JP2668088B2 - How to paint the body - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for coating a vehicle body, and more particularly to a method for coating a vehicle body in which heating and drying are performed after spray coating.

(Prior Art) When painting a vehicle body with a spray gun, electrostatic painting is used to increase the coating efficiency, which is the adhesion rate of the paint to the vehicle body.

In this electrostatic coating, a high voltage generator is used to create a potential difference between the vehicle body and the spray gun, and the coating particles blown out from the spray gun are configured to be attracted to the outer wall surface of the vehicle body using electrostatic force. Was there.

(Problems to be Solved by the Invention) By the way, the steel sheet to which the voltage is applied in this way has a required electric potential over the entire outer wall surface, but the electric potential is not uniform. It is known that the electric potential becomes high.

For example, as shown in FIGS. 3 and 4, when an outer panel 1 of a vehicle door is electrostatically coated, a potential is applied to the outer panel 1. In this case, the outer plate 1 is formed with a mounting hole 2 for a door handle and a mounting hole 3 for a key cylinder below the door handle, and the edges 201 and 301 of these holes have a higher potential than peripheral portions thereof. . However, in this case, the mounting hole 2 of the door handle has its edge 201 turned inward and extends in the horizontal direction, so that the potential maximization is small. Edge 301
Is formed in the up-down direction while facing the outside, and there is a tendency that the maximization of the potential of the same portion is particularly large.

When the electrostatic coating is performed in such a state, the sprayed coating particles are sucked toward the outer wall surface to form the coating film 4. In particular, a large amount of paint that has adhered to the edge portion 301 of the key cylinder mounting hole 3 causes dripping 401 immediately below the edge 301 immediately after the application of this paint.

For this reason, when coating an outer plate having a hole in the vertical direction, the amount of coating at the time of coating is regulated.
There is a problem that it becomes difficult to secure a sufficient thickness.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for coating a vehicle body that can ensure a sufficient thickness of a coating film of a vehicle body component plate having a hole.

(Means for Solving the Problems) In order to achieve the above-described object, the present invention provides a method for spraying and painting an outer surface of a vehicle body component plate having a hole formed therein. It is characterized by performing a drying step of heating and drying in a drying chamber using a heating source, and in particular, joining a backup material formed in a film shape with a low melting point alloy to a back side edge of a hole portion of the vehicle body component plate. After that, it is characterized in that the above-mentioned painting process is started.

(Operation) Since the back-up material is attached to the back surface side edge of the hole, the potential of the edge is not maximized, and the back-up material can be eliminated during heating and drying after coating.

(Example) Hereinafter, a method for coating a vehicle body of the present invention will be described with reference to FIG.

FIG. 1 shows a case where a backup material 11 is adhered to an outer plate 10 of a door as a vehicle body component plate.

The outer plate 10 here is that of a door 12 of a passenger car C shown in FIG. 2, and a door handle 13 and a key cylinder 14 are attached to an upper portion thereof.

The outer surface 15 of the outer plate 10 is formed as a substantially vertical surface that keeps a required curvature extending vertically, and a hole for mounting the door handle 13 (not shown) and a key cylinder mounting hole for mounting the key cylinder 14 directly below the upper surface of the outer surface 15. 15 are formed.

The vehicle C having such a door 12 performs a joining process of the backup material 11 shown in FIG. 1A after the undercoating process, the washing process, and the drying process of the vehicle body.

The backup material 11 used here is formed of a low melting point alloy film. This low melting point alloy film is selected and used by being heated and dried in the heating and drying step.
The conditions are, for example, (1) those that completely melt and fall off in a heating process at 150 ° C for 30 minutes. (2) Do not promote corrosion of the vehicle body when it remains in the vehicle body. If possible, have sacrificial corrosion. Therefore, the standard electrode potential is -0,440VvsSHE (Saturat Hydrogen Electrode) of iron.
It must be lower. (3) The electrostatic characteristics are equal to or slightly higher than those of iron. (4) Do not contain elements that are harmful to the human body.

Examples of the low melting point alloy that satisfies all of the above conditions include Bi 20 to 60 (%), Sn 40 to 80 (%), and Zn (remainder).
The alloy of can be used.

The backup material 11 is formed into a film having a required thickness by the low melting point alloy having such characteristics. This backup material
Numeral 11 has a joint area enough to cover the entire key cylinder mounting hole 15, and the thickness T is selected to be a thickness that can maintain shape retention as a film at the time of sticking.

Such a backup material 11 is adhered to the back surface of the outer plate 10 at a position covering the key cylinder mounting hole 15 with an appropriate adhesive.

Thereafter, the vehicle body transferred to the coating room SB is subjected to middle coating or top coating with a predetermined coating material by a spray gun 17 supported by a well-known coating robot arm 16. In this case, the high pressure generator 18 between the vehicle body side and the paint side,
It is charged by applying a voltage of −60 to −90 kV.

In this case, the edge 151 of the key cylinder mounting hole can suppress the potential maximization by the function of the backup material 11. Therefore, the thickness T of the coating film 19 does not increase sharply at the edge 151, and the coating film thickness is almost uniform at the portions of the outer plate 10 and the backup material 11 facing the holes.

After that, the vehicle body is transported to the drying chamber DB and heated and dried by the heating source 20 such as an infrared lamp for a required time. here,
With the vehicle body surface temperature kept at 150 ° C. or higher, the vehicle body is dried for 40 Mmin, the drying step is completed, the process proceeds to the next cooling step, etc., and the intermediate coating and top coating of the vehicle are completed. In this heating and drying process, backup material
11 is heated sufficiently, melts, and falls downward. The molten fallout adheres to, for example, the bottom plate inside the door, but since the material of the backup material 11 exhibits sacrificial corrosion, it does not promote corrosion of the vehicle body.

As described above, in the method of the present invention, the backup material 11 can prevent the paint from excessively adhering to the edge 151 of the key cylinder mounting hole 15, and therefore, the paint does not turtle from the edge 151, and as a result, The coating film thickness T can be made sufficiently thick.

In particular, the backup material 11 melts and falls off in the heating and drying step, and the work of removing the backup material 11 is not required, and the workability is good.

Although the backup material is melted in the above-mentioned place, it may be formed of a material having good conductivity such as aluminum foil. In this case, the aluminum foil will be removed after use. Further, although the backup material 11 is adhered to the back surface of the outer plate 10, it may be point-adhered by an adhesive tape in some cases.

(Effect of the Invention) As described above, according to the method of the present invention, the maximization of the potential of the edge of the hole can be prevented by the bonding process of the backup material, so that the paint dripping can be suppressed and the coating film thickness can be made relatively large. Done,
In particular, the backup material can be eliminated during heating and drying after painting, and workability can be improved.

[Brief description of the drawings]

1 (a), 1 (b) and 1 (c) are process explanatory views for explaining main steps of the method of the present invention, FIG. 2 is a schematic perspective view of a vehicle having a door shown in FIG. 1, and FIG. FIG. 4 is a cross-sectional view of an outer plate coated by a conventional method, and FIG. 4 is a side cutaway view of a main part of the outer plate of FIG. 10 …… Outer panel, 11 …… Backup material, 12 …… Door, 15…
... key cylinder mounting hole, 151 ... edge, 17 ... spray gun, 20 ... heating source, SB ... painting room.

Claims (1)

(57) [Claims] 1. A drying step of performing a coating step of spray-coating an outer surface of a vehicle body component plate having a hole formed therein, and then heating and drying the vehicle body component plate in a drying chamber using a heating source. In the method for coating a vehicle body, the backup material formed in a film shape from a low-melting alloy is joined to the back surface side edge of the hole of the vehicle body component plate, and then the coating process is started. How to paint the car body.