Leak tester

Abstract

To solve the issue that it has been difficult to share an air pressure circuit for a small leak test and an air pressure circuit for a large leak test since the large leak test has been run before the small leak test by a quantitative injection method.SOLUTION: A leak tester which solves the above issue includes a master container, a master-side air circuit, a workpiece container, a workpiece-side air circuit, a first valve, a second valve, a flow rate control valve, and a differential pressure meter. The master container stores a standard item and is connected to the master-side air circuit. The workpiece container stores a test item and is connected to the workpiece-side air circuit. The first valve controls pressure air supplied to the master-side air circuit and the workpiece-side air circuit. The second valve connects the master-side air circuit and the workpiece-side air circuit to the outside. The flow rate control valve controls an amount of air discharged from the master-side air circuit and the workpiece-side air circuit to the outside or controls an amount of air injected from the outside to the master-side air circuit and the workpiece-side air circuit. The differential pressure meter measures a pressure difference between the master-side air circuit and the workpiece-side air circuit.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The disclosed technology relates to a device that uses an external pressure method to check for air leaks in sealed products. [Background technology]

[0002] To detect air leakage defects in a sealed product, for example, a test product is subjected to pressure from all sides in a sealed container to check whether air gets into the sealed product. At this time, if the defect is small (small defect), air will gradually enter the test item (small leak), and the internal pressure of the sealed container will gradually decrease. On the other hand, if the defect is large (large defect), air will suddenly enter the test item during the process of pressurizing the sealed container (large leak), and even if you observe the change in pressure over time inside the sealed container after pressurization is complete, you will not be able to detect the change. Therefore, small leak tests and large leak tests must be performed separately.

[0003] [Principle of small leak test] The principle of the small leak test will be explained using Figure 1. Reference numeral 101 denotes a sealed container, and 102 denotes an item to be inspected. An inspection product at atmospheric pressure (P0) is stored in a sealed container 101, and a pressure P1 greater than P0 is applied inside the sealed container. The volume of the sealed container 101 excluding the outer volume of the inspection product is V C The internal volume of the inspection item (the volume into which air can enter) is V S Then, in the initial state, there is air with pressure P0 and volume V in the closed container. S , the volume of air at pressure P1 is V C exist. The air at pressure P1 gradually flows into the test item. Then, the pressure in the sealed container gradually decreases and the pressure in the test item gradually increases. If the pressure inside the sealed container after t seconds is P1-ΔP, and the amount of gas flowing into the test item converted to atmospheric pressure (P0) is Q [ml / s], then

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[0004] Although the above small leak test has been described by way of example in which the test item is pressurized, the test can also be performed by reducing the pressure around the test item.

[0005] [Principle of large leak test] The principle of the large leak test will be explained using Figure 2. A master container 201 for storing a reference product 202 and a work container 203 for storing an inspection product 204 are prepared. The master container and the work container have the same volume. If the test product has a large leak, it is expected that there will be a difference between the amount of air in the master container after the reference product is placed in the master container and the amount of air in the work container after the test product is placed in the work container. This difference in air amount is used to detect the presence of a large leak.

[0006] The volume of the master container 201 excluding the external volume of the reference product is V C , the initial pressure is P1, and the amount of gas in the master vessel is n M [mol], temperature is T, and gas constant is R.

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[0007] The master container and the work container have the same amount of material (n e After the injection, the pressure in the master vessel is P M , the pressure in the work vessel is P W Then,

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[0008] In the above large leak test, a predetermined amount of gas was "injected", but a predetermined amount of gas may be "released" from the master container and the work container. From equation (9), if E is positive (injected), P M >P W But if E is negative (emission), then P M <P W It becomes. In this specification, the case of E>0 is referred to as the "fixed-rate injection method," and the case of E<0 is referred to as the "fixed-rate release method."

[0009] Based on the above principle, the prior art will be described. 3 is an air circuit diagram of a leak tester 3 for sealed products according to the prior art. The air leak tester 3 includes a master container 301, a work container 303, a pressurized air supply source 305, a primary pressure regulating valve 306, a pressure gauge 307, a first valve 308, a differential pressure gauge 309, a second valve 310, a pressure regulating valve 312, and a third valve 311. Each container, air supply source, valve, and measuring instrument are connected by a pipe (air path) that carries air. The first valve, second valve, and third valve may be abbreviated as V1, V2, and V3, respectively.

[0010] The first valve 308 is a pair of two-way control valves (a two-way control valve having a pair of output ports that are separated and independent when closed) and distributes the pressurized air supplied from the primary pressure regulating valve 306 to the master container 301 and the work container 303. The differential pressure gauge 309 is connected to point A on the air path connecting the first valve and the master container, and to point B on the air path connecting the first valve and the work container 303 . The second valve 310 is connected to point C on the air path connecting the first valve and the master container, and to point D on the air path connecting the first valve and the work container 303 .

[0011] The air path connected to the V1-AC-master vessel is called the "master side air system." The master side air system includes the "A-differential pressure gauge" and "C-V2" air paths, as well as the master vessel. The air path connected to V1-BD-work container is called the "work side air system." The work side air system includes the "B-differential pressure gauge" and "D-V2" air paths, as well as the work container. The gap volumes of the master side air system and the work side air system are adjusted in advance to be equal. In addition, where there is no risk of misunderstanding, the "master side air system" may be called the "master side" and the "work side air system" may be called the "work side".

[0012] The differential pressure gauge 309 measures the pressure difference between the master side air system and the work side air system. The second valve 310 is a pair of two-way control valves that discharges air from the master side air system and the work side air system to the outside. The second valve can allow a large amount of air to flow at one time. The third valve 311 is a pair of two-way control valves capable of controlling the gas flow rate, and supplies the same amount of pressurized air supplied from the pressure adjustment valve 312 to the master side air system and the work side air system simultaneously. The third valve 311 cannot flow a large amount of air at one time.

[0013] <Preparation of reference and inspection items> The first and third valves are closed, and the second valve is opened. Then, both the master side air system and the work side air system are at atmospheric pressure. In this state, a reference product 302 without air leakage is stored in the master container 301, and an inspection product 304 is stored in the work container 303. The inspection product 304 may be a non-defective product without air leakage, or a defective product with air leakage.

[0014] <Large leak test> Close the second valve. The volume obtained by subtracting the external volume of the reference product from the master air system is V. C , V C The amount of substance contained in n M If the atmospheric pressure is P0 and the temperature is T, the state of the master side air system is given by equation (3). The test item may have a volume in which air can enter. This is called V S Let us assume that V S +V C The amount of substance contained in n W Then, the state of the workpiece side air system is given by equation (4).

[0015] Open the third valve and let the same amount of air into the master and workpiece. e Then, the state of equations (5) and (6) is reached, and V S If is not zero (if there is a large leak), a differential pressure given by equation (9) occurs between the master side and the work side, and this is detected by the differential pressure gauge 309.

[0016] <Small leak test> If no differential pressure is detected during the large leak test, proceed to the small leak test. At the end of the large leak test, the first, second and third valves are closed. Open the first valve and apply equal pressure to the master side air system and the work side air system. This is called P1. Pressure P1 is maintained on the master side without leaks. Even if the test item has a small leak, the internal pressure of the test item at the start of the test can be considered to be atmospheric pressure P0. However, air gradually enters the test item due to the pressure difference between P1 and P0. A pressure difference ΔP of formula (2) occurs between the work side and the master side, and this is detected by the differential pressure gauge 309. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] International Publication No. WO2014 / 184895 Summary of the Invention [Problem to be solved by the invention]

[0018] Flow-controllable valves generally need to be used below a "critical pressure ratio," which is the condition for the amount of gas flowing through a flow-controllable valve to be constant. The pressure ratio is defined as [secondary pressure] ÷ [primary pressure], with the side of the valve at higher pressure being the primary side and the side at lower pressure being the secondary side. When the primary pressure is constant, lowering the secondary pressure increases the amount of gas flowing through the valve (the speed of the flowing air increases). The flow velocity cannot be faster than the speed of sound, and when the flow velocity reaches the speed of sound, the flow rate saturates (becomes a constant value). The pressure ratio at this point is called the critical pressure ratio. In the conventional technology, in addition to the master side air circuit and the work side air circuit, an air circuit was required to apply an appropriate primary side pressure to the flow rate controllable third valve. This made it difficult to miniaturize the leak tester. In addition, conventional flow rate controllable valves were expensive or had low durability. [Means for solving the problem]

[0019] In order to solve the above problems, the leak tester according to the disclosed technology includes a master container, a master side air circuit, a work container, a work side air circuit, a first valve, a second valve, a flow control valve, and a differential pressure gauge. A reference product is stored in the master container and is connected to the master side air circuit. The work container stores the inspection items and is connected to the work side air circuit. The first valve controls the compressed air supplied to the master side air circuit and the work side air circuit. The second valve connects the master side air circuit and the work side air circuit to the outside. The flow rate control valve controls the amount of air discharged from the master side air circuit and the work side air circuit to the outside, or the amount of air injected from the outside into the master side air circuit and the work side air circuit. The differential pressure gauge measures the differential pressure between the master side air circuit and the work side air circuit. Effect of the Invention

[0020] According to the disclosed technology, it is possible to realize a leak tester that is low cost, has high durability, and can perform a short test time. It is also possible to provide a leak tester that can perform both positive pressure testing and negative pressure testing. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 is a diagram for explaining the principle of a small leak test. [Diagram 2] FIG. 2 is a diagram for explaining the principle of a large leak test. [Diagram 3] FIG. 1 is an air circuit diagram for explaining a leak tester according to a conventional technique. [Figure 4] FIG. 2 is an air circuit diagram for explaining the leak tester according to the first embodiment. [Diagram 5] FIG. 4 is an air circuit diagram for explaining a leak tester according to a first modified example. [Figure 6] FIG. 6 is an air circuit diagram for explaining a leak tester according to a second embodiment. [Figure 7] FIG. 11 is an air circuit diagram for explaining a leak tester according to a second modified example. [Figure 8] FIG. 1 is an exploded view (perspective view) of a flow control valve suitable for the disclosed technology. [Figure 9] FIG. 2 is an assembly diagram (cross-sectional view) of a flow control valve suitable for the disclosed technology. [Figure 10] 13 is an enlarged view of a countersunk portion for explaining a modified example of the flow control valve. FIG. [Figure 11] FIG. 11 is a graph comparing experimental values ​​and theoretical values ​​of the second modified example. [Figure 12] FIG. 4 is a diagram for explaining experimental results (dependence of detected differential pressure on primary pressure) for the first embodiment and the first modified example. [Figure 13] FIG. 11 is a diagram for explaining an estimated critical pressure ratio of an orifice by comparing experimental results of the first embodiment and the first modified example. [Figure 14] FIG. 11 is an air circuit diagram for explaining a leak tester according to a third embodiment. [Figure 15] FIG. 13 is a diagram for explaining a leak tester according to a third modified example. [Figure 16] FIG. 4 is a diagram for explaining the conditions of the master side volume and the work side volume for canceling out the manufacturing error of the orifice. [Figure 17] This diagram explains how the differential pressure can be made proportional to VS by adjusting the volume on the work side, even if there is a manufacturing error in the orifice. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, embodiments of the disclosed technology will be described in detail. Note that components having the same functions are given the same reference numbers and duplicated descriptions will be omitted.

[0023] In both the positive pressure small leak test and the negative pressure small leak test, a pressure difference is set between the atmospheric pressure and the test. As a result of intensive research, the inventors have developed an apparatus / method for performing a large leak test by utilizing the pressure difference between the pressure used in the small leak test and the atmospheric pressure, and an "orifice-integrated valve" suitable for the apparatus / method. The developed technology (disclosed technology) is different from the conventional technology in that it first performs a small leak test, and then performs a large leak test. In the first embodiment, the fixed-volume release method is explained, and in the second embodiment, the fixed-volume injection method is explained. After that, the orifice-integrated valve is explained.

[0024] [First embodiment] FIG. 4 is an air circuit diagram showing an example of the configuration of the leak tester 4 according to the first embodiment. 3 in that a fourth valve 401 is provided instead of the pressure adjustment valve 312 and the third valve 311. The fourth valve may be abbreviated as V4. The fourth valve 401 is connected to a point E on the air path connecting the first valve 308 and the master container 301 , and to a point F on the air path connecting the first valve and the work container 303 . The fourth valve 401 is a pair of two-way control valves capable of controlling the gas flow rate, and can simultaneously release the same amount of gas from the master side air system and the work side air system to the outside.

[0025] In the first embodiment, the air path connected to "V1-AEC-master vessel" is called the "master-side air system." The master-side air system includes the air paths of "A-differential pressure gauge," "C-V2," and "E-V4," and the master vessel. The air path connected to "V1-BFD-work vessel" is called the "work side air system." The work side air system also includes the air paths of "B-differential pressure gauge," "D-V2," and "F-V4" and the work vessel. The volumes of the master side air system and the work side air system are adjusted in advance so that no pressure difference occurs at the specified test pressure.

[0026] <Preparation of reference and inspection items> The first and fourth valves are closed, and the second valve is opened. Then, both the master side air system and the work side air system are at atmospheric pressure (=P0). In this state, a reference product 302 with no air leakage is stored in the master container 301, and an inspection product 304 is stored in the work container 303. The inspection product 304 may be a non-defective product with no air leakage, or a defective product with air leakage.

[0027] <Small leak test> When the second valve is closed and the first valve is opened, pressurized air is supplied to the master side air system and the work side air system. The pressure gauge 307 is monitored, and when the desired air pressure is reached, the first valve is closed. At this stage, the pressure in the master side air system and the work side air system are equal, regardless of whether the inspected product is a non-defective product, a product with a major defect, or a product with a minor defect. This is designated as P1.

[0028] The volume obtained by subtracting the external volume of the reference product from the master air system is V C Let us assume that. The test item may have a volume through which air can enter. S Then, the volume of the workpiece air system is V S +V C It becomes.

[0029] If the inspection product 104 has a small defect, the pressure on the workpiece side gradually decreases. The differential pressure gauge 309 detects the pressure difference given by equation (2) of the principle of the small leak test, and the leakage flow rate Q is measured.

[0030] If the product being inspected is a good product or a product with a major defect, no pressure difference will be detected in the small leak test. This is because air does not invade the workpiece side in the case of a good product. In the case of a major defect, the area of ​​the product into which air can invade immediately becomes pressure P1.

[0031] <Large leak test> If the product is judged to be good in the small leak test, the test proceeds to the large leak test. At the end of the small leak test, the first, second and fourth valves are all closed.

[0032] Even if the small leak test is judged to be good, ΔP in formula (2) is not necessarily zero. In the disclosed technology, the large leak test is performed using the pressure from the small leak test, so this point will be explained. In the explanation of "The Principle of Large Leak Testing", it was assumed that the master side pressure and the work side pressure before the large leak test were equal, P1. If, instead, the work side pressure before the large leak test was P1-ΔP, then equation (8) becomes as follows:

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[0033] Then, the P detected by the differential pressure gauge 309 M and P W The differential pressure is given by equation (11). M -P W If we subtract ΔP from the right side of equation (9) (large leak V S The pressure difference caused by the presence of However, since this is a quantitative release method, the sign of E is reversed. In other words, (V S In the fixed quantity discharge method, the work side pressure P W is the master pressure P M will be greater than.

[0034] <Test End> At the end of the large leak test, the first, second and fourth valves are closed. The second valve is opened to return the master side air system and the work side air system to atmospheric pressure. After that, the work container is opened, the inspection product is replaced, and the next inspection is carried out.

[0035] The above is a description of the leak tester according to the first embodiment.

[0036] [First Modification] In the first embodiment, the secondary side (low pressure side) of the fourth valve (flow rate control valve) is set to atmospheric pressure. There are cases where it is necessary to perform a leak test under pressurized conditions close to atmospheric pressure. In such cases, the pressure ratio between the primary side (high pressure side) and the secondary side cannot be made small enough, and the critical pressure ratio may not be reached. This causes the flow control in the fourth valve (controlled gas release from the master side and the work side) to become unstable. Therefore, in the first modified example, the secondary side of the fourth valve is made negative pressure to reduce the pressure ratio.

[0037] Note that positive pressure is the pressure that is a positive value when atmospheric pressure is subtracted from absolute pressure, and negative pressure is the pressure that is a negative value when atmospheric pressure is subtracted from absolute pressure. The pressure obtained by subtracting atmospheric pressure from absolute pressure is called "gauge pressure." Absolute pressure is the pressure where a vacuum is zero [Pa] and one atmosphere is 101.3 [kPa].

[0038] FIG. 5 is an air circuit diagram showing a configuration example of a leak tester according to a first modified example. 4 in that a negative pressure generator 501 is connected to the exhaust side of the fourth valve. Except for the fact that the primary / secondary pressure ratio of the fourth valve is reduced or controlled by the negative pressure generator, the operation of the first modified example is similar to that of the first embodiment.

[0039] [Second embodiment] In the first embodiment, a positive pressure is applied to a sealed object to test whether air enters the sealed object. In the second embodiment, a negative pressure is applied to a sealed object to test whether there is a leak.

[0040] FIG. 6 is an air circuit diagram showing an example of the configuration of the leak tester according to the second embodiment. 4 in that a negative pressure generator 601 is provided instead of the positive pressure supply source 305 and the primary pressure regulating valve 306.

[0041] <Preparation of reference and inspection items> The first and fourth valves are closed, and the second valve is opened. Then, both the master side air system and the work side air system are at atmospheric pressure (=P0). In this state, a reference product 302 with no air leakage is stored in the master container 301, and an inspection product 304 is stored in the work container 303. The inspection product 304 may be a non-defective product with no air leakage, or a defective product with air leakage.

[0042] <Small leak test> When the second valve is closed and the first valve is opened, the negative pressure generator 601 reduces the pressure in the master side air system and the work side air system. The pressure gauge 307 is monitored, and the first valve is closed when the desired air pressure (negative pressure) is reached. At this stage, the pressure in the master side air system and the work side air system are equal, regardless of whether the inspected product is a non-defective product, a product with a major defect, or a product with a minor defect. This is designated as P1.

[0043] The volume obtained by subtracting the external volume of the reference product from the master air system is V C Let us assume that. The test item may have a volume with air that can escape. S Then, the volume of the workpiece air system is V S +V C It becomes.

[0044] If the inspection product 304 has a small defect, the pressure on the work side gradually increases. The differential pressure gauge 309 detects the pressure difference given by the equation (2) of the principle of the small leak test, and the leakage flow rate Q is measured.

[0045] If the test item is a good product or a defective product with a large leak, no pressure difference will be detected in the small leak test. This is because no air leaks will occur on the work side in the case of a good product. In the case of a defective product, the area where air can leak from in the test item immediately becomes pressure P1.

[0046] <Large leak test> If the product passes the small leak test, the test proceeds to the large leak test. At the end of the small leak test, the first, second and fourth valves are all closed.

[0047] First, the differential pressure ΔP at the time when the test is judged to be good is recorded. Next, the fourth valve is opened and closed for a specified time, and a specified amount of material (n e After the injection, the pressure in the master air system is P M , the pressure of the work air system is P W Let us assume that.

[0048] Then, the P detected by the differential pressure gauge 309 M and P W The differential pressure is given by equation (11). M -P W If we subtract ΔP from the right side of equation (9) (large leak V S The pressure difference caused by the presence of Since the second embodiment is a constant-volume injection method, the sign of E is positive. S In the fixed injection method, the master pressure P M is the work pressure P W will be greater than.

[0049] <Test End> At the end of the large leak test, the first, second and fourth valves are closed. The second valve is opened to return the master side air system and the work side air system to atmospheric pressure. After that, the work container is opened, the inspection product is replaced, and the next inspection is carried out.

[0050] [Second modified example] In the second embodiment, the primary side (high pressure side) of the fourth valve (flow rate control valve) is set to atmospheric pressure. There are cases where it is necessary to perform a leak test at a low vacuum close to atmospheric pressure. In such cases, the pressure ratio between the primary side and the secondary side (low pressure side / work side / master side) cannot be made small enough, which can cause the flow control in the fourth valve to become unstable. Therefore, in the second modified example, the primary side of the fourth valve is made to have a positive pressure, thereby reducing the pressure ratio.

[0051] FIG. 7 is an air circuit diagram showing a configuration example of a leak tester according to a second modified example. 6 in that a positive pressure air supply source 701 and a pressure regulating valve 702 are connected to the intake side of the fourth valve. The operation of the second modified example is similar to that of the second embodiment, except that the primary / secondary pressure ratio of the fourth valve is reduced or controlled by the positive pressure air supply source.

[0052] [Flow control valve (with built-in orifice)] A valve suitable for the above embodiment will now be described. Note that an "orifice" is a small hole opened in a thin wall through which a fluid flows, and a thin plate with such a hole is called an orifice plate. FIG. 8 is an exploded view (perspective view) of a flow control valve suitable as the fourth valve in the first and second embodiments, and FIG. 9 is an assembly view (sectional view). Fig. 8(a) is an overall exploded view, (b) is a symbol on an air circuit diagram, where block 850 of the flow control valve 8 corresponds to the valve section, and block 860 corresponds to the flow control section. Fig. 8(c) is a side view of the manifold 806 observed from the A direction. Figure 9(a) is an overall assembly drawing, and (b) is an enlarged view of the orifice and its surroundings. The structure and opening / closing operation of the flow control valve 8 will be described in detail below with reference to FIGS.

[0053] <Operating valve> The actuating valve 801 has a movable piston 901 therein (see FIG. 9(a)).

[0054] <Chip plate> The chip plate 802 has two protrusions 814 , an intake and exhaust hole 811 , and four fixing holes 808 . The intake and exhaust hole 811 and the fixing hole 808 are through holes. The protrusion 813 also has a through hole in the center.

[0055] <Manifold> The manifold 806 includes two countersunk portions 807, an intake / exhaust hole 812, four fixing holes 809, two inlets 810, and an intake / exhaust port 813 (see FIG. 8(c)). The countersunk portion 807 has a hole at the bottom, which communicates with an inlet 810 inside the manifold. The intake and exhaust holes 812 communicate with an intake and exhaust port 813 inside the manifold. The fixing holes 809 are through holes.

[0056] <Orifice> The orifice plate 804 is a metal plate with a small hole in the center, and is housed in the counterbore of the manifold together with O-rings 803 and 805.

[0057] <Assembly drawing> Actuation valve 801 , tip plate 802 and manifold 806 are fixed together by screws 902 passing through fixing holes 808 and 809 . Orifice plate 804 is sandwiched between O-rings 803 and 805 and accommodated in counterbore portion 807, and the O-rings are compressed by tip plate 802 and manifold 806 to make it airtight (see FIG. 9(b)). The space 903 between the operating valve 801 and the tip plate 802 is in communication with the outside air via the intake and exhaust holes 811 in the tip plate, the intake and exhaust holes 812 in the manifold, and the intake and exhaust port 813 . The two inlets are connected to the master side air system and the work side air system. As a result, the space 903 is connected to the master side air system and the work side air system by the through hole of the protrusion 814, the hole at the bottom of the countersunk portion 807, and the inlet 810.

[0058] <Valve opening and closing operation> Piston 901 moves up and down. It descends to block the through hole of protrusion 814, thereby blocking the air path between inlet 810 and intake / exhaust port 813 (valve closed). It ascends to open the through hole of protrusion 814, thereby connecting the air path between inlet 810 and intake / exhaust port 813 (valve open).

[0059] [Modification of flow control valve] When trying to obtain an orifice plate with a small hole diameter, it is difficult to drill holes if the plate is thick. However, if the plate is made thinner, the rigidity of the orifice plate decreases, and distortion occurs when a large pressure difference is applied. If distortion occurs, the flow characteristics of the valve with an orifice will change. Therefore, the orifice plate is double-layered to increase pressure resistance. Fig. 10 is an enlarged view of the orifice and its periphery in a flow control valve according to a modified example, and corresponds to Fig. 9(b). 1001 denotes a backup orifice plate.

[0060] The inlet 810 communicates with the master side air system or the work side air system. The protrusion 814 communicates with the intake and exhaust port 813 (i.e., with the outside air). Therefore, in the case of a positive pressure test as in the first embodiment (and modified example 1), the 810 direction is the high pressure side and the 814 direction is the low pressure side, and a force is applied to the orifice plate in the direction of 814. Therefore, in the case of a positive pressure test, as shown in Fig. 10(a), a backup orifice plate 1001 is placed between the orifice plate 804 and the O-ring 803 so as to support the orifice plate 804 from the low pressure side. In the case of a negative pressure test as in the second embodiment (and modified example 2), the 814 direction is the high pressure side and the 810 direction is the low pressure side, and a force is applied to the orifice plate in the direction of 810. Therefore, in the case of a negative pressure test, as shown in Fig. 10(b), a backup orifice plate 1001 is placed between the orifice plate 804 and the O-ring 805 so as to support the orifice plate 804 from the low pressure side. The backup orifice plate 1001 has holes with a larger diameter that are concentric with the fine holes of the orifice plate 804. This makes it possible to increase the rigidity of the orifice portion without affecting the flow rate characteristics determined by the diameter of the fine holes of the orifice plate 804.

[0061] [Test results for valves with built-in orifices] Below, we will show that the orifice-integrated valve has flow characteristics similar to those of a critical nozzle. We will also show the operating conditions when the orifice is considered as a pseudo-critical nozzle. <Experiment 1> The results are shown when the orifice-integrated valve is applied to a large leak test of the second modified example. Figure 11(a) shows the orifice diameter d = 0.15 mm, V C = 50 ml, secondary pressure P3 = 11.3 kPa (= gauge pressure - 90 kPa), primary pressure 201.3 kPa (= gauge pressure 100 kPa), valve open 0.5 s, V S The pressure difference (P M -P W In a test system with an internal volume of 50 ml, when the test product had a large leak space of 0.5 ml, a differential pressure of approximately 70 Pa was detected. In addition, since this is a "fixed-volume injection" situation, E is positive, and when Vs is positive, as shown in equation (9), P M >P W It is as follows.

[0062] The experimental results are compared with the theoretical values ​​for the critical flow of compressible gases. The pressure ratio in experiment 1 is

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[0063] First, the critical gas flow rate Q CR [Pa m 3 / s] (mass flow converted into energy at temperature T) is known to be given by equation (13) (for example, equation (19) in Reference 1: Yoshida et al., "Calculation formula for gas flow rate through a cylindrical conduit in various gas flow regions," Surface and Vacuum, Vol. 63, No. 6, pp. 304-310, 2020).

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[0064] Substitute the following values ​​into equation (13):

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[0065] Q CR × Time (t) is E(=n e RT).

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[0066] The results of Table 1 are shown in Figure 11(b). The experimental values ​​and theoretical values ​​show good agreement, and it is estimated that a critical flow occurs in the orifice under the conditions of Experiment 1.

[0067] <Experiment 2> FIG. 12(a) is a graph showing the detected differential pressure when a large leak test is performed using the first embodiment (secondary atmospheric pressure) and the primary pressure is changed. Cis set to 200 ml, and the figures show the cases of VS = -2 ml, 0 ml, and 2 ml. When the primary pressure P1 exceeds 80 kPa (= absolute pressure 181.3 kPa), the behavior of the differential pressure becomes stable. FIG. 12(b) is a graph showing the detected differential pressure when a large leak test is performed using the second embodiment (secondary negative pressure) and the primary pressure is changed. C is set to 200ml, and the figures show the cases of VS=-2ml, 0ml, and 2ml. Throughout the entire test pressure range, the primary pressure and the differential pressure are roughly proportional to each other. The diameter of the orifice used in the above tests was 0.15 mm, the same as in Experiment 1. S The reason why a pressure difference occurs even at 0 ml is thought to be mainly due to manufacturing errors in the orifice diameters on the master side and the work side. How to deal with manufacturing errors in the orifice diameter will be described later.

[0068] Figure 13 shows the results of Fig. 12(a) and (b) with the test volume difference (V S In any volume difference case, when the primary pressure exceeds a gauge pressure of 200 kPa (absolute pressure of 301.3 kPa), the behavior of the differential pressure change in the first and second embodiments is the same. When the pressure ratio in the first embodiment is calculated at a gauge pressure of 200 kPa (absolute pressure of 301.3 kPa), it is as follows.

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[0069] From the above, it is considered that the orifice-integrated valve in Experiment 2 behaves similarly to the critical nozzle at pressure ratios below 0.33.

[0070] <Summary> In summary, an orifice valve behaves as a critical pressure nozzle under the appropriate pressure ratio. The critical pressure ratio of an orifice valve is different from that of a critical pressure nozzle. The critical pressure ratio is considered to differ for each orifice diameter, and when the orifice-integrated valve is used as a critical nozzle, the critical pressure ratio is determined by experiment, for example, as described above.

[0071] [Third embodiment] In the first and second embodiments, small leak tests and large leak tests were performed using the differential pressure method. ΔP in equation (2) of the "Principle of Small Leak Testing" can be measured as the pressure fluctuation on the work side. In addition, in the large leak test, if the amount of gas released is constant (the opening time of the flow control valve is constant), the P M Since the value of can be known in advance, P in equation (9) of "Principle of Large Leak Test" can be calculated as M -P W Also, P W It can be known simply by measuring Therefore, a leak test method and leak tester that do not use a master will be described as a third embodiment.

[0072] FIG. 14 is an air circuit diagram showing an example of the configuration of a leak tester 14 according to the third embodiment. The air leak tester 14 includes a work container 303, a pressurized air supply source 1401, a pressure adjusting valve 1402, a pressure gauge 1403, a pressurizing valve 1404, a test pressure gauge 1405, an exhaust valve 1406, a flow control valve 1407, and a negative pressure generator 1408. Each container, air supply source, valve, and instrument are connected by a pipeline (air path) for carrying air. Note that the pressurizing valve 1404, the exhaust valve 1406, and the flow control valve 1407 may be abbreviated as V7, V8, and V9, respectively.

[0073] The pressure gauge 1403 is connected to a point G on the air path connecting the pressure regulating valve 1402 and the pressurizing valve 1404 . The test pressure gauge 1405 is connected to a point H on the air path connecting the pressurizing valve 1404 and the work container 303 . The exhaust valve 1406 and the flow rate control valve 1407 are connected to a point Q on the air path connecting the pressurizing valve 1404 and the work container 303 . The air path connected to "V7-HQ-work vessel" is called the "work air system." The work air system includes the "H-test pressure gauge," the "Q-V8" and "Q-V9" air paths, and the work vessel.

[0074] The pressure regulator valve 1402 regulates the pressure of the pressurized air supply. A pressurized valve 1404 provides pressurized air to the work air system. An exhaust valve 1406 connects the work air system to the outside. The flow control valve 1407 controls the amount of air discharged from the work air system to the negative pressure generator 1408 .

[0075] <Preparing for inspection items> The pressurizing valve 1404 and the flow control valve 1407 are closed, and the exhaust valve 1406 is opened. Then, the work air system is at atmospheric pressure. In this state, the inspection product 304 is placed in the work container 303. The inspection product 304 may be a non-defective product with no air leakage, or a defective product with air leakage.

[0076] <Small leak test> Pressurized air is supplied to the work air system by closing the exhaust valve 1406 and opening the pressurizing valve 1404. The test pressure gauge 1405 is monitored, and when the specified test pressure (P1) is reached, the pressurizing valve 1404 is closed.

[0077] If the inspection product 304 is a small defective product, the pressure of the work air system gradually decreases. The volume obtained by subtracting the external volume of the reference product from the work air system is V. C Then, the test pressure gauge 1405 detects the pressure drop given by equation (2) of the small leak test principle, and the leak flow rate Q is measured.

[0078] If the product being inspected is a good product or a product with a major defect, the small leak test will not detect a pressure drop. This is because air does not enter the product if it is a good product. If it is a product with a major defect, the area of ​​the product into which air can enter will immediately reach pressure P1.

[0079] <Large leak test> In the small leak test, pressure changes due to leakage are checked, and if the product is judged to be good (good), the test proceeds to the large leak test. At the end of the small leak test, the pressurizing valve 1404, the exhaust valve 1406, and the flow control valve 1407 are all closed.

[0080] Here, a large leak test using only the work air system will be described. The reference product is placed in the work container (the internal volume of the work container is V C ), a test pressure P1 is applied, and the pressure resulting from opening and closing the flow control valve 1407 for a specified time is P M , P M By substituting -P1 for ΔP0, we obtain equation (20).

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[0081] <If pressure change is not zero during small leak testing> As in the first and second embodiments, even if the small leak test is judged to be good, the test pressure does not necessarily remain at P1. E Then, the amount of material in the work air system is n x Then, the state of the work air system after the small leak test is expressed by equation (22).

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[0082] Based on the above, in the large leak test, the pressure P E Then, the flow control valve 1407 is opened and closed for a specified time to dispense a specified amount of substance (n e [mol]) of gas is released from the flow control valve 1407. The measured pressure (P' W ) to P E The value obtained by subtracting T The presence or absence of a large leak is determined by comparing with the above.

[0083] <Test End> At the end of the large leak test, the pressurization valve 1404, the exhaust valve 1406, and the flow control valve 1407 are closed. Open the exhaust valve 1406 to return the work air system to atmospheric pressure. Then, open the work container, replace the test piece, and conduct the next test.

[0084] [Third Modified Example]

[0085] In the leak test, it is difficult to always keep the test pressure at the specified value. The amount of gas released from the flow control valve is proportional to the primary side (high-pressure side) pressure. Therefore, if the test pressure is P' instead of P1, the pressure change ΔP' on the work side is given by Equation (25). [Equation] When Equation (25) is plotted as a graph with the horizontal axis V S and the vertical axis ΔP', it becomes Figure 15(b). The top graph is for the case of P' < P1, the middle is for the case of P' = P1, and the bottom is for the case of P' > P1. Assuming that ΔP T is determined on the premise that the test pressure is P1, if P' is smaller than P1, even if V S is actually zero, there is a possibility of detecting a differential pressure smaller than the threshold value ΔP T and misjudging it as "large leak detected". Conversely, if P' is larger than P1, even if there is a large V S there is a possibility of detecting a differential pressure (in absolute value) larger than the threshold value ΔP T and misjudging it as "no large leak".

[0086] Therefore, monitor the actual test pressure P' and correct the detected ΔP' using the following Equation (26). [Equation] Then, the value of the corrected ΔP' will be consistent with Equation (21), and the pass / fail of the large leak test can be determined by comparing it with the threshold value ΔP T determined on the premise of the test pressure P1.

[0087] [Fourth Embodiment] In the third embodiment, a positive test pressure is applied by a pressurized air supply source 1401, and a negative pressure generator 1408 is connected to the secondary side (low pressure side) of the flow control valve. In the fourth embodiment, a negative test pressure is applied by a negative pressure generator instead of the pressurized air supply source 1401 in Fig. 14, and a pressurized air supply source is connected to the primary side (high pressure side) of the flow control valve instead of the negative pressure generator 1480. This makes it possible to realize a negative pressure leak test without using a master.

[0088] [Manufacturing errors of orifices in differential pressure systems] It is difficult to precisely align the diameters of the two orifices in a valve with a pair of built-in orifices. Because the gas flow rate is proportional to the diameter of the orifices, any discrepancy in the diameters will result in unequal amounts of gas being supplied from the orifices to the master side and the work side.

[0089] In the equations (5) and (6) of the principle of the large leak test, the amount of gas injected into or released from the flow control valve is equal to n e First, let us consider the case where this differs due to an error in the orifice diameter. The amount of gas supplied to the master side is e M The amount of gas supplied to the workpiece is e W Then, equations (5) and (6) can be rewritten as follows:

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[0090] Next, consider the case where the internal volumes of the master side and the work side are different and air is supplied from orifices with different diameters (see also Figure 16). The internal volume of the work side is V X , the master side internal volume continues to be V C Let us assume that. Test pressure is P1, and the master side is M , e on the work side W After supplying the gas, the pressure inside the master vessel is P M , the pressure inside the workpiece container is P W Then, the respective pressure changes are expressed by equations (30) and (31).

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[0091] Let us reconsider equations (5) and (6) under the condition of equation (32) (see also Figure 17). The pressure change on the master side is given by equation (33).

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[0092] In other words, by adjusting the internal volume of the work side in advance to satisfy equation (32) (to obtain the same pressure fluctuation as on the master side under the specified test pressure), even if there is a difference in the orifice diameter, V S It is possible to obtain a differential pressure proportional to the volume of air that can enter and exit the test item. [Explanation of symbols]

[0093] 3,4,5,6,7 Leak Tester 301 Master Container 302 Standard product 303 Work container 304 Inspection items 305 Pressurized Air Supply Source 306 Primary pressure regulating valve 307 Pressure gauge 307 308 First valve 308 309 Differential pressure gauge 309 310 Second Valve 311 3rd valve 312 Pressure Regulating Valve 401 4th valve 501 Negative Pressure Generator 601 Negative Pressure Generator 701 Positive pressure air supply source 702 Pressure Regulating Valve 8 Flow Control Valve 801 Actuating valve 802 Chip Plate 803 O-ring 804 Orifice Plate 605 O-ring 806 Manifold 901 Piston 902 Screw 1001 Backup orifice plate

Claims

1. 1. A flow controller having two air paths, comprising: an orifice plate having holes for restricting the flow rate of each air path; A valve that simultaneously opens and closes two air paths A flow controller comprising:

2. 2. The flow rate controller according to claim 1, a backup orifice plate disposed in contact with the orifice plate on the low pressure side of the orifice plate; A flow controller comprising:

3. A master container for storing standard products; a master side air circuit connected to the master container; A work container for storing the inspection items; A work side air circuit connected to the work container; a first valve for controlling compressed air supplied to the master side air circuit and the work side air circuit; A second valve that connects the master side air circuit and the work side air circuit to the outside; a flow control valve for controlling the amount of air discharged from the master side air circuit and the work side air circuit to the outside, or the amount of air injected from the outside into the master side air circuit and the work side air circuit; A differential pressure gauge that measures the differential pressure between the master side air circuit and the work side air circuit. A leak tester equipped with

4. 4. The leak tester according to claim 3, The flow control valve includes two air paths, an orifice plate having small holes for restricting the flow rate of each air path, and a valve for simultaneously opening and closing the two air paths. A leak tester characterized by:

5. 4. The leak tester according to claim 3, a positive pressure air source connected to the first valve; a negative pressure generator connected to the external side of the flow control valve; A leak tester equipped with

6. 4. The leak tester according to claim 3, a negative pressure generator connected to the first valve; a positive pressure air supply source connected to the external side of the flow control valve; A leak tester equipped with

7. A work container for storing the inspection items; A work air circuit connected to the work container; A first valve that controls compressed air supplied to the work air circuit; a second valve connecting the work air circuit to the outside; A flow control valve that controls the amount of air discharged from the work air circuit to the outside or injected from the outside into the work air circuit; A pressure gauge to measure the test pressure of the work air circuit and A leak tester equipped with

8. 8. The leak tester according to claim 7, a positive pressure source connected to the first valve; a negative pressure generator connected to the external side of the flow control valve; A leak tester equipped with

9. 8. The leak tester according to claim 7, a negative pressure generator connected to the first valve; a positive pressure air supply source connected to the external side of the flow control valve; A leak tester equipped with

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