JPH0915083A - Helium leak detector - Google Patents

Abstract

PURPOSE: To resume the leak test effectively by lowering the background level in an analytical tube quickly in safety 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 an analytical tube exceeds a threshold level, a microcomputer unit 10 judges that gross leak has occurred. An isolation valve FV is then closed to isolate an RP4 temporarily from the system and power is turned off. After opening the system to the atmosphere, drain valve 41a and oil injection valve 42a are opened sequentially to replace the oil in RP with new oil. Subsequently, the RP4 is started again and the isolation valve FV is opened to resume the state for carrying out leak test. Consequently, a large quantity of He is prevented from being discharged to the system during leak test after occurrence of gross leak without interrupting the leak test and the safety is ensured through automatic control.

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 powerful means for performing a sealing inspection or a sealing inspection. This equipment connects an oil rotary vacuum pump as a back pump to the exhaust port of a high vacuum pump that exhausts the analysis tube, and after the oil rotary vacuum pump exhausts the test object to a predetermined vacuum degree, Helium (He) is sprayed, and He leaking from the DUT is introduced into the analysis tube by back diffusion in the high vacuum pump, etc., and the amount of helium leaked from the DUT based on the introduced amount. Is measured indirectly.

[0003]

However, the hermeticity and sealing condition of the DUT are extremely poor, or the vacuum seal at the connection between the DUT and the roughing line is insufficient or damaged. Then, if a large amount of He leaks (called a gross leak), during the subsequent test,
The background value of He (zero point) in the analysis tube does not decrease sufficiently, so that a good test object with no problem in the degree of sealing or sealing can be judged as a defective product and an effective test can be performed. It often happens that you can't do it.

Upon investigating the cause, a large amount of air having an extremely high He concentration is sucked into the oil rotary vacuum pump that acts as a back pump of the high vacuum pump at the time of gross leak, and at this time, He is dissolved in the oil. , It was revealed that the dissolved He bubbles were again discharged from the inlet side with the passage of time, and this flowed back to the analysis tube and increased the background. In this way, once He is mixed in oil, it takes at least half a day to one day to completely release He even if the equipment is completely stopped and He is spontaneously released from the oil, during which time there is no leak. Since it cannot be tested, the operating efficiency of the device must be extremely low.

In order to cope with such a problem, a method of replacing the oil in the oil rotary vacuum pump once a gross leak is considered as one effective means.
However, in the case of simply stopping the entire device and manually changing the oil, it takes time and time to start up the analysis tube and high vacuum pump again, and there is a considerable adverse effect on operating efficiency. In addition, there is no change, and when the oil exchange of the oil rotary vacuum pump is performed immediately after stopping the device, the pump surface is hot (about 60 ° C) and the oil temperature rises to the same temperature.
It can also be a cause of accidents such as burns.

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.
An object of the present invention is to provide a helium leak detector capable of promptly and safely lowering the background of the analysis tube and effectively restarting the leak test even when the gas is mixed.

[0007]

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

That is, in the helium leak detector according to the present invention, an oil rotary vacuum pump, which is a back pump, is connected to the exhaust port of a high vacuum pump for exhausting an analysis tube. Electromagnetic shutoff valve to shut off from the system, electromagnetic drain valve and lubrication valve to selectively open and close the drain port and lubrication port of the oil rotary vacuum pump respectively, and the helium measurement value of the analysis tube has a certain threshold value. A gross leak determination means for determining a gross leak when the value exceeds the limit and a control means that operates when the gross leak determination means determines a gross leak are provided, and the control valve first holds the shutoff valve closed for a certain period of time. Then
In the meantime, the power supply of the oil rotary vacuum pump is turned off to open to the atmosphere, and during that period, control is performed such that the drain valve and the oil supply valve are sequentially held open for a certain period of time.

[0009]

In such a structure, if the threshold value corresponding to the gross leak is given to the gross leak determination means, the helium measurement value of the analytical tube actually rises above the threshold value, and the gross leak determination means becomes When a gross leak is determined, the control means operates to first disconnect the oil rotary vacuum pump from the system by closing the shutoff valve.
Stop the oil rotary vacuum pump and open to the atmosphere. Then, during that period, the oil of the oil rotary vacuum pump is replaced by sequentially opening the drain valve and the oil supply valve. Further, since the shutoff valve opens again after a certain period of time, the oil rotary vacuum pump is connected to the system and returns to the measurable state. At this time, since He is not mixed in the oil of the oil rotary vacuum pump, the problem of re-emission of helium, which has a bad influence on the analysis, is effectively solved. Moreover, according to the present invention, it is not necessary to stop the operation of other device parts such as the analysis tube and the high vacuum pump when changing the oil of the oil rotary vacuum pump, so that the continuous operability of the device is not impaired. Since the oil change is automatically performed, it is possible to effectively avoid the harm to the human body.

[0010]

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

As shown in FIG. 1, the helium leak detector includes an analysis tube 1, a turbo molecular pump (TMP) 2 which is a high vacuum pump for exhausting the analysis tube 1, and the T tube.
It is provided with a pair of oil rotary vacuum pumps (RP) 3 and 4 which are back pumps connected to the exhaust port 2b of the MP2.
And these analysis tubes 1, TMP2 and RP3, RP
4 is connected to a roughing line L communicating with the device under test EXP.

More specifically, the device under test EXP is detachably attached to the starting end of the roughing line L and the connecting portion is attached in an airtight state. An intermediate valve RV is provided in the middle of the roughing line L, the intake port 3a of the RP3 is connected to the end of the roughing line L on the downstream side of the intermediate valve RV, and the upstream side of the intermediate valve RV. To the roughing line L of the analysis tube 1 and the TMP2 via the test valve TV.
Is connected in parallel with the intake port 2a. Also, TMP2
The exhaust port 2b is connected to the roughing line L between the intermediate valve RV and RP3 via the gross leak flow valve GV, and at the same time connected to the intake port 4a of RP4 via the electromagnetic shutoff valve FV. . The upstream side of the intermediate valve RV and the upstream side (sometimes the downstream side) of the gross leak flow valve GV are connected via a counter flow valve CV. In FIG. 1, PLV1 and PLV2 are electromagnetic atmosphere release valves, and 40 is electromagnetically ON / OFF.
It is a power supply unit of RP4 that is turned off.

Here, the basic operation of this helium leak detector will be described. First, the device under test EXP is connected to the roughing line L, the test valve TV, the counter flow valve CV, and the gross leak flow valve GV are held closed, and the intermediate valve RV is opened to set R
The test object EXP is evacuated to a predetermined vacuum degree via the roughing line L by P3. In parallel with this, the shutoff valve FV
Is held open, TMP2 and RP4 are operated, and the analysis tube 1 is evacuated to a predetermined vacuum degree. FIG. 3 shows a state where the exhaust gas is advancing along the thick line portion.

From this state, first, the gross leak flow valve GV is turned on, and He is introduced into the device under test EXP. At this time, the exhaust gas is in a state shown by a thick line in FIG. 4, and if there is a leak location such as a crack or an opening in the test object EXP, after the He leaking from the leak location flows out to the roughing line L,
3, while being sucked in parallel by RP4, a part thereof wraps around in the exhaust port 2b of the TMP2 and after back diffusion in the TMP2, reaches the analysis tube 1 through the intake port 2a.
Then, the leak amount is measured inside the analysis tube 1. If the leak amount is too large at this point, another sequence control is performed such that the measurement is quickly ended in order to prevent contamination in the analysis tube 1. If not, then the gross flow leak valve GV is closed and the counter flow valve CV is opened. The counter flow valve CV is set to have a smaller throttle than the gross flow leak valve GV and allows a larger amount of He to pass therethrough. Then, the exhaust gas becomes the state shown by the thick line in FIG. That is, He that has flown from the roughing line L to the counter flow valve CV side is sucked into RP3 and RP4 as described above after passing through it, and part of it is introduced into the analysis tube 1 through TMP2. , The amount of leak is measured. Further, if the leak amount is not so large even at this stage, the process when the leak is not a gross leak is started. That is, the intermediate valve RV is closed, the counter flow valve CV is closed (of course, the gross leak flow valve GV remains closed), and the test valve TV is opened. At this time, the exhaust gas is in the state shown by the bold line in FIG. 6, the roughing line L is directly connected to the analysis tube 1, and also to the intake port 2a of the TMP 2, and R
Only P4 plays the role of the back pump of TMP. Then, He leaked from the device under test EXP is exhausted by RP4 via TMP2, and a part thereof is analyzed by the analysis tube 1
And the measurement is performed with high accuracy even with a minute leak amount.

In the above, focusing on, for example, RP4, the hermetically sealed or sealed state of the device under test EXP is extremely poor, or the vacuum seal at the connection portion between the device under test EXP and the roughing line L is insufficient or insufficient. It ’s damaged,
When a large amount of He leaks, R is discharged at any of the exhaust stages shown in FIGS. 4 to 6 (especially the exhaust stage shown in FIGS. 4 and 5).
A large amount of air with an extremely high He concentration is sucked into P4, at which time He dissolves in the oil and the dissolved He
Bubbles are again discharged from the intake port 4a side with time during the next leak test, and this flows back to the analysis tube 1 and causes an inconvenience of raising the background value.

Therefore, in this embodiment, the shutoff valve FV described above is used.
As shown in FIGS. 1 and 2, an electromagnetic drain valve 41a and a lubrication valve 42a for selectively opening and closing the drain port 41 and the lubrication port 42 of the RP4 are provided. It also serves both as a gross leak determining means for determining a gross leak when the helium measurement value of 1 exceeds a certain threshold value, and as a control means for operating when the gross leak determining means determines a gross leak. The microcomputer unit 10 is provided and the RP4
The oil is replaced automatically.

More specifically, the microcomputer unit 10 is a known unit including a CPU 10a, a memory 10b and an interface 10c. A predetermined program is stored in the memory 10b, and analysis is performed according to the program. The measured value S is input from the pipe 1 to perform predetermined comparison and calculation, and the shutoff valve FV and the power supply unit 4 are connected.
0, the atmosphere release valve PLV1, the drain valve 41a, and the oiling valve 42a are output the necessary signals a, b, c, d, and e.

An outline of control will be described below according to the program. First, it is determined whether or not the input measurement value S exceeds a threshold value S0 corresponding to a predetermined gross leak. Then, when it is determined that it exceeds the above, it is determined to be a gross leak, and a series of sequence control is performed. That is, first, the signal a is output to the shutoff valve FV and kept closed for a certain period of time, thereby disconnecting the RP4 from the system, outputting the signal b to the power supply unit 40 of the RP4 to stop the RP4, and further to the atmosphere release valve. A signal c is output to PLV1 to open RP4 to the atmosphere. Next, the signal d is output to the drain valve 41a to drain all or a fixed amount of the oil inside, and then the drain valve 41a is closed. This time, the signal e is output to the oil filling valve 42a, and the oil is almost the same as the drained oil. A quantity of oil is poured from the oil tank 43 (see FIG. 2). After that, the power supply unit 40 is turned on, the cutoff valve FV is opened when the intake port 4a of the RP4 falls below a predetermined pressure, and the RP4 is connected again as a back pump of the TMP2. At this point, the system is once again ready for the helium leak test.

By performing the above-described processing, this helium leak detector can surely eliminate the phenomenon that He is released from RP4 and flows back to the analysis tube 1 during the subsequent leak test, and the gross leak is prevented. It is possible to continue to effectively perform the leak test after the occurrence. Moreover, since it is not necessary to stop the operation of the analysis tube 1 and the TMP2 and other device parts when changing the oil of the RP4, there is no need to restart the analysis tube 1 and the TMP2, and the continuous operation of the system is possible. Can be effectively stopped. In this example, it was confirmed that the downtime for oil change can be shortened to about 1 minute at most. Moreover, according to such processing,
Since all the oil changes can be performed automatically, even if the oil on the surface of the RP4 or in it is heated to a high level, it is possible to effectively prevent the human body from being injured such as burns. It becomes possible to do.

The specific construction 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. For example, although the present invention is applied to RP4, which has a particularly large problem in the above-mentioned embodiment, by taking the same measures as above for RP3, the re-release of He from RP3 and the resulting analysis tube A rise in background can be prevented as well. Further, in order to shorten the time required to reach a predetermined pressure when the RP is restarted, the RP may be provided with a function of remaining heat and defoaming of oil.

[0021]

Since the helium leak detector according to the present invention has the structure described above, when a gross leak occurs, it is detected and He that has entered the oil of the oil rotary vacuum pump is discharged together with the oil. Then, it can be promptly replaced with new oil. For this reason, it is possible to quickly reduce the background value of the analysis tube after the occurrence of the gross leak and effectively restart the subsequent leak test without impairing the continuous operation of the apparatus. In addition, all of the above operations are performed automatically, so even if the temperature of the oil on the pump surface or inside rises to a high temperature, it is safe and does not suffer any human injury such as burns. It is possible to achieve the purpose.

[Brief description of the drawings]

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

FIG. 2 is a view showing the outer appearance of the entire apparatus in the same embodiment.

FIG. 3 is an operation explanatory view corresponding to FIG.

FIG. 4 is an operation explanatory view corresponding to FIG. 1;

FIG. 5 is an operation explanatory view corresponding to FIG. 1;

FIG. 6 is an operation explanatory view corresponding to FIG. 1.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Analysis tube 2 ... High vacuum pump (turbo molecular pump; TMP) 3 ... Oil rotary vacuum pump; RP 4 ... Oil rotary vacuum pump; RP FV ... Shutoff valve 10 ... Gross leak determination means, control means (microcomputer unit) 41 ... Drain port 41a ... Drain valve 42 ... Lubrication port 42a ... Lubrication valve

Claims (1)

[Claims] 1. An electromagnetic shutoff valve for selectively shutting off an oil rotary vacuum pump from a system, wherein an oil rotary vacuum pump, which is a back pump, is connected to an exhaust port of a high vacuum pump for exhausting an analysis tube. And an electromagnetic drain valve and oil supply valve for selectively opening and closing the drain port and oil supply port of the oil rotary vacuum pump,
The helium measurement value of the analysis tube is provided with a gross leak determination means for determining a gross leak when the measured threshold value exceeds a certain threshold value, and a control means that operates by the gross leak determination means determining a gross leak. By means of the means, the shut-off valve is first kept closed for a certain period of time, during which the power of the oil rotary vacuum pump is turned off and opened to the atmosphere, while the drain valve and the lubrication valve are sequentially kept open for a certain period of time. A helium leak detector characterized in that