JP2023043985A - Defect inspection method - Google Patents

Abstract

To determine quality of an inspection object on the basis of a bore diameter of a defect of the inspection object.SOLUTION: A reference leakage bore 25a of a reference leakage instrument 25 provided in a leakage inspection device has a passage length that is determined by modeling defects to be assumed in an inspection object to a linear tubular defect of a circular cross-sectional shape. A defect inspection method includes: obtaining a reference amount of leakage Qs under a specified condition, which is a leakage amount of the reference leakage instrument 25, at a specified test pressure, atmospheric pressure (external air pressure) and ambient temperature; obtaining a reference amount of leakage Qr under an inspection condition from a pseudo leakage in the reference leakage instrument 25 under an actual inspection condition; performing leakage inspection by connecting the leakage inspection device to an inspection object W to obtain an amount of leakage Qm of the inspection object under the inspection condition; then, converting the amount of leakage Qm of the inspection object under the inspection condition to an amount of leakage Qx of the inspection object under the specified condition on the basis of the reference amount of leakage Qs under the specified condition and the reference amount of leakage Qr under the inspection condition; and computing a bore diameter Dx of a defect of the inspection object on the basis of the converted amount of leakage Qx, and determining quality of the inspection object.SELECTED DRAWING: Figure 1

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection method for judging acceptance/rejection of an inspection target based on the size of the defect to be inspected.

Taking a pressurized air type leak test device as an example, this leak test device includes a test pressure source, a test path connected to the test pressure source, a valve provided in the test path, and a downstream side of the valve. and a pressure measuring means connected to the basic structure. After connecting the inspection object to the end of the inspection path and supplying the test pressure from the test pressure source to the inspection object, the valve is closed to close the inspection path and the inspection object, and the pressure change in this closed system is measured by the pressure measuring means. Measure. A defect in the test object causes a pressure drop in the closed system due to a leak in the test object.

Different volumes of test objects with the same amount of leakage will have different pressure drops. For this reason, a method is generally adopted in which a leakage amount per unit time is calculated based on the pressure drop and the volume of the inspection object, and a pass/fail judgment is made based on this leakage amount.
However, the leakage amount to be inspected does not uniquely represent the defect itself. This is because even if the leak rate is the same, the shape and size of the defect may differ, and even if the defect is the same, the leak rate will change if the leak test conditions such as test pressure, atmospheric pressure, and ambient temperature change. be.

In addition, the amount of leakage itself may not serve as a criterion for judging the quality of the object to be inspected. An example will be described in which the inspection object is a package containing contents, and the internal pressure of this package is approximately the same as the atmospheric pressure or the difference between them is small. This content degrades by reacting with certain substances such as water vapor and oxygen. Therefore, it is required to suppress the intrusion amount of specific substances through packaging defects to less than the allowable value before the expiration date of the quality assurance of the contents. If the shape and size of the defect are specified, the permissible value of this intrusion amount can be obtained based on the principle of diffusion.
On the other hand, in the above-described leak tester, a test pressure is applied and the leak amount is measured by causing the fluid to pass through the defect due to the pressure difference between the inside and outside of the object to be inspected. Therefore, the specific amount of intrusion and the amount of leakage do not correspond one-to-one, and it is impossible to make an accurate determination of quality based on the permissible value of the amount of intrusion. This is because, for example, even if the leak amount is the same, the penetration amount differs several times to several tens of times due to the difference in the shape of the defect.

The leak test device of Patent Document 1 is equipped with a pseudo leak path connected to a test path and a reference leaker provided in this pseudo leak path. This reference leaker has a reference leak that behaves like the defect under test. The amount of leakage from this reference leaker at specified atmospheric pressure and ambient temperature, that is, the "reference amount of leakage under specified conditions" is obtained in advance.
Under inspection conditions, a test pressure is supplied to the inspection path to cause a pseudo leak through the reference leaker, and the amount of leakage, that is, " Calculate the standard leakage amount under the inspection conditions.
Next, under the inspection conditions, a test pressure is supplied with the object to be inspected connected to the inspection path, and based on the pressure change in the inspection path measured by the pressure measuring means, the amount of leakage to find the amount of leakage to be inspected.
Based on the above "reference leakage amount under specified conditions" and the above "reference leakage amount under inspection conditions", the above "leakage amount to be inspected under inspection conditions" This converted leakage amount is compared with the threshold value of the leakage amount to make pass/fail judgment.

According to the method of Patent Document 1, the leakage amount corresponding to the size of the defect to be inspected can be obtained by calculation regardless of changes in atmospheric pressure and ambient temperature, so that highly accurate pass/fail judgment can be performed. can be done.

Patent Literature 2 discloses a method for determining the diameter of a hole to be inspected from information including upstream pressure, downstream pressure, gas flow rate, temperature, and length of the hole to be inspected.

Patent No. 6636044 WO2021/079833A1

In the method of Patent Document 1, the converted leakage amount under specified conditions corresponds to the hole diameter of the defect to be inspected, but since the hole diameter itself is unknown, it cannot meet the demand for more accurate pass/fail judgment. That is, as described above, the contents of the sealed product to be inspected are subject to deterioration due to specific substances. Depends on conditions. However, with the above-described converted leakage amount, it is not possible to easily set a threshold value corresponding to the allowable value of the intrusion amount under the envisaged environmental conditions, and consequently it is not possible to make a pass/fail judgment with high accuracy.
The method of Patent Literature 2 does not disclose a specific procedure for making pass/fail judgments for inspection objects.

The present invention has been made to solve the above problems. In the defect inspection step, a test pressure is supplied to an inspection object connected to the inspection path through an inspection path, and the inspection is performed. After the passage is closed, the pressure change in the inspection passage is measured, the pore diameter Dx of the defect to be inspected is calculated based on the pressure change or the amount of gas leakage calculated from the pressure change, and the calculated pore diameter By comparing Dx with the threshold value Do of the hole diameter, the acceptance/rejection determination of the inspection object is performed.

According to the above method, the defect is modeled to determine its path length, the threshold Do of the hole diameter is determined, and the hole diameter Dx calculated in the inspection process is compared with this threshold Do. It is possible to make a highly accurate pass/fail judgment without being overwhelmed.

Preferably, a substance that should be prevented or suppressed from entering or leaking into the object to be inspected is specified, a permissible value for the amount of this specific substance entering or leaking into the object to be inspected is determined, and a model having the path length is determined. The amount of the specific substance that penetrates or leaks into the inspection object through the defect is determined theoretically or experimentally, and the threshold Do of the hole diameter is determined based on the hole diameter that reaches the permissible value for the amount of penetration or leakage.
According to the above method, the pass/fail judgment threshold can be determined accurately from the viewpoint of quality assurance of the contents to be inspected.
When the difference between the internal pressure of the object to be inspected and the atmospheric pressure is small, the threshold value Do of the pore size is obtained from the diffusion theory.

If there are multiple possible defects to be inspected, determine the pore size at which each of the modeled defects with different path lengths reaches the same amount of penetration or leakage, and among these defects, In the inspection process, the defect with the smallest pressure change or the smallest amount of leakage is selected as a specific defect, and the hole diameter threshold value for this specific defect is set as the hole diameter threshold value Do used in the inspection process.
According to the above method, when there are multiple defects assumed to be inspected, pass/fail judgment is performed based on the defect for which the amount of leakage is most difficult to detect. can do,

A specific aspect of the present invention is a test pressure source, an inspection path having an end connected to an object to be inspected and supplying the test pressure from the test pressure source to the object to be inspected; a valve, a pressure measuring means connected to the inspection path between the first valve and the terminal, and a pseudo leak path connected to the inspection path between the first valve and the terminal and connected to the outside; a reference leaker provided in the pseudo leak path and having a reference leak hole; and a second valve provided in the pseudo leak path between the test path and the reference leaker. In the defect inspection method using
The reference leak hole has a length corresponding to a passage length determined by modeling a defect assumed to be inspected as a straight tube defect having a circular cross section, and has a known diameter. The amount of gas leaking through the reference leak hole under the conditions of the test pressure and the external air pressure is obtained as a reference leakage amount Qs under specified conditions,
Under inspection conditions, after supplying a test pressure in a state in which a non-defective product having the same volume as the inspection object and having no leakage is connected to the inspection path, the first valve is closed and the second valve is opened, whereby the reference leakage is detected. A pseudo leak is generated through a device, and a reference leak amount Qr under inspection conditions is obtained based on the pressure change in the inspection path measured by the pressure measuring means at this time,
Under the inspection conditions, the test path is measured by the pressure measuring means while the first valve and the second valve are closed after a test pressure is supplied to the inspection path while the object to be inspected is connected to the inspection path. Based on the pressure change in
Based on the reference leakage amount Qs under the specified conditions and the reference leakage amount Qr under the inspection conditions, the leakage amount Qm to be inspected under the inspection conditions is converted to the converted leakage amount Qx to be inspected under the specified conditions. converted to
Furthermore, the hole diameter Dx of the defect to be inspected is calculated based on the converted leak amount Qx and at least information on the test pressure and the external air pressure under the specified conditions, and the calculated hole diameter Dx is modeled The pass/fail judgment of the inspection object is performed by comparing with the threshold value Do of the hole diameter of the defect.

According to the above-described method, the pass/fail judgment can be made based on the hole diameter of the modeled defect to be inspected, so that the pass/fail judgment can be made with high accuracy. In addition, even if the inspection conditions change, the hole diameter of the defect can be obtained accurately, and from this point as well, the pass/fail judgment can be performed with high accuracy.

Further, the hole diameter Dx is calculated by adding the length of the reference leak hole and information on the ambient temperature under the specified conditions.
According to this method, even if the defect is a long hole model, the hole diameter of the defect can be obtained accurately.

Another specific aspect of the present invention is a test pressure source, an inspection path having an end connected to an object to be inspected and supplying the test pressure from the test pressure source to the object to be inspected; A defect inspection method using a leak inspection device comprising a first valve, pressure measuring means connected to the inspection path between the first valve and the end, and an air pressure sensor for measuring external air pressure ,
Prior to the inspection process, model the assumed defect to be inspected as a straight tubular passage with a circular cross section, determine the passage length of this modeled defect, and determine the threshold Do of the hole diameter,
In the inspection step, after a test pressure is supplied to the inspection path while the object to be inspected is connected, the first valve is closed, and based on the pressure change in the inspection path measured by the pressure measuring means, A leak amount Qm to be inspected is obtained, a defect hole diameter Dx is calculated based on the leak amount Qm, at least the information of the test pressure and the external air pressure from the air pressure sensor, and the calculated hole diameter Dx is used as the hole diameter. It is characterized in that the pass/fail judgment of the inspection object is performed by comparing with the threshold value Do of .
This method can also make pass/fail judgments based on the hole diameter of the defect to be inspected.

Preferably, the leak tester further comprises a temperature sensor for detecting ambient temperature, and the hole diameter Dx is calculated by adding the path length of the modeled defect and ambient temperature information from the temperature sensor. do.
According to this method, even if the defect is a long hole model, the hole diameter of the defect can be obtained accurately.

More preferably, the leak test device further comprises a pseudo leak path connected to the test path between the first valve and the terminal end and continuing to the outside, and a reference provided in the pseudo leak path and having a reference leak hole. a leaker; and a second valve provided in the pseudo leak path between the test channel and the reference leaker, the reference leak having a length equal to the path length of the modeled defect. and has a known diameter,
Prior to the inspection of the inspection target, after supplying a test pressure in a state in which a non-defective product having the same volume as the inspection target and having no leakage is connected to the inspection path, the first valve is closed and the second valve is opened, Pseudo-leakage is generated through the reference leaker, and based on the pressure change in the test path measured by the pressure measuring means at this time, the actually measured reference leak amount under the test conditions is obtained, and the length of the reference leak hole is determined. A theoretical reference leak rate is calculated based on the information of the height and diameter, the test pressure, the external air pressure from the air pressure sensor, and the ambient temperature from the temperature sensor, and the actually measured reference leak rate is the theoretical calibrate the output value of the leakage amount from the leakage inspection device so as to match the reference leakage amount of .
According to this method, calibration can be performed accurately.

According to the present invention, since the hole diameter, which is an absolute reference for the defect to be inspected, is used as a reference, it is possible to accurately determine whether the inspection object is acceptable.

1 is a circuit diagram of a leak test device according to a first embodiment of the present invention; FIG. FIG. 4 is a circuit diagram of a leak test device according to a second embodiment of the present invention;

Embodiments of the present invention will be described below.
<Defect modeling and threshold setting>
Prior to the inspection process of the inspection object, the assumed defect of the inspection object is modeled as a straight tubular passage with a circular cross section, the passage length of this modeled defect is determined, and the threshold value Do of the hole diameter is determined.
A description will be given by taking as an example a package containing contents as an object to be inspected. The internal pressure of the package is approximately equal to or has a small difference from the atmospheric pressure, and the principle of diffusion, which will be described later, can be applied. Depending on the type of the contents of the package, substances that cause deterioration are different, and include, for example, gas molecules such as water vapor and oxygen, molds, bacteria, and the like. First, a defect caused by the packaging manufacturing process is assumed and modeled. For example, when there is a possibility that a defect may occur in the welded portion of the two sheet portions, a relatively long straight pipe is modeled, and the passage length L of the modeled straight pipe is determined. If there is a possibility that pinholes in the seat may occur as defects, the wall thickness of the seat is determined as the path length.

Next, based on the permissible intrusion amount of the specific substance that causes deterioration and the path length L of the modeled defect, the permissible value of the hole diameter of the defect is calculated using a known diffusion theoretical formula, and this permissible value or this The value multiplied by the safety factor is determined as the pore diameter threshold value Do. Note that the pore diameter threshold value Do may be obtained by experiment instead of the theoretical formula.

It may be assumed that the inspection object contains multiple defects of different forms. For example, a defect with a long path as described above and a defect with a short path such as a pinhole may coexist. In this case, the pore size is determined when each of the modeled defects with different path lengths reaches the same penetration (e.g., the allowable penetration), and from these defects the leakage measured in the inspection step described below. The defect with the lowest amount is selected as the specific defect. The threshold value of the hole diameter related to this specific defect is set as the threshold value Do of the hole diameter used in the inspection process.

As described above, the hole diameter threshold value Do can be uniquely determined prior to the inspection process regardless of the inspection conditions.

<Inspection process>
To explain the outline of the inspection process, a test pressure is supplied to the object to be inspected through the inspection path, and after the inspection path is closed, the pressure change in the inspection path is measured. The gas leakage amount is calculated from this pressure change, and the pore diameter Dx of the defect to be inspected is calculated from the calculated leakage amount. By comparing the calculated hole diameter Dx with the threshold value Do of the hole diameter, the pass/fail judgment of the inspection target is performed.

<First Embodiment>
A first embodiment will be described below with reference to the drawings.
Configuration of leak test equipment
As shown in FIG. 1, the leak test device comprises a test pressure source 1 and a pressure circuit 2. As shown in FIG. The test pressure source 1 has a pressure source 1a that supplies pressurized air and a pressure regulating valve 1b that reduces the air pressure of the pressure source 1a to the test pressure. The pressure circuit 2 has a common path 3 connected to the test pressure source 1, a reference path 4 and a test path 5 branched from the common path 3, and a pseudo leak path 6 connected to the test path 5. there is

A pressure gauge 12 and a three-way valve 13 are provided in the common channel 3 . On-off valves 14, 15, and 16 are provided in the reference path 4, the inspection path 5, and the pseudo leak path 6, respectively. The pseudo leak path 6 is connected downstream of the on-off valve 15 in the inspection path 5 .

A differential pressure sensor 20 (pressure measuring means) is connected between the reference path 4 and the inspection path 5 downstream of the on-off valves 14 and 15 . A master container 21 is connected to the downstream end (end) of the reference path 4 . The downstream end (end) of the inspection path 5 is directly connected to the inspection target W, or is connected to a work capsule (closed container) containing the inspection target W. Each product to be inspected W has its own unique manufacturing process and structure, and it is possible to assume locations where defects may occur, and model defects as described above.

A reference leaker 25 is connected to the downstream end of the pseudo leak path 6 . The reference leaker 25 has a reference leak hole 25a having a shape and size corresponding to the modeled defect of the inspection object W, as described later.

The leak test device further comprises a computer system 30 and a drive circuit 35. FIG. The computer system 30 includes a control calculation section 31 (control calculation means), an input section 32 such as a keyboard connected to the control calculation section 31, and a display section 33 such as a display. The drive circuit 35 controls the valves 13 to 16 based on the sequence control signal from the control calculation section 31 in the leak inspection process, which will be described later. The control calculation unit 31 incorporates a memory 31m.

ここで、Ｐ１はテスト圧、Ｐ２は外部気圧（本実施形態では大気圧）である。Ｌは欠陥の通路長さ、Ｄは欠陥の孔径である。ηは気体の粘性係数であり、気体の種類（本実施形態では空気）と周囲温度に依存して変化する。 Theoretical formula for leak amount An example of a theoretical formula for the leak amount Q (Pa·m ³ /s) caused by defects in the inspection object W will be described. The defect is simplified (modeled) as a straight tubular hole with a circular cross section as described above. If the defect is a long pore model, i.e. if the path length of the defect is more than 10 times longer than the pore diameter of the defect (e.g. if the defect length is 10 mm and the pore diameter is 50 μm), a representative calculation of viscous flow The leakage amount Q can be obtained from the Hagen-Poiseuille formula, that is, the following formula (1).

Here, P1 is the test pressure and P2 is the external pressure (atmospheric pressure in this embodiment). L is the defect path length and D is the defect pore size. η is the viscosity coefficient of the gas, and varies depending on the type of gas (air in this embodiment) and the ambient temperature.

When the defect is a short hole model, that is, when the wall thickness of the inspection target W is thin and the path length of the defect (pinhole) is less than 10 times the hole diameter of the defect (for example, when the defect length is 15 μm and the hole diameter is 20 μm) ), and the leakage amount Q (Qs) can be obtained from the following equation (2).
Q=0.016×D ² (P1−P2) (2)

In the following description, the symbols P1 and P2 used in the above general formula are used as common symbols indicating the test pressure and external air pressure under specified conditions and the test pressure and external air pressure under inspection conditions.

Size of reference leak hole If the assumed defect of the inspection object W is a long hole model, the reference leak hole 25a of the reference leaker 25 has a length approximately equal to the length of this defect. there is Even when the wall thickness of the inspection object W is thin and the assumed defect is a short hole model, the reference leak hole 25a preferably has a length substantially equal to the length of the defect, but the above equation (2) holds. not necessarily equal to the length of the defect as long as it has a length short enough to
The diameter D of the reference leak hole 5a is preferably set to be approximately the same as the pass/fail judgment threshold of the inspection object W, but may be different from this threshold.

Reference leak rate under specified conditions For the reference leaker 25, the leak rate per unit time (Pa· ^m3 /s) (hereinafter simply referred to as the amount of leakage) is obtained in advance. The leak amount Qs can be theoretically obtained from the above-described formula (1) or formula (2), but the leak amount Qs may be obtained by actual measurement as described later. This leakage amount Qs is defined as "a reference leakage amount under specified conditions".

Defect inspection method A defect inspection method using the leak inspection apparatus configured as described above will be described.
The memory 31m stores the following information input from the input unit 32 in addition to the sequence control programs for the valves 13-16.
・Specified ambient temperature ・Specified atmospheric pressure (external pressure)
・Specified test pressure ・Standard leak rate _QS under specified conditions,
・Volume of inspection target W ・Length L of reference leak hole 25a of reference leaker 25
・Threshold Do of hole diameter for leak determination

<Pseudo leak measurement>
First, the leak amount Qr passing through the reference leaker 25 under test conditions is obtained at the time and place where the leak test for the test object W is actually performed. This leak amount Qr is defined as "a reference leak amount under inspection conditions". Ambient temperature and atmospheric pressure under test conditions are generally different from regulation conditions. The test pressure under inspection conditions is preferably equal to the test pressure under normal conditions, but may be different.

To be more specific, the inspection path 5 is connected to a leak-free non-defective object having the same configuration (same volume) as the inspection object W. The three-way valve 13 communicates the common path 3 with the reference path 4 and the inspection path 5, and opens the on-off valves 14 and 15 (however, the on-off valve 16 remains closed). As a result, air pressure from the test pressure source 1 is introduced from the reference path 4 to the master container 21 and from the inspection path 5 to the non-defective product.

Next, the on-off valves 14 and 15 are closed. As a result, the space containing the reference path 4 and the master container 21 on the downstream side of the on-off valve 14 and the space containing the inspection path 5 and non-defective product objects on the downstream side of the on-off valve 15 form mutually independent closed spaces.

Next, the on-off valve 16 is opened to connect the pseudo leak path 6 to the inspection path 5 . As a result, the pressurized air in the inspection path 5 leaks from the reference leak hole 25a of the reference leaker 25 to the atmosphere. As a result, a pressure difference is generated between the reference channel 4 and the test channel 5 . This pressure difference, that is, the pressure change ΔP of the inspection path 5 is detected by the differential pressure sensor 20 . Information on the pressure change ΔP is input to the control calculation unit 31 .

The control calculation unit 31 calculates the leakage amount Q from the reference leaker 25 by calculating the following equation (3). This leakage amount Q is defined as "a reference leakage amount Qr under inspection conditions".
Q=Vw·ΔP/Δt (3)
Here, Δt is the detection time of the pressure change ΔP, and Vw is the volume of the non-defective product (that is, the volume of the inspection object).

<Conversion factor calculation>
Furthermore, the control calculation unit 31 obtains a conversion factor k according to the following equation (4) and stores it in the memory 31m.
k=Qs/Qr (4)
As described above, Qs is the standard leak rate under specified conditions, and Qr is the standard leak rate under inspection conditions.

Although the explanation is back and forth, the reference leak amount Qs under the specified conditions can also be obtained by executing the above pseudo leak process using a leak test device instead of the theoretical value. This leak checker preferably has the same configuration as the leak checker shown in the figure, but may be different.

<Leak inspection>
Next, a method for inspecting the presence or absence of defects in the manufactured inspection target W will be described in detail.
With the inspection object W connected to the inspection path 5, the three-way valve 13 communicates the common path 3 with the reference path 4 and the inspection path 5, and the on-off valves 14 and 15 are opened (however, the on-off valve 16 remains closed). . As a result, the test pressure from the test pressure source 1 is introduced into the master container 21 through the reference path 4 and into the inspection object W through the inspection path 5 .

Next, the on-off valves 14 and 15 are closed. As a result, the space containing the reference path 4 and the master container 21 on the downstream side of the on-off valve 14 and the space containing the inspection path 5 and the inspection object W on the downstream side of the on-off valve 15 form mutually independent closed spaces.

Next, the differential pressure sensor 20 detects the time change of the pressure difference between the reference path 4 and the inspection path 5, that is, the pressure change ΔP of the inspection object W. FIG. The control calculation unit 31 calculates the leak amount Q of the inspection object W by substituting this pressure change ΔP into the above-described formula (3). This leak amount is defined as "the leak amount Qm to be inspected under inspection conditions".

Furthermore, as shown in the following equation (5), the leakage amount Qm to be inspected under inspection conditions is converted into the leakage amount Qx to be inspected under specified conditions using the conversion coefficient k.
Qx=kQm (5)

The converted leak amount Qx of the inspection target under the above specified conditions cancels the effects of changes in the ambient temperature and atmospheric pressure under the inspection conditions. is the same value even if is changed.

ここで、Ｐ１は規定のテスト圧、Ｐ２は規定の大気圧（外部気圧）である。ηは規定温度での気体（本実施形態では空気）の粘性係数である。Ｌは基準漏れ孔２５aの長さ（すなわちモデル化した欠陥の通路長さ）である。 Next, the pore diameter Dx of the defect is calculated from the converted leakage amount Qx of the inspection object under the above specified conditions.
When the defect is a long hole model, it is obtained from the following formula (6) obtained by modifying the Hagen-Poiseuille formula (1).

Here, P1 is the prescribed test pressure and P2 is the prescribed atmospheric pressure (external pressure). η is the viscosity coefficient of gas (air in this embodiment) at a specified temperature. L is the length of the reference leak 25a (ie the path length of the modeled defect).

ここで、Ｐ１は規定のテスト圧であり、Ｐ２は規定の大気圧（外部気圧）である。 If the defect is a short hole model, the hole diameter Dx is obtained from the following formula (7) obtained by modifying the formula (2).

where P1 is the prescribed test pressure and P2 is the prescribed atmospheric pressure (external pressure).

<Leak judgment>
Next, the calculated hole diameter Dx and the threshold value Do are compared to make a pass/fail decision. That is, if the hole diameter Dx is equal to or less than the threshold value Do, the inspection object W is determined to be non-defective (no leakage). If the hole diameter Dx exceeds the threshold value Do, the inspection object W is determined to be defective (with leakage).
The display unit 33 displays the result of pass/fail judgment, as well as the calculated hole diameter Dx and the threshold value Do.

After the measurement is finished, the open/close valves 14 and 15 are opened and the three-way valve 13 is set to the atmospheric release position to discharge the test pressure in the master container 21 and the object W to be inspected.

As described above, the pass/fail judgment is made based on the hole diameter Dx of the defect which is not influenced by the pressure conditions and the temperature conditions, so the pass/fail judgment can be performed with high accuracy.
For example, when making pass/fail judgments based on the permissible amount of penetration of a specific substance into an object to be inspected, the threshold value (threshold for pore diameter) can be easily and appropriately set based on this allowable value and the environmental conditions to which the object to be inspected is exposed. It is also possible to perform a highly accurate pass/fail judgment from this point.

As can be understood from the above description, when the defect is a short hole model and the hole diameter Dx is calculated using the equation (7), the length of the reference leak hole 25a (path length of the modeled defect ) and ambient temperature information under specified conditions can be dispensed with.

Second Embodiment Next, a second embodiment of the present invention will be described. As shown in FIG. 2, the leak inspection device used in the second embodiment is equipped with an atmospheric pressure sensor 41 for detecting atmospheric pressure (external pressure) and a temperature sensor 42 for detecting ambient temperature. Information detected by the atmospheric pressure sensor 41 and the temperature sensor 42 is sent to the control calculation section 31 . Other configurations are the same as in FIG.

<Leak inspection>
Leakage inspection of the inspection object W is performed in the same manner as in the first embodiment, and the pressure change ΔP detected by the differential pressure sensor 20 and the leakage amount Qm of the inspection object under the inspection conditions are obtained from the above-described equation (3). can get.

ここでａはセンサ係数、Ｖｗは検査対象Ｗの容積、Ｖｓはマスタ容器２１の容積である。Ｐ１はテスト圧、Ｐ２は気圧センサ４１で検出された大気圧である。 Note that the leak amount Qm to be inspected under the inspection conditions may be obtained from the following equation (8) instead of the equation (3).

Here, a is the sensor coefficient, Vw is the volume of the inspection target W, and Vs is the volume of the master container 21 . P1 is the test pressure and P2 is the atmospheric pressure detected by the atmospheric pressure sensor 41 .

ここで、Ｐ１は検査条件下でのテスト圧であり、Ｐ２は検査条件下で検出された大気圧（外部気圧）である。Ｌはモデル化欠陥の通路長さである。ηは検査条件下で検出された周囲温度での気体（本実施形態では空気）の粘性係数である。 Next, the hole diameter Dx of the defect of the inspection object W is calculated from the leak amount Qm of the inspection object W under the above inspection conditions.
When the defect is a long hole model, it is obtained from the following formula (9) obtained by modifying the Hagen-Poiseuille formula (1).

where P1 is the test pressure under test conditions and P2 is the atmospheric pressure (external pressure) detected under test conditions. L is the path length of the modeled defect. η is the viscosity coefficient of the gas (air in this embodiment) at ambient temperature detected under the test conditions.

ここで、Ｐ１はテスト圧であり、Ｐ２は検査条件下で検出された大気圧（外部気圧）である。 If the defect is a short hole model, the hole diameter Dx is obtained from the following formula (10) obtained by modifying the formula (2).

where P1 is the test pressure and P2 is the atmospheric pressure (external pressure) detected under test conditions.

Similar to the first embodiment, the calculated hole diameter Dx and the threshold value Do are compared to determine acceptance, and the calculated hole diameter Dx and the threshold value Do are displayed on the display unit 33 .

As can be seen from the above description, if the defect is a short hole model and equation (10) is used to determine the hole diameter Dx, the ambient temperature and defect length information can be dispensed with. The inspection device may not be equipped with the temperature sensor 42 .

<Calibration>
In this embodiment, the reference leaker 25 can be used to calibrate the output of the leak test device. More specifically, from a comparison between the theoretical leakage amount of the reference leak hole 25a obtained by the above formula (1) or (2) and the reference leakage amount actually measured in the same pseudo-leakage process as in the first embodiment, Calibrate the output of the leak tester so that the actually measured leak rate matches the theoretical leak rate.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention.
In the above-described embodiment, the threshold value of the pore size of the modeled defect is determined from the viewpoint of preventing or suppressing the intrusion of the specific substance into the inspection object. From a point of view, a threshold pore size may be determined. For example, there are cases where an inert gas such as nitrogen is filled in a bag containing contents as an object of inspection. Determine the pore size threshold based on Since it can be easily understood by replacing "intrusion" with "leakage" in the explanation of the above embodiment, detailed explanation is omitted.
The pressure source is not limited to a positive pressure source such as an air compressor, and may be a negative pressure source such as a vacuum pump.
Helium gas, hydrogen gas, or the like may be used instead of air as the gas used in the leak inspection process.
Although relatively simplified formulas were used in the above embodiment as formulas for obtaining the leakage amount and the pore diameter, other theoretical formulas may be used.
The pore size is calculated based on the leak rate, which is obtained from the measured pressure change. Therefore, it can be said that the pore size is calculated based on the measured pressure change.

INDUSTRIAL APPLICABILITY The present invention can be applied to acceptance/rejection determination of sealed goods.

1 Test pressure source 5 Inspection path 6 Pseudo leak path 15 Open/close valve (first valve)
16 on-off valve (second valve)
20 differential pressure sensor (pressure measuring means)
25 reference leaker 25a reference leak hole 31 control calculation section (control calculation means)
33 Display unit 41 Atmospheric pressure sensor 42 Temperature sensor W Inspection object

Claims (9)

Prior to the inspection process of the inspection object, the assumed defect of the inspection object is modeled as a straight tubular passage with a circular cross section, the passage length of this modeled defect is determined, and the hole diameter threshold value Do is determined,
In the defect inspection process,
After supplying a test pressure to an object to be inspected connected to the inspection path through the inspection path and closing the inspection path, measuring a pressure change in the inspection path,
Based on the pressure change or the amount of gas leakage calculated from the pressure change, the hole diameter Dx of the defect to be inspected is calculated, and the calculated hole diameter Dx and the threshold value Do of the hole diameter are compared to determine the A defect inspection method characterized by performing a pass/fail judgment of. Identifying a substance that should be prevented or suppressed from entering or leaking into the inspection object, determining an allowable amount of the specified substance to enter or leak into the inspection object, and through a modeled defect having the path length 2. The method of claim 1, wherein the amount of the specific substance that intrudes or leaks into the object to be inspected is obtained theoretically or experimentally, and the pore diameter threshold value Do is determined based on the pore diameter that reaches the permissible value for the amount of intrusion or the amount of leakage. Defect inspection method described. 3. The defect inspection method according to claim 2, wherein when the difference between the internal pressure of the object to be inspected and the atmospheric pressure is small, the threshold value Do of the hole diameter is obtained from a theoretical equation of diffusion. When there are multiple possible defects to be inspected, determine the pore diameter at which each of the modeled defects with different path lengths reaches the same amount of penetration or leakage; 2. A defect having the smallest pressure change or the smallest amount of leakage is selected as a specific defect in the inspection process, and a hole diameter threshold Do used in the inspection process is set as a hole diameter threshold for the specific defect. Or the defect inspection method according to 3. a test pressure source, an inspection path having an end to which an inspection object is connected and supplying the test pressure from the test pressure source to the inspection object, a first valve provided in the inspection path, and the first valve a pressure measuring means connected to the inspection path between the first valve and the terminal; a pseudo leak path connected to the inspection path between the first valve and the terminal and continuing to the outside; and a pseudo leak path provided in the pseudo leak path. and a reference leaker having a reference leak hole and a second valve provided between the inspection path and the reference leaker in the pseudo leak path,
The reference leak hole has a length corresponding to a passage length determined by modeling a defect assumed to be inspected as a straight tube defect having a circular cross section, and has a known diameter. The amount of gas leaking through the reference leak hole under the conditions of the test pressure and the external air pressure is obtained as a reference leakage amount Qs under specified conditions,
Under inspection conditions, after supplying a test pressure in a state in which a non-defective product having the same volume as the inspection object and having no leakage is connected to the inspection path, the first valve is closed and the second valve is opened, whereby the reference leakage is detected. A pseudo leak is generated through a device, and a reference leak amount Qr under inspection conditions is obtained based on the pressure change in the inspection path measured by the pressure measuring means at this time,
Under the inspection conditions, the test path is measured by the pressure measuring means while the first valve and the second valve are closed after a test pressure is supplied to the inspection path while the object to be inspected is connected to the inspection path. Based on the pressure change in
Based on the reference leakage amount Qs under the specified conditions and the reference leakage amount Qr under the inspection conditions, the leakage amount Qm to be inspected under the inspection conditions is converted to the converted leakage amount Qx to be inspected under the specified conditions. converted to
Further, calculating the hole diameter Dx of the defect to be inspected based on the converted leakage amount Qx and at least information on the test pressure and the external air pressure under the specified conditions,
A defect inspection method comprising the step of comparing the calculated hole diameter Dx with a threshold value Do of the hole diameter of a modeled defect to determine whether an object to be inspected is pass/fail. 6. The defect inspection method according to claim 5, wherein the hole diameter Dx is calculated by adding information on the length of the reference leak hole and the ambient temperature under the specified condition. a test pressure source, an inspection path having an end to which an inspection object is connected and supplying the test pressure from the test pressure source to the inspection object, a first valve provided in the inspection path, and the first valve In a defect inspection method using a leak inspection device comprising pressure measuring means connected to the inspection path between the end and an air pressure sensor for measuring external air pressure,
Prior to the inspection process, model the assumed defect to be inspected as a straight tubular passage with a circular cross section, determine the passage length of this modeled defect, and determine the threshold Do of the hole diameter,
In the inspection process,
After supplying the test pressure with the test object connected to the test path, the leakage amount of the test object is measured based on the pressure change in the test path measured by the pressure measuring means while the first valve is closed. Find Qm,
calculating a defect pore diameter Dx based on information on the leak amount Qm and at least the test pressure and the external air pressure from the air pressure sensor;
A defect inspection method, comprising: comparing the calculated hole diameter Dx with a hole diameter threshold value Do to determine whether or not an object to be inspected is acceptable. The leak test device further comprises a temperature sensor for detecting ambient temperature,
8. The defect inspection method according to claim 7, wherein the hole diameter Dx is calculated by adding the path length of the modeled defect and ambient temperature information from the temperature sensor. The leak test device further includes a pseudo leak path connected to the test path between the first valve and the terminal end and continuing to the outside, a reference leaker provided in the pseudo leak path and having a reference leak hole, a second valve provided between the test path and the reference leaker in the pseudo leak path;
the reference leak has a length equal to the path length of the modeled defect and a known diameter;
Prior to the inspection of the inspection target, after supplying a test pressure in a state in which a non-defective product having the same volume as the inspection target and having no leakage is connected to the inspection path, the first valve is closed and the second valve is opened, Pseudo-leakage is generated through the reference leaker, and based on the pressure change in the test path measured by the pressure measuring means at this time, an actually measured reference leak amount under test conditions is obtained;
calculating a theoretical reference leak rate based on the length and diameter of the reference leak hole, the test pressure, the external air pressure from the air pressure sensor, and the ambient temperature information from the temperature sensor;
9. The defect inspection method according to claim 8, further comprising calibrating an output value of the leak amount from the leak inspection device so that the actually measured reference leak amount matches the theoretical reference leak amount.

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