JP5753147B2 - Electrostatic coating apparatus and grounding state inspection method - Google Patents

Description

  The present invention relates to an electrostatic coating apparatus, and more particularly to a technique for inspecting a ground state in an object to be coated.

  When electrostatic coating is performed, it is necessary that at least a portion (painted surface) to which the coating material is applied has conductivity. Therefore, when performing electrostatic coating on highly insulating objects such as resin parts, in general, conductive materials such as carbon black are mixed into the material of the object to be coated, or the surface of the object is electrically conductive. By forming a conductive film (conductive primer), conductivity is imparted to the object to be coated. And in the case of electrostatic coating, a to-be-coated object (application surface) is earth | grounded (grounding).

  By the way, if there is a variation in the conductive performance in each part of the object to be coated (painted surface), there will be a variation in the amount of paint applied, resulting in uneven coating thickness, Color unevenness may occur. In addition, if the ground connection of the object to be coated (painted surface) is uncertain, charges will accumulate on the object to be coated (painted surface) during electrostatic coating, and the object to be coated and the jig placed around this There is a risk that a spark will occur between the device and the like. Therefore, the quality of the ground state of the object to be coated is inspected before electrostatic coating is performed.

  Conventionally, as a technique for inspecting the ground state of an object to be coated, a technique of measuring a resistance value of the object to be coated by bringing a predetermined terminal into contact with the object to be coated (painted surface) is known. However, with this method, there is a risk that wrinkles may adhere to the object to be coated with the contact of the terminals. Therefore, a method for inspecting the ground state of a coating object without contacting the coating object by measuring the surface potential of the coating object after applying an electric charge to the coating object is proposed. (See, for example, Patent Document 1). In addition, by applying a charge to the object to be coated and measuring the surface potential with a coating gun used for electrostatic coating, a dedicated device for inspecting the ground condition is not required, and the production line is shortened. In addition, a technique for reducing the equipment cost has been proposed (see, for example, Patent Document 2).

JP-A-2005-58998 JP 2012-71224 A

  By the way, in the above-mentioned technique, two steps, a step of applying an electric charge to the object to be coated and a step of measuring the surface potential of the object to be coated, are required. Therefore, there is a possibility that it takes time to inspect the ground state of the object to be coated. On the other hand, for example, a device for applying an electric charge to the object to be coated and a device for measuring the surface potential of the object to be coated are provided separately (for example, in the technique disclosed in Patent Document 2, By providing a plurality of guns), it is conceivable to apply the voltage to the object to be coated and measure the surface potential at the same time to shorten the inspection time. However, in this case, there is a possibility that the manufacturing equipment becomes larger and complicated, and the equipment cost increases.

  Further, when the object to be coated is disposed at a position shifted from the normal position during inspection, and a part of the object to be coated is largely separated from the coating gun, the surface potential to be measured is decreased. As a result, there is a possibility that it is erroneously determined that the ground state is abnormal although the ground state is normal. Furthermore, if the object to be coated is supplied to the painting process with the displacement being left at the arrangement position, there is a risk that uneven coating or the like may occur.

  The present invention has been made in view of the above circumstances, and its purpose is to shorten the inspection time of the ground state of the object to be coated, to reduce the size and simplify the manufacturing equipment, and to reduce the equipment cost. An object of the present invention is to provide an electrostatic coating apparatus and a grounding state inspection method capable of detecting the displacement of the arrangement position of the object to be coated and improving the inspection accuracy.

  In the following, each means suitable for solving the above-described object will be described in terms of items. In addition, the effect specific to the means to respond | corresponds as needed is added.

Means 1. A paint gun that sprays paint toward the object,
An electrostatic coating apparatus comprising a voltage applying device that applies a high voltage to the coating gun,
A current measuring device for measuring a discharge current flowing through the coating gun when a high voltage is applied to the coating gun ;
A high voltage is applied from the voltage application device to at least three or more positions that are a fixed distance from the object to be coated when the paint is not sprayed on the object to be coated. Is arranged to measure the current flowing through the coating gun by the current measuring device at each position,
An electrostatic coating apparatus that inspects the ground state of the object to be coated based on a plurality of currents measured by the current measuring apparatus.

  According to the means 1, the ground state of the object to be coated is inspected by the electrostatic coating apparatus having a coating gun without using a dedicated apparatus. Therefore, it is possible to reduce the size and simplification of the manufacturing equipment and reduce the equipment cost.

  Furthermore, according to the means 1, the current flowing through the painting gun is measured by the current measuring device in a state where the voltage is applied from the voltage applying device to the painting gun, and the ground state of the object to be coated is determined based on the measured current. Inspected. In other words, the current used to check the ground condition of the object to be coated is acquired when a voltage is applied to the paint gun, and the voltage applied to the paint gun and the current flowing through the paint gun are Measurement is performed at the same time (that is, in one step). Therefore, it is possible to remarkably shorten the time for inspecting the ground state of the object to be coated, and to improve the productivity.

  Further, according to the means 1, it is not necessary to provide a plurality of coating guns in order to shorten the inspection time. Therefore, it is possible to more effectively reduce the size and simplification of the manufacturing equipment and reduce the equipment cost.

  In order to stably perform electrostatic painting, the current flowing through the painting gun may be measured during painting, but the current flowing through the painting gun during painting varies greatly due to the effects of paint, painting trajectory, etc. . Therefore, if the ground state of the object to be coated is inspected based on the current flowing through the painting gun during painting, the inspection accuracy may be significantly reduced. On the other hand, the current flowing through the coating gun during non-painting does not fluctuate due to the influence of the paint or the paint trajectory. Therefore, as in the above-described means 1, it is possible to realize a good inspection accuracy by inspecting the ground state of the object to be coated based on the current flowing through the coating gun in a state where the paint is not sprayed on the object. it can.

  By the way, when the object to be coated is arranged out of the normal position, the distance between the object to be coated and the coating gun may be different at each position. Therefore, the measured current varies with the difference in distance. obtain. In this regard, according to the above means 1, the coating gun to which a voltage is applied is disposed at at least three or more positions that are a fixed distance from the object to be coated when it is disposed at the normal position. The current through the paint gun is measured at the location and the ground condition is checked based on the measured currents. Therefore, the inspection accuracy of the ground state can be further improved.

  Moreover, according to the said means 1, it can be confirmed from the aspect of the measured several electric current whether the shift | offset | difference has arisen in the arrangement position of to-be-coated object. Therefore, it is possible to more reliably prevent the situation where the object to be coated is supplied to the painting process in a state in which the displacement is left in the arrangement position, and the relative position of the painting gun with respect to the object to be coated is more reliably applied during painting. It can be a predetermined position. As a result, the occurrence of coating unevenness can be effectively prevented, and the coating quality can be further improved.

  Mean 2. When the current flowing through the coating gun is measured by the current measuring device, the distance between the coating gun and the object to be coated when placed at a normal position is that the object to be coated is coated by the coating gun. The electrostatic coating apparatus according to claim 1, wherein the electrostatic coating apparatus is made smaller than a distance between the coating gun and the object to be coated when the coating gun is disposed at a normal position.

  According to the above means 2, the difference between the current flowing through the coating gun when the ground state of the object to be coated is normal and the current flowing through the coating gun when there is an abnormality in the ground state of the object to be coated is ensured. Can be bigger. Accordingly, normality / abnormality of the ground state in the object to be coated can be more easily discriminated, and the inspection accuracy of the ground state can be further improved.

  Means 3. When the current flowing through the coating gun is measured by the current measuring device, the distance between the coating gun and the object to be coated when placed at a normal position is 40 mm or more and 100 mm or less. The electrostatic coating apparatus as described in the means 1 or 2.

  According to the means 3, the distance between the coating gun and the object to be coated when placed at the normal position is set to 40 mm or more. Therefore, when there is a deviation in the position of the object to be coated, the paint gun may come into contact with the object to be coated, or a spark may occur between the paint gun and a jig or the like located around the object to be coated. It can prevent more reliably that it arises. As a result, the ground state can be inspected more accurately.

  Further, according to the means 3, since the distance is 100 mm or less, the current flowing through the coating gun when the grounding state is normal and the current flowing through the coating gun when the grounding state is abnormal The difference can be further increased. Thereby, the test | inspection precision of a ground state can be raised more.

  Means 4. When the current flowing through the coating gun is measured by the current measuring device, a distance between the coating gun and the object to be coated when arranged at a normal position is set to 60 mm or more and 80 mm or less. The electrostatic coating apparatus according to any one of means 1 to 3.

  According to the said means 4, the distance between a coating gun and the to-be-coated object when arrange | positioned in a normal position shall be 60 mm or more. Therefore, the contact of the coating gun with the object to be coated and the occurrence of sparks between the coating gun and the jig can be extremely effectively prevented.

  Further, according to the above means 4, since the distance is 80 mm or less, the current flowing through the coating gun when the grounding state is normal and the current flowing through the coating gun when the grounding state is abnormal The difference can be further increased. As a result, the inspection accuracy can be further improved.

Means 5. An earth state inspection method for inspecting the ground state of the object to be coated by an electrostatic coating apparatus having a paint gun for spraying a paint toward the object to be coated and a voltage applying device for applying a voltage to the paint gun. There,
In a state where the coating material is not sprayed on the object to be coated, a voltage is applied from the voltage application device to at least three or more positions that are a fixed distance from the object to be coated when arranged at a normal position. When the applied paint gun is placed, the discharge current flowing through the paint gun when a high voltage is applied to the paint gun is measured at each position,
A ground state inspection method, wherein the ground state of the object to be coated is inspected based on a measured current.

  According to the means 5, the same effect as that of the means 1 is achieved.

  Means 6. When measuring the current flowing through the paint gun, the distance between the paint gun and the object to be coated when placed in a normal position is the distance when the object to be coated is applied by the paint gun. 6. The ground state inspection method according to claim 5, wherein the ground state inspection method is smaller than a distance between the coating gun and the object to be coated when placed at a normal position.

  According to the means 6, the same effect as that of the means 2 is achieved.

  Mean 7 Means 5 or 6 characterized in that, when measuring the current flowing through the coating gun, the distance between the coating gun and the object to be coated when placed in a normal position is 40 mm or more and 100 mm or less. The ground state inspection method described in 1.

  According to the means 7, the same effect as that of the means 3 is achieved.

  Means 8. Means 5 to 7 characterized in that, when measuring the current flowing through the coating gun, the distance between the coating gun and the object to be coated when placed in a normal position is 60 mm or more and 80 mm or less. The ground state inspection method according to any of the above.

  According to the means 8, the same effect as that of the means 4 is achieved.

It is a schematic diagram which shows the structure of an electrostatic coating apparatus. It is a schematic diagram which shows structures, such as a painting gun and a robot arm. It is a schematic diagram which shows the coating gun etc. at the time of test | inspecting the earth state of to-be-coated material. (A)-(d) is a schematic diagram which shows the coating gun etc. which are arrange | positioned at each position AD. It is a graph which shows the threshold current used when determining the electric current measured by an electric current measuring apparatus when the to-be-coated object is arrange | positioned in a normal position, and the earthing state of to-be-coated object. It is a schematic diagram which shows the to-be-coated object etc. which are arrange | positioned in the state shifted | deviated from the normal position. (A)-(d) is a schematic diagram which shows the coating gun etc. which are arrange | positioned at each position AD, when a to-be-coated article is arrange | positioned in the state which shifted | deviated from the normal position. It is a graph which shows the electric current etc. which are measured with an electric current measuring apparatus when a to-be-coated article shifts | deviates from a normal position. It is a schematic diagram which shows the distance etc. between a coating gun and the to-be-coated object at the time of coating with respect to the to-be-coated object.

  Hereinafter, an embodiment will be described with reference to the drawings. The electrostatic coating apparatus 1 performs electrostatic coating on a coated object CD having at least a coated surface having conductivity. As shown in FIG. 1 and FIG. A supporting robot arm 3, a voltage application device 4, and a current measurement device 5 are provided. In the present embodiment, a conductive primer having a conductive material is provided on the coated surface of a normal object CD.

  The painting gun 2 is for injecting paint onto the article CD and includes a bell cup 21. Further, the coating gun 2 rotates so that the liquid paint spread on the inner surface of the bell cup 21 can be atomized by centrifugal force by rotating the bell cup 21 by a driving means (for example, an air motor) (not shown). Atomized type.

  The robot arm 3 has an upper and lower arm 31 whose one end is rotatably connected to the base portion 33, and a horizontal arm 32 whose one end is rotatably connected to the other end of the upper and lower arm 31. It has. A coating gun 2 is provided at the other end of the horizontal arm 32. By rotating the upper and lower arms 31 and the horizontal arm 32 at respective rotation fulcrums, the coating gun 2 is applied to the object CD. It can be moved relatively.

  In addition, the horizontal arm 32 includes a first arm part 321, a second arm part 322, and a third arm part 323 connected in series. The first arm portion 321 is provided with two refracting portions 321A and 321B, and the first arm portion 321 can be refracted at the respective refracting portions 321A and 321B. Further, a cylindrical connecting cylinder 324 that connects the first arm part 321 and the coating gun 2 is provided at the other end of the horizontal arm 32, and the connecting cylinder 324 is connected to the first arm part 321. It can be rotated with its own central axis as a rotation axis. By adjusting the refraction angle of the first arm portion 321 and the rotation amount of the connecting cylinder 324, the orientation of the coating gun 2 with respect to the workpiece CD can be adjusted.

  The voltage applying device 4 generates a high voltage to be applied to the coating gun 2 and includes a voltage generating unit 41 and a voltage boosting unit 42.

  The voltage generator 41 generates a voltage that is a source of a high voltage applied to the coating gun 2, and the generated voltage is input to the voltage booster 42. The voltage booster 42 boosts the voltage input from the voltage generator 41 and applies a high voltage to the coating gun 2 via the transmission cable 43. The voltage application device 4 is controlled by a control device 6 having a CPU, a RAM, and the like, so that the voltage applied to the coating gun 2 can be adjusted.

  The current measuring device 5 is provided downstream of the voltage booster 42 and measures the current flowing through the coating gun 2 (in this embodiment, the current flowing through the transmission cable 43). In addition, the current measured by the current measuring device 5 is output to the control device 6.

  The control device 6 determines the voltage to be applied to the coating gun 2 and the application timing of the voltage, and based on the current (current value) measured by the current measuring device 5, the object CD (in this embodiment, the object to be coated). The grounding state of the conductive primer formed on the surface of the object CD is inspected.

  The inspection method for the ground state of the article CD will be described in detail. First, as shown in FIG. 3, the coating gun 2 is arranged at an interval with respect to the article CD mounted on a predetermined conveyor CN. . At this time, the distance L1 between the coating gun 2 and the article CD to be coated when placed at the normal position is 40 mm or more and 100 mm or less (more preferably, 60 mm or more and 80 mm or less). Normally, the article CD (conductive primer) is electrically connected to the conveyor CN by the earth clip EC, and the article CD (conductive primer) is grounded.

  Next, as shown in FIGS. 3 and 4, application of a negative high voltage (for example, −50 kV, preferably −60 kV or more and −40 kV or less) from the voltage application device 4 to the coating gun 2, release of application, The coating gun 2 is moved relative to the object CD along a predetermined trajectory set in advance (in this embodiment, a trajectory passing over the entire surface of the conductive primer). Then, the current flowing through the painting gun 2 is measured by the current measuring device 5 when a high voltage is applied to the painting gun 2. In the present embodiment, the coating gun 2 is relatively moved along a trajectory that maintains the distance L1 between the coating object CD and the coating object CD when placed at the normal position. The coating gun 2 to which a voltage is applied is disposed at least at three or more positions (in this embodiment, at least positions A, B, C, and D) having a constant distance. Then, a plurality of currents IA, IB, IC, ID flowing through the coating gun 2 are measured by the current measuring device 5 at the respective positions A, B, C, D [the current (current value) measured at the position A is IA, the current (current value) measured at position B is IB, the current (current value) measured at position C is IC, and the current (current value) measured at position D is ID. is there〕.

  A plurality of currents (current values) IA, IB, IC, ID measured by the current measuring device 5 are input to the control device 6, and the control device 6 receives the input currents (current values) IA, IB, Based on the IC and ID, the ground state of the article CD to be coated is determined. Specifically, as shown in FIGS. 5 and 6, the control device 6 is preset with a maximum value among the currents (current values) IA, IB, IC, ID measured by the current measurement device 5. When the current is equal to or greater than a predetermined threshold current TI (μA), it is determined that the ground state of the article CD is normal. On the other hand, if the maximum value of the currents (current values) IA, IB, IC, ID measured by the current measuring device 5 is less than the threshold current TI, the ground state of the article CD is abnormal. judge.

  The ground state determination method by the control device 6 is set as described above for the following reason.

That is, when the coating object CD (conductive primer) is normally connected to the ground and the conductive primer is normally formed, the charge applied to the coating object CD by the coating gun 2 is conductive. It flows to the ground side through the primer. Therefore, the discharge amount from the painting gun 2 is relatively large. Therefore, as shown in FIG. 5, the currents IA, IB, IC, ID flowing through the coating gun 2 are relatively large. On the other hand, when the ground connection of the object CD (conductive primer) is abnormal (for example, when the earth clip EC is not attached or when the insulating clip adheres to the earth clip EC, etc.) And when the conductive primer is not properly provided (for example, when the conductive primer is not formed), the coating gun 2 applies to the object CD. The applied charge remains on the object CD. Thus, a relatively small discharge amount from the painting gun 2. Therefore, the currents IA, IB, IC and ID flowing through the coating gun 2 are relatively small. In consideration of this point, basically, the ground state of the article CD to be coated is determined based on the magnitudes of the measured current (current value) currents IA, IB, IC, ID with respect to the threshold current TI.

  However, even when the ground state of the article CD is normal, as shown in FIGS. 6 and 7, each position is different when the article CD is arranged at a position shifted from the normal position. In A, B, C, and D, the distance between the coating gun 2 and the object CD is different. Accordingly, as shown in FIG. 8, the currents IA, IB, IC, ID measured at the positions A, B, C, D vary with the difference in distance. Therefore, the measured current may be lower than the threshold current TI although the ground state of the article CD is normal. In consideration of this point, in the present embodiment, the ground state of the article CD to be coated is determined based on the maximum value among the measured currents (current values) IA, IB, IC, and ID.

  Furthermore, in this embodiment, when it is determined by the control device 6 that there is an abnormality in the ground state of the article CD, an operator or the like indicates that there is an abnormality in the ground state by a predetermined notification device (not shown). To be notified. Moreover, when the change of the measured current (current value) is in a predetermined mode (for example, when the measured current is in a mode of gradually increasing or decreasing), the object CD An operator or the like is notified that a displacement has occurred in the arrangement position.

  Further, in the present embodiment, as described above, when the current flowing through the coating gun 2 is measured by the current measuring device 5, the distance between the coating gun 2 and the object CD when placed at the normal position. L1 is 40 mm or more and 100 mm or less (more preferably, 60 mm or more and 80 mm or less). The reason why the distance L1 is in this range is as follows.

  That is, as shown in Table 1, when the applied voltage to the coating gun 2 and the distance L1 between the coating gun 2 and the coating CD are variously changed, the ground state of the coating CD is normal. The difference (current difference) between the current flowing through the coating gun 2 and the current flowing through the coating gun 2 when the ground state of the article CD to be coated is abnormal was determined.

  At this time, by setting the distance L1 to 40 mm or more, it is possible to suppress the current difference from becoming extremely large, so that the occurrence of a spark is sufficiently generated between the coating gun 2 and the jig positioned around the object CD. By making the distance L1 60 mm or more, an excessive increase in the current difference can be more reliably suppressed, and the occurrence of sparks can be more reliably prevented. From this result, in this embodiment, the distance L1 is set to 40 mm or more (more preferably, 60 mm or more). Further, by setting the distance L1 to 100 mm or less, the current difference can be set to 30 μA or more, and it is easy to judge whether the ground state of the article CD is good. By setting the distance L1 to 80 mm or less, the current difference can be reduced. It can be set to 40 μA or more, and it has been found that it is easier to judge whether the ground state is good or bad. Based on this result, in this embodiment, the distance L1 is 100 mm or less (more preferably, 80 mm or less).

  Further, in the present embodiment, as shown in FIG. 9, the distance L <b> 1 is between the coating gun 2 and the object CD when placed at a normal position when electrostatic coating is performed by the coating gun 2. Distance L2 (for example, 150 mm to 200 mm).

  As described above in detail, according to the present embodiment, the ground state of the article CD to be coated is inspected by the electrostatic coating apparatus 1 having the coating gun 2 without using a dedicated apparatus. Therefore, it is possible to reduce the size and simplification of the manufacturing equipment and reduce the equipment cost.

  Further, in the present embodiment, the current used for the inspection of the ground state of the article CD to be coated is configured to be acquired when a voltage is applied to the coating gun 2. The application and the measurement of the current flowing through the coating gun 2 are performed at the same time (that is, in one step). Therefore, the inspection time of the ground state in the article CD can be remarkably shortened, and the productivity can be improved.

  Further, since it is not necessary to provide a plurality of coating guns 2 in order to shorten the inspection time, it is possible to further effectively reduce the size and simplification of the manufacturing equipment and reduce the equipment cost.

  Furthermore, in the present embodiment, the coating gun 2 to which a voltage is applied is disposed at at least three or more positions that are a fixed distance from the object CD when disposed at the normal position. , The current flowing through the coating gun 2 is measured, and the ground state is inspected based on the plurality of measured currents. Therefore, the inspection accuracy of the ground state can be further improved.

  In addition, it is possible to confirm whether or not a deviation occurs in the arrangement position of the object CD from the plurality of measured current modes. Accordingly, it is possible to more reliably prevent the situation where the coating object CD is supplied to the painting process in a state where the arrangement position remains displaced, and the relative position of the coating gun 2 with respect to the coating object CD can be determined during painting. The predetermined position can be more reliably obtained. As a result, the occurrence of coating unevenness can be effectively prevented, and the coating quality can be further improved.

  In the present embodiment, since the distance L1 is smaller than the distance L2, the current flowing through the coating gun 2 when the ground state of the article CD is normal and the ground state of the article CD When there is an abnormality, the difference from the current flowing through the coating gun 2 can be increased more reliably. Therefore, normality / abnormality of the ground state in the article CD can be more easily determined, and the inspection accuracy of the ground state can be further improved.

  Furthermore, since the distance L1 is 40 mm or more (more preferably, 60 mm or more), the coating gun 2 is in contact with the article CD when the arrangement position of the article CD is shifted. It is possible to more reliably prevent sparks from occurring between the coating gun 2 and the jig or the like positioned around the object CD. As a result, the ground state can be inspected more accurately.

  In addition, since the distance L1 is 100 mm or less (more preferably, 80 mm or less), the current flowing through the coating gun 2 when the grounding state is normal and the painting gun 2 when the grounding state is abnormal The difference from the flowing current can be further increased. Thereby, the test | inspection precision of a ground state can be improved further.

  In addition, it is not limited to the description content of the said embodiment, For example, you may implement as follows. Of course, other application examples and modification examples not illustrated below are also possible.

  (A) In the above embodiment, the ground state of the object CD is inspected using the maximum value among the currents (current values) IA, IB, IC, ID measured by the current measuring device 5 as a criterion. However, the maximum value does not necessarily have to be used as a criterion. Therefore, for example, the ground state of the article CD to be coated may be inspected based on the average values of the measured currents (current values) IA, IB, IC, and ID.

  (B) In the above embodiment, the electrostatic coating apparatus 1 includes one coating gun 2, but may include two or more coating guns 2.

  (C) In the above-described embodiment, the voltage application device 4 and the current measurement device 5 are separated, but both may be integrated. Therefore, for example, the voltage application device 4 may have the function of the current measurement device 5.

  DESCRIPTION OF SYMBOLS 1 ... Electrostatic coating apparatus, 2 ... Coating gun, 4 ... Voltage application apparatus, 5 ... Current measuring apparatus, CD ... Coated object.

Claims (8)

A paint gun that sprays paint toward the object,
An electrostatic coating apparatus comprising a voltage applying device that applies a high voltage to the coating gun,
A current measuring device for measuring a discharge current flowing through the coating gun when a high voltage is applied to the coating gun ;
A high voltage is applied from the voltage application device to at least three or more positions that are a fixed distance from the object to be coated when the paint is not sprayed on the object to be coated. Is arranged to measure the current flowing through the coating gun by the current measuring device at each position,
An electrostatic coating apparatus that inspects the ground state of the object to be coated based on a plurality of currents measured by the current measuring apparatus.   When the current flowing through the coating gun is measured by the current measuring device, the distance between the coating gun and the object to be coated when placed at a normal position is that the object to be coated is coated by the coating gun. The electrostatic coating apparatus according to claim 1, wherein the electrostatic coating apparatus is made smaller than a distance between the coating gun and the object to be coated when arranged at a normal position.   When the current flowing through the coating gun is measured by the current measuring device, the distance between the coating gun and the object to be coated when placed at a normal position is 40 mm or more and 100 mm or less. The electrostatic coating apparatus according to claim 1 or 2.   When the current flowing through the coating gun is measured by the current measuring device, a distance between the coating gun and the object to be coated when arranged at a normal position is set to 60 mm or more and 80 mm or less. The electrostatic coating apparatus according to any one of claims 1 to 3. An earth state inspection method for inspecting the ground state of the object to be coated by an electrostatic coating apparatus having a paint gun for spraying a paint toward the object to be coated and a voltage applying device for applying a voltage to the paint gun. There,
In a state where the coating material is not sprayed on the object to be coated, a voltage is applied from the voltage application device to at least three or more positions that are a fixed distance from the object to be coated when arranged at a normal position. When the applied paint gun is placed, the discharge current flowing through the paint gun when a high voltage is applied to the paint gun is measured at each position,
A ground state inspection method, wherein the ground state of the object to be coated is inspected based on a measured current.   When measuring the current flowing through the paint gun, the distance between the paint gun and the object to be coated when placed in a normal position is the distance when the object to be coated is applied by the paint gun. The ground state inspection method according to claim 5, wherein the grounding state inspection method is smaller than a distance between the coating gun and the object to be coated when placed at a normal position.   The distance between the coating gun and the object to be coated when placed in a normal position when measuring the current flowing through the coating gun is set to 40 mm or more and 100 mm or less. 6. Ground state inspection method according to 6.   The distance between the coating gun and the object to be coated when placed in a normal position when measuring the current flowing through the coating gun is set to 60 mm or more and 80 mm or less. The ground state inspection method according to any one of 7 above.

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