JPH061169B2 - Method for detecting running state of strip in furnace - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for detecting a running state of a strip (metal ribbon) running in a continuous annealing furnace, and particularly to a hanging amount (catenary) of the strip. Amount) and the amount of strip meandering.

[Prior Art] It is extremely important to measure the amount of catenary, meandering amount, etc. of a strip running in a continuous annealing furnace and to accurately control the running state of the strip based on the measurement result.

For example, when the amount of the catenary of the strip is too small, the tension applied to the strip becomes excessive, which may cause abnormal elongation of the strip and further breakage. In addition, if the amount of catenary is too large, the strip may come into contact with the hearth and the surface may be flawed. Therefore, if the inside of the furnace is enlarged so that the strip does not come into contact with the hearth, not only the construction cost of the furnace increases and it is difficult to maintain a uniform temperature distribution in the furnace, but A large amount of energy is consumed in raising the temperature.

Therefore, it is necessary to measure the amount of catenary in real time in order to suppress the catenary fluctuation in the strip as small as possible. A method for detecting the amount of the catenary has already been filed by the same applicant (Japanese Patent Laid-Open No. Sho 57-57)
-206806, JP-A-58-151428, JP-A-59-6327).
According to this method, the amount of catenary is obtained by irradiating a spot-shaped laser beam on the strip and photographing the light spot obtained on the strip with an image pickup device such as a television camera or an image sensor with a solid-state image pickup device. Became possible.

However, this method cannot determine the meandering amount of the strip and the variation of the strip width. In order to detect the meandering of the strip, there is a method of measuring the meandering amount etc. by providing a light source and a photodetector at the upper and lower sides of the strip at the entrance of the furnace. There wasn't.

[Problems to be Solved by the Invention] As described above, in the conventional strip furnace, it is possible to measure the catenary amount in real time, but the strip meandering amount and the strip width variation are measured. There was no suitable method.

Therefore, since the meandering of the strip cannot be controlled appropriately, there are problems that shear stress occurs in the strip, uniform heat treatment becomes difficult, and the like.

In view of these problems, an object of the present invention is to provide a strip running condition detection method capable of simultaneously measuring strip catenary amount and meandering amount, and further strip width variation as needed. To do.

[Means for Solving the Problems] In order to achieve this object, in the present invention, specifically, as a first invention, a straight line including an edge portion of a strip is provided on a strip running in a furnace. Irradiating a narrow light beam with its length direction aligned with the width direction of the strip, and the irradiation part on the strip is photographed by an imaging device,
The catenary amount is made to correspond to the screen position in the direction perpendicular to the length direction of the linear image obtained by this imaging device, and the meandering amount of the strip is made to correspond to the screen position in the length direction of the image. As a second aspect of the invention, for both edge portions of the strip, a straight narrow light beam including the edge portions of the strip is separately provided on the strip in the length direction and the width direction of the strip. And irradiate each other, and the respective irradiation portions on the strip are photographed by separate image pickup devices, and the strip width variation of the strip is obtained by the change in the length of two images obtained by these image pickup devices. is there.

[Operation] According to the present invention, the strip catenary amount is changed by making the strip catenary amount correspond to the screen position in the direction perpendicular to the length direction of the linear image obtained by the imaging device. Since the screen position changes, the strip catenary amount can be obtained from the change in the screen position.

Further, by irradiating a linear light beam including the edge portion of the strip and making the strip meandering amount correspond to the screen position in the lengthwise direction of the linear image obtained by the imaging device, the strip can be made to meander. Along with this, the length of this image changes (the length of this image is an image from one end of a linear ray to the edge part of the strip, so that the edge moves due to the meandering of the strip, and the image changes accordingly. Also changes), it is possible to determine the amount of meandering from the change in the length of this image.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic side sectional view of a measuring unit for explaining an embodiment of a method for detecting a running state of a strip in a furnace according to the present invention, FIG. 2 is a plan view of the same, and FIG. 3 is a monitor screen of a television camera. And FIG. 4 are explanatory diagrams for obtaining the amount of catenary. In this figure, 1 is a strip, 2 and 2
a and 2b are laser oscillators that output a linear laser beam having a narrow width, and 3, 3a and 3b are Cs as an image pickup device.
A television camera using a CD, 4 a continuous annealing furnace, 5 rolls for conveying the strip 1, 20a and 20a
b is an irradiation part of the laser beam irradiated on the strip 1,
31 is a monitor screen of the TV camera 3a or 3b, 3
Reference numeral 0 is an image of the irradiation unit 20a or 20b displayed on the monitor screen 31.

The strip 1 is rotated by the roll 5 rotating in the direction of the arrow,
It is conveyed from right to left in the continuous annealing furnace 4 and annealed. The chain line in FIG. 1 indicates the reference catenary of strip 1, and the minimum catenary is taken as this reference catenary. A indicates an irradiation portion of the laser beam irradiated on the strip 1 in the reference catenary state. A, B in FIGS. 1, 3, and 4 respectively correspond to the irradiation unit in the reference catenary state and the irradiation unit at the time of measurement.

Further, the laser oscillator 2 and the television camera 3 are provided in the upper part of the continuous annealing furnace 4 so as to face a hole through which the inside of the furnace can be seen. Although not shown, heat in the furnace is cut off by providing heat-resistant glass or air purge in these holes.

In addition, the irradiation angle α of the laser light from the laser oscillator 2 and the imaging angle β of the television camera 3 are set to be different in order to prevent halation due to specular reflection light.

Further, as a matter of course, the images in the allowable minimum catenary and the maximum catenary are set so as to be included in the image pickup screen of the television camera 3.

Further, the width of the laser beam in the longitudinal direction is larger than the possible meandering amount of the strip 1, and an image formed by projecting the laser beam on the strip 1 is the television camera 3.
It goes without saying that it is set so as to enter the image pickup screen.

Further, on the monitor screen shown in FIG. 3, the television camera 3 is attached so that the strip 1 is conveyed in the vertical direction (Y direction). Further, the horizontal direction of the screen (X direction) is the scanning direction of the television camera 3. Incidentally, a chain line M on the left side in the Y direction shows a reference position for showing the amount of meandering. Also, l
And m are distances corresponding to the catenary amount and the meandering amount, respectively.

Next, the amount of catenary of the strip 1 by this measuring unit,
A method of detecting the amount of meandering etc. will be described.

The laser beams emitted from the laser oscillators 2a and 2b are
It is converted into a linear narrow beam by a cylindrical lens or the like provided in the laser oscillators 2a and 2b, and the length direction of the beam is aligned with the width direction of the strip 1,
The strip 1 is illuminated so that the edge of the strip 1 is always included. The irradiation parts 20a, 20b
Is projected by the television cameras 3a and 3b. An example of the monitor image is shown in FIG.

In this image, the distance l corresponding to the amount of catenary is
It is the distance from the reference position A corresponding to the reference catenary to the median value B of the image 30. The median B of this image 30 is
It is obtained by adding video signals in the scanning line direction (X direction) on the screen for each scanning line and obtaining the median value of the values obtained by the addition.

The apparent catenary amount h in FIG. 4 is obtained from the distance l on the screen by performing a correction peculiar to the optical system.
To find the actual amount of catenary from this h, sin a = h / a (where α + β = θ) cos α = H / a By eliminating a from both equations, H = hcos α / sin (α + β ) Can be obtained as

Further, in FIG. 3, the distance m corresponding to the meandering amount is represented by the distance from the reference position M of the meandering amount to the edge portion E. The position of the edge portion E is obtained as follows. The video signal at each bit in the direction from the reference bit position N to the edge E is binarized at a constant level. When this binarized value is added in the Y direction for each bit, a graph as shown in FIG. 5 is obtained. Here, the horizontal axis is the X direction and the vertical axis is the value obtained by adding (addition value). Since the output becomes unstable near the edge portion E, this added value converges to 0 with a certain gradient as shown in the figure. The X coordinate x _{E of the} bit corresponding to the average value of this inclined portion corresponds to the actual edge portion E. Here, x _N represents the reference bit position. By counting the number of bits to x _E from this x _N, the value of the edge portion E is obtained. In this way
Once the distance m corresponding to the amount of meandering is obtained, the actual amount of meandering of the strip 1 is obtained by making a correction unique to the optical system.

Further, since the TV cameras 3a and 3b determine the meandering amount at both edge portions of the strip 1,
By taking the difference between these meandering amounts, the effect of the strip width of the strip 1 can be obtained. That is, the irradiation unit reference length on the irradiation unit 20a side is Sa, the measured irradiation unit actual length is Xa,
Further, if the irradiation unit reference length on the irradiation unit 20b side is Sb and the actual length is Xb, (Xa + Xb)-(Sa + Sb) indicates the plate width variation amount (positive is wide, negative is narrow). Here, the reference length of the irradiation part is a cutting length on the strip of the laser beam irradiated on the edge part of the strip in a normal traveling state in which there is no meandering and plate width variation.

FIG. 6 is an overall configuration diagram of a measurement processing device for detecting the running state of the strip in the furnace by using the measuring unit described above. In this figure, 51 is a laser oscillator 2a,
2b is a power supply for driving 2b, 52 is an image input / output device, 5
3 is an image processing apparatus, 54 is an external memory, 55 is a monitor CRT, 56 is a printer, and 57 is an analog display unit.

The image input / output device 52 writes the video signals from the television cameras 3a and 3b into the image memory as image data,
It is for displaying the data accumulated in the image memory on a monitor.

Further, the image processing device 53 is composed of a microcomputer, and performs image capturing, display on a monitor, calculation processing for obtaining the catenary amount of the strip 1, meandering amount, etc., output to the printer 56, laser oscillator 2a, 2b and the television cameras 3a and 3b are controlled to move.

The external memory 54 is for storing information regarding the amount of catenary and the amount of meandering of the strip 1.

In this measurement processing device, when the images of the laser beams emitted from the laser oscillators 2a and 2b on the strip 1 are detected by the television cameras 3a and 3b, the video signals output from the television cameras 3a and 3b are imaged. The image is processed by the image processing device 53 via the input / output device 52,
The amount of catenary of the strip 1, the amount of meandering, the amount of plate width variation, and the like are obtained. The result is displayed on the analog display unit 57 and also output to the printer 56. The image processing time by the image processing device 53 is 1 second or less, and it is possible to detect the running state of the strip in the furnace in real time.

By controlling the rotation of the roll 5 using the measurement result, it is possible to automatically control the amount of the catenary of the strip, the amount of meandering, and the like.

[Effects of the Invention] As is clear from the above description, according to the present invention, labor saving is achieved because the amount of strip catenary, the amount of meandering, the amount of plate width variation, etc. can be automatically measured simultaneously in real time with high accuracy. At the same time, it is possible to carry out close quality control such as reducing variations in heat treatment temperature of the strip and preventing the strip from being flawed. Further, since the strip traveling control can be performed with high accuracy, the continuous annealing furnace can be configured compactly, and the energy saving effect can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side sectional view of a measuring unit for explaining an embodiment of a method for detecting the running state of a strip in a furnace according to the present invention, FIG. 2 is a plan view of the same, and FIG. FIG. 4 is a diagram showing a monitor screen of a television camera, FIG. 4 is an explanatory diagram for obtaining a strip catenary amount, FIG. 5 is an explanatory diagram for obtaining a strip meandering amount, and FIG. 6 is a measurement in the same embodiment. It is a whole block diagram of a processing apparatus. In the figure, 1: strip 2: laser oscillator 3: TV camera 4: continuous annealing furnace

Claims (2)

[Claims] 1. A strip traveling on the inside of a furnace is irradiated with a light beam having a narrow straight line including the edge portion of the strip so that the length direction of the strip and the width direction of the strip coincide with each other. The portion irradiated with the light beam is photographed by the image pickup device, and the amount of the catenary of the strip is determined based on the distance from the first reference position in the direction perpendicular to the length direction of the linear image obtained by the image pickup device. A method for detecting the running state of a strip in a furnace, which comprises detecting the strip meandering amount based on the distance from the second reference position in the length direction of the image. 2. A strip furnace according to claim 1, characterized in that the meandering amount is obtained for both edge portions of the strip, and the strip width variation is detected by the meandering amount. Driving state detection method.