JPH0785040B2 - Leak detector for sealed container - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for detecting leaks in a sealed container, and more particularly to an improvement in an apparatus for detecting leaks in a sealed container based on a change in internal pressure in a measurement tank containing the sealed container.

[Prior Art] Containers that are hermetically sealed while leaving an empty space inside are used in various industrial fields. For example, in a seal relay that is a microelectronic component, a movable contact and an exciting coil are housed in a plastic container. By sealing this container, a sealed small power relay element can be obtained. Such a sealed relay has the advantage that the sealed air or inert gas keeps the moving parts of the relay in a stable state and is not affected by dust, and thus has stable operating characteristics for a long period of time. is there.

Of course, the sealed container to which the present invention is applied is not limited to such a microelectronic component, but can be a medical, food, or other wide-range sealed container.

Such a sealed container may not be able to maintain a perfect sealed state due to poor sealing during manufacturing, the presence of holes in the container itself, etc.The sealed container that causes such a leak is definitely a defective product. Must be removed and several leak detection devices have been proposed for this purpose.

In the conventional general leak detection, the presence or absence of a leak was judged by heating or depressurizing a sealed container immersed in a CFC liquid or the like and detecting bubbles generated in the CFC liquid at this time.

Therefore, such leak detection by air bubbles requires a visual judgment by an inspector, and thus the reliability of leak detection is low, and automation is difficult, so that the time required for leak detection is long and inefficient. There was a flaw.

Instead of such conventional leak detection by visual inspection, the sealed container to be measured is housed in a sealed measuring tank, the internal pressure in the measuring tank is changed, and the pressure change in the measuring tank is electrically detected. A device for doing so has been proposed.

According to the leak inspection method based on such pressure measurement, there is an advantage that an automated continuous inspection can be performed instead of the conventional visual inspection.

[Problems to be Solved by the Invention] However, such a conventional device has a problem that a sufficient equilibration time is required to stabilize the pressure in the measurement tank, and the inspection time cannot be shortened. .

In addition, in order to stabilize the internal pressure of the measuring tank, a sufficiently large pressure source or source pressure source is required, the size of the apparatus becomes large, and large energy is required only for leak inspection. there were.

Further, conventionally, in order to reduce the size of the device, it has been proposed to install a piston directly or adjacent to the measuring tank, but in such a device, the sliding contact portion between the piston and the cylinder is provided. Gas leakage or volume variation occurred, and when measuring a small amount of gas movement such as in a leak test, the variation at the sliding contact portion was too large to make actual measurement impossible.

The present invention has been made in view of the above-mentioned conventional problems, and the object thereof is to use the pressure or volume change of the measurement tank due to the sliding contact between the piston and the cylinder in the related art,
An object of the present invention is to provide an improved leak detection device capable of detecting a minute amount of gas leak with high sensitivity.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an airtight measurement tank that stores a sealed container to be measured, a pressure setting mechanism that changes an internal pressure of the measurement tank by a predetermined amount, and the measurement. Including a pressure sensor to detect the pressure change in the layer, the pressure and pressure change after measuring the internal pressure of the measurement tank to a predetermined value and after depressurizing it to a predetermined value are measured. To be judged.

Further, according to the present invention, the measurement tank kept in an airtight state is formed by a measurement tank lid and a measurement tank body, and the pressure setting mechanism includes a movable plate provided movably in the measurement tank, An elastically deformable member such as an O-ring provided between the movable plate and the inner wall of the measurement tank, a drive unit for moving the movable plate, and a stopper for limiting the movement of the movable plate to a predetermined value,
An elastic deformation member for the lid such as an O-ring provided between the measurement tank lid and the measurement tank main body, a measurement tank lid drive unit for moving the measurement tank lid and sealing the measurement tank under pressure, and this measurement Including the stopper that limits the movement of the tank lid to a predetermined value, by moving the measurement layer lid and the movable plate by a predetermined amount, the internal volume or internal pressure of the measurement tank is constantly changed, and the actual measurement tank at this time Leak detection is performed by measuring the pressure inside and the pressure change.

[Operation] Therefore, according to the present invention, the sealed containers to be measured are normally housed in the measuring tank one by one in an airtight state, and then, after the pressure sealing by the measuring tank lid, the movable plate is determined by the stopper. Move by a predetermined amount to change the volume or internal pressure in the measuring tank by a certain amount, and take the pressure and pressure difference after pressure sealing and after pressure setting, and leak depending on the change in the measuring tank internal pressure and the magnitude of the change. Existence is determined.

That is, according to the present invention, the movable plate simply expands and contracts the elastically deformable member without using a conventional piston that slidably contacts the inside of the cylinder, and the inner volume of the measurement tank is set to a predetermined amount without any sliding contact action. Therefore, it is possible to predetermine a desired internal volume or pressure change while completely eliminating conventional volume or pressure fluctuation factors.

Therefore, the internal pressure change from after the pressure sealing to after the pressure setting is instantly given to the measuring tank, and due to the pressure change at that time, a constant pressure change occurs when there is no leak, while on the other hand, when there is a leak. The pressure difference corresponding thereto is detected, and it becomes possible to perform leak detection with high sensitivity.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a schematic configuration of a leak detection device according to the present invention, which is composed of a mechanism unit 100 and a control unit 200.

The mechanical unit 100 includes a measuring tank 10 kept in an airtight state, which is composed of a measuring tank body 10a and a measuring tank lid 10b. The measured sealed container is housed inside the measuring tank main body 10a, and then, by the pressure sealing mechanism 12 by the measuring tank lid 10b, the internal volume of the measuring tank 10 is always kept at a constant initial value. Measuring tank
10 are sealed.

The measurement tank 10 is sealed by the pressure sealing mechanism 12 and then continuously pressurized by this pressure sealing mechanism. On the other hand, a pressure setting mechanism 14 is continuously provided in the measurement tank 10, so that the internal pressure of the sealed measurement tank 10 can be increased or decreased by a predetermined amount.

The internal pressure of the measuring tank 10 is constantly measured by the pressure sensor 16, and according to this embodiment, the internal pressure of the measuring tank 10 and its change by the pressure setting mechanism 14 are monitored.

The measurement tank internal pressure setting and the pressure change measurement at this time of the mechanism unit 100 as described above are controlled by the control unit 200, and the control of the pressure sealing mechanism 12 and the pressure setting mechanism 14 is performed by the mechanism control unit 20. It is performed by the control signal from.

Further, the measurement value of the pressure sensor 16 is sent to the pressure measuring device 22,
The electric detection signal is captured by the control unit 200.

The mechanism control unit 20 and the pressure measurement unit 22 described above are the central control unit 24
The central control unit 24 determines the presence / absence of a leak by comparing the pressure change after the pressure setting with a predetermined reference value in the comparison / determination unit 26, and the determination signal output unit 28 leaks to the outside. Output a judgment signal.

FIG. 1 shows a more detailed structure of the mechanical section 100 described above.

The measurement tank 10 is formed of a substantially cylindrical measurement tank body 10a and a measurement lid 10b, and an elastic deformation member for the lid is provided between the measurement tank body 10a and the measurement lid 10b, and in the embodiment, According to
The elastic deformation member for the lid is an O-link 34, and the O-ring 34 keeps the measuring tank 10 airtight in a closed state between the measuring tank body 10a and the measuring lid 10b.

In the embodiment, the O-ring 34 is placed in the recess 10c provided in the measuring lid 10b, and its position is determined.

The inner chamber of the measuring tank 10 is further divided into two chambers in the embodiment, and in this embodiment, this separation is performed by the container support plate 36 mounted on the step portion 10d provided in the measuring tank main body 10a. And is divided into a first chamber 38 in which the measured sealed container 300 is housed and a second chamber 40 in which a pressure setting mechanism described later is incorporated.

Of course, the first chamber 38 and the second chamber 40 are connected to each other by the container support plate 36.
Are communicated with each other through a small hole 36a provided in
40 is kept at the same pressure.

In the embodiment, the measured sealed container 300 is shown as a seal relay, and the case lid 46 is sealed to the case 42 in a state in which a well-known relay contact and relay coil (not shown) are housed in the chamber 44 of the case 42. And a sealed container is formed.

Therefore, in the normal case, the chamber 44 of the closed container 300 is completely airtightly shielded from the outside, but if a leak occurs due to a poor seal or other causes, it must be removed as a defective product. Of course, the leak detection device shown in the embodiment can perform a leak inspection for each relay in the manufacturing inspection process of the seal relay.

In carrying out this leak inspection, first, when the sealed container 300 to be measured is stored in the first chamber 38 in the measurement tank body 10a, the measurement tank body 10a is closed by the measurement lid 10b, and the measurement is performed in this lid closed state. The tank 10 is kept airtight. The pressure sealing mechanism 12 subsequently pushes the measurement lid 10b downward, so that the internal pressure in the measurement tank 10 rises while being sealed.

At this time, according to the embodiment, the airtight state is maintained by the O-ring 34 installed between the measuring tank body 10a and the measuring lid 10b, and at the same time, the O-ring 34 responds to the pressurizing action of the pressurizing shaft 33. As a result of the deformation, the measuring tank 10 is pressurized while being sealed.

Next, the pressure setting mechanism that changes the internal pressure of the measurement layer by a predetermined amount includes a disk-shaped movable plate 48, in order to change the internal volume of the measurement tank as large as possible with respect to the moving amount of the movable plate 48, The movable plate 48 is formed in a disk shape having an area substantially equal to the cross-sectional area of the second chamber 40. Therefore, if the movable plate 48 moves, the internal volume of the measuring tank changes, and according to the embodiment, by pulling down the movable plate 48, the internal volume of the measuring tank is increased to bring the inside into a decompressed state. .

An elastic deformation member is provided between the movable plate 48 and the inner wall of the measuring tank. According to the embodiment, the elastic deformation member is 3
In this embodiment, the O-rings 50, 52, 54 are stacked in a stack, and when the movable plate 48 is pulled down, the O-rings 50, 52, 54 are compressed to increase the internal volume of the measuring tank. can do.

In the embodiment, the O-ring 50 is guided by the guide portion 48a provided on the movable plate 48, and its position is determined.

Further, the O-rings 52 and 54 are respectively positioned by guide plates 58 and 60 slidably supported by the movable shaft 56 of the movable plate 48.

Therefore, when the movable plate 48 is pulled down, each O-ring
48, 50, 52 are compressed at predetermined positions respectively, and it is possible to obtain the desired internal volume change simply by deforming the elastically deforming member without causing the sliding contact action of the conventional piston / cylinder mechanism. Becomes

A pressure seal drive unit is provided to move the measurement lid 10b, and according to the embodiment, an air pressure mechanism hydraulic mechanism or a motor drive mechanism (not shown) is provided at the upper end of the pressure shaft 33. By pressing the pressing shaft 3 downward, the measuring lid 10b can be moved by a predetermined amount while deforming the O-ring 34.

In the embodiment, the movement amount of the measurement lid 10b is the measurement body 1
It is limited by 0a, which serves as a stopper. As a result, the downward movement position of the measurement lid 10b is regulated, and the movement distance of the measurement lid 10b can be kept constant.

On the other hand, a piston drive unit is provided to move the movable plate 48, and according to the embodiment, a pneumatic mechanism hydraulic mechanism or a motor drive mechanism (not shown) is provided at the lower end of the drive shaft 56. , The O-rings 48, 50, without pulling out the gas in the measuring tank by pulling down the drive shaft 40,
The movable plate 48 can be moved by a predetermined amount while deforming 52.

The amount of movement of the movable plate 48 is limited by a stopper, and in the embodiment, the stopper is composed of a step portion provided on the drive shaft 56 and a stopper ring 62 fixed to the drive shaft 56. The downward movement position and the upward movement position of the movable plate 48 are regulated, respectively, so that the amount of change in the measuring tank internal volume during the movement of the movable plate 48 can be maintained at a constant value.

When the movable plate 48 moves, air is removed from the air gaps regulated by the O-rings 48, 50, 52.
0 and small holes 58a, 60a,
0e is provided.

Therefore, when the movable plate driving unit lowers the movable plate 48 downward, this lowering is instantaneously performed, and the time required for the leak inspection can be significantly shortened.

In order to detect the change in the internal pressure of the measuring tank, in the embodiment, the pressure sensor 16 is connected to the second chamber 42 via the conduit 64, and the measuring tank is operated by the pressure detecting action using a well-known semiconductor strain gauge or the like. The internal pressure can be measured continuously.

The mechanism section shown in FIG. 1 has the above-mentioned configuration, and its measuring operation will be described below.

First, the measurement layer main body 10a is closed by the measurement lid 10b while the sealed container 300 to be measured is housed in the first chamber 38 of the measurement tank, and then the measurement lid 10b is pushed downward by the pressure sealing mechanism 12. To be At this time, the measuring tank body 10a and the measuring lid 10b
O-ring 34 installed between keeps the airtight state,
At the same time, the O-ring 34 is deformed in response to the pressurizing action of the pressurizing shaft 33, so that the inside of the measuring tank 10 is pressurized while being sealed, and the internal pressure thereof is increased.

Next, in this state, the movable plate drive unit pulls down the movable plate 48, and this pulling down is performed by stacking three O-rings.
Since it is performed while compressing 48, 50, and 52, unlike the conventional cylinder / piston method, such movement is performed only by the deformation of the elastically deformable member without any sliding contact action. As a result, the unstable element in the conventional sliding contact portion can be reliably removed.

Then, the movement of the measuring tank lid 10b and the movable plate 48 are instantaneously performed, and the movement amount is restricted by the measuring tank body 10a and the stopper, so that the change in the internal volume of the measuring tank is always kept at a constant value. Be drunk

FIG. 3 shows changes in the pressure inside the measuring tank in the leak detection device for a sealed container, which has been previously filed by the applicant, that is, in the leak detection device for a sealed container having no pressure sealing mechanism. The measurement tank lid 10b is merely a fixed lid portion, and the internal pressure is changed only with the change in the internal volume of the measurement tank 10 by lowering the movable plate 48. At this time,
When the movable plate 48 is pulled down at time t ₀ ,
The internal volume of the measuring tank 10 is increased in a short time until time t ₁ ,
Thereby, the internal pressure of the measuring tank is reduced to a predetermined value.

After that, a slight increase in pressure occurs due to the influence of the gas temperature decrease due to adiabatic expansion in the measurement tank, and after time t ₂ , a stable pressure state where there is no leakage is obtained.

The solid line in FIG. 3 shows the characteristics when there is no leak in the container 300, and as is clear from the figure, the internal pressure of the measuring tank is maintained at a substantially constant value even after the time t ₂ , for example, a predetermined value until the time t _3. It can be determined that there is no leak by observing the pressure change after the passage of time.

On the other hand, the coin in FIG. 3 shows the pressure change when the container 300 is leaking, and at this time, the gas in the container 300 gradually leaks into the measuring tank, and the pressure in the measuring layer is Since it increases by the amount of leak, it can be determined that there is a leak by the change up to time t ₃ .

However, such measurement can be performed when a leaking hole is small, that is, when a so-called small leak occurs. When the small leak, since the reduction of the movable plate 48 is performed in a short period of time, measuring tank pressure to the time up to time t ₁ decreases to a predetermined value, then the gas in the container 300 is slightly within the measuring tank Since the leaks occur one by one, the presence or absence of the leak can be determined by the change until the time t ₃ when the steady state starts.

On the other hand, when the movable plate 48 is pulled down for a short time when there is a large leaking hole, that is, a large leak, the movable plate 48 leaks at the same time as this pulling down, and as shown by the one-dot chain line in FIG. The steady state begins at t ₂ . Therefore, the presence or absence of a large leak cannot be determined by the method of detecting the change from time t ₂ to time t ₃ as in the case of a small leak.

Therefore, in reality, the difference between the normal state and the large leak state is Δ
The presence or absence of a large leak was determined by detecting p ₁ .

However, when the O-link for the lid, which is an elastically deformable member, is crushed due to deterioration and the like, the O-link for the lid is closed when the measurement tank 10 is closed.
If the ring was new, the air that would have been contained in the measuring tank 10 would leak out. As a result, the internal pressure of the measurement tank 10 set at the initial stage of leak detection becomes low, and when the pressure inside the measurement tank 10 is reduced by the pressure setting mechanism 14, as shown by the chain double-dashed line in FIG. In addition, the value is lower than the normal state by Δp ₂ . Here, if the lid O-ring deteriorates and a large leak occurs at the same time, and Δp ₁
If the magnitudes of Δp ₂ and Δp ₂ are almost equal, it may be almost indistinguishable from the normal state.

Therefore, the leak detection device for a sealed container according to the present invention has a pressure sealing mechanism 12, and before the internal pressure of the measurement tank 10 is changed by lowering the movable plate 48, pressurization by pressing down the measurement tank lid 10b is applied. Done. Here, the pressure measurement value after the pressure seal by the pressure seal mechanism 12 that pushes down the measurement tank lid 10b and the pressure measurement value after the pressure setting by the pressure setting mechanism 14 that pulls down the movable plate 48 are detected. Then, by taking the difference between the measured values, it is possible to discriminate even when the O-ring for the lid is aged and a large leak occurs at the same time.

The operation of the leak detecting device according to the embodiment of the present invention will be described below with reference to FIG.

In FIG. 4, the solid line shows the internal pressure change in the measuring tank 10 when the test object is normal and has not leaked, and the broken line shows the case where only a large leak occurs, and the dashed-dotted line is for the lid of the measuring tank lid 10b. Measuring tank 10 when the O-ring 34 is only deteriorated
The change in pressure inside is shown, and the two-dot chain line shows the measuring tank 10 when a large leak and deterioration of the lid O-link occur at the same time.
The change in internal pressure is shown. Furthermore, the measurement tank 10 is pressurized between t ₁₀ and t ₁₁ by the pressure sealing mechanism, and depressurized from t ₁₂ by the pressure setting mechanism.

That is, when the measurement tank 10 is pressurized, if a large leak occurs, the volume of the measurement tank 10 is increased by the volume of the test object as compared with the case where it does not occur. Is the same as. Therefore, the means for increasing the internal pressure by reducing the internal volume of the measuring tank 10 is used, so that the internal pressure rises less than in the normal state. Similarly, when the pressure in the measuring tank 10 is reduced by the pressure setting mechanism, the decrease of the internal pressure is reduced by the same principle.

Further, when the lid O-ring 34 of the measurement tank lid 10b is crushed due to deterioration or the like, the air in the measurement tank 10 leaks when the measurement tank lid 10b is pushed down, so that the start-up is more than normal. Due to the air that has been delayed and leaked at the same time, the rise in internal pressure will be smaller than it would be under normal conditions. However, despite the air leakage, the change in the initially set internal volume of the measuring tank 10 and the internal volume by the pressure setting mechanism is constant, so that the pressure in the measuring tank 10 is reduced by the pressure setting mechanism that follows. The degree is higher than that under normal conditions.

When a large leak and deterioration of the lid O-ring occur at the same time, a large leak occurs in the place where the measuring tank is pressurized, as compared with the case where only the deterioration of the lid O-ring occurs. The amount of increase in the internal pressure becomes smaller by the amount of, and the degree of decrease in the internal pressure becomes smaller in the place where the measuring tank is decompressed, by a larger leak than in the case where only the O-ring for the lid is deteriorated.

Therefore, the pressure Δp after pressure sealing and after the pressure setting is normal and not leaking Δp ₃ , when a large leak occurs Δp _4, and the lid O-ring 34 of the measuring tank lid 10b is deteriorated due to deterioration or the like. If crushed, Δp ₅ , large leak and measuring tank lid 10
When the O ring 34 for the lid of b is deteriorated at the same time Δp
_By taking ₆ respectively and comparing Δp ₃ and Δp ₄ and Δp ₃ and Δp ₅ and Δp ₃ and Δp ₆ , it is possible to discriminate between the case where a large leak occurs and the case where the O-ring is crushed.

The small leak can be detected by the same means as in the previous application.

As described above, according to the present invention, it is possible to perform an accurate leak inspection with high sensitivity in an extremely short time, without the need for a large-scale pressurization source as in the conventional case, and when the initial pressurization or There is an advantage that a leak inspection can be performed extremely quickly without requiring a stabilization time during depressurization.

[Effects of the Invention] As described above, according to the present invention, leak inspection of a sealed container can be performed quickly and with high sensitivity, and leak is extremely effective for 100% inspection of mass-produced electronic components and the like. An inspection device can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part showing a preferred embodiment of a mechanical part of a leak inspection apparatus according to the present invention, and FIG. 2 is a schematic view of the mechanical part of FIG. 1 and a control part for controlling the mechanical part. Explanatory drawing shown, FIG. 3 is an explanatory view showing the measuring tank internal pressure change characteristic at the time of leak inspection in the embodiment of the previous application, and FIG. 4 is a characteristic diagram showing the measuring tank internal pressure change characteristic at the time of leak inspection in this embodiment. Is. 10 …… Measuring tank 10a …… Measuring tank body 10b …… Measuring tank lid 12 …… Pressure sealing mechanism 14 …… Pressure setting mechanism 16 …… Pressure sensor 48 …… Movable plate 33 …… Pressure shaft 34,50, 52,54 …… Elastic deformation member (O-ring) 56 …… Drive shaft 56a, 62 …… Stopper 300 …… Sealed container to be measured

Claims (1)

[Claims] 1. A measurement tank main body for accommodating a sealed container to be measured, a measurement tank lid for covering the measurement tank main body to form an airtight measurement tank, and a predetermined amount of change in the internal pressure of the measurement tank. And a pressure sensor for detecting a pressure change in the measuring tank, wherein the pressure setting mechanism includes a movable plate movably provided in the measuring tank, a movable plate and a measuring tank. An elastically deformable member provided between the inner wall, a movable plate driving unit that moves the movable plate while deforming the elastically deformable member without letting gas in the measuring tank escape, and a predetermined value for moving the movable plate. The measuring tank lid includes an elastic deformation member for the lid provided between the measuring tank main body and the measuring tank lid, and an elastic deformation member for the lid without letting gas in the measuring tank escape. Move the measuring tank lid while deforming the It has a measurement tank lid drive unit that seals in a state and a stopper that limits the movement of the measurement tank lid to a predetermined value.The measurement tank internal volume is changed by a predetermined amount without releasing the gas in the measurement tank, and the A leak measuring device for a sealed container, wherein a pressure difference between the pressure after sealing and the pressure after setting is taken, and a gas leak in the sealed container to be measured is detected by a change in internal pressure of the measuring tank at this time.