JPH0615060B2 - Paint film control device for painted steel sheets - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus for controlling a coating film in a coated steel sheet production line in which a strip steel is continuously coated and baked.

(Prior Art) Painted steel sheets are used in a wide range of fields such as home appliances and building materials.
In addition, the coated steel sheet has a desired coating film thickness,
Depending on its application, it is required that the coating film has required performance such as workability and scratch resistance, and that the coating has a required color.

As a device for manufacturing coated steel sheets with the required coating thickness,
The coating film thickness automatic control device of Japanese Patent Publication No. 60-54111 is known. In this device, the paint film thickness is detected on the outlet side of the drying furnace, and the paint film thickness is feedback-controlled based on the detected value.

(Problems to be Solved by the Invention) In the above conventional apparatus, the thickness of the coating film is controlled, but the performance and color of the coating film are not considered at all. That is, in the conventional coated steel sheet manufacturing equipment, neither the coating device nor the baking furnace is automatically controlled for these items, and the coating device and the baking device are not visually controlled by the operator immediately before the winding roll or based on the feeling. The furnace was manually controlled.
Therefore, the painting work is not only inefficient,
There were large variations in the performance and color of the coating film.

The present invention has been made to solve the above problems, and an object thereof is to obtain an apparatus capable of controlling not only the coating film thickness, but also the coating film performance and color efficiently and accurately. .

(Means for Solving Problems) The coating film control apparatus of the present invention is a steel device having a coating film baked in a coating facility for continuously applying the coating material to a steel strip and baking the coating material to the steel strip in a baking furnace. A strip surface temperature detector, a coating film thickness detector, and a coating film surface color detector are respectively arranged on the outlet side of the baking furnace. And a device for adjusting the furnace temperature of the baking furnace based on the surface temperature signal from the surface temperature detector, and the coating thickness signal from the coating thickness detector and the coating from the coating surface color detector. It is equipped with a device for adjusting the coating amount based on the film surface color signal. A radiation thermometer is used for the surface temperature, an infrared coating thickness meter is used for the coating pressure, and a non-contact type detector such as a color difference meter is used for the color of the coating surface.

(Function) The furnace temperature is adjusted based on the surface temperature of the steel strip, and the coating amount is adjusted based on the coating thickness and the color of the coating surface. That is, the control deviation is obtained by comparing and calculating these detected values with a preset allowable target range. And
Feedback control is performed so that the surface temperature is within the allowable range. The surface temperature is controlled by, for example, adjusting the amount of fuel or hot air supplied to the baking furnace. Further, the coating amount is controlled by adjusting the gap between coater rolls, for example.

Since the coating film performance such as workability and scratch resistance depends on the baking temperature of the paint, the required coating film performance can be obtained by controlling the baking temperature appropriately. Further, the coating amount is controlled not only based on the detected value of the coating film thickness, but also based on the detected value of color. Since the color of the coated surface has a certain relationship with the thickness of the coating film, the required color can be obtained. Further, since the baking temperature and the coating amount of the coating material are feedback-controlled, variations in coating film thickness, coating film performance and color are small.

(Embodiment) FIG. 1 shows an example of the apparatus of the present invention.

As shown in the drawing, a coating device 11 for coating the steel strip S with paint.
Is composed of a pickup roll 12, a transfer roll 13 and an applicator roll 14, and each roll is rotationally driven by an electric motor 16. The pickup roll 12 picks up the paint from a paint pan (not shown) and supplies it to the applicator roll 14 via the transfer roll 13. The applicator roll 14 attaches the paint to the steel strip S with which it is in contact. Further, each roll is equipped with a roll gap adjusting device 18 including a servo motor and a screw mechanism, and the amount of paint adhered is adjusted by the gap between the rolls.

A baking furnace 21 is arranged on the exit side of the coating apparatus 11. Baking oven
21 is heated by combustion of fuel gas and supply of hot air gas, and paint is baked on the steel strip S. The amount of fuel gas controls the opening of the fuel control valve 23, and the amount of hot air controls the rotation speed of the motor 26 that drives the hot air blower 25 to control the furnace temperature, that is, the baking temperature.

Immediately after the baking furnace 21, a radiation thermometer 31 for detecting the surface temperature of the steel strip S on which the coating film is formed is arranged. Further, on the downstream side, a film thickness meter 32 and a color difference meter 33 are arranged. The radiation thermometer 31, the film thickness meter 32, and the color difference meter 33 are connected to comparators 34, 35, 36 and dead zone circuits 37, 38, 39, respectively. These dead band circuits prevent hunting of the control system.

The main computer 41 uses the manufacturing instruction file 43 and the detectors 31 and 3 described above.
Based on the signals from 2, 33, the required coating film thickness, fuel supply amount, and hot air amount are calculated, and the calculation results are output to the coating film thickness controller 45, the fuel controller 46, and the hot air amount controller 47, respectively. These regulators 45, 46 and 47 output regulation signals to the roll gap regulating device 18, the fuel regulating valve 23 and the drive motor 26, respectively.

Next, coating film control by the apparatus configured as described above will be described.

First, in the manufacturing instruction file 43, the plate thickness / width / length of the steel strip S, the film thickness setting value of the product coating, the allowable range of the film thickness, the dead zone setting value of the film thickness, the type of paint to be applied, the film thickness・ Color specially made (relationship between film thickness and color after baking), proper baking plate temperature and its dead zone setting value. Record the color setting value of the painted surface of the product and its dead zone setting value. The color is quantitatively expressed using ^* , a ^* , and b ^* surface pigments.

Next, the main computer 41 obtains a required roll gap according to the coating film thickness setting value, and sets the roll gap adjusting device 18 of the coating device 11 via the coating film adjusting device 45. Also, the baking furnace 21
Regarding, regarding the sheet width / thickness of the steel strip S, the type of paint, the appropriate baking temperature, etc., the main computer 41 predetermines the appropriate fuel valve opening and hot air blower air volume, and the fuel valve opening controller 46 And the opening degree of the fuel control valve 46 and the rotation speed of the motor 47 are set via the blower air flow controller 47.

In FIG. 1, the steel strip S is fed from an uncoiler (not shown) and the coating device 11 continuously applies the coating material. The steel strip S to which the paint is applied is heated in the baking oven 21 and the coating film is baked. Then, the steel strip S having the coating film baked thereon is cooled and wound around a coiler (not shown). During this period, the plate temperature, the plate thickness and the color are continuously measured by the measuring instruments 31, 32 and 33. Each measured value is output to each comparison calculator 34, 35, 36.

The main computer 41 refers to the contents of the manufacturing instruction file 43, and transfers necessary information to the respective comparison calculators 34, 35, 36 and the dead zone circuits 37, 38, 39. That is, the plate temperature comparison calculator 34 has an appropriate baking plate temperature, the plate temperature dead zone circuit 37 has a baking plate temperature dead zone set value, the film thickness comparison calculator 32 has a film thickness set value, and a film thickness dead zone circuit 38. To the color difference comparison calculator 36, and to the color difference dead zone circuit 39, the color difference dead zone set value.

According to the data returned to the main computer 41 via the dead zone circuits 37, 38, 39, the main computer 41 sends a control command to the coating film thickness controller 45, the fuel valve opening controller 46 and the blower air flow controller 47, respectively.

FIG. 2 is a flowchart showing the calculation procedure in the main computer 41. Here, a case where one type of green polyester paint is applied will be described as an example.

When the measured value of the plate temperature exceeds the dead zone set value and has a difference with the appropriate baking plate temperature, the main computer 41 instructs the controllers 45, 46, 47 to adjust the fuel valve opening and the hot air blower air volume. put out.

Further, when the measured value of the film thickness exceeds the dead zone setting value and has a difference from the film thickness setting value, the main computer 41 issues an instruction to adjust the roll gap amount to the controller 45.

Regarding the color, the color difference meter 33 measures the color, that is, each value of L ^* , a ^* , and b ^* . The measured value is compared with each set value by the color comparison calculator 35. Normally, the color changes peculiar to the paint depending on the film thickness. This is due to the effect of transmission of the pigments and organic properties of the paint and the color of the original plate. In the case of the green polyester paint, the film thickness-color characteristics as shown in FIG. 3 are exhibited. Therefore, the color can be controlled by the film thickness. In addition, in FIG.
n μm is the film thickness and the allowable range.

The difference between the color setting value and the measured value in the color comparison calculator 36,
The control deviation is calculated by the following formula.

ΔL ^* = L ^* set value − L ^* measured value Δa ^* = a ^* set value − a ^* measured value Δb ^* = b ^* set value − b ^* measured value When the control deviation is smaller than the dead zone set value, the color dead zone circuit The output signal from 39 is zero. Control deviation ΔL ^* , Δ
From the results of a ^* and Δb ^* , the main computer 41 changes the film thickness setting value and issues an instruction to change the film thickness to the coating film thickness controller 45 according to the flow shown in FIG.

In the above control, if the film thickness cannot be changed at any of the upper and lower limits, or if the change in film thickness cannot be determined from the positive or negative of the control deviations ΔL ^* , Δa ^* , Δb ^* values, the steel strip S Is memorized as "abnormal color", and is utilized as information at the time of use, shipping, etc. of this coated steel strip S.

Further, a new set value of the baking plate temperature is calculated by changing the film thickness set value, and the main computer 41 issues an instruction to the two controllers 46 and 47.

(Effects of the Invention) According to the present invention, a coated steel sheet that satisfies not only the coating thickness but also the conditions that the coated steel sheet should have, that is, the coating performance and color such as workability and scratch resistance, is manufactured. In addition, there is little variation in the thickness, performance and color of the coating film.

[Brief description of drawings]

FIG. 1 is a device configuration diagram showing an example of the device of the present invention, and FIG.
The figure is a flowchart showing the calculation procedure in the main computer,
And FIG. 3 is a diagram showing an example of film thickness-color characteristics. 11 ... Painting device, 18 ... Roll gap adjusting device, 21 ...
… Baking furnace, 23 …… Fuel control valve, 25 …… Hot air blower, 31…
… Radiation thermometer, 32 …… Thickness gauge, 33 …… Color difference meter, 34-36…
… Comparison calculator, 37-39 …… dead zone circuit, 41 …… main computer, 43 …… manufacturing instruction file, 45–47 …… controller.

Claims (1)

[Claims] Claim: What is claimed is: 1. A coating facility for continuously applying a coating material to a steel strip and baking the coating material on the steel strip in a baking oven, wherein a surface temperature detector, a coating film thickness detector, and a coating device for the steel strip having the coating film baked thereon are provided. A film surface color detector is arranged on each of the baking furnace outlet sides, a device for adjusting the furnace temperature of the baking furnace based on a surface temperature signal from the surface temperature detector, and the coating film thickness detector. A coating film thickness control device for a coated steel sheet, comprising a device for adjusting the coating material application amount based on the coating film thickness signal from the coating film surface color signal from the coating film surface color signal.