Electrostatic coating system and electrostatic coating program

Abstract

Even if the distance between the tip of the electrostatic gun and the object being coated changes, the coating process can be safely and reliably completed without stopping the coating process. [Solution] The electrostatic painting system comprises 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 can switch 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 the current value at which sparks occur. Furthermore, if the output current exceeds a preset first current threshold while constant voltage control is being performed, the controller switches to current limiting control. If the output voltage exceeds a preset voltage threshold while current limiting control is being performed, the controller applies a pulse voltage set to a voltage with an absolute value greater than the voltage threshold. If the output current at the time of pulse voltage application is less than a second current threshold set to a value less than the first current threshold, the controller switches from current limiting control to constant voltage control.

Description

Technical Field

[0001] Embodiments of the present invention relate to an electrostatic coating system and an electrostatic coating program.

Background Art

[0002] Electrostatic coating is widely used as a method of attaching charged paint from an electrostatic gun to an object to be coated. In such electrostatic coating, there is known a technique for controlling the application of a high voltage while monitoring the output current in order to avoid the occurrence of overcurrent abnormalities and sparks.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, at the painting site, due to changes in the conveyance line of the object to be painted, shaking of the object to be painted, diversification of the shape of the object to be painted, etc., the number of scenes where the distance between the tip of the electrostatic gun and the object to be painted changes is increasing. Especially in an automatic painting line using a painting robot, if the hanging state of the object to be painted is insufficient or the line conveyance speed is increased, the distance between the tip of the electrostatic gun and the object to be painted may unintentionally become close.

[0005] When the tip of the electrostatic gun approaches the object to be painted in this way, the output current from the high-voltage output section rapidly increases, the output voltage becomes unstable, and an overcurrent abnormality may occur. If an overcurrent abnormality occurs, the high-voltage output must be stopped from the viewpoint of device protection, resulting in a decrease in productivity. In addition, large fluctuations in the output voltage and output current disrupt the charging state of the paint particles, causing damage to the intended painting pattern and coating film quality.

[0006] ​The present invention has been made in view 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 the coating process, even when the distance between the tip of the electrostatic gun and the object to be coated changes. [Means for solving the problem]

[0007] The electrostatic coating system according to this embodiment 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 can switch 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 the current value at which sparks occur. The controller switches to current limiting control when the output current exceeds a preset first current threshold during the execution of constant voltage control, and when the output voltage exceeds a preset voltage threshold during the execution of current limiting control, it applies a pulse voltage set to a voltage with an absolute value greater than the voltage threshold, and switches from current limiting control to constant voltage control when the output current at the time of pulse voltage application is less than a second current threshold set to a value less than the first current threshold.

[0008] The electrostatic painting program according to the embodiment is a program executed by the electrostatic controller in an electrostatic painting system comprising an electrostatic gun and an electrostatic controller that controls the voltage output from the electrostatic gun. The electrostatic painting program causes the electrostatic controller to switch between constant voltage control, which monitors the output voltage and output current from the electrostatic controller and maintains the output voltage at a constant level, and current limiting control, which limits the output current to a range that does not exceed the current value at which sparks occur, and to switch to current limiting control when the output current exceeds a first current threshold during the execution of constant voltage control, and when the output voltage exceeds a preset voltage threshold during the execution of current limiting control, a pulse voltage set to a voltage with an absolute value greater than the voltage threshold is applied, and when the output current at the time of application of the pulse voltage is less than a second current threshold set to a value less than the first current threshold, the program causes the electrostatic controller to execute a process that switches from current limiting control to constant voltage control. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram showing the configuration of an example of an electrostatic coating system according to one embodiment. [Figure 2] Figure 2 is a flowchart showing an example of the processing performed during electrostatic work by the electrostatic controller of an electrostatic painting system according to one embodiment. [Figure 3] Figure 3 shows the changes in the state during electrostatic work in an electrostatic painting system according to one embodiment over time, where (A) shows the stopping and operation of high voltage application 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. [Modes for carrying out the invention]

[0010] The following describes one embodiment with reference to the drawings. First, with reference to Figure 1, the configuration of the electrostatic painting system 1 according to the embodiment will be described. The electrostatic painting 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 painting robot 20, a painting controller 30, and an electrostatic controller 40.

[0011] The electrostatic gun 10 receives liquid paint from a paint supply source 21 and compressed air from an air supply source 23, and electrostatically atomizes the liquid paint in a predetermined pattern and discharges it to perform electrostatic painting on the object to be painted 90. The electrostatic gun 10 has a cascade 11 and electrodes 12 built in. The cascade 11 outputs a high DC voltage proportional to the AC voltage input to the electrostatic gun 10. The cascade 11 boosts the input voltage by several thousand times before outputting it.

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

[0013] The object to be coated 90 may be transported or its rotational position controlled by, for example, a conveyor or turntable (not shown). Alternatively, the object to be coated 90 may be transported while suspended by a hanger provided above it.

[0014] The paint supply source 21 consists of, for example, a tank for storing liquid paint and a pump for pressurizing the paint in the tank. The paint supply source 21 is connected to the electrostatic gun 10 via a paint supply path 25 consisting of hoses, and supplies paint to the electrostatic gun 10. The air supply source 23 consists of, for example, an air compressor. The air supply source 23 is connected to the electrostatic gun 10 via an air supply path 26 consisting of hoses, and supplies compressed air to the electrostatic gun 10.

[0015] The paint on / off valve 22 is located, for example, in the middle of the paint supply path 25. The paint on / off valve 22 is a solenoid valve for liquid paint and controls the supply of paint to the electrostatic gun 10 by opening and closing the paint supply path 25 under control from the painting controller 30. The air on / off valve 24 is located, for example, in the middle of the air supply path 26. The air on / off valve 24 is, for example, a solenoid valve for gas and controls the supply of air to the electrostatic gun 10 by opening and closing the air supply path 26 under control from the painting controller 30. The painting controller 30 is connected to, for example, a higher-level control device that manages manufacturing on the production line, and determines the start and end of painting work based on instructions from this control device.

[0016] The painting robot 20 can be configured as, for example, a multi-joint arm robot or a Cartesian axis arm robot. The painting robot 20 has an electrostatic gun 10 attached to the tip of its arm and functions as a means of moving the electrostatic gun 10 in three dimensions. The painting robot 20 moves the electrostatic gun 10 to any position and orientation according to commands from the painting controller 30. The electrostatic painting system 1 can also be configured with a hand gun that is 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 controls the opening and closing of the paint valve 22 and the air valve 24 to supply and stop paint and air. The painting controller 30 also controls the posture 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 includes a control unit 41, a storage unit 42, a detection unit 43, and a power supply unit 44. The control unit 41 is mainly composed of a microcomputer with a processor, and performs sequence processing and arithmetic processing. The electrostatic controller 40, like the painting controller 30, is connected to a higher-level control device that manages manufacturing on a production line, for example, and determines the start and end of painting work based on instructions from this control device.

[0019] The storage unit 42 is composed of non-temporary storage media such as ROM, RAM, and 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 necessary for executing the electrostatic painting program 421, that is, controlling the voltage or current applied to the electrostatic gun 10, and the control unit 41 reads these parameters and thresholds as needed and uses them for control.

[0020] The detection unit 43 is connected to the cascade 11 of the electrostatic gun 10, for example, via 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. In other words, 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 via, for example, the power line 46, and supplies an alternating voltage to the cascade 11. In this case, the negative electrode side of the power supply unit 44 is connected to the cascade 11 of the electrostatic gun 10, and the positive electrode side is connected to the ground 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 about 2V to 20V, and outputs an alternating pulse voltage with a frequency of about 20 kHz.

[0022] Next, referring also to FIGS. 2 and 3, the operation of the electrostatic coating system 1 will be described. The electrostatic controller 40 executes control to switch between constant voltage control and current limit control according to the distance between the electrostatic gun 10 and the workpiece 90 by executing the electrostatic coating program 421 stored in the storage unit 42 by the control unit 41.

[0023] The constant voltage control is control for monitoring the output voltage V detected by the detection unit 43 and maintaining the voltage output from the electrostatic gun 10 at a preset voltage, for example, a set voltage set by a user or the like. Since the constant voltage control can stably apply a predetermined high voltage to the paint discharged from the electrostatic gun 10, the coating efficiency and quality can be stabilized. On the other hand, in the constant voltage control, the output current changes 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 spark generation between the electrostatic gun 10 and the workpiece 90 increases. Thus, the constant voltage control can perform coating with high efficiency and stable quality by ensuring a distance of a certain amount or more between the electrostatic gun 10 and the workpiece 90. For this reason, the state in which the constant voltage control is being performed can be referred to as the distal mode. Also, the electrostatic coating system 1 executes constant voltage control during normal times when the electrostatic gun 10 and the workpiece 90 are not approaching too closely. For this reason, the state in which the constant voltage control is being performed can also be referred to as the normal mode.

[0024] Current limiting control monitors the output current I detected by the detection unit 43 and maintains the output current output from the electrostatic gun 10 at a predetermined current value that does not cause sparks, for example, considering the risk of sparks. In other words, current limiting control in this embodiment limits the output current I output 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 object to be coated 90. In this case, the current value at which sparks occur, that is, the upper limit of the current in current limiting control, is determined experimentally in advance according to the distance between the electrostatic gun 10 and the object to be coated 90 in the electrostatic coating system 1, and can be a value equivalent to or smaller than the second current threshold I2 described later.

[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, thus reducing the likelihood of sparks. On the other hand, with current limiting control, as the distance between the electrostatic gun 10 and the workpiece 90 decreases and the resistance between the electrostatic gun 10 and the workpiece 90 decreases, the output voltage drops, making it difficult to apply a high voltage to the paint, and thus reducing painting efficiency. Thus, current limiting control allows for safe painting even when the electrostatic gun 10 and the workpiece 90 are in close proximity. For this reason, the state in which current limiting control is performed can be called proximity mode.

[0026] When painting begins, the painting controller 30 operates the painting robot 20 to control the position of the electrostatic gun 10, and also controls the discharge and stopping of paint from the electrostatic gun 10 by opening and closing the paint valve 22 and the air valve 24. Furthermore, once painting begins, 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 Figure 2, for example, based on instructions from a higher-level management device. In addition, the electrostatic controller 40 appropriately decides whether or not to end the painting operation, for example, based on instructions from a higher-level management device, separate from the flow shown in Figure 2. When the electrostatic controller 40 decides to end the painting operation, it stops supplying voltage to the electrostatic gun 10 and ends the flow shown in Figure 2.

[0028] The electrostatic controller 40 stores the following parameters in the 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 for determining whether to switch from constant voltage control to current limit control. During constant voltage control, the controller monitors the output current I, and if the output current I exceeds the first current threshold I1, it executes a process to switch to current limit control. The first current threshold I1 is, for example, a value that, if it becomes larger than this, may cause sparks to occur, and is set to, for example, around 60μA to 80μA.

[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 also parameters used to determine whether to switch from current limit control to constant voltage control. The voltage threshold V1 is set, for example, to be less than or equal to the set voltage for constant voltage control. The determination period T can be set, for example, to be longer than or equal to the time TP during which the pulse voltage VP is applied. Alternatively, the determination period T can be set to be shorter than the time TP during which the pulse voltage VP is applied.

[0030] The second current threshold I2 can be set based, for example, on the maximum voltage that the electrostatic controller 40 can output and the safety distance defined 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 object to be coated 90 that must be ensured to reliably prevent sparks when the maximum voltage is applied. The safety distance can be, for example, twice the distance at which sparks occur when the maximum voltage is applied, and can be set within a range of, for example, several tens of millimeters to several hundred millimeters.

[0031] In this case, the second current threshold I2 can be set to the output current value when the maximum voltage is applied while maintaining a safe distance between the electrostatic gun 10 and the object to be coated 90. Furthermore, the pulse voltage VP is set to a voltage with an absolute value greater than the voltage threshold V1, specifically matching 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 maintaining a safe distance between the electrostatic gun 10 and the object to be coated 90.

[0032] The electrostatic controller 40 makes a decision to switch from current limit control to constant voltage control as follows. First, the electrostatic controller 40 monitors the output voltage V while current limit control is being performed, and if the absolute value of the output voltage V exceeds the voltage threshold V1 for a certain period, for example, the judgment period T, it instantaneously applies a pulse voltage VP. The electrostatic controller 40 sets the time TP for which the pulse voltage VP is applied to a number of microseconds to a number of milliseconds. Then, the electrostatic controller 40 switches from current limit control to constant voltage control if the output current I at the time the pulse voltage VP is applied is smaller than the second current threshold I2.

[0033] Specifically, when the painting operation begins, the electrostatic controller 40 performs constant voltage control in step S11 of Figure 2. The output voltage V gradually increases and then remains constant, as shown at points P0-P1 in Figure 3(B). The output current I also changes according to the distance between the electrostatic gun 10 and the object to be painted 90, as shown at points P0-P1 in Figure 3(C).

[0034] In step S12 of Figure 2, the electrostatic controller 40 determines whether the output current I exceeds the first current threshold I1. If the output current I is less than or equal to 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 moves to step S13 and switches from constant voltage control to current limiting control. As a result, as shown at points P1-P2 in Figure 3(C), the output current I is kept constant. Also, as shown at points P1-P2 in Figures 3(B) and 3(C), the output voltage V changes in the direction that the output voltage V increases as the distance between the electrostatic gun 10 and the object to be coated 90 increases.

[0036] When the electrostatic controller 40 switches to current limit control, in step S14 it determines whether the absolute value of the output voltage V has remained above the voltage threshold V1 for the determination period T. If the absolute value of the output voltage V has not remained above the voltage threshold V1 for the determination period T (NO in step S14), the electrostatic controller 40 repeats step S14 to maintain current limit control.

[0037] As shown at point P2 in Figure 3(B), if the absolute value of the output voltage V exceeds the voltage threshold V1 for the determination period T (YES in step S14 in Figure 2), the electrostatic controller 40 moves 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 point P2-P3 in Figure 3(C), if the output current I is greater than or equal to the second current threshold I2 even after applying the pulse voltage VP (NO in step S16 in Figure 2), the electrostatic controller 40 returns to step S14 and makes a decision to switch to constant voltage control while maintaining current limit control.

[0038] On the other hand, for example, as shown at points P4-P5 in Figure 3(C), 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 Figure 2), the electrostatic controller 40 moves the process to step S11 and switches to constant voltage control. In this way, the electrostatic controller 40 repeats the processes of steps S11 to S16, performing the painting work while appropriately switching between constant voltage control and current limiting control according to the distance between the electrostatic gun 10 and the object to be painted 90.

[0039] According to the embodiment described above, the electrostatic painting system 1 comprises an electrostatic gun 10 and an 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 switch between constant voltage control, which maintains the output voltage V at a constant level, and current limiting control, which maintains the output current I at a constant level. The electrostatic controller 40 switches to current limiting control when the output current I exceeds a preset first current threshold I1 while constant voltage control is being performed.

[0040] According to this, if, during constant voltage control, the distance between the tip of the electrostatic gun 10 and the object to be coated 90 becomes close and the output current I suddenly rises and exceeds the first current threshold I1, the system automatically switches to current limiting control, which allows for safe operation even when the tip of the electrostatic gun 10 and the object to be coated 90 are in close proximity. Therefore, even if the tip of the electrostatic gun 10 and the object to be coated 90 unexpectedly come into close proximity during painting, there is no need to stop the electrostatic painting system 1, thus achieving 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 decreases, there is a concern that the output voltage V will continue to rise to near the 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 the control is switched from current limiting control to constant voltage control simply because the output voltage V has risen above a certain level, the switching between current limiting control and constant voltage control may occur frequently, potentially compromising 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 the execution of current limit control. The pulse voltage VP is set to a voltage with an absolute value greater than the voltage threshold V1. The electrostatic controller 40 then switches from current limit control to constant voltage control when the output current I at the time the pulse voltage VP is applied is less than the second current threshold I2. The second current threshold I2 is set to a value less than the first current threshold I1.

[0043] Thus, in this embodiment, when the output voltage V exceeds the voltage threshold V1 during the execution of current limit control, a 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 system switches 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 limit 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 a pulse voltage VP if the output voltage V remains above the voltage threshold V1 for a certain period T while current limit control is being performed. In this case, the certain period T can be set to a period longer than, for example, the application time TP of the pulse voltage VP. This prevents unnecessary changes in the control mode due to short-term, slight voltage fluctuations that temporarily cause the output voltage V to exceed the voltage threshold V1. As a result, frequent switching between constant voltage control and current limit control can be suppressed, and the stability of the painting operation can be improved.

[0045] Furthermore, since the second current threshold I2 is set to a smaller value than the first current threshold I1, the switch to constant voltage control is performed when the output current I has decreased more stably. As a result, it is possible to return to constant voltage control only after confirming that the distance between the electrostatic gun 10 and the workpiece 90 has recovered sufficiently. This makes it possible to achieve both safety and production efficiency without stopping the painting work, and to stabilize the quality of the coating film by resuming appropriate voltage application when returning from a close-proximity state.

[0046] Furthermore, the electrostatic coating system 1 and electrostatic coating program 421 of this embodiment can be applied in situations other than those where the distance between the tip of the electrostatic gun and the object to be coated is unintentionally close, as described above. For example, when the shape of the object to be coated is a mixture of continuous flat surfaces and areas with partially uneven surfaces, there is a need to paint efficiently in a short time, and to simplify the instruction of the robot's movements and the voltage setting of the electrostatic controller 40 as much as possible. Note that coating efficiency refers to the proportion of the discharged paint that actually adheres to the object to be coated.

[0047] In proximity mode painting, paint scattering is minimal and coating efficiency is high when painting continuous, smooth surfaces. However, with conventional constant-current proximity mode painting, it is difficult to maintain a constant film thickness when the distance between the electrostatic gun tip and the workpiece changes rapidly, such as when the workpiece has many irregularities on the surface, due to voltage fluctuations. Also, if interference with the surroundings prevents the tip of the paint gun from reaching recesses in the workpiece, sufficient voltage cannot be applied with constant-current proximity mode painting. In such cases, conventionally, painting was often done in distal mode with constant voltage control, even if it meant sacrificing some coating efficiency.

[0048] In contrast, according to the embodiment described above, even if the object to be coated 90 has uneven surfaces, the system automatically switches between proximity mode and distal mode depending on the distance between those surfaces and the tip of the electrostatic gun 10. Therefore, when teaching the trajectory for painting using a robot, it is not necessary to set the voltage value for each uneven surface or to pre-set the mode switching. As a result, according to this embodiment, it is possible to paint smoothly with simple teaching and by applying the maximum voltage that can be applied in that situation. This enables efficient electrostatic painting regardless of the uneven shape of the surface of the object to be coated.

[0049] The embodiments described above are not limited to those described above and shown in the drawings, and can be modified as appropriate without departing from the spirit 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, The system includes an electrostatic controller that controls the voltage output from the electrostatic gun, The electrostatic controller is The electrostatic gun monitors the output voltage and output current, and is switchable 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 the current value at which sparks occur. Furthermore, if the output current exceeds a preset first current threshold while the constant voltage control is being executed, the system switches to current limiting control. If the output voltage exceeds a preset voltage threshold during the execution of the current limiting control, a pulse voltage set to a voltage with an absolute value greater than the voltage threshold is applied, and if the output current when the pulse voltage is applied is less than a second current threshold set to a value less than the first current threshold, the system switches from the current limiting control to the constant voltage control. Electrostatic coating system.

2. The electrostatic controller applies the pulse voltage when the output voltage remains above the voltage threshold for a certain period of time during the execution of the current limiting control. The electrostatic coating system according to claim 1.

3. A program executed by the electrostatic controller in an electrostatic painting system comprising an electrostatic gun and an electrostatic controller that controls the voltage output from the electrostatic gun, The electrostatic controller, The electrostatic controller monitors the output voltage and output current, and is switchable 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 the current value at which sparks occur, and a process to switch to current limiting control when the output current exceeds a first current threshold during the execution of the constant voltage control. If the output voltage exceeds a preset voltage threshold during the execution of the current limiting control, a pulse voltage set to a voltage with an absolute value greater than the voltage threshold is applied, and if the output current when the pulse voltage is applied is less than a second current threshold set to a value less than the first current threshold, the process of switching from the current limiting control to the constant voltage control is executed. Electrostatic coating program.

4. The process of switching from the current limiting control to the constant voltage control includes the process of applying the pulse voltage if the output voltage remains above the voltage threshold for a certain period of time during the execution of the current limiting control. The electrostatic coating program according to claim 3.

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