JPS609900A - Metsuki control system - Google Patents

Abstract

PURPOSE:To improve controllability by detecting the change in the metallic ion in a plating liquid in the state of a change in plating current, incorporating feedforward-control by the integrated value of the plating current to control the charging of the metallic ion and correcting the error by said control from the output of an analyzer. CONSTITUTION:Showers S1-S3 of a plating liquid are sprinkled on a steel plate 3 to perform electroplating and the used liquid is gathered in a circulating tank 1 and is again used as the liquid for the showers S1-S3 with this control system for plating. The charging of the metallic ion from the tank 5 is feedforward- controlled by the integrated value of the plating current and the weight of the feedforward rate is automatically corrected by the ion analyzed value from an analyzer 4 installed in the tank 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a system for controlling the concentration of metal ions in an electrolyte when electroplating metals.

In the plating process of plating the surface of steel plates,
Controlling the composition of the plating solution is one of the most important issues. Conventionally, various methods have been devised to control the composition of the plating solution, such as control using a combination of a pH meter and a hydrometer.

In recent years, as the composition of plating solutions has become more complex, methods are being adopted to incorporate online analyzers to directly measure the composition of plating solutions and feed back the results. The plating solution is usually controlled by adding acid and several types of metals, but this method has the following disadvantages.

Group (1) There is a large amount of wasted time after the gold 2 injection until the result can be measured.

(2) As an online analyzer, a sampling method is used, but the time interval between obtaining analysis values is long. Furthermore, there is a high probability that the analyzer will break down.

Therefore, it has been impossible to control the plating solution with good controllability.

The present invention has been made in view of these points, and
Changes in metal ions in the plating solution are detected as changes in the plating current, and the metal ion injection is controlled in a feedforward manner based on the integrated value of the plating current, and the error caused by this feedforward control is obtained from the analyzer output. By making corrections based on the analyzed values, a plating control system has been realized that improves controllability without being affected by the time delay in changing the composition of the plating solution after metal ions are added.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, 1 is a circulation tank filled with plating solution, 2 is a pump that pumps the plating solution to the shower room (described later), R1-R3 are shower rooms, and 81 to S3 are installed in each shower room. Shower, RO, to RO3 are rollers that hold the plate 3 between them. The steel plate advances from the left side in the figure, is plated (for example, nickel plated) while passing through each shower room, and exits from the right side. Reference numeral 4 denotes a sampling type analyzer for measuring the metal ion concentration in the plating solution, and a titrator is used, for example. 5 is a tank in which a predetermined metal ion is stored; 6 is a control valve that controls the flow rate of the electrolyte from the tank; the metal ion solution in the tank 5 is injected into the circulation tank 1 by a predetermined amount; The concentration of metal ions inside is kept constant. The operation of the device configured as described above will be explained as follows.

In the f value shown in the figure, the plating solution in the circulation tank 1 is pumped to the shower rooms R1 to R3 by the pump 2, and sprinkles on the steel plate 3 passing through each shower room. At this time, steel plate 3
Since a potential is applied to each city through the rollers RO and RO3, electroplating is performed using the same principle as if the steel plate 3 were placed in a plating solution, and the surface of the steel plate 3 is plated with metal. . The plating solution sprinkled on the steel plate 3 falls and is returned to the circulation tank 1, but the metal ions are reduced by the amount of plating. Therefore, the metal ion liquid previously stored in the tank 5 is injected into the circulation tank 1 to remove the gold in the tank! It is necessary to keep the ion concentration almost constant.

The present invention relates to means for keeping the metal ion concentration in this tank constant.

Under normal operating conditions, it can be considered that the amount of plating and the plating current are in a proportional relationship. Therefore, the integrated value of plating current within a certain period corresponds to the amount of metal consumed during that period. That is, (3) the consumed metal tQ is expressed by the following formula.

Here, 1(t) is a plating current, α is a constant including a feedback correction coefficient, and K plating efficiency.

K changes depending on the type of steel plate. This amount of consumed metal Q,
It is also the amount of metal that must be replenished into the plating solution. Let this amount be FF.

Therefore, if the amount of metal determined by equation (1) is replenished into the plating solution in a feedforward manner, the metal ion concentration in the plating solution can be kept almost constant.

By the way, the above-mentioned control is carried out successfully when the metal amount and the integrated value of the plating current are in an accurate proportional relationship, and in reality, an accurate proportional relationship is difficult to achieve. The exact metal ion concentration in the tank 1 depends on the output of the analyzer 4. Therefore, if the result pv of the measurement value of the analyzer 4 can be reflected in the metal ion injection control, more accurate metal ion concentration control can be performed. In the present invention, a method is adopted in which the constant α in equation (1) is corrected by the value FB (=SV-PV) obtained from the analyzer output. Here S
V is the target (4) concentration. In other words, the quick response of the control is achieved by feedforward control using the integrated value of the plating current, and the reliability and accuracy of the control is determined by the output of the analyzer.Feedback control is added by modifying the constant α in equation (1). . By adopting such a configuration, metal ion concentration control can be performed with both quick response and accuracy. The frequency with which the value of the constant α is corrected depends on each case. This correction operation is performed by an arithmetic and control device (not shown) that receives the output of the analyzer 4. As the arithmetic and control device, for example, a control computer or a microcomputer is used. The arithmetic and control unit adjusts the control valve 6 according to the corrected amount of metal, and injects a predetermined amount of metal ions into the circulation tank 1. Although the device for measuring the plating current is not shown in the figure, an ammeter is connected between the electrodes RO and -RO3 and the source, and the output is integrated to obtain the integrated value of the plating current. It looks like this.

FIG. 2 is a diagram showing the ψh operation waveform of each part. In the figure (a)
is a diagram showing the waveform of plating current ■, (b) is a diagram showing the waveform of plating current ■
(C) is a diagram showing the metal input tQ, and (d) is a diagram showing the measured value pv of the analyzer.

The first metal input amount Q+ is determined from the first plating current integrated value S1, and a correction amount is calculated from the first analysis values PV and K to correct the next input amount Q2. By repeating such operations, metal ion concentration control is performed. Note that the correction based on the analysis value does not need to be performed every time, and the amount of correction may be determined by averaging several sampled values. The features of the present invention are listed below.

(1) Even if analysis values cannot be obtained, metal injection control can be continued by integrating the plating current.

(2) When the plating conditions change, the input amount can be changed by 1 in a feedforward manner.

(3) Based on the difference with the analysis results, the feedforward class weights can be automatically corrected so that the deviation becomes smaller.

(4) Process waste time can be easily reflected.

As described in detail above, according to the present invention, changes in metal ions in the plating solution are detected as changes in the plating current, and the injection of metal ions is controlled in a feedforward manner based on the integrated value of the plating current. Errors caused by this feedforward control are corrected based on the analysis value obtained from the analyzer output, improving plating controllability without being affected by the time delay of changes in plating solution composition after metal ion injection. A control system can be realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing operating waveforms of each part. 1... Circulation tank, 2... Pump, 3... Steel plate,
4...Analyzer, 5...Tank, 6...Control valve, 8
1-S3...Shower, R1-R3...Shower room, RO, ~Ro3=roller. (7) (8) Figure 2 (a) (d) V

Claims (1)

[Claims] In a plating control system that performs electroplating by showering a plating solution onto a steel plate, and collecting the used solution in a circulation tank and using it again as a shower of plating solution, the injection of metal ions is controlled in a feedforward manner using the integrated value of the plating current. A plating control system characterized in that the weight of the feedforward amount is automatically corrected based on the ion analysis value of an analyzer installed in the circulation tank.