JP6290797B2 - Electrostatic coating equipment - Google Patents

Description

  The present invention relates to an electrostatic coating apparatus, for example, an electrostatic coating apparatus that requires confirmation of the conductivity of an object to be coated after applying a conductive primer to the object to be coated.

  One of the methods for painting an object is electrostatic painting. In this electrostatic coating, a high voltage is applied to a coating gun or the like to generate an electric field between the coating gun and the object to be coated. In electrostatic coating, a coating material is applied by spraying a coating material charged with a high voltage from the coating gun onto the coating material. At this time, when the object to be coated is a part having low conductivity such as a resin part, a conductive primer is applied to the surface to be coated, and electrostatic coating is performed after ensuring the conductivity. Thus, when applying a conductive primer to a to-be-coated object beforehand, it is necessary to confirm that electroconductivity is ensured after apply | coating a conductive primer. This conductivity is confirmed by confirming whether or not the object to be coated is grounded. An example of a technique for confirming the ground state of an object to be coated is disclosed in Patent Document 1.

  An electrostatic coating apparatus described in Patent Document 1 generates a coating gun for spraying paint on an object to be coated, a robot arm that supports the coating gun so as to be displaceable, a high voltage applied to the coating gun, A high voltage generator for adjusting a high voltage to be generated by detecting a discharge current generated between the gun and the object to be coated. And in the electrostatic coating apparatus of patent document 1, in the state which has not sprayed the coating material toward the to-be-coated object with the coating gun, an electric field is formed toward the to-be-coated object, and this to-be-coated object In the state where the high voltage generator is not applying a high voltage to the coating gun, the electric charge charged to the coating object is used to detect the discharge current generated between the coating gun and the coating object. To do.

JP 2012-071224 A

  However, in the technique described in Patent Document 1, it is necessary to charge the object to be coated in order to confirm the ground state. At this time, if the object to be coated is not correctly connected to the ground, the state in which the object to be coated is charged continues for a long time. When the object to be coated comes into contact with the object to be charged, sparks or the like are generated due to discharge. Therefore, it is necessary to wait for a long time until the charged state is relaxed in order to ensure safety. In other words, the technique described in Patent Document 1 has a problem that it takes a long time to ensure safety when a failure occurs in the discharge path of the object to be coated.

  This invention is made | formed in view of the said situation, and aims at ensuring the safety | security in a coating process in a short time.

  An aspect of the electrostatic coating apparatus according to the present invention includes: a coating gun that sprays paint toward an object to be coated; a high-voltage applying device that applies a high voltage to the coating gun; A workpiece fixing jig that is grounded to a ground, a ground electrode that electrically connects the workpiece and the workpiece fixing jig, a pedestal portion that is grounded to ground, the pedestal portion, and the workpiece An insulator that connects a coating material fixing jig and insulates the pedestal portion from the coating material fixing jig; and a discharge unit that discharges electric charges from the coated material fixing jig to the pedestal portion. Have.

  In the electrostatic coating apparatus according to the present invention, the object to be coated is fixed, and the object fixing jig electrically connected to the object to be coated is connected via the object fixing jig and the insulator. The pedestal portion to be connected is connected to the discharge portion. Thereby, the electric charge accumulate | stored in to-be-coated object can be discharged to a base part.

  According to the electrostatic coating apparatus of the present invention, since the electric charge accumulated in the object to be coated can be discharged from the pedestal portion, it is possible to prevent the object from being withstand and improve the safety.

1 is a block diagram of an electrostatic coating apparatus according to a first embodiment. 1 is a block diagram of a bell coating machine and a high voltage applying device according to a first embodiment. 3 is a flowchart for explaining the operation of the electrostatic coating apparatus according to the first exemplary embodiment. 6 is a graph for explaining a change in current value in the electrostatic coating apparatus according to the first exemplary embodiment; 6 is a table for explaining a difference between a bell-side current and a ground-side current depending on presence / absence of ground in the electrostatic coating apparatus according to the first exemplary embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted as necessary.

  FIG. 1 is a block diagram of an electrostatic coating apparatus 1 according to the first embodiment. The electrostatic coating apparatus 1 is an apparatus that performs coating on an object 10 using a coating gun 20. As shown in FIG. 1, the electrostatic coating apparatus 1 includes a workpiece fixing jig 11, an insulator 12, a pedestal portion 13, a ground electrode 14, a ground-side current measurement unit (for example, an ammeter 15), and a discharge unit 16. A coating gun 20, a high voltage applying device 22, and a ground inspection unit 23.

  The workpiece fixing jig 11 fixes the workpiece 10. The article fixing jig 11 is fixed to the pedestal portion 13 via the insulator 12. The insulator 12 insulates the article fixing jig 11 from the article fixing jig 11. The pedestal portion 13 is electrically grounded. Further, the article fixing jig 11 has a ground electrode 14 connected through a conductive wiring. The ground electrode 14 is connected to the workpiece 10 and is used to connect the workpiece 10 to the ground. The ground electrode 14 is grounded via an ammeter 15. Further, the article fixing jig 11 is connected to a ground electrode. The ammeter 15 detects a current flowing from the article 10 to the ground as a ground-side current i2.

  As shown in FIG. 1, in the electrostatic coating apparatus 1 according to the first embodiment, the workpiece fixing jig 11 and the pedestal portion 13 are connected by a discharge portion 16. The discharge part 16 discharges electric charges from the article fixing jig 11 to the pedestal part 13. Moreover, the discharge part 16 connects the both ends of an insulator with a predetermined resistance value. The discharge unit 16 is, for example, a semiconductor having a predetermined resistance value.

  The coating gun 20 sprays spray paint 21. A high voltage is applied to the coating gun 20 from a high voltage applying device 22. The coating gun 20 generates an electric field between the coating gun 20 and the workpiece 10 by this high voltage and charges the coating material. The high voltage application device 22 generates a high voltage to be applied to the coating gun 20 and calculates a bell-side current i <b> 1 that flows from the coating gun 20 to the workpiece 10.

  The ground inspection unit 23 detects an abnormality in the ground state of the article to be coated 10 based on the bell-side current i1 and the ground-side current i2. In the present embodiment, when the ground inspection unit 23 determines that the ground state of the article 10 is abnormal, the ground inspection unit 23 enables the control signal CNT that causes the high voltage applying device 22 to stop generating a high voltage. Details of the method for inspecting the conductivity of the object to be coated 10 in the earth inspection unit 23 will be described later.

  Here, the coating gun 20 and the high voltage applying device 22 will be described in more detail. FIG. 2 shows a block diagram of the bell coating machine and the high voltage applying device according to the first embodiment. As shown in FIG. 2, the painting gun 20 is a part of the bell painting machine 30. Further, the high voltage application device 22 includes a high voltage generator 31 and a high voltage controller 40 in the bell coating machine 30. The bell coating machine 30 and the high voltage controller 40 are connected by, for example, a 6-core to 8-core cable CAB.

  The bell coating machine 30 is obtained by adding a high voltage generator 31 to the coating gun 20. Further, the bell coating machine 30 is provided with a leak current detection unit 36. The high voltage generator 31 includes a booster circuit 32, high voltage measurement resistors 33a and 33b, a total current measurement resistor 34, and a leak current measurement resistor 35. The input voltage supplied from the booster circuit 32 and the high voltage controller 40 is boosted by a drive pulse to generate a high voltage HV to be applied to the coating gun 20. As the booster circuit 32, for example, a Cockcroft-Walton booster circuit (CW circuit) can be used. Further, in the booster circuit 32, a transformer is provided, and a total current measurement resistor 34 is provided between one end of the secondary side coil of the transformer and a ground wiring to which a ground voltage is supplied. Then, the voltage V 0 is generated at the terminal on the high voltage generator 31 side of the total current measuring resistor 34. The total current IM can be calculated by dividing the voltage V0 by the resistance value of the total current measuring resistor 34.

  A high voltage measuring resistor 33a and a high voltage measuring resistor 33b are connected in series between the output terminal of the high voltage generator 31 and the ground wiring. The voltage V1 at the connection point between the high voltage measuring resistor 33a and the high voltage measuring resistor 33b is a voltage obtained by dividing the high voltage HV output from the high voltage generator 31 by the high voltage measuring resistor 33a and the high voltage measuring resistor 33b. Become. Here, since the high voltage measuring resistor 33a and the high voltage measuring resistor 33b have known resistance values, the voltage value of the high voltage HV can be calculated from the voltage V1. The bleeder current IM1 flows through the high voltage measuring resistor 33a and the high voltage measuring resistor 33b. The bleeder current IM1 can also be calculated by dividing the high voltage HV by the sum of the resistance values of the high voltage measuring resistor 33a and the high voltage measuring resistor 33b.

  Further, in the bell coating machine 30, the rear plate side leakage current IM2 flows along with the dirt on the outer surface of the bell coating machine 30. Therefore, the bell coating machine 30 detects the rear plate side leakage current IM2 by the leakage current detector 36. Specifically, a leakage current measurement resistor 35 is provided between the leakage current detector 36 and the ground wiring. Therefore, the rear plate side leakage current IM2 that has flowed to the leakage current detector 36 flows to the ground wiring via the leakage current measuring resistor 35. As a result, the voltage V <b> 2 is generated on the leakage current detection unit 36 side of the leakage current measuring resistor 35. Therefore, the rear plate side leakage current IM2 can be calculated by dividing the voltage V2 by the resistance value of the leakage current measuring resistor 35.

  The high voltage controller 40 includes a calculation unit 41, a high voltage generation control unit 42, a total current measurement unit 43, a voltage measurement unit 44, and a leak current measurement unit 45. The high voltage generation control unit 42 generates an input voltage and a driving pulse to be given to the high voltage generator 31. The high voltage generation control unit 42 changes the voltage level of the input voltage, the duty ratio of the drive pulse, and the like according to an instruction from the calculation unit 41. The total current measurement unit 43 acquires the voltage V0, calculates the total current IM based on the acquired voltage V0, and outputs the calculated value of the total current IM to the calculation unit 41. The voltage measurement unit 44 measures the voltage V1 and outputs the measured voltage value to the calculation unit 41. The leakage current measuring unit 45 acquires the voltage V2, calculates the rear plate side leakage current IM2 based on the acquired voltage V2, and outputs the calculated value of the rear plate side leakage current IM2 to the calculation unit 41.

  The calculation unit 41 calculates a voltage value of the high voltage HV based on the voltage V1 acquired from the voltage measurement unit 44, and controls the high voltage generation control unit 42 based on the calculated value of the high voltage HV. In addition, the calculation unit 41 has a function of stopping the output of the high voltage HV by stopping the operation of the high voltage generation control unit 42 in accordance with the control signal CNT given from the ground inspection unit 23. Moreover, the calculating part 41 contains a bell side current calculation part. In this bell-side current calculation unit, the total current IM acquired from the total current measurement unit 43, the bleeder current IM1 calculated based on the voltage V1 acquired from the voltage measurement unit 44, and the rear plate acquired from the leak current measurement unit 45 The bell side current i1 is calculated based on the side leakage current IM2. Then, the calculation unit 41 outputs the calculated bell-side current i1 to the ground inspection unit 23.

Here, a method of calculating the bell-side current i1 will be described. The bell side current calculation unit included in the calculation unit 41 calculates the bell side current i1 based on the equation (1).
i1 = IM-IM1-IM2 (1)
In the equation (1), the total current IM1 and the rear plate side leakage current IM2 are actual measured values. On the other hand, the bleeder current IM1 is a calculated value calculated from the high voltage HV output from the booster circuit 32 and the resistance values of the high voltage measuring resistor 33a and the high voltage measuring resistor 33b.

  In the electrostatic coating apparatus 1 according to the first embodiment, a value obtained by subtracting the bleeder current IM1 from the total current IM is referred to as an output current theoretical value.

  Then, operation | movement of the electrostatic coating apparatus 1 concerning Embodiment 1 is demonstrated. FIG. 3 is a flowchart for explaining the operation of the electrostatic coating apparatus 1 according to the first embodiment. As shown in FIG. 3, the electrostatic coating apparatus 1 according to the first embodiment inspects the conductivity of the article to be coated 10 while performing electrostatic coating.

  The electrostatic coating apparatus 1 calculates the bell-side current i1 when the spray paint 21 charged from the coating gun 20 is sprayed onto the article 10 (step S1). Moreover, the electrostatic coating apparatus 1 detects the earth-side current i2 flowing from the article 10 to the ground during the electrostatic coating with the ammeter 15 (step S2). And the electrostatic coating apparatus 1 judges the earth | ground state of the to-be-coated article 10 based on the bell side current i1 and the earth side current i2 (step S3).

  Here, a method for determining the ground state in the electrostatic coating apparatus 1 will be described. In the electrostatic coating apparatus 1, the ground side of the object to be coated 10 is correctly determined (hereinafter referred to as a grounded state) and abnormal state (hereinafter referred to as no grounding) in which the ground is not correctly removed. There is a large difference between the current i1 and the ground side current i2. FIG. 4 shows a graph for explaining a change in the current value in the electrostatic coating apparatus 1 according to the first embodiment. In FIG. 4, the current change of the electrostatic coating apparatus 1 with a ground is shown on the left side, and the current change of the electrostatic coating apparatus 1 without a ground is shown on the right. As shown in FIG. 4, there is a large difference between the total current IM and the ground-side current i2 depending on whether or not the ground is taken.

  Further, FIG. 5 shows a table for comparing the bell-side current i1 and the ground-side current i2 with and without the ground. In the example shown in FIG. 5, the bell-side current i <b> 1 has a difference of about two times depending on the presence or absence of ground. There is a difference of three times or more in the ground side current. Further, even when the ratio of the bell-side current i1 and the ground-side current is compared, a difference of 32% occurs depending on whether or not the ground is taken.

  Since the difference in current as shown in FIG. 4 and FIG. 5 occurs, the ground inspection unit 23 of the electrostatic coating apparatus 1 according to the first embodiment uses either the first determination method or the second determination method. Use the method to determine the ground fault.

  In the first determination method, the bell-side current i1 and the ground-side current i2 when the ground is normally taken are set in advance as reference values. In the first determination method, one of the difference between the calculated bell-side current i1 and the reference value and the difference between the measured ground-side current i2 and the reference value is equal to or greater than a predetermined threshold. It is determined that a ground fault has occurred.

  In the second determination method, a ratio (for example, i2 / i1) between the bell-side current i1 and the ground-side current i2 when the ground is normally taken is set in advance as a reference value. In the second determination method, a ground abnormality occurs when the difference between the calculated bell-side current i1 and the measured ground-side current i2 and the reference value is equal to or greater than a predetermined threshold value. Judge that

  As shown in FIG. 3, in the electrostatic coating apparatus 1 according to the first embodiment, when an abnormality in the ground state of the article 10 is detected based on the above determination method, a control signal output from the ground inspection unit 23. CNT is enabled and electrostatic coating is interrupted (NO branch of step S4). On the other hand, in the electrostatic coating apparatus 1 according to the first embodiment, when it is determined that there is no abnormality in the ground state of the article to be coated 10 based on the above determination method (YES branch of step S4), the electrostatic coating is continued. (Step S5), electrostatic coating is completed.

  Here, in the electrostatic coating apparatus 1 according to the first embodiment, the workpiece fixing jig 11 and the pedestal portion 13 are connected by the discharge portion 16. The discharge unit 16 is not properly grounded to the ground due to a problem such as disconnection of a wiring path for grounding the workpiece fixing jig 11 or failure of the ammeter 15. In such a case, the charge charged on the article 10 is discharged. The resistance value of the discharge portion 16 is a resistance value that does not affect the measurement of the ammeter 15 and has a resistance value that can discharge the charge of the object to be coated 10 within a predetermined time. preferable.

  From the above description, according to the electrostatic coating apparatus 1 according to the first embodiment, the discharge portion 16 is provided in parallel with the insulator 12 that connects the workpiece fixing jig 11 and the pedestal portion 13. Thereby, in the electrostatic coating apparatus 1 according to the first exemplary embodiment, even if the ground state of the article to be coated 10 is abnormal and in other cases, the charge charged on the article to be coated 10 is discharged in a short time. Can do. That is, the electrostatic coating apparatus 1 according to the first embodiment can improve the safety by shortening the time for discharging the charge charged on the article 10 to be coated.

  In particular, in the electrostatic coating apparatus 1 according to the first embodiment, the ground side generated when the workpiece fixing jig 11 and the pedestal portion 13 are connected by the insulator 12 and the workpiece 10 is charged. Conductivity inspection of the article to be coated 10 is performed by measuring the current value. In such an electrostatic coating apparatus 1, there is a high risk that the charge charged on the object to be coated 10 is not discharged due to a defect in the wiring path for grounding the object fixing jig 11 to ground. Therefore, in the electrostatic coating apparatus 1 according to the first embodiment, it is significant to provide the discharge unit 16 to enhance safety.

  In the above description, the invention made by the present inventor has been specifically described based on the embodiments. However, the present invention is not limited to the embodiments already described, and various modifications can be made without departing from the scope of the invention. It goes without saying that changes are possible.

DESCRIPTION OF SYMBOLS 1 Electrostatic coating apparatus 10 Coated object 11 Coated object fixing jig 12 Insulator 13 Base part 14 Ground electrode 15 Ammeter 16 Discharge part 20 Painting gun 21 Spray paint 22 High voltage application apparatus 23 Ground inspection part 30 Bell coating machine 31 Booster circuit 32 Bleeder resistance 41 Total current measurement unit 42 High voltage application unit 43 Bell side current calculation unit

Claims (4)

A paint gun that sprays paint toward the object,
A high voltage application device for applying a high voltage to the coating gun;
An object fixing jig which fixes the object to be coated and is grounded to the ground;
An earth electrode for electrically connecting the object to be coated and the object fixing jig;
A pedestal that is grounded to earth,
An insulator for connecting the pedestal portion and the workpiece fixing jig and insulating the pedestal portion and the workpiece fixing jig;
A discharge part for discharging electric charges from the workpiece fixing jig to the pedestal part;
An electrostatic coating apparatus having: A bell-side current calculation unit for calculating a bell-side current flowing from the coating gun to the object to be coated;
An earth side current measuring unit for measuring an earth side current flowing from the object to be grounded to the earth;
Abnormality of the ground state of the object to be coated according to the magnitude relationship between the bell-side current and the ground-side current in a state where the bell-side current and the ground-side current and the ground are correctly connected measured during electrostatic coating An earth inspection unit for detecting the state;
The electrostatic coating apparatus according to claim 1, further comprising:   The electrostatic coating apparatus according to claim 1, wherein the discharge unit connects both ends of the insulator with a predetermined resistance value.   The electrostatic coating apparatus according to claim 1, wherein the discharge unit is a semiconductor that connects both ends of the insulator with a predetermined resistance value.

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