JPH07188986A - Electrodeposition coating method of automotive body - Google Patents

Abstract

PURPOSE:To surely form uniform coating films over the entire part of an automotive body with extremely simple control. CONSTITUTION:The automotive body W immersed in a horizontal posture into an electrodepositing tank 12 is subjected to electrodeposition coating of respective surfaces to be coated in the first cycle time set at a relatively short time and is then further subjected to electrodeposition coating on the surfaces to be coated in the second cycle time set at a relatively long time. The thin film-like coating films formed on the respective surfaces to be coated of the automotive body W with coating by the first cycle time prohibit concentrated flow of currents to parts in proximity to electrodes 14 and 16 during coating by the second cycle time. The formation of the uniform coating films by the second cycle time is thus made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrodeposition coating method for an automobile body in which the vehicle body is rocked in an electrodeposition tank to apply the electrodeposition coating to the vehicle body.

[0002]

2. Description of the Related Art Generally, the work of applying electrodeposition coating to the entire surface of an automobile body by immersing the automobile body in an electrodeposition tank is widely performed.

As a method of performing this type of electrodeposition coating, as disclosed in Japanese Patent Laid-Open No. 64-75700, a vehicle body immersed in an electrodeposition tank is placed in a rollover posture in which the vehicle width direction is oriented vertically. There is known a technique of intermittently swinging about the vehicle length direction as an axis while stationary for a certain time. This has the advantage that a desired coating film can be formed on a floor portion of an automobile body where a particularly large film thickness is required.

[0004]

By the way, in the above-mentioned prior art, although the coating film can be intensively formed on the lower portion of the automobile body (floor portion or the like), other coatings such as the hood, the roof and the door can be formed. It is difficult to form a uniform coating film on the plate portion. Since the coating film is formed intensively on the portion near the electrodes arranged in the electrodeposition tank and where the current easily flows, in order to form a uniform coating film on the entire outer plate portion, the timing of rocking, This is because it is necessary to strictly control the applied voltage and current, the processing time, and the like.

The present invention solves this kind of problem, and provides an electrodeposition coating method for an automobile body capable of reliably forming a uniform coating film on the entire automobile body with extremely simple control. The purpose is to

[0006]

In order to achieve the above object, the present invention sways the vehicle body with the vehicle body immersed in an electrodeposition tank about the vehicle longitudinal direction as an axis. A method of electro-deposition coating an automobile body by performing electro-deposition coating on the automobile body by moving the automobile body, immersing the automobile body in the electrodeposition tank, and then shaking the automobile body at a first cycle time. It is characterized by including a first step of moving the vehicle body and a second step of rocking the automobile body with a second cycle time longer than the first cycle time after the first step.

[0007]

In the electrodeposition coating method for automobile bodies according to the present invention,
In the state where the automobile body is immersed in the electrodeposition tank, first, the automobile body is swung for the first cycle time set to a relatively short time, so that a thin film coating film is formed on the automobile body. Next, the automobile body is swung for the second cycle time set for a relatively long time, so that a coating film having a desired film thickness is formed on the entire automobile body. After that, since the thin film is formed on the car body in advance, the current does not flow partially in the car body in the second step,
A uniform coating film can be obtained over the entire automobile body.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electrodeposition coating method for an automobile body according to the present invention will be described in detail below with reference to the accompanying drawings in connection with an electrodeposition coating apparatus for carrying out the method.

1 and 2, reference numeral 10
Shows an electrodeposition coating apparatus according to the present embodiment. The electrodeposition coating apparatus 10 includes an electrodeposition tank 12 into which an automobile body W is immersed, and a plurality of electrodeposition tanks 12 are arranged in the longitudinal direction corresponding to both side surfaces of the automobile body W. An electrode 14 and a plurality of electrodes 16 arranged in the lateral direction corresponding to the front surface and the rear surface of the automobile body W are provided. In addition, an electrode may be arranged on the bottom surface in the electrode tank 12 as necessary.

A rail member 18 is provided above the electrodeposition tank 12 so as to extend in the direction of arrow A in FIG. 2, and a movable frame 20 is provided on the rail member 18 under the guiding action of a plurality of rollers 22. It is movably held via a drive motor 23.
A pair of hoists 24 is mounted on the upper side of the movable frame 20, and sprockets 28a and 28b are supported by a pair of chains 26 extending from the hoists 24, respectively.

The sprockets 28a, 28b are fixed to the jig 30 so as to face both ends of the vehicle body W in the vehicle length direction (direction of arrow B in FIG. 1), that is, the front and rear surfaces of the vehicle body W. . The jig 30 is configured to support the vehicle body W and swing the vehicle body W about the longitudinal direction of the vehicle body W as an axis.

The upper part of the electrodeposition tank 12 and the jig 30 are surrounded by a booth 32 extending in the direction of arrow A.

Next, the operation of the electrodeposition coating apparatus 10 thus constructed will be described in relation to the electrodeposition coating method according to this embodiment.

First, the movable frame 20 is connected to the rail member 18
The rollers 22 are conveyed in the direction of arrow A via the drive motor 23 under the guiding action of the rollers 22, and the positioning is stopped above the electrodeposition tank 12. Then, the hoist 24 is driven, and one of the chains 26 is pulled out and the other is wound, whereby the sprockets 28a and 28b are rotated at the same height position. As a result, the jig 30 on which the automobile body W is supported is swung 90 ° about the vehicle length direction of the automobile body W at the position shown in FIG. 1, and the automobile body W is vertically moved in the vehicle width direction. The posture is converted into a rollover posture (see FIG. 3A).

Next, when the hoist 24 is driven and both chains 26 are pulled out, the vehicle body W in the rollover posture is lowered integrally with the jig 30 and immersed in the electrodeposition tank 12. Therefore, the electrodeposition process is performed at the first cycle time as shown in FIGS. 3B to 3D (first step).

That is, as shown in FIG. 3B, the vehicle body W is stopped in the electrodeposition tank 12 in a rollover posture for a certain period of time (for example, about 2 seconds), and then, in the clockwise direction in FIG.
After being oscillated by 0 ° and converted to a horizontal posture, the robot stands still for about 10 seconds (see FIG. 3C). The vehicle body W is further oscillated 90 ° clockwise to be converted into the posture shown in FIG. 3D, and is held in this posture for about 2 seconds.
Cycle time ends.

The vehicle body W is swung 90 ° counterclockwise from the posture shown in FIG. 3D (see FIG. 3E), and after resting for about 10 seconds in this posture, it is swung 90 ° counterclockwise. The second cycle time is started (second step).
That is, as shown in FIG. 4A, the vehicle body W is stationary in the electrodeposition tank 12 for about 30 seconds in a rollover posture, and further swung 90 ° to be converted into a horizontal posture.
In this posture, the robot stands still for about 60 seconds (see FIG. 4B). The car body W is further swung 90 ° clockwise, as shown in FIG. 4C.
The posture is converted to the posture shown in and the posture is maintained for about 30 seconds. This ends the second cycle time.

Thereafter, the vehicle body W is lifted up integrally with the jig 30 in the reverse rollover posture, taken out from the electrodeposition tank 12 (see FIG. 4D), and moved in the direction of arrow A through the movable frame 20. Be transported. Above the electrodeposition tank 12,
A new vehicle body W before electro-deposition coating is arranged, and the electro-deposition coating work is performed according to the above procedure.

In this case, in this embodiment, the car body W immersed in the electrodeposition tank 12 in the rollover posture is rocked at the first cycle time set for a relatively short time so that each surface to be coated is swung. After the electrodeposition coating is performed, the surface to be coated is further subjected to the electrodeposition coating at the second cycle time set to a relatively long time. Specifically, the first cycle time shown in FIGS. 3B to 3D is about 26 seconds as a whole because the swing time of the automobile body W is required to be about 6 seconds each, while FIGS. 4A to 4C are shown. The second cycle time shown in (1) is about 132 seconds as a whole.

Therefore, first, a thin film coating film is formed on each surface to be coated such as the roof, the trunk, the hood and the fender of the automobile body W by the coating in the first cycle time. As described above, since the thin film-like coating film is formed on each coated surface in advance, the current is concentrated and flows corresponding to the portions near the electrodes 14 and 16 during the coating in the second cycle time. Can be stopped. Therefore, it is possible to obtain an effect that a coating film having a predetermined film thickness can be uniformly formed on each surface to be coated on which a thin film coating film is previously formed by the coating in the second cycle time. To be Moreover, it is only necessary to set the first cycle time and the second cycle time, and it is not necessary to strictly control the swing timing, applied voltage and current control, processing time, and the like. This has the advantage that a uniform coating film can be formed efficiently and reliably with extremely simple control.

By the way, the result of the electrodeposition coating experiment by the coating method according to the present embodiment is shown in FIG. In the figure, the straight line of the film thickness distribution indicated by the broken line shows the result of the electrodeposition coating experiment when the first cycle time and the second cycle time are the same (conventional method). In this conventional method, since the flow velocity of the electrodeposition liquid on the surface of the automobile body W is high, the coating efficiency is lowered and, for example, a portion such as a trunk or a roof where a necessary film thickness cannot be obtained is generated.

On the other hand, in this embodiment, since the second cycle time is set to a relatively long time, the required film thickness can be obtained especially for the trunk, the roof, etc. It becomes possible to form a uniform coating film over the entire surface.

In this embodiment, the vehicle body W is intermittently oscillated by a predetermined angle (90 °), and the waiting time at each stop position is variously selected, whereby the first cycle time and the second cycle time are set. Although the cycle times are set respectively, the vehicle body W may be continuously swung. At that time, the vehicle body W is continuously oscillated in one direction (eg, clockwise in FIG. 2) at a relatively high speed, while the vehicle body W is compared to the other direction (eg, counterclockwise in FIG. 2). By continuously rocking at a relatively low speed, the first cycle time, which is a relatively short time, is set, and the second cycle time, which is a relatively long time, is set, which is the same as that during the intermittent rocking. The effect will be obtained.

[0024]

The following effects and advantages are obtained by the electrodeposition coating method for automobile bodies according to the present invention.

Since the automobile body is first immersed in the electrodeposition tank and is oscillated at the first cycle time set for a relatively short time (first step), a thin film-like body is formed on the automobile body. Coating film is formed. Next, since the automobile body is oscillated at the second cycle time set for a relatively long time (second step), a coating film having a desired film thickness is formed on the entire automobile body. After that, since the thin film is formed on the automobile body in advance, the electric current does not flow partially concentrated on the automobile body in the second step, which allows the uniform control over the entire automobile body with simple control. The coating film can be formed reliably and easily.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of an electrodeposition coating apparatus for carrying out an electrodeposition coating method for an automobile body according to the present invention.

FIG. 2 is a partially vertical front view of the electrodeposition coating apparatus.

FIG. 3 is an explanatory diagram of a first cycle time of the electrodeposition coating method, FIG. 3A is an explanatory diagram showing a state where an automobile body is arranged above the electrodeposition tank, and FIG. 3B is the electrodeposition tank. FIG. 3C is an explanatory view of a state where the automobile body is immersed in the inside, FIG. 3C is an explanatory view of a state where the automobile body is swung 90 ° clockwise in the electrodeposition tank, and FIG. 3D is inside the electrodeposition tank. The car body is 3C
Explanatory view of a state in which it is swung 90 ° clockwise from the posture of
FIG. 3E is an explanatory diagram of a state in which the vehicle body is swung 90 ° counterclockwise from the posture of FIG. 3D in the electrodeposition tank.

FIG. 4 is an explanatory diagram of a second cycle time of the electrodeposition coating method, and FIG. 4A shows a state in which the automobile body is swung 90 ° counterclockwise from the posture of FIG. 3E in the electrodeposition tank. 4B is an explanatory view of a state in which the automobile body is swung 90 ° clockwise from the posture of FIG. 4A in the electrodeposition tank, and FIG. 4C is a diagram showing the automobile body in the electrodeposition tank. 4B is an explanatory view of a state of being swung 90 ° clockwise from the posture of 4B, FIG.
It is explanatory drawing of the state where the vehicle body was taken out from the said electrodeposition tank.

FIG. 5 is an explanatory diagram of film thickness distribution comparison between the conventional coating method and the coating method of the present embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Electrodeposition coating device 12 ... Electrodeposition tank 14, 16 ... Electrode 18 ... Rail member 20 ... Movable frame 30 ... Jig W ... Automotive body

Claims (1)

[Claims] 1. A vehicle body immersed in an electrodeposition tank,
A method for electrodeposition coating an automobile body by swinging the vehicle body about the longitudinal direction of the vehicle body as an axis, wherein the vehicle body is immersed in the electrodeposition tank. And then swinging the vehicle body for a first cycle time, and swinging the vehicle body for a second cycle time longer than the first cycle time after the first step. A second step of: and a method for electro-deposition coating of an automobile body.