JP7162952B1 - Air leak inspection device and method - Google Patents

Abstract

An air leak inspection device capable of shortening the time required to evacuate an object to be inspected and the inside of the device to a predetermined pressure that allows inspection is provided. An exhaust pipe (4) connected to an object to be inspected (2), exhaust narrow pipes (5a, 5b) branching from the exhaust pipe via on-off valves (V1, V2) and having a diameter smaller than that of the exhaust pipe, and connected to the exhaust pipe. , a vacuum gauge 6 for detecting the pressure in the object to be inspected, a first vacuum pump 3a connected to an exhaust pipe via a shutoff valve V0, and a second vacuum pump 3b connected to an exhaust narrow pipe. The shut-off valve V0 is opened, the on-off valves V1 and V2 are closed, and the inspected object 2 and the inside of the exhaust pipe 4 are evacuated through the exhaust pipe 4 by the first vacuum pump 3a, and the exhaust narrow pipe 5a is evacuated by the second vacuum pump 3b. , 5b are evacuated. When the shut-off valve V0 is closed and the on-off valves V1 and V2 are opened to communicate the exhaust pipe 4 with the exhaust narrow pipes 5a and 5b, it is determined that there is a leak if the pressure detected by the vacuum gauge exceeds a predetermined threshold value. [Selection drawing] Fig. 1

Description

The present invention relates to an air leak inspection apparatus and method for inspecting for leaks in an object to be inspected, such as a vacuum device, a pressurized device, and a sealed device.

In general, leak inspection includes inspection using an air leak detector and a helium leak detector in addition to a submerged inspection. There are two types of air leak detectors: pressurization type and suction type (negative pressure type). In the pressurization type, the object to be inspected is filled with a detection gas and pressurized, and leaks are inspected by the decrease in pressure. In the suction type, the object to be inspected is evacuated and leaks are inspected by increasing the pressure. These air leak detectors can detect leaks up to about 1×10 ⁻³ Pa·m ³ /sec (converted to a pressure difference of 1 atmosphere). A helium leak detector fills the object to be inspected with helium and detects the leaked helium. When inspecting only whether or not the leak amount is less than the allowable amount in a production line, etc., the inspection time can be shortened and the sensitivity can be improved. For reasons such as extension of the maintenance time, leak inspection is performed up to about 1×10 ^-6 Pa·m ³ /sec, and in research, investigation, analysis, etc., it is about 1×10 ^-10 Pa·m ³ /sec. Small leaks up to

Air leak detectors are inexpensive and easy to handle, but their accuracy is low. Helium leak detectors are highly accurate, but they are very expensive, and running costs are also high due to the use of helium gas. In recent years, in response to the depletion of helium gas, expensive recovery equipment is also commonly used. Furthermore, since it has precision components such as analysis tubes, high-vacuum pumps, liquid nitrogen coolers, etc., which are sensitive to contamination, if a test object with a large amount of leakage and water or oil adhered is inspected, the accuracy may decrease or malfunction may occur. There are problems such as that it is easy to repair and that it takes a lot of time and effort to repair.

Patent Document 1 describes a leak detector that is less than the same price as conventional air leak detectors, is easy to handle, and has an accuracy close to that of helium leak detectors (a level that only inspects whether or not the leak amount is less than the allowable leak amount on a production line, etc.). The present inventor has proposed an air leak inspection device that can In the air leak inspection apparatus of Patent Document 1, after exhausting an object to be inspected to a predetermined pressure through an exhaust pipe by a vacuum pump, the shutoff valve of the exhaust pipe is closed and exhaust is performed only by the exhaust narrow pipe. A leak is detected depending on whether the pressure rises or not.

In the air leak inspection device of Patent Literature 1, by closing the shutoff valve by exhausting the pressure as close as possible to the reachable pressure of the vacuum pump, it is estimated that the pressure on the downstream side of the exhaust capillary is the reachable pressure of the vacuum pump. was Moreover, the air leak inspection device of Patent Document 1 has a problem that it takes time to exhaust the object to be inspected and the inside of the device to a predetermined pressure that allows inspection. When evacuating from atmospheric pressure to a range of about 10 to 1 Pa, it is common to use a vacuum pump with a reachable pressure of 0.5 to 1 Pa, but the closer to the reachable pressure, the slower the evacuation speed. This is because it takes a very long time to drop from 10 Pa to 1 Pa.

Japanese Patent No. 6228285

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and provides an air leak inspection apparatus capable of shortening the time required to evacuate an object to be inspected and the inside of the apparatus to a predetermined pressure that allows inspection. The task is to

Means for solving the above problems are as follows.
(1) an exhaust pipe connected to an object to be inspected;
an exhaust narrow pipe branched from the exhaust pipe via an on-off valve and having a diameter smaller than that of the exhaust pipe;
a vacuum gauge that is connected to the exhaust pipe and detects the pressure inside the test subject;
a first vacuum pump connected to the exhaust pipe via a shutoff valve;
A second vacuum pump connected to the exhaust capillary,
The on-off valve is closed and the shut-off valve is opened to evacuate the inspected object and the inside of the exhaust pipe through the exhaust pipe by the first vacuum pump, and evacuate the inside of the exhaust narrow pipe by the second vacuum pump. do,
An air leak inspection apparatus, comprising: a control unit that performs an inspection step of determining that there is a leak when the pressure detected by the vacuum gauge exceeds a predetermined threshold value when the on-off valve is opened and the cutoff valve is closed.

In the means (1), the object to be inspected and the inside of the exhaust pipe are evacuated through the exhaust pipe by the first vacuum pump, and the inside of the exhaust narrow pipe is evacuated by the second vacuum pump, and the downstream side of the exhaust pipe in the exhaust direction is discharged. is evacuated to a pressure lower than that on the upstream side, the exhaust pipe is communicated with the exhaust narrow pipe, and the pressure difference between the upstream side and the downstream side of the exhaust narrow pipe generates a minute flow rate in the exhaust narrow pipe. If there is a leak in the object to be inspected and the amount of leakage is greater than the exhaust speed of the narrow exhaust pipe, the pressure in the exhaust pipe will rise. If the leakage amount is small, the air will be exhausted from the narrow exhaust pipe, so the pressure in the exhaust pipe will not increase. If the pressure of the vacuum gauge is greater than a predetermined threshold value, it can be determined that there is a leak, and if it is less than the threshold value, it can be determined that there is no leak.

Evacuation of the object to be inspected and the inside of the exhaust pipe by the first vacuum pump can be completed in a short period of time, compared to conventionally evacuating the entire system to a predetermined degree of vacuum with one vacuum pump. In addition, since the inner volume of the exhaust narrow tube is smaller than that of the object to be inspected and the inner volume of the exhaust pipe, the second vacuum pump suffices to evacuate the exhaust narrow tube with a pump that is smaller and less expensive than the first vacuum pump. Therefore, when the shut-off valve is closed and the on-off valve is opened, the pressure on the downstream side of the exhaust pipe is already lower than the pressure on the upstream side. Evacuation time required for generation is shortened, and inspection time can be shortened. When multiple inspections are continuously performed on multiple objects to be inspected, the on-off valve is closed at the end of the inspection to keep the inside of the exhaust pipe in an exhausted state. Since it is not necessary to evacuate the inside of the exhaust narrow pipe immediately, it is only necessary to evacuate the inside of the exhaust pipe, so the inspection time for the entire inspection can be greatly shortened.

(2) The air leak inspection device according to (1), wherein the on-off valve is provided upstream of the exhaust narrow pipe in the exhaust direction.

In the above means (2), since the on-off valve is provided on the upstream side of the exhaust narrow pipe, by closing the on-off valve when the inspection is completed, it is possible to continuously inspect a plurality of objects to be inspected. , the inside of the exhaust narrow tube can always be kept in an exhausted state. On the other hand, in the method of Patent Document 1, even if the on-off valve is provided on the upstream side of the exhaust narrow pipe, as soon as V0 and Vw are opened, a large amount of air enters the exhaust narrow pipe from the downstream side. Each time an object was inspected, it was necessary to evacuate the inside of the narrow tube, which took time and effort.

(3) The air leak inspection apparatus according to (1) or (2), wherein the reachable pressure of the second vacuum pump is equal to or lower than the reachable pressure of the first vacuum pump.

In the above means (3), the second vacuum pump evacuates the inside of the narrow exhaust tube having an inner volume smaller than that of the object to be inspected and the exhaust tube. A smaller and relatively inexpensive pump can be used.

(4) The air leak inspection device according to any one of (1) to (3), wherein the exhaust narrow pipe is connected in parallel with a plurality of exhaust narrow pipes having different conductances.

In the above means (4), it is possible to determine a plurality of leak levels by selecting one or a combination of a plurality of exhaust tubules having different conductances. Further, by screening the value to be inspected with an exhaust narrow tube having good conductance, even when leak gas enters the exhaust narrow tube, the recovery time of the degree of vacuum in the exhaust narrow tube can be shortened.

(5) Before the inspection step, the control unit opens the shut-off valve and the on-off valve, evacuates the inside of the narrow exhaust pipe and the exhaust pipe by the first vacuum pump, and The air leak inspection device according to any one of (1) to (4), characterized in that a preparatory step of evacuating the inside of the exhaust narrow pipe is performed.

In the above means (5), since the preparation process of evacuating the inside of the exhaust pipe and the narrow exhaust pipe is performed before the inspection process, it is not necessary to exhaust the air from the beginning in the inspection process, and the inspection can be performed immediately.

(6) When the control unit determines that there is a leak in the inspection step, the control unit opens the shut-off valve and the on-off valve, evacuates the narrow exhaust pipe and the exhaust pipe by the first vacuum pump, and 2. The air leak inspection device according to any one of (1) to (5), characterized in that a narrow tube evacuation process is performed to evacuate the inside of the exhaust narrow tube by a vacuum pump.

In the above means (6), since the air in the object to be inspected that has a leak enters the exhaust narrow pipe, it is necessary to evacuate the inside of the exhaust narrow pipe so as not to affect the inspection of the next object to be inspected. can.

(7) an exhaust pipe connected to an object to be inspected;
an exhaust narrow pipe branched from the exhaust pipe via an on-off valve and having a diameter smaller than that of the exhaust pipe;
a vacuum gauge that is connected to the exhaust pipe and detects the pressure inside the test subject;
a first vacuum pump connected to the exhaust pipe via a shutoff valve;
A second vacuum pump connected to the exhaust capillary,
The on-off valve is closed and the shut-off valve is opened to evacuate the inspected object and the inside of the exhaust pipe through the exhaust pipe by the first vacuum pump, and evacuate the inside of the exhaust narrow pipe by the second vacuum pump. an exhaust process to
an inspection step of determining that there is a leak when the pressure detected by the vacuum gauge exceeds a predetermined threshold value when the on-off valve is opened after the exhaust step and the shutoff valve is closed after the exhaust step. Method.

(8) Before the inspection step, the shut-off valve and the on-off valve are opened to evacuate the exhaust tube and the inside of the exhaust tube by the first vacuum pump, and evacuate the inside of the exhaust tube by the second vacuum pump. The air leak inspection method according to (7), further comprising a preparatory step for evacuation.

(9) When it is determined that there is a leak in the inspection step, the shut-off valve and the on-off valve are opened, the first vacuum pump evacuates the narrow exhaust pipe and the exhaust pipe, and the second vacuum pump The air leak inspection method according to (7) or (8), further comprising a narrow tube exhaust step of exhausting the inside of the exhaust narrow tube.

According to the present invention, evacuation of the object to be inspected and the inside of the evacuation pipe by the first vacuum pump can be completed in a short period of time compared to conventional evacuation of the entire system to a predetermined degree of vacuum by one vacuum pump. In addition, since the inner volume of the exhaust narrow tube is smaller than that of the object to be inspected and the inner volume of the exhaust pipe, the second vacuum pump suffices to evacuate the exhaust narrow tube with a pump that is smaller and less expensive than the first vacuum pump. Therefore, the exhaust time required to generate the pressure difference necessary for the leak inspection between the upstream side and the downstream side of the exhaust narrow tube is shortened, and the inspection time can be shortened. Since the inspection can be started only by evacuating the inside of the exhaust pipe after the inside of the narrow tube is evacuated, the inspection time for the entire inspection can be significantly shortened.

1 is a system diagram of an air leak inspection device according to an embodiment of the present invention; FIG. 2 is a flow chart showing the operation of the preparation process of the air leak inspection device of FIG. 1; 2 is a flow chart showing the operation of the inspection process of the air leak inspection apparatus of FIG. 1; 2 is a flow chart showing the operation of the narrow tube exhaust process of the air leak inspection device of FIG. 1; FIG. 2 is a diagram showing the difference in exhaust time between the air leak inspection device of FIG. 1 and a conventional air leak inspection device; FIG. 2 is a diagram showing a temporal change in detected pressure by the air leak inspection device of FIG. 1;

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an air leak inspection device 1 according to an embodiment of the present invention. This air leak inspection device 1 is for inspecting leaks in an object 2 to be inspected, and includes a first vacuum pump 3a and a second vacuum pump 3b (they are collectively referred to as vacuum pumps 3), an exhaust pipe 4, and a first vacuum pump 3b. A first exhaust narrow tube 5 a and a second exhaust narrow tube 5 b (both are collectively referred to as an exhaust narrow tube 5 ), a vacuum gauge 6 , and a control section 7 are provided.

The object 2 to be inspected is an object to be inspected for an air leak inspection. In the present invention, various devices such as a vacuum device having an evacuated space such as a thermos bottle or a vacuum jacket, a pressurized device having a pressurized space such as a pressure vessel, and a sealed device having an airtight or liquid-tight sealed portion are used. Can be inspected. FIG. 1 shows a vacuum vessel to which a tip tube 2b communicating with a space 2a to be evacuated is connected.

The first vacuum pump 3a may be a rotary pump capable of evacuating the inspected object 2 and the exhaust pipe 4 to a vacuum of about 0.5 to 1 Pa, and does not require a mechanical booster pump or a diffusion pump.

The second vacuum pump 3b is a vacuum pump capable of evacuating the insides of the first exhaust narrow tube 5a and the second exhaust narrow tube 5b to a vacuum of about 0.5 to 1 Pa, and may be a rotary pump. However, if the sensitivity is to be further enhanced or if the inner diameter of the exhaust narrow tube is to be relatively large, a high vacuum pump such as a small molecular turbopump may be used.

The exhaust pipe 4 is made of stainless steel pipe and has an inner diameter of 10 to 100 mm. The inner diameter of the exhaust pipe 4 may be selected according to the exhaust volume of the object 2 to be inspected, and is 20 to 25 mm when the exhaust volume is 1 liter. One end of the exhaust pipe 4 is connected to the tip tube 2b of the device under test 2, and the other end is connected to the first vacuum pump 3a. Hereinafter, when the first vacuum pump 3a evacuates the inspected object 2 through the exhaust pipe 4, the inspected object side in the exhaust direction of the exhaust pipe 4 is called the "upstream side", and the vacuum pump side is called the "downstream side". A filter 8 is provided on the upstream side of the exhaust pipe 4, a work valve Vw is provided on the downstream side of the filter 8, a shutoff valve V0 is provided on the downstream side, and a leak valve VL is provided on the downstream side of the shutoff valve V0. there is The work valve Vw is closed when the inspected object 2 is replaced, etc., to prevent water or oil from adhering to the inner surface of the exhaust pipe 4 due to inadvertent entry of air into the exhaust pipe 4. is. The leak valve VL is opened when the operation of the first vacuum pump 3a, which is a rotary pump, is stopped to prevent the working oil of the pump from flowing back into the exhaust pipe 4. FIG. A branch pipe 4a is provided downstream of the work valve Vw. A cleaning gas such as nitrogen (N ₂ ), carbon dioxide (CO ₂ ), argon (Ar), or the like is introduced into the exhaust pipe 4 , that is, the object 2 to be inspected, upstream of the shutoff valve V 0 of the exhaust pipe 4 . A gas introduction section 9 is provided.

The first exhaust narrow pipe 5a and the second exhaust narrow pipe 5b are made of stainless steel pipe or copper pipe, are thinner than the exhaust pipe 4, and have an inner diameter of 1 to 6 mm. In the embodiment, the first exhaust narrow tube 5a has an inner diameter of 3 mm and a length of 50 cm, and the second exhaust narrow tube 5b has an inner diameter of 1 mm and a length of 1 m, but the present invention is not limited to this. The first exhaust narrow tube 5a and the second exhaust narrow tube 5b are provided in parallel. That is, one end of the first exhaust narrow pipe 5a is connected to the branch pipe 4a of the exhaust pipe 4 via the first on-off valve V1, and the other end is connected to the second vacuum pump 3b via the collecting pipe 4b. One end of the second exhaust narrow pipe 5b is connected to the branch pipe 4a of the exhaust pipe 4 via the second on-off valve V2, and the other end is connected to the second vacuum pump 3b via the collecting pipe 4b. The first exhaust narrow pipe 5a and the second exhaust narrow pipe 5b may be directly connected to the exhaust pipe 4 via the first on-off valve V1 and the second on-off valve V2, respectively, without providing the branch pipe 4a.

A Pirani vacuum gauge or a thermocouple vacuum gauge can be used as the vacuum gauge 6, but the Pirani vacuum gauge is preferable. The Pirani vacuum gauge obtains the pressure from changes in the resistance value of a platinum thin wire that loses heat due to the collision of gas molecules. A sensor portion 6a of the vacuum gauge 6 is connected downstream of the filter 8 in the vicinity of the branch pipe 4a. The main body 6b of the vacuum gauge 6 detects and displays the pressure (degree of vacuum) in the exhaust pipe 4, that is, in the inspection object 2, and outputs a digital value of the detected pressure to the control unit 7, which will be described later. Like the vacuum gauge 6, the collecting pipe 4b is also provided with a vacuum gauge 11 comprising a sensor portion 11a and a main body 11b. A vacuum gauge 11 detects the pressure downstream of the first exhaust narrow tube 5a and the second exhaust narrow tube 5b. It should be noted that the vacuum gauge 6 and the vacuum gauge 11 may be provided with two sensor portions, the sensor portion 6 and the sensor portion 11, and the body portion 6b and the body portion 11b may be shared and switched to communicate with the control portion 7. .

The control unit 7 controls opening and closing of the shut-off valve V0, the first opening/closing valve V1, and the second opening/closing valve V2 based on the detected pressure output from the vacuum gauge 6 by sequence control, and controls the leakage of the inspection object 2. The presence or absence of leakage is determined and the presence or absence of leakage is displayed on the display unit 10 .

Here, a method for selecting the diameter D and the length L of the exhaust narrow pipe 5 will be described. Exhaust resistance is generated when the gas flows through the pipe during evacuation. To indicate how easily the pipe flows, the reciprocal of the exhaust resistance is called conductance. Assuming that the conductance is C [m ³ /s] and the pressures at both ends of the pipe are P ₁ [Pa] and P ₀ [Pa], the flow rate Q [Pa·m ³ /s] is expressed by the following equation.
Q=C(P ₁ -P ₀ )

Assuming that the gas flow in the pipe is a viscous flow region, P = (P ₁ + P ₀ )/2 [Pa], the diameter (inner diameter) of the pipe is D [m], and the length of the pipe is L [m]. The conductance C [m / s] of a long pipe is expressed by the following equation ⁽ Hirohiko Senda, "Theoretical calculation of evacuation in the viscous flow region and its application", January 2010, SEI Technical Review, No. 176 No., page 2).
C= ^1349D4P /L

Assuming that the flow rate Q is the permissible leak amount of the inspected object 2, the pressures P ₁ and P ₀ at both ends of the exhaust tube 5 are assumed according to the situation, and the diameter D of the exhaust tube 5 is fixed, from the above equation 2, the exhaust The length L of tubule 5 can be determined. Further, if the length L of the exhaust narrow tube 5 is fixed, the diameter D of the exhaust narrow tube 5 can be determined. When the diameter D of the exhaust narrow pipe 5 and the length L of the pipe are fixed, the allowable leak amount Q can be determined.

For example, assuming that the pressures P ₁ and P ₀ at both ends of the exhaust tube 5 are 10 Pa and 1 Pa, respectively, and the exhaust tube 5 has an inner diameter of 1 mm and a length of 50 cm,
P=(10+1)/2=5.5 [Pa]
D=1.0×10 ⁻³ [m]
L = 0.5 [m]
So the conductance C and flow rate Q are:
C=1349×(1.0×10 ⁻³ ) ⁴ ×5.5/0.5
= 1.48 × 10 ^-8 [m ³ /s]
Q=1.48× ^10-8 ×(10-1)
= 1.34 × 10 ^-7 [Pa·m ³ /s]

In this case, the presence or absence of leakage can be inspected based on the flow rate Q=1.34×10 ⁻⁷ [Pa·m ³ /s]. That is, in the present invention, if the amount of leakage exceeds the flow rate Q of the narrow exhaust pipe 5, the pressure P1 on the side of the inspected object 2 in the narrow exhaust pipe ₅ rises (the degree of vacuum decreases), and the inspected object 2 It can be determined that there is a leak. Conversely, if there is a leak amount equal to or less than the flow rate Q, it will be exhausted through the narrow exhaust pipe 5, so there will be _no rise in the pressure P1 (lower degree of vacuum) on the side of the inspected object 2 in the narrow exhaust pipe 5, and there will be no increase in the degree of vacuum. It can be determined that there is no leak in the body 2.

Table ₁ shows the flow rate Q of the exhaust tubule when the pressure P0 on the downstream side of the exhaust tubule is ₁ Pa, the length L of the exhaust tubule, the inner diameter D, and the pressure P1 on the upstream side of the exhaust tubule are changed. It is calculated. The flow rate Q of the exhaust narrow tube becomes smaller as the length L of the exhaust narrow tube becomes longer and the inner diameter D becomes smaller, indicating that leak detection on the order of -7 and -8 is possible.

The leak inspection device of this embodiment needs to be periodically inspected using a He leak standard to ensure accuracy. Since the above formula representing the conductance C [m ³ /s] and the flow rate Q [Pa m ³ /s] of a thin and long pipe is a case where the gas molecule is nitrogen (N ₂ ), N ₂ is replaced by He When the Pirani correction for conversion is performed and the flow rate Q of the exhaust narrow pipe is calculated under the same conditions as in Table 1, the results are as shown in Table 2. Table 2 shows that leak detection in the -7 order is possible using the He leak standard. In other words, by performing periodic inspections based on the He leak standard, it is possible to perform leak inspections on a scale equivalent to that of a He leak detector without using expensive He gas as the inspection gas.

When a plurality of exhaust capillaries 5a and 5b are connected in parallel as the exhaust capillaries 5, the combined conductance C is expressed by the following equation, and the combined conductance can be increased by combining a plurality of exhaust capillaries.
C=C1+C2

Next, the operation of the air leak inspection device 1 of the embodiment will be described based on the flow charts of FIGS. 2A, 2B and 2C and the pressure change diagrams of FIGS.

First, as shown in FIG. 2A, a preparatory step is performed before the air leak inspection of the object 2 to be inspected.
In FIG. 2A, at step 001, the shut-off valve V0, the first on-off valve V1 and the second on-off valve V2 are opened, the work valve Vw and the leak valve VL are closed, and at step 002 the first vacuum pump 3a and the second vacuum pump 3b are opened. to drive. As a result, the air in the exhaust pipe 4 is exhausted to the outside from the first vacuum pump 3a through the exhaust pipe 4, and the air in the first exhaust narrow pipe 5a and the second exhaust narrow pipe 5b is discharged to the branch pipe 4a and the exhaust pipe. 4 to the outside from the first vacuum pump 3a and through the collection pipe 4b to the outside from the second vacuum pump 3b.

FIG. 3 shows the difference in exhaust time between the conventional system and the present invention. Conventionally, one vacuum pump was used to evacuate the air from the entire system, so it was necessary to wait until the pressure of the entire system reached 1 Pa in order for the downstream side of the exhaust narrow tube to reach 1 Pa, which required tj time. . Moreover, since both the narrow exhaust tube and the exhaust pipe are evacuated for each inspection, the exhaust time is lengthened for each inspection, as indicated by the dashed line in FIG.
In contrast, in the present invention, the first vacuum pump 3a evacuates the air on the upstream side of the first exhaust narrow tube 5a and the second exhaust narrow tube 5b, and the second vacuum pump 3b evacuates the first exhaust narrow tube 5a and the second exhaust narrow tube 5b. Since the air on the downstream side including the exhaust narrow pipe 5b is exhausted, as shown by the solid line in FIG. reach. Further, since the inner volume of the downstream side including the first exhaust narrow tube 5a and the second exhaust narrow tube 5b is much smaller than that of the upstream side, as indicated by the broken line in FIG. , at a time tp0 shorter than the exhaust time tp1 of the first vacuum pump 3a, the downstream side of the first exhaust capillary 5a and the second exhaust capillary 5b reaches 1 Pa. Therefore, from time tp1 when the upstream side of the first exhaust narrow pipe 5a and the second exhaust narrow pipe 5b reaches 2 Pa, the inspection can be started immediately in the inspection process. In the inspection process, the object to be inspected and the exhaust pipe are evacuated each time, but the narrow exhaust pipe is not evacuated, so the time corresponding to tp1 is shortened.

In addition, by attaching the object to be inspected in the inspection process, the upstream side of the first exhaust narrow pipe 5a and the second exhaust narrow pipe 5b (the first on-off valve V1 and the second on-off valve V2 are closed, so the valve portions thereof The pressure on the upstream side) rises sharply, but the pressure on the downstream side of the first exhaust narrow pipe 5a and the second exhaust narrow pipe 5b remains at 1 Pa. Therefore, in the inspection process, it is sufficient to evacuate by the amount of the pressure increase on the upstream side of the first exhaust narrow tube 5a and the second exhaust narrow tube 5b, so the time required for the inspection process can be shortened.

When a plurality of inspection objects are continuously inspected a plurality of times, the first on-off valve V1 and the second on-off valve V2 are closed when the inspection is completed, and the first exhaust capillary 5a and the second exhaust capillary are closed. By keeping the inside of 5b in an exhausted state, it is not necessary to evacuate the inside of the first exhaust narrow pipe 5a and the second exhaust narrow pipe 5b each time the next inspection is performed, and it is only necessary to evacuate the inside of the exhaust pipe 4. , the inspection time for the entire inspection can be greatly reduced.

In step 003, it is determined whether or not t01 seconds (for example, 10 seconds) have elapsed since the vacuum pump 3 was driven. If not, the evacuation by the first vacuum pump 3a and the second vacuum pump 3b is continued. do. If t01 seconds have elapsed, the pressure P1 of the vacuum gauge 6 is read at step 104 . At step 005, it is determined whether the pressure P1 is 2 Pa or less. If the pressure P1 exceeds 2 Pa, it is considered that the exhaust is insufficient due to a leak in the apparatus or an abnormality in the second vacuum pump 3b or the like, and it is determined that there is a leak in the apparatus (leak level: L0) in step 006. and complete the preparation process. Further, when the pressure P1 is 2 Pa or less in step 005, it is determined that the inside of the apparatus is exhausted without leakage. Further, at step 007, the pressure P0 of the vacuum gauge 11 provided downstream of the first exhaust narrow tube 5a and the second exhaust narrow tube 5b is read, and at step 008, it is determined whether or not the pressure P0 is 1 Pa or less. If the pressure P0 exceeds 1 Pa, it is determined that the second vacuum pump 3b is malfunctioning, and in step 009, an alarm or the like is issued. Further, when the pressure P0 is 1 Pa or less in step 008, it is determined that the second vacuum pump 3b is normally evacuating, and t02 seconds (for example, 20 seconds) have elapsed since the vacuum pump 3 was driven in step 010. The preparation process is finished when the time has passed.

Next, as shown in FIG. 2B, an inspection process for air leak inspection of the object 2 to be inspected is performed.
In FIG. 2B, at step 101, the first on-off valve V1 and the second on-off valve V2 are closed. At time t0, the inside of the exhaust pipe 4 and the narrow exhaust pipes 5a and 5b has already been evacuated to 2 Pa by the evacuation of the first vacuum pump 3a and the second vacuum pump 3b in the preparation process described above. A leak test can be performed. Since the insides of the exhaust pipe 4 and the narrow exhaust pipes 5a and 5b are continuously evacuated by the first vacuum pump 3a and the second vacuum pump 3b, the pressure detected by the vacuum gauge 6 decreases as shown in FIG. In step 104, it is determined whether or not t03 seconds (for example, 30 seconds) have passed since the work valve Vw was opened. If not, the evacuation by the first vacuum pump 3a and the second vacuum pump 3b is continued. . If t03 seconds have elapsed, at step 105, the pressure P1 of the vacuum gauge 6 is read. At step 106, it is determined whether or not the pressure P1 is equal to or less than a predetermined first threshold value Pth1. The first threshold Pth1 is 1.5 Pa in this embodiment. If the pressure P1 exceeds the first threshold value Pth1 as indicated by the two-dot chain line x in FIG. It is determined that there is a leak (leakage level: L1), the inspection of the subject 2 is terminated, and the next subject is inspected. If the pressure P1 is equal to or less than the first threshold value Pth1, it means that there is no large leakage and the exhaust is being sufficiently performed. Therefore, from step 108 onward, a leak test is performed for the exhaust tubes 5a and 5b with a small flow rate.

At step 108, the first on-off valve V1 is opened while the second on-off valve V2 remains closed, and at step 109, the cut-off valve V0 is closed. When the shut-off valve V0 is closed at time t1, the inside of the object 2 to be inspected is cooled by the adiabatic expansion, but is then heated by the surrounding air to evaporate water and oil in the space 2a of the object 2 to be inspected. 4, the pressure detected by the vacuum gauge 6 rises for a while (ta).

Although the evacuation by the exhaust pipe 4 is stopped by shutting off the shut-off valve V0, since the first on-off valve V1 is open, the evacuation by the second vacuum pump 3b and the exhaust narrow pipe 5a is continued. However, since the conductance of the exhaust narrow tube 5a is smaller than the conductance of the exhaust tube 4, the flow rate is limited. When the pressure P1 is reached and the shut-off valve V0 is closed, if there is no leak in the test object 2, there is no flow in the first exhaust tubule 5a, and as indicated by the chain double-dashed line y in FIG. The degree of vacuum detected by 6 maintains P1+α. If there is a leak in the object to be inspected 2 and the amount of leakage is equal to or less than the allowable flow rate of the first exhaust narrow tube 5a, the leak amount passes through the first exhaust narrow tube 5a and is exhausted from the second vacuum pump 3b. The change in pressure detected by the total 6 is small. Also, if there is a leak in the inspected object 2 and the amount of leakage is equal to or greater than the allowable flow rate of the first exhaust narrow pipe 5a, the leak does not pass through the first exhaust narrow pipe 5a. As a result, the pressure detected by the vacuum gauge 6 rises as indicated by the chain double-dashed line z in FIG.

Therefore, in step 110, it is determined whether or not t04 seconds have passed since the shutoff valve V0 was closed. read the pressure P2 of At step 112, it is determined whether or not the pressure P2 is equal to or less than a predetermined second threshold value Pth2. As indicated by the chain double-dashed line z in FIG. 2, when the pressure P2 exceeds the second threshold value Pth2, it is considered that the pressure increases due to leakage of the test object 2 and the degree of vacuum deteriorates. , step 113 determines that there is a leak (leak level: L2). If the pressure P2 is equal to or less than the second threshold value Pth2, the process proceeds to step 114 and subsequent steps for leak testing of the exhaust tubule 5b using a minute flow rate.

At step 114, the first on-off valve V1 is closed and the second on-off valve V2 is opened. At step 115, it is determined whether or not t05 seconds have passed since the first on-off valve V1 was closed. Read the pressure P3. At step 117, it is determined whether or not the pressure P3 is equal to or less than a predetermined third threshold value Pth3. If the pressure P3 exceeds the third threshold value Pth3, it is considered that the pressure has increased due to the leak (leakage) of the object to be inspected 2 and the degree of vacuum has deteriorated. I judge. If the pressure P3 is equal to or less than the third threshold value Pth3, it is determined in step 119 that the leak (leakage) of the inspected object 2 is below the allowable level, and it is determined that there is no leak. The valve V2 is closed to end the inspection of the subject 1 and proceed to the inspection of the next subject.

If it is determined that there is a leak (leak level: L2) in step 113, and if it is determined that there is a leak (leak level: L3) in step 118, steps 113-1 and 118-1 are performed to exhaust the narrow tube shown in FIG. 2C. After the process is performed, the next object to be inspected is inspected. This is because it is considered that the leak was caused by the entry of air into the inspected object 2 when the work valve Vw was opened. This is to prepare so as not to affect the inspection.

As shown in FIG. 2C, in the narrow tube exhaust process, in step 201, the shutoff valve V0, the first on-off valve V1 and the second on-off valve V2 are opened, and the work valve Vw and the leak valve VL are closed. As a result, the air in the first exhaust narrow pipe 5a, the second exhaust narrow pipe 5b, and the exhaust pipe 4 passes through the branch pipe 4a and the exhaust pipe 4 by the first vacuum pump 3a and the second vacuum pump 3b, and the first vacuum pump 3a The air in the first exhaust narrow tube 5a and the second exhaust narrow tube 5b is exhausted outside from the second vacuum pump 3b through the collecting pipe 4b.

In step 202, it is determined whether or not t01 seconds (for example, 10 seconds) have passed since the opening and closing of each valve in step 201. Continue to exhaust. If t01 seconds have elapsed, the pressure P1 of the vacuum gauge 6 is read in step 203 . At step 204, it is determined whether the pressure P1 is 2 Pa or less. If the pressure P1 exceeds 2 Pa, it is considered that the exhaust is insufficient due to a leak in the device or an abnormality in the second vacuum pump 3b or the like, and it is determined in step 205 that there is a leak in the device (leak level: L0). to complete the narrow tube exhaust process. Further, when the pressure P1 is 2 Pa or less in step 206, it is determined that the inside of the apparatus is exhausted without leakage. ) has passed, the first on-off valve V1 and the second on-off valve V2 are closed in step 207, and the narrow tube exhaust process is completed.

Following the leak test (first time) on the first object to be inspected, the leak test (second and subsequent times) is performed on the next object to be inspected. When the leak test for the first object to be inspected is completed, the first on-off valve V1 and the second on-off valve V2 are closed, and the first vacuum pump 3a and the second vacuum pump 3b remain driven. Also, the first object to be inspected is replaced with the next object to be inspected while the work valve Vw remains closed. As a result, when the inspection of the next object to be inspected starts, the inside of the exhaust pipe 4 will be at or near the atmospheric pressure, but the exposure to the atmosphere will be very short. Further, 1 Pa is maintained in the first exhaust narrow tube 5a and the second exhaust narrow tube 5b. If the first on-off valve V1 and the second on-off valve V2 are open, the air enters not only the exhaust pipe 4 but also the first exhaust narrow pipe 5a and the second exhaust narrow pipe 5b when exchanging the inspection object. It takes a lot of time to evacuate the next inspected object. In this embodiment, at the end of the inspection of the previous object to be inspected, the first on-off valve V1 and the second on-off valve V2 are closed to maintain the insides of the first exhaust narrow pipe 5a and the second exhaust narrow pipe 5b at 1 Pa. Therefore, when starting the inspection of the next object to be inspected, it is only necessary to open the shut-off valve V0 and evacuate the object to be inspected and the inside of the exhaust pipe 4 by the first vacuum pump 3a, thereby greatly shortening the time. After the inspection object and the exhaust pipe 4 are evacuated, the same steps as shown in the flowchart of FIG. 2B are repeated.

If, as in the conventional method, pressure is increased or decompressed and the pressure change is determined after a certain period of time, the same level of accuracy can be achieved even after a very long period of time after closing the shutoff valve of the exhaust pipe compared to the present invention. is not obtained. Further complicating the problem is the phenomenon of adiabatic expansion or adiabatic compression, which affects the pressure even if there is no leak, making it difficult to make an accurate judgment in a short time. However, in the present invention, when the leak amount is less than the allowable leak from the first exhaust narrow tube 5a and the second exhaust narrow tube 5b, the leak amount is exhausted from the first exhaust narrow tube 5a and the second exhaust narrow tube 5b. does not rise and it is determined that there is no leak. Therefore, compared to the conventional leak inspection apparatus in which even a product with an allowable leak is judged as a defective product, the leak inspection apparatus of the present invention can judge a product with an allowable leak or less as a non-defective product. , inspection accuracy is high.

If water or oil adheres to the space 2a of the object to be inspected 2, as indicated by the dotted line in FIG. By activating the gas introduction part 9, clean gas such as nitrogen (N ₂ ), carbon dioxide (CO ₂ ), argon (Ar), etc., is supplied to the inspection object 2 through the exhaust pipe 4 up to 100,000 to 110,000 Pa. can be introduced. By introducing the clean gas, the test object 2 is heated by adiabatic compression, and water and oil are evaporated and discharged. As a result, it is possible to reduce the pressure rise due to the influence of adiabatic expansion after reaching the pressure P1. can.

In this embodiment, the first vacuum pump 3a evacuates the test object 2 and the exhaust pipe 4 in a short time compared to conventionally evacuating the entire system to a predetermined degree of vacuum with one vacuum pump. is enough. In addition, since the internal volume of the exhaust narrow tube 5 is smaller than the internal volume of the inspected object 2 and the exhaust pipe 4, the evacuation of the exhaust narrow pipe 5 by the second vacuum pump 3b is performed by the first vacuum pump 3a. Compared to the evacuation in 4, a small and relatively inexpensive vacuum pump is sufficient. Therefore, when the shut-off valve V0 is closed and the on-off valves V1 and V2 are opened, the pressure on the downstream side of the exhaust pipe 5 is already lower than that on the upstream side. The exhaust time required to generate the required pressure difference is shortened, and the inspection time can be shortened.

In addition, the reachable pressure of the second vacuum pump 3b is equal to or lower than the reachable pressure of the first vacuum pump 3a, and the inside of the exhaust tube 5, which has a smaller internal volume than the test object 2 and the exhaust tube 4, is evacuated. Therefore, even a high-vacuum pump that can evacuate to a pressure lower than the reachable pressure of the first vacuum pump 3a can employ a pump that is smaller and relatively inexpensive than the first vacuum pump 3a.

By sealing the exhaust tubes 5a and 5b so that the atmosphere does not enter, the maintenance cycle due to the deterioration of the exhaust tubes 5a and 5b themselves and the deterioration of the performance of the second vacuum pump 3b can be extended.

The invention is not limited to the embodiments described above, but can be varied within the scope of the invention described in the claims.

For example, in the above-described embodiment, the first exhaust narrow tube 5a and the second exhaust narrow tube 5b are provided as the exhaust narrow tube 5, but one or three exhaust narrow tubes may be provided. In this case, by selecting one or a combination of a plurality of exhaust tubules with different conductances, it is possible to determine a plurality of leak levels. In addition, by screening with an exhaust tube with good conductance, even if leak gas enters another exhaust tube during the previous inspection, the recovery time of the degree of vacuum in the exhaust tube by the second vacuum pump while waiting for the next inspection is reduced. can be shortened.

In the above-described embodiment, the conductance of the exhaust tube 5 and the inspection pressures P1 and P0 are set so that a leak equal to or less than the minute flow rate of the exhaust tube 5 is determined to be acceptable. , they can be set to accept leaks exceeding the minute flow rate of the exhaust tubule 5 in order to save time. Reliability can be ensured means that the flow rate in the predetermined He leak standard inspection clearly has a significant difference and is larger than the pass/fail judgment line. The predetermined He leak standard is not limited to a single leak standard, but may be a plurality of composite values, preferably a value close to and not exceeding the allowable leak amount of each inspection line.

DESCRIPTION OF SYMBOLS 1... Air leak inspection apparatus 2... Object to be inspected 2a... Space 2b... Tip tube 3a... First vacuum pump 3b... Second vacuum pump 4... Exhaust pipe 4a... Branch pipe 4b... Collective pipe 5... Exhaust narrow pipe 5a... First exhaust Thin tube 5b Second exhaust thin tube 6 Vacuum gauge 7 Control unit 8 Filter 9 Clean gas introduction unit 10 Display unit V0 Shutoff valve V Open/close valve V1 First open/close valve V2 Second open/close valve Vw work valve

Claims (9)

an exhaust pipe connected to an object to be inspected;
an exhaust narrow pipe branched from the exhaust pipe via an on-off valve and having a diameter smaller than that of the exhaust pipe;
a vacuum gauge that is connected to the exhaust pipe and detects the pressure inside the test subject;
a first vacuum pump connected to the exhaust pipe via a shutoff valve;
A second vacuum pump connected to the exhaust capillary,
The on-off valve is closed and the shut-off valve is opened to evacuate the inspected object and the inside of the exhaust pipe through the exhaust pipe by the first vacuum pump, and evacuate the inside of the exhaust narrow pipe by the second vacuum pump. do,
An air leak inspection apparatus, comprising: a control unit that performs an inspection step of determining that there is a leak when the pressure detected by the vacuum gauge exceeds a predetermined threshold value when the on-off valve is opened and the cutoff valve is closed. 2. The air leak inspection device according to claim 1, wherein the on-off valve is provided on the upstream side of the exhaust narrow pipe in the exhaust direction. 2. The air leak inspection apparatus according to claim 1, wherein the reachable pressure of said second vacuum pump is equal to or lower than the reachable pressure of said first vacuum pump. 2. The air leak inspection device according to claim 1, wherein the exhaust narrow pipes are connected in parallel with a plurality of exhaust narrow pipes having different conductances. Before the inspection step, the control unit opens the shut-off valve and the on-off valve, evacuates the exhaust tube and the inside of the exhaust tube by the first vacuum pump, and evacuates the exhaust tube by the second vacuum pump. 2. The air leak inspection device according to claim 1, wherein a preparatory step of evacuating the inside is performed. When it is determined that there is a leak in the inspection step, the control unit opens the shut-off valve and the on-off valve, evacuates the narrow exhaust pipe and the exhaust pipe by the first vacuum pump, and the second vacuum pump. 2. The air leak inspection device according to claim 1, wherein a narrow tube evacuation process is performed to evacuate the inside of said exhaust narrow tube. an exhaust pipe connected to an object to be inspected;
an exhaust narrow pipe branched from the exhaust pipe via an on-off valve and having a diameter smaller than that of the exhaust pipe;
a vacuum gauge that is connected to the exhaust pipe and detects the pressure inside the test subject;
a first vacuum pump connected to the exhaust pipe via a shutoff valve;
A second vacuum pump connected to the exhaust capillary,
The on-off valve is closed and the shut-off valve is opened to evacuate the inspected object and the inside of the exhaust pipe through the exhaust pipe by the first vacuum pump, and evacuate the inside of the exhaust narrow pipe by the second vacuum pump. an exhaust process to
an inspection step of determining that there is a leak when the pressure detected by the vacuum gauge exceeds a predetermined threshold value when the on-off valve is opened after the exhaust step and the shutoff valve is closed after the exhaust step. Method. Before the inspection step, the shut-off valve and the on-off valve are opened to evacuate the exhaust tube and the inside of the exhaust tube by the first vacuum pump, and prepare to evacuate the inside of the exhaust tube by the second vacuum pump. 8. The air leak inspection method according to claim 7, further comprising steps. When it is determined that there is a leak in the inspection step, the shutoff valve and the on-off valve are opened to evacuate the narrow exhaust tube and the inside of the exhaust tube by the first vacuum pump, and the inside of the narrow exhaust tube by the second vacuum pump. 8. The air leak inspection method according to claim 7, further comprising a narrow tube evacuation step of evacuating the air leak.

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