JPH0690108B2 - Leak detector for sealed container - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a leak detection device for a sealed container, and more particularly to an improvement of a leak detection device for a sealed container based on a change in internal pressure in a measurement tank that houses the sealed container.

[Prior Art] Containers that are hermetically sealed while leaving an empty chamber 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 operation 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 completely sealed state due to a defective seal during manufacture, the presence of holes in the container itself, etc.A 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 is 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 bubbles requires visual judgment by an inspector, and therefore the reliability of leak detection is low, and since automation is difficult, the time required for leak detection is long and inefficient. was there.

In place 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 decompression source is required, the size of the apparatus is increased, and large energy is required only for leak inspection. It was

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. A pressure sensor for detecting a pressure change in the tank is measured, and a subsequent pressure change is measured in a state where the pressure in the measurement tank is increased or decreased to a predetermined value, and thereby the presence or absence of a leak from the sealed container is determined.

Further, according to the present invention, the pressure setting mechanism includes a movable plate movably provided in the measuring tank, and an elastic deformation of an O-ring or the like provided between the movable plate and the inner wall of the measuring tank. A member, a drive unit that moves the movable plate, and a stopper that limits the movement of the movable plate to a predetermined value, and by moving the movable plate by a predetermined amount, the internal volume or internal pressure of the measurement tank is changed to a constant value. Then, the leak detection is performed by measuring the actual change in the internal pressure of the measuring tank at this time.

[Operation] Therefore, according to the present invention, the sealed containers to be measured are usually housed in the measuring tank one by one in an airtight state, and then the movable plate is moved by a predetermined amount determined by the stopper to measure the inside of the measuring tank. The volume or internal pressure is changed by a fixed amount, and the presence or absence of leak is determined by the change in the internal pressure of the measuring tank at this time.

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. It is possible to vary, and for this purpose the desired predetermined internal volume or pressure variation can be obtained with the conventional volume or pressure fluctuation factors completely eliminated.

Therefore, such a change in the internal volume or the internal pressure is instantaneously given to the measuring tank, and a constant pressure change is caused by the subsequent pressure change when there is no leak, and a corresponding change is made when there is a leak. The pressure change is detected, and the leak detection can be performed 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, and a lid closing mechanism 12 keeps the internal volume of the measuring tank 10 at a constant initial value with a closed container to be measured stored therein. Seal 10

In the measuring tank 10, a pressure setting mechanism 14 is continuously provided,
The internal pressure of the closed measuring tank 10 can be increased or decreased by a predetermined amount.

Then, the internal pressure of the measuring tank 10 is constantly measured by the pressure sensor 16, and according to the present embodiment, the pressure change after the internal pressure change of the measuring tank 10 by the pressure setting mechanism 14 is 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 lid closing mechanism 12 and the pressure setting mechanism 14 are the mechanism control unit.
It is performed by the control signal from 20.

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 measuring tank is composed of a substantially cylindrical tank body 30 and a lid body 32. In the embodiment, the disc-shaped lid body 32 is screwed to the tank body 30.

That is, a male screw flange portion 30a is provided at the opposite portion of the tank body 30, the female screw flange portion 32a of the lid 32 is screw-fitted to the male screw flange portion 30a, and the lower end of the female screw flange portion 32a is the tank. The lid tightening position is defined at a position where it abuts on the upper surface of the body 30.

Therefore, the volume of the inner chamber of the measuring tank should be such that the lid 32 is firmly attached to the tank 30.
It is properly screwed to and kept in a predetermined volume.

An O-ring 34 is provided on the outer side of the female screw flange portion 32a of the lid 32, and the measurement tank is kept airtight in the lid closed state.

The inner chamber of the measuring tank 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 30b provided in the tank body 30,
It is divided into a first chamber 38 in which the measured closed 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 sealed container 300 to be measured is shown as a seal relay, and the case lid 46 is housed in the case 42 with well-known relay contacts and relay coils accommodated in the inner chamber 44 of the case 42. A sealed container is formed by sealing.

Therefore, in a normal case, the inner chamber 44 of the closed container 300 is completely and airtightly shielded from the outside, but if a leak occurs due to a poor seal or other reasons, this must be removed as a defective product. The leak detecting device shown in the embodiment can inspect each relay one by one in the manufacturing inspection process of the seal relay.

The pressure setting mechanism for changing the internal pressure of the measuring tank by a predetermined amount includes a disk-shaped movable plate 48. In order to change the internal volume of the measuring tank as much 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, the movable plate 48 moves.
By pulling 48 downward, the internal volume of the measuring tank is increased and the inside is depressurized.

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 drive shaft 56 of the movable plate 48.

Therefore, when the movable plate 48 is pulled down, each O-ring
48, 50, 52 are each compressed at a predetermined position, 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. Become.

In order to move the movable plate 48, a piston drive unit is provided, 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 to drive the movable shaft. By pulling the shaft 40 downward, the movable plate 48 can be moved by a predetermined amount while deforming the O-rings 48, 50, 52 without letting the gas in the measuring tank escape.

The moving amount of the movable plate 48 is limited by a stopper, and in the embodiment, the stopper is the drive shaft.
The movable plate 48 is provided with a step portion and a stopper ring 62 fixed to the drive shaft 56. By this, the downward moving position and the upward moving position of the movable plate 48 are restricted, and the movable plate 48 is prevented.
The amount of change in the internal volume of the measuring tank during movement 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, 3
0c 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, the pressure sensor 16 is connected to the second chamber 42 through the conduit 64 in the embodiment, and the internal pressure of the measuring tank is detected by the pressure detecting action using a well-known semiconductor strain gauge or the like. Can be measured continuously.

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

The lid 32 is tightly closed to the tank 30 in a state where the measured sealed container 300 is housed in the first chamber 38 of the measuring tank,
This keeps the initial volume in the measuring tank constant.

In this state, the movable drive unit pulls down the movable plate 48,
This pulling down is performed while compressing the three stacked O-rings 48, 50, 52, and unlike the conventional cylinder / piston system, it does not involve any sliding contact action, but only by the deformation of the elastically deformable member. Such movement is performed, and as a result, the unstable element in the conventional sliding contact portion can be reliably removed.

Then, such a movement of the movable plate 48 is instantaneously performed, and since the movement amount is regulated by the stopper, when the movable plate 48 is positioned at the pulling down position, the change in the internal volume of the measuring tank is always constant. To be kept at a value.

FIG. 3 shows changes in the measurement tank internal pressure in the embodiment. When the movable plate 48 is lowered at time t ₀ , the measurement tank internal pressure reaches a predetermined value within a short time until time t _1. It is done by increasing the product.

Thereafter, until the time t _2, the slight pressure increase due to the influence of the gas temperature drop caused by adiabatic expansion in the measurement tank occurs, the pressure stable state when there is no leakage obtained in this time t _2.

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, the predetermined time until the time t _3. It can be determined that there is no leak by observing the pressure change after the elapse.

On the other hand, the broken line in FIG. 3 shows the pressure change when a leak occurs in the container 300. At this time, the gas in the container 300 leaks into the measuring tank, so the pressure in the measuring tank rises by the leak amount. and, this change can be determined as there leakage at time t _3.

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.

In the above-described embodiment, the measuring tank obtains the initial state by fixing the lid 32 of the tank body 30 by screwing the lid body 32, but in order to shorten the inspection cycle, the lid body 32 is not screwed but simply It is also possible to obtain the initial state by simply pressing the tank body 30 in an airtight state via the O-ring.

[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. The explanatory diagram shown in FIG. 3 is an explanatory diagram showing the change characteristic of the pressure inside the measuring tank at the time of the leak inspection in the present embodiment. 10 ... Measuring tank 14 ... Pressure setting mechanism 16 ... Pressure sensor 48 ... Movable plate 50,52,54 ... Elastic deformation member (O-ring) 56 ... Drive shaft 56a, 62 ... Stopper 300 ... Measured closed container

Claims (1)

[Claims] 1. An airtight measuring tank for accommodating a sealed container to be measured, a pressure setting mechanism for changing an internal pressure of the measuring tank by a predetermined amount, and a pressure sensor for detecting a pressure change in the measuring tank. The pressure setting mechanism includes a movable plate movably provided in the measurement tank, an elastically deformable member provided between the movable plate and an inner wall of the measurement tank, and a gas in the measurement tank. A movable plate driving unit that moves the movable plate while deforming the elastically deformable member without letting it escape, and a stopper that limits the movement of the movable plate to a predetermined value, without letting the gas in the measuring tank escape. A leak measuring device for a hermetically sealed container, characterized in that a gas leak in a sealed container to be measured is detected based on a change in the internal pressure of the measuring tank at a predetermined amount by changing the internal volume of the measuring tank.