JP2000346635A - Method and apparatus for controlling thickness of coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a thickness of a coating film of a metal band to a predetermined thickness of the film by stably, accurately and rapidly measuring the thickness of the film immediately after coating in a line for coating the continuously running band with a coating liquid. SOLUTION: The apparatus for controlling a thickness of a coating film comprises a first displacement sensor 5 for measuring a distance to a surface of a coating film near a surface of a roll 2 rotating while being brought into contact with a metal band 1 installed between coating of the band 1 with a coating liquid 3 by a coating unit 4 to drying, and a second displacement sensor 6 for measuring a distance to the surface of the roll. Further, the apparatus also comprises an arithmetic unit 7 for calculating the thickness-of the film based on signals of the sensors 5, 6, and a controller 8 for controlling a coating liquid amount coating the band by the coating unit based on the calculated thickness of the film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating thickness control for controlling a coating thickness of a metal strip to a predetermined coating thickness in a line for applying a coating liquid to a metal strip such as a steel strip running continuously. The present invention relates to an apparatus and a control method.

[0002]

2. Description of the Related Art The thickness of a coating solution applied to a metal strip such as a steel strip is an essential parameter for satisfying required performances such as corrosion resistance and aesthetics. Measurement and control of the coating thickness is an indispensable step in the line where the coating liquid is applied to the metal strip. High precision is required for the coating thickness measurement, and it is also necessary to be able to control the coating thickness with good responsiveness. It is.

Conventionally, in a continuous coating line of a metal strip using a roll coater or the like, a method of measuring a coating thickness necessary for controlling the coating thickness of the metal strip to a predetermined coating thickness is as follows.
A method of sampling and measuring the thickness of the coating film after drying the coating film offline or a method of measuring the thickness of the coating film online using a coating thickness gauge installed downstream of a drying furnace is generally used.

However, in these measurement methods, since the thickness of the coating after drying is measured, it takes some time from the application of the coating solution to the metal strip to the measurement of the thickness of the coating. As a result, the operating conditions for controlling the thickness of the coating film were changed, so that it was not possible to control the thickness of the coating film with good responsiveness.

In order to solve this problem, it is necessary to measure the thickness of the coating immediately after coating.
The following method is disclosed.

Japanese Patent Publication No. 4-68562 discloses an eddy current or electromagnetic distance sensor for measuring the distance to a metal surface to which a coating liquid is applied, and an optical distance sensor for measuring the distance to the coating surface. A method is disclosed in which the distance is measured and the coating thickness is calculated from these differences.

Japanese Patent Application Laid-Open No. 5-322549 discloses that the position of the surface of a coating film is detected by a laser outer diameter measuring device, and the distance to a metal band is detected by an overcurrent displacement sensor. There is disclosed a method of calculating the coating film thickness and controlling the coating film thickness based on the calculation result.

Further, Japanese Patent Application Laid-Open No. Hei 6-102034 discloses that the weight change of each of the paint supply amount and the recovered paint amount is detected, the paint amount applied to the steel plate is obtained from the difference between these, and the coating film thickness is further determined. Is disclosed.

[0009]

However, according to the methods disclosed in Japanese Patent Publication No. 4-68562 and Japanese Patent Application Laid-Open No. 5-322549, in order to perform a highly accurate measurement,
Due to its characteristics, an eddy current or electromagnetic distance sensor must be installed very close to the metal strip surface. For example, in order to obtain an accuracy of a coating thickness of 1 μm, it is necessary to set the distance between the sensor and the metal belt surface close to about 5 mm. It is not preferable in terms of operation to dispose the sensor in proximity to the running metal strip, since the sensor may damage the coating surface or the metal strip. For this reason, the sensor needs to be installed at a certain distance from the metal strip, so that there is a problem that sufficient accuracy of the coating film thickness cannot be obtained.

In the method disclosed in Japanese Patent Application Laid-Open No. 6-102034, since the amount applied to the amount of circulating paint is small, it is difficult to perform highly accurate measurement, and rapid measurement is required. Is also difficult.

Accordingly, an object of the present invention is to measure the thickness of a coating film immediately after coating on a line for applying a coating liquid to a continuously running metal band stably, accurately and quickly, and to obtain a coating film of the metal band. An object of the present invention is to provide a coating film thickness control device and a control method capable of controlling the thickness to a predetermined coating film thickness.

[0012]

The above object is achieved by the following means.

(1) A coating film thickness control device provided on a line for applying a coating liquid to a continuously running metal strip,
The coating film thickness control device is arranged in close proximity to a roll surface that rotates while being in contact with a metal band that is provided between the time when the coating liquid is applied to the metal band in the coating section and the time when the coating solution is dried. A first displacement sensor for measuring the distance to the roll surface and a second displacement sensor for measuring the distance to the roll surface, and based on signals from the first displacement sensor and the second displacement sensor, a coating film thickness. And a controller for controlling the amount of coating liquid applied to the metal strip in the coating section based on the calculated thickness of the coating film.

(2) The coating film thickness control apparatus according to (1), wherein a laser displacement sensor is used as the first displacement sensor and the second displacement sensor.

(3) In controlling the coating thickness of the metal strip in the line for applying the coating liquid to the metal strip running continuously, the time until the coating liquid applied to the metal strip in the coating section is dried. The distance to the coating surface is measured by a first displacement sensor, and the distance to the roll surface is measured by a second displacement sensor. An arithmetic unit calculates the coating thickness of the metal strip based on the distances measured by the first displacement sensor and the second displacement sensor. Then, the calculated coating thickness becomes a predetermined coating thickness. A coating film thickness control method, comprising controlling an amount of a coating liquid applied to a metal strip in an application section.

(4) In the method (3), a laser displacement sensor is used as the first displacement sensor and the second displacement sensor.

[0017]

Embodiments of the present invention will be described below in detail.

FIG. 1 is a schematic diagram showing essential equipment in the vicinity of a coating portion of a continuous coating line for a metal strip provided with a coating film thickness control device according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a metal band, 2 denotes a backup roll, and 4 denotes a roll coater, which comprises a pan 11 containing a coating liquid 3, a pickup roll 9, and an applicator roll 10. 5 is a first displacement sensor for measuring the distance to the coating film surface, 6 is a second displacement sensor for measuring the distance to the roll surface, and 7 is the coating film based on signals detected from the displacement sensors 5 and 6. Calculation device for calculating thickness, 8
Is a control device for controlling the thickness of the coating liquid 3 applied to the metal strip 1 based on the signal of the coating thickness calculated by the arithmetic unit 7. 21a and 21b are pressurizing devices for adjusting the pressing force of the pick-up roll 9 against the applicator roll 10, 22a and 22b are pressurizing devices for adjusting the pressing force of the applicator roll 10 to the metal strip 1, and 23a is a pressurizing device for adjusting the pick-up roll 9. A driving motor 24a is a rotation speed detector (PL) for detecting the rotation speed of the pickup roll 9.
G) and 23b are electric motors for driving the applicator roll 10, and 24b is a rotation speed detector (PLG) for detecting the rotation speed of the applicator roll 10.

In the present apparatus, the amount of coating liquid applied to the metal strip 1 can be adjusted by changing the number of rotations of the pickup roll 9, the number of rotations of the applicator roll 10, or the pressing force between the rolls 9, 10. It is possible.

FIG. 2 is a sectional view of a main part of the apparatus shown in FIG. 1, and FIG. 3 is a view taken along the line AA of FIG. 2 (however, the pan 11 is not shown). As shown in FIGS. 2 and 3, the first displacement sensor 5 is located near the center of the backup roll 2 in the width direction, and the second displacement sensor 6 is located near the end of the backup roll 2 in the width direction. It is installed close to the roll 2. Since the second displacement sensor 6 is not shielded by the metal strip 1, it can always detect the distance L2 to the backup roll 2.

In the present apparatus, the coating liquid 3 in the pan 11
Is pumped up by a rotating pickup roll 9, the applied coating solution 3 is transferred to a rotating applicator roll 10, and further applied to a metal strip 1 wound around a rotating backup roll 2 and continuously transported.

Immediately after the coating liquid 3 is applied to the metal strip 1,
The first displacement sensor 5 detects the distance L1 to the coating film surface, the second displacement sensor 6 detects the distance L2 to the backup roll 2, and the plate thickness of the metal strip 1 is taken into the arithmetic unit 7, and Calculate the coating thickness of band 1. As the plate thickness of the metal strip 1, a known value is previously input to the arithmetic unit 7, or a value measured before application is input. In addition, each of the displacement sensors 5, 6
Is not always located at the same height with respect to the backup roll 2, the distances to the backup roll 2 are measured and calibrated in advance before manufacturing, and the values are calculated by the arithmetic unit 7. Put in.

The coating thickness before drying can be calculated by subtracting L1 and the plate thickness from L2. By determining the heating residue amount contained in the coating solution, the coating thickness after drying can be easily calculated from the coating thickness before drying and the heating residue amount contained in the coating solution calculated above. Can be calculated.

Further, by using a laser type displacement sensor as each of the displacement sensors 5 and 6, the displacement sensors 5 and 6 can be used.
6 about 50 to metal strip 1 or backup roll 2
mm, and a sufficient distance that does not damage the coating film surface and the metal band 1 can be maintained.

When measuring the distance to the rotating roll, a measurement error occurs due to deflection during rotation due to eccentricity and roundness of the roll. In this apparatus, however, the first displacement sensor 5 and the second By measuring the distance between the two points using the displacement sensor 6 and determining the difference between the measurement results, the deviation during rotation is canceled out, and the thickness of the coating film can be derived without being affected by rotational fluctuation. In addition, since the thickness of the coating film immediately after being applied to the metal strip 1 is detected, the thickness of the coating film can be quickly measured.

The film thickness calculated by the arithmetic unit 7 is calculated by the control unit 8
Is output to The control device 8 compares the calculated coating film thickness with the target coating film thickness, and according to the deviation, the rotation speed of the pickup roll 9 and the electric motor The number of rotations of the applicator roll 10 via the 23b and the applicator roll 1 of the pickup roll 9 via the pressurizing devices 21a and 21b
Adjust any one or more of the pressing force to 0,
The amount of the coating liquid applied to the metal strip 1 is controlled.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A continuous coating line for a metal strip shown in FIG. 1 equipped with a coating thickness control device according to an embodiment of the present invention and having a two-roll coater in a coating section was used.
An example in which the coating solution is applied to a 5 mm steel strip is shown below.

A metal pickup roll 9 for pumping the coating solution 3 from the pan 11 and an applicator roll 10 rubber-lined to an iron core roll for transferring the coating solution 3 to the steel strip 1 were used. Both have a roll diameter of 250 mm and a roll length of 3
A 00 mm roll was used. Further, the coating liquid 3 is applied to the steel strip 1 at a position sandwiched between the metal backup roll 2 having a roll diameter of 500 mm and a roll length of 500 mm and the applicator roll 10. One laser type displacement sensor 5 and 6 were respectively disposed above the backup roll 2 substantially above the center and above the vicinity of 50 mm inside from the end of the backup roll 2. The distance between each of the laser displacement sensors 5 and 6 and the backup roll 2 is approximately 5
It was adjusted to 0 mm and fixed. In order to calibrate each of the laser displacement sensors 5 and 6 before coating, the thickness of the steel strip is
A known thickness was input to the arithmetic unit 7.

Table 1 shows that a resin coating material was used as the coating liquid 3,
The steel strip 1 was run at a line speed of 60 mpm, and the results of outputting the measured values of the coating film thickness to the monitor while performing the coating and the coating film thickness of the sample cut out after drying in a drying furnace were measured using fluorescent X It shows a comparison with the result measured by a line. The online measurement result and the offline measurement result show almost the same value. Since the off-line measured values are considered to indicate almost true values, it can be seen that the measurement accuracy of the method of the present invention is sufficiently high.

[0031]

[Table 1]

FIG. 4 shows an example in which the coating film thickness calculated by the arithmetic unit 7 is controlled to a target value. Pickup roll 9 and applicator roll 10 via control device 8
The pressing force was controlled so that the target coating film thickness became 10 μm. It can be seen that the method of the present invention can be controlled with extremely high responsiveness as compared with the result of the conventional method controlled by a coating film thickness meter installed downstream of the drying furnace shown for comparison.

Further, even when the thickness of the steel strip 1 and each of the laser displacement sensors 5 and 6 are sufficiently large when the welding point is passed or the plate thickness is changed, the steel strip 1 and the laser displacement sensors 5 and 6 do not come into contact with each other, so that the coating thickness can be stably increased. Could be measured.

In this embodiment, the coating thickness is measured only at the center of the steel strip 1, but a plurality of displacement sensors 5 are arranged in the width direction to measure the coating thickness. By measuring while operating the displacement sensor 5 in the width direction, it is possible to measure the coating thickness distribution in the width direction, and based on the measurement result, the roll width between the rolls 9 and 10 via the pressurizing devices 21a and 21b. By adjusting the pressing force in the direction, the variation of the coating thickness in the steel strip width direction can be reduced, and the coating quality can be controlled with higher quality.

[0035]

As described above, according to the present invention, the thickness of a coating film immediately after coating can be detected stably and accurately.
Because it is possible to control the target coating thickness with good responsiveness,
The production efficiency can be improved, defects due to coating film thickness deviation can be reduced, and quality can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing main facilities near a coating section of a continuous coating line for a metal strip provided with a coating film thickness control device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a main part of the apparatus of FIG.

FIG. 3 is a view taken in the direction of arrows AA in FIG. 2;

FIG. 4 is a diagram showing a comparison of the responsiveness in the coating thickness control between the method of the present invention and the conventional method in Examples.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 metal strip 2 backup roll 3 coating liquid 4 roll coater 5 first displacement sensor (laser displacement sensor) 6 second displacement sensor (laser displacement sensor) 7 arithmetic unit 8 control unit 9 pickup roll 10 applicator roll 11 pan 21a, 21b, 22a, 22b Pressing device 23a, 23b Electric motor 24a, 24b Rotation speed detector

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2F065 AA30 BB15 CC06 CC31 DD03 DD06 FF09 FF11 GG04 HH04 HH13 JJ05 JJ15 JJ16 MM03 MM14 MM24 MM28 PP22 QQ25 2F069 AA46 BB19 BB34 BB40 DD15 DD19 GG30Z09 AC07 CA48 DA03 DB01 4F040 AA24 AB04 AC01 BA25 CB40 DA05 DA14 DA20

Claims (4)

[Claims] 1. A coating film thickness control device provided on a line for applying a coating liquid to a continuously running metal band, wherein the coating film thickness control device is configured to apply the coating liquid to the metal band in a coating section. A first displacement sensor that measures the distance to the coating surface in close proximity to the rotating roll surface while contacting the metal strip installed between coating and drying, and the distance to the roll surface A second displacement sensor that measures the thickness of the first displacement sensor and the second displacement sensor, and a computing device that computes a coating thickness based on signals from the first displacement sensor and the second displacement sensor. A coating film thickness control device comprising a control device for controlling an amount of a coating liquid applied to a metal strip in an application section. 2. The coating film thickness control device according to claim 1, wherein a laser displacement sensor is used as the first displacement sensor and the second displacement sensor. 3. A method for controlling a coating thickness of a metal strip on a line for applying a coating liquid to a metal strip that is continuously running. The distance to the coating surface is measured by a first displacement sensor, and the distance to the roll surface is measured by a second displacement sensor. Based on the distance measured by the displacement sensor and the second displacement sensor, the arithmetic unit calculates the coating thickness of the metal strip, and the coating unit calculates the coating thickness so that the calculated coating thickness becomes a predetermined coating thickness. A method for controlling the thickness of a coating film, comprising controlling an amount of a coating solution applied to a metal strip. 4. The method according to claim 3, wherein laser displacement sensors are used as the first displacement sensor and the second displacement sensor.