0039] The computer 600 includes a RIP (Routing Information Protocol) unit 601. The RIP unit 601 can execute image processing in accordance with a color profile and user settings.

[0040] The RIP unit 601 includes a lettering unit 602. The lettering unit 602 breaks down data of the paint 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. "For each scan" refers, for example, to each movement of the ejection head 10 along the main scanning direction. The "main scanning direction" may be, for example, a direction along the longitudinal direction of the object 3000, or any other direction.

[0041] An input device 603 is connected to the computer 600. A user can operate the input device 603 to input various data to the computer 600. Image data and coordinate data indicating the area to be painted on the target object 3000 can be input to the computer 600 via the input device 603.

[0042] The computer 600 can input a signal from the input device 603 to set the painting mode. The user can operate the input device 603 to select the painting mode. The computer 600 can input a signal from the input device 603 to set the painting range. The computer 600 can set the painting start position and painting end position. The computer 600 can set the painting start timing. The user can operate the computer 600 via the input device 603 to change various settings.

[0043] The input device 603 may include, for example, a keyboard, a mouse, a touch panel, etc. The computer 600 can also acquire position data of the discharge head 10 from the position measurement device 15 provided in the painting robot 1000. The computer 600 can generate a painting route for the discharge head 10 based on the acquired position data. The painting route includes position data related to the movement path along which the discharge head 10 moves. The painting route may also include other data.

[0044] The coating system 2000 is an example of a liquid ejection system. The coating system 2000 includes a liquid ejection device 200 and a computer 600.

[0045] <Functional configuration> Next, the functional configuration of the liquid ejection device 200 according to the embodiment will be described with reference to Fig. 4. Fig. 4 is a functional block diagram of the liquid ejection device 200 according to the embodiment. A CPU 501 shown in Fig. 3 executes a program stored in a storage unit such as a ROM 502 to realize the functions of a system control unit 221, a valve opening time control unit 231, an ejection period signal generation unit 232, a memory generation unit 233, a data storage unit 234, and a synchronization control unit 235 shown in Fig. 4.

[0046] The system control unit 221 controls the overall operation of the painting system 2000. The system control unit 221 receives image data of the painting area and command signals from the computer 600, and controls the overall operation of the painting system 2000.

[0047] The valve open time control unit 231 controls the valve open time of the on-off valve 12. The valve open time is the length of time during which the on-off valve 12 is open and liquid can be ejected.

[0048] The memory control unit 9013 controls memories such as the ROM 502, the RAM 503, the NVRAM 504, and the HDD 508.

[0049] The synchronization control unit 235 generates a discharge period signal based on the output signal output from the encoder sensor 32 and information indicating the resolution of the image data output from the computer 600. The discharge period signal is a signal that indicates the discharge period of the paint discharged from the nozzle hole N.

[0050] The synchronization control unit 235 coordinates the movements of the multiple painting robots 1000 with the paint dispensing operations of the dispensing heads 10 based on image data, painting instruction signals, and the like received from the computer 600 .

[0051] The head control device 510 receives the discharge period signal and controls the liquid discharge operation of the discharge head 10 based on the received discharge period signal. The robot control device 511 receives the 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.

[0052] The system control unit 221, valve opening time control unit 231, discharge period signal generation unit 232, memory generation unit 233, data storage unit 234, and synchronization control unit 235 can be realized by software using programs stored in a storage unit. All or part of the system control unit 221, valve opening time control unit 231, discharge period signal generation unit 232, memory generation unit 233, data storage unit 234, and synchronization control unit 235 may be realized by hardware such as an integrated circuit (IC).

[0053] The program may be recorded in the form of file information in an installable or executable format on a computer-readable recording medium such as a CD-ROM or a flexible disk (FD), and provided to the liquid ejection device 200 via such a recording medium. The program may be recorded on a computer-readable recording medium such as a CD-R, a DVD (Digital Versatile Disk), a Blu-ray (registered trademark) disk, or a semiconductor memory, and provided to the liquid ejection device 200 via such a recording medium. The program may also be provided to the liquid ejection device 200 in a form in which it is installed via a network such as the Internet. The program may also be pre-installed in a ROM or the like within the liquid ejection device 200.

[0054] Additionally, the control device 500 may perform the functions performed by the computer 600. Similarly, the computer 600 may perform the functions performed by the control device 500.

[0055] <Painting route generation> Next, the generation of a painting route will be described. Fig. 5 is a flowchart showing the procedure for the painting route generation process. The CPU 501 generates a painting route based on the input image data and the relative positional relationship between the discharge head 10 and the target object 3000.

[0056] The computer 600 inputs image data (step S11). The image data is, for example, image data of the object 3000. Next, the computer 600 creates painting data based on the image data (step S12). The painting data includes, for example, position data indicating the area to be painted.

[0057] The position measuring device 15 detects the relative position between the discharge head 10 and the target object 3000 (step S13). The position measuring device 15 outputs data relating to the detected relative position to the computer 600.

[0058] The computer 600 breaks down the painting data into scan data and generates a painting route (step S14). The painting route includes position information related to the movement path of the discharge head 10. The computer 600 outputs information related to the generated painting route to the control device 500. The control device 500 controls the robot drive mechanism 31 according to the painting route.

[0059] <Issues with conventional technology> Next, the problems of the prior art will be described. Liquid discharge devices according to the prior art have had the problem that the quality of the coating deteriorates at the beginning of coating due to the thixotropy of the paint and the drop in liquid pressure caused by discharge.

[0060] The paint may be, for example, a paint for painting a car body. "Thixotropy" is a property exhibited by a substance intermediate between a gel, which is a plastic solid, and a sol, which is a non-Newtonian liquid. "Thixotropy" refers to the property of a liquid's viscosity changing over time. A paint having thixotropy is in a state of relatively high viscosity against shear stress immediately after the start of dispensing. The viscosity of a paint having thixotropy gradually decreases over time.

[0061] In a liquid ejection device that pressurizes paint to eject droplets, the liquid pressure drops after ejection. After a certain time, the pressure inside the ejection head 10 balances with the supply pressure, and the pressure drop stabilizes. Immediately after the start of coating in the liquid ejection device, the liquid pressure inside the ejection head 10 gradually decreases.

[0062] <Paint viscosity and fluid pressure> Next, the relationship between the droplet ejection time and the viscosity and liquid pressure of the paint will be described with reference to Figures 6 and 7. Figure 6 is a graph showing the relationship between the droplet ejection time and the viscosity of the paint. Figure 7 is a graph showing the relationship between the droplet ejection time and the viscosity of the paint. In Figure 6, the horizontal axis shows the droplet ejection time, and the vertical axis shows the viscosity of the paint. In Figure 7, the horizontal axis shows the droplet ejection time, and the vertical axis shows the liquid pressure of the paint.

[0063] Discharge time T0 is the start time of painting. The viscosity and liquid pressure of the paint gradually decrease from the start of discharge, which is discharge time T0. As the discharge time passes and the discharge amount exceeds a certain amount, the viscosity and liquid pressure of the paint become constant values. After discharge time T1, the viscosity V1 of the paint stabilizes. After discharge time T1, the liquid pressure P1 of the paint stabilizes.

[0064] The liquid ejection device 200 performs a blank ejection operation before printing. The liquid ejection device 200 performs the blank ejection operation until the viscosity and liquid pressure of the paint stabilize. Note that the "blank ejection operation" refers to the operation of ejecting droplets from the ejection head 10 before printing, in which droplets are ejected onto the target object 3000. In the "blank ejection operation", droplets may be ejected, for example, into a container for waste liquid. Also, "printing" refers to the operation of ejecting droplets onto the target object 3000 to paint it. Also, "printing" only requires that droplets are ejected onto the target object 3000 and attached thereto, and characters do not have to be printed.

[0065] For example, the memory of the control device 500 can store data showing the relationship between the dispensing time and the viscosity of the paint. The memory of the control device 500 can store data showing the relationship between the dispensing time and the liquid pressure of the paint. The memory of the control device 500 can store data related to the number of blank dispensing operations and the amount of droplets discharged during the blank dispensing operation.

[0066] Next, referring to Figure 8, there is shown a graph illustrating the relationship between the droplet ejection time and the paint liquid pressure when the number of driven nozzles varies. In Figure 8, the horizontal axis represents the droplet ejection time, and the vertical axis represents the paint liquid pressure. Figure 8 shows the liquid pressure profile PA when the number of driven nozzles is small (Case 1), and the liquid pressure profile PB when the number of driven nozzles is large (Case 2). The "number of driven nozzles" refers to the number of nozzle holes N that eject droplets.

[0067] For example, the time required for the ink chamber 11 to become saturated and the saturated liquid pressure differ depending on the number of driven nozzles. As the number of driven nozzles increases, the amount of waste liquid discharged by idle ejection increases. The memory of the control device 500 pre-stores liquid pressure profiles PA and PB for each number of driven nozzles. The control unit 500 can determine the total amount of idle ejection based on the pressure drop for each number of driven nozzles. The "total amount of idle ejection" is, for example, the total flow rate of droplets ejected from the nozzle holes N corresponding to the number of driven nozzles from the time the liquid pressure starts to drop until the liquid pressure stabilizes.

[0068] For example, when the number of driven nozzles is small (Case 1), the total idling discharge amount is the flow rate of droplets discharged from the nozzle hole N from discharge time T0 to discharge time T1. In Case 1, at discharge time T0, the liquid pressure is liquid pressure P0, and at discharge time T1, the liquid pressure drops to liquid pressure P1. In Case 1, once discharge time T1 is exceeded, the liquid pressure stabilizes at liquid pressure P1.

[0069] For example, when the number of driven nozzles is large (Case 2), the total idling discharge amount is the flow rate of droplets discharged from the nozzle hole N from discharge time T0 to discharge time T2. In Case 2, at discharge time T0, the liquid pressure is liquid pressure P0, and at discharge time T2, the liquid pressure drops to liquid pressure P2. In Case 2, once discharge time T2 is exceeded, the liquid pressure stabilizes at liquid pressure P2. Discharge time T2 is a value greater than discharge time T1. Liquid pressure P2 is a value smaller than liquid pressure P1.

[0070] The liquid discharge device 200 can adjust the total idle discharge amount for each number of driven nozzles based on the drop in liquid pressure, so that coating can be carried out with stable paint viscosity and liquid pressure while minimizing the total idle discharge amount.

[0071] Note that the hydraulic pressure based on the number of driven nozzles used at the start of painting may be greater than the number of nozzles used for idle discharge or the valve open time. In Case 1, "start of painting" refers to discharge time T1, and in Case 2, it refers to discharge time T2.

[0072] Next, referring to Figure 9, there is shown a graph illustrating the relationship between the droplet discharge time and the paint liquid pressure when blank discharge is performed using nozzle holes N equal to or greater than the number of driven nozzles used during painting. Figure 9 shows a liquid pressure profile PC when the number of driven nozzles used at the start of painting is the same as the number of driven nozzles used during blank discharge (Case 3), and a liquid pressure profile PD when blank discharge is performed using nozzle holes N equal to or greater than the number of driven nozzles used at the start of painting (Case 4). Note that the liquid pressure profile when the valve open time is longer than the valve open time at the start of painting is similar to the profile PD shown in Figure 9.

[0073] In Case 3, at time T0, the hydraulic pressure is hydraulic pressure P0, and at time T12, the hydraulic pressure drops to hydraulic pressure P11. In Case 3, after time T12, the hydraulic pressure stabilizes at hydraulic pressure P11.

[0074] In Case 4, at time T0, the liquid pressure is liquid pressure P0, and at time T11, the liquid pressure drops to liquid pressure P12. When idle discharge is stopped at time T11, the liquid pressure rises and reaches liquid pressure P12 at time T12. When coating starts at time T12, the liquid pressure stabilizes at liquid pressure P12.

[0075] When the idle discharge is stopped, the viscosity and fluid pressure of the paint change to approach the state before the idle discharge. Therefore, there is a limit to the decap time before the start of painting. The "decap time" refers to the time during which the on-off valve 12 is closed and no discharge is occurring.

[0076] Next, referring to Fig. 10, we will explain the relationship between the decap time from the end of idle discharging to the start of coating and the viscosity of the paint at the start of discharging when the viscosity of the paint is dominant. Fig. 10 is a graph showing the relationship between decap time and paint viscosity. In Fig. 10, the horizontal axis represents decap time and the vertical axis represents paint viscosity.

[0077] Figure 10 shows the viscosity profile PE when the number of driven nozzles is "small" (case 5), the viscosity profile PF when the number of driven nozzles is "medium" (case 6), and the viscosity profile PG when the number of driven nozzles is "large" (case 7).

[0078] In Case 5, at time T20, the viscosity is V21, and increases slightly until time T23. In Case 5, the increase in viscosity ΔV between time T20 and time T23 is slight and does not affect the coating quality. In Case 5, after time T23, the viscosity increases, and at time T24, the viscosity becomes V20. After time T24, the viscosity stabilizes at V20.

[0079] In Case 6, the viscosity is V22 at time T20, and increases slightly until time T22. In Case 6, the increase in viscosity ΔV between time T20 and time T22 is slight and does not affect the coating quality. In Case 6, the viscosity increases after time T22, and reaches V20 at time T24. After time T24, the viscosity stabilizes at V20. Note that the value at time T22 is smaller than that at time T23. Furthermore, viscosity V22 is smaller than viscosity V21. In Case 6, the viscosity begins to increase earlier than in Case 5.

[0080] In Case 7, the viscosity is V23 at time T20, and increases slightly until time T21. In Case 7, the increase in viscosity ΔV between time T20 and time T21 is slight and does not affect the coating quality. In Case 7, the viscosity increases after time T21, and reaches V20 at time T24. After time T24, the viscosity stabilizes at V20. Note that the value at time T21 is smaller than that at time T22. Furthermore, viscosity V23 is smaller than viscosity V22. In Case 7, the viscosity begins to increase earlier than in Cases 5 and 6.

[0081] The viscosity increases slightly until a certain time has elapsed since the start of the decap time. After that, the viscosity increases due to the thixotropy of the paint. By starting coating within the time when the viscosity is stable, the liquid ejection device 200 can maintain a stable ejection volume and droplet velocity immediately after the start of coating.

[0082] FIG. 10 shows the abnormal discharge occurrence time TI, which is the time when the abnormal discharge is expected to occur. The greater the number of driven nozzles, the shorter the abnormal discharge occurrence time TI. The abnormal discharge occurrence time TI may be the shortest time until the increase in viscosity causes the abnormal discharge. If the increase in viscosity ΔV is below a certain level, it will not affect the coating quality. If the increase in viscosity exceeds the threshold increase ΔV, there is a risk of abnormal discharge occurring.

[0083] The memory of the control device 500 can store information showing the relationship between decap time and paint viscosity for each number of driven nozzles shown in Figure 10. The memory of the control device 500 may also store information related to the discharge abnormality occurrence time TI. The control device 500 can perform control so that droplets are discharged from the nozzle holes N and painting begins before the discharge abnormality occurrence time TI has elapsed. In a state in which droplets are not being discharged from the nozzle holes N, when the number of driven nozzles is small, the discharge abnormality occurrence time TI is longer than when the number of driven nozzles is large.

[0084] The control device 500 can change the time from the end of idle discharge to the start of painting depending on the number of driven nozzles. When the number of driven nozzles is large, the control device 500 can shorten the time from the end of idle discharge to the start of painting compared to when the number of driven nozzles is small. This allows the liquid discharge device 200 to start painting when the viscosity and liquid pressure are stable, achieving stable painting quality.

[0085] The ejection head 10 of the liquid ejection device 200 according to this embodiment is capable of performing a first ejection operation in which liquid is ejected from nozzle holes N having a first number of driven nozzles into a first region R1 at the start of scanning, a second ejection operation in which liquid is ejected from nozzle holes N having a second number of driven nozzles that is greater than the first number of driven nozzles into a second region R2 at the start of scanning, a first blank ejection operation in which liquid is ejected before the first ejection operation, and a second blank ejection operation in which liquid is ejected before the second ejection operation.

[0086] FIG. 11 is a plan view showing a first region R1 and a second region R2 included in the target object 3000. For example, the second region R2 is larger than the first region R1. At the start of scanning, the discharge head 10 discharges liquid from the nozzle holes N of the first number of driven nozzles onto the first region R1, thereby performing a first discharge operation to coat the first region R1. At the start of scanning, the discharge head 10 discharges liquid from the nozzle holes N of the second driven nozzle onto the second region R2, thereby performing a second discharge operation to coat the second region R2. Note that the positions, sizes, and shapes of the first region R1 and the second region R2 are not particularly limited.

[0087] The discharge head 10 can perform a first dummy discharge operation to discharge liquid from the nozzle holes N before the first discharge operation. The dummy discharge performed in the first dummy discharge operation refers to the discharge of liquid that does not contribute to coating. The discharge head 10 can perform a second dummy discharge operation to discharge liquid from the nozzle holes N before the second discharge operation. The dummy discharge performed in the second dummy discharge operation refers to the discharge of liquid that does not contribute to coating.

[0088] The second total dummy discharge amount, which is the total discharge amount of liquid in the second dummy discharge operation, is greater than the first total dummy discharge amount, which is the total discharge amount of liquid in the first dummy discharge operation. The discharge head 10 dummy discharges the first total dummy discharge amount of liquid in the first dummy discharge operation. The discharge head 10 dummy discharges the second total dummy discharge amount of liquid, which is greater than the first total dummy discharge amount, in the second dummy discharge operation.

[0089] According to the liquid discharger 200, by adjusting the first total idling discharge amount in the first idling operation and the second total idling discharge amount in the second idling operation, it is possible to suppress the first total idling discharge amount and the second total idling discharge amount while suppressing the drop in liquid pressure and viscosity at the start of coating, thereby suppressing deterioration of coating quality. The liquid discharger 200 can improve coating quality.

[0090] The liquid ejection device 200 can perform the first blank ejection operation using a larger number of nozzle holes N than the number of first driven nozzles. The control device 500 can set the number of first driven nozzles in the first ejection operation at the start of scanning as a reference, and control the first blank ejection operation so that liquid is ejected from a larger number of nozzle holes than the number of first driven nozzles in the first blank ejection operation. The ejection head 10 can perform the first blank ejection operation using a larger number of nozzle holes than the number of first driven nozzles in the first ejection operation. This allows the liquid ejection device 200 to shorten the time required for the first blank ejection operation. Note that the liquid ejection device 200 can perform the first blank ejection operation using a number of nozzle holes N equal to the number of first driven nozzles.

[0091] The liquid ejection device 200 can perform the second blank ejection operation using a larger number of nozzle holes N than the number of second driven nozzles. The control device 500 can set the number of second driven nozzles in the second ejection operation at the start of scanning as a reference, and control the second blank ejection operation so that liquid is ejected from a larger number of nozzle holes than the number of second driven nozzles in the second blank ejection operation. The ejection head 10 can perform the second blank ejection operation using a larger number of nozzle holes than the number of second driven nozzles in the second ejection operation. This allows the liquid ejection device 200 to shorten the time required for the second blank ejection operation. Note that the liquid ejection device 200 can perform the second blank ejection operation using a number of nozzle holes N equal to the number of second driven nozzles.

[0092] Furthermore, in the first discharge operation, the liquid discharger 200 can discharge liquid from the nozzle hole N for a first valve open time at the start of scanning. The first valve open time is, for example, the length of time the valve is open in one discharge. In the first dummy discharge operation, the liquid discharger 200 can perform dummy discharge with a valve open time longer than the first valve open time. The liquid discharger 200 can make the valve open time in the first dummy discharge operation longer than the first valve open time in the first discharge operation. This allows the liquid discharger 200 to shorten the time of the first dummy discharge operation. In addition, in the first dummy discharge operation, the liquid discharger 200 can perform dummy discharge with the valve open time set to the same length as the first open time.

[0093] Furthermore, in the second discharge operation, the liquid discharger 200 can discharge liquid from the nozzle hole N for the second valve open time at the start of scanning. The second valve open time is, for example, the length of time the valve is open in one discharge. In the second blank discharge operation, the liquid discharger 200 can perform blank discharge with a valve open time longer than the second valve open time. The liquid discharger 200 can make the valve open time in the second blank discharge operation longer than the second valve open time in the second discharge operation. This allows the liquid discharger 200 to shorten the time of the second blank discharge operation. Note that in the second blank discharge operation, the first member 200 can perform blank discharge with the valve open time set to the same length as the second open time.

[0094] According to the liquid ejection device 200 of this embodiment, when the non-ejection time during which liquid is not ejected from the plurality of nozzle holes exceeds a predetermined ejection abnormality occurrence time TI, the ejection head 10 can perform blank ejection. The control device 500 measures the non-ejection time, and when the insufficient ejection time exceeds the ejection abnormality occurrence time TI, controls the ejection head 10 to perform blank ejection.

[0095] The control device 500 can change the abnormal ejection occurrence time TI depending on the number of driven nozzles at the start of scanning. The control device 500 can make the abnormal ejection occurrence time longer when the number of driven nozzles at the start of scanning is small compared to when the number of driven nozzles at the start of scanning is large.

[0096] The control device 500 may determine the ejection abnormality occurrence time TI based on the amount of change per unit time in viscosity due to the thixotropy of the liquid. For example, data regarding the amount of change per unit time in viscosity due to the thixotropy of the liquid may be obtained by conducting experiments in advance. The memory of the control device 500 can store data indicating the relationship between the amount of change per unit time in viscosity due to the thixotropy of the liquid and the ejection abnormality occurrence time TI. The control device 500 can determine the ejection abnormality occurrence time TI based on the data stored in the memory.

[0097] The control device 500 may determine the ejection abnormality occurrence time TI based on the amount of change per unit time of the liquid pressure. The memory of the control device 500 can store data indicating the relationship between the amount of change per unit time of the liquid pressure inside the ejection head 10 and the ejection abnormality occurrence time TI. The control device 500 can determine the ejection abnormality occurrence time TI based on the data stored in the memory.

[0098] The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the present invention without departing from or changing the technical concept of the present invention. [Explanation of symbols]

[0099] 200 Liquid discharge device 10. Discharge head (liquid discharge head) 12 On-off valve 13 Valve drive mechanism 500 control device (control unit) N Nozzle hole [Prior art documents] [Patent documents]

[0100] [Patent Document 1] Patent No. 4123897 specification

Claims

1. A liquid ejection device that ejects liquid from a plurality of nozzle holes of a liquid ejection head and applies the liquid to a target object, The liquid ejection head includes: an on-off valve that opens and closes the nozzle hole; a valve drive mechanism that drives the on-off valve, a first ejection operation of ejecting liquid from a first number of nozzle holes driven onto a first region of the object at the start of scanning the first region; a second ejection operation of ejecting liquid from the nozzle holes of a second number of driven nozzles, the second number of driven nozzles being greater than the first number of driven nozzles, onto the second region of the object at the start of scanning the second region; a first dummy discharge operation of discharging liquid before the first discharge operation; a second blank ejection operation that ejects liquid before the second ejection operation, In the first ejection operation, liquid is ejected from the nozzle hole for a first valve opening time at the start of scanning the first region of the object; In the first blank discharge operation, blank discharge is performed for a valve opening time longer than the first valve opening time, In the second ejection operation, liquid is ejected from the nozzle hole for a second valve opening time at the start of scanning the second region of the object, and In the second blank discharge operation, blank discharge is performed for a valve opening time longer than the second valve opening time, A liquid ejection device characterized in that a second total idling amount, which is a total amount of liquid ejected in the second idling operation, is greater than a first total idling amount, which is a total amount of liquid ejected in the first idling operation.

2. In the first blank discharge operation, performing blank discharge using the nozzle holes in a number greater than the number of the first driven nozzles; In the second blank discharge operation, 2. The liquid ejection device according to claim 1, wherein the blank ejection is performed using a number of the nozzle holes greater than the number of the second driven nozzles.

3. A liquid ejection method for ejecting liquid from a plurality of nozzle holes of a liquid ejection head, the liquid ejection head comprising an on-off valve for opening and closing nozzle holes and a valve driving mechanism for driving the on-off valve, and applying the liquid to an object, comprising: performing a first ejection operation of ejecting liquid from a first number of nozzle holes driven onto a first region of the object at the start of scanning the first region of the object; performing a second ejection operation of ejecting liquid from the nozzle holes of a second number of driven nozzles, the second number of driven nozzles being greater than the first number of driven nozzles, onto the second region of the object at the start of scanning the second region of the object; performing a first dummy discharge operation of discharging liquid before the first discharge operation; performing a second dummy ejection operation of ejecting liquid before the second ejection operation, In the first ejection operation, liquid is ejected from the nozzle hole for a first valve opening time at the start of scanning the first region of the object; In the first blank discharge operation, blank discharge is performed for a valve opening time longer than the first valve opening time, In the second ejection operation, liquid is ejected from the nozzle hole for a second valve opening time at the start of scanning the second region of the object, and In the second blank discharge operation, blank discharge is performed for a valve opening time longer than the second valve opening time, A liquid ejection method, characterized in that a second total idling ejection amount, which is a total ejection amount of liquid in the second idling ejection operation, is greater than a first total idling ejection amount, which is a total ejection amount of liquid in the first idling ejection operation.

4. A program that causes a computer to execute a process of ejecting liquid from a plurality of nozzle holes of a liquid ejection head that includes an on-off valve that opens and closes the nozzle holes and a valve drive mechanism that drives the on-off valve, and applying the liquid to an object, The program a process of executing a first ejection operation of ejecting liquid from a first number of nozzle holes driven onto a first region of the object at the start of scanning the first region of the object; a process of executing a second ejection operation of ejecting liquid from the nozzle holes of a second number of driven nozzles, the second number of driven nozzles being greater than the first number of driven nozzles, onto the second region of the object at the start of scanning the second region; a process of executing a first blank ejection operation to eject liquid before the first ejection operation; a process of causing the computer to execute a second blank ejection operation of ejecting liquid before the second ejection operation; In the first ejection operation, liquid is ejected from the nozzle hole for a first valve opening time at the start of scanning the first region of the object; In the first blank discharge operation, blank discharge is performed for a valve opening time longer than the first valve opening time, In the second ejection operation, liquid is ejected from the nozzle hole for a second valve opening time at the start of scanning the second region of the object, and In the second blank discharge operation, blank discharge is performed for a valve opening time longer than the second valve opening time, A program characterized in that a second total idling amount, which is a total amount of liquid discharged in the second idling operation, is greater than a first total idling amount, which is a total amount of liquid discharged in the first idling operation.

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