JP3348489B2 - Leak test method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leak test method suitable for a leak test for a test object such as a container having low strength.
The present invention relates to a leak test method in which detection sensitivity is improved by previously replacing air in the test object with a replacement gas such as N ₂ or CO ₂ .

[0002]

2. Description of the Related Art Conventionally, there are the following leak test devices (leak testers). That is, in the vacuum spray type leak test apparatus shown in FIG. 2, the tracer gas detector 2 is connected to the inside of the DUT 1 so as to be able to conduct.
A roughing pump 3 for evacuating the inside of the DUT 1 is connected to the DUT 1. Then, He gas can be blown to the device under test 1 from a He gas blowing pipe 5 connected to a He (helium) gas cylinder 4.

In this apparatus, after evacuating the inside of the DUT 1 with a pump 3, a tracer gas detector 2 is connected to the inside of the DUT 1, and He gas is blown through a spray pipe 5.
A gas is blown to the DUT 1. Then, if there is a leak location in the DUT 1, He gas enters the DUT 1 from the leak location and is detected by the tracer gas detector 2.

[0004] In the vacuum hood type leak test apparatus shown in FIG. 3, similarly to the case of FIG. 2, the inside of the test object 1 is connected to the tracer gas detector 2 and the roughing pump 3 so as to be selectively connected. Then, the DUT 1 is covered with a hood 6 by inserting the DUT 1 into a container or the like.

In this apparatus, the inside of the device under test 1 is evacuated by a pump 3 to a vacuum, and
Fill with e gas. Then, if there is a leak in the DUT 1, He gas enters the tracer gas detector 2 via that leak, and He is detected. According to this device,
It is possible to detect the presence or absence of the entire leak of the DUT 1 and determine the entire leak amount.

In the vacuum internal pressure method shown in FIG. 4, a test object 1 in which He gas is sealed in advance is charged into a chamber 7, and the inside of the chamber 7 is evacuated by a pump 3. Then, if there is a leak in the DUT 1, He
The gas leaks and is detected by the tracer gas detector 2.

In the leak test apparatus according to the sniffer method shown in FIG. 5, the periphery of the test object 1 pressurized with He gas is searched by the sniffer probe 4, and
He gas leaked from the leaked portion is detected by the tracer gas detector 2.

Further, in the leak detecting apparatus based on the integration method shown in FIG. 6, a test object 1 into which a He gas is pressurized and press-fitted is charged into a hood 8 having a known capacity, and a pump 3 is provided in the hood 8.
And then leave it for a long time.
The change in the He concentration due to the He gas leaking from the sensor is measured by the tracer gas detector 2, and the result is integrated to detect the minute leak amount.

[0009]

However, all of these conventional leak test devices have the following problems. That is, since He is contained in the air at a concentration of about 6 ppm, in the sniffer method shown in FIG. 5, He contained in the air is detected by the tracer gas detector and becomes a noise component. Therefore, it is difficult for the sniffer method to detect a minute leak. Further, in this method, there is a possibility that He contained in the air may be determined to be due to leakage, and the reliability of the test result is low.

In the method shown in FIGS. 2 and 3, by performing a leak test with a high vacuum inside the device under test, the influence of He contained in the air can be suppressed, and the He gas leaking into the device under test can be suppressed. Is promoted, and the responsiveness to leakage of He gas is improved. But in this case,
Since the difference between the inner pressure and the outer pressure of the test object increases, for example, when a leak test is performed on a container having a low strength (hereinafter, referred to as a soft container) such as a fuel tank and a drum can, There is a problem that the test object is deformed or damaged. Further, when these methods are applied to, for example, the measurement of the amount of leak from the engine body, the leak significantly increases and a so-called large leak occurs. On the other hand, if the degree of vacuum in the test object is reduced, deformation and breakage of the test object can be avoided, but the detection sensitivity decreases due to He contained in the air, making it impossible to detect minute leaks. Would.

In the leak test method shown in FIGS.
In order to obtain good detection sensitivity, it is necessary to increase the difference between the inner pressure and the outer pressure of the test object, which is disadvantageous in that it cannot be applied to a weak container or the like.

The present invention has been made in view of the above problems, and has a leak test method which has a high detection sensitivity, can detect minute leaks with high accuracy, and can be applied to a soft container or the like. The purpose is to provide.

[0013]

According to the present invention, there is provided a leak test method comprising the steps of: replacing air in a test object with a replacement gas;
He gas is supplied to the outside of the test object and the test object is
While supplying the replacement gas into the test body,
Evacuated, and having a step of detecting the leaked text was He gas wherein the body under test.

[0014]

In the present invention, the air in the test subject is converted into He gas.
Or a gas having a very low He content (for example, N ₂ or CO ₂ ). This allows
Since the amount of He serving as a noise component is significantly reduced, He leaked into the device under test can be detected with high sensitivity without applying a high vacuum to the device under test. Further, in the present invention, since it is not necessary to apply a high vacuum to the inside of the test object, deformation and breakage of the test object can be avoided even when applied to a leak test of a soft container or the like.

In the present invention, the H leaked into the test object by increasing the pressure in the test object relatively high.
It is conceivable that the diffusion speed of the e-gas becomes slow and the response speed decreases. To avoid a decrease in response speed ,
In the step of detecting the He gas leaked into the device under test, the device under test may be evacuated while supplying the replacement gas into the device under test. As a result, a gas flow is formed in the device under test. By arranging the tracer gas detector downstream of this gas flow, good response characteristics can be obtained.

[0016]

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing a leak test method according to an embodiment of the present invention. First, the DUT 11 is connected to the hood 1.
2 and pipes 15 and 16 are connected to the DUT 11. Pipe 15 is connected to a replacement gas supply,
The replacement gas can be supplied into the device under test 11 through the pipe 15. The pipe 16 is the exhaust pump 1
4 and a tracer gas detector (He detector) 13. The replacement gas is, for example, N ₂ or C
There is a gas such as O ₂ , but contains no He or He
Other gases may be used as long as the content is extremely small.

Next, pipes 17 and 19 are connected to the hood 12. The pipe 19 is connected to a He gas supply source, and He gas can be supplied into the hood 12 through the pipe 19. The pipe 17 is connected to an exhaust pump 18.

Next, the air in the DUT 11 is evacuated by the exhaust pump 14 and the DUT 1 is
The replacement gas is intermittently or continuously supplied into the unit 1. Then, after the air in the DUT 11 has been sufficiently replaced with the replacement gas, the supply of the replacement gas into the DUT 11 is continued.
The air in the hood 12 is exhausted by the exhaust pump 18, and the hood 12 is filled with He gas via the pipe 19.
In this case, the pressure inside the test object 11 is set lower than the pressure outside the same. Also, the supply rate of the replacement gas or the exhaust pump 14 is set so that the pressure difference between the inside and the outside of the DUT 11 becomes large and the DUT 11 is not deformed or damaged.
And adjust the pumping speed.

As described above, by setting the pressure in the test object 11 lower than the pressure outside the test object 11 and filling the hood 12 with the He gas as the tracer gas, when the test object 11 has a leak location, The He gas enters the device under test 11 through the leak location, and the He gas is detected by the tracer gas detector 13.

In the present embodiment, since the air in the DUT 11 is replaced with a replacement gas such as N ₂ or CO ₂ , the amount of He gas as a noise component is extremely small. Therefore, the He gas leaked into the test object can be detected with high accuracy. Further, in the present embodiment, since the difference between the pressure inside the test object 11 and the pressure outside the test object 11 is small, the test object 11
Even if the container is a soft container, deformation and breakage of the test object 11 can be reliably avoided.

Further, in this embodiment, since the inside of the test object 11 is evacuated by the exhaust pump 14 while the replacement gas is supplied into the test object 11 through the pipe 15, the exhaust gas is exhausted from the inside of the test object 11. A gas flow towards the pump 14 is formed. Therefore, the He gas leaked into the device under test quickly enters the pipe 16 due to the flow of this gas,
It is detected by the tracer gas detector 13. Therefore, according to the present embodiment, good response characteristics can be obtained.

In the above-described embodiment, the case where the present invention is applied to the hood method has been described. However, it is needless to say that the present invention is not limited to the leak test method by the hood method. The invention can be applied to other methods such as a spraying method.

[0024]

As described above, according to the leak test method of the present invention, since the air in the test object is replaced with the replacement gas, the amount of He which is a noise component can be significantly reduced, and the detection sensitivity can be reduced. It is possible to detect small leaks. Further, according to the method of the present invention, since it is not necessary to apply a high vacuum to the test object, even when applied to a leak test of a soft container such as a fuel tank and a drum can and an engine body,
Deformation, breakage and large leakage of the test object can be avoided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a leak test method according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a conventional vacuum spray type leak test apparatus.

FIG. 3 is a schematic view showing a conventional vacuum hood type leak test apparatus.

FIG. 4 is a schematic view showing a conventional vacuum internal pressure type leak test apparatus.

FIG. 5 is a schematic view showing a conventional sniffer type leak test apparatus.

FIG. 6 is a schematic view showing a conventional integral type leak test apparatus.

[Explanation of symbols]

1, 11: test object, 2, 13: tracer gas detector,
3, 14, 18 ... pump, 6, 8, 12 ... hood, 7 ...
Chamber

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01M 3/20

Claims (1)

(57) [Claims] 1. A a process of replacing the air replacing gas in the body under test, supplied Then co He gas to the outside of the test object
The test sample is supplied while supplying the replacement gas into the test object.
Exhausting the test object and detecting He gas leaking into the test object.