JPS6319228B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of painting an automobile body, and more particularly to a method of applying a chipping-resistant paint to an outer panel of a vehicle body, including side sills and a lower part of a fender, by partially changing the thickness of the coating film. Generally, in the car body painting process, in order to protect the car body surface from pebbles etc. thrown up when the car is running and improve chipping resistance, the outer skin of the car body, including the side sills and the lower part of the fender, is coated with an undercoat. A chipping-resistant paint such as a vinyl chloride resin paint is applied to the surface of the paint to form a resilient paint film. When applying chipping-resistant paint in this way, conventionally the so-called airless method, in which the paint itself is pressurized and ejected from a paint gun, is used, which has a high adhesion rate to the exterior of the car body and has excellent painting efficiency. Painting is performed using a spray painting method. By the way, in recent years, car bodies have been formed with the lower part of the door curved inward for design reasons, and for such car bodies, chipping-resistant paint is applied not only to the side sills and the lower part of the fender. It is necessary to apply a relatively wide coating width to the bottom of the door (above the side sill). In that case, for the upper part of the car body to be painted, the difference in level between the painted part and the non-painted part (upper part of the car body) should be reduced to give a beautiful appearance to the parting line between the two. In order to improve chipping resistance, the paint was applied thinly to make the film thickness relatively small, while for the lower part, in order to improve chipping resistance, the paint was applied thicker and the film thickness was compared. There is a demand for a larger target. However, in order to meet such requirements, when a part of the painted area is overcoated using the above airless spray coating method, a build-up of paint, called a tail, which is unique to the airless spray coating method, occurs at the upper and lower ends of the coated area. A problem arises in that the appearance of the paint film deteriorates due to this. Instead of using the airless spray coating method, which generates such tails, the above chipping-resistant paint can be applied by applying the above-mentioned chipping-resistant paint using the conventional air spray coating method, in which the paint is sucked out by a negative pressure in a bench by increasing the flow rate of compressed air and ejected from the paint gun. When painting, compressed air causes the previously applied paint to wave, causing a so-called waving phenomenon, which deteriorates the appearance of the paint film, as well as the so-called overspray phenomenon, where the paint flows to non-painted areas with the flow of air, causing the paint to undulate. A problem arises in that the rate of adhesion of the paint to the outer panel of the vehicle body decreases, resulting in a significant decrease in coating efficiency. The present invention satisfies the above requirements and eliminates the above drawbacks. First, the lower parts of the car body, such as the side sills and the lower part of the fender, which require a thick coating, are air-sprayed to a predetermined width, and then the car body By applying airless spray coating to the entire part to be painted while masking the upper non-painted part, it eliminates the occurrence of paint film appearance defects such as tails, and while efficiently painting the entire part to be painted. It is possible to paint the upper part thinly and the lower part thickly, thereby improving the coating efficiency and appearance of the paint film when applying chipping-resistant paint to the outer panel of the car body by partially changing the film thickness. The purpose is to improve the quality of the environment. Therefore, the configuration of the present invention is such that after painting a predetermined width of the vehicle body outer panel including at least the side sills and the lower part of the fender of the automobile body by air spray painting, the upper vehicle body outer panel is masked at a distance from the air spray painted portion. In this state, the air-spray-painted portion and the outer panel of the vehicle body in the above-mentioned spaced portions are painted by an airless spray coating method, thereby efficiently applying chipping-resistant paint to the vehicle body and making the appearance of the paint film beautiful. This is how it was done. Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a car body A to be painted by the painting method of the present invention, in which 1 is a side sill, 2 is a front fender, 3 is a rear fender, and 4 is a door. Thus, the side portion of the vehicle body A is constituted. When applying a chipping-resistant paint after applying an undercoat to such a car body A, a second coating is applied.
As shown in the figure, first, the outer panel of the vehicle body including the side sill 1 and the lower part of both fenders 2 and 3 (the area marked with diagonal lines in the upper left direction in Figure 1) is coated with chipping-resistant paint such as vinyl chloride resin paint. 5 is applied to a predetermined width by an air spray coating method in which the compressed air is sucked out by a bench lily negative pressure due to an increase in the flow rate of compressed air and ejected from a coating gun 6, thereby forming an air spray coating film 7 having an average film thickness of about 100 μm. In that case, when the vehicle body A is painted by the air spray painting method described above, a so-called overspray phenomenon occurs in which the paint 5 moves to non-painted areas along with the flow of air, and the paint 5 is ejected from the paint gun 6. The disadvantage of the air spray painting method, which is that the amount of paint is small and the painting efficiency is low, is that the area to be painted is limited to the lower part of the car body A, mainly the side sill 1 and the lower part of both fenders 2 and 3, and its vertical width is small. , Paint gun 6 and car body outer panel (side sill 1)
etc.), and a good coating film can be formed with just one coat without multiple coats, so there is no substantial decrease in coating efficiency. . In addition, since only one air spray painting is required in this way, there is no waving of the paint film due to air pressure that occurs when multiple coats are applied, and there is no tailing that occurs with airless spray painting. The surface of the coating film 7 becomes smooth and beautiful. Next, a masking sheet 8 is applied to the upper body outer panel (the upper parts of both fenders 2 and 3 and the door 4) at a predetermined distance from this air spray painted part (air spray coating film 7). Masking is done by pasting or placing a masking plate near the painting gun, and in the masked state, the above air spray painting area and the air spray painting area and the masking sheet 8
(Masking plate) The outer panel of the vehicle body (the area indicated by diagonal lines in the upward right direction in Fig. 1) is airless spray coated by pressurizing the chipping-resistant paint 5 and spraying it from the paint gun 9. An airless spray coating film 10 having an average film thickness of about 200 μm is formed by coating by a method. In this case, in the above airless spray coating method, the amount of paint 5 ejected from the paint gun 9 is large, and the overspray phenomenon does not occur, so that the paint can be applied efficiently. Furthermore, since the surface of the air spray coating film 7 before airless spray painting is smooth and beautiful as described above, the surface of the airless spray coating film 10 formed thereon can also be beautiful. . Furthermore, when painting with the above-mentioned airless spray coating method, tails occur at the upper and lower ends of the applied area, but the tails occur on the masking sheet 8 (masking plate) when they are on the upper side, and on the masking sheet 8 (masking plate) when on the lower side. This occurs at the lower end of the side sill 1, etc., which is difficult to see from the outside, or paint 5 is applied to the lower part of the outer skin of the vehicle.
This does not occur due to scattering of particles, and the appearance of the coating film can therefore be improved. Thereafter, the masking sheet 8 (masking plate) is removed, and both the coating films 7 and 10 are baked and hardened. The above completes the painting of the automobile body according to the present invention. Therefore, since the upper part of the coating film formed in this way is composed only of the airless spray coating film 10 and has a thin film thickness of about 200 μm, there is a difference between the painted part and the non-painted part that will be formed after the masking sheet 8 is removed. The difference in level between the two is small, and the appearance of the parting line between the two is good. On the other hand, the lower part of the coating film is composed of both the air spray coating film 7 and the airless spray coating film 10, and the film thickness is about 300μ, so
The chipping resistance is greatly improved and the outer panel of the vehicle body can be reliably protected. Next, to explain a specific example, first, a vinyl chloride resin paint with a paint viscosity of 18,000 to 28,000 enchipoise (cps) is applied to the lower part of the outer panel of an automobile that has undergone the undercoating process (the lower part of the side sill and fender). Then, apply the same paint as above to the entire area to be coated with a larger spray pattern width using an airless spray coating method, and then apply the same paint as above to the entire area to be coated using an airless spray coating method in a small spray pattern width. The film thickness is approx.
A coating film was formed with a thickness of 200μ and a lower film thickness of approximately 300μ.
The coating conditions in that case are as shown in Table 1 below.

[Table] In addition to the coating according to the method of the present invention, coating was also carried out using seven comparative methods. That is, the comparison methods are Comparative Method 1, in which a part (lower part) of the part to be painted is air-sprayed and then the whole is also air-spray-painted, and Comparative Method 2, in which a part is airless-spray-painted and then the whole is air-spray-painted. Comparative method 3, in which a part is airless spray-painted and then the whole is also airless spray-painted,
Namely, there are three methods similar to the present invention in which a part of the part to be painted is first painted and then the entire part is painted from above, and a comparative method in which the whole part to be painted is airless spray coated and then a part is air spray painted. 4,
Comparative method 5: air-spray painting the whole part and then air-spray-painting a part; Comparative method 6: air-spray-painting the whole part, then air-spray-painting a part; and comparison method 6: air-spray-painting the whole part, then air-spray painting a part. There is a comparison method 7, that is, four methods in which the entire part to be painted is first painted and then a part is painted over it. Incidentally, the coating conditions and coating film thickness in these comparative methods were set to be the same as in the above-mentioned method of the present invention. Then, the appearance of the paint film and the presence or absence of overspray of the coated parts painted by the method of the present invention and comparative methods 1 to 7 were inspected, and the test results are summarized in Table 2 below.

[Table] As is clear from Table 2, the painted parts painted by the method of the present invention were coated with other comparative methods 1 to 7.
There is no waving or tailing that occurs on the painted parts, and a good paint film appearance can be obtained, and there is no overspray, so there is no loss of paint, and the painting can be done efficiently. I understand. As explained above, according to the present invention, after the outer panel of the vehicle body including the side sills and the lower part of the fender is coated to a predetermined width using an air spray coating method, the outer panel of the vehicle body above the side sill and the lower part of the fender is coated with a predetermined width. By masking the board and painting the above-mentioned air spray painted areas and interval areas using the airless spray painting method, the chipping-resistant paint can be applied efficiently by suppressing the occurrence of overspray, and the appearance of the paint film is not wavy. While maintaining good quality with no tails or tails, the thickness of the coating on the upper part of the painted area is thinner to create a beautiful parting line from the non-painted area, while the thickness of the lower coating is thickened to prevent chipping. As a result, it is possible to improve the appearance of the paint film and improve the coating efficiency when applying chipping-resistant paint to an automobile body by partially changing the film thickness.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a side view of an automobile body, and FIG. 2 is a schematic explanatory diagram showing a painted state. A...Vehicle body, 1...Side sill, 2...Front fender, 3...Rear fender, 4...Door,
5...Chipping-resistant paint, 7...Air spray coating film, 8...Masking sheet, 10...Airless spray coating film.

Claims (1)

[Claims] 1. After painting a predetermined width of the car body outer panel including at least the side sills and the lower part of the fender of the automobile body by air spray painting method, apply the air spray coating while masking the upper car body outer panel at a distance from the air spray painting part. A method for painting an automobile body, characterized in that the outer panel of the vehicle body in the painted portion and the above-mentioned spaced portion is painted by an airless spray coating method.