JP2012255687A - Pressure leakage measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accelerate a processing speed by reducing the required storage amount of master data in pressure leakage measurement and operation amount in calculating an actual leakage rate of an object to be checked.SOLUTION: The aging of a differential pressure between a space 9a to be checked without leakage and a reference space 8a is created with gradients a, a, a... of each primary function as master data on the assumption that the inside of time zones τ, τ, τ... becomes the primary function (creation step). Next, gradients a, a, a... of the aging of a measured differential pressure between the space 9a to be checked and the reference space 8a for each of the time zones τ, τ, τ... are determined as measured data (measurement step). The master data of the same time zone are then subtracted from the measured data (arithmetic step).

Description

  The present invention relates to a pressure leak measurement method for measuring pressure leak from a space to be examined by introducing pressurized gas from a pressurized gas source into a sealed space to be examined.

  In order to inspect the tightness of the measurement object having a sealed internal space (inspection space), a pressurized gas such as compressed air is introduced into the internal space of the measurement object from a pressurized gas source such as an air compressor. It is known to measure pressure leakage from the internal space. The pressure leak measurement method is a pressure method that detects changes in the pressure of the space under test using a pressure detector, and a pressure difference detector that detects changes in the pressure difference between the space under test and the reference space. It is roughly divided into the differential pressure method. The former pressure method is limited in the measurement accuracy of the pressure detector. The latter differential pressure method is suitable for measuring pressure leakage with high accuracy.

  In the differential pressure method, a reference container having a sealed space (reference space) independent of the space to be inspected is prepared, and the space to be inspected and the reference space are connected via a differential pressure detector. Then, the pressurized gas is introduced into the spaces to be inspected and the reference space in communication with each other. After the pressure equilibrates, the space to be inspected and the reference space are shut off to form a closed system. When there is a defect such as a pinhole in the object to be measured, the pressurized gas leaks from there and a differential pressure is generated between the inspection space and the reference space. By detecting the change in the differential pressure with a differential pressure detector, it is possible to measure pressure leakage from the space to be inspected. As a result, the quality of the object to be measured can be determined.

  On the other hand, the pressure in the space to be inspected also varies due to a temperature change due to adiabatic compression accompanying the introduction of pressurized gas. The pressure fluctuation caused by this temperature change converges with time. Generally, pressure leak measurement is performed after this convergence, but this requires a long time.

  Therefore, in Patent Document 1, the change over time in the differential pressure when there is no leakage in the space to be inspected is stored as master data. Then, the leak rate is calculated by comparing the measured data of the differential pressure with the master data. Specifically, the master data is a set of differential pressure values that change with time after the time when the inspected space and the reference space that are not leaked are shut off, and the temporal data of pressure fluctuations caused by temperature changes due to adiabatic compression. It corresponds to. Then, the differential pressure value of the master data at the measurement time corresponding thereto is subtracted from the actual measurement differential pressure value at a certain measurement time after the time when the inspected space at the actual measurement and the reference space are blocked. As a result, a differential pressure (leakage differential pressure) due to leakage is extracted from the actually measured differential pressure value. Further, the leakage differential pressure at two or more measurement times is obtained, and the differential value (difference between the two leakage differential pressures) is calculated, thereby obtaining the amount of change in the leakage differential pressure, that is, the leakage rate.

  In Patent Document 2, an equation representing the change over time in the differential pressure taking temperature change and leakage into account is set approximately, and the coefficient relating to leakage of the above equation is obtained by fitting the measured data to the above equation to determine the leakage. Judgment is performed.

Japanese Patent No. 3181199 JP 2004-062011 A

According to the methods described in the above-mentioned Patent Documents 1 and 2, it is possible to determine leakage even without waiting for the pressure fluctuation caused by the temperature change due to adiabatic compression to converge. However, in Patent Document 1, since the differential pressure value is used as master data, the number of data to be stored for obtaining the amount of change in leak differential pressure increases, and the amount of computation when obtaining the amount of change in leak differential pressure is also large. Become.
In Patent Document 2, calculation software for setting and fitting a differential pressure equation becomes complicated.
In view of the above circumstances, an object of the present invention is to reduce the required storage amount of master data and further reduce the amount of calculation when calculating the leakage rate of an actual inspection object to increase the processing speed.

  As described above, when the pressurized gas is introduced into the inspection space, the temperature of the inspection space rises due to adiabatic compression and then gradually decreases due to heat dissipation. Due to this temperature change, the pressure in the inspection space fluctuates. Therefore, if the space to be inspected and the reference space are shut off after the introduction of the pressurized gas, the differential pressure between these spaces changes.

As shown by a thin solid curve in FIG. 2, the time-dependent change P _M (t) of the differential pressure component due to the above temperature change is approximately expressed by the initial response (formula (1)) of the first-order lag element. It is known that Hereinafter, in order to simplify the description, it is assumed that the expression (1) holds.
P _M (t) = b {1-exp (-ct)} (1)
Here, b and c are constants related to the differential pressure change caused by the temperature change. Specifically, b indicates a convergence point of the differential pressure when the temperature change is settled. c indicates how quickly the temperature change is settled. t is time.

Further, as shown by a two-dot chain line in FIG. 2, the change with time of the differential pressure component P _L due to leakage is a linear function proportional to time (formula (2)).
P _L (t) = at (2)
Here, a is a constant related to the differential pressure change caused by leakage, and corresponds to the leakage amount (leakage rate) per unit time from the space to be inspected.

As shown in the thin broken curve in FIG. 2, the actual change P _T (t) of the differential pressure over time is the sum of the differential pressure component P _M resulting from the temperature change and the differential pressure component P _L resulting from leakage. (Formula (3)).
P _T (t) = P _M (t) + P _L (t) = at + b {1-exp (-ct)} (3)

The derivative P _M ′ (t) of the differential pressure change expression P _M (t) (expression (1)) resulting from the temperature change is expressed by the following expression (4).
P _M '(t) = bc ・ exp (-ct) (4)
As shown by a thin solid curve in FIG. 3, the derivative P _M ′ (t) gradually decreases with the passage of time t.

The derivative P _T ′ (t) of the actual differential pressure change equation P _T (t) (equation (3)) is expressed by the following equation (5).
P _T '(t) = a + bc ・ exp (-ct) (5)
As shown by a thin fracture curve in FIG. 3, the derivative P _T ′ (t) gradually decreases with the passage of time t.

The difference between the derivative P _T ′ (t) (equation (5)) of the actual differential pressure change and the derivative P _M ′ (t) (equation (4)) of the differential pressure change due to the temperature change is As the following equation (6), it is equal to the leakage rate a.
P _T '(t)-P _M ' (t) = a (6)
Therefore, the derivative P _M ′ (t) (Equation (4)) of the differential pressure change caused by the temperature change is stored as master data, and the actual differential pressure change derivative P _T ′ ( t) (Equation (5)) is calculated and the difference between them is calculated (Equation (6)). However, in order to establish a nonlinear continuous function (Equations (1) and (3)) and obtain its derivatives (Equations (4) and (5)), many calculations are required.

Therefore, the present invention cuts off the inspected space and the reference space after introducing pressurized gas into the inspected space and the reference space in a state where the inspected space and the reference space are in communication with each other. In the pressure leak measurement method, each of which is a closed system, and the pressure leak from the test space is measured by the differential pressure between the test space and the reference space.
A creation step of creating, as master data, the gradient of each linear function when the temporal change in the differential pressure between the test space without leakage and the reference space is simulated as a linear function within each time zone When,
An actual measurement step for obtaining, as actual measurement data, a gradient for each time zone of the temporal change of the actual measurement differential pressure between the inspection space and the reference space;
A calculation step of subtracting the master data of the same time zone from the measured data;
It is provided with.

That is, as shown by a solid and thick polygonal line in FIG. 2, the present invention, the time course of differential pressure, time zone _{τ 1, τ 2, τ 3} ..., separated for each tau _n ..., 1 single time slot It is assumed that the differential pressure changes linearly within τ _n . Here, the time zone τ _n is a time region from time t _{n −1} to time t _n . Thus, aging of the pressure difference between the leakage is not inspected space and the reference space, time zone _{τ 1, τ 2, τ 3} ..., τ n ... each of the line segment _{s M1, s M2, s M3} ..., s It is approximated by _Mn polygonal line which ... had been chosen discontinuous function P _Mn (t). Segment s _Mn is a straight line segment connecting the differential pressure values P _Mn in differential pressure values P _Mn-1 and the time t _n at time t _n-1.

上記不連続関数P_Mn(t)の導関数P_Mn’ (t)は、不連続点を除いて次式(12)となる。

The discontinuous function P _Mn (t) is expressed by the following equation (11).

The discontinuous function P derivative of _Mn (t) P _Mn '(t) is represented by the following formula (12) with the exception of the discontinuities.

As is clear from the equation (12), the value of the derivative P _Mn ′ (t) in one time zone τ _n between time t _n−1 and time t _n becomes a constant value regardless of t. . Further, the value of the derivative P _Mn 'decreases as the time zone τ later (as n increases). That is,
P _M1 '> P _M2 '> P _M3 '… (13)
It becomes. This is indicated by the solid solid line in the step shape of FIG. In the present invention, the derivative values P _M1 ′, P _M2 ′, P _M3 ′, etc. are used as master data. Therefore, according to the present invention, the conventional method of using the differential pressure values P _M0 , P _M1 , P _M2 , P _M3 ... At each time t ₀ , t ₁ , t ₂ , t ₃ . The required number of master data can be reduced as compared with 1).

Similarly, as shown by a thick line fracture of polygonal line in FIG. 2, the time course of the pressure difference between the actual inspection space and reference space also, the time period _{τ 1, τ 2, τ 3} ..., τ n ... Each line segment s _T1 , s _T2 , s _T3 ..., s _Tn ... is approximated by a broken line discontinuous function P _Tn (t). Segment s _Tn is a straight line connecting the actual differential pressure values P _Tn in the actual differential pressure values P _Tn-1 and the time t _n at time t _n-1.

上記不連続関数P_Tn(t)の導関数P_Tn’(t)は、不連続点を除いて次式(15)となる。

The discontinuous function P _Tn (t) is expressed by the following equation (14).

The discontinuous function P derivative of _Tn (t) P _Tn '(t) is represented by the following formula (15) with the exception of the discontinuities.

As is clear from equation (15), the value of the derivative P _Tn ′ (t) in one time zone τ _n between time t _n−1 and time t _n is a constant value regardless of t. . In addition, the value of the derivative P _Tn 'decreases as the time zone τ later (as n increases). That is,
P _T1 '> P _T2 '> P _T3 '… (16)
It becomes. This is shown by the stepped broken lines in FIG. In the present invention, values P _T1 ′, P _T2 ′, P _T3 ′... Of this derivative are obtained as measured data. Then, the difference between the measured data and the master data in the same time zone τ is obtained.

Here, if the master derivative P _Mn '(t) (Equation (12)) is subtracted from the measured derivative P _Tn ' (t) (Equation (15)), the leakage rate is obtained as shown in the following equation (17). The constant a indicating
P _Tn '(t)-P _Mn ' (t) = a (17)
This result is the same as the leakage rate (equation (6)) obtained for the continuous function. That is, the difference (equation (17)) between the derivatives P _Mn '(t) and P _Tn ' (t) of the discontinuous functions P _Mn (t) and P _Tn (t) in the same time period τ _n is continuous. function P _M (t), P _T derivative P _M of (t) becomes the same as '(t), P _T' (t) How to difference (equation (6)).

したがって、従来の、差圧からなるマスタデータと実測差圧との差を取って更に一回微分するやり方（特許文献１）よりも、実際の被検査物に対する洩れ検査時の演算量を減らすことができる。よって、判定処理の速度を高めることができる。 In short, according to the present invention, as shown in FIG. 3, each other the same time period _{τ 1, τ 2, τ 3} ..., τ n ... measured data P _T1 of _{', P T2', P T3} '..., P Tn '... master data P _{M1 from', P M2 ', P M3} ' ..., P Mn '... by subtracting a leakage rate _{a 1, a 2, a 3} ..., can be obtained directly a _n ... (Formula (18)).

Therefore, compared with the conventional method of taking the difference between the master data consisting of the differential pressure and the actual measurement differential pressure and further differentiating it once (Patent Document 1), the amount of calculation at the time of leak inspection for the actual inspection object is reduced. Can do. Therefore, the speed of the determination process can be increased.

The calculation results a ₁ , a ₂ , a ₃ ..., A _n .
a ₁ ≒ a ₂ ≒ a ₃ ... ≒ a _n ... (19)
By averaging these values a ₁ , a ₂ , a ₃ ..., A _n ..., The measurement variation can be corrected and the leak rate a can be obtained with high accuracy.

As shown in FIG. 2, the master data of the present invention, that is, the value of the derivative P _Mn ′ (t) is represented by a broken line (solid line in FIG. 2) representing the differential pressure change equation P _M (t) due to temperature change. Each segment _{s M1, s M2, s M3} ..., s Mn ... gradient _{a M1, a M2, a M3} ..., corresponding to a _Mn .... The gradients a _M1 , a _M2 , a _M3 ..., A _Mn ... Can be calculated as in the following equation (21).

In addition, the measured data of the present invention, that is, the value of the derivative P _Tn ′ (t) is the line segment s _T1 , s _T2 , s of the broken line (abundant line in FIG. 2) representing the measured differential pressure change equation P _T (t). _T3 ..., s _Tn ... gradient of _{a T1, a T2, a T3} ..., equivalent to a _Tn .... The gradients a _T1 , a _T2 , a _T3 ..., A _Tn ... Can be calculated as in the following equation (22).

Thus, in the generating step, the gradient _{a M1, a M2, a M3} ..., seeking a _Mn ... as the master data, in the actual process determined as the gradient _{a T1, a T2, a T3} ..., a Tn ... measured data In the above calculation step, as shown in the equation (23), from the measured gradients a _T1 , a _T2 , a _T3 ..., a _Tn ... in the same time zone τ ₁ , τ ₂ , τ ₃ ..., τ _n ... gradient _{a M1, a M2, a M3} ..., by subtracting the a _Mn ..., leakage rate _{a 1, a 2, a 3} ..., it is preferable to calculate the a _n ....

The lengths of the time zones τ ₁ , τ ₂ , τ ₃ ..., Τ _n . That is, it is preferable that the following formula (24) holds.
(t ₁ -t ₀ ) = (t ₂ -t ₁ ) = (t ₃ -t ₂ ) =… = (t _n -t _n-1 ) =… (24)
By doing so, the denominator on the right side of all equations (21) and (22) can be replaced with 1 (equations (21a) and (22a)), making it easy to create master data and calculate actual data Can be

  According to the present invention, the required storage amount of master data can be reduced, and further, the calculation amount when calculating the leakage rate can be reduced, and the processing speed can be increased.

It is a circuit diagram which shows schematic structure of the pressure leak measuring apparatus which concerns on one Embodiment of this invention. It is the graph which illustrated change with time of differential pressure in order to explain master data and actual measurement data of the present invention. It is the graph which illustrated the derivative (gradient) of the time-dependent change of differential pressure in order to explain the master data and actual measurement data of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a pressure leak measuring apparatus 1 for measuring pressure leak from an object 9 to be inspected. The inspection object 9 is not particularly limited and is, for example, an engine cylinder block, a fuel tank, or the like. The inspection object 9 has an internal space. This internal space is the inspection space 9a. An inspected space 9 a is defined by the inner peripheral surface of the inspection object 9. Although detailed illustration is omitted, the opening of the space 9a to be inspected is closed by a jig or the like. As a result, the space 9a to be inspected is sealed. The inspected object 9 may be accommodated in the capsule, and the space between the inner periphery of the capsule and the outer periphery of the inspected object 9 may constitute the inspected space 9a.

  The pressure leak measuring apparatus 1 includes a measuring unit 2 and a controller 3 (control means). The measurement unit 2 includes a supply path 10, an inspection path 11, and a reference path 12. These passages 10 to 12 may be formed in the block or may be constituted by piping.

  An air pressure source (not shown) is connected to the connection terminal 10 a at the upstream end of the supply path 10. The supply path 10 is provided with a regulator 13 (pressure reducing valve), a pressure gauge 14, and a two-position three-way electromagnetic directional control valve 15 in this order from the upstream side (connection terminal 10a side). The inspection path 11 and the reference path 12 are branched from the downstream end of the supply path 10. The downstream end of the inspection path 11 is connected to the inspection space 9 a of the inspection object 9.

  The downstream end of the reference path 12 is connected to the internal space 8a (reference space) of the reference container 8 through a jig (not shown). The reference space 8a is sealed. The shapes and volumes of the space 9a to be inspected and the reference space 8a may be substantially the same or different.

  The inspection path 11 is provided with an electromagnetic open / close valve 16, and the reference path 12 is provided with an electromagnetic open / close valve 17. A differential pressure detector 20 is provided between the passages 11 and 12 downstream of the on-off valves 16 and 17. The inside of the differential pressure detector 20 is partitioned into a test chamber 23 and a reference chamber 24 by a diaphragm 21. A port of the test chamber 23 is connected to the test path 11 via the test pressure introduction path 25. A port of the reference chamber 24 is connected to the reference path 12 through a reference pressure introduction path 26. When a differential pressure is generated between the test space 9a and the reference space 8a, a differential pressure is generated between the test chamber 23 and the reference chamber 24, and the diaphragm 21 is deformed according to the magnitude of the differential pressure. The differential pressure detector 20 converts this deformation into a voltage and outputs it to the controller 3. Thereby, the differential pressure between the space 9a to be inspected and the reference space 8a can be detected.

The operation of the measurement unit 2 is controlled by the controller 3. The controller 3 is provided with a drive circuit (not shown) for the valves 15 to 17 and a microcomputer 31. The microcomputer 31 is provided with an arithmetic processing unit 32 including a CPU, a storage unit 33 including a RAM and a ROM, and the like. The storage unit 33 stores programs and master data for control operations. As shown in FIG. 2, the master data represents the time-dependent change P _M (t) of the differential pressure between the space 9a to be inspected and the reference space 8a without leakage, in each time zone τ ₁ (= t _{0 to} t ₁ ). , Τ ₂ (= t _{1 to} t ₂ ), τ ₃ (= t _{2 to} t ₃ ) ... τ _n (= t _{n-1 to} t _n ) ... The function, that is, the gradients a _M1 , a _M2 , a _M3 ... a _Mn ... of each straight line segment s _M1 , s _M2 , s _M3 ... s _Mn ... The method for creating the master data will be described in detail later. The arithmetic processing unit 32 performs a leak test from the inspected space 9a by performing a predetermined arithmetic process based on the actually measured differential pressure data of the differential pressure detector 20 and the master data.

  In the leak inspection, the direction control valve 15 is turned on to connect the supply passage 10 and the on-off valves 16 and 17 are opened, so that the gas pressure of the pressurized gas source is changed from the supply passage 10 to the inspection passage 11 and the reference passage. 12 and further into the inspection space 9a and the reference space 8a. The temperature of the spaces 9a and 8a is increased by the adiabatic compression at the time of introducing the pressure, and then the temperature is decreased by heat radiation. The inspected object 9 and the reference container 8 differ in the degree of temperature change accompanying adiabatic compression due to differences in various conditions.

After a while, the on-off valves 16 and 17 are closed, the inspection path 11 and the reference path 12 are shut off, and the inspection space 9a and the reference space 8a are shut off to form a closed system. As a result, a difference in temperature change due to the adiabatic compression appears as a pressure difference between the space 9a to be inspected and the reference space 8a. This differential pressure is detected by the differential pressure detector 20. The solid thin line P _M (t) in FIG. 2 shows the state of the differential pressure change caused by the temperature change due to the adiabatic compression. This change in differential pressure becomes an initial response of a first-order lag element.

Furthermore, if there is a leak in the space 9a to be inspected, the pressure drop in the space 9a to be inspected due to this leakage is added to the differential pressure between the spaces 9a and 8a. As shown by the two-dot chain line P _L (t) in FIG. 2, the change in differential pressure due to the leakage is linear. As shown by the broken line P _T (t) in FIG. 2, the actual differential pressure change is the sum of the differential pressure change caused by the temperature change due to adiabatic compression and the differential pressure change caused by leakage.

In FIG. 2, the time t ₀ is the time when the inspected space 9a and the reference space 8a are shut off by the on-off valves 16 and 17, or the time when the pressure disturbance accompanying the shut-off operation after that is stopped (from the shut-off time). 1 to several seconds later). It is preferable to reset the reading of the differential pressure detector 20 at this time t ₀ to zero.

The method for measuring pressure leakage using the apparatus 1 will be described in more detail.
The pressure leak inspection is performed in the order of the master data creation process, the actual measurement process for the actual inspection object 9, and the calculation process for determining the pressure leak.

[Master data creation process]
In the master data creation process, first, the measurement unit 2 is operated in the above-described procedure, and the change with time after time t ₀ of the differential pressure between the space 9a to be inspected and the reference space 8a is checked for the differential pressure detector 20. Measure with Specifically, the differential pressure change data P _M0 , P _M1 , P _M2 , P _M3 ... P _Mn ... On the solid thin line P _M (t) in FIG. 2 are set to a certain time interval τ _n (= τ ₁ = τ ₂ = τ ₃ ...) at a time _{t 1, t 2, t 3} ..., to get every t _n .... In this case, the inspection object 9 may be one that has actually been found to be free of leakage, or may be one whose leakage is unknown. In the former case, the measured differential pressure between the inspected space 9a and the reference space 8a can be used as it is as differential pressure data resulting from the temperature change due to the adiabatic compression. In the latter case, the differential pressure measurement is performed for a long time to the linear region where the differential pressure varies linearly, and the difference in pressure difference in the linear region is subtracted from the measured differential pressure in the non-linear region before becoming linear. Pressure data, that is, differential pressure change data resulting from temperature changes due to adiabatic compression can be obtained. In the linear region, since the temperature change has sufficiently converged, the change in the differential pressure corresponds to a change caused by leakage.

Then, the non-linear temporal change P _M (t) of the differential pressure is converted into each time zone τ ₁ (= t _{0 to} t ₁ ), τ ₂ (= t _{1 to} t ₂ ), τ ₃ (= t _{2 to} t _{3) ... τ n (= t} n-1 ~t n) ... in the above gradient a _M1 of the linear function when the fiction becomes a linear _{function, a M2, a M3 ... a} Mn ... seek. In short, the continuous curved solid thin line P _M (t) in FIG. ₂ is not changed every time t ₁ , t ₂ , t ₃ ..., T _n ... as shown by the solid thick line P _Mn (t) in FIG. and constructive with and continuously bent fold line, said fold line the line segments s of _{M1, s M2, s M3 ...} s Mn ... gradient _{a M1, a M2, a M3} ... a Mn ... seek. Specifically, the calculation of Expression (21) is performed.

このようにして求めた勾配a_M1，a_M2，a_M3…，a_Mn…の値をマスタデータとして記憶部３３に記憶しておく。本発明方法によれば、上記差圧変化データP_M0，P_M1，P_M2，P_M3…P_Mn…そのものをマスタデータとする従来方法（特許文献１）よりもマスタデータの所要記憶数を減らすことができる。例えば、t₀からt₃までのマスタデータ数を比較すると、上記従来方法では４つのデータP_M0，P_M1，P_M2，P_M3が必要であるが、本発明方法では３つのデータa_M1，a_M2，a_M3で済む。 Each time zone τ ₁ (= t _{0 to} t ₁ ), τ ₂ (= t _{1 to} t ₂ ), τ ₃ (= t _{2 to} t ₃ ) ... τ _n (= t _{n-1 to} t _n ) By making the lengths equal to each other, the arithmetic expression of the gradients a _M1 , a _M2 , a _M3 ..., A _Mn ... Can be simplified as the following expression (21a).

The values of gradients a _M1 , a _M2 , a _M3 ..., A _Mn ... Thus obtained are stored in the storage unit 33 as master data. According to the present invention method reduces the required number of stored master data than the conventional method of the difference pressure change data P _M0, a _{P M1, P M2, P M3} ... P Mn ... itself as master data (Patent Document 1) be able to. For example, when comparing the number of master data from t ₀ to t ₃ , the above-described conventional method requires four data P _M0 , P _M1 , P _M2 , and P _M3, but the method of the present invention provides three data a _M1 , a _M2 and a _M3 are sufficient.

[Measurement process]
After acquiring the master data, an actual measurement process is performed on the actual inspection object 9. In the actual measurement step, the actual inspection object 9 is connected to the inspection path 11, and then the measuring unit 2 is operated in the above-described procedure, so that the time t ₀ of the differential pressure between the inspection space 9a and the reference space 8a is obtained. Subsequent changes over time are measured by the differential pressure detector 20. As shown by the broken line P _T (t) in FIG. 2, when there is a pressure leak from the space 9a to be inspected, the measured differential pressure is the differential pressure change P _M (t) caused by the temperature change due to adiabatic compression. FIG. 4 shows a behavior in which a differential pressure change PL (t) caused by leakage is added. The differential pressure change data P _T0 , P _T1 , P _T2 , P _T3 … P _Tn … on this broken line P _T (t) are set at a fixed time interval τ _n (= τ ₁ = τ ₂ = τ ₃ …). And obtained at every time t ₁ , t ₂ , t ₃ ..., T _n . Next, discontinuous continuous curved difference pressure change P _T (t), as shown in dashed heavy line P _Tn (t) in FIG. 2, the time _{t 1, t 2, t 3} ..., each t _n ... to each time period tau ₁ when the fictitious a line which is bent, τ _2, τ ₃ ..., line segments of _{τ n ... s T1, s T2} , s T3 ..., s Tn ... gradient a _T1, a the _T2 , _aT3 ..., _aTn ... are obtained. Specifically, the calculation of Expression (22) is performed.

このようにして求めた勾配a_T1，a_T2，a_T3…，a_Tn…の値を実測データとする。 By making the lengths of the respective time zones τ ₁ , τ ₂ , τ _3, ..., _N ... Equal to each other, the arithmetic expressions of the gradients a _T1 , a _T2 , a _T3 , a _Tn . It can be simplified as follows.

The values of the gradients a _T1 , a _T2 , a _T3 ..., A _Tn .

[Calculation process]
Subsequently, the master data and the actually measured data are compared. Specifically, the master data a _M1 , a _M2 , a _M3 ... from the measured data a _T1 , a _T2 , a _T3 ..., a _Tn ... for each same time zone τ ₁ , τ ₂ , τ ₃ ..., τ _n ... , A _Mn ... are subtracted (formula (23)). Thus, each time zone _{τ 1, τ 2, τ 3} ..., rate a ₁ leakage in _{τ n ..., a 2, a} 3 ..., a n ... are obtained.

That is, according to the method of the present invention, the leak rates a ₁ , a ₂ , a ₃ ..., A _n . Further, the number of master data to be read from the storage unit 33 during the calculation is small, and the number of subtraction calculations is also small. Therefore, the calculation amount in the calculation process can be reduced as compared with the conventional method (Patent Document 1) in which the difference between the master data including the differential pressure and the actual measurement differential pressure is taken and differentiated once more. Therefore, the speed of arithmetic processing can be increased.

As shown in FIG. 3, the equation (23) of the operation result i.e. leakage rate _{a 1, a 2, a 3} ..., a n ... , the time period _{τ 1, τ 2, τ 3} ..., τ n ... to depend It becomes the same size mutually.
a ₁ ≒ a ₂ ≒ a ₃ ... ≒ a _n ... (25)
By calculating the average value a _av of these leak rates a ₁ , a ₂ , a ₃ ..., A _n .

[Judgment process]
Based on this average leakage rate a _av , pressure leakage determination is performed. That is, if the leakage rate a _av is equal to or less than the threshold value, the inspection object 9 is determined as a non-defective product. If the leakage rate a _av exceeds the threshold value, the inspection object 9 is determined to be defective.

The present invention is not limited to the above-described embodiment, and various modifications can be made without changing the gist of the invention.
For example, in the above description, the master data and the actual measurement data are acquired every time period τ ₁ , τ ₂ , τ ₃ , τ ₄ , τ ₅ ..., For example, τ ₁ , τ ₃ , τ _5. , Τ ₇ , τ ₉ ..., Τ ₁ , τ ₄ , τ ₇ , τ ₁₀ , τ ₁₃ . On the contrary, it is more practical to make it skipped because it is possible to reflect a change in differential pressure in a wide time domain in the pressure leak determination with a small number of operations, and to facilitate programming.
Of the time zones τ ₁ , τ ₂ , τ ₃ ..., Τ _n , the lengths of the two time zones may be different from each other.
In the determination step, without calculating the average value a _av, it may perform leakage determination based on one of the leakage rate a _n.

  The present invention can be applied to determine whether the sealed state of a sealed container-like object is good or bad.

DESCRIPTION OF SYMBOLS 1 Pressure leak measuring apparatus 2 Measuring part 8 Reference container 8a Reference space 9 Inspected object 9a Inspected space 10 Common path 10a Connection terminal 11 Inspection path 12 Reference path 13 Regulator 14 Pressure gauge 15 Directional control valve 16 On-off valve 17 On-off valve 20 Differential pressure detector 21 Diaphragm 23 Test chamber 24 Reference chamber 25 Inspection pressure introduction path 26 Reference pressure introduction path 3 Controller (control means)
31 microcomputer 32 arithmetic processing unit 33 storage unit

Claims (3)

After introducing pressurized gas into the inspected space and the reference space in a state where the inspected space and the reference space are in communication with each other, the inspected space and the reference space are shut off to form a closed system, In a pressure leak measurement method for measuring pressure leak from the inspection space by a differential pressure between the inspection space and the reference space,
A creation step of creating, as master data, the gradient of each linear function when the temporal change in the differential pressure between the test space without leakage and the reference space is simulated as a linear function within each time zone When,
An actual measurement step for obtaining, as actual measurement data, a gradient for each time zone of the temporal change of the actual measurement differential pressure between the inspection space and the reference space;
A calculation step of subtracting the master data of the same time zone from the measured data;
A method for measuring pressure leakage, comprising:   The pressure leak measurement method according to claim 1, wherein, in the calculation step, an average value of a difference between the actual measurement data and the master data for each time period is calculated.   3. The pressure leak measuring method according to claim 1, wherein the lengths of the respective time zones are equal to each other.

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