JPH059796A - Electrodeposition coating method and device - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the coating quality by automatically judging and controlling the coating conditions. [Structure] The coating object 4 conveyed by the conveyor 5 is recognized by the recognition means 6, and the total coating material area within a predetermined time is calculated by the calculation means 28. The current and voltage within the predetermined time, and the coating film resistivity is calculated from the total area to be coated, and the control liquid temperature of the electrodeposition coating composition is calculated from the relationship between the coating film resistivity and throwing power, Controls the temperature of electrodeposition paint liquid.

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 property and a change in coating film specific resistance and automatically control the voltage, so that the film thickness can be accurately controlled. There is a problem in that it is not possible to cope with fluctuations 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]

SUMMARY OF THE INVENTION According to the present invention, an article to be coated is conveyed into an electrodeposition tank containing an electrodeposition coating material, and between the article to be coated and an electrode stored in the electrodeposition tank. Connect the DC power supply to
In the electrodeposition coating method for performing electrodeposition coating, the current and voltage of the power source, and further the coating area of the object to be coated are detected, and the coating film specific resistance is calculated by performing calculation between the current, voltage and coating area. Then, the liquid temperature of the electrodeposition coating material corresponding to the parameters of the coating film specific resistance and the predetermined throwing power is calculated, and the temperature of the coating is changed so as to reach the liquid temperature. It is an electrodeposition coating method characterized by controlling.

Further, in the present invention, the temperature of the electrodeposition coating solution is determined by a predetermined coefficient using the coating film resistivity and throwing power as parameters, and the coefficient and the temperature of the electrodeposition coating material in the electrodeposition tank are calculated. Is calculated and obtained.

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 supplying electric power between the object to be coated and the electrode, a current detection means for detecting a current of the power supply, a voltage detection means for detecting a voltage of the power supply,
A first calculation for calculating the coating film specific resistance in response to each output of the coating area signal generating means for deriving a signal representing the coating area of the object to be coated, the current detecting means, the voltage detecting means and the coating area signal generating means. Means, a throwing power signal deriving means for deriving a signal indicating throwing power, a temperature detecting means for detecting the temperature of the electrodeposition paint in the electrodeposition tank, and a temperature rise of the electrodeposition paint in the electrodeposition tank Alternatively, in response to each output of the descending heat exchanger, the first calculation means and the throwing power signal deriving means, the coating film specific resistance, throwing power and the temperature of the electrodeposition paint are calculated to obtain the target liquid temperature. A second computing means to be obtained and, in response to the output of the second computing means, so that the electrodeposition paint in the electrodeposition tank reaches the target liquid temperature,
An electrodeposition coating apparatus comprising: a control unit that controls the heat exchanger.

[0010]

According to the present invention, the object to be coated is conveyed into the electrodeposition tank containing the electrodeposition coating material, and a DC power supply is provided between the object to be coated and the electrode stored in the electrodeposition tank. In the electrodeposition coating method of connecting and dipping to perform electrodeposition coating, first, the current and voltage, and further the coating area of the object to be coated are detected. An arithmetic operation is performed among the current, the voltage and the coating area to obtain the coating film specific resistance, and the liquid temperature of the electrodeposition coating composition corresponding to the parameters of the coating film specific resistance and the predetermined throwing power is calculated. The temperature of the paint is changed so as to reach the liquid temperature, and the throwing power is controlled by this.

Further, according to the present invention, a predetermined coefficient having the coating film resistivity and throwing power as parameters is calculated,
By calculating the coefficient and the temperature of the electrodeposition paint in the electrodeposition tank, the liquid temperature of the electrodeposition paint can be obtained.

According to the present invention, the electrodeposition coating apparatus includes an electrodeposition tank for containing an electrodeposition coating material, a transfer means for transferring and immersing an object to be coated in the electrodeposition tank, and an electrodeposition tank in the electrodeposition tank. An electrode provided,
A power supply for supplying electric power between the object to be coated and the electrode, a current detecting means for detecting the current of the power source, a voltage detecting means for detecting the voltage of the power source, and a signal representing the coating area of the object to be coated. A coating area signal generating means for deriving, a first calculating means for calculating a coating film specific resistance in response to each output of the current detecting means, the voltage detecting means and the coating area signal generating means, and a signal representing the throwing power. A throwing power signal deriving means for deriving, a temperature detecting means for detecting the temperature of the electrodeposition coating material in the electrodeposition tank, a heat exchanger for raising or lowering the temperature of the electrodeposition coating material in the electrodeposition vessel; Second computing means for responding to the outputs of the computing means and the throwing power signal deriving means to obtain the target liquid temperature by computing the coating film specific resistance, throwing power and the temperature of the electrodeposition paint, and second computing means. In response to the output of the means, the electrodeposition paint in the electrodeposition tank reaches the target liquid temperature. A and a control means for controlling the heat exchanger.

[0013]

1 is a view showing an electrodeposition coating apparatus 1 which is an embodiment of the present invention, and FIG. 2 is a heat exchange means 1 shown in FIG.
It is a figure which shows 7. The electrodeposition coating tank 3 is filled with the electrodeposition coating material 3, and the conveyor 5 which is a transfer means for transferring the coating object 4 on the electrodeposition tank 2 and dipping the coating object 4 in the electrodeposition coating material 3
Is installed. Before the article 4 to be coated on the conveyor 5 is dipped in the electrodeposition coating material 3, the recognition means 6 for the article to be coated is installed. The recognizing means 6 recognizes the type and the number of the objects to be coated 4 in response to the video signal from the camera. The coating area for each type of the coating object 4 is input in advance from the input means to the calculating means 28 described later, and the coating area corresponding to the various coating objects 4 recognized by the recognizing means 6 and the various coating objects. The total product area S, which is the total value of the surface areas of the objects 4 to be dipped in the electrodeposition tank 2, can be obtained by the sum of the products of the number of objects for each item 4.

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-based paint is supplied from the clear-based replenishment paint tank 13 into 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. Clear clear paint does not contain pigment, but contains resin and water.

The mixer 12 is further mixed with the electrodeposition paint 3 extracted by the heat exchange means 17 and the electrodeposition paint 3 extracted by the pump 18, and the electrodeposition tank is prepared. It is thrown in 2.

FIG. 2 is a view showing the heat exchange means 17 shown in FIG. 1. FIG. 2 (1) shows the heat exchange means 17 when heat exchange is not performed, and FIG. 2 (2) is heat exchange. The heat exchange means 17 for performing is shown. A pipe line 19 connecting the mixer 12 and the electrodeposition tank 2 and a flow passage 20 through which the cooling water passes are in contact with each other at a heat exchanger 21 portion. A heat exchanger 21 is provided in the flow path 20.
Is formed on the outlet side of the heat exchanger 21 of the bypass passage 22.
A three-way valve 23 is provided. The three-way valve 23 is connected to the calculating means 28 as described later, and the calculating means 28 is
By controlling the three-way valve 23, the cooling water is passed through the heat exchanger 21 when the liquid temperature of the electrodeposition coating material 3 is lowered, and the cooling water is passed through the bypass flow passage 22 when the liquid temperature of the electrodeposition coating material 3 is not lowered to control the temperature. To do.

The electrode 24 is immersed in the electrodeposition paint 3 in the electrodeposition tank 2, and the electrode 24 and the electrode for the object 4 to be coated (not shown) measure the current as a current detecting means by integrating with time. It is connected to an AC power supply 27 which is a power supply having an integrating ammeter 25 and a voltmeter 26 which is a voltage detecting means, via a power supply circuit 30 including a rectifier and a power supply adjusting circuit 31.

The AC power supplied from the AC power supply 27 is rectified and smoothed by the power supply circuit 30, and then adjusted to a predetermined current and voltage by the power supply adjusting circuit 31, and the electrode 2
A voltage is applied between the electrode 24 and an electrode (not shown) that is in contact with the object to be coated 4 so that 4 becomes an anode.

The electrodeposition paint 3 in the electrodeposition tank 2 includes the electrodeposition paint 3
A thermometer 29 which is a temperature detecting means for measuring the liquid temperature is immersed.

Recognition means 6, flow meters 11, 15 and three-way valve 2
3, the integrating ammeter 25, the voltmeter 26, and the thermometer 29 are connected to the calculating means 28.

FIG. 3 is a graph showing the relationship between the liquid temperature of the electrodeposition paint and the coating film specific resistance and throwing power. The relationship between the temperature and the coating film resistivity is shown by the straight line L1, and the relationship between the temperature and the throwing power is shown by the straight line L2. This graph shows that increasing the temperature improves throwing power, but decreases the coating film resistivity.

When the electrodeposition coating is carried out, the composition of the electrodeposition coating 3 changes, and the coating film resistivity changes. When the coating resistance of a value is obtained, the coating resistance is changed by changing the composition of the electrodeposition coating b
If it falls to the value, the temperature of the electrodeposition coating liquid is the temperature B corresponding to the value b.
It can be seen that by lowering the value to the A value, it is possible to obtain a coating film having an a value as the coating resistance.
Further, even when the coating film resistivity fluctuates to the c value, the liquid temperature of the electrodeposition coating material may be raised from the C value, which is the temperature corresponding to the c value, to the A value.

The control liquid temperature T1 for obtaining an arbitrary coating film resistivity is a coefficient k to the current temperature T as shown in the equation 1.
It can be obtained by multiplying by.

[0024]

## EQU00001 ## T1 = T.times.k Next, a method for obtaining the coefficient k will be described. Figure 4
It is sectional drawing at the time of forming the coating films 36 and 37 on the cylindrical object 35 to be coated. A coating film 36 is formed on the outside of the article 35, and a coating film 37 is formed on the inside. The thickness of the coating film 37 is d.

The thickness of the inner coating film 37 when electrodeposition coating is performed using an electrodeposition coating material having a predetermined coating film specific resistance and throwing power is d1. The thickness of the inner coating film 37 when electrodeposition coating is performed using an electrodeposition coating material having a coating film resistivity different from that described above is d2. The coefficient k is obtained by dividing the thickness d1 by the thickness d2 as shown in Equation 2.

[0026]

[Equation 2]

When the composition of the electrodeposition coating material 3 changes so that the coating film has a specific resistance such that the thickness d2 is obtained, the coefficient k can be calculated from the temperature T at that time by using Equation 1. It is used when determining the control temperature T1.

As the coating film resistivity decreases, the thickness d increases, so the coefficient k becomes less than 1, and the control temperature T1 becomes lower than the temperature T. Also, if the coating film resistivity increases,
Since the thickness d becomes thin, the coefficient k becomes larger than 1, and the control liquid temperature T1 becomes higher than the liquid temperature T.

As the coefficient k, a plurality of coefficients k are calculated according to the change in the composition of the electrodeposition coating material 3, and are stored in the calculating means 18. Similarly, the coefficient k is similarly obtained for the electrodeposition coating material showing throwing power different from the above, and a table showing the coefficient k corresponding to the parameters of the coating film specific resistance and throwing power as shown in Table 1 below is obtained. It is created and stored in advance in the calculating means 28.

FIG. 5 is a flow chart showing an embodiment of the present invention. In step s1, the recognition unit 6 recognizes the type and quantity of the article 4 to be conveyed by the conveyor 5 into the electrodeposition tank 2. In step s2, the type and quantity of the article 4 recognized in step s1 are recognized. It is output from the means 6 to the calculating means 28. In step s3, the voltmeter 2
The voltage measured by 6 is output to the calculating means 28.

At step s4, it is judged by the calculating means 28 whether or not the time W which is set in advance and inputted to the calculating means 28 has elapsed. When the time W has elapsed, the routine proceeds to step s5, If the time W has not elapsed, the process returns to step s1. The time W may be set corresponding to the working time, or may be set based on the time from when the object to be coated 4 is recognized by the recognition means 6 to when the coating is completed.

In step s5, the integrated current I measured by the integrating ammeter 25 is output to the calculating means 28, and in step s6, the voltage input in step s3 while the time W has elapsed is integrated by the calculating means 28, Further, it is divided by the time W to calculate the average voltage V.

At step s7, the calculating means 28
By summing the integrated values of the coating area and the quantity corresponding to each type of the article 4 input in step s2,
The total coated object area S is calculated.

In step s8, the calculating means 28 uses the integrated current I, the average voltage E, and the total area S of the object to be coated,
The coating film specific resistance is calculated from Equation 3. Since the resistance of the article to be coated 4 is extremely smaller than the resistance of the coating film, it does not have to be taken into consideration when calculating the coating film specific resistance.

[0035]

[Equation 3]

In step s9, from the table 1 which has been input to the calculating means 28 in advance, a predetermined calculating means 2 is also used.
The throwing power inputted in 8 and the coating film specific resistance calculated in step s8 are used to obtain the coefficient k.

[0037]

[Table 1]

In step s10, the liquid temperature T output from the thermometer 29 to the calculating means 28 by the calculating means 28.
Then, the control liquid temperature is calculated using the equation 1 from the coefficient k obtained in step s9.

[0039]

## EQU1 ## T1 = T.times.k At step s11, the calculating means 2 is operated so that the control liquid temperature is obtained.
The three-way valve 23 is controlled by 8 to control the liquid temperature of the electrodeposition coating material 3 in the electrodeposition tank 2.

In step s12, it is judged whether or not the coating is completed. If it is not completed, the process returns to step s1. If it is completed, the coating operation is completed.

As described above, according to this embodiment, the coating film specific resistance can be automatically obtained during the electrodeposition coating, and the control for obtaining the predetermined throwing power from the obtained coating film specific resistance. The liquid temperature is required, and the liquid temperature of the electrodeposition paint in the electrodeposition tank 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.

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

[0044]

According to the present invention, the current, voltage and coating area are detected, and calculation is performed between the current, voltage and coating area to obtain the coating film specific resistance. The liquid temperature corresponding to the parameters of the coating film specific resistance and the predetermined throwing power can be calculated, and the throwing power can be controlled based on the liquid temperature.

Therefore, the liquid temperature is automatically controlled so that the throwing power becomes 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 a diagram showing a heat exchange means 17 shown in FIG.

FIG. 3 is a graph showing the relationship between the liquid temperature of the electrodeposition coating composition and the coating film specific resistance and throwing power.

FIG. 4 is a cross-sectional view when coating films 36 and 37 are formed on a tubular article 35 to be coated.

FIG. 5 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 6 recognition means 17 Heat exchange means 21 heat exchanger 24 electrodes 25 Integrated ammeter 26 Voltmeter 27 AC power supply 28 computing means 29 Thermometer 30 power circuit 31 Current 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 object to be coated is conveyed into an electrodeposition tank containing an electrodeposition coating material, and a DC power source is connected between the object to be coated and an electrode stored in the electrodeposition tank to obtain an electrodeposition. In the electrodeposition coating method of performing coating, the current and voltage of the power source, and the coating area of the object to be coated are detected, and the coating resistance is calculated by performing a calculation between the current and voltage and the coating area. Obtained, calculate the liquid temperature of the electrodeposition paint corresponding to the parameters of the coating film specific resistance and the predetermined throwing power, change the temperature of the paint so as to be the liquid temperature, thereby controlling throwing power. An electrodeposition coating method characterized by: 2. The electrodeposition coating liquid temperature is obtained by calculating a predetermined coefficient using the coating film resistivity and throwing power as parameters, and calculating the coefficient and the temperature of the electrodeposition coating material in the electrodeposition tank. The electrodeposition coating method according to claim 1, which is obtained by 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 supply for supplying electric power between the two, a current detection means for detecting the current of the power supply, a voltage detection means for detecting the voltage of the power supply, and a coating area signal generator for deriving a signal representing the coating area of the object to be coated. Means, a first calculating means for calculating a coating film specific resistance in response to each output of the current detecting means, the voltage detecting means and the coating area signal generating means, and a throwing power signal for deriving a signal showing throwing power. Derivation means, temperature detection means for detecting the temperature of the electrodeposition coating material in the electrodeposition tank, heat exchanger for raising or lowering the temperature of the electrodeposition coating material in the electrodeposition tank, first computing means and throwing power. Responsive to each output from the signal deriving means, the coating film resistivity, throwing power and electrodeposition A second calculation means for calculating the target liquid temperature by calculating the temperature of the material, and the heat exchange so that the electrodeposition coating material in the electrodeposition tank reaches the target liquid temperature in response to the output of the second calculation means. An electrodeposition coating apparatus comprising a control means for controlling the container.