JPH059793A - Method and device for electrodeposition coating - Google Patents

Abstract

PURPOSE:To improve the quality of a coating by automatically judging and controlling the coating condition. CONSTITUTION:Coulomb efficiency is calculated by an arithmetic means 28 from the amt. of solid in an electrodeposition paint 2 consumed in a predetermined time and the coulombs, and the desired control voltage is calculated from the relation between the coulomb efficiency and coating film thickness. A power source adjusting circuit 31 is controlled by the arithmetic means 28, and a desired control voltage is impressed between an electrode 24 and a material 4 to be coated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrodeposition coating method and apparatus for coating with an electrodeposition coating.

[0002]

2. Description of the Related Art Conventionally, as a coating method, an electrostatic coating method, a spray coating method, an airless coating method, a dipping coating method, an electrodeposition coating method and the like have been performed. Among them, the electrodeposition coating method has excellent characteristics in various aspects as compared with the rest of the coating methods. For example, the bag-shaped structure portion of the article to be coated and the joint portion between each portion of the article to be coated. It also has the feature that it can be painted. In addition to the features described above, it is easy to control throwing power by controlling the amount of electricity, etc. Moreover, there is no "dripping" or "armpits" in the applied paint, and workability is good. Is known to be.

[0003]

The throwing power as described above is generally controlled by the applied voltage, but other factors,
For example, coating resistivity, coating liquid temperature, transfer speed of the coated object,
It is also affected by the number of objects to be dipped in the paint and paint control. That is, even if the coating is performed under a constant voltage, the coating area may change, the coating film resistivity may change, or the coating property may change, so that the coating film may not be formed easily. In such a case, the paint film thickness will be reduced, the anticorrosion performance of the object to be coated will deteriorate, and the resulting product will rust early and the mechanical strength will deteriorate and the appearance will be impaired. .

Further, under the condition that the coating film is formed unnecessarily thick, the paint is consumed unnecessarily and the economical efficiency is deteriorated. Further, there is a problem that the finish appearance and quality are deteriorated due to the excessive increase of the coating film thickness.

This prior art is not configured to automatically detect a change in paint properties, a change in Coulombic efficiency, etc., and automatically control the voltage, so that the film thickness cannot be accurately controlled. In addition, there is a problem that it is not possible to cope with changes in coating conditions during operation.

The object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide an electrodeposition coating method and apparatus capable of significantly improving coating quality and automatically controlling the coating quality.

[0007]

According to the present invention, an electrode is provided in an electrodeposition tank containing an electrodeposition coating material, and a voltage is applied between the electrode to be coated and the electrode to be transported and immersed in the electrodeposition tank. In the electrodeposition coating method in which the electrodeposition coating is performed by applying, the coulomb efficiency is obtained based on the solid amount of the electrodeposition coating in the electrodeposition tank and the coulomb amount supplied during the electrodeposition coating, and the coulomb efficiency is The electrodeposition coating method is characterized in that a target voltage corresponding to a parameter with a predetermined coating film thickness is calculated, and the coating film thickness is controlled based on the target voltage.

Further, in the present invention, the target voltage obtains a predetermined coefficient having Coulomb efficiency and coating film thickness as parameters, and calculates the coefficient and the voltage applied between the object to be coated and the electrode. It is characterized by being asked.

The present invention further comprises an electrodeposition tank for containing the electrodeposition coating material, and a transfer means for transferring and immersing the object to be coated in the electrodeposition tank.
An electrode provided in the electrodeposition tank, a power supply for applying a variable voltage between the object to be coated and the electrode, a coulomb amount detecting means for detecting a coulomb amount supplied by the power source, and an application of the power source. First calculating means for calculating coulombic efficiency in response to the outputs of the voltage detecting means for detecting the voltage, the solid amount detecting means for detecting the solid amount of the electrodeposition coating material, the solid amount detecting means and the coulomb amount detecting means And a film thickness signal deriving means for deriving a signal representing a coating film thickness, and a Coulomb efficiency, a coating film thickness and a voltage in response to the outputs of the first computing means and the film thickness signal deriving means. The electro-deposition coating apparatus is characterized in that it includes a second calculation means for obtaining a target voltage by means of the second calculation means, and a control means for controlling the voltage applied to the power source in response to the output of the second calculation means.

[0010]

According to the present invention, an electrode is provided in the electrodeposition tank containing the electrodeposition coating material, and a voltage is applied between the electrode to be coated and the electrode to be transported and immersed in the electrodeposition tank. In the electrodeposition coating method of performing electrodeposition coating, first, the Coulomb efficiency is obtained based on the solid amount of the electrodeposition coating in the electrodeposition tank and the Coulomb amount supplied during the electrodeposition coating. Next, the target voltage corresponding to the parameters of the Coulombic efficiency and the predetermined coating film thickness is calculated, and the coating film thickness is controlled based on the target voltage.

The target voltage is obtained by calculating a predetermined coefficient having Coulomb efficiency and coating film thickness as parameters, and calculating the coefficient and the voltage applied between the object to be coated and the electrode.

Further, according to the present invention, the electrodeposition coating apparatus conveys an electrodeposition tank containing an electrodeposition coating composed of, for example, a pigment-based coating and a clear-based coating, and an object to be coated into the electrodeposition coating tank. Conveying means for immersing, electrode provided in the electrodeposition tank, power supply for supplying variable voltage between the object to be coated and the electrode, and coulomb amount detecting means for detecting the coulomb amount supplied by the power source. A voltage detecting means for detecting an applied voltage of the power source, a solid amount detecting means for detecting a solid amount of the electrodeposition coating material, a solid amount detecting means and a coulomb amount detecting means in response to respective outputs, and the coulomb efficiency is improved. Coulomb efficiency and coating film thickness in response to the outputs of the first computing means for computing, the film thickness signal deriving means for deriving a signal representing the coating film thickness, and the first computing means and the film thickness signal deriving means. Second calculator for calculating the target voltage by calculating the voltage and the voltage When, and a control means for controlling the applied voltage in response to an output of the second operational means.

[0013]

FIG. 1 is a diagram showing an electrodeposition coating apparatus 1 which is an embodiment of the present invention. The electrodeposition tank 2 is filled with the electrodeposition coating material 3, and the object 4 is conveyed onto the electrodeposition tank 2 to transfer the electrodeposition coating material 3
A conveyer 5 is installed as a conveying means so that the article 4 to be coated can be dipped therein.

The pigment-based paint is supplied from the pigment-based replenishment paint tank 9 to the mixer 12 via the flow meter 11 by the pump 10.
The clear main paint is supplied from the clear main supply paint tank 13 to the mixer 12 by the pump 14 via the flow meter 15. The main component of the pigment-based paint is a pigment, which additionally contains resin, water and the like, and the solid content is NV1. The clear-based paint does not contain pigments, its main component is resin, and it also contains water, etc., and its solid content is NV2.
Is.

The flowmeters 11 and 15 are the calculation means 2 described later.
8 to detect the replenishment amount F1 of the pigment-based paint or the replenishment amount F2 of the clear-based paint, and the detection result is output to the calculation means 28.

In the mixer 12, the electrodeposition paint 3 is further extracted and the temperature is adjusted by the heat exchanger 21, and the electrodeposition paint 3 extracted by the pump 18 is mixed to form an electrodeposition tank. It is thrown in 2. The heat exchange in the heat exchanger 21 is controlled by the calculating means 28 described later via the three-way valve 23.

An electrode 24 is immersed in the electrodeposition coating material 3 in the electrodeposition tank 2, and the electrode 24 and the electrode for the article 4 to be coated (not shown) are an ammeter 25 and a voltage detecting means which are current detecting means. An AC power supply 27, which is a power supply having a voltmeter 26, is connected via a power supply circuit 30 including a rectifier and a power supply adjustment circuit 31.

The AC power supplied from the AC power supply 27 is
After being rectified and smoothed by the power supply circuit 30, it is adjusted to a predetermined current and voltage by the power supply adjustment circuit 31 and is in contact with the electrode 24 and the object to be coated 4 so that the electrode 24 becomes an anode (not shown). A voltage is applied between the electrodes.

The power supply adjusting circuit 31 comprises a calculating means 2 which will be described later.
8 and the calculation means 28 is connected to the power supply adjusting circuit 31.
The applied voltage is adjusted by controlling.

The flow meters 11 and 15, the automatic measuring device 8, the three-way valve 23, the ammeter 25, the voltmeter 26, and the power supply adjusting circuit 31.
Is connected to the computing means 28.

The calculating means 28 has a clock circuit 28a, and the coulomb amount can be obtained by integrating the output of the ammeter 25 and the time measured by the clock circuit 28a.

When performing electrodeposition coating, a good quality coating film can be obtained by controlling the Coulomb efficiency calculated using the Coulomb amount and the coating film thickness so as to have predetermined values. However, if the electrodeposition coating is performed, the composition of the electrodeposition coating 3 changes, and the Coulombic efficiency changes. Coulombic efficiency can be controlled by varying the applied voltage. By multiplying the current applied voltage V by the coefficient k as shown in Equation 1, the target control voltage V1
Can be asked.

[0023]

## EQU00001 ## V1 = V.times.k Next, a method of obtaining the coefficient k will be described. A flat plate is electrodeposited by using an electrodeposition coating that achieves the target Coulombic efficiency and coating film thickness when performing electrodeposition coating. The coating film thickness obtained at this time is defined as d1. Perform electrodeposition coating using an electrodeposition coating that provides Coulomb efficiency different from the above,
The obtained coating film thickness is d2. The coefficient k can be obtained by dividing the coating film thickness d1 by the coating film thickness d2 as shown in Equation 2.

[0024]

[Equation 2]

This coefficient k is used by substituting it into the equation 1 when the composition of the electrodeposition coating material 3 changes and the Coulombic efficiency is obtained to obtain the coating film thickness d2.

Therefore, a plurality of coefficients k are obtained in advance according to the range of change in the composition of the electrodeposition coating material 3 and stored in the calculating means 28. Similarly, the coefficient k is similarly obtained for the electrodeposition paint having a coating film thickness different from the above, and a table showing the coefficient k corresponding to the parameters of the Coulomb efficiency and the coating film thickness as shown in Table 1 described later is obtained. It is created and stored in advance in the calculating means 28.

FIG. 2 is an example of a flow chart showing an embodiment of the present invention. In step s1, the solid content content NV3 of the electrodeposition coating material 3 in the electrodeposition tank 2 is measured by the automatic measuring device 8. In step s2, the solid content content NV3 measured in step s1 is output to the computing means 28. To be done.

In step s3, the calculating means 28 determines whether or not a predetermined time W input to the calculating means 28 has elapsed. If the time W has elapsed, the process proceeds to step s4. If the time W has not elapsed, the process waits in step s3 until the time W has elapsed. The time W may be set corresponding to the working time, or may be set based on the time until the coating of the article 4 is completed.

In step s4, the pigment-based replenishment paint tank 9 is used.
The replenishment amount F1 of the pigment-based paint that has flowed into the electrodeposition tank 2 from the pump 10 is output from the flow meter 11 to the calculation unit 28.

In step s5, the replenishment amount F2 of the clear main paint supplied from the clear main replenishment paint tank 13 into the electrodeposition tank 2 via the pump 14 is calculated from the flow meter 15 to the calculation means 2
8 is output.

At step s6, the solid content content NV4 of the electrodeposition coating material 3 in the electrodeposition tank 2 is measured by the automatic measuring device 8. At step s7, the solid content content NV4 measured at step s6 is calculated. 28 is output.

In step s8, the calculating means 28 calculates the Coulomb amount C by integrating the output of the ammeter 25 and the output of the clock circuit 28a.

In step s9, the solid content content NV1 of the pigment-based paint, the solid content content NV2 of the clear-based paint, the capacity T of the electrodeposition tank 2, and the pigment-based paint Replenishment amount F1, clear-based paint replenishment amount F2, solid content contents NV3, NV4 of electrodeposition coating material 3 in electrodeposition tank 2, and Coulomb amount C calculated in step s8 Then, the Coulombic efficiency is calculated by the calculating means 28.

[0034]

[Equation 3]

In step s10, the coating film thickness which is predetermined and similarly input into the calculating means 28 from Table 1 which is input into the calculating means 28 in advance and the Coulombic efficiency calculated in step s9 are used. The coefficient k is obtained.

[0036]

[Table 1]

In step s11, the equation 2 is calculated from the applied voltage V output from the voltmeter 26 to the computing means 28 by the computing means 28 and the coefficient k obtained in step s10.
Is used to calculate the target control voltage.

[0038]

## EQU00001 ## V1 = V.times.k In step s12, the power supply adjusting circuit 31 is controlled by the calculating means 28 so that the target control voltage is obtained, and the object to be coated 4
The voltage applied between the electrode and the electrode 24 is controlled.

In step s13, it is determined whether or not the coating is completed. If the coating is not completed, the process returns to step s1. If it is completed, the electrodeposition coating operation is completed.

As described above, according to this embodiment, the Coulomb efficiency can be automatically obtained during the electrodeposition coating, and the target control voltage for obtaining the predetermined coating film thickness from the obtained Coulomb efficiency is The voltage required and applied between the article 4 and the electrode 24 can be controlled.

Therefore, the control of the electrodeposition coating conditions can be automatically performed during the electrodeposition coating, and the coating quality can be improved.

In this embodiment, although a voltage was applied between the electrode 24 and the electrode for the article 4 to be coated (not shown), the electrodeposition vessel 2 was made of metal and the electrode for the article 4 to be coated and the electrodeposition vessel 4 were made. The same effect can be obtained by applying a voltage between the two.

[0043]

According to the present invention, the coulombic efficiency is calculated in advance by calculating the coulombic efficiency between the solid amount of the electrodeposition paint in the electrodeposition tank and the coulomb amount supplied during the electrocoating. It is possible to calculate a target control voltage corresponding to the parameter of the coating film thickness to be determined and control the coating film thickness based on the target control voltage.

Therefore, the applied voltage is automatically controlled so that the coating film thickness has a predetermined value, and the coating quality can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an electrodeposition coating apparatus 1 which is an embodiment of the present invention.

FIG. 2 is an example of a flowchart showing an embodiment of the present invention.

[Explanation of symbols]

1 Electro-deposition coating device 2 electrodeposition tank 3 electrodeposition paint 4 coated objects 5 conveyors 8 automatic measuring instruments 24 electrodes 25 ammeter 26 Voltmeter 27 AC power supply 28 computing means 28a Clock circuit 30 power circuit 31 Power supply adjustment circuit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Nobuo Kurami             6-1073 God, Minamitsukaguchi-cho, Amagasaki-shi, Hyogo             Inside the East Paint Co., Ltd.

Claims (3)

[Claims] 1. An electrode is provided in an electrodeposition tank containing an electrodeposition coating material, and a voltage is applied between the electrode to be coated and conveyed in the electrodeposition tank to immerse the electrodeposition coating. In the electrodeposition coating method to be performed, the Coulomb efficiency is calculated based on the solid amount of the electrodeposition coating in the electrodeposition tank and the Coulomb amount supplied during the electrodeposition coating, and the Coulomb efficiency and the predetermined coating film thickness An electrodeposition coating method, wherein a target voltage corresponding to a parameter is calculated, and the coating film thickness is controlled based on the target voltage. 2. The target voltage is obtained by calculating a predetermined coefficient with Coulomb efficiency and coating film thickness as parameters, and calculating the coefficient and the voltage applied between the object to be coated and the electrode. The electrodeposition coating method according to claim 1, wherein: 3. An electrodeposition tank containing an electrodeposition coating material, a transfer means for transferring and immersing an object to be coated into the electrodeposition tank, an electrode provided in the electrodeposition tank, and an object to be coated and an electrode. A power source for applying a variable voltage between them, a coulomb amount detecting means for detecting a coulomb amount supplied by the power source, a voltage detecting means for detecting an applied voltage of the power source, and a solid amount of the electrodeposition paint. Solid amount detecting means for detecting, first calculating means for calculating the coulombic efficiency in response to the outputs of the solid amount detecting means and the coulomb amount detecting means, and a film thickness signal deriving means for deriving a signal representing the coating film thickness Means, the first computing means and the film thickness signal deriving means, and
A second calculation means for calculating the target voltage by calculating the Coulombic efficiency, the coating film thickness, and the voltage; and a control means for controlling the voltage applied to the power source in response to the output of the second calculation means. Electro-deposition coating equipment.