JP3422348B2 - Leak inspection method and device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leak inspection method used for inspecting various containers for leaks and a leak inspection apparatus using the leak inspection method.

[0002]

2. Description of the Related Art Conventionally, equal air pressures are applied to an object to be inspected and a leak-free reference tank having the same internal volume as the object to be inspected, and a pressure difference generated between the two is detected by a differential pressure detector. A leak inspection device of a type that determines whether or not there is a leak in an object to be inspected by detecting the leak is in practical use.

According to the leak detection device adopting the differential pressure detection method, the detection output signal of the differential pressure detector is 0 if there is no differential pressure, so that the amplifier does not saturate even when amplified by the high sensitivity amplifier. Whether or not a differential pressure is generated can be detected with high sensitivity. As a result, there is an advantage that even a minute leak can be detected with high sensitivity. By the way, when the method of detecting the presence or absence of the differential pressure between the leak-free reference tank and the inspected object is adopted, since the reference tank is repeatedly supplied with air pressure, the temperature of the reference tank gradually rises, Since the air on the side of the reference tank thermally expands due to the temperature rise, there is a disadvantage that a differential pressure is generated between the inspected object and the inspected object even if there is no leakage.

As described above, according to the method using the reference tank, a temperature difference in the reference tank causes a differential pressure, which causes a phenomenon that the zero point fluctuates. In order to eliminate the fluctuation of the zero point, the present applicant sequentially accumulates and stores the drift value of the zero point, and uses the stored zero drift value to cancel the zero drift. Has been developed and put into practical use.

Even if the fluctuation of the zero point can be eliminated, the method using the reference tank has a disadvantage that only one inspected object can be inspected by one inspection. That is, there is a drawback that the inspection efficiency is low. In order to eliminate this drawback, a method of inspecting two inspected objects at one time by supplying air to the two inspected objects and determining whether a differential pressure is generated between them is considered. When using this inspection method, 2 at a time
The efficiency of the inspection is doubled because individual inspection objects can be inspected. However, since the new inspection object is replaced for each inspection, the two inspection objects can be inspected at the same temperature. As a result, there is an advantage that the fluctuation of the zero point can be reduced.

However, this inspection method has the following disadvantages. In other words, there is a disadvantage that it is determined that there is no leakage even when the two inspection objects have the same leakage. In order to eliminate this inconvenience, the applicant of the present invention has filed “Japanese Patent Application No. 87422/1993: Name, Leakage Inspection Device” (1995
Public announcement decision on September 5, 2013) was proposed. FIG. 3 shows the configuration of the leak inspection device previously proposed. The leak inspection apparatus proposed above is configured to inspect the two inspection objects 9A and 9B for leakage by commonly using one reference tank 11. For this purpose, a differential pressure detector 12A is connected between the inspection object 9A and the reference tank 11, and a differential pressure detector 12B is also connected between the reference tank 11 and the inspection object 9B. The differential pressure detectors 12A and 12B detect whether or not a differential pressure is generated between each inspected object 9A and the reference tank 11 and between the reference tank 11 and the inspected object 9B to detect two inspected objects at a time. 9A and 9B are configured to be inspected.

In FIG. 3, 1 is an air pressure source, 2 is a pipe line, and 3 is a pipe line.
Is a pressure regulating valve, 4 is a three-way solenoid valve, 5 is a branch device, 6A, 6
B, 7 and 6A ', 6B', 7'are branch pipes, 8A, 8
B and 8C are cutoff valves, 13 is an amplifier, 14 is a pass / fail judgment device, 15 is its display, 16 is a controller, and 19 is an analog adder.

[0008]

According to the leak inspection apparatus proposed above, two differential pressure detectors 12A and 12B are required. Since the differential pressure detector is an expensive component in the leak inspection device, there is a disadvantage that the cost is increased by using two of them. Further, in the previous proposal, when the two differential pressure detectors 12A and 12B are present, the detection output signal is reversed in polarity and added by the adder 19. Therefore, for example, when the temperature of the reference tank 11 rises. On the other hand, the advantage of eliminating the influence of zero drift can be obtained. However, if there is an equivalent leak in both of the two inspection objects 9A and 9B, the output of the adder 19 becomes zero. There is an inconvenience that the leak state cannot be detected.

Therefore, in the above proposal, the differential pressure detector 12A is used.
A simple determination means for separately monitoring the detection output of each of 12 and 12B is added, and the presence or absence of leakage is determined by whether or not the detection output of the simple determination means exceeds a predetermined value to eliminate the inconvenience. There is. Therefore, it is necessary to add a simple determination means, and there is a drawback that the cost is increased accordingly.

An object of the present invention is to provide a leakage inspection apparatus having a structure capable of inspecting two inspected objects at the same time, using only one differential pressure detector, and two inspected objects still have the same leakage. However, a leak inspection method that can detect this,
It is intended to provide a leak inspection device.

[0011]

According to the present invention, the air pressure stored in the air pressure source is distributed to a pair of branch pipes, and the air pressure is distributed to the pair of branch pipes to supply the air pressure to the object to be inspected. In the leakage inspection method, in which the difference in air pressure between the two is detected by a differential pressure detector, and the occurrence of the differential pressure is detected to determine that there is a leak in either one of the pair of DUTs, Whether or not a leak-proof reference tank is connected to the device under test through a first shutoff valve and a second shutoff valve that operate as switching means, and whether a differential pressure is generated between the devices under test in the initial state If the occurrence of differential pressure is detected, the inspected object with leakage is specified by the polarity of the differential pressure, the inspected object determined to be defective is replaced with a new inspected object, and the Inspect for the occurrence of differential pressure between alternate test bodies, and detect the occurrence of differential pressure. In this case, switch the switching means to disconnect the DUT from the branch pipe, and instead connect the reference tank to the branch pipe to detect the differential pressure between the reference tank and the DUT connected to the other branch pipe. However, if no differential pressure is generated, it is determined that the pair of inspected objects connected to it is leak-free, and if differential pressure is generated, the pair of inspected objects connected to it is both It proposes a leak inspection method that determines that there is an equivalent leak.

The present invention further proposes a leakage inspection apparatus using this leakage inspection method. The leak inspection apparatus according to the present invention is connected between a pneumatic source for supplying air pressure to a pair of branch pipes, a pair of inspection objects connected to the ends of the pair of branch pipes, and a pair of branch pipes. The differential pressure detector and the first cutoff valve inserted on the side of the object to be inspected from the connection point of the differential pressure detector of either one of the pair of branch pipes, and the differential pressure detector side from the insertion point of the first cutoff valve A reference tank connected via a second cutoff valve connected to the, and a judgment means for amplifying the detection output signal of the differential pressure detector and judging whether or not there is a leak, and opening the first cutoff valve and the second cutoff valve. While controlling, the air pressure from the air pressure source is applied to all of the reference tank and the pair of inspected objects, and after the pressurization, the second shutoff valve is closed to disconnect the reference tank from the branch pipe,
A controller for inspecting a pair of objects to be inspected for leak, and executing a control to close the first shutoff valve and open the second shutoff valve if no differential pressure is generated by this examination.

According to the leakage inspection method and the leakage inspection device of the present invention, it is inspected in the initial state whether or not a differential pressure is generated between the pair of inspection objects. When a differential pressure is generated by this inspection, it is possible to specify that any one of the inspection objects has a leak according to the polarity of the differential pressure.
Therefore, the inspected object having the leakage is removed, a new inspected object is connected, and the air pressure is applied again to detect the occurrence of the differential pressure. If no differential pressure is generated, it can be seen that either the pair of inspected objects connected thereto has no leakage, or both have the same leakage.

In order to confirm which of these is the case, in the present invention, one of the test objects is separated from the measurement system by the first shutoff valve,
The second cutoff is opened and the reference tank is connected to inspect whether a differential pressure is generated between the reference tank and the other object to be inspected.
If a differential pressure does not occur in this state, it can be determined that there is no leakage in the pair of inspected objects connected thereto. When the differential pressure is generated, it can be determined that both of the inspection objects have the same leakage. In this way, it is possible to inspect the presence or absence of leakage of two inspection objects by one inspection.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail with reference to the embodiment shown in FIG. In FIG.
The parts corresponding to are indicated by the same reference numerals. In this embodiment, a bipolar valve 21 is used instead of the three-way solenoid valve 4 shown in FIG. 3 to intermittently control the air pressure of the air pressure source 1. The bipolar valve 21 has two valves built therein and has a structure for simultaneously controlling the opening and closing of the two valves. Therefore, the branch pipes 6A and 6B are connected to the output sides of the two valves, and the branch pipes 6A and 6B are connected.
Air pressure is supplied to the inspection objects 9A and 9B and the reference tank 11 through B.

A differential pressure detector 12 is connected between the branch pipes 6A and 6B, and an exhaust bipolar valve 22 is also connected. By controlling the exhaust bipolar valve 22 to open, the inspection object 9A,
The air pressure applied to 9B and the reference tank 11 is released to the atmosphere. The feature of the present invention is that the first shutoff valve 8A and the second shutoff valve 8 are provided for one of the inspection object 9A and the reference tank 11.
The air pressure is supplied via B, and the air pressure is directly supplied from the bipolar valve 21 to the other test object 9B.

The connection point between the first cutoff valve 8A and the second cutoff valve 8B and the branch pipe 6A is closer to the object 9A than the connection point of the exhaust bipolar valve 22. Branch pipe 6 of differential pressure detector 12
The connection point to A and 6B is selected on the air pressure source 1 side from the connection point of the exhaust bipolar valve 22. In this way, by assuming each connection point, water droplets and the like generated on the inspected objects 9A and 9B and the reference tank 11 side during exhaust are discharged by the exhaust bipolar valve 22 to protect the differential pressure detector 12. You can

Further, in this embodiment, the bipolar valves 21, 22 and the first shutoff valve 8A and the second shutoff valve 8B are valves which are controlled to open and close by using air pressure. By using the air pressure control type valve as described above, heat is not generated during the opening / closing control unlike the solenoid valve, and thus the air pressure can be operated without being changed by heat. The operation of the leakage inspection method according to the present invention and the operation of the leakage inspection apparatus using this inspection method will be described with reference to FIG.

FIG. 2A shows the opening / closing control of the bipolar valve 21. At the time points T _{1 to} T ₈ shown in FIG. 2, one inspection period is shown. The inspected bodies 9A and 9B are connected to the ends of the branch pipes 6A and 6B, and the inspection is started from timing T1. At the inspection start timing T ₁ , the bipolar valve 21 is opened and the exhaust bipolar valve 22 is opened.
Is closed, the first shutoff valve 8A is opened, and the second shutoff valve 8B is opened.

The bipolar valve 21 is controlled to be in an open state between timings T _{1 and} T _2, and air pressure is applied to the inspection objects 9A and 9B and the reference tank 11 during that time. When the air pressure becomes stable, the bipolar valve 21 is controlled to be closed, and the pneumatic source 1 is disconnected from the measurement system. At the same time, the second shutoff valve 8B is also controlled to be closed, and the reference tank 11 is disconnected from the measurement system. Therefore, only the two test objects 9A and 9B are connected to the differential pressure detector 12.

Timings T _{2 to} T ₃ are the stable process after pressurization. In this stable process, the determination device 14 determines whether or not a large differential pressure is generated. After it passed the timing T ₂ through T _3, to increase the gain of the amplifier 13, the determination device 1
At 4, the differential pressure detection operation is executed. If the value of the differential pressure does not exceed the predetermined value between the timings T ₃ and T _4, it is determined that the inspection objects 9A and 9B have no leakage or both have the same degree of leakage.

When a pressure difference of a specified value or more occurs up to the timing T ₄ , the inspected object 9 connected at that time
It can be determined that there is a leak in either A or 9B. The location of the leak can be specified by the polarity of the differential pressure. For example, when the diaphragm swings to the branch pipe 6A side, a positive differential pressure detection signal is generated in the differential pressure detector, and when the diaphragm swings to the branch pipe 6B side, a negative differential pressure detection signal is output. Then, it is possible to determine which of the inspection objects is leaking according to the polarity of the differential pressure. By identifying the leaking test object, the leaking test object is removed, a new test object is connected, and the test is restarted from the initial state.

[0023] with a differential pressure equal to or greater than a predetermined value until the timing T ₄ is a first shut-off valve 8A is controlled to the closed at the timing T ₄ to be generated to control the second shut-off valve 8B on behalf of the open, The bipolar valve 21 is also controlled to open. By this control, the inspection object 9A is separated from the measurement system, and the inspection object 9A
Instead of, the reference tank 11 is connected to the measuring system. Therefore, after the timing T ₄ , the reference tank 11 and the device under test 9B are connected to the measurement system.

Between the timings T ₄ and T ₅ , the bipolar valve 21 is controlled to open again, and the reference tank 11 and the inspection object 9 are controlled.
Air pressure is applied to B to pressurize. This timing is the shutoff valve 8
It is a time provided to cancel the pressure fluctuation due to the operation of A and 8B, and may be about 0.5 seconds. Timing T _{5 to} T ₆ is the equilibrium stroke, and the bipolar valve 2
It is provided as a time for canceling the pressure fluctuation caused by the operation of No. 1 and may be about 0.5 seconds.

When the timing T ₆ has passed, the gain of the amplifier 13 is increased again, and the judging device 14 judges whether or not a slight differential pressure is generated. If the differential pressure equal to or more than the specified value does not occur until the timing T _7, it is determined that the inspected body 9B has no leakage, and as a result, the inspected body 9A can also be determined to have no leakage. If a differential pressure equal to or higher than the specified value occurs up to the timing T ₇ , the object to be inspected 9
B can be determined to have a leak, and in this case, the inspected body 9A is also determined to have a leak.

At timing T ₇ , the exhaust bipolar valve 22 and the first
The shutoff valve 8A and the second shutoff valve 8B are controlled to be open to control the inspection object 9
Air is discharged from A and 9B and the reference tank 11.
In addition, in this embodiment, the bipolar valve 21 is also controlled to open, and the air pressure source 1
A case is also shown in which air is discharged from the device and the air from the inspection objects 9A and 9B and the reference tank 11 is controlled so as to be prevented from flowing into the differential pressure detector 12 side.

[0027]

As described above, according to the present invention, two inspection objects 9A and 9B are inspected by one inspection, even though only one differential pressure detector is used. be able to. Therefore, it is possible to provide a leak inspection device having high inspection efficiency despite the low manufacturing cost.

Further, in the present invention, the inspection result of the two inspection objects 9A and 9B is clearly specified to be no leak or there is a leak, although it is constituted by one differential pressure detector. be able to. Therefore, it is possible to obtain superior operational effects to the previously proposed leak inspection device.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining a leakage inspection method and a leakage inspection device according to the present invention.

FIG. 2 is a waveform chart for explaining the operation of FIG.

FIG. 3 is a block diagram for explaining a conventional technique.

[Explanation of symbols]

1 Air pressure source 2 pipelines 6A, 6B Branch pipe 8A, 8B 1st cutoff valve, 2nd cutoff valve 9A, 9B Inspection object 11 Standard tank 12 Differential pressure detector 13 Amplifier 14 Judgment device 15 Indicator 16 Controller 21 Bipolar valve 22 Exhaust bipolar valve

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01M 3/26

Claims (2)

(57) [Claims] 1. An air pressure stored in an air pressure source is distributed to a pair of branch pipes, the air pressures distributed to the pair of branch pipes are supplied to an object to be inspected, and a difference in air pressure between the two is detected by a differential pressure detector. In the leakage inspection method, which detects the occurrence of differential pressure and determines that there is a leak in one of the pair of inspected objects, the one of the pair of branch pipes is in contact with the pair of inspected parts. If a leak-free reference tank is connected to one of the inspection objects via a shut-off valve, and if no differential pressure is detected between the pair of inspection objects, the reference tank and the other inspection object If the differential pressure is not generated, it is determined that the pair of inspected objects are not leaked, and if the differential pressure is generated, the pair of inspected objects is checked. A leak inspection method characterized by determining that there is a leak. 2. A. An air source for supplying air pressure to the pair of branch pipes, and B. A pair of inspection objects connected to the ends of the pair of branch pipes; A differential pressure detector connected between the pair of branch pipes, and D. A first cutoff valve inserted between a connection point of the differential pressure detector on any one of the pair of branch pipes and an object to be inspected; E. A reference tank connected through a second shutoff valve connected to the differential pressure detector side from the insertion point of the first shutoff valve, and F. Determination means for amplifying the detection output signal of the differential pressure detector and determining the presence or absence of leakage; G. The first shutoff valve and the second shutoff valve are controlled to be open, the air pressure from the pneumatic pressure source is applied to all of the reference tank and the pair of inspected objects, and the second shutoff valve is turned on after the pressurization. The control is performed by closing and disconnecting the reference tank from the branch pipe, inspecting a pair of inspected objects for leakage, and closing the first shutoff valve and opening the second shutoff valve if no differential pressure is generated by this inspection. A leak checking apparatus comprising: a controller for executing the leak checking apparatus.