JPH0125412B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a leak testing method for parts to be tested using a chamber type leak testing device incorporating a helium leak detector and using a vacuum internal pressure method.

Air-tight parts for air conditioning and refrigeration compressors, as well as air-tight parts for automobiles, are all produced in large quantities and require a high degree of reliability in their airtightness, so leak testing is performed online. It must be possible to carry out a rigorous leak test without overlooking minute leaks, and it must also be able to be carried out quickly and labor-savingly.

By the way, as shown in FIG. 1, a conventional chamber type leak testing device houses a part to be tested 1 filled with helium in a chamber 2 equipped with an elevating device using a hydraulic cylinder or the like, and the air inside the chamber 2 is pumped out. For example, if the chamber 2 is evacuated by an evacuation device consisting of a diffusion pump 3 and an oil rotary vacuum pump 4, and the chamber 2 is brought to a vacuum state of, for example, about 10 ^-2 Torr,
If there is a defect such as a minute pinhole or crack in the component 1, the helium sealed therein leaks into the chamber 2, diffuses, and passes through the pipe of the exhaust system as shown in the figure. This helium reaches the helium leak detector (LD) connected to it, which detects this helium and then compares the detected value with a predetermined reference value. It is designed to determine whether the component 1 passes or fails the leakage test.

Therefore, before placing the part to be inspected 1 (hereinafter referred to as a workpiece) in the chamber 2, a preparatory step is required to fill the lever with helium. For example, as shown in FIG. The attached leak-proof auxiliary cover 6 is attached to the workpiece 1 to form a sealed container, and after the inside of the container is sufficiently evacuated, helium is introduced into the container from the helium cylinder 7, the pressure reducing valve 8, the tube 9, the detachable joint 10, and the valve. 5
, then close valve 5 and connect fitting 1.
If you remove 0, you must perform the helium filling process.

Furthermore, since helium is an expensive gas, in order to make effective use of it, when a large number of parts are tested for leaks, the residual helium in the workpiece is usually recovered after the test.

Although it is suitable to use a leak inspection device incorporating such an LD for strict leak inspection that does not miss minute leaks, the quality of the workpieces varies, and it is expected that there will be quite large leakage defects. In this case, the work 1 sealed as described above is connected to the exhaust set via the valve 5, and an abnormal pattern of pressure fluctuation in the exhaust system that occurs when the inside is evacuated is detected using a vacuum gauge, for example. A growth leak test is performed using a vacuum exhaust type leak test device, and rejected products with growth leaks are eliminated in advance before being passed to a leak test device that incorporates an LD.

Therefore, in order to save labor and speed up leak testing using a helium LD, it is necessary to seal the workpiece, exhaust the air inside the sealed workpiece, perform a growth leak test in conjunction with this, and fill in helium for products that pass the test. , the chamber is housed in a chamber, the chamber is evacuated, a part of the exhaust gas is guided to a helium LD, and a micro-leakage test is performed on the workpiece to detect leaked helium contained in the exhaust gas, and the remaining helium sealed in the workpiece is inspected. It is desirable that the main steps, such as helium recovery, be performed in a series of sequential operations as a continuous process, rather than in separate steps as described above.

FIG. 3 is an example of a circuit system diagram of a leakage testing device in which each of the above-mentioned main steps is treated as a continuous step and processed by a series of sequential operations. In the figure, 1 is a workpiece having a flange at its lower end, 2 is a bell-shaped chamber that houses the workpiece, 12 is its bottom plate, which is fixed to a base (not shown), and the chamber 2 is connected to the workpiece by, for example, a hydraulic cylinder. When the lower end flange surface is pressed against the bottom plate 12,
The chamber 2 is kept airtight. A pressure block 13 is attached to the ceiling of the chamber 2, and when the chamber 2 is pressed down as described above, its lower end surface touches the flange of the workpiece 1 as shown by the parallel arrow. The workpiece 1 is pressed against the bottom plate 12, and the workpiece 1 and the bottom plate 12 form a closed container. The hermetically sealed workpiece 1 is kept airtight even when pressurized helium is introduced into it. Reference numeral 14 denotes a packing block, which is attached to the workpiece 1 with a slight gap between it and the inner peripheral surface of the workpiece 1, and serves to reduce the purge capacity of the air inside the workpiece 1, and its lower end outer peripheral surface is attached to the workpiece 1. The bottom plate 12 is in contact with the inner circumferential surface of the workpiece 1 with almost no gap, and an O-ring is attached to this portion and the portion of the bottom plate 12 that contacts the flange surface of the workpiece 1, respectively. When the O-rings are made of rubber or silicone rubber, the helium sealed in the workpiece 1 gradually passes through them, and enters the chamber 2 from the contact area between the flange surface of the workpiece 1 and the bottom plate 12.
In order to prevent this from happening, as soon as the helium is filled, the exhaust gas in the gap between the two O-rings is connected to the exhaust gas connected to it. The leak test is continuously performed through the conduit 28 during the leak test. Reference numeral 31 denotes a through passage for introducing helium or a mixed gas of helium and nitrogen to be sealed in the sealed workpiece 1, and communicates with the introduction pipe 32, and 33 is a main exhaust pipe. 40, 41, 42 and 43 are oil rotary vacuum pumps, 44 is a Roots type mechanical booster,
45 is a three-way electromagnetic on-off valve, 46, 47, 48, 4
9, 50, 51 are air-operated on-off valves, 52, 53,
54, 55, 56, 57 are electromagnetic on-off valves, 60, 6
1 is a compound gauge with upper and lower limit pressure contacts, 62 is a Bourdon tube vacuum gauge with lower limit contacts, 63 is a Pirani vacuum gauge,
64 is a pressure gauge. 32 is a conduit for introducing helium or a mixed gas of helium and nitrogen, 32-1 is a helium recovery conduit, and 32-2 is an exhaust conduit for air in the workpiece 1. Leakage testing in the apparatus having the circuit system shown in FIG. 3 is performed by the following sequence of operations.

It is assumed that the chamber 2 is being pulled upward by a hydraulic cylinder. The work 1 is set on the bottom plate 12 so as to cover the packing block 14. When the start switch is turned on, the limit switches LS ₁ and LS ₂ mounted at fixed positions above and below the chamber 2 come into contact with a dog (not shown) to restrict the movement of the hydraulic cylinder, and the chamber 2, the descent starts, pressurization is applied, and it stops. This action causes chamber 2
While the flange portion of is pressed against the bottom plate 12,
The flange surface of the workpiece 1 is pressed against the bottom plate 12.
When the work 1 and the chamber 2 are sealed in this way, the oil rotary pumps 40, 41, 42, 4
3. The mechanical booster 44 operates. Next, the electromagnetic on-off valve 55 connected to the main exhaust pipe 33 is opened, the air inside the chamber 2 is exhausted, and the internal pressure is set to the value set on the compound gauge 61 (for example, 90 Torr).
When the pressure is reduced to , the solenoid valve 55 is closed and the air-operated on-off valve 51 is opened in response to the signal, and the inside of the chamber 2 is subsequently evacuated. During this time, the air-operated on-off valve 46 is open, and the inside of the workpiece 1 is connected to the introduction pipe 32.
If there is a fairly large leakage defect in the workpiece 1, the chamber 2 will not reach a predetermined vacuum pressure of 0.04 Torr even if the evacuation continues for a certain period of time, for example, 25 to 30 seconds. Since this does not occur, a signal is output from the Pirani vacuum gauge 63, a buzzer and a lamp are activated, and the growth leak of the workpiece 1 is displayed.

The flow is then interrupted and further progress requires appropriate operator action. When there is no growth leak in the workpiece 1, the inside of the chamber 2 reaches the predetermined degree of vacuum, and a helium gas filling step is started based on a signal from the Pirani vacuum gauge 63 that detects this.

Next, helium is sealed inside the workpiece 1, but this filling is normally done at a pressure equivalent to the pressure when the workpiece 1 is used.If the working pressure is as high as several tens of atmospheres, for example, helium and nitrogen A high-pressure mixed gas is used, which is a uniform mixture of 10% and 90% of both. Now, when enclosing this high-pressure mixed gas, the air-operated on-off valve 46 is closed, the on-off valve 48 is also opened, and the introduction pipe 32 and the through-hole 3 are closed.
1, the air remaining in the workpiece 1 is sealed inside the workpiece 1 without being purged. When the working pressure of the workpiece 1 is low, for example, only helium of about 3 to 5 kg/cm ² G is sealed, and in this case, the air-operated on-off valve 46 is closed, the on-off valve 49 is also opened, and the rotary pump is closed. 41 purges the residual air in the workpiece 1, the on-off valve 49 is closed, and helium is filled in the same way as the high-pressure mixed gas described above.

If there is a defect such as a minute pinhole or crack that does not cause a cross leak in the workpiece 1, the sealed helium will leak into the chamber 2.
When the test valve (electromagnetic on-off valve) 57 is opened, leaked helium contained in a part of the exhaust gas sucked into the branch pipe from the main exhaust pipe 33 is sent to the LD, causing micro leakage of the workpiece 1 due to the LD. A leak test is performed on the

When the leak test by LD is completed, both the air-operated on-off valve 48 and the test valve 57 are closed, the air-operated on-off valve 47 is opened, and the through passage 3 is closed.
1. Helium sealed in the workpiece 1 is recovered through the conduit 32 and the helium recovery conduit 32-1. When the contact link 60 detects that the pressure of helium in the recovery pipe 32-1 has reached atmospheric pressure, the air-operated on-off valve 47 closes in response to the signal, and the three-way solenoid valve 45 and the air-operated valve 47 close. Both on-off valves 51 are closed, and then on-off valve 49 is also closed.
is opened, and the residual helium inside the workpiece 1, which has reached an atmospheric pressure state, is discharged to the outside air.

When the inside of the workpiece 1 is made into a vacuum of, for example, about 10 ^-2 Torr, the on-off valve 49 is closed. On the other hand, when the air-operated on-off valve 49 is opened, the air-operated on-off valve 50 is simultaneously opened, and outside air flows backward through the main exhaust pipe 33 and is introduced into the chamber 2, and the air-operated on-off valve 46 is opened. Similarly, outside air flows through the introduction pipe 32 and the through passage 31 to the workpiece 1.
Further, the three-way electromagnetic on-off valve 45 is switched to communicate the exhaust pipe line 28 with the outside air, and the vacuum state of the chamber 2 and the workpiece 1 is broken. When the atmosphere is introduced to all the required locations in this way, the chamber 2 is pulled upward by the hydraulic cylinder, the workpiece 1 is freely removed, and one cycle of leakage testing of the workpiece 1 is completed.

As explained above, the workpiece leakage inspection method using the vacuum internal pressure method using a chamber-type leakage inspection device incorporating a helium leak detector, the circuit system of which is shown in Figure 3, can cause variations in the quality of the workpieces. If the inspection is carried out primarily to eliminate workpieces with small leakage defects and no fairly large leakage defects, each inspection process can be processed as a continuous process by a series of sequential operations, speeding up leak inspection. In addition, labor saving is achieved, but if there is a growth leak in the workpiece, as mentioned above, a signal is output from the Pirani vacuum gauge 63, and the buzzer and lamp are activated to display the growth leakage in the workpiece. When it is done,
Since the flow is interrupted at this point, there is an inconvenience that the operator must take appropriate measures regarding the subsequent progress. Furthermore, when the high-pressure mixed gas with a pressure similar to the pressure when the workpiece is used is sealed in a sealed workpiece, if the workpiece is distorted by the pressure of the filled gas and leaks from the gap, there will be a considerable amount of leakage. Since helium flows into the main exhaust pipe 33, the leaked helium does not need to be detected by the LD, and can be detected by the Pirani vacuum gauge 63 in the same way as a growth leak. Therefore, it is meaningless to perform a leak test using LD on a workpiece that has such gap leakage.
This will result in unnecessary tests. What's worse is that since the exhaust gas containing such gap leakage is sent to the LD, a considerable amount of helium is
The background of the LD will be disturbed, leading to errors in the subsequent detection of helium by the LD. If this situation occurs, the conduit 33 leading to the LD must be thoroughly cleaned up. However, the inconvenience of requiring more effort and time is increasing.

This invention aims to eliminate the waste and inconvenience of conventional leakage testing methods using devices similar to those described above.
In a leak test method in which pressurized helium is sealed in a part to be inspected housed in an exhaust sealed chamber, and helium leaking into the sealed chamber is detected by a helium leak detector, the above-mentioned A pressurized gas having almost the same pressure as the helium leak test is sealed inside the hermetic inspection part, the airtight chamber is evacuated, and the internal pressure is checked to see if it reaches a predetermined degree of vacuum within a certain period of time. Therefore, a preliminary leakage test is performed to check for gap leakage caused by strain due to pressurization of the gas sealed in the part to be tested, and the helium sealed inside the part to be tested is recovered in the subsequent stage of the helium leak test. and a step of breaking the vacuum of the inspected part and the exhaust sealed chamber after the recovery process, and if the preliminary leakage test fails, the inspected part is checked for leakage due to helium. A leak test method characterized in that the test is skipped and the process moves to the helium recovery step and the vacuum breaking step, so that even if the preliminary leak test fails, the test step is allowed to proceed without stagnation. Such is the case.

Embodiments of the leakage testing method according to the present invention will be described below with reference to the drawings.

FIG. 4 shows the main parts of the flow diaphragm of the embodiment of the leak test method according to the present invention with respect to the operation of the leak test device having the circuit system shown in FIG. The same numbers are assigned to the on-off valves and instruments that are the same as those shown in Figure 3. Using this flow diaphragm together with the circuit diagram in Figure 3, this inspection method can be used for each major inspection. Explain.

(i) Primary growth leak test of workpiece: As mentioned above, workpiece 1 is set on the bottom plate 12 of chamber 2, and when the start switch is pressed, the flow progresses as shown in the figure, and the lamp
LO lights up, indicating that the pressure on the bottom plate 12 of the workpiece 1 and chamber 2 has been completed, and that the sealing of both has been completed. Then, as the flow progresses, the air-operated on-off valve 46 is opened as described above, and the inside of the sealed workpiece 1 is communicated with the atmosphere.
When there is a defect in workpiece 1 that causes a growth leak, the internal pressure of chamber 2 does not reach the predetermined degree of vacuum (for example, 0.04 Torr) even after being evacuated for a certain period of time (for example, 25 to 30 seconds). It is detected by a Pirani vacuum gauge 63. The time delay T ₁ is adjusted to the above-described constant exhaust time.

In this case, lamp L ₁ lights up and the buzzer
B ₁ will sound and issue an alarm, indicating that Work 1 has failed the primary growth leak test. When the reset switch is pressed, the operation of the lamp L ₁ and the buzzer B ₁ is stopped, the flow advances to P through an intermediate step, the air-operated shut-off valve 51 is closed, and then the shut-off valve 50 is also closed. After being opened, the chamber 2 is stopped from being evacuated, outside air is introduced into the chamber 2, and the vacuum state within the chamber 2 is broken, after which the chamber 2 is pulled upward by a hydraulic cylinder.

(ii) Secondary growth leak test of the workpiece: If the workpiece 1 passes the above-mentioned primary growth leakage test, the air-operated on-off valve 46 is closed and the closed workpiece 1 is separated from the outside air, as shown in the flowchart. When the ^{communication} with
A high-pressure mixed gas of G is introduced into the closed workpiece 1. When the workpiece 1 is strained and leaks from the gap due to the pressurization of the high-pressure mixed gas, the mixed gas flows out into the main exhaust pipe 33. Even after a certain period of time, the predetermined degree of vacuum (e.g.
0.04 Torr), which is detected by the Pirani vacuum gauge 63. The time delay T ₂ is adjusted to the above-mentioned fixed waiting time after helium filling.

In this case, lamp L ₂ and buzzer B ₂ operate,
Displays that Work 1 has failed the secondary growth leak test. When the reset switch is pressed, the lamp L ₂ and buzzer B ₂ are deactivated, the flow advances to Q through an intermediate step, and the air-operated on-off valve 48 and test valve 57 are both closed. The helium inlet is blocked and the exhaust from chamber 2 is removed.
The inflow to the LD is stopped. Then, the air-operated on-off valve 47 is opened, the helium sealed in the workpiece is recovered until it reaches atmospheric pressure, and the air-operated valve 49 is opened to remove the residual helium in the workpiece 1, which has reached atmospheric pressure. Exhausted to the outside air.
Then, following the same flow as in the primary leak test, the vacuum state of the chamber 2 and workpiece 1 is broken, and then the chamber 2 is pulled upward by the hydraulic cylinder.

In this secondary leak test, the test valve 57 remains closed, so no helium flows into the pipeline downstream of the test valve 57, and therefore a considerable amount of helium is contained in the gap leakage caused by the strain in the workpiece 1. The background of the LD is prevented from being disturbed by the helium of There is not enough helium remaining to affect the background of the LD, and there is no need to spend extra time cleaning up the adsorbed helium gas.

(iii) Workpiece helium leak test: This test is the original leak test using helium, and the above-mentioned primary and secondary growth tests both fall under the category of preliminary leak tests.

If Work 1 passes the secondary growth leak test described above, the LD leak rate meter indicates that the helium content in the atmosphere existing in the LD is below the specified standard value, and there is an abnormality in the background. When it is confirmed that there is no leakage, the test valve 57 is opened, and if a minute leak occurs due to a minute pinhole or crack in the workpiece 1, the leaked helium in the exhaust gas is detected by the leak rate meter of the LD. At the same time, the detected value is compared with a predetermined reference value. If the detected value is equal to or higher than the reference value, the lamp L ₃ and buzzer B ₃ are activated to indicate that the workpiece 1 has failed the helium leak test. When the reset switch is pressed, the operation of the lamp L ₃ and buzzer B ₃ is stopped, and the same flow as in the secondary growth leak test is performed until the helium sealed in the workpiece 1 reaches atmospheric pressure. collection of,
The remaining helium at a pressure lower than that is discharged to the outside air, and then the vacuum state of the chamber 2 and workpiece 1 is broken, and then the chamber 2 is pulled upward by a hydraulic cylinder.

Work 1 passes the helium leak test unless the detected value of leaked helium is equal to or higher than the reference value. At this time, the lamp _L4 is lit and the flow continues, but the hydraulic cylinder prevents the chamber 2 from being raised unless the reset switch is pressed. This is because such a step allows the operator to confirm that the test has passed.

In addition, for the secondary leak test, in this method, helium or a high-pressure mixed gas of helium and nitrogen is sealed in the workpiece 1, but an air-operated switching valve is installed in the helium introduction pipe 32 and the Even if only a high-pressure gas that does not contain helium, such as nitrogen gas, is sealed, a secondary leak test is performed, and the air-operated on-off valve 49 is a three-way on-off valve, through which the residual nitrogen gas is released to the outside air after the test. good.

It is also possible to provide two or more sets of chambers 2, each with one set of hydraulic power source, exhaust set, and LD, and to perform the above-mentioned tests in parallel using this test method. FIG. 5 shows a circuit system diagram when two sets of chambers 2 are provided. In this figure, the electromagnetic on-off valve, air-operated on-off valve, compound gauge, and Pirani vacuum gauge correspond to the case where there is one chamber 2 shown in FIG.
Although the same numbers are assigned to each number, the number with a dash symbol added corresponds to the operation of No. 2 chamber 2. And No.
If an appropriate interlock is provided in the sequence circuit so that the leakage inspection of the workpiece 1 described above can be carried out alternately for each chamber 1 and No. 2 by this inspection method, each of the above-mentioned Each operation can be performed automatically by simply pressing the start switch without interfering with each other.

As is clear from the above description, the leak testing method according to the present invention includes, for example, means for tightly pressing the opening of the component to be inspected housed in the exhaust sealed chamber against the bottom plate of the chamber;
Pressurized helium is sealed inside the inspection part sealed by this means from an inlet pipe provided on the bottom plate, and leakage of helium into the sealed chamber is detected by a helium leak detector in series or in series. When testing the parts to be tested for leaks using this equipment, if the part to be tested is distorted when filled with pressurized helium and leaks from gaps, a preliminary leak test can be performed so that it can be rejected as a defective product. This eliminates the waste of conducting meaningless helium leak tests and increases inspection efficiency.In addition, it reduces the amount of helium gas adsorbed by conventionally performing helium leak tests on parts to be inspected. The time required for clean-up can be almost completely eliminated, and even if any leak inspection failure occurs, the inspection process can proceed without any stagnation as long as the inspection results are confirmed and the reset switch is pressed. As a result, strict leakage inspection of mass-produced airtight parts can be performed online much more quickly and with less labor than conventional inspection methods.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of a conventional chamber-type leak testing device incorporating a helium leak detector, Figure 2 is an explanatory diagram of the conventional helium filling operation into leak detection parts, and Figure 3 is an illustration of workpiece sealing and growth. 1 of the circuit diagrams of a leak testing device that processes main processes such as leak testing, helium leak testing, and helium recovery through a series of sequential operations.
For example, FIG. 4 shows the main parts of the flow diaphragm of the embodiment of the leak test method according to the present invention for the operation of the leak test device having the circuit system shown in FIG. 3, and FIG. This is an example of a circuit diagram of a leakage testing device in which two sets of leakage testing devices are provided to perform tests in parallel. 1...Leakage inspection parts (work), 2...Chamber,
12... Bottom plate, 13... Pressurizing block, 28... Exhaust pipe, 32... Helium introduction pipe, 32-1... Helium recovery pipe, 32-2... Exhaust pipe, 33... Main exhaust pipe, 41, 42 , 43...oil rotary vacuum pump, 4
4...Mechanical booster, 63...Pirani vacuum gauge,
LD...Helium leak detector.

Claims (1)

[Claims] 1. In a leak test method in which pressurized helium is sealed in a part to be inspected housed in an exhaust sealed chamber, and helium leaking into the sealed chamber is detected by a helium leak detector, in the pre-stage of the leak test. A pressurized gas having a pressure substantially equal to that of the helium leak test is sealed inside the hermetic inspection part, and the airtight chamber is evacuated, and whether or not the internal pressure reaches a predetermined degree of vacuum within a certain period of time is determined. Accordingly, a preliminary leakage test is performed to check for gap leakage caused by strain caused by pressurization of the sealed gas in the part to be tested, and in a subsequent stage of the leakage test using helium, the helium sealed inside the part to be tested is checked. and a step of breaking the vacuum of the inspected part and the exhaust sealed chamber after the recovery process, and if the preliminary leakage test fails, the helium is removed from the inspected part. 1. A leakage test method, characterized in that the leakage test is skipped and the helium recovery step and the vacuum breaking step are performed.