JP3238242B2 - Airtightness inspection method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for performing an airtight inspection of various test works using a leakage inspection medium such as helium gas.

[0002]

2. Description of the Related Art Various types of industrial products such as die-cast products are subjected to an airtight inspection of this kind. Conventionally, for example, in a gas-type airtightness inspection apparatus, Freon gas has been used as a leakage inspection medium, and a charge tank type leak detector has been used. Helium gas can be used as an inspection medium instead of Freon gas.
However, in these cases, there are problems such as an environmental problem and a long inspection time. The present applicant has already proposed, in Japanese Patent Application No. 5-55286, an airtightness inspection method and apparatus which can solve such a problem, have a relatively simple apparatus configuration, and improve the inspection accuracy. I have.

Next, the above-described airtightness inspection device proposed by the present applicant will be schematically described. FIG. 2 shows the overall configuration of the airtightness inspection apparatus.
Is a chamber for accommodating a subject 3 described later. An exhaust pipe 2 a for scavenging is connected to the chamber 2. 4 is O
A seal member 5 such as a ring is a driving device including a pneumatic or hydraulic cylinder for moving the chamber 2 forward and backward with respect to the apparatus main body 1. The subject 3 is, for example, an aluminum wheel for a vehicle. The subject 3 is stored and set at a predetermined position in the chamber 2 as shown in the figure. At this time, the subject 3 is pressed from both sides by a seal pressure plate 7 via a clamp seal 6. This seal pressure plate 7
Is advanced and retracted by a driving device 8 including a pneumatic or hydraulic cylinder.

[0004] Reference numerals 9, 10 and 11 denote air pressure sources, respectively. The air pressure source 9 supplies air into the chamber 2, and the air pressure sources 10 and 11 supply air into the subject 3. The air pressure source 11 is provided with a differential pressure gauge 12. Reference numeral 13 denotes a helium gas pressure source that supplies helium gas into the subject 3. Reference numeral 14 denotes a discharge pipe leading to the inside of the subject 3. Furthermore, 15 is chamber 2
A stirring fan installed in the
Is driven to rotate.

Reference numeral 17 denotes a charge tank for collecting a sample gas to be inspected.
Is connected to the chamber 2 via an opening / closing valve 18. 19 is a charge tank 17 via an opening / closing valve 20
Is a helium leak detector for introducing a sample gas from the charge tank 17, and the helium leak detector 21 is connected to the charge tank 17 via an opening / closing valve 22.

In the above case, an opening / closing valve 23 may be provided at an appropriate position in the exhaust pipe 2a, and the chamber 2 can be evacuated by controlling the opening / closing valve 23 as appropriate. The opening / closing valves 18, 20, 22 and the driving devices 5, 8
The operation of the drive motor 16 and the like are controlled by a control circuit (not shown).

An airtightness inspection method using the above airtightness inspection apparatus is as follows.
As described in the above-mentioned Japanese Patent Application No. 5-55286, the method will be schematically described here. Subject 3
Is set at a predetermined position in the chamber 2 and is sealed from both sides by a clamp seal 6. Then, the chamber 2 is shut off from the outside air at atmospheric pressure and is sealed. Next, air is supplied from the air pressure source 9 into the chamber 2, and the air is exhausted from the exhaust pipe 2a to clean the inside of the chamber 2.

After cleaning the inside of the chamber 2, a gas, for example, air (4 kg /
cm ² G) and a differential pressure leak test (gross leak) is performed. This differential pressure leak test is a preliminary test for checking whether or not a relatively large hole or the like exists in the subject 3. After the differential pressure leak test is completed, the sealed air is removed from the discharge pipe 14. Is exhausted again. As the gas, other than air, for example, a mixed gas of nitrogen gas and air may be used.

After completion of the preliminary inspection, helium gas is sealed in the subject 3 from the helium gas pressure source 13. Further, air is supplied into the subject 3 from the air pressure source 10 and pressurized to a certain pressure, whereby helium gas and air are mixed in the subject 3. Thereafter, the fan 15 is driven to rotate by the drive motor 16 to diffuse and stir the sample gas in the chamber 3 for a certain period of time.

Next, when charging the sample gas diffused and agitated in the chamber 2 to the charge tank 17, the charge tank 17 is evacuated by the vacuum pump 19. That is, the opening and closing valves 18 and 20 are opened,
The on-off valve 22 is closed, and in this state, the vacuum pump 19 is closed.
Is operated, the sample gas is collected into the charge tank 17.

As described above, the sample gas is charged from the chamber 2 into the charge tank 17, and further charged into the charge tank 1.
When collecting and introducing from 7 into the helium leak detector 21, the open / closed state of the open / close valve 18, 20, or 22 is set as described above, and evacuation is performed as appropriate. This causes the charge tank 17 and then helium
A sample gas can be efficiently and quickly collected into the leak detector 21, and as a result, high measurement accuracy can be obtained.

As described above, the preliminary inspection is performed on the subject 3, whereby the gross leak of the subject 3 can be inspected and determined in advance. In a helium leak test, helium gas used as a test medium has no concern about environmental problems and the like. In particular, during the differential pressure leak test, the inside of the chamber 2 accommodating the subject 3 can be performed under atmospheric pressure, so that there is no need for a vacuum step or the like. It can be simplified. On the other hand, when a gas is collected from the chamber 2 to the charge tank 17 and a helium leak test is performed, the charge tank 17 is evacuated to efficiently enter the charge tank 17 and then into the helium leak detector 21. The sample gas can be collected quickly.

[0013]

As described above, according to the inspection method and apparatus proposed by the present applicant, the differential pressure leak test is performed under the atmospheric pressure in the chamber 2 accommodating the subject 3. Can be. However, the atmosphere contains a small amount of the same helium gas as the detection gas (test medium). For this reason, when using the atmosphere as described above, there is a problem that an error may occur particularly in the detection accuracy of the PPM order.

The charge tank 17 includes the vacuum pump 1
The helium leak detector 2 which is a so-called vacuum system, which is used in a vacuum state, is a so-called vacuum system in which the sample gas is taken in by opening and closing the opening / closing valve 18 by reducing the pressure by 9.
Since it has the same degree of vacuum as that of 1, a vacuum method that can achieve consistency between the two is desirable. However, in an actual inspection apparatus, a plurality of chambers 2 may be attached to one helium leak detector 21 in order to improve the inspection efficiency. If the charge tank 17 is increased in response to this, it is necessary to increase the number of the vacuum pumps 19, which causes a problem that the apparatus becomes significantly complicated.

In view of the above, it is an object of the present invention to provide an airtightness inspection method and apparatus capable of further improving detection accuracy and inspection efficiency while taking advantage of the conventional apparatus.

[0016]

According to the method of the present invention, an object is set at a predetermined position in a chamber in a sealed state,
After the inside of the chamber is cleaned, a step of supplying nitrogen gas or carbon dioxide gas to replace the air, and a step of sealing the gas in the subject, performing a differential pressure leak test, and exhausting the sealed gas again Enclosing and mixing helium gas and air in the subject at a predetermined pressure, and diffusing and stirring the sample gas in the chamber for a certain period of time; and collecting the sample gas from the chamber to the first charge tank And supplying the sample gas from the first charge tank charged with the sample gas to the second charge tank, and introducing the sample gas from the second charge tank to the helium leak detector. Have.

The apparatus of the present invention also includes a chamber for accommodating a subject.
And a system for sealing the subject contained in this chamber.
Control means, differential pressure leak inspection means, chamber and subject
Air supply / exhaust means to the subject and helium to the subject
Gas supply / exhaust means, sample gas diffusion / stirring in chamber
Means for supplying nitrogen gas or carbon dioxide gas into the chamber.
Nitrogen or carbon dioxide gas pressure source and a large sample gas
An air suction type first charge tank, and a first charge tank
Vacuum type second channel that is connected in series with the
Large tank and the second charge tank.
Helium leak detector that detects helium from source gas
And a rectifier .

[0018]

According to the present invention, the basic operation of the inspection apparatus is basically performed in the same manner as that of the conventional apparatus. By using helium gas as the inspection medium, it is possible to eliminate concerns about environmental problems and the like. it can. In addition, the airtight inspection can be performed under the atmospheric pressure in the chamber accommodating the subject, so that a vacuum step or the like is not required. Therefore, it is possible to simplify the vacuum equipment and the device configuration for controlling the vacuum equipment.

In particular, in the present invention, when performing a helium leak test, after cleaning the inside of the chamber, a nitrogen gas or a carbon dioxide gas is supplied to replace the air. In addition, this is performed by supplying nitrogen gas or carbon dioxide gas into the chamber by a nitrogen gas or carbon dioxide gas pressure source. In addition, the inspection accuracy can be further improved at atmospheric pressure.

Further, a sample gas is collected from the chamber,
A sample gas sampling means for introducing the sample gas into the helium leak detector is provided. In this case, the sampling is performed by an atmospheric pressure suction type first charge tank and a vacuum type second charge tank. In particular, when a plurality of chambers are installed, by adding the first charge tank as one vacuum pump, it is possible to effectively cope with the plurality of chambers, and to perform appropriate inspection by a vacuum method in the second charge tank. And inspection efficiency can be improved.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of an airtightness inspection method and apparatus according to the present invention will be described below with reference to FIG. FIG. 1 shows the overall configuration of the device of the present invention. However, since the configuration and operation of the members corresponding to those of the conventional device shown in FIG. 2 are basically the same as those of the conventional device as described above, The detailed description is omitted here.

The apparatus of the present invention is provided with a nitrogen gas or carbon dioxide gas pressure source 24 capable of supplying a nitrogen gas or carbon dioxide gas into the chamber 2. The nitrogen gas or carbon dioxide gas pressure source 24 supplies nitrogen gas or carbon dioxide gas to an appropriate position in the chamber 2 via an opening / closing valve 25 as shown in FIG. The gas is replaced.

In FIG. 1, reference numeral 26 denotes a first charge tank, which is connected to the chamber 2 via an opening / closing valve 27. The first charge tank 26 is of an atmospheric pressure suction type, and samples the sample gas in the chamber 2 by moving the piston rod 26a forward and backward. The first charge tank 26 and the charge tank 17 (second charge tank) are connected in series via the opening / closing valve 18.

According to the present invention, in order to perform a helium leak test accurately, after cleaning the inside of the chamber 2,
The on-off valve 25 is opened to supply nitrogen gas or carbon dioxide gas from the nitrogen gas or carbon dioxide gas pressure source 24. Thus, the air in the chamber 2 is replaced by the nitrogen gas or the carbon dioxide gas. Then, from the air pressure source 11 to the subject 3
A gas (air) is sealed therein, and a differential pressure leak test is performed. After the differential pressure leak test is completed, helium gas and air are filled and mixed in the subject 3 at a predetermined pressure, and the sample gas in the chamber 2 is diffused and stirred for a certain period of time.

As described above, by replacing the inside of the chamber 2 with nitrogen gas or carbon dioxide gas at the time of inspection, it is possible to eliminate the influence of the helium gas contained in the atmosphere in particular, and to effectively detect PPM order. Can respond.

Next, the sample gas is supplied to a first charge tank.
In this case, the sample gas is collected at atmospheric pressure by opening and closing valve 27 and opening and closing valve 18 in this case.

When the sample gas is further charged into the second charge tank 17, the second charge tank 17 is evacuated by a vacuum pump 19. In this case, the open / close valves 18 and 20 are opened and the open / close valve is opened. Valves 22 and 27 are closed. By operating the vacuum pump 19 in this state, the sample gas is collected into the second charge tank 17.

As described above, the sample gas flows from the chamber 2
1 charge tank26And the second charge tank 17
Helium leak detector 21
be introduced. Atmospheric pressure suction type first charge tank26
And the vacuum type second charge tank 17.
Thus, for example, when a plurality of chambers 2 are installed,
A single vacuum pump without increasing the vacuum pump 19
First charge tank at 1926To add
This does not complicate the structure or configuration of the entire device, and
In addition, inspection efficiency is significantly improved without increasing costs
be able to.

[0029]

As described above, according to the present invention, not only there is no danger of causing environmental problems, but also the apparatus can be simplified and the sample gas can be efficiently collected, but the advantages of the conventional apparatus can be further utilized. On the other hand, there is an advantage that the detection accuracy and the inspection efficiency can be further improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an overall configuration of an airtightness inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing the entire configuration of a conventional airtightness inspection apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Device main body 2 Chamber 2a Exhaust pipe 3 Subject 5 Drive device 6 Clamp seal 7 Seal pressure plate 8 Drive device 9 Air pressure source 10 Air pressure source 11 Air pressure source 13 Helium gas pressure source 15 Fan 17 Second charge tank 18, 20, 22 , 23, 25, 27 Opening / closing valve 19 Vacuum pump 21 Helium leak detector 24 Nitrogen gas or carbon dioxide gas pressure source 26 First charge tank

Claims (2)

(57) [Claims] A step of setting a subject in a sealed state at a predetermined position in a chamber, cleaning the inside of the chamber, supplying nitrogen gas or carbon dioxide gas and replacing the air with air, Fill the gas, perform differential pressure leak inspection,
Evacuating the sealed gas again, enclosing and mixing helium gas and air in the subject at a predetermined pressure, and diffusing and stirring the sample gas in the chamber for a certain period of time; Collecting the sample gas from the chamber to the first charge tank, supplying the sample gas from the first charge tank charged with the sample gas to the second charge tank, and sampling the sample from the second charge tank to the helium leak detector. And a step of introducing a gas. 2. A chamber for accommodating an object, sealing means for sealing the object accommodated in the chamber, differential pressure leak inspection means, air supply and supply to the chamber and the object. and exhaust means, and a helium gas supply and exhaust means for said analyte, and the sample gas diffusion and stirring means within the chamber, a nitrogen gas or carbon dioxide gas pressure source capable of supplying nitrogen gas or carbon dioxide gas in the upper Symbol chamber , Sample gas
Atmospheric pressure suction type first charge tank for collecting
Connected in series with the first charge tank to collect sample gas
Vacuum type second charge tank and second charge tank
To detect helium from the sample gas collected at
And a leak detector .