JPH04364436A - Calibrating method for leakage inspecting apparatus - Google Patents

Abstract

PURPOSE:To obtain a leakage inspecting apparatus which can perform calibration without replacing calibrating devices even if the inner volume of a container under inspection is large or small. CONSTITUTION:The equal air pressure is applied to a container under inspection 16 whose inner volume is given as the known number and a reference tank 17 for a specified time. The amount of the air which is leaking from the container under inspection 16 is directly read based on the value of the pressure difference generated between the container and the tank. In the leakage inspecting apparatus of this type, a minute leak valve 37 whose flow rate is known is mounted on a pipe which gives air pressure on the container under inspection 16. The air is made to leak through the minute leak valve 37 for a specified time. It can be regarded that the leakage is equivalent to change of the inner volume of the container under inspection 16 by the known amount. The equivalent inner volume of the container under inspection 16 is obtained based on the change in equivalent inner volume, and calibration is performed.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a leak testing device for testing the presence or absence of leaks in waterproof appliances or sealed containers, and in particular to calibration for obtaining calibration values used in calculations for directly reading and displaying leakage amounts. This paper proposes a method.

0002

2. Description of the Related Art As one method for inspecting sealed containers, etc. for leaks, the same air pressure is applied from an air pressure source to the container to be inspected and a reference container with no leaks, and after the supply path is cut off, Check whether a pressure difference occurs between the two, and if no differential pressure occurs, it is determined that there is no leak, and if the differential pressure occurs above the specified value, it is determined that there is a leak, and the quality is determined. A leak testing method is in practical use.

According to this leakage testing method, since the measured value is obtained as a differential pressure value, it is necessary to convert the differential pressure value into a leakage rate (cc/min) in order to know the amount of leakage from a container or the like. In addition, when the standard for determining pass/fail is given as the leakage amount, the leakage amount (cc/min) serving as the standard must be converted into a differential pressure value and set as the determination reference value of the inspection device. In other words, if the test is simply asking whether there is a leak in the container to be inspected, it will function effectively as it only needs to be tested based on the presence or absence of differential pressure, but if you want to measure the amount of leakage, or If the allowable value is given by the amount of leakage, it is necessary to convert the differential pressure value to the amount of leakage, which is a tedious task.

[0004] For this reason, the present applicant has filed a patent application for
No. 229: Leak Testing Device", we proposed a leak testing device that can directly read and display the amount of leakage (cc/min) leaking from a container to be tested. FIG. 7 shows the configuration of the previously proposed leakage testing device. In the figure, reference numeral 11 indicates an air pressure source that generates positive or negative air pressure. The air pressure generated by the air pressure source 11 is transferred to the pressure reducing valve 12.
and two branch pipes 22 which are divided into two through the three-way solenoid valve 13.
, 23, and the air pressure given to the two branch pipes 22, 23 is supplied to the first control valve 1 constituted by a two-way solenoid valve.
4 and the second control valve 15 to the test container 16 and the reference tank 17. Further, a pressure difference between the container to be inspected 16 and the reference tank 17 is detected by a differential pressure detector 18, and the detected signal is amplified by an amplifier 19. The configuration up to this point is the same as a general differential pressure detection type leak testing device.

The characteristic configuration of the leakage testing device proposed earlier is that a volume change adder 24 is attached to the piping on the side of the container 16 to be tested.
and that an arithmetic processing unit 25 is provided in the signal system of the differential pressure detector 18. The volume change adder 24 operates to change the internal volume of the container to be inspected 16 by a certain amount in response to the switching operation of the three-way solenoid valve 26.

That is, a chamber 27 communicates with the container 16 to be inspected, and a chamber 29 communicates with the pneumatic source 11 through the three-way solenoid valve 26.
When the three-way solenoid valve 26 is opened to increase the pressure in the chamber 29, the piston 31 moves to the right. It moves back and forth inside, changing the volume of the chamber 27.

[0007] 33 indicates a micrometer head. This micrometer head allows the piston rod 32
The amount of change in the volume of the chamber 27 can be set by specifying the amount of movement of the chamber 27. The three-way solenoid valve 26 performs a switching operation between directly supplying the pressure of the air pressure source 11 to the chamber 29 and opening the chamber 29 to the atmosphere. Normally, chamber 29 is at atmospheric pressure. Therefore, the piston is pushed to the left by the spring 40, and the piston 31 is in contact with the left wall.

To change the internal volume of the container 16 to be inspected by a certain amount, the three-way solenoid valve 26 is operated to apply pressure from the air pressure source 11 to the chamber 29 . The pressure in the chamber 29 overcomes the force of the spring 40, causing the piston 31 to move rightward and stop at the position set by the micrometer head 33. As the piston rod 32 withdraws, the internal volume of the chamber 27 increases by the amount by which the piston rod 32 withdraws.

When measuring the equivalent internal volume, the container to be inspected 1
6, install a non-defective product with no leakage, and place the container to be inspected 1.
6 and the reference tank 17, the first control valve 14 and the second control valve 15 are closed. In this state, the internal volume of the chamber 27 is changed. A change in the volume of the chamber 27 causes a change in the internal volume including the piping on the side of the container 16 to be inspected. If the internal volume change is ΔV and the generated differential pressure is ΔP, the equivalent internal volume VE can be determined by equation (1).

VE=(1.03+P)ΔV/ΔP……(1)P:
Test pressure [kg/cm2 G] ΔV: Volume change [cc] ΔP: Generated differential pressure [kg/cm2] The differential pressure ΔP is detected by the differential pressure detector 18, and the amplifier 1
9 and is amplified and provided to the AD converter 34. The differential pressure signal converted into a digital signal by the AD converter 34 is input to the arithmetic processing unit 25 .

[0011] The arithmetic processing unit 25 can be constituted by, for example, a microcomputer. As is well known, a microcomputer includes a central processing unit 25A, a ROM 25B that stores a program for operating the central processing unit 25A in a predetermined order, a RAM 25C that stores input data and processed data, and an input port 25D. and an output port 25E.

When measuring the equivalent internal volume of the container 16 to be inspected, the microcomputer constituting the arithmetic processing unit 25 is operated in an equivalent internal volume measuring mode. In the equivalent internal volume measurement mode, when differential pressure data is input to the input port 25D, the central processing unit 25A uses the test pressure P input in advance from the keyboard 35 and the volume change amount ΔV of the chamber 27 to calculate the equivalent internal volume VE. Calculate. The calculated equivalent internal volume VE is stored, for example, in the RAM 25C, and if necessary, written and saved in an externally provided RAM card or magnetic disk (not particularly shown).

If there are various types of containers 16 to be inspected with different internal volumes, the equivalent internal volume VE is measured for each type of container to be inspected, and the equivalent internal volume VE is stored in the RAM 25C or other storage means. By determining the equivalent internal volume VE, the arithmetic processing unit 25 can calculate the leakage amount ΔQ [cc/min] from equation (2) shown below when operating in the inspection mode.

ΔQ=VE (ΔP/1.03)60/T3
(2) By displaying this calculation result on the display 36, the leakage amount of the container 16 to be inspected can be directly read and displayed.

[0015]

The previously proposed leakage display type leakage testing device uses a volume change adder 24 to determine the equivalent internal volume of the container 16 to be tested. The volume change adder 24 can set various amounts of change in volume by adjusting the micrometer head 33. By the way, various internal volumes of the containers 16 to be inspected are subject to inspection. The volume change provided by the volume change adder 24 is required to be approximately 0.5 to 1.0% of the internal volume of the container to be inspected. Therefore, when the internal volume of the container 16 to be inspected is large, the volume change amount ΔV of the volume change adder 24 must also be increased. Further, when the internal volume of the container 16 to be inspected is small, the volume change amount ΔV of the volume change adder 24 must be small.

The volume change amount ΔV of the volume change adder 24 can be adjusted by adjusting the micrometer head 33 as described above, but the adjustment range is limited. Therefore, if there are various types of containers 16 to be inspected, ranging from large to small internal volumes, it is necessary to prepare volume change adders 24 with different volume setting ranges.

[0017] Furthermore, it is necessary to replace the container 24 to be inspected each time, which is troublesome. Further, in the case of a container that must be inspected using negative pressure, even if a volume change is applied by the volume change adder 24, a pressure change cannot be generated. Therefore, when inspecting using negative pressure, there is a drawback that an inspection method that directly reads and displays the amount of leakage cannot be used. The purpose of this invention is to eliminate the need to replace the volume change adder even if the internal volume of the container to be inspected is large or small, and to directly read and display the leakage amount on a leakage testing device of the type that tests using negative pressure. This paper proposes a method for calibrating a leak inspection device that can perform the following steps.

[0018]

[Means for Solving the Problems] In the present invention, a small leak valve whose leakage amount has been calibrated in advance is used in place of the volume change adder. This minute leak valve has a flow rate of 0.1 cc to several cc per minute.
The leak amount is set so that a minute leak of about c is obtained. By providing this minute leak valve, for example, in the piping on the side of the container to be inspected, the air pressure on the side of the container to be inspected can be changed over time, and a phenomenon equivalent to changing the internal volume of the container to be inspected can be obtained. Can be done.

Therefore, a certain period of time T3 is defined from the timing when the differential pressure value is reset to zero, and after the elapse of this certain period of time T3, the differential pressure value ΔP (mmH2O) is calculated by the arithmetic processing unit 25.
The equivalent internal volume VE can be obtained by reading in the equation (3) and calculating the equation (3). VE =1.03(ΔQ/ΔP)T3/60...
(3) ΔQ: Leakage amount of minute leak valve (cc/min) T3
: Detection time (seconds) Therefore, according to the calibration method of the present invention, the equivalent internal volume of the container to be inspected from large to small can be determined by simply changing the time T3 for leaking from the minute leak valve. Furthermore, calibration can be performed even when the air pressure source 11 is under negative pressure.

[0020]

[Embodiment] FIG. 1 shows an embodiment of the present invention. In FIG. 1, parts corresponding to those in the figure are designated by the same reference numerals, and redundant explanation thereof will be omitted. A feature of this invention is a structure in which a minute leak valve 37 is provided in the piping on the side of the container 16 to be inspected. That is, this side shows the case where the minute leak valve 37 is connected to the piping of the container 16 to be inspected via the two-way valve 38. The two-way valve 38 is controlled to be open in the calibration mode, and allows the minute leak valve 37 to communicate with the piping of the container 16 to be inspected in the calibration mode.

As the minute leak valve 37, for example, ``Minute Leak Valve'' proposed by the applicant of the present application No. 1-87260 can be used. 2 to 5 show the structure of the previously proposed micro leak valve. In FIG. 2, 1 indicates a metal block. The metal block 1 has a cross-sectional shape, for example, as shown in FIG. 3, where the body of a cylindrical body is cut off at 180° opposing positions.

Coaxial holes 2A and 2B are formed on both end faces of the metal block 1, and female threads 3A and 3B are formed on the inner peripheral surfaces of the holes 2A and 2B. A joint 20 shown in FIGS. 4 and 5 is connected to the female threads 3A and 3B. Hole 2A, 2
A thin tube through hole 4 is formed at the back of B, and this thin tube through hole 4 communicates between the holes 2A and 2B. The thin tube 5 is passed through the thin tube through hole 4. For example, the thin tube 5 has an outer diameter of 0.8 mm.
A stainless steel pipe with an inner diameter of 0.5 mm can be used. The thin tube through hole 4 is formed to have an inner diameter slightly larger than the outer diameter of the thin tube 5, and the sealing material 6A,
6B seals between the outer periphery of the thin tube 5 and the inner wall of the thin tube through hole 4. O-rings can be used as the sealing materials 6A and 6B, and the O-rings are pressed against the inner wall surface of the capillary through hole 4 with seal retainers 7A and 7B formed by ring-shaped screws, and the O-rings are pressed against the inner wall surface of the capillary tube through hole 4 and the outer periphery of the capillary tube 5 and the capillary through hole are sealed. A seal is formed between the inner wall of the hole 4 and the inner wall of the hole 4.

A threaded hole 8 formed in a direction perpendicular to the thin tube through hole 4 communicates with the thin tube through hole 4 . A screw 9 is screwed into the screw hole 8, and by tightening the screw 9, the thin tube 5 can be crushed. In this example, a piece 9A made separately from the screw 9 is connected to the tip of the screw 9, and the tightening force of the screw 9 is applied to the thin tube 5 via the piece 9A. By inserting the piece 9A in this way, the twisting force of the screw 9 is not directly applied to the thin tube 5,
This is to prevent an accident of threading the thin tube 5.

FIG. 6 shows a measuring device for calibrating the leakage amount of the minute leakage valve. In this measuring instrument, a transparent outer cylinder 41 is installed on the upper surface of a base 40, and a transparent inner cylinder 42 is installed in the axis of this outer cylinder 41 as well. The upper end of the inner cylinder 42 is sealed with a lid 43, and the outer cylinder 41 and the inner cylinder 42 communicate with each other at the lower end. A thin tube 5 extending from a minute leak valve is inserted upward into the inner cylinder 42 . Liquid is sealed in the outer cylinder 41 and the inner cylinder 42 up to the position indicated by F.

By feeding air into the inner cylinder 42 through the minute leak valve, the liquid level within the inner cylinder 42 gradually drops from the position indicated by F. By attaching a scale corresponding to the volume inside the inner cylinder 42 to the outer cylinder 41, the amount of air accumulated in the inner cylinder 42 can be measured. It is possible to measure minute amounts of air such as .1cc to 1cc.

As mentioned above, according to this micro-leak valve, since the part that should become the throttle is formed by crushing the thin tube 5, it is possible to stably maintain a micro-cross-sectional area, and therefore the amount of micro-leakage can be accurately controlled. Can be set to . Moreover, by loosening the screw 9 while the thin tube 5 is being crushed, the thin tube 5 returns to its original state. Therefore, the cross-sectional area of the thin tube 5 can be set arbitrarily, and the amount of leakage can be set freely. Further, by using the calibrator shown in FIG. 6, minute leaks can be set accurately.

The explanation returns to FIG. 1 again. In order to obtain the equivalent internal volume on the side of the container to be inspected 16, the following operation is performed. A leak-free container is selected as the container 16 to be inspected and connected. Open the three-way solenoid valve 13, the first control valve 14, and the second control valve 15,
The air pressure generated by the air pressure source 11 is applied to the container 16 to be inspected and the reference tank 17. When a predetermined period of time (about 1 to 2 seconds) has elapsed, the first control valve 14 and the second control valve 15 are closed to disconnect the air pressure source 11 from the container to be inspected 16 and the reference tank 17.

In this state, the pressure inside the test container 16 and the reference tank 17 is stabilized (for about 1 to 2 seconds). At the timing when the air is expected to be stabilized, the detection voltage output from the differential pressure detector 18 is forcibly reset to zero on the input side of the amplifier 19, and at the timing of this zero reset, the two-way electromagnetic circuit 38 is opened to Air pressure is applied to the leak valve 37 to leak air from the side to be inspected at a pre-calibrated leakage amount (in the case of negative pressure, air enters the container to be inspected 16 from the outside air).

[0029] Predetermined time (T3 seconds) from the start of leakage
At the time when the differential pressure value ΔP has elapsed, the differential pressure value ΔP is taken into the arithmetic processing unit 25. By specifying the time T3, the amount of air ΔQ (cc/
T3) is defined. Therefore, the calculation of equation (3) can be performed by reading the differential pressure ΔP after the time T3 (seconds) has elapsed. The equivalent internal volume VE of the container 16 to be inspected can be determined by calculating equation (3).

By determining the equivalent internal volume VE of the container 16 to be inspected, it is possible to switch to the inspection mode. Note that the equivalent internal volumes VE of the containers 16 to be inspected of various sizes are determined in advance, and each equivalent internal volume VE is calculated by the arithmetic processing unit 25.
By storing this in the memory, it is possible to directly enter the inspection mode without performing calibration afterwards.

[0031]

As explained above, according to the present invention, in the leakage testing device that calculates the equivalent internal volume of the container 16 to be inspected and directly reads and displays the amount of leakage of the container 16 to be inspected based on this equivalent internal volume, Since the volume change adder used for calibration is replaced with the minute leak valve 37, the amount of air leaked through the minute leak valve can be freely set depending on the length of time.

Therefore, if the volume of the container 16 to be inspected is large, the time T3 may be set longer. Furthermore, if the volume of the container 16 to be inspected is small, the time T3 may be shortened. As a result, regardless of the volume of the container 16 to be inspected, the equivalent internal volume V of the container 16 to be inspected is
This provides the advantage of being able to perform a calibration to determine E. Further, since the minute leak valve 37 is provided, calibration can be performed using the minute leak valve 37 in the inspection mode. That is, by comparing the leakage amount ΔQ calculated by the arithmetic processing unit 25 with the leakage amount of the minute leak valve 37, the sensitivity of the measurement system can be calibrated and checked.

[Brief explanation of drawings]

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

FIG. 2 is a sectional view for explaining the structure of a minute leak valve used in the present invention.

FIG. 3 is a front view of the minute leak valve shown in FIG. 2.

4 is a sectional view for explaining the structure of a joint used in the minute leak valve shown in FIG. 2. FIG.

FIG. 5 is a front view of FIG. 4.

6 is a sectional view for explaining the structure of a calibrator used when calibrating the minute leak valve shown in FIG. 2. FIG.

FIG. 7 is a block diagram for explaining a conventional technique.

[Explanation of symbols]

11 Pneumatic source 12 Pressure reducing valve 13 3-way solenoid valve 14 First control valve 15 Second control valve 16 Container to be inspected 17 Standard tank 18 Differential pressure detector 19 Amplifier 25 Arithmetic processing unit ３７　　　　Minute leak valve

Claims (1)

[Claims] Claim 1: A measurement system comprising: a pneumatic source that generates positive or negative pneumatic pressure; and a leak-free test container connected to the terminal end of which the pneumatic pressure supplied from the pneumatic source is supplied through a first control valve. Measure the pressure difference between the side piping, the reference side piping to which air pressure from the air pressure source is applied through the second control valve and the reference container is connected to the terminal end, and the reference side piping and the measurement piping. In a leak inspection device equipped with a differential pressure detector, a small leak valve is installed in the measurement side piping,
By leaking a known amount of air per unit time through this minute leak valve, a differential pressure is generated between the measurement side piping and the reference side piping, and the differential pressure value generated within a certain time and the minute leak valve are A method for calibrating a leak testing device, in which the equivalent internal volume of the measurement side piping is determined as a calibration value based on the amount of air leaking through the pipe.