JP2019100732A - Leak inspection method, leak inspection device and program - Google Patents

Abstract

To provide a leak inspection method allowing determining a leak with high accuracy by removing the influence of temperature while minimizing a measurement period.SOLUTION: After measuring a differential pressure between internal pressures of both containers after sealing a workpiece and a master from an atmospheric pressure Popening for a predetermined period, subsequently, the workpiece and the master are pressurized and a differential pressure after sealing is measured for a predetermined period, a measurement time Twhen the difference of a gradient (rate of change of differential pressure) of a differential pressure curve obtained by atmospheric pressure sealing measurement becomes less than an allowable value, and the rate of change Q of differential pressure at that time are determined, a measurement time Twhen the difference of the gradient of the differential pressure curve obtained by a test pressure sealing measurement becomes below an allowable value, and the rate of change R at that time are determined, a time difference when continuously counting from Tto Tis set to be T, and a leak of the workpiece is determined by an operation of leak L=R-exp (-T/large time constant)×(P/P)×Q. The large time constant is a larger time constant, which is determined in advance, of two time constants that govern a temperature-based change in the pressure difference between the internal pressures after sealing the workpiece and the master from atmospheric pressure Popening.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a leak inspection method for inspecting a leak of a container to be inspected, a leak inspection apparatus and a program thereof.

  When a leak of a container is inspected, a gas such as air is pressurized and introduced to the container to be inspected and the leak-free reference container at high pressure, and then sealed, and then the internal pressure of the container to be inspected and the internal pressure of the reference container Generally, a method of determining the presence or absence of a leak of a container to be inspected by observing a change in differential pressure between the The basic idea is that if there is a leak in the container to be inspected, a differential pressure will occur, and the magnitude will be proportional to time.

  However, the observed changes in differential pressure include, in addition to leakage, changes in differential pressure due to temperature fluctuations. That is, even if the gas temperature in the container to be inspected and the gas temperature in the reference container differ for some reason, a differential pressure is generated. Therefore, various techniques have been proposed for removing the influence of differential pressure caused by temperature from the change in differential pressure measured in the leak test.

  For example, in Patent Document 1 below, a change in differential pressure is measured for a predetermined time when a work as a container to be inspected and a master that is a leak-free reference container are pressurized to the same pressure and then sealed. Perform a leak inspection. Further, before and after the leak inspection, a temperature compensation measurement step is performed to measure a change in differential pressure between the work and the master when the work and the master are left open to the atmosphere and then sealed, for a predetermined time. Then, using the average value of the temperature compensation values (rate of change in differential pressure) determined in the preceding and subsequent temperature compensation measurement steps, the change in differential pressure based on the temperature fluctuation at the time of leak inspection is estimated to Temperature compensation of measurement results.

  Further, in Patent Document 1, a first time from when the temperature compensation measurement process before the leakage inspection is performed to the time when the leakage inspection is performed and a first time until the temperature compensation measurement process after the leakage inspection is performed In consideration of the case where a difference occurs between 2 hours, the temperature compensation value obtained in the measurement process for temperature compensation before the leak test and the temperature compensation value obtained in the measurement process for temperature compensation after the leak test are It is disclosed to temperature compensate the measurement result at the time of leak inspection with a value that is weighted and averaged by the inverse ratio of the second time.

Patent No. 4994494

  In Patent Document 1, temperature compensation is performed on the assumption that the temperature compensation value obtained in the measurement for temperature compensation before and after the leak inspection changes linearly. However, since the temperature effect does not change linearly in practice, the temperature correction is not accurate. Therefore, when the differential pressure change rate is finally detected, it can not be distinguished whether it is due to temperature noise that could not be removed or due to leakage. Furthermore, it was not possible to determine an appropriate measurement period to minimize the measurement period.

  The present invention is intended to solve the above problems, and a leak inspection method and a leak inspection apparatus capable of judging a leak with high accuracy by removing the influence of temperature while minimizing the measurement period, The purpose is to provide a program.

  The subject matter of the present invention for achieving such an object resides in the inventions of the following items.

[1] the pressure difference in the internal pressure of both container after sealing of both the inspected container and a leaktight reference container from atmospheric pressure P _E opened repeatedly measured over a predetermined period, each differential pressure and the measured time measured And the atmospheric pressure sealing measurement step of correlating and recording;
It continues after the end of the atmospheric pressure sealing measurement step, and after introducing a gas into the inspection object container and the reference container and pressurizing them to a predetermined test pressure _PT , both are sealed and sealed. A test pressure sealing measurement step of repeatedly measuring the differential pressure of the internal pressure of both containers after that over a predetermined period, and correlating and recording each measured differential pressure and measurement time;
From the data recorded in the atmospheric pressure sealing measurement step, the measurement time T _a in the atmospheric pressure sealing measurement step of the differential pressure data when the difference in the rate of change of the differential pressure with the passage of time becomes less than a certain value. And a first gradient acquisition step for determining a rate of change Q of the differential pressure at that time,
From the data measured in the test pressure sealing measurement step, the measurement time T _b in the test pressure sealing measurement step of the differential pressure data when the difference in change rate of the differential pressure with the passage of time becomes less than or equal to a certain value And a second gradient acquisition step of determining a rate of change R of the differential pressure at that time,
_Let T _S be the time difference when measuring from measurement time T _a to measurement time T _b continuously.
A leak judgment step of judging presence or absence of a leak of the container to be inspected based on the value of L obtained by the calculation of
Have
The Daitoki constant is greater of the two time constants governing the change based on the temperature of the differential pressure of the internal pressure of both container after sealing the said object container and the reference container from atmospheric pressure P _E open Leak check method characterized in that the time constant of the

The time constant governing the change based on the temperature of the differential pressure of the internal pressure of both the container after sealing work and master from atmospheric pressure P _E opening is two of Daitoki constant and small time constant, according to the small time constant of which The change in differential pressure decays to negligible magnitude in a short time. In addition, with regard to the change in differential pressure related to the large time constant, the effect of the change in temperature of the container that caused the change in differential pressure based on the temperature obtained by atmospheric pressure sealing measurement is almost as it is also in the test pressure sealing measurement. It is considered to be continuing. Therefore, the measurement time T _a of the differential pressure data when the rate of change of the gradient of the differential pressure curve in atmospheric pressure measurement is below a certain level (when the change related to the small time constant is negligible) and its time The gradient (rate of change of differential pressure) Q is determined. In addition, the measurement time T _b of differential pressure data when the rate of change of the gradient of the differential pressure curve in the test pressure sealing measurement becomes lower than a certain level (when the change related to the small time constant is negligible) and the time The rate of change R of the differential pressure is determined. R includes the change in differential pressure due to leakage and the change in differential pressure due to temperature. The change in differential pressure due to the temperature contained in R corresponds to the value when the gradient Q at the measurement time T _a of atmospheric pressure sealing measurement has elapsed until the measurement time T _b according to the large time constant. That is, the time from the measurement time T _a to the measurement time T _b and Ts, considering the pressure ratio,
It is. Therefore, the leak L can be obtained by subtracting this from R.

[2] The pressure difference in the internal pressure of both container after sealing of both the inspected container and a leaktight reference container from atmospheric pressure P _E opened repeatedly measuring period T _M, each measured pressure difference Atmospheric pressure sealing measurement step which is recorded along with the order from the start of measurement,
The atmospheric pressure sealing measurement step is performed continuously after the atmospheric pressure sealing measurement step, after introducing a gas into the inspection object container and the reference container and pressurizing the gas to a predetermined test pressure _PT. After the interval time T _I has elapsed since the end of the measurement period T _M , both are sealed, and the differential pressure of the internal pressure of both containers after sealing is repeatedly measured over the measurement period T _M , and each measured difference Test pressure measurement step which records the pressure with the order from the start of the measurement;
The data recorded in the atmospheric pressure sealing measurement step is divided into groups (group numbers m = 1, 2,... M) for each time T from the sealing time, and the average value P _{ED, m} (m (m Find = 1, 2, ... M),
A first gradient acquisition step for obtaining a differential sequence
The data recorded in the test pressure sealing measurement step is divided into groups (group number m = 1, 2,... M) for each time T from the sealing time, and the average value P _{DD, m} (m (m Find = 1, 2, ... M),
A second gradient acquisition step for obtaining a differential sequence
_Let the sum of the measurement period T _M and the interval time T _{I be} T _S ,
If the value of L _m converges to a constant value as _m increases, the convergence value is judged as a leak, or if there is _{m where} the absolute value of L _m falls below a predetermined allowable value Leak judgment step to judge that there is no leak in the
Have
The Daitoki constant is greater of the two time constants governing the change based on the temperature of the differential pressure of the internal pressure of both container after sealing the said object container and the reference container from atmospheric pressure P _E open Time constant of
The α ₂ is
A leak inspection method characterized in that

In the above invention, the leak is determined from the measured value of the differential pressure by a simple calculation. That is, Q _m is a value corresponding to the slope of the differential pressure curve after time T × m from the measurement start of the atmospheric pressure sealing measurement, and R _m is after time T × m from the measurement start of the test pressure sealing measurement. L _m is a value corresponding to the slope of the differential pressure curve, and L _m represents a leak after a time T × m from the start of measurement of the test pressure seal measurement. By averaging every time T, the noise of the measurement is removed. When m is increased and L _m converges to a constant value, it indicates that a transient change such as a change related to a small time constant is settled, and the convergence value at this time indicates a leak (the convergence value is 0). No leaks).

[3] In the leak determination step, when the absolute value of LM _-1 exceeds the allowable value,
The leak inspection method according to [2], wherein, when D _m converges to 0, it is determined that there is a leak.

In the above invention, when the absolute value of LM _{-1 in} the leak judgment exceeds the allowable value, it can not be distinguished whether there is a leak in the container to be inspected or the measurement time _TM is insufficient,
The following sequence is created, and the distinction is made depending on whether D _m converges to 0 or not. If it does not converge to 0, it is a shortage of the measurement period T _M , and if it converges to 0, the leak can be judged correctly by L _M−1 . That is, there is a leak.

[4] The leak inspection method according to [3], wherein when the D _m does not converge to 0, the measurement period T _M is extended, and the measurement is performed again from the atmospheric pressure sealing measurement step.

[5] The leak inspection method according to any one of [2] to [4], wherein the measurement period T _M is set based on the minimum _{m at} which L _m converges.

In the above invention, if L _m converges, it can be correctly determined whether or not there is a leak in the container to be inspected. Therefore, the measurement period T _M determined based on the minimum m when L _m converges is the minimum measurement period in which correct determination can be made.

[6] the pressure difference in the internal pressure of both container after sealing of both the inspected container and a leaktight reference container from atmospheric pressure P _E opened repeatedly measuring period T _M, each measured pressure difference Atmospheric pressure sealing measurement step which is recorded along with the order from the start of measurement,
The atmospheric pressure sealing measurement step is performed continuously after the atmospheric pressure sealing measurement step, after introducing a gas into the inspection object container and the reference container and pressurizing the gas to a predetermined test pressure _PT. After the end of the measurement period T _M , both are sealed after the interval time T _I elapses, and the differential pressure of the internal pressure of both containers after sealing is repeatedly measured over a predetermined period, and each differential pressure measured Test pressure sealing measurement step which records with the order from the start of measurement,
The data recorded in the atmospheric pressure sealing measurement step is divided into groups (group numbers k = 1, 2,... M) for each time T from the sealing time, and the average value P _{ED, m} (m (m Find = 1, 2, ... M),
As
A first gradient acquisition step of obtaining _a value m _a of m for which the absolute value of n is less than or equal to a predetermined allowable value;
The data recorded in the test pressure sealing measurement step is divided into groups (group number m = 1, 2,... M) for each time T from the sealing time, and the average value P _{DD, m} (m (m Find = 1, 2, ... M),
As
Absolute value calculated values m _b of m becomes less than a predetermined tolerance, the value towards not smaller among the m _a and m _b as k, and the second gradient acquisition step of obtaining the Q _k and R _k,
Let the sum of the measurement period T _M and the interval time T _{I be} T _S ,
A leak judgment step of judging presence or absence of a leak of the container to be inspected based on the value of L obtained by the calculation of
Have
The Daitoki constant is greater of the two time constants governing the change based on the temperature of the differential pressure of the internal pressure of both container after sealing the said object container and the reference container from atmospheric pressure P _E open Time constant of
The α ₂ is
A leak inspection method characterized in that

In the invention according to the above [2], the difference string L _m is formed, but in the invention according to [6], the change according to the small time constant is converged at the stage of Q _{m and} R _m (set to the allowable value or less) Calculate L using the converged Q _k and R _k . It is the same as [2] except in terms of at which stage the convergence is made.

[7] If either m _a or m _b can not be determined, the measurement period T _M is extended, and if k can be determined, the measurement period T _M is set based on the value of k. The leak inspection method according to [6].

In the above invention, when either of m _a and m _b can not be obtained, that is, when either of Q _M-1 and R _{M -1} does not fall below the allowable value (does not converge), the measurement period T _M is If it extends and k is determined (both Q and R converge), the measurement period T _M is set based on the k.

[8] the inspected container and a leaktight reference vessel pressure difference in the internal pressure of both container after sealing both repeatedly measuring period T _M from the atmospheric pressure P _E opened, each measured pressure difference Atmospheric pressure sealing measurement step which is recorded along with the order from the start of measurement,
The atmospheric pressure sealing measurement step is performed continuously after the atmospheric pressure sealing measurement step, after introducing a gas into the inspection object container and the reference container and pressurizing the gas to a predetermined test pressure _PT. After the end of the measurement period T _M , both are sealed after the interval time T _I elapses, and the differential pressure of the internal pressure of both containers after sealing is repeatedly measured over a predetermined period, and each differential pressure measured Test pressure sealing measurement step which records with the order from the start of measurement,
The data recorded in the atmospheric pressure sealing measurement step is divided into groups (group numbers k = 1, 2,... M) for each time T from the sealing time, and the average value P _{ED, m} (m (m = 1, 2, ... M),
A first gradient acquisition step for determining
The data recorded in the test pressure sealing measurement step is divided into groups (group number m = 1, 2,... M) for each time T from the sealing time, and the average value P _{DD, m} (m (m = 1, 2, ... M),
A second gradient acquisition step for determining
_Let the sum of the measurement period T _M and the interval time T _{I be} T _S ,
A leak judgment step of judging presence or absence of a leak of the container to be inspected based on the value of L obtained by the calculation of
Have
The Daitoki constant is greater of the two time constants governing the change based on the temperature of the differential pressure of the internal pressure of both container after sealing the said object container and the reference container from atmospheric pressure P _E open Time constant of
The α ₂ is
A leak inspection method characterized in that

The above invention shows a measurement method after the appropriate measurement period T _M has been determined. The slopes Q _M-1 and R _M-1 of the differential pressure curve at the end of the measurement period T _M may be determined, and L may be calculated from these.

[9] A leak inspection apparatus for inspecting the presence or absence of a leak in a container to be inspected using the leak inspection method according to any one of [1] to [8].

[10] Among the leak inspection methods described in any one of [1] to [8],
Receiving the data recorded in the atmospheric pressure sealing measurement step and the data recorded in the test pressure sealing measurement step,
A leak inspection apparatus that performs processing of the first gradient acquisition step, the second gradient acquisition step, and the leak determination step to determine the presence or absence of a leak of a container to be inspected.

  In the above invention, measurement of the differential pressure is performed by another device, data of the measurement result is input from the other device, and only calculation and determination on the data of the input measurement result are performed by the leak inspection device.

[11] In the leak inspection device,
A program comprising: executing each step of the leak inspection method according to any one of [1] to [8] or the first gradient acquisition step, the second gradient acquisition step, and the leak determination step.

  According to the leak inspection method and the leak inspection apparatus according to the present invention, an appropriate measurement time can be determined, and the presence or absence of a leak can be determined with high accuracy with the minimum necessary time.

It is a figure which shows schematic structure of the leak test | inspection apparatus which enforces the leak test | inspection method which concerns on this invention. It is the graph which represented the differential pressure curve based on the measurement data obtained at the atmospheric pressure sealing measurement process, and the differential pressure curve based on the measurement data obtained at the test pressure sealing measurement process by a continuous time-axis. It is a figure which shows the change of the temperature difference of the gas in the workpiece | work and a master in a test pressure sealing measurement process from an atmospheric pressure sealing measurement process. It is a figure which shows an example of the differential pressure curve measured when calculating | requiring a large time constant.

  Hereinafter, embodiments of the present invention will be described based on the drawings.

  FIG. 1 shows a schematic configuration of a leak inspection apparatus 10 that carries out a leak inspection method according to the present invention. The leak inspection apparatus 10 is an apparatus for inspecting a leak of a container to be inspected (for example, a heat exchanger of a water heater or a hot water storage tank). Use the container to be inspected as a work. In addition, a container made of the same material and the same shape as the work, and confirmed to have no leak, is used as a master. The work and the master are different containers with the same mechanical and thermodynamic parameters.

  The leak inspection apparatus 10 includes a pressure source connection port 11, a work connection port 12, and a master connection port 13. The leak inspection apparatus 10 has one end connected to the pressure source connection port 11 as an internal conduit. The first pipe 21 is branched on the way to the second pipe 22 and the third pipe 23, and the other end of the second pipe 22 is connected to the work connection port 12 as a third pipe. The other ends of the pipes 23 are connected to the master connection port 13 respectively.

  A first on-off valve 31 is inserted in the first pipe 21. A second on-off valve 32 is inserted in the second pipe 22. In addition, a third on-off valve 33 is inserted in the third pipe 23. The second pipe 22 between the second on-off valve 32 and the work connection port 12 branches midway and is connected to one connection port of the differential pressure gauge 37. Similarly, the third pipe 23 between the third on-off valve 33 and the master connection port 13 branches halfway and is connected to the other connection port of the differential pressure gauge 37. The differential pressure gauge measures the differential pressure between the pressure applied to one of the connection ports and the pressure applied to the other connection port. The third pipe 23 to the fourth pipe line 24 are branched at a predetermined position between the first on-off valve 31 and the third on-off valve 33, and the fourth on-off valve 34 is provided in the middle of the fourth pipe line 24. It is The end of the fourth conduit 24 is open to the atmosphere.

  The leak inspection apparatus 10 includes an inspection processing unit 15 which performs control of the flow of inspection, measurement of a differential pressure, recording of a measurement result, and leakage determination based on the recorded measurement result. The inspection processing unit 15 is a circuit mainly including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and the like, and the CPU executes processing in accordance with a program stored in the ROM. Then, the inspection operation, calculation, and determination in the leak inspection apparatus 10 are performed.

  A pressure source, which is a supply source of pressurized gas, is connected to the pressure source connection port 11 via an electropneumatic regulator or the like (not shown).

  A work 41 is connected to the work connection 12, and a master 42 is connected to the master connection 13.

  Next, an outline of the present invention will be described.

The leak inspection by a leakage inspecting device 10 according to the present invention, sealing both the workpiece 41 and the master 42 after opening the atmospheric pressure P _E, a predetermined differential pressure in the internal pressure of both the container after sealing by the differential pressure gauge 37 An atmospheric pressure sealing measurement step is performed in which measurement is repeatedly performed over a period, and each measured differential pressure is recorded in association with measurement time (in place of measurement time, measurement order may be used if measurement time can be specified). Next, subsequently to the end of the atmospheric pressure sealing measurement process, a gas is introduced into the work 41 and the master 42 and pressurized to a predetermined test pressure _PT , and then both are sealed to seal both containers after sealing. Test pressure sealing measurement that measures the differential pressure of internal pressure repeatedly for a predetermined period, and associates each measured differential pressure with the measurement time (in place of the measurement time, it may be the measurement order if the measurement time can be specified) Perform the process.

And when the difference of the gradient (rate of change of differential pressure) of the graph (differential pressure curve) representing the change of differential pressure with the passage of time from the data recorded in the atmospheric pressure sealing measurement step becomes less than a certain value Measurement time T _a in the atmospheric pressure sealing measurement process of differential pressure data and the first gradient acquisition process for obtaining the rate of change (gradient) Q of the differential pressure at that time, and recorded in the test pressure sealing measurement process from the data, the differential pressure over time gradient of the test圧封stop measurement process data differential pressure difference became constant below (differential pressure rate of change) measurement time T _b and at that time A second gradient acquisition step is performed to obtain a rate of change (gradient) R of the differential pressure.

Then, a time difference in the case of counting from the measurement time T _a to the measurement time T _b continuously and T _S, leakage L of the workpiece 41,
The leakage determination step of determining the presence or absence of the leakage of the work 41 based on the value of L or the value of L is performed.

  FIG. 2 shows atmospheric pressure sealing of differential pressure change over time based on measurement data obtained in the atmospheric pressure sealing measurement process and differential pressure change based on measurement data obtained in the test pressure sealing measurement process. It is the graph (differential pressure curve) represented by the time-axis continuous from the start time of a measurement process. The differential pressure change in the test pressure sealing measurement process is the sum of the differential pressure change due to the leak from the work 41 and the differential pressure change based on the temperature. On the other hand, the differential pressure change in the atmospheric pressure sealing measurement process is considered to be only the differential pressure change based on the temperature.

  However, the atmospheric pressure sealing measurement process and the test pressure sealing measurement process can not be simultaneously performed on the same work 41. Therefore, in the present invention, the temperature in the test pressure sealing measurement step is determined from the slope Q (rate of change of differential pressure) of the differential pressure curve obtained in the atmospheric pressure sealing measurement step performed immediately before the test pressure sealing measurement step. Test pressure seal measurement by estimating the rate of change of the differential pressure due to and subtracting the ratio of the test pressure and the atmospheric pressure from the gradient R of the differential pressure curve obtained in the test pressure seal measurement process. Estimate the rate of change in differential pressure (leakage L) due to leaks in the process.

  Incidentally, the change in the temperature difference between the gas temperature in the work 41 and the gas temperature in the master 42 on the same time axis as FIG. 2 is as shown in FIG. The gas temperature in the work 41 changes as shown by curve AB in the atmospheric pressure sealing measurement process, and if the pressurization to the test pressure is not performed after the atmospheric pressure sealing measurement process, the change continues as it is, As shown by the broken line BC. In practice, the gas inside the container is adiabatically compressed by being pressurized to the test pressure, and the temperature rises, so it changes like BDE (the graph is drawn with exaggeration).

  However, because the heat capacity of the container is sufficiently large compared to air, and the heat generated by pressurization is almost the same for both the work 41 and the master 42, etc. The difference in gas temperature inside the workpiece 41 and the master 42 is almost the same as in the case where no pressure is applied. That is, in reality, it becomes a curve substantially overlapping ABC, as in ABD'C of FIG.

  And, since the absolute temperature and the pressure are in proportion, the change in differential pressure due to the temperature at the test pressure is similar to the change in temperature. That is, it is assumed that the change in differential pressure due to temperature in the atmospheric pressure sealing measurement process continues as it is in the subsequent test pressure sealing measurement if the sealing pressure ratio is determined.

Therefore, the differential pressure changes in the inner pressure of both container after sealing the workpiece 41 and the master 42 with a temperature difference from the atmospheric pressure P _E open (which varies based on the temperature) of the two time constants governing the The large time constant, which is the larger one of the two, is previously measured and obtained. Then, in the leakage determination process is to correct the elapsed time T _S and slope Q between Daitoki constant from measurement time T _a gradient Q to the measurement time T _b of the gradient R, becomes the measurement time T _b of the gradient R Rate of change in differential pressure due to temperature. Also correct the difference between atmospheric pressure and test pressure by P _T / P _E. That is,
The leakage L is obtained by the calculation of to determine the presence or absence of the leakage. The smaller one of the two time constants that govern the change in differential pressure due to the temperature is taken as the small time constant.

  In the first gradient acquisition step and the second gradient acquisition step, by acquiring the gradient (rate of change of differential pressure) after the rate of change of the gradient of the differential pressure curve falls below a certain level, the time related to temperature changes is small. It waits for sufficient attenuation to a negligible extent such as a change in differential pressure related to the constant.

  Next, the theoretical explanation of the present invention will be made in more detail.

  Here, the case where the ambient temperature change within the measurement time can be ignored is dealt with. If the ambient temperature changes significantly beyond the measurement time, another method should be considered. It occurs when measurement time is long or ventilation is performed fast. The present invention relates to a leak test method which terminates measurement in such a short time that a change in environmental temperature of a container or the like can be ignored.

The differential pressure used below is
Differential pressure P _D = (master internal pressure)-(work internal pressure)
I assume.

In FIG. 1, when the time at which the second on-off valve 32 and the third on-off valve 33 are sealed is t = 0, the differential pressure generated when the ambient temperature does not change is
It is. However, when P _C is the sealing pressure
Where G is the mass flow and M _C is the sealed air mass. This mass flow rate G is a constant determined by P _E as an environmental pressure and K _V as a hole causing a leak.
It is. Since C ₁ and C ₂ is determined by the initial conditions of temperature, it can not be known before the leak measurement.

The parameters that can be known before leak measurement are:
Gas constant: R
Parameters to be determined by the product (time constant of temperature change): T1 _, T2 _,
Known quantities determined by test conditions: P _C, P _E, M _C, μ _, θ _0,
μ is the air viscosity, and θ ₀ is the air temperature. T ₁ is a small time constant, and T ₂ is a large time constant.

Equation (1) holds true also when the even test pressure when P _C is the atmospheric pressure. However, the parameters are all different and the origin of time is also different.

The container to which the present invention can be suitably applied is
Is true. Measurement and recording of the differential pressure are performed over a time period T _M which is a measurement period. The standard of the size of T _M is
It is. Note that an interval T _I is necessary to pressurize between the start of the differential pressure measurement over the time T _{M at} atmospheric pressure and the differential pressure measurement at the next test pressure. Roughly
Choose a degree T
far. These are used in the comparison of temporal changes in differential pressure.

<Approximate pressure change with one exponential function>
Now, substituting t + T for t in equation (1)
It is. By subtracting α ₂ times Expression (1) from Expression (9), the exponential function of the large time constant can be eliminated. The left side of equation (10) is a function for evaluating the leak.

First, consider the first measurement by atmospheric pressure.
If a differential pressure is generated after the inside of the container is sealed by being filled with the environmental pressure P _E (atmospheric pressure), it can be said that the differential pressure is generated by a change in internal gas temperature. At this time, in equation (2)
However, according to equations (4), (3) and (2),
It is. Substituting this in equation (10), we obtain
If you plot the observation on the left side, it is the sum of a constant and an exponential function. The left side of equation (13) is determined from the measured value, and if the change becomes small, the measurement is aborted.

Equation (13) indicates that the differential pressure does not become zero even if the temperature difference between the two containers (work and master) becomes zero after a sufficient time has elapsed. The time required for measurement is the time required for the value of equation (13) to converge to such a degree that it can be considered constant. therefore
(13) becomes small, and the pressure change rate caused by temperature becomes
And is required. This is because the time constant T ₂ is very large, the mass change ratio of the spurious (false leak).

Next, the second measurement is performed by sealing the test pressure _PT in both containers. Since the pressure changes, it can not be said that C ₀ = 0. Moreover, since the time origin changes, the temperature initial value is changed. Therefore, instead of equation (13)
It must be done. Since the constant determined by the initial value is different from before, the symbols are distinguished from C ' ₁ and C' ₂ here. The temporal relationship between the first measurement by atmospheric pressure and the second measurement by test pressure is shown in FIG.

  When test pressure is applied to the container, any leaks will cause a leak. On the other hand, regardless of the presence or absence of a leak, a change in gas pressure occurs due to a temperature change in the container. The observed differential pressure change is the sum of the differential pressure change due to leakage and the differential pressure change due to temperature. Because it is not possible to make simultaneous measurements with and without pressure on the same container, some separation is necessary for these separations. Therefore, a differential pressure change due to temperature is estimated, and if a differential pressure different from the estimated value is observed, it is assumed that the difference is a pressure change due to "leakage".

First find the next quantity.
Substituting equations (13) and (16) into this

Now, heat exchange between the container and the external environment continues with or without the measurement. However, when the container is pressurized, the gas inside is compressed and heat is generated. This causes the temperature of the air to rise, and the heat transfer to the vessel also raises the vessel temperature. Since the amount of heat generated by pressurization almost equal in the master and the workpiece, the vessel temperature difference is approximated by continuous change determined by the time constant T _2, allows the container temperature difference estimation in that situation. FIG. 3 illustrates the change in container temperature difference through two measurements.

  The temperature difference of the air in the container when measured by atmospheric pressure sealing is represented by curve AB. Without pressurization, this curve continues as a dashed line BD'C. This curve is an extension of AB and is mathematically determined by the progression to AB. Since BD 'is a pressurization process, the temperature difference becomes like BD, but since D' and D often overlap, such a case is considered here. The temperature after that follows a change process represented by heat dissipation of a container such as DE, but it can be assumed that the curve almost overlaps with D'C. Although there are cases where this assumption does not hold, applying the present invention to such cases leads to inaccurate results.

Well, curve ABC is
It can be approximated that the origin of the time after pressurization is T _M + T _I , which is later than the atmospheric pressure sealing measurement before pressurization. The time after pressurization and the related values such as the initial value are indicated by adding a dash (') to the symbol in the case of atmospheric pressure sealing. Since BC and DE almost overlap each other,
However, since T ₂ >> T ₁ , the second term is usually smaller than the first term.

therefore
It can be estimated. Therefore, the pressure change rate due to leakage is
It becomes. The second term of this right side decays by observing the data and examining the time to wait. This is not necessary to check every time if observing the time constant T _{1 of} decay from the time-dependent characteristic of L. Since the first term of the right side remaining after the second term of the right side of the formula (23) is attenuated represents a leak, the calculation result of the formula (17) obtained from the measured value indicates the leak.

  The right side of equation (17) obtained from the measured value contains noise. Also, to see the leak, it is necessary to wait for the decay of the exponential term of the left side (equation (23)). With regard to noise, an average value over a time width T of L is determined and approximately eliminated. Even though this averaging is performed before the above data processing, the results are the same.

Leakage estimation is performed by calculating Formula (17) from data. In this calculation, it is necessary to have prior knowledge Daitoki constant T _2. If the workpiece is heated and the differential pressure time curve is obtained once without heating the master, the numerical value of T ₂ can be known sufficiently accurately.

  Next, an inspection process of measuring a differential pressure and performing an operation corresponding to Expression (17) to determine the presence or absence of a leak will be described.

When the time used for leak measurement is about one minute to several minutes, the differential pressure is measured and recorded every time step s of about 0.1 seconds. The n times the time step s (n is an integer, generally 10 or more) as a T, (the M approximately 4 or more integer) M times T and = T _M differential pressure recording time (measurement period T _M) . From the completion of the measurement recording over T _M to the next differential pressure measurement start is set to T _I, T _I is set as short as possible. If the time used for leak measurement is long, the value of s may be increased accordingly.

  The measuring instrument is used as follows. Once the item (workpiece) to be leaked is determined, first measure the larger one of the two time constants that govern the pressure change due to the temperature of the sealed item (hereinafter referred to as the large time constant). Do. Then enter the general inspection process. The measurement of the large time constant may be performed once for one type of measurement object, and in the individual leak inspection, only the general inspection process may be performed.

<Measurement of Large Time Constant (T ₂ )>
The master and the work are connected to the leak inspection apparatus 10 as in the normal leak measurement. This work and the master use what has been confirmed in advance that there is no leak. The workpiece is brought to a temperature different from the ambient temperature by an appropriate method, and then the workpiece and the master are released to ambient air and then sealed, and differential pressure measurement is started. This differential pressure shuts off the valves (the second on-off valve 32 and the third on-off valve 33) at time t = 0 to start the differential pressure gauge side, opens the valve after a certain time T _A , and returns to zero. Do the operation. Let T _B be the time taken to seal the valve again. The differential pressure curve thus obtained has a T _A that is short enough to be linearly approximated.

The gradient of the differential pressure curve at this time is G ₁ . The same operation is repeated to obtain number sequences G ₁ , G ₂ ,. FIG. 4 is an example of a plurality of differential pressure curves measured in this manner. The horizontal axis in FIG. 4 is time, and the vertical axis is differential pressure.

Individual differences pressure curve, T _A is short enough that almost regarded as a straight line. At this time,
Form, taking the logarithm of both sides
From this, 1 / T ₂ may be obtained by the least squares method. Since data up to about k = 3 may be affected by another time constant, deleting it and using the remaining data to find T ₂ is closer to the true value.

<Determination of α and β>
The pressure transient response is represented by one linear function and the sum of two first order lag step responses. The time constant of the first-order lag step response, the larger one being the previously described large time constant, and using it
It is. T, T _M , and T _I can be arbitrarily determined by the tester, but for convenience, M is a positive integer and T _M is set to M times T. T ₂ are those determined by the eigenvalues determined by the specimen (workpiece), determined by the test body. T ₂ because the product to determine if Kimare, if you measure it, it is possible that subsequent to the same product, continue to use.

<General inspection process>
The work 41 is connected to the work connection port 12 of the leak inspection apparatus 10 in the state where the first on-off valve 31 is closed, and the master 42 is connected to the master connection port 13. The second on-off valve 32, the third on-off valve 33, the fourth on-off valve 34 open to the atmospheric pressure P _E open, then close the fourth on-off valve 34, further the second on-off valve 32, closes the third on-off valve 33 at the same time, sealing the workpiece 41 and the master 42 at atmospheric pressure . The differential pressure of the internal pressure of both containers is repeatedly measured over a measurement period T _M every time s, with the time when both are sealed as the start time of measurement, and each differential pressure measured together with the order from the start of measurement In order) to record. As described above, n times the time s is T, and an integral multiple of T (M times, for example, 10 times) is the measurement period T _M. Instead of the order of measurement, the time of measurement may be linked and recorded.

When the measurement in the atmospheric pressure sealing is completed, the measurement in the test pressure sealing is continuously performed. Specifically, after the second on-off valve 32 and the third on-off valve 33 are opened, the first on-off valve 31 is opened, gas is introduced from both the work 41 and the master 42 from the pressure source and pressurized to the test pressure. After pressurization to the test pressure, the first on-off valve 31 is closed, and the second on-off valve 32 and the third on-off valve 33 are closed simultaneously to seal the work 41 and the master 42 at the test pressure. The differential pressure of the internal pressure of both containers is repeatedly measured over a measurement period T _M every time s, with the time when both are sealed as the start time of measurement, and each differential pressure measured together with the order from the start of measurement In order) to record. Shall proceed measurement end from time to the start of measurement in the test圧封stop (charge time) testing such that within a predetermined time interval T _I at atmospheric pressure sealing. Differential pressure measurement is performed by recording atmospheric pressure sealing measurement and test pressure sealing measurement performed subsequently as a pair. Note that previously obtained a Daitoki constant T ₂ of the inspection target workpiece as the above, further alpha, the β equation (26), obtained in advance by (27).

  Next, calculation is performed based on the measured differential pressure data.

[Calculation based on differential pressure data of atmospheric pressure sealing]
The differential pressure recorded is
I assume. From this, an average value every n (time T) is made and recorded. This process may be performed during the measurement and only the results may be recorded.
The following sequence is formed from this.
Q _m is a sequence of terms whose number of terms is M-1.

[Calculation based on differential pressure data of test pressure seal]
As in the case of atmospheric pressure sealing, the differential pressure is divided into n pieces, and the average value is made and recorded. This process may be performed during the measurement and only the results may be recorded.
Than this
Make R _m is a sequence of which the number of terms is M−1.

[Calculation of leak judgment based on Q _m and R _m ]
Make the following sequence from Q _m and R _m .
This series is an approximation of the rate of change of differential pressure caused by leakage, and approaches a constant value as m increases. Leakage U is represented by following Formula using this convergence value.
When the allowable value U _{C of} leakage is determined, the case where the following expression is satisfied is regarded as a leakage inspection pass.

  In general measurement, formula (35) may not hold. At that time, I suspect the leak, but it may not be the leak. Therefore, if equation (35) does not hold, the following process is performed.

[Process when a leak is suspected]
If the value of L _M-1 is large, a leak is suspected. At this time, the recorded number sequence {L _M } is examined. Difference column ie _{L M}
When D _m converges to 0, L _{M −1} obtained represents a leak.
At this time
Then, the difference sequence D _m does not converge to zero. If D _m does not converge to 0, it indicates that the temperature transient has not settled within the measurement time. In this case, the obtained result is discarded, and remeasurement is simply performed, or the value of M is increased and remeasurement is performed, and the determination of the equation (36) or less is performed again. This is the end of the measurement.

If D _m does not converge to 0 at this stage, the measuring instrument or measuring system is inappropriate or there is a suspicion of incorrect input of parameters.

The following cautions need to be made regarding this re-measurement. The measurement time may be insufficient when the conveyed workpiece is particularly high or low compared to the environmental temperature. In such a case, since the temperature approaches the environmental temperature by the first measurement, LM _-1 converges to 0 even if mere remeasurement is performed without extending the measurement time, and the equation (35) May become true. At this time, the second measurement value is correct, and the first LM _-1 is a value that did not reach convergence because the initial temperature difference was too large.

[Minimum measurement period T _M ]
If L _m converges to a constant value at _m less than M-1, measure the smallest m (or a value obtained by adding a small amount of margin (for example, 1 or 2) to this value) as a new M The period T _M may be determined. Similarly, the measurement period T _M may be defined as a new M, which is the minimum m (or a value obtained by adding a small allowance (eg, 1 or 2)) to which the equation (35) holds. In this way, the minimum measurement period T _M can be set. This measurement period T _M may be used in the subsequent test on the same product.

<Modification of inspection process>
In the modification, the convergence is confirmed at the stage of the equation (30) and the equation (32). That is, after obtaining the number sequence of equation (30),
The minimum value m _a of m for which the absolute value of x is less than or equal to a predetermined tolerance is determined. Also, after finding the number sequence of equation (32),
The minimum m value m _{b for} which the absolute value of _x is less than a predetermined allowable value is determined. Then a small no better value of one of _{m a} and _{m b} as k, determine the _{Q k} and _{R k.} Here, for _{r m,} determine the _{r m} first with m = _{m a,} the absolute value of the k a _{m a} if below a predetermined allowable value. If that be the absolute value is less than a predetermined tolerance value, the value of m gradually increased from m _a by +1, the absolute value of the value of the smallest m which falls below a predetermined allowable value of r _m and k.

And
Based on the value of L obtained by the calculation in the above, it is determined whether or not there is a workpiece leak. If the absolute value of L is less than a predetermined allowable value, it is determined that there is no leak (acceptable product), and if the absolute value of L exceeds the allowable value, it is determined that there is a leak (rejected product).

If either m _a or m _b can not be determined, that is, if the absolute values of q _m and r _m do not converge below the allowable value, the measurement period T _M is extended. On the other hand, if k can be determined, the subsequent measurement period T _M is set based on the value of k. For example, the measurement period T _M may be determined by setting the value of k (or the value obtained by adding this to a small allowance (1 or 2)) as a new M. Thus, the minimum measurement period can be set.

This measurement period T _M may be used in a subsequent test on another work of the same product. In the calculation, final gradients Q _M-1 and R _M-1 may be obtained, and the leak may be determined from L _M-1 .

As described above, according to the present invention, if the large time constant is determined, the leak can be determined by simple arithmetic operations without using the least squares method or the simultaneous equations. Further, to determine the excess and deficiency of the measurement period T _M, it is possible to set the minimum measurement period T _M. Also, the theoretical basis of the leak free judgment is clear.

  The embodiment of the present invention has been described above with reference to the drawings, but the specific configuration is not limited to that shown in the embodiment, and changes and additions may be made without departing from the scope of the present invention. Also included in the present invention.

  The present invention is not limited to the leak inspection apparatus, and includes a leak inspection method and a program that causes the information processing apparatus to function as the leak inspection apparatus of the present invention.

Equations (30) and (32) may be divided by time T to be Q _m and R _m .

  The leak inspection apparatus 10 shown in the embodiment is an example, and the present invention is not limited to this, as long as it is an inspection apparatus capable of performing test pressure seal measurement following atmospheric pressure seal measurement.

  In the embodiment, although the calculation processing is performed by the inspection processing unit 15, measurement data may be transferred to a personal computer or the like, and calculation / determination according to the leak inspection method of the present invention may be performed there. In addition, the case where the calculation and the creation of the graph are performed using commercially available spreadsheet software or the like is also included in the leak inspection method of the present invention. Furthermore, the present invention is a program that causes an information processing apparatus to function so as to receive an input of measured data, execute an operation performed by the leak inspection apparatus of the present invention on the data, and determine the presence or absence of a leak. May be

DESCRIPTION OF SYMBOLS 10 ... Leak inspection apparatus 11 ... Pressurization source connection port 12 ... Work connection port 13 ... Master connection port 15 ... Inspection processing part 21 ... 1st piping 22 ... 2nd piping 23 ... 3rd piping 24 ... 4th pipe line 31 ... 1st on-off valve 32 ... 2nd on-off valve 33 ... 3rd on-off valve 34 ... 4th on-off valve 37 ... differential pressure gauge 41 ... work 42 ... master

Claims (11)

The pressure difference in the internal pressure of both container after sealing of both the inspected container and a leak-free reference container from atmospheric pressure P _E open repeatedly measured over a predetermined time period, corresponding to the respective pressure difference between the measured time measured Atmospheric pressure sealing measurement step to record
It continues after the end of the atmospheric pressure sealing measurement step, and after introducing a gas into the inspection object container and the reference container and pressurizing them to a predetermined test pressure _PT , both are sealed and sealed. A test pressure sealing measurement step of repeatedly measuring the differential pressure of the internal pressure of both containers after that over a predetermined period, and correlating and recording each measured differential pressure and measurement time;
From the data recorded in the atmospheric pressure sealing measurement step, the measurement time T in the atmospheric pressure sealing measurement step of the differential pressure data when the rate of change of the rate of change of the differential pressure over time becomes constant or less _a first gradient acquisition step of determining _a and _a rate of change Q of differential pressure at that time;
From the data measured in the test pressure sealing measurement step, the measurement time T in the test pressure sealing measurement step of the differential pressure data when the rate of change of the rate of change in differential pressure with the passage of time becomes constant or less. _a second gradient acquisition step of determining _b and a rate of change R of differential pressure at that time;
_Let T _S be the time difference when measuring from measurement time T _a to measurement time T _b continuously.
A leak judgment step of judging presence or absence of a leak of the container to be inspected based on the value of L obtained by the calculation of
Have
The Daitoki constant is greater of the two time constants governing the change based on the temperature of the differential pressure of the internal pressure of both container after sealing the said object container and the reference container from atmospheric pressure P _E open Leak check method characterized in that the time constant of the The pressure difference in the internal pressure of both container after sealing of both the inspected container and a leak-free reference container from atmospheric pressure P _E opened repeatedly measuring period T _M, each measured pressure difference from the start of measurement Atmospheric pressure seal measurement step which is recorded along with the order of
The atmospheric pressure sealing measurement step is performed continuously after the atmospheric pressure sealing measurement step, after introducing a gas into the inspection object container and the reference container and pressurizing the gas to a predetermined test pressure _PT. After the interval time T _I has elapsed since the end of the measurement period T _M , both are sealed, and the differential pressure of the internal pressure of both containers after sealing is repeatedly measured over the measurement period T _M , and each measured difference Test pressure measurement step which records the pressure with the order from the start of the measurement;
The data recorded in the atmospheric pressure sealing measurement step is divided into groups (group numbers m = 1, 2,... M) for each time T from the sealing time, and the average value P _{ED, m} (m (m Find = 1, 2, ... M),
A first gradient acquisition step for obtaining a differential sequence
The data recorded in the test pressure sealing measurement step is divided into groups (group number m = 1, 2,... M) for each time T from the sealing time, and the average value P _{DD, m} (m (m Find = 1, 2, ... M),
A second gradient acquisition step for obtaining a differential sequence
_Let the sum of the measurement period T _M and the interval time T _{I be} T _S ,
If the value of L _m converges to a constant value as _m increases, the convergence value is judged as a leak, or if there is _{m where} the absolute value of L _m falls below a predetermined allowable value Leak judgment step to judge that there is no leak in the
Have
The Daitoki constant is greater of the two time constants governing the change based on the temperature of the differential pressure of the internal pressure of both container after sealing the said object container and the reference container from atmospheric pressure P _E open Time constant of
The α ₂ is
A leak inspection method characterized in that In the leak determination step, when the absolute value of LM _-1 exceeds the allowable value,
The leak inspection method according to claim 2, wherein a numerical sequence is generated, and when D _m converges to 0, it is determined that there is a leak. 4. The leak inspection method according to claim 3, wherein when the D _m does not converge to 0, the measurement period T _M is extended and the atmospheric pressure sealing measurement step is performed again. The leak check method according to any one of claims 2 to 4, wherein the measurement period T _M is set based on the minimum _{m at} which L _m converges. The pressure difference in the internal pressure of both container after sealing of both the inspected container and a leak-free reference container from atmospheric pressure P _E opened repeatedly measuring period T _M, each measured pressure difference from the start of measurement Atmospheric pressure seal measurement step which is recorded along with the order of
The atmospheric pressure sealing measurement step is performed continuously after the atmospheric pressure sealing measurement step, after introducing a gas into the inspection object container and the reference container and pressurizing the gas to a predetermined test pressure _PT. After the end of the measurement period T _M , both are sealed after the interval time T _I elapses, and the differential pressure of the internal pressure of both containers after sealing is repeatedly measured over a predetermined period, and each differential pressure measured Test pressure sealing measurement step which records with the order from the start of measurement,
The data recorded in the atmospheric pressure sealing measurement step is divided into groups (group numbers k = 1, 2,... M) for each time T from the sealing time, and the average value P _{ED, m} (m (m Find = 1, 2, ... M),
As
A first gradient acquisition step of obtaining _a value m _a of m for which the absolute value of n is less than or equal to a predetermined allowable value;
The data recorded in the test pressure sealing measurement step is divided into groups (group number m = 1, 2,... M) for each time T from the sealing time, and the average value P _{DD, m} (m (m Find = 1, 2, ... M),
As
Absolute value calculated values m _b of m becomes less than a predetermined tolerance, the value towards not smaller among the m _a and m _b as k, and the second gradient acquisition step of obtaining the Q _k and R _k,
Let the sum of the measurement period T _M and the interval time T _{I be} T _S ,
A leak judgment step of judging presence or absence of a leak of the container to be inspected based on the value of L obtained by the calculation of
Have
The Daitoki constant is greater of the two time constants governing the change based on the temperature of the differential pressure of the internal pressure of both container after sealing the said object container and the reference container from atmospheric pressure P _E open Time constant of
The α ₂ is
A leak inspection method characterized in that When either of m _a and m _b can not be determined, the measurement period T _M is extended, and when k can be determined, the subsequent measurement period T _M is set based on the value of k. The leak inspection method according to claim 6. The pressure difference in the internal pressure of both container after sealing of both the inspected container and a leak-free reference container from atmospheric pressure P _E opened repeatedly measuring period T _M, each measured pressure difference from the start of measurement Atmospheric pressure seal measurement step which is recorded along with the order of
The atmospheric pressure sealing measurement step is performed continuously after the atmospheric pressure sealing measurement step, after introducing a gas into the inspection object container and the reference container and pressurizing the gas to a predetermined test pressure _PT. After the end of the measurement period T _M , both are sealed after the interval time T _I elapses, and the differential pressure of the internal pressure of both containers after sealing is repeatedly measured over a predetermined period, and each differential pressure measured Test pressure sealing measurement step which records with the order from the start of measurement,
The data recorded in the atmospheric pressure sealing measurement step is divided into groups (group numbers k = 1, 2,... M) for each time T from the sealing time, and the average value P _{ED, m} (m (m = 1, 2, ... M),
A first gradient acquisition step for determining
The data recorded in the test pressure sealing measurement step is divided into groups (group number m = 1, 2,... M) for each time T from the sealing time, and the average value P _{DD, m} (m (m = 1, 2, ... M),
A second gradient acquisition step for determining
_Let the sum of the measurement period T _M and the interval time T _{I be} T _S ,
A leak judgment step of judging presence or absence of a leak of the container to be inspected based on the value of L obtained by the calculation of
Have
The Daitoki constant is greater of the two time constants governing the change based on the temperature of the differential pressure of the internal pressure of both container after sealing the said object container and the reference container from atmospheric pressure P _E open Time constant of
The α ₂ is
A leak inspection method characterized in that   A leak inspection apparatus for inspecting the presence or absence of a leak of a container to be inspected using the leak inspection method according to any one of claims 1 to 8. The leak inspection method according to any one of claims 1 to 8,
Receiving the data recorded in the atmospheric pressure sealing measurement step and the data recorded in the test pressure sealing measurement step,
A leak inspection apparatus that performs processing of the first gradient acquisition step, the second gradient acquisition step, and the leak determination step to determine the presence or absence of a leak of a container to be inspected. In the leak inspection device,
A program comprising: executing each step of the leak inspection method according to any one of claims 1 to 8 or the first gradient acquisition step, the second gradient acquisition step, and the leak determination step.