JPH0489542A - Inspection of airtightness for hollow container - Google Patents

Abstract

PURPOSE:To achieve a higher inspection accuracy along with improvement in working environment by measuring a leak value of a gas to an inspection chamber from a hollow container by a gas measuring means connected to the inspection chamber. CONSTITUTION:A hollow container 4 as object to be inspected is arranged in an inspection chamber 2. The hollow container 4 and the inspection chamber 2 are evacuated separately to a specified vacuum so that the inspection chamber 2 becomes higher in vacuum than the hollow container 4 and a specified gas is supplied to the hollow container 4 from a gas supply circuit 18 containing a gas cylinder 23, reservoir tanks 24 and 25 and a vacuum pump 26 to measure the amount of the gas leaked to the inspection chamber 2 by a gas measuring means 8 connected to the inspection chamber 2. This eliminate overlooking of a leaking defect thereby achieving a higher inspection accuracy. The inspection within the inspection chamber closed also enables improvement in working environment with no fear of surrounding pollution or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for testing the airtightness of a hollow container, such as a fuel tank for an automobile.

As a conventional method for testing the airtightness of fuel tanks for automobiles, for example, as shown in FIG.
For example, 0 and 3 are submerged in the tank 51.
Apply a pressure of about kg/am1 and let it stand for a predetermined time. If there is a defect in the joint due to welding or soldering, bubbles 53 will be generated from the defect, so visually check it. A method is used in which the quality of airtightness is determined by checking.

Problems to be Solved by the Invention According to the conventional so-called submersion type airtightness inspection method, since the generation of air bubbles 53 is visually confirmed, it is easy to overlook the occurrence of air bubbles 53, and it is also difficult to determine the extent of defects. It is difficult to understand quantitatively, and there are limits to improving test accuracy.

Further, for example, when the tank 51 is pulled up from the water tank 52, water drips and scatters around the water tank 52, resulting in deterioration of the working environment.

The present invention was made in view of the above problems.
The purpose is to provide an inspection method that improves inspection accuracy and work environment, among other things.

Means for Solving the Problems In the inspection method of the present invention, a hollow container to be inspected is placed in an inspection chamber and sealed, so that the degree of vacuum inside the inspection chamber is higher than that inside the hollow container. A process of simultaneously evacuating the inspection chamber and the hollow container to a predetermined degree of vacuum, a process of supplying a specific gas into the hollow container maintained at a predetermined degree of vacuum, and a process of evacuating the hollow container by a gas measuring means connected to the inspection chamber. and measuring the amount of gas leaking from the container into the test chamber.

The gas used for the inspection is, for example, helium (He), and in that case, a mass spectrometer called a helium detector is used as the gas measuring means, and the presence or absence of helium leaking from the hollow container and the amount of leakage are detected by mass spectrometry. To detect.

Effect: According to the above method, by measuring the amount of gas leaking from the hollow container to the inspection chamber using a gas measuring means, it is possible to identify not only whether there is a defect but also the extent of the defect from the amount of gas leaking. can do.

Embodiment FIGS. 2 and 3 are diagrams showing a schematic configuration of the entire system in which the present invention is applied to the airtightness test of a fuel tank. In the figure, 1 is a rotary chamber support provided with three inspection chambers 2, 3 is a pallet that holds a fuel tank (hereinafter simply referred to as a tank) 4 to be inspected, and 5 is this pallet 4 to be inspected. This is a transfer device that takes in and out of the chamber 2.

Further, 6 is a vacuum pump unit, 7 is a control panel, and 8 is a helium detector as a gas measuring means.

The inspection chamber 2 has a structure that can be opened and closed in the vertical direction, and as described later, when the tank 4 supported on the pallet 3 is loaded from the transfer device 5 in the work setting process S, the inspection chamber 2 is in a sealed state. The airtightness is inspected while the chamber support 1 rotates once and returns to the work setting step S again.

The pallet 3 is used to restrain the tank 4 from being deformed, and is composed of an upper frame 10 and a lower frame 11 that are hinged to each other via a shaft 9, as shown in FIG. When the pallet 3 is in the inspection chamber 2, the tank 4 is restrained by the upper frame IO and the lower frame 11. On the other hand, when the pallet 3 is pulled out to the front side of the transfer device 5 by the push-pull mechanism 12 of the transfer device 5 as shown in FIG. The roller 14 engages with the groove 15 on the pallet 3 side. In this state, by rotating the link 13 with the cylinder 16, the upper frame 1o is opened, and the restraint of the tank 4 by the pallet 3 is released.

As shown in FIG. 3, each inspection chamber 2 includes a helium recovery circuit 17, a helium supply circuit 18, a fuel tank vacuum pump 19, and a clean air flushing circuit 20.
, a helium detector 8, a chamber rough quoting vacuum pump 21, and a chamber main quoting vacuum pump 22 are connected through piping within the chamber support 1, respectively.

The helium supply circuit 18 includes a helium gas cylinder 23, a reservoir tank 24, 25, and a vacuum pump 26, while the helium recovery circuit 17 includes a helium supply circuit 18.
The helium supply circuit 18, the helium recovery circuit 17, and the fuel tank vacuum pump 19 include a reservoir tank 24 and a vacuum pump 27 shared with the test chamber 2. Once sealed, it will be connected to the tank 4 inside the inspection chamber 2 via a connector (not shown). The vacuum pump unit 6 of FIG. 2 is formed by combining the vacuum pumps 19, 21, 22 and 26, 27.

Note that the clean air flushing circuit 2o is used to flush out the helium in the test chamber 2 before opening the test chamber 2 after the test is completed.

Next, a procedure for an airtightness test using the test device as described above will be explained.

As shown in FIG. 1 in addition to FIGS. 2 and 3, the tank 4 restrained by the pallet 3 on the transfer device 5 was sent into the inspection chamber 2 of the work cut process S by the push-pull mechanism 12. After the inspection chamber 2 is sealed, the helium supply circuit 18, helium recovery circuit 17, and fuel tank vacuum pump 19 are connected to the tank 4 in the inspection chamber 2, as described above.

When the inspection chamber 2 is sealed, the chamber rough evacuating pump 21 is started to start evacuation inside the inspection chamber 2, and at the same time, the fuel tank vacuum pump 19 is started to start evacuation inside the tank 4. .

When the degree of vacuum in the tank 4 reaches 200 torr, the operation of the fuel tank vacuum pump 19 is temporarily stopped, and under that degree of vacuum, the differential pressure is measured as the first stage airtightness (leakage) test. Do a test.

That is, when there is no leakage defect in the tank 4, the tank 4
The pressure inside is kept constant at 200 torr, but if the leakage defect is large, air leaks from the tank 4 to the inspection chamber 2, and the pressure inside the tank 4 becomes higher than the 200 torr. .

Therefore, the pressure change as described above is detected by the pressure control system of the tank 4, and only those tanks 4 in which no leakage defects are found are moved to the next inspection.If not, the subsequent inspection is determined to be poor airtightness. Abort.

At this time, in order to prevent the tank 4 from being dented, the pressure inside the inspection chamber 2 is continuously evacuated by the chamber coarse vacuum pump 21 so that the degree of vacuum is always greater than the degree of vacuum inside the tank 4. When the pressure inside the inspection chamber 2 reaches 20 torr, the operation is switched from the inspection chamber coarse vacuum pump 21 to the inspection chamber main vacuum pump 22, and evacuation continues.

Next, the pressure inside the tank 4 is reduced to 0.5 Torr, and when the pressure reaches 0.5 Torr, the auto-zero adjustment of the helium detector 8 is performed, and then helium is supplied into the tank 4 from the helium supply circuit 18 and the second Move on to the next stage inspection, ie leak test. At this time, the pressure inside the inspection chamber 2 is reduced to about 0.03), which is higher than the pressure inside the tank 4.

When the pressure inside the tank 4 reached 90 torr due to the supply of helium into the tank 4, a second stage leak test was conducted.
If helium leaks from the tank 4 to the inspection chamber 2, the helium detector 8 reacts and the amount of leakage is detected by the helium detector 8. Then, only if no leak defect is found in the second stage leak test, the next third stage test is performed.

In the third stage of inspection, the pressure inside the tank 4 is kept at 230 Torr by supplying helium, and a leakage inspection is performed. In this case as well, if helium leaks from the tank 4, the amount of helium leaked is detected by the helium detector 8.

In this way, only those in which no leakage defects are found in all of the first to third stage inspections are finally determined to have "passed" airtightness performance.

Here, the inspection is conducted in three stages to avoid excessive adhesion of helium molecules to the detector circuit and prevent deterioration of the helium detector 8, and also to detect any leakage defects during the process. This is to shorten the tank scavenging time and improve the detection level of the detector.

After the third-stage inspection is completed, the helium in the tank 4 is recovered by the helium recovery circuit 17, while the pressure inside the inspection chamber 2 and the tank 4 is restored, and as shown in FIG. One cycle is completed by performing the exchange.

Effects of the Invention As described above, according to the present invention, the hollow container to be inspected is placed in the inspection chamber, and the hollow container and the inspection chamber are arranged so that the degree of vacuum in the inspection chamber is higher than that in the hollow container. By evacuation to a predetermined degree of vacuum, supplying a specific gas to the hollow container, and measuring the amount of gas leaking from the hollow container to the inspection chamber using a gas measuring means connected to the inspection chamber, Unlike conventional visual inspection, it is possible to quantitatively grasp the extent of leakage defects based on the amount of gas leakage, and no leakage defects are overlooked, improving the inspection accuracy itself and improving the reliability of the inspection results.

In addition, unlike conventional methods, water is not used, and the test is conducted in a sealed test chamber, so there is no risk of contamination of the surrounding environment, and the work environment can be improved.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an embodiment of the present invention, and is an explanatory diagram showing pressure changes in the inspection chamber and fuel tank, Fig. 2 is a schematic explanatory diagram of the entire inspection device, and Fig. 3 is an explanatory diagram showing the pressure changes in the inspection chamber and the fuel tank. FIG. 4 is a perspective view of a pallet, and FIG. 5 is an explanatory diagram showing an example of a conventional airtightness inspection method. 2... Inspection chamber, 4... Fuel tank (hollow container), 8... Helium detector (gas measuring means)
, 18... Helium supply circuit, 19... Vacuum pump for fuel tank, 21... Chamber rough reference vacuum pump, 22... Chamber main reference vacuum pump. Figure 2 Figure 3 Connection 'tffi gift/habatarifunfuheliu JAγuntefufuhelium i sixty sweats same f■ kaotomeihafufu 7 outki 1 sea and Noah 5 soba-1 ■ quotation part 2'2po/fi H Sohahozu 1 for Yanhuang Bob 7bu

Claims (1)

[Claims] (1) A hollow container to be inspected is placed in the inspection chamber and sealed, and the inspection chamber and the hollow container are simultaneously vacuumed to a specified level so that the degree of vacuum is higher inside the inspection chamber than inside the hollow container. A process of evacuation to a certain degree, a process of supplying a specific gas into the hollow container maintained at a predetermined degree of vacuum, and a gas measuring means connected to the test chamber to measure the amount of gas leaking from the hollow container to the test chamber. A method for testing the airtightness of a hollow container, the method comprising: measuring the airtightness of a hollow container.