JP2011069834A - Helium leak detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the response of a measurement value from being extended by restraining a change in the exhausting velocity, when switched from a roughing pump mode to a test mode. <P>SOLUTION: A helium leak detector includes a first high vacuum pump 4 connected to an analysis tube 3, a second high vacuum pump 5 for exhausting the outlet 4b of the first high vacuum pump, a back pump 1 for exhausting the outlet 5b of the second high vacuum pump through a first exhaust line, a test chamber 10 for guiding a helium leak from a body to be tested, a roughing pump 2 for exhausting the test chamber through a second exhaust line, and a test valve for allowing the connection edge between the first and second high vacuum pumps to communicate with the second exhaust line. Each pump is driven, while the test valve is closed, thus after the analysis tube and the test chamber are exhausted in parallel, opening the test valve and making the outlet of the first high vacuum pump to communicate with the second exhaust line, and inversely diffusing the first high vacuum pump from the test chamber for measuring the amount of helium leakage that goes around to the analysis tube. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

The present invention relates to a helium leak detector used for a sealing inspection for inspecting the presence or absence of leakage (leakage) in an airtight container or piping such as a sealing inspection or a sealing inspection.

There is a helium leak detector by a helium bombing method as means for performing sealing inspection and sealing inspection. As this helium leak detector, a reverse diffusion leak test method is known in which only helium reversely diffused by a high vacuum pump is guided to an analysis tube. In this reverse diffusion leak test method, the leak test can be performed by introducing the minimum amount of helium into the analysis tube, and the background value of the analysis tube is expected to decrease rapidly, reducing the tact time of the leak test. can do.

FIG. 8 is a diagram showing a configuration example of the helium leak detector based on the reverse diffusion leak test method. This helium leak detector includes an exhaust port of a high vacuum pump 7 (for example, a turbo molecular pump TMP) connected to the analysis tube 3 and a test chamber 10 that is configured to be able to introduce a converted helium leak from the test object W. A common roughing pump 2 (for example, an oil rotary vacuum pump RP) is connected via a fore valve FV and a roughing valve RV. In this configuration, first, the fore valve FV is opened and the roughing valve RV is closed, and then the analysis tube 3 is exhausted by the roughing pump 2 to obtain a predetermined background value. Close and open the roughing valve RV to roughen the test chamber 10 to induce helium leak. Finally, both valves RV and FV are opened to enter the test mode, and the leaked helium is reversed to the high vacuum pump 7. The sample is diffused and introduced into the analysis tube 3, and the amount of helium leak from the test object W is indirectly measured.

In the above-described helium leak detector, the exhaust port side of the high vacuum pump 7 is in a vacuum-sealed state during roughing, so that the analysis tube 3 picks up the surrounding residual helium and the background value rises, causing the analysis tube 3 to become contaminated. There is concern about being done.

Therefore, as a configuration for solving this problem, a configuration has been proposed in which a back pump is connected to the exhaust side of the high vacuum pump, and the analysis tube and the test chamber are exhausted in parallel by the roughing pump and the back pump. According to this configuration, an increase in the background value of the analysis tube can be avoided, and further, the rough pumping mode is changed to the test mode by setting the pumping speed of the back pump to be smaller than the pumping speed of the roughing pump. The change in the exhaust speed at the time of switching can be suppressed within a negligible range, thereby preventing an increase in the response time of the measured value. (See Patent Document 1)

FIG. 9 is a diagram for explaining a configuration example of the helium leak detector. In FIG. 9, a high vacuum pump 7 connected to the analysis tube 3, a back pump 1 (RP1) that exhausts the exhaust port of the high vacuum pump 7 through the first line L1, and a helium leak from the test object W. The test chamber 10 to be guided and the roughing pump 2 (RP2) for exhausting the test chamber 10 through the second exhaust line L2 are provided, and the analysis tube 3 and the test chamber 10 are exhausted in parallel by these pumps. First, the second exhaust line is connected, and the amount of helium leaked around the analysis tube 3 by back diffusion of the high vacuum pump 5 from the test chamber 10 is measured.

FIG. 10 is a flow showing the operation procedure of the above helium leak detector. In the process of waiting for the test, only the forevalve FV is opened, the exhaust port of the high vacuum pump 7 is exhausted by the back pump 1 through the first line L1, and the high vacuum pump 7 is operated while being backed up by the back pump 1. The inside of the analysis tube 3 is evacuated (S11).

Next, after a predetermined background value is obtained in the analysis tube 3, only the roughing valve RV is switched to open to start roughing. As a result, the exhaust of the test chamber 10 through the second exhaust line L2 by the roughing pump 2 is started in parallel with the exhaust of the first exhaust line. At this time, if helium gas leaks from the test object W, the leaked helium gas flows out to the second exhaust line L2 (S12).

After a predetermined time elapses, only the bypass valve BV is switched to open and the test mode is entered. In this test mode, the second exhaust line L2 and the first exhaust line communicate with each other, and a part of the helium gas in the second exhaust line L2 passes through the intermediate path LM to the first exhaust line L1, Further, a part of the reverse diffusion of the high vacuum pump 7 reaches the analysis tube 3. The amount of leak of helium gas is measured from the measured value of the analysis tube 3 (S13). The bypass valve BV and the roughing valve RV are closed, the leak valve LV is opened, and the test chamber 10 is opened to the atmosphere (vented) (S14).

After the release to the atmosphere, the leak valve LV is closed again to return to the test standby state of S11, the test object W in the test chamber 10 is replaced, and the next measurement is performed (S15).

Japanese Patent Laid-Open No. 10-48087

In the above-described helium leak detector, when a back pump, such as an oil rotary vacuum pump, a diaphragm vacuum pump, or a scroll pump, is used that has a reduced exhaust speed in the vicinity of the ultimate pressure. Depending on the ultimate pressure obtained after evacuating the test chamber with the roughing pump, the pumping speed of the back pump becomes too small, the time for helium gas to reach the analysis tube is prolonged, and the intended response time can be shortened. There is no problem.

In view of the above, an object of the present invention is to solve the above-described problems, to suppress a change in the exhaust speed when switching from the roughing mode to the test mode, and to prevent an increase in the response time of the measured value.

The present invention switches from the roughing mode to the test mode by connecting a high vacuum pump having a stable exhaust speed at a pressure in the vicinity of the ultimate pressure in the test mode to the first exhaust line connected to the analysis tube. The change in the exhaust speed at the time of switching is suppressed, thereby preventing an increase in the response time of the measured value.

The helium leak detector of the present invention includes a first high vacuum pump connected to the analysis tube, a second high vacuum pump for exhausting the exhaust port of the first high vacuum pump, and the second high vacuum pump. A back pump for exhausting the exhaust port through the first exhaust line, a test chamber for inducing helium leak from the DUT, a roughing pump for exhausting the test chamber through the second exhaust line, and a first high pump A test valve is provided that allows the communication between the connection end of the vacuum pump and the second high vacuum pump and the second exhaust line to be switched.

By driving each of these pumps with the test valve closed, the analysis tube and the test chamber are exhausted in parallel, and then the test valve is opened to connect the exhaust port of the first high vacuum pump and the second exhaust line. Then, the amount of helium leaked around the analysis tube by back diffusion of the first high vacuum pump from the test chamber is measured.

In the test mode, when the exhaust speed of the roughing pump is too high, the speed at which helium that enters the analysis tube from the first exhaust line decreases, and the response time until the measured value is stabilized in the analysis tube is prolonged. On the other hand, when the exhaust speed of the roughing pump is too low, the amount of helium flowing from the first exhaust line to the analysis tube becomes excessive, and in this case as well, it takes a long time to stabilize at a constant value.

Therefore, the exhaust speed of the second high vacuum pump is set smaller than the exhaust speed of the roughing pump. The exhaust speed is set so that the amount of helium flowing from the first exhaust line to the analysis tube is not excessive.

Also, as shown in the above problem section, when the exhaust pressure of the back pump that exhausts the high vacuum pump connected to the analysis tube becomes too low in the vicinity of the ultimate pressure in the test mode, The time for helium gas to reach will be prolonged.

The helium leak detector of the present invention is provided with a second high vacuum pump between the first high vacuum pump and the back pump, instead of connecting the back pump to the exhaust port of the first high vacuum pump. By connecting the connection end of the first high vacuum pump and the second high vacuum pump and the second exhaust line so that the communication can be switched through the test valve, the analysis tube side in the test mode can be switched. The pumping speed of the pump is dependent on the second high vacuum pump instead of the conventional back pump. Further, the second high vacuum pump has a pumping speed fluctuation rate at a pressure close to the ultimate pressure in the test mode. Change in pumping speed when switching from roughing mode to test mode by using a drag pump, for example, which can obtain a small and constant pumping speed After switching to the test mode, the exhaust speed of the system on the analysis tube side can be made almost constant without being attenuated depending on the ultimate pressure at the time of measurement. It can be shortened without depending on the ultimate pressure.

Further, when a drag pump is used as the second high vacuum pump provided between the first high vacuum pump and the back pump, helium gas accumulated in the back pump is obtained due to the high compression performance of the drag pump. Even if the gas remains on the exhaust port side, the amount of helium gas that appears on the intake port side is reduced, so the back diffusion amount of the helium gas introduced into the analysis tube by back diffusion of the turbo molecular pump is reduced. Can be reduced.

According to the present invention, it is possible to suppress a change in the exhaust speed when switching from the roughing mode to the test mode, and to prevent an increase in the response time of the measurement value.

It is the schematic for demonstrating the structure of the helium leak detector of this invention. It is a flowchart for demonstrating the operation | movement procedure of the leak test of the helium leak detector of this invention. It is a figure which shows the state of the test standby of the helium leak detector of this invention. It is a figure which shows the state of roughing of the helium leak detector of this invention. It is a figure which shows the state of the test mode of the helium leak detector of this invention. It is a figure which shows the vent state of the helium leak detector of this invention. It is a figure which shows the characteristic of the exhaust speed with respect to a pressure. It is a figure which shows one structural example of the helium leak detector by a reverse diffusion leak test system. It is also a figure for demonstrating the structural example of the conventional helium leak detector. It is the flow which showed the operation | movement procedure of the conventional helium leak detector.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic view for explaining the configuration of the helium leak detector of the present invention. In FIG. 1, the helium leak detector includes a first high vacuum pump 4 that connects an intake port 4 a to an analysis tube 3, and a second high vacuum pump 5 that exhausts an exhaust port 4 b of the first high vacuum pump 4. A back pump 1 (RP1) that exhausts the exhaust port 5b of the second high vacuum pump 5 through the first exhaust line L1, a test chamber 10 that induces helium leak from the object W, and this test chamber 10 is connected to the roughing pump 2 (RP2) that exhausts the gas 10 through the second exhaust line L2, and the first high vacuum pump 4 and the second high vacuum pump 5 (or the first high vacuum pump 4). A test valve TV is provided that can switch the communication between the exhaust port 4b or the intake port 5a of the second high vacuum pump 5 and the second exhaust line L2.

Further, in the first exhaust line L1, a roughing valve RV is provided between the test chamber 10 and the roughing pump 2, and in the second exhaust line L2, the exhaust port 5b of the second high vacuum pump 5 is provided. And a fore valve FV is provided between the intake port 1a of the back pump 1. A leak valve LV is provided between the test chamber 10 and the test valve TV, and a connection point between the leak valve LV and the test valve FV and a connection point between the fore valve FV and the intake port 1a of the back pump 1 are provided. A bypass valve BV is provided between them. Further, a Pirani vacuum gauge 6 (PM1) is provided on the second exhaust line L2 side of the test valve TV for measuring the pressure reached in the roughing mode or the like.

In this configuration, the connection point of the test valve TV, the leak valve LV, and the bypass valve BV is a sample point for taking helium into the analysis tube 3.

Here, as the back pump 1 (RP1) and the roughing pump 2 (RP2), an oil rotary vacuum pump, a diaphragm vacuum pump, or a scroll pump can be used, and the first high vacuum pump is a turbo molecular pump or a drag pump. The second high vacuum pump can be a drag pump.

After the analysis tube 3 and the test chamber 10 are evacuated in parallel by these pumps 1, 2, 4 and 5, the test valve TV is opened and the second exhaust line L2 and the exhaust port 4b of the first high vacuum pump 4 are connected. The analysis tube 3 measures the amount of helium leak that has been communicated and back-diffused from the test chamber 10 through the first high vacuum pump 4 into the analysis tube 3.

In the measurement by the helium leak detector of the present invention, the test object W filled with helium is set in the test chamber 10 in advance, and helium leaked from the test object W to the second exhaust line L2 in the roughing mode. Next, in the test mode, the second exhaust line L2 is communicated with the exhaust port 4b of the first high vacuum pump 4, and the first high vacuum pump 4 is back-diffused from the second exhaust line L2. Then, the amount of helium reaching the analysis tube 3 is measured.

In the above-described configuration, the exhaust speed of the second high vacuum pump is set smaller than the exhaust speed of the roughing pump. For example, as a second high vacuum pump, a standard drag pump having an exhaust speed of 1 L / sec is used, and a vacuum pump having an exhaust speed of 18 L / sec (exhaust speed at atmospheric pressure) is used as a roughing pump.

Hereinafter, the operation procedure of the leak test of the helium leak detector having the above configuration will be described with reference to the flowchart of FIG. 2, the operation diagrams of FIGS. 3 to 6, and the exhaust velocity characteristic diagram with respect to the pressure of FIG. In FIG. 3 to FIG. 6, a thick line indicates a line portion during exhaust.

FIG. 3 shows a test standby state. In the process of waiting for the test, only the fore valve FV is opened, and the exhaust port 4b of the first high vacuum pump 4 is exhausted by the back pump 1 through the first exhaust line L1 and the second high vacuum pump 5. At this time, the first high vacuum pump 4 is operated while being mainly backed up by the back pump 1 to evacuate the analysis tube 3. In this test standby pressure state, the second high vacuum pump 5 such as a drag pump cannot obtain a sufficient exhaust speed, so the back pump 1 mainly backs up the exhaust of the first high vacuum pump 4 (S1). : Test waiting).

Next, after a predetermined background value is obtained in the analysis tube 3, only the roughing valve RV is switched to open to start roughing. During this time, the test standby state is maintained by driving the first high vacuum pump 4, the second high vacuum pump 5, and the back pump 1. FIG. 4 shows a roughing state.

As a result, the exhaust of the test chamber 10 through the second exhaust line L2 by the roughing pump 2 is started in parallel with the exhaust of the first exhaust line.

As the exhaust gas advances, if there is a leak location such as a crack or a pinhole in the test object W, helium rich in diffusibility leaks into the test chamber 10 through the leak location and enters the test chamber 10. The leaked helium flows out into the second exhaust line L2 (S2: roughing).

After a predetermined time has elapsed, only the test valve TV is switched to open and the test mode is entered. FIG. 5 shows the state of the test mode. In this test mode, the second exhaust line L2 and the exhaust port 4b of the first high vacuum pump 4 communicate with each other, and part of the helium gas in the second exhaust line L2 is reversely diffused through the high vacuum pump 4. It reaches into the analysis tube 3. As a result, the gas at the sample point A is introduced into the analysis tube 3. The analysis tube 3 detects helium from the introduced gas and measures the leak amount of the helium gas.

Further, a part of the gas in the second exhaust line L2 passes through the second high vacuum pump 5 to the first exhaust line L1, and is exhausted through the back pump 1 (S3: test).

Next, the test valve TV and the roughing valve RV are closed, the leak valve LV is opened, and the inside of the test chamber 10 is opened (vented) from the leak valve LV. FIG. 6 shows the state of the vent operation (S4: vent).

After the release to the atmosphere, the leak valve LV is closed again to return to the test standby state of S1, the test object W in the test chamber 10 is replaced, and then the next measurement is performed as the test standby (S5: test standby) ).

As described above, by evacuating the test chamber 10 and the analysis tube 3 in parallel, the exhaust port 4b of the first high vacuum pump 4 is not vacuum-sealed during the exhaust of the test chamber 10, and the analysis is performed. Problems such as an increase in the background value and contamination of the analysis tube due to the tube 3 picking up residual helium in the vicinity can be avoided.

Further, by setting the pumping speed of the second high vacuum pump 5 to be smaller than the pumping speed of the roughing pump 2 , it is within a range in which the change in pumping speed can be ignored when switching from the roughing state to the test state. The problem that the time (response time) from the start of the test until the measurement value becomes stable can be avoided.

In addition, the helium leak detector having the above-described configuration has a second configuration between the first high vacuum pump 4 and the back pump 1 in place of the configuration in which the back pump 1 is connected to the exhaust port 4 b of the first high vacuum pump 4. The high vacuum pump 5 is provided, the connection end of the exhaust port 4b of the first high vacuum pump 4 and the intake port 5a of the second high vacuum pump 5, and the second exhaust line L2 through the test valve TV. Therefore, the exhaust speed on the analysis tube 3 side in the test mode is not dependent on the conventional back pump 1 but dependent on the second high vacuum pump 5. .

Furthermore, as the second high vacuum pump 5, by using, for example, a drag pump, which has a small fluctuation rate of the exhaust speed at a pressure close to the ultimate pressure in the test mode and can obtain a constant exhaust speed, The change in the exhaust speed when switching from the roughing mode to the test mode is kept small, and after switching to the test mode, the exhaust speed of the system on the analysis tube 3 side is attenuated depending on the ultimate pressure at the time of measurement. Without being dependent on the ultimate pressure, so that the response time can be reduced.

In the characteristic chart of the exhaust velocity with respect to the pressure shown in FIG. 7, in the roughing mode, the first exhaust line L2 on the test chamber 10 side is exhausted by the roughing pump 2 (RP2), and the second exhaust on the analysis tube 3 side. Line L1 is exhausted by back pump 1 (RP1).

Here, when the exhaust pressure of the test chamber is P1 (for example, 10 Pa), the test valve TV is opened to switch from the roughing mode to the test mode.

In the test mode, the pressure decreases as the exhaust proceeds, and the exhaust speeds of the roughing pump 2 (RP2) and the back pump 1 (RP1) decrease and reach the vicinity of 1 Pa within about 1 second.

At this stage, the exhaust speed of the back pump 1 (RP1) is greatly reduced (indicated by B in the figure). In the conventional configuration, since the first high vacuum pump 4 is backed up by the back pump 1, when the exhaust speed of the back pump 1 (RP1) is greatly reduced, the amount of sneaking into the analysis tube 3 becomes excessive. It takes time for the measured value to stabilize. On the other hand, according to the configuration of the present invention described above, the second high vacuum pump 5 having a characteristic that the exhaust speed at the ultimate pressure is not attenuated between the first high vacuum pump 4 and the back pump 1. By arranging this, it is possible to obtain the exhaust speed indicated by C in the figure. In the actual data at a pressure in the vicinity of 1 Pa, the exhaust speed of the second high vacuum pump 5 (for example, a drag pump) is about 4 to 5 times the exhaust speed of the back pump 1.

As a result, the exhaust speed of the system on the analysis tube side in the test mode can be kept almost constant without being attenuated, and the response time can be shortened without depending on the ultimate pressure when the test mode is switched. it can.

In one configuration example using a second high vacuum pump (drag pump) with an exhaust speed of 1 L / sec and a roughing pump with an exhaust speed of 18 L / sec (exhaust speed in the atmosphere), the exhaust pressure of the test chamber is When switching at 10 Pa, the response time until the measured value reaches from 0% to 95% is about 1.5 seconds. On the other hand, in the conventional configuration, when a back pump having an exhaust speed of 0.5 L / sec (exhaust speed at atmospheric pressure) is used, the response time is 2.0 seconds.

In addition, after a large amount of helium gas is sucked, the helium gas is accumulated in the back pump. In the conventional configuration, the helium gas is analyzed by the reverse diffusion of the first high vacuum pump (turbo molecular pump). In the case of using a drag pump as the second high vacuum pump provided between the first high vacuum pump and the back pump as in the configuration of the present invention, the drag is caused. Even if helium gas accumulated in the back pump remains on the exhaust port side due to the high compression performance provided by the pump, the helium gas that appears on the intake port side of this high vacuum pump is reduced. It is possible to reduce the amount of reverse diffusion of helium gas introduced into the analysis tube by reverse diffusion of the first high vacuum pump (turbo molecular pump).

Therefore, according to the helium leak detector configured as described above, it is possible to suppress the change in the exhaust speed when switching from the roughing mode to the test mode, and to prevent an increase in the response time of the measured value. The amount of back diffusion of helium gas introduced into the analysis tube can be reduced.

The present invention can be applied to the presence or absence of leakage (leakage) in an airtight container or piping.

DESCRIPTION OF SYMBOLS 1 ... Back pump, 1a ... Intake port, 2 ... Roughing pump, 2a ... Intake port, 3 ... Analysis tube, 4 ... First high vacuum pump, 4a ... Intake port, 4b ... Exhaust port, 5 ... Second High vacuum pump, 5a ... intake port, 5b ... exhaust port, 6 ... Pirani gauge, 7 ... vacuum pump, 10 ... test chamber, W ... DUT, RV ... roughing valve, LV ... leak valve, BV ... bypass Valve, FV ... Fore valve.

Claims (2)

A first high vacuum pump connected to the analysis tube;
A second high vacuum pump for exhausting an exhaust port of the first high vacuum pump;
A back pump for exhausting an exhaust port of said second high vacuum pump through a first exhaust line,
A test chamber for inducing helium leak from the device under test;
A roughing pump for evacuating the test chamber through the second exhaust line,
The first high vacuum pump and the connection end of said second high vacuum pump and freely switch the communication between the second exhaust line, the first high vacuum pump at the time of non-communication, the second A roughing mode in which the analysis tube and the test chamber are evacuated in parallel by the high vacuum pump, the back pump, and the roughing pump, and the first high vacuum pump is back-diffused from the test chamber to the analysis tube during communication. With a test valve that switches to a test mode that measures the amount of helium leak that wraps around,
The helium leak detector according to claim 2, wherein the second high vacuum pump is a drag pump, and an exhaust speed of the drag pump is lower than an exhaust speed of the roughing pump . The helium leak detector according to claim 1 , wherein the first high vacuum pump is a turbo molecular pump .

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