Since the body of an automobile may include a complicated surface shape, multi-nozzle heads 700A and 700B different in the number of nozzles may be provided as illustrated in FIG. 5, and the multi-nozzle heads 700A and 700B may be selectively used according to the shape of the surface to be coated. For example, the multi-nozzle head 700A includes a nozzle surface 101A having 96 nozzles 102A, and the multi-nozzle head 700B includes a nozzle surface 101B having eight nozzles 102B.

The multi-nozzle head 700A and the multi-nozzle head 700B are held by a head holding member 720 with the nozzle surfaces 101A and 101B facing different directions. In the present embodiment, the nozzle surface 101A and the nozzle surface 101B are shifted by 90 degrees from each other. The nozzle surface 101B has a smaller area than the nozzle surface 101A, and has a size adaptable for applying a coating to a narrow portion of the vehicle body U.

In the above-described configuration, attaching the head holding member 720 to the end effector 1004 of the coating robot 1000 and switching between the multi-nozzle heads 700A and 700B according to the shape of the vehicle body U makes it possible to apply a coating to a complicated surface shape. The number and arrangement of the nozzles 102A and 102B are examples, and the number and arrangement are not limited thereto. In the present example, the nozzle surface 101A and the nozzle surface 101B face in different directions. However, the nozzle surface 101A and the nozzle surface 101B may face in the same direction.

Configuration Example of Medium Plate

Next, a configuration example of a medium plate will be described with reference to FIG. 6. FIG. 6 is a diagram illustrating a configuration example of a medium plate.

The maintenance/cleaning unit 2001 of the maintenance station 2000 includes a medium plate 2002 that holds a test pattern formed through a discharge operation performed by all the nozzles, before the coating or when the coating time has passed a predetermined time. Here, the medium plate 2002 is an example of a detection target member.

The medium plate 2002 is secured to a medium plate supporting member 2003 with screws or the like. A base plate 2005 is secured to a frame 2004 of the maintenance station 2000, and a cover member 2006 is attached to the frame 2004 with the base plate 2005 in between. The medium plate supporting member 2003 with the medium plate 2002 thereon can reciprocate in the directions of arrow B, and the medium plate supporting member 2003 can pass through the cover member 2006 to the rear side of the base plate 2005. A cleaning mechanism for removing the test pattern formed on the surface of the medium plate 2002 is provided on the rear side of the base plate 2005.

After the removal of the test pattern, the medium plate supporting member 2003 with the medium plate 2002 thereon passes through the cover member 2006 and moves to the front side of the base plate 2005 for formation of the next test pattern. At the time of formation of a test pattern on the medium plate 2002, the head 100 (700, 700A, 700B) is positioned directly above the medium plate 2002 as indicated by broken lines, and in this state, the discharge operation is executed by all the nozzles.

In the above description, the medium plate 2002 is provided in the maintenance station 2000. However, the medium plate 2002 may be placed at a location different from the maintenance station 2000.

Functional Configuration of Coating System

Next, a functional configuration of the coating system according to the embodiment will be described with reference to FIG. 7. FIG. 7 is a diagram illustrating an example of a functional configuration of the coating system.

In FIG. 7, the coating system 10000 includes a control device 901, a head controller 902, a terminal device 903, a robot controller 904, a maintenance controller 905, the coating robot 1000, and the maintenance station 2000.

The control device 901 includes a calculation unit 9011, a specification unit 9012, a determination unit 9013, a storage/reading unit 9014, a storage 9015, an imaging controller 9016, an image processing unit 9017, a synchronization controller 9018, an environment information acquisition unit 9019, and others.

The control device 901 receives coating data and instructions of the vehicle body U from the terminal device 903 and controls the entire operation of the coating system 10000.

The calculation unit 9011 is implemented through processing performed by a central processing unit (CPU) 9001 described later, and calculates the moving direction of the head 100 (700, 700A, 700B) in a coating area of the vehicle body U and the number of nozzles for discharging the coating material in the coating area, based on the coating data received from the terminal device 903.

The specification unit 9012 is implemented through processing performed by the CPU 9001 described later, and specifies the coating area of the vehicle body U based on the coating data received from the terminal device 903.

The determination unit 9013 is implemented through processing performed by the CPU 9001 described later, and makes various determinations.

The storage/reading unit 9014 is mainly implemented through processing performed the CPU 9001 described later, and stores various types of data (or information) in the storage 9015 and reads various types of data (or information) from the storage 9015.

The storage 9015 is constructed by a read only memory (ROM) 9002, a random access memory (RAM) 9003, a hard disk drive (HDD)/solid state drive (SSD) 9004, and the like described later, and stores the coating data, coating target range (coating target size) data, coating area data, coating specification data, and the like received from the terminal device 903.

The imaging controller 9016 is mainly implemented through processing performed by the CPU 9001 on an input/output (I/O) interface 9005 described later. For example, if the coating robot 1000 includes an imaging apparatus such as a camera, the imaging controller 9016 controls imaging processing on the imaging unit 1010 of the coating robot 1000.

For example, the imaging controller 9016 instructs the imaging unit 1010 to perform imaging processing. The imaging controller 9016 acquires a captured image obtained by imaging processing by the imaging unit 1010, for example.

The image processing unit 9017 is mainly implemented through processing performed by the CPU 9001 described later, and executes predetermined processing on the captured image acquired by the imaging controller 9016 from the imaging unit 1010. For example, the image processing unit 9017 executes predetermined processing on a trial shot image (an image obtained by capturing the test pattern) of the head 100 acquired by the imaging controller 9016, and generates image data used for determining the discharge state of the coating material.

The synchronization controller 9018 is implemented through processing performed by the CPU 9001 described later, and synchronizes the operation of the coating robot 1000 with the discharge operation of a coating material discharger 1030, based on the coating data, coating instructions, and the like received from the terminal device 903.

The environment information acquisition unit 9019 is mainly implemented through processing performed by the CPU 9001 on the I/O interface 9005 described later, and acquires temperature information indicating the environmental temperature in the coating system 10000, the temperature of the coating material, or the like, for example.

The head controller 902 controls the coating material discharging operation by the coating material discharger 1030 in response to an instruction from the control device 901.

The terminal device 903 includes a routing information protocol (RIP) unit 9031, a rendering unit 9032, a display controller 9033, and a reception unit 9034.

The RIP unit 9031 has a function of performing image processing in accordance with a color profile and user settings.

The rendering unit 9032 decomposes the coating data into image data for each scan (for example, for each movement of the head 100 in the main scanning direction).

The display controller 9033 is mainly implemented through processing performed by the CPU 9001 described later, and displays various screens on a display unit such as a display.

The reception unit 9034 is mainly implemented through processing performed by the CPU 9001 on the communication interface 9006, and receives various selections or inputs from the user. The reception unit 9034 receives settings of coating data and coordinate data to be applied to the vehicle body U, selection of a coating mode, setting of a coating range (coating start position and coating end position), a coating instruction, and the like, for example. The reception unit 9034 may include a touch panel.

The terminal device 903 generates a movement trajectory of the coating robot 1000, based on the coating data received by the reception unit 9034 and the position data acquired from a head position measurement unit 1020 included in the coating robot 1000.

The robot controller 904 controls driving of an arm driving unit 1050 in response to an instruction from the control device 901. The driving of the arm driving unit 1050 is controlled to move the first arm 1002, the second arm 1003, and the end effector 1004 (head 100) of the coating robot 1000 to desired positions. The robot controller 904 also transmits driving state information indicating the driving state of the arm driving unit 1050 to the control device 901.

The maintenance controller 905 controls a cleaning liquid supply unit 2010, a cleaning air supply unit 2020, and a maintenance driving unit 2030 of the maintenance station 2000, in response to an instruction from the control device 901.

The maintenance controller 905 also transmits operation state information indicating the operation state of the maintenance station 2000 to the control device 901.

The coating robot 1000 includes the imaging unit 1010, a head position measurement unit 1020, the coating material discharger 1030, an arm position detector 1040, and the arm driving unit 1050.

The imaging unit 1010 is implemented by, for example, an imaging device such as a camera installed near the head 100 attached to the coating robot 1000, and executes imaging processing in response to an instruction from the imaging controller 9016. The imaging unit 1010 also transmits the captured image obtained by the imaging processing in response to an instruction from the imaging controller 9016 to the control device 901.

The head position measurement unit 1020 is implemented by a sensor installed in the vicinity of the head 100 attached to the coating robot 1000, for example, and measures the position and posture (inclination with respect to the coating surface or the like) of the head 100 with respect to the surface (coating surface) of the vehicle body U. As the head position measurement unit 1020, a three-dimensional (3D) sensor, a 3D camera, a laser displacement meter, or the like can be used. For example, the 3D sensor or the 3D camera measures the position and inclination in the XY direction, detects the coating start position, and detects the coating target size. In addition, the laser displacement meter measures the Z direction, detects the distance to the coating surface, and detects the surface shape (curvature or the like) of the coating surface. The head position measurement unit 1020 also transmits the measurement results and the detection results to the control device 901.

The coating material discharger 1030 is implemented by the head 100 (700, 700A, 700B) attached to the coating robot 1000, and discharges a coating material in response to an instruction from the head controller 902. The coating material discharger 1030 is an example of a liquid discharger.

The arm position detector 1040 optically detects each slit of an encoder included in the first joint 1005, the second joint 1006, the third joint 1007, and the like, for example. The arm position detector 1040 detects the positions of the first arm 1002, the second arm 1003, and the end effector 1004 from their rotation amounts, and acquires three-dimensional position information of the end effector 1004.

The arm driving unit 1050 moves the first arm 1002, the second arm 1003, the end effector 1004 (head 100), and the like of the coating robot 1000 to desired positions in response to an instruction from the robot controller 904. The arm driving unit 1050 also transmits driving state information and the like indicating the driving states of the first arm 1002, the second arm 1003, the end effector 1004, and the like to the robot controller 904.

The maintenance station 2000 includes the cleaning liquid supply unit 2010, the cleaning air supply unit 2020, and the maintenance driving unit 2030. The maintenance station transmits, to the maintenance controller 905, operating state information indicating the states of supply operations by the cleaning liquid supply unit 2010 and the cleaning air supply unit 2020, and driving state information indicating the driving state of the maintenance driving unit 2030.

The cleaning liquid supply unit 2010 includes cleaning nozzles that blow a cleaning liquid Lc to the nozzle plate 101 and the nozzle 102 of the head 100 (700, 700A, 700B), and discharges the cleaning liquid in response to an instruction from the maintenance controller 905.

The cleaning air supply unit 2020 includes, for example, air nozzles that blow cleaning air to the nozzle plate 101 and the nozzle 102 of the head 100 (700, 700A, 700B), and discharges the cleaning air in response to an instruction from the maintenance controller 905.

The maintenance driving unit 2030 drives various movement mechanisms such as a movement mechanism that moves the cleaning nozzles or the air nozzles forward and backward with respect to the head 100 (700, 700A, 700B), a movement mechanism that moves a cleaning member that wipes and cleans the nozzle surface, and a movement mechanism that moves the dummy discharge receiver forward and backward with respect to the head 100. If the maintenance station 2000 includes a medium plate for causing the head 100 to make a test pattern, the maintenance driving unit 2030 drives a movement mechanism that moves the medium plate forward and backward with respect to the head 100.

In the case of installing a plurality of coating robots (1000A, 1000B, . . . ), the head controller 902 and the robot controller 904 are provided for each coating robot. The functions of the RIP unit 9031 and rendering unit 9032 in the terminal device 903, and the functions of the head controller 902, the robot controller 904, and the maintenance controller 905 may be provided in the control device 901.

Hardware Configuration of Control Device

Next, a hardware configuration of the control device 901 will be described with reference to FIG. 8. FIG. 8 is an explanatory diagram illustrating an example of a hardware configuration of the control device. In the hardware configuration illustrated in FIG. 8, components may be added or deleted as necessary.

The control device 901 includes the central processing unit (CPU) 9001, the read only memory (ROM) 9002, the random access memory (RAM) 9003, the hard disk drive (HDD)/solid state drive (SSD) 9004, the input/output (I/O) interface 9005, the communication interface 9006, and a bus line 9007.

The CPU 9001 is an arithmetic device that implements each function of a target device or a target unit by reading a program or data stored in the ROM 9002 onto the RAM 9003 and executing processing.

The ROM 9002 is a non-volatile memory holding programs or data even after the power is turned off.

The RAM 9003 is a volatile memory used as a work area or the like of the CPU 9001.

The HDD/SSD 9004 controls reading or writing of various types of data under control of the CPU 9001.

The I/O interface 9005 is an interface for inputting/outputting to/from devices such as the coating robot 1000, the head controller 902, the robot controller 904, and the maintenance controller 905.

The communication interface 9006 is an interface that communicates (connects) with a device that performs data processing such as the terminal device 903 via a communication network.

The bus line 9007 is an address bus, a data bus, or the like for electrically connecting the above-described components, and transmits an address signal, a data signal, various control signals, and the like. The CPU 9001, the ROM 9002, the RAM 9003, the HDD/SSD 9004, the I/O interface 9005, and the communication interface 9006 are connected to one another via the bus line 9007.

Outline of Test Pattern

Next, an outline of a test pattern will be described with reference to FIGS. 9A to 11B. FIGS. 9A and 9B are explanatory diagrams illustrating an example of test pattern, FIGS. 10A to 10D are diagrams illustrating the relationship between the state of nozzles and the test pattern, and FIGS. 11A and 11B are diagrams illustrating the relationship between solid coating and nozzle bending.

FIG. 9A is a plan view of an example of the medium plate on which the test pattern is formed, and FIG. 9B is an enlarged view of a portion P in FIG. 9A.

FIG. 9A illustrates the test pattern formed on the medium plate 2002 by the multi-nozzle heads 700A and 700B illustrated in FIG. 5. In order to obtain this test pattern, the multi-nozzle head 700A is moved by the coating robot 1000 so that the nozzle surface 101A of the head faces the medium plate 2002, and all the nozzles 102A of the multi-nozzle head 700A execute the discharging operation. When all the nozzles 102A of the multi-nozzle head 700A are normal, a test pattern TPA as illustrated in FIG. 9A can be obtained.

Next, the head holding member 720 is rotated by 90 degrees by the coating robot 1000, so that the nozzle surface 101B of the multi-nozzle head 700B faces a region of the medium plate 2002 where the test pattern TPA is not formed. Next, all the nozzles 102B of the multi-nozzle head 700B execute the discharge operation. When all the nozzles 102B of the multi-nozzle head 700B are normal, a test pattern TPB as illustrated in FIG. 9A can be obtained.

In the following description, the length of the test pattern will be also referred to as “pattern length”, and the pattern length means the length of the test pattern in the main-scanning direction as illustrated in FIG. 9B. In addition, the width of the test pattern will be also referred to as “pattern width”, and the pattern width means the length of the test pattern in the sub-scanning direction as illustrated in FIG. 9B.

FIGS. 10A to 10D illustrate the relationship between the state of the nozzles and the test pattern. Here, the test pattern TPA formed by the multi-nozzle head 700A will be described as an example. Nozzle states as described below can be grasped from the test pattern TPA on the medium plate 2002.

The nozzle state is determined by comparing the area value of a preset reference pattern with the area value of the test pattern TPA on the medium plate 2002.

FIG. 10A illustrates a normal state. In this case, since the area value of the reference pattern and the area value of the test pattern TPA are equal, the control device 901 determines that the nozzles are normal.

FIG. 10B illustrates a constant discharge state. In this case, for example, one nozzle continues to discharge the coating material, and thus one line T1 appears in the test pattern TPA. As a result, since the area value of the test pattern TPA is larger than the area value of the reference pattern, the control device 901 determines that there is a nozzle that has been in the constant discharge state.

FIG. 10C illustrates a non-discharge state. In this case, for example, since one nozzle did not discharge the coating material, a blank T2 appears in the test pattern TPA. As a result, since the area value of the test pattern TPA is smaller than the area value of the reference pattern, the control device 901 determines that there is a nozzle that has been in the non-discharge state.

FIG. 10D illustrates a bending state. In this case, the coating material discharged from a nozzle did not correctly land on the target position, and a pattern T3 appears as a positional shift in the test pattern TPA. In the case of the bending state, since the area value of the test pattern TPA is equal to the area value of the reference pattern, it is difficult to detect the bend by the method of comparing the area values. Therefore, for the bending state, reference data on a state with no bend is acquired in advance, and the bending amount of the pattern is measured by comparing the barycentric position of the reference data with the barycentric position of each pattern constituting the test pattern TPA. As a result of the measurement, if the bending amount exceeds a prescribed value, the control device 901 determines that the test pattern is in the bending state. FIG. 10D illustrates the position of the pattern T3 that is greatly shifted for easy understanding of the phenomenon, but the actual shift amount (bending amount) is minute.

FIGS. 11A and 11B illustrate a case where solid coating is applied by a normal nozzle (FIG. 11A) and a case where solid coating is applied by a bending nozzle (FIG. 11B). When the nozzle is bent in the sub-scanning direction, a portion where the coating material did not land appears as a streak extending in the main-scanning direction as illustrated in FIG. 11B. Naturally, a discharge target object (a vehicle body or the like) with a streak is a defective product.

As described above, the constant discharge state and the non-discharge state are determined based on the area value of the test pattern, whereas the bending state of the nozzle is determined based on the barycentric position of the test pattern. Moreover, since the bending amount of the nozzle (shift amount of the barycentric position) is minute, high accuracy is required for detecting the shift amount of the barycentric position.

Detection of Nozzle Bend

A method of detecting a nozzle bend will be described with reference to FIGS. 12A to 13B. FIGS. 12A and 12B are diagrams illustrating an example of bend detection in a comparative example, and FIGS. 13A and 13B are diagrams illustrating an example of bend detection in the embodiment.

FIG. 12A illustrates a pattern shape to be originally acquired. The oval indicated by solid line represents the outer shape of the pattern, and the coating material is discharged from the nozzles so as to follow the solid line, thereby to form a pattern on the medium plate 2002. The pattern (test pattern) formed on the medium plate 2002 is captured (acquired) by the imaging unit 1010 of the coating robot 1000, for example. The image processing unit 9017 of the control device 901 performs predetermined image processing on the test pattern image acquired by the imaging unit 1010.

In the image processing, it is desired to recognize an area (gray area) inside the solid line as a pattern. However, there is an area (hatched area) that is recognized or not recognized depending on the resolution or the like of the imaging unit 1010 around the gray area. Therefore, the actually recognized pattern may be a pattern including an error portion as illustrated in FIG. 12B, for example. When the pattern including the error portion is recognized as the pattern, the barycentric position of the pattern moves to the negative side by ΔP1 in the sub-scanning direction. As a result, in the comparative example, the control device 901 may determine that the nozzle is bent even though the nozzle is actually not bent, which may cause a decrease in the accuracy of detecting the barycentric position.

In contrast to the comparative example described above, in the present embodiment, a test pattern is formed on the medium plate such that the amount of coating material per unit area is larger than that in the case of applying a coating material to the vehicle body U.

FIG. 13A illustrates a pattern that is formed with the amount of a coating material to be applied to the discharge target object (vehicle body U). At the time of forming the test patterns TPA and TPB on the medium plate 2002, the liquid amount per unit area is made larger than that in the case of applying a coating material to the vehicle body U, thereby to increase the pattern width as illustrated in FIG. 13B. Increasing the pattern width makes the area per pattern large and decreases the proportion of the error portion in the area of the pattern.

Accordingly, a movement amount ΔP2 of the barycentric position in the sub-scanning direction is smaller than the movement amount ΔP1 in the case of the comparative example, and as a result, the detection accuracy of the barycentric position in the sub-scanning direction can be improved. Examples of a method of increasing the liquid amount per unit area at the time of forming the test pattern include increasing the discharge amount (Mj) of the coating material from the nozzles, reducing the distance between the dots (droplets) of the coating material discharged from the nozzles, and the like.

As described above, the present embodiment is the coating system 10000 including the coating material discharger 1030 (head 100, 700, 700A, 700B) that discharges the coating material from the nozzle 102 to form the test patterns TPA and TPB on the medium plate 2002, the imaging unit 1010 that captures the test patterns TPA and TPB to acquire the test pattern image, the image processing unit 9017 that performs the image processing on the test pattern image acquired by the imaging unit 1010, and the determination unit 9013 that determines the presence or absence of abnormality in the nozzle 102 based on the results of processing by the image processing unit 9017. The test patterns TPA and TPB are formed on the medium plate 2002 such that the amount of the coating material per unit area is larger than that in the case where the coating material discharger 1030 discharges the coating material to the vehicle body U.

As described above, the test patterns TPA and TPB are formed such that the discharge amount (Mj) of the coating material from the nozzle 102 is larger than that in the case where the coating material discharger 1030 (head 100, 700, 700A, 700B) discharges the coating material to the vehicle body U.

As described above, the test patterns TPA and TPB are formed such that the inter-dot distance of the coating material is shorter than that in the case where the coating material discharger 1030 (head 100, 700, 700A, 700B) discharges the coating material to the vehicle body U.

The CPU 9001 (circuitry) causes the liquid discharger 1030 to discharge a first discharge amount of the liquid from the nozzle 102 onto the vehicle body U (target object); and causes the liquid discharger 1030 to discharge a second discharge amount of the liquid larger than the first discharge amount from the nozzle 102 onto the medium plate 2002 (detection target member) to form the test pattern on the medium plate 2002 (detection target member).

The CPU 9001 (circuitry) causes the liquid discharger 1030 to discharge the liquid from the nozzle 102 onto the vehicle body U (target object) multiple times to form multiple dots each having a first inter-dot distance with adjacent dot; and causes the liquid discharger 1030 to discharge the liquid from the nozzle 102 onto the medium plate 2002 (detection target object) multiple times to form multiple dots each having a second inter-dot distance shorter than the first inter-dot distance with adjacent dot.

The CPU 9001 (circuitry) reduces the second inter-dot distance in response to a change in the environmental temperature that decreases a discharge amount of the liquid from the liquid discharger 1030; and increase the second inter-dot distance in response to a change in the environmental temperature that increases the discharge amount of the liquid from the liquid discharger 1030.

Accordingly, even if the pattern is recognized in the shape including the error portion, the movement amount of the barycentric position of the pattern is decreased, and the detection accuracy of a nozzle bend based on the positional shift of the barycentric position can be improved.

Cleaning Liquid Handling

Next, handling of a defect caused by the cleaning liquid will be described with reference to FIGS. 14A to 18.

FIGS. 14A to 14C are diagrams describing a state of nozzle contamination, FIG. 15 is a diagram describing nozzle cleaning, FIGS. 16A and 16B are diagrams describing a defect caused by the cleaning liquid to the test pattern, and FIGS. 17A to 18 are diagrams illustrating examples of test pattern formation.

In the case of using a valve opening/closing head that discharges the coating material with nozzle opening/closing by the needle valves 131 as in the embodiment, since the nozzle 102 are closed by the needle valve 131 before the start of discharge, the coating material in the liquid chamber 114 is not dried or thickened. However, once discharge is performed, a thickened coating material La may remain on the nozzle 102 and the nozzle plate 101 as illustrated in FIGS. 14A and 14B. In addition, a residual liquid may adhere to the periphery of the nozzle 102 due to mist generated at the time of discharge, and may remain as an adhesion substance Lb as illustrated in FIG. 14C.

The thickened liquid La and the adhesion substance Lb become resistance to discharge of the coating material from the nozzle 102, cause discharge bending of the coating material, so that the coating material cannot be correctly discharged to a target position. In addition, if the liquid La is heavily thickened, discharge failure may occur (the liquid cannot be discharged from the nozzle 102). Therefore, in order to maintain the discharge quality, it is necessary to remove the thickened liquid La and the adhesion substance Lb.

The thickened liquid La and the adhesion substance Lb are removed by wiping (or scraping) the surface of the nozzle plate 101, for example. Alternatively, the thickened liquid La and the adhered substance Lb are removed by performing a dummy discharge (also referred to as preliminary discharge, spitting, and the like) of periodically discharging liquid droplets that do not contribute to coating to wash out the thickened liquid La and the adhered substance Lb from the nozzle 102, for example. Alternatively, the thickened liquid La and the adhered substance Lb are removed by cleaning the nozzle plate 101 and the nozzle 102, for example.

In the present embodiment, the nozzle plate 101 and the nozzle 102 are cleaned by blowing a pressurized cleaning liquid Lc from the cleaning nozzle to the nozzle plate 101, for example. In cleaning the nozzle 102, the leading end of the needle valve 131 is brought into contact (close contact) with the nozzle 102 as illustrated in FIG. 15, and the cleaning liquid Lc is sprayed onto the nozzle 102 in the closed state. This makes it possible to wash away the foreign matter such as the adhesion substance Lb and the thickened liquid La adhering to the nozzle plate 101 and the nozzle 102, and to maintain the discharge quality of the head 100. A head maintenance mechanism such as a cleaning liquid supply mechanism is provided in the maintenance/cleaning unit 2001 of the maintenance station 2000 illustrated in FIG. 2.

However, if the nozzle plate 101 and the nozzle 102 are cleaned with the cleaning liquid, the cleaning liquid Lc may remain in the nozzle 102 as illustrated in FIG. 16A. If a test pattern is formed on the medium plate 2002 with the cleaning liquid Lc remaining in the nozzle 102, the cleaning liquid Lc appears at the beginning of the test pattern as illustrated in FIG. 16B, and the shape of the pattern may not be correctly recognized.

For example, if the cleaning liquid Lc lands at a position where the coating material should land as the first drop, the pattern length in the main-scanning direction becomes shorter than the pattern length of the pattern shape to be acquired, and thus correct determination cannot be performed. In addition, if a pattern shape to be acquired is formed after the dropping of the cleaning liquid Lc from the nozzle and the cleaning liquid Lc is recognized as a pattern, the pattern length in the main scanning direction becomes longer than the pattern shape to be acquired, so that correct determination cannot be performed.

In this case, it is conceivable to perform a dummy discharge before executing the test pattern forming operation to wash out the foreign matter from the nozzle 102. However, time and equipment for the dummy discharge are required with cost increase.

In the above description, as an example of a method of increasing the amount of liquid per unit area at the time of forming the test pattern, decreasing the inter-dot distance of the coating material discharged from the nozzle has been exemplified. This method is also effective against the above-described defects caused by the cleaning liquid.

FIG. 17A illustrates a pattern that is formed with the amount of a coating material to be applied to the discharge target object (vehicle body U), and illustrates a state in which the cleaning liquid Lc is discharged as the first drop. In this state, the droplet of the cleaning liquid Lc is likely to cause a failure of the test pattern recognition.

On the other hand, if a pattern is formed with the shortened inter-dot distance of the droplets as illustrated in FIG. 17B, most of the droplet portion of the cleaning liquid Lc is hidden by the coating material dropped as the second droplet, so that the droplet portion of the cleaning liquid Lc is unlikely to be erroneously recognized as a pattern. This makes it possible to suppress the influence of the cleaning liquid without a dummy discharge.

In the formation of a test pattern with the inter-dot distance shortened, if the discharge frequency of the head is constant, the formation of a test pattern may be started while the arm movement speed of the coating robot including the head is in an acceleration section TA (for example, time Ttp) as illustrated in FIG. 18. Also in this case, since the inter-dot distance of the first drop and the second drop is shortened, the same effect as in the case of FIG. 17B can be obtained.

Handling of Environmental Temperature and Coating Material Replacement

Next, handling of a change in the environmental temperature or replacement of the coating material used will be described with reference to FIGS. 19A and 19B. FIGS. 19A and 19B are diagrams illustrating adjustment examples of the inter-dot distance.

If the environmental temperature at the time of coating changes, the discharge amount (Mj) of the coating material from the nozzle 102 may change unless the discharge condition in the coating material discharger 1030 (head 100, 700, 700A, 700B) is changed. In the embodiment, the environment information acquisition unit 9019 acquires temperature information indicating the environmental temperature in the coating system 10000, the temperature of the coating material, or the like, and adjusts the inter-dot distance of the test pattern based on the acquired temperature information so that the pattern width is kept constant.

Specifically, if the discharge amount decreases due to a change in environmental temperature, the test pattern is formed with the inter-dot distance shortened as illustrated in FIG. 19A. On the other hand, if the discharge amount increases due to a change in environmental temperature, the test pattern is formed with the inter-dot distance extended as illustrated in FIG. 19B. This keeps the pattern width constant. Automatically adjusting the inter-dot distance makes it possible to detect the state of the nozzle with high accuracy without lowering the detection accuracy.

In the coating system 10000 of the embodiment, the coating material to be used is replaced in the head 100 (700, 700A, 700B). For example, the color is changed. If the coating material to be used is replaced with a different type of coating material, the discharge amount (Mj) of the coating material from the nozzle 102 may change due to a difference in characteristics between the coating materials unless the discharge condition in the coating material discharger 1030 (head 100, 700, 700A, 700B) is changed.

In the embodiment, for example, coating material information indicating the characteristics of the coating material used in the coating system 10000 is stored in advance in the storage 9015. When the user selects the coating material in the terminal device 903, the storage/reading unit 9014 reads the coating material information corresponding to the coating material selected by the user from the storage 9015, and the specification unit 9012 specifies the inter-dot distance of the test pattern based on the read coating material information. The control device 901 adjusts the inter-dot distance of the test pattern based on the result of the specification by the specification unit 9012 so that the pattern width is kept constant.

Specifically, if the discharge amount is decreased by replacing the coating material with a different type of coating material, the test pattern is formed with the inter-dot distance shortened as illustrated in FIG. 19A. Conversely, if the discharge amount is increased by replacing the coating material with a different type of coating material, the test pattern is formed with the inter-dot distance extended as illustrated in FIG. 19B. This keeps the pattern width constant. Automatically adjusting the inter-dot distance makes it possible to detect the state of the nozzle with high accuracy without lowering the detection accuracy.

As described above, in the present embodiment, the inter-dot distance is changed according to the environmental temperature.

As described above, the test pattern is formed with the inter-dot distance shortened if the environmental temperature changes such that the discharge amount of the coating material from the coating material discharger 1030 decreases, and if the environmental temperature changes such that the discharge amount of the coating material from the coating material discharger 1030 increases, a test pattern is formed with the inter-dot distance extended.

As described above, the inter-dot distance is changed according to the type of the coating material.

As described above, if the discharge amount of the coating material from the coating material discharger 1030 decreases due to the replacement of the coating material with a different type of coating material, the test pattern is formed with the inter-dot distance shortened, and if the discharge amount of the coating material from the coating material discharger 1030 increases due to the replacement of the coating material with a different type of liquid, the test pattern is formed with the inter-dot distance extended.

Accordingly, the pattern width is kept constant, and the state of the nozzle can be constantly detected with high accuracy.

Flow of Abnormality Determination

A flow of abnormality determination in the embodiment will be described with reference to FIG. 20. FIG. 20 is a flowchart illustrating an example of abnormality determination.

In the abnormality determination, first, the number of counts of cleaning the head 100 (700, 700A, 700B) attached to the end effector 1004 of the coating robot 1000 is reset (step S1). Next, the number of counts of cleaning the head 100 (700, 700A, 700B) is checked (step S2).

If it is determined in step S2 that the number of cleaning counts exceeds a predetermined value M (N>M), the coating is stopped (step S8) and the process is ended (system stop). This means that cleaning was performed M times, but the abnormal state was not eliminated by cleaning alone. If it is determined in step S