JP6639896B2 - Airtightness inspection device - Google Patents

Description

  The present invention relates to an apparatus for checking the airtightness of, for example, an automobile part.

  As an inspection device for a component requiring airtightness, Patent Literature 1 discloses a liquid tank containing a liquid for immersing an object to be inspected, a laser beam light source that irradiates a laser beam into the liquid tank, and a liquid tank. There is disclosed a camera including a CCD camera that images the upper part of an inspection object from a side and an image processing device that analyzes an image signal obtained from the CCD camera.

  This inspection apparatus irradiates a liquid in a liquid tank with a laser beam by a laser beam light source to form a laser beam band passing over the inspection object, and then attaches the upper part of the inspection object to a side wall of the liquid tank. The image is taken by a CCD camera arranged outside the camera. By irradiating a laser beam into the liquid, if bubbles exist in the liquid, they can be emitted. When an image is taken with a CCD camera, the bubbles contained in the image data are recognized by the image processing device. Easier to do.

JP-A-11-264781

  In the conventional airtightness inspection device, since the upper part of the inspection target is imaged by a CCD camera arranged outside the side wall of the liquid tank, the side wall of the liquid tank is formed of a transparent plate glass. The liquid contained in the liquid tank must be transparent.

  However, when inspecting mass-produced parts such as automobile parts, the adherence of cutting fluid and the like used for the parts during processing is immersed together with many parts, and the transparency of this liquid decreases. However, there is a problem that it is difficult to detect bubbles.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an airtightness inspection device capable of suitably inspecting the airtightness of a large number of inspection objects.

  The present invention is to solve the above problems, by the presence or absence of air bubbles leaking from the inspection target, in a device for inspecting the airtightness, a liquid tank containing a liquid to immerse the inspection target, An imaging device that captures a plurality of image data by capturing a liquid level of the liquid from above the liquid tank for a predetermined time, and an image processing device that recognizes the presence or absence of the bubble based on a change in the luminance of the liquid surface in the image data And the following.

  As described above, according to the present invention, the liquid level of the liquid stored in the liquid tank is imaged by the upper image pickup device for a predetermined time, and the change in luminance in the image data is detected as air bubbles. Is immersed in a liquid, and even if the transparency of the liquid is reduced, it is possible to determine the presence / absence of air bubbles over a long period of time without being affected by the influence, that is, to determine the airtightness of a large number of inspection objects.

  The image processing apparatus may further include, among the bubbles included in the plurality of pieces of image data captured by the image capturing apparatus with the elapse of the predetermined time, a first bubble recognized first and a second bubble recognized later. It is preferable that the image processing apparatus further includes an arithmetic processing unit that calculates a luminance difference from the air bubbles and determines whether the airtightness of the inspection object is good or not based on the luminance difference.

  When the first bubble and the second bubble leak from the inspection object, the luminance does not change significantly. Therefore, when these luminance differences are within the range of the predetermined reference value, it can be determined that the airtightness of the inspection object is poor. Thereby, the detection accuracy of bubbles in the airtightness inspection device can be improved.

  Further, it is preferable that the liquid contained in the liquid tank contains an adjusting material for reducing the reflectance of the liquid surface to 50% or less.

  When inspecting a mass-produced part, many inspection objects (parts) are sequentially immersed in the liquid tank. As a result, a ripple always occurs on the liquid surface, and the image processing apparatus may erroneously recognize a change in luminance of the liquid surface due to the ripple as a bubble. By adding the adjusting material to the liquid as described above to reduce the reflectivity of the liquid surface, this erroneous recognition can be prevented as much as possible, and as a result, air bubbles leaking from the inspection object can be reliably captured. .

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to test suitably the airtightness of many test objects.

It is a side view which shows the whole structure of an airtightness inspection apparatus. FIG. 4 is a plan view showing a state in which bubbles are generated on the surface of the liquid stored in the liquid tank. FIG. 2 is a functional block diagram of the image processing apparatus.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. 1 to 3 show an embodiment of an airtightness inspection apparatus according to the present invention.

  As shown in FIG. 1, an airtightness inspection apparatus 1 includes a liquid tank 2 that stores a liquid L in which an inspection object W is immersed, an illumination device 3 that irradiates light to a liquid surface La of the liquid L, and a liquid tank. An imaging device 4 is disposed at a position above the imaging device 2 and an image processing device 5 that analyzes image data acquired by the imaging device 4. The airtightness inspection apparatus 1 is used, for example, in a mass production line of industrial products in a factory or the like. In the present embodiment, a mission case of an automobile is illustrated as the inspection target W, but the inspection case is not limited to this.

  The liquid tank 2 is made of, for example, metal or resin, and is configured in a rectangular parallelepiped shape having an opening at an upper portion. However, the material and shape of the liquid tank 2 are not limited thereto. Further, in the present embodiment, water is used as the liquid L stored in the liquid tank 2, but is not limited to this.

  The illumination device 3 is arranged at a position above the liquid tank 2 and irradiates the light toward a liquid surface La of the liquid L in the liquid tank 2 located below. Although FIG. 1 illustrates two lighting devices 3 arranged above the liquid tank 2, the number of the lighting devices 3 is not limited to this.

  The imaging device 4 is for imaging the liquid level La of the liquid L stored in the liquid tank 2. The imaging device 4 is configured by, for example, a CCD camera, but is not limited thereto, and may use a CMOS camera or other various imaging devices. FIG. 1 illustrates two imaging devices 4 arranged above the liquid tank 2, but the number of the imaging devices 4 is not limited to this. The imaging device 4 is connected to the image processing device 5, and sequentially transmits a plurality of image data obtained by imaging the liquid level La for a predetermined time to the image processing device 5.

  The image processing apparatus 5 is configured by a PC on which various hardware such as a CPU, an MPU, a ROM, a RAM, an HDD, a monitor, and an input interface are mounted, but is not limited thereto. As shown in FIG. 3, the image processing device 5 includes an arithmetic processing unit 6 including a CPU, a storage unit 7 including a ROM, a RAM, an HDD, and the like, and a communication that performs communication with the imaging device 4. It mainly includes a control unit 8. These components are interconnected by a bus (not shown).

  The image data acquired by the imaging device 4 includes, in addition to the bubbles B leaking from the inspection object W, bubbles generated when the inspection object W is immersed in the liquid L, ripples generated on the liquid surface La, and liquids. The image includes dust and other foreign matters floating on the surface La. The image processing device 5 reliably recognizes the air bubbles B leaking from the inspection object W and removes bubbles, ripples, and foreign matters floating on the liquid surface La generated when the inspection object W is immersed in the liquid L. , So as not to erroneously recognize the bubble B as a leak.

  Specifically, the arithmetic processing unit 6 calculates the area of a portion where the luminance has changed (the portion where the luminance has increased) in the image data acquired by the imaging device 4 by calculation, and this area is determined to be a predetermined area. It is determined whether the value is within a range of a reference value (an upper limit value and a lower limit value). When the area of the part where the luminance has changed is within the range of the reference value, the arithmetic processing unit 6 identifies the part as the bubble B.

  Further, when the area of the portion where the luminance has changed on the liquid surface La is within the range of the reference value as described above, the arithmetic processing section 6 identifies this portion as the bubble B, and then, as shown in FIG. An inspection area X (an area indicated by a two-dot chain line in FIG. 2) including a position of the bubble B is set in the area, and thereafter, not all of the image data but the range of the set inspection area X Inspection only in the inside.

  The inspection area X is set in view of the regularity that the next bubble B appears at almost the same position when the bubble B leaked from the inspection object W appears on the liquid surface La. By limiting the inspection area X in this way, the processing speed of the image processing apparatus 5 can be improved, and the inspection can be performed in a short time.

  When the detected change in the luminance is out of the range of the reference value, the arithmetic processing unit 6 recognizes the change as a bubble, a ripple, or a foreign substance generated when the test object W is immersed in the liquid L. It is not added to the evaluation of the presence or absence of a leak.

  The storage unit 7 stores a program for analyzing image data captured by the imaging device 4 and various reference values for determining the presence or absence of the bubble B. This program detects bubbles B leaking from the inspection object W from the image data, calculates a luminance difference between a plurality of bubbles B generated with the passage of time, and, when the luminance difference satisfies a predetermined criterion, This certifies that a leak has occurred in the inspection object W. Further, the storage unit 7 can store the image data transmitted from the imaging device 4.

  The communication control unit 8 is connected to the imaging device 4 and receives the image data of the liquid level La acquired by the imaging device 4. Further, the communication control unit 8 can transmit a control signal to the imaging device 4 according to a command from the arithmetic processing unit 6. Note that the communication control unit 8 may be connected to the lighting device 3, and may transmit a control signal related to ON / OFF thereof to the lighting device 3.

  When inspecting mass-produced parts such as automobile parts, a large number of inspection objects W are sequentially immersed in the liquid tank 2 one by one or a plurality of them. As a result, large and small ripples always occur on the liquid surface La. Further, depending on the type of the inspection object W, there is a case where the workpiece W is immersed in the liquid L in a state where the cutting fluid (coolant) or the like remains attached during processing.

  In this case, the inventor has confirmed that the liquid L becomes cloudy due to the mixing of the cutting liquid into the liquid L. When the liquid L becomes cloudy and loses transparency, the reflectance of the liquid surface La increases. In this case, depending on the reflection of the light emitted from the illumination device 3, the image processing device 5 may erroneously recognize the ripples generated on the liquid surface La as bubbles B.

  In order to prevent the above problems, an adjusting material for adjusting the reflectance of the liquid surface La is added to the liquid L. This adjusting material, when added to the liquid L, changes the color of the liquid L, thereby lowering the reflectance of the liquid surface La. With this adjusting material, the reflectance of the liquid surface La is adjusted to 50% or less, more preferably 30% or less in the wavelength range of 400 nm to 700 nm. In the present embodiment, black ink is used as the adjusting material, but is not limited to this. Specifically, black ink is added to the clouded liquid L, and the liquid L is blackened to adjust the reflectance of the liquid surface La to 30% or less.

  Hereinafter, an inspection method by the airtightness inspection apparatus 1 having the above configuration will be described.

  In this method, the inspection object W is immersed in the liquid L stored in the liquid tank 2 after air is press-fitted therein. Alternatively, after the test object W is immersed in the liquid L, air is press-fitted therein. The liquid L in the liquid tank 2 is preliminarily added with black ink as an adjusting material.

  When the inspection object W is immersed in the liquid tank 2, ripples occur on the liquid surface La. In order to reduce the ripple as much as possible, the apparatus waits in this state for a predetermined time (for example, 7 seconds). Thereafter, the lighting device 3 is turned on, and imaging of the liquid level La starts (imaging process). The imaging device 4 images the liquid surface La at a predetermined time (for example, 5 seconds) at predetermined time intervals (for example, 0.1 seconds), and transmits the obtained plurality of image data to the image processing device 5. . The imaging device 4 repeats such imaging of the liquid surface La for a predetermined time a plurality of times (for example, three times in total).

When the image data is received by the communication control unit 8, the image processing device 5 stores the image data in the storage unit 7 and starts the analysis of the image data by the arithmetic processing unit 6. The image processing device 5 detects a portion where the luminance (cd / m ² ) of the liquid surface La changes from a plurality of pieces of image data acquired over time.

  When detecting the portion of the liquid surface La where the luminance changes with the passage of time, the calculation processing section 6 of the image processing device 5 calculates the area of the portion. Further, the arithmetic processing unit 6 compares the calculated area with reference values (upper limit value and lower limit value) stored in the storage unit 7, and only when the value of this area is within the range of the reference value, Is determined to be bubble B.

  When the arithmetic processing unit 6 first detects an air bubble (hereinafter, referred to as a “first air bubble”) B1 among the air bubbles B recognized over time, the inspection area X (see FIG. 2) is provided around the first air bubble B1. ) Is set.

  When the arithmetic processing unit 6 detects a bubble (hereinafter, referred to as a “second bubble”) B2 that satisfies the luminance and area criteria in the inspection area X after the first bubble B1, the luminance of the first bubble B1 is determined. The difference from the brightness of the second bubble B2 is calculated. When the calculated luminance difference is within the range of the predetermined reference value stored in the storage unit 7, the arithmetic processing unit 6 determines that the inspection object W is leaking, and determines the luminance difference and the determination result. Are displayed on the monitor. The inspection object W for which the inspection has been completed is pulled up from the liquid tank 2, and the new inspection object W is immersed in the liquid L.

  According to the above-described airtightness inspection apparatus 1 according to the present embodiment, the liquid level La of the liquid L stored in the liquid tank 2 is imaged by the imaging device 4 for a predetermined time, and the change in luminance in the image data is detected by the bubble B. Therefore, even if a large number of test objects W are immersed in the liquid L and the transparency of the liquid L is reduced, the airtightness inspection apparatus 1 can detect the leakage of the test object W without being affected by the test object W. Can be determined. Therefore, in a mass production line, even if the cycle time is short, it is possible to surely inspect a large number of inspection objects W for the presence or absence of a leak.

  In addition, the image processing device 5 includes a first bubble B1 recognized first and a second bubble recognized later among bubbles B included in a plurality of image data captured by the image capturing device 4 with the elapse of a predetermined time. A luminance difference from B2 is calculated and compared with a reference value. By determining the presence or absence of a leak in the inspection object W in this manner, it is possible to increase the leak detection accuracy. Further, by adjusting the liquid L contained in the liquid tank 2 with the adjusting material so that the reflectance of the liquid surface La is reduced, the leak detection accuracy can be improved.

  According to the above, the airtightness inspection apparatus 1 can efficiently inspect a large number of inspection objects W such as mass-produced parts, thereby dramatically increasing the production efficiency of the product and reducing the production cost. It is possible to greatly reduce.

  Note that the present invention is not limited to the configuration of the above-described embodiment, nor is it limited to the above-described effects. The present invention can be variously modified without departing from the gist of the present invention.

  In the above embodiment, among the plurality of bubbles B included in the plurality of image data captured by the imaging device 4, the brightness of the first bubble B1 recognized first and the brightness of the second bubble B2 recognized later are determined. Although the example of the image processing apparatus 5 that determines the quality of the airtightness of the inspection object W based on the difference has been described, the invention is not limited thereto. For example, the image processing apparatus 5 airtightly seals the inspection object W based on the luminance difference between the first bubble B1 and the third bubble and the fourth bubble that appear on the liquid surface La after the second bubble B2. It is also possible to determine the quality of the sex.

  Further, the image processing apparatus 5 determines the area of the portion where the luminance is increased when the luminance is changed on the liquid level La without being based on the luminance difference between the first bubble B1 and the second bubble B. When the area is within the range of the predetermined reference value, it is possible to determine that the area is the bubble B leaked from the inspection object W, and to determine the airtightness defect.

  In the above-described embodiment, an example has been described in which the inspection area X having a predetermined area is set as image data after the image processing device 5 detects the first bubble B1, but the invention is not limited to this. The image processing device 5 can naturally inspect all areas of the image data. In this case, the image processing device 5 can detect a foreign substance included in the image data as follows. The bubble B to be detected by the image processing device 5 disappears when it reaches the liquid level La. On the other hand, in the case of the foreign matter, the foreign matter stays at the liquid level La and floats. Even when the presence of the foreign matter is detected as a change in luminance, the image processing device 5 determines that the foreign matter is not a bubble B when the change of the foreign matter moves a certain distance on the liquid surface La for a certain time. Can be excluded from the detection target. Thereby, the robustness of the airtightness inspection device 1 used in the mass production line can be improved.

REFERENCE SIGNS LIST 1 airtightness inspection device 2 liquid tank 4 imaging device 5 image processing device 6 arithmetic processing unit L liquid W inspection object B bubble B1 first bubble B2 second bubble

Claims (3)

In the device to check the airtightness by the presence or absence of air bubbles leaking from the inspection object,
A liquid tank containing a liquid for immersing the test object,
An imaging device that images a liquid surface of the liquid from above the liquid tank for a predetermined time to acquire a plurality of image data;
An image processing device that recognizes the presence or absence of the bubble based on a change in the brightness of the liquid surface in the image data ,
The image processing apparatus may include, among the bubbles included in the plurality of pieces of image data captured with the elapse of the predetermined time by the imaging apparatus, a first bubble recognized first, and a second bubble recognized later. of calculating the brightness difference, the arithmetic processing unit airtightness testing apparatus according to claim Rukoto comprises determining the airtightness of quality of the inspection object based on the luminance difference. The airtightness inspection apparatus according to claim 1, wherein the liquid contained in the liquid tank includes an adjusting material that makes a reflectance of the liquid surface 50% or less. In the device to check the airtightness by the presence or absence of air bubbles leaking from the inspection object,
A liquid tank containing a liquid for immersing the test object,
An imaging device that images a liquid surface of the liquid from above the liquid tank for a predetermined time to acquire a plurality of image data;
An image processing device that recognizes the presence or absence of the bubble based on a change in the brightness of the liquid surface in the image data,
The airtightness inspection apparatus according to claim 1, wherein the liquid contained in the liquid tank includes an adjusting material for reducing the reflectance of the liquid surface to 50% or less.

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