JPS61231199A - Method and apparatus for electrodeposition coating - Google Patents

Abstract

PURPOSE:To carry out electrodeposition coating always at a fixed film thickness, by carrying out coating while varrying the effective working area of the electrode plate opposed to a material to be coated, according to electricity conduction time or transferring velocity thereof in electrodeposition cell. CONSTITUTION:When the material 1 to be coated such as car body is transferred by a hanger 2 and an overhead conveyer 3, and attained to a position B, a limit switch 8 is functioned and contactors 10a-10j are turned on through a control part 6a of a DC source apparatus 6. At the position B, passing time or transferring velocity of the material 1 are detected by a detecting means 23. The material 1 is further dipped in bath, and whole thereof is sunk therein. During this, both collector rings 5a, 5b are engaged with a bus bar 3, and electrodeposition is carried out between the cathode material 1 and the first anode plate 15 connected to the apparatus 6. Thereat, members of the contactors 10a-10j to be turned on are varied, based on a prescribed electricity conduction time or transferring velocity measured during transferring.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to an electrodeposition coating method and its Vi position, in particular, to control the area on which a return electrode acts according to the energization time or conveyance speed of the object to be coated. This invention relates to an electrodeposition coating method and apparatus.

(Prior art) Electrodeposition coating is a process in which when a water-based paint is dispersed or dissolved in water, the paint particles are electrophoresed using the fact that they are positively or negatively charged, and the paint is deposited on the object to be coated. Since the resulting coating film has excellent corrosion resistance, it is widely used for coating various industrial products such as automobile bodies, electric refrigerators, and electric washing machines.

There are two types of electrodeposition I1 coatings: anionic and cationic. Conventionally, anionic electrodeposition coating has been mainly used because the coating is inexpensive and has relatively good coverage. However, since anionic electrodeposition has a problem in that metals or chemical conversion coatings are leached from the object to be coated, cationic electrodeposition coating methods have recently come into use. That is, according to this method, the adhesion of the coating film to the object to be coated is good, and the corrosion resistance of the resulting coating film is superior to that of the anionic electrodeposition coating film. 'R electrodeposition coating, such as cationic electrodeposition coating, has been carried out using an apparatus as shown in FIGS. 3 and 4. That is, in the same figure, when the hanger 2 on which the object 1 to be coated, such as an automobile body, on which the chemical conversion coating has been formed, is placed is conveyed by the overhead conveyor 3, the +i end position A ( When the current collectors 5a and 5b of the current collector 5 installed on the hanger 2 are connected to the first DC power source 6 to which a negative electrodeposition coating voltage is applied, 1 contact bus par 4.

However, at this position, the object 1 to be coated is not yet immersed in the cationic electrodeposition paint bath 7 housed in the electrodeposition bath 19, so no current flows.

In this way, the hanger 2 is connected to the overhead conveyor 3.
When it reaches the 8th position (just before the start of immersion), the first limit switch 8 is activated, and the activation signal is transmitted via the wiring 9 to the control unit 5a of the DC power supply 6, such as a thyristor. input to the SCR and sent to the contactor 10 via a relay circuit (not shown) provided in the control section 6a.
Turn off. Therefore, no voltage is applied to the object 1 from the time the object 1 begins to be immersed in the electrodeposition paint bath 7 until the object 1 is half immersed in the C position as described later. Not done.

On the other hand, even if the signal is input to the control unit, the predetermined negative voltage is maintained applied to the second buspar 11, and therefore the second buspar 11 is engaged and fully submerged. Another object 1 to be coated continues to be electrocoated. When the hanger 2 reaches position C along the overhead conveyor 3, the object 1 to be coated is in a half-submerged state. At this C position, the second limit switch 12 is activated, and its activation signal is input to the control section 6a of the DC power supply device 6 via the wiring 13.
The contactor 10 is turned on via a relay circuit (not shown) provided in the control section 6a.

Therefore, a regular electrodeposition voltage is applied to the part of the object 1 immersed in the bath via the first busper 4, the current collector 5, and the hanger 2.

When the hanger 2 further travels on the overhead conveyor 3, the object 1 to be coated is further immersed in the liquid, and eventually completely submerged. During this time, the current collectors 5a15b are both engaged with the first busper 3, and a negative voltage is applied to the object 1 to be coated to form a cathode, and an anode plate connected to the DC power supply 16 via the conductor 14. Electrodeposition is performed by applying electricity between the electrode 15 and the cationic electrode 11 through the cationic paint 11. However, D
Once in position, the collector 5a engages the first buspar 3 and the collector 5b engages the insulator 16, then the collector 5a engages the insulator 16 and the collector 5b engages the second buspar 11. When the hanger 2 is engaged and further travels, the collectors 5a, 5
b engages with the second hanger 11. Moreover, the first
Since both the bus spar 3 and the second bus spar 11 have the same potential, the transfer is performed smoothly while the coating voltage remains applied to the object 1 to be coated. Next, another new object 1 to be coated is carried into the electrocoating line and the same cycle as described above is repeated. In addition, in FIG. 2, the reference numeral 17
is the bottom anode. Also, during this period, the M11 paint is partially extracted from the conduit 18, passed through the pump P and the filter F, and is circulated from the conduit 1!20 to the electrodeposition bath 19.

(Problems to be Solved by the Invention) However, in such a conventional electrodeposition coating method, a 'RIt coating device in which the area of the anode plate remains constant is used, and the anode plate installed therein is used to act on the anode plate. Since the current application method was based on the current application method, in order to obtain a coating film of a predetermined thickness, if the current application time is long, the applied voltage should be lowered, and on the other hand, if the current application time is short, the applied voltage should be increased. There was a problem in that the applied voltage had to be changed each time depending on the situation.

(Means for Solving the Problem) The present invention has been made by focusing on such conventional problems, and firstly, the object to be coated is immersed in an electrodeposition paint bath, and the object to be coated is immersed in an electrodeposition paint bath. In a method of electrocoating the object to be coated by applying current between the object and a counter electrode, the coating is performed by changing the area on which the counter electrode acts depending on the energization interval or conveyance speed of the object. It is an object of the present invention to solve the above-mentioned problems by using an electrodeposition coating method characterized by the following.

Second, an electrodeposition tank containing electrodeposition paint, a coating object conveyance device, a return electrode provided in the electrodeposition tank, and a power supply connected to the return electrode and the object to be coated, respectively. In the electrodeposition coating apparatus, there is provided an energization time or conveyance speed detection means for the object to be coated on the input side of the object conveyance device, and an action area control means for a return electrode connected to the energization time or conveyance speed detection means. It is an object of the present invention to solve the above-mentioned problems by an electrodeposition coating apparatus characterized by being provided with the following.

(Example) Hereinafter, the method of the present invention using the electrodeposition coating apparatus according to the present invention will be explained based on the drawings. 1 and 2 are diagrams showing one embodiment of the present invention, and based on the same figures, the method and apparatus thereof according to the present invention will be explained at the same time, taking the case of cationic electrodeposition coating as an example.

That is, in the figure, an object to be coated 1, such as an automobile body, on which a chemical conversion film has been formed by treatment with a chemical conversion treatment liquid such as a phosphate, is conveyed by an object conveying device comprising a hanger 2 and an overhead conveyor 3. First, at the rear end position IA of the busper 4 (the position where it is carried into the electrodeposition coating line), the current collector 5 of the current collector 5 installed (pulled) on the hanger 2 is
A and 5b connect the conductor 21 from the DC power supply 16 and contact the busper 4 to which a negative electrodeposition coating voltage is applied. However, at this position, the object 1 to be coated is not yet immersed in the cationic electrodeposition coating bath 7 used in the m-deposition bath 19, so no current flows.

In this way, the hanger 2 is connected to the overhead conveyor 3.
When it reaches the 8th position 1 (the position just before the start of immersion), the limit switch 8 is activated, and the activation signal is input to the control unit 8a of the DC power supply 6, for example, the thyristor SCR, via the wiring 9. contactors 10a, 1 via a relay circuit (not shown) provided in the control section 6a.
0b.

Turn on... At this position, the energization time or conveyance speed of the object to be coated 1 is detected by the object energization time or conveyance speed detection means 23 .

As the current application time detection means 23 for the object to be coated, for example, by detecting the type of car body of the object to be coated using a phototube,
There is a method of detection based on the energization time, which is stored in advance in the control device for each vehicle type. Further, as the conveyance speed detection means 23, there is an electrical or mechanical speed meter.

As the hanger 2 further travels on the overhead conveyor 3, the object 1 to be coated is further immersed in the bath and is completely immersed. During this time, both current collectors 5a and 5b are connected to the busper 3.
A cationic electric current is formed between the coated object 1 which forms a cathode by applying a negative voltage to the first anode plate 15 and the first anode plate 15 which is connected to the DC power supply 6 via a conductor 14. Electrodeposition coating is performed by applying electricity through the coating material. Thus, as described above, the contactor 10a is turned on depending on the predetermined energization time or the conveyance speed measured during conveyance.

The numbers of 10b, 10c, etc. change.

For example, when the conveyance speed is a standard speed (normally, it takes 3 minutes for the object 1 to be removed from the electrodeposition bath 19 after it is completely immersed in the electrodeposition coating bath), the anode plate weighing 48 to 4g is transferred to the contactor 10a. 1
When 0g is turned on, the 'w1 source 6 becomes energized, the object 1 to be coated is energized, and electrodeposition coating is performed. on the other hand,
When the conveyance speed is faster than the standard speed, the speed detecting means 23 detects how many percent faster it is than the standard speed, and the controller 6a calculates the speed, and then the contactors 10a, 10b, etc.
・If the increase is up to 10%, one anode plate is added, and if the increase is 1.20%, two anodes are added and the contactor is turned on. Conversely, if the conveyance speed is slow, 10
The contactors are turned off to reduce the number of anode plates f and 10e. Moreover, such a change in the current-carrying area of the anode plate or the cathode plate is effected not only on the side electrode plates but also on the bottom electrode plates 17a to 17e.

In addition, when controlling by a predetermined energization time, it is sufficient to energize the required number of contactors 10a, 10b, . . . based on information recorded in advance depending on the type of the object to be coated.

During this time, the electrolyte paint is partially discharged from the conduit 18, passes through the pump P and the filter F, and then enters the electrodeposition bath from the conduit 10! It is circulated to fJ19.

The above is about cationic electrodeposition coating, but anion 1
Of course, the same method can be applied to coating.

(Effects of the Invention) As described above, the first invention of the present application can
i@ In a method of electrocoating the object by electrodeposition by immersing the object in paint and passing current between the object and the return electrode, the voltage of the return electrode changes depending on the energization time or conveyance speed of the object. Since this is an electrodeposition coating method that performs coating by changing the effective area of application, there is no need to vary the voltage, etc. even if the conveyance speed of the object to be coated changes due to fluctuations in productivity. Not only does this save management effort, but the effective area for lt and it coating on the return electrode plate can be changed, so the polarity ratio can be kept constant. Electrical equipment can be installed. Furthermore, since the voltage is constant, there is no deterioration in the coverage of the bag structure, and the rust prevention ability is improved.

Further, the second invention of the present application provides an electrodeposition tank containing an electrodeposition paint, an object conveying device, a return electrode plate provided in the electrodeposition tank, and a connection between the return electrode plate and the object to be coated. In an electrodeposition coating apparatus comprising power supplies connected to each other, an energizing time or conveying speed detecting means for the to-be-coated object is introduced into the conveying device for the to-be-coated object, and a counter electrode connected to the energizing time or conveying speed detecting means. l!, characterized by: means for controlling the active area of the plate; 11 coating device, the energization time or conveyance speed of the object to be coated can be detected by means for detecting the energization time or conveyance speed of the object to be coated provided on the loading side, and the The control device controls the current-carrying area of the return electrode plate to tiI.
Therefore, the polar ratio can be kept constant, and therefore 1R coating can always be performed with a predetermined constant film thickness. Furthermore, since the counter electrode area can be changed by the control device without changing various tR11 conditions within the same device, work management is extremely easy and the device cost is low.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an electrodeposition coating apparatus according to the present invention;
FIG. 2 is a schematic plan view of the apparatus, FIG. 3 is a schematic sectional view showing a conventional electrodeposition coating apparatus, and FIG. 4 is a schematic plan view of the electrodeposition coating apparatus according to the present invention. DESCRIPTION OF SYMBOLS 1... Object to be coated, 2... Hanger, 3... Overhead conveyor, 6... Power supply, 7... Electrodeposition paint, 10a-10j... Contactor, 15
8-15j... Return electrode plate, 19... Electrodeposition tank, 23.
... Means for detecting the energization time or conveyance speed of the object to be coated.

Claims (2)

[Claims] (1) In a method of electrocoating the object by immersing the object in electrodeposition paint and applying electricity between the object and the return electrode,
An electrodeposition coating method, characterized in that coating is performed by changing the effective area on which the counter electrode acts depending on the current application time or conveyance speed of the object to be coated. (2) An electrodeposition tank containing electrodeposition paint, a coating object conveyance device, a return electrode provided in the electrodeposition tank, and a power source connected to the return electrode and the object to be coated, respectively. In the electrodeposition coating apparatus, there is provided an energization time or conveyance speed detection means for the object to be coated on the input side of the object conveyance device, and an action area control means for a return electrode connected to the energization time or conveyance speed detection means. An electrodeposition coating device characterized by being provided with.