JP2024048184A - Inspection method of hole defect detection device for metal band, and hole defect detection device for metal band - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection method of a hole defect detection device for a metal band, and a hole defect detection device for a metal band.

SOLUTION: An inspection method of a hole defect detection device for a metal band which optically detects a hole defect of a metal band, includes: irradiating over the whole width of the metal band with light from a first light source; detecting passing light that has passed through a hole of the metal band by an optical detector arranged on the opposite side to the first light source with the metal band held therebetween in a thickness direction to detect a hole defect; detecting diffuse reflection light reflected by the metal band by the optical detector by irradiating over the whole width of the metal band with light from a second light source arranged on the opposite side to the first light source with the metal band held therebetween in the thickness direction; and determining whether the optical detector is normal or abnormal on the basis of a characteristic value of the light detected by the optical detector.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to an inspection method for a metal strip hole defect detection device and a metal strip hole defect detection device.

Conventionally, in continuous production lines for metal strips such as steel strips, a hole defect detection device is known in which a light source and a detector are arranged above and below the continuously transported metal strip, and the detector detects the light emitted from the light source that passes through holes in the metal strip. In such optical hole defect detection devices, when the detector continues to not detect the passing light, it is difficult to determine whether this is because there is actually no hole defect or because an abnormality in the detector is preventing it from detecting the passing light.

Patent Document 1 discloses a technology in which diagnostic light is incident on the photodetector of the receiver while hole defect detection is being performed on the welded portion between coils of steel strip, and the receiver is diagnosed based on the light detection signal from the photodetector of the receiver.

Patent document 2 discloses a technology in which a spot light simulating a perforated portion is irradiated onto a metal strip or a light receiving portion, and if the spot light can be detected as a perforated portion, the detection device determines that it is normal, and if the spot light cannot be detected as a perforated portion, the detection device determines that it is abnormal.

Patent document 3 discloses a technology in which, when inspecting a camera acting as a light receiving unit, a small inspection shutter is closed to block the camera's field of view, and light is irradiated from a small inspection light toward a transparent glass; if the camera detects the light reflected by the transparent glass, the operator is informed that the camera is in good condition, and if the camera does not detect the light reflected by the transparent glass, the operator is informed that the camera is defective.

JP 2013-11561 A JP 2010-185679 A JP 2017-3269 A

However, in the technology disclosed in Patent Document 1, when diagnosing the receiver, it is not possible to distinguish whether the light detection by the photodetector is due only to reception of diagnostic light or includes reception of light from the projector associated with the presence of a hole defect, making it impossible to perform accurate hole defect detection. As a result, it is not possible to diagnose the receiver other than at the welded parts of the steel strip.

The technology disclosed in Patent Document 2 makes it impossible to check for abnormalities in areas not hit by the spot light within the field of view in the metal strip width direction of the same detector.

In the technology disclosed in Patent Document 3, when inspecting the camera, the light used to detect holes in the metal band is blocked by the inspection shutter, making it impossible to check for holes in the metal band during camera inspection.

The present invention has been made in consideration of the above problems, and its purpose is to provide an inspection method for a metal strip perforation defect detection device that can detect abnormalities in a photodetector while detecting perforation defects in the metal strip, and a metal strip perforation defect detection device.

In order to solve the above-mentioned problems and achieve the object, the inspection method for a metal strip perforation defect detection device according to the present invention is a method for optically detecting perforation defects in a metal strip, which is characterized in that light is irradiated from a first light source across the entire width of the metal strip, and a photodetector arranged on the opposite side of the metal strip from the first light source across the thickness of the metal strip detects the light that passes through the holes in the metal strip to detect the perforation defects, and light is irradiated from a second light source arranged on the opposite side of the metal strip from the first light source across the thickness of the metal strip to detect the diffuse reflected light reflected by the metal strip with the photodetector, and whether the photodetector is normal or abnormal is determined based on the characteristic value of the light detected by the photodetector.

The inspection method for the metal strip hole defect detection device according to the present invention is characterized in that, in the above invention, the characteristic value of the light is the intensity of the light, and when the intensity of the light detected by the photodetector is equal to or greater than an abnormality threshold, which is a preset threshold value of the light intensity for detecting an abnormality of the photodetector, the photodetector is determined to be normal, and when the intensity of the light detected by the photodetector is less than the abnormality threshold, the photodetector is determined to be abnormal.

The metal strip perforation defect detection device according to the present invention is a metal strip perforation defect detection device that optically detects perforation defects in a metal strip, and is characterized by comprising: a first light source that irradiates light across the entire width of the metal strip; a photodetector that is arranged on the opposite side of the metal strip from the first light source across the thickness of the metal strip; a second light source that is arranged on the opposite side of the metal strip from the first light source across the thickness of the metal strip and irradiates light across the entire width of the metal strip; and a determination device that determines whether the photodetector is normal or abnormal based on the characteristic values of the light detected by the photodetector.

The metal strip hole defect detection device according to the present invention is characterized in that, in the above invention, the characteristic value of the light is the intensity of the light, and the determination device determines that the light detector is normal when the intensity of the light detected by the light detector is equal to or greater than an abnormality threshold, which is a preset threshold value of the light intensity for detecting an abnormality of the light detector, and determines that the light detector is abnormal when the intensity of the light detected by the light detector is less than the abnormality threshold.

The inspection method and the metal strip perforation defect detection device according to the present invention have the advantage of being able to detect abnormalities in the photodetector while detecting perforation defects in the metal strip.

FIG. 1 is a diagram for explaining a continuous production line according to an embodiment. FIG. 2 is a schematic diagram of the perforation defect detection device according to the embodiment, as viewed from the downstream side in the steel strip transport direction. FIG. 3 is a schematic diagram showing a schematic configuration of a perforation defect detection device according to an embodiment, as viewed in the width direction of a steel strip. FIG. 4 is a diagram showing an example of the intensity of light detected by the photodetector in the absence of irradiation of the inspection light from the second light source. FIG. 5 is a diagram showing an example of the intensity of light detected by the photodetector when the inspection light is irradiated from the second light source. FIG. 6 is a diagram showing an example of the intensity of light detected by the photodetector when the photodetector is abnormal.

The following describes an embodiment of the inspection method for the metal strip perforation defect detection device according to the present invention, and the metal strip perforation defect detection device. Note that the present invention is not limited to this embodiment.

Figure 1 is a diagram for explaining the continuous production line 1 according to the embodiment.

As shown in FIG. 1, the continuous manufacturing line 1 includes a payoff reel 2, a tension reel 3, a welding machine 4, and a hole defect detection device 5. In the continuous manufacturing line 1, a steel strip S, which is a metal strip wound into a coil shape, is unwound from the payoff reel 2, and after a predetermined process is performed, it is wound into a coil shape by the tension reel 3. The welding machine 4 welds the preceding steel strip S to the following steel strip S. The hole defect detection device 5 continuously detects hole defects in the steel strip S as the steel strip S is transported. The judgment device 54 in FIG. 1 is a control device that constitutes the hole defect detection device 5, and judges the presence or absence of hole defects in the steel strip S.

Figure 2 is a schematic diagram of the perforation defect detection device 5 according to the embodiment, as viewed from the downstream side in the steel strip conveying direction. Figure 3 is a schematic diagram of the general configuration of the perforation defect detection device 5 according to the embodiment, as viewed from the steel strip width direction.

2 and 3, the hole defect detection device 5 according to the embodiment includes a first light source 51, a second light source 52, a plurality of photodetectors 53a, 53b, 53c, and 53d, and a determination device 54. In the following description, when the plurality of photodetectors 53a, 53b, 53c, and 53d are not particularly distinguished from each other, they are also simply referred to as photodetectors 53.

The first light source 51 is an illumination source used to detect perforation defects that penetrate the front and back of the steel strip S, and irradiates detection light L1 from below the steel strip S toward the back of the steel strip S over the entire width of the steel strip S (entire area in the width direction of the steel strip) to detect perforation defects.

The second light source 52 is a light source used to inspect the multiple photodetectors 53a, 53b, 53c, and 53d for abnormalities (failures). It is positioned on the opposite side of the steel strip S from the first light source 51, sandwiching the steel strip S in the thickness direction, and irradiates inspection light L3 from above the steel strip S toward the front surface of the steel strip S, across the entire width of the steel strip S, for inspecting the multiple photodetectors 53a, 53b, 53c, and 53d.

The multiple photodetectors 53a, 53b, 53c, and 53d are arranged side by side along the width direction of the steel strip S on the opposite side of the first light source 51, sandwiching the steel strip S in the thickness direction, so that perforation defects can be detected over the entire width of the steel strip S. The multiple photodetectors 53a, 53b, 53c, and 53d are, for example, composed of line sensor cameras having CCD image sensors, and are arranged so that their respective optical axes are perpendicular to the front surface of the steel strip S, and the light receiving ranges (field of view) of the multiple photodetectors 53a, 53b, 53c, and 53d in the width direction of the steel strip S are set so that adjacent photodetectors 53 partially overlap each other. Note that, as long as perforation defects can be detected over the entire width direction of the steel strip S, it is not necessary that adjacent photodetectors 53 have a portion of the light receiving range (field of view) overlap each other.

When there is no hole defect in the steel strip S, the detection light L1 irradiated from the first light source 51 toward the back surface of the steel strip S is reflected by the back surface of the steel strip S over the entire width of the steel strip S, and does not reach any of the multiple 53a, 53b, 53c, 53d and is not detected. On the other hand, when there is a hole defect in the steel strip S, the transmitted light L2, which is part of the detection light L1 irradiated from the first light source 51 toward the back surface of the steel strip S and passes through the hole in the steel strip S, reaches at least one of the multiple photodetectors 53a, 53b, 53c, 53d and is detected.

In addition, the inspection light L3 irradiated from the second light source 52 toward the front surface of the steel strip S is reflected by the front surface of the steel strip S over the entire width of the steel strip S, and diffuse reflected light L4 reaches and is detected by multiple photodetectors 53a, 53b, 53c, and 53d.

In the hole defect detection device 5 according to the embodiment, as shown in FIG. 3, the second light source 52 is arranged upstream of the light detector 53 in the steel strip transport direction, and the optical system is configured such that inspection light L3 is irradiated toward the front surface of the steel strip S, and diffuse reflected light L4 of the light reflected by the front surface of the steel strip S reaches the light detector 53 and is detected. The second light source 52 may also be arranged downstream of the light detector 53 in the steel strip transport direction.

The determination device 54 determines whether or not there is a hole defect and whether or not there is an abnormality (failure) in the multiple photodetectors 53a, 53b, 53c, and 53d based on the detection results of the multiple photodetectors 53a, 53b, 53c, and 53d, specifically, based on the light intensity, which is a characteristic value of the light detected by the multiple photodetectors 53a, 53b, 53c, and 53d. Note that the characteristic value of the light is not limited to the light intensity, and may be, for example, the amount of light.

In the perforation defect detection device 5 according to the embodiment, while the steel strip S is being transported, a detection light L1 is constantly irradiated from the first light source 51 onto the back surface of the steel strip S across the entire width of the steel strip S to detect perforation defects in the steel strip S, and an inspection light L3 is constantly irradiated from the second light source 52 onto the front surface of the steel strip S across the entire width of the steel strip S to detect abnormalities in the multiple photodetectors 53a, 53b, 53c, and 53d.

Figure 4 shows an example of the light intensity detected by the photodetector 53 when the inspection light L3 is not irradiated from the second light source 52.

In the hole defect detection device 5 according to the embodiment, when the first light source 51 irradiates the detection light L1 toward the back surface of the steel strip S and the second light source 52 does not irradiate the inspection light L3, the light detected by the multiple photodetectors 53a, 53b, 53c, and 53d may include some ambient light, but is mostly composed of the transmitted light L2 that has passed through the holes in the steel strip S. Therefore, as shown in FIG. 4, the intensity of the light detected by the multiple photodetectors 53a, 53b, 53c, and 53d is such that the steel strip portion, which is the portion of the steel strip S where the hole defect does not exist, is a dark portion with low light intensity, while the hole defect portion, which is the portion of the steel strip S where the hole defect exists, is a bright portion with high light intensity.

Figure 5 shows an example of the light intensity detected by the photodetector 53 when the inspection light L3 is irradiated from the second light source 52.

In the hole defect detection device 5 according to the embodiment, when the first light source 51 irradiates the detection light L1 toward the back surface of the steel strip S and the second light source 52 irradiates the inspection light L3 toward the front surface of the steel strip S, the light detected by the multiple photodetectors 53a, 53b, 53c, and 53d is dominated by the transmitted light L2 that passes through the holes in the steel strip S and the diffuse reflected light L4 that is reflected by the front surface of the steel strip S. Therefore, as shown in FIG. 5, the light intensity detected by the multiple photodetectors 53a, 53b, 53c, and 53d is such that the hole defect portion is a bright portion with a high light intensity, and the steel strip portion is a bright portion with a light intensity that is higher than the light intensity of the steel strip portion shown in FIG. 4 by the intensity of the diffuse reflected light L4.

Here, in the hole defect detection device 5 according to the embodiment, the intensity of the inspection light L3 emitted from the second light source 52 is set to be smaller than the intensity of the detection light L1 emitted from the first light source 51, and the intensity of the diffuse reflected light L4 detected by the multiple photodetectors 53a, 53b, 53c, and 53d is set to be smaller than the intensity of the transmitted light L2 detected by the multiple photodetectors 53a, 53b, 53c, and 53d. As a result, even if the multiple photodetectors 53a, 53b, 53c, and 53d detect the diffuse reflected light L4, it is possible to reduce or eliminate the influence on the detection of hole defects performed by detecting the transmitted light L2.

In the hole defect detection device 5 according to the embodiment, inspection light L3 is irradiated from the second light source 52 toward the front surface of the steel strip S, and the diffuse reflected light L4 reflected by the front surface of the steel strip S is detected by the multiple photodetectors 53a, 53b, 53c, and 53d, resulting in a state in which a certain light intensity is detected. Therefore, in this state, it is possible to detect abnormalities (failures) in the multiple photodetectors 53a, 53b, 53c, and 53d based on the light intensity detected by the multiple photodetectors 53a, 53b, 53c, and 53d.

Figure 6 shows an example of the intensity of light detected by the photodetector 53 when the photodetector 53 is abnormal.

In the hole defect detection device 5 according to the embodiment, when an abnormality occurs in at least one of the multiple photodetectors 53a, 53b, 53c, and 53d, the photodetector 53 in which the abnormality occurred is unable to properly detect light. Therefore, for example, when the photodetector 53 in which the abnormality occurred is unable to detect any light at all, as shown in FIG. 6, the intensity of the light output as the detection result of the photodetector 53 in which the abnormality occurred becomes small, like the steel strip portion shown in FIG. 4. Therefore, in the hole defect detection device 5 according to the embodiment, the abnormality in the photodetector 53 can be detected as an abnormal portion with a very small light intensity.

As shown in FIG. 6, in the perforation defect detection device 5 according to the embodiment, a perforation defect threshold, which is a threshold value of the light intensity for detecting perforation defects in the steel strip S, and an abnormality threshold, which is a threshold value of the light intensity for detecting an abnormality in the light detector 53, are set. The perforation defect threshold is a value greater than the intensity of the diffuse reflected light L4 detected by a normal light detector 53, and the abnormality threshold is a value less than the intensity of the diffuse reflected light L4 detected by a normal light detector 53.

Then, the determination device 54 determines that there is a hole defect when the light intensity detected by the multiple photodetectors 53a, 53b, 53c, and 53d is equal to or greater than the hole defect threshold, and determines that there is no hole defect when the light intensity is less than the hole defect threshold. The determination device 54 also determines that the photodetector 53 is normal when the light intensity detected by the multiple photodetectors 53a, 53b, 53c, and 53d is equal to or greater than the abnormality threshold, and determines that the photodetector 53 is abnormal when the light intensity is less than the abnormality threshold. Note that which of the multiple photodetectors 53a, 53b, 53c, and 53d is abnormal can be identified, for example, by the determination device 54 identifying the photodetector 53 that detected a light intensity less than the abnormality threshold.

In addition, in the hole defect detection device 5 according to the embodiment, the detected abnormality of the optical detector 53 may be detected as a defect separate from the hole defect, and may be registered, for example, in a memory unit of the determination device 54 so that they can be distinguished from each other.

In this way, in the hole defect detection device 5 according to the embodiment, when an abnormality occurs in at least one of the multiple photodetectors 53a, 53b, 53c, and 53d and light cannot be detected properly, the photodetector 53 in which the abnormality occurred can be detected based on the intensity of light detected by each of the multiple photodetectors 53a, 53b, 53c, and 53d.

When an abnormality in the photodetector 53 is detected, for example, a signal related to the abnormality in the photodetector 53 is output from the judgment device 54 to a higher-level system or the like. This allows information related to the abnormality in the photodetector 53 to be displayed on a display device provided in the higher-level system, and an operator or the like is notified, allowing the operator or the like to take measures such as inspection or repair of the photodetector 53 in which the abnormality was detected. In addition to the above measures, the operator or the like can take measures to classify the coil of steel strip S in which the perforation defect detection device 5 was used to detect the perforation defect when the abnormality in the photodetector 53 was detected as a rejected coil in which the perforation defect was not properly detected due to the abnormality in the photodetector 53.

As described above, the perforation defect detection device 5 according to the embodiment is installed in the continuous production line 1, and can continuously detect perforation defects in the steel strip S as the steel strip S is transported without stopping the operation of the continuous production line 1, while inspecting the perforation defect detection device 5 to detect abnormalities in the optical detector 53. Furthermore, in the perforation defect detection device 5 according to the embodiment, the metal strip for which perforation defects are detected is not limited to a steel strip, and may be, for example, an aluminum strip.

Reference Signs List 1 Continuous manufacturing line 2 Payoff reel 3 Tension reel 4 Welding machine 5 Hole defect detection device 51 First light source 52 Second light source 53 Light detector 54 Judgment device

Claims (4)

1. An inspection method for a metal strip perforation defect detection device that optically detects perforation defects in a metal strip, comprising:
A method for inspecting a metal strip perforation defect detection device, comprising the steps of: irradiating light from a first light source across the entire width of the metal strip; detecting perforation defects by detecting light that passes through holes in the metal strip using a photodetector that is positioned on the opposite side of the metal strip from the first light source, sandwiching the metal strip in the thickness direction; irradiating light from a second light source that is positioned on the opposite side of the metal strip from the first light source, sandwiching the metal strip in the thickness direction, across the entire width of the metal strip; detecting diffuse reflected light from the metal strip using the photodetector; and determining whether the photodetector is normal or abnormal based on a characteristic value of the light detected by the photodetector. the characteristic value of the light is the intensity of the light;
2. An inspection method for a metal strip perforation defect detection device as described in claim 1, characterized in that when the intensity of light detected by the photodetector is equal to or greater than an abnormality threshold, which is a preset threshold value of the light intensity for detecting abnormalities in the photodetector, the photodetector is determined to be normal, and when the intensity of light detected by the photodetector is less than the abnormality threshold, the photodetector is determined to be abnormal. A metal strip perforation defect detection device for optically detecting a perforation defect in a metal strip, comprising:
a first light source that irradiates light across the entire width of the metal strip;
a photodetector disposed on an opposite side of the metal strip from the first light source in a thickness direction;
a second light source disposed on the opposite side of the metal strip from the first light source across the thickness direction of the metal strip and configured to irradiate light across the entire width of the metal strip;
a determination device that determines whether the photodetector is normal or abnormal based on a characteristic value of the light detected by the photodetector;
A metal strip hole defect detection device comprising: the characteristic value of the light is the intensity of the light;
The metal strip perforation defect detection device according to claim 3, characterized in that the judgment device judges that the photodetector is normal when the intensity of light detected by the photodetector is equal to or greater than an abnormality threshold, which is a preset threshold value of the light intensity for detecting abnormalities in the photodetector, and judges that the photodetector is abnormal when the intensity of light detected by the photodetector is less than the abnormality threshold.

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