JP2020169888A - Leakage inspection method - Google Patents

Abstract

To determine with high accuracy whether or not the sealability of an inspection object in which a content is encapsulated in a flexible package is good, and eliminate the need for strictly managing items not directly linked to the quality of content of the inspection object to reduce manufacturing and management costs.SOLUTION: An inspection object 90 in which a content 91 is enclosed in a flexible package 92 is inspected for leakage by a leakage inspection device 1. Measured data P9B, P9B, etc., on leakage amounts of a plurality of bad samples 90B, 90B, etc., having leakage as samples of the inspection object 90 are acquired. A threshold Ps of leakage inspection is set on the basis of a variation σ in the measured data P9B, P9B, etc.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for leak-inspecting the sealability of an inspection target, and more particularly to a leak inspection method suitable for an inspection target in which the contents are enclosed inside a flexible package.

The leak inspection (leak test) is known as a technique for determining the quality of the sealing property of an inspection target by detecting a leak from the inspection target (see Patent Documents 1 and 2 and the like). The fluid pressure (test pressure) from the pressure source is introduced into the inspection space defined by the inspection target. Then, the pressure in the inspection space is measured. If there is a defect in the sealability of the inspection target, the measured pressure will exceed the threshold value and deviate from the non-defective range due to fluid leakage from the defect. As a result, the presence or absence of leakage can be detected, and by extension, the quality of the sealing property of the inspection target can be determined.

Normally, when setting the threshold value for quality judgment, pressure measurement data of a good sample without leakage is collected. The threshold value is set based on the degree of variation (for example, deviation σ) of the data distribution. For details, for example
Threshold = μ + n · σ, or threshold = μ−n · σ (1)
It is said. Here, μ is the average value of the data distribution. n is an integer of 1 or more.

Japanese Unexamined Patent Publication No. 2013-002812 Japanese Unexamined Patent Publication No. 2012-2556887

In the case of an inspection target in which the contents are enclosed inside the flexible package, the amount of the contents is usually strictly controlled, but the position and width of the sealing portion by heat sealing of the flexible package and the encapsulation are performed. The amount of gas is often less rigorous. Therefore, even if it is a good product without leakage, the volume is not uniform, and the variation (deviation σ) of the measurement data of the leakage inspection becomes large. Therefore, if the value of n in the above equation 1 is increased when setting the threshold value, there is a high probability that a defective product with leakage will be erroneously determined as a non-defective product. If the value of n in Equation 1 is reduced, the probability of erroneously determining a defective product even though it is a good product increases.
On the other hand, the position and width of the sealing portion of the flexible package, the amount of filled gas, etc. are items that affect the volume of the inspection target but do not directly affect the quality of the contents, and even such items are strictly defined. If you try to manage it, the cost of manufacturing and management will be high.

In order to solve the above problems, the method of the present invention
This is a method of leak inspection of the inspection target whose contents are enclosed inside the flexible package.
A leak data acquisition step for acquiring measurement data of the amount of leakage of a plurality of defective samples having leakage as the sample to be inspected, and a leakage data acquisition step.
A threshold setting step for setting a threshold value for the leak inspection based on the degree of variation in the measurement data, and
It is characterized by being equipped with.

In the inspection target in which the amount and volume of the contents are strictly controlled, the variation in the measurement data of the defective sample is small. Therefore, it is possible to accurately determine the presence or absence of leakage of the inspection target by determining leakage using a threshold value based on the degree of variation. That is, it is possible to sufficiently reduce the probability that a defective product with leakage is erroneously determined as a non-defective product, or that a defective product is erroneously determined as a defective product even though it is a non-defective product. Thereby, the reliability of the leakage determination can be improved.
To put it the other way around, even if the volume of a non-leakage non-defective product to be inspected varies slightly, it does not hinder the leak determination. Therefore, it is not necessary to strictly control items such as the position and width of the sealing portion and the amount of filled gas, which affect the volume of the inspection target but do not directly affect the quality of the contents. As a result, the production and management costs of the inspection target can be reduced.

It is preferable to obtain the defective sample by forming a sealing defect in the flexible package.
As a result, the measurement data of the leakage amount can be accurately acquired. The sealing defect is, for example, a hole (including a notch) penetrating from the outer surface to the inner surface of the flexible package. The size of the sealing defect is preferably a large leakage level. When the test pressure is introduced to the outside of the xenolith, the outside and the inside of the xenolith are equal to each other in a short time (preferably within 1 second to several seconds) through the large leakage level sealing defect. It is preferable to be pressure. The leak data acquisition step and the threshold setting step are suitable for measuring and determining a relatively large leak (sealing defect).

The leak inspection method includes a large leak measurement step of measuring a relatively large leak in the inspection target, and a large leak measurement step.
A small leak measurement step for measuring a relatively small leak in the inspection target, and
A large leakage determination step of determining the presence or absence of the large leakage based on the threshold value,
A small leak data correction step of obtaining small leak correction data by correcting the small leak measurement data in the small leak measurement step based on the large leak measurement data in the large leak measurement step.
A small leakage determination step for determining the presence or absence of the large leakage based on the small leakage correction data,
It is preferable to further provide.
In the large leak determination, whether or not the soft package to be inspected has a large leakage level sealing defect can be accurately determined by using the threshold value.
In addition, for inspection targets that do not have sealing defects at the large leakage level (inspection targets that are subject to small leakage determination), the measurement data in the large leakage measurement process varies, and the variation correlates with the volume of the inspection target. .. Furthermore, the measurement sensitivity in the small leakage measurement step is affected by the volume. Therefore, by correcting the measurement data in the small leak measurement step based on the measurement data in the large leak measurement step, the leak can be determined with high accuracy even in the small leak determination regardless of the variation in the volume of the inspection target. , The reliability can be further improved.

The leak inspection method acquires large leak measurement data and small leak measurement data for a plurality of non-defective samples that do not leak as the sample to be inspected, and good product data acquisition that acquires small leak measurement data in a pseudo-leak state equivalent to a small leak. Process and
A non-defective small leak data correction step of obtaining non-defective small leak correction data by correcting the small leak measurement data of the good product based on the large leak measurement data of the good product sample and the small leak measurement data in the pseudo-leak state. ,
A small leakage threshold setting step of setting a determination threshold value in the small leakage determination process based on the non-defective small leakage correction data, and a small leakage threshold setting step.
It is preferable to further provide.
As a result, the threshold value for determining small leakage can be appropriately set regardless of the variation in the volume of the inspection target.

According to the present invention, it is possible to accurately determine the quality of the sealing property of the inspection target in which the content is enclosed inside the flexible package. Moreover, it is not necessary to strictly control items that are not directly related to the quality of the contents to be inspected, and manufacturing / management costs can be reduced.

FIG. 1 is a circuit diagram of a leak inspection device according to an embodiment of the present invention. FIG. 2A is an explanatory diagram showing a state in which a non-defective product inspection target or a non-defective product sample or a small leak inspection target having a relatively small volume is arranged in the capsule into which the test pressure in the leak inspection device has been introduced. .. FIG. 2B is an explanatory diagram showing a state in which a non-defective product inspection target, a non-defective product sample, or a small leakage inspection target having a relatively large volume is arranged in the capsule. FIG. 2C is an explanatory diagram showing a state in which a large leak inspection target or a large leak defective sample having a relatively small volume is arranged in the capsule. FIG. 2D is an explanatory diagram showing a state in which a large leak inspection target or a large leak defective sample having a relatively large volume is arranged in the capsule. FIG. 3 is a flowchart showing a procedure for setting a threshold value for determining a large leak by the leak inspection device. FIG. 4 is a flowchart showing the first aspect of the procedure for leak inspection (main inspection) for an actual inspection target. FIG. 5 is a histogram showing the distribution of large leakage measurement data with respect to an actual inspection target or sample. FIG. 6 is a flowchart showing a second aspect of the procedure for leak inspection (main inspection) for an actual inspection target. FIG. 7 is a flowchart showing a third aspect of the leak inspection method by the leak inspection device. FIG. 8 is a histogram showing the results of Example 1. FIG. 9 is a histogram showing the results of Example 2.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the inspection target 90 includes a content 91 and a soft packet 92. The type of the content 91 is not particularly limited. The content 91 may be a solid (solid), a liquid, a mixture of a solid and a liquid, or a solid impregnated body impregnated with a liquid. Further, the content 91 may be a resin, a metal, a food material, a drug or other chemical product.
In general, in this type of inspection target 90, the amount and volume of the content 91 are strictly controlled. That is, the variation in the amount and volume of the content 91 in each inspection target 90 is extremely small.

The inspection target 90 is manufactured by, for example, a pillow packaging machine. The material of the flexible package 92 is mainly a soft resin. It may have a laminated structure of a resin layer and a metal layer. The form of the flexible package 92 is not particularly limited, and may be a two-way sealing bag, a three-way sealing bag, a four-way sealing bag, a gusset bag, or the like. It may be an SP package (strip package) or a PTP package (press through package). A sealing portion 94 by heat sealing is provided on the peripheral edge portion, the back surface portion, and the like of the flexible package 92. An internal packaging space 93 is formed between the content 91 and the flexible package 92. An enclosed gas such as nitrogen is sealed in the packaging inner space 93.
Generally, in this type of inspection target 90, the position and width of the sealing portion 94 and the accuracy of the amount of filled gas are not strictly controlled as much as the amount and volume of the content 91, and are not strictly controlled for each inspection target 90. There are variations.

Here, as shown in FIGS. 2A and 2B, the inspection target 90 having no omission is referred to as a non-defective product inspection target 90A. The packaging inner space 93 of the non-defective product inspection target 90A is sealed. Further, among the inspection targets 90, those having a relatively small leak are referred to as a small leak inspection target 90C. The soft packet 25 of the small leak inspection target 90C has a minute sealing defect (not shown) corresponding to a small leak. Here, the small leakage means that the pressure leakage under a test pressure of, for example, about several tens of kPa is on the order of several Pa.

As shown in FIGS. 2 (c) and 2 (d), the inspection target 90 having a relatively large leak is referred to as a large leak inspection target 90B. A sealing defect 95 corresponding to a large leak is formed in the flexible package 92 of the large leak inspection target 90B. Here, the large leak means that the pressure leak under a test pressure of, for example, about several tens of kPa is on the order of several tens of Pa to several kPa.

As will be described later, the inspection target 90 also serves as a sample for setting a threshold value for leak determination. That is, the non-defective product inspection target 90A is also a non-defective product sample 90A. The large leak inspection target 90B is also a large leak defective sample 90B.

As shown in FIG. 1, the leak inspection device 1 includes an inspection circuit 10 and a capsule 20 (inspection target container). The capsule 20 is openable and closable and can be sealed. The inspection target 90 is contained in the capsule 20. An inspection space 29 is defined between the inner wall of the capsule 20 and the inspection target 90. In other words, the inspection target 90 defines the inspection space 29 in cooperation with the capsule 20.

As will be described later, a test pressure is introduced into the sealed capsule 20. The test pressure in this embodiment is a negative pressure. Therefore, as shown in FIG. 2, the flexible package 92 swells. The inspection space 29 is between the outer surface of the swollen flexible package 92 and the inner wall of the capsule 20. As described above, in the inspection target 90, the position and width of the sealing portion 94 and the amount of the enclosed gas are not strict, so that the degree of swelling of the flexible package 92 and thus the volume of the inspection target 90 are not uniform. Therefore, the volume of the inspection space 29 is also not uniform.

On the other hand, as shown in FIGS. 2 (c) and 2 (d), in the large leak inspection target 90B among the inspection targets 90, the packaging inner space 93 is integrally connected to the inspection space 29 via the sealing defect 95. Hereinafter, the space in which the packaging inner space 93 and the inspection space 29 are combined is referred to as a large leak inspection space 29B. The volume of the inspection space 29B at the time of large leakage is the size obtained by subtracting the volume of the content 91 and the volume of the soft envelope 92 (the volume of the real part excluding the internal volume) from the volume of the empty capsule 20. Since the volume of the content 91 and the volume of the flexible package 92 (the volume of the real part excluding the internal volume) have a small variation, the volume of the inspection space 29B at the time of large leakage also has a small variation.

As shown in FIG. 1, the inspection circuit 10 of the leak inspection device 1 includes a tank pressure adjusting path 11, a common measurement path 10a, a large leakage measurement path 12, and a small leakage measurement path 13.
The tank pressure adjusting path 11 extends from the vacuum pump 2 (pressure source). A vacuum regulator 3, a tank shutoff valve V1, and a tank 4 (pressure tank) are sequentially arranged in the tank pressure adjusting path 11 from the vacuum pump 2 side. Vacuum regulator 3 (pressure control means) is adjusted so that the secondary pressure to a predetermined negative pressure (set pressure P _3). The tank shutoff valve V1 is composed of, for example, a normally open electromagnetic on-off valve. Preferably, the internal volume of the tank 4 is the internal volume of the inspection space 29 (to be exact, in addition to the inspection space 29, the large leakage measurement path 12 connected to the inspection space 29, the measurement common path 10a on the downstream side of the valve V2, and the small leakage. It is smaller than the measurement paths 13a and 13c, the residual pressure release path 14 on the upstream side of the valve V4 described later, and the total volume of the test chamber 31).

A pressure gauge 40 (large leak measuring means) is connected to the tank 4. The pressure gauge 40 measures the pressure in the tank 4. A gauge pressure gauge is used as the pressure gauge 40, but an absolute pressure gauge may be used.

A common measurement path 10a extends from the tank pressure adjusting path 11. A large leak measuring valve V2 is provided on the common measurement path 10a. The large leak measuring valve V2 is composed of, for example, a normally closed electromagnetic on-off valve. A large leak measurement path 12 and a small leak measurement path 13 are connected to the downstream end (the end opposite to the tank 4) of the common measurement path 10a. The large leak measurement path 12 extends to the capsule 20 and is connected to the inspection space 29.

The small leak measuring path 13 includes a differential pressure sensor 30 (small leakage measuring means), a test chamber path 13a, a reference chamber path 13b, a test side communication passage 13c, and a reference side communication passage 13d. The test room road 13a and the test side communication passage 13c are connected to the measurement common road 10a.
The differential pressure sensor 30 includes a test chamber 31 and a reference chamber 32. The test room 31 is connected to the test room road 13a. The reference chamber 32 is connected to the reference chamber road 13b, and the reference chamber road 13b is connected to the reference side connecting passage 13d. A small leak measuring valve V3 is interposed between the test side communication passage 13c and the reference side communication passage 13d. The small leakage measuring valve V3 is composed of, for example, a normally open electromagnetic on-off valve.

The residual pressure release path 14 extends from the test side continuous passage 13c. A residual pressure release valve V4 is provided in the residual pressure release path 14. The residual pressure release valve V4 is composed of, for example, a normally open electromagnetic on-off valve. The end of the residual pressure release path 14 is released to the atmosphere.

A pseudo leak path 16 extends from the connection portion between the test side continuous passage 13c and the residual pressure release path 14. A pseudo leak generator 6 is provided in the pseudo leak path 16.

The rapid destruction path 15 is connected to the connection portion between the reference chamber path 13b and the reference side communication passage 13d. A rapid destruction valve V5 is provided on the rapid destruction path 15. The rapid break valve V5 is composed of, for example, a normally closed electromagnetic on-off valve. A compressor 5 is connected to the end of the rapid destruction path 15.

Further, the leak inspection device 1 is provided with a controller 8 (control means). The controller 8 drives the valves V1 to V5, reads the measured values of the pressure gauge 40 and the differential pressure sensor 30, performs arithmetic processing, determines leakage, and the like. Although detailed illustration is omitted, the controller 8 has a storage unit 8 m in addition to a CPU and drive circuits such as valves V1 to V5. In addition to the control program, the storage unit 8m stores a threshold value Ps for determining a large leakage, a threshold value Pf for determining a small leakage, and the like.

[Leak inspection method by leak inspection device 1 (first aspect)]
The first aspect of the method of leak-inspecting the inspection target 90 by the leak inspection apparatus 1 will be described. Prior to the inspection, the threshold values Ps and Pf are set in advance.
<Method of setting threshold Ps>
The threshold value Ps for determining a large leak is set as follows.
As shown in the flowchart of FIG. 3, first, a plurality of non-defective samples 90A made of inspection target 90 without leakage are prepared (step 100).
A sealing defect 95 is formed in the flexible package 92 of each non-defective sample 90A (see FIGS. 2 (c) and 2 (d)). As a result, a defective sample 90B is obtained (step 101).

<Leakage data acquisition process>
Using the defective sample 90B and the leak inspection device 1, the leak amount data is acquired as follows (step 110).
After opening the capsule 20 of the leak inspection device 1 and accommodating one defective sample 90B in the capsule 20 (step 111), the capsule 20 is sealed (see FIGS. 2 (c) and 2 (d)). The inspection space 29 at this stage is at atmospheric pressure.
As shown in FIG. 1, the tank shutoff valve V1 in the initial state of the leak inspection device 1 is in the open state, the large leak measurement valve V2 is in the closed state, the small leak measurement valve V3 is in the open state, and the residual pressure release valve V4 is open. State, the rapid break valve V5 is in the closed state. Further, the pseudo leak generator 6 is completely closed.

The gas in the tank 4 is evacuated by driving the vacuum pump 2. As a result, the vacuum pressure is accumulated in the tank 4 (step 112). At this time, the vacuum regulator 3 is adjusted so that the internal pressure of the tank 4 to the set pressure P _3.
Next, the tank shutoff valve V1 and the residual pressure release valve V4 are closed. By closing the tank shutoff valve V1, the tank 4 is shut off from the vacuum regulator 3 (step 113).

Next, the large leak measuring valve V2 is opened. As a result, the tank 4 and the inspection space 29 are communicated with each other, and a test pressure (negative pressure) is introduced from the tank 4 into the inspection space 29 (step 115). The size of the test pressure, the set pressure P ₃ of the vacuum regulator 3, the volume of the tank 4, determined by the volume of the examination space 29, close to the atmospheric pressure than the set pressure P _3.

Further, in the defective sample 90B, pressure leaks from the inspection space 29 to the inner space 93 of the package through the sealing defect 95 in a short time (at least earlier than the timing of the pressure measurement (step 116) described later). In short, the test pressure is introduced into the inspection space 29B at the time of large leakage, which is the combination of the inspection space 29 and the space inside the package 93.

One to several seconds after the large leak measuring valve V2 is opened, the pressure in the tank 4 and thus the large leak inspection space 29B is measured by the pressure gauge 40 (step 116). Let this measurement pressure be the measurement data P _9B of the leakage amount of the defective sample 90B.

Before the test pressure introduction step of step 115, the internal pressure of the tank 4 (tank pressure P ₄ before communication) is measured by the pressure gauge 40, and the ratio of the set pressure P ₃ to the tank pressure P ₄ before communication (P _3). The value obtained by multiplying / P ₄ ) by the measurement pressure in the inspection space 29B at the time of large leakage may be used as the measurement data P _9B of the leakage amount of the defective sample 90B (regulator accuracy correction processing step). Ideally, the secondary pressure of the vacuum regulator 3 and thus the tank pressure P ₄ before communication should be stably set to the set pressure P _3, but due to the performance of the vacuum regulator 3, the set pressure P is actually used. _It may be slightly larger or smaller than ₃ . This variation can be compensated for by executing the regulator accuracy correction process. By doing so, it is not necessary to make the vacuum regulator 3 ultra-sensitive or ultra-high performance, and the product cost of the leak inspection device 1 can be suppressed.

After measuring the pressure (after obtaining the measurement data P _9B ), the defective sample 90B is taken out from the capsule 20 (step 117).
Further, by executing the same processing (steps 111 to 118) on the unmeasured defective sample 90B (step 118), measurement data P _9B , P _9B ... Of a plurality of defective samples 90B, 90B ... Are obtained.

<Threshold setting>
Subsequently, the mean value Pμ and the standard deviation σ (variation degree) of the measurement data P _9B , P _9B ... Of these defective samples 90B, 90B ... Are obtained (step 120). As described above, since the variation in the volume of the inspection space 29B at the time of large leakage is small, the variation in the measurement data P _9B is also small, and the value of the standard deviation σ is small.
Further, based on the mean value Pμ and the standard deviation σ, the threshold value Ps for determining the large leakage is set by, for example, the following equation 2 (step 121).
Ps = Pμ-n · σ (2)
Here, n is an integer of 1 or more. Preferably, n = 3 to 16, and more preferably n = 4 to 8.

It should be noted that, preferably, the validity of the set threshold value Ps is verified. Specifically, for example, the measurement data P _9A , P _9A ... Of the non-defective product samples 90A, 90A ... Are also acquired in the same procedure as the defective product measurement data P _9B , P _9B .... Then, the threshold value Ps is plotted on the distributions of the non-defective product measurement data P _9A , P _9A ... And the defective product measurement data P _9B , P _9B ..., And it is confirmed whether the threshold value Ps is between the two distributions.

The threshold value Pf for determining small leakage is set based on the measurement data _P8C of the differential pressure sensor 30 when a pseudo leakage of a small leakage level is caused from the pseudo leakage generator 6. The threshold value Pf may also be set by performing the same procedure as the threshold value Ps. More preferably, the validity of the set threshold value Pf is verified from the measurement data _P8C or the like.

<Main inspection>
After that, a leak inspection (main inspection) is performed on the actual inspection target 90.
<Main inspection-Large leak measurement process>
As shown in the flowchart of FIG. 4, in this inspection, a large leak measurement step of measuring a relatively large leak in the inspection target 90 is first performed (step 201). The procedure of the large leakage measurement (step 201) is substantially the same as the procedure of acquiring leakage data (FIG. 3) for setting the threshold value Ps described above. That is, accommodated into the capsule 20 to be inspected 90, the accumulator to the tank 4, blocking of the tank 4 and the vacuum regulator 3, the test pressure introduction into the examination space 29, the pressure measurement (measurement data P ₉ of the examination space 29 Acquisition) is executed in sequence. As shown in FIG. 2, the flexible package 92 swells due to the introduction of the test pressure (negative pressure).
In addition, when the correction processing for the secondary pressure fluctuation of the vacuum regulator 3 is performed in the leakage data acquisition for setting the threshold value Ps, the same correction processing is performed in the main inspection for the actual inspection target 90.

<Small leak measurement process>
As shown in FIG. 4, a small leak measurement step of measuring a relatively small leak in the inspection target 90 is subsequently performed (step 202). Specifically, the large leak measuring valve V2 is closed and the small leak measuring valve V3 is closed to shut off the test chamber 31 and the reference chamber 32. Then, the differential pressure between the test chamber 31 and the reference chamber 32 is measured by the differential pressure sensor 30. The measurement differential pressure, the measurement data P ₈ small leak.

<Large leak judgment process>
Next, the presence or absence of a large leak in the inspection target 90 is determined (step 203). Specifically, the measurement data P ₉ is compared with the threshold Ps. When the measurement data P ₉ is on the non-defective product pressure range side (high negative pressure side) from the threshold value Ps, the inspection target 90 is determined to be “no major leakage (non-defective product or small leakage)”. When the measurement data P ₉ is on the defective product pressure range side (low negative pressure side) from the threshold value Ps, the inspection target 90 is determined to have "large leakage" and processed as "NG (defective product)" (step 209). ).

As described above, in this type of inspection target 90, the volume of the inspection target 90 inflated by the test pressure (negative pressure) is not uniform, and the volume of the inspection space 29 is also not uniform (FIG. 2). Further, the pressure in the inspection space 29, that is, the measurement data P _9A in the case where the inspection target 90 is a good product 90A without leakage or a small leakage product 90C (FIGS. 2A and 2B) depends on the volume of the inspection space 29. To do. Therefore, as shown in FIG. 5, the measurement data P _9A has a large variation. Therefore, if the threshold value Ps is set using the non-defective product inspection target 90A, if the threshold value is set to, for example, a value equivalent to 3σ or more (n ≧ 3 in Equation 1), as shown in the shaded portion Rb in FIG. Even though there is a large leak (defective product), there is a high probability that it will be mistakenly judged as a good product. On the other hand, when the threshold value is set to, for example, a value equivalent to 1σ to 2σ (n = 1 to 2 in Equation 1), it is erroneously determined that there is a large leak (defective product) even though it is a good product, as shown in the shaded portion Ra in FIG. The probability of doing so increases.

On the other hand, the measurement data P _9B in the large leak product 90B (FIGS. 2 (c) and 2 (d)) depends on the volume of the large leak inspection space 29B, and the volume of the large leak inspection space 29B is constant. Is. Therefore, as shown in FIG. 5, the variation of the measurement data P _9B of the large leaked product 90B is small. Therefore, by setting the threshold value Ps based on the deviation σ of the measurement data P _9B of the large leaked product 90B, the sealing property of the inspection target 90 can be accurately determined. That is, when setting the threshold value Ps, the n value of Equation 2 can be taken sufficiently large. For example, the threshold value Ps can be set to a value equivalent to 3σ to 16σ (n = 3 to 16 in Equation 2). As a result, the probability of erroneously determining a non-defective product even though it is a large leaked product can be sufficiently reduced. Moreover, even if the n value in Equation 2 is increased, the possibility that the threshold value Ps is included in the data distribution of non-defective products (P _9A ) is extremely small, and the probability that a non-defective product is erroneously determined even though it is a non-defective product without omission is determined. Can be low enough.

Conversely, even if the volume of the inspection target 90 varies, it does not hinder the leakage determination. Therefore, it is not necessary to strictly control items such as the position and width of the sealing portion 94 and the amount of filled gas, which affect the volume of the inspection target 90 but do not directly affect the quality of the content 91. As a result, the production and management costs of the inspection target 90 can be reduced.

<Small leak judgment process>
As shown in FIG. 4, the inspection target 90 determined to have “no major leakage” is further determined to have a small leakage (step 205). Specifically, when the measured differential pressure P ₈ small leak, a good pressure range side than the threshold value Pf of the small leak (high negative pressure side) is determined as "OK (good)" (Step 208). Small leak measurement When the differential pressure P ₈ is on the defective product pressure range side (low negative pressure side) from the small leak threshold Pf, it is determined that there is a small leak and treated as "NG (defective product)". (Step 209).

<End process>
After the small leak measurement step (step 202) is completed, the tank shutoff valve V1 is opened.
Further, the small leakage measurement valve V3 and the residual pressure release valve V4 are opened, and the rapid break valve V5 is opened. Then, air is forcibly introduced from the compressor 5 into the inspection space 29 through the rapid destruction path 15, the reference side communication path 13d, the test side communication passage 13c, and the large leakage measurement path 12 in that order. As a result, the inspection space 29 can be returned to atmospheric pressure in a short time.
Then, the capsule 20 is opened and the inspection target 90 is replaced.
Then, the next leak inspection of the inspection target 90 is performed in the same procedure.

[Leak inspection method by leak inspection device 1 (second aspect)]
Next, a second aspect of the leak inspection method by the leak inspection device 1 will be described with reference to the flowchart of FIG. In the second aspect, the influence of the volume variation of the inspection target 90 on the small leak measurement data P ₈ is corrected by using the large leak measurement data P ₉ , and then the small leak is determined.
That is, when the volume of the non-defective product inspection target 90A and the small leakage inspection target 90C is large (see FIG. 2B), the inspection space 29 becomes small, so that the detection sensitivity of the differential pressure sensor 30 becomes high and the measurement differential pressure (see FIG. 2B). P ₈₎ is shifted to the side of increase. Conversely, the test object 90A, the volume of 90C is small (see FIG. 2 (a)), for examination space 29 is large, becomes the detection sensitivity of the differential pressure sensor 30 is low, the measurement differential pressure _{(P 8)} Shift to the decreasing side. On the other hand, as shown in FIG. 5, the large leakage measurement data P _9A of the inspection targets 90A and 90C depends on the volume of the inspection targets 90A and 90C.

ここで、ｆ（Ｐ_９Ａ）は、Ｐ_９Ａの一次関数であるが、これに限られず、Ｐ_９Ａの二次関数その他の高次関数等であってもよい。また、αは、定数であるが、これに限られず、ｆ（Ｐ_９Ａ）よりも低次のＰ_９Ａの関数等でもよい。
これによって、大漏れ測定データＰ_９Ａが大きい値である程、小漏れ測定データＰ_８をより大きく減少するように補正したり、大漏れ測定データＰ_９Ａが小さい値である程、小漏れ測定データＰ_８をより大きく増大するように補正したりすることで、小漏れ補正データＰ'_８を得る。そして、小漏れ補正データＰ'_８に基づいて小漏れ判定を行う（ステップ２０５）。これによって、検査対象９０の体積のバラツキに拘わらず、高精度に小漏れ判定でき、信頼性を一層高めることができる。
第２態様におけるその他の操作は、第１態様又は第２態様と同様である。 Therefore, as shown in the flowchart of FIG. 6, after the large leak measurement (step 201) and the small leak measurement (step 202), there is no large leak in the large leak determination (step 203), that is, the non-defective product 90A or the small leak product 90C. If it is determined, the small leak measurement data P ₈ is corrected based on the large leak measurement data P _9A (step 204). For details, for example, the calculation of Equation 3 or the like is performed.

Here, f (P _9A ) is a linear function of P _9A , but is not limited to this, and may be a quadratic function of P _9A or another higher-order function. Further, α is a constant, but is not limited to this, and may be a function of P _{9A having} a lower order than f (P _9A ) or the like.
As a result, the larger the value of the large leakage measurement data P _9A , the larger the correction is made so that the small leakage measurement data P ₈ is reduced, and the smaller the value of the large leakage measurement data P _9A , the smaller the leakage measurement data. by or corrected so as to increase greater P _8, to obtain small leakage correction data P _'8. Then, the small leak judgment based on a small leakage correction data P _'8 (step 205). As a result, small leaks can be determined with high accuracy regardless of the variation in the volume of the inspection target 90, and the reliability can be further improved.
Other operations in the second aspect are the same as in the first or second aspect.

[Leak inspection method by leak inspection device 1 (third aspect)]
Next, a third aspect of the leak inspection method by the leak inspection device 1 will be described. In the third aspect, the influence of the volume variation of the inspection target 90 is reflected in the setting of the small leakage threshold value Pf.
<Good product data acquisition process>
Specifically, as shown in the flowchart of FIG. 7, first, non-defective product data is acquired (step 300). That is, a plurality of non-defective samples 90A, 90A ... Are prepared (step 301). Then, as follows, the measurement in a leak-free state (step 310) and the measurement in a pseudo-leakage state corresponding to a small leak (step 320) are performed.

The measurement procedure in the leak-free state is the same as the large leak measurement and the small leak measurement (steps 201 to 202 in FIG. 4) in the main inspection for the actual inspection target 90. The pseudo leak generator 6 is completely closed (step 311). The large leak measurement provides the large leak measurement data P _9A (step 312). The small leak measurement obtains the small leak measurement data P _8A (step 313). By repeatedly executing the same operation for a plurality of non-defective samples 90A, 90A ... (Step 314), a plurality of large leakage measurement data P _9A , P _9A ... And a plurality of small leakage measurement data P _8A , P _8A ... obtain.

Next, a pseudo leak of a predetermined small leak level is generated from the pseudo leak generator 6 (step 321). Preferably, for example, the measurement data P _8C of the differential pressure sensor 30 under a test pressure of about several tens of kPa causes a pseudo leakage to the extent that P _8C = several Pa orders or less. In this pseudo-leakage state, the same operation as the large leak measurement and the small leak measurement (steps 201 to 202 in FIG. 4) in the main inspection for the actual inspection target 90 is performed. The large leak measurement provides the large leak measurement data P _9C (step 322). Note that step 322 may be omitted. The small leak measurement obtains the small leak measurement data P _8c (step 323). By repeatedly executing the same operation for a plurality of non-defective samples 90A, 90A ... (Step 324), a plurality of large leak measurement data P _9C , P _9C ... And a plurality of small leak measurement data P _{8C in} a pseudo leak state. , P _8C ...
The measurement in the pseudo-leakage state (step 320) may be executed first, and then the measurement in the no-leakage state (step 310) may be executed.

<Good product small leakage data correction process>
Next, based on the large leakage measurement data P _9A , P _9A ... Of these non-defective samples 90A, 90A ... And the small leakage measurement data P _8C , P _8C ... In the pseudo-leakage state, the small non-defective samples 90A, 90A ... The leak measurement data P _8A , P _8A ... _Are corrected (step 330).
Specifically, the correction coefficient (for example, the value of β in the following equation 4) is calculated from the large leak measurement data P _9A , P _9A ... In the no leak state and the small leak measurement data P _8C , P _8C ... In the pseudo leak state. (Step 331). Preferably, the small leak correction data _{P'8C in} the pseudo-leakage state after correction (for example, after the calculation on the right side of Equation 4) is the pseudo-leakage of the pseudo-leakage generator 6 regardless of the corresponding values of P _9A and P _8C. Try to make the quantity as close as possible.

Next, each small leak measurement data P _8A in the leak-free state is corrected by using the corresponding large leak measurement data P _9A and the correction coefficient β, for example, in the following equation 5, to correct non-defective small leaks. Data _P'8A is calculated (step 332).

<Small leakage threshold setting process>
Then, based on the plurality of non-defective small leakage correction data _P'8A , the small leakage threshold value Pf is set by using, for example, Equation 1 (step 340). Preferably, sets 'and _8A, a small leakage correction data P for a pseudo leak state' more good small leakage correction data P small leakage threshold Pf from the _8C. Thereby, the small leakage threshold value Pf can be appropriately set regardless of the variation in the volume of the inspection target 90.
More preferably, the validity of the set small leakage threshold value Pf is verified from the measurement data P _8A and P _8C .
Other operations in the third aspect are the same as in the first or second aspect.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the flowchart of FIG. 4, after the large leakage measurement (step 201), the large leakage determination (step 203) is performed, and only when there is no large leakage, the small leakage measurement (step 202) and the small leakage determination (step). 205) may be performed, and if there is a large leak, the small leak measurement and the small leak determination may be omitted. In the flowchart of FIG. 6, after the large leakage measurement (step 201), the large leakage determination (step 203) is performed, and only when there is no large leakage, the small leakage measurement (step 202), the correction (step 204) and the small leakage are performed. Leakage determination (step 205) may be performed, and if there is a large leakage, the small leakage measurement, correction, and small leakage determination may be omitted.
The test pressure may be positive. As the pressure source, a compressed air supply means such as a compressor may be used instead of the vacuum pump 2. As the pressure control means, a positive pressure regulator may be used instead of the vacuum regulator 3. In this case, a vacuum pump is connected to the rapid destruction path 15 instead of the compressor 5.
A dedicated pressure gauge for measuring the large leak measurement data P ₉ may be provided in the capsule 20 or the large leak measurement path 12 separately from the pressure gauge 40.
The circuit configuration of the leak inspection device 1 may be appropriately modified.

An embodiment will be described. However, the present invention is not limited to this embodiment.
An apparatus having the same circuit as the leak inspection apparatus 1 of FIG. 1 was used.
As the vacuum regulator 3, an electropneumatic regulator APU manufactured by Fukuda Co., Ltd. was used. The pressure fluctuation range of this electropneumatic regulator (APU) is about 0.1% of the set pressure, which is smaller than that of a general regulator (about 0.5%).
The volume of the tank 4 was 20 cc.
The volume of the inspection space 29 (to be exact, in addition to the inspection space 29, the large leak measurement path 12 connected to the inspection space 29, the measurement common path 10a on the downstream side of the valve V2, the small leak measurement paths 13a and 13c, and the upstream of the valve V4. The residual pressure release path 14 on the side and the total volume of the test chamber 31) were 50 cc.

A large number of Calorie Mate (registered trademark) manufactured by Otsuka Pharmaceutical Co., Ltd. were prepared as the inspection target 90 of Example 1. The content 91 of the inspection target 90 is a solid having a weight of 40 g, the soft package (inner bag) 92 is a soft package sealed body of a gusset bag, and the soft package (inner bag) 92 is made of paper. It is housed in a box.
The inspection target 90, that is, the non-defective sample 90A, which had not been opened in the outer box, was housed in the capsule 20 one by one, and the capsule 20 was sealed.
Subsequently, after the inside of the tank 4 was evacuated, the tank 4 and the vacuum regulator 3 were shut off. The set pressure of the vacuum regulator 3 was −70 kPa.
After that, the tank 4 and the capsule 20 were communicated with each other, and a test pressure (about −20 kPa) was introduced into the inspection space 29.
Then, the measurement data P _9A of the non-defective sample _9A was acquired by the pressure sensor 40.

Next, a plurality of defective samples 90B were prepared by opening the outer box of each inspection target 90 and making a hole (sealing defect 95) in the flexible package (inner bag) 92 with a needle. The defective samples 90B (in the outer box) were housed in the capsule 20 one by one, and the capsule 20 was sealed.
Subsequently, after the inside of the tank 4 was evacuated, the tank 4 and the vacuum regulator 3 were shut off. The set pressure of the vacuum regulator 3 was −70 kPa.
After that, the tank 4 and the capsule 20 were communicated with each other, and a test pressure (about −20 kPa) was introduced into the inspection space 29.
Then, the measurement data P _9B of the defective sample 90B was acquired by the pressure sensor 40.

The results are shown in the histogram of FIG. The horizontal axis in the figure is based on the vicinity of the minimum value of the measurement data P _9A of the non-defective sample 90A as a reference (0 kPa), and represents the pressure difference from the reference pressure.
Defective sample 90B are variations in the measurement data P ₉ may be very small was confirmed as compared with the non-defective 90A.
The deviation σ of the measurement data P _9B of the defective sample 90B was σ = 0.0492.
As a result, by setting the threshold value Ps to 8σ equivalent (Ps = Pμ-8σ), a large leaked product can be reliably detected, and the probability that a good product is erroneously determined as a large leaked product is almost zero. found. Further, it is possible to set the threshold value Ps to be equivalent to 16σ (Ps = Pμ-16σ), so that a large leaked product can be detected more reliably and a good product is determined to be a large leaked product. It was confirmed that the value can be lowered sufficiently.
On the other hand, the deviation of the measurement data P _9A of the non-defective sample 90A was σ = 1.00. Therefore, when trying to set the threshold value based on the measurement data P _9A of a non-defective product, the limit is at most 2σ equivalent (threshold value = average value + 2σ), and when it is set to 3σ equivalent (threshold value = average value + 3σ), it is large. It was confirmed that even the leaked product was erroneously judged as a good product. With a threshold value equivalent to 2σ, there is a high probability that a defective product will be erroneously determined even though it is a good product.

In Example 2, a large number of eyeglass cleaners manufactured by Kobayashi Pharmaceutical Co., Ltd. were prepared as inspection targets. The soft package to be inspected was a four-sided sealed bag. The content 91 was in a state in which the non-woven fabric was impregnated with the liquid agent.
The experimental procedure was the same as in Example 1. First, measurement data P _9A was acquired in an unopened non-defective state. Next, the measurement data P _9B was acquired from a defective sample in which a notch (sealing defect 95) was made in the soft package to be inspected with scissors.

The results are shown in the histogram of FIG. The horizontal axis in the figure is based on the average value of the measurement data P _9A of a non-defective product (0 kPa), and represents the pressure difference from the reference pressure.
The deviation σ of the measurement data P _9B of the defective product was σ = 0.01847. It was confirmed that the variation in the inspection pressure of the defective sample was sufficiently smaller than that of the non-defective sample. As a result, it was confirmed that by setting the threshold value Ps to be equivalent to 4σ (Ps = Pμ-4σ), it is possible to accurately determine whether or not the product is a large leak product.
On the other hand, the deviation σ of the measurement data P _9A of the non-defective product was σ = 0.08339. Therefore, when trying to set the threshold value based on the measurement data P _9A of a non-defective product, the limit is at most 2σ equivalent (threshold value = average value + 2σ), and when it is set to 3σ equivalent (threshold value = average value + 3σ), it is large. It was confirmed that even the leaked product was erroneously judged as a good product.

The present invention can be applied to a sealability test of, for example, a flexible package sealed bag manufactured by pillow packaging.

1 Leakage inspection device 90 Inspection target 90A Good product 90B Large leak product (defective sample)
90C Small leak product 91 Contents 92 Flexible package 95 Sealing defect P ₉ Large leak measurement data P _9A Large leak measurement data for non-defective product or small leak product P _9B Large leak measurement data for large leak product (leakage measurement data)
P ₈ Small leak measurement data P _8A Good product small leak measurement data P ' _8A Good product small leak correction data P _8C Small leak measurement data in a small leak product or pseudo leak state P ' _8C Small leak measurement data in a small leak product or pseudo leak state Leakage correction data Pf Small leak judgment threshold Ps Large leak judgment threshold (leakage inspection threshold)
σ Deviation (variation)

Claims (4)

This is a method of leak inspection of the inspection target whose contents are enclosed inside the flexible package.
A leak data acquisition step for acquiring measurement data of the amount of leakage of a plurality of defective samples having leakage as the sample to be inspected, and a leakage data acquisition step.
A threshold setting step for setting a threshold value for the leak inspection based on the degree of variation in the measurement data, and
A leak inspection method characterized by being equipped with. The leak inspection method according to claim 1, wherein a defective sample is obtained by forming a sealing defect in the flexible package. A large leak measurement step for measuring a relatively large leak in the inspection target, and
A small leak measurement step for measuring a relatively small leak in the inspection target, and
A large leakage determination step of determining the presence or absence of the large leakage based on the threshold value,
A small leak data correction step of obtaining small leak correction data by correcting the small leak measurement data in the small leak measurement step based on the large leak measurement data in the large leak measurement step.
A small leakage determination step for determining the presence or absence of the large leakage based on the small leakage correction data,
The leak inspection method according to claim 1 or 2, further comprising. A non-defective data acquisition process for acquiring large-leakage measurement data and small-leakage measurement data for a plurality of non-defective samples as the samples to be inspected, and small-leakage measurement data in a pseudo-leakage state equivalent to small-leakage.
A non-defective small leak data correction step of obtaining non-defective small leak correction data by correcting the small leak measurement data of the good product based on the large leak measurement data of the good product sample and the small leak measurement data in the pseudo-leak state. ,
A small leakage threshold setting step of setting a determination threshold value in the small leakage determination process based on the non-defective small leakage correction data, and a small leakage threshold setting step.
The leak inspection method according to claim 3, further comprising.

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