Electrostatic coating machine

Abstract

A system includes a workpiece and an electrostatic coater configured to electrostatically adsorb a coating on the workpiece by charging the coating with a voltage output supplied from a high voltage generator, the high voltage safety control unit is configured to monitor the voltage output and reduce the voltage output of the high voltage generator based on the detected current being above a first overcurrent threshold, wherein the first overcurrent threshold is based on a dynamic threshold of the voltage output.

Description

Background Art

[0001] Embodiments of the present invention relate to an electrostatic coating machine, and more particularly to a system including an electrostatic loader and a workpiece having improved spark protection characteristics.

[0002] As used herein, "remote coating" refers to a distance between the workpiece and the loader set to about 150 mm to 300 mm. As used herein, "proximity coating" refers to a distance less than 150 mm. As used herein, "ultra-proximity coating" refers to a distance less than 100 mm.

[0003] like Figures 8 to 10 As shown, with prior art systems, proximity coating is difficult and dangerous, and ultra-proximity coating is almost impossible. Figure 8 The conventional absolute sensitivity value and current limit value settings of the remote coating method are illustrated. Both the absolute sensitivity value and the current limit value are constant current values ​​for high voltage. The relative relationship between the absolute sensitivity value and the current limit value can be current limit value (CB) < absolute sensitivity value (CL), and vice versa, absolute sensitivity value (CL) < current limit value (CB), as shown in the figure.

[0004] Figure 8 The illustrated current limit value (CB) < absolute sensitivity value (CL) is applicable to an indirect charging electrostatic coating machine (a coating machine with an external electrode). In a coating machine with an external electrode, the main body (rotary atomizer head) of the coating machine and the paint supply route are grounded, and a high voltage is applied to the electrode installed on the side of the machine body. The indirect charging method is mainly used for external charging of water-based paints with low resistance, and the high voltage application part of the external electrode is mainly a needle-shaped electrode. The needle-shaped electrode has a small volume and holds very little energy, so the risk of igniting discharge (hereinafter referred to as "spark") is extremely small. "Spark" is a spark discharge with a discharge energy of 0.24mJ or more, which ignites solvent vapor. In addition, water-based paint has a low ignition risk. For this reason, the indirect charging coating machine mainly uses an output high voltage control based on the current limit value (CB), and an overcurrent safety control based on the absolute value sensitivity (CL) is used as a backup measure. The electrostatic coating method of water-based paint is not limited to the indirect charging method, but the direct charging method described below is also possible when a device that electrically insulates the paint supply path is used.

[0005] Absolute sensitivity value (CL) < current limit value (CB) can be used in direct charging electrostatic coating method, in which solvent-based paint with high resistance is directly charged by rotary atomizer head. Because the rotary atomizer head includes a rotating mechanism (such as a metal air motor), its electrostatic volume is large, and therefore its retained energy is also large. Therefore, the spark risk is high, so the output of the high voltage generator is stopped before it enters the danger zone based on the absolute sensitivity value.

[0006] When the current limit value (CB) < absolute sensitivity value (CL) as described above, when the electrostatic coating machine is abnormally close to the workpiece to be coated (hereinafter referred to as the "workpiece"), the output current rises. When the electrostatic coating machine is abnormally close to the workpiece (hereinafter referred to as the "workpiece"), the output current rises. When the rising output current reaches the current limit value, the absolute value of the output voltage of the high voltage generator is reduced (output high voltage control function). This controls the output of the high voltage generator, that is, the high voltage applied to the end of the electrostatic coating machine, so that the output current does not exceed the normal current value range. In other words, the output high voltage control function prevents sparks by controlling the output of the high voltage. In the output high voltage control function, the output of the high voltage generator is not cut off as described above.

[0007] In addition to the above-mentioned output high voltage control function, when the output current rises abnormally and reaches the absolute value sensitivity (CL), the output of the high voltage generator stops, which is an overcurrent safety control function.

[0008] exist Figure 8 In the figure, the reference symbol UV represents the high voltage lower limit sensitivity. When the output voltage of the high voltage generator drops to the high voltage lower limit sensitivity (UV), the output of the high voltage generator is stopped (minimum high voltage protection control function). In other words, the output of the high voltage generator is stopped in the area below the high voltage lower limit sensitivity (UV).

[0009] The distance between the electrostatic coater and the workpiece, or "coating distance", has been reduced from about 150 mm to 300 mm (remote coating method) to a smaller distance of 150 mm (proximity coating method). Although the proximity coating method has the advantage of increasing the efficiency of coating transfer, the application of the proximity coating method is considered to be limited to coating distances of up to 100 mm.

[0010] In addition, in recent years, there has been a trend to increase the coating speed ("line speed") of the coating machine in order to improve production efficiency. However, in recent years, there has been a trend to increase the coating speed ("line speed") of the coating machine more and more to improve production efficiency. Specifically, the speed tends to increase from the conventional 30 to 500 mm / sec to 50 to 120 mm / sec. In order to adopt the proximity coating method in this environment, it is necessary to ensure a high safety level and achieve proper operation of the proximity coating method.

[0011] For example, at a linear speed of 50 mm / sec, according to experiments, it takes about 0.1 seconds from the detection of the abnormal rise of the high voltage current caused by the abnormal approach of the electrostatic coating machine to the workpiece until the coating robot stops completely. During this 0.1 second period, the electrostatic coating machine advances 50 mm. Therefore, it is necessary to avoid the situation where the robot enters the spark zone where sparks may occur. In addition, the frequency of passing through the spark generation zone must be reduced in order to avoid a decrease in productivity.

[0012] The above-mentioned high voltage safety control function is used in the remote coating method. In order to confirm whether this high voltage safety control function can be applied to the proximity coating method, experiments were conducted and verified using a plate-shaped bottom and a spherical bottom. This experiment was conducted by arranging the plate-shaped bottom or the spherical bottom close to the stationary electrostatic coating machine.

[0013] In the automobile manufacturing process, automobile bodies and parts such as bumpers and door mirrors are each coated in different factories and delivered to an assembly plant where the finished automobile is manufactured.

[0014] A plate-shaped bottom is a typical example of a workpiece such as a car body in which a discharge current easily flows between the surface to be coated on the workpiece and the coating machine. On the other hand, a spherical bottom as represented by the curved surface of a door mirror cover is a typical example of a workpiece in which a discharge current is more difficult to flow than a plate-shaped bottom, making it most difficult to ensure safety by implementing a high voltage safety control function.

[0015] Fig. 9 An example experiment using a plate-shaped bottom is shown. The current limit value (CB) is set to 50 μA. The electrostatic coating machine used is a direct-charged rotary atomizing coating machine. The experiment was started with a high voltage of -60 kV applied to the electrostatic coating machine, and the plate-shaped bottom was gradually brought closer to the coating machine. As can be seen in FIG. Fig. 9 It can be seen from FIG. 1 that when the distance between the coating machine and the workpiece is about 120 mm, the output high voltage control function starts to work, resulting in a gradual decrease in the output voltage of the high voltage generator.

[0016] Considering the above-mentioned high line speed of 50mm / sec, it is desirable to stop the output of the high voltage generator before the distance between the plate bottom and the electrostatic coating machine reaches 70mm. This can be achieved by setting the high voltage sensitivity lower limit (UV) to -45kV. When the absolute value of the output voltage of the high voltage generator drops to 45kV through the output high voltage control, the minimum high voltage protection control function is activated. That is, the output of the high voltage generator is stopped based on the high voltage lower limit sensitivity (set value: -45kV). Fig. 9 The dashed line in shows the output current 402 .

[0017] Fig.10 An example experiment using a spherical bottom is shown. As in the plate bottom experiment ( Fig. 9 ), the current limit value (CB) was set to 50 μA. The electrostatic coating machine used was a direct charging rotary atomizing coating machine. The experiment was started with a high voltage of -60 kV applied to the electrostatic coating machine, and the spherical bottom was gradually brought close to the coating machine.

[0018] As described above, the spherical bottom makes it difficult for the discharge current to flow. Therefore, the output high voltage control function does not work well. Therefore, the distance between the electrostatic coating machine and the spherical bottom becomes smaller, accompanied by insufficient output drop of the high voltage generator, and sparks occur when entering the spark generation area 401 without performing the forced output stop of the high voltage generator by the minimum high voltage protection control function. As can be seen from Fig.10 The experimental results show that the spherical bottom is the most demanding workpiece in the high voltage safety control function. Fig.10 The single-point dashed line in represents the output current 402 .

[0019] As shown in the above experiments, in a proximity coating method, in which the electrostatic coating machine is operated at a short distance from the workpiece, the risk of sparks increases when the coating distance during operation is set to a smaller value. In addition, as described above, a higher line speed is required. Proximity coating under these conditions further increases the risk of sparks. This means that when operating under a conventional high voltage safety control function, the output of the high voltage generator can be stopped frequently. If the output of the high voltage generator is stopped frequently, productivity will be reduced. For this reason, as described above, a coating distance of up to 100 mm is considered to be the application limit of proximity coating.

[0020] In the proximity coating method, the closer the coating distance is, the higher the transfer efficiency is. Therefore, it is natural to operate the electrostatic coating machine as close to the workpiece as possible. Therefore, the proximity coating method needs to take into account both safety and productivity.

[0021] An object of embodiments of the present invention is to provide a coating system and a high voltage safety control method, which can reduce the risk of sparks in a proximity coating method.

[0022] From a safety perspective, when there is a risk of sparking, it may be desirable to cut off the high voltage in order to avoid sparking. In proximity coating, the electrostatic coating machine operates near the workpiece, so detection of increased discharge current (in other words, overcurrent detection) occurs frequently, and each need to cut off the high voltage may result in reduced productivity. Summary of the invention

[0023] A system may be improved that includes a workpiece and an electrostatic coater configured to electrostatically adsorb a coating on the workpiece by charging the coating with a voltage output supplied from a high voltage generator, wherein a high voltage safety control unit is configured to monitor the voltage output and reduce the voltage output of the high voltage generator based on a detected current being above a first overcurrent threshold, wherein the first overcurrent threshold is a dynamic threshold based on the voltage output. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 An example non-limiting view of the system disclosed herein is shown.

[0025] Figure 2 An example non-limiting view of an electrostatic coating machine disclosed herein is shown.

[0026] Figure 3 An example non-limiting block diagram illustrating the logic of a high voltage safety control unit disclosed herein.

[0027] Figure 4 Example non-limiting curves are shown for settings of the current limit value (CB) and the absolute sensitivity value (CL).

[0028] Figure 5 Shown according to Figure 4 Example non-limiting curves of voltage varying with current are shown.

[0029] Figure 6 The use of a spherical bottom is shown to confirm Figure 4 and Figure 5 Example of an experiment to show the effect of .

[0030] Figure 7 Example non-limiting graphs of current limit values ​​(CB) and absolute sensitivity values ​​(CL) varying according to current output are shown.

[0031] Figure 8 A prior art example of a current limit value (CB) and an absolute sensitivity value (CL) that vary according to voltage is shown.

[0032] Fig. 9 It shows the Figure 8 Graphs of current and voltage as a function of coating distance for an example of the prior art.

[0033] Fig.10 For a spherical bottom, Figure 8 Graphs of current and voltage of a prior art example showing a current limit value (CB) and an absolute sensitivity value (CL) varying according to a coating distance.

[0034] Fig.11 Example non-limiting graphs showing current limit values ​​(CB) and absolute sensitivity values ​​(CL) varying according to detection voltage are shown. DETAILED DESCRIPTION

[0035] like Figures 1 to 7 and Fig.11 As shown, the coating device 405 may include: an electrostatic coating machine (14) that electrostatically adsorbs the coating on the workpiece 412 by charging the coating with an output voltage 406 supplied from a high voltage generator (24); and a high voltage safety control unit (30) that controls the output voltage 406 applied to the electrostatic coating machine (14) to ensure safety during operation. The high voltage safety control unit (30) includes an output high voltage control unit (302). When the output current 402 reaches the current limit value (CB), the output high voltage control unit (302) does not stop the output of the high voltage generator (24), but controls the output voltage 406 to reduce the absolute value of the output voltage 406. The high voltage safety control unit (30) includes a CB setting change unit (320) that changes the setting value of the current limit value (CB) based on the real-time value of the output voltage 406. In the CB setting change section (320), the current limit value (CB) is set to a smaller value when the absolute value of the output voltage 406 is larger and smaller within a relatively low voltage range 407 in which the absolute value of the high voltage of the output voltage 406 is lower than a predetermined threshold value.

[0036] The coating device 405 may include: an electrostatic coating machine (14) that electrostatically adsorbs the coating on the workpiece 412 by charging the coating with an output voltage 406 supplied from a high voltage generator (24); and a high voltage safety control unit (30) that controls the high voltage applied to the electrostatic coating machine (14) to ensure safety during operation. The high voltage safety control unit (30) includes an overcurrent safety control unit (304). The overcurrent safety control unit (304) performs control to stop the output of the high voltage generator (24) when an abnormal increase in the output current 402 is detected based on the absolute value sensitivity (CL). The high voltage safety control unit (30) includes a CL setting change unit (322) that can change the set value of the absolute value sensitivity (CL) based on the real-time value of the output voltage 406. In the CL setting change section (322), the absolute value sensitivity (CL) is set to a smaller value when the absolute value of the output voltage 406 is larger and smaller within a relatively low voltage range 407, in which the absolute value of the high voltage of the output voltage 406 is lower than a predetermined threshold value.

[0037] According to another aspect of an embodiment of the present invention, the above technical problem can be solved by a high voltage safety control method, which is performed using the following components: an electrostatic coating machine (14) that electrostatically adsorbs the coating on a workpiece 412 by charging the coating with an output voltage 406 supplied from a high voltage generator (24); and a high voltage safety control unit (30) that controls the high voltage applied to the electrostatic coating machine (14) to ensure safety during operation. The high voltage safety control unit (30) may include an output high voltage control unit (302). When the output current 402 reaches a current limit value (CB), the output high voltage control unit (302) does not stop the output of the high voltage generator (24), but controls the output voltage 406 to reduce the absolute value of the output voltage 406. The method includes a high voltage monitoring process for monitoring the output voltage 406, and a CB setting change process for changing the set value of the current limit value (CB) based on the real-time value of the output voltage 406 obtained in the high voltage monitoring process. In the CB setting change process, the current limit value (CB) is set to a smaller value when the absolute value of the output voltage 406 is larger and smaller within the relatively low voltage range 407 in which the absolute value of the high voltage of the output voltage 406 is lower than the predetermined threshold value.

[0038] A high voltage safety control method may include using an electrostatic coating machine (14) that electrostatically adsorbs a coating on a workpiece 412 by charging the coating with an output voltage 406 supplied from a high voltage generator (24); and a high voltage safety control unit (30) that controls the high voltage applied to the electrostatic coating machine (14) to ensure safety during operation. The high voltage safety control unit (30) includes an overcurrent safety control unit (304). The overcurrent safety control unit (304) performs control to stop the output of the high voltage generator (24) when an abnormal increase in an output current 402 is detected based on an absolute value sensitivity (CL). The method may include a high voltage monitoring process for monitoring an output voltage 406, and a CL setting change process for changing a set value of an absolute value sensitivity (CL) based on a real-time value of the output voltage 406 obtained in the high voltage monitoring process. During the CL setting change process, the absolute value sensitivity (CL) is set to a smaller value when the absolute value of the output voltage 406 is larger and smaller within a relatively low voltage range 407, in comparison, in which the absolute value of the high voltage of the output voltage 406 is lower than a predetermined threshold.

[0039] In some embodiments, the high voltage safety control unit (30) includes: an overcurrent safety control unit (304) that performs control to stop the output of the high voltage generator (24) when an abnormal increase in the output current 402 is detected based on the absolute value sensitivity (CL); and a CL setting change unit (322) that changes the setting value of the absolute value sensitivity (CL) based on the currently detected value of the output voltage 406. The detected value of the output voltage 406 may be the absolute value of the output voltage 406 after it has been filtered to remove ripple. In the CL setting change unit (322), in comparison, when the absolute value of the output voltage 406 is larger and smaller within a relatively low voltage range 407, the absolute value sensitivity (CL) is set to a smaller value. The high voltage safety control unit (30) may include an output high voltage control unit (302). The output high voltage control unit (302) is configured to control the output voltage 406. When the output current 402 reaches the current limit value (CB), the output high voltage control unit (302) does not stop the output of the high voltage generator (24), but controls the output voltage 406 to reduce the absolute value of the output voltage 406. The high voltage safety control unit (30) includes a CB setting change unit (320) that changes the setting value of the current limit value (CB) based on the real-time value of the output voltage 406. In the CB setting change unit (320), the current limit value (CB) is set to a smaller value when the absolute value of the output voltage 406 is larger and smaller in a relatively low voltage range 407 in which the absolute value of the high voltage of the output voltage 406 is lower than a predetermined threshold.

[0040] Embodiments of the present invention can be applied to a rotary atomizing coating machine (14), wherein a high voltage is applied to a rotary atomizing head (14a). In conventional proximity coating methods, a coating distance of 100 mm is considered to be a limit. According to embodiments of the present invention, in response to changes in output current 402, current limit value (CB) and absolute sensitivity value (CL), at least the set value of absolute value sensitivity (CL) can be changed to quickly respond to the control of the electrostatic coating machine, thereby preventing the occurrence of sparks. Embodiments of the present invention can achieve ultra-close-range coating, wherein the coating distance is set to, for example, about 100 mm to 20 mm.

[0041] like Figure 1As shown, the electrostatic coating machine 14 can be assembled to the wrist 12 at the end of the robot arm 11. The electrostatic coating machine 14 can have a rotary atomizing head 14a, which can be positioned at the end of the coating machine body 14b. The electrostatic coating machine 14 can be a rotary atomizing type coating machine. The coating robot 10 (including the electrostatic coating machine 14) can be controlled by a control unit 16.

[0042] The high voltage control of the electrostatic coating machine 14 may be controlled by other units than the control unit 16. The control unit 16 controlling the coating robot 10 may include a high voltage safety control unit 30. The high voltage safety control unit 30 constitutes a coating system SY together with the electrostatic coating machine 14. The high voltage safety control unit 30 may be incorporated into the control unit 16 or as an independent unit. The high voltage safety control unit 30 has an output high voltage control unit 302, an overcurrent safety control unit 304, and a minimum high voltage protection control unit 306 ( Figure 3 ).

[0043] The high voltage safety control unit 30 includes: a high voltage real-time value monitoring unit 310, which continuously monitors the current output current 402; and high voltage monitoring units 312 (A), (B), which continuously monitor the current high voltage V. The output current 402 received by the high voltage current value monitoring unit 310 is not affected by the pulsating component ΔV caused by the Cockcroft-Walton circuit.

[0044] The current value of the output current 402 is supplied from the high voltage real-time value monitoring section 310 to the output high voltage control section 302 and the overcurrent safety control section 304. As usual, the output high voltage control section 302 generates an output high voltage control signal when the rising output current 402 reaches the current limit value (CB) value, which is used to reduce the value of the output voltage 406 of the cascade circuit 24. The output of the cascade circuit 24 is controlled based on this output high voltage control signal (output high voltage control function (CB)).

[0045] As usual, the overcurrent safety control unit 304 generates an output stop signal when the output current 402 abnormally rises to a value higher than the absolute value sensitivity (CL). Based on this output stop signal, the output of the cascade circuit 24 is stopped (overcurrent safety control function (CL)).

[0046] like Figure 2As shown, the electrostatic coating machine 14 may have an air motor 20, and a rotary atomizing head 14a is connected to a motor output shaft 20a of the air motor 20. The rotary atomizing head 14a is driven by the air motor 20. The motor output shaft 20a is hollow. The paint supply pipe 22 is positioned at the central axis 413 of the air motor 20 in the hollow motor output shaft 20a, and the paint is supplied to the center of the rotary atomizing head 14a through the paint supply pipe 22. In other words, the electrostatic coating machine 14 is a center feed coating machine.

[0047] The electrostatic coating machine 14 can have a high voltage generator (hereinafter referred to as "cascade circuit") 24 built into the machine. The cascade circuit 24 generates an output voltage 406 by the well-known Cockcroft-Walton circuit. The output voltage 406 generated by the cascade circuit 24 is supplied to the rotary atomizing head 14a via the air motor 20. In other words, the air motor 20 described above is made of metal, and the metal air motor 20 constitutes a part of the high voltage application channel for applying a high voltage to the rotary atomizing head 14a. The paint supplied to the rotary atomizing head 14a can be directly charged by the rotary atomizing head 14a when atomizing. In other words, the electrostatic coating machine 14 is a direct charging coating machine. Instead of the cascade circuit 24 built into the electrostatic coating machine 14, the high voltage generated by the high voltage generator (not shown) separated from the electrostatic coating machine 14 can be supplied to the rotary atomizing head 14a.

[0048] exist Figure 3 , reference numeral 320 denotes a CB setting change unit, and reference numeral 322 denotes a CL setting change unit. The current limit value (CB) setting may be changed in the CB setting change unit 320 to a current limit value (CB) corresponding to a current value based on the current value of the output voltage 406. Figure 4 The data related to the current limit value (CB) shown in FIG. 4 can be pre-registered in the memory 410. In the CL setting change unit 322, the data related to the current limit value (CB) from the memory 410 ( Figure 2 ) and the set value of the absolute sensitivity value (CL) can be changed in the CL setting change unit 322 to change to the absolute sensitivity value (CL) corresponding to the current value based on the real-time value of the output voltage 406. Figure 4 The data related to the absolute value sensitivity (CL) shown may be pre-registered in the memory 410 .

[0049] The current value of the output voltage 406 supplied from the high voltage monitoring section 312 (A) and 312 (B) to the CB setting change section 320 and the CL setting change section 322 may be a value obtained after passing through a strong filter that mitigates the influence of the pulsation component ΔV described above. The current limit value (CB) may be implemented in the output high voltage control section 302 based on the current limit value (CB) setting received from the CB setting change section 320. The overcurrent safety control section 304 performs overcurrent safety control (CL) based on the set value of the absolute sensitivity value (CL) received from the CL setting change section 322.

[0050] The value of the output voltage 406 generated by the output high voltage control section 302 may be supplied to the minimum high voltage protection control section 306 through the high voltage value monitoring section 314, as it may be a real-time output voltage 406 value. The minimum high voltage protection control section 306 receives the registered value of the high voltage lower limit sensitivity UV read from the memory 410 ( Figure 2 ), and the minimum high voltage protection control unit 306 performs the minimum high voltage protection control based on the registered value of the high voltage lower limit sensitivity UV. In other words, when the absolute value of the output voltage of the cascade circuit 24 drops below the registered value of the high voltage lower limit sensitivity UV, the output of the high voltage generator of the cascade circuit 24 can be stopped.

[0051] First Example Regarding Setting Value Change (CB Setting Value Change)

[0052] Figure 4 A first example regarding setting of the current limit value (CB) is illustrated. Figure 4 A second example regarding the setting of the current limit value (CB) and the absolute sensitivity value (CL) is also illustrated.

[0053] refer to Figure 4 , in this example, the high voltage change region (voltage drop due to the current limit value (CB)) in the proximity coating operation is that the absolute value of the output voltage 406 may be 60 kV or less. The region above this output voltage 406 change region may be referred to as a "relatively high voltage region 408". The relatively high voltage region 408 corresponds to a coating distance 411 of 200 mm or more. On the other hand, the region where the absolute value of the output voltage 406 may be lower than the relatively high voltage region 408 may be referred to as a "relatively low voltage region 407". The relatively low voltage region 407 corresponds to a coating distance 411 of 20 mm to 200 mm.

[0054] In the relatively high voltage range 408, the current limit value (CB) may be a constant value relative to the output voltage 406 (CB may be approximately 50 μA). On the other hand, in the relatively low voltage range 407, the set value of the current limit value (CB) may be changed. Specifically, in the relatively low voltage range 407, when the absolute value of the output voltage 406 may be larger than the relatively low voltage range of the output voltage 406, and when the absolute value of the output voltage 406 may be small, the set value of the current limit value (CB) may be changed to a smaller value. In the relatively low voltage range 407, as the absolute value of the output voltage 402 becomes lower, the set value of the current limit value (CB) may be changed to a smaller value (from approximately 50 μA to approximately 30 μA or lower). In some embodiments, as may be Figure 4 It can be seen from FIG. 4 that in the relatively low voltage region 407, as the absolute value of the output voltage 406 decreases, the current limit value (CB) can be gradually changed to a smaller value. This setting change of the current limit value (CB) can be performed by the CB setting change unit 320 ( Figure 3 Each value of the output voltage 406 and the corresponding current limit value (CB) setting can be stored in the memory 410 ( Figure 2 ).

[0055] In operation, the CB setting change section 320 reads the registered value of the current limit value (CB) corresponding to the real-time value of the output voltage 406 from the memory 410, and provides the setting value of the current limit value (CB) based on this read registered value of the current limit value (CB) to the output high voltage control section 302 ( Figure 3 The output high voltage control performed in the output high voltage control section 302 may be based on the setting value of the current limit value (CB) received from the CB setting change section 320 .

[0056] Figure 5 This second example ( Figure 4 ) is a variation of the second example ( Figure 4 ) is that the set value of the absolute sensitivity value (CL) can be changed, but the set value of the current limit value (CB) can be constant even if the value of the output voltage 406 changes. When the set value of the current limit value (CB) can be set to a relatively small value (e.g., 30 μA), the set value of the current limit value (CB) can be kept constant even when the value of the output voltage changes.

[0057] refer to Figure 4 and Figure 5, in the relatively low voltage range 407, when the absolute value of the output voltage 406 can be large and when it can be small, when the absolute value of the output voltage 406 can be small, the set value of the absolute value sensitivity (CL) can be set to a smaller value. In the relatively low voltage range 407, as the absolute value of the output voltage 406 becomes lower, the set value of the absolute value sensitivity (CL) can be changed to a smaller value. In some embodiments, as can be seen in Figure 4 and Figure 5 , in the relatively low voltage range 407, as the absolute value of the output voltage 406 becomes lower, the set value of the absolute value sensitivity (CL) can be gradually changed to a smaller value. Then, when comparing at the same output voltage, the absolute value sensitivity (CL) can be set to a value greater than the current limit value (CB) (CB < CL). The lower the absolute value of the high voltage V, the greater the difference between the absolute value sensitivity (CL) and the current limit value (CB) should be set.

[0058] According to the second example ( Figure 4 ) and the variant ( Figure 5 ), for example, when a spark occurs due to a fault or accident, that is, when the current limit value (CB) cannot keep up in time, overcurrent safety control can be performed based on the absolute value sensitivity (CL), which can be set to a small value as the absolute value of the output voltage 406 decreases. Control can be performed, and the output of the cascade circuit 24 can be cut off. This overcurrent safety control can be used as a backup measure for safety assurance.

[0059] In the second example ( Figure 4 ) and the variant ( Figure 5 ), as in the first example, the corresponding set values of each value of the output voltage 406 and the current limit value (CB) and the corresponding set values of each value of the output voltage 406 and the absolute value sensitivity (CL) should be stored in advance in the memory 410 ( Figure 2 ).

[0060] Third Example Regarding Setting Value Change (Intersection of CB Setting Change Characteristic Line and CL Setting Change Characteristic Line) :

[0061] As can be seen from Figure 4 and Figure 5It can be seen that it is recommended that the characteristic line of the CB setting change of the current limit value (CB) intersects with the characteristic line of the CL setting change of the absolute sensitivity (CL). At the intersection point where the absolute sensitivity value (CL) and the current limit value (CB) become the same value (about 30 μA), the set voltage value of Cp can be the stored value of the lower limit sensitivity (UV) (about -30 kV). The stored value of the lower high-voltage sensitivity (UV) can be the threshold value of the minimum high-voltage protection control as described above, and when the absolute value of the output voltage 406 of the cascade circuit 24 drops below the stored value of the lower high-voltage sensitivity (UV) below the intersection point 105, the output of the cascade circuit 24 can be stopped. This region where the output can be stopped can be called the "minimum high-voltage protection region M V ar".

[0062] In Figure 4 and Figure 5 in the relatively low voltage range 407, when compared at the same output voltage, the current limit value (CB) can be lower than the absolute sensitivity value (CL). On the other hand, in the minimum high-voltage protection region M V ar in the region that can be below the stored value of the high-voltage lower limit sensitivity (UV), the relationship between the current limit value (CB) and the absolute sensitivity value (CL) can be reversed, and the absolute sensitivity value (CL) < the current limit value (CB), which is different from that in the relatively low voltage region 407.

[0063] The advantages of the current limit value < the absolute sensitivity value (CB < CL) when compared with the same output voltage in the relatively low voltage range 407 can be explained below. If the workpiece 412 (such as the body of a vehicle) has edges, the discharge current easily flows at the edges, and the output current 402 temporarily rises. Even if the coating line cannot be stopped due to the action of the absolute sensitivity value (CL) at the edges, the electric field concentrates at the edges, resulting in the coating film of the paint adhering to the edges becoming too thick. In addition, when the electric field can concentrate at the edges, the paint does not spread to areas deeper than the edges, resulting in the problem of insufficient coating film on the surface to be coated except at the edges.

[0064] For the workpiece 412 with many edges, the manipulator control program uses a coating method of reducing the absolute value of the output voltage or enhancing the forming air, and the coating can be performed under a coating program that can adapt to the workpiece 412 with many edges.

[0065] As described above, in recent years, there has been a demand for faster line speeds in coating. However, the coating process can only operate in units of the part to be coated (e.g., 1 second). Therefore, for example, if the output voltage remains at a low absolute value for the remaining 0.9 seconds due to an edge with a passing time of only 0.1 sec (in the case of a line speed of 500 mm / sec, a 450 mm area), or if the coating can be carried out with continuously strong shaping air, the transfer efficiency will decrease.

[0066] In the relatively low voltage range 407, if CB < CL when compared at the same output voltage, the output voltage can be suppressed only when necessary, where the current limit value (CB) is suitable for the edge condition (appropriate field strength), thus maintaining the high transfer efficiency achievable with proximity coating.

[0067] In the relatively low voltage range 407, when compared at the same output voltage as described above, CB < CL, and the difference between the current limit value (CB) and the absolute sensitivity value (CL) should gradually decrease as the absolute value of the output voltage 406 decreases.

[0068] In the relatively low voltage region 407, the relatively larger the absolute value of the output voltage 406 (in the regions between Figure 4 and Figure 5 and away from the intersection point 105), the greater the fluctuation in the value of the output current 402 with respect to the change in the absolute value of the output voltage 406. If the fluctuation of the output current 402 may be large, the output high voltage control based on the current limit value (CB) cannot keep up, and the output current 402 becomes greater than the current limit value (CB), and the possibility of its reaching the absolute sensitivity (CL) may be large. When the absolute sensitivity value (CL) can be detected, the overcurrent safety control function can be activated, and the output of the cascade circuit 24 can be stopped. The less frequently this output stops, the better. For this purpose, when the absolute value of the output voltage 406 can be relatively large in the relatively low voltage range 407, it is recommended to set the values of the current limit value (CB) and the absolute sensitivity value (CL) such that the difference between the current limit value (CB) and the absolute sensitivity value (CL) gradually increases, so that CB can be significantly less than CL when compared at the same output voltage. It is recommended to set the values of the current limit value (CB) and the absolute sensitivity value (CL) such that the difference between CB and the absolute sensitivity value (CL) gradually increases.

[0069] In the relatively low voltage region 407, when the absolute value of the output voltage 406 can be relatively small (region close to the intersection point 105), the amount of change in the value of the output current 402 can be small relative to the change in the absolute value of the output voltage 406. In this region, it is recommended to set the values ​​of the current limit value (CB) and the absolute sensitivity value (CL) so that the difference between the current limit value (CB) and the absolute sensitivity value (CL) can be small. By gradually reducing the difference between the current limit value (CB) and the absolute value sensitivity (CL), the backup function of the overcurrent safety control function (CL) can be quickly activated to ensure safety.

[0070] On the other hand, in the minimum high voltage protection range MVar below the registered value of the high voltage lower limit sensitivity (UV) (whose absolute value may be about 30 kV), that is, below the intersection Cp, the relationship between the current limit value (CB) and the absolute sensitivity value (CL) may be reversed, and when compared at the same output voltage, the absolute sensitivity value (CL) < the current limit value (CB). As can be seen from Figure 4 and Figure 5 It is seen that, in the minimum high voltage protection range MVar, the lower the absolute value of the high voltage, the greater the difference between the absolute sensitivity value (CL) and the current limit value (CB).

[0071] The Cockcroft-Walton circuit may cause a large amount of pulsating component ΔV to be included in the output voltage 406. For this reason, a strong filter may be required to detect the output voltage 406. Therefore, a sudden drop in the absolute value of the output voltage 406 due to the current limit value (CB) may be mitigated by the filter, and the timing for detecting the output change may be delayed. In contrast, because the output current 402 may be a current value before it may be input to the Cockcroft-Walton circuit, the pulsating component ΔV may not exist. Therefore, it may not be necessary to equalize the output current 402 with a filter, and fluctuations in the output current 402 may be detected immediately.

[0072] The delay in detecting a change in the output voltage 406 may be due to a delay in detecting that the current output voltage 406 has dropped below the registered value of the high voltage lower limit sensitivity (UV), and if the output voltage (V) has entered the minimum high voltage protection range MVar, this entry may essentially be caused by the output current 402, which is detected without delay.

[0073] In the minimum high voltage protection range MVar, when compared at the same output voltage, the absolute sensitivity value (CL) < the current limit value (CB), the overcurrent safety control can be first performed to stop the output of the cascade circuit 24 by the absolute sensitivity value (CL). The current limit value (CB) is used as a backup measure for the overcurrent safety control (CL).

[0074] As described above, even if the current output voltage (V) can be detected by monitoring the output voltage 406, the detection of this output voltage 406 may be slow. Fast control based on the pre-registered absolute sensitivity value (CL) and current limit value (CB) can take into account both productivity and safety.

[0075] Set the change of feature line ( Figure 7 )

[0076] Figure 7 The change of the characteristic line when the current limit value (CB) and the absolute sensitivity value (CL) are set is shown. Figure 7 , the area above the minimum high voltage protection range MVar, that is, the area where the absolute value of the output voltage 406 can be higher than the registered value of the high voltage lower limit sensitivity (UV), can be divided into three areas.

[0077] The range of the high voltage lower limit sensitivity (UV) between the register value (-30 kV) and -60 kV may be referred to as a "relatively low voltage range 407". The relatively low voltage range 407 corresponds to a coating distance 411 of 50 mm to 200 mm. In the relatively low voltage range 407, the change range of the current limit value (CB) setting value may be 30 μA to 50 μA, and the change range of the absolute sensitivity value (CL) setting value may be 30 μA to 60 μA. When compared at the same output voltage, the relative relationship between the current limit value (CB) and the absolute sensitivity value (CL) may be CB. <CL。

[0078] The range of -60kV to -90kV may be referred to as a "relative intermediate voltage range 409". The relative intermediate voltage range 409 corresponds to a coating distance 411 of 200mm to 300mm. This relative intermediate voltage range 409 may be an applicable range for a remote coating method. When the coating distance 411 may be 200mm, the initial high voltage may be set to -60kV. When the coating distance 411 may be 300mm, the initial high voltage may be set to -90kV. An area where the absolute value of the output voltage may be 90kV or higher may be referred to as a "relative high voltage area 408". The relative high voltage area 408 corresponds to a coating distance 411 of 300mm or greater.

[0079] In the relatively high voltage range 408, the absolute sensitivity value (CL) can be set to be less than the current limit value (CB). In other words, the CB setting change characteristic line and the CL setting change characteristic line should intersect at the boundary between the relatively high voltage range 408 and the relatively intermediate voltage range 409, and in the relatively high voltage range 408, the absolute sensitivity value (CL) should be set to < the current limit value (CB). In this relatively high voltage region 408, the absolute value of the output voltage 406 may be extremely high and the spark risk may be high. Therefore, an overcurrent safety control based on the absolute value sensitivity (CL) can be pre-operated. This can be a good way to prevent sparks from occurring.

[0080] Figure 7 The illustrated characteristic line has the following advantages. That is, when the application of the coating robot 10 including the electrostatic coating machine 14 may not be limited to the proximity coating method but may include the remote coating method (that is, the coating system may be applied not only to the proximity coating method but also to the remote coating method), it may be appropriately applied. Figure 7 Characteristic lines shown.

[0081] Fig.11An example of a current limit value (CB) and an absolute sensitivity value (CL) that can be retrieved from a memory 410 is shown. A system 413 includes a workpiece 412 and an electrostatic coating machine 10 configured to electrostatically adsorb a coating on the workpiece 412 by charging the coating with a voltage output 406 supplied from a high voltage generator 24, wherein the high voltage safety control unit is configured to monitor the voltage output and reduce the voltage output of the high voltage generator based on the detected current 402 being above a first overcurrent threshold, the first overcurrent threshold 104 that can be the current limit value (CB) can be a first dynamic threshold 104 based on the voltage output 406. The voltage output 406 can be an absolute value of a detected voltage that is filtered to remove ripples. In some embodiments, the high voltage safety control unit 30 is configured to stop the output of the high voltage generator 24 based on the detected current 402 being above a second overcurrent threshold 103, the second overcurrent threshold can be an absolute sensitivity value (CL), wherein the second overcurrent threshold is based on the second dynamic threshold 103 of the voltage output 406. In some embodiments, the high voltage safety control unit 30 may include at least one output voltage monitor to receive a detection voltage corresponding to the absolute value of the voltage output, wherein the first dynamic threshold 104 includes at least one first overcurrent range and at least one second overcurrent range, wherein the first overcurrent range is lower than the second overcurrent range. According to some embodiments, the second dynamic threshold 103 increases as the detection voltage increases within the first voltage domain 106. The first dynamic threshold 104 may increase within this range, but may increase linearly or nonlinearly. According to some embodiments, when the detection voltage is within the first voltage domain 106, the second dynamic threshold 103 is defined as the second dynamic threshold 103 (μA) = k1 * detection voltage + k2, wherein k1 and k2 are constants, wherein k1 is positive. In some embodiments, the first voltage domain 106 may be between UV and 60 kV, k1 may be between 0.5 and 2, and in some embodiments is 1, and k2 may be between -10 and 10, and in some embodiments is 0. In some embodiments, when the detection voltage is within the second voltage domain 151, the second dynamic threshold 103 is defined as second dynamic threshold 103 (μA) = k3, where k3 is a constant, where the second voltage domain 151 is at an absolute value higher than the first voltage domain 106. In some embodiments, the second voltage domain 151 can be when the detection voltage is greater than 60 kV. In some embodiments, k3 can be between 50 and 70, and in some embodiments is 60. According to certain embodiments, the first dynamic threshold 104 increases as the detection voltage increases within the first voltage domain 106. In some embodiments, when the detection voltage is within the first voltage domain 106, the first dynamic threshold 104 is defined as first dynamic threshold 104 (μA) = k4*detection voltage + k5, where k4 and k5 are constants, where k4 is positive.In some embodiments, k4 may be between 1 / 2 and 3 / 4, and in some embodiments 2 / 3, and k5 may be between 0 and 20, and in some embodiments 10. According to some embodiments, when the detection voltage is within the first portion 107 of the second voltage domain 151, the first dynamic threshold 104 is defined as the first dynamic threshold 104 (μA) = k6, where k6 is a positive constant. In some embodiments, the first portion 107 of the second voltage domain 151 may be between 60 kV and 80 kV, and k6 may be between 40 and 60, and in some embodiments 50. In some embodiments, the first dynamic threshold 104 increases as the detection voltage increases within the second portion 108 of the second voltage domain 151. According to some embodiments, when the detection voltage is within the second portion 108 of the second voltage domain 151, the first dynamic threshold 104 may be defined by first dynamic threshold 104 (μA) = k7 * detection voltage + k8, where k7 and k8 are constants, where k7 is positive, where the second portion 108 of the second voltage domain 151 is higher than the first portion 107 of the second voltage domain 151. In some embodiments, k7 may be between 0.5 and 3, and in some embodiments is 1, and k8 may be between -50 and -10, and in some embodiments is -30. In some embodiments, when the detection voltage is within the third portion 109 of the second voltage domain 151, the first dynamic threshold 104 is defined by first dynamic threshold 104 (μA) = k9, where k9 is a positive constant, where the third portion 109 of the second voltage domain 151 is higher than the second portion 108 of the third voltage domain. In some embodiments, k9 may be between 60 and 80, and in some embodiments is 70. In some embodiments, the second dynamic threshold 103 is the same as the first dynamic threshold 104 at a voltage output 406 equal to a lower bound of the first voltage domain 106, wherein the lower bound of the first voltage domain 106 is the minimum voltage threshold 104 (UV) of the high voltage safety control unit. In some embodiments, the second dynamic threshold 103 is lower than the first dynamic threshold 104 at a voltage output 406 above the lower bound of the first voltage domain 106 and below the upper bound, wherein the upper bound is in the second portion 108 of the second voltage domain 151, wherein the second dynamic threshold 103 is higher than the first dynamic threshold 104 at a voltage output above the upper bound. In some embodiments, the electrostatic coating machine includes a loader, wherein the system includes a distance 411 between a workpiece 412 and the loader, wherein, when the detection voltage is in a first voltage domain 106, the distance 411 between the workpiece 412 and the loader is between 50 mm and 200 mm, wherein, when the detection voltage is in a second voltage domain 151 below an upper limit, the distance 411 between the workpiece 412 and the loader is between 200 mm and 300 mm, and wherein, at a detection voltage above the upper limit, the distance 411 between the workpiece 412 and the loader is greater than 300 mm.

[0082] The description of the embodiments of the present invention has been presented for the purpose of illustration and description, but the description is not intended to be exhaustive or limited to the present disclosure in the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope of the present disclosure. The described embodiments are selected and described in order to best explain the principles of the present disclosure and its practical application, and to enable those of ordinary skill in the art to understand the present disclosure for various embodiments and to make various modifications to suit the intended specific use.

[0083] Although the present disclosure has been described with reference to exemplary embodiments, it will be appreciated by those of ordinary skill in the art that various changes may be made and elements thereof may be replaced with equivalents without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt specific systems, devices, or components thereof to the teachings of the present disclosure without departing from the basic scope of the present disclosure. Therefore, the present disclosure is not intended to be limited to the specific embodiments disclosed for the purpose of performing the present disclosure, but the present disclosure will include all embodiments falling within the scope of the appended claims.

Claims

1. A system comprising a workpiece and an electrostatic coating machine configured to electrostatically adsorb a coating onto the workpiece by charging the coating with a voltage output supplied from a high voltage generator, wherein: The high voltage safety control unit is configured to monitor the voltage output and reduce the voltage output of the high voltage generator based on the detected current being higher than a first overcurrent threshold, the improvement being that: The first over-current threshold is a first dynamic threshold based on the voltage output.

2. The improvement as claimed in claim 1, wherein: The high voltage safety control unit is configured to stop the output of the high voltage generator based on the detected current being higher than a second over-current threshold, wherein the second over-current threshold is a second dynamic threshold based on the voltage output.

3. The improvement as claimed in claim 2, wherein: The high voltage safety control unit includes at least one output voltage monitor to receive a detection voltage corresponding to an absolute value of the voltage output, wherein the first dynamic threshold includes at least one first overcurrent range and at least one second overcurrent range, wherein the first overcurrent range is lower than the second overcurrent range.

4. The improvement as claimed in claim 3, wherein: The second dynamic threshold increases as the detection voltage increases within the first voltage domain.

5. The improvement as claimed in claim 4, wherein: When the detection voltage is within the first voltage domain, the second dynamic threshold is defined as the second dynamic threshold (μA)=k1*the detection voltage+k2; Wherein, k1 and k2 are constants, and k1 is positive.

6. The improvement as claimed in claim 5, wherein: When the detection voltage is within the second voltage domain, the second dynamic threshold is defined as a second dynamic threshold (μA)=k3, Here, k3 is a constant, wherein the second voltage domain is at a higher absolute value than the first voltage domain.

7. The improvement as claimed in claim 6, wherein: The second dynamic threshold increases as the detection voltage increases within the first voltage domain.

8. The improvement as claimed in claim 7, wherein: When the detection voltage is within the first voltage domain, the first dynamic threshold is defined as first dynamic threshold (μA)=k4*the detection voltage+k5, Among them, k4 and k5 are constants, among which k4 is positive.

9. The improvement as claimed in claim 8, wherein: When the detection voltage is within the first part of the second voltage domain, the first dynamic threshold is defined as a first dynamic threshold (μA)=k6, Wherein, k6 is a positive constant.

10. The improvement of claim 9, wherein: The first dynamic threshold increases as the detection voltage increases within a second portion of the second voltage domain.

11. The improvement of claim 10, wherein: When the detection voltage is within the second portion of the second voltage domain, the first dynamic threshold is defined as a first dynamic threshold (μA)=k7*the detection voltage+k8, Wherein k7 and k8 are constants, wherein k7 is positive, and wherein the second portion of the second voltage domain is higher than the first portion of the second voltage domain.

12. The improvement of claim 11, wherein: When the detection voltage is within the third portion of the second voltage domain, the first dynamic threshold is defined as a first dynamic threshold (μA)=k9, Wherein k9 is a positive constant, wherein the third portion of the second voltage domain is higher than the second portion of the third voltage domain.

13. The improvement of claim 12, wherein: At a voltage output equal to a lower limit of the first voltage domain, the second dynamic threshold is the same as the first dynamic threshold, wherein the lower limit of the first voltage domain is a minimum voltage threshold of the high voltage safety control unit.

14. The improvement of claim 13, wherein: The second dynamic threshold is lower than the first dynamic threshold at a voltage output above a lower limit and below an upper limit of the first voltage domain, wherein the upper limit is in a second portion of the second voltage domain, wherein the second dynamic threshold is higher than the first dynamic threshold at a voltage output above the upper limit.

15. The improvement of claim 14, wherein the electrostatic coating machine includes a loader, wherein: The system includes a distance between the workpiece and the loader, wherein, when the detection voltage is in the first voltage domain, the distance between the workpiece and the loader is between 50 mm and 200 mm, wherein, when the detection voltage is below the upper limit in the second voltage domain, the distance between the workpiece and the loader is between 200 mm and 300 mm, and wherein, at a detection voltage above the upper limit, the distance between the workpiece and the loader is greater than 300 mm.

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