JP7205207B2 - A device that prevents dirt from adhering to the photographing window - Google Patents

Description

The present application discloses a device for preventing dirt from adhering to a photographing window.

2. Description of the Related Art In the manufacture of steel sheets, a method of photographing the surface of a steel sheet using an imaging device and analyzing the acquired image is often used in order to ensure the quality of the steel sheet that will be the product.

A steel plate is generally photographed at the final stage of the manufacturing process, and photographing devices are arranged above and below the conveying path of the steel plate to photograph the front and rear surfaces of the conveyed steel plate.

The important thing when photographing the surface of a steel plate is to obtain a clear image suitable for analysis. However, there is a problem that in the imaging device arranged below the conveyed steel plate, an appropriate image cannot be obtained due to accumulation of dust generated when the steel plate is conveyed on the imaging window of the imaging device.

The dust is powdered iron oxide or iron powder peeled off from the steel plate, which once floats in the air and then falls downward due to gravity. Therefore, dust tends to accumulate on the photographing window of the photographing device arranged below the conveyed steel plate. Accumulation of dust on the imaging window reduces the brightness of the acquired image or causes noise in the acquired image, which sometimes makes it impossible to acquire a clear image suitable for analysis.

In order to solve such a problem, Japanese Patent Application Laid-Open No. 2002-200000 describes an air purge that injects a curtain-like air flow over substantially the entire area of the window surface of an optical window (photographing window), which is directed upward at a predetermined angle. A nozzle is provided in front of the window surface. It is described that the injection from the air purge nozzle can generate an upward airflow from the window surface side, thereby preventing the adhesion of dirt to the optical window. Further, in Patent Document 2, an optical device is provided with a magnet that exerts a magnetic force on the transparent window in a container that houses an optical device with the light receiving portion facing upward and has a transparent window at the top that guides light to the light receiving portion. discloses a window surface stain remover, which is described for removing stains on the window surface of an optical instrument.

JP-A-11-231255 Japanese Utility Model Laid-Open No. 58-133117

If the photographing window of the photographing device becomes dirty with dust, it becomes impossible to obtain a clear image suitable for analysis. In addition, it is necessary to clean the photographing window of the photographing device, and the steel plate cannot be manufactured during the cleaning. Therefore, it is important for production activities to reduce the frequency of cleaning the imaging window.
By using the techniques described in Patent Documents 1 and 2, it is possible to reduce the amount of dust deposited on the photographing window of the photographing device arranged below the conveyed steel plate, so that the number of cleanings of the photographing window can be reduced. Although it can be reduced, there is still room for improvement from the viewpoint of improving the production efficiency of steel sheets.

Therefore, an object of the present application is to provide a device for preventing the adhesion of dirt to the photographing window of the photographing device.

As a result of intensive studies, the present inventors found that a hood covering the photographing window, which is provided with an opening in the field of view of the photographing device, and an upstream of the conveying direction of the steel plate between the hood and the conveyed steel plate. By combining an air injection device installed on the side that injects air from the upstream side to the downstream side in the conveying direction and a shielding plate installed between the opening and the air injection device. The inventors have found that it is possible to suppress the adhesion of dirt to windows, and have completed the present invention.

That is, the present application, as one means for solving the above problems,
A device for preventing dirt from adhering to an imaging window of an imaging device positioned below the steel plate for imaging the back surface of the steel plate being conveyed, and the field of view of the imaging device is provided with an open opening. A hood that covers the photographing window and a hood that is installed upstream in the conveying direction of the steel plate from the opening between the hood and the steel plate that is conveyed, and injects air from the upstream side to the downstream side in the conveying direction. and a shielding plate installed between the opening and the air injector, the shielding plate extending in the width direction of the steel plate, and the shielding plate in the cross section in the conveying direction of the shielding plate The straight line connecting the upstream end in the conveying direction and the downstream end in the conveying direction is inclined upward with respect to the conveying direction at an angle of 10° or more and 50° or less. An apparatus for preventing is disclosed.

In the above device, in the cross section of the shielding plate in the conveying direction, a straight line connecting the upstream end of the shielding plate in the conveying direction and the downstream end of the conveying direction is 10° or more upward with respect to the conveying direction. It is preferably inclined at an angle of ° or less. Further, it is preferable that the upstream end portion of the shielding plate in the conveying direction is supported by the hood. Furthermore, the shielding plate is arranged so as not to cover the upper part of the opening, and the end of the shielding plate on the downstream side in the conveying direction is arranged at a position 5 mm or more and 50 mm or less above the hood, and from the opening It is preferably arranged at a position of 0 mm or more and 50 mm or less on the upstream side in the conveying direction.

Further, in the above apparatus, at least one magnet is installed below the opening and upstream from the opening in the transport direction inside the hood covering the imaging window, and the at least one magnet is installed at the opening. It is preferably installed below the opening and downstream in the conveying direction from the opening. More preferably, in a combination of magnets in which the distance between the center of gravity of the magnet installed on the upstream side in the conveying direction from the opening and the center of gravity of the magnet installed on the downstream side in the conveying direction from the opening is the shortest, The pole on the downstream side in the conveying direction of the magnet installed on the upstream side in the conveying direction and the pole on the upstream side in the conveying direction of the magnet installed on the downstream side in the conveying direction are a combination of poles that attract each other. The straight line connecting the center of gravity of the magnet installed upstream in the conveying direction from the opening and the center of gravity of the magnet installed downstream in the conveying direction from the opening is oblique to the conveying direction. It is that you are.

Further, in the above apparatus, the pressure of the injected air is 3 kgf/cm ² or more and 10 kgf/cm ² or less, the wind speed of the injected air is 10 m/sec or more and 30 m/sec or less, and the opening is in the conveying direction. It is preferable that the length is 10 mm or more and 50 mm or less.

According to the device of the present disclosure, adhesion of dirt to the photographing window is suppressed. Therefore, an image suitable for image analysis of the steel plate can be acquired, the frequency of cleaning the photographing window can be reduced, and the production efficiency of the steel plate can be improved.

2 is a plan view of the device 10 observed from above; FIG. 2 is a cross-sectional view of the device 10 in the transport direction; FIG. 2 is a cross-sectional view of the device 10 in the width direction; FIG. 2 is a cross-sectional view of the device 20 in the conveying direction; FIG. 2 is a cross-sectional view of the device 20 in the width direction; FIG. It is a figure explaining the arrangement system of the magnets 21 and 22. FIG. It is a figure which shows the relationship between the angle of the magnets 21 and 22 with respect to a conveyance direction, and the strength of a magnetic field. 4 is a graph showing the results of Experiment 1; 4 is a graph showing the results of Experiment 2; 10 is a graph showing the results of Experiment 3;

<First embodiment>
FIGS. 1 to 3 show a device for preventing dirt from adhering to a photographing window according to the present disclosure, which is a first embodiment of a device 10 for preventing dirt from adhering to a photographing window (hereinafter sometimes referred to as “device 10”. ) is a diagram for explaining. FIG. 1 is a plan view of the photographing device 2 and the device 10 viewed from above. FIG. 2 is a cross-sectional view of the photographing device 2 and the device 10 in the conveying direction, more specifically, a cross-sectional view taken along II-II in FIG. FIG. 3 is a widthwise cross-sectional view of the device 10, more specifically, a cross-sectional view taken along line III--III in FIG. 2 and 3 additionally show the steel plate 1, the conveying direction, and the width direction for reference.
As shown in FIGS. 2 and 3, the photographing device 2 is arranged below the steel plate 1 being conveyed, and the device 10 is arranged above the photographing device 2 .

The steel plate 1 is conveyed by a conveying roll (not shown), and the photographing device 2 is a device for photographing the back surface of the conveyed steel plate. The photographing device 2 includes a photographing window 2a, a housing 2b having the photographing window 2a on its upper surface, and a photographing device main body 2c as a camera housed inside the housing 2b. An optical method using a dimensional camera or the like is adopted. Then, the image of the back surface of the steel plate 1 photographed by the photographing device main body 2c is analyzed.

(Apparatus 10)
The device 10 has a hood 11, an air injection device 12, and a shielding plate 13, which suppress the deposition of dirt on the photographing window 2a.

Here, hereinafter, the “conveying direction” is the moving direction of the steel plate 1 being conveyed, the “upstream side in the conveying direction” is the upstream side in the moving direction of the steel plate 1, and the “downstream side in the conveying direction”. is the downstream side in the moving direction of the steel plate 1 . Moreover, the “width direction” hereinafter is the width direction of the steel plate 1 . Note that the transport direction and the width direction are perpendicular to each other.

In FIG. 1, the direction from the upper side to the lower side of the paper is the conveying direction, and the horizontal direction of the paper is the width direction. In FIG. 2, the direction from the right side to the left side of the paper surface is the conveying method, and the front direction of the paper surface is the width direction. In FIG. 3, the direction from the back side to the front side of the paper is the conveying direction, and the horizontal direction of the paper is the width direction.

(hood 11)
The hood 11 is a hood-shaped structure that includes an opening 11 a that opens to the field of view of the imaging device 2 and covers the imaging window 2 a of the imaging device 2 . be. Although the box-shaped hood 11 is shown in FIGS. 1 to 3, the shape of the hood 11 is not limited to this. Moreover, although the material constituting the hood 11 is not particularly limited, it is preferably made of a metal material.

The hood 11 covers the photographing window 2a to prevent dirt from adhering to the photographing window 2a. It is possible to photograph the surface of the back side. Contamination of dust entering from the opening 11a is suppressed by the air injection device 12 and the shielding plate 13 as will be described later.

The length of the opening 11a of the hood 11 in the conveying direction is preferably 10 mm or more and 50 mm or less. If the length of the opening 11a in the transport direction is less than 10 mm, it is difficult to secure a sufficient field of view of the photographing device 2. 11, and the dirt adhesion suppression performance of the photographing window 2a is reduced. The length of the opening 11a in the width direction can be appropriately set according to the length of the imaging window 2a of the imaging device 2 in the width direction.

(Air injection device 12)
The air injection device 12 has legs 12a that support the air injection device 12, and is installed upstream in the conveying direction of the opening 11a between the hood 11 and the steel plate 1 being conveyed. The air injection device 12 is a device for injecting air from the upstream side toward the downstream side in the conveying direction, thereby suppressing entry of contaminants such as dust from the opening 11a. That is, the installation of the air injection device 12 improves the ability to suppress the adhesion of dirt to the photographing window.

Here, "inject air from the upstream side to the downstream side in the conveying direction" means to inject air having a direction from the upstream side to the downstream side in the conveying direction as a component. Specifically, it includes jetting air not only in the direction along the conveying direction, but also in a direction obliquely upward with respect to the conveying direction. The range of angles is 0° or more and less than 90°.
However, the lower limit of the air injection angle is preferably 5° or more, more preferably 15° or more. The upper limit of the air injection angle range is preferably 45° or less, more preferably 35° or less, and still more preferably 20° or less. This further improves the capability of suppressing the adhesion of dirt to the photographing window.

The pressure and wind speed of the air injected from the air injection device are not particularly limited, but the pressure is preferably 3 kgf/cm ² or more and 10 kgf/cm ² or less. By keeping the air pressure within the above range, it becomes more difficult for contaminants such as dust to enter the inside of the hood 11 through the opening 11a.
Moreover, it is preferable that the wind velocity of air is 10 m/sec or more and 30 m/sec or less. When the air velocity is within the above range, it becomes more difficult for contaminants such as dust to enter the inside of the hood 11 through the opening 11a.

As shown in FIGS. 1 to 3, the air injection device 12 preferably has a shape extending in the width direction so as to be able to inject air covering the entire upper side of the opening 11a. Moreover, it is preferable that the air that covers the entire upper side of the opening 11a is air (curtain-like air) that has a uniform wind speed and a uniform wind volume regardless of the injection position. As a result, unevenness in the jetted air is eliminated, uniform air is obtained in the width direction, and the capability of suppressing the adhesion of dirt to the photographing window is further improved.

(Shielding plate 13)
The shield plate 13 is installed between the opening 11 a and the air injection device 12 and has a shape extending in the width direction of the steel plate 1 . The cross-sectional shape of the shielding plate 13 in the transport direction may be linear as shown in FIGS. 1 to 3, but is not limited to this and may be concave or convex. However, in the cross section of the shield plate 13 in the transport direction, the straight line connecting the upstream end 13a in the transport direction of the shield plate 13 and the downstream end 13b in the transport direction is 10° upward with respect to the transport direction. It is necessary to incline at an angle of 50° or more. The angle is preferably 10° or more and 35° or less, more preferably 15° or more and 35° or less, and still more preferably 20° or more and 30° or less.

The air behind the air injection device 12 is caught in the air injected by the air injection device 12 . Since the entrained air contains dust that contaminates the photographing window 2a, it is important to prevent the dust carried by the entrained air from entering the opening 11a. Among the entrained air, the air entrained from above the air injection device 12 passes above the air ejected from the air injection device 12, and therefore poses no particular problem. On the other hand, since the air that is drawn in from below the air injection device 12 passes below the air that is injected from the air injection device 12, dust contained in the air that is drawn in from below may enter the opening 11a. .
In the apparatus 10, in order to solve such a problem, a shielding plate 13 is arranged between the opening 11a and the air injection device 12 so that the dust contained in the air drawn in from below the air injection device 12 is prevented from entering the opening 11a. prevent intrusion into

The shielding plate 13 is preferably supported by the hood 11 at the upstream end 13a in the transport direction. As a result, there is no gap between the shielding plate 13 and the hood 11, so that the air drawn in from below the air injection device 12 is prevented from passing below the shielding plate 13, and the dust contained in the air drawn in from below is prevented. Intrusion into the opening 11a can be further suppressed. A method for supporting the end portion 13a of the shielding plate 13 on the hood 11 is not particularly limited, but fixing the end portion 13a of the shielding plate 13 and the hood 11 with an adhesive, a filler, a nail, a screw, or the like is mentioned. be done.

Moreover, the shielding plate 13 is preferably arranged so as not to cover the upper part of the opening 11a. This is because the field of view of the photographing device 2 is not obstructed. Furthermore, the downstream end 13b of the shielding plate 13 in the transport direction is preferably arranged at a position above the hood 11 of 5 mm or more and 50 mm or less, more preferably at a position of 5 mm or more and 30 mm or less above the hood 11 . In addition, the end portion 13b is arranged at a position of preferably 0 mm or more and 50 mm or less, more preferably 0 mm or more and 30 mm or less, on the upstream side in the conveying direction from the opening portion 11a. As a result, it is possible to further prevent dust contained in the air drawn in from below the air injection device 12 from entering the opening 11a.

<Second embodiment>
FIG. 4 and FIG. 5 show a device for preventing dirt from adhering to a photographing window according to the present disclosure, and a device 20 for preventing dirt from adhering to a photographing window (hereinafter sometimes referred to as “device 20”), which is a second embodiment. ) is a diagram for explaining. FIG. 4 is a cross-sectional view of the apparatus 20 in the conveying direction of the steel plate 1, and corresponds to FIG. FIG. 5 is a cross-sectional view of the apparatus 20 in the width direction of the steel plate 1, more specifically, a cross-sectional view taken along line VV in FIG. 4, corresponding to FIG.

As shown in FIGS. 4 and 5, the device 20 includes a hood 11, an air injection device 12, and a shielding plate 13, and magnets 21 and 22 are arranged inside the hood 11. FIG. The difference between device 10 and device 20 is that device 20 has magnets 21 , 22 located inside hood 11 . Therefore, only configurations different from the apparatus 10 will be described below, and descriptions of common configurations will be omitted.

(Magnets 21, 22)
As shown in FIGS. 4 and 5, inside the hood 11 covering the photographing window, a plurality of magnets 21 are installed below the opening 11a and upstream in the transport direction from the opening 11a. A plurality of magnets 22 are installed below the opening 11a and downstream from the opening 11a in the conveying direction. However, the number of magnets 21 and 22 is not limited to plural, and may be at least one. However, from the viewpoint of suppressing the adhesion of dirt to the photographing window, it is preferable that there are a plurality of magnets 21 and 22 as shown in FIGS. Although the strength of the magnets 21 and 22 is not particularly limited, it is preferable to use magnets with a strength of 0.4 tesla or more.
In this manner, the magnets 21 and 22 are arranged inside the hood, and the magnets attract the dust that enters the hood 11 through the opening 11a, thereby suppressing dirt adhering to the photographing window 2a.

The magnets 21 and 22 are installed via a metal plate 23 arranged inside the hood 11 and arranged in line in the width direction. Examples of arrangement methods of the magnets 21 and 22 arranged on the metal plate are shown in FIGS. 6(a) to 6(c). FIGS. 6(a) to 6(c) are diagrams showing only the magnets 21 and 22, which are observed from above. FIG. 6(a) is a diagram in which the magnets 21 and 22 are arranged in a staggered manner, and FIG. 6(b) is a diagram in which the magnets 21 and 22 are arranged to face each other. FIG. 6(c) is an example in which one magnet 21 and one magnet 22 are used.

Here, the "staggered arrangement" means that the distance between the center of gravity of the magnet 21 installed on the upstream side in the transport direction from the opening 11a and the center of gravity of the magnet 22 installed on the downstream side in the transport direction from the opening 11a is In the shortest combination of magnets, the pole on the downstream side in the conveying direction of the magnet 21 installed on the upstream side in the conveying direction and the pole on the upstream side in the conveying direction of the magnet 22 installed on the downstream side in the conveying direction The poles of the surface are a combination of poles that attract each other, the center of gravity of the magnet 21 installed upstream in the conveying direction from the opening 11a and the center of gravity of the magnet 22 installed downstream in the conveying direction from the opening 11a. is slanted with respect to the conveying direction.
On the other hand, "opposed arrangement" means that the distance between the center of gravity of the magnet 21 installed on the upstream side in the transport direction from the opening 11a and the center of gravity of the magnet 22 installed on the downstream side in the transport direction from the opening 11a is , in the combination of the shortest magnets, the pole on the downstream side in the conveying direction of the magnet 21 installed on the upstream side in the conveying direction and the upstream side in the conveying direction of the magnet 22 installed on the downstream side in the conveying direction is a combination of poles that attract each other. It means that the straight line connecting the center of gravity is parallel to the conveying direction.
In addition, in the following, "when the distance between the center of gravity of the magnet 21 installed on the upstream side in the conveying direction from the opening 11a and the center of gravity of the magnet 22 installed on the downstream side in the conveying direction from the opening 11a is the shortest "the combination of magnets" may be referred to as a pair of magnets 21 and 22.

The magnetic field generated between the magnets 21 and 22 varies depending on the arrangement of the magnets 21 and 22 . FIG. 7 shows the relationship between the angle formed by the straight line connecting the center of gravity of the magnet 21 and the center of gravity of the magnet 22 and the conveying direction, and the strength of the magnetic field generated between the magnets 21 and 22 . As shown in FIG. 7, the magnetic force generated between the magnets 21 and 22 is the strongest when the angle between the straight line connecting the center of gravity of the magnet 21 and the center of gravity of the magnet 22 and the conveying direction is 0°. It can be seen that the magnetic force is attenuated as the size increases. The stronger the magnetic field generated between the magnets 21 and 22, the stronger the force of attracting magnetic substances (such as dust).

Therefore, considering only the strength of the magnetic field generated between the magnets 21 and 22, in FIGS. , and is considered preferable from the viewpoint of suppressing the adhesion of dirt to the photographing window 2a. However, for example, in the opposing arrangement shown in FIG. 6(b), a magnetic field having a strong magnetic force is generated between the opposing magnets 21 and 22, but the magnetic field may become weak in other portions. There is unevenness in the strength of the As a result, the force of attracting dust is strong between the magnets 21 and 22 facing each other, but the force of attracting dust is weak elsewhere, and there is a risk that the dust will accumulate on the photographing window 2a. In addition, since the force of attracting dust between the opposing magnets 21 and 22 is strong, the attracted dust may connect between the magnets 21 and 22 and form a dust bridge across the opposing magnets 21 and 22. There is When the dust bridge is formed, it blocks the field of view of the photographing device 2. Therefore, in the photographed image, the brightness of the portion where the field of view is blocked decreases, making it difficult to obtain an appropriate image. In the case of FIG. 6C, since the magnets 21 and 22 extend in the width direction, the intensity of the magnetic field generated between the magnets 21 and 22 is uniform. However, since the magnets extending in the width direction are used, a bridge of dust across the opposing magnets 21 and 22 is formed in the conveying direction. As a result, the field of view of the photographing device 2 may be blocked by a small amount of dust adhering. Therefore, the arrangement schemes of FIGS. 6(b) and 6(c) are not suitable for long-term use.

On the other hand, in the arrangement method of FIG. 6(a), as described above, the straight line connecting the center of gravity of the magnet 21 and the center of gravity of the magnet 22 is inclined with respect to the conveying direction. Although the magnetic field between the magnets 21 and 22 is not as strong as in the arrangement shown in c), the magnetic field is less uneven than in the arrangement shown in FIG. 6(b). 6A uses a plurality of magnets 21 and 22, the length of the dust bridge formed between the magnets 21 and 22 is longer than that of the arrangement method of FIG. 6C. The longer it is, the more dust the magnet will attract. Therefore, even if the arrangement method of FIG. 6A is used for a long period of time, there is a low possibility that the field of view of the imaging device 2 will be blocked by dust. Therefore, the staggered arrangement shown in FIG. 6A is preferable from the viewpoint of sufficiently securing the field of view of the photographing device 2 while absorbing dust that enters from the opening 11a.
In the pair of magnets 21 and 22 arranged in a staggered arrangement in FIG. The connecting straight line is preferably inclined at an angle of 20° or more and 60° or less, more preferably 25° or more and 40° or less, and particularly preferably 30°, with respect to the conveying direction. As a result, the unevenness of the magnetic field generated between the magnets 21 and 22 as a whole can be further reduced, and the strength of the magnetic field can be ensured to be strong enough to trap the dust.
The pitch distance x between the centers of gravity of the magnets 21 aligned in the width direction shown in FIG. 6A is not particularly limited, but is preferably 10 mm or more and 50 mm or less. Similarly, the pitch distance y between the centers of gravity of the magnets 22 aligned in the width direction is not particularly limited, but is preferably 10 mm or more and 50 mm or less. The distance z between the centers of gravity of the paired magnets 21 and 22 is also not particularly limited, but is preferably 10 mm or more and 50 mm or less. A particularly preferred form is that the distances x, y, z are the same. If the distances x, y, and z are the same, the plurality of magnets 21 aligned in the width direction on the upstream side in the conveying direction and the plurality of magnets 21 aligned in the width direction on the downstream side in the conveying direction. Since the distance between the two magnets 22 and the paired magnets 21 and 22 are the same, the strength of the magnetic field is uniform, and the unevenness of the strength of the magnetic field is minimized as a whole.

It is preferable that the distance in the conveying direction from the opening 11a to the center of gravity of the magnets 21 and 22 be 10 mm or more and 50 mm or less. Moreover, although the length in the width direction of the magnets 21 and 22 is not particularly limited, it is preferably in the range of 10 mm or more and 30 mm or less when a plurality of magnets 21 and 22 are used.

The device for preventing dirt from adhering to the photographing window of the present disclosure will be further described below using examples.

<Experiment 1>
Experiment 1 examined the air injection angle of the air injection device.
As an apparatus, a configuration was used in which the shield plate was removed from the apparatus described in FIGS. 1 to 3. FIG. Specifically, a hood covering the photographing window of the photographing device was installed on the photographing device, and an air injection device was arranged upstream of the opening provided in the hood in the conveying direction. Then, 50 g of dust was dropped by a method described later in a state in which the air jetting device jetted air from the upstream side to the downstream side in the conveying direction. After the dust has fallen, measure the brightness of the image captured by the imaging device in the area of 30 mm x 30 mm where the dust has fallen, and from the obtained measurement results, calculate the amount of luminance drop (%) before and after the dust falls. Calculated. The results are shown in FIG.
Here, the brightness drop amount (%) on the vertical axis in FIG. 8 is the brightness drop amount (%) before and after the dust fall described above, and the air injection angle on the horizontal axis is the air injection direction of the air injection device. and the conveying direction.

Here, in Experiment 1, the length of the opening in the conveying direction was 10 mm, the pressure of the air injected from the air injection device was 6 kgf/cm ² , and the wind speed of the air was 20 m/sec.

A method of descent of dust will be described. A sieve with 3 mm diameter holes aligned vertically and horizontally at 10 mm intervals was prepared, 50 g of dust was placed on the sieve, and placed above the opening of the hood. Then, while the air injection device was blowing air, the sieve was shaken to drop dust into the opening.

When 50 g of dust was dropped in the same manner as above without air being jetted from the air jetting device, the brightness of the image at the dust-dropped portion became zero (0). That is, the luminance drop amount (%) before and after the dust fall was 100%.

From the relationship between the brightness drop amount before and after the dust fall and the air injection angle in FIG. 8, it can be seen that the brightness drop amount changes depending on the air injection angle. Further, it was found that when the air injection angle is 5° or more, the amount of luminance drop is further reduced, and when it is 20° or less, it is further reduced. When the air injection angle was 15°, the amount of decrease in luminance was the smallest. Therefore, in subsequent experiments, the air injection angle was set to 15°.

<Experiment 2>
In Experiment 2, a shielding plate was added to the device structure of Experiment 1, and the angle of the shielding plate was examined as the device structure shown in FIGS. The experimental method was the same as Experiment 1, except that the amount of dust was changed to 150 g. The results are shown in FIG.
Here, the luminance drop amount (%) on the vertical axis in FIG. The angle formed by the straight line connecting the upstream end in the transport direction and the downstream end in the transport direction and the transport direction.

Here, in Experiment 2, the shielding plate was arranged so as not to cover the upper part of the opening, and the shielding plate was arranged so that the end on the upstream side in the transport direction was supported by the hood. In addition, the downstream end of the shielding plate in the conveying direction is arranged at a position of 5 mm or more and 30 mm or less above the hood, and is arranged at a position of 0 mm or more and 30 mm or less upstream in the conveying direction from the opening. set as

When the amount of luminance drop before and after the dust fall is taken as a reference when the angle of the shield plate is 0°, the range of the angle of the shield plate in which the amount of luminance drop before and after the dust fall is smaller than the reference is 10° or more and 35° or less. was the case. Also, the amount of decrease in luminance was the smallest when the angle of the shielding plate was 30°. Therefore, the angle of the shielding plate was set to 30° in subsequent experiments.

<Experiment 3>
In Experiment 3, a magnet was added to the apparatus configuration of Experiment 2, and the method of arranging the magnet was examined. As a method of arranging the magnets, the zigzag arrangement shown in FIG. 6(a) and the facing arrangement shown in FIG. 6(b) were used.
In the experimental method in which a magnet was added, the amount of dust to be dropped was changed to 300 g in order to make the conditions more severe, and the other conditions were the same as in Experiment 2.
When the magnets were arranged facing each other as shown in FIG. 6(b) and when the magnets were not arranged, an experiment was conducted and compared. , the amount of luminance drop was 30% when no magnet was installed. That is, it was possible to reduce the amount of luminance drop by installing the magnet.
In addition, we examined the arrangement of magnets. FIG. 10 shows the result of successively performing dust falling several times with the magnets arranged in a zigzag arrangement as shown in FIG. 6(a) and in a facing arrangement as shown in FIG. 6(b).
Here, the brightness drop amount (%) on the vertical axis in FIG. 10 is the brightness drop amount (%) before and after the dust fall, and the number of dust fall on the horizontal axis is the number of times the dust falls.

Here, the pair of magnets 21 and 22 in the staggered arrangement of Experiment 3 is a straight line connecting the center of gravity of the magnet 21 installed on the upstream side in the conveying direction and the center of gravity of the magnet 22 installed on the downstream side in the conveying direction. was set to be inclined at 30° with respect to the conveying direction. Also, the distance between the centers of gravity of the magnets 21, the distance between the centers of gravity of the magnets 22, and the distance between the centers of gravity of the paired magnets 21 and 22 were each set to 20 mm.
On the other hand, the pair of magnets 21 and 22 in the opposing arrangement in Experiment 3 is a straight line connecting the center of gravity of the magnet 21 installed on the upstream side in the conveying direction and the center of gravity of the magnet 22 installed on the downstream side in the conveying direction. was set so as to be parallel to the conveying direction. Moreover, the distance between the centers of gravity of the magnets 21 and the distance between the centers of gravity of the magnets 22 are each 20 mm, and the distance between the centers of gravity of the paired magnets 21 and 22 is arranged to be 10 mm.

From the amount of luminance drop before and after dust fall in FIG. 10, it was found that the amount of luminance drop is small when the magnets are arranged in a staggered arrangement, even if 300 g of dust is used. Also, even if the dust fall was performed 16 times, the amount of luminance fall did not exceed 50%. Therefore, it was found that the zigzag arrangement is suitable for long-term use because the drop in luminance can be greatly suppressed by using the zigzag arrangement.

Reference Signs List 1 Steel plate 2 Imaging device 2a Imaging window 2b Housing 2c Imaging device main body 10, 20 Device for preventing adhesion of dirt to imaging window 11 Hood 11a Opening 12 Air injection device 13 Shielding plates 21, 22 Magnet 23 Metal plate

Claims (6)

Take a picture of the back surface of the steel plate being conveyed,
A device for preventing dirt from adhering to a photographing window of a photographing device located below the steel plate,
a portion of the field of view of the imaging device comprising an open aperture;
a hood covering the photographing window;
Between the hood and the conveyed steel plate,
installed upstream of the opening in the conveying direction of the steel plate,
an air injection device that injects air from the upstream side toward the downstream side in the conveying direction;
a shielding plate installed between the opening and the air injection device;
with
The range of the angle formed by the air injection direction and the conveying direction is 5° or more and 35° or less,
The shielding plate extends in the width direction of the steel plate,
In the cross section of the shielding plate in the transport direction,
A straight line connecting an upstream end of the shielding plate in the conveying direction and a downstream end of the conveying direction,
inclined upward with respect to the conveying direction at an angle of 10° or more and 35 ° or less,
A device that prevents dirt from adhering to the photographing window. an upstream end of the shielding plate in the conveying direction is supported by the hood;
A device according to claim 1 . The shielding plate is arranged so as not to cover the upper part of the opening,
the end portion of the shield plate on the downstream side in the conveying direction,
arranged at a position of 5 mm or more and 50 mm or less above the hood,
And,
arranged at a position of 0 mm or more and 50 mm or less on the upstream side in the conveying direction from the opening,
3. Apparatus according to claim 1 or 2 . Inside the hood covering the imaging window,
at least one magnet
below the opening,
is installed on the upstream side in the conveying direction from the opening,
at least one magnet
below the opening,
installed on the downstream side in the conveying direction from the opening,
A device according to any one of claims 1-3 . a center of gravity of a magnet installed on the upstream side in the conveying direction from the opening;
The distance from the opening to the center of gravity of the magnet installed on the downstream side in the conveying direction is
In the combination of magnets in the shortest case,
a pole of the surface on the downstream side in the conveying direction of the magnet installed on the upstream side in the conveying direction;
The pole of the surface on the upstream side in the conveying direction of the magnet installed on the downstream side in the conveying direction is
is a combination of poles that attract each other,
a center of gravity of a magnet installed on the upstream side in the conveying direction from the opening;
A straight line connecting the center of gravity of the magnet installed on the downstream side in the conveying direction from the opening is
oblique to the conveying direction,
A device according to any one of claims 1-4 . The pressure of the injected air is 3 kgf/cm ² or more and 10 kgf/cm ² or less,
the jetted air has a wind speed of 10 m/sec or more and 30 m/sec or less;
The length of the opening in the conveying direction is 10 mm or more and 50 mm or less,
A device according to any one of claims 1-5 .

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