JP7343781B2 - Metal plate surface defect inspection equipment - Google Patents

Description

The present invention irradiates illumination light from a light source onto a metal plate that is the object of surface inspection, images the reflected light with an imaging camera, and processes the obtained image signal to inspect surface defects. The present invention relates to a surface defect inspection device for metal plates.

Steel plates, which are a type of metal plate and are produced through an annealing process and a temper rolling process, have appearance abnormalities that appear on their surfaces, such as sagging defects, rolling defects, and lateral deviation defects. Steel plates containing this material will be of poor quality. Unlike plated products and stainless steel products, during the final inspection process for special steel and ordinary steel, in order to prevent scratches due to rust during the process or misalignment between layers of the coil, the final inspection process is carried out with oil from cold rolling or temper rolling applied. It is necessary to conduct an inspection. In addition, it also includes annealing stripes that inevitably occur due to annealing. Steel plates with these appearance abnormalities are not considered to be of poor quality, depending on the product use. For this reason, in steel plate manufacturing sites, it is required to accurately distinguish these appearance abnormalities.
Note that which of the above-mentioned various appearance abnormalities are harmful and which are harmless differs depending on the user of the metal plate. Therefore, the quality-related contract between the user and the manufacturer determines what is considered harmful and what is not harmful among external appearance abnormalities, and the manufacturer must determine the inspection items and standards according to the contract. It is necessary to distinguish between harmful and harmless appearance abnormalities.

Conventionally, as this type of technology, for example, the following Patent Document 1 (Japanese Patent No. 6117398) discloses an illumination unit that illuminates an imaging target part supported from below by rolls on the surface of a running steel plate. and a first diffusely reflected light imaging unit that images the diffusely reflected light in a direction in which the angle formed by the specular reflection direction is a first angle γ, and the angle formed by the specular reflection direction is a second angle δ (however, δ >γ); a second diffusely reflected light image signal obtained by imaging by the first diffusely reflected light imager; and a second diffusely reflected light image signal. an image signal processing section that processes a second diffuse reflection image signal obtained by imaging the first diffuse reflection image signal, and the image signal processing section has a luminance lower than a predetermined first threshold value of the first diffuse reflection image signal. A surface defect inspection apparatus has been disclosed that detects, as a surface defect site, a site for which a second diffuse reflection image signal has a higher luminance than a predetermined second threshold value.
According to this technique, it is possible to distinguish between harmful and non-hazardous appearance abnormalities by using a steel plate whose surface has not been subjected to surface treatment such as plating to be inspected.

Patent No. 6117398

However, the above conventional technology has the following problems.
As mentioned above, there is no problem when inspecting the surface defects of the metal plate at the imaging target area formed on the surface (upper surface) of the metal plate by supporting the metal plate from below with a roll. For example, in order to simultaneously inspect both the front and back surfaces (both upper and lower surfaces) of a moving metal plate, the metal plate is supported from above with a roll and the surface defects of the imaged area formed on the back (lower surface) of the metal plate are detected. When inspecting, if the metal plate to be inspected is, for example, a thin material with high malleability, a problem arises in that the inspection accuracy of the back surface of the metal plate is reduced. To elaborate on this point, the part to be imaged on a metal plate is set at a position where the pass line supported by rolls is extremely stable. When supporting the metal plate by pressing a roll onto it from above, there is nothing to support the metal plate, so the metal plate (supported by the roll from above) will sag due to its own weight and the pass line will flap. It becomes like this. As a result, the signal reflection level at the imaging target site cannot be stabilized, making it difficult to distinguish between harmful and harmless appearance abnormalities. In order to solve this problem, the pass line can be stabilized by applying back tension to the running metal plate. In the case of thin annealed materials of 0.5 mm or less, if back tension is applied to the extent that the pass line is stabilized, slip defects may occur on the urethane pinch rolls (powered), or the line entry and exit sides may be damaged. Problems such as speed synchronization between the two sides become difficult, making high-speed operation impossible.

Therefore, an object of the present invention is to provide a surface defect inspection device for a metal plate that can clearly distinguish between harmful and harmless appearance abnormalities on the back side of a running metal plate.

In order to achieve the above object, the present invention, for example, as shown in FIGS. 1 and 2, has a metal plate surface defect inspection apparatus 10 configured as follows.
That is, a set of upper and lower front pinch rolls 12, a set of upper and lower rear pinch rolls 16 forming a pass line along which the metal plate 14 runs between the front pinch rolls 12, and a set of rear pinch rolls 16 that run on the pass line. A backside inspection roll 18 that contacts the metal plate 14 from above is disposed below the traveling metal plate 14, and when the backside inspection roll 18 comes into contact with the metal plate 14, the An illumination section 22 that irradiates light toward the imaging target region 20 formed on the back surface of the metal plate 14, a reflected light imaging section 24 that images the reflected light from the imaging target region 20, and the reflected light imaging section. The image signal processing section 26 detects a surface defect site of the metal plate 14 based on an image signal obtained from the reflected light imaged at 24. A guide roll 30 that is not in contact with the back surface inspection roll 18 is disposed between the back surface inspection roll 18 and the rear pinch roll 16, and the guide roll 30 is used to inspect the metal plate 14. Lift and energize the pass line upward.

The metal plate surface defect inspection apparatus of the present invention has the following effects.
A guide roll is installed between the back inspection roll and the rear pinch roll, and the guide roll lifts and biases the pass line of the metal plate upward, so that the lowest point of the back inspection roll A metal plate is wrapped around the front and rear surfaces to form an imaging target region. As a result, there is no flapping of the metal plate in the area to be imaged, the reflection level of the signal (reflected light) in the area to be imaged is stabilized, and it is possible to clearly distinguish between harmful and harmless appearance abnormalities on the back side of the moving metal plate. A device capable of detecting surface defects on a metal plate can be provided.
In addition, since the guide roll is not in contact with the back inspection roll, the oil coated on the surface of the metal plate may be squeezed and dripped, contaminating the reflected light imaging section, lighting section, etc. Interference with the shaft can be prevented.

In the present invention, the diameter of the backside inspection roll 18 is 100 mm or more, and the winding angle θ1 of the metal plate 14 around the backside inspection roll 18 at the imaging target region 20 is 10° or more. It is preferable that
Further, among the winding angle θ1 of the metal plate 14 around the back inspection roll 18 in the imaging target region 20, the movement of the metal plate 14 is performed from the lowest point P1 of the back inspection roll 18. It is preferable that the angle θ2 on the downstream side in the direction is 2° or more.
In these cases, in addition to the above-mentioned effects becoming even more remarkable, the entire surface defect inspection device can be made compact, and it is possible to prevent the metal plate from being warped after passing through the guide rolls. You will be able to do this.

Furthermore, it is preferable that the present invention adds the unique configuration described in the embodiment described later.

1 is a flow diagram schematically showing a surface defect inspection apparatus for a metal plate according to an embodiment of the present invention. FIG. 2 is an enlarged schematic flow diagram of main parts in FIG. 1. FIG. This is a flaw information image output when inspecting locations where minute lateral deviation flaws occur on the front and back of a metal plate using the metal plate surface defect inspection apparatus according to one embodiment of the present invention. This is a flaw information image output when a conventional metal plate surface defect inspection device is used to inspect locations where minute lateral deviation flaws occur on the front and back of a metal plate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A surface defect inspection apparatus for metal plates according to the present invention will be described below with reference to the drawings.
FIG. 1 is a flow diagram schematically showing a surface defect inspection apparatus 10 for a metal plate according to an embodiment of the present invention. The metal plate surface defect inspection device 10 of the present invention is installed on the pass line of the metal plate 14 in a continuous pickling line, plating/color painting line, slitter line, etc. As shown in this figure, the front pinch roll 12, the rear pinch roll 16, the front side inspection roll 17, the back side inspection roll 18, the illumination units 21 and 22, and reflected light imaging. It is roughly composed of sections 23 and 24, an image signal processing section 26, an inspection result output section 28, and a guide roll 30.
Note that the metal plate 14 in this embodiment is a steel plate, the surface of which has not been subjected to plating treatment, and has oil applied thereto.

The front pinch roll 12 is a roll (rotating body) that forms the starting point of the pass line of the metal plate 14 introduced into the surface defect inspection apparatus 10 of the present invention, and comes into contact with the back surface of the metal plate 14 to support it. The front lower roll 12a and the front upper roll 12b, which is disposed directly above the front lower roll 12a and cooperates with the front lower roll 12a to send out the sandwiched metal plate 14 downstream in the running direction, are aligned vertically. It consists of a set of roles.

The rear pinch roll 16 is a roll (rotating body) that forms the end point of the pass line of the metal plate 14 introduced into the surface defect inspection apparatus 10 of the present invention, and comes into contact with the back surface of the metal plate 14 to support it. a rear lower roll 16a, which is disposed directly above the rear lower roll 16a, and a rear upper part that cooperates with the rear lower roll 16a to send the sandwiched metal plate 14 to a subsequent process for surface defect inspection. It is composed of a pair of upper and lower rolls including the roll 16b.

The surface inspection roll 17 contacts and supports the back surface of the metal plate 14 running immediately after the front pinch roll 12 in the pass line formed in the surface defect inspection apparatus 10, and supports the metal plate 14 running immediately after the front pinch roll 12. This is a roll (rotating body) for forming an imaging target region 19 on the surface of the metal plate 14 so that the metal plate 14 does not sway in the thickness direction. The surface inspection roll 17 preferably has a diameter of 100 mm or more. If the diameter of the surface inspection roll 17 is 100 mm or more in this way, it is possible to form an imaging target region 19 suitable for inspecting surface defects. In the illustrated embodiment, a hard urethane rubber roll with a diameter of 200 mm is used as the surface inspection roll 17.

The back surface inspection roll 18 is in contact with the surface of the metal plate 14 that runs between the surface inspection roll 17 and the rear pinch roll 16 among the pass lines formed in the surface defect inspection device 10. This is a roll (rotating body) for supporting the metal plate 14 from above and forming an imaging target region 20 on the back surface of the metal plate 14 so that the metal plate 14 does not sway in the thickness direction. Like the above-mentioned front surface inspection roll 17, this back surface inspection roll 18 also preferably has a diameter of 100 mm or more. In the illustrated embodiment, the backside inspection roll 18 is also a hard urethane rubber roll with a diameter of 200 mm.

Here, to explain the positional relationship between the above-mentioned front surface inspection roll 17 and back surface inspection roll 18, in side view, the contact point of the upper and lower pair of front pinch rolls 12 (the front lower roll that contacts via the metal plate 14) 12a and the front upper roll 12b) and the contact point of the pair of upper and lower rear pinch rolls 16 (the contact point between the lower rear roll 16a and the upper rear roll 16b, which are in contact via the metal plate 14). With respect to the horizontal line L1, the highest point P0 of the front surface inspection roll 17 is arranged above the horizontal line L1, and conversely, the lowest point P1 of the back surface inspection roll 18 is disposed below the horizontal line L1. will be placed in With this configuration, the metal plate 14 is wound around the surface of each of the front surface inspection roll 17 and the back surface inspection roll 18, and in particular, in the surface inspection roll 17, the flapping of the metal plate 14 is suppressed. It is possible to form a region 19 to be imaged.

The illumination unit 21 irradiates illumination light onto the imaging target region 19 on the surface (upper surface) of the metal plate 14, and its light source is an LED type line illumination that irradiates illumination light in the width direction of the metal plate 14. is used. Note that the light source of the illumination section 21 is not limited to this, and a halogen lamp, HID lamp, fluorescent lamp, etc. can also be used instead of the LED.
In the metal plate surface defect inspection apparatus 10 of the illustrated embodiment, the illumination unit 21 is configured to provide a surface 31 (hereinafter also referred to as "orthogonal surface 31") perpendicular to the running direction of the metal plate 14 at the imaging target region 19 on the surface of the metal plate 14. ) is installed upstream in the running direction of the metal plate 14, and the incident angle α of the illumination light on the surface of the metal plate 14 is set to a predetermined acute angle with respect to the orthogonal plane 31.

The illumination unit 22 irradiates illumination light to the imaging target region 20 on the back surface (lower surface) of the metal plate 14, and serves as a light source for illuminating the metal plate 14 in the width direction of the metal plate 14, similarly to the above-mentioned illumination unit 21. LED type line illumination that emits light is used. Note that the light source of the illumination unit 22 is not limited to this, and a halogen lamp, HID lamp, fluorescent lamp, etc. can also be used instead of the LED.
In the metal plate surface defect inspection apparatus 10 of the illustrated embodiment, the illumination unit 22 is configured to provide a surface 32 (hereinafter also referred to as "orthogonal surface 32") perpendicular to the running direction of the metal plate 14 at the imaging target site 20 on the surface of the metal plate 14. ) is installed upstream in the traveling direction of the metal plate 14, and the incident angle β of the illumination light on the surface of the metal plate 14 is set to a predetermined acute angle with respect to the orthogonal plane 32.

The reflected light imaging unit 23 images diffusely reflected light, which is less susceptible to the effects of uneven oil application on the surface of the metal plate 14, out of the light emitted from the illumination unit 21 and reflected by the imaging target region 19 on the surface of the metal plate 14. A high-resolution CMOS line sensor camera is used. Note that the reflected light imaging unit 23 is not limited to this, and instead of the CMOS line sensor camera, a CMOS area sensor camera, a CCD line sensor camera, or the like may be used. Further, the spatial resolution and density resolution of the reflected light imaging section 23 are appropriately selected depending on the type of appearance abnormality to be detected.
In the present embodiment, the reflected light imaging section 23 is installed downstream of the orthogonal surface 31 in the traveling direction of the metal plate 14, and out of the reflected light from the surface of the metal plate 14, the reflected light imaging section 23 is located more downstream than the regular reflected light. A low-angle camera 23a that images the first diffusely reflected light 34 that forms a large angle with the orthogonal surface 31, and a second diffusely reflected light that forms a larger angle with the orthogonal surface 31 than the first diffusely reflected light 34. 36. Note that the reflected light imaging unit 23 is not limited to a camera that captures two types of diffusely reflected light, such as a low-angle camera 23a and a high-angle camera 23b, but may be configured with one type of camera depending on the purpose. It may also be configured with a device that images the diffusely reflected light.

The reflected light imaging unit 24 images diffusely reflected light, which is less affected by uneven oil application on the surface of the metal plate 14, out of the light emitted from the illumination unit 22 and reflected by the imaging target region 20 on the surface of the metal plate 14. As with the reflected light imaging section 23 described above, a high-resolution CMOS line sensor camera is used. Note that the reflected light imaging unit 24 is not limited to this, and instead of the CMOS line sensor camera, a CMOS area sensor camera, a CCD line sensor camera, or the like may be used. Further, the spatial resolution and concentration resolution of the reflected light imaging section 24 are appropriately selected depending on the type of appearance abnormality to be detected.
In the present embodiment, the reflected light imaging section 24 is installed downstream of the orthogonal surface 32 in the running direction of the metal plate 14, and out of the reflected light from the surface of the metal plate 14, the reflected light is smaller than the regular reflected light. A low-angle camera 24a that images the first diffusely reflected light 38 that forms a large angle with the orthogonal surface 32, and a second diffusely reflected light that forms a larger angle with the orthogonal surface 32 than the first diffusely reflected light 38. 40 and a high-angle camera 24b. Note that the reflected light imaging unit 24 is not limited to a camera that captures two types of diffusely reflected light, such as a low-angle camera 24a and a high-angle camera 24b, but may be configured with one type of camera depending on the purpose. It may also be configured with a device that images the diffusely reflected light.

The image signal processing unit 26 processes the image signal obtained by imaging the diffusely reflected light by the reflected light imaging units 23 and 24, extracts the appearance abnormality of the metal plate 14, and further determines whether the extracted appearance abnormality is harmful or harmless. Determine the classification. The image signal processing unit 26 is constituted by, for example, an arithmetic processing device such as a PC (personal computer) or a microcomputer in which various programs necessary for executing logic for determining external appearance abnormalities such as surface flaws are stored. One example of this necessary program is a threshold selection program that selects a threshold when binarizing the image signals obtained by the reflected light imaging units 23 and 24.

The inspection result output unit 28 is installed as necessary, and when a harmful appearance abnormality is extracted by the image signal processing unit 26, it outputs information indicating that a harmful appearance abnormality has been detected and the type of the detected harmful appearance abnormality. This is to inform the user of the current manufacturing process, the next manufacturing process, and as necessary by means such as display or printing. This test result output unit 28 is configured with, for example, a monitor device, a printer device, and the like.

The guide roll 30 is disposed between the back inspection roll 18 and the rear pinch roll 16 without contacting the back inspection roll 18, and the metal plate 14 is placed between the back inspection roll 18 and the rear pinch roll 16. This is a roll (rotating body) for lifting and biasing the pass line upward so that the metal plate 14 does not sag when being supported and forming the imaging target region 20 on the back surface thereof.
In this embodiment, a hard urethane rubber roll with a diameter of less than 100 mm (more specifically, a diameter of 90 mm) is used as the guide roll 30. By using a roll having a smaller diameter than the back surface inspection roll 18 in this manner, it is possible to prevent the guide roll 30 from interfering with the path of the second diffusely reflected light 40 heading toward the reflected light imaging section 24.

It is preferable that the winding angle θ1 of the metal plate 14 around the back inspection roll 18 in the imaging target region 20, which is caused by lifting the pass line of the metal plate 14 due to the arrangement of the guide roll 30, is 10° or more. . Here, the winding angle θ1 is defined as a point P2 at which the metal plate 14 and the back surface inspection roll 18 contact each other on the upstream side of the pass line when the guide roll 30 is viewed from the side as shown in FIG. This is the central angle formed at the center C of the back surface inspection roll 18 corresponding to the circular arc up to the point P3 where the metal plate 14 and the back surface inspection roll 18 separate on the downstream side thereof.
Also, among the winding angle θ1 of the metal plate 14 around the back inspection roll 18 in this imaging target region 20, the angle θ2 is on the downstream side in the traveling direction of the metal plate 14 from the lowest point P1 of the back inspection roll 18. is more preferably 2° or more.
By providing the winding angle θ1 as described above, there is no flapping of the metal plate 14 in the imaging target region 20, and the reflection level of the signal (in the case of this embodiment, the diffusely reflected lights 38 and 40) in the imaging target region 20 is reduced. is further stabilized, and it becomes possible to more clearly distinguish between harmful and non-hazardous appearance abnormalities on the back side of the running metal plate 14 and detect them. In addition, the entire surface defect inspection apparatus can be made compact, and it is possible to prevent the metal plate 14 from being warped after passing through the guide rolls 30.

In addition, in this embodiment, in order to realize the above-mentioned winding angle θ1, the guide roll 30 was installed at the following position. That is, the highest point P4 of the guide roll 30 is located above the lowest point P1 of the back inspection roll 18, and the path line L2 from the back inspection roll 18 to the rear pinch roll 16 is tangent to the guide roll 30. The guide roll 30 was placed at a height where it could be lifted by 7 mm at position (h). Further, a point P5 on the most upstream side of the pass line on the guide roll 30 was arranged so as to be located slightly upstream of the pass line with respect to a point P6 on the most downstream side of the pass line on the back inspection roll 18.

Among the elements (members) constituting the metal plate surface defect inspection apparatus 10 of the present invention as described above, all other components except the image signal processing section 26 and the inspection result output section 28 are mounted on a frame (not shown). etc., and are configured as one unit.

Next, we will discuss the surface defect inspection device 10 of the present embodiment (hereinafter referred to as “this embodiment device”) equipped with the guide roll 30 as described above, and the present embodiment except that it does not have such a guide roll 30. The difference in surface defect detection ability between the embodiment and a surface defect inspection apparatus having the same configuration (hereinafter referred to as "conventional apparatus") will be explained.
FIG. 3 shows a flaw information image output by inspecting a location where a minute lateral shift flaw has occurred on the metal plate 14 using the apparatus of this embodiment, and FIG. This is a flaw information image output after inspecting a location where a minute horizontal deviation flaw has occurred.
Here, the minute lateral deviation flaw is a minute flaw that occurs when the layers of the metal plate 14 are rubbed against each other when the metal plate 14 is wound up into a coil shape, and is generated on both the front and back sides of the metal plate 14. Further, the minute lateral displacement flaw is mainly localized in a form that spreads in the width direction of the metal plate 14 (the portion surrounded by the horizontally oblong ellipse in FIGS. 3 and 4 is the minute lateral displacement flaw). Note that, as shown in the upper right frame of FIG. 3, the silhouette of this minute horizontal deviation imaged by the reflected light imaging units 23 and 24 of the device of this embodiment and the conventional device is clearly visible with the low-angle cameras 23a and 24a. The high-angle cameras 23b and 24b capture an image with an unclear silhouette (below the level of a trace).

As shown in FIG. 3, the device of this embodiment can detect minute horizontal displacement flaws on both the front and back surfaces of the metal plate 14. On the other hand, with the conventional device, as shown in FIG. 4, minute horizontal displacement flaws can be detected on the front side of the metal plate 14, but no minute horizontal displacement flaws can be detected on the back side. Looking at the low-angle camera image and the high-angle camera image shown in the upper right frame of Figure 4, the image of the part detected as a defect is different from that of the minute lateral shift flaw shown in the upper right frame of Figure 3. It is. As described above, the reason why the conventional device could not detect minute horizontal deviation flaws on the back surface of the metal plate 14 is that the running of the metal plate 14 fluctuates during inspection of the back surface of the metal plate 14, making the pass line unstable, and the image signal One example of this is that the processing unit 26 was unable to set a strict threshold value. Therefore, by using the apparatus of this embodiment, it is possible to set a strict threshold value for the back surface as well as the front surface, thereby achieving high inspection accuracy.

In the above-described embodiment, the front surface inspection roll 17 and the back surface inspection roll 18 are arranged in this order from the upstream side to the downstream side of the pass line of the metal plate 14, but this is not necessary. If not, the surface inspection roll 17 and the accompanying illumination section 21 and reflected light imaging section 23 may be omitted.
Further, the back surface inspection roll 18 and the front surface inspection roll 17 may be arranged in this order from the upstream side to the downstream side of the pass line of the metal plate 14. In this case, instead of providing a separate guide roll 30, the surface inspection roll 17 may be adjusted so that it can also be used as the guide roll 30.

Furthermore, it goes without saying that the present invention can be modified in other ways within the scope of those skilled in the art.

10: Metal plate surface defect detection device, 12: Front pinch roll, 14: Metal plate, 16: Back pinch roll, 18: Back inspection roll, 20: Imaging target region, 22: Illumination unit, 24: Reflected light Imaging unit, 26: image signal processing unit, 28: inspection result output unit, 30: guide roll, P1: lowest point of the roll for back side inspection.

Claims (3)

a pair of upper and lower front pinch rolls (12); a pair of upper and lower rear pinch rolls (16) forming a pass line along which a metal plate (14) runs between the front pinch rolls (12); A backside inspection roll (18) that contacts the metal plate (14) running on the pass line from above, and a backside inspection roll (18) that is disposed below the running metal plate (14). 18) that irradiates light toward an imaging target region (20) formed on the back surface of the metal plate (14) by contacting the metal plate (14); A reflected light imaging unit (24) that images the reflected light at the target site (20), and an image signal obtained from the reflected light imaged by the reflected light imaging unit (24), the metal plate (14) is In a metal plate surface defect inspection device comprising an image signal processing unit (26) for detecting a surface defect site,
A guide roll (30) that is not in contact with the back surface inspection roll (18) is disposed between the back surface inspection roll (18) and the rear pinch roll (16), and the guide roll ( 30) lifts and biases the pass line of the metal plate (14) upward;
A surface defect inspection device for metal plates characterized by the following. The metal plate surface defect inspection device according to claim 1,
The diameter of the back surface inspection roll (18) is 100 mm or more,
A surface of a metal plate characterized in that a winding angle (θ1) of the metal plate (14) around the back surface inspection roll (18) at the imaging target region (20) is 10° or more. Defect inspection equipment. The metal plate surface defect inspection device according to claim 2,
Among the winding angles (θ1) of the metal plate (14) around the back inspection roll (18) at the imaging target region (20), the lowest point of the back inspection roll (18) A metal plate surface defect inspection apparatus characterized in that an angle (θ2) on the downstream side in the running direction of the metal plate (14) from (P1) is 2° or more.