JPH01127675A - Method for controlling amount of evaporation in vacuum evaporator - Google Patents

Abstract

PURPOSE:To control the amount of metallic vapor to the desired coating weight with high responsibility by adding heating power for metal evaporation according to the change of its amount by evaporation at the time of vapor-depositing a metallic vapor onto a steel strip in a vacuum evaporator to carry out continuous plating. CONSTITUTION:A metallic vapor 3 from a hot dipping metallic bath 1 in a bath tank 2 is allowed to adhere via a shutter 8 and a channel 6 to the surface of a steel strip 7 continuously passing through a vacuum tank while changing direction by means of a coiler roll 11. The amount of evaporation of the metallic vapor is regulated by means of the electric power for heating the bath tank 2 and the opening of the shutter 8, and, at the time of regulating coating weight by changing the amount of evaporation of the metallic vapor, first the opening of the shutter 8 is regulated to supply required metallic vapor into the channel 6. Since the temp. of the metallic bath 1 is lowered and the required amount of evaporation cannot be obtained when the shutter opening is increased, the power of a heater 4 for heating the metallic bath 1 is increased and the shutter opening is returned to adjustable range, by which the subsequent control of the amount of evaporation of metallic vapor can be carried out with high responsibility.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling the amount of evaporation in a vacuum evaporator, and more particularly to a method for controlling the amount of evaporation in a continuous vacuum evaporator that deposits plating material onto a moving metal strip.

[Conventional technology]

According to Japanese Unexamined Patent Publication No. 60-251275, an example of the configuration of an evaporator tank of a continuous vacuum evaporator as shown in FIG. 4 is proposed.

In FIG. 4, when the metal bath 1 in the evaporating bath 2 is heated by the heater 4, the metal vapor 3 evaporates in proportion to the difference between the saturation pressure with respect to the bath temperature and the atmospheric pressure above the bath 2. The evaporated metal vapor 3 adheres to the strip 7 passing through the vapor flow port 5, channel/I/6 and the winding roll 11fI.

The evaporation amount is controlled as follows.

The metal bath 1 is equipped with a highly responsive 7-layer 8 that can adjust the flow rate of steam passing by changing the opening area of the steam flow port 5.
For example, when the target value of evaporation (C) increases, the shutter is rapidly opened by 8 ft to achieve a rapid change in the evaporation. That is, this rapid change in the amount of evaporation is caused by the shutter opening controller 15 operating the shutter 8 with the shutter drive device 17 so that the shutter opening detected by the shutter opening detector 16 becomes equal to a predetermined set value. It is often done. The shutter opening degree setting value is calculated by the calculation device 22 according to the evaporation amount target value.

Further, the metal vapor 3 evaporates in an amount corresponding to the difference between the amount of heating by the heater 4 and the amount of heat radiated from the walls of the bathtub 2 and the like. Therefore, it is necessary to give the heater 4 the necessary heater power determined by the heat balance between the amount of heating and the amount of heat dissipation depending on the target value of evaporation amount (0). Therefore, the calculation device 12 calculates the necessary heater puff (4) determined by one doparance according to the evaporation amount target value (C), and outputs it to the heater power controller 13.

In addition, the calculation device 24 calculates the addition amount of the opening setting value of 7 points so that the plating thickness detected by the film thickness meter 23 becomes the film thickness target value Φ), and adds it to the output of the calculation device 22 described above. The shutter opening control amount is given to the shutter opening controller 15.

Now, since the evaporation bath wall and the metal bath 1 have a large heat capacity, the rate of change in the amount of heat input to the metal bath 1 due to changes in the heater power body (heater power body), as well as the rate of change in the amount of evaporation due to changes in the shutter opening (latent heat of evaporation) The rate of change in the amount of heat dissipated due to

Therefore, for example, if the target evaporation value (0) increases, -
Sometimes the bath temperature drops. As mentioned above, since metal 3 has a large heat capacity such as 1, it takes a long time for the bath temperature to return to its original state. If the next evaporation amount target value (0) is a request for increase before the bath temperature returns to the original value, an operation is performed to open the shutter 8t further than the current value. If you repeat this, the fifth
As shown in the figure, even if the shutter opening is opened to 100%, the bath temperature will continue to be low unless sufficient heat is supplied. Due to the insufficient driving force for the amount of evaporation from the shim, the required amount of evaporation cannot be obtained. As a result, the desired steaming of the plating material cannot be performed.

Note that FIG. 5 is a graph showing the relationship between the actual evaporation amount and the evaporation amount target value. In the graph, the solid line represents the actual evaporation amount, and the broken line represents the target value of evaporation jt.

Therefore, according to Japanese Patent Application No. 61-112714, when the target value of evaporation changes, the heater power (A) determined by the heat balance is sometimes applied too much or too little, and the bath temperature is changed. We propose ways to improve responsiveness. That is, in this method, when the target value of evaporation amount changes, the maximum heater power is temporarily given as the heater power when the target value "increases", and the minimum heater power 1-- when the target value "decreases".

If such an iJ method is adopted, the response of the bath temperature can be improved, and the shutter opening can be quickly returned to a position where a control margin for the shutter opening can be secured for the next change in the evaporative wave target value. becomes possible.

[Problem that the invention seeks to solve]

By the way, if the amount of increase in the target value of evaporation is small, -
Since the temporal bath temperature drop 1t (the maximum amount of change from the initial value) is also the same, there is no need to give an excessive maximum heater power.

However, according to the above-mentioned Japanese Patent Application No. 112714/1983,
The target value “increases” even in the amount of change in the target value of evaporation.

At this time, the heater power is changed stepwise to the maximum heater power, so the heater body is thermally deformed due to the thermal shock caused by the repetition of this stepwise change.
This may even lead to damage to the heater.

[Means for solving problems]

The present invention was made by focusing on the fact that the amount of temporary change in bath temperature (the maximum amount of change from the initial value) when the target value of evaporation changes depends on the amount of change in the target value of evaporation.

That is, the present invention provides a method for controlling the amount of evaporation in a vacuum evaporator in which the amount of evaporation from the evaporator is adjusted by the opening degree of the shutter provided at the outlet of the evaporator and the power of the heater that heats the evaporator. When the target value changes, the sum of the heater power required for heat balance according to the target evaporation value and the additional heater power calculated as a function of the amount of change in the target evaporation value is applied to the evaporator tank as heater power, and the shutter is activated. The present invention relates to a method for controlling the amount of evaporation in a vacuum evaporator, characterized in that, once the degree of opening falls within a predetermined allowable range, a heater power calculated so that the degree of shutter opening becomes a predetermined value is applied to the evaporator tank.

Specifically, when the target value of evaporation changes, the heater power required for heat balance is given as a function of the amount of change in the target value of evaporation Δa (kg/h) over time. Additional amount of heater power (additional heater power)
Add ΔE (kw).

Here, ΔH is expressed as ΔB=f (ΔG ) (1), and if ΔG is positive! ! When ΔG is negative, it is a negative function.

The above addition result is given to the evaporation tank as the total heater power, and 7
After the degree of opening of the yakuta falls within a predetermined allowable range, a heater power calculated so that the degree of opening of the yakuta reaches a predetermined target value is applied to the evaporation tank.

[Effect]

When the evaporation amount target value (0) changes, the heater power (4) required for one doparance is calculated according to the value of 0, and at the same time, the additional heater power (4) which is a function of the amount of change in 00 is calculated. Calculated. An amount of heat corresponding to the sum of these sums and B is supplied to the bathtub in order to make the evaporation amount match the new evaporation amount target value (C).

Here, when the change of 00 is an "increase", the sign of iB is positive, and when the change of 0 is a "decrease", the sign of frame B is negative.

At this time, the value calculated based on the film thickness setting value CD) and the actual film thickness deposited on the metal strip is added to the nine values calculated according to the shutter opening adjustment fia, a. .

After the shutter opening reaches the specified tolerance range,
The heater power required for heat balance is calculated according to the value of 0, and at the same time, the heater power is calculated based on the deviation between the target opening degree (6) determined according to the value of C and the actual shutter opening degree. ) of the determined heater power is calculated. The amount of heat corresponding to the sum of these sums and B is supplied to the bathtub in order to match the amount of evaporation ta. The shutter opening degree at this time is adjusted in the same manner as in the case of the change to 00 described above.

Note that when the evaporation amount target value (0) does not change, the same control as described above when the shutter opening falls within a predetermined allowable range is performed.

[Executive Fee] FIG. 1 shows an example of the configuration of an evaporation amount control system for implementing the method of the present invention.

In FIG. 1, the same reference numerals as those in FIG. 4 are the same as those in FIG. 4, so the description thereof will be omitted.

In FIG. 1, the arithmetic unit 18 performs the following processing when the target value of evaporation changes.

1) First, the shift heater power φ) is determined and output using the above equation (1). Note that ΔE in equation (1) is positive when ΔG)O, and ΔG
It is negative when <O.

ΔH=f (Δ(3) (1)2)Next, after the shutter@shield exceeds the tolerance range with the predetermined target value@), the heater power fluctuation of equation (1) is increased until it returns to within the tolerance range again. ) is output.

The reason why the shutter opening degree moves like this is, for example, when the amount of evaporation "increases" - as the bath temperature drops from time to time, the film thickness decreases.
In order to correct this, the arithmetic unit 24 changes the shutter opening to “
This is because the correction amount for opening is outputted to the opening controller 15.

3) Once the shutter opening degree has returned to within the allowable range, the heater power is adjusted by the calculation device 18 (proportional integral derivative) so that the shutter opening degree reaches the predetermined target value (6). Φ) and output it.

Therefore, the heater power controller 13 includes the output heater power (output heater power) of the arithmetic unit 18 and the output heater power body (output heater power body) of the arithmetic unit 12.
The heater power obtained by adding the above is given as a set value.

Note that the shutter opening degree target value (2) is calculated by the calculation device 19 according to the evaporation amount target value (0). The amount of evaporation
It is determined by the shutter opening and the bath temperature, which is the driving source for evaporation. Therefore, by calculating process static characteristics, for example, a relational expression between the amount of evaporation and the shutter opening degree may be determined in advance under the condition of a constant bath temperature, and the relational expression may be incorporated into the calculation device 19.

The control method other than the above is the same as the control method in a conventional control system.

FIG. 2 shows an example of control according to the method of the present invention, and FIG. 3 shows the formula (
This is an example of the relational expression 1).

Equation (1) calculates in advance the temporary addition of heater power to various amounts of change in the target evaporation value so that, for example, the time required for the Kuyatsuta opening degree to return to the allowable range after a change in the target evaporation value is constant. The quantity φ) is determined by process dynamic characteristic analysis calculation.

〔Effect of the invention〕

According to the method of the present invention, the low responsiveness of bath temperature, which is a problem when constantly ensuring high responsiveness due to rapid shutter changes to changes in the target value of evaporation, is improved, and highly responsive evaporation can be controlled.

In addition, in the method of the present invention, by taking reasonable measures to increase bath temperature response, the heater power is increased by repeating step changes to the maximum heater power whenever the target value of evaporation increases in the prior art. There is no need to worry about deterioration or damage.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of the control method in the evaporation amount control system of the vacuum evaporator of the present invention, FIG. 2 is a graph showing an example of evaporation amount control by the method of the present invention, and FIG. 3 is an evaporation amount target. A graph showing an example of the relationship between the amount of change in value and the amount of additional heater power), Fig. 4 is an explanatory diagram showing the control method in the evaporation amount control system of a conventional vacuum evaporator, and Fig. 5 shows the evaporation amount by the conventional control method. It is a graph showing control 91. DESCRIPTION OF SYMBOLS 1... Metal bath, 2... Evaporation bath, 3... Metal vapor, 4... Heater, 5... Steam distribution port, 6... Channel, 7... Strip, 8... ...Shutter, 1
1... Winding roll, 13... Heater power controller, 1
5...7 Yatsuta opening controller, 16... Shutter opening detector, 17. Shutter drive device, 12.18.1
9,22.24...Arithmetic device, 23...Film thickness meter

Claims (1)

[Claims] In the evaporation amount control method for a vacuum evaporator, which adjusts the evaporation amount from the evaporation tank by the opening degree of the shutter installed at the evaporation tank outlet and the magnitude of the heater power that heats the evaporation tank, when the evaporation amount target value changes, the evaporation amount target value changes. The sum of the heater power required for heat balance according to the value and the additional heater power calculated as a function of the amount of change in the target value of evaporation is applied to the evaporation tank as heater power, and the shutter opening is within a predetermined tolerance range. 1. A method for controlling the amount of evaporation in a vacuum evaporator, comprising: applying a heater power calculated such that the shutter opening degree becomes a predetermined value to the evaporator tank once the shutter opening degree has reached a predetermined value.