JPS6311850A - Method and apparatus for detecting pin hole or the like of insulator - Google Patents

Abstract

PURPOSE:To enable detection of the entire area of a sample in a short time, by attaching ions generated by a corona discharge onto the surface of a sample comprising a insulated body to detect a pin hole or the like from the size of current leaking from the sample. CONSTITUTION:A sample 5 has one side of metal base material 6 covered with an insulation this film 7 and an open periphery of an insulated container 1 is put tight on the surface of the thin film 7 to form a closed space with both the parts. Now, when an output voltage of a DC power source 3 to be applied to a corona discharge electrode 2 is increased to generate a corona discharge, ions generated by the corona discharge diffuse within the close space formed with the container 1 and the thin film 7 with a potential gradient between the electrode 2 and the thin film 7, a part of the diffused ions attach onto the surface of the thin film 7 and leakage current due to the ions attached flows to a circuit of a current detector 8 through the thin film 7 and the base material 6. Thus, the presence of a pin hole or the like can be detected in the thin film 7 depending on a difference between readings of the detector 8 when the thin film 7 has no flaw and when it 7 has a pin hole or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to coating a bottomed cylindrical metal base material with an insulating thin film made of a synthetic resin film or the like, such as a container for canned beer or canned coffee. The present invention relates to a method and apparatus for detecting the presence or absence of pinholes or scratches in an insulating thin film of a container, or the presence or absence of pinholes or scratches in a general insulating film, insulating plate, bottle, or the like.

Conventional technology A conventional pinhole detection device uses an insulating film, for example, in which a metal base material of the sample is used as a counter electrode, and a brush-like movable electrode to which a high voltage is applied is provided on the surface of the metal base material between the counter electrode and the counter electrode. The structure is such that the presence or absence of pinholes, etc. is detected by sliding the electrodes in direct contact with the electrodes and checking the magnitude of the discharge current between the two electrodes.

Problems to be Solved by the Invention In the conventional device, the brush-like movable electrode is brought into direct contact with the insulating film of the sample. There is a risk of damaging the membrane, and there is also a risk of causing non-sliding areas, that is, areas where detection is missed.If the applied voltage is too high for the thickness of the insulating film of the sample, the insulating film may be destroyed. However, if the voltage is too low, detection becomes impossible, so it is necessary to determine the optimum applied voltage experimentally in advance depending on the thickness of the insulating film, which requires a relatively large amount of time and effort to prepare for detection.

Means to solve problems The present invention uses ions generated due to corona discharge.

Insulation 11 of the specimen brought into close contact with the insulating container and its opening
diffused in a closed space formed by
A method and apparatus for detecting the presence or absence of pinholes, scratches, etc. in an insulating film of a specimen by determining the magnitude of leakage current from the insulating film caused by ions attached to the inner surface of the insulating film of the specimen.

Function In the present invention, it is possible to produce a significant difference in the magnitude of the current leaking through the insulating film of the specimen depending on the presence or absence of pinholes etc. in the insulating film of the specimen, and therefore, it is possible to make a significant difference in the magnitude of the current leaking through the insulating film of the specimen. By measuring, the presence or absence of pinholes etc. can be detected.

Embodiment FIG. 1 is a diagram showing an embodiment of the present invention, in which 1 is an electrically insulating container in the form of a hemispherical, circular or rectangular bottomed cylinder; 2 is a corona discharge electrode; It consists of an electrode or a needle-like electrode with a sharp tip. Reference numeral 3 is a DC power supply, which can vary the output voltage in the range of Ov to several tens of kV.

Reference numeral 4 indicates a discharge current limiting resistor, and reference numeral 5 indicates a specimen, which is made up of a metal base material 6 with an insulating thin film 7 coated on one side, and the periphery of the opening of the insulating container 1 is brought into close contact with the surface of this insulating thin film 7. form. 8 is a current detector such as an ammeter or an oscilloscope.

When the output voltage of the DC power supply 3 applied to the corona discharge electrode 2 is increased to generate a corona discharge, the ions generated due to this corona discharge are caused by the repulsion between the ions and the upper layer between the corona discharge electrode 2 and the insulating oil 1197. Due to the gradient, the ions are diffused into the closed space formed by the insulating container l and the insulating thin film 7, and a part of the diffused ions adheres to the surface of the insulating thin film 7, and furthermore, a leakage current due to the - part of the old ions is generated. The current flows through the insulating thin film 7 and the metal base material 6 to the circuit of the current detector 8 .

The presence of pinholes, etc. in the insulating thin film 7 can be determined from the difference between the indicated value of the current detector 8 when the insulating thin film 7 is intact and the indicated value of the current detector 8 when the insulating thin film 7 has pinholes or scratches. (Can detect nothingness.

The present inventors will explain this using specific numerical values based on experiments conducted on each prototype device.The insulating container l is made of rubber, its diameter is approximately 100 mm, and the corona discharge electrode 2 is a needle-like electrode with a sharp tip. The distance between the tip and the surface of the insulating thin film 7 is approximately 50 mm, and the metal base material 6 in the specimen is formed using an aluminum plate.
were formed from polyethylene with a thickness of about 35 gm, and the resistance value of the discharge current limiting resistor 4 was selected to be 100 MΩ.According to the results of observing the current value using an oscilloscope as the current detector 8, it was found that the voltage of the DC power supply 3 When the voltage is gradually increased, corona discharge occurs at around 2kV and leakage current begins to flow, and when the voltage is increased to 10kV, the leakage current value is approximately 2. At GJLA, we measured the leakage current value by replacing the sample with another sample of the same material, same configuration, and same dimensions. Although there were some differences depending on the sample, the change range of the leakage current value was approximately 2.3. JLA or approximately 2.7 pA, and both the magnitude of the leakage current value and its variation range were extremely small.

Next, when the surface of the insulating thin film 7 in the specimen is scratched with a length of approximately 1 mg+ in length and width, and the voltage of the DC power supply 3 is increased to 10 kV as above, the leakage current value from the insulating thin film 7 is When the size of the flaw is changed at approximately Ei and 0 JLA, and even in the case of a minute flaw that cannot be discerned with the naked eye, the leakage current value is approximately 8.0. Leakage current value 2.3JLA to 2.7 when no change is observed in A and there is no damage
It was approximately two to three times that of jLA, and the difference between the two was extremely large.

Figure 2 is a curve diagram showing the leakage current in the L experiment.
The horizontal axis is the elapsed time T (seconds), and the vertical axis is the leakage current value I (gA
), the curve shown with a solid line shows the change in leakage current in a specimen without any pinholes or scratches, and the curve shown with a broken line shows the change in leakage current in a specimen with scratches.

In the case of this curve diagram, 10k is applied to the corona discharge electrode from the beginning.
A DC voltage of V was applied, but after a few seconds, it stabilized at approximately Ei and 0JLA in the case of the broken line.

In the case of a solid line, approximately 2.3. It was stable at A to about 2.7 ILA.

In addition, the voltage of DC power supply 3 can be set to 15kV to 17kV.
Some specimens caused dielectric breakdown when the temperature was increased to 100 kW, and this dielectric breakdown was recognized by the rapid change in the leakage current value before and after the dielectric breakdown. The leakage current value measured after lowering was approximately 6.0 μA.

As is clear from the experimental results described in Section 2, an arbitrary specimen was extracted from a group of specimens of the same material, same configuration, and same size, and the DC voltage applied to the corona discharge voltage was gradually increased from zero volts. It detects the beginning of leakage current flow, and then increases the DC voltage to detect a significant increase in leakage current due to dielectric breakdown. The presence or absence of pinholes, etc. in the insulating thin film of the specimen can be detected from the leakage current value when an arbitrary DC voltage between the DC power supply voltage and the corona discharge electrode is applied.

In practice, taking into account the individual differences between samples, detection is performed by applying a voltage to the corona discharge electrode that is between a voltage that is appropriately lower than the dielectric breakdown voltage of any extracted sample and a voltage that is appropriately higher than the applied voltage at which leakage current begins to flow. It is desirable to do so.

If the leakage current of an arbitrarily extracted sample is a relatively large current at a stage where the voltage applied to the corona discharge electrode is low,
Of course, the detection voltage range may be determined by replacing the sample with another sample and gradually increasing the voltage applied to the corona discharge electrode from zero volts.

In the following, we have explained the detection of the presence or absence of pinholes or scratches in the insulating thin film of a specimen made of a metal HI material with an insulating thin film coated on one side. If a base material is not used, the detection is performed in the same manner as explained in Figure 1 by placing a metal plate or metal foil in close contact with one side of the sample and the opening edge of the insulating container with the other side of the sample. That's fine.

If the specimen is, for example, a food packaging bag made of a synthetic resin membrane, etc., insert a metal plate or metal foil into the bag and bring it into close contact.
A current detector is connected to this metal plate or metal foil, and the opening rim of the insulating container is brought into close contact with the outer surface of one side of the bag to detect the current.First, the opening rim of the insulating container is brought into close contact with the other outer surface of the bag. At the very least, detection will be carried out.

If the area of the specimen is large and the entire area of the specimen cannot be detected in one detection, the detection will be repeated by sequentially shifting the contact points around the opening of the insulating container, but if the specimen has a metal base material, If not, place a metal plate or metal foil in close contact with the entire surface of one side of the specimen, and repeat the detection by sequentially shifting the contact points around one edge of the insulating container, or measure the area of the metal plate or metal foil that is brought into close contact with one side of the specimen. may be made larger than the area of the opening of the insulating container, and the detection may be repeated by sequentially moving the contact point of the metal plate or metal foil in accordance with the movement of the contact point around the opening of the insulating container.

FIG. 3 shows pinholes or scratches in the synthetic resin 119 of a container for, for example, canned beer or various canned soft drinks, that is, a container made by coating a thin film of synthetic resin on the inner and outer surfaces of a metal can. The present invention is implemented to detect the presence or absence of
The opening periphery 62 of the gold FfS base material 61 is coated with the metal m material 6 without being coated with an insulating thin film for fitting with the lid.
1 is exposed. The current detector 8 is connected to this peripheral exposed portion 62. The diameter of the opening of the insulating container l is
This is formed approximately equal to the diameter of the opening peripheral portion 62 of the specimen,
When the opening periphery of the insulating container 1 is brought into close contact with the opening periphery of the specimen to form a sealed space, the metal 1 of the specimen
If there is a risk that the opening periphery B2 where iI4+8+ is exposed may be exposed in the closed space, take measures such as providing a step on the opening periphery of the insulating container 1 as shown in the figure.
Of course, it is necessary to shield the opening periphery 62 of the specimen.

In this embodiment, as shown in an enlarged perspective view of the main part in FIG.
For example, a corona discharge electrode is formed by attaching it to the tip of the electrode supporting conductor 21 at a distance of approximately 20 m+o.

Other symbols and configurations are the same as in FIG. 1.

In this embodiment as well, when the voltage of the DC power supply 3 is increased to an appropriate high voltage, ions generated due to corona discharge diffuse into the closed space and some of them adhere to the insulating thin film 7I of the specimen, causing the stuck ions to Since some leakage current flows to the external circuit, by measuring the magnitude of the leakage current with the current detector 8, it is possible to detect the presence or absence of pinholes, etc. in the insulating thin film 71.

In this embodiment, since the corona discharge electrode is formed by providing a plurality of thin wire electrodes or needle electrodes 22 at the tip of the electrode supporting conductor 21, by adjusting the length of the electrode supporting conductor 21 appropriately. Since the electrode 22 can be inserted into the internal space of the specimen, it has the advantage that some of the ions generated due to corona discharge can be quickly attached to the entire surface of the insulating thin film 71. A single thin wire or needle electrode as shown may also be used.

The presence or absence of pinholes, etc. in the insulating thin film of the lid of a can-shaped container can be detected by forming the diameter of the opening of the insulating container l to be approximately equal to the diameter of the lid in the embodiment shown in FIG. The periphery is brought into close contact with the periphery of the lid, and the exposed part of the metal base material at the periphery of the lid, that is, the exposed part of the metal base material, is fitted to the opening periphery of the container body, so the entire periphery is coated with an insulating thin film. Detection can be carried out in exactly the same manner as described in connection with FIG. 1 by connecting a current detector to the edge where the metal matrix is exposed.

The above are corona discharge electrodes such as thin wire electrodes and needle electrodes (
(Fig. 1) or an electrode formed by providing a plurality of thin wire-like electrodes or needle-like electrodes at the tip of a supporting conductor (Figs. 3 and 4)
In addition to this, for example, an electrode may be used in which a large number of thin conductive wires are twisted together to form a single conductor, and the tips are loosened. By using this method, corona discharge can be generated at a relatively low pressure, and the amount of ions generated due to corona discharge can be greatly reduced compared to when a corona discharge electrode is formed using a single thin wire electrode or needle electrode. This can be used to quickly stop the spread.

Even in the above-mentioned embodiments, some of the ions diffused into the closed space due to the mutual repulsion of ions generated by corona discharge and the potential gradient between the corona discharge electrode and the insulating thin film reach the insulating thin film of the specimen. Although the case in which the corona discharge electrode 2 is configured to adhere is illustrated as an example, as shown in FIG. If the diameter of the accelerating electrode 9, the distance between the accelerating electrode surface and the tip of the corona discharge electrode 2, the voltage of the DC power source lO, etc. are adjusted appropriately, the area near the tip of the corona discharge electrode 2 The generated ions are attracted and accelerated by the accelerating electrode 9, and some are captured by the accelerating electrode 9, but most of them pass through the accelerating electrode 9 and pass through the insulating oil of the specimen + 1! I! 7 and is distributed almost uniformly.

Therefore, compared to the case where ions are diffused by mutual repulsion and the potential gradient between the corona discharge electrode and the insulating thin film, the detection time for pinholes etc. can be shortened.

Instead of providing a ring-shaped accelerating electrode, as shown in FIG. 6, a voltage with the opposite polarity to the voltage applied to the corona discharge electrode 2 is applied to the metal IJ material 6 of the specimen by the DC power supply 11, and the mutual repulsive force between ions is applied. , the structure may be such that the potential gradient between the corona discharge electrode 2 and the insulating thin film 7 and the attractive force of the metal base material 6 speed up the diffusion of ions, and the ring-shaped accelerating electrode 9 shown in FIG. The ion acceleration means may be used in combination with the ion attraction means by applying an attraction voltage to the metal base material 6 shown in FIG.

In any of the above-mentioned embodiments, it is necessary to minimize the gap between the periphery of the opening of the insulating container 1 and the insulating thin film of the sample. In other words, if a gap is created between the close contact parts and the air in the closed space and the air in the outside space interact with each other through this gap, ions in the closed space will flow out due to this exchange of air. However, since accurate detection may be impossible, for example, the periphery of at least the opening of the insulating container l should be made of a material with appropriate elasticity or flexibility, such as rubber, or As shown in the figure, a ring-shaped repulsion electrode 12 is provided at the edge of the opening in the insulating container l,
By applying a voltage of the same polarity as the voltage applied to the corona discharge electrode 2 by the DC power supply 13, it may be configured to suppress the outflow of ions from the gap in the close contact part.
A method of forming the edge of the opening in the insulating container l using a flexible or flexible material and a method of providing a repulsion electrode at the edge of the opening may be used in combination.

Note that other symbols and configurations in FIGS. 5 to 7 are the same as in FIG. 1.

In each of the above embodiments, the corona radiation electrode 2
Or, the case where negative ions (oxygen ions) are generated by applying a negative voltage to the corona discharge electrode is illustrated, but in any of the examples, even if a positive voltage is applied to the corona discharge electrode to generate positive ions (nitrogen ions), the present invention will not occur. Able to carry out inventions.

In this case, the voltage applied to the ring-shaped accelerating electrode 9 shown in FIG. 5 and the voltage applied to the metal base material 6 shown in FIG. Of course, the voltage applied to the repulsion electrode 12 should be a positive voltage.

”2 In each embodiment, the corona discharge electrode 2 or 22
Although a DC voltage is applied to the voltage, the present invention can also be carried out by applying an AC voltage at the commercial power frequency, for example.

When an AC voltage is applied to the corona discharge electrode, the accelerating electrode 9 shown in FIG. 5 and the metal base material 6 in FIG. An AC voltage is applied to the repulsion electrode 12 shown in FIG. 7, which has the same frequency and phase as the AC voltage applied to the corona discharge electrode 2. 9. If the distance between the metal base material 6 and the repulsion electrode 12 is several hundred meters or less, the influence of the delay time of ion movement on the cycle of the AC voltage will hardly be recognized, and the acceleration, attraction, or repulsion effect will be sufficiently achieved. It can be shown.

Furthermore, in each of the embodiments described above, the corona discharge electrode 2 or 22 is sealed in the insulating container 1, and ions are generated by corona discharge in the insulating container 1. Although the example has been given, the present invention may also be implemented by generating ions outside the insulating container and introducing them into the closed space formed by the insulating container and the sample through a suitable insulating flow path. It can be implemented.

FIG. 8 is a diagram showing an embodiment thereof, in which i is an ionizer, which has the same configuration as a conventionally known ionizer, and ttU also has a metal casing 15. It consists of a corona discharge electrode IB, an insulator 17, a compressed air inlet 118, etc. 18 is an ion flow path, for example, made of an insulated pipe. 20 is an air outlet of 1i9 orders of magnitude into the insulating container l.

Other symbols and configurations are the same as in FIG. 1.

When a DC high voltage is applied to the corona discharge electrode 1G of the ionizer 14 and compressed air is allowed to flow in from the inlet 11B, air containing no ions flows into the metal casing 15.
, flows out from the insulating pipe 18 and the insulating container l. After the outflow of air that does not contain any ions, or from the beginning, the insulating container l
When the opening of is brought into close contact with the surface of the insulating thin film 7 of the specimen,
The ions flowing into the space formed by the insulating container l and the insulating base film 7 through the insulating pipe 19 adhere to the surface of the insulating thin film 7, and the presence or absence of pinholes etc. is determined in the same manner as in the previous embodiments. Detection can be performed.

゛In this case, the compressed air that has flowed into the space formed by the insulating container 1 and the insulating base membrane 7 flows out from the air outlet 20 immersed in the insulating container 1, but the ions contained in the compressed air Since the adhesion of the insulating thin film 7-2 is not inhibited,
There is no risk of interfering with detection.

FIG. 8 shows an example of detection of a specimen made by coating an insulating thin film 7 on the surface of a metal base material 6, but when the specimen consists only of an insulator and does not have a metal 11 material Of course, detection can be performed by closely adhering a metal plate or metal foil to one side of the specimen and connecting a current detector to this.

-L is a specimen with a thin insulating film on one side of a metal base material, a specimen with a thin insulating film on both sides of a metal material such as a can-shaped container for drinking liquid and its lid, or a food packaging bag. As described above, the detection of pinholes or scratches in the insulating thin film of a sample consisting only of an insulating thin film has been explained. The present invention can also be implemented to detect scratches on bottles made of synthetic resin, etc., but in the case of paint films on automobiles, aircraft, etc., detection can be performed in the same manner as explained with reference to FIG. 1 or 3. In the case of a bottle or the like, detection may be performed in the same manner as described with reference to FIG. 3 or FIG.

Effects of the Invention In the present invention, ions generated due to corona discharge are attached to the surface of the specimen without directly sliding the movable electrode on the surface of the specimen as in the past, thereby reducing leakage from the specimen. Since it detects the presence or absence of pinholes or scratches by determining The DC voltage applied to the corona discharge electrode can be applied to the corona discharge electrode by applying an arbitrary voltage to the corona discharge electrode, as long as it is in the range of a voltage that is suitably lower than the voltage that causes dielectric breakdown of the specimen, which causes corona discharge. It is possible to perform detection, the selection range is extremely wide, and the -L limit and lower limit can be detected easily and quickly, so there is no need for a lot of time and effort for detection preparation as in the past. It has many advantages and its effects are great.

[Brief explanation of the drawing]

1, 3, 5 to 8 are diagrams showing embodiments of the present invention, FIG. 2 is a curve diagram for explaining its operation, and FIG. 4 is a configuration of a corona discharge electrode. An enlarged perspective view showing an example of ~, l: insulating container, 2: corona discharge electrode, 2! : Electrode supporting conductor, 21: Corona discharge electrode, 3: DC power supply, 4: Discharge current limiting resistor. 5 and 5 specimens, 6 and 6 metal base materials, 62: Metal Il
edge of material, 7.71 and 72: insulating thin film, 8: current detector, 9: ring-shaped accelerating electrode, lO and 11: DC power supply,
12: Ring-shaped repulsive electrode, 13: DC power supply, 14: Ionizer, 15: Metal casing, 16 Nicorona discharge electrode, 17
: insulator, 18: compressed air inflow, 18: insulating pipe, 20: air outlet.

Claims (16)

[Claims] (1) Ions generated due to corona discharge are attached to the surface of a specimen made of an insulator, and the presence or absence of pinholes, etc. in the specimen is detected from the magnitude of the current leaking through the specimen. Method for detecting pinholes, etc. in insulators. (2) an insulating container that forms a sealed space together with an insulator provided on the surface of a metal base material in the specimen, a corona discharge electrode provided in the sealed space, and a power source that applies voltage to the corona discharge electrode; A device for detecting pinholes, etc. in an insulator, comprising a current detector connected to the metal base material of the specimen. (3) an insulating container that forms a sealed space together with the specimen made of an insulator; a corona discharge electrode provided in the sealed space;
The insulator is characterized by comprising a power source that applies voltage to the corona discharge electrode, a metal body that is brought into close contact with the outer surface of the specimen, and a current detector that is connected to this metal body. Detection device. (4) A device for detecting pinholes, etc. in an insulator according to claim 2 or 3, wherein the corona discharge electrode is a thin wire electrode. (5) A device for detecting pinholes, etc. in an insulator according to claim 2 or 3, wherein the corona discharge electrode is a needle-like electrode with a sharp tip. (6) A device for detecting pinholes or the like in an insulator according to claim 2 or 3, wherein the corona discharge electrode comprises a plurality of thin wire electrodes provided on an electrode supporting conductor. (7) A device for detecting pinholes or the like in an insulator according to claim 2 or 3, wherein the corona discharge electrode comprises a plurality of needle-like electrodes provided on an electrode supporting conductor. (8) A device for detecting pinholes or the like in an insulator according to claim 2 or 3, wherein the corona discharge electrode is formed by twisting together a large number of thin wires and loosening their tips. (9) A device for detecting pinholes or the like in an insulator according to claim 2 or 3, wherein the power source is a DC power source. (10) The device for detecting pinholes, etc. in an insulator according to claim 2 or 3, wherein the power source is an AC power source. (11) The insulation according to claim 2 or 3, comprising a ring-shaped accelerating electrode to which a voltage of opposite polarity to the voltage applied to the corona discharge electrode is provided on the front surface of the corona discharge electrode. A device to detect pinholes, etc. in the body. (12) In the insulator according to claim 2, the insulator is connected in series with the current detector and is provided with a power source that applies a voltage of opposite polarity to the voltage applied to the corona discharge electrode to the metal base material of the specimen. Detection device for pinholes, etc. (13) Claim 3, which is provided with a power supply connected in series with the current detector and applying a voltage of opposite polarity to the voltage applied to the corona discharge electrode to a metal body that is brought into close contact with the outer surface of the specimen. A device for detecting pinholes, etc. in the described insulator. (14) Claim 2 or 3, wherein a ring-shaped repulsion electrode to which a voltage of the same polarity as the voltage applied to the corona discharge electrode is applied is provided on the edge of the opening in the insulating container.
A device for detecting pinholes, etc. in an insulator as described in 2. (15) An insulating container that forms a sealed space together with an insulator provided on the surface of the metal base material of the specimen, an ionizer that causes ions to flow into the sealed space, and a current detection device that is connected to the metal base material of the specimen. A device for detecting pinholes, etc. in an insulator, characterized by comprising a container. (16) An insulating container that forms a sealed space together with the specimen made of an insulator, an ionizer that causes ions to flow into the sealed space, and a current detector that is connected to a metal body that is brought into close contact with the outer surface of the specimen. A device for detecting pinholes, etc. in an insulator, characterized by: