METHOD FOR DETECTING PERFORATED DEFECTS IN METAL STRIPES AND DEVICE FOR DETECTING PERFORATED DEFECTS IN METAL STRIPES

Abstract

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

Description

[Technical field]

[0001] The present invention relates to an inspection method for a metal strip perforation defect detection device and a metal strip perforation defect detection device. [Background technology]

[0002] Conventionally, in a continuous production line for a metal strip such as a steel strip, a hole defect detection device is provided in which a light source and a detector are disposed above and below the continuously transported metal strip, and the light emitted from the light source and passing through holes in the metal strip is detected by the detector to detect hole defects in the metal strip. In such an optical hole defect detection device, 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 has prevented the detector from detecting the passing light.

[0003] Patent Document 1 discloses a technology in which diagnostic light is incident on a photodetector of a receiver while hole defect detection is being performed on a welded portion between coils of a steel strip, and the receiver is diagnosed based on a light detection signal from the photodetector of the receiver.

[0004] Patent document 2 discloses a technology in which a spot light simulating a hole is irradiated onto a metal strip or a light receiving unit, and if the spot light is detected as a hole, the detection device determines that it is normal, and if the spot light is not detected as a hole, the detection device determines that it is abnormal.

[0005] 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 shone from a small inspection light towards 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. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2013-11561 A [Patent Document 2] JP 2010-185679 A [Patent Document 3] JP 2017-3269 A Summary of the Invention [Problem to be solved by the invention]

[0007] 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, and accurate hole defect detection cannot be performed. Therefore, it is not possible to diagnose the receiver other than at the welded part of the steel strip.

[0008] The technique disclosed in Patent Document 2 makes it impossible to check for abnormalities in parts not hit by the spot light within the field of view in the metal strip width direction of the same detector.

[0009] In the technology disclosed in Patent Document 3, when inspecting the camera, the light used to detect holes in the metal strip is blocked by the inspection shutter, making it impossible to check for the presence or absence of holes in the metal strip during camera inspection.

[0010] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide an inspection method for a metal strip perforation defect detection device that can detect perforation defects in a metal strip while detecting abnormalities in a photodetector, and a metal strip perforation defect detection device. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems and achieve the object, the inspection method for a metal strip perforation defect detection device of the present invention is an inspection method for a metal strip perforation defect detection device that optically detects perforation defects in a metal strip, and is characterized in that light is irradiated from a first light source over the entire width of the metal strip, and a photodetector arranged on the opposite side of the first light source across the metal strip in the thickness direction detects the light that has passed 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 first light source across the metal strip in the thickness direction over the entire width of the metal strip, and the diffuse reflected light reflected by the metal strip is detected by the photodetector, and whether the photodetector is normal or abnormal is determined based on the characteristic value of the light detected by the photodetector.

[0012] In addition, the inspection method for a 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 light intensity, 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.

[0013] In addition, the metal strip perforation defect detection device of the present invention is a metal strip perforation defect detection device that optically detects perforation defects in a metal strip, and is characterized in that it comprises 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 first light source across the metal strip in the thickness direction, a second light source that is arranged on the opposite side of the first light source across the metal strip in the thickness direction and that 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 characteristic values ​​of the light detected by the photodetector.

[0014] In addition, the metal strip hole defect detection device of the present invention is characterized in that, in the above invention, the characteristic value of the light is light intensity, and the judgment device judges 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 abnormalities in the light detector, and judges that the light detector is abnormal when the intensity of the light detected by the light detector is less than the abnormality threshold. Effect of the Invention

[0015] The inspection method for a metal strip perforation defect detection device 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. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram for explaining a continuous production line according to an embodiment. [Diagram 2] 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. [Diagram 3] 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. [Figure 4] 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. [Diagram 5] 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. [Figure 6] FIG. 6 is a diagram showing an example of the intensity of light detected by the photodetector when the photodetector is abnormal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the inspection method for detecting a perforation defect in a metal strip and the perforation defect detection device for a metal strip according to the present invention will be described. Note that the present invention is not limited to the embodiment.

[0018] FIG. 1 is a diagram for explaining a continuous production line 1 according to an embodiment.

[0019] As shown in FIG. 1, the continuous production line 1 includes a pay-off reel 2, a tension reel 3, a welding machine 4, and a hole defect detection device 5. In the continuous production line 1, a steel strip S, which is a metal strip wound in a coil shape, is unwound from the pay-off reel 2, subjected to a predetermined process, and then wound in 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. Note that a 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 a hole defect in the steel strip S.

[0020] Fig. 2 is a schematic diagram of the hole defect detection device 5 according to the embodiment as viewed from the downstream side in the steel strip transport direction. Fig. 3 is a schematic diagram of the schematic configuration of the hole defect detection device 5 according to the embodiment as viewed from the steel strip width direction.

[0021] 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 one another, they are also simply referred to as photodetectors 53.

[0022] 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 for detecting perforation defects from below the steel strip S toward the back side of the steel strip S, over the entire width of the steel strip S (the entire width direction of the steel strip).

[0023] The second light source 52 is a light used to inspect the multiple photodetectors 53a, 53b, 53c, and 53d for abnormalities (failures), and is positioned on the opposite side of the steel strip S from the first light source 51 across 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.

[0024] The multiple photodetectors 53a, 53b, 53c, 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 across the thickness direction of the steel strip S so that perforation defects can be detected over the entire width of the steel strip S. The multiple photodetectors 53a, 53b, 53c, 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, 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 partially overlap each other in the light receiving ranges (field of view).

[0025] When no hole defect is present 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 from 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 light detectors 53a, 53b, 53c, 53d and is not detected. On the other hand, when a hole defect is present in the steel strip S, the transmitted light L2 of the detection light L1 irradiated from the first light source 51 toward the back surface of the steel strip S that passes through the hole in the steel strip S reaches and is detected by at least one of the multiple light detectors 53a, 53b, 53c, 53d.

[0026] 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.

[0027] In the hole defect detection device 5 according to the embodiment, as shown in Fig. 3, the second light source 52 is disposed upstream of the light detector 53 in the steel strip transport direction, and an optical system is configured in which 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 disposed downstream of the light detector 53 in the steel strip transport direction.

[0028] The determination device 54 determines the presence or absence of a hole defect and the presence or absence of an abnormality (failure) of 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.

[0029] In the perforation defect detection device 5 of the embodiment, while the steel strip S is being transported, a detection light L1 is constantly irradiated from a first light source 51 toward the back surface of the steel strip S over 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 a second light source 52 toward the front surface of the steel strip S over the entire width of the steel strip S to detect abnormalities in the multiple photodetectors 53a, 53b, 53c, 53d.

[0030] FIG. 4 is a diagram showing an example of the intensity of light detected by the photodetector 53 when the second light source 52 is not irradiated with the inspection light L3.

[0031] In the perforation 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, 53d may include some ambient light, but is mostly comprised 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, 53d is such that the steel strip portion where the perforation defect of the steel strip S does not exist is a dark portion with low light intensity, whereas the perforation defect portion where the perforation defect of the steel strip S exists is a bright portion with high light intensity.

[0032] FIG. 5 is a diagram showing an example of the intensity of light detected by the photodetector 53 when the inspection light L3 is irradiated from the second light source 52. As shown in FIG.

[0033] In the hole defect detection device 5 according to the embodiment, when the first light source 51 irradiates the back surface of the steel strip S with detection light L1 and the second light source 52 irradiates the front surface of the steel strip S with inspection light L3, the light detected by the multiple photodetectors 53a, 53b, 53c, 53d is dominated by transmitted light L2 that passes through the holes in the steel strip S and 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, 53d is such that the hole defect portion becomes a bright portion with a high light intensity, and the steel strip portion becomes a bright portion with a light intensity higher than the light intensity of the steel strip portion shown in Fig. 4 by the intensity of the diffuse reflected light L4.

[0034] 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 passing light L2 detected by the multiple photodetectors 53a, 53b, 53c, and 53d. This makes it possible to reduce or eliminate the influence of the diffuse reflected light L4 detected by the multiple photodetectors 53a, 53b, 53c, and 53d on the detection of the hole defect performed by detecting the passing light L2.

[0035] 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 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 constant light intensity is detected. Therefore, in this state, it is possible to detect an abnormality (failure) of the multiple photodetectors 53a, 53b, 53c, and 53d based on the light intensity detected by the multiple photodetectors 53a, 53b, 53c, and 53d.

[0036] FIG. 6 is a diagram showing an example of the intensity of light detected by the photodetector 53 when the photodetector 53 is abnormal.

[0037] 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 cannot properly detect light. Therefore, for example, when the photodetector 53 in which the abnormality occurred cannot detect light at all, as shown in Fig. 6, the intensity of light output as the detection result of the photodetector 53 in which the abnormality occurred becomes small like the steel strip part shown in Fig. 4. Therefore, in the hole defect detection device 5 according to the embodiment, the abnormality of the photodetector 53 can be detected as an abnormal part with a very small intensity of light.

[0038] 6, in the perforation defect detection device 5 according to the embodiment, a perforation defect threshold, which is a threshold of the light intensity for detecting a perforation defect in the steel strip S, and an abnormality threshold, which is a threshold of the light intensity for detecting an abnormality in the photodetector 53, are set. The perforation defect threshold is a value greater than the intensity of the diffuse reflected light L4 detected by the photodetector 53 when it is functioning properly, and the abnormality threshold is a value less than the intensity of the diffuse reflected light L4 detected by the photodetector 53 when it is functioning properly.

[0039] 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. It is to be noted that which of the multiple photodetectors 53a, 53b, 53c, and 53d is abnormal can be grasped by, for example, using the determination device 54 to identify the photodetector 53 that detected the light intensity less than the abnormality threshold.

[0040] In addition, in the perforation defect detection device 5 according to the embodiment, the detected abnormality of the photodetector 53 may be detected as a defect separate from the perforation defect, and may be registered, for example, in a memory unit of the judgment device 54 so that each can be distinguished.

[0041] In this way, in the hole defect detection device 5 of the embodiment, when an abnormality occurs in at least one of the multiple photodetectors 53a, 53b, 53c, and 53d and the photodetector 53 is no longer able to detect light properly, the photodetector 53 in which the abnormality has occurred can be detected based on the intensity of light detected by each of the multiple photodetectors 53a, 53b, 53c, and 53d.

[0042] 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 about 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, so that the operator or the like can 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 was detected by the perforation defect detection device 5 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.

[0043] As described above, the perforation defect detection device 5 according to the embodiment is installed in the continuous production line 1, and thus 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. [Explanation of symbols]

[0044] 1 Continuous production line 2 Payoff Reel 3 Tension reel 4. Welding machine 5. Hole defect detection device 51 First Light Source 52 Second Light Source 53 Photodetector 54 Judgment device

Claims

1. A method for inspecting a metal strip for a perforation defect detection device, which optically detects perforation defects in a metal strip continuously in accordance with conveyance of the metal strip, comprising: During transport of the metal strip, light is constantly irradiated from a first light source across the entire width of the metal strip, and a photodetector disposed on the opposite side of the metal strip from the first light source across the thickness of the metal strip detects light passing through holes in the metal strip to detect hole defects; During transport of the metal strip, light is constantly irradiated across the entire width of the metal strip from a second light source disposed on the opposite side of the metal strip from the first light source, and diffuse reflected light reflected by the metal strip is detected by the photodetector, and it is determined 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; an intensity of the light emitted from the second light source is set to be smaller than an intensity of the light emitted from the first light source, and an intensity of the diffuse reflected light detected by the photodetector is set to be smaller than an intensity of the transmitted light detected by the photodetector; 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 intensity of light for detecting an abnormality of 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; The abnormality threshold is a value smaller than the intensity of the diffuse reflected light detected by the photodetector when the photodetector is normal.

2. A method for inspecting a metal strip using a perforation defect detection device.

2. A metal strip perforation defect detection device for optically detecting perforation defects in a metal strip continuously in accordance with conveyance of the metal strip, comprising: a first light source that constantly irradiates light over the entire width of the metal strip while the metal strip is being transported; a photodetector disposed on an opposite side of the first light source across the metal strip in a thickness direction; a second light source that is disposed on the opposite side of the metal strip from the first light source across the thickness direction of the metal strip and that constantly irradiates light across the entire width of the metal strip while the metal strip is being transported; a determination device that determines whether the photodetector is normal or abnormal based on a characteristic value of the light detected by the photodetector; It is equipped with the characteristic value of the light is the intensity of the light; an intensity of light emitted from the second light source is set to be smaller than an intensity of light emitted from the first light source, and an intensity of diffuse reflected light reflected by the metal strip and detected by the photodetector is set to be smaller than an intensity of transmitted light passing through a hole in the metal strip and detected by the photodetector; the determination device determines 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 intensity of light for detecting an abnormality of the photodetector, and determines that the photodetector is abnormal when the intensity of light detected by the photodetector is less than the abnormality threshold; The abnormality threshold is a value smaller than the intensity of the diffuse reflected light detected by the photodetector when the photodetector is normal.

1. A metal strip hole defect detection device comprising:

Images