JPS648080B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrodeposition coating apparatus. More specifically, the present invention relates to an electrodeposition coating apparatus that prevents coating defects from occurring.

[Prior Art] Electrodeposition coating apparatuses have been widely used for coating automobile bodies and the like.

In such an electrodeposition coating device, objects to be coated, such as automobile bodies, mounted on movable hangers are sequentially placed in an electrodeposition bath, and the electrodeposition is carried out while the objects are moved from the entry section to the exit section of the bath. It is to be painted. Such an electrodeposition coating apparatus is equipped with a large number of diaphragm electrodes in the tank along the moving direction of the automobile body, and a DC voltage is applied between the diaphragm electrodes and the automobile body. Generally, such applied voltage is consistently applied to all diaphragm electrodes from the start of operation to the end of operation of the electrodeposition coating apparatus.

Furthermore, JP-A No. 54-112949 states that when the object to be coated is moving quickly, all diaphragm electrodes are energized, and when the object to be coated is entering the tank slowly, 1/3 to 1/4 of the diaphragm electrodes are not energized. A coating method has been proposed that prevents the step pattern in the paint film that tends to occur when the tank is in operation and the loading speed is slow. However, this method also
Although there is a difference in whether the diaphragm electrode is energized in its entirety or in part, the above-mentioned general coating method applies a constant voltage from the time the object to be coated enters the tank until it exits the tank. There is no difference.

[Problems to be Solved by the Invention] When painting an automobile body using a conventional electro-deposition coating apparatus, the automobile body Z that is first placed in the electro-deposition bath at the start of the operation of the coating line has a fifth coating.
As shown in the figure, when the paint film is immersed in the paint liquid, uneven streaks M (hereinafter referred to as a stepped pattern) appear in the paint film, which resemble a wave pattern.

The reason for this is that at the start of operation, when no other car bodies are in the electrocoating bath, the current density for the car body that entered the bath first becomes high, resulting in a partially thick coating film. This is thought to be due to the fact that it is easily precipitated. This tendency is particularly strong in the case of cationic electrodeposition paints, since the coulomb yield is high and a coating film is easily formed with a small current.

Also, during the operation of the painting line, one of the car bodies sent sequentially may fall off due to circumstances in the previous process, and the same cause as above will occur for the car body that enters the tank after it falls off. A stepped pattern may occur.

Regarding this point, even in the conventional example disclosed in JP-A-54-112949, the same voltage is applied from entering the tank to exiting the tank, so the occurrence of a stepped tank cannot be eliminated. .

In view of the above circumstances, it is an object of the present invention to provide an electrodeposition coating apparatus that can prevent the occurrence of stepped patterns.

[Means for Solving the Problems] The electrodeposition coating apparatus of the present invention includes a large number of diaphragm electrodes in an electrodeposition bath, and a movable hanger to sequentially feed objects to be coated into the electrodeposition bath. An electrodeposition coating apparatus whose steady operating state is a state in which the objects to be coated are loaded on all movable hangers at the position where the objects to be coated are loaded into the deposition bath, and (a) the objects are sequentially loaded into the tank. (b) a detection means for detecting that a higher priority workpiece is not entering the tank when the workpiece to be painted is entering the tank; and (b) the detection means detects that a higher priority workpiece is not entering the tank. (c) means for cutting off the electricity to some of the diaphragm electrodes provided near the bath entry section, and (c) the object to be coated at the relevant rank enters the electrodeposition bath and advances halfway into the melting bath. The present invention is characterized in that it includes a means for restoring energization to the diaphragm electrode after a certain period of time.

[Function] When using the electrocoating apparatus of the present invention, the number of objects to be coated placed in the electrocoating bath can be reduced, such as when a dropout occurs in the objects to be coated placed in the bath at the start of operation or during operation. If it is less than the steady state of operation, this is detected by the detection means.

When the detection means is activated, electricity to some of the diaphragm electrodes provided near the tank entry section is cut off.
The current density for the objects to be coated entering the tank can be kept at approximately the same level as normal. In addition, the current density in the electrodeposition bath can be kept almost constant throughout the operation because the electricity to the diaphragm electrode can be restored in accordance with the time when the number of objects to be coated that are sequentially fed into the bath reaches the normal number. .

[Example] Next, an example of the present invention will be described based on the drawings.

FIG. 1 is an explanatory diagram of the configuration of an electrodeposition coating apparatus which is an embodiment of the present invention, FIG. 2 is an explanatory diagram of the state of the electrodeposition coating apparatus shown in FIG. 1 at the start of operation, and FIG. An explanatory diagram of the state in which the electrodeposition coating equipment shown in Fig. 1 is in an out-of-service state during operation, Figs. 4a, 4b, and 4c are shown in Figs. 2 and 3 when the electricity supply is cut off. It is an explanatory view showing a state where electricity supply to a diaphragm electrode is restored.

The electro-deposition coating apparatus A shown in FIG. 1 is an electro-deposition coating apparatus for applying coating to an automobile body Z, which is an object to be coated. The electrodeposition bath 1 is of a known type, and a cationic electrodeposition paint is placed in the bath.
A diaphragm electrode 2 is also provided. There are nine diaphragm electrodes 2 (21 to 29) on one side of the electrodeposition bath 1, and 9 on both sides.
There are 18 of them. On the other hand, an automobile body Z is placed on a movable hanger 4 that is moved in the direction of arrow X by a conveyor 3, and is immersed in a progressive electrodeposition bath 1. The diaphragm electrode 2 is connected to the anode of a DC power source, and the automobile body Z is connected to the cathode of the power source via a conductive cable that is in sliding contact with the movable hanger 4. In addition, when an anionic electrodeposition paint is used, a cathode is connected to the diaphragm electrode 2, and an anode is connected to the automobile body Z. Of the diaphragm electrodes 2, the diaphragm electrodes 21, 22 on the inlet side,
23 is configured to be able to freely cut off and restore current flow using a DC electromagnetic contactor. Note that the DC electromagnetic contactor corresponds to means for interrupting current flow in the claims. In this electrodeposition coating apparatus A, the number of automobile bodies Z sequentially placed in the electrodeposition bath 1 is about three in a steady state of operation, and the voltage of the DC power supply has a steady voltage value, for example. It is set to 300V.

In addition to the above configuration, the electrodeposition coating apparatus A of the present invention is additionally provided with limit switches 5 and 6.
This constitutes a detection means for detecting that the water is not entering the tank. For example, when the movable hanger 4 with the car body Z on it comes, the limit switches 5 and 6 come into contact with it and turn ON, but when the car body Z and the movable hanger 4 are not coming, the limit switches 5 and 6 turn on.
It is installed so that it is turned off.
Further, the limit switch 5 is placed in a position where it can be activated slightly before the car body Z enters the electrocoating bath 1, and the limit switch 6 is placed in a position where it can be activated in the initial state when the car body Z is completely immersed in the electrocoating bath 1. located at the location.

With the above configuration, the limit switches 5, 6
If both are ON, it is detected that the car body Z immediately before the car body Z that is about to enter the tank is entering the tank, and limit switch 5 is turned on.
If the limit switch 6 is turned ON and the limit switch 6 is turned OFF, it is detected that no car body Z is entering the tank immediately before the car body Z that is about to enter the tank.

For example, as shown in FIG. 2, when a state-of-the-art car body Z carried by a conveyor 3 is about to enter the electrocoating bath 1 at the start of operation of the electrocoating apparatus A, the car Since there is no movable hanger 4 and the automobile body Z in front of the body Z, in this case, the limit switch 6 is turned off, and it is detected that the automobile body Z is not placed in the electrodeposition bath 1.

Moreover, as shown in FIG.
During operation, if there is no movable hanger and the car body immediately before the car body Z4 being carried by the conveyor 3, when the car body Z4 is about to enter the tank, the limit switch 5 is turned on and the limit switch 6 is turned off, It is detected that only two car bodies Z1 and Z2 are placed in the electrodeposition bath 1.

It is preferable to provide two limit switches 5 and 6 each, because even if one of them fails, normal detection can be performed with the other one.

Furthermore, in the electrodeposition coating apparatus of the present invention, the DC electromagnetic contactor is controlled to be opened and closed by the detection signal from the detection means. For example, the diaphragm electrodes 21, 22, and 23 are shut off all at once by a detection signal indicating that the limit switch 5 is ON and the limit switch 6 is OFF, and then an on-day relay or the like is used to reverse the direction of movement of the automobile body Z. In other words, the energization is controlled to be restored at predetermined time intervals in the order of diaphragm electrode 23 → diaphragm electrode 22 → diaphragm electrode 21. The on-day relay in this case corresponds to the means for restoring energization in the claims. The time interval when electricity is restored is set according to the speed at which the conveyor 3 transports the car body Z.
Before the electrodes enter and leave the electrodeposition bath 1, that is, when electricity is restored to all of the diaphragm electrodes 21, 22, and 23, a constant number of three electrodes are installed in the electrodeposition bath 1. It is preferable that the car body Z is placed in the tank.

Next, electrodeposition coating apparatus A configured as above
The control operation will be explained in detail. If there is a shortage of vehicles at the start of operation or during operation, please refer to Figures 2 and 3.
As shown in the figure, just before the first car body Z and the car body Z4 after the car is out of stock enter the tank, the electricity to the diaphragm electrodes 21, 22, and 23 is cut off all at once. Note that the other diaphragm electrodes are energized.

Next, as shown in FIG. 4a, when the car bodies Z1 and Z4 have their tip portions soaked,
Electricity to the diaphragm electrode 23 is restored. When the automobile bodies Z1 and Z4 are approximately half immersed, the energization to the diaphragm electrode 22 is restored as shown in FIG. 4b. Further, the automobile body Z1, Z
4 is completely immersed, electricity is restored to the diaphragm electrode 21 as shown in FIG. 4c, and the steady state is restored. As described above, in the present invention, the current density when the foremost automobile body Z1 or the automobile body Z4 after the car is out of stock enters the tank can be made to be approximately the same level as the current density in a steady state. As a result, it is possible to effectively prevent the occurrence of stepped patterns on the automobile bodies Z1 and Z4.

Note that even if the applied voltage is temporarily lowered as described above, the quality of the finished coating film is not adversely affected, so that a good painted surface can be obtained.

[Effects of the Invention] The electrodeposition coating apparatus of the present invention can change the number of diaphragm electrodes to be energized depending on the number of automobile bodies placed in the electrodeposition bath. Therefore, the current density can be made substantially uniform during the operation from the start of operation to the end of operation, so that the generation of stepped patterns can be effectively prevented.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of an electrodeposition coating apparatus which is an embodiment of the present invention, FIG. 2 is an explanatory diagram of the state of the electrodeposition coating apparatus shown in FIG. 1 at the start of operation, and FIG. An explanatory diagram of the state in which the electrodeposition coating equipment shown in Fig. 1 is in an out-of-service state during operation, Figs. 4a, 4b, and 4c are shown in Figs. 2 and 3 when the electricity supply is cut off. FIG. 5 is an explanatory diagram showing a state in which electricity is restored to the diaphragm electrode, and FIG. 5 is an explanatory diagram showing problems with the conventional device. (Main symbols in the drawings), 1: electrodeposition bath, 2: diaphragm electrode, 3: conveyor, 4: movable hanger, 5: limit switch, 6: limit switch.

Claims (1)

[Claims] 1 A large number of diaphragm electrodes are provided in the electrocoating bath, and the objects to be coated are sequentially introduced into the electrocoating bath using movable hangers, and all of the movable hangers at the positions where the objects to be coated are introduced into the electrocoating bath. This is an electro-deposition coating device whose steady operating state is when the objects to be coated are mounted on the tank, and (a) when the objects to be coated are placed in the tank sequentially, the objects to be coated in the order of priority are placed in the tank. and (b) when the detection means detects that the priority workpiece is not in the tank, energizing some diaphragm electrodes provided near the tank entry section. and (c) means for restoring energization to the diaphragm electrode after the object to be coated in the relevant rank enters the electrodeposition bath and travels halfway through the bath. Electrodeposition coating equipment featuring: