Leak inspection method for sealed container having narrow opening and leak inspection apparatus for performing the same

Abstract

To provide a leakage inspection method and a leakage inspection device capable of accurately detecting a leakage flow rate of an exploration gas leaking from the inside of a sealed container in a short time, in a vacuum covering method for performing leakage inspection by evacuating the inside of the sealed container having a narrow opening and replacing and pressurizing the outside thereof with the exploration gas.SOLUTION: In a narrow part 12 consisting of the 10a of the narrow end part of a body 10 to be tested and a seal jig 11, a roughing valve 2a is first opened, and the internal pressure on the upstream side and the downstream side of the narrow part 12 is rough-evacuated to a low vacuum of less than 1 / 10 of the atmosphere. Next, the roughing valves 2a are closed and the tank valves 3a are opened, and the downstream side of the narrow part 12 is evacuated by the vacuum tank 50 while expanding the exhaust gas so that the internal pressure on the downstream side of the narrow part 12 becomes a medium vacuum or less, which is less than 1 / 1000 of the atmosphere pressure, while maintaining the internal pressure on the upstream side of the narrow part 12 at a low vacuum.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a leak inspection method and a leak inspection device that can accurately detect the leak flow rate of a probe gas leaking from inside a sealed container in a short time in a vacuum outer jacket method in which a leak inspection is performed by creating a vacuum inside a sealed container with a narrow opening and replacing and pressurizing the outside with a probe gas. [Background technology]

[0002] Vacuum insulated products with relatively narrow openings, vacuum sealed products such as electron tubes, packages for electronic devices, and various containers such as liquid crystal cells and battery cells require leak testing from the outside to the inside of the product under atmospheric pressure.

[0003] Generally, leak tests for vacuum-sealed products and various containers (hereinafter also referred to as "sealed containers") are performed using the so-called immersion method. The "immersion method" is a leak test method in which, after sealing, the test object is placed in a pressurized tank and left pressurized with a probe gas for a certain period of time, then removed and the outside of the test object is evacuated to a vacuum in a vacuum chamber to detect the probe gas leaking from the test object. However, the immersion method has the disadvantage that it is difficult to detect leaks because the leak flow rate detection range is narrow. For this reason, a separate leak test before sealing is required. A leak test before sealing is performed as follows.

[0004] Figure 11 is an explanatory diagram of a conventional leak testing system for pre-sealing leak testing. The detection gas is helium. First, (1) the roughing valve is opened, and the inside of the test specimen and the first and second pipes are evacuated using a vacuum pump. At this time, the inside of the test specimen outer container is also evacuated via the vacuum pumping line. Next, (2) when the vacuum gauge reaches a desired pressure (e.g., 50 Pa) or below, the roughing valve is closed, the test valve is opened, and the detection gas detector (He leak detector) begins detecting leak signals. Since no detection gas is being introduced at this time, a leak-free measurement is obtained. Then, (3) the evacuation of the test specimen outer container is stopped, and the detection gas (helium gas) is introduced under pressure through the detection gas pressure line. If a leak is present, the helium gas will be detected by the He leak detector. This leak testing method, in which the inside of the test specimen is evacuated and the outside is replaced and pressurized with the detection gas (helium gas), is called the vacuum outer container method. In addition, leak detection using helium gas as the detection gas has been established as a helium leak detection method and is widely used.

[0005] Generally, leak testing for vacuum sealed products and various containers requires 10 -10 ~10 -4 Pa·m 3 The detection of minute leak flow rates of 1 / s is required. Therefore, the internal pressure of the test object must be approximately 100 Pa, and the inlet pressure of the He leak detector must be less than several tens of Pa. Meanwhile, the openings of vacuum-sealed products and various containers are often narrow, ranging from several hundred microns to several millimeters. For this reason, the conventional leak testing system shown in Figure 11 requires a perforated sealing jig with a sealing hole (narrow hole) and piping with a diameter of several hundred microns to several millimeters. In other words, because the test object has a narrow opening, the sealing jig has a narrow hole, and the first piping connected to it is relatively thin and long, it is difficult to evacuate the inside of the test object. As a result, it can take as long as 50 to 100 seconds to reach the target vacuum level (approximately 100 Pa) inside the test object.

[0006] Possible means for shortening the evacuation time include using multiple vacuum pumps to reduce the ultimate pressure or using a vacuum tank for high-speed evacuation, both of which have already been disclosed as prior art. Japanese Patent Application Publication No. 2007-40769 (JP 2007-40769A) relates to leak testing using a cavity-equipped package as a test object, and discloses the use of multiple high-vacuum pumps as a means for evacuating the pressure of the device including the test object to a testable pressure. Here, a "high-vacuum pump" refers to a vacuum pump capable of evacuating to a high vacuum of 0.1 Pa or less at an operating pressure. In the prior art example shown in FIG. 11, a separate low-vacuum pump (not shown) is provided below the first vacuum pump 30. The low-vacuum pump performs rough evacuation from atmospheric pressure to approximately 100 Pa, followed by evacuation to a high vacuum using the first vacuum pump 30. This shortens the evacuation time to 100 Pa or less and enables the pressure to be reduced to several tens of Pa to several Pa.

[0007] Vacuum evacuation using a vacuum tank is used to reduce pulsation caused by a vacuum pump for evacuation to near atmospheric pressure, and for instantaneous evacuation in a few to 10 seconds at a high pumping speed. Instantaneous evacuation in a few to 10 seconds at a high pumping speed using a vacuum tank is disclosed in Japanese Patent Application Laid-Open Nos. 11-230034, 2001-47209, 2006-75850, and 2009-52432. It is obvious that when high-speed evacuation using a vacuum tank is applied to leak testing of test objects having narrow openings, the pressure in the device containing the test object can be further reduced by constantly evacuating the vacuum tank. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-40769 [Patent Document 2] Japanese Patent Application Publication No. 11-230034 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-47209 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-75850 [Patent Document 5] Japanese Patent Application Laid-Open No. 2009-52432 Summary of the Invention [Problem to be solved by the invention]

[0009] As mentioned above, when the test object has a narrow opening, the sealing jig also has a narrow diameter, and the piping connected to it is relatively thin and long (first piping in Figure 11), for example, the conductance from the test object's narrow opening to the various piping becomes small, and the effective pumping speed of the leak testing device becomes small, resulting in the problem that it takes 50 to 100 seconds to vacuum pump down for leak testing of these products.

[0010] In order to increase the effective pumping speed of the leak inspection device, it is possible to increase the pumping speed of the vacuum pump itself, that is, to use the high vacuum pump mentioned above, or to place the vacuum tank mentioned above in the middle of the roughing piping (the second piping in Figure 11) to increase the pumping speed and perform vacuum evacuation.

[0011] However, even if the pump exhaust speed is increased, the inside of the test object is evacuated through a narrow conductance, so the effective exhaust speed of the leak inspection device does not increase that much. Therefore, the means of increasing the pump exhaust speed is not very effective, and it still takes more than 20 seconds to evacuate.

[0012] Incidentally, if the pressure of the test object is set to about 100 Pa after rough evacuation, the pressure difference between this pressure and the inlet pressure (50 Pa) of the He leak detector located downstream will be several tens of Pa. At this time, the conductance of the narrow opening of the test object and the sealing jig becomes very small, so the leak response time from the start of helium gas introduction until the leak flow rate reaches 63% of the constant leak flow rate (the flow rate at which the leak saturates) will be as long as 60 seconds or more. This is about six times longer than the leak response time of 10 to 20 seconds in leak testing of general mass-produced parts. The leak response time is the time required to measure the volume V [m 3] vacuum chamber has an effective pumping speed Se [m 3 / s], and the vacuum chamber is evacuated at Q [Pa m 3 / s], and is defined as the leak response time t = V / Se.

[0013] Additionally, various containers with narrow openings include flexible resin containers (low-rigidity containers) with pouch processing. Such flexible containers are widely used to store gel-like drinks such as jelly or cleaning liquids such as body soap. Flexible containers are also required to have a certain level of airtightness, just like vacuum-sealed components. When leak testing flexible containers such as pouches using the vacuum jacketing method, the test object may be compressed and deformed when the inside of the test object is evacuated or when a probe gas is introduced at high pressure into the test object jacketing container. A method to avoid this must be devised.

[0014] Therefore, the present invention has been made in consideration of the above-mentioned problems of the prior art, and its object is to provide a leak testing method and a leak testing device that can accurately detect the leakage flow rate of a probe gas leaking from the inside of a sealed container in a short time in a vacuum outer jacket method in which a leak test is performed by creating a vacuum inside a sealed container with a narrow mouth and replacing and pressurizing the outside with a probe gas, and to implement the same. [Means for solving the problem]

[0015] The leak detection method according to the present invention for achieving the above object is a leak detection method for detecting the flow rate of the probe gas contained in the exhaust gas by evacuating the inside of the sealed container (10, 10') having an exhaust port (10a) on the surface while creating a low vacuum inside the sealed container (10, 10') and replacing and pressurizing the outside (20) with a probe gas, the leak detection method comprising: a first process (S2, S3, S4) of evacuating the inside of the sealed container (10, 10') to a vacuum in a narrow section (12) formed by the exhaust port (10a) and a sealing jig (11b) that tightly connects the exhaust port (10a) to a vacuum exhaust pipe (1) until the internal pressure on the upstream and downstream sides of the narrow section (12) reaches a low vacuum of less than 1 / 10 of atmospheric pressure; The process further comprises a second process (S5, S6, S7) of evacuating the downstream side of the narrow section (12) by expanding the exhaust gas using a vacuum tank (50) connected to a vacuum pump (40) so that the internal pressure on the upstream side of the narrow section (12) is maintained at a low vacuum of less than 1 / 10 of atmospheric pressure while the internal pressure on the downstream side of the narrow section (12) is at a medium vacuum of less than 1 / 1000 of atmospheric pressure, after the processes (S2, S3, S4). The process further comprises a third process (S10) of evacuating the inside of the sealed container (10, 10') by replacing and pressurizing the outside (20) of the sealed container (10, 10') with a probe gas, thereby evacuating the inside of the sealed container (10, 10'), and detecting the leakage flow rate of the probe gas leaking from the inside of the sealed container (10, 10').

[0016] In the above configuration, the first process (S2, S3, S4) performs rough evacuation so that the internal pressures on both the upstream and downstream sides of the narrow section (12) are low vacuums of several thousand to several hundred Pa (less than 1 / 10 to 1 / 1000 of atmospheric pressure), and then the second process (S5, S6, S7) performs instantaneous evacuation (in a few seconds) at a high pumping speed so that the internal pressure on the upstream side of the narrow section (12) is maintained at a low vacuum, while the internal pressure on the downstream side of the narrow section (12) is reduced to a medium vacuum (less than 1 / 1000 of atmospheric pressure) of several tens of Pa or less. This increases the pressure difference between the upstream and downstream sides of the narrow section (12), thereby increasing the conductance of the narrow section (12). This allows the remaining gas, including the test gas, inside the sealed container to be efficiently transported to the detection gas detector (60), shortening the time it takes for the detection gas detector (60) to detect a leak.

[0017] A second feature of the leak testing method according to the present invention is that when the inside of the sealed container (10, 10') is evacuated while the exhaust gas is expanded by the vacuum tank (50), the evacuation of the vacuum tank (50) by the vacuum pump (40) is stopped at the beginning or during the evacuation.

[0018] In the above configuration, pressure fluctuations due to valve switching are less likely to occur downstream of the narrow section (12).

[0019] A third feature of the leak testing method according to the present invention is that in the first process (S2, S3, S4), the inside of the sealed container (10') is evacuated while the outside (20) of the sealed container (10') is evacuated.

[0020] With the above configuration, the inside of the sealed container (10') can be evacuated while maintaining a small pressure difference between the inside and outside of the sealed container (10'). This makes it possible to shorten the evacuation time and leak detection time during leak testing even for sealed containers (10') made of synthetic resin with low pressure resistance.

[0021] A fourth feature of the leak testing method according to the present invention is that the pipe (3) used in the second process (S5, S6, S7) has a larger inner diameter than the pipe (2) used in the first process (S2, S3, S4).

[0022] In the above configuration, the conductance of the piping (3) is increased, so that the internal pressure downstream of the narrow section (12) can be reduced to below the allowable introduction pressure of the detection gas detector (60) in a short time (a few seconds).

[0023] A fifth feature of the leak detection method according to the present invention is that the molecular flow conductance of the narrow portion (12) is 1×10 in air at a temperature of 20° C. -6 m 3 / s or more.

[0024] In the above configuration, the internal pressure on the upstream and downstream sides of the narrow section (12) is set to a low vacuum in the first process (S2, S3, S4), and the internal pressure on the downstream side of the narrow section (12) can be set to a medium vacuum or less while maintaining a low vacuum on the upstream side of the narrow section (12) in the second process (S5, S6, S7).

[0025] A first feature of the leak test device according to the present invention is that it includes an outer container (20) that houses an airtight container (10, 10') having an exhaust port (10a) on its surface, a first pipe (1) that is inserted into the outer container (20) and transfers gas inside the airtight container (10, 10') to the outside, a sealing jig (11b) that airtightly connects the airtight container (10, 10') and the first pipe (1), a narrow section (12) that is composed of the exhaust port (10a) and the sealing jig (11b) and has a predetermined molecular flow conductance, a vacuum pump (30, 40, 70) that evacuates the inside of the airtight container (10, 10') to a predetermined pressure, and a second pipe (30) that connects the first pipe (1) and the vacuum pump (30). (2), a detection gas detector (60) for detecting the flow rate of detection gas leaking from the inside of the sealed container (10, 10'), and a detection gas detection line (4) connecting the first pipe (1) and the detection gas detector (40), wherein a third pipe (3) separate and independent from the second pipe (2) is connected to the first pipe (1), and the third pipe (3) is provided with a vacuum tank (50) capable of evacuating the internal pressure downstream of the narrowed section (12) to a predetermined pressure while expanding the exhaust gas evacuated from the inside of the sealed container (10, 10'), and the vacuum pump (40) is connected to the exhaust side of the vacuum tank (50).

[0026] With the above configuration, the first feature of the leak inspection method can be suitably implemented.

[0027] A second feature of the leak test device according to the present invention is that a gate valve (3b) is provided between the vacuum tank (50) and the vacuum pump (40).

[0028] With the above configuration, the second feature of the leak inspection method can be suitably implemented.

[0029] The third feature of the leak testing device of the present invention is that downstream of the narrow section (12), a second narrow section (13a) having a predetermined molecular flow conductance and a gate valve (13b) that opens when a leak flow rate of the detection gas is detected are connected in parallel.

[0030] With the above configuration, the third feature of the leak inspection method can be suitably implemented.

[0031] A fourth feature of the leak test device according to the present invention is that the inner diameter of the third pipe (3) is larger than the inner diameter of the second pipe (2).

[0032] With the above configuration, the fourth feature of the leak inspection method can be suitably implemented.

[0033] A fifth feature of the leak test device according to the present invention is that the molecular flow conductance of the narrow portion (12) is 1×10 in air at a temperature of 20° C. -6 m 3 / s or more.

[0034] With the above configuration, the fifth feature of the leak inspection method can be suitably implemented. [Effects of the Invention]

[0035] According to the leak testing method and leak testing device of the present invention, the leak flow rate of the detection gas leaking from the inside of a sealed container can be accurately detected in a short time in a vacuum outer jacket method in which the inside of a sealed container with a narrow mouth is made vacuum and the outside is replaced and pressurized with the detection gas to perform a leak test. [Brief explanation of the drawings]

[0036] [Figure 1] 1 is an explanatory diagram showing the configuration of a main part of a leak test device according to a first embodiment of the present invention; [Figure 2] FIG. 2 is a process diagram showing a leak test process using the leak test device according to the first embodiment of the present invention. [Figure 3] FIG. 3 is an explanatory diagram showing the evacuation time and leak detection time of the leak test device according to the first embodiment of the present invention. [Figure 4]FIG. 4 is an explanatory diagram showing the evacuation time and leak detection time for a large-capacity test object when there is no evacuation by a vacuum tank in the leak test device according to the first embodiment of the present invention. [Figure 5] 4 is an explanatory diagram showing the evacuation time and leak detection time for a large-capacity test device when evacuation is performed by a vacuum tank in the leak test device according to the first embodiment of the present invention. FIG. [Figure 6] FIG. 3 is an explanatory diagram showing the evacuation time and leak detection time for a small-capacity test object when there is no evacuation by a vacuum tank in the leak test device according to the first embodiment of the present invention. [Figure 7] FIG. 4 is an explanatory diagram showing the evacuation time and leak detection time for a small-capacity test device when evacuation is performed by a vacuum tank in the leak test device according to the first embodiment of the present invention. [Figure 8] FIG. 4 is an explanatory diagram showing the configuration of the main parts of a leak test device according to a second embodiment of the present invention. [Figure 9] FIG. 6 is a process diagram showing a leak test process using a leak test device according to a second embodiment of the present invention. [Figure 10] FIG. 10 is an explanatory diagram showing the evacuation time and leak detection time for a low-rigidity test object when a slow evacuation section is provided in the leak test device according to the second embodiment of the present invention. [Figure 11] FIG. 10 is an explanatory diagram showing the configuration of a main part of a conventional leak test device. [Figure 12] 10 is an explanatory diagram showing pressure changes for each conductance of the first pipe and the narrow portion of a conventional leak test device. FIG. [Figure 13] 1 is an explanatory diagram showing the time variations in the internal pressure of a test object and the indicated pressure of a vacuum gauge when the test object is evacuated from atmospheric pressure to a vacuum in a conventional leak test device. FIG. [Figure 14] 10 is an explanatory diagram showing the change in leakage flow rate over time after a test object of a conventional leak test device is evacuated from atmospheric pressure to a predetermined ultimate pressure. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0037] The present invention will now be described with reference to the accompanying drawings.

[0038] (First embodiment) FIG. 1 is an explanatory diagram showing the configuration of the main parts of a leak test device 100 according to a first embodiment of the present invention. This leak testing device 100 is configured to perform accurate leak testing in a short time for a sealed container (test object 10) with a small conductance opening, such as a narrow opening of several hundred μm to several mm, by creating a vacuum inside and filling the outside with a probe gas, evacuating the narrow opening 10a of the test object 10, and detecting the probe gas with a probe gas detector 60. The probe gas used in the leak testing is helium.

[0039] To achieve this, the leak testing device 100 is configured to include an outer container 20 for the test object 10, which can accommodate the test object 10 and can evacuate the outside or pressurize it with a detection gas; a first vacuum pump 30 which roughly evacuates the inside of the test object 10; a second vacuum pump 40 which evacuates the inside of the test object 10 at a high pumping speed; a vacuum tank 50 which is located on the inlet side (suction side) of the second vacuum pump 40 and evacuates the downstream side of the narrow section 12 while expanding the exhaust gas; a detection gas detector 60 which detects the amount of leakage of the detection gas contained in the gas evacuated from the inside of the test object 10; a gas detector vacuum pump 70 which introduces the gas inside the test object 10 into the detection gas detector 60; a detection gas source 80 which stores the detection gas; a vacuum gauge 90 which measures the degree of vacuum downstream from the narrow section 12; and piping and valves which connect these to each other.

[0040] The piping and valves include a first piping 1 connected to the narrowed portion 12 of the test object 10, an atmospheric valve 1a for returning the downstream side of the test object 10 to atmospheric pressure, a sealing jig 11 having a through hole and airtightly connecting the narrowed opening portion 10a of the test object 10 and the first piping 1, a second piping 2 connecting the first piping 1 and the first vacuum pump 30, a roughing valve 2a for blocking or passing the flow of exhaust gas from the inside of the test object 10 sucked by the first vacuum pump 30 through the second piping 2, and a valve 40 connecting the first piping 1 and the second vacuum pump 40. The test fixture 11 has a third pipe 3 for connecting the test object 10 to the third pipe 3, a tank valve 3a for blocking or passing the flow of exhaust gas from the inside of the test object 10 that is sucked through the third pipe 3 by the second vacuum pump 40, a fourth pipe 4 for introducing gas evacuated from the inside of the test object 10 into the detection gas detector 60, a test valve 4a for blocking or passing the flow of exhaust gas introduced into the detection gas detector 60, a pressurization valve 5a for pressurizing the outside of the test object 10 with the detection gas, and an exhaust valve 6a for creating a vacuum on the outside of the test object 10. The sealing jig 11 includes a short pipe 11a.

[0041] FIG. 2 is a process diagram showing a leak test method using the leak test device 100 according to the first embodiment of the present invention. First, in step S1, the test object 10 is set in the test object covering container 20, and all valves are closed.

[0042] Next, in step S2, the roughing valve 2a is opened and the inside of the test object 10 is evacuated by the first vacuum pump 30. This evacuation is rough evacuation (ultimate pressure is low vacuum), and the ultimate pressure is several thousand to several hundred Pa, for example, 1000 Pa.

[0043] Next, in step S3, it is determined whether the pressure indicated by the vacuum gauge 90 has reached a predetermined pressure. If the indicated pressure has reached the predetermined pressure (e.g., 1000 Pa) (YES), step S4 is executed. On the other hand, if the indicated pressure has not reached the predetermined pressure (e.g., 1000 Pa) (NO), step S2 is executed again.

[0044] Next, in step S4, the roughing valve 2a is closed, and roughing evacuation by the first vacuum pump 30 is stopped.

[0045] Next, in step S5, the tank valve 3a is opened, and the inside of the test object 10 is evacuated by the vacuum tank 50. This evacuation is performed at a high pumping speed using the vacuum tank 50, and the ultimate pressure is below a medium vacuum (below several tens of Pa), for example, below 50 Pa.

[0046] Next, in step S6, it is determined whether the pressure indicated by the vacuum gauge 90 has reached a predetermined pressure. If the indicated pressure has reached the predetermined pressure (for example, 50 Pa or less) (YES), step S7 is executed. On the other hand, if the indicated pressure has not reached the predetermined pressure (for example, 50 Pa or less) (NO), step S5 is executed again.

[0047] Next, in step S7, the tank valve 3a is closed, and the evacuation by the vacuum tank 50 is stopped.

[0048] Next, in step S8, the test valve 4a and the exhaust valve 6a are opened to evacuate the outside of the test object 10 to a vacuum.

[0049] Next, in step S9, it is confirmed that the detection gas is not detected by the detection gas detector 60. Because the detection gas has not yet been supplied to the inside of the outer container 20 for the test specimen, the gas evacuated from the inside of the test specimen 10 does not contain the detection gas. Therefore, if the detection gas detector 60 is in a normal state, it will output zero as the leakage flow rate of the detection gas. This zero output indicates that the detection gas detector 60 is normal.

[0050] Next, in step S10, the exhaust valve 6a is closed, the pressurization valve 5a is opened, and the leak is measured while the probe gas is introduced to the outside of the test object 10.

[0051] Next, in step S11, the test valve 4a and the pressurizing valve 5a are closed.

[0052] Next, in step S12, the atmospheric valve 1a is opened, whereby the first pipe 1, the sealing jig 11, and the test object 10 are returned to atmospheric pressure.

[0053] Next, in step S13, when the pressure indicated by the vacuum gauge 90 indicates atmospheric pressure, the atmospheric valve 1a is closed.

[0054] Next, in step S14, the test object 10 is taken out from the outer container 20 for the test object.

[0055] [Theoretical verification of the present invention] The essential components of the leak test apparatus 100 and leak test method of the present invention were theoretically verified. Prior to the theoretical verification of the present invention, the evacuation process and the change in leak flow rate over time of the conventional leak test apparatus shown in Figure 11 were calculated. To carry out this calculation, various parameters of the conventional leak test apparatus were set as follows:

[0056] Internal volume of test piece 10: 1 x 10 -4 m 3 Molecular flow conductance value of narrow section 12: 1.1 × 10 -5 m 3 / s (room temperature, air). Here, the molecular flow conductance value of the narrow portion 12 represents a composite conductance value obtained by combining the molecular flow conductance values ​​of the narrow opening portion 10a of the test object 10 and the sealing jig 11. Molecular flow conductance value of the first pipe 1: 3.0 × 10 -4 m 3 / s (room temperature, air). Molecular flow conductance of second pipe 2: 7.0 × 10 -5 m 3 / s (room temperature, air). Molecular flow conductance of the fourth pipe 4: 7.0 × 10 -5 m 3 / s (room temperature, air). Pumping speed of first vacuum pump 30: 2×10 -3 m 3 / s. Pumping speed at the inlet of the gas detector 60: 5 x 10 -3 m 3 / s.

[0057] (1) Vacuum pumping process and leak detection in conventional leak testing equipment [Gas flow] To understand the vacuum pumping process of conventional leak testing equipment, -1 Pa to 10 of atmospheric pressure 5 The conductance of each of the first pipe 1 and the narrow section 12 in the pressure region of 1.0 Pa was analyzed (calculated). In the calculation, Knudsen's empirical formula, which continuously expresses the conductance from low pressure molecular flow to high pressure viscous flow, was used, and the pressure region was divided into narrow pressure intervals (e.g., 1.00, 1.01, 1.02, 9.99, 10.0).

[0058] FIG. 12 shows the calculation results of the conductance of the first pipe 1 and the narrowed portion 12 with respect to pressure changes. The conductance of the first pipe 1 is 10 -1 Almost constant at around 2×10 Pa -4 m 3 / s, while showing a small value of 10 0 At pressures above 1 Pa, the conductance gradually increases and reaches approximately 2 × 10 1 On the other hand, the conductance of the narrow portion 12, which has a hole diameter and length smaller than those of the first pipe 1, increases linearly at 10 Pa or more. 1 Since gas flows in a molecular flow state up to a high pressure of 1×10 Pa, -5 m 3 / s, and at higher pressures the conductance gradually increases to about 6 × 10 2 The conductance increases linearly above atmospheric pressure. Therefore, when evacuating from atmospheric pressure, it is easier to evacuate the first pipe 1, which has a relatively large conductance, and it is difficult to evacuate the inside of the test object 10, which is connected to the narrow portion 12, which has a relatively small conductance.

[0059] [Vacuum evacuation process] Using the conventional leak inspection device shown in Fig. 11, we analyzed (calculated) the time changes in the indicated pressure of the test object 10 located upstream of the narrowed section 12 and the vacuum gauge 90 located downstream when the test object 10 was evacuated from atmospheric pressure. In the analysis, we calculated the evacuation time t for each pressure section from P1 to P2 [Pa] using the following (Equation 1). (Formula 1):t=[(V / Se)×ln(P1 / P2)]·K, ln is the logarithm with the natural logarithm base e. K is the correction coefficient.

[0060] In the above formula (1), t is the evacuation time when the pressure drops from P1 to P2. V is the volume, and Se is the effective pumping speed. When the pressures P1 and P2 are the internal pressures of the test object 10, V is the internal volume of the test object 10, and Se is the effective pumping speed obtained by combining the narrow section 12, the conductance of the first pipe 1 and the second pipe 2, and the pumping speed of the first vacuum pump 30. On the other hand, when the pressures P1 and P2 are the indicated pressures of the vacuum gauge 90, V is the volume from the test object 10 - narrow section 12 - first pipe 1 - second pipe 2, and Se is the effective pumping speed obtained by combining the conductance of the second pipe 2 and the pumping speed of the first vacuum pump 30. K is a correction coefficient, which is determined based on experience and the influence of water vapor, which is difficult to evacuate because it easily adsorbs to surfaces, and is generally set at 10 5 ~10 3 When Pa, K=1, 10 3 ~10 2 When Pa is used, K is about 1.5, 10 2 ~10 1 When Pa is used, K is set to about 3.

[0061] Figure 13 shows the calculation results of the time change in the pressure indicated by the test object 10 and the vacuum gauge 90 when a conventional leak testing device is evacuated from atmospheric pressure. Because the conductance of the narrow section 12 is small, the internal pressure of the test object 10 changes over time at a high pressure, while because the conductance of the first pipe 1 and the second pipe 2 is large, the pressure indicated by the vacuum gauge 90 changes over time at a low pressure.

[0062] [Leak detection] As shown in Figure 13, in the conventional leak inspection device, the time when the indicated pressure of the vacuum gauge 90 becomes less than 50 Pa is 45 seconds after the start of rough evacuation by the first vacuum pump 30. Therefore, Figure 14 shows the time change in the indicated pressure of the test object 10 and the vacuum gauge 90 when switching to evacuation to the detection gas detector 60 (gas detector vacuum pump 70) 45 seconds after the start of rough evacuation by the first vacuum pump 30, and the calculation results of the time change in leak detection when helium gas, the detection gas, is introduced under pressure to the outside of the test object 10 from 48 seconds later. For the sake of explanation, the leak flow rate of helium gas used for leak detection by the detection gas detector 60 is assumed to be 1 x 10 -5 Pam 3 The effective pumping speed of the test object 10 during leak detection was set to approximately 1×10 -5 m 3 / s, the leakage flow rate of the exploration gas is 1×10 -5 Pam 3 The internal pressure increase in the test object 10 due to the flow rate of the test object 10 is very low, at approximately 1 Pa. This means that most of the gas flowing from the test object 10 upstream of the narrow portion 12 is air remaining in the test object 10.

[0063] The time change in the internal pressure of the test piece 10 was similar to that shown in Figure 13. This is because the effective pumping speed of the test piece 10 depends heavily on the conductance of the narrow section 12. Meanwhile, the time change in the indicated pressure of the vacuum gauge 90 was also similar to that shown in Figure 13. This is because the second pipe 2 for roughing vacuum pumping and the fourth pipe 4 to the detection gas detector 60 have the same diameter and length.

[0064] In the leak detection signal of the probe gas shown in the upper part of Figure 14, the leak response time of 0.63 × leak flow rate was 53 seconds after the start of helium gas introduction. This is because the pressure difference indicated by the test object 10 and the vacuum gauge 90 was small, at 100 to 40 Pa, after 48 seconds when leak detection was being performed, and the effective pumping speed of the test object 10 was 3.3 × 10 -5 ~1.0×10 -5 m 3 / s, and the total volume of the test object 10, the first pipe 1, and the fourth pipe 4 is approximately 1.4 × 10 -3 m 3 As a result of the above, in conventional leak inspection devices, the time from the start of evacuation from atmospheric pressure to the end of leak detection (0.63 × detection of leak flow rate) was a long 101 seconds.

[0065] From the theoretical verification of the above-mentioned conventional leak testing device, it became clear that the reason why the leak test for the test object 10 having the narrow opening 10a takes so long is that the test object 10 is evacuated for more than several tens of seconds (45 seconds in the conventional leak testing device) to reduce the inlet pressure of the detection gas detector 60 to below the allowable introduction pressure of several tens of Pa (e.g., 50 Pa), and this long evacuation also reduces the internal pressure of the test object 10, reducing the conductance of the narrow opening 12 and lengthening the leak response time (53 seconds in the conventional leak testing device). Furthermore, when the test object 10 is evacuated for more than several tens of seconds, the internal pressure of the test object 10 reaches approximately 100 Pa in the conventional leak testing device, and the pressure fluctuates by several tens of percent due to the effect of adsorption of water vapor in the air, which may lead to erroneous leak test results.

[0066] (2) Vacuum evacuation process and leak detection of the leak inspection device 100 of the present invention The leak test device 100 of the present invention is configured to perform evacuation at a high pumping speed for several seconds using a vacuum tank 50 to evacuate the internal pressures upstream and downstream of the narrow portion 12 to several thousand to several hundred Pa (low vacuum), and then evacuate the internal pressure downstream of the narrow portion 12 to several tens of Pa (medium vacuum) while maintaining the internal pressure upstream of the narrow portion 12 at a low vacuum. This not only makes it possible to reach the pressure indicated by the vacuum gauge 90 below the allowable introduction pressure (several tens of Pa) in a short time of several seconds, but also makes it possible to raise the internal pressure of the test object 10 to a high pressure of several thousand to several hundred Pa. This increases the conductance of the narrow opening 10a of the test object 10 and the hole in the sealing jig 11 (conductance of the narrow portion 12), and also increases the pressure difference between the internal pressure of the test object 10 (upstream of the narrow portion 12) and the pressure indicated by the vacuum gauge 90 (downstream of the narrow portion 12). This allows the detection gas (helium gas) mixed in the residual gas in the test object 10 to be effectively guided to the detection gas detector 60, thereby achieving a short leak response time. 2 Pa, 10 4 When the pressure is 100MPa (Pa), the air component gases (nitrogen and oxygen) are dominant and the influence of water vapor adsorption is small, so the pressure fluctuation is small.

[0067] Next, the effect of evacuation for several seconds by the vacuum tank 50 of the leak test apparatus 100 of the present invention will be theoretically explained.

[0068] The leak test apparatus 100 of the present invention is different from the conventional leak test apparatus shown in Fig. 11 in that the third pipe 3 is connected to a vacuum tank 50 via a tank valve 3a, and the second vacuum pump 40 is connected to the latter stage via a gate valve 3b. For theoretical verification of this leak test apparatus 100, the following various parameters of the vacuum exhaust line from the vacuum tank 50 were newly set. Molecular flow conductance of the third pipe 3: 1.2 × 10 -3 m 3 / s (room temperature, air). Internal volume of vacuum tank 50: 1.8 x 10 -2 m 3Pumping speed of gas detector vacuum pump 70: 1 x 10 -2 m 3 / s.

[0069] [Vacuum evacuation process] 3 shows the calculation results of the time change in the indicated pressure of the vacuum gauge 90 when the test object 10 is evacuated from atmospheric pressure using the leak inspection device 100 of the present invention. Four seconds after the start of evacuation by the first vacuum pump 30, evacuation is switched to evacuation by the vacuum tank 50, and 10 seconds later, evacuation is switched to the detection gas detector 60. After 13 seconds, helium gas is introduced into the outer container 20 for the test object to perform leak detection. At this time, the internal pressure of the test object 10 (internal pressure upstream of the narrowed portion 12) after 4 seconds is 8.9 x 10 3 Pa, 8.1 x 10 after 10 seconds 2 Pa, and after 30 seconds 1.2 x 10 2 On the other hand, the pressure indicated by the vacuum gauge 90 (the internal pressure downstream of the narrowed portion 12) was 6.7×10 Pa after 4 seconds. 3 When the exhaust was switched from 0.05 Pa to 0.05 Pa using the vacuum tank 50, the pressure dropped significantly to 40 Pa after 10 seconds. After 13 seconds, the exhaust was switched to the probe gas detector 60, and after 30 seconds, the pressure dropped gradually to 16 Pa. Thus, the pressure difference between the internal pressure of the test object 10 (internal pressure upstream of the narrowed portion 12) and the indicated pressure of the vacuum gauge 90 (internal pressure downstream of the narrowed portion 12) was 2.2 x 10 after 4 seconds. 3 Pa, 7.7 × 10 after 10 seconds 2 After that, the pressure difference was about 450 Pa after 13 seconds and about 100 Pa after 30 seconds after switching to vacuum evacuation to the probe gas detector 60.

[0070] [Leak detection] In the leak testing device 100 of the present invention, 10 seconds after the start of evacuation, the device switched to evacuation of the detection gas detector 60, and 13 seconds after that, the detection gas (helium gas) was introduced into the outer container 20 for the test specimen, and leak detection was performed. The time change in the detection gas leak detection signal is shown in the upper part of Figure 3. The leak response time for the detection gas leak detection signal, which is 0.63 x the leak flow rate, was 16 seconds after the introduction of helium gas. This was shorter than the leak response time of 53 seconds for conventional leak testing devices.

[0071] This is because, after 13 seconds of leak detection, the pressure difference between the internal pressure of the test object 10 (the internal pressure upstream of the narrowed portion 12) and the indicated pressure of the vacuum gauge 90 (the internal pressure downstream of the narrowed portion 12) is 450 to 100 Pa, which is larger than that of conventional leak inspection devices, and the effective pumping speed of the test object 10 is 8.7 × 10 -5 ~2.7×10 -5 m 3 / s, which is larger than that of conventional devices. From the above, in the leak test device 100 of the present invention, the time from the start of evacuation from atmospheric pressure to the end of leak detection (0.63 × detection of leak flow rate) was 30 seconds, which was significantly shorter than the conventional leak detection time (101 seconds). Furthermore, the internal pressure of the test object 10 from 9 seconds to 35 seconds while leak detection is being performed in the leak test device 100 of the present invention is 700 to 330 Pa, which reduces the influence of pressure fluctuations due to water vapor compared to the 100 to 60 Pa of conventional leak test devices. This makes it possible to prevent the leak detection time from being extended to avoid erroneous judgments.

[0072] [Study of leak response time] Here, the volume V [m 3 ], a leak test is performed in an analytical model in which a detection gas detector is connected to a vacuum vessel with a leakage flow rate Q[Pam 3 / s], the time change Q(t) of the leakage flow rate Q is expressed as Se[m 3 / s], it can be written as follows (Equation 2). (Formula 2):Q(t)=Q[1-exp{-(Se / V)t}] When t=V / Se, the above (Equation 2) becomes Q(t)=Q[1-exp(-1)] =0.63Q The time when t=V / Se is reached is called the "leak response time."

[0073] Table 1 shows the correlation between the "total internal volume from the test object 10 to the detection gas detector 60", the "effective pumping speed Se of the test object 10 at the time of leak detection", and the "leak response time" in leak testing of the test object 10 with a narrow opening. -3 m 3 When the leak detection time is large, the effective pumping speed Se of the test object 10 is 10 -4 m 3 On the other hand, the total volume from the test object to the detection gas detector needs to be increased to the order of 5 × 10 -4 m 3 When the effective pumping speed Se of the test object 10 at the time of leak detection is small, -5 m 3 It can be seen that a relatively small value of the order of / s is sufficient.

[0074] The effective pumping speed Se of the test object 10 at the time of leak detection is composed of the combined conductance of "the conductance of the narrow mouth portion 10a of the test object 10," "the conductance with the hole of the sealing jig 11 including the short pipe 11a," "the conductance of other piping leading to the detection gas detector 60," and "the pumping speed at the inlet of the detection gas detector 60." Among these, the conductance of the narrow portion 12, which is the combined conductance of "the conductance of the narrow mouth portion 10a of the test object 10" and "the conductance with the hole of the sealing jig 11 including the short pipe 11a," is small. Therefore, the conductance of the narrow portion 12 at the time of leak detection is set to 1 × 10 -5 m 3 / s or more is desirable. In the leak inspection device 100 of the present invention, taking into consideration that the internal pressure of the test object 10 during leak detection may be several thousand to several hundred Pa, the molecular flow conductance value of the narrow portion 12 is preferably 1×10 -6 m 3 / s or more is desirable. [Table 1]

[0075] Example 1 Internal volume 2×10 -3 m 3 A leak test was carried out using the leak test device 100 of the present invention using a large-volume test object 10. Various parameters of the leak test device 100 of the present invention were set as follows.

[0076] Internal volume of test piece 10: 2 x 10 -3 m 3 Molecular flow conductance value of narrow mouth portion 10a: 1.1 × 10 -4 m 3 / s (room temperature, air). Molecular flow conductance value of sealing jig 11: 4.3 × 10 -5 m 3 / s (room temperature, air). Test object 10 - first pipe 1 - vacuum gauge 90 - fourth pipe 4 internal volume: 2.9 x 10 -3 m 3 Molecular flow conductance value of first pipe 1: 2.8 x 10 -5 m 3 / s (room temperature, air). Molecular flow conductance value of second pipe 2: 1.4 × 10 -5 m 3 / s (room temperature, air). Pumping speed of first vacuum pump 30: 7.0 x 10 -2 m 3 / s. Molecular flow conductance of the third pipe 3: 9.1 x 10 -4 m 3 / s (room temperature, air). Internal volume of vacuum tank 50: 4.0 x 10 -2 m 3 Molecular flow conductance value of the fourth pipe 4: 4.4 × 10 -4 m 3 / s (room temperature, air). Inlet pumping speed of the detection gas detector 60: 5 × 10 -3 m 3 / s.

[0077] [Without evacuation by vacuum tank 50] A leak test was performed using the leak test apparatus 100 of the present invention using a conventional leak test method that does not involve evacuation for several seconds using the vacuum tank 50. Figure 4 shows the time-dependent changes in the internal pressure of the test object 10 (internal pressure upstream of the narrowed section 12), the pressure indicated by the vacuum gauge 90 (internal pressure downstream of the narrowed section 12), and the leak detection signal. Here, the internal pressure of the test object 10 (internal pressure upstream of the narrowed section 12) is a calculated value, while the pressure indicated by the vacuum gauge 90 (internal pressure downstream of the narrowed section 12) and the leak detection signal are both measured values. The pressure indicated by the vacuum gauge 90 (internal pressure downstream of the narrowed section 12) fell below 50 Pa 45 seconds after the start of rough evacuation using the first vacuum pump 30. Therefore, after 45 seconds, the probe gas detector 60 was switched to evacuation, and after 48 seconds, helium gas, the probe gas, was introduced under pressure into the test object outer container 20, and leak detection began.

[0078] The upper part of Figure 4 shows the measurement results of the time change of the leak detection signal. The internal pressure of the test object 10 was approximately 700 Pa 48 seconds after the start of leak detection, and 500 Pa 62 seconds later. At this time, the effective pumping speed for the test object 10 was 2.1 x 10 after 48 seconds. -4 m 3 / s, 1.7 × 10 after 62 seconds -4 m 3 This resulted in a leak response time of approximately 15 seconds from the start of leak detection. From the above, in the leak test apparatus 100 of the present invention, the leak test method without evacuation of the vacuum tank 50 for several seconds was performed. -3 m 3 The leak test time for the large-volume test piece 10 was 63 seconds.

[0079] [With vacuum evacuation using vacuum tank 50] In the leak testing apparatus 100 of the present invention, a leak test was carried out using the testing method of the present invention, which involves evacuation for several seconds using the vacuum tank 50. Here, rough evacuation was performed using the first vacuum pump 30 for three seconds, then evacuation was switched to evacuation using the vacuum tank 50 for three seconds, and then evacuation was switched to evacuation using the detection gas detector 60. Nine seconds after the start of the test, helium gas was introduced under pressure into the outer container 20 for the test object, and leak detection began.

[0080] Here, in order to cancel pressure fluctuations due to time fluctuations in the opening and closing of the roughing valve 2a and the tank valve 3a, during vacuum evacuation by the vacuum tank 50, the downstream gate valve 3b is closed one second after evacuation by the vacuum tank 50 begins (four seconds after evacuation begins), stopping the evacuation of the vacuum tank 50 by the second vacuum pump 40, and stabilizing the time trends of the internal pressure of the test piece 10 (internal pressure upstream of the narrow section 12) and the indicated pressure of the vacuum gauge 90 (internal pressure downstream of the narrow section 12).

[0081] Figure 5 shows the calculation results for the time change in the internal pressure of the test object 10, the measurement results for the time change in the indicated pressure of the vacuum gauge 90, and the measurement results for the time change in the leak detection signal. The pressure indicated by the vacuum gauge 90 (internal pressure downstream of the narrowed portion 12) dropped sharply from 450 Pa (low vacuum) to 20 Pa (high vacuum) before and after the three-second evacuation of the vacuum tank 50. Meanwhile, the internal pressure of the test object 10 (internal pressure upstream of the narrowed portion 12) dropped by 8 x 10 3 Pa to 4 x 10 3 The pressure changed over time from 0.2 Pa (low vacuum) to high pressure.

[0082] The upper part of Fig. 5 shows the measurement results of the change over time of the leak detection signal. The internal pressure of the test object 10 (the internal pressure on the upstream side of the narrowed portion 12) increased by approximately 3 × 10 9 seconds after the start of leak detection. 3 Pa, 2 × 10 after 15 seconds 3 At this time, the effective pumping speed for the test object 10 is 6.5 × 10 after 9 seconds. -4 m 3 / s, 4.5 × 10 after 15 seconds -4 m 3This resulted in a short leak response time of approximately 7 seconds from the start of leak detection. From the above, the leak test device 100 of the present invention and the test method of the present invention are used to test a leak with an internal volume of 2×10 -3 m 3 The leak inspection time for the test piece 10 was 16 seconds. This leak inspection time of 16 seconds was short, about 1 / 4 of the leak inspection time (63 seconds) according to the conventional leak inspection method.

[0083] Example 2 Internal volume 2×10 -5 m 3 A leak test was carried out using the leak test device 100 of the present invention using a test object 10 having a small volume of 100. The various parameters of the leak test device 100 of the present invention were set as follows.

[0084] Internal volume of test piece 10: 2 x 10 -5 m 3 Molecular flow conductance value of narrow mouth portion 10a: 3.6 × 10 -5 m 3 / s (room temperature, air). Molecular flow conductance value of sealing jig 11: 6.4 × 10 -6 m 3 / s (room temperature, air). Internal volume of test object 10 - first pipe 1 - vacuum gauge 90 - fourth pipe 4: 9.1 x 10 -4 m 3 Molecular flow conductance value of first pipe 1: 1.2 × 10 -5 m 3 / s (room temperature, air). Molecular flow conductance of second pipe 2: 1.4 × 10 -5 m 3 / s (room temperature, air). Pumping speed of first vacuum pump 30: 7.0 x 10 -2 m 3 / s. Molecular flow conductance of the third pipe 3: 9.1 x 10 -4 m 3 / s (room temperature, air). Internal volume of vacuum tank 50: 1.6 x 10 -2 m 3 Molecular flow conductance value of the fourth pipe 4: 4.4 × 10 -4 m 3 / s (room temperature, air). Inlet pumping speed of the detection gas detector 60: 5 × 10-3 m 3 / s.

[0085] [Without evacuation by vacuum tank 50] A leak test was performed using the leak test apparatus 100 of the present invention using a conventional leak test method that does not involve evacuation for several seconds using the vacuum tank 50. Figure 6 shows the results of the time changes in the internal pressure of the test object 10 (internal pressure upstream of the narrow portion 12), the pressure indicated by the vacuum gauge 90 (internal pressure downstream of the narrow portion 12), and the leak detection signal. Here, the internal pressure of the test object 10 (internal pressure upstream of the narrow portion 12) is a calculated value, while the pressure indicated by the vacuum gauge 90 (internal pressure downstream of the narrow portion 12) and the leak detection signal are both measured values. The pressure indicated by the vacuum gauge 90 (internal pressure downstream of the narrow portion 12) became less than 50 Pa 45 seconds after the start of rough evacuation using the first vacuum pump 30.

[0086] This evacuation time of 45 seconds is almost the same as that of the leak test "for a large-volume test object 10 without evacuation by the vacuum tank 50" according to Example 1 above. The reason for this is that the device configuration downstream of the narrow section 12 is almost the same. After 45 seconds, the probe gas detector 60 was switched to evacuation, and after 48 seconds, helium gas, the probe gas, was introduced into the test object outer container 20 to start the leak test.

[0087] The upper part of Fig. 6 shows the measurement results of the change over time of the leak detection signal. The internal pressure of the test object 10 (internal pressure on the upstream side of the narrowed portion 12) was 140 Pa 48 seconds after the start of leak detection, and 65 Pa 100 seconds later. At this time, the effective pumping speed for the test object 10 was 1.3 x 10 after 48 seconds. -5 m 3 / s, 8.8 × 10 after 100 seconds -6 m 3 This resulted in a long leak response time of approximately 70 seconds from the start of leak detection. From the above, in the leak test apparatus 100 of the present invention, the leak test method without evacuation of the vacuum tank 50 for several seconds was performed. -5 m 3The leak test time for the small volume test piece 10 was 118 seconds.

[0088] [With vacuum evacuation using vacuum tank 50] A leak test was carried out using the leak test method of the present invention, which involves evacuation for several seconds using a vacuum tank in the leak test apparatus 100 of the present invention. Rough evacuation was performed for three seconds using the first vacuum pump 30, followed by evacuation for three seconds using the vacuum tank 50, after which evacuation was switched to evacuation using the detection gas detector 60. Nine seconds after the start of the test, helium gas was introduced under pressure into the outer container 20 for the test object, and leak detection began.

[0089] Figure 7 shows the calculation results of the time change in the internal pressure of the test object 10, the measurement results of the time change of the vacuum gauge 90, and the measurement results of the time change of the leak detection signal. Due to the evacuation of the vacuum tank 50, the indicated pressure of the vacuum gauge 90 (internal pressure downstream of the narrow section 12) dropped suddenly from 400 Pa (low vacuum) to 20 Pa (medium vacuum). Meanwhile, the internal pressure of the test object 10 (internal pressure upstream of the narrow section 12) dropped to 2 x 10 3 Pa to 1 x 10 3 The pressure changed over time from 0.2 Pa (low vacuum) to high pressure.

[0090] The upper part of Figure 7 shows the measurement results of the change over time in the leak detection signal. The internal pressure of the test object 10 (internal pressure on the upstream side of the narrowed portion 12) is approximately 750 Pa 9 seconds after the start of leak detection, and 200 Pa 30 seconds later. At this time, the effective pumping speed for the test object 10 is 4.3 x 10 after 9 seconds. -5 m 3 / s, 1.7 × 10 after 30 seconds -5 m 3 This resulted in a relatively short leak response time of 21 seconds from the start of leak detection. From the above, in the leak test apparatus 100 of the present invention, the leak test method of the present invention, in which evacuation by the vacuum tank 50 for several seconds is performed, -5 m 3The leak inspection time for the small-volume test object 10 was 30 seconds. This leak inspection time of 30 seconds was short, about 1 / 4 of the inspection time (118 seconds) of the conventional leak inspection method.

[0091] (Second embodiment) FIG. 8 is an explanatory diagram showing a leak test device 200 for a low-rigidity test object according to a second embodiment of the present invention. The test piece 10' according to the second embodiment is a resin product (hereinafter referred to as a "low-rigidity test piece") that has been pouched and has a thin plate thickness. The internal volume of the low-rigidity test piece 10' is 2×10 -5 m 3 1, the housing and narrow opening 10a of the test object 10 are deformed in the early stages of rough evacuation by the first vacuum pump 30, causing vacuum leaks in the leak test apparatus and making leak testing impossible. Therefore, the leak test apparatus 200 for low-rigidity test objects shown in FIG. 8 is configured to enable stable leak testing of the low-rigidity test object 10' while effectively preventing deformation of the housing and narrow opening 10a of the low-rigidity test object 10'.

[0092] When we investigated the pressure resistance of thin resin parts with pouch processing, we found that the pressure resistance was 5 x 10 4 Pa (0.5 atmospheres). Therefore, in the leak inspection device 200 for low-rigidity test objects, a slow exhaust section 13 consisting of a second minimum section 12a, a second gate valve 13b, and a second vacuum gauge 13c is added midway along the first piping 1 to the leak inspection device 100 shown in FIG.

[0093] In addition, a third vacuum gauge 21 was newly added to the outer container 20 for the test object. Here, the second narrow portion 13a was set to a pressure of 5×10 from atmospheric pressure. 4 This component is used to reduce the time required for evacuation to a vacuum of 10 Pa to approximately 5 seconds. The molecular flow conductance of the second narrow section 13a is 3.7×10 -8 m 3This value is set to 3.7×10 / s, which is the molecular flow conductance value of the narrow portion 12 formed by the narrow opening 10a of the low-rigidity test object 10′ and the sealing jig 11. -6 m 3 The slow exhaust section 13 is also designed to prevent a pressure drop due to the evacuation (rough evacuation by the first vacuum pump 30 and evacuation at a high evacuation speed of several seconds by the vacuum tank 50) of the small-volume, low-rigidity test object 10' until leak detection.

[0094] Fig. 9 is a process diagram showing a leak inspection method using a leak inspection device 200 for a low-rigidity test object according to a second embodiment of the present invention. Fig. 10 shows the calculation results of the change in the internal pressure of the low-rigidity test object 10' over time, the measurement results of the change in the indicated pressures of the vacuum gauge 90 and the second vacuum gauge 13c over time, and the change in the leak detection signal over time.

[0095] The leak inspection method using the leak inspection device 200 for low-rigidity test objects is different from the leak inspection method using the leak inspection device 100 shown in Fig. 2 in that step S3 in Fig. 2 is changed to step S3-1 and step S3-2, and step S8 in Fig. 2 is changed to step S8'. The leak inspection method using the leak inspection device 200 for low-rigidity test objects will be briefly described below.

[0096] As shown in steps S1 and S2, the gate valve 12b of the slow exhaust section 13 was closed, and the low-rigidity test object 10' was evacuated via the second narrow section 13a. Rough evacuation was performed for 7 seconds by the first vacuum pump 30. At this time, the internal pressure of the low-rigidity test object 10' and the indicated pressure of the second vacuum gauge 13c were 4×10 4 The pressure on the first vacuum gauge 90 was 200 Pa.

[0097] As shown in steps S3-1 and S3-2, the pressure on the second vacuum gauge 13c is 5.5×10 4When the pressure reached 10 Pa (approximately 4 seconds after the start of evacuation), evacuation of the outer container 20 for the test specimen was started. Through the processes from step S1 to step S3-2, the pressure difference between the inside of the outer container 20 for the test specimen and the inside of the low-rigidity test specimen 10' became 5×10 4 Pa, and deformation of the housing and narrow opening 10a of the low-rigidity test piece 10' due to pressure could be avoided.

[0098] As shown in step S5, seven seconds after the start of evacuation, evacuation was performed at a high evacuation speed by the vacuum tank 50 for three seconds (until ten seconds after the start of evacuation). The low-rigidity test object 10' was also evacuated via the second minimum part 12a during this time. After ten seconds, the internal pressure of the low-rigidity test object 10' and the indicated pressure of the second vacuum gauge 13c were both 3×10 4 On the other hand, the pressure indicated on the vacuum gauge 90 was 30 Pa, which was a pressure at which the exhaust to the detection gas detector 60 could be switched on.

[0099] As shown in step S8', 10 seconds after the completion of the high-speed evacuation by the vacuum tank 50, the second gate valve 13b of the slow evacuation section 13 was opened to end the slow evacuation, and the gas from the low-rigidity test object 10' was led to the detection gas detector 60, and a leak-free measurement was performed for 3 seconds (until 13 seconds after the start of evacuation).

[0100] As shown in step S10, 5×10 helium gas, which is the probe gas, is poured into the outer container 20 for the test object. -4 Pa and started leak detection.

[0101] The upper part of Fig. 10 shows the measurement results of the change in the leak detection signal over time. The pressure in the low-rigidity test object 10' was 3.3 x 10 3 Pa, 9.0 × 10 after 20 seconds 2 At this time, the effective pumping speed for the low-rigidity test piece 10' is 1.6 x 10 after 13 seconds. -4 m 3 / s, 5.0 × 10 after 20 seconds -5 m 3 / s. This resulted in a short leak response time of 7 seconds from the start of leak detection. Here, the introduced helium gas was 5 × 10 -4 Since the pressure is low at 10 Pa, the saturated leakage flow rate is 1×10 -5 Pam 3 / s to 1.2 × 10 -6 Pam 3 This decrease in saturated leak flow rate does not become a problem if leak detection is performed using the leak master.

[0102] From the above, the leak inspection device 200 for low-rigidity test objects of the present invention equipped with the slow exhaust section 13 has an internal volume of 2×10 -5 m 3 The leak inspection time for the low-rigidity test object 10' was 20 seconds, which was shorter than the 30 seconds required for the leak inspection without the slow exhaust section 13. 3 Since the pressure was 1 Pa and the leak response time was 7 seconds, the influence of pressure fluctuations due to water vapor was reduced, making it possible to avoid erroneous determinations.

[0103] 1. First pipe (vacuum exhaust pipe) 1a Atmospheric valve 2. Second piping 2a Roughing valve 3. Third piping 3a Tank valve 3b Gate valve 4. Fourth Pipe 4a Test valve 5. Exploration gas pressure line 5a Pressure valve 6 Exhaust line 6a Exhaust valve 10 Test object (sealed container) 10' Low rigidity test object (closed container) 10a Narrow mouth section (exhaust port section) 11 Sealing jig 11a short tube 12 Narrow area 13 Slow exhaust section 13a 2nd narrow part 13b Second gate valve 13c 2nd vacuum gauge 20 Outer container for test object 21 3rd vacuum gauge 30 First vacuum pump 40 Second vacuum pump 50 Vacuum Tank 60 Gas detector (He leak detector) 70 Vacuum pump for gas detector 80 Exploration gas source (He gas source) 90 vacuum gauge 100 Leak Testing Device 200 Leak inspection device for low-rigidity test objects

Claims

1. A leak detection method for detecting a flow rate of a probe gas contained in an exhaust gas by evacuating the inside of a sealed container (10') having a narrow opening (10a) with a small conductance on the surface where an opening for gas molecules to pass through is narrowed, while the inside of the sealed container (10') is made low vacuum and the outside (20) is replaced and pressurized with a probe gas, a first process (S2, S3, S4) of evacuating the inside of the sealed container (10') through a second narrow section 13a of a slow exhaust section (13) added midway along the vacuum exhaust pipe (1) until the internal pressures on the upstream and downstream sides of the narrow section (12) constituted by the narrow mouth section (10a) and a sealing jig (11) tightly connecting the narrow mouth section (10a) and the vacuum exhaust pipe (1) reach a low vacuum of less than 1 / 10 of atmospheric pressure; After the first process (S2, S3, S4), a second process (S5, S6, S7) is performed in which the downstream side of the narrow section (12) is evacuated to a vacuum by a vacuum pump (40) while expanding the exhaust gas by a vacuum tank (50) connected to the vacuum pump (40) so that the internal pressure on the upstream side of the narrow section (12) is maintained at a low vacuum of less than 1 / 10 of atmospheric pressure and the internal pressure on the downstream side of the narrow section (12) is at a medium vacuum of less than 1 / 1000 of atmospheric pressure; and a third process (S10) for replacing and pressurizing the outside (20) of the sealed container (10') with a detection gas after the second process, evacuating the inside of the sealed container (10'), and detecting the leakage flow rate of the detection gas leaking from the inside of the sealed container (10'). A leak inspection method characterized by:

2. 2. The leak detection method according to claim 1, When the inside of the sealed container (10') is evacuated by the vacuum tank (50), the evacuation of the vacuum tank (50) by the vacuum pump (40) is stopped at the beginning or during the evacuation. A leak inspection method characterized by:

3. 2. The leak detection method according to claim 1, In the first process (S2, S3, S4), the inside of the sealed container (10') is evacuated while the outside (20) of the sealed container (10') is evacuated. A leak inspection method characterized by:

4. 2. The leak detection method according to claim 1, The pipe (3) used in the second process (S5, S6, S7) has a larger inner diameter than the pipe (2) used in the first process (S2, S3, S4). A leak inspection method characterized by:

5. 2. The leak detection method according to claim 1, The molecular flow conductance of the narrowed portion (12) is 1×10 m / s or more in air at a temperature of 20°C. A leak inspection method characterized by:

6. 2. The leak detection method according to claim 1, After the second process (S5, S6, S7) and before the third process (S10), and a process (S8') of opening a second gate valve 13b connected in parallel to the second narrow section 13a. A leak inspection method characterized by:

7. an outer container (20) that houses therein a sealed container (10') having a small conductance narrow mouth (10a) on the surface where an opening through which molecules pass is narrowed; a first pipe (1) inserted through the outer container (20) for transferring gas in the sealed container (10') to the outside; a sealing jig (11) for airtightly connecting the sealed container (10') and the first pipe (1); a narrow portion (12) consisting of the narrow opening portion (10a) and the sealing jig (11) and having a predetermined molecular flow conductance; a first vacuum pump (30) for evacuating the inside of the sealed container (10') to a predetermined pressure; a second pipe (2) connecting the first pipe (1) and the first vacuum pump (30); a detection gas detector (60) equipped with a vacuum pump (70) for detecting the flow rate of detection gas leaking from the inside of the sealed container (10'); a detection gas detection line (4) connecting the first pipe (1) and the detection gas detector (40); a slow exhaust section (13) having a second narrow section (12a) and added midway along the first pipe (1); A leak testing device (200) comprising: A third pipe (3) separate and independent from the second pipe (2) is connected to the first pipe (1), The third pipe (3) is provided with a vacuum tank (50) capable of evacuating the internal pressure downstream of the narrowed portion (12) to a predetermined pressure while expanding exhaust gas evacuated from the inside of the sealed container (10'), A second vacuum pump (40) is connected to the exhaust side of the vacuum tank (50) to evacuate the downstream side of the narrow section (12) via the vacuum tank (50), The inside of the sealed container (10') is evacuated by the first vacuum pump (30) until the internal pressures on the upstream and downstream sides of the narrow portion (12) reach a low vacuum of less than 1 / 10 of atmospheric pressure, and then the downstream side of the narrow portion (12) is evacuated by the second vacuum pump (40) while expanding the exhaust gas by the vacuum tank (50) so that the internal pressure on the upstream side of the narrow portion (12) is maintained at a low vacuum of less than 1 / 10 of atmospheric pressure and the internal pressure on the downstream side of the narrow portion (12) reaches a medium vacuum of less than 1 / 1000 of atmospheric pressure. A leak inspection device characterized by:

8. 8. The leak test device according to claim 7, A gate valve (3b) is provided between the vacuum tank (50) and the second vacuum pump (40). A leak inspection device characterized by:

9. 8. The leak test device according to claim 7, A second narrow section (13a) having a predetermined molecular flow conductance and a second gate valve (13b) that opens when a leak flow rate of the detection gas is detected are connected in parallel downstream of the narrow section (12). A leak inspection device characterized by:

10. 8. The leak test device according to claim 7, The inner diameter of the third pipe (3) is larger than the inner diameter of the second pipe (2). A leak inspection device characterized by:

11. 8. The leak test device according to claim 7, The molecular flow conductance of the narrowed portion (12) is 1×10 m / s or more for air at a temperature of 20° C. A leak inspection device characterized by:

12. 8. The leak test device according to claim 7, An exhaust valve (6a) is provided for evacuating the outer container (20), A leak inspection device characterized by:

13. 8. The leak test device according to claim 7, A second gate valve 13b is provided which is connected in parallel with the second narrow portion 13a. A leak inspection device characterized by:

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