Coating robot and coating method

Abstract

To provide a coating robot which suppresses decrease in a coating film thickness and can achieve improvement in coating quality.SOLUTION: A head control part 90 of a coating robot 10 performs recovery control for controlling drive of a piezoelectric substrate 62 so that when it is determined that a specific nozzle 54 is a defective nozzle 54a that is defective in discharge of droplets, a size of droplets of good dot D2 around defective dot D1 increases. In the recovery control, when the good dot D2 around the defective dot D1 reaches a boundary of a coating range in a coating part, boundary discharge such that the size of droplets of the good dot D2 becomes equal to a droplet size in a usual discharge state when the recovery control is performed is executed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a painting robot. [Background technology]

[0002] Robotic painting using robots has become mainstream in painting lines for vehicles such as automobiles. As an example of a configuration related to this robotic painting, for example, Patent Document 1 discloses the following configuration. Patent Document 1 discloses a technology for the painting robot that, when there is a discharge defect in a nozzle, vibrates the head to cover the location of the discharge defect. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-052170 Summary of the Invention [Problem to be solved by the invention]

[0004] The configuration disclosed in Patent Document 1 can prevent white streaks and the like that occur when no coating is applied at all. However, since the coating thickness tends to decrease near areas with poor coating, it is difficult to improve the coating quality.

[0005] The present invention has been made in light of the above circumstances, and has as its object to provide a painting robot that can suppress a decrease in paint film thickness and improve painting quality. [Means for solving the problem]

[0006] In order to solve the above problems, according to a first aspect of the present invention, there is provided a painting robot for painting a part of a vehicle, the robot comprising: a paint head unit having a paint head with a plurality of nozzles for ejecting paint droplets and a piezoelectric substrate for forcing the droplets out of the nozzles when driven; a robot arm having the paint head unit attached to its tip and for moving the paint head unit to a desired position; a head control unit for controlling the operation of the piezoelectric substrate of the paint head; and a control unit having a robot arm control unit for controlling the operation of the robot arm, the head control unit being configured to, when a specific nozzle is determined to be a defective nozzle that is defective in ejecting droplets during painting on a vehicle, display a dot around the defective nozzle corresponding to the defective nozzle. The painting robot performs recovery control to control the driving of the piezoelectric substrate so that the droplet size of good dots corresponding to good nozzles that have no problem with droplet ejection increases, and in the recovery control, when good dots around a defective dot have reached the boundary of the painting range in the painting area, boundary ejection control is performed to make the droplet size of the good dots equivalent to the droplet size in the normal ejection state when recovery control is not performed, while for good dots around the defective dot that are located inside the painting range beyond the boundary, non-boundary ejection control is performed to make the droplet size of the good dots larger than that of the good dots in the normal ejection state. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a painting robot that can suppress a decrease in paint film thickness and improve painting quality. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing the overall configuration of a painting robot according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram showing a schematic configuration of a painting system including the painting robot shown in FIG. [Figure 3]2 is a front view of a nozzle forming surface that ejects paint, of a paint head unit provided in the paint robot shown in FIG. 1. FIG. [Figure 4] 2 is a diagram showing a schematic configuration for supplying paint to each nozzle in the painting robot shown in FIG. 1. FIG. [Figure 5] 2 is a cross-sectional view showing the configuration of the vicinity of a column-directional supply flow path, a nozzle pressurizing chamber, and a column-directional discharge flow path in the painting robot shown in FIG. 1. FIG. [Figure 6] 4 is a plan view showing the configuration of a nozzle formation surface of another paint head unit different from the paint head unit shown in FIG. 3. FIG. [Figure 7] 2A and 2B are diagrams showing the state of dots when painting is performed by the painting robot shown in FIG. 1, where (a) shows the state of the dots before recovery control is performed, and (b) shows the state of the dots after recovery control is performed. [Figure 8] 1A and 1B are diagrams showing the state of dots when painting near the boundary B1 of the painting range by the painting robot shown in FIG. 1, where (a) shows the state of the dots before boundary discharge control is performed, and (b) shows the state of the dots after boundary discharge control is performed. [Figure 9] (a) shows the painted area of ​​the vehicle as seen from the side, and (b) shows the arrangement of dots in the area surrounded by dashed line A in (a). [Figure 10] (a) shows the painted area of ​​the vehicle as seen from the side, and (b) shows the arrangement of dots in the area surrounded by dashed line A in (a). [Figure 11] 2 is a diagram showing a state in which an overlapping area is provided between a first painting pass and a second painting pass when painting is performed by the painting robot shown in FIG. 1. FIG. [Figure 12] 10A shows the state of dots before boundary discharge control is performed, and FIG. 10B shows the state of dots when small-sized droplets are discharged using boundary discharge control. [Figure 13] FIG. 1(a) is a diagram showing a state in which a faulty nozzle is located above the paint head, and FIG. 1(b) is a diagram showing a state in which the paint head is rotated in the state shown in FIG. [Figure 14] 2 is a diagram showing a state in which the number of defective nozzles exceeds a predetermined threshold in the painting head of the painting robot shown in FIG. 1. FIG. [Figure 15] This shows a modified example of the present invention in which when two defective dots are adjacent to each other, the droplet sizes of the surrounding good dots are increased. [Figure 16] This shows a modified example of the present invention in which the droplet size of not only the good dot immediately adjacent to the defective dot but also the good dot adjacent to the defective dot is increased. DETAILED DESCRIPTION OF THE INVENTION

[0009] A painting robot 10 according to one embodiment of the present invention will be described below with reference to the drawings. In the following description, where necessary, the X direction will be taken as the longitudinal direction of the nozzle forming surface 52 (painting head 53), the X1 side will be taken as the right side in Fig. 3, and the X2 side will be taken as the left side in Fig. 3. The Y direction will be taken as the lateral direction (width direction) of the nozzle forming surface 52 (painting head 53), the Y1 side will be taken as the upper side in Fig. 3, and the Y2 side will be taken as the lower side in Fig. 3.

[0010] (1. Overview of Painting Robot 10) The painting robot 10 of this embodiment "paints" objects to be painted, such as vehicles or vehicle parts (hereinafter, vehicle parts that are part of a vehicle will also be described as vehicles) located on a painting line in an automobile manufacturing factory, and its purpose is to form a paint film on the surface of the object to be painted to protect the surface and provide a beautiful appearance. Therefore, it is necessary to paint vehicles moving along the painting line at predetermined intervals within a certain time with the desired painting quality.

[0011] Furthermore, the painting robot 10 of this embodiment is capable of not only forming the above-described coating film but also forming various designs and images on objects to be painted, such as vehicles and vehicle parts. Note that the objects to be painted are not limited to vehicles and vehicle parts, but may be any other parts other than automobiles (for example, exterior parts of airplanes and trains) that require painting.

[0012] (1-1. Overall Configuration of Painting System 1 and Painting Robot 10) Fig. 1 is a schematic diagram showing the overall configuration of a painting robot 10 according to an embodiment of the present invention. Fig. 2 is a diagram showing the schematic configuration of a painting system 1 including the painting robot 10 shown in Fig. 1. As shown in Fig. 2, the painting system 1 includes the painting robot 10 and an image processing device 200.

[0013] (1-2. About Painting Robot 10) As shown in Fig. 1, the painting robot 10 mainly comprises a robot body 20 and a painting head unit 50. The painting robot 10 shown in Fig. 1 is, as an example, a six-axis vertical articulated robot, but the painting robot 10 may be any type of robot, such as a vertical articulated type other than six axes, a horizontal articulated type, or an Cartesian robot.

[0014] (1-3. About the robot body 20) 1, the robot main body 20 mainly comprises a base 21, first to sixth rotation shafts 22a to 22f, legs 23, a first rotating arm 24, a second rotating arm 25, a rotating arm 26, a wrist 27, and motors M1 to M6 (see FIG. 2) that drive these components. The portion from the legs 23 to the wrist 27 corresponds to the robot arm R1, but other portions such as the base 21 may also correspond to the robot arm R1.

[0015] Of these, the base 21 is a part that is installed on an installation site such as a floor, but the base 21 may be movable relative to the installation site. The legs 23 are parts that stand upward from the base 21 and are provided so as to be rotatable relative to the base 21 via a first rotation shaft 22a driven by a motor M1 (see FIG. 2). The legs 23 may also be configured not to rotate relative to the base 21.

[0016] A first rotating arm 24 is provided at the upper end of leg 23 so as to be rotatable via second rotating shaft 22b when driven by motor M2. Furthermore, a second rotating arm 25 is provided at the tip end of first rotating arm 24 so as to be rotatable via third rotating shaft 22c when driven by motor M3.

[0017] A rotating arm 26 is provided at the tip of the second rotating arm 25, rotatably about the center axis of the second rotating arm 25. This rotating arm 26 is rotatable via a fourth rotating shaft 22d when driven by a motor M4. A wrist unit 27 is provided at the tip of the rotating arm 26. This wrist unit 27 is capable of rotational movement around a plurality of, e.g., two, differently oriented shafts when driven by motors M5 and M6. In FIG. 1, the rotational shafts capable of this rotational movement are designated as a fifth rotating shaft 22e and a sixth rotating shaft 22f, respectively. This allows for precise control of the orientation of the painting head unit 50. The number of shafts may be any number greater than two.

[0018] Furthermore, the painting head unit 50 is attached to the wrist portion 27, but this painting head unit 50 may be provided so as to be detachable from the wrist portion 27.

[0019] (1-4. Regarding the paint supply unit 40) As shown in Fig. 2, the painting system 1 and the painting robot 10 are provided with a paint supply unit 40. The paint supply unit 40 is a part for supplying paint toward the painting head unit 50. For this purpose, the paint supply unit 40 includes a supply path 41 (see Fig. 4) for supplying paint from a paint reservoir (not shown), a pump (not shown), a valve (not shown), and a return flow path 42 for recovering unspent paint.

[0020] In addition, when a configuration is adopted in which paint is supplied from outside the painting robot 10, the painting robot 10 does not need to have a part for storing paint, and may have a part for storing paint outside the painting robot 10.

[0021] (1-5. About the painting head unit 50) Next, the paint head unit 50 will be described. FIG. 3 is a front view of the nozzle forming surface 52 of the paint head unit 50, from which paint is ejected. As shown in FIG. 3, the paint head unit 50 is equipped with a head cover (not shown), and various components are housed within the head cover. As shown in FIG. 3, the nozzle forming surface 52 is provided with a plurality of nozzle rows 55, in which nozzles 54 are arranged in a direction inclined with respect to the longitudinal direction of the paint head unit 50. In this embodiment, the nozzle rows 55 include a first nozzle row 55A located on one side (Y2 side) in the main scanning direction (Y direction) and a second nozzle row 55B located on the other side (Y1 side) in the main scanning direction.

[0022] When discharging paint, the drive timing of each nozzle 54 is controlled so that droplets discharged from nozzles 54 in the second nozzle row 55B land between droplets discharged from adjacent nozzles 54 in the first nozzle row 55A, thereby improving dot density during coating.

[0023] 3, a single paint head 53 is present on the nozzle forming surface 52. However, the nozzle forming surface 52 may also have a head group made up of a plurality of paint heads 53. In this case, one example is a configuration in which the plurality of paint heads 53 are aligned and arranged in a staggered pattern, but the arrangement of the paint heads 53 in the head group does not have to be staggered.

[0024] Fig. 4 is a diagram showing a schematic configuration for supplying paint to each nozzle 54. Fig. 5 is a cross-sectional view showing the configuration in the vicinity of the column-directional supply flow channel 58, the nozzle pressurizing chamber 59, and the column-directional discharge flow channel 60. As shown in Figs. 4 and 5, the coating head 53 is equipped with a large supply flow channel 57, a column-directional supply flow channel 58, the nozzle pressurizing chamber 59, a column-directional discharge flow channel 60, and a large discharge flow channel 61. The large supply flow channel 57 is a flow channel through which paint is supplied from the supply channel 41. The column-directional supply flow channel 58 is a flow channel into which the paint in the large supply flow channel 57 is diverted.

[0025] Furthermore, the nozzle pressurizing chambers 59 are connected to the column-directional supply channels 58 via the nozzle supply channels 59a. As a result, paint is supplied to the nozzle pressurizing chambers 59 from the column-directional supply channels 58. The nozzle pressurizing chambers 59 are provided in a number corresponding to the number of nozzles 54, and the paint inside can be ejected from the nozzles 54 using a piezoelectric substrate 62, which will be described later.

[0026] The nozzle pressurizing chamber 59 is also connected to the column-directional discharge flow path 60 via the nozzle discharge flow path 59b. Therefore, paint not ejected from the nozzle 54 is discharged from the nozzle pressurizing chamber 59 to the column-directional discharge flow path 60 via the nozzle discharge flow path 59b. The column-directional discharge flow path 60 is also connected to a large discharge flow path 61. The large discharge flow path 61 is a flow path where the paint discharged from each column-directional discharge flow path 60 joins together. This large discharge flow path 61 is connected to the return flow path 42.

[0027] With this configuration, paint supplied from the supply passage 41 passes through the supply-side large flow passage 57, the column-directional supply flow passage 58, the nozzle supply flow passage 59a, and the nozzle pressurizing chamber 59, before being ejected from the nozzle 54. Furthermore, paint that is not ejected from the nozzle 54 passes from the nozzle pressurizing chamber 59 through the nozzle discharge flow passage 59b, the column-directional discharge flow passage 60, and the discharge-side large flow passage 61, and is returned to the return flow passage 42.

[0028] 4, one column-directional supply flow path 58 is arranged to correspond to one column-directional discharge flow path 60. However, a plurality of (for example, two) column-directional discharge flow paths 60 may be arranged to correspond to one column-directional supply flow path 58. Also, a plurality of column-directional supply flow paths 58 may be arranged to correspond to one column-directional discharge flow path 60.

[0029] 5, a piezoelectric substrate 62 is disposed on the ceiling surface of the nozzle pressurizing chamber 59 (the surface opposite to the nozzle 54). The piezoelectric substrate 62 includes two piezoelectric ceramic layers 63a and 63b, which are piezoelectric bodies, and further includes a common electrode 64 and an individual electrode 65. The piezoelectric ceramic layers 63a and 63b are members that can expand and contract when a voltage is applied from the outside. Ferroelectric ceramic materials such as lead zirconate titanate (PZT), NaNbO3, BaTiO3, (BiNa)NbO3, and BiNaNb5O15 can be used for the piezoelectric ceramic layers 63a and 63b.

[0030] As shown in FIG. 5, the common electrode 64 is disposed between the piezoelectric ceramic layer 63a and the piezoelectric ceramic layer 63b. A surface electrode (not shown) for the common electrode is formed on the upper surface of the piezoelectric substrate 62. The common electrode 64 and the surface electrode for the common electrode are electrically connected through a through conductor (not shown) in the piezoelectric ceramic layer 63a. The individual electrodes 65 are disposed in positions facing the nozzle pressurizing chamber 59. The portion of the piezoelectric ceramic layer 63a sandwiched between the common electrode 64 and the individual electrode 65 is polarized in the thickness direction. Therefore, when a voltage is applied to the individual electrode 65, the piezoelectric ceramic layer 63a is distorted due to the piezoelectric effect. Therefore, when a predetermined drive signal is applied to the individual electrode 65, the piezoelectric ceramic layer 63b moves relatively to the nozzle pressurizing chamber 59, reducing the volume of the nozzle pressurizing chamber 59, thereby ejecting paint.

[0031] 5, the common electrode 64 is arranged on the ceiling surface of the nozzle pressurizing chamber 59, but the common electrode 64 is not limited to being arranged on the ceiling surface of the nozzle pressurizing chamber 59 as shown in Fig. 5. For example, the common electrode 64 may be arranged on a side surface of the nozzle pressurizing chamber 59 (a surface perpendicular or nearly perpendicular to the ceiling surface), or any other configuration may be adopted as long as the paint can be ejected from the nozzle 54 satisfactorily.

[0032] (1-6. Other configurations of the painting head unit) Next, another configuration of the paint head unit 50 will be described. FIG. 6 is a plan view showing the configuration of the nozzle formation surface 52 of another paint head unit 50. As shown in FIG. 6, a nozzle row 55 may be formed by arranging a plurality of nozzles 54 along the short side direction (width direction; Y direction) of the paint head 53. Note that in the configuration shown in FIG. 6, the nozzle row 55 is formed by arranging a plurality of nozzles 54 along the short side direction (width direction; main scanning direction) of the paint head 53. However, a configuration in which only one (single) nozzle 54 is arranged in the short side direction (width direction; main scanning direction) of the paint head 53 may also be used. In other words, the nozzle row 55 may be formed by a single nozzle 54.

[0033] Furthermore, when painting a vehicle using a paint head 53 such as that shown in Fig. 6, painting may be performed with the longitudinal direction of the paint head 53 slightly tilted relative to the main scanning direction of the paint head 53. For example, in the configuration of the paint head 53 shown in Fig. 3, if the nozzle rows 55 are tilted at a predetermined angle relative to the main scanning direction, then the shorter side of the paint head 53 shown in Fig. 6 can be tilted at a predetermined angle relative to the main scanning direction of the paint head 53. When tilted in this way, painting equivalent to that achieved by the paint head 53 shown in Fig. 3 can be achieved simply by adjusting the timing at which paint is ejected from each nozzle 54.

[0034] (1-7. Control configuration of painting system 1) Next, a description will be given of the control configuration for controlling the operation of the painting system 1. The control configuration described below corresponds to the control unit. As shown in FIG. 2, the painting robot 10 includes a robot arm control unit 70, a paint supply control unit 80, a head control unit 90, a main control unit 100, a position sensor 110, and an inclination sensor 120. The painting robot 10 is connected to an image processing device 200, thereby constituting the painting system 1.

[0035] The robot arm control unit 70, paint supply control unit 80, head control unit 90, main control unit 100, and image processing unit 210 (described later) are configured with a CPU (Central Processing Unit), memories such as storage units (ROM (Read Only Memory), RAM (Random Access Memory), non-volatile memory, etc.), and other elements. The image processing unit 210 may use a GPU (Graphics Processing Unit) together with or instead of a CPU with excellent image processing performance.

[0036] The painting robot 10 also includes various sensors (not shown), and the outputs from these sensors are input to one of the robot arm control unit 70, the paint supply control unit 80, the head control unit 90, and the main control unit 100. Examples of the various sensors include acceleration sensors, angular velocity sensors, position detection sensors that detect the position of each driving unit, and image sensors, but other sensors may also be used.

[0037] Of these, the robot arm control unit 70 is a part that controls the driving of the above-mentioned motors M1 to M6. The robot arm control unit 70 is provided with a memory 71, which stores programs and data created by robot teaching.

[0038] The robot arm control unit 70 controls the driving of the motors M1 to M6 based on the programs and data stored in the memory 71 and the image processing by the image processing unit 210 of the image processing device 200. This control allows the paint head unit 50 to pass through desired positions for painting at a desired speed and to stop at a predetermined position.

[0039] The memory 71 stores data on the trajectory of the paint head 53 (trajectory data), which is created by robot teaching that takes into account the paint width that can be painted by the paint head 53, and posture data on the posture, such as the tilt of the paint head 53. The memory 71 may be provided in the paint robot 10, but it may also be external to the paint robot 10, and information may be sent and received to the memory 71 via wired or wireless communication means.

[0040] The paint supply control unit 80 is a part that controls the supply of paint to the paint head unit 50, and specifically controls the operation of the pumps, valves, etc. provided in the paint supply unit 40. It is preferable that the paint supply control unit 80 controls the operation of the pumps and valves so that paint is supplied at a constant pressure to the paint head unit 50 to which paint is supplied. The paint supply control unit 80 corresponds to a pressure control unit.

[0041] The head control unit 90 also controls the operation of the piezoelectric substrate 62 in the paint head unit 50 based on image processing by the image processing unit 210. When the head control unit 90 reaches a predetermined position in the trajectory data using position detection means such as a position sensor 110 and tilt sensor 120 (described below), it controls the discharge of paint based on the divided paint data corresponding to that position and the paint pass. In this case, the drive frequency of the piezoelectric substrate 62 is controlled to control the number of dots (number of droplets) discharged from the nozzle 54, and the deformation amount of the piezoelectric substrate 62 is controlled based on the drive frequency and / or voltage applied to the piezoelectric substrate 62, thereby controlling the size of the droplets discharged from the nozzle 54, so as to achieve a uniform film thickness on the vehicle.

[0042] When controlling the droplet size by controlling the deformation amount of the piezoelectric substrate 62 based on the drive frequency applied to the piezoelectric substrate 62, the droplet size is largest when the piezoelectric substrate 62 is driven at a drive frequency that matches the natural frequency of the piezoelectric substrate 62. Therefore, the droplet size can be controlled to become smaller as the applied drive frequency deviates from the natural frequency. Furthermore, when controlling the droplet size by controlling the deformation amount of the piezoelectric substrate 62 based on the voltage applied to the piezoelectric substrate 62, the droplet size can be controlled to become larger as the voltage applied to the piezoelectric substrate 62 increases.

[0043] In addition, the main control unit 100 is a part that sends predetermined control signals to the above-mentioned robot arm control unit 70, paint supply control unit 80, and head control unit 90 so that the above-mentioned motors M1 to M6, paint supply unit 40, and piezoelectric substrate 62 work together to paint the object to be painted.

[0044] The position sensor 110 is a sensor that detects the current position of the paint head 53. Various sensors such as a rotary encoder, a resolver, or a laser sensor can be used as the position sensor 110. The tilt sensor 120 is a sensor that detects the tilt angle of the paint head 53. Various sensors such as a gyro sensor, an acceleration sensor, or a tilt sensor can be used as the tilt sensor 120.

[0045] The painting system 1 is also provided with an image processing device 200. The image processing device 200 includes an image processing unit 210 and a memory 220. The image processing unit 210 is a part that creates image data for each painting pass, which is a path along which the painting head 53 performs painting.

[0046] The memory 220 stores image data for each painting pass in accordance with the painting sequence.

[0047] The image processing device 200 corresponds to, for example, a computer, but the computer may be a component of the painting robot 10 or may be provided separately from the painting robot 10. When the image processing device 200 is provided separately from the painting robot 10, data is transmitted and received between the image processing device 200 and the painting robot 10 via wired or wireless communication. Even if the image processing device 200 is provided separately from the painting robot 10, it may or may not be included in the concept of the painting robot 10.

[0048] (2. Droplet ejection control) In the coating system 1 and coating robot 10 configured as described above, the head control unit 90 drives the piezoelectric substrate 62 in response to a command from the main control unit 100 to eject paint onto the object to be coated and print a predetermined test pattern (not shown). This test pattern is used to check for missing paint ejection from the nozzles 54, as is commonly done in inkjet printers. By checking this test pattern, it is possible to determine which nozzle 54 is experiencing a paint ejection failure.

[0049] After printing the above test pattern, a camera (not shown) is operated to capture an image of the test pattern and obtain image data in response to a command from the main control unit 100. The image data is then sent via wireless or wired communication to the image processing device 200, which compares the image data with the image data for determination and extracts unpainted lines from the test pattern, thereby identifying nozzles 54 that are defective in ejecting droplets (defective nozzles 54a in FIG. 3).

[0050] (a) Basic control in recovery control If a defective nozzle 54a is identified as described above, the head control unit 90 performs recovery control (basic recovery control) to compensate for the defective nozzle 54a when painting a vehicle, in response to a command from the main control unit 100. Here, Figure 7 is a diagram showing the state of dots when painting, where (a) shows the state of the dots before recovery control is performed, and (b) shows the state of the dots after recovery control is performed.

[0051] 7(b), this recovery control controls the driving of the piezoelectric substrate 62 so that the droplet size of the good dot D2 (i.e., the droplet ejection portion) corresponding to the nozzle 54 that has no problem ejecting droplets (hereinafter referred to as the good nozzle 54b) that is the dot surrounding the defective dot D1 (i.e., the portion where the droplet does not eject) corresponding to the defective nozzle 54a is increased. Therefore, compared to the case of FIG. 7(a) where recovery control is not performed, it is possible to prevent the formation of paint voids due to the presence of the defective dot D1.

[0052] (b) Boundary discharge control and non-boundary discharge control at the coating area Figure 8 shows the state of dots when painting near the boundary B1 of the painting range, where (a) shows the state of the dots before boundary discharge control is performed, and (b) shows the state of the dots after boundary discharge control is performed.

[0053] As shown in Figure 8(a), when a good dot D2 surrounding a bad dot D1 reaches the boundary B1 (edge) of the coating area in the coating area CP1 (see Figure 9), if the basic recovery control described above is performed, the presence of dots formed by the impact of large droplets makes the coating resolution at the boundary B1 appear coarse, giving the impression that the coating quality has deteriorated.

[0054] Therefore, as shown in Figure 8(b), the head control unit 90 controls the operation of the piezoelectric substrate 62 so that the size of the droplets at the good dots D2 that have reached the boundary B1 of the coating range becomes the same as the droplet size in the normal ejection state when recovery control is not performed (corresponding to boundary ejection control).

[0055] On the other hand, for good dots D2 that are present around the defective dot D1 and are located inside the coating area (non-boundary) rather than the boundary B1 of the coating area, the head control unit 90 controls the operation of the piezoelectric substrate 62 to increase the droplet size (corresponding to non-boundary ejection control).

[0056] This control makes it possible to prevent a deterioration in coating quality at the boundary B1 of the coating range. Also, for non-boundary good dots D2, the drive of the piezoelectric substrate 62 is controlled to increase the droplet size, so that the defective dots D1 corresponding to the defective nozzle 54a are covered, making it possible to prevent a deterioration in coating quality.

[0057] (c) Regarding the inclination of the painted area As shown in Figure 9(a), when the vehicle coating area CP1 is horizontal or within a predetermined inclination angle range close to the horizontal, the dots of the landing droplets do not flow significantly downward. Note that in Figure 9(a), (a) shows the vehicle coating area CP1 as viewed from the side, and (b) shows the arrangement of dots (defective dot D1 and good dots D2) in the area surrounded by dashed line A in (a). In such a case, as shown in Figure 9(b), the head control unit 90 controls the operation of the piezoelectric substrate 62 so that the droplet size of the multiple good dots D2 surrounding the defective dot D1 is larger than the good dots D2 under normal ejection conditions.

[0058] On the other hand, as shown in Figure 10(a), if the vehicle coating area CP1 is tilted at an angle greater than a predetermined angle, the landing droplets are likely to flow downward. In such a case, as shown in Figure 10(b), the head control unit 90 controls the operation of the piezoelectric substrate 62 so that, for multiple good dots D2 surrounding a defective dot D1, the good dot D2 located above the defective dot D1 has the largest droplet size among the surrounding good dots D2. Note that in Figure 10(a), Figure 10(a) shows the vehicle coating area CP1 as viewed from the side, and Figure 10(b) shows the arrangement of the dots (defective dots D1 and good dots D2) in the area surrounded by dashed line A in Figure 10(a).

[0059] Therefore, when paint flows from the droplet of the good dot D2 downward, the bad dot D1 can be covered with the flowing paint.

[0060] In addition, for a good dot D2 that is not located above the bad dot D1, even if paint flows from the droplet of the good dot D2, the flowing paint cannot cover the bad dot D1. In this case, the head control unit 90 controls the operation of the piezoelectric substrate 62 so that the droplet size of the good dot D2 is larger than in the normal ejection state (however, it is preferable that it is smaller than the good dot D2 located above), or so that the droplet size is the same as in the normal ejection state.

[0061] (d) Complementary control by overlapping region OL 11 shows a state in which an overlap area OL is provided between the first painting pass P1 and the second painting pass P2. As shown in FIG. 11, depending on the droplet size control within the first painting pass P1, it is possible that the defective dot D1 remains and the painting defect due to the defective dot D1 is not resolved. When it is determined that the defective dot D1 remains within the first painting pass P1, the head control unit 90, in response to a command from the main control unit 100, performs complementary control to provide an overlap area OL that overlaps with the first painting pass P1 in the next painting pass, the second painting pass P2, and to provide a non-defective dot D2 that overlaps with the defective dot D1 within the overlap area OL.

[0062] Therefore, the remaining defective dots D1 are covered with the non-defective dots D2, so that it is possible to prevent the paint from coming off at the locations of the remaining defective dots D1.

[0063] (e) Discharge of small droplets using boundary discharge control 12, (a) shows the state of the dots before boundary discharge control is performed, and (b) shows the state of the dots when small-sized droplets are discharged using boundary discharge control. As shown in Fig. 12, when a good dot D2 surrounding a bad dot D1 has reached the boundary B1 of the coating range in the coating area CP1, the head control unit 90 may control the piezoelectric substrate 62, in response to a command from the main control unit 100, to change the size of the droplets of the good dots D2 to a droplet size smaller than that of the droplet size in the normal discharge state.

[0064] When controlled in this manner, the resolution of the coating becomes higher at the boundary B1 of the coating range, making it possible to improve the coating quality.

[0065] (f) Rotation of the painting head 53 13A shows a state in which the defective nozzle 54a is located above the paint head 53, and FIG. 13B shows a state in which the paint head 53 is rotated in the state shown in FIG. 13A. As shown in FIG. 13A, during recovery control, when the vehicle's painting area CP1 is tilted beyond a predetermined inclination angle, it is possible that no good dot D2 exists above the defective dot D1, for example, because the defective nozzle 54a is located above the nozzle forming surface 52. If it is determined that no good dot D2 exists above the defective dot D1, the robot arm control unit 70 may control the operation of the robot arm R1 to rotate the paint head unit 50 while maintaining it parallel to the painting area CP1, as shown in FIG. 13B.

[0066] When controlled in this manner, the rotation of the paint head unit 50 makes it possible to position the good dot D2 above the bad dot D1, thereby preventing a decrease in paint quality.

[0067] (g) Moving speed of the painting head unit 50 FIG. 14 is a diagram showing a state in which the number of defective nozzles 54a exceeds a predetermined threshold. While FIG. 14 shows six defective nozzles 54a as a state in which the predetermined threshold has been exceeded, the number is not limited to six. As shown in FIG. 14, it is also possible that the number of defective dots D1 corresponding to the defective nozzles 54a in the paint head 53 exceeds the predetermined threshold. In such a case, the robot arm control unit 70 may control the operation of the robot arm R1 so that the movement speed of the paint head unit 50 during recovery control is slower than when the movement speed does not exceed the predetermined threshold.

[0068] In this case, the painting head unit 50 moves at a slower speed than normal, so it is possible to increase the amount of droplets in the good dots D2 that surround the defective dot D1, making it possible to cover the defective dot D1.

[0069] (3. Supplementary Note) The contents described in the above-described embodiment can be understood, for example, as follows. [1] That is, the painting robot 10 that paints the painting area CP1 of the vehicle comprises a painting head unit 50 having a plurality of nozzles 54 that eject droplets of paint, a painting head 53 that has a piezoelectric substrate 62 that is driven to push the droplets out of the nozzles 54, a robot arm R1 that has the painting head unit 50 attached to its tip and moves the painting head unit 50 to a desired position, and a control unit that includes a head control unit 90 that controls the operation of the piezoelectric substrate 62 of the painting head 53, and a robot arm control unit 70 that controls the operation of the robot arm R1.

[0070] When a particular nozzle 54 is determined to be a defective nozzle 54a that is defective in droplet ejection during vehicle painting, the head control unit 90 performs recovery control to control the drive of the piezoelectric substrate 62 so that the droplet size of the good dot D2 that is a dot surrounding the defective dot D1 corresponding to the defective nozzle 54a and that corresponds to a good nozzle 54b that has no problems with droplet ejection is increased.In the recovery control, when the good dots D2 surrounding the defective dot D1 have reached the boundary B1 of the painting range in the painting area CP1, boundary ejection control is performed to change the droplet size of the good dots D2 to the same droplet size as in the normal ejection state when recovery control is not performed, and non-boundary ejection control is performed to change the droplet size of the good dots D2 surrounding the defective dot D1 that are located inside the painting range beyond the boundary B1 so that the droplet size of the good dots D2 is larger than that of the good dots D2 in the normal ejection state.

[0071] In this way, by performing recovery control, good dots D2 are arranged around the defective dot D1, which makes it possible to suppress a decrease in coating thickness and improve coating quality. Furthermore, by performing boundary discharge control at the boundary B1 of the coating range, it is possible to suppress a decrease in coating resolution at the boundary B1 of the coating range, thereby preventing a decrease in coating quality. Furthermore, for the non-boundary defective dot D1, non-boundary discharge control is performed, in which the drive of the piezoelectric substrate 62 is controlled to increase the droplet size, so that the defective dot D1 corresponding to the defective nozzle 54a is covered, making it possible to suppress a decrease in coating quality.

[0072] [2] In addition to the contents described in [1] above, in the above embodiment, the head control unit 90 may, in the recovery control, (A) when the vehicle's painted area CP1 is horizontal or within a predetermined inclination angle range close to the horizontal, control the piezoelectric substrate 62 so that the droplet size of the multiple good dots D2 around the defective dot D1 is larger than that of the good dots D2 in a normal ejection state, and (B) when the vehicle's painted area CP1 is inclined beyond the predetermined inclination angle, control the piezoelectric substrate 62 so that, among the multiple good dots D2 around the defective dot D1, the good dot D2 located above the defective dot D1 has the largest droplet size among the good dots D2 around the defective dot D1, while controlling the piezoelectric substrate 62 so that, for the good dots D2 located other than above the defective dot D1, the droplet size of the good dot D2 is larger than that in a normal ejection state or is the same as that in a normal ejection state.

[0073] When controlled in this manner, if the vehicle's coating area CP1 is horizontal or within a predetermined range of inclination angles close to the horizontal, the dots of droplets that land will not flow downwards much, so by controlling the operation of the piezoelectric substrate 62 so that the droplet size of multiple good dots D2 (not limited to those on the upper side) surrounding the bad dot D1 is larger than the good dots D2 in normal ejection conditions, it is possible to cover the bad dot D1 corresponding to the bad nozzle 54a and prevent a deterioration in coating quality.

[0074] In this way, when the paint area CP1 of the vehicle is tilted beyond a predetermined tilt angle, the operation of the piezoelectric substrate 62 is controlled so that the droplet size of the good dot D2 located above the defective dot D1 is the largest among the surrounding good dots D2. As a result, when paint flows from the droplet of the good dot D2 from above to below, the flowing paint can cover the defective dot D1, making it possible to prevent a deterioration in paint quality.

[0075] Furthermore, for good dots D2 that are not located above the defective dot D1, even if paint flows from the droplets of the good dots D2, the flowing paint cannot cover the defective dot D1. For this reason, by controlling the operation of the piezoelectric substrate 62 so that the droplet size of the good dots D2 is larger than in the normal ejection state (however, it is preferable that it is smaller than the good dots D2 located above), or so that the droplet size is the same as in the normal ejection state, it is possible to suppress fluctuations in the paint film thickness and prevent a deterioration in paint quality.

[0076] [3] In addition to the above-described embodiments, in addition to the contents described in [1] and [2] above, or a combination thereof, when the head control unit 90 determines during recovery control that there is a defective dot D1 whose painting defect caused by the defective nozzle 54a cannot be eliminated by controlling the droplet size within the first painting pass P1, which is the same painting pass, the head control unit 90 may perform complementary control to provide an overlap area OL that overlaps with the first painting pass P1 in the next painting pass, the second painting pass P2, and to provide a good dot D2 that overlaps with the defective dot D1 within the overlap area OL.

[0077] By doing this, the defective dots D1 remaining in the first painting pass P1 are covered with the good dots D2, which makes it possible to prevent the paint from being missing from the areas of the remaining defective dots D1, thereby preventing a deterioration in painting quality.

[0078] [4] Furthermore, in the above embodiment, in addition to any of the above items [1] to [3] or a combination thereof, in the boundary ejection control in the recovery control, the head control unit 90 may control the piezoelectric substrate 62 so that the droplet size of the good dot D2 is smaller than that in the normal ejection state, instead of being the same as that in the normal ejection state.

[0079] By controlling in this way, it is possible to increase the resolution of the coating at the boundary B1 of the coating range, thereby improving the coating quality.

[0080] [5] In addition to any of the above-mentioned embodiments [1] to [4] or a combination thereof, the robot arm control unit 70 may control the operation of the robot arm R1 during recovery control so that the paint head unit 50 rotates while maintaining parallelism with the paint area CP1 when the paint area CP1 of the vehicle is tilted beyond a predetermined tilt angle and it is determined that there are no good dots D2 located above the bad dots D1.

[0081] By controlling in this way, it is possible to position the good dots D2 above the defective dots D1 by rotating the paint head unit 50. This allows paint to flow from the good dots D2 toward the defective dots D1, covering the defective dots D1, and prevents a decrease in paint quality.

[0082] [6] In addition to any of the above-mentioned items [1] to [5] or a combination thereof, in the above-mentioned embodiment, when it is determined that the number of defective dots D1 corresponding to defective nozzles 54a in the paint head 53 exceeds a predetermined threshold, the robot arm control unit 70 may control the operation of the robot arm R1 so that the movement speed of the paint head unit 50 in recovery control is slower than when the movement speed does not exceed the predetermined threshold.

[0083] When controlled in this way, the paint head 53 passes over the good dots D2 and the defective dots D1 slower than the normal movement speed of the paint head 53. This makes it possible to increase the amount of droplets on the good dots D2 surrounding the defective dot D1, making it possible to cover the defective dot D1. This makes it possible to prevent a decrease in paint quality.

[0084] (4. Modifications) Although one embodiment of the present invention has been described above, the present invention can be modified in various ways other than the above embodiment. Modifications will be described below.

[0085] In the above-described embodiment, painting may be performed by applying a slight vibration to the paint head 53. By applying a slight vibration to the paint head 53 in this way, it becomes possible to land paint on the defective dot D1.

[0086] Furthermore, in the recovery control in the above-described embodiment, when there is one defective dot D1, the driving of the piezoelectric substrate 62 of the corresponding good dot D2 is controlled so that the droplet size of the corresponding good dot D2 around the defective dot D1 is increased. However, in the recovery control, even if there are multiple adjacent defective dots D1, the driving of the piezoelectric substrate 62 may be controlled so that the droplet size of the surrounding good dots D2 is increased, thereby preventing paint defects and deterioration of paint quality.

[0087] An example of such a situation is shown in Figure 15. Figure 15 shows a situation in which two defective dots D1 are adjacent to each other, and good dots D2 with larger droplet sizes are placed around them as a result of recovery control. Note that while Figure 15 shows a situation in which two defective dots D1 are adjacent to each other, recovery control can be performed to increase the droplet sizes of the good dots D2 around them, even if three or more defective dots D1 are adjacent to each other, as long as no paint voids occur.

[0088] Furthermore, in the recovery control in the above-described embodiment, the driving of the piezoelectric substrate 62 of the corresponding good dot D2 adjacent to the defective dot D1 is controlled so that the droplet size of the corresponding good dot D2 is increased. However, if paint voids can be prevented, the droplet size may be increased not only for the good dot D2 immediately adjacent to the defective dot D1, but also for the good dots D2 adjacent to that good dot D2, as shown in Figure 16, for example. Furthermore, the droplet size of the good dot D2 immediately adjacent to the defective dot D1 may be normal, but the droplet size of the good dot D2 adjacent to that normal-sized good dot D2 may be increased. Furthermore, the droplet size of any of the good dots D2 present within a predetermined range from the defective dot D1 may be increased. [Explanation of symbols]

[0089] 1...painting system, 10...painting robot, 20...robot body, 21...base, 22a...first rotating shaft, 22b...second rotating shaft, 22c...third rotating shaft, 22d...fourth rotating shaft, 22e...fifth rotating shaft, 22f...sixth rotating shaft, 23...leg, 24...first rotating arm, 25...second rotating arm, 26...rotating arm, 27...wrist section, 40...paint supply section, 41...supply path, 42...return path, 50...painting head unit, 52...nozzle forming surface, 53...painting head, 54...nozzle, 54a...faulty nozzle, 54b...good nozzle, 55...nozzle row, 55A...first nozzle row, 55B...second nozzle row, 57...supply-side large flow path, 58...row-direction supply flow path, 59...nozzle pressurization chamber, 59a ...Nozzle supply flow path, 59b...Nozzle discharge flow path, 60...Column-direction discharge flow path, 61...Discharge-side large flow path, 62...Piezoelectric substrate, 63a...Piezoelectric ceramic layer, 63b...Piezoelectric ceramic layer, 64...Common electrode, 65...Individual electrode, 70...Robot arm control unit, 71...Memory, 80...Paint supply control unit (corresponding to pressure control unit), 90...Head control unit, 100...Main control unit, 110...Position sensor, 120...Tilt sensor, 200...Image processing device, 210...Image processing unit, 220...Memory, B1...Boundary, CP1...Painting area, D1...Defective dot, D2...Good dot, M1 to M6...Motor, OL...Overlap area, P1...First painting pass, P2...Second painting pass, R1...Robot arm

Claims

1. A painting robot that paints a painting portion of a vehicle, a paint head unit including a paint head having a plurality of nozzles for ejecting paint droplets and a piezoelectric substrate for driving the nozzles to push out the droplets; a robot arm having the painting head unit attached to its tip and moving the painting head unit to a desired position; a control unit including a head control unit that controls the operation of the piezoelectric substrate of the painting head, and a robot arm control unit that controls the operation of the robot arm; when a specific nozzle is determined to be a defective nozzle that is defective in ejecting droplets during painting on the vehicle, the head control unit performs recovery control to control driving of the piezoelectric substrate so that the size of the droplets of good dots that are surrounding the defective dots corresponding to the defective nozzle and that correspond to good nozzles that have no problem in ejecting the droplets increases; In the recovery control, When the good dots around the defective dots have reached the boundary of the coating range in the coating area, boundary discharge control is performed to change the size of the droplets of the good dots to the same size as droplets in a normal discharge state when the recovery control is not performed, For the good dots surrounding the defective dots and located inside the coating range relative to the boundary, non-boundary ejection control is performed such that the droplet size of the good dots is larger than that of the good dots in the normal ejection state. A painting robot characterized by:

2. The painting robot according to claim 1, In the recovery control, the head control unit (A) when the painted portion of the vehicle is horizontal or within a predetermined range of inclination angles close to the horizontal, the piezoelectric substrate is controlled so that the droplet size of the plurality of good dots surrounding the defective dot is larger than that of the good dots in the normal ejection state; (B) When the painted portion of the vehicle is tilted at an angle exceeding the predetermined tilt angle, the defective dots are For the good dots located above the defective dots, the piezoelectric substrate is controlled so that the droplet size is the largest among the good dots surrounding the defective dots, For the good dots located other than above the defective dots, the piezoelectric substrate is controlled so that the droplet size of the good dots is larger than that in the normal ejection state, or is the same as that in the normal ejection state. A painting robot characterized by:

3. The painting robot according to claim 1, In the recovery control, the head control unit When it is determined that there is a defective dot in which the coating defect caused by the defective nozzle cannot be resolved by controlling the droplet size in the first coating pass, which is the same coating pass, In a second painting pass, which is a next painting pass, an overlapping area is provided that overlaps with the first painting pass, and complementary control is performed to provide the good dots that overlap with the bad dots within the overlapping area. A painting robot characterized by:

4. The painting robot according to claim 1, In the boundary ejection control in the recovery control, the head control unit controlling the piezoelectric substrate so that the droplet size of the good dots is changed to a droplet size equivalent to that in the normal ejection state, and is made smaller than that in the normal ejection state; A painting robot characterized by:

5. 3. The painting robot according to claim 2, In the recovery control, the robot arm control unit When the painting portion of the vehicle is tilted beyond the predetermined tilt angle and it is determined that there are no good dots located above the defective dots, the operation of the robot arm is controlled so as to rotate the painting head unit while maintaining it parallel to the painting portion. A painting robot characterized by:

6. The painting robot according to claim 1, When it is determined that the number of defective dots corresponding to the defective nozzles in the paint head exceeds a predetermined threshold, the robot arm control unit controls the operation of the robot arm so that the movement speed of the paint head unit in the recovery control is slower than when the number of defective dots corresponding to the defective nozzles in the paint head does not exceed the predetermined threshold. A painting robot characterized by:

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