JP3204470B2 - Control method of coating film thickness of band by roll coater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a coating thickness of a band by using a roll coater, and more particularly, to a method for controlling a film thickness with high precision when continuously coating a band such as a cold-rolled steel sheet with a roll coater. The present invention relates to a method for controlling a coating film thickness of a belt-like body using a controllable roll coater.

[0002]

2. Description of the Related Art In steel sheets, in order to improve the performance such as corrosion resistance, it is common practice to coat chromium, resin or the like on, for example, a galvanized steel sheet.

[0003] The steel sheet is coated by passing the steel sheet paid out from a pay-off reel in the entrance facility through successive steps of degreasing, coating with a roll coater, and drying in an oven while continuously transporting the steel sheet. (The same process may be repeated as necessary). Then, the coated steel sheet is wound up by a winding device in a delivery-side facility.

[0004] Generally, a roll coater used for continuous coating of a steel sheet is a steel pick-up roll for pulling up the paint in a paint pan and receiving the paint from the pick-up roll and transferring the paint to the surface of the steel sheet for coating. Rubber-lined applicator roll. When coating with this roll coater, the coating film thickness is controlled by appropriately controlling the peripheral speed of the roll, the pressing force between the pick-up roll and the applicator roll, and the pressing force between the steel plate and the applicator roll with respect to the conveying speed of the steel sheet. It is done by that.

However, in recent years, coated steel sheets have been used for a wide range of applications such as home appliances, automobiles, building materials, etc., and the quality required in order to improve rust prevention capability has been increased, and the accuracy of the coating film thickness has been improved. Has also become very demanding.

Conventionally, as a method of controlling the coating film thickness when coating with a roll coater, for example, Japanese Patent Laid-Open No.
-6268, JP-B-60-56553, JP-B-62-4
No. 1077, a method of constantly controlling the pressing force between the pickup roll and the applicator roll and the pressing force between the steel plate and the applicator roll to a constant value. A method of controlling a pressing force between a pickup roll and an applicator roll based on data on a relationship between a pressing force applied in the past and a coating film thickness, as disclosed in US Pat. However, JP-B-3-23225 does not describe any specific control method or model formula.

As another method of controlling the coating film thickness, a method using a control model formula experimentally obtained by regression by focusing only on the peripheral speed of the roll and the moving speed of the steel sheet is also adopted.

Next, a description will be given of a case where the back surface of the strip is continuously coated, such as a case where the strip is coated on both sides.

In general, in a continuous double-side coating process for a belt-like body, for example, a steel plate, as shown in FIG. 43, a steel plate S is first coated on the front side with a first roll coater 10 at the front stage, and then with a second roll coater 20 on the back side. After painting the side, heating furnace 2
After drying by passing through a cooling furnace 24 and cooling by passing through a cooling furnace 24, it is sent to the next step. In the drawing, reference numeral 26 denotes a lift roll, and reference numeral 28 denotes a delivery-side fulcrum roll.

The first roll coater 10 includes a pickup roll 14 for pulling up the paint P in a paint pan (paint reservoir) 12 and a part of the paint P pulled by the pickup roll 14 in the direction of the steel sheet S. An applicator roll 16 for transferring paint to the steel sheet S, and a backup roll 18 for pressing the steel sheet S against the applicator roll 16 when the paint is transferred by the applicator roll 16. The second roll coater 20 has substantially the same configuration as the first roll coater 10 except that there is no backup roll.

When the steel sheet S is coated on both sides, the steel sheet S
Is passed between the applicator roll 16 and the backup roll 18 in a state of being wound around the backup roll 18 of the roll coater 10 to coat the front side, and then continuously transferred in a catenary form (suspended state). Steel plate S
Is passed over the second roll coater 20 while being pushed up from below by the applicator roll 16 of the second roll coater 20, thereby painting the back side.

At this time, since the film thickness applied to the steel sheet S is greatly affected by the pressing force between the steel sheet S and the applicator roll 16, it is important to control the pressing force to a target value. Become. However, when the front side is coated with the first roll coater 10, the pressing force between the steel sheet S and the applicator roll 16 can be positively controlled by the backup roll 18, whereas When the back side is coated by the roll coater 20, the pressing force between the steel sheet S and the applicator roll 16 is determined by the tension acting on the steel sheet S, and therefore the pressing force cannot be actively controlled. .

Therefore, when the back surface of the steel sheet S is painted by the second roll coater 20, it is conceivable to carry out painting while keeping the catenary shape at the time of painting constant.
In order to keep the catenary shape constant, the unit tension (tension / cross-sectional area of the steel sheet) may be controlled to be constant in a steady state in which the same steel sheet S is continuously coated. However, for example, when coating a steel sheet having a plate joint (joint contact) having a difference in cross-sectional area where a preceding steel sheet and a succeeding steel sheet having different dimensions are joined, the sheet joint point is not passed through the catenary. Under normal conditions, it is necessary to change the tension momentarily in order to minimize fluctuations in the catenary shape.

As a method for changing the tension with time when the plate joint passes through the catenary, there is, for example, a method disclosed in JP-A-2-305750. This is because the tension in the catenary is determined from the tracking information of the connection position of the long material having different dimensions or materials existing in the catenary, and the information on the dimensions and materials of the preceding and succeeding materials before and after the connection position. Calculate, sequentially calculate the catenary height according to the connection position by the tracking information and the information of the dimensions and materials, and the calculated catenary tension,
While monitoring the catenary tension, the feeding speed of the long material is adjusted in accordance with the deviation between the catenary height and the catenary height before the connection position enters the catenary, or when the catenary tension exceeds a predetermined value. This is a method of controlling the excessive tension of the catenary or the fluctuation of the height of the catenary lowest point by adjusting.

As described above, when the catenary shape is kept constant, when a plate joint of steel plates having different cross-sectional areas passes through the catenary portion, tension is applied according to the passage position of the plate joint. Since it is necessary to change the pressing force, the pressing force between the steel sheet S and the applicator roll 16 changes every moment.

As described above, when the pressing force on the applicator roll 16 changes, as shown schematically in FIG. 44, when the pressing force N _A becomes smaller than the target value, the paint P adhesion amount of the steel sheet S for leak flow rate q _L of thus pass through without being transferred to the steel sheet S becomes larger less than the steady state, when the pressing force N _a conversely is larger than the target value, the leak flow rate q _L is And the amount of adhesion to the steel sheet S increases.

If the amount of paint P adhered to the steel sheet S changes because the pressing force N _A changes every moment, the coating film thickness inevitably increases or decreases. It becomes a defect.

More specifically, when the plate joint is passing through the catenary part, the tension acting on the catenary part is changed from the tension of the preceding steel sheet (the tension required to maintain the catenary shape of the preceding steel sheet) to the succeeding steel sheet. In spite of the momentary change to the tension of the steel sheet (the tension required to maintain the catenary shape of the subsequent steel sheet), conventionally, as soon as the sheet joint passes over the applicator roll 16, since the set nip pressure (pressing force) N _P as became tension (referred to as the preceding material in the figures) preceding steel sheet as shown in FIG. 45 is expressed as the following material to the subsequent steel plate (FIG. If the cross-sectional area is larger than (1), there is a problem that, for example, although the chromate coating with a target film thickness of 50 mg / m ² is performed, the amount of adhesion changes greatly.

Therefore, conventionally, in order to prevent a change in the amount of adhering due to the above-described plate joint passing over the applicator roll 16, when steel plates having greatly different cross-sectional areas are continuously coated, In order to compensate for the difference in the cross-sectional area ratio between the two, a connecting steel plate having a cross-sectional area having a value between the two is sequentially connected so as to fall within a predetermined cross-sectional area ratio. The cross-sectional area ratio at the joint between the steel sheet and the succeeding steel sheet was limited to a small value so that the amount of adhesion did not significantly change.

[0020]

However, in the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 58-6268, in which the pressing force between the rolls is controlled to a constant value, the coating film thickness is determined by the type of the coating material and the applicator. Since it greatly varies depending on coating conditions such as the peripheral speed of a roll such as a roll and the moving speed of a steel sheet, it is difficult to control the coating film thickness to be constant over a wide range of coating conditions.

The rubber lined on the applicator roll swells due to the thinner or the like in the paint, and the elastic modulus (a function of hardness) changes with time. Therefore, when the pressing force between the pick-up roll and the applicator roll is constant, the swelling of the rubber progresses, and as the degree of the swelling increases, the surface pressure between the rolls decreases. The amount of paint to be applied increases, and the coating film thickness increases.

In order to eliminate the influence of the swelling of the rubber, it is necessary to perform a swelling operation for 1 to 2 hours (operation in which only a coater is operated without performing painting) until the swelling is stabilized. Means that the production efficiency is greatly deteriorated.

In the method of controlling the pressing force between the pick-up roll and the applicator roll based on past data, disclosed in Japanese Patent Application Laid-Open No. 58-166959, etc., the type of paint, its dilution rate, A great deal of time and effort is required to experimentally determine in advance the conditions for keeping the coating film thickness consistent with all conditions such as the steel sheet transfer speed, roll peripheral speed, and target coating film thickness. Will be required. In addition, in the case of this method, there is no guarantee that the change over time in the elastic modulus of the rubber of the applicator roll due to swelling is always constant. The film thickness cannot be guaranteed.

Further, the method of evaluating only the peripheral speed of the pickup roll, the peripheral speed of the applicator roll, and the moving speed of the steel plate and experimentally determining a coefficient by regression to perform control enables stable control. Long term (for example, 1
Years), and the applicable control range is narrow.

Further, for example, when the back surface of a steel sheet is continuously coated with the second roll coater shown in FIG. 43, a method for limiting the cross-sectional area ratio between the preceding steel sheet and the succeeding steel sheet to be small is adopted. When the difference in cross-sectional area is large, it is necessary to prepare a large amount of connecting steel sheets, and the time required for passing the connecting steel sheets interposed therebetween becomes large, which is a bottleneck in improving productivity. I was

The present invention has been made in order to solve the above-mentioned conventional problems, and when coating a belt-like body such as a steel plate with a roll coater, the coating film thickness can be precisely adjusted over a wide range of coating conditions. A first object is to provide a method for controlling a coating film thickness of a belt-like body by a roll coater that can be controlled.

Further, the present invention provides a method for coating a belt-like body such as a steel plate with a roll coater even when the degree of swelling of an elastic material such as rubber in an applicator roll changes with time.
A second object of the present invention is to provide a method for controlling a coating film thickness of a belt-like body by a roll coater capable of always performing stable film thickness control.
Subject.

Furthermore, the present invention provides a method for coating a backside of a strip-shaped body, wherein the preceding first strip-shaped body having a greatly different cross-sectional area and the succeeding second strip-shaped body are connected. The cross-sectional area ratio between the first band and the second band when the band is continuously transported in a suspended state and the suspension (catenary part) is painted while being supported by an applicator roll of a roll coater. A method for controlling the coating film thickness of a band by a roll coater that can apply a uniform film thickness to the first and second bands without using a connecting band for compensating for the difference in Providing is a third subject.

[0029]

SUMMARY OF THE INVENTION The present invention relates to a pickup.
A method for controlling the coating film thickness of a band by a roll coater when transferring and coating a paint on a continuously moving band by a roll and a roll coater including an applicator roll having at least a surface formed of an elastic material. , Pick up
Determine the gap h _PA between the roll and applicator roll and
Click up the peripheral speed V _P and the periphery of the applicator roll of the roll
The speed V _A is determined, and the determined roll gap h _PA and roll peripheral speed are determined.
V _P, the total flow rate q _PA is determined based on the V _A, the said total flow rate q _PA
Based on, to determine the supply flow rate q _A of the paint to be sent to the band-like side by the rotation of the applicator roll, app cable tallow
The gap h _AS between the tool and the band is determined and the determined application
Tarol peripheral speed V _A , and applicator roll and band
Based on the gap h _AS supply determines the leak flow rate q _L remaining on the applicator roll without being transferred to the strip, it was determined
Based on the flow rate q _A and the leak flow rate q _L, by controlling the film thickness to be coated on the strip is obtained by achieving the first object.

The present invention also provides that at least the surface is made of an elastic material.
For roll coaters with formed applicator rolls
Transfer and paint the paint on a continuously moving strip
Control method for the coating film thickness of a band by using a roll coater.
And sent to the strip by rotating the applicator roll.
A supply flow rate q _A of the coating material, the application without being transferred to the strip
A model that evaluated the difference from the leak flow rate q _L remaining in the cater roll
When controlling the film thickness applied to the strip based on the
Determined the gap between the front roll which connects upstream of the applicator roll and the applicator roll to apply the elastohydrodynamic lubrication theory, leads to expression giving the supply flow rate q _A with the gap, and the applicator roll expression and that the calculated and applied similarly to elastohydrodynamic lubrication theory the gap between the strip leads to expression yielding the leakage flow rate q _L with the gap, gives an expression and leakage flow rate q _L giving the supply flow rate q _a Is applied to the model formula to achieve the first object more reliably even when the coating film thickness is small.

According to the present invention, in the method for controlling the coating film thickness of a belt-like body by the roll coater, the elastic coefficient of the applicator roll included in the model formula is obtained with time, and the change with time is reflected in the film thickness control. By doing so, the second
Has achieved the above task.

The present invention further provides a method for controlling the coating film thickness of a strip by a roll coater when the strip is continuously transported in a suspended state and the strip is coated while being supported by an applicator roll of a roll coater. In the method, when passing the joint of the first and second belts having different dimensions over the roll coater, the tension of the belt which changes with time is reflected in a film thickness control factor in the roll coater. Thereby, the third object has been achieved.

According to the present invention, in the method for controlling the coating film thickness of a strip by the roll coater, at least the surface of the applicator roll is formed of an elastic material, and the applicator roll is fed to the strip by rotation of the applicator roll. a supply flow rate q _a of the paint, before setting the basic equation of the evaluation of the difference between the leakage flow rate q _L remaining on the applicator roll without being transferred to the strip, is connected upstream of the applicator roll and said applicator roll calculated by applying the elastohydrodynamic lubrication theory the gap between the rolls, guide the expression giving the supply flow rate q _a with the gap, and, equally applicable to elastohydrodynamic lubrication theory the gap between the applicator roll and the strip Using the gap, an equation giving the leak flow rate q _L is derived, and the supply flow rate q _A
A formula giving the expression and leakage flow rate q _L to give, by applying to the basic formula to create a film thickness controlled to reflect the tension of the strip to the film thickness control factor contained in the film thickness control equation Thereby, the third object is also achieved.

[0034]

According to the present invention, the film thickness applied to the continuously moving strip is determined by a pickup roll and an applicator.
Determine the roll gap h _PA and determine the peripheral speed of the pickup roll.
To determine the circumferential speed V _A of the V _P and the applicator roll, it is determined
Total flow based on the roll gap h _PA and roll peripheral speeds V _P and V _A
The amount q _PA is determined, and based on the total flow rate q _PA , the supply flow rate of the paint to be sent to the band side by the rotation of the applicator roll.
to determine the q _A, the gap h _AS of the applicator roll and the strip
Determined and the determined peripheral speed _VA of the applicator roll ;
Based on the gap h _AS of the applicator roll and the strip, the remaining Ru leakage flow q _L determines the applicator roll without being transferred to the strip was determined in the supply flow rate q _A and the leak flow rate q _L
Based on the control of the film thickness applied to the strip, it is possible to logically control the film thickness, and therefore the thickness of the coating film by the roll coater over a wide range of coating conditions. Can be controlled with high accuracy and stability.

Further, the belt is formed by rotating the applicator roll.
A supply flow rate q _A of the paint delivered to the body side is transferred to strip
Commentary the difference between the leak flow rate q _L remaining on the applicator roll without
The thickness of the coating on the belt is controlled based on the model formula
When controlling, the gap between the applicator roll and the front roll located in front of the applicator roll (corresponding to a pickup roll in the case of a dual roll coater) is formed by an elastic fluid in consideration of the elastic coefficient of the elastic material. calculated by applying the lubrication theory, guiding the formula giving the supply flow rate q _a with the gap
Come, and, determined by applying the same manner elastohydrodynamic lubrication theory the gap between the applicator roll and the strip leads to expression giving the leak flow rate q _L with the gap, the formula providing a supply flow rate q _A
And wherein providing a leak flow rate q _L, when applied to the model equation, it can be performed and stable thickness control at high accuracy for very thin film thickness of the coating roll gap makes a negative state Become.

Furthermore, the supply flow rate q _A and the leak flow rate q
_{When the} elastic coefficient included in the model equation of the film thickness control created by applying the elastohydrodynamic lubrication theory to the calculation of _L is obtained over time, and when the change over time is reflected in the film thickness control, the above elastic coefficient is used. By sequentially correcting based on the actually measured values, it is possible to always accurately control the film thickness even when the degree of swelling of the elastic material of the applicator roll changes with time.

In the present invention, when the back surface is coated while the belt-shaped body continuously transferred in a suspended state is pushed up from below and supported by an applicator roll of a roll coater, there is a preceding cross-sectional area having a difference in cross-sectional area. The junction of the strip and the subsequent strip was measured for the tension of the catenary part, which changes momentarily while passing through the catenary part, and the tension value was reflected in the film thickness control factor in the roll coater. Even when the cross-sectional area difference is large at the contact point, it is possible to apply a uniform film thickness to both the preceding and succeeding strips.

Specifically, for example, by controlling the pressing force (nip pressure) between the pick-up roll and the applicator roll in accordance with the actually measured tension value, when the plate joint passes through the catenary part, This makes it possible to keep the amount of paint applied constant.

At this time, the thickness of the gap between the pick-up roll and the applicator roll and the gap between the applicator and the band are evaluated by the elastic fluid lubrication theory. By applying the formula, it was possible to apply a uniform thickness even in the case of thin film coating.

Instead of actually measuring the tension of the catenary part, the joint contact is tracked, and a tension set to suppress the fluctuation of the catenary shape is used. For example, the pressing force between the pickup roll and the applicator roll is controlled. By doing so, it is also possible to control the coating film to keep the amount of paint applied constant.

[0041]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, the same parts as those shown in the above-mentioned prior art are in principle denoted by the same reference numerals.

FIG. 1 is a schematic structural view showing a roll coater applied to the first embodiment according to the present invention together with the operation thereof, and FIG. 2 is a simplified diagram showing an example of a coating facility to which the roll coater can be applied. It is a schematic explanatory diagram shown, this coating equipment,
This corresponds to a system in which two facilities shown in FIG. 43 are provided consecutively at the front stage and the rear stage.

Generally, coating on a steel plate (strip) is performed according to the flow shown in FIG.
That is, the steel sheet S paid out from the pay-off reel (not shown) of the entrance equipment and subjected to the degreasing process is transported to the first roll coater 10 and the second roll coater 20 of the preceding equipment and is coated with the base material. After drying in one oven and cooling in a first cooler, the amount of paint applied is measured by a first coater.

The steel sheet S whose undercoat has been completed in the above equipment
After the upper layer is similarly coated by the first roll coater 10A and the second roll coater 20A in the subsequent subsequent equipment, after being dried and cooled by the second oven and the second cooler, respectively,
The adhesion amount is measured by the second adhesion amount meter, and then sent to, for example, a take-up reel (not shown) of the output-side facility and wound up. Depending on the product, reference numerals 10, 10A, 2A and 2B may be used depending on the case where only one side is coated, the case where the base coating is omitted, or the like.
Coaters 0 and 20A can be used properly.

In the present embodiment, a roll coater used in the above-mentioned coating equipment (in FIG.
When the surface of the steel sheet S is coated by the roll coaters 10, 10A), the thickness of the steel sheet S can be controlled with high accuracy.

The method for controlling the film thickness of the present embodiment will be described in detail by taking as an example the case of coating with the roll coater 10 shown in FIG.

The roll coater 10 picks up the paint P in the paint pan (paint reservoir) 12, pulls up the paint together with the pickup roll 14, transfers a part of the paint in the direction of the steel sheet S, and An applicator roll 16 transfers the paint to the steel sheet S, and a backup roll 18 presses the steel sheet S against the applicator roll 16 when the paint is transferred by the applicator roll 16.

The pickup roll 14 has a radius R _P
Of a steel roll, which rotates at a circumferential speed V _P, the applicator roll 16 is a roll radius R _A which rubber lined on the surface, the pick up roll 14
, At the peripheral speed _VA in the forward direction. On the other hand, the backup roll 18 is a steel roll having a radius R _S , and rotates with the steel plate S at a peripheral speed LS in a direction opposite to the applicator roll 16.

[0049] In the roll coater 10, when the gap between the pickup roll 14 and applicator roll 16 and h _PA, the total flow rate q _PA paint passing between the gap h _PA
Is the pickup roll 14 side and the applicator roll 1
It is separated into 6 sides. Return flow q _P coating deposited on the pickup roll 14 is returned to the paint pan 12, paint deposited on the applicator roll 16 is a supply flow rate q _A is sent to the steel sheet S side.

The supply flow rate q _A, the gap between the rest and at the same time when sent to the steel sheet S part (referred strip flow) q _S is transferred onto the steel sheet S is applicator roll 16 and the backup roll 18 h Leak flow through _AS q
_L.

[0051] Thus, (a solid deposition amount per unit area, corresponding to a paint film thickness) coating weight after drying when a is M, paint adhesion of the strip flow rate q steel sheet S coated under _S The quantity M is given by the following equation (1). The unit of the paint adhesion amount M is [g / m ² ], γ is the specific gravity of the paint, C
Is the solids concentration of the paint.

[0052] _{M = q S · γ · C} / LS ... (1)

[0053] The strip flow q _S is is equal to the difference between the supply flow rate q _A and the leak flow rate q _L, the equation (1) may be the following equation (2).

[0054] _{M = (q A - q L} ) · γ · C / LS ... (2)

In this embodiment, the film thickness is controlled by the roll coater 10 using the above equation (2) as a basic model equation for film thickness control. The actual model formula is shown in the above (2)
Equation q _A, created by substituting the controllable specific expression as q _L. This supply flow q _A , leak flow q
_L can be obtained as follows.

In the roll coater 10, the following equations (3) to (5) are established. That is, the equation (3) gives the total flow rate q _PA as the product of the gap between the pickup roll 14 and the applicator roll 16 and the average speed of the rolls 14 and 16, and the equation (4) gives the return flow rate q _P And supply flow q _A
The sum of the total flow rate q _PA, given from equation (5) ratio of the peripheral speed of the rolls (the ratio of q _A and q _P) distribution ratio of the total flow rate q _PA (alpha, beta is a constant) This is shown respectively.

[0057]

(Equation 1)

[0058] From the relationship of the above (3) to (5), the supply flow rate q _A is given by the following equation (6).

[0059]

(Equation 2)

On the other hand, the leak flow rate q _L is given by the following equation (7). Here, λ is a constant.

Q _L = λ h _AS ( _VA− LS) (7)

[0062] substituted (6) and the supply flow rate q _A of the formula (7) of the leak flow rate q _L to each of the (2) basic model equation of Formula, a specific model equation of the following equation (8) obtain.

[0063]

(Equation 3)

The model formula (8) indicates that the gaps h _PA and h _PA between the pickup roll 14 and the applicator roll 16 and between the applicator roll 16 and the steel sheet S, respectively.
When h _AS is positively provided as a predetermined value, that is, the distance between the axes of the two rolls is larger than the sum of the roll radii of the pickup roll 14 and the applicator roll 16, and there is a positive gap between the two rolls. Similarly, this is effective when there is a positive gap between the applicator roll and the steel sheet S.

Therefore, the above model equation (8) is applied to the control of the film thickness when the coating film thickness is relatively large.

Next, when the distance between the axes of the pickup roll 14 and the applicator roll 16 is smaller than the sum of the roll radii of the pickup roll 14 and the applicator roll 16, that is, the gap between the pickup roll 14 and the applicator roll 16 is apparent. A description will be given of a model formula applicable in the case of a negative result. As described above, the phenomenon that the apparent gap between the rolls is a negative gap is caused by the fact that the rubber lined to the applicator roll 16 is rolled when the pressing force between the rolls is increased to obtain a thin coating film thickness. It is caused by deformation that shrinks in the radial direction. This phenomenon similarly occurs between the applicator roll 16 and the backup roll 18, that is, between the steel plate S.

When the rolls are strongly pressed to obtain a thin coating film as described above, there is a negative gap between the rolls or between the rolls and the steel sheet S. Will not do. Therefore, the roll gaps h _PA and h _AS included in the model equation (8) are evaluated based on the theory of elastohydrodynamic lubrication, and the values are substituted into the equation (8) to obtain the pickup roll 14 and the applicator roll 16. , Or a new model formula that can be applied even when the gap between the applicator roll 16 and the steel sheet S has an apparently negative gap.

According to one embodiment to which the elastohydrodynamic lubrication theory is applied, the gap h _PA is given by the following equation (9).

[0069]

(Equation 4)

[0070] In this _{case, 2 / E PA = (1} -ν P 2) / E P + (1-ν A 2) / E A ... (10) R PA = (R P · R A) / (R P + R _a) where, N _P: nip pressure between the rolls (total) l: roll surface length E _P: pickup roll Young's modulus [nu _P: pickup roll Poisson's ratio E _a: applicator roll Young's modulus [nu _a: applicator roll Poisson ratio

The gap h _AS is given by the following equation (11) according to one embodiment to which the elastohydrodynamic lubrication theory is applied.

[0072]

(Equation 5)

[0073] In this _{case, 2 / E AS = (1} -ν A 2) / E A + (1-ν S 2) / E S ... (12) R AS = R A · R S / (R A + R S ) However, N _A: the pressing force (total) B: plate width E _S: strip Young's modulus [nu _S: strip Poisson's ratio E _A: applicator roll Young's modulus [nu _A: applicator roll Poisson's ratio

By substituting the above equations (9) and (11) into the above equation (8) and rearranging, the following model equation (13) is obtained.

[0075]

(Equation 6)

Using the above model equation, the roll coater 1
By controlling the coating with 0, the coating film thickness can be accurately controlled even when the gap between the pickup roll 14 and the applicator roll 16 and the gap between the applicator roll 16 and the steel sheet S are apparently negative. It becomes possible. A specific example of the control result will be described later in detail together with the other examples.

According to the present embodiment, as described above, since the model formula for controlling the film thickness was theoretically derived, the film thickness can be accurately controlled under a wide range of coating conditions. Become. Therefore, when the coating conditions are changed, for example, when the type of the coating material to be used is changed, the desired film thickness can be easily controlled.

In this embodiment, even when the viscosity and concentration of the paint change with time due to evaporation, temperature change, etc., the paint adhesion amount to the steel sheet S is controlled to be constant as follows. be able to.

That is, as shown in FIG. 3, for example, a viscometer V and a densitometer C, which can be measured online, are installed in a circulation tank T for supplying paint to the paint pan 12 of the roll coater 10. While the paint in the tank T is being circulated, its viscosity and concentration are sequentially detected. Next, these detected values are input to the arithmetic unit A, and at least one of the predetermined nip pressure and the peripheral speed of the roll obtained by executing the following arithmetic operation in the arithmetic unit A is transmitted to the drive unit of the roll coater 10. And the roll coater 10 is feed-forward controlled.

In the arithmetic unit A, the following formulas (15) and (16), which are obtained by modifying the following formula (14) representing the relationship between the viscosity μ and concentration C of the paint and the amount of adhesion M, are actually measured. respectively calculating a nip pressure N _P and the roll peripheral speed V _a by substituting viscosity μ and density C. M = C · μ ^0.6 · f (V _A , V _P , N _A , N _P , LS, E, R, γ) (14)

[0081] In the formula, V _P is the pickup roll peripheral speed, N _A is (corresponds to E _AS of the equation (11)) contact pressure, LS is the line speed, E is the equivalent modulus, R represents the equivalent roll diameter (corresponds to R _aS of the equation (11)), gamma is the specific gravity.

[0082] _{N P = {1 / (C} · μ 0.6)} × f -1 (M, V A, V P, N A, LS, E, R, γ) ... (15) V A = {1 / (C · μ ^0.6 )｝ × f ⁻¹ (M, V _p , N _A , N _P , LS, E, R, γ) (16)

Even when there is only one of the viscometer V and the densitometer C, the previously measured viscosity-concentration-temperature curve as shown in FIG. 4 is input to the arithmetic unit A as a function or a table. If the viscosity is measured, the concentration is
When the concentration is actually measured, the viscosity may be calculated, and the result may be similarly substituted into the above equation (15) or (16) to perform feedforward control.

When the viscosity and the concentration of the coating material change with time, the above-mentioned feedforward control is carried out by continuously coating an organic solvent-based coating material having an initial concentration of 10%, an initial viscosity of 20 cP and a specific gravity of 0.92 for about 48 hours. Fig. 5 shows the result of applying
7 to FIG. The target weight is 1.2 ± 0.2 g / m ² .

The coating conditions were as follows: LS = 30 mpm, V _A = 80
mpm, V _P = 40 mpm, N _A = 100 kg / one side, N _P =
334 kg / one side, roll diameter: pickup roll φ300, applicator roll φ300, backup roll φ900, applicator roll rubber hardness: 52 °
It is.

As shown in FIG. 5, the paint properties changed over time, and after 48 hours, the concentration was 11%, the viscosity was 24 cP, and the specific gravity was 0.92. As a result of controlling _P as shown in FIG.
As shown in the figure, the amount of paint applied could be controlled to be substantially constant.

When the model formula (13) is used, the degree of swelling of the rubber lining the applicator roll 16 changes with time, and the elastic coefficient (Young's modulus) of the rubber lining changes with time. Even in the case of a change, it is possible to control with a constant film thickness following the change. That is, the equivalent elastic modulus E _{PA of} the pick-up roll 14 and the applicator roll 16 and the equivalent elastic modulus E _AS of the applicator roll 16 and the steel sheet S included in the model equation (13) are calculated by the equations (10), respectively. (12) using the equation by modifying measures sequentially varying the elastic modulus E _a (Young's modulus of the applicator roll) by swelling of the rubber, the both equivalent elastic modulus E _PA, a time of E _aS The model equation (13) can be corrected while evaluating the change.

As an example of a specific measuring method of E _A ,
The pressing force between the pickup roll 14 and the applicator roll 16 to detect the axial distance between the centers between (nip pressure) Np and the roll, there is a method such as calculating a E _A from both detected values.

Therefore, according to this embodiment, as in the case where the applicator roll of the roll coater 10 is exchanged,
Even when the degree of swelling of the rubber lining the applicator roll 16 changes every moment, it is possible to accurately control the thickness to a desired thickness. A specific example of this control result will be described later in detail.

Next, a second embodiment according to the present invention will be described.

In the present embodiment, as shown in FIG.
This is a coating film thickness control method in the case of sequentially coating both front and back surfaces of a steel sheet S using equipment provided with one more roll coater 20 behind the roll coater 10 used in the embodiment. Reference numeral 26 in the figure is a lift roll for correcting the winding angle of the steel sheet S with respect to the applicator roll 16 as in the case of FIG.

When the surface of the steel sheet S is coated by the former roll coater (hereinafter also referred to as the first roll coater) 10, the coating film thickness can be controlled in the same manner as in the first embodiment. However, in the case where the back surface is coated with a roll coater (hereinafter, also referred to as a second roll coater) 20 in the subsequent stage, the model formula (8) or (13) is applied similarly to the first embodiment. The film thickness can be controlled.

[0093] However, the steel sheet S is
Meanwhile, while the first roll coater 10 is circumscribed,
Since the roll coater 20 is inscribed, the above (13)
The equivalent roll radius R _AS between the applicator roll 16 and the steel sheet S in the equation is represented by the following equation (17). Also, in this case,
The radius R _{S of the} backup roll is the radius of curvature of the steel sheet S, and the pressing pressure N _A is obtained from the tension of the steel sheet S.

R _AS = R _A · R _S / (R _S -R _A ) (17)

FIG. 9 is a schematic configuration diagram showing a roll coater applied to the third embodiment according to the present invention.

In the roll coater 10, a transfer roll 30 is further interposed between the pickup roll 14 and the applicator roll 16, and the paint supply side is constituted by three rolls. As described above, even in the case of the roll coater 10 composed of three rolls, the model formula substantially the same as the formula (8) or (13) can be applied to control the coating film thickness.

[0097] At this time, when the leakage flow rate in the transfer roll 30 and q _T, q _S in the equation (1)
Is, q _A - q _L - since the q _T, the basic model equation corresponding to the equation (2) is given by the following equation (18).

[0098] _{M = (q A - q L} - q T) · γ · C / LS ... (18)

Although not shown, the above model formula can be similarly applied even when the number of rolls on the paint supply side is four or more. At that time, the following principle is applied.

[0100] If the two rolls of the roll 1 and the rear roll 2 before the connecting exists, the flow rate q ₂ of the paint to be sent to the rear roll 2 from the front roll 1 is calculated as follows (flow rate
q ₂ is the rear roll 2 corresponds to the supply flow rate q _A where a applicator roll).

As shown in FIG. 10A, when the front roll 1 and the rear roll 2 are rotating in the forward direction, the same relation as shown in the above equations (3) to (5) holds. because there, the flow rate q ₂ is given by the following equation (19) corresponding to the equation (6).

[0102]

(Equation 7)

Conversely, as shown in FIG. 10 (B), when the front roll 1 and the rear roll 2 are rotating in opposite directions, the relationship of the above equation (7) holds, so The flow rate q ₂ is given by the equation (20).

Q ₂ = q ₁ −λ h ₁₂ (V ₁ −V ₂ ) (20)

By creating the model equations (8) and (13) in consideration of the relations of the above equations (19) and (20), there is no limit to the number of rolls connected, Can be applied in either the forward direction or the reverse direction.

Since the relations of the above equations (19) and (20) also hold between the applicator roll and the steel sheet S, even when the applicator roll rotates in the forward direction with respect to the moving direction of the steel sheet S, , The model equations are equally applicable. Specifically, for example, the above-described model expressions (8) and (13) can be applied to a roll coater operated in a combination of rotation directions shown in FIGS. 11 to 20.

FIGS. 21 to 29 show the results of actually controlling the film thickness using the equation (13). The control results in FIGS. 21 to 29 are obtained by actually coating under different coating conditions, and the coating conditions are shown in Table 1 below.

[0108]

[Table 1]

In the column of the roll coater type in Table 1 above, A
Is the roll coater shown in FIG. 1 (the same applies to the first roll coater in the former stage shown in FIG. 8), B is the second roll coater in the latter stage shown in FIG. 8, and C is the same in FIG. The indicated roll coaters were used.

The control results and some of the conditions described in Table 1 above will be specifically described. FIG.
Using a roll coater, the steel sheet S has a concentration of 3% and a viscosity of 1c.
P, a result of coating with a paint having a specific gravity of 1.0.
No. 2 uses the same type A roll coater and has a concentration of 1
The result is obtained by applying a paint having a viscosity of 8 cP and a specific gravity of 1.0 at 0.5%. FIG. 24 shows the result of applying a paint having a concentration of 14%, a viscosity of 3.1 cP and a specific gravity of 1.0 using a type B roll coater.

From FIG. 21 to FIG. 29, the adhesion amount (film thickness) after drying was calculated (horizontal axis) and measured value (vertical axis).
It is evident that the present invention is in good agreement with the above, which shows that the present invention is effective over a wide range of coating conditions.

Next, an example of controlling the coating film thickness according to the present invention when the line speed is changed will be described.

In this control example, in the second embodiment, the first roll coater (type A) and the second roll coater (type B) are arranged in the same manner as shown in FIG.
A continuous roll coater was used. Painting target is thickness 0.5
mm, width of 1220 mm.
A water-soluble paint having 4%, a viscosity of 3.1 cP and a specific gravity of 1.0 was used.

FIG. 30 (A) shows the case where the present invention is applied to the case where the line speed (mpm) is changed in the order of 60 → 80 → 60 → 40 → 60 as shown in FIG. This is the result of controlling the thickness. In the drawing, the two-dot chain line indicates the amount of paint applied (film thickness) on the front side coated with the first roll coater, and the solid line indicates the change over time of the amount of paint applied on the back side with the second roll coater.

The result of controlling the film thickness shown in FIG.
Force N_AAnd pickup roll peripheral speed V _PAnd constant, and
Peripheral speed V of the predicator roll_AAs shown in FIG. 31 (A).
A change corresponding to the line speed LS shown in FIG.
Nip pressure N_PBased on the model equation (13)
It is obtained by controlling as shown in FIG.
is there.

The peripheral speed _VA was set to LS + 40 (mpm) for the first roll coater (front surface coating) and LS + 30 (mpm) for the model B roll coater (back surface coating).

The nip pressure N _P is obtained by applying the line speed LS and the peripheral speed _VA together with known values to the following equation (21) obtained by modifying the equation (13). It was determined as a value corresponding to the change.

[0118]

(Equation 8)

FIG. 30A shows the result of controlling the coating film thickness as described above. As is apparent from FIG. 30A, according to the present invention, even when the line speed LS changes, the front and back sides are changed. It can be seen that extremely accurate film thickness control is possible for both surfaces.

Next, in the case where the rubber lining the applicator roll swells and its degree changes with time, a specific example of controlling the coating film thickness by applying the present invention is shown in FIGS. This will be described with reference to FIG.

This control example corresponds to the roll control shown in FIG.
Data (type A), the model formula of the above formula (13)
Is applied, as described above, the model equation (13)
Pickup roll 14 and applicator included in the formula
Equivalent elastic modulus E of roll 16 _PAAnd the applicator roll
16 and the equivalent elastic modulus E of steel sheet S_ASWith the above (1)
Using the formulas (0) and (12), the swelling of the rubber causes the
Elastic modulus E_A(Young's modulus of applicator roll)
Is measured and corrected, the equivalent elastic modulus E
_PA, E_ASWhile evaluating the change over time of the
The coating thickness was controlled by correcting (13).
It is.

The object to be painted is 0.7 mm thick and 1200 mm wide
The steel sheet has a concentration of 14% and a viscosity of 8c with respect to the steel sheet.
When the paint having a specific gravity of 1.0 and a specific gravity of 1.0 was continuously applied for 36 hours, the following results were obtained.

[0123] Figure 32 is a result of measuring the time course of Gomuyangu rate (corresponding to the elastic modulus E _A).

FIG. 33 shows that the rubber Young's modulus varies as described above.
Conditions for a roll coater under changing conditions
The change in the amount of paint applied when the paint was applied at a constant
It is. The setting condition for the roll coater is LS = 6
0mpm, V_A= 90 mpm, V _P= 30 mpm, N_P= 32
0 kg, N_A= 200 kg, and the target adhesion amount is 1.0 kg.
± 0.2g / m^TwoIt is.

FIG. 34 is a graph showing the above-described method for controlling the film thickness according to the model equation (13).
FIG. 35 shows the nip pressure N _P changed corresponding to the change of the rubber Young's modulus shown in FIG. 0, and FIG. 35 shows a model equation (13) using the nip pressure N _P thus changed over time. 3) shows the result of controlling according to the method of the present invention while correcting the above.

As is apparent from FIG. 35, according to the present invention, even when the rubber lining the pickup roll 16 swells as the coating operation is continued, the coating is performed with extremely high precision. It can be seen that the film thickness can be controlled.

Next, in the coating equipment shown in FIG. 2, when the lining rubber of the applicator roll 16 swells with time, for example, the adhesion amount actually measured by the first adhesion meter is calculated by the equation (13). The following describes the feedback control of the coating film thickness applied to the present invention.

[0128] measuring the actual value M _R of the coating film thickness by the coating weight meter, as well as calculated back elastic modulus E _A of the applicator roll 16 which satisfies M = M _R from (13), obtained elastic a rate E _a, a feedback control and other required value (13) the first roll coater 10 and the second roll coater 20 applies the expression online.

By continuously executing this operation,
Since the variation of the coating film thickness due to the swelling of the rubber of the applicator roll 16 can be corrected, the coating can be always performed with a uniform thickness. Note that other factors (for example, V _A , V _P , N _A , N _P , C, γ, μ, etc.) included in the equation (13) are also measured at the same time, and the actual value is _calculated together with the above MR (13) ) is applied to equation may be calculated back elastic modulus E _a.

A galvanized steel sheet S having a thickness of 0.8 mm and a width of 1220 mm was prepared by applying a speed LS = 100 mpm, an applicator roll peripheral speed V _A = 130 mpm, and a pickup roll peripheral speed V _P =
Under the conditions of 30 mpm, paint viscosity μ = 30 cP, and applicator roll elasticity (before swelling) = 0.32 kg / mm ² , the result of the above feedback control performed using the actual value M _R of the coating film thickness was obtained. , Shown in FIG. In addition, the result of this figure is
Neither the present invention nor the conventional one is a case where swelling operation is performed.

FIG. 37 is a schematic explanatory view showing the arrangement of a roll coater applied to the fourth embodiment according to the present invention.

FIG. 37 is an enlarged view of the first roll coater 10 and the second roll coater 20 of FIG. 43.
This is substantially the same as that shown in FIG. 8 used in the second embodiment. In the present embodiment, as shown in the drawing, in the step of transporting the steel sheet S whose front side has been coated by the first roll coater 10 in a suspended state and coating while supporting it with the second roll coater 20 from below, the dimensions are different. 1st steel plate and 2nd steel plate
At the time of coating the steel sheet by passing it over the second roll coater 20, the thickness of the steel sheet is controlled using a film thickness control formula created by applying an elastic fluid lubrication theory.

In this embodiment, the first roll coater 1
When the surface of the steel sheet S is coated with 0, the coating thickness is controlled by applying the expression (8) or (13) as in the case of the second embodiment, but the second roll coater is used. 20 is performed as follows.

When the back surface of the steel sheet S is painted by the second roll coater 20, the film thickness control formula (8) or (13) applied to the first roll coater 10 is applied in the same manner as in the second embodiment. However, when this equation (13) is applied, the equivalent roll radius R _AS between the applicator roll 16 and the steel sheet S is set by the above equation (17).

Further, when the above-mentioned expression (13) is applied, in the surface coating by the first roll coater 10, the pressing force N _A between the steel sheet S and the applicator roll 16 can be positively controlled. On the other hand, in the backside coating by the second roll coater 20, the pressing force N _A is determined by the tension H acting on the catenary portion of the steel sheet S, and therefore needs to be set by the following equation (22).

N _A = 2H sin (θ / 2) (22) (θ: winding angle)

By substituting the above equation (22) into the above equation (13), the pickup roll 14 and the applicator roll 16
Is solved for the nip pressure N _P between the following equation (23) corresponding to the above equation (21).

[0138]

(Equation 9)

In this embodiment, the tension H is actually measured by a tension measuring device (not shown), and the measured tension value of the catenary portion is applied to the term of the tension H in the above equation (23). and controls the nip pressure N _P in accordance with the tension value H to. Therefore, according to the present embodiment, even when the tension acting on the catenary portion changes over time as the plate joint having a large cross-sectional area passes through the catenary portion, the film thickness is uniform on both the preceding and succeeding steel plates. It is possible to paint with.

Next, a fifth embodiment according to the present invention will be described.

In this embodiment, the tension H for suppressing the change in the catenary shape is tracked while tracking the plate joint point.
The tension H is calculated by the method described in detail below, and
Is applied to the film thickness control equation of the formula, except for controlling the nip pressure N _P, which is the fourth embodiment is substantially the same.

In this embodiment, in the step of coating the back surface with the second roll coater 20 while continuously transporting the suspended steel sheet S between the entrance roll and the exit roll, the first steel plate and the second steel plate having different dimensions are used. When passing the joint portion (plate joint point) through the catenary portion, the tension H (Xs) of the steel sheet S is corrected using only the degree of penetration (Xs / L) from the entrance roll of the joint portion as a variable. The following formula (24) including the function f (Xs / L) is set, the catenary shape is controlled by the tension H (Xs), and the steel sheet S is painted. Here, the entrance roll is the applicator roll 16 of the second roll coater 20 shown in FIG. 43, and the exit roll is the fulcrum roll 28 located on the exit side.

H (Xs) = H2− (H2−H1) f (Xs / L) (24) where H2: tension of the first steel sheet H1: tension of the second steel sheet Xs: entrance side of the joint Approach position from the roll L: Total length of catenary

Hereinafter, the method of deriving the above equation (24) will be described in detail.

FIG. 38 shows an entrance-side fulcrum roll (corresponding to the applicator roll 16 of the second roll coater 20 in FIG. 43) and an exit-side fulcrum roll (see FIG. 43).
(Corresponding to the fulcrum roll 28 in FIG. 1) 34 is a schematic explanatory view schematically showing a steel plate (band-shaped body) S suspended in a catenary shape and continuously transported in the direction of the arrow.

The catenary equation representing the shape of the steel sheet S in the suspended state, that is, the curve of the catenary shape (hereinafter, also referred to as the catenary curve) is represented by the following XY coordinate system with the origin fulcrum roll 32 as the origin. It is given by equation (25).

Y = a cosh ｛(X−C 1) / a｝ + C 2 (25)

However, since the above equation (25) is a high-order function and is complicated to incorporate as a control model,
Approximation is made with a quadratic function using the relationship of the following equation (26).

[0149]

(Equation 10)

Now, assuming that the catenary equation in the case of the steel sheet S having no joints is Y0, it can be transformed as the following equation (27).

[0151]

[Equation 11]

Here, a = H / W H: tension [kg] W: weight per unit length of steel sheet [kg / mm] L: total length of catenary (span) [mm]

The boundary conditions in the above equation (27) are as follows.

[0154] when X = 0, since it is ^{Y0 = 0, C1 2 / 2a} + C2 = 0 ... (28) when X = L, since it is Y0 = h0, (L-C1 ) 2 / 2a + C2 = h0 ... (29) where h0: fulcrum height difference [mm]

From the above equations (29)-(28), C 1,
C2 is obtained as follows.

[0156] ^{(L-C1) 2 / 2a} -C1 2 / 2a = h0 L 2 / 2a -LC1 / a = h0 ∴C1 = L / 2-aho / L, C2 = -C1 2 / 2a ... (30)

From the above, the basic catenary formula in a steady state where there is no junction on the steel sheet S is the above-mentioned formula (26) and the above (3)
0).

On the other hand, as shown in FIG. 39 corresponding to FIG. 38, when the preceding first steel sheet indicated by the thin line and the succeeding second steel sheet indicated by the thick line are welded, By the calculation, the catenary curve Y2 of the preceding steel sheet is given by the equation (32), and the catenary curve Y1 of the succeeding steel sheet is given by the equation (31). In the drawing, Xs indicates the entry position of the welded portion (joint portion) between the preceding steel plate and the following steel plate.

[0159]

(Equation 12)

Here, a1: H / W1 [mm] a2: H / W2 [mm] W1: Weight per unit length of succeeding steel sheet [kg / mm] W2: Weight per unit length of preceding steel sheet [Kg / mm]

The boundary conditions are as follows.

[0162] X = 0 time, because it is Y1 = 0, when the ^{C1 2 / 2a1 + C2 = 0} ... (33) X = L, since it is Y2 = h0, (L-C3 ) 2 / 2a2 + C4 = h0 ... ( 34) When X = Xs, since Y1 = Y2, (Xs-C1) ² / 2a1 + C2 = (Xs-C3) ² / 2a2 + C4 (35) X = Xs means that dY1 / dX = dY2 / dX. Therefore, (Xs-C1) / a1 = (Xs-C3) / a2 (36)

By solving the above equations (33) to (36), the catenary equation when the weld (plate joint) passes through the catenary is as follows.

Successive steel sheet when 0 ≦ X ≦ Xs Y1 = 1 / 2a1 · (X−C1) ² + C2 (31) Leading steel sheet when Xs ≦ X ≦ L Y2 = 1 / 2a2 · (X− C3) ² + C4 (32) where C1 = Xs + a1 (L-Xs) ² / 2a2L-Xs
^{2 / 2L-a1h0 / L C2} = -C1 2 / 2a1 C3 = Xs -a2 / a1 · (Xs -C1) C4 = Xs 2 / 2a1-Xs C1 / a1-a2 / 2a1 2 (Xs -C1) 2

With respect to the catenary equation given by the above equations (31) and (32), the amount of change in catenary (difference from the steady state) is evaluated by the following equation.

Δ (X) = ｛Y1−Y0 (0 ≦ X ≦ Xs) ｛Y2−Y0 (Xs ≦ X ≦ L) (37)

The present inventors have studied various patterns of changing the tension in order to minimize the catenary fluctuation amount given by the above equation (37). As a result, when only the first steel sheet (first band-shaped body) is used, From the tension H2 of the second steel plate (second
Tension H during the transition to tension H1 for the band only)
(Xs) is calculated as the degree of penetration (X
It has been found that by applying the correction function f (Xs / L) having only s / L) as a variable, the correction function f (Xs / L) can be uniquely given by the above equation (24) regardless of the dimensional difference between the front and rear steel plates. This equation (24) is shown again here.

H (Xs) = H2− (H2−H1) f (Xs / L) (24) H (Xs): tension when the plate joint point is at Xs H2: tension when the first steel plate is alone U. T × t1 × B1 H1: Tension when the second steel sheet is used alone. T × t2 × B2 U. T: Reference unit tension t2, t1: Thickness of the first and second steel plates, respectively B2, B1: Width of the first and second steel plates, respectively Xs: Position of the plate joint

Then, the correction function f (Xs / L) is
By using the following equation (38), the variation δ (X) can be made extremely small.

F (Xs / L) = α (Xs / L) + β (Xs / L) ² −γ (Xs / L) ³ + δ (Xs / L) ⁴ −ε (Xs / L) ⁵ (38) (Α is around 0.05, β is around 4, γ is around 7, δ is around 6, and ε is around 2.5)

Since the above equation (38) is a higher-order function, the tension can be controlled simply and with sufficient accuracy by using the following equation (39) which is a polygonal line approximation. . FIG. 40 shows the relationship between Expressions (38) and (39).

F (Xs / L) = α ′ (Xs / L) (0 ≦ Xs / L ≦ 0.25) = β ′ (Xs / L) −γ ′ (0.25 ≦ Xs / L ≦ 0. 75) = δ ′ (Xs / L) + ε ′ (0.75 ≦ Xs / L ≦ 1.0) (39) (α ′ is around 0.7, β ′ is around 1.3, γ ′ is 0 .About.1, δ 'is about 0.7, ε' is about 0.3)

As described in detail above, based on the tracking information of the joint, control is performed so that the tension is calculated by applying equation (38) or (39) to equation (24). Thereby, the catenary shape can be maintained substantially constant.

Therefore, when the joint between the first steel sheet and the second steel sheet having a difference in cross-sectional area is passed through the second roll coater 20 for painting, the above equation (24) can be replaced by equation (38) or equation (38). (3
The nip pressure N _P is obtained by applying the tension obtained by applying the equation (9) to the equation (23), and the nip pressure N _P can be used for controlling the film thickness.

According to the present embodiment described in detail above, since the tension set value for controlling the catenary shape to be constant is taken into the control formula, the plate joint point having a difference in cross-sectional area passes through the catenary part. even if the pressing force N _a to the applicator roll 16 by the steel sheet is changed every moment while you are, it is possible to correct the nip pressure N _P the change in pressing with force N _a. As a result, it is possible to prevent a change in the amount of paint applied to the steel sheet, and to apply a uniform film thickness, thereby stabilizing the quality.

Next, a specific example in the case where coating is performed by applying this embodiment will be described.

As the steel plate, a steel plate in which a second steel plate having the same width and a thickness of 1.0 mm was connected to a preceding first steel plate having a thickness of 0.5 mm and a width of 1220 mm was used. Conventionally, a connecting steel plate having a thickness of 0.7 to 0.8 mm was interposed between the first steel plate and the second steel plate.

The coating conditions are as follows.

Paint: Chromate (concentration: 1.3%, viscosity: 1.7 cP, specific gravity: 1.06) Line speed: LS = 30 mpm Applicator roll peripheral speed: V _A = 75 mpm Pickup roll peripheral speed: V _P = 40 mpm Applicator Roll rubber hardness: 52 °

As the tension H applied to the equation (23), the calculated tension required for controlling the catenary shape to be constant by the method described above was used. That is, while tracking the plate joint position Xs, the set tension H (Xs) was calculated by applying the function f of the following equation (40) corresponding to the above equation (38) to the above equation (24).

F = 0.05 (Xs / L) +4.1 (Xs / L) ² −6.9 (Xs / L) ³ +6.3 (Xs / L) ⁴ −2.5 (Xs / L) _{^{5 ... (40) (H 2}} = 1678kg, H 1 = 3355kg, L = 60m)

The calculated tension H (Xs) is calculated by the equation (2)
3) was controlled nip pressure N _P is applied to the equation. The result is shown in FIG. FIG. 4 shows the change in the amount of paint applied at this time.
It is shown in FIG. For comparison, the results obtained when conventional stepwise control is performed are also shown in the same drawing.

As is clear from FIGS. 41 and 42, according to the present embodiment, it is possible to prevent a change in the amount of paint applied, which has conventionally occurred when the plate joint passes through the catenary portion. It can be seen that the first and second steel plates are coated with a uniform film thickness.

Although the present invention has been specifically described above, the present invention is not limited to the above-described embodiments.

For example, the film thickness control formula applied to the back surface coating according to the present invention is not limited to the formula (23) to which the theory of the elastohydrodynamic lubrication shown in the above embodiment is applied, but the formula (8) described above. Or other control type.

The film thickness control factor reflecting the tension H that changes with time is not limited to the pressing force (nip pressure) N _P between the pickup roll and the applicator roll. And the peripheral speed of the pickup roll.

The method for obtaining the tension H is not limited to the method described in the above embodiment, but may be the method disclosed in, for example, the above-mentioned JP-A-2-305750.

Further, the type of roll coater, the number of rolls, and the direction of rotation of the rolls can be arbitrarily changed. Therefore,
The front roll is not limited to the pickup roll.

[0189]

As described above, according to the present invention, when a belt-like body such as a steel plate is coated with a roll coater, the coating film thickness can be controlled with high accuracy over a wide range of coating conditions. . Further, at this time, even when the degree of swelling of the rubber of the applicator roll changes with time, stable film thickness control can be always performed.

In addition, according to the present invention, a belt in which a first belt and a second belt having different dimensions are joined to each other is continuously transported in a suspended state, and the suspension of the belt is rolled. When the back surface is coated while being supported by the applicator roll of the coater, it is possible to accurately apply both the first and second belt-like bodies with a uniform film thickness.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a roll coater applied to a first embodiment according to the present invention.

FIG. 2 is a schematic explanatory view simply showing a coating equipment to which the roll coater is applied.

FIG. 3 is an explanatory diagram of coating control based on a change in paint properties.

FIG. 4 is a diagram showing the relationship between temperature, viscosity and concentration.

FIG. 5 is a diagram showing a temporal change in paint properties.

FIG. 6 is a diagram showing a temporal change of a nip pressure controlled by the present invention.

FIG. 7 is a diagram showing the effect of the present invention.

FIG. 8 is a schematic explanatory view showing an arrangement of a roll coater applied to a second embodiment according to the present invention.

FIG. 9 is a schematic configuration diagram showing a roll coater applied to a third embodiment according to the present invention.

FIG. 10 is an explanatory diagram for explaining a relationship between a rotation direction of a roll constituting an applicator roll and a flow rate of a paint;

FIG. 11 is an explanatory view showing an example of a combination of rotation directions of each roll constituting the roll coater.

FIG. 12 is an explanatory view showing another example of the combination of the rotation directions of the rolls constituting the roll coater.

FIG. 13 is an explanatory view showing still another example of the combination of the rotation directions of the rolls constituting the roll coater.

FIG. 14 is an explanatory view showing still another example of the combination of the rotation directions of the rolls constituting the roll coater.

FIG. 15 is an explanatory view showing still another example of the combination of the rotation directions of the rolls constituting the roll coater.

FIG. 16 is an explanatory view showing still another example of the combination of the rotation directions of the rolls constituting the roll coater.

FIG. 17 is an explanatory view showing still another example of the combination of the rotation directions of the rolls constituting the roll coater.

FIG. 18 is an explanatory view showing still another example of the combination of the rotation directions of the rolls constituting the roll coater.

FIG. 19 is an explanatory view showing still another example of the combination of the rotation directions of the rolls constituting the roll coater.

FIG. 20 is an explanatory view showing still another example of the combination of the rotation directions of the rolls constituting the roll coater.

FIG. 21 is a diagram showing the effect of the present invention.

FIG. 22 is another diagram showing the effect of the present invention.

FIG. 23 is still another diagram showing the effect of the present invention.

FIG. 24 is still another diagram showing the effect of the present invention.

FIG. 25 is still another diagram showing the effect of the present invention.

FIG. 26 is still another diagram showing the effect of the present invention.

FIG. 27 is still another diagram showing the effect of the present invention.

FIG. 28 is still another diagram showing the effect of the present invention.

FIG. 29 is still another diagram showing the effect of the present invention.

FIG. 30 is a diagram showing the paint adhesion amount and the line speed when the line speed is changed.

FIG. 31 is a diagram showing applicator roll peripheral speed and nip pressure controlled in accordance with changes in line speed.

FIG. 32 is a diagram showing a change in rubber Young's modulus due to swelling of a lining rubber of an applicator roll.

FIG. 33 is a diagram showing a change in the amount of adhesion caused by swelling of the lining rubber of the applicator roll.

FIG. 34 is a diagram showing a change in nip pressure applied to the model formula of the present invention.

FIG. 35 is a diagram showing the results of the present invention when the lining rubber of the applicator roll swells.

FIG. 36 is a diagram showing the effect of the present invention.

FIG. 37 is a schematic explanatory view showing an arrangement of a roll coater applied to four embodiments according to the present invention.

FIG. 38 is a diagram showing a catenary shape in a steady state;

FIG. 39 is a diagram showing a catenary shape in an unsteady state;

FIG. 40 is a diagram showing characteristics of a correction function used for catenary control.

FIG. 41 is a diagram showing the relationship between nip pressure and elapsed time when one embodiment of the present invention is applied.

FIG. 42 is a diagram showing the relationship between the amount of paint applied and the elapsed time when the above embodiment is applied.

FIG. 43 is a diagram schematically illustrating an example of a coating line.

FIG. 44 is a schematic explanatory view showing a state of painting the back surface of the steel sheet S.

FIG. 45 is a diagram showing the change over time in tension, nip pressure, and adhesion amount according to a conventional method.

[Explanation of symbols]

10, 20 ... roll coater 12 ... paint pan 14 ... pick-up roll 16 ... applicator roll 18 ... backup roll 30 ... transfer roll S ... steel plate q _A ... the supply flow rate q _L ... leak flow rate q _PA ... the total flow rate q _P ... return flow rate

Continuation of the front page (56) References JP-A-3-177578 (JP, A) JP-A-3-270759 (JP, A) JP-A-3-178357 (JP, A) JP-A-57-167765 (JP) , A) Yuji Harazaki, "Introduction to Coating Equipment and Operation Technology", 3rd Edition, Sogo Gijutsu Center, April 1991, p. 75-89 (58) Field surveyed (Int.Cl. ⁷ , DB name) B05D 1/28 B05D 3/00 B05D 7/14 B05C 1/08

Claims (7)

(57) [Claims] A paint is transferred to a continuously moving strip by a roll coater having a pickup roll and an applicator roll having at least a surface formed of an elastic material.
In the method of controlling the coating film thickness of the belt-shaped body by a roll coater at the time of coating, the gap h _PA between the pickup roll and the applicator roll is set to
Determined, of the pick-up roll peripheral speed V _P and of the applicator roll
Determining the circumferential speed V _A, determined roll gap h _PA and the roll peripheral speed V _P, based on V _A
There was determined the total flow rate q _PA, on the basis of said total flow rate q _PA, to determine the supply flow rate q _A of the paint to be sent to the band-like side by the rotation of the applicator roll, the gap h _AS applicator roll and strip Is determined, and the determined peripheral speed _VA of the applicator roll and the application
Based on the gap h _AS of Taroru and strip, determine the leak flow rate q _L remaining on the applicator roll without being transferred to the strip
Constant and, on the basis of the supply flow rate is determined q _A and the leak flow rate q _L, painted film thickness control method of the belt by a roll coater and controlling the film thickness to be coated on the strip. 2. An apple having at least a surface formed of an elastic material.
Continuous roll coater with locator roll
Roll coating for transferring and painting paint on a moving strip
In the method of controlling the coating film thickness of the band by the applicator, the coating sent to the band by rotation of the applicator roll.
Feed rate q _{A of the material} and the applicator
The model formula that evaluates the difference from the leak flow rate q _L remaining in the roll
When controlling the film thickness to be coated on the belt-shaped body based on the gap between the applicator roll and the front roll connected to the previous stage of the applicator roll is determined by applying the theory of elastic fluid lubrication, the gap using the gap leads to the formula giving the supply flow rate q _a, and, determined by applying also an elastohydrodynamic lubrication theory the gap between the applicator roll and the strip leads to expression yielding the leakage flow rate q _L with the gap, the supply a formula giving the expression and leakage flow rate q _L giving the flow rate q _a,
A method for controlling a coating film thickness of a belt-like body by a roll coater, which is applied to the model formula. 3. The coating of a belt-like body by a roll coater according to claim 2, wherein the elastic coefficient of the applicator roll included in the model formula is obtained with time, and the change with time is reflected in the film thickness control. Film thickness control method. 4. A method for controlling a coating film thickness of a strip by a roll coater when the strip is continuously transported in a suspended state and the strip is coated while being supported by an applicator roll of a roll coater. When passing the joint between the first and second belts, which are different from each other, over the roll coater, the tension of the belt which changes with time is reflected in a film thickness control factor in the roll coater. Method of controlling coating film thickness of a belt-like body by using a roll coater. 5. The method of claim 4, wherein the roll applicator roll coater was equipped with, and at least the surface is formed of an elastic material, and the supply flow rate q _A of the paint to be sent to the band-like side by the rotation of the applicator roll , set the base and rated the difference between the leakage flow rate q _L remaining on the applicator roll without being transferred to the strip type, pore elastic fluid between the roll before connecting to the front of the applicator roll and said applicator roll calculated by applying the lubrication theory, leads to expression giving the supply flow rate q _a with the gap, and, calculated by applying the same elastohydrodynamic lubrication theory the gap between the applicator roll and the strip, the said gap leads to the formula giving the leak flow rate q _L is used, the expression giving the expression and leakage flow rate q _L giving the supply flow rate q _a,
A film thickness control formula is created by applying to the above basic formula, and the tension of the band is reflected on a film thickness control factor included in the film thickness control formula. Control method. 6. The roll coater according to claim 2 , wherein the roll coater includes a pickup roll for pulling paint from a paint reservoir, and an applicator roll connected to the pickup roll. Method of controlling coating film thickness of a belt-like body by using a roll coater. 7. The pick-up roll according to claim 2 , wherein the roll coater pulls up paint from a paint reservoir, a transfer roll connected to the pick-up roll, and an application roll connected to the transfer roll. A method for controlling a coating film thickness of a belt-shaped body by a roll coater, comprising: