JP2020134287A - Method and device for inspecting pinhole - Google Patents

Abstract

To provide a method for inspecting a pinhole, capable of reducing an inspection time compared with a vacuum leak type inspection, high in safety and capable of obtaining inspection accuracy equivalent to that of voltage application type inspection.SOLUTION: A method for applying voltage to a vessel 40 to be inspected to inspect a pinhole comprises: arranging the entire vessel 40 to be inspected or a portion to be inspected in the vessel 40 to be inspected in reduced pressure environment; arranging a high voltage electrode 30 in the vicinity of the portion to be inspected in the vessel 40 to be inspected positioned in the reduced pressure environment; and contacting a low voltage electrode 32 to a portion except the portion to be inspected to apply voltage between the high voltage electrode 30 and the low voltage electrode 32.SELECTED DRAWING: Figure 1

Description

The present invention relates to a pinhole inspection method and an apparatus, and more particularly to a method and an apparatus for inspecting the presence or absence of pinholes by applying a voltage.

As a method for detecting pinholes and the like generated in a package or container, a leak inspection in a vacuum as disclosed in Patent Document 1 and a voltage application type inspection as disclosed in Patent Documents 2 and 3 are performed. It has been known.

In the vacuum leak type inspection disclosed in Patent Document 1, the container to be inspected is arranged in a closed region such as a chamber, and the inside of the closed region is depressurized to create a vacuum state. In this state, the pressure state in the closed region after a lapse of a predetermined time is measured, the presence or absence of a leak from the container to be inspected is detected, and the quality of the container to be inspected is judged.

On the other hand, in the voltage application type inspection, a current is passed between the electrodes in a state where the high voltage electrode and the low voltage electrode are in contact with the container to be inspected, and a pinhole (leakage) is caused based on the difference in the current value detected when energized. It detects the presence or absence of the voltage and determines the quality of the container to be inspected. In the voltage application type inspection, it is necessary that the inspection area is in contact with a conductive substance such as a liquid.

Japanese Unexamined Patent Publication No. 6-307792 Japanese Unexamined Patent Publication No. 2003-254941 Japanese Unexamined Patent Publication No. 2005-331469

In each inspection technique, in the vacuum leak type inspection, it is necessary to generate a decompression space having a predetermined degree of vacuum when performing the inspection and to maintain this for a predetermined time. Therefore, the inspection itself takes a long time and is inefficient. Further, there is a problem that the size of the pinhole that can be detected is larger than the size generally known as the size of bacteria or bacteria (about 1 μm) and is set to 10 μm to 50 μm.

On the other hand, in the voltage application type inspection, the size of the pinhole that can be detected can be up to 0.1 μm, but when a high voltage is applied between the electrodes, a spark discharge occurs between the electrodes and the container to be inspected. At this time, depending on the material and strength of the container to be inspected, there is a problem that pinholes may be formed in the container to be inspected due to this spark discharge.

Therefore, in the present invention, a pinhole inspection method, which shortens the inspection time as compared with the vacuum leak type inspection, has high safety, and can obtain the inspection accuracy equivalent to the voltage application type inspection, and this method are implemented. It is an object of the present invention to provide a possible pinhole inspection apparatus.

The pinhole inspection method according to the present invention for achieving the above object is a method in which a voltage is applied to a container to be inspected to perform a pinhole inspection, and the entire container to be inspected or the container to be inspected is inspected. The part is arranged in a reduced pressure environment, the high voltage electrode is arranged in the vicinity of the part to be inspected in the container to be inspected located in the reduced pressure environment, and the low pressure electrode is brought into contact with a part other than the part to be inspected. Therefore, a voltage is applied between the high voltage electrode and the low voltage electrode.

Further, in the pinhole inspection apparatus having the above-mentioned characteristics, the product of the atmospheric pressure P [mmHg] in the depressurized environment and the distance L [cm] between the high-pressure electrode and the inspected portion PL [mmHg. cm] should be within the range of 1 <P · L <760. With such a feature, it is possible to perform an inspection that causes a spark discharge at a voltage lower than that at least performing a pinhole inspection under normal pressure.

Further, the pinhole inspection device for achieving the above object is a device that applies a voltage to the container to be inspected to perform a pinhole inspection, and is an entire device to be inspected or a part to be inspected in the container to be inspected. A vacuum chamber covering the above, at least a high-voltage electrode and a low-voltage electrode, and a voltage-applied inspection means having a high-voltage power supply are provided, and the high-voltage electrode is located in the vacuum chamber in the vicinity of the inspection site. The low-voltage electrode is configured to be in contact with a portion of the vessel to be inspected other than the portion to be inspected.

According to the pinhole inspection method and device having the above characteristics, the inspection time is shorter than the vacuum leak type inspection, and the inspection can be performed at a low voltage, so the safety is high and equivalent to the voltage application type inspection. Inspection accuracy can be obtained.

It is a figure which shows the structural example of the pinhole inspection apparatus which concerns on 1st Embodiment. It is an equivalent circuit diagram when the container to be inspected is a good product in a voltage application type pinhole inspection. It is an equivalent circuit diagram when the container to be inspected is a defective product in a voltage application type pinhole inspection. This is a flow in the case of performing pinhole inspection of the container to be inspected by using the pinhole inspection apparatus according to the embodiment. It is a graph which shows the relationship between the minimum voltage at which a spark discharge occurs, and the product of the atmospheric pressure and the distance between electrodes. It is a figure which shows the structural example of the pinhole inspection apparatus which concerns on 2nd Embodiment. It is a figure which shows the inspection form by the pinhole inspection apparatus which concerns on 2nd Embodiment.

Hereinafter, the pinhole inspection method of the present invention and the embodiment according to the pinhole inspection apparatus will be described in detail with reference to the drawings.

[First Embodiment]
The pinhole inspection method according to the present invention mainly involves performing a voltage application type inspection with all or part of the container to be inspected placed in a vacuum. As a specific method thereof, the pinhole inspection device 10 according to the first embodiment shown in FIG. 1 will be taken as an example, and the inspection method by the pinhole inspection device 10 will be described. The form of the container 40 to be inspected is not particularly limited. For example, it may be a bag-shaped product containing retort food, pickles, or the like, or a container containing pudding, jelly, or the like. The contents shall be conductive.

The pinhole inspection device 10 according to the present embodiment is basically composed of a vacuum chamber 12 and a voltage application type inspection means 24. The vacuum chamber 12 according to the present embodiment is a box body capable of accommodating the entire container 40 to be inspected. At least the vacuum pump 14, the release valve 16, and the vacuum gauge 18 are attached to the vacuum chamber 12. The vacuum pump 14 is an element for evacuating the inside of the vacuum chamber 12, and a vacuum valve 20 and a pressure adjusting valve 22 are provided in a path connecting the vacuum chamber 12 and the vacuum pump 14. The vacuum chamber 12 capable of accommodating the entire container 40 to be inspected is effective when inspecting a container such as a bag-shaped container whose shape changes due to pressing or the like.

The voltage application type inspection means 24 has at least a high voltage power supply 26, a current measurement sensor 28, a high voltage electrode 30, and a low voltage electrode 32. The current output from the high-voltage power supply 26 is passed from the high-voltage electrode 30 to the low-voltage electrode 32 via the container 40 to be inspected, and the current measurement sensor 28 measures the energization value to determine the presence or absence of pinholes in the container 40 to be inspected. judge.

The voltage of the high voltage power supply 26 is V, the resistance value of the conductive content in the circuit is R ₁ , the capacitance value of the container 40 to be inspected on the high voltage electrode 30 side is C ₁ , and the circuit capacitance value on the low voltage electrode 32 side is C _2. Once determined, it can be shown by an electrical equivalent circuit as shown in FIG. Incidentally, I _g in FIG. 2 is a current value measured by the current measuring sensor 28 when the inspected container 40 is non-defective (if pinholes no). Here, if a pinhole is present in the container 40 to be inspected, the container 40 to be inspected is in a short-circuited state. Therefore, as shown in FIG. 3, the electrically equivalent circuit can be represented as having no capacity value C _{1 of the} container 40 to be inspected. Note that _{Ip in} FIG. 3 is a current value measured by the current measurement sensor 28 when the container 40 to be inspected is a defective product (when there is a pinhole).

The circuit equation in the electrically equivalent circuit shown in FIG. 2 can be expressed by Equation 1.

From Equation 1, the voltage V in the circuit equation when there is no pinhole in the container 40 to be inspected can be expressed by Equation 2. Here, j is an imaginary unit.

On the other hand, when the pinhole is present in the container 40 to be inspected, the capacitance value C ₁ is not taken into consideration, so that the voltage V in the circuit equation can be expressed by Equation 3.

From Equations 2 and 3, when the output voltage V of the high-voltage power supply 26 is common, the relationship (1 / jωC ₁ + 1 / jωC ₂ )> (1 / jωC ₂ ) holds. Therefore, the relationship between _{I g} and _{I p,} as shown in Equation 4, from the _{I p} is _{I g} increases. Therefore, by measuring the current value with the current measurement sensor 28, it is possible to determine the presence or absence of a pinhole in the container 40 to be inspected.

In the present embodiment, as shown in FIG. 1, the high-voltage electrode 30 and the low-voltage electrode 32 are each drawn into the vacuum chamber 12. The specific arrangement positions of the high-voltage electrode 30 and the low-voltage electrode 32 are determined by the shape of the container 40 to be inspected and the position of the part to be inspected. The low-voltage electrode 32 is arranged so as to be located in contact with a portion of the container 40 to be inspected other than the portion to be inspected.

[Inspection method]
A pinhole inspection using the pinhole inspection device 10 having the above configuration will be described with reference to FIG. First, the container 40 to be inspected is carried into the vacuum chamber 12 from the object input port (not shown) of the vacuum chamber 12 and accommodated. The container 40 to be inspected is arranged so that at least a part thereof comes into contact with the low-voltage electrode 32 and the high-voltage electrode 30 is located near the site to be inspected (step 10).

After the container 40 to be inspected is housed inside the vacuum chamber 12 and shielded, the vacuum pump 14 is moved to evacuate the internal region in the vacuum chamber 12. At this time, by setting the target pressure by the pressure adjusting valve 22, even when the pinhole inspection of the container 40 to be inspected is repeatedly performed, the inspection can be performed under similar conditions.

Here, the reason why the container 40 to be inspected is housed in the vacuum chamber 12 and evacuated will be described with reference to the graph shown in FIG. In the graph shown in FIG. 5, the horizontal axis represents the product of the atmospheric pressure P [mmHg] and the distance between the electrodes L [cm], and the vertical axis represents the spark start voltage [V]. From FIG. 5, it can be read that the smaller the product P / L of the atmospheric pressure and the distance between the electrodes, the lower the spark start voltage. Further, according to FIG. 5, it can be read that spark discharge does not occur in the complete vacuum region where the product P / L of the atmospheric pressure P and the distance L between the electrodes is 0.

Taking FIG. 5 into consideration, when the distance between the electrodes L (in this embodiment, the distance between the high-voltage electrode 30 and the container 40 to be inspected) is constant, the lower the atmospheric pressure P [mmHg], the lower the starting voltage of spark discharge. It can be seen that (however, the atmospheric pressure P × the distance L between the electrodes is 1 [mmHg · cm] or more). For example, when the distance L between the electrodes is 1 [cm] under atmospheric pressure, the position indicated by A in FIG. 5, that is, the product P / L of the pressure P and the distance L between the electrodes is 760 [mmHg · cm]. The spark starting voltage at this time is about 30 kV. On the other hand, when the atmospheric pressure P is set to 1/10 while maintaining the distance L between the electrodes, the product P · L of the barometric pressure P and the distance L between the electrodes is 76 [mmHg · cm] indicated by B, and the spark start voltage. Is about 5 kV.

Therefore, in the present embodiment, the container 40 to be inspected is housed in the vacuum chamber 12 and vacuumed to reduce the starting voltage of the spark discharge at the time of inspection, and the container 40 to be inspected due to the spark discharge. I try to prevent damage (step 20).

After evacuating the internal region of the vacuum chamber 12, a voltage is applied between the high-voltage electrode 30 and the low-voltage electrode 32 to perform a pinhole inspection of the container 40 to be inspected in a reduced pressure environment. As described above, the pinhole inspection is performed by measuring the current value when the voltage is applied with the current measurement sensor 28. The presence or absence of a pinhole in the container 40 to be inspected may be determined based on whether or not the measured current value is within a predetermined threshold value with reference to the current value at the time of measuring a non-defective product (step 30).

After the pinhole inspection is completed, the release valve 16 is opened, the region inside the vacuum chamber 12 is returned to normal pressure, and the container 40 to be inspected is taken out from the vacuum chamber 12 (step 40).

[effect]
In the pinhole inspection by the above method, it is possible to perform an inspection accompanied by spark discharge (corona discharge) at a lower voltage than the conventional one. Therefore, it is possible to prevent the container 40 to be inspected from being damaged due to the spark discharge. Further, in the above method, it is not necessary to wait for gas or liquid to leak from the container 40 to be inspected after evacuating the vacuum chamber 12. Therefore, the inspection time can be shortened as compared with the vacuum leak type inspection.

[Second Embodiment]
Next, a second embodiment according to the pinhole inspection apparatus of the present invention will be described with reference to FIGS. 6 and 7. The basic configuration of the pinhole inspection device 10A according to the present embodiment is the same as that of the pinhole inspection device 10 according to the first embodiment described above.

That is, the pinhole inspection device 10A according to the present embodiment is also configured based on the vacuum chamber 12 and the voltage application type inspection means 24. The difference from the pinhole inspection device 10 according to the first embodiment is the form of the vacuum chamber 12 and the arrangement of the low pressure electrode 32.

Specifically, the vacuum chamber 12 in the pinhole inspection device 10 according to the first embodiment has a form in which the entire container 40 to be inspected can be accommodated inside, whereas the vacuum chamber 12 according to the present embodiment is covered. It is a part of the inspection container 40 and covers the periphery of the inspection site. The volume of the internal space of the vacuum chamber 12 can be reduced by covering only a part of the container 40 to be inspected. Therefore, the time required for evacuation can be shortened and the inspection time can be shortened as compared with the type of vacuum chamber that accommodates the entire container 40 to be inspected.

The vacuum chamber 12 having such a configuration is basically a dedicated product that matches the form of the container 40 to be inspected. For example, when the ampoule as shown in FIG. 6 is the container 40 to be inspected and the part to be inspected is the tip of the ampoule, the vacuum chamber 12 is composed of a casing having an opening on the side as shown in FIG. It is good to set it to. The opening provided on the side of the casing is a place where the tip of the ampoule is inserted. It is desirable to arrange the shielding contact member 12a at the contact portion with the ampoule. The shielding contact member 12a may be any member such as silicon rubber or rubber having flexibility that can be deformed along the contact portion to ensure airtightness. With such a configuration, when the vacuum chamber 12 is pressed against the container 40 to be inspected, there is no risk of damaging the contact portion of the container 40 to be inspected.

When the vacuum chamber 12 has such a configuration, the high-voltage electrode 30 can be the only electrode that is drawn into the vacuum chamber 12. The low-pressure electrode 32 that comes into contact with the ampoule, which is the container 40 to be inspected, does not have to be placed in a vacuum environment, and the vacuum chamber 12 can be miniaturized accordingly.

In the pinhole inspection device 10A having such a configuration, when performing a pinhole inspection, it is necessary to press the vacuum chamber 12 against the container 40 to be inspected. Therefore, it is preferable to provide a moving means in at least one of the vacuum chamber 12 and the container 40 to be inspected so that the two can be automatically brought into contact with each other. This is because the vacuum chamber 12 and the container 40 to be inspected are brought into contact with each other by the automatic moving means, so that the degree of pressing of the vacuum chamber 12 against the container 40 to be inspected is less likely to vary.

In the example shown in FIG. 6, a moving rail 34 is provided above the vacuum chamber 12, and a moving column 36 that can move along the moving rail 34 is provided between the moving rail 34 and the vacuum chamber 12, so that FIG. 7 shows. As shown, the vacuum chamber 12 can be moved along the moving rail 34. Further, the mounting table 38 on which the container 40 to be inspected is placed may be provided with a transport function so that the container 40 to be inspected can be transported from the front side to the back side in the drawing, for example.

With such a configuration, after the container 40 to be inspected placed on the mounting table 38 is conveyed to the arrangement position of the vacuum chamber 12, the vacuum chamber 12 is moved along the moving rail 34, and the container 40 to be inspected is moved. Can be pressed against.

[Inspection method]
The basic method of the pinhole inspection using the pinhole inspection device 10A having such a configuration is the same as the pinhole inspection using the pinhole inspection device 10 according to the first embodiment described above. The difference is that the pinhole inspection device 10 according to the first embodiment accommodates the entire container 40 to be inspected in the vacuum chamber 12, whereas the pinhole inspection device 10A according to the present embodiment is subject to inspection. The point is that the vacuum chamber 12 is pressed against a part of the inspection container 40 to create a vacuum region.

As a result, the time required for evacuation can be shortened, and the time required for pinhole inspection can be shortened. Other methods are the same as the inspection by the pinhole inspection device 10 according to the first embodiment described above.

10, 10A ……… Pinhole inspection device, 12 ……… Vacuum chamber, 12a ……… Shielding contact member, 14 ……… Vacuum pump, 16 ……… Open valve, 18 ……… Vacuum gauge, 20… …… Vacuum valve, 22 ………… Pressure control valve, 24 ………… Voltage application type inspection means, 26 ………… High voltage power supply, 28 ………… Current measurement sensor, 30 ………… High voltage electrode, 32 ………… Low-voltage electrode, 34 ……… Moving rail, 36 ……… Moving support, 38 ……… Mounting stand, 40 ……… Container to be inspected.

Claims (3)

It is a method of applying a voltage to the container to be inspected to perform a pinhole inspection.
The entire container to be inspected or the part to be inspected in the container to be inspected is placed in a reduced pressure environment.
A high-voltage electrode is placed in the vicinity of the inspected portion of the container to be inspected located under the reduced pressure environment, and the low-voltage electrode is brought into contact with a portion other than the inspected portion.
A pinhole inspection method comprising applying a voltage between the high voltage electrode and the low voltage electrode. The product PL [mmHg · cm] of the atmospheric pressure P [mmHg] in the depressurized environment and the distance L [cm] between the high pressure electrode and the site to be inspected is
1 <PL <760
The pinhole inspection method according to claim 1, wherein the pinhole inspection method is within the range of. A device that applies a voltage to the container to be inspected to perform pinhole inspection.
A vacuum chamber that covers the entire container to be inspected or the part to be inspected in the container to be inspected.
It is provided with at least a high voltage electrode, a low voltage electrode, and a voltage application type inspection means having a high voltage power supply.
The high-voltage electrode is arranged in the vacuum chamber at a position located near the site to be inspected, and the low-voltage electrode is configured to be able to contact a site other than the site to be inspected in the container to be inspected. A pinhole inspection device characterized by this.

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