JP2993793B2 - Airtightness 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 an airtightness inspection method and apparatus for inspecting the airtightness of a sealed container.

[0002]

2. Description of the Related Art Conventionally, in the industry for manufacturing a sealed container, the inside of a manufactured product is pressurized and immersed in a water tank, and the presence or absence of air bubbles leaking from a defective portion is detected. Is determined.

By the way, when the sealed container is submerged,
When submerged, air bubbles adhere to the outer wall surface of the sealed container, and the adhered air bubbles release the outer wall surface to generate air bubbles in the water tank (hereinafter referred to as residual air bubbles).

Since it is difficult to discriminate between the residual air bubbles and the air bubbles leaking from the inside of the inspection object (hereinafter referred to as leak air bubbles), it is determined whether the inspection object is acceptable or not only based on the amount of detected air bubbles. Can not do.

Therefore, in order to eliminate the influence of such residual air bubbles, a rocking operation such as reversing an object to be inspected is added, or a vibration generator disposed in the water tank is energized to seal the tank. Inspection methods such as promoting removal of residual air bubbles adhered to the outer wall surface of the container and delaying the start of inspection until the residual air bubbles are eliminated are used.

On the other hand, the technical idea of the airtightness inspection method is disclosed in Japanese Patent Application Laid-Open No. Sho 57-54832, "Airtightness Inspection Method".
No. 27140, “Airtightness inspection device”.

The "airtightness inspection method" and the "airtightness inspection apparatus" calculate the total amount of change in the number of generated bubbles detected at each sampling time, and introduce the total amount information of the change amount into a determination circuit to perform airtightness. Determine whether the sex is acceptable.

[0008]

However, the conventional method and apparatus for airtightness described above have a disadvantage that it is difficult to determine the presence or absence of leaking bubbles when the amount of leaking bubbles is smaller than that of residual bubbles. is there.

Further, there is a problem that the inspection time cannot be shortened because the residual air bubbles cannot be removed promptly.

The present invention has been made in order to solve such a conventional problem. By extracting only leaked bubble data from detected bubble data, the number of leaked bubbles is smaller than that of residual bubbles. Airtightness inspection method that can reliably detect the airtightness and can start the airtightness inspection even when the residual air bubbles are not completely removed, thereby shortening the inspection time. And an apparatus.

[0011]

In order to achieve the above object, a first aspect of the present invention is to check the airtightness of the sealed container by detecting bubbles generated from the sealed container immersed in a liquid. An airtightness inspection method, comprising: a first step of detecting air bubbles generated from the sealed container by an air bubble detection sensor; a second step of counting the air bubbles at each preset sampling time; A third step of converting the number of generated bubbles for each sampling time counted in the step to a frequency, and obtaining the respective frequency information obtained in the third step from a generation interval of leaked bubbles leaking from the sealed container. A fourth step of averaging over a long time; and a fifth step of searching for a lowest frequency from the averaged frequency information and comparing it with a preset reference frequency. When, wherein the sixth step of determining the airtightness of acceptance of the sealed container by the comparison result, that it consists.

Further, a second invention is an airtightness inspection device for inspecting the airtightness of the sealed container by detecting air bubbles generated from the sealed container immersed in a liquid, wherein the airtightness inspection device generates the airtightness from the sealed container. A bubble detection sensor for detecting bubbles to be generated, a counting circuit for counting the number of detected bubbles generated at each preset sampling time, and a frequency for converting the counted number of generated bubbles at each sampling time to a frequency A conversion circuit, an averaging circuit for averaging the respective frequency information converted by the frequency conversion circuit for a time longer than the generation interval of the leak bubbles leaking from the sealed container, and an averaging circuit for the averaged bubbles. A frequency comparison circuit that searches for the lowest frequency from the frequency information and compares it with a preset reference frequency, and the sealed capacitor according to the comparison result of the frequency comparison circuit. Characterized in that it comprises between the acceptance determination circuit that performs acceptability determination of airtightness, the.

[0013]

In the airtightness inspection method and apparatus according to the present invention, air bubbles generated from the sealed container immersed in the liquid are detected by the air bubble detection sensor, and the detected air bubbles are counted by the counting circuit at every preset sampling time. Count. Then
The frequency conversion circuit converts the counted number of generated bubbles for each sampling time into a frequency, and the averaging circuit averages this frequency information for a time longer than the interval between the occurrence of leak bubbles.

The lowest frequency is retrieved from the averaged frequency information and compared with a preset reference frequency. Based on the result of the comparison, a pass / fail judgment circuit judges pass / fail of the airtightness of the sealed container.

By averaging the detected bubble data, the presence / absence of a leak bubble can be determined from the detected bubble data in which the data of the residual bubble and the leak bubble are mixed. The airtightness of the sealed container can be inspected.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the method and apparatus for checking airtightness according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an airtightness inspection apparatus 1 embodying the present invention.
FIG. 2 is a perspective view showing a configuration of a No. 0.

The airtightness inspection apparatus 10 includes an inspection liquid tank 12 for submerging a vehicle fuel tank W to be inspected, an umbrella-shaped foam collecting hood 14, and an arithmetic circuit 16.

A fuel tank W is provided inside the test liquid tank 12.
A holding housing 20 to which holding fittings 18a and 18b for holding the holding member are engaged, a rotating shaft 21 to be attached to the holding fitting 18a, and a rotating mechanism 22 for driving the rotating shaft 21 to rotate.

The rotation mechanism 22 includes a motor 24 fixed to the outside of the test liquid tank 12, a pulley 28 mounted on a rotating shaft 26 of the motor 24, and a pulley 30 disposed in the test liquid tank 12. , And a belt 32 is stretched between the pulley 28 and the pulley 30. In addition, the pulley 30 is
4 and the other of the rotating shafts 34 is connected to the rotating shaft 2.
When the motor 24 is energized, the holding bracket 18a is rotated by the rotation of the motor 24 via the rotating shaft 26, the pulley 28, the belt 32, the pulley 30, and the rotating shafts 34 and 21. By being driven to rotate, the fuel tank W
Is rotated.

The umbrella-shaped foam collecting hood 14 has a fuel tank W
A hood section 36 for collecting bubbles generated from the hood section, and an inspection tube 38 disposed at the top of the hood section 36, the piston rods 40a and 40b are engaged with the hood section 36, and a lifting cylinder 42a, The foam collecting hood 14 is raised and lowered under the action of 42b. An optical bubble detection sensor 44 is attached to the inspection tube 38, and the output of the optical bubble detection sensor 44 is introduced to the arithmetic circuit 16.

FIG. 2 is a block diagram showing the configuration of the arithmetic circuit 16.

The arithmetic circuit 16 includes a sensor amplifier circuit 46 for amplifying the output of the bubble detection sensor 44, a counter circuit 48 for counting the number of amplified bubbles generated, and converting the counted number of generated bubbles to a frequency. Frequency conversion circuit 5
0, an averaging circuit 52, a frequency comparison circuit 54 for comparing the number of generated and averaged bubbles in frequency conversion with a preset reference frequency, and the airtightness of the fuel tank W is determined based on the comparison result. A control circuit 56 for making a pass / fail determination and the like
And

Further, the arithmetic circuit 16 includes a storage circuit 58 for storing the respective arithmetic results and the like, and a display 60 for displaying the results of the pass / fail judgment.

The airtightness inspection apparatus 1 configured as described above
The operation of performing an airtightness inspection of the vehicle fuel tank W at 0 will be described with reference to FIGS.

1.5 kg / gauge pressure in the fuel tank W
cm ² of compressed air (step S31), the fuel tank is submerged in the test liquid tank 12, and the holding fittings 18a,
18b (step S32). Next, the motor 24 is energized to rotate the rotating shaft 26, the pulley 28, the belt 3
2, holding fitting 1 via pulley 30, rotating shafts 34 and 21
By rotating the fuel tank W by 180 degrees, the fuel tank W is rotated by 180 degrees to eliminate the residual air bubbles remaining on the bottom side of the concave fuel tank W (step S33), and the lifting cylinders 42a and 42b are attached. Energize, piston rod 40
Under the action of a and 40b, the foam collecting hood 14 is lowered to a predetermined position above the fuel tank W (step S34). After the elapse of the inspection start time set in advance by the shape of the fuel tank W, the detection of air bubbles is started, and a calculation is performed to determine whether or not the air is acceptable (step S35). This inspection method will be described later.

Next, similarly to step S33, the motor 24 is energized to rotate the fuel tank W by 180 degrees (step S36), and after a preset standby time, bubbles on the upper side of the fuel tank W are removed. Detect and determine (step S3
7).

In the above steps, the detection of bubbles at the bottom and the top of the fuel tank W is completed.

Next, a description will be given of a method of detecting air bubbles and determining whether airtightness is satisfactory or not in steps S35 and S37.

The bubble signal detected by the bubble detection sensor 44 is amplified by the sensor amplifier circuit 46 and counted by the counter circuit 48. The control circuit 62 outputs a sampling trigger to the counter circuit 48 at a preset sampling time, for example, every 0.1 second, and reads the quantity information of the bubbles output from the counter circuit 48 by the sampling trigger (FIG. 5 ( a)) (Step S4)
1).

The read bubble number data is led to the frequency conversion circuit 50, and is converted from "bubble number / sampling rate" to "bubble number / sec" frequency data (see FIG. 5B). (Step S42).

Next, the frequency-converted bubble number data is averaged by the averaging circuit 52 for a time sufficiently longer than the interval between the generated leaking bubbles, for example, 10 seconds (see FIG. 5C) (step). S43).

In this case, the first data obtained by the averaging operation is obtained by averaging the data from the first second to the tenth second, and the second data is obtained from the second second by 11 seconds. The data up to the eye data are averaged. In this way, all data up to the last sampling time is averaged.

The frequency comparison circuit 54 performs a comparison operation as to whether or not the minimum value of the averaged data obtained as described above is lower than threshold data indicating a predetermined pass / fail decision criterion. (See FIG. 5D) (step S44). If the minimum value of the averaged data <the threshold value, the control circuit 62 determines that the airtightness of the fuel tank W, which is the inspection object, is acceptable and displays it. Is displayed on the device 60 (step S
45), if the minimum value of the averaged data is not smaller than the threshold value,
A rejection is displayed on the display 60 (step S46),
End the airtightness inspection.

In this case, the set threshold value and the averaging time of the averaging operation are determined by the smallest missing hole diameter to be detected. For example, if the minimum missing hole diameter to be detected is 6 μm, the generated leak bubbles are 0.6 μm.
cps, ie, 6/10 seconds, it is known that the threshold value is 1 cps, and the time for averaging is 10 seconds. Can be detected.

FIG. 6 is an embodiment showing the result of the airtightness inspection of the fuel tank W performed by the airtightness inspection apparatus 10 shown in FIG. In the figure, (a) is a graph when the frequency-converted data is cumulatively added in step S42, and (b) is a graph when the cumulatively added data is divided by each time and averaged. It is. In the figure, indicates the result of the airtightness inspection on one side of the fuel tank W,
Indicates the result of the airtightness inspection of the other surface, and indicates a threshold value.

In FIG. 6B, the time indicates the air remaining at the bottom of the fuel tank W, and since the time becomes lower than the threshold value after the time, that is, the lowest frequency becomes lower than the threshold value. The tank W indicates a good product.

FIG. 7 is a graph showing the results of an airtightness inspection of another fuel tank W. FIG. 7A shows frequency-converted detected bubbles for each sampling time, and FIG. A curve of the cumulative value of the detected bubbles, a curve obtained by averaging the data of FIG. 7A, and a plurality of thresholds are shown.
In this case, the broken line indicates the result of the airtightness inspection on the back surface, and the solid line indicates the result on the front surface.

In FIG. 7 (b), when the threshold value for the pass / fail judgment is "1", the searched minimum frequency indicated by the solid line is less than the threshold value in 30 seconds. Indicates a pass, and a threshold value of “2” indicates that both the back surface and the front surface pass.

As described above, according to the present embodiment,
Focusing on the fact that leaked bubbles are generated regularly and residual bubbles are generated irregularly, the detected bubble data is frequency-converted and averaged, so that bubbles containing residual bubbles and leaked bubbles are mixed. Since only the leak bubble information can be extracted from the data, the airtightness test can be started even when the residual bubbles are not completely removed from the fuel tank W.

Therefore, conventionally, since the start of the airtightness inspection is waited until the residual air bubbles are eliminated, the fuel tank W
The standby time, which was uncertain due to the difference in the shape or the like, can be reduced to a preset standby time.

In this embodiment, the air bubble detection sensor 4
4 is an optical type, but the same effect can be obtained by using a bubble detection sensor of an ultrasonic type or the like.

[0043]

In the airtightness inspection method and apparatus according to the present invention, by averaging the detected bubble data, only the leaked bubble data is extracted from the detected bubble data in which the data of the residual bubble and the leaked bubble are mixed. Therefore, even if the residual bubbles are not completely removed, the detection of the leak bubbles can be started.

Therefore, after the closed container is immersed in the liquid, the waiting time until the start of the airtightness inspection can be shortened, and the cycle time of the airtightness inspection including submersion, air bubble detection and judgment can be shortened. And the inspection efficiency of the entire inspection line can be improved.

Furthermore, since only leaked bubble data can be extracted, the accuracy of the airtightness inspection can be improved, and even if the amount of leaked bubbles is extremely small compared to the remaining bubbles, it can be detected. In addition, it is possible to perform a highly accurate airtightness inspection.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an airtightness inspection apparatus that implements an airtightness inspection method and apparatus of the present invention.

FIG. 2 is a block diagram showing a configuration of an arithmetic circuit of the embodiment shown in FIG.

FIG. 3 is a flowchart showing an outline of an airtightness inspection method of the embodiment shown in FIG. 1;

FIG. 4 is a flowchart showing an airtightness inspection method of the embodiment shown in FIG.

FIG. 5 is a diagram illustrating the number-of-bubbles data calculated in the airtightness inspection method shown in FIG. 4;

FIG. 6 is a graph showing a result of a fuel tank airtightness inspection performed by the airtightness inspection apparatus shown in FIG. 1;

7 is a graph showing a result of an airtightness inspection of another fuel tank performed by the airtightness inspection apparatus shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Airtightness inspection apparatus 12 ... Inspection liquid tank 14 ... Foam collection hood 16 ... Operation circuit 18a, 18b ... Holding metal fitting 24 ... Motor 38 ... Inspection tube 44 ... Bubble detection sensor 46 ... Sensor amplifier circuit 48 ... Counter circuit 50 ... Frequency Conversion circuit 52 ... Averaging circuit 54 ... Frequency comparison circuit 56 ... Control circuit 58 ... Storage circuit 60 ... Display W ... Fuel tank

Claims (2)

(57) [Claims] 1. An airtightness inspection method for inspecting airtightness of a sealed container by detecting air bubbles generated from a sealed container immersed in a liquid, wherein the air bubbles generated from the sealed container are detected by an air bubble detection sensor. A first step of detecting the number of bubbles at each sampling time set in advance, and a second step of converting the number of generated bubbles at each sampling time counted by the second step into a frequency. A third step, a fourth step of averaging the respective frequency information obtained in the third step for a time longer than an interval of occurrence of leak bubbles leaking from the sealed container, and the averaged frequency Find the lowest frequency from the information,
A fifth step of comparing with a preset reference frequency, and a sixth step of judging whether the airtightness of the sealed container is acceptable or not based on the comparison result. 2. An airtightness inspection apparatus for inspecting airtightness of a sealed container by detecting air bubbles generated from a sealed container immersed in a liquid, wherein the air bubbles detect air bubbles generated from the sealed container. A detection sensor; a counting circuit that counts the number of detected bubbles generated at each preset sampling time; a frequency conversion circuit that converts the counted number of generated bubbles at each sampling time into a frequency; An averaging circuit for averaging the respective frequency information converted by the conversion circuit for a time longer than the generation interval of the leak bubbles leaking from the sealed container, and calculating the lowest frequency from the averaged frequency information of the respective bubbles. A frequency comparison circuit that searches and compares the frequency with a preset reference frequency; Airtightness inspection apparatus characterized by comprising: a pass-fail decision circuit, the performing.