Coating method and automobile

Abstract

To form a coating film having even thickness on an inclined surface.SOLUTION: According to a coating method, a coating target range 3 on an inclined surface 2 inclined with respect to a perpendicular direction is coated. At this time, a coating film 4 is formed by jetting coating 6 toward the coating target range 3 from a jetting nozzle 5 such that a thickness of a coating film 4U formed in an upper part of the coating target range 3 is thicker than a thickness of a coating film 4L formed in a lower part of the coating target range 3.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a painting method and an automobile painted by the painting method. [Background technology]

[0002] Patent Document 1 below discloses a method for painting inclined surfaces. Paint applied to an inclined surface moves downward due to gravity before it dries, so some ingenuity is required to form a paint film of uniform thickness. The painting method disclosed in Patent Document 1 attempts to form a paint film of uniform thickness without causing paint dripping by performing the following steps (1) to (3) in order: (1) a first coating step in which multiple paint films are formed at intervals in the direction of the inclined gradient; (2) an intermediate drying step in which the paint films formed in the first coating step are dried; and (3) a second coating step in which paint films are formed so as to fill the gaps between the paint films formed in the first coating step. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-167101 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the coating method disclosed in Patent Document 1 requires an intermediate drying step (2) between the first coating step (1) and the second coating step (3), which requires a correspondingly longer time for the entire coating process. For example, the takt time for the coating process of a standard passenger car is approximately one minute per vehicle, and the coating method disclosed in Patent Document 1 cannot meet the desired production speed. If the intermediate drying step is omitted to increase production speed, the coating film formed in the first coating step will not dry properly, and the function of the coating film formed in the first coating step to prevent paint dripping will be reduced.

[0005] An object of the present invention is to provide a coating method capable of forming a coating film of uniform thickness on an inclined surface, and an automobile having an inclined surface on which a coating film of uniform thickness is formed. [Means for solving the problem]

[0006] According to the coating method of the first aspect of the present invention, a coating area on an inclined surface that is inclined relative to the vertical direction is coated. During this coating, paint is sprayed from a spray nozzle toward the coating area to form a coating film, and the coating film formed at the top of the coating area is thicker than the coating film formed at the bottom of the coating area.

[0007] In a second aspect of the present invention, at least a part of the inclined surface of the outer panel of the vehicle body is painted by the above-described painting method. [Effects of the Invention]

[0008] According to the first invention, a coating film of uniform thickness can be formed on an inclined surface, and according to the second invention, an automobile having an inclined surface on which a coating film of uniform thickness is formed can be realized. [Brief explanation of the drawings]

[0009] [Figure 1A] FIG. 1A is a schematic side view (coating step) illustrating an outline of a coating method according to a first embodiment. [Figure 1B] FIG. 1B is a schematic side view (after coating) illustrating an outline of the coating method according to the first embodiment. [Figure 2A] FIG. 2A is a schematic side view showing the first step of forming the coating film shown in FIG. [Figure 2B] FIG. 2B is a schematic side view showing a second step of forming the coating film shown in FIG. [Figure 3] FIG. 3 is a schematic side view showing an outline of a coating method according to the second embodiment. [Figure 4] FIG. 4 is a schematic side view showing an outline of a coating method according to a third embodiment. [Figure 5]FIG. 5 is a schematic side view showing an outline of a coating method according to a fourth embodiment. [Figure 6] FIG. 6 is a schematic side view showing an outline of a coating method according to a fifth embodiment. [Figure 7] FIG. 7 is a schematic side view showing an outline of a coating method according to a sixth embodiment. [Figure 8A] FIG. 8A is an explanatory diagram for a coating method according to a seventh embodiment. [Figure 8B] FIG. 8B is a schematic side view showing an outline of the coating method according to the seventh embodiment. [Figure 9] 1 is a perspective view of an automobile in which an inclined surface of an outer body panel has been painted by the painting method according to the embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] A painting method according to an embodiment will be described with reference to the drawings. In the drawings, identical parts are designated by the same reference numerals and their description will be omitted. These painting methods are used to paint a painting target area 3 on an inclined surface 2 that is inclined relative to the vertical direction. In the following embodiment, painting of the inclined surface 2 of the outer panel 1 of an automobile 9 is particularly assumed. Currently, painting processes using robotic arms are common in outer panel painting lines in automobile manufacturing lines.

[0011] A paint head having at least one spray nozzle 5 is attached to the tip of the robot arm, and by moving the paint head with the robot arm, paint droplets 6 sprayed from the spray nozzle 5 are deposited on the surface of the outer panel 1. As a result, a paint film 4 is formed on the surface of the outer panel 1. The paint head may spray paint in a cone shape from a single spray nozzle 5, or it may have multiple spray nozzles 5.

[0012] When a painting head has multiple spray nozzles 5, the spray nozzles 5 are arranged in a row (or may be arranged in a matrix), for example. In this case, during painting, the painting head is often moved in a direction approximately perpendicular to the direction in which the spray nozzles 5 are arranged so that a wider area can be painted in a single movement path of the painting head by the robot arm, but this is not limited to this. In the figures described below, only a single spray nozzle 5 is shown, and the direction of its movement is assumed to be perpendicular to the plane of the figure.

[0013] In the figures described below, the up-down direction in the figures is the vertical direction, and the exterior panel 1 has an inclined surface 2 that is inclined relative to the vertical direction. A paint film 4 is formed in a painting target area 3 on the inclined surface 2. The exterior panel 1 of an automobile 9 is generally painted using a multi-layer coating, and the paint film 4 may be formed directly on the surface of the exterior panel 1, or may be formed by forming a dried paint film 4X on the exterior panel 1. In the figures described below, a case in which the paint film 4 is formed directly on the surface of the exterior panel 1 is shown as an example.

[0014] (First embodiment) A coating method according to a first embodiment will be described with reference to Figures 1A to 2B. First, the basics of the coating method according to this embodiment will be described with reference to Figures 1A and 1B. In the coating method of this embodiment, as shown in Figure 1A, paint (droplets 6) is sprayed from a spray nozzle 5 toward a coating target area 3 to form a coating film 4. At this time, the coating film 4 is formed so that the thickness of the coating film formed above the coating target area 3 (hereinafter also referred to as the upper coating film 4U) is thicker than the thickness of the coating film formed below the coating target area 3 (hereinafter also referred to as the lower coating film 4L). The thickness of the coating film 4, i.e., the film thickness, is the thickness in the direction perpendicular to the surface of the exterior panel 1 (or the dried underlying coating film).

[0015] When a coating film 4 is formed as shown in Figure 1A, a portion of the coating film 4 flows downward due to gravity before it dries. In the coating film 4 shown in Figure 1A, the upper portion 4U of the coating film is thicker than the lower portion 4L of the coating film, so that the paint in the upper portion 4U of the coating film tends to move to the lower portion 4L of the coating film before it dries, and when it dries, the thickness of the dried coating film (hereinafter also referred to as dried coating film 4X) becomes uniform as shown in Figure 1B. The concept of the coating method described using Figures 1A and 1B is also applicable to other embodiments described below.

[0016] There are various possible methods for forming a coating film 4 consisting of an upper coating film 4U and a lower coating film 4L of different thicknesses, as shown in Figure 1A. In this embodiment, as shown in Figure 2A, a first coating film 41 is first formed over the entire area to be coated 3, and then, as shown in Figure 2B, a second coating film 42 is formed above the area to be coated 3 before the first coating film 41 dries. In this way, the thickness of the upper coating film 4U can be made thicker than the thickness of the lower coating film 4L.

[0017] When droplets 6 that form the second coating film 42 adhere to the first coating film 41, the paint adheres between the first coating film 41 and the second coating film 42. After that, some of the paint in the upper coating film 4U flows down to the lower coating film 4L. The flow of paint at this time stops at the bottom end of the lower coating film 4L (first coating film 41) due to the adhesion between the layers. In other words, unnecessary paint is prevented from flowing down below the coating target area 3.

[0018] Furthermore, in this embodiment, the first coating film 41 is formed with a thickness T1 that prevents the paint from flowing along the inclined surface 2, and the second coating film 42 is formed with a thickness T2 that causes the paint to flow along the inclined surface 2. That is, the film thickness of the lower coating film 4L is T1, and the film thickness of the upper coating film 4U is (T1 + T2). In this way, the movement of the paint from Figure 1A to Figure 1B can be more effectively achieved.

[0019] (Second embodiment) A second embodiment will be described with reference to Figure 3. As shown in Figure 3, in this embodiment, the area to be coated 3 is divided into a plurality of divided areas 3D. When forming a coating film 4 in each divided area 3D, the coating film 4 is formed so that the thickness of the coating film formed in the upper part of the divided area 3D (upper coating film 4U) is thicker than the thickness of the coating film formed in the lower part of the divided area 3D (lower coating film 4L). In this way, a coating film 4 with a uniform thickness can be formed over a wider area.

[0020] It should be noted that, here, it has been explained that the area to be coated 3 is divided into multiple divided areas 3D. However, this embodiment can also be considered as carrying out the coating methods described in the first embodiment with reference to Figures 1A and 1B in parallel. From the state shown in Figure 3, as explained using Figures 1A and 1B, the coating film 4 becomes a uniform, continuous dried coating film 4X in each divided area 3D.

[0021] (Third embodiment) The third embodiment will be described with reference to Figure 4. In Figure 4, for ease of understanding, each sprayed droplet 6 is represented by a square in the formed coating film 4. This representation is used to clearly explain the concept of this embodiment. During the formation of the coating film 4 as shown in Figure 1A, an upper portion 4U of the coating film moves to a lower portion 4L of the coating film, and a film thickness change region 7 in which the thickness of the coating film 4 changes is formed, as shown in Figure 4. The film thickness change region 7 is the portion where the film thickness changes between the upper portion 4U of the coating film and the lower portion 4L of the coating film.

[0022] In this embodiment, droplets 6 of paint sprayed from the spray nozzle 5 are repeatedly placed in this film thickness change region 7. In other words, a certain number of droplets 6, one or more, are placed on the step surface of the droplets 6 (film thickness change region 7). By doing this, it is possible to continue forming the coating film 4 such that the film thickness of the upper part 4U of the coating film is thicker than the film thickness of the lower part 4L of the coating film. This also makes it possible to reduce the amount of paint required for the lower part of the coating film 4.

[0023] (Fourth embodiment) The fourth embodiment will be described with reference to Figure 5. In Figure 5, each sprayed droplet 6 is represented by a square on the formed coating film 4. This embodiment can also be considered a variation of the third embodiment. In this embodiment, droplets 6 are arranged in the film thickness change region 7 so that the change in film thickness within the film thickness change region 7 becomes gradual from bottom to top.

[0024] That is, the number of droplets 6 arranged is changed for each of the stepped treads described above, and the droplets 6 are arranged in the film thickness changing region 7. In this way, the transition from Fig. 1A to Fig. 1B can be made gentle, and the film thickness uniformity (smoothness of the coating surface) can be improved.

[0025] (Fifth embodiment) The fifth embodiment will be described with reference to Figure 6. In Figure 6, each sprayed droplet 6 is shown as a square on the formed coating film 4. This embodiment can also be considered a variation of the third embodiment. In this embodiment, droplets 6 are arranged only above the midpoint between the lower and upper edges of the film thickness changing region 7 (see arrow Y in Figure 6).

[0026] That is, the droplets 6 are arranged so as to form a step-like pattern from the middle layer in the thickness direction of the coating film 4. This prevents the film thickness of the lower coating film 4L from becoming too thin, improving the strength of the lower part of the dried coating film 4X.

[0027] (Sixth embodiment) A sixth embodiment will be described with reference to Figure 7. In this embodiment, as in the first embodiment, the coating film 4 is formed so that the upper portion 4U is thicker than the lower portion 4L (see Figure 1A). However, in this embodiment, the coating film 4 as shown in Figure 1A is formed by setting the overlap ratio of the paint droplets 6 sprayed from the spray nozzle 5 to be higher at the top of the coating target area 3 than at the bottom while the coating film 4 is being formed on the inclined surface 2. In this way, controlling the overlap ratio of the droplets 6 also makes it possible to form a coating film 4 consisting of the upper portion 4U and the lower portion 4L of different film thicknesses, thereby improving the paint adhesion to both the upper portion 4U and the lower portion 4L.

[0028] 7, in this embodiment, droplets 6 are arranged so that the overlap ratio in the upper part 4U of the coating film is equal to the overlap ratio in the lower part 4L of the coating film only when droplets 6 are sprayed to form the top layer of the coating film 4. This allows smooth transition of the top layer of the upper part 4U of the coating film to the lower part 4L of the coating film, improving the surface quality of the dried coating film 4X.

[0029] (Seventh embodiment) The seventh embodiment will be described with reference to Figures 8A and 8B. Figure 8A illustrates the difference in film thickness due to differences in the spray speed of droplets 6. In Figure 8A, paint droplets 6 are sprayed from directly above onto a horizontal plate 8 to make the difference in film thickness easier to understand. In Figure 8A, the speed of the droplets 6 on the right side is faster than the speed of the droplets 6 on the left side. Therefore, due to the difference in kinetic energy of the droplets 6 that adhere to the horizontal plate 8, the droplets 6 on the right side, which have a faster speed, adhere to a wider area. In other words, the thickness of the coating film 4a formed by the droplets 6 on the right side, which have a faster speed, is thinner than the thickness of the coating film 4b formed by the droplets 6 on the left side, which have a slower speed. This embodiment utilizes this property.

[0030] Specifically, as shown in Fig. 8B, the speed of the paint droplets 6 sprayed from the spray nozzle 5 is made slower in the upper part of the coating target area 3 than in the lower part. In this way, by controlling the speed of the droplets 6, it is possible to form a coating film 4 consisting of an upper coating film 4U and a lower coating film 4L with different film thicknesses.

[0031] Figure 9 shows an automobile 9 whose body has been tilted using one of the coating methods of the above embodiments. At least a portion of the inclined surface 2 of the outer panel 1 of the body has been painted using the above coating method. This automobile 9 has a dry coating film 4X with a uniform thickness on its inclined surface 2, allowing it to have a high-quality painted appearance.

[0032] In the coating method according to the above embodiment, a coating target area 3 on an inclined surface 2 that is inclined relative to the vertical direction is coated. Paint (droplets 6) is sprayed from a spray nozzle 5 toward the coating target area 3 to form a coating film 4. In this process, the coating film 4 is formed so that the thickness of the coating film formed above the coating target area 3 (upper coating film 4U) is thicker than the thickness of the coating film formed below the coating target area 3 (lower coating film 4L) (see FIG. 1A). Therefore, according to the coating method according to the above embodiment, the paint in the upper coating film 4U moves to the lower coating film 4L before the coating film 4 dries, forming a dried coating film 4X with a uniform thickness (see FIG. 1B).

[0033] Furthermore, the coating method according to the above embodiment does not require a step such as the intermediate drying step disclosed in the above-mentioned Patent Document 1. Therefore, the coating method according to the above embodiment does not lengthen the takt time of the coating process, and therefore the production speed can be improved.

[0034] In particular, according to the coating method of the first embodiment, a first layer of coating film 41 is formed over the entire area to be coated 3 (see FIG. 2A), and then a second layer of coating film 42 is formed on the upper part of the area to be coated 3 before the first layer of coating film 41 dries (see FIG. 2B). This results in the formation of a coating film 4 such that the thickness of the upper part of the coating film 4U is greater than the thickness of the lower part of the coating film 4L. Therefore, according to the coating method of the first embodiment, a dried coating film 4X of uniform thickness can be formed over the area to be coated 3 of a desired size, even on an inclined surface 2.

[0035] Here, the first coating film 41 is formed with a thickness T1 that prevents the paint from flowing along the inclined surface 2, and the second coating film 42 is formed with a thickness T2 that causes the paint to flow along the inclined surface 2. In this way, a dry coating film 4X of uniform thickness can be formed on the inclined surface 2 in the desired size of the coating target area 3.

[0036] Furthermore, according to the coating method of the second embodiment, the area to be coated 3 is divided into a plurality of divided areas 3D. When forming the coating film 4 in each divided area 3D, the coating film 4 is formed so that the thickness of the coating film formed in the upper part of the divided area 3D (upper part of the coating film 4U) is thicker than the thickness of the coating film formed in the lower part of the divided area 3D (lower part of the coating film 4L) (see FIG. 3). Therefore, according to the coating method of the second embodiment, the thickness of the dried coating film 4X can be made uniform in each divided area 3D, and the thickness of the dried coating film 4X can also be made uniform over the entire area to be coated 3.

[0037] Furthermore, according to the coating methods of the third to fifth embodiments, droplets 6 of paint sprayed from the spray nozzle 5 are repeatedly placed in the film thickness change region 7 that is formed during the formation of the coating film 4 on the inclined surface 2 (see FIG. 4). As a result, the coating film 4 is formed so that the thickness of the upper portion 4U of the coating film is greater than the thickness of the lower portion 4L of the coating film. Therefore, according to the coating methods of the third to fifth embodiments, a dried coating film 4X of uniform thickness can be formed even on the inclined surface 2.

[0038] In particular, according to the coating method of the fourth embodiment, droplets 6 are arranged in the film thickness change region 7 so that the change in film thickness within the film thickness change region 7 becomes gradual from bottom to top (see FIG. 5). Therefore, according to the coating method of the fourth embodiment, the shape of the film thickness change region 7 in the coating film 4 can be made smooth, and film thickness uniformity (smoothness of the coating film surface) can be improved.

[0039] Alternatively, in particular, according to the coating method of the fifth embodiment, droplets 6 are positioned only above the midpoint between the lower and upper edges of the film thickness varying region 7 (see arrow Y in FIG. 6). Therefore, according to the coating method of the fifth embodiment, the film thickness of the lower part 4L of the coating film does not become too thin, and the strength of the lower part of the dried coating film 4X is improved.

[0040] Furthermore, according to the coating method of the sixth embodiment, while a coating film 4 is being formed on the inclined surface 2, the overlap ratio of the paint droplets 6 sprayed from the spray nozzle 5 is made higher in the upper part of the coating target area 3 than in the lower part (see FIG. 7). As a result, the coating film 4 is formed so that the thickness of the upper part 4U of the coating film is thicker than the thickness of the lower part 4L of the coating film. Therefore, according to the coating method of the sixth embodiment, a dried coating film 4X of uniform thickness can be formed even on the inclined surface 2.

[0041] Here, droplets 6 are arranged so that the overlap ratio at the upper part (upper part 4U of the coating film) of the coating film 4 is equal to the overlap ratio at the lower part (lower part 4L of the coating film) only when droplets 6 are sprayed to form the top layer of the coating film 4. In this way, the top layer of the upper part 4U of the coating film smoothly transitions to the lower part 4L of the coating film, improving the surface quality of the dried coating film 4X.

[0042] Furthermore, according to the coating method of the seventh embodiment, the speed of the paint droplets 6 sprayed from the spray nozzle 5 is slower in the upper part of the coating target area 3 than in the lower part. This results in the formation of a coating film 4 such that the thickness of the upper part 4U of the coating film is greater than the thickness of the lower part 4L of the coating film. Therefore, according to the coating method of the seventh embodiment, a dried coating film 4X of uniform thickness can be formed even on the inclined surface 2.

[0043] Furthermore, as shown in Figure 9, an automobile in which at least a portion of the inclined surface 2 of the body outer panel is painted by the painting method according to the above embodiment has a dried coating film 4X with a uniform thickness on the inclined surface 2, thereby providing a high-quality painted appearance. In addition, the production speed can be improved.

[0044] Although the embodiments of the present invention have been described above, the descriptions and drawings that form part of this disclosure should not be understood to limit the present invention. Various alternative embodiments, examples, and operational techniques will become apparent to those skilled in the art from this disclosure. While the above description generally describes the use of a robot arm to fix paint, the present invention may also be applied to manual painting by a worker. [Explanation of symbols]

[0045] 1. Outer panel 2 Slope 3. Painting area 3D Divided Range 4 Coating 4L Lower part of the coating (coating formed on the top of the coating target area 3) 4U Upper part of the coating (coating formed below the coating target area 3) 41 First coating 42 Second layer of paint T1 (First Coating 41) Thickness T2 (second coating 42) thickness 5 spray nozzle 6 (paint) droplets 7. Film thickness change region 9. Automobiles

Claims

1. A coating method for coating a coating target area on an inclined surface that is inclined with respect to the vertical direction, comprising: A coating method in which, when paint is sprayed from a spray nozzle toward the area to be coated to form a coating film, the coating film is formed so that the thickness of the coating film formed in the upper part of the area to be coated is thicker than the thickness of the coating film formed in the lower part of the area to be coated.

2. The coating method according to claim 1, A coating method in which a first layer of coating film is formed over the entire area to be coated, and a second layer of coating film is formed on the upper part of the area to be coated before the first layer of coating film dries, so that the thickness of the coating film formed on the upper part of the area to be coated is thicker than the thickness of the coating film formed on the lower part of the area to be coated.

3. The coating method according to claim 2, A coating method in which the first coating film is formed with a thickness that does not cause the paint to flow along the inclined surface, and the second coating film is formed with a thickness that causes the paint to flow along the inclined surface.

4. The coating method according to claim 1, The painting target area is divided into a plurality of divided areas, a coating method in which, when forming the coating film on each of the divided areas, the coating film is formed so that the thickness of the coating film formed on the upper part of the divided area is thicker than the thickness of the coating film formed on the lower part of the divided area.

5. The coating method according to claim 1, The coating method includes repeatedly placing droplets of the paint sprayed from the spray nozzle in a film thickness change region where the thickness of the coating film changes, which is formed during the formation of the coating film on the inclined surface, so that the thickness of the coating film formed in the upper part of the range to be coated is thicker than the thickness of the coating film formed in the lower part of the range to be coated.

6. The coating method according to claim 5, a coating method in which the droplets are placed in the film thickness change region so that the change in film thickness within the film thickness change region becomes gradual from bottom to top.

7. The coating method according to claim 5, The coating method includes disposing the droplets only above a midpoint between the lower edge and the upper edge of the film thickness change region.

8. The coating method according to claim 1, a coating method in which, during the formation of the coating film on the inclined surface, the overlap rate of the paint droplets sprayed from the spray nozzle is made higher at the upper part of the range to be coated than at the lower part, thereby forming the coating film so that the thickness of the coating film formed at the upper part of the range to be coated is thicker than the thickness of the coating film formed at the lower part of the range to be coated.

9. The coating method according to claim 8, A coating method in which, only when the droplets are sprayed to form the top layer of the coating film, the droplets are arranged so that the overlap ratio in the upper part is equal to the overlap ratio in the lower part.

10. The coating method according to claim 1, A coating method in which the speed of the paint droplets sprayed from the spray nozzle is slower at the upper part of the area to be coated than at the lower part, thereby forming a coating film so that the thickness of the coating film formed at the upper part of the area to be coated is thicker than the thickness of the coating film formed at the lower part of the area to be coated.

11. An automobile in which at least a part of an inclined surface of an outer body panel is painted by the painting method according to any one of claims 1 to 10.

Images