JPH0230462B2 - MOREKENSASOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a leak testing device for detecting internal airtightness of a product that requires airtightness.

[Conventional technology]

2. Description of the Related Art Leakage testing devices are used to detect the airtightness of products that need to be sealed off from the outside, such as waterproof watches or automobile headlights. FIG. 3 is a block diagram showing the principle of a volumetric detection type leak testing device for detecting internal airtightness.

The principle of testing airtightness using this testing device will be briefly explained.

This volumetric detection type leak testing device performs a test by exposing two objects, a reference product called a master and a measured object called a workpiece, under the same conditions, and measures the difference in airtightness between the two objects to be measured. Determine whether the product is relatively inferior to the reference product.

The reference product is a product whose degree of airtightness is known in advance and is the same as the product to be measured. First, the object to be measured 1 and the reference product 2 are housed in separate measuring sections 3 and 4 having the same internal volume. High-pressure air is charged from a high-pressure tank 5 to each measuring section 3, 4,
The valves 6, 7 are closed when the pressure in each measuring section 3, 4 is increased to the same predetermined pressure V. After a predetermined period of time has elapsed, the differential pressure gauge 8 connected to each measuring section 3, 4 measures the difference in gas pressure within each measuring section 3, 4.

If the airtightness of the object 1 to be measured is poor, the high-pressure air within the measuring section 3 will enter the object 1 to be measured. Therefore, the pressure in the internal space of the measuring section 3 decreases, and the worse the airtightness, the greater the degree of pressure drop. The difference ΔV between the pressure drops in the two measurement parts 3 and 4 is observed, and if the pressure drop in the measured object 1 is larger, the airtightness of the measured object 1 is determined to be inferior to the reference product 2, and the measured object If the pressure drop of the measurement object 1 is equal to or smaller than the pressure drop of the reference product 2, it can be determined that the measurement object 1 has better airtightness than the reference product 2.

[Problem that the invention seeks to solve]

In this way, as long as a reference product is prepared, the volume detection type leak test device can relatively easily and accurately inspect and measure the relative performance with respect to the reference product.

However, if it is known that the quality of the group of objects to be measured is relatively good, in order to perform the inspection quickly, the objects to be measured are placed in both measuring sections without using the reference product. Comparative inspection tests may be conducted on the objects to be measured. At such times, it may happen that there is a large leak on both of the objects to be measured.

That is, if the airtightness is significantly lacking, the pressure inside and outside the airtight product will become equal when the predetermined time of the leakage test has elapsed. In other words, when there is a large leak, the gas pressure within the measuring section is at its final state where it is lowest. Therefore, in such a case, the pressure within each measuring section will be the lowest.
In other words, both objects to be measured have the same physical shape, and the pressure drop in each measuring section is equal.
If there is a large leak in both objects to be measured at the same time, the differential pressure detector that detects the difference in the degree of decrease in gas pressure within each measuring section will not detect the difference in pressure between the two measuring sections. As a result, the user makes the mistake of determining that the airtightness of the object to be measured is good.

The present invention provides a means for detecting such simultaneous large leaks without being affected by fluctuations in charge pressure from a pneumatic source.

[Means for solving problems]

Positive or negative air pressure is supplied from the air pressure source through a branch pipe,
The sample is taken out into two separate flow tubes, and a measuring section is provided at each end of the separate flow tubes. On the other hand, a tank for storing air pressure from the branch pipe via a first control valve is provided in each branch pipe, a second control valve is provided between these tanks and the measuring section, and after closing the first control valve, Supply tank air pressure to the measurement unit.

On the other hand, a differential pressure detector is provided for extracting the air pressure in each measuring section and detecting the pressure difference therebetween, and means for detecting that the pressure difference has exceeded a predetermined value is provided.

Furthermore, one of the tanks is provided with a pressure detector for detecting the tank internal pressure, an initial pressure signal of the tank internal pressure is obtained from this pressure sensor, and a memory holding means is provided for holding this initial pressure signal. The difference between the initial pressure signal of the tank internal pressure obtained from this memory holding means and the pressure signal of the pressure detection signal obtained when air pressure is applied from the tank to the measuring section is calculated, and the subtracted output reaches a predetermined value or more. A large leak detection means is provided for detecting the presence of a simultaneous large leak and determining that a simultaneous large leak exists.

According to the configuration of the present invention, when applying air pressure from the tank to the measuring section, the initial value of the tank internal pressure,
It is possible to compare the pressure value inside the tank after applying air pressure from the tank to the measuring section. Therefore, if there is a large leak in the object to be measured, the pressure inside the tank will decrease significantly, and the value of the difference will be outputted as a large value.

As a result, if the differential pressure value between the two measuring parts is almost zero, and the value of the difference is greater than a predetermined value, a "large leak" will occur in both of the two objects to be measured attached to the two measuring parts. It can be determined that "exists".

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention.

To test airtightness, a pressure difference is applied between the inside and outside of an airtight product, and the extent to which air enters the product or leaks to the outside is measured based on the pressure difference. Therefore, a pneumatic source 11 with a more positive or negative pressure than in a general test environment is required. Leak test air of positive or negative pressure is branched into two by a branch pipe 13 and taken out from an air pressure source 11 via a control valve 12 .

Branch end 13 of the branch pipe 13 branched into two parts
Separate flow pipes 14 and 15 are installed in A and 13B, respectively.
is connected, and a pneumatic source 1 is connected to the branch pipes 14 and 15.
1 is supplied with positive or negative leak test air pressure.

End portions 14A, 1 of branch pipes 14, 15, respectively
Two measurement units 16 and 17 are provided in 5A.
These measurement units 16 and 17 have the same internal volume V, and objects to be measured 18 and 19 are housed therein. When these objects to be measured 18 and 19 are stored,
The measurement parts 16 and 17 are sealed and the inside thereof can be completely isolated from the outside.

Each measurement part 16, 17 and the branch end 13 of the branch pipe 13
Between A and 13B, there are tanks 21 and 13B, respectively.
22 is provided. It is preferable that these tanks 21 and 22 are configured to have approximately the same internal volume as the internal volume V of the measuring sections 16 and 17.

These tanks 21 and 22 are connected to branch ends 13A and 22 through branch pipes 14 and 15 and first control valves 23 and 24, respectively.
Connects to 13B. Therefore, the first control valves 23, 2
4, the tanks 21 and 22 are charged with positive or negative air pressure from the air pressure source 11.

Further, second control valves 25 and 26 are provided between the tanks 21 and 22 and the measurement units 16 and 17. These second control valves 25, 26 and first control valves 23, 24
The opening and closing operations are performed in a completely opposite manner. That is, when the first control valves 23 and 24 are open, the second control valve is controlled to be closed. In this state, tanks 21 and 22
is charged to positive or negative test air pressure. Next, when the first control valves 23 and 24 are closed and the second control valves 25 and 26 are opened, leak test air pressure is applied from the tanks 21 and 22 to the measurement units 16 and 17.

Branch pipes _s 1 and s ₂ are provided in each of the branch pipes 14 and 15 between the second control valves 25 and 26 and the measurement units 16 and 17,
Both the branch pipes 14 and 15 are connected to both input terminals of the differential pressure detector 27 by the branch pipes s ₁ and s ₂ . In other words, the pressure difference between the measuring sections 16 and 17 is applied to the differential pressure detector 27, and the differential pressure value is detected.

This differential pressure detector 27 is connected to each supplied measuring section 1.
The difference in pressure between 6 and 17 is converted into an electric signal e, and this electric signal e is passed through an amplifier 28 and the differential pressure output is displayed on a meter 29 or the like.

In this invention, one of the two tanks 21 and 22, in this example, the tank 21 on the side of the object to be measured 18, is connected to the air pressure P in the tank 21.
A pressure detector 31 is provided to detect the pressure inside the tank 21, and converts it into an electric signal E corresponding to the pressure inside the tank 21 and outputs it.

This pressure detection signal E is given to an electric circuit 32 for signal processing. FIG. 2 is a diagram showing an example of an electric circuit. This electric circuit 32 is provided with a memory holding means 33, and the pressure detection signal E is sent to the switch _SW1.
It is applied to the memory holding means 33 through. The initial pressure P ₀ charged to the tank 21 is stored in the memory storage means 33. In this example, the memory holding means 33 consists of a capacitor 34 and an operational amplifier 35, and the initial pressure P ₀ is held in the capacitor 34.
The operational amplifier 35 outputs the held value.

On the other hand, the pressure detection signal E is amplified by the amplifier circuit 36, and its output _E1 is given to the subtraction means 38 via the coefficient circuit 37. In this example, the subtraction means 38 consists of an operational amplifier 39, and one input terminal 39A of the subtraction means 38 is supplied with the output signal αE ₁ from the coefficient circuit 37 as well as the storage signal E ₀ from the memory holding means 33. The pressure detection signal αE ₁ is subtracted from the stored signal E ₀ and output.

The output of the subtraction means 38 is given to the large leak detection means 42 through the signal switching circuit 41, and the large leak detection means 42 determines whether or not there is a large leak and outputs the result. In this example, the meter 42 is used as a large leak detection means, the switch SW ₃ constituting the signal switching circuit 41 is on, the switch SW ₂ ,
When SW ₄ is off, the meter 42 displays the output signal from the subtraction means 38. In other words, if the value displayed on the display 42 is equal to or greater than a predetermined value, it can be determined that a large leak exists in the object 19 to be measured.

The variable resistor R ₀ of the signal switching circuit 41 has an output E ₀ ,
Used for E ₁ calibration. This signal switching circuit 41 is connected to the tank 2 when the leakage inspection device is inactive, for example.
The signal E ₀ corresponding to the charge pressure Pt of 1, and the signal E ₂ from the subtraction means 38 when a large leak is detected.
While inspecting for the presence or absence of a small leak, the measurement unit 16,
SW ₂ , SW ₃ , and SW ₄ are controlled so that the signal E ₁ of the charge pressure Pw of No. 17 is displayed on the meter 42 .

[Effect]

Next, the operation of the present invention will be explained regarding the leakage testing device configured as described above.

The object to be measured is placed in the measuring sections 16 and 17, and the object insertion opening is sealed.

The second control valves 25 and 26 are closed and the first control valve 2
3 and 24 are opened to charge air pressure Pt from the air pressure source 11 to the tanks 21 and 22. However, air pressure will be explained as positive pressure.

The first control valves 23 and 24 are closed, and the second control valve 2
5, 26 are controlled to be open, and the measurement units 16, 17 are charged with the air pressure Pt charged in the tanks 21, 22.

A normal measuring device, ie, the display 29, is used to confirm whether or not there is a large leak in the measuring body. In other words, if there is a large leak in either of the objects to be measured 18 or 19, the charged air pressure will immediately leak into the object to be measured 18 or 19, and the measuring portion that does not have a large leak will leak into the object to be measured. Since a large pressure difference occurs between the two pressures, the value of the pressure difference is displayed on the display 29 and can be observed.

If it is confirmed by the display 29 that there is no major leak in either measuring body 18 or 19,
Close the second control valves 25 and 26 for a predetermined period of time,
For example, leave it for about 1 to 2 seconds, and then
and 17, wait for the air movement to subside,
2 with the gain of the amplifier 28 increased and the sensitivity increased.
The difference in pressure between the two measurement units 16 and 17 is detected.
This makes it possible to detect the presence or absence of a small leak.

As described above, even if there is a large leak in both the object to be measured 18 and the reference product 19 at the same time, there is no difference in the pressures between the two measurement parts 16 and 17.

Next, detection of simultaneous large leaks, which is the main part of the present invention, will be explained.

(1) When pneumatic pressure is charged from the pneumatic source 11 to the tanks 21 and 22 in the step described above, the charge pressure in the tank is detected as the initial pressure Pt by the pressure detector 31, and the detection signal E ₀ is detected by the switch. It is applied to the memory holding means 33 via SW ₁ , and the detection signal E ₀ is stored in the memory holding means 33 as an initial value.

(2) Measurement part 1 from tanks 21 and 22 with steps
Let _E1 be the pressure Pw in the tank 21 when the air pressure Pt in the tank is charged at times 6 and 17, and the output of the pressure detector 31 corresponding to this pressure Pw.

The internal volumes of the tanks 21 and 22 are Vt, and the measurement unit 16,
The void volume obtained by subtracting the volume of the objects to be measured 18 and 19 from the internal volume of the object 17 is expressed as Vw. Assuming that the objects to be measured have ideal airtightness and no leakage, the following equation (1) Pt× Vt=Pw (Vt+Vw) ...(1) holds true. However, it was assumed that the tank charge pressure Pt was sufficiently higher than that inside the measurement section before the inspection started (at the time when the object to be measured was stored). This formula (1)
By transforming, we obtain Pt={(Vt+Vw)/Vt}・Pw...(1)′. Here, if we set (Vt+Vw)/Vt=α...(2), equation (1)' becomes Pt=α・Pw...(3). If there is no large leak in the object to be measured 18, Pt−αPw≈0.

In the above, it has been assumed that there is no major leak in the object to be measured 18. Now, if there is a large leak in the object to be measured 18 and the air charged in the measuring section 16 enters the object to be measured, the charge pressure inside the measuring section, or the inside of the tank 21 when the valve 25 is opened, will increase. pressure of
Pw decreases to Pw′. Since Pw>Pw', it is clear that Pt−αPw'>0...(4). That is, in the present invention, by measuring the change in the pressure inside the tank, the object to be measured 18 and the
9, the simultaneous large leak can be detected.

Here, Pt is the charge pressure of the tank 21, and at that time, the pressure signal E ₀ from the pressure detector 31 is
is output. This pressure signal E ₀ is stored in the memory holding means 33. The subtraction means 38 calculates the difference between the signal E ₀ outputted from the memory holding means and αE ₁ given from the coefficient circuit 37, E ₂ =E ₀ −αE ₁ . The coefficient value α is defined in the coefficient circuit 37 so that E ₂ =E ₀ −αE ₁ =0 when there is no leak in the measured object 18 . That is, set the resistor R ₃ .

If there is no large leak, it is clear from equation (2) that
E ₂ =0. If a large leak exists, the pressure within the tank 21 changes from the initial value Pt to Pw'. The subtraction at this time is E ₂ =E ₀ −αE ₁ . Pt−
Since αPw′>0, E ₀ >αE ₁ and E ₂ >0. Therefore, it is possible to detect simultaneous large leaks.

Now, here, there is a pressure fluctuation in the pneumatic source 11,
For example, a case will be explained in which the charge pressure to the tanks 21 and 22 changes and the test pressure changes to Pt'=Pt+ΔP.

If the measured object 18 has good airtightness and there is no leakage, Pw' = (1/α)Pt' ... (3)', that is, αPw' - Pt' = 0, as in equation (3). be. There is a leak
If Pw′ changes and changes to Pw″ due to a large leak, αPw′−αPw″>0. Therefore, a large leak can be detected without being affected by fluctuations in test pressure Pt.

〔Effect of the invention〕

As explained above, in a volume detection type leak testing device that has a pair of equal measuring parts, two objects to be measured are tested simultaneously and the presence or absence of a leak is determined relative to each other. The disadvantage is that both of the two objects to be measured have extremely poor airtightness, allowing charged air to enter almost all at once.
Therefore, if both objects to be measured settle down to their final state, no differential pressure will occur between the measuring parts, so both will be judged as good.
According to the present invention, the serious drawbacks of such volume detection methods can be solved. Moreover, it is not affected by fluctuations in test pressure, and its effects are great.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an example of a volumetric leak detection system according to the present invention, FIG. 2 is a diagram showing a configuration example of a large leak detection circuit according to the invention, and FIG. FIG. 3 is a diagram for explaining the principle. 1: Reference product, 2: Measured object, 3, 4: Measuring part,
5: Air pressure source, 6, 7: Control valve, 8: Differential pressure detector,
11: Air pressure source, 12: Control valve, 13: Branch pipe, 1
4, 15: Diversion tube, 16, 17: Measurement part, 18:
Measured object, 19: Reference product, 21: Tank, 22:
Tank, 23, 24: First control valve, 25, 26:
2nd control valve, 27: differential pressure detector, 28: amplifier,
29: Meter, 31: Pressure detector, 32: Electric circuit, 33: Memory holding means, 34: Capacitor, 3
5: operational amplifier, 36: amplifier circuit, 37: coefficient circuit, 38: subtraction means, 39: operational amplifier, 41:
Signal switching circuit, 42: Large leak detection means, P ₁ ,
P ₂ : Pressure detection point of each branch pipe, e: Output of differential pressure detector, E ₀ : Initial pressure in the tank, Vt: Internal volume of the tank, Vw: Volume of the object to be measured from the internal volume of the measuring part. Subtracted void volume, Pt: Test pressure inside the tank, Pw: Pressure between the tank and the measuring section after charging from the tank to the measuring section.

Claims (1)

[Claims] 1. A branch pipe that branches positive or negative air pressure generated by a pneumatic source into two parts, B. Two branch pipes connected to one branch end and the other branch end of this branch pipe, and C. D: two measuring sections connected to respective ends of the branch pipe; D; two tanks provided between the two measuring sections and each branch end of the branch pipe and having a volume close to the volume of the measuring section; , E: a first control valve provided between the tank and the branch end for supplying air pressure from the pneumatic source to the tank; F: a first control valve provided between the two tanks and the measuring section. a second control valve that is controlled to open after the first control valve is closed with equal amounts of air pressure stored in the two tanks; A differential pressure detector connected between the A leak detection means for detecting the presence of a leak in the measurement object; I A pressure detector for detecting the pressure in either one of the tanks; J A pneumatic source for the tank when the first control valve is open. memory holding means for storing and holding a detection signal output from the pressure detector in a state in which air pressure given by K is accumulated; subtracting means for subtracting the detection signal output from the pressure detector from the value held in the memory holding means in the state; A leak testing device comprising: large leak detection means for detecting the presence of a large leak in a measured object.