JPH07114999B2 - Coating thickness measurement method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for measuring the thickness of a coating film applied to a coating line of, for example, a coating strip using infrared rays.

[Prior art]

Paint strips, which are in widespread demand for applications such as building materials, automobiles, and home appliances, have an axial length dimension that is greater than the width dimension of the strip-shaped steel sheet that is the object to be coated, and roll onto the screen of the steel sheet. A cylindrical backup roll and a coating roll, and having a dimension in the axial length direction substantially equal to the coating roll, while rolling the steel plate of the coating roll to a position different from the rolling contact position, and immersing part of it in the coating A coating section provided with a cylindrical pickup roll formed in the middle of the moving line of the steel plate, and the coating material adhering to the outer circumference of the pickup roll is transferred to the coating roll at a rolling contact position with the roll. Further, when it passes between the coating roll and the backup roll, it is transferred to the steel plate, and a coating film is formed on one surface of the steel plate to manufacture.

By the way, since the main application of such a coated strip is the application requiring corrosion resistance, in its production, it is necessary to automate the coating line and save labor, and at the same time, to make its quality, especially the thickness of the coating film uniform. It has become an important issue. Therefore, in the coating line of the coating strip, online measurement of the thickness of the coating film formed on the painted steel plate, based on the measurement results, for example, transfer of the paint from the pickup roll to the coating roll In order to adjust the amount, the surface pressure between the two is automatically adjusted to achieve a uniform coating film thickness on the coated strip.

In such a case, as a method for measuring the coating film thickness, there is a method using an infrared film thickness meter utilizing infrared rays. this is,
When the coating film is irradiated with infrared rays having a specific wavelength, the irradiated infrared rays penetrate the coating film to reach the surface where the coating film is formed, and are reflected by the surface, and the reflected infrared rays penetrate the coating film again. Energy of reflected infrared rays (I) as a result of being partially absorbed by the organic matter contained in the coating film until reaching the outside.
It is based on the fact that the Lambert-Beer law as shown in the following equation is established between the ratio of the irradiation infrared ray to the energy (I ₀ ) and the thickness (t) of the coating film.

I / I ₀ = R · e ^{−2 kt} (1) where R: reflectance of the coating film forming surface K: infrared absorption of the coating film However, in the above formula (1), R is the material of the coating film forming surface. And the surface roughness of the strip-shaped steel sheet, which is the coating film forming surface of the coating strip, varies depending on each position on the surface, while changing depending on the surface roughness, etc., so online measurement of the coating film on the coating line is performed. When using the infrared film thickness meter as described above, the reflectance R is different for each measurement position,
There is a drawback in that a measurement error occurs due to this.

Therefore, the following two methods have been proposed in order to eliminate the above-mentioned error and ensure online measurement of the coating film thickness.

The first method is to detect the intensity of the reflected infrared light at a specific wavelength absorbed in the coating film and the intensity of the reflected infrared light at one wavelength other than the specified wavelength, respectively, and to determine the coating film based on the ratio between the detected values. How to obtain thickness (Sumitomo Heavy Industries Technical Report Vol.32 No.9
4) and the second method is to detect the intensity of the reflected infrared light at a wavelength absorbed by the coating film, and a wavelength and a wavelength longer than this wavelength, and the coating film is based on these three detection values. This is the method shown in Japanese Patent Application No. 61-68157 filed by the applicant of the present application for determining the thickness.

[Problems to be solved by the invention]

However, in the first method, the Japanese Patent Application No.
As described in detail in No. 61-68157, the influence of the fluctuation of the reflectance R is not completely removed, and an error may occur when measuring a thin coating film thickness of about 1 μm. Further, the coating strip to be measured moves while slightly swinging in the direction orthogonal to the moving direction thereof, and in both the first method and the second method, the amount of reflected infrared light received due to this swinging. Fluctuations are unavoidable, which may lead to measurement errors, and when this fluctuation is large, it becomes impossible to receive reflected infrared rays, and as a result, it may be impossible to measure the coating thickness. . Further, in the above two methods, since infrared rays of two or three kinds of wavelengths are used, it is necessary to provide a light receiver for each wavelength, a mirror for separating reflected infrared rays, and an infrared ray after spectral separation. Due to the need for a filter that selectively transmits wavelength components and the inability to use a lens to eliminate errors in measured values due to chromatic aberration between wavelengths, there is a limit to the miniaturization of infrared film thickness meters. There was a drawback that there was.

The present invention has been made in view of such circumstances, the surface roughness of the coating film forming surface, and the thickness of the coating film without being affected by the shake of the coating film forming surface due to the movement of the object to be coated. It is possible to accurately measure the thickness online, and for example, by using this in a coating line for coating strips, it is possible to provide a coating film thickness measuring method that can improve the quality and production efficiency of coated strips. The purpose is to

[Means for solving problems]

The coating film measuring method according to the present invention comprises a pick-up roll which is partially immersed in a paint and rotates, and a paint roll which is rotated by rolling contact with the pick-up roll and a strip-shaped object to be moved in its longitudinal direction. In a coating line in which the coating material adhered to the outer peripheral surface of the pickup roll is transferred to the coating roll and then transferred from the coating roll to the object to be coated to form a coating film on the surface of the object to be coated. Infrared rays having a wavelength that causes absorption by the coating material, on the outer peripheral surface of the coating roll before and after transfer to the object to be coated, or on the outer peripheral surface of the pickup roll before and after transfer to the coating roll. Respectively, the energy of the reflected light is detected, and the rotation speed of the coating roll or the pickup roll and the moving speed of the object to be coated are respectively detected. Out, from the detected values of these four, and calculates the thickness of the coating on the object to be coated surfaces.

[Action]

In the present invention, the thickness of the coating adhered to the coating roll or the pickup roll, before and after the transfer of the coating material to the coating object or the coating roll, respectively detected by using infrared rays, the detection value and As a result of the transfer of the coating material through the coating roll, the thickness of the coating film formed on the object to be coated is calculated from the rotation speed and line speed of the coating roll or the pickup roll.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing an embodiment thereof. FIG. 1 is a schematic block diagram showing an implementation state of a coating film thickness measuring method according to the present invention (hereinafter referred to as the present invention method) on a coating line for a coated strip.

In the figure, reference numeral 1 is a strip steel plate, and the steel plate 1 moves at a predetermined speed in a direction indicated by an outline arrow in the drawing, and when passing through a coating part 3 provided in the middle of the moving path. The coating strip 2 is coated on one side thereof to become a coated strip 2, which is wound in a coil shape on a winding roll (not shown) provided on the most downstream side of the moving path.

The coating part 3 is a cylindrical backup roll 3 having an axial dimension longer than the widthwise dimension of the strip steel plate 1.
0, a coating roll 31, a pickup roll 32, and a paint tank 33 filled with the paint 34 to be applied to the coating strip 2.
Etc. The backup roll 30 and the coating roll 31 are respectively rolled on both sides of the steel plate 1 so that the strip steel plate 1 is sandwiched between them.
Is rotatably supported about respective pivots parallel to the width direction of the backup roll 30, and the backup roll 30 is in the same direction as the moving direction of the strip steel plate 1 at the rolling contact position with the strip steel plate 1 and the coating roll 31. In the same manner, they are rotationally driven in the opposite directions at predetermined speeds by respective drive motors (not shown). The pick-up roll 32 is located at a position different from the rolling contact position with the strip steel plate 1 and is located at the coating roll.
The upper part of the roll 31 is rotatably contacted and is rotatably supported around a pivot parallel to the pivot of the roll 31, and the lower part thereof is
It is immersed in the paint 34 in the paint tank 33, and is driven to rotate in the opposite direction to the paint roll 31 by a drive motor (not shown). Further, between the pivot shaft of the pickup roll 32 and the pivot shaft of the coating roll 31, a direction in which the pickup roll 32 approaches or separates from the coating roll 31 in order to change the surface pressure at the rolling contact portion between them. A surface pressure adjuster 35 for slightly moving to is installed.

Thus, in the paint tank 33, the pickup roll 32
The paint 34 attached to the outer peripheral surface of the roller 32 is lifted up as the roll 32 rotates, and at the rolling contact position between the pickup roll 32 and the coating roll 31, the contact surface between them is set by the surface pressure adjuster 35. In accordance with the pressure, most of it is transferred to the coating roll 31 and adheres to it, and further moves with the rotation of the coating roll 31, and between the roll 31 and the strip-shaped steel sheet 1 at the rolling contact position. By sliding, almost the entire amount of the strip-shaped steel plate 1 is transferred to form a coating film on the surface of the steel plate 1,
The steel plate 1 becomes a coated strip 2.

By the way, the roll rotation speed detector 4 using, for example, a rotary encoder is coaxially attached to the pivot shaft of the pickup roll 32 of the coating unit 3 configured as described above, and On the upstream side (or the downstream side) in the rotation direction of the pickup roll 32 with respect to the rolling contact position with the coating roll 31, at a position facing the same with a proper distance from the outer peripheral surface of the pickup roll 32, the outer peripheral surface is provided. Paint that is irradiated with infrared rays and receives light reflected from the surface to form the paint 8 attached to the pickup roll 32 on the surface before (or after) being transferred to the coating roll 31. layer
Infrared film thickness meters 5a (or infrared film thickness meters 5b), which will be described later, are installed to detect the thickness of 32a (or coating layer 32b). The outputs of the infrared film thickness meters 5a and 5b and the roll rotation number detector 4 are the same as the output of the line speed detector 6 that detects the moving speed of the coating strip 2 and the coating thickness control using a microprocessor. Given to part 7. The line speed detector 6 is, for example, arranged so as to be brought into contact with one surface of the coating strip 2 after the coating film on the coating strip 2 is sufficiently dried. On the rotation axis of the line speed detection roll 6a that rotates due to the frictional force between the plate 2 and
In order to detect the rotation speed of the roll 6a, a rotary encoder mounted coaxially therewith may be used. Then, the coating film thickness control section 7 performs the calculation described later based on the input signals from the respective detectors, calculates the thickness of the coating film formed on the coating strip 2, and outputs the result. In response to this, a drive signal is issued to the surface pressure adjuster 35 to adjust the surface pressure between the pickup roll 32 and the coating roll 31, thereby operating to maintain the coating film at a predetermined thickness.

2 shows the coating layer 32a (or 3) on the outer peripheral surface of the pickup roll 32 by the infrared film thickness meter 5a (or 5b).
It is a schematic diagram which shows the state which is detecting the thickness of 2b).

The infrared film pressure gauge 5a includes a semiconductor laser oscillating unit 50 that emits laser light A having a predetermined wavelength within an infrared wavelength range where absorption occurs in the paint layer 32a, a collimator lens 51 that condenses the laser light A, and the laser light A described above. Pickup roll 32,3
It is composed of a light receiving section 52 which receives the reflected light from 2. The laser light A emitted from the semiconductor laser oscillator 50 is condensed by the collimator lens 51 and then, within a plane including the axis of the pickup roll 32, as shown in FIG. The paint layer 32a is irradiated from a direction inclined by a predetermined angle α with respect to the axial direction of 32, passes through the paint layer 32a, reaches the outer peripheral surface of the pickup roll 32, and is reflected by the surface. After that, the laser light receiving portion 52 is again transmitted through the paint layer 32a and is received by the laser light receiving portion 52, and the laser light receiving portion 52 outputs a signal corresponding to the energy of the reflected light entering the coating film. It is output to the thickness control unit 7.

The procedure for carrying out the method of the present invention will be described below based on the contents of calculation in the coating film thickness control section 7.

As described above, the control section 7 receives the signals corresponding to the energies Ia and Ib of the reflected light received by the laser light receiving sections 52 and 52 from the infrared film thickness gauges 5a and 5b, respectively, and rolls the signals. from the rotation speed detector 4 and the line speed detector 6, the signal corresponding to the rotational speed N ₂ of the rotational speed N ₁ and line speed detection roll 6a of the pickup roll 32 is entered.

By the way, first, the coating film thickness control unit 7 calculates from the Ia and Ib,
The difference Δt between the thickness t ₁ of the paint layer 32a and the thickness t ₂ of the paint layer 32b is calculated. By the way, between t ₁ or t ₂ and Ia or Ib, the relations shown in the following equations are established in accordance with the Lambert-Beer law shown in the equation (1).

However, I ₀ : Energy of irradiation infrared rays in infrared film thickness meters 5a and 5b R: Infrared reflectance of outer surface of pickup roll 32 K: Infrared absorption rate in coating layers 32a and 32b Equations (2) and (3) Since the values of R in R are equal to each other, Δt is calculated by the following equation.

Further, even when the radiated infrared energy in the infrared film thickness meters 5a and 5b is different and the radiated infrared energy in the infrared film thickness meter 5b is I ₀ ′, the Δt is calculated by the following equation.

I ₀ (or I ₀ and I ₀ included in the formulas (4) and (5)
I ₀ ′) and α are values peculiar to the infrared film thickness meters 5a and 5b, and K is a value peculiar to the coating material 34, and are outside the pickup roll 32 in the formulas (4) and (5). Since the infrared reflectance R on the surface is not included, the value of Δt is accurate in the controller 7 even when the outer surface of the pickup roll 32 changes with time and the roughness of the surface changes. It is possible to calculate various values.

On the other hand, the coating film thickness control unit 7 calculates the peripheral speed V ₁ or the line speed V ₂ of the pickup roll 32 from the rotation speed N ₁ of the pickup roll 32 or the rotation speed N ₂ of the line speed detection roll 6a by the following formulas, respectively. To do.

V ₁ = πD ₁ · N ₁ (6) V ₂ = πD ₂ · N ₂ (7) where D _{1 is} the outer diameter of the pickup roll 32 D _{2 is} the outer diameter of the line speed detection roll 6 a Equation (4) above Alternatively, the Δt is calculated by the formula (5), and the peripheral speed V ₁ and the line speed are calculated by the formulas (6) and (7).
After calculating V _{2 respectively} , the coating film thickness control unit 7 then transfers the transfer amount Q of the paint 34 transferred from the unit length portion of the pickup roll 32 in the axial direction to the coating roll 31 within a unit time.
Is calculated by the following formula.

Q = Δt · V ₁ (8) As described above, the paint 34 transferred from the pickup roll 32 to the coating roll 31 is transferred to the strip-shaped steel plate 1 in a substantially total amount, and a coating film is formed on the steel plate 1. Therefore, based on the transfer amount Q calculated by the equation (8) and the line speed V ₂ calculated by the equation (7), the coating film thickness control unit 7 determines the thickness t ₀ of the coating film on the coating strip 2. It is calculated by the following formula.

t ₀ = Q / V ₂ (9) The coating film thickness control section 7 calculates the thickness t ₀ of the coating film on the coating strip 2 in this way, and then based on this calculated value, as described above. Drive signal to the surface pressure adjuster 35, and the adjuster 35
By adjusting the surface pressure between the pick-up roll 32 and the coating roll 31, the operation is performed so as to maintain the coating film thickness on the coating strip 2 at a predetermined thickness.

In this embodiment, the case of detecting the thickness of the paint layers 32a and 32b on the outer peripheral surface of the pickup roll 32 has been described, but the coating roll 31 before and after the transfer of the coating material to the coating strip 2 is described. Infrared film thickness meters 5a, 5b are arranged facing each other on the outer peripheral surface of the coating roll 31, and the thickness of the coating layer on the outer peripheral surface of the coating roll 31 may be detected by these. Instead of the outer diameter D ₁ of the pickup roll 32 and its rotation speed N ₁ , the outer diameter of the coating roll 31 and its rotation speed may be used, respectively.

Further, in the embodiments of the present invention, the implementation of the method of the present invention in the coating line of the coating strip has been described, but the method of the present invention is not limited to this, and can be applied to other coating lines having similar coating portions. Needless to say.

〔effect〕

As described above in detail, in the method of the present invention, the thickness of the coating material adhering to the coating roll or the pickup roll is detected before and after the transfer of the coating material to the object to be coated or the coating roll, respectively, and the detected value and the coating roll. Alternatively, since the thickness of the coating film formed by transferring the coating material onto the object to be coated is calculated from the number of revolutions of the pickup roll and the moving speed of the object to be coated, the surface roughness of the object to be coated is calculated. The thickness of the coating film can be accurately measured on-line without being affected by the fluctuation of the coating film surface due to the movement of the coating material and the coating layer. It has excellent effects such as high quality of products.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a schematic block diagram showing an implementation state of the method of the present invention, and FIG. 2 shows a detection state of a coating layer thickness by an infrared film thickness meter. It is a schematic diagram. 1 ... Strip steel plate, 2 ... Painted strip plate, 3 ... Painting part, 4 ...
… Roll speed detectors, 5a, 5b …… Infrared film thickness meter, 6…
… Line speed detector, 7 …… Paint thickness control unit, 31 …… Paint roll, 32 …… Pickup roll, 35 …… Surface pressure regulator

Claims (1)

[Claims] 1. A pickup roll comprising: a pick-up roll which is partially immersed in a coating material to rotate; and a pick-up roll which is rotated by rolling contact with the pick-up roll and a strip-shaped object to be moved which moves in the longitudinal direction thereof. In a coating line for transferring the coating material adhered to the outer peripheral surface of the coating roll to the coating roll, and then transferring the coating roll to the coating object to form a coating film on the surface of the coating object. To the outer peripheral surface of the coating roll before and after transfer to, or the outer peripheral surface of the pickup roll before and after transfer to the coating roll, irradiating infrared rays of wavelengths that cause absorption in the coating material, The energy of the reflected light is detected, and the rotational speed of the coating roll or pickup roll and the moving speed of the object to be coated are detected. A coating film thickness measuring method, characterized in that the thickness of the coating film on the surface of the object to be coated is calculated from the detected value of the seed.