JP3419612B2 - Leak detection 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 leak detection device used in a probe method in which a probe gas such as helium is sprayed around a hollow leak detection target to detect a leak portion of the target.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 1, this type of leak detection device is used by being attached to a hollow leak detection target a whose inside is evacuated to a vacuum by a vacuum pump b. If a leak portion is present in the object a, when a probe gas such as helium gas is sprayed around the atmosphere side, the leak is detected by detecting the probe gas that enters the inside of the leak portion of the object a. To do. If there is a leakage portion, air molecules will infiltrate into the object a in addition to the probe gas. However, the leakage detection device has an ionization chamber e, a magnetic field deflection type analyzer f and a detection chamber as shown in FIG. The gas atoms and molecules of the probe gas or the like that enter the ionization chamber are ionized by the impact of electrons from the filament c of the ionization chamber e, and the ionized gas atoms and the like are extracted by the extraction electrode d. It is accelerated and extracted from e, and the ions of the probe gas are deflected by the magnetic field of the permanent magnet that constitutes the magnetic field deflection type analyzer f and are selected so as to enter the ion collector h of the detection chamber g. The existence and size of the leak portion can be detected by the ion current flowing with the incidence. The driver i displays, for example, a bar graph on the display section j based on the ion current.

The deflection of ions by the magnetic field deflection type analyzer f is

[0004]

[Equation 1]

It is represented by Where r: radius of gyration, M
u: mass number, V: ion acceleration voltage, B: magnetic flux density. Since the analyzer f uses a permanent magnet, the magnetic field is constant. Therefore, if the potential of the ionization chamber e is constant, the number of detected ions is limited to one. In a leak detection device using helium as a probe gas, that is, a helium leak detector, the potential of the ionization chamber e is fixed to a potential at which helium ions can be detected.

[0006]

A conventional leak detection device using helium has only a function of detecting helium as a probe gas and searching for a leak location. In general, the detection of leakage of the airtight device is performed, for example, in the case of a vacuum container, when the pressure reduction by the vacuum pump is slower than expected. However, the reason why the pressure decrease is slower than expected is not only due to leakage but also due to water adsorbed in large amounts on the wall surface. In particular, such a phenomenon often occurs when a leak test is performed immediately after the airtight container is assembled, and is often mistaken for a leak. This is because a large amount of water adhered to the wall surface of the airtight container when left in the atmosphere remains. In addition, there is a case where the water adhered during the washing with water before the assembly remains. When the oil component is attached to the wall surface, the pressure drop is slower than when water is attached. Therefore, in such a case, it is difficult to find the leak location even if the leak detection device searches for the leak location, and it takes time for mischief.

[0007] The present invention, which, oxygen and nitrogen in the air in addition to the probe gas, water molecules ions be detected, and an object thereof is to provide a leakage detection device which can perform determination of the leakage relatively quickly is there.

[0008]

According to the present invention, the inside of a hollow leak detection target object is evacuated to a vacuum, and a probe gas such as helium gas is blown around the target object to remove the leak gas from the leak portion of the target object. Uses an ionization chamber that has an extraction electrode that ionizes gas atoms and molecules such as probe gas that infiltrate into the interior by electron impact and extracts ions, and a permanent magnet that selects specific ions among the ions ionized in the ionization chamber. And a magnetic field deflection type analyzer, a detection chamber having an ion collector for detecting the amount of the specific ions, and a display unit connected to the collector for displaying the amount of the specific ions. the power supply connected to said ionization chamber in order to detect the ions other than the ion of the probe gas in said collector together with a variable voltage power supply,
It shows the amount of ions ions other than the ion of the probe gas in said display unit by changing the voltage of the power source
By the the like, and to achieve the above object. The variable voltage power supply is set to a voltage at which helium ions, oxygen ions, nitrogen ions, and water molecule ions can be detected by the ion collector, and the display unit displays these four types of ions. It has preferred.
Further, the display unit can be clearly proportion of ions of a plurality of ions detected at the said ion collector
Yes .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows an embodiment of the present invention. In FIG. 2, reference numeral 1 denotes a leak detection object which is a hollow vacuum container. In order to search for a leak location of the object 1, a suction pipe 4 of a leak detection device 3 is provided in the interior 1a thereof via a partition valve 2a and a vacuum pump 2 and a partition valve 4a.
Are connected. After the inside 1a is evacuated by the vacuum pump 2 to a vacuum, a probe gas such as helium gas is sprayed on the outer periphery of the object 1, and when the object 1 has a leak portion, the probe gas enters the inside 1a, This is detected by the leak detection device 3, and the leaked portion is detected.

The leak detection device 3 is provided with a bent container 5 whose inside is evacuated to 10 ⁻³ Torr by a suitable vacuum pump (not shown), and the suction pipe 4 is provided at the inlet side of the container 5. Is provided with an ionization chamber 8 having a filament 6 for ionizing gas atoms and water molecules by electron impact and ionizing the generated ions, and an extraction electrode 7 for extracting the generated ions. The ionization chamber 8 is composed of a permanent magnet at the bent portion of the container 5. A magnetic field deflection type analyzer 9 is interposed, and a detection chamber 11 having an ion collector 10 is provided at the back of the container 5. The ion collector 10 has display portions 12a, 12b, 12c.
A driver 13 for operating the is electrically connected. 1
4a is a power supply for applying an ionization voltage to the ionization chamber 8, 14
b is a power supply for increasing the efficiency of the ion collector 10,
14c is a power source for applying an acceleration voltage to the extraction electrode 7, and 15
Is the power source of the filament 6, and especially the power source 14a is 0
As a variable voltage power source that can be varied from V to 300 V, the potential of the ionization chamber 8 was varied so that various ions generated in the ionization chamber 8 could be guided to the ion collector 10. Each display unit can be arbitrarily switched and displayed by operating the changeover switch 16, and the display unit 12a displays helium, water molecules,
It is assumed that the ion currents of nitrogen and oxygen ions are simultaneously displayed, and the change in the partial pressure of one of the partial pressures of helium, oxygen, nitrogen, or water with the passage of time is displayed on the display unit 12b. The display unit 12c is adapted to display the ion current due to the incidence of the probe gas ions on the collector 10 as in the conventional case.

When the leakage of the object 1 is to be detected, the partition valve 2a is opened to open the inside 1a of the object 1 to, for example, 10 ^-3.
It is possible to determine that there is no leakage point if the vacuum pump 2 exhausts to Torr and the pressure drop state of the inside 1a is good. If the pressure drop is worse than expected, the intake pipe 4
The partition valve 4a is opened to connect the leak detection device 3.
Then, a probe gas of, for example, helium is sprayed on the outer circumference of the object 1. If there is a leakage point in the object 1,
If the probe gas penetrates into the interior 1a and the leaked portion is large, air also penetrates into the interior 1a. Atoms and air of the probe gas that have infiltrated diffuse into the ionization chamber 8 where they are ionized by electron impact and accelerated by the extraction electrode 7 toward the magnetic field deflection type analyzer 9 and extracted. Since the magnetic field deflection type analyzer 9 is a permanent magnet and the magnetic field is constant, if the power supply 14a connected to the ionization chamber 8 is set to, for example, DC 250V, helium ions will enter the ion collector 10, and for example, DC 35.7V or 31.2V
Then, nitrogen ions or oxygen ions can be made incident on the collector 10. Therefore, if the display unit 12a is connected to the collector 10 and the voltage of the power supply 14a is changed to the above three levels, the display of the amount of ions corresponding to helium, nitrogen, and oxygen appears, and the leakage is caused by looking at this. Can be confirmed.

[0012] The object when water or oil during assembly is attached becomes poor pressure drop of the interior 1a as if it leaks to the inside of 1, conventionally such a case, the object 1
Even if there is a leak point, the detection of probe gas will be delayed.
As a result, the probe gas is repeatedly sprayed on the peripheral surface of the object 1 to search for the leaked point, which results in a long detection time . However , in the apparatus of the present invention, by changing the voltage of the power supply 14a connected to the ionization chamber 8 and displaying the amount of ions other than the probe gas ions on the display unit 12a, the partial pressure of a specific gas can be further reduced if necessary. By displaying the temporal change on the display unit 12b, it can be confirmed that the pressure drop is delayed due to the moisture or the like in the interior 1a, and the leak detection work can be completed relatively quickly. In this case, to display the many ions of water molecules, water, oxygen, the partial pressure of nitrogen appears to be both reduced and inter-time, the probe gas ions almost detected such Ino not leak location It can be confirmed that the water inside the object 1 is the cause.

[0013] The display unit of the present invention, as shown in FIG. 3, flop
Focusing on a gas other than Robugasu may be a display unit 1 2 for displaying the temporal change.

[0014]

As described above, according to the present invention, the power supply of the ionization chamber of the leak detection device used in the probe method is a variable voltage power supply and the display unit connected to the ion collector of the detection unit of the device. Since the amount of ions other than the ions of the probe gas is displayed, it is possible to reliably detect the leak location of the leak detection target object in a relatively short time even if moisture or the like inside the target object exists. The structure is relatively simple and has an effect that it can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a leak detection device used for leak detection of a conventional probe method.

FIG. 2 is an explanatory diagram of a leak detection device according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of another embodiment of the present invention.

[Explanation of symbols]

1 Leakage Detection Target, 1a Inside, 3 Leakage Detection Device, 7 Extraction Electrode, 8 Ionization Chamber, 9 Magnetic Field Deflection Analyzer, 10 Ion Collector, 11 Detection Chamber, 12, 12a, 12b, 12c Display, 14
a, 14b, 14c power supply .

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01M 3/20

Claims (3)

(57) [Claims] 1. A hollow leak detection target object is evacuated to a vacuum, a probe gas such as helium gas is sprayed around the target object, and a probe gas, etc., which penetrates into the interior from the leaked part of the target object. An ionization chamber having an extraction electrode for extracting ions as well as ionizing gas atoms or molecules by electron impact, and a magnetic field deflection type analyzer using a permanent magnet for selecting specific ions in the ions ionized in the ionization chamber, In a leak detection device equipped with a detection chamber having an ion collector for detecting the amount of the specific ions and a display unit connected to the collector for displaying the amount of the specific ions, In order to detect ions other than ions, the power supply connected to the ionization chamber should be a variable voltage power supply and the voltage of the power supply should be changed.
The leak detection device is characterized in that the amount of ions of ions other than the ions of the probe gas can be displayed on the display unit by. Wherein the upper hear varying voltage power supply, helium ions,
The oxygen ion, nitrogen ion, and water molecule ion are changed to a voltage that can be detected by the ion collector, and the display unit displays these four kinds of ions. Leak detection device. Wherein said display unit includes leakage detection device according to claim 1, characterized in that to express the percentage of ions of a plurality of ions detected in the above-mentioned ion collector.