JPH1025599A - Electrodeposition coating method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten tact time without degrading the throwing quality of coating films to materials to be coated and to eliminate the need for changing the voltage between the materials to be coated and electrodes even if the tact time is changed. SOLUTION: Adjacent first and second electrodeposition cells 11, 12 respectively have the same electrodes 21a, 22a therein and the same coating liquids 11a, 12a are stored therein. A transporting device 14 successively supplies many materials 13a, 13b to be coated, simultaneously inserts the materials 13a, 13b to be coated one by one into the first and second electrodeposition cells 11, 12 in the state of respectively separately holding the materials 13a, 13b to be coated and transports the materials above the first and second electrodeposition cells 11, 12. Energizing devices 21, 22 supply DC currents for the prescribed time between the two materials 13a, 13b to be coated respectively separated inserted into the first and second electrodeposition cells 11, 12 by the transporting device 14 and immersed into the coating liquids 11a, 12a and the electrodes 21a, 22a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method and an apparatus for forming a coating film on the surface of an object by applying a direct current between the electrode and the object immersed in an electrolyte coating liquid. It is about.

[0002]

2. Description of the Related Art Conventionally, as this kind of electrodeposition coating apparatus, as shown in FIG. 6, a coating liquid 2a is stored in an electrodeposition tank 2 having an electrode 6a therein, and a plurality of transfer apparatuses 5 are sequentially supplied. The objects to be coated 3a, 3b are inserted into the electrodeposition tank 2 one by one while holding the objects to be coated 3a, 3b, pulled up and transported over the electrodeposition tank 2, and the energizing device 6 is turned on in the electrodeposition tank 2. 2. Description of the Related Art An electrodeposition coating apparatus is known in which a DC current is applied between a workpiece 3a, 3b immersed in a coating liquid 2a and an electrode 6a for a predetermined time. The electrodeposition coating process using this apparatus includes a loading process of the objects 3a and 3b to be loaded on the loading table 1, a coating process in the electrodeposition bath 2, a first cleaning process in the first cleaning bath 4, and a second cleaning bath. (Not shown)
Cleaning process and work piece 3 on carry-out stand (not shown)
a and 3b are carried out, and the time required for the painting process is set as a takt time, and the process is performed in a flow operation in the order of the above processes.

However, in the above-mentioned conventional electrodeposition coating apparatus, while the first cleaning time in the first cleaning tank 4 and the second cleaning time in the second cleaning tank are each within one minute, 2, the energization time is 2-3 minutes, twice or more times, and there is a problem that the tact time, which is the addition of the energization time and the transport time, cannot be shorter than 3 to 4 minutes. In the conventional electrodeposition coating apparatus, when the tact time is changed, the energization time in the electrodeposition tank 2 must be changed. As a result, in order to make the thicknesses of the coating films on the surfaces of the objects 3a and 3b uniform, the voltage is increased when the energizing time is shortened, and the voltage is decreased when the energizing time is prolonged. The settings had to be changed each time.

In order to solve these problems, as shown in FIGS. 7 and 8, an electrodeposition tank 7 is formed in a horizontally long shape extending in the longitudinal direction of the transfer device 5, and a cover inserted into the electrodeposition tank 7 is formed. There is known an electrodeposition coating apparatus configured to move from the loading stand 1 side to the first cleaning tank 4 side while immersing the coating objects 3a, 3b, 3c in the coating liquid 2a. In this improved device,
While the first workpiece 3a is being immersed in the coating liquid 2a of the electrodeposition tank 7, the subsequent second workpiece 3b is transported by the transport device 5 above the electrodeposition tank 7, and the first Since the object to be coated 3a is pulled up and the second object to be coated 3b is inserted into the electrodeposition tank 7 at the same time, most of the transport time of the objects to be coated 3a, 3b, 3c can be excluded from the tact time. , The tact time can be shortened.

[0005]

However, in the above-mentioned conventional improved electrodeposition coating apparatus, the electrodeposition tank is horizontally long and the object moves within the electrodeposition tank. The distance from the electrode changes, and the quality of the coating film on the surface of the object to be coated may deteriorate. Further, in the conventional improved electrodeposition coating apparatus, when the tact time is changed, it is necessary to change the voltage setting each time as in the case of the electrodeposition coating apparatus before the improvement. An object of the present invention is to reduce the tact time without deteriorating the coating quality on the surface of the object to be coated and to change the voltage between the object and the electrode even when the tact time is changed. An object of the present invention is to provide an electrodeposition coating method and an apparatus which do not need to be used.

[0006]

Conventionally, in the course of the electrodeposition coating process, an object to be coated is once pulled up from the electrodeposition tank, immersed again in the coating liquid in the electrodeposition tank, and coated by electrodeposition. The inventor repeated the experiment, but was exposed to the outside air during the transition from the first electrodeposition coating to the second electrodeposition coating, although this was considered to be a cause of poor appearance quality of the object to be coated. If the time is within about 60 seconds, even if it is pulled up from the electrodeposition tank and then immersed in the coating liquid in the electrodeposition tank again and applied by electrodeposition, there is no problem in the appearance quality of the object to be coated. The present invention has been found, and the present invention has been achieved.

The invention according to claim 1 is an improvement of an electrodeposition coating method in which an electrodeposition coating step including a coating step and a cleaning step is performed in a flow operation in the order of the above steps, and a required time of the coating step is a tact time. . The characteristic configuration is that the painting process includes a first painting process and a second painting process in which the same paint is painted, and the process shifts to the second painting process within a required time after the end of the first painting process. In the electrodeposition coating method according to the first aspect, since the coating step for determining the tact time of the electrodeposition coating step is divided into two steps, a first and a second coating step, a predetermined energizing time in the coating step is secured. In addition, the tact time can be reduced.

As shown in FIG. 1, the invention according to claim 2 is arranged adjacent to each other and has the same electrodes 21a, 22a therein and the same coating liquid 11a, 12a.
The first and second electrodeposition tanks 11 and 12 in which are stored, and a large number of objects to be coated 13a and 13b are sequentially supplied, and the first and second electrodes 13 and 13b are held separately. A transfer device 14 that inserts the objects 13a and 13b into the baths 11 and 12 one by one simultaneously or at a different timing, and pulls them up at the same time to transfer them on the first and second electrodeposition baths 11 and 12; The first and second electrodeposition tanks 1 by the device 14
1 and 12 and two objects 13a and 13b and electrodes 21a and 13a, which are separately immersed in the coating liquids 11a and 12a, respectively.
22a, and energizing devices 21 and 22 for energizing a direct current for a predetermined time between the power supply devices 22 and 22a. In the electrodeposition coating apparatus according to the second aspect, the object 13 to be coated is placed in the first electrodeposition tank 11.
A coating film having a thickness approximately half the desired thickness is formed on the surfaces of the substrates 13a and 13b.
The remaining thickness of the coating film is formed on the surface of b. Further, while the remaining thickness of the coating film is formed on the surface of the object 13a in the second electrodeposition tank 12, the surface of the subsequent object 13b in the first electrodeposition tank 11 has a desired thickness. Since a coating film having a thickness almost half of the thickness is formed, the tact time can be reduced while securing a predetermined energizing time. When the tact time is further increased, the energization time can be kept constant by delaying the timing of lowering the objects 13a, 13b to the first electrodeposition tank 11, so that the objects 13a, 13b and the electrodes can be maintained. It is not necessary to change the voltage between 21a and 22a.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings. As shown in FIGS. 1 to 4, the electrodeposition coating apparatus 10 includes first and second electrodeposition tanks 11 and 12 arranged adjacent to each other, and a large number of objects 13a and 13b to be coated.
, A conveying device 14 for sequentially supplying the objects 13a and 13b to the first and second electrodeposition tanks 11 and 12 and pulling them up and conveying them on the first and second electrodeposition tanks 11 and 12; Two objects 13a and 13b to be coated separately inserted into the first and second electrodeposition tanks 11 and 12 by the transport device 14, and first and second electrodes provided in the electrodeposition tanks 11 and 12, respectively. There are first and second current supply devices 21 and 22 for supplying a direct current between the first and second power supply devices 21a and 22a for a predetermined time. A loading table 16 is provided next to the first electrodeposition tank 11, a first cleaning tank 17 is provided next to the second electrodeposition tank 12 (FIGS. 1 and 2). Although not shown, an unloading table is provided via a second cleaning tank. Loading table 16, 1st
The electrodeposition tank 11, the second electrodeposition tank 12, the first cleaning tank 17, the second cleaning tank, and the carrying-out stand are arranged in a line in this order. The objects to be coated 13a, 13 before electrodeposition coating, on which a hanger 18 (FIGS. 1 to 4) is attached on the upper surface of the loading table 16 are shown.
b is placed.

The first and second electrodes 21a and 22a are formed of the same material, respectively, and the first and second electrodeposition tanks 11 and 22a are respectively formed.
12, the same first and second coating liquids 11a and 12a are stored (FIGS. 1 and 2). Also, the first cleaning tank 1
The cleaning liquid 17a is stored in each of the seventh and second cleaning tanks. Although not shown, the first and second electrodeposition tanks 11 and 12 are connected by a circulation pipe and a communication pipe. A pump (not shown) is provided in the circulation line, and the first and second coating liquids 11 are provided.
The first and second coating liquids 11a and 12a are made uniform by circulating the first and second coating liquids 11a and 12a by circulating the first and second coating liquids 11a and 12a by a pump.
The liquid levels of a and 12a are equalized. The first and second coating liquids 11a and 12a are configured to be able to be separated into a concentrated liquid and a filtrate 17a by a filtering device (not shown) provided in a pipe (not shown) branched from the circulation pipe. The concentrate is supplied to the second electrodeposition tank 12, and the filtrate 17a is supplied to the second washing tank, and the filtrate 17 overflowing from the second washing tank is supplied.
a is supplied to the first cleaning tank 17, and the filtrate 17 a having a higher paint concentration and overflowing from the first cleaning tank 17 is supplied to the second electrodeposition tank 12.

The transport device 14 is provided horizontally from above the loading table 16 to above the first electrodeposition tank 11, the second electrodeposition tank 12, the first cleaning tank 17, and the second cleaning tank, and above the carry-out table. The belt conveyor 19, the loading table 16, the first electrodeposition tank 11, the second electrodeposition tank 12, the first cleaning tank 17, the second cleaning tank, and the unloading table are disposed opposite to each other.
a loading lifter 23 capable of raising and lowering a and 13b, a first electrodeposition lifter 24, a second electrodeposition lifter 25, a first cleaning lifter 26,
A second cleaning lifter (not shown) and a carry-out lifter (not shown) are provided. The belt conveyor 19 has a pair of belt wheels 19a (FIGS. 1 and 2) and an endless annular belt 19b stretched over these belt wheels 19a (FIG. 1).
~ FIG. 4). Among the belts 19b, a belt 19b that is stretched under a pair of belt wheels 19a has an opening 19e on the lower surface.
(See FIGS. 3 and 4). A plurality of locking pieces 19c are fixed to the belt 19b at predetermined intervals, and these locking pieces 19c are connected to the conveyor rail 19d.
(FIGS. 1 to 4).

The loading lifter 23 has a first lifter pole 23a erected on the floor so as to face the front and rear surfaces of the loading table 16, and a pair of lifters 23 which are fitted into the first lifter pole 23a and can move up and down along the lifter poles 23a. And a pair of lifter rails 23b provided integrally with these lifter arms and parallel to the belt 19b (FIGS. 1 and 2). First electrodeposition lifter 24, second electrodeposition lifter 25, first cleaning lifter 2
6 and the second cleaning lifter are the first electrodeposition tank 11 and the second electrodeposition tank 1
2. second to fifth lifter poles 24a, 25a, 26a (fifth lifter pole not shown) standing on the floor so as to face the front and rear surfaces of the first cleaning lifter 17 and the second cleaning lifter, respectively; The second to fifth lifter poles 24a,
25a and 26a and these lifter poles 24
a, 25a, 26a, the second to fifth lifter arms 24c, 25c (fourth and fifth lifter arms are not shown), and the second to fifth lifter arms 24c, 25c
And second and fifth lifter rails 24b, 25b, 26b (the fifth lifter rail is not shown) which are provided integrally with the belt 19b (FIGS. 1 to 3). The unloading lifter is not shown, but a sixth lifter pole erected on the floor so as to face the front and rear surfaces of the lifter, a sixth lifter arm fitted into the sixth lifter pole and capable of moving up and down along the lifter pole, A sixth lifter rail is provided integrally with the sixth lifter arm and is parallel to the belt 19b.

The first to sixth lifter rails 23b, 24b,
Reference numerals 25b and 26b are formed of a C-shaped channel material having an opening 25d on the lower surface, respectively.
The hanger 18 attached to the upper surface of the b has rollers 18a (FIG. 4) that can roll on the inner bottom surfaces of the first to sixth lifter rails 23b, 24b, 25b, 26b. Conveyor 1
9 or slightly below the conveyor 19,
A pair of first fixed rails 27a are located between the loading table 16 and the first electrodeposition tank 11, and a pair of second fixed rails 27a are located between the first electrodeposition tank 11 and the second electrodeposition tank 12. The fixed rail 27b is
A pair of third fixed rails 27c are located between the second electrodeposition tank 12 and the first cleaning tank 17, and a pair of fourth fixed rails are located between the first cleaning tank 17 and the second cleaning tank. A rail 27d is located between the second cleaning tank and the carry-out stand, and a pair of fifth fixed rails (not shown) are provided in parallel with the belt 19b (FIGS. 1 to 3). The first to fifth fixed rails 27a,
27b, 27c, 27d are the first to sixth lifter rails 23
The first to sixth lifter rails 23b, 24b, 25b, are formed of the same material as b, 24b, 25b, 26b.
The first to sixth lifter rails 23 when 26b rises
b, 24b, 25b, 26b and first to fifth fixed rails 2
7a, 27b, 27c, 27d are arranged in a straight line. That is, in this state, the rollers 18a in the first to fifth lifter rails 23b, 24b, 25b, 26b are connected to the first to fifth fixed rails 27a, 27b. Rolls inside 27b, 27c, 27d to move between the adjacent second to sixth lifter rails 24b, 25
b, 26b.

The first power supply device 21 is connected to the first electrode 21.
a and a first DC power supply 21b, and the first electrode 21a includes a first DC power supply 21b, a second lifter pole 24a, a second lifter arm 24c, a second lifter rail 24b, and a hanger 18.
Are electrically connected to the objects to be coated 13a and 13b through the terminals (FIGS. 1 and 2). The second energizing device 22 is connected to the second electrode 2.
2a and a second DC power supply 22b. The second electrode 22a includes a second DC power supply 22b, a third lifter pole 25a, a third lifter arm 25c, a third lifter rail 25b, and a hanger 1.
8 are electrically connected to the objects 13a and 13b to be coated. The first and second DC power supplies 21b, 22b are used to supply the first and second coating liquids 11a, 12a of the first and second electrodeposition tanks 11, 12, respectively.
The first and second DC power supplies 21b and 22b are turned on when the objects to be coated 13a and 13b are completely immersed in a. A timer is provided which is turned off a predetermined time after the DC power supplies 21b and 22b are turned on. In the electrodeposition coating apparatus 10, the object 13 to be coated
a, a loading step of 13b, a first coating step in the first electrodeposition tank 11, a second coating step in the second electrodeposition tank 12, a first cleaning step in the first cleaning tank 17, 2
The method includes a second cleaning step in the cleaning tank and a step of carrying out the objects to be coated 13a and 13b in the carry-out stand. First and second
Since the total energization time in the electrodeposition tanks 11 and 12 is usually 2 to 3 minutes, the energization time in the first and second electrodeposition tanks 11 and 12 is 1 to 1.5 minutes. . In addition, the first cleaning time in the first cleaning tank 17 and the second cleaning time in the second cleaning tank are each usually within 1 minute, and the tact time is determined by the first and second coating steps.

In this embodiment, the first and second cleaning tanks are used as the cleaning tank, but one or three or more cleaning tanks may be used. In this embodiment, a dip-type cleaning tank is used, but a spray-type cleaning tank may be used. Further, in this embodiment, the object to be coated is transported by a belt conveyor, but may be transported by a chain conveyor, an air pusher, a shuttle conveyor, or the like.

The operation of the electrodeposition coating apparatus thus configured will be described. First, the first lifter rail 23b is lowered, and the roller 18a of the hanger 18 attached to the first workpiece 13a on the loading table 16 is moved to the first lifter rail 23b.
In this state, the first lifter rail 23b is
It is raised in the direction shown by the solid arrow in FIG. When the belt conveyor is rotated in the direction shown by the dashed arrow, the locking pieces 19
c pushes the first workpiece 13a in the direction of the dashed line arrow, and the first workpiece 13a reaches above the first electrodeposition tank 11 (FIG. 1B). Next, the second lifter rail 24b is lowered, and the first object 13a is inserted into the first electrodeposition tank 11 and immersed in the first coating liquid 11a (FIG. 1C), and the first DC power supply 21b is turned on. Then, a predetermined direct current flows between the first workpiece 13a and the first electrode 21a, and the paint in the first coating liquid 11a is deposited on the surface of the first workpiece 13a. On the other hand, at the same time as lowering the second lifter rail 24b, the first lifter rail 23b is lowered, and the second second lifter rail 23b is placed on the loading table 16 during the energization between the first workpiece 13a and the first electrode 21a. Place the object 13b to be painted,
The roller 18a of the hanger 18 of the second object 13b is inserted into the first lifter rail 23b. First object to be coated 1
After a predetermined time has elapsed from the start of energization between the first electrode 3a and the first electrode 21a, the first and second lifter rails 23b and 24b are simultaneously raised to approximately half the thickness of the subsequent second object 13b. The first coated object 13a on which the coated film is formed is simultaneously pulled up and moved by the belt conveyor 19 above the first and second electrodeposition tanks 11 and 12 (FIG. 2).
(D)).

Next, the second and third lifter rails 24b, 2b
5b at the same time, the second and first workpieces 13
When the b and 13a are inserted into the first and second electrodeposition tanks 11 and 12 and immersed in the first and second coating liquids 11a and 12a, respectively (FIG. 2E), the first and second DC power sources 21b and 22
b is turned on, and predetermined DC currents flow between the second object 13b and the first electrode 21a and between the first object 13a and the second electrode 22a, respectively. 2 The paint in the paint liquids 11a and 12a is the second and first
b and 13a, respectively. Between the second object 13b and the first electrode 21a, and the first object 1
After a lapse of a predetermined time from the start of energization between the first electrode 3a and the second electrode 21a, the second and third lifter rails 24b and 25b are simultaneously raised to form a second half having a coating film having a thickness of about half. And the first object to be coated 13a on which a coating film having a desired thickness is formed, are simultaneously pulled up, and are respectively moved above the second electrodeposition tank 12 and the first cleaning tank 17 by the belt conveyor 19. The third and fourth lifter rails 25b, 2
6b is lowered simultaneously and inserted into the second electrodeposition tank 12 and the first cleaning tank 17 (FIG. 2 (f)). Further, after inserting the first workpiece 13a into the second cleaning tank (not shown),
It is carried out from a carry-out stand (not shown), and the second object 13b is
Is inserted into the first washing tank 17 and the second washing tank, and then carried out from the carry-out stand.

The time during which the object to be coated is exposed to outside air during the transition from the first electrodeposition tank to the second electrodeposition tank is set within about 60 seconds. Further, when the tact time becomes long, after the preceding object to be coated is lowered into the second electrodeposition tank and inserted, after a predetermined time elapses, the subsequent object to be coated is lowered and inserted into the first electrodeposition tank. That is, by delaying the timing at which the subsequent object is lowered to the first electrodeposition tank, the energization time can be kept constant, so that the voltage between the object and the electrode does not need to be changed. Further, it is preferable that the voltage applied between the first electrode and the object to be coated is lower than the voltage applied between the second electrode and the object to be coated. If an excessive current flows at the initial stage of electrodeposition in the first electrodeposition tank, the electrolysis reaction is promoted more than the deposition reaction of the coating film, and a coating defect called gas pin occurs, or the coating film is defective. There is a problem that the thickness of the film becomes uneven. Therefore, by lowering the voltage at the initial stage of the electrodeposition, it is possible to prevent the excessive current from flowing, thereby preventing the occurrence of the problem. Further, it is preferable that the current flowing between the second electrode and the object to be coated is the same as the current flowing between the first electrode and the object to be coated. However, since a coating film having a thickness of about half of a predetermined thickness is already formed on the surface of the object inserted into the second electrodeposition tank, the coating film resistance (electric resistance) is large. In reality, the current flowing between the two electrodes and the object to be coated is smaller than the current flowing between the first electrode and the object to be coated.

[0019]

Next, embodiments of the present invention will be described in detail with reference to the drawings together with comparative examples. <Embodiment> As shown in FIGS.
Is a loading table 16 for loading the workpieces 13a and 13b.
To be coated 13a, 13 provided next to the loading table 16
a first electrodeposition tank 11 for forming a first coating film on the surface of b,
Objects to be coated 13a, 13b provided next to the first electrodeposition tank 11
A second electrodeposition tank 12 for forming a second coating film on the surface of the substrate and a first cleaning of the objects 13a and 13b provided next to the second electrodeposition tank 12 and having the coating film formed on the surface. A first cleaning tank 17 to be performed, and an object 13 to be coated provided next to the first cleaning tank 17.
a second cleaning tank (not shown) for performing the second cleaning of a and 13b, and an unloading table (not shown) provided adjacent to the second cleaning tank and for discharging the washed objects 13a and 13b. And a transfer device 14 provided from above the loading table 16 to above the unloading table, and first and second electrodes 21a and 22b provided inside the first and second electrodeposition tanks 11 and 12, respectively. First and second energizing devices 21 and 22 for flowing a DC current between the objects 13a and 13b are provided.

The objects to be coated 13a and 13b are automobile parts such as side doors in this example, and the first and second electrodeposition tanks 1 are provided.
Each of the volumes 1 and 12 is the same, approximately 120 m ³ .
The first and second electrodes 21a and 22a are formed of a stainless steel material, and the first and second electrodeposition tanks 11 and 12 have the first and second coating liquids 11a and 11a formed of the same cationic electrodeposition coating solution. About 12 tons of 12a are stored. The transport device 14 includes a belt conveyor 19 having a plurality of locking pieces 19c, a loading lifter 23, a first electrodeposition lifter 24, a second electrodeposition lifter 25, a first cleaning lifter 26, and a second cleaning lifter ( (Not shown) and a carry-out lifter (not shown). Loading lifter 23, first electrodeposition lifter 24, second electrodeposition lifter 25, first cleaning lifter 2
6. The second cleaning lifter and the carry-out lifter are first to sixth lifter rails 23b which can be moved up and down along first to sixth lifter poles 23a, 24a, 25a, 26a (fifth and sixth lifter poles are not shown). , 24b, 25b, 2
6b (the fifth and sixth lifter rails are not shown).

The first and second power supply devices 21 and 22 have first and second electrodes 21a and 22a and first and second DC power supplies 21b and 22b, respectively. Also, the first electrodeposition tank 1
1, a voltage of DC 200 V is applied between the objects to be coated 13a and 13b and the first electrode 21a,
The second electrodeposition tank 12 is set so that a current of
Is set so that a voltage of 300 V DC is applied between the objects to be coated 13a and 13b and the second electrode 22a, and a current of 700 A flows at the maximum. The operation of the electrodeposition coating apparatus configured as described above is as described in the above-described embodiment, and a repeated description will be omitted.

<Comparative Example 1> As shown in FIG. 6, the electrodeposition coating apparatus includes a loading table 1 for loading objects 3a and 3b.
And an electrodeposition tank 2 provided next to the loading table 1 and forming a coating on the surface of the objects 3a and 3b to be coated, and an object provided next to the electrodeposition tank 2 and having a coating formed on the surface A first cleaning tank 4 for performing the first cleaning of 3a and 3b, and a second cleaning tank (not shown) provided adjacent to the first cleaning tank 4 for performing the second cleaning of the workpieces 3a and 3b. An unloading table (not shown) provided next to the second cleaning tank for unloading the cleaned objects 3a and 3b.
And a transfer device 5 provided from above the loading table 1 to above the unloading table, and an electrode 6 a provided inside the electrodeposition tank 2.
And an energizing device 6 for flowing a current between the object 3a and the objects 3a and 3b.

The objects to be coated 3a and 3b are the same automobile parts such as side doors as the objects to be coated in the first embodiment.
Has a volume of about 120 m ³ . The electrode 6a is formed of a stainless steel material, and about 130 tons of a coating liquid 2a composed of a cationic electrodeposition coating solution is stored in the electrodeposition tank 2. The transport device 5 includes a belt conveyor 5a having a plurality of locking pieces 5c, a loading lifter 5d, and an electrodeposition lifter 5e.
, A first cleaning lifter 5f, a second cleaning lifter (not shown), and an unloading lifter (not shown). Loading lifter 5d, electrodeposition lifter 5e, first cleaning lifter 5f, second lifter
The cleaning lifter and the carry-out lifter can be respectively moved up and down along first to fifth lifter poles 5j, 5k, and 5m (fourth and fifth lifter poles are not shown). The fourth and fifth lifter rails are not shown). Reference numerals 5n, 5p and 5r are the first,
2 shows second and third fixed rails. The power supply device 6 has an electrode 6a and a DC power supply 6b. A voltage of 250 V DC is applied between the objects 3a and 3b to be coated in the electrodeposition tank 2 and the electrode 6a so that a current of 1200 A at the maximum flows. Is set.

The operation of the electrodeposition coating apparatus thus configured will be described. First, loading stand 1 with 5g of first lifter rail
The first objects to be coated 3a, 3b are raised in the direction indicated by the solid arrows in FIG. 6A, and the locking pieces 5 of the belt conveyor 5a are lifted.
When the first object to be coated 3a is pushed in the direction of the dashed-dotted arrow at c, the first object to be coated 3a reaches above the electrodeposition tank 2. Next, the second lifter rail 5h is lowered, and the first workpiece 3
a is inserted into the electrodeposition tank 2 and immersed in the coating liquid 2a (FIG. 6).
(B)), the DC power supply 6b is turned on, a predetermined current flows between the electrode 6a and the first object 3a, and the paint in the coating liquid 2a deposits on the surface of the first object 3a. I do. On the other hand, the lowering of the second lifter rail 5h and the lowering of the first lifter rail 5g simultaneously with the lowering of the electrode 6a and the first object 3
a, the subsequent second object 3b is placed on the loading table 1 and the hanger 5b of the second object 3b.
Roller (not shown) is inserted into the first lifter rail 5g. After a predetermined time has elapsed from the start of energization, the first and second lifter rails 5g and 5h are simultaneously raised to simultaneously pull up the subsequent second and first workpieces 3b and 3a, and the electrodeposition tank is moved by the belt conveyor 5a. 2 and above the first washing tank 4 respectively.

Next, the second and third lifter rails 5h, 5i
At the same time, the second and first objects to be coated 3b, 3a
Is inserted into the electrodeposition tank 2 and the first cleaning tank 4 and immersed in the coating liquid 2a and the cleaning liquid 4a, respectively (FIG. 6C). When the DC power supply 6b is turned on, a predetermined current flows between the electrode 6a and the second object 3b, and the paint in the coating liquid 2a precipitates on the surface of the second object 3b. Is cleaned. Further, after inserting the first object to be coated 3a into the second cleaning tank (not shown), the first object to be coated 3b was unloaded from the carry-out stand, and the second object to be coated 3b was inserted into the first cleaning tank 4 and the second cleaning tank. rear,
Unload from the loading platform.

Comparative Example 2 As shown in FIGS. 7 and 8,
The electrodeposition tank 7 is formed in a horizontally long shape extending in the longitudinal direction of the belt conveyor 5a, and a second lifter rail 8 provided above and below the electrodeposition tank 7 so as to be vertically movable is divided into two front rails 8a and rear rails 8b. Is done. The front rail 8a is provided with an extruding cylinder 8c for extruding the objects 3a, 3b, 3c suspended on the rail 8a toward the rear rail 8b. The extruding cylinder 8c is extruded on the rear rail 8b. A take-up cylinder 8d that takes out the objects to be coated 3a, 3b, and 3c and that is positioned below the rear rail 8b is attached. The volume of the electrodeposition tank 7 is about 260 m ³ ,
Approximately 280 tons of a coating liquid 2a composed of a cationic electrodeposition coating solution is stored in the electrodeposition tank 7. A DC 30 is provided between the electrode 9a and the workpieces 3a, 3b, 3c in the electrodeposition tank 7.
It is set so that a voltage of 0 V is applied and a current of 1500 A at maximum flows. Except for the above, the configuration is almost the same as the electrodeposition coating apparatus of Comparative Example 1. 7 and FIG.
The same reference numerals indicate the same parts.

The operation of the electrodeposition coating apparatus thus configured will be described. First, the first lifter rail 5g is lowered, and a roller (not shown) of the hanger 5b attached to the first workpiece 3a on the loading stand 1 is inserted into the first lifter rail 5g. Fig. 7 (a)
In the direction indicated by the solid arrow. Belt conveyor 5
is rotated in the direction indicated by the dashed arrow, the locking piece 5c pushes the first workpiece 3a in the direction of the dashed-dotted arrow, and
Is reached above the electrodeposition tank 7. Next, the front rail 8a of the second lifter rail 8 is lowered, and the first object 3a is inserted into the electrodeposition tank 7 and immersed in the coating liquid 2a (FIG. 7 (b)). A predetermined direct current flows between the first workpiece 3a and the electrode 9a, and the paint in the coating liquid 2a precipitates on the surface of the workpiece 3a. On the other hand, the first lifter rail 5g is lowered at the same time as the front rail 8a is lowered, and the first object 3a and the electrode 9 are lowered.
a, the subsequent second object 3b is placed on the loading table 1 and the hanger 5b of the second object 3b.
Roller (not shown) is inserted into the first lifter rail 5g. Also, during the energization, the rear rail 8b of the second lifter rail 8 is lowered to coincide with the front rail 8a.

Next, after a predetermined time has elapsed from the start of energization between the first object to be coated 3a and the electrode 9a, the object to be coated 3a is immersed in the coating liquid 2a and the extrusion cylinder 8 is energized.
c extrudes toward the rear rail 8b, and
Is taken up by the take-up cylinder 8d and positioned below the rear rail 8b (FIG. 7 (c)). In this state, the energization is further continued. During this energization, the first lifter rail 5g and the front rail 8a are raised, and the subsequent second workpiece 3b is moved below the front rail 8a by the belt conveyor 5a (FIG. 7). (D)). The first workpiece 3a is connected to the rear rail 8b.
After a predetermined time elapses after moving the second object 3b downward, the second object 3b starts to descend, and the second object 3b
Before touching a, the power supply is stopped, and the first workpiece 3a is raised. The end of the lowering of the second object 3b and the first
8 is finished simultaneously (see FIG. 8).
(E)).

At the same time when the lowering of the second object 3b is completed, the energization between the second object 3b and the electrode 9a is started.
Simultaneously with the completion of the lifting of the first workpiece 3a, the first workpiece 3a is moved above the first cleaning tank 4 by the belt conveyor 5a, and the third lifter rail 5i is lowered to move the first workpiece 3a. 3a is inserted into the first cleaning tank 4 (FIG. 8 (f)). The rear rail 8b is also lowered simultaneously with the lowering of the third lifter rail 5i, and after a predetermined time has elapsed from the start of energization, the second workpiece 3b is moved from below the front rail 8a to below the rear rail 8b ( FIG. 8 (g)). In this state, energization is further continued, and during this energization, the first lifter rail 5g and the front rail 8a are raised, and the subsequent third workpiece 3c is moved below the front rail 8a by the belt conveyor 5a (FIG. 8). (H)). Stop the energization and apply the second object 3b
At the same time as the first object 3a is raised,
The second and first objects to be coated 3b and 3a are moved above the first cleaning tank 4 and the second cleaning tank (not shown). Further first
After the object to be coated 3a is inserted into the second cleaning tank, the object is unloaded from a carry-out stand (not shown), and the second object to be coated 3b is inserted into the first cleaning tank 4 and the second cleaning tank and then unloaded. Remove from table.

<Comparative Test and Evaluation> The total energization time in the first and second electrodeposition tanks of the example was 120 seconds, and the energization time in the electrodeposition tanks of Comparative Examples 1 and 2 was respectively 12
The cycle time was set to 0 second, and the tact time and the coating quality of the coating film on the surface of the object to be coated were compared by each of the electrodeposition coating apparatuses of Example, Comparative Example 1 and Comparative Example 2. The transfer time of the object to be coated on the tank by the belt conveyor is set to 20 seconds, the descent time of each lifter in a state where the object to be coated is suspended is set to 30 seconds, and each lifter in a state where the object to be coated is not hung is set. Was set to 20 seconds. Further, the lift time of each lifter was set to 20 seconds, and the transport time in the tank for moving from the front rail to the rear rail while the object to be coated of Comparative Example 2 was immersed in the coating liquid was set to 30 seconds. The result is shown in FIG.

As is clear from FIG. 5, the takt times of the embodiment, comparative example 1 and comparative example 2 are 130 seconds and 1 respectively.
It was 90 seconds and 140 seconds, and the tact time by the apparatus of the example was the shortest. The coating quality of the coating film on the surface of the object to be coated was substantially uniform in Examples and Comparative Example 1 while the coating thickness in Comparative Example 2 was partially uniform. It was uneven. In the embodiment, the transition time from the start of pulling the object to be coated from the first electrodeposition tank to the completion of the insertion into the second electrodeposition tank is 70 seconds, and the time during which the object to be coated is exposed to the outside air at the time of the above-mentioned transition. Was about 60 seconds.

[0032]

As described above, according to the present invention, the painting step comprises the first painting step and the second painting step of painting the same paint, and the second painting step is performed within a required time after the end of the first painting step.
Since the process shifts to the painting process, the takt time can be reduced while securing a predetermined energizing time in the painting process. Further, the first and second electrodeposition tanks adjacent to each other have the same electrode inside and store the same coating liquid,
In the state where the transfer device holds a large number of objects to be coated separately,
The objects to be coated are inserted into the first and second electrodeposition tanks one at a time or at the same time or at different timings, and are simultaneously pulled up and transported on the first and second electrodeposition tanks. If a configuration is adopted in which a DC current is applied for a predetermined time between the two workpieces separately immersed in the coating liquid in the coating tank and the electrode, the surface of the workpiece in the second electrodeposition tank is During the formation of the second coating film, the first coating film is formed on the surface of the subsequent object to be coated in the first electrodeposition tank, so that a predetermined energizing time is secured and the tact time is reduced. it can.

When the tact time becomes longer,
By delaying the timing at which the workpiece is lowered into the first electrodeposition tank, the energization time can be kept constant, so that the voltage between the workpiece and the electrodes does not need to be changed. Furthermore, the electrodeposition coating of the present invention is compared with a conventional improved electrodeposition apparatus in which the distance between the object to be coated and the electrode is changed, so that the coating quality on the surface of the object is reduced. In the apparatus, the distance between the object to be coated and the electrode does not change, and the time during which the object to be coated is exposed to the outside air during the transition from the first coating step to the second coating step is short. It does not degrade the wraparound quality of the film.

[Brief description of the drawings]

FIG. 1 is a process diagram of the first half of electrodeposition coating by an electrodeposition coating apparatus according to an embodiment of the present invention.

FIG. 2 is a process chart of the latter half of the electrodeposition coating.

FIG. 3 is a perspective view of a main part including first and second electrodeposition tanks of the electrodeposition coating apparatus.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is a diagram showing a time cycle of electrodeposition coating by the apparatuses of Examples, Comparative Examples 1 and 2.

FIG. 6 is a process chart of electrodeposition coating by the electrodeposition coating apparatus of Comparative Example 1.

FIG. 7 is a process diagram of the first half of electrodeposition coating by the electrodeposition coating apparatus of Comparative Example 2.

FIG. 8 is a process chart of the latter half of the electrodeposition coating.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 electrodeposition coating apparatus 11, 12 electrodeposition tank 11 a, 12 a coating liquid 13 a, 13 b object to be coated 14 transport means 21, 22 energizing device 21 a, 22 a electrode

Claims (2)

[Claims] 1. An electrodeposition coating method including a coating step and a cleaning step, wherein an electrodeposition coating step is performed in a flow operation in the order of the steps, and a time required for the coating step is a tact time. An electrodeposition coating method comprising a first coating step and a second coating step for coating, and shifting to the second coating step within a required time after the end of the first coating step. 2. The same coating liquid (11a, 12a) disposed adjacent to each other and having the same electrode (21a, 22a) therein.
In the state where the first and second electrodeposition tanks (11, 12) in which are stored and a large number of objects to be coated (13a, 13b) are sequentially supplied, and these objects (13a, 13b) are separately held, The first and second
The objects to be coated (13a, 13b) are inserted into the electrodeposition tanks (11, 12) one by one at the same time or at different timings, and are simultaneously pulled up to lift the first and second electrodeposition tanks (11, 12). And a transfer device (14) for transferring the first and second electrodeposition tanks (11, 1) by the transfer device (14).
2) A DC current is applied for a predetermined time between the two objects (13a, 13b) and the electrodes (21a, 22a) which are separately inserted in the coating liquid (11a, 12a) and immersed in the coating liquid (11a, 12a). An electrodeposition coating apparatus including an energizing device (14).