Electrostatic painting system and electrostatic painting program

Abstract

To safely obtain a stable coating film quality without stopping coating even when the distance between the tip of an electrostatic gun and an object to be coated changes. [Solution] The electrostatic coating system includes an electrostatic gun and an electrostatic controller that controls the voltage output from the electrostatic gun. The electrostatic controller monitors the output voltage and output current of the electrostatic gun and is capable of switching between constant voltage control, which maintains the output voltage constant, and current limiting control, which limits the output current to a range that does not exceed a current value at which sparks are generated. The electrostatic controller switches to current limiting control when the output current exceeds a preset first current threshold during constant voltage control, applies a pulse voltage whose absolute value is greater than the voltage threshold during current limiting control when the output voltage exceeds the preset voltage threshold, and switches from current limiting control to constant voltage control when the output current during pulse voltage application is smaller than a second current threshold whose absolute value is smaller than the first current threshold.

Description

[Technical Field]

[0001] FIELD An embodiment of the present invention relates to an electrostatic painting system and an electrostatic painting program. [Background technology]

[0002] Electrostatic painting is a widely used method of applying electrostatically charged paint from an electrostatic gun to a workpiece. To prevent overcurrent and sparks, a technique for controlling the application of high voltage while monitoring the output current is known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-118030 Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, at painting sites, there are an increasing number of situations where the distance between the tip of the electrostatic gun and the object to be coated changes due to changes in the transport line of the object to be coated, the vibration of the object to be coated, the diversification of the object shapes, etc. In particular, on automated painting lines using painting robots, there is a risk that the distance between the tip of the electrostatic gun and the object to be coated will unintentionally become closer due to insufficient hanging of the object to be coated or an increase in the line transport speed.

[0005] As such, when the tip of the electrostatic gun approaches the workpiece, the output current from the high-voltage output unit rises sharply, causing the output voltage to become unstable and potentially resulting in an overcurrent error. If an overcurrent error occurs, the high-voltage output must be stopped to protect the equipment, resulting in reduced productivity. Furthermore, large fluctuations in the output voltage and current can disrupt the charging state of the paint particles, compromising the desired coating pattern and coating quality.

[0006] The present invention has been made in consideration of the above circumstances, and its purpose is to provide an electrostatic coating system and an electrostatic coating program that can safely obtain stable coating quality without stopping coating even if the distance between the tip of the electrostatic gun and the object to be coated changes. [Means for solving the problem]

[0007] An electrostatic coating system according to an embodiment includes an electrostatic gun and an electrostatic controller that controls a voltage output from the electrostatic gun. The electrostatic controller monitors an output voltage and an output current of the electrostatic gun and is capable of switching between constant voltage control, which maintains the output voltage constant, and current limiting control, which limits the output current to a range that does not exceed a current value at which sparks are generated. The electrostatic controller switches to the current limiting control when the output current exceeds a predetermined first current threshold during execution of the constant voltage control, applies a pulse voltage whose absolute value is greater than the predetermined voltage threshold during execution of the current limiting control, and switches from the current limiting control to the constant voltage control when the output current exceeds the predetermined voltage threshold during execution of the current limiting control.

[0008] An electrostatic painting program according to an embodiment is a program executed by an electrostatic controller in an electrostatic painting system including an electrostatic gun and an electrostatic controller that controls a voltage output from the electrostatic gun. The electrostatic painting program causes the electrostatic controller to monitor an output voltage and an output current from the electrostatic controller, and to switch between a constant voltage control that maintains the output voltage constant and a current limiting control that limits the output current to a range that does not exceed a current value at which sparks are generated, and to execute a process of switching to the current limiting control if the output current exceeds a first current threshold during execution of the constant voltage control, and a process of applying a pulse voltage set to a voltage whose absolute value is greater than the voltage threshold during execution of the current limiting control if the output voltage exceeds a predetermined voltage threshold, and to switch from the current limiting control to the constant voltage control if the output current during application of the pulse voltage is smaller than a second current threshold set to a value smaller than the first current threshold. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram schematically illustrating a configuration of an example of an electrostatic coating system according to an embodiment. [Figure 2] FIG. 2 is a flowchart showing an example of processing content during electrostatic work executed by the electrostatic controller of the electrostatic coating system according to one embodiment. [Figure 3] FIG. 3 shows the change in state over time during electrostatic operation in an electrostatic coating system according to one embodiment, where (A) shows the stopping and starting of application of high voltage by the electrostatic controller, (B) shows the change in output voltage, (C) shows the change in output current, and (D) shows the change in control state. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment will be described below with reference to the drawings. First, the configuration of an electrostatic coating system 1 according to the embodiment will be described with reference to Fig. 1. The electrostatic coating system 1 includes an electrostatic gun 10, a paint supply source 21, a paint on-off valve 22, an air supply source 23, an air on-off valve 24, a coating robot 20, a coating controller 30, and an electrostatic controller 40.

[0011] Electrostatic gun 10 receives a supply of liquid paint from paint supply source 21 and a supply of compressed air from air supply source 23, electrostatically atomizes the liquid paint in a predetermined pattern, and discharges it onto workpiece 90 for electrostatic coating. Electrostatic gun 10 incorporates cascade 11 and electrode 12. Cascade 11 outputs a high DC voltage proportional to the AC voltage input to electrostatic gun 10. Cascade 11 boosts the input voltage several thousand times and outputs it.

[0012] In this embodiment, the cascade 11 boosts the voltage to a negative high voltage of, for example, about -40 kV to -80 kV and outputs it. The electrode 12 outputs the high voltage boosted by the cascade 11 and applies it to the paint being discharged from the electrostatic gun 10 to charge the paint. In the following description, when the relationship in magnitude of voltage values ​​is explained, it refers to magnitude in the negative direction, that is, magnitude of the absolute value of the voltage value, unless otherwise specified.

[0013] The object 90 may be in a form in which its transport or rotational position is controlled by, for example, a conveyor or turntable (not shown).The object 90 may also be transported while being suspended from a hanger provided above the object 90.

[0014] The paint supply source 21 is composed of, for example, a tank that stores liquid paint and a pump that pressure-feeds the paint in the tank. The paint supply source 21 is connected to the electrostatic gun 10 via a paint supply path 25 that is composed of a hose or the like, and supplies paint to the electrostatic gun 10. The air supply source 23 is composed of, for example, an air compressor or the like. The air supply source 23 is connected to the electrostatic gun 10 via an air supply path 26 that is composed of a hose or the like, and supplies compressed air to the electrostatic gun 10.

[0015] The paint on-off valve 22 is provided, for example, in the paint supply path 25. The paint on-off valve 22 is a solenoid valve for liquid paint, and is controlled by the painting controller 30 to open and close the paint supply path 25, thereby controlling the supply of paint to the electrostatic gun 10. The air on-off valve 24 is provided, for example, in the air supply path 26. The air on-off valve 24 is a solenoid valve for gas, for example, and is controlled by the painting controller 30 to open and close the air supply path 26, thereby controlling the supply of air to the electrostatic gun 10. The painting controller 30 is connected, for example, to a higher-level management device that manages manufacturing on a production line, and determines the start and end of painting work based on instructions from this management device.

[0016] The painting robot 20 can be configured, for example, as an articulated arm robot or an orthogonal axis arm robot. The painting robot 20 has the electrostatic gun 10 attached to the tip of its arm and functions as a moving means for moving the electrostatic gun 10 three-dimensionally. The painting robot 20 moves the electrostatic gun 10 to any position and posture in response to commands from a painting controller 30. Note that the electrostatic painting system 1 can also be configured such that the electrostatic gun 10 is a handgun held and operated by an operator. In this case, the electrostatic painting system 1 does not include the painting robot 20.

[0017] The painting controller 30 starts and stops the supply of paint and air by controlling the opening and closing of the paint on-off valve 22 and the air on-off valve 24. The painting controller 30 also controls the attitude of the painting robot 20 to adjust the painting position relative to the workpiece 90.

[0018] The electrostatic controller 40 controls the voltage output from the electrostatic gun 10. The electrostatic controller 40 has a control unit 41, a memory unit 42, a detection unit 43, and a power supply unit 44. The control unit 41 is mainly configured using a microcomputer having a processor and the like, and performs sequence processing, arithmetic processing, and the like. Similarly to the painting controller 30, the electrostatic controller 40 is connected to a higher-level management device that manages, for example, manufacturing on a production line, and determines the start and end of painting work based on instructions from this management device.

[0019] The storage unit 42 is configured with a non-transitory storage medium such as a ROM, a RAM, and a rewritable flash memory. The storage unit 42 stores an electrostatic painting program 421 for controlling the voltage or current applied to the electrostatic gun 10. The storage unit 42 also stores parameters and various thresholds required for executing the electrostatic painting program 421, i.e., for controlling the voltage or current applied to the electrostatic gun 10. The control unit 41 reads out the parameters, thresholds, and the like as needed and uses them for control.

[0020] The detection unit 43 is connected to the cascade 11 of the electrostatic gun 10 via, for example, a detection line 45. The detection unit 43 detects the voltage output from the cascade 11 and the magnitude of the current flowing through the cascade 11, and provides the detection results to the control unit 41. That is, the detection unit 43 detects the voltage and current output from the electrostatic gun 10. In the following description, the voltage detected by the detection unit 43 may be referred to as the output voltage V, and the current detected by the detection unit 43 may be referred to as the output current I.

[0021] The power supply unit 44 is connected to the cascade 11, for example, via a power line 46, and supplies an AC voltage to the cascade 11. In this case, the negative electrode of the power supply unit 44 is connected to the cascade 11 of the electrostatic gun 10, and the positive electrode is connected to the earth on the side of the workpiece 90. The power supply unit 44 is configured to include, for example, a switching power supply, and can arbitrarily set the voltage within a range of approximately 2 V to 20 V, and outputs an AC pulse voltage with a frequency of approximately 20 kHz.

[0022] 2 and 3, the operation of the electrostatic coating system 1 will be described. The electrostatic controller 40 executes, by the control unit 41, an electrostatic coating program 421 stored in the memory unit 42, to perform control for switching between constant voltage control and current limiting control depending on the distance between the electrostatic gun 10 and the workpiece 90.

[0023] Constant voltage control monitors the output voltage V detected by the detector 43 and maintains the voltage output from the electrostatic gun 10 at a preset voltage, such as a set voltage set by a user. Constant voltage control stably applies a predetermined high voltage to the paint sprayed from the electrostatic gun 10, thereby stabilizing the efficiency and quality of the coating. Meanwhile, constant voltage control varies the output current depending on the distance between the electrostatic gun 10 and the workpiece 90. Therefore, if the electrostatic gun 10 approaches the workpiece 90 too closely, the possibility of sparks occurring between the electrostatic gun 10 and the workpiece 90 increases. Thus, constant voltage control ensures high efficiency and stable quality by maintaining a certain distance between the electrostatic gun 10 and the workpiece 90. Therefore, the state in which constant voltage control is being performed can be referred to as a distant mode. Furthermore, the electrostatic coating system 1 performs constant voltage control during normal operation when the electrostatic gun 10 and the workpiece 90 are not too close. Therefore, the state in which constant voltage control is being performed can also be referred to as a normal mode.

[0024] The current limiting control monitors the output current I detected by the detection unit 43 and maintains the output current from the electrostatic gun 10 at a predetermined current value at which sparks do not occur, for example, in consideration of the risk of sparks. That is, the current limiting control in this embodiment limits the output current I from the electrostatic gun 10 by controlling the output voltage V so that it does not exceed the current value at which sparks occur between the electrostatic gun 10 and the workpiece 90. In this case, the current value at which sparks occur, i.e., the upper limit of the current in the current limiting control, is experimentally determined in advance depending on the distance between the electrostatic gun 10 and the workpiece 90 in the electrostatic coating system 1, and can be set to, for example, a value equal to or smaller than the second current threshold value I2 described below.

[0025] Current limiting control maintains the output current I within a range that does not exceed the current value at which sparks occur, regardless of the distance between the electrostatic gun 10 and the workpiece 90, reducing the likelihood of sparks occurring. On the other hand, with current limiting control, when the distance between the electrostatic gun 10 and the workpiece 90 decreases and the resistance between them decreases, the output voltage decreases, making it difficult to apply a high voltage to the paint and reducing painting efficiency. In this way, current limiting control allows safe painting even when the electrostatic gun 10 and the workpiece 90 are close to each other. For this reason, the state in which current limiting control is being performed can be referred to as proximity mode.

[0026] When painting starts, the painting controller 30 operates the painting robot 20 to control the position of the electrostatic gun 10, and opens and closes the paint on-off valve 22 and the air on-off valve 24 to control the start and stop of paint discharge from the electrostatic gun 10. In addition, when painting starts, the electrostatic controller 40 monitors the output voltage V and output current I detected by the detection unit 43, and performs control based on the flow shown in Figure 2.

[0027] The electrostatic controller 40 starts the painting operation based on the flow shown in Fig. 2 in response to an instruction from, for example, a higher-level management device. The electrostatic controller 40 also determines whether to end the painting operation, as appropriate, based on an instruction from, for example, a higher-level management device, separate from the flow shown in Fig. 2. When the painting operation is to be ended, the electrostatic controller 40 stops the voltage supply to the electrostatic gun 10 and ends the flow shown in Fig. 2.

[0028] The electrostatic controller 40 stores in advance in a storage unit 42, as parameters used for control, a first current threshold I1, a voltage threshold V1, a second current threshold I2, a determination period T, and a pulse voltage VP. The first current threshold I1 is a threshold used to determine whether to switch from constant voltage control to current limiting control. During execution of constant voltage control, the output current I is monitored, and if the output current I exceeds the first current threshold I1, processing to switch to current limiting control is executed. The first current threshold I1 is, for example, a value above which there is a risk of sparks occurring, and is set to, for example, approximately 60 μA to 80 μA.

[0029] The voltage threshold V1 and the second current threshold I2 are thresholds used to determine whether to switch from current limit control to constant voltage control. The pulse voltage VP and the determination period T are parameters used to determine whether to switch from current limit control to constant voltage control. The voltage threshold V1 is set, for example, to a value equal to or lower than the set voltage of constant voltage control. The determination period T can be set, for example, to a time equal to or longer than the time TP during which the pulse voltage VP is applied. The determination period T can also be set, for example, to a time shorter than the time TP during which the pulse voltage VP is applied.

[0030] The second current threshold I2 can be set, for example, based on the maximum voltage that the electrostatic controller 40 can output and a safety distance determined by public or manufacturer-specific standards. Here, the maximum voltage refers to the upper limit of the voltage that the electrostatic controller 40 can output. The safety distance is the distance between the electrostatic gun 10 and the workpiece 90 that must be maintained to reliably prevent sparks when the maximum voltage is applied. The safety distance can be set, for example, to twice the distance at which sparks occur when the maximum voltage is applied, and is set, for example, within the range of several tens to several hundreds of mm.

[0031] In this case, the second current threshold I2 can be set to the output current value when the maximum voltage is applied while a safe distance is maintained between the electrostatic gun 10 and the workpiece 90. The pulse voltage VP is set to a voltage having an absolute value greater than that of the voltage threshold V1, and specifically, can be set to the maximum voltage of the electrostatic controller 40. Therefore, the second current threshold I2 is set to the output current value when this pulse voltage VP is applied while a safe distance is maintained between the electrostatic gun 10 and the workpiece 90.

[0032] The electrostatic controller 40 determines whether to switch from current limiting control to constant voltage control as follows. First, the electrostatic controller 40 monitors the output voltage V while executing current limiting control, and if the absolute value of the output voltage V remains above a voltage threshold V1 for a certain period of time, for example, a determination period T, the electrostatic controller 40 instantaneously applies a pulse voltage VP. The electrostatic controller 40 sets the time TP for applying the pulse voltage VP to, for example, several microseconds to several milliseconds. Then, if the output current I during application of the pulse voltage VP is smaller than a second current threshold I2, the electrostatic controller 40 switches from current limiting control to constant voltage control.

[0033] Specifically, when a coating operation starts, the electrostatic controller 40 executes constant voltage control in step S11 of Fig. 2. The output voltage V gradually increases and is then maintained at a constant value, as shown at point P0-P1 in Fig. 3(B). The output current I changes depending on the distance between the electrostatic gun 10 and the workpiece 90, as shown at point P0-P1 in Fig. 3(C).

[0034] 2, the electrostatic controller 40 determines whether the output current I exceeds the first current threshold I1. If the output current I is equal to or less than the first current threshold I1 (NO in step S12), the electrostatic controller 40 repeats step S12 to maintain constant voltage control.

[0035] As shown at point P1 in Figure 3(C), when the output current I exceeds the first current threshold I1 (YES in step S12 in Figure 2), the electrostatic controller 40 proceeds to step S13 and switches from constant voltage control to current limiting control. This maintains the output current I constant, as shown at points P1-P2 in Figure 3(C). Furthermore, as shown at points P1-P2 in Figures 3(B) and 3(C), the output voltage V increases as the distance between the electrostatic gun 10 and the workpiece 90 increases.

[0036] When switching to current limiting control, the electrostatic controller 40 determines in step S14 whether the state in which the absolute value of the output voltage V exceeds the voltage threshold V1 has been maintained for the determination period T. If the state in which the absolute value of the output voltage V exceeds the voltage threshold V1 has not been maintained for the determination period T (NO in step S14), the electrostatic controller 40 repeats step S14 and maintains the current limiting control.

[0037] As shown at point P2 in FIG. 3B, if the absolute value of the output voltage V remains above the voltage threshold V1 for the determination period T (YES in step S14 in FIG. 2), the electrostatic controller 40 proceeds to step S15 and applies a pulse voltage Vp to the electrostatic gun 10. Then, in step S16, the electrostatic controller 40 determines whether the output current I has become smaller than the second current threshold I2. For example, as shown at points P2-P3 in FIG. 3C, if the output current I is equal to or greater than the second current threshold I2 even when the pulse voltage Vp is applied (NO in step S16 in FIG. 2), the electrostatic controller 40 returns to step S14 and determines whether to switch to constant voltage control while maintaining current limit control.

[0038] On the other hand, if the output current I when the pulse voltage VP is applied becomes smaller than the second current threshold I2 (YES in step S16 in FIG. 2), as shown at point P4-P5 in FIG. 3(C), the electrostatic controller 40 proceeds to step S11 and switches to constant voltage control. In this way, the electrostatic controller 40 repeats the processes of steps S11 to S16, and performs the coating operation while appropriately switching between constant voltage control and current limiting control depending on the distance between the electrostatic gun 10 and the workpiece 90.

[0039] According to the embodiment described above, the electrostatic coating system 1 includes the electrostatic gun 10 and the electrostatic controller 40. The electrostatic controller 40 controls the voltage output from the electrostatic gun 10. The electrostatic controller 40 monitors the output voltage V and output current I of the electrostatic gun 10, and is configured to be able to switch between constant voltage control, which maintains the output voltage V constant, and current limiting control, which maintains the output current I constant. The electrostatic controller 40 switches to current limiting control when the output current I exceeds a preset first current threshold I1 during execution of the constant voltage control.

[0040] According to this, if the distance between the tip of the electrostatic gun 10 and the workpiece 90 becomes close while constant voltage control is being executed and the output current I rises sharply and exceeds the first current threshold value I1, the control automatically switches to current limiting control, which allows safe operation even when the tip of the electrostatic gun 10 and the workpiece 90 are close to each other. Therefore, even if the tip of the electrostatic gun 10 and the workpiece 90 suddenly become close to each other during painting work, there is no need to stop the electrostatic painting system 1, and it is possible to achieve both safety and productivity.

[0041] If current limiting control is continued even when the tip of the electrostatic gun 10 moves away from the workpiece 90 again and the output current I begins to decrease, there is a concern that the output voltage V may continue to rise to near its maximum voltage. On the other hand, the output voltage V may temporarily rise due to factors such as an unstable distance between the tip of the electrostatic gun 10 and the workpiece 90. However, if current limiting control were to be switched to constant voltage control only when the output voltage V rose above a certain level, switching between current limiting control and constant voltage control may occur frequently, which could impair the stability of electrostatic coating.

[0042] Therefore, in this embodiment, the electrostatic controller 40 applies a pulse voltage VP when the output voltage V exceeds a preset voltage threshold V1 during current limiting control. The pulse voltage VP is set to a voltage whose absolute value is greater than the voltage threshold V1. Then, the electrostatic controller 40 switches from current limiting control to constant voltage control when the output current I during application of the pulse voltage VP is smaller than a second current threshold I2. The second current threshold I2 is set to a value smaller than the first current threshold I1.

[0043] In this manner, in this embodiment, if the output voltage V exceeds the voltage threshold V1 while current limiting control is being executed, the pulse voltage VP is instantaneously applied, and after confirming that the output current I at that time is less than the second current threshold I2, the control is switched to constant voltage control. Therefore, according to this embodiment, it is possible to prevent the output current I from exceeding the second current threshold I2 when switching from current limiting control to constant voltage control, thereby reliably suppressing the occurrence of sparks and improving safety.

[0044] Furthermore, according to the embodiment, the electrostatic controller 40 applies the pulse voltage VP when the output voltage V remains above the voltage threshold V1 for a certain period T during current limiting control. In this case, the certain period T can be set to, for example, a period longer than the application time TP of the pulse voltage VP. This prevents the control mode from being unnecessarily changed due to a slight voltage fluctuation over a short period of time, such as when the output voltage V temporarily exceeds the voltage threshold V1. As a result, frequent switching between constant voltage control and current limiting control can be suppressed, improving the stability of the painting operation.

[0045] Furthermore, because the second current threshold I2 is set to a value smaller than the first current threshold I1, the switch to constant voltage control occurs when the output current I has decreased more steadily. As a result, it is possible to return to constant voltage control only after reliably confirming that the distance between the electrostatic gun 10 and the workpiece 90 has sufficiently recovered. This allows for both safety and production efficiency without stopping the coating operation, and also allows for the appropriate voltage application to be resumed when the distance returns from the close proximity state, thereby stabilizing the quality of the coating film.

[0046] The electrostatic coating system 1 and electrostatic coating program 421 of this embodiment can also be applied in situations other than the above-mentioned situation where the tip of the electrostatic gun and the workpiece become unintentionally close to each other. For example, when the shape of the workpiece is a mixture of continuous flat surfaces and partially uneven surfaces, there is a need to paint efficiently in a short time, and to simplify as much as possible the teaching of the robot's operation and the voltage setting of the electrostatic controller 40. Note that coating efficiency refers to the proportion of the dispensed paint that actually adheres to the workpiece.

[0047] When painting on a continuous, smooth surface, close-range painting minimizes paint splatter and provides high transfer efficiency. However, when painting on a surface with many irregularities, or when the distance between the tip of the electrostatic gun and the workpiece changes rapidly, conventional close-range painting with a constant current makes it difficult to maintain a consistent film thickness due to voltage changes. Furthermore, when the tip of the paint gun cannot be inserted into a recess in the workpiece due to interference from the surroundings, close-range painting with a constant current cannot apply sufficient voltage. In such cases, conventional painting has often been performed in far-range mode with constant voltage control, even at the expense of some transfer efficiency.

[0048] In contrast, according to the present embodiment described above, even if the workpiece 90 has an uneven surface, the electrostatic gun 10 automatically switches between the close mode and the far mode depending on the distance between the uneven surface and the tip of the electrostatic gun 10. This eliminates the need to meticulously set voltage values ​​for each uneven surface or to pre-set the mode when teaching a trajectory for robotic painting, etc. Therefore, according to this embodiment, painting can be performed smoothly with simple teaching, applying the maximum voltage possible under the given conditions. This enables efficient electrostatic painting regardless of the uneven shape of the workpiece surface.

[0049] The above-described embodiments are not limited to the embodiments described above and illustrated in the drawings, and may be modified as appropriate within the scope of the invention. [Explanation of symbols]

[0050] 1...electrostatic coating system, 10...electrostatic gun, 40...electrostatic controller, 421...electrostatic coating program, I...output current, V...output voltage, VP...pulse voltage, I1...first current threshold, I2...second current threshold, V1...voltage threshold

Claims

1. Electrostatic gun and an electrostatic controller that controls a voltage output from the electrostatic gun; The electrostatic controller a control circuit for controlling the output voltage and output current of the electrostatic gun, and for switching between a constant voltage control for maintaining the output voltage constant and a current limiting control for limiting the output current to a range not exceeding a current value at which a spark occurs, and for switching to the current limiting control when the output current exceeds a preset first current threshold value during execution of the constant voltage control; When the output voltage exceeds a preset voltage threshold during execution of the current limiting control, a pulse voltage set to a voltage having an absolute value greater than the voltage threshold is applied, and when the output current during application of the pulse voltage is smaller than a second current threshold set to a value smaller than the first current threshold, the current limiting control is switched to the constant voltage control. Electrostatic painting system.

2. the electrostatic controller applies the pulse voltage when the output voltage maintains a state in which it exceeds the voltage threshold for a certain period of time while the current limiting control is being executed; 10. The electrostatic coating system of claim 1.

3. A program executed by an electrostatic controller in an electrostatic coating system including an electrostatic gun and an electrostatic controller that controls a voltage output from the electrostatic gun, The electrostatic controller a process for monitoring an output voltage and an output current from the electrostatic controller, and for switching between a constant voltage control for maintaining the output voltage constant and a current limiting control for limiting the output current to a range not exceeding a current value at which a spark occurs, and for switching to the current limiting control when the output current exceeds a first current threshold during execution of the constant voltage control; when the output voltage exceeds a predetermined voltage threshold during execution of the current limiting control, a pulse voltage set to a voltage having an absolute value greater than the voltage threshold is applied, and when the output current during application of the pulse voltage is smaller than a second current threshold set to a value smaller than the first current threshold, a process of switching from the current limiting control to the constant voltage control is executed. Electrostatic painting program.

4. the process of switching from the current limiting control to the constant voltage control includes a process of applying the pulse voltage when the state in which the output voltage exceeds the voltage threshold is maintained for a certain period of time during execution of the current limiting control. The electrostatic coating program according to claim 3 .

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