JPH0442761Y2 - - Google Patents

Description

[Detailed explanation of the invention] "Industrial application field" Equipment or containers that handle fluids, etc. must not leak during use, or must be within a certain standard. 2. Description of the Related Art Leakage testing devices are used to sequentially inspect products or parts during their production process to determine whether they are good or bad. This invention relates to a reference tank used in the device.

``Prior Art'' For example, various types of equipment such as engine cylinders, waterproof watch containers, and gas appliances are required to have no leakage of gas or liquid, or to have the leakage amount within a certain standard. For this reason, such devices or parts are inspected for leaks during the manufacturing process. This leak testing device applies positive fluid pressure to, for example, an object to be inspected (hereinafter referred to as a sample) and a reference tank, and measures changes in the differential pressure therebetween to determine the quality of the sample. In other words, fluid pressure is applied to the sample, and changes in differential pressure are monitored for a certain period of time after the fluid pressure reaches a predetermined value. This is to determine the

In order to facilitate understanding of this invention, a differential pressure detection type leak testing device will be explained using FIGS. 7 and 8.

A flow pipe 10 connected to the output side of the air pressure source 11 is divided into two at the outlet side of the three-way valve 14 via a pressure regulating valve 12 and a three-way valve 14, and is connected to branch passages 15-1 and 15-2, respectively. . A pressure gauge 13 for setting a test pressure is connected between the outlet of the pressure regulating valve 12 and the inlet of the three-way valve 14.

The branch 15-1 connects to the conduit 18 via the solenoid valve 16.
The other end of this conduit 18 is provided with a mechanism for connecting a sample 20 to be tested for leaks. The mechanism at the other end of this conduit 18 allows the sample 2 to
0 are connected in sequence to enable leakage testing. On the other hand, the branch path 15-2 is connected to one end of a conduit 19 via a solenoid valve 17, and the reference tank 21 is connected to the other end of this conduit 19. A differential pressure detector 22 is installed between the conduits 18 and 19 on the outlet side of the solenoid valves 16 and 17.

The output signal of the differential pressure detector 22 is given to a comparator 32 via an amplifier 31, and the comparator 32 is configured to be able to compare it with an output reference value of a reference signal setter 33.

Sample 20 is attached to the end of conduit 18, and conduit 1
A leak-free reference tank 21 is attached to 9, and the three-way valve 14 is closed between the a end and the b end (a end, b end).
(both ends are closed), the pressure regulating valve 12 is opened and the pressure gauge 13 adjusts the air pressure given from the air pressure source 11 to a predetermined value. Next, the solenoid valve 16
and 17 are opened, and air at a constant pressure is supplied between ends a and b of the three-way valve 14 through branch paths 15-1 and 15-2 and conduits 18 and 19 to the sample 20 and reference, respectively. It is supplied to the tank 21. This state is defined as a pressurization period as shown in FIG. 8A, and the time period is represented by _T1 .

A certain period of time after opening the solenoid valves 16 and 17
After T ₁ has elapsed and the pressures in the sample 20 and reference tank 21 have stabilized, the solenoid valves 16 and 17 are closed. After a predetermined time T ₂ during which the change in differential pressure stabilizes to some extent from this point, a zero correction signal 34 is sent to the automatic zero correction amplifier 31 connected to the differential pressure detector 22.
is given by the control circuit 35, and the output of the amplifier 31 is set to zero in advance, and the output signal of the amplifier 31 is read after a certain period of time _T3 from the time of this zero setting. The time _T3 from the time of zero setting to the time of reading is referred to as the measurement time. Amplifier 3
1 is set as the zero point, the sensitivity of the amplifier 31 is switched to a high sensitivity state, and when the quality of the sample 20 is judged, the detection signal of the differential pressure detector 22 is transferred to the amplifier 31.
The image is enlarged to make it easier to read.

Here, there is a period T ₁ in which the solenoid valves 16 and 17 are controlled to open and pressure is applied, a period T ₂ in which the solenoid valves 16 and 17 are closed to stabilize the pressure, and a period from when the amplifier 31 is set to zero to when reading is performed. The inspection time T ₃ is called one inspection cycle. This period T ₁ , T ₂ ,
The switching of T ₃ is performed by the control circuit 35.

When the sample 20 is completely airtight and there is no leakage, the output signal from the amplifier 31 ideally becomes zero during a certain measurement time. If there is a leak in the sample 20, the internal pressure will gradually decrease, and the output signal within the fixed measurement time _T3 will have a value approximately proportional to the amount of leak.

The reference signal given from the reference signal setter 33 and the output signal of the amplifier 31 are compared by the comparator 32,
Depending on whether the output signal exceeds the reference signal, a non-defective product determination output 36 indicating a non-defective product or a defective product is obtained.

When the measurement time T ₃ ends, the a end of the three-way valve is closed, and the b end is connected to the c end, which is open to the atmosphere, and the sample 20, reference tank 21, and related conduits are evacuated to atmospheric pressure. and inspected sample 2
After removing the 0 and installing a new one in the connection mechanism, the test cycle described above is repeated again.

Incidentally, the state of change in the air temperature inside the sample during the measurement cycle varies considerably depending on the shape and size of the sample. Now, if the ambient temperature of the place to be inspected is 20℃, and the temperature of the sample itself (metal part) and compressed air are also equal to this temperature, the inside of two samples a and b with different shapes and dimensions. When the air temperature is measured, it changes as shown in Figure 9. That is, the air inside the sample (equal to atmospheric pressure before pressurization) is compressed by compressed air from the air pressure source 11, but this compression corresponds to a type of adiabatic compression, and the temperature of the compressed air suddenly increases. rise to but,
It is gradually cooled down by heat conduction from the surrounding metal parts.
The magnitude of the air temperature and its rate of change at the measurement time _T3 are different between samples a and b. This change in air temperature causes a change in air pressure. This change in air pressure due to a change in air temperature inside the tank also exists in the reference tank 21, and the air temperature and
Therefore, the state of change in pressure is different. Further, due to changes in ambient temperature, the dimensions and therefore the internal volumes of the sample 20 and the reference tank 21 change, resulting in fluctuations in their respective internal pressures. These changes in internal air temperature due to adiabatic compression and changes in internal pressure due to changes in ambient temperature are observed in sample 20 and reference tank 2.
If it is the same as 1, there will be no measurement error. Therefore, as the reference tank 21, a tank with no (or negligible) leakage is separately selected from the sample group and used as the reference tank.

``Problem that the invention aims to solve'' When using a sample as a reference tank, it must be strong enough to withstand repeated use, not deformed by pressure, and not deformed or altered over time.
There is no problem as long as the dimensions are reasonable. However, there are cases where the sample is made of synthetic resin, for example, and its dimensions and material change significantly over time, and its deformation due to pressure varies widely, making it unreliable to use as a reference tank, or when the sample is too large. Therefore, it may not be possible to use it as a reference tank due to space constraints, and in such cases, a leak test device that detects differential pressure cannot be used, and other methods (for example, a method that directly measures pressure changes within the sample) may not be used. We had no choice but to install equipment.

The purpose of this invention is to provide a reference tank to replace the sample when it cannot be used as a reference tank, and to expand the scope of application of the differential pressure detection type leak testing device.

``Means for Solving the Problems'' The reference tank for the leakage test device of this invention includes a capsule made of a cylindrical metal material with an open end, and an inner end surface of the capsule along the central axis of the capsule. A shaft made of a planted metal material, a plurality of collars made of an annular metal material inserted through the shaft, and a plurality of collars made of a disc-shaped metal material having a central hole inserted through the shaft. fins, a port for applying air pressure inside the capsule, and a lid made of a disc-shaped metal material that closes the opening of the capsule, the number of the fins and collars, and the shaft rod. The internal volume and surface area of the tank are adjusted by changing the order of insertion.

``Example'' The standard tank of this invention is shown in Figure 1.
A cylindrical shaft 2 is planted on the inner end surface of the capsule 1 along the central axis of a cylindrical capsule 1 with one end open. An annular collar 3 (FIG. 2A) having a large inner diameter and a cylindrical fin 4 (FIG. 2B) having a center hole 4a slightly larger than the outer diameter of the shaft 2 are inserted alternately. A cylindrical lid 5 is attached to the top of a capsule 1 containing five collars 3 and 4 by screws 6 to the top of the side wall of the capsule. An annular groove coaxial with the capsule is formed in the upper part of the side wall, and an O-ring 7 is attached to the groove.
This ensures that the tank is airtight. A port 5a is provided in the center of the lid 5 for connecting to a conduit via a connecting mechanism and for applying air pressure.
A mounting piece 8 for fixing the capsule is attached to the outer peripheral surface of the capsule 1. The capsule 1, shaft rod 2, collar 3, fins 4, lid 5, etc. are made of metal materials such as aluminum or iron.

As the reference tank of this invention, a plurality of types are prepared, for example, as shown in FIG. 3. For example, the internal volume is 250~500c.c., 500c.c.~1 and 1~2
There are three types. The volume of the tank can be adjusted by the number of fins and collars to be accommodated, and generally the type and number of fins and collars to be accommodated are determined so as to obtain the inner volume closest to the sample. In the case of Figure 3, the volumes of the fins and collar are each 80
cc and 1.7cc, and the volumes of pieces A and B (to be explained later) used together are 3cc. and 2cc, respectively.
It is considered as cc.

The manner in which the fins 4 and the collar 3 are attached to the shaft 2 can be adjusted even if the internal volume is the same, by changing the internal surface area as shown in FIGS. 4A and 4B, for example, by changing the order in which the fins and collar are assembled. When the reference tank is set as shown in Fig. 4 A or B and the temperature change of the air in the reference tank is measured when a leakage test is actually performed, for example, Fig. 5 A and B are obtained, respectively.
The following characteristics are obtained. In the case of Figure 4 B, the surface area inside the tank is much larger, so the temperature of the air, which has risen due to the adiabatic compression effect, is conducted to the metal part of the tank and cooled down more rapidly than in the case of A. The temperature approaches the metal part of the reference tank (approximately equal to room temperature). The internal air temperature during the measurement time is close to room temperature, and the rate of change is small. Therefore, the pressure of the air should also be close to a stable state. In the case of attaching the fin, several samples are inspected in the preparation stage, and the surface area inside the tank is adjusted so that the change in the output of the amplifier 31 during the inspection time is small to the extent that it does not adversely affect the pass/fail judgment. . If it does not become smaller, increase or decrease the number of fins and collars, and if necessary, change to a reference tank with a different volume and make similar adjustments. In this way, the pressure variation characteristics in the reference tank are adjusted to approximate the actual sample.

In order to finely adjust the state of change in air temperature in the reference tank, one or more short columnar pieces 8 (made of aluminum or iron, for example) are installed on the top surface of the fin 4, as shown in FIG. It is also possible to change the volume and surface area by placing the container on the container. For example, the pieces are 2c.c. and 3c.c.
15 pieces of each will be prepared.

"Effects of the invention" As stated above, according to this invention, the volume and internal surface area are changed by changing the number of fins and collars attached to the reference tank and their mounting form, thereby creating an adiabatic compressed tank. It becomes possible to match the state of the temperature change and therefore the pressure change of the internal air to that of the sample internal air, and thus it can be used in place of the reference tank when the sample cannot be adopted as a reference tank, thus reducing the differential pressure. The scope of application of the detection type leak test device can be greatly expanded.

Further, the reference tank of this invention can be used not only in the above case but also as a dedicated reference tank, thereby improving the usability of the leakage testing device.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the reference tank of this invention, and Fig. 2 is a sectional view showing the collar 3 and fin 4 of Fig. 1.
Fig. 3 is a diagram showing the volume of the standard tank shown in Fig. 1 and an example of the structure of the fins, collar, and frame. Fig. 4 is a diagram showing the internal volume of the standard tank shown in Fig. 1, but with the fins and collar stacked in different order. FIG. 5A is a sectional view of a reference tank of this invention to show an example of adjusting the surface area of
and B are diagrams showing the change characteristics of the air temperature inside the tank when the reference tanks of FIGS. 4 A and B are used for leakage inspection, respectively. A sectional view of a reference tank of this invention to show an example of adjusting the internal volume and surface area, FIG. 7 is a block diagram of a differential pressure detection type leak test device, and FIG. 8 explains the operation of FIG. 7. FIG. 9 is a diagram showing the change characteristics of the air temperature inside the sample 20 in FIG. 7.

Claims (1)

[Claims for Utility Model Registration] A capsule made of a cylindrical metal material with an opening at one end; a shaft rod made of a metal material planted on the inner end surface of the capsule along the central axis of the capsule; a plurality of collars made of an annular metal material inserted through the shaft; a plurality of fins made of a disk-shaped metal material having a center hole inserted through the shaft; A port is formed in the capsule, and a lid made of a disc-shaped metal material that closes the opening of the capsule is provided. A reference tank for a leak testing device, characterized in that the surface area is adjusted.