JP2004093503A - Conductive coating film inspection method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To wholly and partially implement a resistance inspection of a conductive coating film and simultaneously inspect whether a workpiece is grounded without impairment of a base conductive coating film and work for attaching to and detaching from the workpiece. <P>SOLUTION: A surface of the workpiece 1 on which the conductive coating film is formed, is charged by a charger 2 not contacting the work piece. A surface potential is measured by a surface potential meter 6 not contacting the workpiece. While the charger 2 discharges a charge from a discharge electrode, the charge generated by the discharge is applied to the surface of the workpiece by air blasting and the surface of the workpiece is charged. <P>COPYRIGHT: (C)2004,JPO

Description

【００３２】
このようなテストからも分かるように、帯電器２でワーク１の表面を帯電させた後、表面電位センサ４で表面電位を測定すれば、その表面電位はワーク１表面の導電性塗膜の抵抗値を反映したものとなるので、測定した表面電位を比較回路８にて閾値と比較することにより、導電性塗膜の良否や乾燥具合を判定できる。更に、ワーク１が接地されていないと、測定される表面電位が通常よりもはるかに高くなるので、ワーク１が接地されているか否かの確認もできる。
なお、帯電と表面電位の測定をワーク１の複数箇所について行うことも可能である。
【００３３】
【発明の効果】
以上説明したように本発明によれば、下塗りの導電性塗膜の抵抗値検査を非接触状態で行えるので、導電性塗膜を傷つけることがないのは勿論のこと、ワークへの取り付け作業及び取り外し作業が不要であり、しかも全体としてばかりでなく部分的な検査も行え、更にワークが接地されているかどうかの検査も同時に行える。
【００３４】
帯電器において、放電電極の周囲をエアーパージしながら送風することにより、放電により生じた電荷を、ワークの表面に送風により吹き付けることができるので、効率よく平均にかつ広範囲に帯電させることができる。また、放電電極の汚れを防止できるとともに、放電により生じた電荷を吹き出して放電特性を高めることができる。
【図面の簡単な説明】
【図１】本発明の概要を示すブロック図である。
【図２】帯電器の一例を示す側面図である。
【図３】表面電位センサの一例の機構図である。
【符号の説明】
１　ワーク
２　帯電器
３　高電圧発生回路
４　表面電位センサ
５　検出処理回路
６　表面電位計
７　制御回路
８　比較回路
９　本体
１０　エアーチャンバ
１１　放電孔
１１ａ　吹き出し口
１２　蓋板
１３　管継手
１４　エアーホース
１５　電極基板
１６　放電電極
１７　高圧ケーブル
１８　電磁弁
１９　取り付け用バンド
２０　検出孔
２１　センサケース
２２　圧電素子
２３　振動子
２４　検出電極
２５　プリアンプ
２６　振動子駆動回路[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for inspecting a conductive coating by a conductive primer applied to the surface of a work before electrostatic coating.
[0002]
[Prior art]
When a workpiece made of a non-conductive material such as a resin product is electrostatically coated, as a pretreatment, a conductive coating film is formed on the surface of the workpiece using a conductive primer. If the resistance of this conductive coating film is high, the quality of the overcoated electrostatic coating will deteriorate, and the magnitude of the resistance value will affect the quality. Measuring.
[0003]
Conventionally, the resistance value has been generally measured by using an ohmmeter having a metal contact and bringing the metal contact into contact with a conductive coating film. However, there is a problem in that the conductive film is damaged by bringing the metal contactor into contact with the conductive film, and the measurement cannot be performed until the conductive film is completely dried.
[0004]
Patent Document 1 (Japanese Patent Application Laid-Open No. H11-138058) discloses that a clip-type terminal of a first lead wire is attached to one side of a non-conductive work, and a clip-type terminal of a second lead wire is attached to the other side of the work. By attaching a terminal and grounding the end of the second lead wire, and connecting an ohmmeter to the first and second lead wires via a switch, the resistance of the undercoating conductive coating even when it is wet can be improved. A method is disclosed in which a value can be measured, and immediately after the measurement, electrostatic coating for overcoating can be performed.
[0005]
However, according to this, the clip-type terminals of the two lead wires must be attached to each work, so that attachment work and removal work are required, and the installation place is limited to the product such as the end of the work. The work that is specified as a part that does not affect the appearance and the work of connecting the lead wire to the resistance meter must also be performed for each work, and the work efficiency of the measurement is poor. In addition, since the resistance value of the undercoated conductive coating is measured as a whole, it is impossible to perform a partial inspection.
[0006]
[Patent Document 1]
JP-A-11-138058 (pages 2-3, FIG. 1)
[0007]
[Problems to be solved by the invention]
Therefore, an object of the present invention is not to damage the undercoat conductive film, but also does not require any work of attaching and detaching to the work, and the resistance test of the conductive film is performed as a whole. It is an object of the present invention to provide a method and an apparatus for inspecting a conductive coating film, which can be performed not only as a part but also partially, and can simultaneously inspect whether a work is grounded.
[0008]
[Means for Solving the Problems]
In the conductive coating film inspection method of the present invention, the surface of the work on which the conductive coating film is formed is charged by a charger in a non-contact state with the work, and the surface potential is charged in a non-contact state with the work. It is characterized by measuring with a surface electrometer.
[0009]
In the present invention, the resistance of the conductive coating film is not directly measured as the resistance value of the conductive coating film, but the charged value is measured intentionally, and the resistance value of the conductive coating film may not be an accurate value. , Can be indirectly measured as sufficient data to judge pass / fail. That is, if the charged potential measured by the surface voltmeter is not converted into a resistance value but is compared with a threshold value, it is possible to judge pass / fail, and a partial inspection thereof is also possible.
[0010]
Preferably, while discharging in the charging device, the charge by the discharge is applied to the surface of the work by blowing air to be charged.
[0011]
The charger and the surface voltmeter are arranged so that the surface voltmeter does not directly detect the charge from the charger. In the case of a work having a length extending between the charger and the surface voltmeter, the surface potential of the work can be measured by the surface voltmeter while the surface of the work is charged by the charger. In the case of a short work shorter than the distance between the charger and the surface voltmeter, the measurement is performed by moving the work from the position facing the charger to the position facing the surface voltmeter.
[0012]
In addition, if the charging by the charger and the measurement by the surface voltmeter are performed while moving the work, the entire measurement can be performed.
[0013]
The conductive coating film inspection apparatus of the present invention includes a charger for charging a surface of a work on which a conductive coating film is formed in a non-contact state with the work, and a surface potential of the charged work that is different from that of the work. And a surface electrometer for measuring in a contact state.
[0014]
The charger preferably has a structure in which air is blown while air purging around the discharge electrode. Further, a control circuit for controlling the discharging operation of the charger and the measuring operation of the surface voltmeter with timing may be provided. Furthermore, by providing a comparison circuit for comparing the potential measured by the surface voltmeter with a threshold value, whether the conductive coating is good or bad, whether the work is dry, and whether the work is grounded without converting the measured potential to a resistance value. You can check if it is.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
FIG. 1 shows an outline of a conductive coating film inspection apparatus according to the present invention. This conductive coating film inspection apparatus comprises a charger (charger) 2 for charging a surface of a work (resin product or the like) 1 having a conductive coating formed by a conductive primer on a surface thereof in a non-contact state with the work. A high-voltage generating circuit 3 for applying a high voltage, a surface potential sensor 4 for measuring the surface potential of the charged work 1 in a non-contact state with the work 1, and the surface potential sensor 4 constitute a surface voltmeter 6. It comprises a detection processing circuit 5, a control circuit 7 for controlling the high voltage generation circuit 3 and the detection processing circuit 5, and a comparison circuit 8 for comparing the output of the detection processing circuit 5 with a threshold.
[0017]
The charger 2 and the surface potential sensor 4 are arranged at a distance L in the direction in which the workpiece 1 is moved (the direction of the arrow) so that the surface voltmeter 4 does not directly detect the charge from the charger 2. The work 1 is grounded, and the high voltage generation circuit 3 and the detection processing circuit 5 are also grounded.
[0018]
FIG. 2 shows an example of the charger 2. In the charger 2, an air chamber 10 which is a concave portion having an open upper surface is formed in a main body 9 which is a circular block of an electrically insulating material, and an opening extends from the bottom surface of the air chamber 10 to the lower surface of the main body 9. A plurality of discharge holes 11 are provided. The upper opening of the air chamber 10 is closed by a cover plate 12, and air is supplied from the outside into the air chamber 10 through an air hose 14 connected to a pipe joint 13 at the outside center of the cover plate 12. Needle-like discharge electrodes 16 implanted on a common electrode substrate 15 are inserted into each of the plurality of discharge holes 11. The electrode substrate 15 is fixed to the bottom surface of the air chamber 10, but does not block the discharge hole 11, and the air entering the air chamber 10 passes through the discharge hole 11 from the outlet 11 a, which is the tip opening. Be blown out. Since the length of the discharge electrode 16 is shorter than the length of the discharge hole 11, the tip of the discharge electrode 16 does not protrude from the discharge hole 11 but stays inside. A high voltage cable 17 is connected to the electrode substrate 15, and a high voltage is simultaneously applied from the high voltage generating circuit 3 to the plurality of discharge electrodes 16 through the high voltage cable 17.
[0019]
Air supply to the air chamber 10 is performed when the electromagnetic valve 18 is turned on by the control circuit 7 in FIG. 1, and application of a high voltage to the discharge electrode 16 is performed after the electromagnetic valve 18 is turned on. This is performed when the high voltage generating circuit 3 is turned on by the control circuit 7. Accordingly, the discharge electrodes 16 discharge while being air-purged in the respective discharge holes 11.
[0020]
The entire charger 2 is attached to an appropriate support member by an attachment band 19 that grips the outer periphery of the main body 9.
[0021]
FIG. 3 shows an example of the surface potential sensor 4. The surface potential sensor 4 is of a vibration chopper type, and includes a tuning fork vibrator 23 provided with a pair of piezoelectric elements 22, a detection electrode 24, and a preamplifier 25 in a sensor case 21 having a detection hole 20. When the tuning fork vibrator 23 is vibrated by the vibrator driving circuit 26, the lines of electric force from the charged object toward the detection electrode 24 through the detection holes 20 are chopped by the vibration of the tuning fork vibrator 23, and the Is output to the outside.
[0022]
This output is amplified and rectified by the detection processing circuit 5 of FIG. 1, taken out as a DC voltage, and compared with a threshold value by the comparison circuit 8.
[0023]
Next, an inspection method using such an apparatus will be described.
The work 1 having a conductive coating formed on its surface is stopped at a position facing the charger 2, the solenoid valve 18 is turned on by a signal from the control circuit 7, and the supply of air to the charger 2 is started first. Then, the high voltage generating circuit 3 is turned on by a signal from the control circuit 7 to apply a high voltage to the discharge electrode 16 of the charger 2.
[0024]
As a result, the discharge electrode 16 is discharged toward the grounded work 1 while being air-purged in the discharge hole 11, so that the surface of the work 1 is charged. Since the electric charge generated by the discharge is blown to the surface of the work 1 by blowing air, the electric charge can be efficiently averaged and charged over a wide range. In addition, by purging the discharge electrode 16 with air in the discharge hole 11, it is possible to prevent the discharge electrode 16 from being stained and to discharge electric charges generated by the discharge to improve discharge characteristics.
[0025]
In the case of a short work 1 shorter than the distance L between the charger 2 and the surface potential sensor 4, the control circuit 7 turns off the high-voltage generation circuit 3 to stop the discharge of the discharge electrode 16, and then the control circuit At 7, the electromagnetic valve 18 is turned off to stop air supply. Thereafter, the work 1 is moved by the distance L and stopped at a position facing the surface potential sensor 4. In other words, the work 1 facing the charger 2 is moved to a position facing the surface potential sensor 4. Then, the control circuit 7 controls the detection processing circuit 5 and the surface potential sensor 4 detects the surface potential of the work 1.
[0026]
On the other hand, in the case of a long work 1 extending over the distance L between the charger 2 and the surface potential sensor 4, the high voltage generation circuit 3 and the solenoid valve 18 are turned on for a required time by the control circuit 7 to discharge the discharge electrode 16 and The supply of air is performed for a required time, and at the same time or immediately thereafter, the control circuit 7 controls the detection processing circuit 5, and the surface potential sensor 4 detects the surface potential of the work 1. That is, while the surface of the work 1 is charged, the surface potential is measured at a remote position simultaneously or immediately after. In this case, the detection of the surface potential by the surface potential sensor 4 may be performed continuously or for a limited time.
[0027]
The output voltage from the detection processing circuit 5 according to the surface potential is compared with a threshold value by the comparison circuit 8. The threshold is set in advance based on an actual measurement value measured in advance for initial setting. For example, in the case of a work on which a conductive coating film is properly formed and in the case of an improper work, after charging by the charger 2 as described above, the surface potential is measured by the surface potential sensor 4, and the surface potential is measured. Determine a threshold value that is used as a criterion for quality judgment from data, and determine the dryness and wetness of the conductive coating film by performing the same operation for the case where the conductive coating film is dry and the case where the conductive coating film is not dry. Determine a reference threshold value.
[0028]
Although the output voltage of the detection processing circuit 5 does not directly indicate the resistance value of the conductive coating film itself, but indicates the surface potential (residual potential) of the work 1 after being charged by the charger 2, the It will also depend on the resistance of the film. That is, when the resistance value of the conductive coating film is low, the charge immediately disappears even if charged by the charger 2, so that the residual potential is 0 or close to 0, and thus the measured surface potential is also such. However, when the resistance value of the conductive coating film is high, the residual potential increases, so that the measured surface potential also increases.
[0029]
If the charging by the charger 2 and the measurement by the surface voltmeter 6 are performed at the same time while the workpiece 1 is moved, the overall measurement (pass / fail judgment) can be performed.
[0030]
Table 1 shows the following No. No. 1 to No. 5 is a measured data obtained by repeating a test for measuring the surface potential by the surface potential sensor 4 after charging the five types of workpieces by the charger 2 as described above ten times each.
No. No. 1 In the case of only a material that does not form a conductive coating film, 2 When a coating film was formed with a non-conductive normal primer, No. 3 When the conductive coating film was formed only with the conductive primer No. 4 When a conductive coating film was formed with a conductive primer mixed with a silver paint, 5 When a conductive coating film is formed with a conductive primer mixed with a red paint
[Table 1]

[0032]
As can be seen from such a test, after the surface of the work 1 is charged by the charger 2 and the surface potential is measured by the surface potential sensor 4, the surface potential is determined by the resistance of the conductive coating film on the surface of the work 1. Since the value reflects the measured value, the quality of the conductive coating film and the drying condition can be determined by comparing the measured surface potential with a threshold value in the comparison circuit 8. Furthermore, if the work 1 is not grounded, the measured surface potential is much higher than usual, so that it can be confirmed whether the work 1 is grounded.
The charging and the measurement of the surface potential can be performed for a plurality of portions of the work 1.
[0033]
【The invention's effect】
As described above, according to the present invention, since the resistance value inspection of the undercoat conductive film can be performed in a non-contact state, it is needless to say that the conductive film is not damaged, Removal work is not required, and not only the whole but also a partial inspection can be performed, and the inspection whether the work is grounded can be performed at the same time.
[0034]
In the charging device, the electric charge generated by the discharge can be blown to the surface of the work by blowing air by blowing air around the discharge electrode while air purging, so that the charge can be efficiently averaged over a wide range. In addition, it is possible to prevent the discharge electrodes from being stained and to discharge electric charges generated by the discharge to improve discharge characteristics.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an outline of the present invention.
FIG. 2 is a side view illustrating an example of a charger.
FIG. 3 is a mechanism diagram of an example of a surface potential sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Work 2 Charger 3 High voltage generation circuit 4 Surface potential sensor 5 Detection processing circuit 6 Surface potential meter 7 Control circuit 8 Comparison circuit 9 Main body 10 Air chamber 11 Discharge hole 11a Blow-out port 12 Cover plate 13 Fitting 14 Air hose 15 Electrode Substrate 16 Discharge electrode 17 High-voltage cable 18 Solenoid valve 19 Band 20 for attachment Detection hole 21 Sensor case 22 Piezoelectric element 23 Vibrator 24 Detection electrode 25 Preamplifier 26 Vibrator drive circuit

Claims (10)

The surface of the work on which the conductive coating film is formed is charged by a charger in a non-contact state with the work, and the surface potential is measured by a surface voltmeter in a non-contact state with the work. Conductive film inspection method. The method for inspecting a conductive coating film according to claim 1, wherein, while discharging in the charger, the charge by the discharge is applied to the surface of the work by blowing air to charge the work. The charger according to claim 1 or 2, wherein the charger and the surface voltmeter are spaced apart from each other, and the surface potential of the work is measured by the surface voltmeter while the surface of the work is charged by the charger. Conductive coating inspection method. The conductive coating film according to claim 1 or 2, wherein the charger and the surface voltmeter are arranged apart from each other, and the workpiece is moved from a position facing the charger to a position facing the surface voltmeter. Inspection methods. The method for inspecting a conductive coating film according to claim 1, wherein the charger and the surface voltmeter are arranged apart from each other, and while the workpiece is being moved, charging by the charger and measurement by the surface voltmeter are performed. . The method according to claim 1, wherein the potential measured by the surface electrometer is compared with a threshold. It consists of a charger for charging the surface of the work on which the conductive coating film is formed in a non-contact state with the work, and a surface voltmeter for measuring the surface potential of the charged work in a non-contact state with the work. A conductive coating film inspection apparatus, characterized in that: The conductive coating film inspection apparatus according to claim 7, wherein the charging device has a structure in which air is blown while air purging around the discharge electrode. 9. The conductive coating film inspection apparatus according to claim 7, further comprising a control circuit for controlling a discharge operation of the charger and a measurement operation of the surface voltmeter with a timing. 10. The conductive coating film inspection apparatus according to claim 7, further comprising a comparison circuit for comparing a potential measured by a surface voltmeter with a threshold value.

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