Painting robot and painting method

Abstract

To provide a painting robot capable of suppressing a decrease in paint film thickness and improving painting quality. [Solution] When a particular nozzle 54 is determined to be a defective nozzle 54a that is defective in ejecting droplets during painting on a vehicle, the head control unit 90 of the painting robot 10 performs recovery control to control the drive of the piezoelectric substrate 62 so that the droplet size of good dots D2 around the defective dot D1 increases, and in the recovery control, when the good dots D2 around the defective dot D1 have reached the boundary of the painting area at the painted site, boundary ejection control is performed to change the droplet size of the good dots D2 to the same droplet size as the normal ejection state when recovery control is not performed.

Description

[Technical field]

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

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

[0003] [Patent Document 1] JP 2023-052170 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the configuration disclosed in Patent Document 1 can prevent the formation of white streaks and the like caused by no coating 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 view of the above circumstances, and has an object to provide a painting robot capable of suppressing a decrease in paint film thickness and improving 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 which paints a part of a vehicle, the painting robot comprising: a paint head unit including a plurality of nozzles which eject paint droplets, and a paint head which includes a piezoelectric substrate which is driven to push out the droplets from the nozzles; a robot arm which has the paint head unit attached to its tip and which moves the paint head unit to a desired position; a head control unit which controls the operation of the piezoelectric substrate of the paint head, and a control unit which includes a robot arm control unit which controls the operation of the robot arm; and when a specific nozzle is determined to be a defective nozzle which is defective in ejecting droplets during painting on the vehicle, the head control unit controls a surrounding area of ​​a defective dot corresponding to the defective nozzle. The present invention provides a painting robot that performs recovery control to control the driving of the piezoelectric substrate so that the size of droplets of good dots corresponding to good nozzles that have no problems with droplet ejection is increased, and in the recovery control, when good dots around a bad dot have reached the boundary of the painting range in the painting part, 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 bad dots 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. Effect of the Invention

[0007] According to the present invention, it is possible to provide a painting robot capable of suppressing a decrease in paint film thickness and improving painting quality. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing an overall configuration of a painting robot according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram showing a schematic configuration of a painting system including the painting robot shown in FIG. [Diagram 3]2 is a diagram showing a front view of a nozzle forming surface for ejecting paint in a paint head unit included 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. [Diagram 5] 2 is a cross-sectional view showing a configuration in the vicinity of a row-directional supply flow passage, a nozzle pressurizing chamber, and a row-directional discharge flow passage in the painting robot shown in FIG. 1. [Figure 6] 4 is a plan view showing the configuration of a nozzle forming surface of a paint head unit different from the paint head unit shown in FIG. 3. [Figure 7] 2A and 2B show 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] 2A and 2B 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 ​​a vehicle as viewed 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 ​​a vehicle as viewed 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] FIG. 13A shows the state of dots before boundary discharge control is performed, and FIG. 13B shows the state of dots when small-sized droplets are discharged using boundary discharge control. [Figure 13] FIG. 1A is a diagram showing a state in which a defective nozzle is located above the paint head, and FIG. 1B 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 in the painting head of the painting robot shown in FIG. 1 exceeds a predetermined threshold value. [Figure 15] This shows a modification 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 is increased not only for the good dot immediately adjacent to the defective dot, but also for the good dot adjacent to the defective dot. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A painting robot 10 according to an embodiment of the present invention will be described below with reference to the drawings. In the following description, the X direction is the longitudinal direction of the nozzle forming surface 52 (painting head 53), the X1 side is the right side in Fig. 3, and the X2 side is the left side in Fig. 3, as necessary. The Y direction is the lateral direction (width direction) of the nozzle forming surface 52 (painting head 53), the Y1 side is the upper side of the paper in Fig. 3, and the Y2 side is the lower side of the paper 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 aims 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 that move 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 forming not only the above-mentioned coating film but also 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, and may be any parts other than automobiles (for example, exterior parts of airplanes and trains) that require painting.

[0012] (1-1. Overall configuration of the painting system 1 and the 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 Paint 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. Regarding the robot body 20) 1, the robot body 20 mainly comprises a base 21, first to sixth rotating 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. Note that 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 surface, 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 rotatable relative to the base 21 via a first rotating shaft 22a by driving a motor M1 (see FIG. 2). The legs 23 may be configured not to rotate relative to the base 21.

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

[0017] A rotating arm 26 is provided at the tip of the second rotating arm 25 so as to be rotatable around the central axis of the second rotating arm 25. The rotating arm 26 is rotatable around a fourth rotating shaft 22d by the drive of the motor M4. A wrist section 27 is provided at the tip of the rotating arm 26. The wrist section 27 is capable of rotating around a plurality of shafts, for example, two, in different directions, by the drive of the motors M5 and M6. In FIG. 1, the rotating shafts capable of the rotating motion are the fifth rotating shaft 22e and the sixth rotating shaft 22f, respectively. This makes it possible to control the orientation of the painting head unit 50 with high precision. The number of shafts may be any number greater than or equal to two.

[0018] Further, a 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) 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 to 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 storage unit (not shown), a pump (not shown), a valve (not shown), and a return flow path 42 for recovering paint that has not been discharged.

[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 section for storing paint, and may have a section 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 diagram showing 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 includes a head cover (not shown), and various components are built into the head cover. As shown in FIG. 3, the nozzle forming surface 52 includes a plurality of nozzle rows 55 in which the nozzles 54 are aligned 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 on one side (Y2 side) of the main scanning direction (Y direction) and a second nozzle row 55B on the other side (Y1 side) of 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 the 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 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 passage 58, the nozzle pressurizing chamber 59, and the column-directional discharge flow passage 60. As shown in Figs. 4 and 5, the coating head 53 includes a supply-side large flow passage 57, a column-directional supply flow passage 58, the nozzle pressurizing chamber 59, the column-directional discharge flow passage 60, and a discharge-side large flow passage 61. The supply-side large flow passage 57 is a flow passage to which paint is supplied from the above-mentioned supply passage 41. The column-directional supply flow passage 58 is a flow passage to which the paint in the supply-side large flow passage 57 is diverted.

[0025] Furthermore, the nozzle pressurizing chamber 59 is connected to the column-directional supply flow passage 58 via a nozzle supply flow passage 59a. As a result, paint is supplied to the nozzle pressurizing chamber 59 from the column-directional supply flow passage 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 described later.

[0026] Furthermore, the nozzle pressurizing chamber 59 is 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. Furthermore, the column-directional discharge flow path 60 is connected to a discharge-side large flow path 61. The discharge-side large flow path 61 is a flow path where the paint discharged from each column-directional discharge flow path 60 joins together. This discharge-side large 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 passage 57, the column-direction supply passage 58, the nozzle supply passage 59a, and the nozzle pressurizing chamber 59, before being discharged from the nozzle 54. Furthermore, paint that has not been discharged from the nozzle 54 passes from the nozzle pressurizing chamber 59 through the nozzle discharge passage 59b, the column-direction discharge passage 60, and the discharge-side large passage 61, and is returned to the return passage 42.

[0028] 4, one column-directional discharge flow path 60 is arranged to correspond to one column-directional supply flow path 58. 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 top 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. For such piezoelectric ceramic layers 63a and 63b, ceramic materials having ferroelectricity, such as lead zirconate titanate (PZT)-based, NaNbO3-based, BaTiO3-based, (BiNa)NbO3-based, and BiNaNb5O15-based materials, can be used.

[0030] 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) present in the piezoelectric ceramic layer 63a. The individual electrodes 65 are disposed in the portions facing the nozzle pressurizing chamber 59. The portion of the piezoelectric ceramic layer 63a sandwiched between the common electrode 64 and the individual electrodes 65 is polarized in the thickness direction. Therefore, when a voltage is applied to the individual electrodes 65, the piezoelectric ceramic layer 63a is distorted by the piezoelectric effect. Therefore, when a predetermined drive signal is applied to the individual electrodes 65, the piezoelectric ceramic layer 63b is relatively displaced so as to reduce the volume of the nozzle pressurizing chamber 59, thereby discharging the paint.

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

[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 forming surface 52 of another paint head unit 50. As shown in FIG. 6, a nozzle row 55 may be configured by arranging a plurality of nozzles 54 along the short side direction (width direction; Y direction) of the paint head 53. In the configuration shown in FIG. 6, a plurality of nozzles 54 are arranged in the short side direction (width direction; main scanning direction) of the paint head 53 to form the nozzle row 55, but 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 configured by one nozzle 54.

[0033] Furthermore, when painting a vehicle using a paint head 53 as shown in Fig. 6, painting may be performed with the longitudinal direction of the paint head 53 slightly tilted with respect 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 row 55 is tilted at a predetermined angle with respect to the main scanning direction, the short side direction of the paint head 53 shown in Fig. 6 may be tilted at a predetermined angle with respect to the main scanning direction of the paint head 53. When tilted in this way, painting equivalent to that of the paint head 53 shown in Fig. 3 can be achieved simply by adjusting the timing of paint ejection from each nozzle 54.

[0034] (1-7. Control configuration of painting system 1) Next, a control configuration for controlling the operation of the painting system 1 will be described. 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 to configure the painting system 1.

[0035] The robot arm control unit 70, the paint supply control unit 80, the head control unit 90, the main control unit 100, and the image processing unit 210 described below are composed of 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 a CPU with excellent image processing performance, or instead of a CPU.

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

[0037] Among 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 includes a memory 71, and the memory 71 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 enables the paint head unit 50 to pass through a desired position 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) and posture data on the posture, such as the tilt, of the paint head 53, which are created by robot teaching taking into account the painting width that the paint head 53 can paint. Note that the memory 71 may be provided in the paint robot 10, but it may also be possible for the memory 71 to exist outside the paint robot 10 and for information to 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 pumps, valves, and the like provided in the paint supply unit 40. Note that the paint supply control unit 80 preferably 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. Note that the paint supply control unit 80 corresponds to a pressure control unit.

[0041] The head control unit 90 is a part that controls the operation of the piezoelectric substrate 62 in the paint head unit 50 based on the image processing in the image processing unit 210. When the head control unit 90 reaches a predetermined position in the trajectory data by a means for detecting the position, such as a position sensor 110 and an inclination sensor 120 described later, the head control unit 90 controls the discharge of paint based on the divided paint data corresponding to the position and the paint pass. In this case, the drive frequency of the piezoelectric substrate 62 is controlled to control the number of dots (the 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 to control the size of the droplets discharged from the nozzle 54 so that the film thickness on the vehicle is uniform.

[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 becomes 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. 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 becomes higher.

[0043] In addition, the main control unit 100 is a part that transmits 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] Moreover, 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, a laser sensor, etc. can be used as the position sensor 110. Moreover, 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, an inclination sensor, etc. 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 is a section that stores image data for each painting pass in correspondence with the painting sequence.

[0047] The image processing device 200 corresponds to, for example, a computer, but the computer may be a part 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 by wired communication or wireless communication. Even if the image processing device 200 is provided separately from the painting robot 10, it may be included in the concept of the painting robot 10 or may not be included in the concept of the painting robot 10.

[0048] (2. Droplet Discharge 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 for checking for paint leakage 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 paint ejection problems.

[0049] After printing the above test pattern, a camera (not shown) is operated by a command from the main control unit 100 to capture an image of the test pattern and obtain image data. The image data is then sent to the image processing device 200 via wireless or wired communication, and the image processing device 200 compares the captured image data with the judgment image data to extract 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, Fig. 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 size of the droplets of the good dots D2 (i.e., droplet ejection portions) corresponding to the nozzles 54 (good nozzles 54b) that have no problem ejecting droplets, which are dots surrounding the defective dots D1 (i.e., droplet non-ejection portions) corresponding to the defective nozzles 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 dots D1.

[0052] (b) Boundary discharge control and non-boundary discharge control at the coating area FIG. 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 range in the coating area CP1 (see Figure 9), if the basic recovery control described above is performed, the presence of dots formed by the landing of large droplets makes the paint 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 in the good dots D2 that have reached the boundary B1 of the coating area 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 bad dots D1 and are located inside the coating area (non-boundary) relative to 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 the coating quality from deteriorating at the boundary B1 of the coating range. Also, since the driving of the piezoelectric substrate 62 is controlled so that the droplet size of the non-boundary good dots D2 is increased, the defective dots D1 corresponding to the defective nozzle 54a are covered, making it possible to prevent the coating quality from deteriorating.

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

[0058] On the other hand, as shown in Fig. 10(a), when the painting area CP1 of the vehicle is inclined beyond a predetermined inclination angle, the dots of the droplets that land are likely to flow downward. In such a case, as shown in Fig. 10(b), the head control unit 90 controls the operation of the piezoelectric substrate 62 so that, for a plurality of good dots D2 around a defective dot D1, the good dot D2 located above the defective dot D1 has the largest droplet size among the good dots D2 around it. Note that in Fig. 10(a) shows the painting area CP1 of the vehicle as seen from the side, and (b) shows the arrangement of the dots (defective dots D1 and good dots D2) in the area surrounded by the dashed line A in (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 the good dots D2 located other than above the bad dot D1, even if paint flows from the droplets of the good dots D2, the flowed 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 dots D2 is larger than in the normal ejection state (however, it is preferable that the droplet size is smaller than that of the good dots D2 located above), or the droplet size is the same as in the normal ejection state.

[0061] (d) Complementary control by overlap region OL 11 is a diagram showing 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 control of the droplet size in the first painting pass P1, which is the same painting pass, there may be a case in which the defective dot D1 remains without eliminating the painting defect due to the defective dot D1. When it is determined that the remaining defective dot D1 exists in the first painting pass P1, the head control unit 90 performs complementary control in response to a command from the main control unit 100 to provide an overlap area OL that overlaps with the first painting pass P1 in the second painting pass P2, which is the next painting pass, and to provide a good dot D2 that overlaps with the remaining defective dot D1 in the overlap area OL.

[0062] Therefore, the remaining defective dots D1 are covered with the good dots D2, so that it is possible to prevent the paint from coming off at the portions 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 by boundary discharge control. As shown in Fig. 12, when a good dot D2 around a bad dot D1 reaches 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 so that the size of the droplets of the good dots D2 is changed from the same size as in the normal discharge state to a smaller size.

[0064] When controlled in this manner, the painting resolution at the boundary B1 of the painting range is increased, making it possible to improve the painting quality.

[0065] (f) Rotation of the painting head 53 13A shows a state where the defective nozzle 54a is located above the painting head 53, and FIG. 13B shows a state where the painting head 53 is rotated in the state of FIG. 13A. As shown in FIG. 13A, in the recovery control, when the painting site CP1 of the vehicle is inclined beyond a predetermined inclination angle, for example, the defective nozzle 54a is located above the nozzle forming surface 52, and therefore there may be no good dot D2 located above the defective dot D1. In this way, when it is determined that there is no good dot D2 located above the defective dot D1, the robot arm control unit 70 may control the operation of the robot arm R1 so as to rotate the painting head unit 50 while maintaining it parallel to the painting site CP1, as shown in FIG. 13B.

[0066] When controlled in this manner, it is possible to position the good dots D2 above the bad dots D1 by rotating the paint head unit 50, making it possible to prevent a decrease in paint quality.

[0067] (g) Moving Speed ​​of the Paint Head Unit 50 Fig. 14 is a diagram showing a state in which the number of defective nozzles 54a exceeds a predetermined threshold. Note that, in Fig. 14, six defective nozzles 54a are shown as a state in which the predetermined threshold is exceeded, but the number is not limited to six. As shown in Fig. 14, it is also conceivable 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 section 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 slower than usual, so that it is possible to increase the amount of droplets in the good dots D2 surrounding the defective dot D1, thereby making it possible to cover the defective dot D1.

[0069] (3. Notes) The contents described in the above-mentioned embodiment can be understood, for example, as follows. [1] That is, the painting robot 10 which paints the painting part CP1 of the vehicle comprises a painting head unit 50 having a plurality of nozzles 54 which eject droplets of paint, and a painting head 53 which has a piezoelectric substrate 62 which is driven to push the droplets out of the nozzles 54, a robot arm R1 which has the painting head unit 50 attached to its tip and which moves the painting head unit 50 to a desired position, and a control unit which comprises a head control unit 90 which controls the operation of the piezoelectric substrate 62 of the painting head 53, and a robot arm control unit 70 which 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 ejecting droplets during painting on a vehicle, the head control unit 90 performs recovery control to control the drive of the piezoelectric substrate 62 so as to increase the size of droplets of good dots D2 that are surrounding the defective dot D1 corresponding to the defective nozzle 54a and that correspond to a good nozzle 54b that has no problems ejecting droplets. In the recovery control, when the good dots D2 surrounding the defective dot D1 have reached the boundary B1 of the painting range at the painting site CP1, boundary ejection control is performed to make the droplet size of the good dots D2 equivalent to the droplet size in the normal ejection state when recovery control is not performed, while for the good dots D2 surrounding the bad dot D1 and that are located inside the painting range of the boundary B1, non-boundary ejection control is performed to make the droplet size of the good dots D2 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 dots D1, so that it is possible to suppress the decrease in coating thickness and improve coating quality. Also, by performing boundary discharge control at the boundary B1 of the coating range, it is possible to suppress the coating resolution at the boundary B1 of the coating range from becoming coarse, and it is possible to prevent the coating quality from deteriorating. Also, for the non-boundary defective dots D1, non-boundary discharge control is performed in which the drive of the piezoelectric substrate 62 is controlled so that the droplet size becomes large, so that it is possible to cover the defective dots D1 corresponding to the defective nozzle 54a and suppress the coating quality from deteriorating.

[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 painted area CP1 of the vehicle is horizontal or within a predetermined range of inclination angles 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 the normal ejection state, and (B) when the painted area CP1 of the vehicle 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, for the good dot D2 located above the bad dot D1, the droplet size of the good dot D2 around the bad dot D1 is the largest, while controlling the piezoelectric substrate 62 so that for the good dot D2 located other than above the bad dot D1, the droplet size of the good dot D2 is larger than that in the normal ejection state or is the same as that in the normal ejection state.

[0073] When controlling in this manner, when the vehicle's painting area CP1 is on a horizontal plane or within a specified range of inclination angles close to the horizontal plane, the landing droplets do not flow downward significantly, so by controlling the operation of the piezoelectric substrate 62 so that the droplet size of multiple good dots D2 (not limited to 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 painting quality.

[0074] In this way, when the painted part 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 made the largest among the surrounding good dots D2. As a result, when paint flows from the droplet of the good dot D2 from the top to the bottom, the flowed paint can cover the defective dot D1, making it possible to prevent a deterioration in the painting quality.

[0075] Furthermore, for good dots D2 located other than above the bad dot D1, even if paint flows from the droplets of the good dots D2, the flowed paint cannot cover the bad 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 discharge state (however, it is preferable that the droplet size is smaller than that of the good dots D2 located above), or the droplet size is the same as in the normal discharge state, it is possible to suppress fluctuations in the coating thickness and prevent deterioration of the coating quality.

[0076] [3] In addition to the above-described embodiments, in addition to the contents described in [1] and [2] or a combination thereof, when the head control unit 90 determines in the 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 in 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 missing at the areas of the remaining defective dots D1, thereby preventing a deterioration in painting quality.

[0078] [4] In addition to any of the above-mentioned 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 dots D2 is smaller than that in the normal ejection state, instead of being equivalent to the droplet size in the normal ejection state.

[0079] By controlling in this manner, 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 be configured to control the operation of the robot arm R1 in recovery control so as to rotate the painting head unit 50 while maintaining it parallel to the painting area CP1 when the painting area CP1 of the vehicle is tilted beyond a predetermined tilt angle and it is determined that there is no good dot D2 located above the bad dot D1.

[0081] By controlling in this way, it is possible to position the good dots D2 above the bad dots D1 by rotating the paint head unit 50. This allows paint to flow from the good dots D2 toward the bad dots D1, covering the bad dots D1, making it possible to prevent 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, the robot arm control unit 70 may be configured to control the operation of the robot arm R1 so that, when it is determined that the number of defective dots D1 corresponding to the defective nozzles 54a in the painting head 53 exceeds a predetermined threshold, the movement speed of the painting head unit 50 in the recovery control is slower than when the number of defective dots D1 does not exceed a 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 in the good dots D2 that exist around 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 in addition to 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 manner, it becomes possible to land paint on the defective dot D1.

[0086] Furthermore, in the recovery control in the above-described embodiment, when one defective dot D1 exists, the driving of the piezoelectric substrate 62 of the corresponding good dot D2 is controlled so that the droplet size of the good dots D2 surrounding the defective dot D1 is increased. However, in the recovery control, even if multiple defective dots D1 are adjacent to each other, 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 the paint quality.

[0087] An example of such a state is shown in Figure 15. Figure 15 shows a state in which two defective dots D1 are adjacent to each other, and good dots D2 with larger droplet sizes are placed around them through recovery control. Note that, although Figure 15 shows a state in which two defective dots D1 are adjacent to each other, it is possible to perform recovery control to increase the droplet size of the surrounding good dots D2 even if three or more defective dots D1 are adjacent to each other, as long as no paint voids occur.

[0088] In the recovery control in the above embodiment, the driving of the piezoelectric substrate 62 of the corresponding good dot D2 is controlled so that the droplet size of the good dot D2 adjacent to the defective dot D1 is increased. However, if paint voids can be prevented, the droplet size of not only the good dot D2 immediately adjacent to the defective dot D1 but also the good dot D2 adjacent to the good dot D2 may be increased, as shown in Fig. 16 for example. In addition, the droplet size of the good dot D2 immediately adjacent to the defective dot D1 is normal, but the droplet size of the good dot D2 adjacent to the normal-sized good dot D2 may be increased, or further, 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 path, 58...row-direction supply path, 59...nozzle pressurizing 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...Inclination 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 part 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 paint head to push out the droplets from the nozzles; a robot arm having a tip end to which the painting head unit is attached and which moves 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 paint head, and a robot arm control unit that controls the operation of the robot arm, the head control unit, when it is determined that a particular nozzle is a defective nozzle that is defective in ejecting the droplets during painting of the vehicle, performs recovery control to control driving of the piezoelectric substrate so as to increase the size of the droplets of good dots that correspond to good nozzles that have no problem ejecting the droplets and are surrounding the defective dots that correspond to the defective nozzle; In the recovery control, When the good dots around the defective dots reach the boundary of the coating range in the coating area, boundary discharge control is performed so that the size of the droplets of the good dots becomes the same as the droplet size in a normal discharge state when the recovery control is not performed, for the good dots around the defective dots and located inside the coating range from the boundary, a non-boundary ejection control is executed such that the droplet size of the good dots is larger than that of the good dots in the normal ejection state; In the recovery control, the head control unit (A) when the painted portion of the vehicle is on a horizontal plane or within a range of a predetermined inclination angle close to the horizontal plane, the piezoelectric substrate is controlled so that the size of the droplets 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 inclined beyond the predetermined inclination angle, in the plurality of good dots surrounding the defective dot, For the good dots located above the defective dots, the piezoelectric substrate is controlled so that the size of the droplet is the largest among the good dots around 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 the above.

2. A painting robot that paints a part 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 paint head to push out the droplets from the nozzles; a robot arm having a tip end to which the painting head unit is attached and which moves 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 paint head, and a robot arm control unit that controls the operation of the robot arm, the head control unit, when it is determined that a particular nozzle is a defective nozzle that is defective in ejecting the droplets during painting of the vehicle, performs recovery control to control driving of the piezoelectric substrate so as to increase the size of the droplets of good dots that correspond to good nozzles that have no problem ejecting the droplets and are surrounding the defective dots that correspond to the defective nozzle; In the recovery control, When the good dots around the defective dots reach the boundary of the coating range in the coating area, boundary discharge control is performed so that the size of the droplets of the good dots becomes the same as the droplet size in a normal discharge state when the recovery control is not performed, for the good dots around the defective dots and located inside the coating range from the boundary, a non-boundary ejection control is executed such that the droplet size of the good dots is larger than that of the good dots in the normal ejection state; 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 eliminated by controlling the size of the droplets in the first coating pass, which is the same coating pass, a second paint pass that is a next paint pass is provided with an overlapping area that overlaps with the first paint pass, and a complementary control is performed to provide the good dots that overlap with the bad dots within the overlapping area; A painting robot characterized by the above.

3. A painting robot that paints a part 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 paint head to push out the droplets from the nozzles; a robot arm having a tip end to which the painting head unit is attached and which moves 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 paint head, and a robot arm control unit that controls the operation of the robot arm, the head control unit, when it is determined that a particular nozzle is a defective nozzle that is defective in ejecting the droplets during painting of the vehicle, performs recovery control to control driving of the piezoelectric substrate so as to increase the size of the droplets of good dots that correspond to good nozzles that have no problem ejecting the droplets and are surrounding the defective dots that correspond to the defective nozzle; In the recovery control, When the good dots around the defective dots reach the boundary of the coating range in the coating area, boundary discharge control is performed so that the size of the droplets of the good dots becomes the same as the droplet size in a normal discharge state when the recovery control is not performed, for the good dots around the defective dots and located inside the coating range from the boundary, a non-boundary ejection control is executed such that the droplet size of the good dots is larger than that of the good dots in the normal ejection state; In the boundary ejection control in the recovery control, the head control unit controlling the piezoelectric substrate so that the size of the droplets of the good dots is changed to a droplet size equivalent to that in the normal ejection state, and the droplet size is changed to a smaller droplet size than that in the normal ejection state; A painting robot characterized by the above.

4. The painting robot according to claim 1, In the recovery control, the robot arm control unit when the painting portion of the vehicle is inclined beyond the predetermined inclination angle and it is determined that there is no good dot located above the defective dot, 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 the above.

5. A painting robot that paints a part 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 paint head to push out the droplets from the nozzles; a robot arm having a tip end to which the painting head unit is attached and which moves 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 paint head, and a robot arm control unit that controls the operation of the robot arm, the head control unit, when it is determined that a particular nozzle is a defective nozzle that is defective in ejecting the droplets during painting of the vehicle, performs recovery control to control driving of the piezoelectric substrate so as to increase the size of the droplets of good dots that correspond to good nozzles that have no problem ejecting the droplets and are surrounding the defective dots that correspond to the defective nozzle; In the recovery control, When the good dots around the defective dots reach the boundary of the coating range in the coating area, boundary discharge control is performed so that the size of the droplets of the good dots becomes the same as the droplet size in a normal discharge state when the recovery control is not performed, for the good dots around the defective dots and located inside the coating range from the boundary, a non-boundary ejection control is executed such that the droplet size of the good dots is larger than that of the good dots in the normal ejection state; When it is determined that the number of the 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 moving speed of the paint head unit in the recovery control is slower than when the moving speed does not exceed the predetermined threshold. A painting robot characterized by the above.

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