Method for measuring the sensitivity of an air leak test device for detecting large leaks.

Abstract

To measure large leak detection sensitivity of an air leak test device simply at low cost.SOLUTION: An air leak test device acquires, based on a first detection pressure P1 of a pressure sensor 10 in a large leak detection process when a work capsule 20 accommodates an inspection object 100A with no leaks and a loading member 25, a second detection pressure of the pressure sensor 10 in the large leak detection process when the work capsule 20 accommodates only the inspection object 100A with no leaks, and an external volume V of the loading member 25, large leak detection sensitivity S of an air leak test device from the following formula: S=V / (P2-P1).SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for measuring the sensitivity when detecting a large leak in an inspection target in an air leak test device.

Background Art

[0002] As a device for evaluating the airtightness of a hollow product (inspection target), an air leak test device that applies a test pressure to the inspection target is known. Taking the case where the test pressure is a positive pressure as an example, if there is a defect such as a minute pinhole in the inspection target, compressed air gradually enters the inspection target little by little over time. Hereinafter, this is referred to as a minute leak. If there is a relatively large defect in the inspection target, compressed air enters the inspection target instantaneously or within a short period of time. Hereinafter, this is referred to as a large leak. In a general air leak test device, it is possible to detect both minute leaks and large leaks in the inspection target.

[0003] The air leak test device disclosed in Patent Document 1 will be described as an example. This air leak test device includes a test pressure source, a common passage portion connected to this test pressure source, two branch passage portions connected to the downstream end of this common passage portion, work capsules and master capsules respectively connected to the downstream ends of these two branch passage portions, first valves provided in the two branch passage portions respectively, tanks with a predetermined volume connected via auxiliary passage portions on the downstream side of the first valves in the two branch passages, second valves provided in these auxiliary passage portions, and a differential pressure sensor (pressure sensor) for detecting the difference in pressure between the pressure in the work capsule and the pressure in the master capsule.

[0004] In the air leak test apparatus described above, the object to be inspected is sealed in the work capsule, and the master component (the object to be inspected, whose absence of leaks has been confirmed) is sealed in the master capsule. Test pressure is supplied to both capsules, and the branch passage is blocked by the first valve, thereby closing both capsules with the test pressure. If there is a minute defect in the object to be inspected, the air at the test pressure in the work capsule leaks out in minute amounts into the internal space of the object to be inspected, causing the pressure inside the work capsule to decrease over time. If the differential pressure (pressure change in the work capsule) detected by the differential pressure sensor exceeds a threshold, it is determined that there is a minute leak. After this minute leak detection process, a major leak detection process is performed. That is, by opening the second valve, both capsules are connected to their respective tanks. As a result, the test pressure in both capsules is divided and supplied to their respective tanks. If there is a major defect in the object to be inspected, the internal space of the object to be inspected is at the test pressure when the test pressure is supplied, so a pressure difference is created between the two capsules due to the pressure division to the tanks. If the differential pressure detected by the differential pressure sensor exceeds a threshold, it is determined that there is a major leak.

[0005] The air leak test apparatus described above performs leak testing on objects of various sizes and shapes. The size and shape of the work capsule and master capsule also change depending on the object being tested, and it is necessary to measure the detection sensitivity for large leaks each time. Conventionally, the detection sensitivity for large leaks has been measured as follows: A volume converter is connected to the branch passage on the work capsule side. Objects that do not leak are sealed inside the work capsule and master capsule, respectively. With the volume of the volume converter set to, for example, zero, the large leak detection process described above is performed, and the first detection pressure is obtained by the differential pressure sensor. Next, with the volume converter increased to a predetermined volume, the large leak detection process described above is performed, and the second detection pressure is obtained by the differential pressure sensor. Then, the detection sensitivity for large leaks is measured based on the difference between these first and second detection pressures and the increase in the volume of the volume converter. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2003-149076 [Overview of the project] [Problems that the invention aims to solve]

[0007] The volume increase from a volume converter does not need to be exactly the same as the internal volume of the object being inspected, but it should be able to match it to some extent. Therefore, if the internal volume of the object being inspected differs significantly, one type of volume converter will not suffice, and it will be necessary to prepare multiple volume converters of different sizes, which increases costs. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides an air leak test apparatus comprising: a test pressure source; a work capsule that seals a hollow object to be inspected; a passage connecting the test pressure source and the work capsule; a first valve provided in the passage for opening and closing the passage; a pressure sensor for detecting the pressure inside the work capsule; an auxiliary passage section connected between the first valve and the work capsule in the passage; a tank of a predetermined volume connected to the auxiliary passage section; a second valve provided in the auxiliary passage section for opening and closing the connection between the tank and the passage; and a control calculation means, wherein the control calculation means executes an air leak test process including a major leak detection step, and in this major leak detection step, by opening the second valve with the first valve closed, the test pressure inside the work capsule is divided into the tank or the test pressure inside the tank is divided into the work capsule, and at this time, the pressure detected by the pressure sensor determines whether or not there is a defect that would cause a major leak in the object to be inspected. The method is characterized in that a large leak detection sensitivity measurement step is performed using one or more loading members, and in this large leak detection sensitivity measurement step, the large leak detection sensitivity of the air leak test device is measured based on the first detection pressure of the pressure sensor in the large leak detection step when the work capsule contains an object for inspection that does not leak and all of the one or more loading members, the second detection pressure of the pressure sensor in the large leak detection step when the work capsule contains an object for inspection that does not leak and at least one of the one or more loading members is removed from the work capsule, and the external volume of the removed at least one loading member.

[0009] According to the above method, the sensitivity for detecting large leaks can be easily measured using a loading component in the work capsule. Furthermore, it can handle inspection targets of different sizes at a low cost.

[0010] Preferably, in the air leak test step, the control calculation means executes a minute leak detection step before or after the major leak detection step, in which the first valve and the second valve are closed and the time change of the test pressure inside the work capsule is detected by the pressure sensor or other pressure sensor, and it is determined whether or not there is a minute defect in the object to be inspected based on the detected pressure change, and in the air leak test step including the major leak detection step and the minute leak detection step, all of the one or more loading members are housed in the work capsule. This method allows the actual volume of the work capsule (the volume filled by the test pressure) to be reduced compared to when no loading material is present, and in particular, it is possible to maintain the accuracy of detecting minute leaks.

[0011] In one embodiment, there is one loading member, and in the large leak detection sensitivity measurement step, the first detection pressure is obtained when the work capsule contains the inspection object without leaks and the loading member, and the second detection pressure is obtained when the work capsule contains only the inspection object without leaks. This method allows for even simpler measurement of high-leakage detection sensitivity.

[0012] In another embodiment, there are multiple mounting members, and in the large leak detection sensitivity measurement step, the first detection pressure is obtained when the work capsule contains the inspection object without leaks and the multiple loading members, and the second detection pressure is obtained when the work capsule contains only the inspection object without leaks. This method allows for an increase in the total external volume of spacers used to measure the large leak detection sensitivity when multiple spacers are used, thereby improving the measurement accuracy of the large leak detection sensitivity.

[0013] Preferably, one or more housing recesses are formed on the inner surface of the work capsule, and one or more loading members are detachably housed in these one or more housing recesses. This method allows the loading components to be stably housed in the work capsule.

[0014] Preferably, the work capsule has a housing space formed in a shape corresponding to the external shape of the object to be inspected, and one or more spacers are detachably housed in this housing space to reduce the actual volume between the inner surface of the housing space and the outer surface of the object to be inspected, and the one or more spacers are provided as the one or more loading members. This method allows for the measurement of large leak detection sensitivity using spacers designed to improve the accuracy of the minute leak detection process. [Effects of the Invention]

[0015] According to the present invention, the sensitivity for detecting large leaks can be measured easily and at low cost in accordance with the size of the object being inspected. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram of an air leak test apparatus to which the method of the present invention is applied. [Figure 2] This is a cross-sectional view of a work capsule according to one embodiment used in the above-described air leak test apparatus, showing the state when a normal air leak test process is performed. [Figure 3] It is a cross-sectional view of the master capsule used in the air leak test device. [Figure 4] It is a cross-sectional view of the work capsule when performing the process of measuring the large leak detection sensitivity. (A) shows the state when performing the large leak detection process to obtain the first detection pressure, and (b) shows the state when performing the large leak detection process to obtain the second detection pressure. [Figure 5] It is a plan view showing the capsule body of the work capsule according to another embodiment.

Mode for Carrying Out the Invention

[0017] Hereinafter, a first embodiment of the method of the present invention will be described while referring to the drawings. <Configuration of the Air Leak Test Device> First, an air leak test device to which the method of the present invention is applied will be described while referring to FIG. 1. The basic configuration of this air leak test device is known. The air leak test device includes a pressure source 1 and a passage 2. The pressure source 1 in this embodiment is a pressurized (positive pressure) air source, but it may also be a negative pressure. In addition, regardless of positive pressure or negative pressure, the pressure source 1 side of the passage 2 is referred to as the upstream.

[0018] The passage 2 includes a common passage portion 2x whose upstream end is connected to the pressure source 1, and two branch passage portions 2a and 2b respectively connected to the downstream end of the common passage portion 2x. A regulator 3 and a three-way valve 4 on the downstream side thereof are provided in the common passage portion 2x. The regulator 3 maintains the pressure from the pressure source 1 at a set test pressure. Therefore, the pressure source 1 and the regulator 3 constitute a test pressure source 5. The three-way valve 4 supplies the test pressure from the test pressure source 5 to the branch passage portions 2a and 2b at the start of the leak test, and opens the branch passage portions 2a and 2b to the atmosphere at the end of the leak test.

[0019] The branch passage portions 2a and 2b are respectively provided with first valves 6a and 6b. Auxiliary passage portions 7a and 7b are respectively connected to the downstream sides of the first valves 6a and 6b in the branch passage portions 2a and 2b. Second valves 8a and 8b are respectively provided in the auxiliary passage portions 7a and 7b, and tanks 9a and 9b with a predetermined volume are connected to the tips thereof.

[0020] A work capsule 20 is connected to the downstream end of the branch passage portion 2a, and a master capsule 30 is connected to the downstream end of the branch passage portion 2b. Two ports of a differential pressure sensor 10 (pressure sensor) are respectively connected to the downstream sides of the first valves 6a and 6b in the branch passage portions 2a and 2b, whereby the differential pressure between the branch passage portions 2a and 2b, and thus the differential pressure between the work capsule 20 and the master capsule 30 can be detected.

[0021] The work capsule 20 is composed of two openable and closable capsule constituent members. For example, as shown in FIG. 2, it includes a capsule main body 21 in the shape of a container with an upper end opening for accommodating the inspection object 100, and a lid 22. The capsule main body 21 is movable between the loading / unloading position shown by the dashed line in FIG. 2 and the inspection position below the lid 22 shown by the solid line. When the capsule main body 21 is in the inspection position, the capsule main body 21 and the lid 22 are clamped by a clamping mechanism so as to seal the inspection object 100 in its accommodation space 23.

[0022] Although FIG. 2 schematically shows the work capsule 20, the accommodation space 23 of the work capsule 20 has a shape and size corresponding to the inspection object 100, and is designed so as to minimize the actual volume of the accommodation space 23 obtained by subtracting the outer volume of the inspection object 100 from the internal volume of the accommodation space 23 as much as possible.

[0023] A storage recess 24 is formed on the inner surface of the capsule body 21 of the work capsule 20, for example, on the bottom surface on which the object to be inspected 100 is placed. A loading member 25, which is approximately the same shape and size as the storage recess 24, is detachably loaded into this storage recess 24. The external volume of this loading member 25 does not need to be equal to the internal volume of the object to be inspected 100, but it is preferable that it be a size commensurate with the internal volume, for example, 50 to 200% of the internal volume.

[0024] As shown in Figure 3, the master capsule 30 also has a capsule body 31, lid 32, and storage space 33 of the same shape and size as the work capsule 20, and seals the inspection target which has been confirmed to be leak-free as the master member M. In this embodiment, the master capsule 30 also has a storage recess 34 of the same shape and size as the work capsule 20, and the loading member 35 is loaded into this storage recess 34. This loading member 35 remains loaded in the storage recess 34 during the normal air leak test process and the large leak detection sensitivity measurement process described later. Note that the storage recess 34 and the loading member 35 may be omitted from the master capsule 30.

[0025] The valves 4, 6a, 6b, 8a, and 8b are sequence-controlled by the controller 50 (see Figure 1; control calculation means). The controller 50 also opens and closes the work capsule 20 and determines whether the detection target 100 is good or bad (determines whether there is a leak) based on the differential pressure detected by the differential pressure sensor 10.

[0026] <Standard air leak test procedure> The following describes the standard air leak test procedure. When this procedure is performed, the loading member 25 is loaded into the housing recess 24 of the work capsule 20. The air leak test procedure includes a minute leak detection procedure and a major leak detection procedure.

[0027] First, the work capsule 20 containing the object to be inspected 100 is closed as described above, sealing the object to be inspected 100. Next, by turning on the three-way valve 4, the test pressure from the test pressure source 5 is supplied to the work capsule 20 and the master capsule 30 via the branch passages 2a and 2b. Then, the first valves 6a and 6b are closed, isolating and closing the downstream branch passages 2a and 2b from each other.

[0028] Next, a minute leak detection process is performed. Specifically, the differential pressure detected by the differential pressure sensor 10 after a predetermined time has elapsed since closing valves 6a and 6b is compared with a first threshold. If there is a minute defect such as a pinhole in the object to be inspected 100, pressurized air in the work capsule 20 enters the internal space of the object to be inspected 100 in minute amounts, and the pressure in the work capsule 20 gradually decreases from the test pressure. On the other hand, the test pressure is maintained in the master capsule 30. As a result, a difference is created between the pressure in the work capsule 20 and the pressure in the master capsule 30. This differential pressure (pressure change in the work capsule 20) is detected by the differential pressure sensor 10. If the detected differential pressure exceeds the first threshold, it is determined that there is a minute leak, and if the detected differential pressure does not exceed the first threshold, it is determined that there is no minute leak in the object to be inspected 100. Since the loading member 25 is housed in the housing recess 24 of the work capsule 20, the actual volume of the work capsule 20 (the volume filled by the test pressure) can be made smaller than when the loading member 25 is not housed in the housing recess 24, thereby maintaining the accuracy of minute leak detection.

[0029] Next, the large leak detection process is performed. If there is a large defect in the object under inspection 100, the pressurized air of the test pressure will enter the internal space of the object under inspection 100 through the pinhole (large leak) almost simultaneously with the supply of the test pressure, and therefore the small leak detection process described above will not be able to detect the leak.

[0030] In the major leak detection process, with the first valves 6a and 6b closed, the second valves 8a and 8b are opened, connecting tanks 9a and 9b to branch passages 2a and 2b, respectively. Since tanks 9a and 9b are at atmospheric pressure, for example, the test pressure inside the work capsule 20 and master capsule 30 escapes to tanks 9a and 9b, resulting in a pressure division. If there is a major leak, the pressure in branch passage 2a and work capsule 20 is higher than the pressure in branch passage 2b and master capsule 30 by the amount of pressurized air in the internal space of the object under inspection 100. This differential pressure is compared with a second threshold by the differential pressure sensor 10. If it exceeds the second threshold, it is determined that there is a major leak in the object under inspection 100; otherwise, it is determined that there is no major leak.

[0031] <Large Leak Detection Sensitivity Measurement Process> Next, the detection sensitivity measurement step for large leaks, which is the core part of the present invention, will be described. In this step, the large leak detection step in a normal air leak test is performed under two different conditions. Note that, as with a normal air leak test method, the large leak detection step may be performed after the minute leak detection step, or the minute leak detection step may be omitted and only the large leak detection step may be performed.

[0032] <Major leak detection process in the first scenario> As shown in Figure 4(A), in the first scenario, with the loading member 25 loaded into the housing recess 24 of the work capsule 20, the detection target 100A (substantially the same as the master member M), which has been confirmed to be free of leaks, is sealed, and the major leak detection process is performed to obtain the detected differential pressure (first detection pressure P1) of the differential pressure sensor 10. Incidentally, in this embodiment, the first detection pressure is expected to be zero or close to zero.

[0033] <Second scenario: Major leak detection process> As shown in Figure 4(B), in the second situation, with the loading member 25 removed from the housing recess 24 of the work capsule 20, only the detection target 100A, which has been confirmed to be free of leaks, is sealed in the housing space 23, and the major leak detection process is performed to obtain the detected differential pressure (second detection pressure P2) of the differential pressure sensor 10.

[0034] From the first detection pressure P1 (kPa), the second detection pressure P2 (kPa), and the external volume V (mL) of the loading member 25 obtained as described above, the sensitivity S (mL / kPa) for detecting large leaks can be determined by the following formula. S = V / (P2 - P1) ... (1)

[0035] As described above, by loading and unloading the loading member 25 into and out of the work capsule 20, the first and second detection pressures can be obtained, and the large leak detection sensitivity can be easily measured.

[0036] When performing leak tests on inspection targets 100 of different shapes and sizes, work capsules 20 and master capsules 30 of shapes and sizes corresponding to the inspection targets 100 are used. If the internal volume of the inspection target 100 changes significantly, the size of the housing recess 24 and loading member 25 of the work capsule 20 are also changed according to the internal volume of the inspection target 100. In this way, even if the internal volume of the detection target 100 changes significantly, the detection sensitivity for large leaks can be measured simply by changing the loading member 25, and this can be handled at a lower cost compared to changing the volume changer as in the conventional method.

[0037] Figure 5 shows another embodiment. In Figure 5, components corresponding to the previously described embodiment are numbered accordingly. The storage space 23 of the capsule body 21 of the work capsule 20 has an inner surface shape corresponding to the shape of the object to be inspected 100. A spacer 26 is housed between the inner surface of this storage space 23 and the outer surface of the object to be inspected 100 to reduce the volume between them. This spacer 26 is manufactured with high precision and contacts the inner surface of the storage space 23, reducing the gap 27 between the spacer 26 and the outer surface of the object to be inspected 100 as much as possible. An annular sealing material 29 is provided on the upper surface of the capsule body 21 to seal the gap between it and the lid 22 (not shown in Figure 5), surrounding the storage space 23.

[0038] With the spacer 26 installed in the containment space 23, an air leak test process including a minute leak detection process and a major leak detection process is performed. Because the actual volume of the work capsule 20 is small, minute leaks can be detected with high accuracy.

[0039] In the large leak detection sensitivity measurement process, the large leak detection process is performed with the inspection target 100A (not shown in Figure 5) that does not leak and the spacer 26 housed in the housing space 23 of the work capsule 21, thereby obtaining the first detection pressure, similar to the embodiment described above. Then, the large leak detection process is performed with the spacer 26 removed and only the inspection target 100A that does not leak housed in the housing space 23 of the work capsule 21, thereby obtaining the second detection pressure. The large leak detection sensitivity is then measured based on the outer volume of the spacer 26 and the first and second detection pressures. As is clear from this explanation, the spacer 26 in this embodiment plays the role of a loading member for measuring the large leak detection sensitivity.

[0040] The present invention is not limited to the embodiments described above, and various modifications can be made without departing from its spirit. Although not illustrated as it is easily understood, there may be multiple loading members. If a housing recess is formed on the inner surface of the work capsule, multiple housing recesses will be formed according to the number of loading members. The spacer may be divided into multiple parts for each part to be inspected. When there are multiple loading members, it is preferable to house all loading members in the work capsule along with the inspection target that does not leak when obtaining the first detection pressure, and then to remove all of the multiple loading members and house only the inspection target that does not leak when obtaining the second detection pressure. This allows for a larger total external volume of the spacer for measuring the large leak detection sensitivity (see external volume V in equation (1) above), thereby improving the measurement accuracy of the large leak detection sensitivity. However, when detecting the second detection pressure, some of the multiple loading members may be removed from the work capsule, and the rest may be housed in the work capsule. The same applies when there are multiple spacers.

[0041] In a normal air leak test process, the major leak detection process may be performed before the minor leak detection process. In the major leak detection process, the test pressure in the tank may be released into a work capsule at atmospheric pressure, for example, by supplying test pressure to the tank in advance, closing the second valve, and then opening the second valve while the first valve upstream of the tank is closed. In this case, an absolute pressure sensor different from the differential pressure sensor used in the minor leak detection process may be installed in the passage downstream of the first valve, and the detection pressure of this absolute pressure sensor may be used to detect a major leak in the major leak detection process. The volume of the master capsule may differ from the volume of the work capsule, and the master component does not need to be housed in the master capsule. The master capsule and the branching passage to the master capsule may also be omitted. Instead of using a differential pressure sensor, the presence or absence of a major leak may be determined based on the pressure detected by an absolute pressure sensor. The test pressure may be a negative pressure close to a vacuum, rather than a positive pressure. [Industrial applicability]

[0042] The present invention can be applied to a method for measuring the detection sensitivity of large leaks in an air leak test device. [Explanation of symbols]

[0043] 2 aisles 5 Test pressure sources 6a First valve 7a Auxiliary passage section 8a Second valve 9a Tank 10. Differential pressure sensor (pressure sensor) 20 Work Capsules 23 Containment space 24 Receiving recess 25 Loading member 26 Spacer (mounting component) 50 Controller (control calculation means) 100 subjects for testing 100A Leak-free test subject

Claims

1. The system comprises a test pressure source, a work capsule that seals a hollow object to be inspected, a passage connecting the test pressure source and the work capsule, a first valve provided in the passage for opening and closing the passage, a pressure sensor for detecting the pressure inside the work capsule, an auxiliary passage section connected between the first valve and the work capsule in the passage, a tank of a predetermined volume connected to the auxiliary passage section, a second valve provided in the auxiliary passage section for opening and closing the connection between the tank and the passage, and control calculation means. In an air leak test apparatus in which the control calculation means performs an air leak test process including a major leak detection process, and in this major leak detection process, by opening the second valve while the first valve is closed, the test pressure in the work capsule is divided and transferred to the tank, or the test pressure in the tank is divided and transferred to the work capsule, and at this time the pressure detected by the pressure sensor determines whether or not there is a defect that would cause a major leak in the object under inspection, The large leak detection sensitivity measurement process is performed using one or more loading members, and in this large leak detection sensitivity measurement process, The first detected pressure of the pressure sensor in the major leak detection step is determined when the work capsule contains the inspection target which has no leaks and all of the one or more loading members. The second detection pressure of the pressure sensor in the major leak detection step is determined when the work capsule contains an object to be inspected that does not leak and at least one of the one or more loading members is removed from the work capsule. A method for measuring the large leak detection sensitivity of an air leak test device based on the difference between the first detection pressure and the second detection pressure and the outer volume of the excluded at least one loading member.

2. The control calculation means, in the air leak test process, executes a minute leak detection process before or after the major leak detection process, and in this minute leak detection process, with the first valve and the second valve closed, detects the time change of the test pressure inside the work capsule with the pressure sensor or other pressure sensors, and determines whether or not there is a minute defect in the object being inspected based on the detected pressure change. The method according to claim 1, characterized in that, in the air leak test step including the large leak detection step and the small leak detection step, all of the one or more loading members are housed in the work capsule.

3. The method according to claim 1, wherein there is one loading member, and in the large leak detection sensitivity measurement step, the first detection pressure is obtained when the work capsule contains the inspection object without leaks and the loading member, and the second detection pressure is obtained when the work capsule contains only the inspection object without leaks.

4. The method according to claim 1, characterized in that there are multiple loading members, and in the large leak detection sensitivity measurement step, the first detection pressure is obtained when the work capsule contains the inspection object without leaks and the multiple loading members, and the second detection pressure is obtained when the work capsule contains only the inspection object without leaks.

5. The method according to claim 1, characterized in that one or more housing recesses are formed on the bottom surface of the work capsule, and one or more loading members are detachably housed in one or more of these housing recesses.

6. The method according to claim 1, characterized in that the work capsule has a housing space formed in a shape corresponding to the external shape of the object to be inspected, and one or more spacers are detachably housed in this housing space to reduce the actual volume between the inner surface of the housing space and the outer surface of the object to be inspected, and the one or more spacers are provided as one or more loading members.

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