JPH0542311B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a coating method. (Prior Art and its Problems) When painting the outer surface of an object to be coated, such as an automobile body, there are a step of applying a paint to the object and a drying step of drying the applied paint. This drying process is generally carried out in two stages: a setting process and a baking process.The setting process is performed at a temperature lower than that of the baking process, such as room temperature or 40° to 40° (also called calcination), before the baking process. It is carried out in a temperature atmosphere of 60℃ (the baking temperature in the baking process is usually around 140℃). Further, as a method of painting the object to be coated, an intermediate coat and a top coat are often applied after undercoating. Therefore, after undercoating, an intermediate coating process, an intermediate coating drying process, a top coating process, and a top coating drying process are performed. In this painting method, which includes an undercoat, intermediate coat, and topcoat, the undercoat ensures corrosion resistance, the intermediate coat adjusts the roughness of the base and ensures chipping resistance, and the topcoat coats the base. (Intermediate paint) Concealment is done. and,
The thickness of the undercoat film is 15 to 25 μm, the thickness of the intermediate coat is 35 to 45 μm, and the thickness of the top coat is 35 to 25 μm.
45 μm, and the total thickness of these three coating films, that is, the total film thickness, is generally 85 to 115 μm. By the way, top coat paints are extremely expensive compared to intermediate coat paints and undercoat paints. From this perspective,
On the premise that the total film thickness is maintained at the conventional level, it is desirable to make the top coat as thin as possible and to make the intermediate coat as thick as possible. If the top coat is made thinner, the intermediate coat will show through, but this can be solved by using a color similar to the top coat as the intermediate coat, that is, by using a so-called color intermediate coat. It can be solved. However, there is a limit to increasing the thickness of the intermediate coating film because large irregularities such as the so-called welt phenomenon occur, which significantly impairs smoothness. The large irregularities caused by this welting phenomenon cannot be corrected by wet sanding, which is usually done after drying the intermediate coat. Here, we will explain in detail the smoothness of the painted surface.
One factor that inhibits this smoothness is "sagging" of the paint. This sagging is caused by the applied paint flowing downward under the influence of gravity, and the cause of this sagging is that the thicker the paint that is applied at one time, the more likely it is to sag. teeth,
In short, this is due to the effect of gravity, so it is more likely to occur on surfaces of the object to be coated that extend in the vertical direction, that is, so-called vertical surfaces. Therefore, on the horizontally extending surfaces of the object to be coated, ie, the so-called lateral surfaces, where "sagging" of the paint does not pose much of a problem, the thickness of the paint applied can be made larger than on the vertical surfaces. In addition, even if the thickness of the paint film on the horizontal and vertical surfaces is the same, the unevenness on the horizontal surface will be reduced due to slight flow of the paint that does not cause sagging, and the unevenness will be reduced on the vertical surface. This results in a smoothness better than that obtained in . In other words, if the coating thickness is the same,
Assuming no sagging occurs, the greater the fluidity of the paint, the better the smoothness can be obtained. Another factor that impedes smoothness is the welt phenomenon described above, which is ultimately caused by extremely poor fluidity of the paint. In particular, intermediate coatings with poor fluidity that do not sag even at a thickness of 50 μm or more are susceptible to this sagging phenomenon. Conventionally, in order to comprehensively take into account the sagging, wetting phenomenon, and the fluidity of the paint, as mentioned above, both the intermediate and top coats were treated as described above.
The actual situation is that it is about 40 μm. Finally, in order to obtain a coated surface with good smoothness, there is a limit to the thickness of the intermediate coat, which means that the top coat must be made sufficiently thick. was. (Object of the invention) The present invention has been made in consideration of the above circumstances, and it is possible to make the thickness of the intermediate coating film much thicker than before without causing the welt phenomenon. An object of the present invention is to provide a coating method capable of reducing the thickness of a topcoat film. (Means and operations for achieving the object) In order to achieve the above-mentioned object, the present invention has the following configuration. In other words, an intermediate coating process in which intermediate coating paint is applied to the object to be coated;
In a painting method comprising an intermediate coating drying step for drying the applied intermediate coating paint, and a top coating step for applying a top coat paint to the object to be coated after the intermediate coating drying step, in the intermediate coating step, a color similar to that of the top coat paint is applied. The intermediate coating is applied to a thickness that exceeds the sag limit and is sufficiently thicker than the top coat, and in the intermediate coating drying step, the object to be coated is rotated around a horizontal axis. In this way, in the present invention, the direction of gravity acting on the intermediate coating applied to the object to be coated is changed by rotating the object in the horizontal direction. The applied intermediate paint dries without causing any "sag". In this way, applying the intermediate coat to a thickness that exceeds the sag limit without causing sag means that the intermediate coat used can be one with high fluidity that does not cause welts.
It turns out that. Therefore, in the present invention, it is possible to obtain a sufficiently thick intermediate coating film, which could not be obtained conventionally without the welt-down phenomenon, without causing any welt-down phenomenon. The thickness of the top coat can be made thinner by the amount that the intermediate coat can be made thicker. Of course, the concealment effect caused by thinning the top coat can be overcome by using a so-called color intermediate coat using a color similar to that of the top coat as the intermediate coat. (Example) Hereinafter, an example of the present invention will be described based on the attached drawings. Overall Outline FIG. 1 shows the overall process for painting an automobile body W as an object to be coated, and each process is indicated by P1 to P8. First, the body W, which has been undercoated by electrocoating in a known manner, is held on a truck D and sent to a preparatory step P1. In this preparatory step P1, dust inside and outside the body W is removed by, for example, vacuum suction. After that, in step P2, an intermediate coating material is sprayed onto the body W.
Then, the drying of the intermediate paint is the setting process P.
3 and a baking step P4. After the intermediate coating baking step P4, the top coating steps P5 to P8 are performed without performing the conventional wet sanding and drying associated with the wet sanding. Intermediate coating Here, the paint (for intermediate coating) is sprayed in P2 so that the thickness of the coating film exceeds the sag limit. In other words, in conventional paints, the maximum thickness of the paint is about 40 μm, which does not cause "sagging" and does not cause the phenomenon of peeling.
The intermediate coating is sprayed so that the film is much thicker than 40 μm (for example, 65 μm) (applied to a thickness that is above the sag limit). In addition, in the setting process P3, FIG.
As shown by i, the body W is rotated in the horizontal direction. That is, the body W is rotated about a rotation axis l extending in the horizontal direction, and in the embodiment, this rotation axis l extends in the front-rear direction of the body W. In addition, this setting process P
Although the temperature atmosphere in Step 3 is set to room temperature in the embodiment, it may be set to any appropriate temperature within a temperature range lower than the temperature atmosphere in the subsequent baking step P4, such as 40° to 60°C. Of course, this setting step P3 is to volatilize the low boiling point content in the paint in advance,
This prevents the occurrence of pinholes on the painted surface due to rapid volatilization of low boiling point components in the next baking step P4. In the baking step P4, the top coat is baked in an atmosphere at a temperature of 140° C., for example. In this P4, similarly to the setting process of P3,
As shown in FIGS. 2a to 2i, the body W is rotated in the horizontal direction. Due to the horizontal rotation of the body W at P3 and P4 described above, even if the intermediate coating is sprayed to a thickness exceeding the sag limit at P2, the intermediate coating will not sag or cause the phenomenon of sagging. dried. As a result, the thickness of the intermediate coating can be made extremely thick, which cannot be obtained by conventional coating methods, and a high quality intermediate coating surface with extremely high smoothness can be obtained. In addition, in the top coating drying steps P3 and P4, it is also possible to rotate the body W only in the baking step P4. Topcoat The topcoat P6 is applied to a thickness that is sufficiently thinner than the thickness conventionally applied, for example, about 15 to 30 μm. This top coat may be applied within the sag limit, but
Preferably, a material with extremely high fluidity that causes sag even at a thickness of about 15 to 30 μm is used. When applying a top coat that exceeds this sag limit, proceed to the next step P in the same way as the intermediate coating step.
7. Just rotate the body W at P8. As a result, even with a thin topcoat film, the final coated surface has an extremely smooth surface compared to the case where the coating is applied beyond the sag limit and the rotation is not performed. Relationship between paint film thickness, sag limit, smoothness, and horizontal rotation Figure 3 shows the influence of paint film thickness on the sag limit, focusing on the top coat paint. In this Figure 3, the coating film thicknesses are 40μm, 53μm,
Three cases of 65 μm are shown. It is understood that for any of these thicknesses, peaks of "sag" occur both at the beginning of the setting process and at the beginning of the baking process. In addition, the sag limit is the value when the sag normally occurs at a rate of 1 to 2 mm per minute (the painted surface is considered to be defective if the sag occurs at a rate of 2 mm/min or more when visually observed); The maximum film thickness that can be obtained in the range is 40μm with conventional paints.
That's about it. By the way, it is possible to increase the fluidity of the top coat paint by increasing the content of HB (hybrid agent) and increase the sag limit film thickness to 50 μm or more, but in this case, so-called blurring may occur. It's not practical. On the other hand, FIG. 4 shows the influence on the smoothness when the body W is rotated in the horizontal direction and when it is not rotated. In Fig. 4, A is the body W.
It is shown without rotating (conventional painting method). FIG. 4B shows a case where the body W is rotated 90 degrees and then reversed (forward and reverse rotation between FIG. 2 a and c). Figure 4C shows the case where the body W is rotated 135 degrees and then reversed (Figure 2a).
forward and reverse rotation between and d). Figure 4 D is the body W
The figure shows a case in which it is rotated 180 degrees and then reversed (forward and reverse rotation between a and e in Figure 2). Figure 4E is
The case is shown in which the body W is continuously rotated in the same direction (takes the postures in the order of a, b, c...i in FIG. 2, and then returns to a again). As is clear from Fig. 4, if the thickness of the coating film is the same, it is better to rotate the body W (Fig. 4 B, C, D, E) and not to rotate it (Fig. 4 A).
A higher degree of smoothness can be obtained. Furthermore, it is understood that even if the rotation is the same, it is preferable to rotate 360 degrees in the same direction in order to improve smoothness. Of course, if the body W is not rotated, there is a limit to the thickness of the coating film, so there is a limit to how much smoothness can be increased. By the way, the body W is assumed to have a coating thickness of 65 μm.
When rotating 360°, the resulting smoothness is
Image sharpness IG "87" (lower limit of PGD value 1.0)
It is. In addition, when the thickness of the coating film is 40 μm, the IG value is "58" when the body W does not rotate.
(lower limit of 0.7 in PGD value), whereas when body W is rotated 360°, IG is "68" (lower limit in PGD value).
lower limit of 0.8). In addition, as is known, IG in image sharpness
(Image gloss) indicates the ratio of sharpness to the mirror surface (black glass) as 100, and PGD indicates that as the discrimination of the reflected image decreases from 1.0, the smoothness of the painted surface decreases. is the value. Data showing the effects of the present invention Next, the following table shows the effects of the present invention in terms of data.

【table】

[Table] In the above table, the meanings of the numerical values, etc. are as follows. Concealability ○ There is no problem as the base is not see-through Chipping resistance Judging by the number of rust occurrences by Gravelo test 5: 0 to 5 rust spots (excellent) 4: 6 to 15 rust spots (good) 3: 16 to 30 rust spots Rust (normal) 2: Rust of 31 to 50 (bad) Rust of 1:51 or more (unacceptable) The details of the gravel test are as follows. Gravelo test Nozzle diameter: 50% Distance: 300mm Stone: JIS A500/No. 7 crushed stone 30gr Air pressure: 2.5Kg/cm ² After the Gravelo test, the sample was subjected to a salt spray test for 72 hours, and the number of rust spots was observed as described above. . Smoothness is shown as PGD value. ``'' indicates the case where the top coat was applied using the conventional painting method. Among these, "A" indicates the case where there was no wet sanding after drying the intermediate coat, and "B" indicates the case where wet sanding was performed. ``'' indicates the case where the top coat was applied to a level exceeding the sag limit and the body was rotated, and no wet sanding was performed after the intermediate coat dried. The details of the coating specifications for obtaining the above data are as follows. Base: Zinc phosphate treated steel plate Undercoat: Cationic electrodeposition (black) Thickness 20μm Baked at 170℃ for 30 minutes Intermediate coat: Polyester melamine Hue White (matches topcoat) Viscosity 2 seconds/Food Cup #4 Minibell 2-stage blowing (interval 3
(minutes) Baking: 140℃ x 25 minutes Overcoat: Polyester melamine Hue White Viscosity a For smoothness classification "'' in the table above: 16 to 22 seconds/Food cup #4 with the lowest possible viscosity within the range that does not cause sagging. Selectively use b For smoothness classification "'' in the table above: 16 seconds for film thickness of 25 μm or more / Foed cup #4 13 seconds for film thickness of 20 μm or less / Foed cup #4 Minibell 1 stage blowing Baking 140℃ x 25 minutes Rotation The initial setting process is 10 minutes and the baking process is 10 minutes at 10 rpm. Note that in order to cause sagging with a low film thickness, the fat component, solvent structure, proportion, etc. of the paint may be adjusted as appropriate. As is clear from the above table, chipping resistance,
It is possible to make the intermediate coat thicker and the top coat thinner accordingly, without causing the problem of the base coat showing through, and while ensuring good smoothness of the final coated surface. Of course, the film thickness in the above table is the average value of the thick and thin parts. Note that in order to cause sagging with a low film thickness, the resin component, solvent structure, proportion, etc. of the paint may be adjusted as appropriate. Here, the numerical values of the intermediate coating film thickness and the top coating film thickness will be described based on the data shown in the table above. For reference, in the conventional painting method, the smoothness of the final coated surface obtained when the intermediate coating film thickness and top coating film thickness are each 40 μm is the same as that obtained by wet sanding after the intermediate coating dries. In this case, the PGD value is about 0.7. First, the total value of the intermediate coating film thickness and the top coating film thickness is preferably about 70 to 100 μm, as in the conventional coating method, in order to ensure the overall film thickness. Within this total value range, in order to make the intermediate coating film thicker than before, the intermediate coating thickness is preferably 50 μm or more,
In particular, in order to improve chipping resistance, the thickness is preferably 60 μm or more. In addition, the top coating film thickness is preferably 30 μm or less in order to be thinner than conventional ones.
20 to 25 μm to sufficiently reduce consumption of top coat paint
It is best to set it to a certain degree. Of course, it is possible to set the top coat thickness to about 15 μm, but in consideration of the final smoothness, it is preferable to set it to 20 μm or more as described above. Rotation Jig Next, a specific example of a jig used to support the body W in a horizontally rotatable manner relative to the cart D will be described. FIG. 5 shows a front jig 1F attached to the front part of the body W. This jig 1F includes a pair of left and right mounting brackets 2, a pair of left and right stays 3 welded to each of the left and right brackets 2, a connecting bar 4 that connects the left and right pair of stays 3, and a connecting bar 4. It has an integrated rotating shaft 5. The bracket 2 portion of such a jig 1F is fixed to the front strength member of the body W, for example, to the front end of the front side frame 11. That is, since a bracket 12 for mounting a bumper (not shown) is usually welded to the front side frame 11, the bracket 2 is attached to the bracket 12 on the body W side using bolts (not shown). and fix it. On the other hand, a rear jig 1R attached to the rear part of the body W is shown in FIG. This rear jig 1R has the same configuration as the front jig 1F,
Components corresponding to this front jig 1F are given the same reference numerals. The body W of this rear jig 1R
For installation, attach the bracket 2 to the body W.
Floor frame 1 as a strength member at the rear end
This is done by fixing it to 3 with bolts. Of course, since a bumper is generally attached to the rear end of the floor frame 13, a bracket for attaching the bumper is welded in advance, so this bumper attaching bracket is used to attach the rear jig 1R. Installation can also be done. When the front and rear jigs 1F and 1R are attached to the body W, their rotating shafts 5 are positioned on the same straight line extending in the front-rear direction of the body W. This same straight line becomes the rotational axis l of the body W, and preferably this rotational axis l
passes through the center of gravity G of the body W (see FIG. 7). Note that since the rotational axis 1 passes through the center of gravity G, large fluctuations in the rotational speed are prevented when the body W rotates. This prevents impact from occurring on the body W due to rotational fluctuations, which is more preferable in terms of preventing sag. Note that the front and rear jigs 1F and 1R are specially prepared in advance according to the vehicle type (type of body W). Bogie This is a bogie that is used at least in P3, P4 or P7, P8 and has the function of rotating the body W. In FIG. 7, the truck D has a base 21, and wheels 22 attached to the base 21 are
The vehicle is run on a road surface 23. This base 21 consists of one front support 2 that extends upward in sequence from the front side in the running direction to the rear side (from the right side to the left side in Figure 7).
4, has two intermediate struts 25, 26 and one rear strut 27, and the intermediate struts 25, 26 and the rear strut 2
7 is a support space 28 with a large gap in the front-rear direction. The body W is disposed in the support space 28, and its front part is rotatably supported with respect to the intermediate support 26 using the front jig 1F, while its rear part is
It is rotatably supported by the rear support 27 using the rear jig 1R. The front and rear jigs 1F and 1R (rotary shafts 5 of them) can be freely engaged with and disengaged from the columns 26 and 27 from above and below, and the rear jig 1R is immovably engaged in the direction of the rotation axis l. Ru. For this reason, the middle support 26 is formed with a notch 26a opening at its upper end surface (see FIGS. 10 to 12), while the rear support 27 is
A notch 27a is formed in the upper end surface thereof (see FIGS. 10, 14, and 15).
The notches 26a, 27a are sized to fit the rotating shafts 5 of the jigs 1F, 1R. The rotating shaft 5 of the rear jig 1R has a flange portion 5a.
is formed in the rear strut 27, while the notch 2 is formed in the rear strut 27.
A notch 27b having a shape corresponding to the flange portion 5a communicating with the flange portion 7a is formed. As a result, the rear jig 1R cuts through the notches 27a and 27b of the rear support 27.
It is engaged and disengaged from the top and bottom directions, and is immobilized in the front and rear directions with respect to the rear strut 27 by the stopper action of the flange portion 5a. In addition, body W
The rotational force is applied via the rotating shaft 5 of the front jig 1F, and therefore a connecting portion 5b (see also FIG. 5), which will be described later, is provided at the tip of the rotating shaft 5 of the front jig 1F. It is formed. A stay 29 projects downward from the base 21, and a traction wire 30 is connected to the lower end of the stay 29. This wire 30 is of an endless type and is driven in one direction by a motor (not shown), thereby driving the cart D in a predetermined transport direction. Of course, the motor is installed in a safe location from an explosion-proof point of view. The rotation of the body W uses the movement of the trolley D.
That is, this is performed by utilizing the displacement of the truck D with respect to the running road surface 23. The rotation extraction mechanism 31 for extracting the displacement of the truck D as rotation is configured as follows. That is, the rotation take-out mechanism 31
The rotating shaft 32 is vertically extended and rotatably supported on the base 21, the sprocket 33 is fixed to the lower end of the rotating shaft 32, and the sprocket 33 is fixed to the lower end of the rotating shaft 32.
The chain 34 is meshed with the chain 34. This chain 34 is disposed in parallel with the wire 30 in an immovable state with respect to the traveling road surface 23. As a result, when the trolley D is towed via the wire 30, the chain 34 is immovable, so
A sprocket 33 meshes with the chain 34, thereby rotating the rotating shaft 32. The transmission mechanism 35 for transmitting the rotation of the rotating shaft 32 to (the rotating shaft 5 of) the front jig 1F is configured as follows. That is, the transmission mechanism 35 includes a casing 36 fixed to the rear surface of the front strut 24, and a rotating shaft 37 that is rotatably supported by the casing 36 while extending in the lateral direction (back and forth direction).
A pair of bevel gears 38 and 39 that interlock this rotating shaft 37 and the upper rotating shaft 32, and a connecting shaft 40 that is held rotatably and slidably in the front and rear directions with respect to the intermediate support 25. have This connecting shaft 40 is spline-coupled to the rotating shaft 37 (this engaging portion is indicated by reference numeral 41 in FIG. 7),
When the rotating shaft 32 is rotated by this, the connecting shaft 4
0 will also be rotated. Of course, the rotation shaft 37 and the connection shaft 40 are installed so as to be located on the rotation axis l. The connecting shaft 40 is engaged with and disengaged from the rotating shaft 5 of the front jig 1F. That is, Figures 10 to 1
As shown in FIG. 2, a cross-shaped connecting portion 5b is formed at the tip of the rotating shaft 5 for the front jig 1F,
A box portion 40a is formed at the end of the connecting shaft 40, as shown in FIGS. 10 and 13, and has an engaging recess 40c into which the connecting portion 5b is fitted without rattling. Therefore, the connecting shaft 4 is connected via the rod 43 by a pneumatic cylinder 42, for example.
0 by sliding the box part 4.
0a (the engagement recess 40) and the connecting portion 5b are engaged and disengaged, and when engaged, the connecting shaft 40 and the rotating shaft 5 are allowed to rotate together. In addition, the rod 43, the first
As shown in FIG. 0, the connecting shaft 40 is fitted into an annular groove 40b formed on the outer periphery of the box portion 40a so as not to inhibit the rotation of the connecting shaft 40. With the above configuration, the connecting shaft 40 is connected to the seventh
By lowering the body W relative to the trolley D while being displaced to the right side of the figure, the front and rear jigs 1F,
Each rotation shaft 5 of 1R is supported by intermediate struts 26 and 27 so as to be rotatable and immovable in the front-rear direction. After this, the connecting shaft 40 (locking recess 40c)
It is engaged with (the connecting portion 5b of) the rotating shaft 5 in the front jig 1F. As a result, when the trolley D is towed via the wire 30, the body W is moved along the predetermined horizontal axis l.
It will be rotated around. Note that the body W may be removed from the truck D by the reverse procedure to the above-described procedure. 16, 17, 18, and 19 show the rotating shaft 5 of the front jig 1F and the connecting shaft 4, respectively.
This shows a modification of the bonding site with 0. In the ones in Figures 16 and 17, first,
The notch 26a of the intermediate support 26 is connected to the box portion 40.
It is formed in a semicircular shape so as to be able to rotatably support a. Further, the connecting portion 5b-1 of the rotating shaft 5 is L
The engaging recess 40c-1 formed in the box portion 40a is formed in a L-shaped connecting portion 5.
b-1 is shaped so that it is engaged in a manner that prevents relative rotation. The engagement recess 40c-1 is opened on one side of the box portion 40a, and when this opening faces upward, the connection portion 5b-1 is connected to the engagement recess 40c-1. It is adapted to be engaged and disengaged from the vertical direction (sliding of the connecting shaft 40 is not required). 18 and 19, like FIGS. 17 and 18, the front jig 1F is rotated only when the engagement recess 40c-2 formed in the box portion 40a faces upward. Connection portion 5b-2 formed on shaft 5
The connection part 5 can be connected and disconnected.
c-2 has a rectangular cross section, while the engagement recess 40
The difference from the cases shown in FIGS. 16 and 17 is that c-2 has a shape corresponding to this quadrangle. Of course, in the case of FIGS. 16 to 19,
When the connecting shaft 40 and the front jig 1F are in a state where they can be engaged and disengaged (a state in which the engagement recesses 40c-1 and 40c-2 face upward), the body W is in the upright position (the body W shown in FIG. (with the roof panel facing upward). Supplementary Explanation Next, supplementary explanations related to the present invention will be sequentially explained. First, when removing dust in step P1 or P5, it is preferable to remove dust while rotating the body W about the rotation axis l (see FIGS. 2 a to 2).
As a result, the dust adhering to the inner surface of the body W, especially the surface facing downward in the upright position, falls downward due to gravity, so that dust can be removed more reliably. This prevents dust from falling when the body W is rotated during the setting process and the baking process, which is important in obtaining a high-quality painted surface. Regardless of whether the truck D is running or stopping, switching between rotating and stopping the body W and changing the rotation direction can also be performed, for example, as follows. First, in the example shown in FIG. 7, a pair of first and second chains (corresponding to the chain 34) are provided which mesh with the sprocket 33 from opposite sides in the radial direction, and each chain can be driven as appropriate. With such a configuration, the rotation of the body W will be controlled according to the following drive mode. Stopping the first chain and freeing the second chain: In this case, the body W is rotated in one direction as the truck D travels. First chain free and second chain stopped:
In this case, as the truck D travels, the body W is rotated in the opposite direction to that described above. Both chains are free: In this case, the body W is not rotated as the trolley D travels. Drive the first chain in one direction and free the second chain: In this case, even if the truck D is stopped, the body W is rotated in one direction. Drive the first chain in the other direction and make the second chain free (first chain free and second chain free)
(The same applies if the chain is driven in the other direction): In this case, even if the truck D is stopped, the body W is rotated in the opposite direction to that in the above case. Note that the above description also applies when a rack bar is used in place of the chain. If this rack bar is always placed in a fixed state (in this case, the running of the trolley D is a prerequisite for the rotation of the body W), the rack bar may be placed intermittently, or the position of the rack bar may be set arbitrarily to the left or right. By doing so, the body W can be rotated in any direction depending on the traveling position of the truck D, and the rotation of the body W can be stopped at any position. (Effects of the Invention) As is clear from the above, the present invention has the following advantages:
When applying intermediate and top coats, it is now possible to increase the thickness of the intermediate coat beyond the level that was previously thought to be the limit, and the thickness of the top coat can be made thinner by increasing the thickness of the intermediate coat. can do. Furthermore, even if the top coat is made thinner, since the intermediate coat is a so-called color intermediate coat, there will be no problem in terms of the underlying layer showing through.

[Brief explanation of the drawing]

FIG. 1 is an overall process diagram showing one embodiment of the present invention.
FIG. 2 is a diagram showing a state in which the posture of an automobile body as an object to be coated changes as it rotates. Figure 3,
Figure 4 is a graph showing the relationship between paint thickness and sag, paint surface smoothness, and rotation. 5 and 6 are perspective views showing examples of jigs used to rotate the body. FIG. 7 is a side view showing an example of a body transporting trolley in which the body can be rotated. FIG. 8 is a partially cutaway plan view showing the state below the running path of the bogie. FIG. 9 is a sectional view taken along the line X9-X9 in FIG. 1st
FIG. 0 is a side cross-sectional view showing the joint portion between the rotation jig and the trolley. FIG. 11 is a sectional view taken along the line X11-X11 in FIG. 10. FIG. 12 is a plan view of FIG. 11. FIG. 13 is a sectional view taken along the line X13-X13 in FIG. 10. FIG. 14 is a sectional view taken along the line X14-X14 in FIG. 10. FIG. 15 is a plan view of FIG. 14. Figures 16 and 17 show modified examples of the joint portion between the rotating jig and the trolley.
Figure 16 is a sectional view taken along the line X16-X16 in Figure 17;
FIG. 17 is a side sectional view. Figures 18 and 19 show still another modification of the joint portion between the rotation jig and the cart, and Figure 18 shows X18-X in Figure 19.
18 is a cross-sectional view, and FIG. 19 is a side cross-sectional view. P1 to P8: Process, W: Body, l: Rotation axis, D: Conveyance trolley, 1F, 1R: Rotation jig.

Claims (1)

[Scope of Claims] 1. An intermediate coating process in which an intermediate coating is applied to an object to be coated, an intermediate coating drying process in which the applied intermediate coating is dried, and a top coating in which a top coat is applied to the object after the intermediate coating drying process. In the painting method, the intermediate coating step includes applying an intermediate coating of a similar color to the top coating to a thickness that is greater than the sag limit and sufficiently thicker than the top coating, and drying the intermediate coating. A coating method characterized by rotating the object to be coated around a horizontal axis during the process.