JP2020122674A - Method for calculating diffusion flow rate or leakage hole size, reference leakage element selection method, and threshold value setting method for leakage test device - Google Patents

Abstract

To theoretically obtain a relationship between a diffusion flow rate and a leakage hole size for a specific molecule, and to omit or reduce a test.SOLUTION: In a diffusion model, a first space S1 containing a specific molecule and a second space S2 having the same pressure as the first space S1 and a lower molar concentration than the first space S1 are isolated by a partition 1 having a leakage hole 1a. In this model, the specific molecule diffuses from the first space S1 through the leakage hole 1a to the second space S2. A diffusion flow rate Q is expressed by the following equation. Q=ΔM/(Z+Z+Z)...(1). Here, ΔM denotes a molar concentration difference of the specific molecules between the spaces S1 and S2, Zdenotes a diffusion resistance in a process of passing through the leakage hole 1a, Zdenotes a diffusion resistance in a process in which the specific molecule diffuses from the first space S1 toward the leakage hole 1a, and Zdenotes a diffusion resistance in a process in which the specific molecule diffuses from the leakage hole 1a to the second space S2. Based on the equation (1), a relational expression between the diffusion flow rate Q and the leakage hole dimension is obtained.SELECTED DRAWING: Figure 1

Description

The present invention establishes a relationship between the diffusion flow rate of a specific molecule and the leakage hole size in two spaces separated by a partition having a leakage hole, and a method of calculating the diffusion flow rate or the leakage hole size from this relationship, and the diffusion method. A method for selecting a reference leak element based on the diameter of the leak hole calculated based on the allowable limit value of the flow rate, and a threshold value in the leak test apparatus for the inspection target having a closed space using the selected reference leak element On how to do.

Pharmaceutical products are contained in a sealed container and shielded from the atmosphere in order to prevent deterioration of quality within the quality assurance period. However, if the sealed container has a pinhole, there is a possibility that specific molecules such as water vapor and oxygen that deteriorate the contents such as the above-mentioned medicine may enter the sealed space. Therefore, it is necessary to use a leak test device to identify and exclude a sealed container having a pinhole as a defective product.

The leak test apparatus of Patent Document 1 described later includes, as a basic configuration, a test pressure source, a work capsule, and a pressure sensor that detects a pressure fluctuation in the work capsule. The work capsule contains a sealed container to be inspected and sealed, and the test pressure source supplies test pressure air to the work capsule, and then the test pressure source and the work capsule are shut off. Monitor pressure. When the pinhole exists in the sealed container, the air inside the work capsule enters (leaks) into the sealed container through the pinhole, and the pressure inside the work capsule decreases. The determination unit of the leak test device compares the detection output of the pressure sensor corresponding to this pressure fluctuation with a threshold value, and if the detection output is less than the threshold value, determines that the sealed container is a good product, and if it exceeds the threshold value, the pin Judge as a defective product with a hole.

The threshold value in the leak test device needs to be set in correspondence with the allowable limit value of the amount of the specific molecule invading the sealed container.
In Patent Document 1, a reference leakage element selection step and a threshold value setting step are executed in order to set a threshold value corresponding to an allowable limit value of the invasion amount of a specific molecule. The details will be described below.

In the reference leakage element selection step, a test container in which two sealed chambers are partitioned by a partition is prepared. One closed chamber mimics the atmospheric environment. The other closed chamber imitates the inside of a sealed container to be inspected, and is filled with an inert gas such as nitrogen.
A leak element having a leak hole is installed on the partition wall. The leak hole has a path length equal to the thickness (the length of the pinhole) at a position where a pinhole may occur in the sealed container.

After maintaining the two closed chambers of the test container for a certain period (for example, several days or several weeks), measure the amount of invasion of specific molecules (oxygen, water vapor, etc.) in the air in one closed chamber into the other chamber. To do. The measured penetration amount of this specific molecule is compared with the permissible limit value of the penetration amount for maintaining the quality during the quality assurance period.
The above test is performed using a plurality of leak elements having different leak hole diameters, and the leak element in which the amount of intrusion corresponding to the allowable limit value has occurred is selected as the reference leak element.

In the next threshold value setting step, the selected reference leak element is mounted in a sealed container having the same structure as the inspection target to produce a reference leak work. A leak test similar to the inspection target is executed for this reference leak work. The detection output of the pressure sensor in this leak test corresponds to the reference leak amount generated by the selected reference leak element. The threshold value is set based on this detection output.

JP, 2017-215310, A

In the reference leak element selection shown in Patent Document 1, it is necessary to test a plurality of leak elements having different leak hole diameters for a long period of time, and there is a drawback that the cost for setting the threshold increases.

In order to solve the above-mentioned problem, the present inventor theoretically investigated the relationship between the diffusion flow rate of a specific molecule and the leak hole size, and established the relationship. More specifically, it is as follows.
The present invention provides a diffusion model in which a first space containing a specific molecule and a second space having the same pressure as the first space and a molar concentration of the specific molecule lower than the first space are isolated by a partition wall having a leak hole. ,
The total diffusion resistance of the particular molecule from the first space through the leak to the second space, each being a function of leak size,
(A) Diffusion resistance in the leak hole in the process of passing through the leak hole,
(B) a first space diffusion resistance in the process in which the specific molecule moves from the first space to the leak hole,
(C) A second space diffusion resistance in the process in which the specific molecule spreads from the leak hole to the second space,
Defined as the sum of
Based on the total diffusion resistance, the relationship between the leak hole size and the diffusion flow rate at which the specific molecule diffuses from the first space through the leak hole to the second space is determined, and based on this relationship, the leak The diffusion flow rate is calculated from the hole size, or the leak hole size is calculated from the diffusion flow rate.

According to the above method, the relationship between the diffusion flow rate of the specific molecule and the leak hole size in the two spaces isolated via the leak hole is determined not only in the leak hole diffusion resistance but also in the first space diffusion resistance and the second space diffusion resistance. Since the space diffusion resistance is also set, the diffusion flow rate or the leak hole size can be accurately obtained. As a result, the test for determining the diffusion flow rate or the leak hole size can be omitted or the test load can be reduced.
The relationship established as described above can be widely used not only in the leak test described below. For example, it is possible to predict the diffusion flow rate of a specific molecule when there is a known leakage hole (pinhole, etc.), or to specify the size of the leakage hole for causing a predetermined diffusion flow rate of the specific molecule.

Preferably, the path length among the leak hole dimensions is known, and the diffusion flow rate of the specific molecule is calculated from the leak hole diameter, or the leak hole diameter is calculated from the diffusion flow rate.
According to the above method, the diffusion flow rate or the diameter of the leak hole can be accurately calculated.

Preferably, the diameter of the leak hole corresponding to the permissible limit value of the diffusion flow rate of the specific molecule is calculated by simulating the first space as the atmosphere.
According to the above method, in a sealed container placed in the atmosphere, the diameter of the pinhole can be specified from the allowable limit value for the specific molecule in the atmosphere to diffuse into the sealed container through the pinhole.

Preferably, the diffusion flow rate Q, the molar concentration difference ΔM of the specific molecule in the first space and the second space, the diffusion resistance in the leak hole Z ₀ , the first space diffusion resistance Z ₁ , The first relationship with the second space diffusion resistance Z ₂ is defined by the following equation (1),
Q=ΔM/(Z ₀ +Z ₁ +Z ₂ )... (1)
Each of the diffusion resistance in the leak hole Z ₀ , the first space diffusion resistance Z ₁ , the second space diffusion resistance Z ₂ , the mutual diffusion coefficient Dm, and the path length L of the leak hole as the leak hole dimension and the above. A second relationship between the diameters d of the leak holes is defined by the following equations (2) to (4),
Z ₀ =1/(2D _m ·d) (2)
Z ₁ =L/(D _m ·(πd ² /4)) (3)
Z ₂ =1/(2D _m ·d) (4)
Based on the first relationship and the second relationship, the third relationship between the diffusion flow rate Q and the path length L and the diameter d is defined with the molar concentration difference ΔM and the mutual diffusion coefficient Dm being known. Stipulated,
Based on the third relationship, the diffusion flow rate Q is calculated from the leakage hole size, or the leakage hole size is calculated from the diffusion flow rate Q.

Based on the equation (1) and the equations (2), (3) and (4), the third relation is obtained by the following equation.

Preferably, a computer storing the equation (5) or a relational expression equivalent thereto is prepared, and the computer stores the molar concentration difference ΔM, the mutual diffusion coefficient Dm, the path length L of the leak hole, and the diffusion flow rate Q. By inputting an allowable limit value, the diameter d of the leak hole is derived.

According to another aspect of the present invention, a reference leak element having a reference leak hole having the calculated diameter of the leak hole or a diameter obtained by multiplying the leak hole by a safety factor is selected.
According to the above method, when selecting the reference leakage element, the test can be omitted or the test load can be reduced.

According to still another aspect of the present invention, a test pressure source, a work capsule, and a pressure sensor for detecting a pressure fluctuation in the work capsule are provided, and the work capsule contains an inspection target having a closed space. After blocking and supplying test pressure air from the test pressure source to the work capsule, the test pressure source and the work capsule are shut off, and the pressure fluctuation in the work capsule is detected by the pressure sensor, and this pressure is detected. Prepare a leak test device that executes the leak test of the above inspection target by comparing the detection output of the sensor with a threshold,
By attaching the selected reference leakage element to the inspection object for reference leakage having the same configuration as the inspection object, a reference leakage work is obtained,
The reference leaked work is stored in the work capsule of the leak test device instead of the inspection target, the same process as the leak test of the inspection target is performed, and the detection output is obtained, and the threshold value is based on the detection output. To decide.
According to the above method, the burden of the threshold setting work can be reduced.

According to the present invention, the relationship between the diffusion flow rate of a specific molecule and the leak hole size in two spaces isolated via the leak hole can be accurately obtained, and the relationship between the diffusion flow rate or the leak hole size can be obtained. Can the test be omitted or the test burden can be reduced?

FIG. 3 is a schematic view of a diffusion model referred to for explaining a relational expression between a diffusion flow rate of a specific molecule and a leakage hole size obtained by the method of the present invention, showing a partition wall with a leakage hole that separates two spaces in a cross section. There is. It is a flow sheet of leak hole diameter calculation performed by a computer based on the above relational expression. FIG. 6 is an enlarged cross-sectional view of a reference leak element selected corresponding to the calculated leak hole diameter, in which the thickness of each component is exaggerated and the leak hole is exaggerated. 1 is a circuit configuration diagram of a known leak test device to which the present invention is applied. (A) is a cross-sectional view of a tablet container to be inspected by the leak test device, and (B) is a reference leak work configured by mounting the above-mentioned reference leak element on a tablet container having the same basic configuration as the inspection target. FIG. 3 is a cross-sectional view of each of the drawings with the thickness exaggerated.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a diffusion model for explaining the present invention. In this diffusion model, the first and second spaces S1 and S2 are isolated by the partition wall 1 in which the leak hole 1a having a circular cross section is formed. The thickness of the partition wall 1 (the path length of the leak hole 1a) is indicated by the symbol L, and the diameter of the leak hole 1a is indicated by the symbol d.

The first space S1 and the second space S2 have the same pressure. The molar concentration M ₁ of the specific molecule in the first space S1 is higher than the molar concentration M ₂ in the second space S2. A molar amount Q (mol/sec: hereinafter, referred to as a diffusion flow rate) per unit time that the specific molecule diffuses from the first space S1 to the second space S2 through the leak hole 1a can be represented by the following formula. it can.
Q=C·ΔM (6)
Here, C is conductance (m ³ /sec), and ΔM is a molar concentration difference M ₁ -M ₂ (mol/m ³ ) between the spaces S1 and S2.

The present inventor initially focused only on the diffusion phenomenon in the leak hole 1a and tried to find the diffusion flow rate Q based on the conductance C ₀ in the leak hole 1a. The details will be described below.
The conductance C ₀ in the leak hole 1a can be expressed by the following formula.
C ₀ =Dm·S/L (7)
However, S is a cross-sectional area of the leak hole 1a and is represented by (πd ² /4).
Dm is a mutual diffusion coefficient. For example, when the first space S1 is air containing water vapor and the second space S2 is dry air, the mutual diffusion coefficient D _m is a coefficient relating to mutual diffusion between air and water vapor. When the first space S1 is air containing nitrogen and oxygen and the second space S2 is nitrogen, the mutual diffusion coefficient Dm is a coefficient relating to mutual diffusion of nitrogen and oxygen.

By substituting the equation (7) into the equation (6), the following equation is obtained.
Q=ΔM·Dm·(πd ² /4)/L...(8)
When the diffusion flow rate obtained by the equation (8) is compared with the diffusion flow rate measured in an actual test (described later) under substantially the same conditions, when the path length L is sufficiently long, it is almost the same, but the leakage When the size of the hole 1a is close to a general pinhole, that is, when the diameter d of the leak hole 1a is 100 μm or less and the path length L is relatively short (several mm or less, particularly 1 mm or less), the formula (8 A significant difference was found between the diffusion flow rate obtained in () and the test results.

Therefore, the present inventor adds the diffusion phenomenon in which the first space S1 goes to the leakage hole 1a and the diffusion phenomenon that spreads from the leakage hole 1a to the second space S2 to the diffusion phenomenon in the leakage hole 1a to re-create the theoretical formula. Tried to build. The details will be described below.

The diffusion flow rate Q of the specific molecule from the first space S1 toward the leak hole 1a can be expressed by the following formula.
Q=C ₁ (M ₁ −Ma) (9)
Where C ₁ is the conductance in the first space S ₁ , M ₁ is the molar concentration in the first space S 1 (theoretically, the molar concentration at infinity from the leak hole 1 a ), Ma is the first space of the leak hole 1 a It is the molar concentration at the open end on the S1 side.

The diffusion flow rate Q of the specific molecule in the leak hole 1a can be expressed by the following formula.
Q=C ₀ (Ma−Mb) (10)
Where C ₀ is the conductance in the leak hole 1a, Ma is the molar concentration at the open end of the leak hole 1a on the first space S1 side, and Mb is the molar concentration at the open end of the leak hole 1a on the second space S2 side. Is.

The diffusion flow rate Q of the specific molecule spreading from the leak hole 1a to the second space S2 can be expressed by the following formula.
_{Q = C 2 (Mb-M} 2) ··· (11)
Where C ₂ is the conductance in the second space S 2, Mb is the molar concentration at the open end of the leak hole 1 a on the second space 2 side, and M ₂ is the molar concentration in the second space S 2 (theoretical 1a to infinity).

The diffusion flow rates Q in the above equations (9) to (11) are equal to each other. The molar concentration difference ΔM in the equation (6) can be rewritten as follows.
ΔM=(M ₁ −Ma)+(Ma−Mb)+(Mb−M ₂ )... (12)
The following equation is derived from the above equation (12) and equations (9) to (11).
ΔM=Q/C ₁ +Q/C ₀ +Q/C ₂ (13)
The following equation is derived from the equations (6) and (13).
1/C=1/C ₁ +1/C ₀ +1/C ₂ (14)

Expression (14) can be rewritten as the following expression.
Z _total =Z ₁ +Z ₀ +Z ₂ (15)
However, Z _total is the reciprocal of the conductance C from the first space S1 to the second space S2 (hereinafter referred to as diffusion resistance), and Z ₁ =1/C ₁ is the diffusion resistance in the first space S1, Z ₀ =1/C ₀ is the diffusion resistance in the leak hole 1a, and Z ₂ =1/C ₂ is the diffusion resistance in the second space S2.
As is clear from the equation (15), the _total diffusion resistance Z _total from the first space S1 to the second space S2 can be represented by the sum of the flow resistances Z ₁ , Z ₀ , and Z ₂ in each region.

The following equation is derived from the equation (14).
C=1/(Z ₁ +Z ₀ +Z ₂ )...(16)
By substituting the equation (16) into the equation (6), the following equation (an equation representing the first relationship) is obtained.
Q=ΔM/(Z ₀ +Z ₁ +Z ₂ )... (1)

The diffusion resistances Z _{1 to} Z ₃ can theoretically be obtained by the following formula (formula expressing the second relationship).
Z ₁ =1/(2Dm·d) (2)
Z ₀ =L/(Dm·(πd ² /4)) (3)
Z ₂ =1/(2Dm·d) (4)
Expression (3) corresponds to expression (8), and (πd ² /4) in expression (3) is the cross-sectional area of the leak hole 1a.

The equations (2) and (4) are obtained by the diffusion equation, but the calculation process is complicated and will be omitted. In addition, the diffusion phenomenon in which a specific molecule goes from the first space S1 to the leak hole 1a and the diffusion phenomenon in which the specific molecule spreads from the leak hole 1a to the second space S2 is continuous with a conductor in which an electric wire having a diameter d whose resistivity is not 0 has an infinite spread. It is similar to the current diffusion phenomenon in the current model.

Further, by substituting the expressions (2) to (4) into the expression (1), the following expression (expression representing the third relationship) is obtained.

When the diffusion flow rate obtained by the equation (5) is compared with the diffusion flow rate measured in an actual test (described later) under substantially the same conditions, even if the leakage hole 1a has a size close to a general pinhole, The diffusion flow rate obtained by the equation (5) and the test result were substantially the same.

Since the conductances C ₀ , C ₁ , C ₂ are reciprocal numbers of the diffusion resistances Z ₀ , Z ₁ , Z ₂ , the formulas (1) to (4) are represented by conductances C ₀ , C ₁ , C ₂ , (5) may be obtained. This calculation method is equivalent to the above-described calculation method for obtaining the equation (5) from the diffused resistors Z ₀ , Z ₁ and Z ₂ .

As shown in FIG. 2, the above expression (5) or its equivalent expression (for example, the expression in which the expression (5) is rewritten with the left side as the diameter d) is stored in the memory 5a of the computer 5, and the calculation unit 5b leaks it. The diameter d of the hole 1a can be calculated.
For example, assuming that the below-described pharmaceutical tablet container 20 is placed in the atmosphere and the base sheet 21 has a defect such as a pinhole, a case where only nitrogen is sealed in the tablet container 20 at atmospheric pressure will be described. To do. In this case, the first space S1 is simulated as the atmosphere, the closed space 23 of the tablet container 20 is simulated as the second space S2, and the following information is input to the computer.
(1) Path length L of the leak hole 1a... This path length L is equal to the thickness of the base sheet 21.
(2) Molarity difference ΔM ··· When the specific molecule that deteriorates the tablet is oxygen and only nitrogen is sealed in the tablet container 20 at atmospheric pressure, the molarity of oxygen in the atmosphere is defined as the molarity difference.
(3) Mutual diffusion coefficient Dm... Mutual diffusion coefficient between nitrogen and oxygen.
(4) Diffusion flow rate Q... It is an allowable limit value of the oxygen diffusion flow rate at which the tablet can maintain the quality for a predetermined period.
The computer can obtain the diameter d of the leak hole 1a from the input information and the stored information of the formula (5).

When the specific molecule that deteriorates the tablet is water vapor and the tablet container 20 is filled with dry air at atmospheric pressure, the path length L is input to the computer to determine the molar concentration of water vapor in the atmosphere. Input as the molar concentration difference ΔM, input the mutual diffusion coefficient Dm between water vapor and air, and input the limit value of the water vapor diffusion flow rate per unit time that the tablet can maintain the quality for a predetermined period as the diffusion flow rate Q. ..

Next, based on the calculated diameter d of the leak hole 1a, for example, a reference leak element 10 as shown in FIG. 3 is selected. This reference leakage element 10 is, as disclosed in International Patent Publication WO2017/208543, a circular base material 11 having a reference leakage hole 11a in the center and a circular filter attached to both surfaces of the base material 11. It is composed of sheets 12 and 12 and a sheet-shaped annular adhesive member 13 attached to the peripheral portion of the base material 11, and is thin and flexible.

The base material 11 is made of a thin and flexible sheet of stainless steel or the like, and has a thickness (for example, 15 μm) equal to the thickness of the base sheet 21 of the tablet container 20 (closed container) to be inspected to be described later.
The filter 12 has a thickness of about 0.1 mm, and its peripheral portion is attached to both surfaces of the base material 11 by the adhesive layer 15.
The annular adhesive member 13 is made of a thin and flexible resin sheet having a thickness of about 0.2 mm, and the adhesive layer 16 is applied to the entire area of one surface. The peripheral portion of the base material 11 is adhered to the annular region on the radially inner side of the annular adhesive member 13 by the adhesive layer 16. The area outside the adhesive layer 16 is provided for sticking to a tablet container 20' described later.

The reference leak hole 11a of the base material 11 may have a diameter equal to the leak hole diameter d calculated based on the above formula (5), or may be smaller than this. That is, in the computer, the diameter of the reference leak hole 11a may be obtained by multiplying the leak hole diameter obtained based on the equation (5) by a coefficient smaller than 1. Alternatively, the reference leak element 10 having the reference leak hole 11a having a diameter obtained by obtaining the leak hole diameter by a computer based on the equation (5) and multiplying the leak hole diameter by a coefficient smaller than 1 may be selected.

Next, the tablet container 20 to be inspected will be described with reference to FIG. The tablet container 20 is configured by joining and welding a resin base sheet 21 and a transparent resin cover sheet 22 having a plurality of bulged portions 22a. The plurality of bulging portions 22a and the base sheet 21 form a plurality of closed spaces 23 independent of each other, and the tablets 25 are housed in the closed spaces 23. The base sheet 21 is thinner than the cover sheet 22 and has a thickness of, for example, 15 μm, and the tablet 25 can be taken out by breaking it with a finger. Pinholes may occur in the base sheet 21 during the manufacturing process.

As shown in FIG. 5(B), the reference leak element 10 is attached to a tablet container 20′ (hollow member for reference leak) having the same structure as the tablet container 20 to be inspected, so that the workpiece W for reference leak is provided. Create. A hole 29 having a size of several mm, which is much larger than the reference leak hole 11a, is formed in a portion of the base sheet 21 of the tablet container 20' corresponding to one selected sealed space 23. It has been previously confirmed that no defect other than the hole 29 is formed in the tablet container 20'.
By attaching the annular adhesive member 14 to the base sheet 21 in a state where the reference leak hole 11a of the reference leak element 10 is substantially aligned with the hole 29 of the base sheet 21 of the tablet container 20′, the reference leak element 10 is attached to the tablet container 20′. It is attached to 20'. Due to the sealing action of the annular adhesive member 14, the closed space 23 is connected to the outside only through the hole 29 of the base sheet 21 and the reference leak hole 11a.

An example of a known leak test device for testing the tablet container 20 will be described with reference to FIG. The leak test apparatus includes a common passage 51, and a branch passage 52a and a branch passage 52b that are respectively connected to the downstream ends of the common passage 51. A test pressure source 50 including a compressed air source 50a and a regulator 50b is connected to the upstream end of the common passage 51. The test pressure in this embodiment is a positive pressure. A three-way valve 53 is provided in the common passage 1.

Valves 54a and 54b are provided in the branch passages 52a and 52b, respectively.
In the branch passages 52a and 52b, two ports of a differential pressure sensor 55 (pressure sensor) are connected to the downstream sides of the valves 54a and 54b, respectively, so that the differential pressure between the branch passages 52a and 52b can be detected. You can

A work capsule 56 is connected to the downstream end of the branch passage 52a, and a master capsule 57 is connected to the downstream end of the branch passage 52b. The work capsule 56 is composed of two openable and closable capsule halves, and can seal a work, which will be described later, in a housed state. Although the master capsule 57 is schematically shown in the drawing, for example, the master capsule 57 may be configured by a closed container having the same volume as the work capsule 56, or may have the same structure as the work capsule 56. The master capsule 57 contains the same work as the inspection target, which is confirmed to be leak-free.

The valves 53, 54a, 54b are sequence-controlled by a controller (not shown). The controller also opens/closes the work capsule 56 and determines whether the work is good or bad (determines whether there is a leak) based on the differential pressure detected by the differential pressure sensor 55.

A normal leak detection process by the leak test apparatus will be described. The tablet container 20 to be inspected is housed and sealed in the work capsule 56 as shown in FIG.
By turning on the three-way valve 53, the test pressure from the test pressure source 50 is supplied to the work capsule 56 and the master capsule 57 via the branch passages 52a and 52b. Next, the valves 54a and 54b are closed, and the branch passages 52a and 52b on the downstream side are isolated from each other.

Next, the differential pressure detected by the differential pressure sensor 10 after a predetermined time has elapsed since the valves 54a and 54b were closed is compared with a threshold value. When the base sheet 21 of the tablet container 20 has a pinhole, the pressurized air in the work capsule 56 enters the closed space 23 of the tablet container 20 and the pressure in the work capsule 56 gradually decreases from the test pressure. On the other hand, the master capsule 57 maintains the test pressure. As a result, there is a difference between the pressure inside the work capsule 56 and the pressure inside the master capsule 57. This differential pressure (pressure fluctuation of the work capsule 56) is detected by the differential pressure sensor 55. When the detected differential pressure (detection output) is larger than the threshold value, it is determined that there is a leak, and when the detected differential pressure is smaller than the threshold value, the tablet container 20 is determined as a non-defective non-leak product. In addition, the atmospheric pressure conversion leak amount corresponding to the detected differential pressure may be used as the detection output of the differential pressure sensor 55, and the pass/fail judgment may be performed by comparing the atmospheric pressure conversion leak amount with a threshold value.

Next, the reference leak process for setting the threshold value, which is executed when the leak test device is delivered, will be described.
The reference leak work W configured by mounting the reference leak device 30 on the above-mentioned tablet container 20′ is sealed in the work capsule 56 of the leak test apparatus, and the same leak detection process as the above-described normal leak detection process. Is executed.

In the leak detection process, the differential pressure (detection output) detected by the differential pressure sensor 55 corresponds to the reference leak amount by the reference leak hole 11a. The detection output of the differential pressure sensor 55 associated with this reference leak or a value obtained by multiplying this detection output by a coefficient smaller than 1 is used as a threshold value in a normal leak test.
The threshold value corresponds to the permissible limit value of the diffusion flow rate of the specific molecule that deteriorates the tablet 25, and by performing a leak test of the tablet container 20 using this threshold value, it is possible to guarantee the quality of the tablet 25 for a certain period of time. The container 20 and the tablet container 20 that cannot be guaranteed can be accurately distinguished.

It should be noted that the leak detection process involving the reference leak using the reference leak element 20 may be used to evaluate the performance of the air leak test apparatus in the normal leak detection process and obtain reference data for calibrating the detection output. it can.

The present invention is not limited to the embodiment described above, and various modifications can be made without departing from the spirit of the invention.
Equation (5) may include a correction term.
The inspection target is not limited to that of the embodiment, and can be applied to various hollow members having a closed space.
The specific molecule is not limited to water vapor and oxygen.
The air leak test device may use a negative test pressure source.
INDUSTRIAL APPLICABILITY The present invention is not limited to the air leak test, and can be applied to an apparatus that executes various leak tests such as a helium leak test, a hydrogen leak test and the like.

INDUSTRIAL APPLICABILITY The present invention can be applied to, for example, quality evaluation of sealed containers for medicines, foods, electronic parts, sensors and the like.

1 partition wall 1a leak hole 10 reference leak element 11a reference leak hole 20 tablet container (inspection target)
20' tablet container (hollow member for standard leakage)
23 Sealed space 50 Test pressure source 55 Differential pressure sensor (pressure sensor)
56 Work Capsule S1 First Space S2 Second Space W Reference Leak Work

Claims (8)

In a diffusion model in which a first space containing a specific molecule and a second space in which the molar concentration of the specific molecule is lower than the first space at the same pressure as the first space are isolated by partition walls having leak holes,
The total diffusion resistance of the particular molecule from the first space through the leak to the second space, each being a function of leak size,
(A) Diffusion resistance in the leak hole in the process of passing through the leak hole,
(B) a first space diffusion resistance in the process in which the specific molecule moves from the first space to the leak hole,
(C) A second space diffusion resistance in the process in which the specific molecule spreads from the leak hole to the second space,
Defined as the sum of
Based on the total diffusion resistance, the relationship between the leak hole size and the diffusion flow rate at which the specific molecule diffuses from the first space through the leak hole to the second space is determined, and based on this relationship, the leak A method for calculating a diffusion flow rate or a leakage hole size, characterized in that the diffusion flow rate is calculated from the hole size or the leakage hole size is calculated from the diffusion flow rate. Further, the path length among the leak hole dimensions is known, and the diffusion flow rate of the specific molecule is calculated from the leak hole diameter, or the leak hole diameter is calculated from the diffusion flow rate. The method for calculating the diffusion flow rate or the leak hole size according to 1. The diffusion flow rate or leakage hole size according to claim 2, wherein the diameter of the leakage hole corresponding to an allowable limit value of the diffusion flow rate of the specific molecule is calculated by simulating the first space as an atmosphere. Calculation method. The diffusion flow rate Q, the molar concentration difference ΔM of the specific molecule in the first space and the second space, the diffusion resistance in the leak hole Z ₀ , the first space diffusion resistance Z _1, and the second space. The first relationship with the space diffusion resistance Z ₂ is defined by the following equation (1),
Q=ΔM/(Z ₀ +Z ₁ +Z ₂ )... (1)
The in-leakage diffusion resistance Z ₀ , the first spatial diffusion resistance Z ₁ and the second spatial diffusion resistance Z ₂ , respectively, the mutual diffusion coefficient Dm, and the leakage path length L as the leakage hole size and the above. A second relationship between the diameters d of the leak holes is defined by the following equations (2) to (4),
Z ₀ =1/(2D _m ·d) (2)
Z ₁ =L/(D _m ·(πd ² /4)) (3)
Z ₂ =1/(2D _m ·d) (4)
Based on the first relationship and the second relationship, the third relationship between the diffusion flow rate Q and the path length L and the diameter d is set with the molar concentration difference ΔM and the mutual diffusion coefficient Dm known. Stipulated,
The diffusion flow rate Q is calculated from the leakage hole size or the leakage hole size is calculated from the diffusion flow rate Q based on the third relationship. Calculation method of diffusion flow rate or leak hole size. The diffusion flow rate or leakage hole size calculation according to claim 4, wherein the third relation is obtained by the following equation based on the equation (1) and the equations (2), (3), and (4). Method.

Prepare a computer that stores the above equation (5) or a relational expression equivalent thereto,
The diameter d of the leak hole is derived by inputting the molar concentration difference ΔM, the mutual diffusion coefficient Dm, the path length L of the leak hole, and an allowable limit value of the diffusion flow rate Q to the computer. 5. The method for calculating the diffusion flow rate or the leak hole size according to 5. A reference leakage element selection method comprising selecting a reference leakage element having a diameter of the leakage hole calculated in claim 3 or 6 or a reference leakage hole having a diameter obtained by multiplying the diameter by a safety factor. A test pressure source, a work capsule, and a pressure sensor for detecting a pressure fluctuation in the work capsule, and a test object having a sealed space is housed in the work capsule to be sealed. After supplying air to the work capsule, by disconnecting the test pressure source and the work capsule, by detecting the pressure fluctuation in the work capsule by the pressure sensor, by comparing the detection output of this pressure sensor with a threshold value Prepare a leak test device that executes the leak test of the above inspection target,
A reference leak work is obtained by mounting the reference leak element selected in claim 7 on the reference leak hollow member having the same structure as the inspection target,
The reference leaked work is stored in the work capsule of the leak test device instead of the inspection target, the same process as the leak test of the inspection target is performed, and the detection output is obtained, and the threshold value is based on the detection output. A method for determining a threshold in a leak test apparatus, characterized in that

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