JPH081407B2 - Leak inspection 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 device used for automatically inspecting various containers for leaks.

[0002]

2. Description of the Related Art When inspecting a container or the like for the presence or absence of leakage, a method is conceivable in which, for example, air is supplied to the container to be inspected and the decrease in pressure is read to determine the presence or absence of leakage. However, it is difficult to accurately read out the decrease in air pressure applied to the object to be inspected. In particular, in order to detect a minute leak, it is even more difficult to detect a slight drop in the applied pressure value.

As a method for solving this drawback, a method using a differential pressure detector has been conventionally adopted. The differential pressure detection method applies equal air pressure to the container to be inspected and a leak-free reference container equivalent to this, and measures the pressure difference between the two to detect the drop in pressure on the container to be inspected. There is a leak "
Is a method of determining. According to this inspection method, the differential pressure detector can detect this pressure difference if there is even a slight leak in the inspection object. Therefore, a minute leak can be detected.

FIG. 4 shows a schematic structure of a conventional leak inspection apparatus. In the figure, 1 indicates an air pressure source. The air pressure generated by the air pressure source 1 is given to the adjusting valve 3 through the pipe line 2, and the adjusting valve 3
By this, the air pressure is stabilized to a constant air pressure and applied to the three-way solenoid valve 4. A branch pipe 5 is connected to the outlet side of the three-way solenoid valve 4,
The air pressure supplied from the pneumatic source 1 by the branch pipe 5 is branched into two branch paths 6 and 7.

A shutoff valve 8 is provided in each of the two branch paths 6 and 7.
A and 8B are inserted, and the air pressure output from the air pressure source 1 is applied to the device under test 9 and the reference tank 11 through the cutoff valves 8A and 8B. Shut-off valve 8A inserted in the branch paths 6 and 7,
8B (the branch path between the inspection object 9 and the reference tank 11) is referred to as branch paths 6'and 7 '. Forks 6'and 7 '
A differential pressure detector 12 is passed between the two, and branches 6'and 7 '
It is configured so that the pressure difference between the two can be measured. A pressure gauge 17 may be connected to the branch path 6'if necessary.

The detection output of the differential pressure detector 12 is amplified by the amplifier 13, and the amplified output signal is given to the pass / fail judgment device 14 to judge whether or not the inspected body 9 is leaked, and the judgment result is displayed on the display 15. It is possible to automatically display the defective product having the leakage and the good product by displaying the information or operating the good / bad sorting device. The leak inspection is performed as follows. The three-way solenoid valve 4 is controlled to a first state in which A and B are communicated with each other, and the shutoff valves 8A and 8B are controlled to be open to apply air pressure to the device under test 9 and the reference tank 11. This state is called a pressurizing mode (FIG. 5).

The shut-off valves 8A and 8B are closed after a certain time (stable mode) after pressurization. The reference tank 11 is composed of a leakproof container having the same internal volume as the device under test 9. Therefore, if there is no leak in the inspected body 9, there will be no pressure difference between the branch passages 6'and 7 ', but if there is a leak in the inspected body 9, the branch passages 6'and 7'will not flow. There is a pressure difference between them. This pressure difference is detected by the differential pressure detector 12, this detection output signal is amplified by the amplifier 13, and it is judged that there is a leak when the differential pressure detection value reaches a predetermined value or more after a lapse of a predetermined time by the quality determination device 14. Yes (inspection mode).

After completion of the inspection, the three-way solenoid valve 4 is switched to the second state in which B and C are communicated with each other, and the shutoff valves 8A and 8B are controlled to be opened so that the inspection object 9 and the reference tank 11 are provided. The air pressure is released from the exhaust port C of the three-way solenoid valve 4 (exhaust mode), one test cycle is completed, and the inspection object 9 is replaced. Reference numeral 16 is a controller for controlling these steps.

[0009]

Conventionally, the reference tank 11 is used.
Is fixed and the inspected body 9 is sequentially replaced, so that the reference tank 11 is repeatedly supplied with air pressure. The supply of this air pressure raises the temperature of the reference tank 11 and causes a temperature difference between the reference tank 11 and the object 9 to be inspected, and this temperature difference causes a disturbance such as a zero point fluctuation.

Therefore, a method in which the object 9 to be inspected is connected to the side of the reference tank 11 and two objects 9 to be inspected at the same time can be considered. According to this inspection method, since the two inspection objects 9 are exchanged at once, there is no temperature difference between the inspection objects 9. Therefore, it is possible to prevent the zero point variation from occurring due to the accumulation of temperature. However, this inspection method has a drawback in that if both the inspected bodies 9 under inspection have the same degree of leakage, the leakage cannot be detected.

The object of the present invention is provided with the features of both an inspection method for detecting a leak by detecting a pressure difference between inspection objects and an inspection method for detecting a pressure difference between a reference tank and an inspection object. It is intended to provide a leak inspection device.

[0012]

According to the present invention, one reference tank is commonly used to apply a pressure to a pair of objects to be inspected at one time to detect a pressure difference between the objects to be inspected, and a reference tank. This is a structure of an accurate leak inspection device having the advantages of the inspection method using. For this purpose, a three-way branch pipe that branches the air pressure supplied from the air pressure source into three pipe lines, a shut-off valve connected to each of the pipe lines branched by the three-way branch pipe, and the shut-off valve are taken out. A reference tank connected to one air pressure conduit, a pair of inspected objects connected to two air pressure conduits taken out through the shutoff valve, and a conduit and a reference communicating with this pair of inspected materials. It is passed to each of the pipes leading to the tank,
A pair of differential pressure detectors that respectively detect the pressure difference generated between the reference tank and each inspected object, an adder that adds the detection output of this differential pressure detector with the opposite polarity, and the adder of this adder. A determination device for determining whether or not there is a leak of the object to be inspected based on the addition result, and a first state connected between the pneumatic source and the three-way branch pipe to apply air pressure supplied from the pneumatic source to the three-way branch pipe side. Second, the air pressure source side is closed and the three-way branch pipe side is opened to the atmosphere
The three-way solenoid valve for switching to the state of 1., the three-way solenoid valve for switching to the first state, the shut-off valve to the open state, and the pressurization mode for applying air pressure to the reference tank and each inspected object, and the shut-off mode. Inspection mode in which the detection output of the differential pressure detector is measured with the valve closed to determine whether or not there is a leak in each inspected object, and the three-way solenoid valve is switched to the second state for the reference tank and each inspected object. A leak inspection device is configured by a controller that controls switching to an exhaust mode in which the given air is released to the atmosphere.

According to the structure of the present invention, the detection signals of the pair of differential pressure detectors are added by the adder, and the addition result becomes equivalent to the comparison value between the pair of inspected objects. That is, the effect of the reference tank is removed from the addition result, and a highly accurate inspection result can be obtained.

[0014]

FIG. 1 shows an embodiment of the present invention. Portions corresponding to those in FIG. 4 are designated by the same reference numerals. Therefore, controller 1
6 is the same as the conventional description in that it controls the three-way solenoid valve 4 and each of the shutoff valves 8A, 8B and 8C to control the pressurization mode, the stable mode, the inspection mode, and the exhaust mode. In this invention, a three-way branch pipe 18 is provided on the output side of the three-way solenoid valve 4. The cutoff valves 8A, 8B and 8C are respectively connected to the respective branch paths 6A, 6B and 7 of the three-way branch pipe 18. Shut-off valves 8A, 8
The branch paths on the output side that have passed B and 8C are branch paths 6A ′, 6
B ', 7'. The reference tank 11 is connected to the branch path 7 ', and the inspection objects 9A and 9B are connected to the branch paths 6A' and 6B ', respectively.

Along with this, a differential pressure detector 12A is provided between the branch passage 7'which communicates with the reference tank 11 and the branch passage 6A 'which communicates with one of the inspection objects 9A, and between the branch passage 7'and the branch passage 6B'. And 12B will be provided. Due to this connection structure, the differential pressure detector 12A is provided with the reference tank 11 and the inspection object 9
The pressure difference between A and A is detected, and the pressure difference detector 12B detects the pressure difference between the reference tank 11 and the inspection object 9B.

The feature of the present invention is that the detection output signals of these two differential pressure detectors 12A and 12B are added by an adder 19
The point is that the structure is such that the addition is performed at. That is, the differential pressure detector 1
In 2A, if there is a leak in the object 9A to be inspected, the diaphragm DF is displaced in the direction shown by the dotted line, and transmits, for example, a positive detection signal V _A. The diaphragm DF of the pressure difference detector 12B If leakage is present in the pressure difference detector 12B in the test subject 9B displaced in the direction indicated by the dotted line, transmitting the example, a negative polarity of the detection signal -V _B. These two detection signals V _A and −
V _B is added by the adder 19, and the presence or absence of leakage and the object to be inspected on the leakage side can be specified by the polarity of the addition result.

[0017] That is, there is leakage in the test subject 9A, if no leakage is to be inspected. 9B detection signal V _A of the positive polarity is transmitted, the detection signal -V _B of the negative polarity in -V _B = 0 Therefore, the addition result of the adder 19 has a positive polarity. Therefore, in this case, it can be understood that the inspection object 9A has a leak. When the inspection object 9A has no leakage and the inspection object 9B has leakage, the addition result of the adder 19 has a negative polarity.

Here, the temperature of the reference tank 11 rises as a result of repeated pressurization, and immediately after the air pressure is applied, the temperature in the reference tank 11 thermally expands due to this temperature rise, and the pressure in the reference tank 11 increases. If the pressure rises, this pressure rise causes the diaphragms DF of the two differential pressure detectors 12A and 12B to be displaced in directions opposite to each other. This diaphragm DF
The movement of the output of the adder 19 is _VA + (-V _B )
= 0. That is, it can be seen that the temperature rise of the reference tank 11 or the disturbance caused by the deformed pipe is removed. Therefore, according to the configuration of the present invention, it is equivalent to measuring the pressure difference between the objects to be inspected 9A and 9B, and it is possible to obtain a highly accurate inspection result in which the temperature rise of the reference tank 11 and the disturbance due to the deformation pipe are removed.

Therefore, the addition result of the adder 19 is output to the amplifier 13
By amplifying the input signal and inputting the amplified output to the quality determination device 14, the polarity of the signal input in the quality determination device 14 and whether or not there is a leak in the inspection object 9A or 9B depending on the voltage value. It is possible to determine whether or not the leakage amount is within the allowable range, and the determination result is displayed on the display unit 15 for example.
Can be displayed on. FIG. 2 shows an example of the display on the display unit 15. The leak amount of the inspection object 9A is displayed on the positive side of the indicator, and the leakage amount of the inspection object 9B is displayed on the negative side. Therefore, when the pointer 15A is swung to the positive side, it indicates that the inspected body 9A has a leak, and when it is swung to the negative side, the inspected body 9B is leaked. When the instruction 15A swings to the defective zone, it is determined to be defective. It is also possible to use the determination result of the quality determination device 14 to operate the branching device provided on the conveyance path of the inspected objects 9A and 9B to automatically sort defective products into defective products.

In the above description, the case where there is a leak in both the inspected bodies 9A and 9B was not mentioned, but the differential pressure detector 1
By providing a judging device for judging whether the detection outputs of 2A and 12B are good or bad, it is possible to detect both the leaks of the inspection objects 9A and 9B. The determination device for individually determining the presence or absence of leakage is provided as an auxiliary, and may have a simple structure that merely displays the presence or absence of leakage.

FIG. 3 shows a modified embodiment of the present invention. In this example, the three-way solenoid valve 4 and the branch passage 7 leading to the reference tank 11
And 7'are provided independently for the inspection object 9A and 9B. With this configuration, each branch 6
A, 6B and 7, 7'each internal volume (air injection amount) is equalized, and at the time of pressurization, air is supplied to each branch path 6A, 6B,
6A ', 6B' and 7, 7'are evenly injected. Each branch 6A, 6B, 6A ', 6B' and 7,
By equalizing the injection amount of air to 7 ',
The generation of reflected waves of air is reduced, the pressure in the pipeline is quickly stabilized during pressurization, and the inspection mode can be completed in a short time. In this respect, there is an advantage that the inspection speed can be improved.

In the above embodiment, one reference tank 1 is used.
Although the embodiment in which two test objects are provided for one has been described, the number of test objects may be an even number, and the number of test objects is not limited to two. When inspecting two or more even inspected objects, an adder 19, a determination device 14, and a display 15 may be provided for every two inspected objects. The pneumatic pressure source 1, the adjusting valve 3, the reference The tank 11 etc. can be shared.

[0023]

As described above, according to the present invention, each of the two objects 9A and 9B to be inspected and the reference tank 11 are provided.
Reference tank 1 despite measuring the pressure difference between
It is possible to remove the disturbance caused by the temperature rise, deformation, etc. Since the test objects 9A and 9B are replaced after each test, the test objects can be operated at the same temperature and the same condition. Therefore, there is an advantage that the object to be inspected can be accurately inspected. Naturally, as the apparatus, the branch paths 6B and 6B 'for giving air pressure to the object to be inspected, the differential pressure detector and the adder 19
Since it is only necessary to add, there is an advantage that the cost required for the inspection can be reduced.

[Brief description of drawings]

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

FIG. 2 is a front view showing an example of a display device used in the multiple leak type inspection device according to the present invention.

FIG. 3 is a system diagram showing a modified embodiment of the present invention.

FIG. 4 is a system diagram for explaining a conventional technique.

FIG. 5 is a timing chart for explaining the operation of the leak inspection device.

[Explanation of symbols]

 1 Air pressure source 2 Pipe line 3 Regulator valve 4 Three-way solenoid valve 6A, 6B, 6A ', 6B' Branch line 7, 7 'Branch line 8A-8C Shutoff valve 9A, 9B Inspected body 11 Reference tank 12A, 12B Differential pressure Detector 13 Amplifier 14 Pass / Fail Judgment Device 15 Indicator 16 Controller 18 Three-way Branch Tube 19 Adder

Claims (1)

[Claims] 1. A. First Embodiment A three-way branch pipe for branching the air pressure given from an air pressure source into three directions; A shutoff valve connected to each of the pipelines branched by the three-way branch pipe; A reference tank connected to one line of pneumatic pressure taken through this shut-off valve; D. A pair of objects to be inspected connected to the two air pressure pipes taken out through the shutoff valve, and E. A pair of pipes that are respectively passed between the pipe communicating with the pair of inspection objects and the pipe communicating with the reference tank to detect the pressure difference generated between the reference tank and each inspection object. A differential pressure detector, and F. An adder that adds the detection outputs of the differential pressure detector with opposite polarities; A determination device for determining the presence or absence of leakage of each of the inspection objects based on the addition result of the adder; A first state in which the air pressure source and the three-way branch pipe are connected to each other to provide air pressure from the air pressure source to the three-way branch pipe side, and the air pressure source side is closed to open the three-way branch pipe side to the atmosphere. A three-way solenoid valve that switches to a second state, I. In this pressurization mode in which the three-way solenoid valve is switched to the first state, the shutoff valve is opened, and air pressure is applied to each of the reference tank and each object to be inspected, and the shutoff valve is closed. An inspection mode in which the detection output of the differential pressure detector is measured to determine whether or not there is a leak in each inspected object, and the three-way solenoid valve is switched to the second state, is applied to the reference tank and each inspected object. And a controller for switching and controlling the exhaust mode to release the air to the atmosphere.