JPH0471997B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention relates to a method of painting using electrodeposition paint, and more specifically, by detecting various factors related to paint film thickness and performing calculations between them and pre-input information. , relates to an electrodeposition coating method that automatically controls the coating film thickness. Prior Art Conventionally, as coating methods, electrostatic coating methods, spray coating methods, airless coating methods, dipping coating methods, electrodeposition coating methods, etc. have been used. Among these, the electrodeposition coating method has superior characteristics in various aspects compared to the remaining coating methods, such as the bag-like structure of the object to be coated and the joints between each part of the object. It also has the characteristic that it can be painted. In addition to the above-mentioned features, it is easy to control the coating film thickness by controlling the amount of electricity, and there is no sagging or flaking of the applied paint, which improves workability. Known to be good. Problems to be Solved by the Invention As mentioned above, electrodeposition coating is an excellent method compared to other methods, but there are various problems such as the temperature of the paint liquid, the conveyance speed of the object to be coated, and the degree to which the object is immersed in the paint. It is also affected by the number of objects, paint properties, etc. In other words, the coating temperature may drop, the conveying speed of the object to be coated may increase, resulting in a shorter energization time, or the condition of the coating material may change, making it difficult to form a coating film. , the paint film thickness becomes thinner. Furthermore, there are cases where the paint liquid temperature becomes high, the current application time becomes long, or the state of the paint changes, making it easier to form a paint film, and in such cases, the paint film becomes thicker. When the paint film thickness becomes thinner, the rust prevention performance of the coated object decreases, and the resulting product rusts early, resulting in a decrease in mechanical strength and damage to the appearance. Conversely, when the paint film thickness increases,
There is a problem that excessive paint is consumed and the finished appearance and quality deteriorate. In addition, there are two types of electrodeposition coating: constant voltage method and constant current method.The constant current method is economically advantageous and gives a good finished surface, but the number of times the object to be coated is immersed is determined by the paint tank. If the maximum number of immersions is not reached, the area of the electrode, which is the object to be coated, will be smaller than the area of the counter electrode, and the current from the counter electrode will concentrate on the immersed object, causing abnormal paint adhesion and poor appearance. There is a problem in that problems such as a decrease in performance occur. SUMMARY OF THE INVENTION An object of the present invention is to provide an electrodeposition coating method that solves the above-mentioned problems, dramatically improves coating quality, and allows automatic control. Means for Solving the Problems The present invention is a method of carrying out electrodeposition coating by transporting a plurality of objects to be coated into a paint tank containing electrodeposition paint and immersing them in the paint tank, the method comprising: immersing them in the paint tank; The number of objects to be coated (B), the conveyance speed of the objects to be coated (S), and the temperature of the paint liquid (T) are detected, which are unique information related to the deposition of electrodeposited paint on each object to be coated. The amount of paint per object to be coated (Q), information on energization time (K), and the inherent resistance of the paint film related to the paint temperature (T).
(k), the coulombic efficiency (η), which is information related to the physical properties of electrodeposition paint, and the maximum number of immersions, where the number of objects to be coated (B) is determined by the paint bath.
(M), input the voltage for the number of objects to be coated (B), and the calculation control unit will determine that the number of objects to be coated (B) is the maximum number of immersed objects (M).
When B=M, calculate the amount of current (I) using the following formula, and based on this, with a constant current, I=Q×B×K×S× When k/η B<M, this electrodeposition coating method is characterized in that electricity is applied at a constant voltage at a voltage input for the number of objects to be coated (B). Effect According to the present invention, when a plurality of objects to be coated are conveyed and immersed in a paint tank containing electrodeposition paint to perform electrodeposition coating, the number of objects to be coated that are immersed in the paint tank is
(B), the transport speed of the object to be coated (S), and the paint liquid temperature (T) are detected. Also, compare the number of objects to be coated (B) and the maximum number of objects to be coated that can be immersed in the paint tank (M), and if M>B, the voltage will be constant at the voltage for the number of objects to be coated (B) entered in advance. When M=B, specific information related to the deposition of electrodeposited paint on each object to be coated (paint amount per object to be coated, energization time information K, paint The specific information (coulombic efficiency η) related to the physical properties of the electrodeposition paint is input in advance, and between these, I=Q×B×K×S×k. /η …(1) is performed. Thereby, the amount of current corresponding to the number of objects to be coated immersed in the paint tank and the temperature of the paint liquid is calculated, and the current value is used to control the current flow state using the constant current method. Embodiment FIG. 1 is a system diagram illustrating the configuration of a coating apparatus according to an embodiment of the present invention. Referring to Figure 1,
The configuration of the coating apparatus of this embodiment will be explained. The coating apparatus of this embodiment includes a paint tank 2 containing, for example, a cationic electrodeposition paint 1, and a material having good electrical conductivity such as iron, stainless steel, or ferrite is contained in the paint tank 2. The electrode 3, which is a bare electrode or an anode in which a diaphragm is used, is immersed. A coating material 5 transported by a transport means such as a belt conveyor 4 is immersed in such a paint tank 2 . These objects to be coated 5 are, for example, the bodies of automobiles on an automobile manufacturing line, and are attached to the belt conveyor 4 by supporting members 6 having good electrical conductivity and conveyed. A power supply rail 7 is arranged above the paint tank 2, and a support member 6 that supports the object 5 to be coated slides thereon, thereby supplying electricity to the object 5 to be coated. On the other hand, in relation to each of the above-mentioned configurations, there is a conveying speed detecting section 8 realized by, for example, a rotary encoder, which detects the conveying speed of the object to be coated 5 by the belt conveyor 4, and a conveying speed detecting section 8 that is realized by, for example, a rotary encoder, Object detection units 9a, 9b, which are realized by limit switches, etc., for detecting the number of objects 5 being coated
9c, 9d (collectively referred to by reference numeral 9 when necessary)
and a liquid temperature detection section 10 for detecting the liquid temperature of the electrodeposition paint 1 in the paint tank 2. The outputs from these detection units 8, 9, 10 are on lines l1, l2,
13, the signals are applied in parallel to an arithmetic control unit 11 which is realized by, for example, a microcomputer and performs arithmetic control operations as will be described later. The arithmetic control unit 11 includes a key input unit 12 for inputting various information as described later, and a key input unit 12 for inputting various information, for example.
It is realized by a CRT (cathode ray tube) or the like, and is connected to a display section 13 that monitors and displays the input information and the operating status of the coating apparatus. The content displayed on the display section 13 can be printed out by the printing device 14. On the other hand, the electrode 3 and the power supply rail 7 are provided with a rectifier 15 that conducts a predetermined energization as described later, and when a cationic electrodeposition paint is used as described above, the power supply rail 7 is connected to the negative terminal of the rectifier 15. First, each electrode 3 is connected to an anode terminal, respectively. Further, the energizing operation of the rectifier 15 is controlled by the arithmetic control section 11 as described later. The present invention uses the configuration shown in the first diagram to detect various fluctuation factors such as the number of objects to be coated 5 immersed in the paint tank 2, the conveyance speed by the belt conveyor 4, and the liquid temperature of the electrocoating paint 1. In this way, the amount and manner of energization by the rectifier 15 are automatically controlled. For this purpose, Q: Amount of paint required for each object 5 to be coated K: Coefficient related to energization time k: Coefficient defined by the specific resistance value of the coating film (R) and the coating liquid temperature (T°C) η: Coulomb Input each efficiency constant from the key input section 12, and then input B: the number of objects to be coated immersed in the paint tank 2, S: conveyance speed of the belt conveyor 4, and T: the temperature of the paint liquid to the object detection section. 9. Detected by the conveyance speed detection unit 8 and liquid temperature detection unit 10, and the calculation control unit 11 compares the maximum number of immersions (M) determined by the paint tank 2 with the number of objects to be coated (B), When B<M, the number of objects to be coated
Perform constant voltage electrodeposition coating with the voltage input in advance for (B), and when B=M, each of the above constants Q, K,
The first equation above is calculated using k, η, β and the variable S to obtain the amount of current (I), and constant current electrodeposition is performed using this amount of current. Each variable and constant in the first equation will be explained below. Regarding Q. The amount of paint required for each object 5 to be coated is determined based on the unique characteristics of the electrodeposition paint used and various experimental information under the conditions of the production line where the coating equipment shown in Figure 1 is used. Ru. That is, the first
When the illustrated painting apparatus is used on an automobile manufacturing line, the top 17 of the vehicle body 16 shown in FIGS. Since it is difficult to obtain a film thickness, the paint amount Q is set so that the desired film thickness can be obtained even in such a region. About B. As mentioned above, the number of objects to be coated is determined by the object detection section 9a.
~9d, and if the maximum number of immersed objects (M) is 4 as shown in Figure 1, then 1 ~
When up to three objects 5 to be coated are immersed, constant voltage operation is performed using a predetermined constant voltage corresponding to each number of objects, and when it is detected that four objects 5 to be coated are immersed. , the operation is switched to constant current operation as described below. In this way, by detecting the number of objects 5 to be coated immersed in the paint tank 2 and changing the energizing voltage, it is possible to prevent lines entering the tank, pinholes, abnormal adhesion, etc. as explained in the prior art section. Prevent various product-related defects such as deterioration of appearance quality. About K. The constant K related to the energization time is K = 1/(total immersion length L1 (m) x 60 (sec))...(2) L1: It is expressed as the length that all 5 objects to be coated have in the paint tank 2. . About S. Generally, the required energization time differs depending on the conveying speed S of the belt conveyor 4 and the total submerged length L1 in the paint tank 2, and therefore, this conveying speed S is detected. About k The constant k is determined by an empirical formula for each paint used. The paint design is based on a coating resistance of 600 kΩcm ² and a liquid temperature of 28°C, and the throwing power under these conditions is 19 μm. Based on this, if the coating resistance and liquid temperature change, it will change under standard conditions. It is set as a parameter to obtain the throwing power film thickness. This value is determined by measuring the coating resistance at a certain temperature of the paint used, measuring the throwing power at that temperature, and comparing it with the standard throwing power. For example, if the throwing power is 20 μm, k = 19/20 = 0.95, and if the throwing power is 18 μm, k =
19/18=1.06. Generally, as the paint temperature increases, the coating resistance decreases and the throwing power increases. About η Coulombic efficiency η is a value that changes depending on the solid content of the paint used, acid concentration, amount of solvent, etc. Coulombic efficiency is an experimental value obtained by electrodepositing paint under certain conditions such as temperature. A paint with a high coulombic efficiency has a large amount of electrodeposition per coulomb and is likely to form a coating film, whereas a paint with a low coulombic efficiency has a difficulty in forming a coating film. Note that the unit of coulomb efficiency η is mg/coulomb. FIG. 4 is a flowchart showing the operating procedure of an embodiment of the present invention, and FIG. 5 is a graph showing changes in the energizing voltage. With reference to Figures 1 to 5,
The operation of this embodiment will be explained. When the coating apparatus shown in FIG. 1 is started at step n1 in FIG.
A display requesting input of items shown in Nos. 1 to 18 of the table is displayed. Subsequently, in step n3, the following information is input using the key input section 12.

【table】

[Table] The information to be input is the items shown in No. 1 to No. 18 of Table 1. When the maximum number of objects 5 to be coated 5 immersed in the paint tank 2 in FIG. 1 is 4, each constant voltage value of No. 3 to No.
This is the voltage value when performing constant voltage operation when is immersed. Each voltage value V1=282[V],
The changes of V2=295 [V] and V3=307 [V] are shown in FIG. Also, No. 1 to No. 2 and No. 9 to No.
Once each of the 16 items has been input, it becomes a fixed value for the painting equipment, and if the conditions shown in each item during operation are out of the values in Table 1, the situation will be displayed on the display 13. is displayed and, for example, an alarm is generated. Next, the parameters related to the resistance value of the coating film and the paint liquid temperature shown in Table 2 (k in the above equation 1)
is input.

【table】 Next, the items shown in Table 3 are entered.

[Table] Here, the conveyance speed (S) is determined by the conveyance speed detection section 8, the liquid temperature is determined by the liquid temperature detection section 10, and the number of units (B)
are respectively detected by the object detection section 9.
For the remaining items, desired numerical values are input using the key input section 12. Here, a specific example of the input information in step n3 will be explained. (1) Input value determined by the size of the paint tank 2 B is the total number of objects to be coated that are immersed in the paint tank 2, which is four in this embodiment. Of course, this value increases or decreases as the paint tank 2 becomes larger or smaller. K When the total submerged length L1 mentioned above is 22.75 m, K = 1/22.75 m x 60 sec = 7.33 x 10 ^-4 ...(2). (2) The automatically detected input value S is detected by the conveyance speed detection section 8 as described above. After the paint liquid temperature T is detected by the liquid temperature detection section 10, it is replaced with the parameters shown in Table 2 above. (3) Input value by manual operation Q: The amount of paint used (mg) is determined by the amount of paint on the outer panel and the amount of paint on the inner panel. (b) The amount of exterior paint is calculated as follows, as an example. (Film thickness) 25μm x (Area) 34m ² x (Specific gravity) 1.25 x (Coating efficiency) 100/95 x (Volatilization loss) 100/93 = 1.203g...(
3) (b) As an example, the amount of paint on the inner panel is calculated as follows. (film thickness) 17.5μm x (area) 51m ² x (specific gravity) 1.25 x (
Coating efficiency) 100/95 x (volatization loss) 100/93 = 1.263g
...(4) By adding the values of the third and fourth equations above, the following result is obtained: Q=2.466g...(5). (2) k is a parameter input as shown in Table 2. (3) η is similarly input as shown in Table 3. Next, when the belt conveyor 4 is started at step n4 in FIG.
The conveyance speed is detected by. The signal from the conveyance speed detection section 8 is taken into the calculation control section 11 via the line l1, and converted into the coefficient B in the first equation. Continuously, in step n6, the number of objects 5 to be coated immersed in the paint tank 2 is detected by the object detectors 9a to 9d. In step n7, the number of objects to be dipped (B) is 3, which is less than the maximum number of objects to be dipped (4) in this example.
A determination is made as to whether or not it is below the level. If this judgment is affirmative, the arithmetic control unit 11 performs constant voltage operation at step n8 according to the voltage value for each number of dipped objects shown in the items No. 3 to No. 5 of Table 1 above. Let's do it. In step n9, No. 1 to No. 1 in Table 1 above are selected.
It is determined whether the operating conditions corresponding to the items indicated by No. 2 and No. 9 to No. 16 exceed the limit values input for each item. If it exceeds, the process moves to step n10, where the above-mentioned alarm operation is performed and recovery processing is performed. If the judgment result in step n10 is affirmative, the process moves to step n11, and the paint tank 2
The temperature of the liquid inside is detected. In step n12, it is detected whether the liquid temperature has changed from the initial value shown in Table 3. If there is no change, the process moves to step n13 and painting is continued under the same conditions. After this, the process moves to step n5. If the judgment result is negative in step n7 of FIG. Constant current operation is performed.

【table】

[Table] At this time, for each variable in the first equation, Q=
2.46×10 ⁶ , B=4, K=7.33×10 ^-4 , S=5.2,
η = 27, and the coefficient k related to the coating film resistance value and temperature is, for example, the coating film resistance R in Table 2.
is 475Ω to 524Ω and the parameter 0.91 in the column of temperature 28°C is selected. By this, I=2.46×10 ⁶ ×4×7.33×10 ^-4 ×5.2×0.91/27
= 1.264A …(6) is obtained. Next, in step n15, it is detected whether the current I is within the conditions shown in Table 1, and if it is not within the conditions, an alarm operation and subsequent processing are performed in step n10, as described above. If the determination at step n15 is affirmative, the process moves to step n11, and the operations described above are repeated. In step n12, if a request to change the paint liquid temperature or other conditions arises, the process moves to step n16, where a message for re-entering the conditions is displayed on the display section 13, and as shown in Table 5, for example, Coulomb efficiency value η = 25, coating resistance value 617Ω,
Information such that the liquid temperature is 28.8℃ is displayed at step n.
17 is entered.

【table】

[Table] At this time, the flowing current I is calculated as shown in the following equation. I=2.46× ^10-6 ×4×7.33× ^10-4 ×5.2×0.95/
25=1425A (7) After this, the process moves to step n13, where painting is continued, and the process moves to step n5, where the above-described process is repeated. As described above, in this embodiment, when performing electrodeposition coating, the process is adjusted according to various variable factors, such as the number of objects 5 to be coated immersed in the coating tank 2, the temperature of the paint liquid, and the conveyance speed of the belt conveyor 4. Determine whether the energization mode is the constant voltage method or the constant current method, and if the constant voltage method is used, the voltage is controlled, and if the constant current method is used, the current is controlled so that the current value is calculated using the formula (1) above. I made it. Therefore, as described in the prior art section, even if the number of objects 5 to be coated immersed in the paint bath 2 is less than the expected maximum number of objects to be coated, the concentration of current may It is possible to avoid problems such as entry lines, pinholes, abnormal adhesion, and deterioration of appearance quality. Furthermore, various fluctuation factors such as the conveyance speed of the belt conveyor 4, coulomb efficiency value, coating film resistance value, and liquid temperature are detected, and the operating state is automatically controlled in accordance with these factors. Therefore, the operability of the coating apparatus in which such a coating method is applied is greatly improved, and the quality of the coated product is also significantly improved. In the above-mentioned embodiments, the electrodeposition paint 1 was described as being of the cationic type, but it goes without saying that it may be of the anionic type. Further, the coating apparatus of this embodiment can be used not only in automobile production lines but also in a wide range of technical fields where painting is required. At this time, the object 5 to be coated is not limited to an automobile body, but may be any object to be coated in the field. Further, the numerical values shown in the above-mentioned tables are merely examples for implementing the present invention, and the present invention is not limited to such numerical examples. Effects As described above, according to the present invention, the number of objects to be coated immersed in the paint tank, the transport speed of the objects to be coated, and the temperature of the paint are detected, and the number of objects to be coated is determined by the maximum number determined by the paint tank. If the number of immersions is less than the number of immersions, constant voltage coating is performed using the voltage corresponding to the number of objects to be coated that has been entered in advance.If the number of objects to be coated is equal to the maximum number of immersions determined by the paint tank, the electrodeposition is applied using the voltage that has been input in advance. The amount of energization is calculated by performing calculations between the unique information related to the deposition of paint on each object to be coated, the unique information related to the physical characteristics of the electrodeposition paint, and each of the above detected values, and The amount of constant current painting is now applied. Therefore, even if the number of objects to be coated in the paint tank, the liquid temperature, the conveyance speed, etc. change, a desired film thickness can always be obtained, and the quality of the product can be significantly improved. In addition, various fluctuation factors such as paint liquid temperature and conveyance speed are detected and the energization status is controlled accordingly, thereby eliminating problems such as entry lines, pinholes, abnormal adhesion, and deterioration of appearance quality. be able to.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing the configuration of a coating apparatus according to an embodiment of the present invention, FIG. 2 is a side view of the object to be coated 5, FIG. 3 is a front view of the object to be coated 5, and FIG. 4 is the present embodiment. FIG. 5 is a flowchart illustrating the operation procedure of the example, and is a graph showing the operation of this embodiment. DESCRIPTION OF SYMBOLS 1...electrodeposition paint, 2...paint tank, 4...belt conveyor, 5...object to be coated, 8...conveying speed detection section, 9...object detection section, 10...liquid temperature detection section, 11...arithmetic control section, 12...Key input section.

Claims (1)

[Scope of Claims] 1. A method of carrying a plurality of objects to be coated into a paint tank containing electrodeposition paint and performing electrodeposition coating by immersing the objects, the objects being coated immersed in the paint tank. number (B), the conveyance speed of the object to be coated (S), and the temperature of the paint liquid (T). Paint amount (Q), energization time information (K), and paint film specific resistance related to paint temperature (T)
(k), the coulombic efficiency (η), which is information related to the physical properties of electrodeposition paint, and the maximum number of immersions, where the number of objects to be coated (B) is determined by the paint bath.
(M), input the voltage for the number of objects to be coated (B), and the calculation control unit will determine that the number of objects to be coated (B) is the maximum number of immersed objects (M).
When B=M, calculate the amount of current (I) using the following formula, and based on this, with a constant current, I=Q×B×K×S× An electrodeposition coating method characterized in that when k/η B<M, electricity is applied at a constant voltage at a voltage input for the number of objects to be coated (B).