JPH0915082A - Helium leak detector - Google Patents

Abstract

PURPOSE: To resume the leak test effectively by lowering the background level at a mass spectrometric section quickly even when a large quantity of He is mixed into an oil in an oil-sealed rotary vacuum pump due to gross leak. CONSTITUTION: When a measurement at a mass spectrometric section ANAL exceeds a threshold level, a microcomputer unit 4 judges that gross leak has occurred, and controls a solenoid valve GBV fixed to the gas ballast port 21 of an RP2 to open for a predetermined time. Consequently, atmospheric air is introduced through the gas ballast port 21 into the RP2 and He bubbles in the oil are stirred to be discharged quickly through the RP2. Since no He is discharged again from the RP2 at the time of leak test after occurrence of gross leak, the problem of increasing background level at the mass spectrometric section ANAL is solved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helium leak detector used when performing a sealing inspection or a sealing inspection.

[0002]

2. Description of the Related Art A helium leak detector is one of the effective means for inspecting pipes for leaks. As shown in FIG. 3, this apparatus includes a mass spectrometric unit ANAL that detects only helium (He), and a turbo that is a main pump that is arranged at a position where the mass spectrometric unit ANAL can be evacuated together with the device under test EXP. A molecular pump (TMP) 1 and an oil rotary vacuum pump (RP) 2 that functions as a back pump of the TMP 1 are provided, and a test valve TV is provided between the DUT EXP and the TMP 1.
Is arranged, a shutoff valve FV is arranged between TMP1 and RP2, and an intermediate valve BV is arranged in a line which directly communicates the DUT EXP and RP2. In the figure, TP is a test port for attaching / detaching the device under test EXP to / from the device.

The leak test in this device is performed according to the following procedure. First, the intermediate valve BV and the test valve TV are closed, the shutoff valve FV is held open, and the TMP is held.
1 and RP2 are activated,
The L is evacuated to a predetermined vacuum degree. The thick line in FIG. 4 indicates the portion where the exhaust is advancing at this time. Next, the device under test EXP is connected to the test port TP, this time the test valve TV and the shutoff valve FV are closed, and the intermediate valve B.
V is kept open, and the test object EXP is exhausted to a predetermined vacuum degree by RP2 as shown by the thick line in FIG. After that, the intermediate valve BV is closed and the test valve TV and the shutoff valve FV are held open to form an exhaust line as shown by a thick line in FIG. 6, and He is sprayed on the test object EXP. At this time, if there is a leak in the device under test EXP, a part of He flows into the mass spectrometric unit ANAL, He that is substantially proportional to the leak is detected, and as a result, the airtightness of the device under test EXP is indirectly measured. Will be measured.

[0004]

However, the device under test E
When a large amount of He leaks from XP (referred to as gross leak), the background value of He (zero point) in the mass spectrometric unit ANAL during the subsequent leak test.
Does not decrease sufficiently, so that a good quality test object EXP without any problem may be determined to be a defective product, and an effective test may not be performed.

Upon investigating the cause, a large amount of air having an extremely high He concentration is sucked into RP2, which acts as a back pump of TMP1, at the time of gross leak,
At this time, He was dissolved in the oil of RP2, and the dissolved He bubbles were again discharged from the intake port side with time, and this flowed back to the mass spectrometric unit ANAL and increased the background value. became.

In order to solve such inconvenience, it may be possible to deal with it by stopping the operation of the entire apparatus and replacing the oil of RP2 with a new oil. However, if this is done, the entire apparatus is restarted. The down time is long, the operation efficiency of the device is seriously hindered, and the maintenance requires a large cost and labor.

The present invention has been made in view of these problems, and a large amount of He is added to the oil of the oil rotary vacuum pump.
The purpose of the present invention is to provide a helium leak detector capable of promptly evacuating the oil even if it is mixed with the oil, thereby quickly lowering the background value of the mass spectrometric section and effectively restarting the leak test. I am trying.

[0008]

In order to achieve the above object, the present invention employs the following configuration.

That is, the helium leak detector according to the present invention comprises a mass spectrometric section for detecting only helium, a main pump for evacuating the mass spectrometric section together with the DUT, and an oil functioning as a back pump for the main pump. A rotary vacuum pump, wherein the oil rotary vacuum pump is equipped with a gas ballast port, the gas ballast port is provided with a solenoid valve that can be selectively opened and closed, and the mass spectrometry is performed. When the helium measurement value measured by the section exceeds a predetermined threshold value, control means for controlling the solenoid valve to be kept open for a certain period of time is provided.

[0010]

In such a structure, if the threshold value is given a value corresponding to the gross leak, a gross leak actually occurs and a large amount of He is sucked into the oil rotary vacuum pump, which is submerged in the oil. Even if it melts, the control means works when the measured value of helium in the mass spectrometric section exceeds the threshold value,
Since the solenoid valve attached to the gas ballast port of the oil rotary vacuum pump is controlled to be held open for a certain period of time, air is introduced into the oil rotary vacuum pump, and the atmosphere causes the oil in the oil rotary vacuum pump to change. He that is agitated and dissolved in oil in a bubble state is quickly discharged by the agitating action of the atmosphere. Therefore, the concentration of He in the oil rapidly decreases,
Even if the leak test is restarted after that, the amount of released He from the oil rotary vacuum pump is remarkably reduced, and the inconvenience that He enters the mass spectrometric section and raises the background value is dramatically improved. Moreover, according to the present invention, it is not necessary to stop the operation of other device parts such as the mass spectrometric unit and the high vacuum pump, not to mention the oil rotary vacuum pump, during which the operation of the system is greatly adversely affected. Without being extended, it will be possible to continue the leak test after the gross leak effectively after a very short loss time.

[0011]

An embodiment of the present invention will be described below with reference to the drawings.

The helium leak detector shown in FIG.
The structure is basically similar to that shown in FIG. That is, this is also a mass spectrometric unit ANAL that detects only helium (He), and a turbo molecular pump (TMP) that is a main pump that is arranged at a position where the mass spectrometric unit ANAL can be evacuated together with the device under test EXP. 1 and this TMP
Oil rotary vacuum pump (R
P) 2 and the device under test EXP and TMP1
The test valve TV is arranged between the two, the shutoff valve FV is arranged between the TMP1 and the RP2, and the intermediate valve BV is arranged in a line which directly connects the DUT EXP and the RP2. is there.

The procedure for the leak test is also the same as the conventional one described with reference to FIGS. 4 to 6. First, the intermediate valve BV and the test valve TV are closed and the shutoff valve F is closed.
By holding V open and activating TMP1 and RP2, the mass spectrometric unit ANAL is evacuated to a predetermined degree of vacuum (see FIG. 4). Next, the test object E is attached to the test port TP.
XP is connected, this time the test valve TV and the shutoff valve FV are closed, the intermediate valve BV is held open, and the test object EXP is exhausted to a predetermined vacuum degree by RP2 (FIG. 5).
reference). After that, the intermediate valve BV is closed and the test valve T
The V and the shutoff valve FV are held open, and He is sprayed on the test object EXP (see FIG. 6). At this time, the device under test E
If there is a leak in XP, a part of He will enter the mass spectrometric unit ANAL, and He that is approximately proportional to the leak will be detected.
As a result, the airtightness of the device under test EXP is indirectly measured.

In the above, the sealing property and the sealing state of the test object EXP are extremely poor, or the vacuum seal at the connection portion (test port TP part) between the test object EXP and the roughing line is insufficient or damaged. If a large amount of He leaks (gross leak), a different sequence control is taken to quickly end the test. At this time, as a back pump of TMP1. Since a large amount of air having an extremely high He concentration is sucked into working RP2, He dissolves in the oil of RP2. Therefore, when the leak test is restarted after the gross leak, the dissolved He bubbles are again discharged from the intake port side with the lapse of time.
Backflow to increase the background value, effectively stopping the leak test.

Therefore, in this embodiment, the RP2 having the gas ballast port 21 is adopted, and the atmosphere is selectively introduced into the gas ballast port 21 to eliminate the above-mentioned problems. .

More specifically, as shown in FIG. 2, this RP2 is inscribed in an eccentric position in the cylinder 22 in a rotor 2 state.
3 is arranged, and the tip of the vane 24 housed in the rotor 23 so as to be capable of projecting and retracting in the radial direction is slidably contacted with the inner circumference of the cylinder 22, and pump oil is pumped into the pump chamber P partitioned by the cylinder 22, the rotor 23 and the vane 24. Is filled and the rotor 23 is driven to rotate, thereby performing a well-known pump action of discharging the gas sucked from the intake port 25 to the exhaust port 26 while compressing the gas. Also, when the gas to be exhausted is a gas having a condensable property such as water vapor,
In order to prevent liquefaction of the gas due to compression and deterioration of the performance of the entire pump due to the liquefaction, the illustrated RP2 has a gas ballast port 21 opened near the exhaust port 26, and the gas ballast is compressed before the gas is compressed. It also has a function of introducing the atmosphere through the port 21 and exhausting the gas without increasing the partial pressure.

In this embodiment, a solenoid valve GBV is attached to the gas ballast port 21 so as to be openable and closable, and the solenoid valve GBV is provided by the microcomputer unit 4 serving as the control means of the present invention. It is designed to open and close.

The solenoid valve GBV is a conventional one that can selectively hold the gas ballast port 21 at least in an open state and a closed state by an input electric signal.

The microcomputer unit 4 is a CP
U is a known device including a memory, an interface and the like, and a predetermined program is stored in the memory, and the CPU follows the mass analysis unit ANA in accordance with the program.
A measured value S is input from L, a predetermined comparison and calculation are performed, and an opening / closing signal a is output to the solenoid valve GBV.

The control procedure will be described below according to the program. Normally, the solenoid valve GBV is kept closed. The CPU periodically compares the measured value S input from the mass spectrometric unit ANAL with a predetermined threshold value S0. This threshold value S0 is set to a level at which He exceeding the allowable amount may be introduced into RP2, that is, a measurement value corresponding to the gross leak level. When it is determined that the input measured value S is higher than the threshold value S0, it is determined to be gross leak, and the solenoid valve GBV is held open for a certain period of time. As a result, the gas ballast port 2
A large amount of atmospheric air is introduced into the pump chamber P of the RP 2 from the outside via 1. At the time of a gross leak, a large amount of He is sucked into the pump chamber P of the RP2 and is dissolved in the oil in the form of bubbles, but the He is introduced through the gas ballast port 21. The He is rapidly discharged from the exhaust port 26 by the stirring action of the atmosphere because it is internally stirred by the atmosphere. For this reason, the concentration of He in the oil rapidly decreases, and even if the leak test is restarted after that, the amount of He released from RP2 is significantly reduced, and He enters the mass spectrometric unit ANAL and the background value rises. The inconvenience caused is dramatically improved. Moreover, according to the present embodiment, it is not necessary to stop the operation of the RP2 and other device parts such as the mass spectrometric unit ANAL and TMP1 during that time, which may have a great adverse effect on the continuous operation of the device. Without it, it becomes possible to restart the leak test after the gross leak effectively after an extremely short loss time. In addition, since all the above controls are performed automatically, even a person with little knowledge can properly handle the device, and the utilization rate and usability of the device can be effectively improved.

The specific structure of each part is not limited to the above-described embodiment, but various modifications can be made without departing from the spirit of the present invention.

[0022]

Since the helium leak detector according to the present invention has the structure described above, when a gross leak occurs, it is detected and the atmosphere is temporarily introduced into the oil rotary vacuum pump, He dissolved in the oil can be stirred and quickly discharged. Therefore, even if the leak test is restarted after the gross leak, it is possible to hold the background value of the mass spectrometric unit at a low value and perform an effective leak test. Moreover, in the meantime, continuous operation is not impaired, and even if a person who is unfamiliar with the operation handles it, it can automatically recover from the gross leak, which is an excellent effect that the operation efficiency and usability of the device can be effectively improved. Played.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a schematic sectional view of an oil rotary vacuum pump used in the embodiment.

FIG. 3 is a circuit diagram corresponding to FIG. 1 showing a conventional example.

FIG. 4 is a diagram corresponding to FIG. 3 for explaining a general procedure of a leak test.

FIG. 5 is a diagram corresponding to FIG. 3 illustrating a general procedure of a leak test.

FIG. 6 is a diagram corresponding to FIG. 3 for explaining a general procedure of a leak test.

[Explanation of symbols]

 ANAL ... Mass spectrometry unit EXP ... Device under test GBV ... Solenoid valve 1 ... Main pump (turbo molecular pump; TMP) 2 ... Oil rotary vacuum pump; RP 4 ... Control means (microcomputer unit) 21 ... Gas ballast port

Claims (1)

[Claims] 1. A mass spectrometric section for detecting only helium, a main pump for evacuating the mass spectrometric section together with an object to be tested, and an oil rotary vacuum pump functioning as a back pump of the main pump. In the thing, the oil rotary vacuum pump adopts one having a gas ballast port, and a helium measurement value measured by the mass spectrometric unit is provided with a solenoid valve that can be selectively opened and closed at the gas ballast port. A helium leak detector characterized by comprising control means for controlling the solenoid valve to remain open for a certain period of time when a predetermined threshold value is exceeded.