JPH04132926A - Method and apparatus for leak test - Google Patents

Abstract

PURPOSE:To discern a variety of test specimens in accordance with the actual condition by discerning the test specimens to be good if the leaking component is not larger than a permissible value even when it is not zero. CONSTITUTION:A pseudo leak test of a reference container which is already known to have no leak is performed, thereby to detect the pressure change Pr does not include leaking components, error components Eo can be obtained based on the pressure change Pr. Immediately after the error components Eo are detected, namely, before the error components are changed, a leak test for a test specimen is carried out to detect the pressure change Ps. The average value Ao of the leaking components of the good test specimen is obtained on the basis of the pressure change Ps and error components Eo. Subsequently, a leak test for many test specimens is sequentially carried out. At this time, the leaking components Ai are obtained b an equation Ai= Pi- Pav+Ao wherein Pav is the virtual average value of the pressure change of the good test specimens tested before the specimens being tested.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and apparatus for leak testing a specimen such as a container.

[Prior Art] The configuration of a general leak test device will be explained by taking a differential pressure detection type as an example. This leak test device includes an air passage (fluid passage), and a compressed air source (fluid pressure source) is connected to one end of the air passage. The other end of the air passage is branched into two, and a valve is installed in each of these branch passages. A reference container and a sample are connected to the ends of the two branched paths, respectively. The reference container is a container that has been previously confirmed to have no leakage, and is continuously used while being connected to one branch path. Then, a leak test described below is performed by sequentially connecting a large number of specimens to the other branch path. First, the two valves are opened to introduce test pressure into the reference container and the specimen, and then the valves are closed, and after a predetermined period of time, the differential pressure between the specimen and the reference container is detected. If the test pressure is positive, if there is a leak in the sample, the pressure of the sample will drop, creating a pressure difference between the reference container and the sample. By detecting this differential pressure with a differential pressure sensor (pressure detection means), leakage of the sample can be detected.

The differential pressure described above theoretically represents the pressure fluctuation of the specimen due to leakage of the specimen. However, in reality, the differential pressure sensor detects a differential pressure even if there is no leakage in the sample. The error component included in this differential pressure is caused by, for example, the influence of ambient temperature, humidity, etc. on the reference container and the specimen being different.

The leak test device disclosed in Japanese Patent Publication No. 1-34333 subtracts this error component from the detected differential pressure to detect only the component caused by the leakage of the specimen, and determines whether the leakage component is zero or not. Judging whether it is good or bad. Here, since the error component changes depending on the ambient temperature and the like, the average of the differential pressures of a plurality of samples determined to be good before the sample being tested for leakage is provided as the error component.

[Problems to be Solved by the Invention] In the case of the above-mentioned publication, zero leakage of the sample is used as a criterion for determining pass/fail. However, there may be cases where it is required to determine that the product is non-defective if the leakage of the sample is within an acceptable range. For example, a container (specimen) used to enclose a liquid is subjected to a leak test using compressed air.

The device disclosed in the above publication cannot meet this requirement.

This is because if the leak component is determined to be good if it is within the allowable range, the average value of the differential pressure of the above-mentioned non-defective sample includes not only the error component but also the average value of the leak component within the allowable range. Yes, the value obtained by subtracting this average differential pressure from the differential pressure of the specimen under test does not represent the actual leakage component;
This results in a value lower than this. As a result, it becomes impossible to determine pass/fail.

[Means for Solving the Problems] In order to solve the above problems, the gist of the first invention resides in a leak test method characterized by comprising the following steps.

(a) First, a pseudo-leak test is performed on a leak-free reference container, the pressure fluctuation ΔPr that occurs at that time is detected, and the initial error component E○ is determined based on this pressure fluctuation.

(b) Immediately thereafter, perform leak tests on the specimens one after another. That is, the leakage component of the detected pressure fluctuation is compared with the allowable value Amax, and when it is below the allowable value, it is determined to be a good product, and when it exceeds the allowable value, it is determined to be a defective product. The leakage component As immediately after the pseudo-leak test is determined from the following equation.

In the following equation, ΔPS is the detected pressure fluctuation.

As=ΔPs−Eo In addition to the above quality determination, the average value Ao of the leakage component As of a plurality of samples determined to be non-defective is determined.

(c) In the subsequent leak test of the sample, the leakage component Ai is calculated from the following equation. In the following equation, ΔPi is the detected pressure variation, and ΔPav is the substantial average value of the pressure variation in the sample determined to be good before the sample currently being tested.

Ai=ΔPi−ΔPav+Ao The gist of the second invention resides in a leak test method characterized by comprising the following steps.

(a) First, a pseudo-leak test is performed on a leak-free reference container, a pressure fluctuation ΔPr occurring at that time is detected, and an initial error component Eo is determined based on this pressure fluctuation.

(b) Immediately after that, perform a pseudo leak test on multiple non-defective samples to detect the pressure fluctuation ΔPs, and calculate the average value Ao of the leakage components of the non-defective samples based on this pressure variation and the above initial error component Eo. demand.

(c) Next, perform leak tests on the specimens one after another.

That is, the leakage component Ai of the detected pressure fluctuation ΔPi is compared with the allowable value Amax, and when it is less than the allowable value, it is determined to be a good product, and when it exceeds the allowable value, it is determined to be a defective product.

The above leakage component Ai is determined from the following equation. In the following equation, Δ
Pav is a substantial average value of pressure fluctuations in samples that were determined to be good before the sample currently being tested.

Ai-ΔPi-ΔPav+Ao The third gist of the invention is to include a fluid passage, a fluid pressure source connected to one end of the fluid passage, a valve means disposed in the middle of the fluid passage, and a valve connected to the other end of the fluid passage. A leak test device comprising a pressure detection means for detecting pressure between the pressure detection means and a microcomputer connected to the pressure detection means,
A leak test device is characterized in that it includes the above-mentioned microcomputer and the following configuration.

(a) Calculate the average value of the pressure fluctuation ΔPr detected by the pressure detection means when performing a pseudo leak test by connecting multiple reference containers with no leakage to the other end of the fluid passage, and calculate the initial error. Initial error component calculation means for calculating component Eo.

(b) Leak component average value calculation means for calculating the average value Ao of the leak component based on the pressure fluctuation ΔPs of a plurality of non-defective specimens detected in a test immediately after the pseudo leak test of the reference container and the initial error component Eo. .

(c) Substantial average value ΔPa of pressure fluctuations in multiple samples determined to be good before the sample currently undergoing leak testing
Pressure fluctuation average value calculation means for calculating v.

(d) Pressure fluctuation ΔPi detected in the current leak test
Leakage component calculation means for calculating the leakage component Ai of the leakage components based on the following equation.

Ai-ΔPi-ΔPav-! -A.

(e) Compare the above leakage component Ai with the allowable value Amax,
A quality determination means that determines the product to be non-defective if it is below the tolerance value, and determines it to be defective if it exceeds the tolerance value.

[Effect] Generally, the pressure fluctuation ΔPi of the tested specimen is composed of a fluctuation component caused by leakage, that is, leakage component Ai, and a fluctuation component caused by effects other than leakage, that is, error component Ei.
Contains. Expressed as a formula, it is as follows.

ΔPi=Ai+Ei The most important point of the present invention is to determine that the product is good if the leakage component Ai is not substantially zero (but is below a certain tolerance value Amax).The leakage component Ai is accurately detected. In order to do so, special measures are required, which will be explained in detail below.

First, a pseudo leak test is performed on a reference container that is known to have no leakage, and pressure fluctuation ΔPr is detected.

Since this pressure fluctuation ΔPr does not include a leakage component, the error component Eo can be determined based on this pressure fluctuation ΔPr.

Immediately after the error component Eo is detected, that is, before the error component Eo changes, a leak test is performed on the sample to detect the pressure fluctuation ΔP.
Detect s. Then, based on this pressure fluctuation ΔPs and the error component Eo, the average value Ao of the leakage component in the non-defective specimen is determined.

When calculating this average value Ao, use a sample that is not determined to be good or bad, compare the leakage component of the sample with the allowable value Amax to determine the quality of the sample, and then calculate the average value of the leakage component for the samples that are determined to be good. You can. Alternatively, the average value Ao may be determined using samples that have been previously determined to be non-defective.

Subsequently, leak tests are performed on a large number of samples in sequence. At this time, the leakage component Ai is determined by the following equation.

Ai=ΔPi−ΔPav+Ao where ΔPav is a substantial average value of pressure fluctuations in good specimens tested before the specimen under test.

As mentioned above, in the present invention, the leakage component or the allowable value A ma
If it is less than or equal to x, the sample is determined to be good, so ΔP
av includes not only the average value of error components but also the average value Ao of leakage components of non-defective products.

However, by adding the average value Ao of the leakage components as in the above equation, an accurate leakage component Ai can be determined. I will explain the reason further. The above formula can be rewritten as follows.

Ai=ΔPi-(ΔPav-Ao) In this equation, (ΔPav-Ao) accurately represents the error component Ei during the above test. Therefore, by subtracting the accurate error component Ei from the detected pressure fluctuation ΔPi, the accurate leakage component Ai can be determined, and as a result, accurate quality determination can be performed.

[Example 1] Hereinafter, an example of the present invention will be described based on the drawings from FIG. 1 to FIG. 3. The differential pressure detection type leak test device shown in FIG. 1 includes an air passage 10 (fluid passage) consisting of a hole or a vibrator formed in a block. The air passage 10 has a connecting end 10a on the upstream side and two branch passages 11.degree. 12 on the downstream side.These branch passages 11.
Twelve ends are provided as connection ends 10b, IOCs.

The connecting end 10a is connected to a compressed air source 20 (fluid pressure source).

In the air passage 10, from upstream to downstream, there is a regulator 21 consisting of a pressure reducing valve with a relief valve, and a pressure gauge 22.
．． A two-position three-boat solenoid valve 23 is provided. Also,
Each branch 11.12 of the air passage 10 is provided with a normally open two-position, two-port solenoid valve 2425.

The leak test device further includes a differential pressure sensor 26 (pressure detection means). Although this differential pressure sensor 26 is well known and will not be described in detail, it has two pressure introduction ports.
One pressure introduction port is connected to the one branch path 11 located between the solenoid valve 24 and the connection end 10b, and the other pressure introduction port is connected to the other branch path 11 located between the solenoid valve 25 and the connection end 10c. 12. The differential pressure between both ports is converted into a voltage signal by the differential pressure sensor 26.

The leak test device further includes a microcomputer 30.
It is equipped with The output of the differential pressure sensor 26 is connected to the human power port of the microcomputer through an amplifier 27. It is input via an analog-to-digital converter 28. An alarm device 29 consisting of a buzzer, lamp, etc. is connected to the output port of the microcomputer 30. The microcomputer 30 has the function of sequentially controlling the electromagnetic valves 23, 24, 25, and the differential pressure sensor 2 as shown in FIG.
It has a function to perform leak detection based on the output from 6. That is, the microcomputer 30 includes an initial error component calculation means 31, a leakage component average value calculation means 32,
It includes a differential pressure average value calculation means 33 (pressure fluctuation average value calculation means), leakage component calculation means 34a, 34k), permissible value setting means 35, and quality determination means 36a, 36b.

In the above configuration, as shown in FIG. 1, the reference container 100, which has been confirmed to be free of leakage, is maintained connected to the connection end 10b of one branch path 11.

In this state, a pseudo-leak test is sequentially performed on several reference containers 100' in the pond that have been confirmed to be leak-free. It is preferable that these reference containers 100, 100' have the same shape as a specimen 200, which will be described later. In particular, it is preferable that the reference containers 100' have the same shape. However, these reference containers 100, 100' may differ in shape and capacity from the sample 200.

To explain in detail the pseudo-leak test of the reference container 100', when the solenoid valves 23, 24, and 25 are off, that is, as shown in FIG.
The reference container 100' is connected to the other connection end 10c in a state where the reference container 100' is shut off from zero and opened to the atmosphere. In this state, the solenoid valve 23 is turned on to communicate the regulator 21 and the reference container 100.1.
The pressure in 00' is set to the set pressure of the regulator 21, that is, the test pressure. After this state continues for a predetermined period of time to stabilize the pressure inside the reference containers 100 and 100', the solenoid valves 24 and 25 are turned on and closed, thereby causing the reference containers 1
Make 00,100' a closed system. After a predetermined period of time has elapsed, the microcomputer 30 reads a voltage signal representing the differential pressure ΔPr (pressure fluctuation in the reference container 100') from the differential pressure sensor 26. Thereafter, the solenoid valves 23, 24, 25 are turned off, the reference containers 100, 100' are exposed to the atmosphere, and the reference containers 100' are removed from the connection end 10C.

As described above, pseudo-leak tests are sequentially performed on several reference containers 100'. The microcomputer 30 calculates the average value of the differential pressure ΔPr.

Since this differential pressure ΔPr has no leakage component, its average value is the initial error component Eo determined by the ambient temperature, etc.
represents. Therefore, the microcomputer 30
substantially includes the above-mentioned initial error component calculation means 31.

Immediately after the pseudo-leak test, ie, before the initial error component Eo changes, 17-cut testing of the specimen is started. That is, the specimen 200 is connected to the connection end 10C, and a test similar to the above-described pseudo leak test is performed to determine the differential pressure ΔPs (pressure fluctuation). This differential pressure ΔPs includes an initial error component Eo and a leakage component As. Therefore,
The microcomputer 30 determines the leakage component As using the following equation. This function is shown by leakage component calculation means 34a in FIG.

As-ΔPs-Eo-(1) Then, the leakage component As is compared with the allowable value Amax from the allowable value setting section 35 to determine the quality.

This function is shown by the quality determining means 3.6a in FIG.

The microcomputer 30 is a sample 2 determined to be good.
The average value Ao of the leakage component As of 00 is calculated. In other words, the microcomputer 30 essentially operates the leakage component average value calculation means 32 that calculates the average value Ao based on the non-defective determination signal Sok from the quality determination means 36a and the leakage component As from the leakage component calculation means 34a. It is equipped with

In the leak test for determining the leakage component average value Ao, the sample 200 may be a sample whose quality is known in advance. In this case, the quality determining means 36a becomes unnecessary.

Next, a full-scale leak test is performed on a large number of samples one after another. In this leak test, the error component due to the ambient temperature etc. changes over time and is different from the initial error component Eo, so the leak component can no longer be determined in the same way as the above equation (1). Therefore, the microcomputer 30 performs the following calculation. Note that this function is shown in the leakage component calculation means 34b in FIG.

Ai-ΔPi-ΔPav+Ao・ (2) Here, At
is the leakage component in the leak test of the i-th sample 200,
ΔPi is the detected differential pressure (pressure fluctuation), ΔPav is the number of specimens 200 tested before the i-th specimen 200 (
However, this is the average value of the detected differential pressures of only those determined to be non-defective products. For example, when the (i-1)th specimen 200 is a non-defective product, it is expressed by the following equation.

ΔPav= (ΔP(i-11+ (n -1)ΔPa
v'l/n... (3) However, ΔP(i-11 is the (i-1)th sample 200
ΔPav is (i-
1) It is the average value of the detected differential pressures of the specimens 200 detected before the second specimen 200 (limited to those determined to be non-defective products). The function of calculating the differential pressure average value ΔPav in equation (3) is shown by the differential pressure average value calculating means 33 in FIG.

In addition, when calculating the leakage component of the first sample 200 in a full-scale leak test, ΔPav in equation (2) is the average of the differential pressure ΔPs in the good sample detected when calculating the leakage component average value Eo. Use value.

In the formula for calculating the average value ΔPav, if n is set small, the ratio of the differential pressure ΔPi obtained in the leak test of the immediately preceding (i-1)th specimen 200 will increase, making it less sensitive to changes in ambient temperature. Become.

Note that n may not be an integer.

The microcomputer 30 also calculates the leakage component average value A.
Since it is sufficient to store o and the differential pressure average value component ΔPav and calculate the leakage component of the sample, a microcomputer with a small storage capacity can be used.

The microcomputer 30 compares the leakage component Ai with the allowable value Amax, and when it is below the allowable value, it is determined to be a good product, and when it is below the allowable value, it is determined to be a defective product, and N
A G-times signal is output and the alarm 29 is activated. This function is shown by the quality determining means 36b in FIG.

In the above embodiment, the leakage component average value Ao of the non-defective samples may be determined by calculating the average value of the differential pressure ΔPs (pressure fluctuation) of the non-defective samples, and subtracting the initial error component Eo from this average value.

Further, the average differential pressure value ΔPav may be a simple average of the differential pressures of a certain number m of specimens that were determined to be non-defective immediately before. In other words, the microcomputer has m memory units for differential pressure, and the oldest differential pressure data is replaced with the new differential pressure data determined to be good, and the simple average of the m differential pressure data is Calculated. This is generally referred to as a moving average.

FIG. 4 shows another embodiment of the invention. In the device shown in FIG. 4, the downstream side of the air passage 10' is not branched. Here, the reference container 100 of the previous embodiment is not used. One pressure introduction port of the differential pressure sensor 26 is open to the atmosphere. When using this device, when a test pressure is introduced with the reference container too' and the specimen 200 connected to the downstream connection end 10d, the differential pressure sensor 26 detects a voltage due to the differential pressure between the atmospheric pressure and the test pressure. occurs. The differential pressure sensor 26 detects a voltage signal that changes in response to changes in the pressure fluctuation of the specimen 200 using this voltage as a reference. The other points are the same as those of the previous embodiment, so the explanation will be omitted.

The present invention is not limited to the above embodiments, and various embodiments are possible.

[Effects of the Invention] As explained above, in the present invention, when determining whether a sample is good or bad, even if the leakage component is not zero, if it is less than the allowable value, it is considered to be a good product. A wide range of pass/fail judgments can be made.

In addition, we first perform a pseudo-leak test on the reference container to determine the initial error component, and based on this initial error component and the pressure fluctuation detected in the non-defective sample, we determine the average value of the leakage component in the non-defective sample. In a typical leak test,
By subtracting the average value of the pressure fluctuations of previous non-defective samples from the detected pressure fluctuation and adding the average value of the leakage component, it is possible to obtain accurate leakage components, and as a result, it is possible to accurately perform the above-mentioned pass/fail judgment. can.

[Brief Description of the Drawings] Figures 1 and 2 are schematic configuration diagrams showing an embodiment of the device according to the present invention, and Figure 1 shows a case in which a reference container is connected to both branches of the irises passage. Figure 2 shows the state in which the reference container is connected to one branch of the air passage and the sample is connected to the other branch. 1 is a diagram schematically showing, in blocks, tasks executed by a computer; FIG. FIG. 4 is a schematic configuration diagram showing another embodiment of the present invention. 10...Fluid passage (air passage), 20...Fluid pressure source (compressed air source), 24.25 Valve means (two-position two-port valve), 26. Pressure detection means (differential pressure sensor), 30.
Microcomputer, 31: Initial error component calculation means, 32: Leakage component average value calculation means, 33 Pressure fluctuation average value calculation means (differential pressure average value calculation means), 34b-Leakage component calculation means, 35: Allowance Value setting means, 36b - Good/failure judging means.

Claims (3)

[Claims] (1) A leak test method in which the presence or absence of a leak is determined by applying a predetermined fluid pressure to a sample and detecting changes in the pressure of the sample, the method comprising the following steps. (a) First, a pseudo-leak test is performed on a leak-free reference container, a pressure fluctuation ΔPr occurring at that time is detected, and an initial error component Eo is determined based on this pressure fluctuation. (b) Immediately thereafter, perform leak tests on the specimens one after another. That is, the leakage component of the detected pressure fluctuation is compared with the allowable value Amax, and when it is below the allowable value, it is determined to be a good product.
If the value exceeds the allowable value, the product is determined to be defective. The leakage component As immediately after the pseudo-leak test is determined from the following equation. In the following equation, ΔPs is the detected pressure fluctuation. As=ΔPs−Eo In addition to the above quality determination, the average value Ao of the leakage component As of a plurality of samples determined to be non-defective is determined. (c) In the subsequent leak test of the sample, the leakage component Ai is calculated from the following equation. In the following equation, ΔPi is the detected pressure variation, and ΔPav is the substantial average value of the pressure variation in the sample determined to be good before the sample currently being tested. Ai=ΔPi−ΔPav+Ao (2) A leak test method in which the presence or absence of a leak is determined by applying a predetermined fluid pressure to a sample and detecting changes in the pressure of the sample, the method comprising the following steps. (a) First, a pseudo-leak test is performed on a leak-free reference container, a pressure fluctuation ΔPr occurring at that time is detected, and an initial error component Eo is determined based on this pressure fluctuation. (b) Immediately after that, perform a pseudo-leak test on multiple non-defective samples to detect the pressure fluctuation ΔPs, and calculate the average value Ao of the leakage components of the non-defective samples based on this pressure variation and the above initial error component Eo. demand. (c) Next, perform leak tests on the specimens one after another. That is, the leakage component Ai of the detected pressure fluctuation ΔPi is compared with the allowable value Amax, and when it is less than the allowable value, it is determined to be a good product, and when it exceeds the allowable value, it is determined to be a defective product. The above leakage component Ai is determined from the following equation. In the following equation, Δ
Pav is a substantial average value of pressure fluctuations in samples that were determined to be good before the sample currently being tested. Ai=ΔPi−ΔPav+Ao (3) Pressure for detecting the pressure between the fluid passage, the fluid pressure source connected to one end of the fluid passage, the valve means arranged in the middle of the fluid passage, and the other end of the fluid passage and the valve means A leak test device comprising a detection means and a microcomputer connected to the pressure detection means, wherein the microcomputer has the following configuration. (a) Calculate the average value of the pressure fluctuation ΔPr detected by the pressure detection means when performing a pseudo leak test by connecting multiple reference containers with no leakage to the other end of the fluid passage, and calculate the initial error. Initial error component calculation means for calculating component Eo. (b) Leak component average value calculation means for calculating the average value Ao of the leak components based on the pressure fluctuation Δps of a plurality of non-defective specimens detected in a test immediately after the pseudo leak test of the reference container and the initial error component Eo. . (c) Substantial average value ΔPa of pressure fluctuations in multiple samples determined to be good before the sample currently undergoing leak testing
Pressure fluctuation average value calculation means for calculating v. (d) Pressure fluctuation ΔPi detected in the current leak test
Leakage component calculation means for calculating the leakage component Ai of the leakage components based on the following equation. Ai=ΔPi−ΔPav+Ao (e) Compare the above leakage component Ai with the allowable value Amax,
A quality determination means that determines the product to be non-defective if it is below the tolerance value, and determines it to be defective if it exceeds the tolerance value.