JP2810431B2 - Painting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a coating method.

(Prior art) When coating an object to be coated, for example, the outer surface of an automobile body,
The method includes a preparation step of removing dust adhering to the object to be coated, a step of spraying a paint on the object to be coated, and a drying step of drying the sprayed paint. This drying step is generally performed in two stages, a setting step and a baking step. The setting step is performed before the baking step at a lower temperature than the baking step, for example, at room temperature or 40 ° C. to 60 ° C. It is performed in a temperature atmosphere of ° C. (the baking temperature in the baking step is usually around 140 ° C.).

The object to be coated usually undergoes the above-described preparation step, coating step, and drying step while being conveyed by a conveying means such as a cart, but the posture of the object to be coated is maintained at a predetermined position in each step. It is being done as it is.

By the way, as one criterion for evaluating the quality of a painted surface, there is smoothness (flatness). The greater the smoothness, the smaller the degree of unevenness of the painted surface, and the better the painted surface. It is already known that the smoothness of the painted surface can be improved by increasing the thickness of the coating film, that is, the thickness of the applied paint.

On the other hand, there is a "drip" of the paint as an obstacle to the quality of the painted surface. The term “drip of paint” means that a trace of 1 to 2 mm from the position where the paint is sprayed on the object to be coated is cured by a drying process, and can be visually confirmed on the painted surface. Therefore, the trace is at least
If it exceeds 2mm, it means sagging. Therefore, to have a thickness within the sagging limit means that
It is a thickness that does not cause sagging in the drying process even if it is left as it is after spraying the paint. Conversely, the term "thickness equal to or greater than the sagging limit" means a thickness that causes sagging at least in the drying step if left as it is after spraying the paint.

The dripping of the paint is caused by the flow of the paint applied downward due to gravity, so that the greater the thickness of the paint applied at one time, the more easily the dripping occurs. Is, due to the effect of gravity, that tends to occur on the surface of the object to be coated extending in the vertical direction, that is, the so-called vertical surface.

Therefore, the thickness of the coating material to be applied to the surface extending in the horizontal direction, that is, the so-called horizontal surface, of the object to be coated on which the “sagging” of the coating does not become a problem can be made larger than the vertical surface. Even if the thickness of the coating on the horizontal surface is the same as the thickness of the coating on the vertical surface, the unevenness is reduced by a slight flow of paint that does not cause dripping on the horizontal surface, and the vertical surface is smooth. The degree of smoothness better than the degree is obtained.

From the point of view described above, conventionally, this "paint"
In order to obtain a coated surface with as large a smoothness as possible while preventing the occurrence of a coating, the coating is performed using a coating material having a low fluidity (a low viscosity) as much as possible. The so-called "sagging limit", at which "sagging" of the coating occurs on the vertical surface, was about 40 [mu] m in the thickness of the coating film of the conventional thermosetting coating. More specifically, the “sag” of the paint is likely to occur at the beginning of the setting step and at the beginning of the baking step, particularly at the beginning of the baking step. Is determined, and the determined maximum value of the thickness, that is, the sag limit value is about 40 μm. Therefore, in order to obtain a coated surface having a much higher degree of smoothness, in the conventional coating method, it is necessary to repeat a series of steps from the coating step to the baking step a plurality of times, for example, twice coating. was there.

(Problems to be Solved by the Invention) Overcoming the sagging limit, which is a problem when coating by spraying as described above, a coated surface with better smoothness can be obtained if the coating thickness is the same. Applicants have developed a coating method that can be obtained. That is, after spraying the coating material to have a film thickness equal to or greater than the sagging limit, at least at least until the coating surface of the object hardens until sagging does not occur on the coated surface, the object to be coated is rotated about a substantially horizontal axis. We have developed a painting method that rotates it. According to this method, the action of gravity, which is a fundamental cause of sagging, is positively utilized, and the direction of gravity acting on the paint applied to the object is appropriately changed, whereby the paint is removed. By taking advantage of the fluidity of the paint, it is possible to obtain a painted surface having a high smoothness.

However, when the above-mentioned coating method is carried out, a problem arises in that, since the paint having a large fluidity is applied beyond the sag limit, the paint swells at the end of the object to be coated. found. Considering this problem, a paint having a high fluidity flows due to surface tension acting on the painted surface, and smoothes the unevenness of the painted surface. However, once the coating surface is smoothed, the surface tension acts in one direction toward the edge of the object, and the paint concentrates toward the edge of the object, causing the swelling of the paint. A phenomenon occurs.

Therefore, an object of the present invention is to provide a coating method that suppresses the swelling of the paint at the end of the object to be coated.

(Means and Actions for Solving the Problems) The present invention has been made by paying attention to the point that the swelling of the paint occurs after the smoothing of the paint surface. That is,
Considering that there is a time lapse between the smoothing phenomenon of the paint and the swelling phenomenon of the edge of the object to be coated, the characteristics of the paint are as follows. Utilizing surface tension, secondly, after smoothness is obtained on the painted surface, the fluidity is reduced to overcome the surface tension.

Specifically, after spraying the paint so that the coating material has a film thickness equal to or greater than the sag limit, at least at least until the coating surface of the work hardens until sagging does not occur on the coating surface, the work is substantially applied. A coating method of rotating around a horizontal axis, wherein the spraying viscosity of the coating material sprayed on the object is 18 seconds or less (Ford cup # 4, 20 ° C), and the solvent contained in the coating material has a boiling point of 110 ° C or less. A low boiling solvent is contained, and the low boiling solvent is contained in an amount of 50% by weight or more of the total solvent.

The rotation speed of the object to be coated is faster than the level at which the surface of the object to be coated transitions from a substantially vertical state to a substantially horizontal state before the sagging of the coating material due to gravity, and the coating material is centrifugally generated due to the rotation. The speed can be set as a speed lower than the speed at which dripping occurs.

According to the present invention, basically, the thickness of a coating applied at one time is made much thicker than in the past, and an extremely good coated surface with a smoothness far exceeding the level which has been conventionally regarded as a limit. Can be obtained.

Also, even if the thickness of the coating film is the same as before,
By utilizing the fluidity of the paint, it is possible to obtain an excellent painted surface having less unevenness, that is, a greater smoothness.

Furthermore, if it is intended to obtain a coated surface having the same smoothness, for example, the same smoothness as that obtained by a conventional coating method, the thickness of the paint to be applied can be made thinner than the conventional one, The amount of paint used can be reduced by the amount that can be made thinner.

In the present invention, the use of the paint described in the claims makes it possible to suppress the swelling of the paint at the end of the object to be coated.

Here, the spraying of the paint may be spraying by electrostatic painting. In addition, the dripping of the paint means the movement of the paint that can be visually confirmed when the paint is left in a sprayed state (appears as a streak when the paint is cured),
Generally, it is assumed that dripping occurs when the movement of the paint by about 2 mm is confirmed. Therefore, spraying paint to a thickness greater than the sag limit means that if the paint is left as it is, a thickness of at least about 2 mm will cause the paint to move. Becomes thinner. In order to make the thickness equal to or more than the sagging limit, the spraying may be performed by one spraying (one stage blowing), and the thickness may be finally equal to or more than the sagging limit by two or three or more sprayings ( Multistage blowing). Furthermore, the rotation of the object to be coated about the substantially horizontal axis may be performed so that a large movement of the coating does not occur due to the effect of gravity, so that the coating does not have a large flow state that causes dripping, that is, Until the paint is hardened, the coating may be performed continuously or intermittently in a predetermined direction, or the forward and reverse rotation may be performed continuously or intermittently. The rotation angle range of the object to be coated may be such that the direction in which gravity acts on an arbitrary portion where the coating material is sprayed to a thickness greater than the sagging limit is reversed, and 270 degrees is sufficient. Then, the rotation axis of the object to be coated may be inclined within a range of about 30 degrees with respect to the true horizontal axis, and the rotation axis may be swung.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

Overview of Overall FIG. 1 shows the overall steps in the case of coating an automobile body W as an object to be coated, and the steps are indicated by P1 to P4.

First, the body W, for which undercoating has been completed as is known by electrodeposition coating, is sent to the preparation process P1 while being held by the carriage D. In the preparation process P1, dust inside and outside the body W is removed by, for example, air blow or vacuum suction. Thereafter, in step P2, paint is sprayed on the body W. Then, the paint is dried in the setting step P3 and the baking step P4.

When the processes P1 to P4 are for intermediate coating, after the process P4, the body W is sent to the process for top coating. In addition, steps P1 to P4
Is for overcoating, the body W is transported to the assembly line in a known manner.

Dust Removal The dust removal in the process P1 is performed while rotating the body W around the horizontal axis l, as shown in FIG. That is, for example, first, the rotation of the body W is stopped in the state shown in FIG. 2A to remove dust, and then, FIG.
The posture of the body W is changed to the state described above, the vehicle is stopped at this position, and the dust is removed again. In this manner, dust is removed while the body W is intermittently rotated as shown in (c), (d),... (I) in FIG.

As described above, by removing the dust while rotating the body W, the dust adhered to the inside of the closed section such as the inner corner of the roof panel or the side sill of the body W, that is, the body W must be rotated. It is possible to completely remove dust that does not fall.

Spraying and drying of paint First, spraying of paint in P2 is performed in the drying process P3 or P4
It is preferable to use a paint that does not cause sagging for at least 2 minutes on the painted surface on which sagging occurs and coating is completed. The value of 2 minutes is 1
This corresponds to less than two minutes from the start of painting on one body W to the completion of painting over the entire body (including the transition to the setting step P3). More specifically, until the entire body W has been completely painted, sagging does not occur in the area where painting is completed the earliest, thus preventing drooling in the painting process P2. It is meant to be. The spraying of the paint is preferably performed by electrostatic atomization coating.

The application of the paint is performed by spraying because it is possible to control the thickness of the coating film as desired. The concept of the spraying is the electrostatic coating (electrostatic coating) as described above. Atomization coating). On the other hand, in the case of applying the paint by dipping, at the stage where the object to be coated is pulled up from the dipping tank, it is 1 to 1 visually as described above.
Much more than 2 mm of paint movement occurs. Then, if the coating is done more than the sagging limit and the spinning is performed after the sagging once occurs,
The coated surface of the portion where the sag has once occurred cannot have the same smoothness as the other painted surface where the sag does not occur.

The thickness of the coating film does not cause sagging in the drying process P3 or P4. The thickness can be made larger than the thickness which has been conventionally regarded as a limit. Of course, it is optional to make the thickness the same as or less than the conventional thickness.

After P2, the paint adhered to the object is transferred to the setting step of P3 without dripping. In this setting step P3, the body W is rotated in the horizontal direction as shown in FIGS. 2 (a) to 2 (i). That is, the body W is rotated around the rotation axis l extending in the horizontal direction, and in the embodiment, the rotation axis l extends in the front-rear direction of the body W.

The rotation speed of the body W varies depending on the thickness and viscosity of the sprayed paint, but is basically set to a rotation speed in the range between the lower limit and the upper limit as described below. That is, the lower limit of the rotation speed is the minimum rotation speed at which the coating surface can be at least changed from the vertical state to the horizontal state before the paint on the coating surface moves due to gravity and sags. The upper limit value is a maximum value among rotation speeds at which no dripping occurs due to centrifugal force generated by rotation, and is preferably 380 cm / sec or less at the tip of rotation of the object to be coated. When the body W is rotated about a substantially horizontal axis, the rotation axis may be inclined by about 30 ° with respect to the horizontal axis, but it is preferable that the inclination be within 10 °.

The period during which the body W is rotated about the substantially horizontal axis may be at least in a drying step before the coating surface is sagged until it hardens until no sagging occurs. Of course, the object to be coated may be rotated over the entire drying process from the viewpoint of equipment and the like.

This rotation may be any of continuous rotation in one direction, forward / reverse rotation alternately performing forward rotation and reverse rotation, and intermittent rotation in the middle of a rotation stop period.

The temperature atmosphere in the setting step P3 is room temperature in the embodiment, but the temperature in the next baking step such as 40 ° C. to 60 ° C.
An appropriate temperature can be set in a temperature range lower than the temperature atmosphere in P4. Of course, this setting step P3 is for preliminarily evaporating the low-boiling components in the paint, thereby causing pinholes on the painted surface due to the rapid evaporation of the low-boiling components in the next baking step P4. Is prevented.

In the baking step P4, for example, the paint is baked in a 140 ° C. temperature atmosphere. At P4, the body W is rotated in the horizontal direction as shown in FIGS. 2 (a) to 2 (i), similarly to the setting step of P3.

Due to the horizontal rotation of the body W at P3 and P4 described above, the paint is dried without sagging. As a result, a high-quality coated surface having extremely high smoothness, which cannot be obtained by the conventional coating method, can be obtained.

Relationship between coating thickness, sag limit and smoothness and horizontal rotation FIG. 3 shows the effect of coating thickness on sag limit. In FIG. 3, the coating thickness is 40
The three cases of μm, 53 μm and 65 μm are shown. It is understood that, in any of these thicknesses, a "drip" peak occurs both at the beginning of the setting step and at the beginning of the printing step. In addition, the sag limit refers to a value when a sag of 1 to 2 mm occurs during the drying process as described above (specifically, in the drying process, the sag limit is moved by 1 to 2 mm from the position where the paint adheres. This is the limit of the coating thickness at which traces of the paint movement are visually observed on the coating surface after the drying step). It is about 35 to 40 μm for the paint.

FIG. 4 shows the effect on the smoothness when the body W is rotated in the horizontal direction and when it is not. A in FIG. 4 shows a state in which the body W is not rotated (conventional coating method). FIG. 4B shows the body W
Is rotated 90 ° and then reversed (second
(Forward and reverse rotation between FIGS. (A) and (c)). FIG. 4C shows a case where the body W is rotated by 135 ° and then reversed (forward and reverse rotation between FIGS. 2 (a) and (d)). FIG. 4D shows a case where the body W is rotated by 180 ° and then reversely rotated (forward and reverse rotation between FIGS. 2 (a) and (e)). FIG. 4E shows a case where the body W is continuously rotated in the same direction (FIGS. 2 (a), (b),
(C)... (I) are taken in this order, and the process returns to (a) again).

As is apparent 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) When the rotation is not performed (FIG. 4A), a greater smoothness can be obtained. Further, it is understood that even in the same rotation, it is preferable to rotate in the same direction by 360 ° in order to increase the smoothness. Of course, when the body W does not rotate,
Since the thickness of the coating film is limited, there is a limit in increasing the smoothness.

By the way, the body W is 360
゜ When rotating, the resulting smoothness is
It is "87" (lower limit of 1.0 in PGD value) in IG. When the thickness of the coating film is 40 μm, the IG is “58” (lower limit of 0.7 in the PGD value) when the body W is not rotated. If the IG is "68"
(Lower limit of 0.8 in PGD value).

As is known, IG (image gloss) in the image definition clarity indicates a ratio of the image clarity with respect to the mirror surface (black glass) as 100. Is a value at which the smoothness of the painted surface decreases as the value decreases.

The test conditions of the data shown in FIGS. 3 and 4 are as follows, and the test conditions are the same as those in the case of performing the overcoating at P2.

a. Paint: Melamine alkyd (black) Viscosity: 22 seconds / 20 ° C with Ford cup # 4 b. Coating machine: mini bell (16,000 rpm) Shaving air 2.0 kg / cm ₂ c. Discharge amount: divided into two 100 cc / min 2nd time 150-200 cc / min d. Setting time: 10 minutes x normal temperature e. Baking conditions: 140 ° C x 25 minutes f. Substrate smoothness: 0.6 (PGD value) (Medium coating, on PE tape) g. Rotating or reversing operation area: Setting (10 minutes) to baking (10 minutes) h. Coating object: Paint on the side of a 30 cm square cylinder, center Rotatably supported i. Rotation speed of the object to be coated: 6 rotations, 30 rotations, and 60 rotations, but there was virtually no difference due to the difference in rotation speed.

Here, in the paint shown in FIG.
In the case of μm coating, dripping starts to occur within 1 minute from the start of setting, that is, the time of completion of painting, and there is no problem if rotating immediately after completion of painting, but production equipment that can be immediately rotated after painting If you don't have any, during the transition from the painting process to the setting process (about 1 minute)
This may cause dripping.

Relationship between paint viscosity etc. and edge pooling When a paint with high fluidity is used, it is advantageous for improving the smoothness of the coating surface, but on the contrary, paint pooling tends to occur at the end of the object to be coated (hereinafter referred to as , The edge pool). This point will be described in more detail with reference to FIGS. 16 to 18. As shown in FIG. 16, the unevenness (see FIG. 16) existing on the coating surface immediately after spraying the paint is such that the paint of the convex portion 100 fills the concave portion 101. It is smoothed by the fluidity of the migrating paint (see FIG. 17). That is, in the case of a paint having a high fluidity, the paint easily moves by the surface tension acting on the paint surface, is dispersed in four directions in a narrow range, and the unevenness is flattened. However, once the coating surface becomes flat, the surface tension acts in one direction (edge direction E), so that the coating material accumulates at the end T of the work W to be coated. A phenomenon occurs in which the paint rises (see Fig. 18). This is the edge pool 102. That is, in the edge pool, an edge pool phenomenon occurs after the smoothing of the coating surface.

Therefore, as a paint for preventing edge accumulation, firstly, it has a large fluidity immediately after spraying and utilizes the effect of surface tension, and secondly, the fluidity decreases after the smoothness of the painted surface is obtained. That is, it is only necessary to impart the following characteristics to overcome the surface tension.

To impart the first property, lower the spray viscosity,
It is conceivable to reduce the amount of the sag inhibitor.

In order to impart the second characteristic, it is conceivable to increase the amount of the solvent that volatilizes early.

Based on the above viewpoints, using the paints shown in Tables 1 and 2 below, Tables 3-1 and 3-2, Tables 4-1 and
Samples as shown in Table 4-2 were prepared. In each table, the spraying viscosities were all Ford cup # 4, 20 ° C
It is the value in.

The boiling point of each solvent used for preparing the above sample is as follows.

Ethyl acetate 77.1 ° C Toluene 110 ° C Xylene 135-145 ° C Soleveso 100 (manufactured by Esso) 157-174 ° C Solvesso 150 (same as above) 188-210 ° C
The sagging from the punched holes and the sharpness were tested.

Specimen shape (mm) A flat plate of (vertical) 300 x (horizontal) 100 x (height) 0.7 having a punched hole with a diameter of 15 mm at the center thereof was used.

Base treatment Cationic electrodeposition 20μm Baking at 175 ℃ for 30 minutes Middle coating 35μm Baking at 140 ℃ × 25 minutes (thermosetting oil-free polyester paint; gray) Medium coating water lab # 800 water resistant paper Top coating paint As shown in Tables 1 and 2 above A: Thermosetting melamine alkyd paint (black) B: Thermosetting melamine acrylic paint (black) The above coating conditions Coating machine Mini bell (bell diameter 60 mm) Rotation speed 22.000 rpm, voltage -90 KV Shaping air pressure 3.0 kg / cm ² Gun distance 30cm spraying position Set vertically in the longitudinal direction of the test plate.

Spraying speed The test plate was moved at 3m / min (fixed to the coating machine).

Stage 2 stages (interval 3 minutes) Coating thickness ratio between 1 stage and 2 stages 1: 2 Booth environment temperature 20 ° C Wind speed 0.2m / sec Baking conditions 140 ° C x 25 minutes after setting 10 minutes (heating rate 20 ° C → 140 ℃ / 8min) Thickness level (μm) 60,70 (Dry) Specimen rotation condition Spraying position is 2 minutes after spraying is completed to match the actual painting condition, taking into account the car body painting conditions After being left as it is, the test plate was set at a position 80 cm from the axis of the rotating device, rotated at 10 rpm for 8 minutes, rotated for 5 minutes after the start of printing, and then printed with rotation stopped.

In Tables 3-1 to 4-2, the column of evaluation at the right end indicates, in principle, the case where the coating film thickness is
m, the edge pool is 3.5 or less and the sharpness is
A reference value of 1.0 or more is considered as OK (pass). In addition, even if the above standard values are satisfied, if a pinhole is generated by heating in the baking process, NG (fail)
There is.

Assuming the above, samples A-11 and B-19 are OK when the film thickness is 60 μm, but are NG at the edge pool point when the film thickness is 70 μm. In the case of samples A-14, B-2, and B-3, when the film thickness was 70 μm, the result was OK, but in the case of 60 μm,
NG. In addition, samples which are regarded as NG due to generation of pinholes at the time of baking are A-17, A-25, B-15, B-16, B-
21, B-28.

Here, as the content of the anti-sagging agent becomes larger than 6%, the gloss is reduced (glossy) while the content is 6%.
As the value becomes smaller, the data of the edge pool tends to deteriorate. Therefore, the content of the anti-sagging agent is preferably set to a range that does not greatly deviate from 6%, more specifically, to a range of about 5 to 7%.

In the case of paint A, when the spray viscosity is 16 seconds, the low boiling solvent is 55% to 75% of toluene alone (A-12, A-13, A-
15 and A-16), but the data of the edge pool is improved by replacing a part of the toluene with a solvent having a lower boiling point (see A-11 and A13).

If the low boiling point solvent is excessively used, only the surface of the wet coating film is rapidly thickened (hardened), and the surface becomes rough due to the deterioration of the fluidity, and pinholes are easily generated at the time of baking. From such a viewpoint, the low boiling point solvent is preferably set to a range of 75% or less. In particular, in the case of paint A, when the spray viscosity is 16 seconds, if the low-boiling solvent alone exceeds 75% with toluene alone, pinholes are generated and practicality is not recognized.

In the case of the coating material A, when the whole amount of toluene was replaced with ethyl acetate having a lower boiling point alone, there was no region that sufficiently satisfied both the edge pooling and the sharpness.

50% each of the following solvents having a boiling point of 110 ° C. or less, which are known as coating solvents, and 25% of Solvesso 100, and Solvesso 1
When 50 was set to 25%, the fluidity of the coated ethyl acetate material became extremely poor, and practicality was not recognized. However, these can be used by substituting a part of toluene (see Sample A-13 using ethyl acetate).

Acetone (51 ° C), methyl acetate (59 ° C), methanol (64.5 ° C), ethanol (78.5 ° C), industrial gasoline (60-90 ° C, JISK 2201), methyl ethyl ketone (79
° C), isopropyl alcohol (82.5 ° C), isopropyl acetate (89 ° C), butyl alcohol (99.5 ° C).

In the case of paint B, if the low boiling solvent is toluene alone, a spray viscosity of more than 70% at 16 seconds is not preferable because pinholes are generated. Further, as understood from the comparison between Samples B-8 and B-10, a part of toluene can be used by replacing it with ethyl acetate.

By the way, as shown in Table 5 below, the paint used for painting the automobile body W preferably has a paint resin field average molecular weight in the range of 2,000 to 20,000. For this reason, paints that are cured by electron beam or ultraviolet light correspond to paints less than 2,000, and this paint has a high crosslinking density but is not durable (2 to 3 years), and is used for automotive outer panels. Is less preferred. On the other hand, when the viscosity exceeds 20,000, a large amount of solvent is required because the viscosity becomes high, and it is not preferable because a large amount of solvent is discharged. Further, for a latex polymer exceeding 20,000, the viscosity becomes high immediately after spraying (fluidity). Insufficient), and the smoothness cannot be improved.

Next, a specific example of a jig used to support the body W so as to be rotatable in the horizontal direction with respect to the carriage D will be described.

FIG. 5 shows a front jig attached to the front of the body W.
Shows 1F. The jig 1F includes a pair of left and right mounting brackets 2, a pair of left and right stays 3 welded to the left and right brackets 2, a connecting bar 4 for connecting the pair of left and right stays 3, and a connecting bar 4. And an integrated rotation shaft 5. In such a jig 1F, the bracket 2 is
It is fixed to a front strength member of the body W, for example, a 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 bolted (not shown) to the bracket 12 on the body W side.
Use to fix.

On the other hand, the rear jig 1R attached to the rear of the body W
Is shown in FIG. The rear jig 1R has the same configuration as the front jig 1F, and the components corresponding to the front jig 1F are denoted by the same reference numerals. This rear jig
To attach the 1R to the body W, the bracket 2 is attached to the floor frame 13 as a strength member at the rear end of the body W.
By fixing with bolts. Of course, the rear end of the floor frame 13 is generally pre-welded with a bumper mounting bracket because the bumper is generally mounted, so that the rear jig 1R can be mounted using the bumper mounting bracket. You can do it.

When the jigs 1F and 1R are attached to the body W, the 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 rotation axis l of the body W. Preferably, this rotation axis l is the center of gravity G of the body W (see FIG. 7).
Through. It should be noted that the rotation axis l passes through the center of gravity G, thereby preventing a large fluctuation in the rotation speed when the body W rotates. This prevents the body W from receiving an impact due to the rotation fluctuation, which is more preferable for preventing dripping.

The front and rear jigs 1F and 1R are for the type of vehicle (the type of body W)
A special one is prepared in advance in accordance with.

Dolly Used at least in P3 and P4, this dolly has a function to rotate the body W.

In FIG. 7, the trolley D has a base 21, and this base 21
Is mounted on the road surface 23. The base 21 has a single front support extending sequentially upward from the front side to the rear side (from right to left in FIG. 7) in the traveling direction.
24, two intermediate struts 25, 26 and one rear strut 27, and a space between the intermediate struts 25, 26 and the rear strut 27 is a support space 28 with a large space in the front-rear direction. .

The body W is disposed in the support space 28, and its front portion is rotatably supported on the intermediate support 26 using the front jig 1F, while its rear portion uses the rear jig 1R. Then, it is rotatably supported by the rear column 27.

The front and rear jigs 1F and 1R (the rotating shaft 5) can be freely disengaged from the columns 26 and 27 from above and below, and the rear jig is also provided.
1R is immovably engaged in the direction of the rotation axis l. For this reason, the notch 26a which opens in the upper end surface is formed in the intermediate support | pillar 26 (refer FIG. 10-12), The notch 27a which opens in the upper support surface is formed in the rear support | pillar 27. (First
FIG. 0, FIG. 14, FIG. 15). These two notches 26a, 27a
Is large enough to fit the rotating shafts 5 of the jigs 1F and 1R. The flange 5a is attached to the rotating shaft 5 of the rear jig 1R.
On the other hand, a notch 27b having a shape corresponding to the flange portion 5a communicating with the notch 27a is formed in the rear support column 27. As a result, the rear jig 1R has the notch
It is disengaged from the vertical direction with respect to 27a, 27b, and is immovable in the front-rear direction with respect to the rear support column 27 by the stopper action of the flange portion 5a. The rotation force is applied to the body W by rotating the rotary shaft 5 of the front jig 1F. Therefore, a connecting portion 5b to be described later is attached to the tip of the rotary shaft 5 of the front jig 1F.
(See also FIG. 5).

A stay 29 protrudes downward from the base 21, and a tow wire 30 is connected to a lower end of the stay 29. The wire 30 is of an endless type and is driven in one direction by a motor (not shown), whereby the carriage D is driven in a predetermined transport direction. Of course, the motor is installed at a safe place from the viewpoint of explosion protection.

The rotation of the body W is performed using the movement of the bogie D, that is, using the displacement of the bogie D with respect to the traveling road surface 23. The rotation take-out mechanism 31 for taking out the displacement of the cart D as a rotation is configured as follows. That is, the rotation take-out mechanism 31 includes a rotation shaft 32 extended vertically in the base 21 and supported rotatably, a sprocket 33 fixed to a lower end of the rotation shaft 32, and a chain 34 meshed with the sprocket 33. And is composed of This chain 34
Is disposed in parallel with the wire 30 and in a stationary state with respect to the traveling road surface 23. Thus, when the trolley D is pulled through the wire 30, the chain 34 is immovable, and the sprocket 33 meshing with the chain 34 and thus the rotating shaft
32 is rotated.

A transmission mechanism 35 for transmitting the rotation of the rotation shaft 32 to (the rotation 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 support 24 and a rotating shaft 37 that extends in the lateral direction (front-rear direction) and is rotatably supported by the casing 36.
A pair of bevel gears 38 and 39 for interlocking the rotation shaft 37 and the upper rotation shaft 32, and a connection shaft 40 held rotatably and slidably in the front-rear direction with respect to the intermediate support 25. Have. The connecting shaft 40 is spline-coupled to the rotating shaft 37 (the engaging portion is indicated by reference numeral 41 in FIG. 7). When the rotating shaft 32 is rotated, the connecting shaft 40 is also rotated. become. Of course, it is installed so as to be located on the rotation axis l, which is the rotation shaft 37 and the connection shaft 40.

The connecting shaft 40 is disengaged from the rotating shaft 5 of the front jig 1F. That is, as shown in FIGS. 10 to 12, a cross-shaped connecting portion 5b is formed at the tip of the rotary shaft 5 for the front jig 1F, while the connecting shaft 40 has As shown in FIGS. 10 and 13, a box portion 40a having an engagement recess 40c into which the connecting portion 5b is fitted without play is formed. Thus, for example, the rod 43 is
By sliding the connecting shaft 40 through the connector, the box portion 40a (engaging recess 40c) and the connecting portion 5b are disengaged, and the connecting shaft 40 and the rotating shaft 5 can be integrally rotated during the engagement. It is said. As shown in FIG. 10, the rod 43 is fitted into an annular groove 40b formed on the outer periphery of the box 40a so as not to hinder the rotation of the connecting shaft 40.

With the above configuration, the body W is lowered with respect to the bogie D while the connecting shaft 40 is displaced to the right in FIG. 7, so that the rotary shafts 5 of the front and rear jigs 1F and 1R are It is rotatably supported by the columns 26 and 27 and is immovable in the front-rear direction. Thereafter, the connecting shaft 40 (locking recess 40c) is engaged with (the connection portion 5b of) the rotating shaft 5 in the front jig 1F.
Thus, if the trolley D is pulled through the wire 30, the body W will be rotated about the predetermined horizontal axis l. The removal of the body W from the carriage D may be performed in a procedure reverse to the procedure described above.

(Effects of the Invention) As is clear from the above description, the present invention can obtain a high-quality coated surface with high smoothness using the fluidity and rotation of the paint.

In addition, by using a special coating material, it is possible to suppress the swelling phenomenon of the coating material at the end of the object to be coated, which is caused by applying the coating material beyond the sag limit.

[Brief description of the drawings]

FIG. 1 is an overall process diagram showing one embodiment of the present invention. FIG. 2 is a view showing a state of a posture change accompanying rotation of an automobile body as an object to be coated. FIG. 3 and FIG. 4 are graphs showing the relationship among paint thickness, sag, smoothness of the painted surface, and rotation. 5 and 6 are perspective views showing examples of jigs used for rotating the body. FIG. 7 is a side view showing an example of a bogie for body transportation in which the body is rotated. FIG. 8 is a partially cutaway plan view showing a state of the bogie below the traveling path. FIG. 9 is a sectional view taken along line X9-X9 in FIG. FIG. 10 is a side cross-sectional view showing a connecting portion between the rotating jig and the bogie. FIG. 11 is a sectional view taken along the line X11-X11 in FIG. FIG. 12 is a plan view of FIG. FIG. 13 is a sectional view taken along line X13-X13 of FIG. FIG. 14 is a sectional view taken along line X14-X14 of FIG. FIG. 15 is a plan view of FIG. FIG. 16 to FIG. 18 are explanatory views showing the smoothing of the paint and the mechanism of occurrence of the edge accumulation phenomenon. P1 to P4: Process W: Body (substrate) T: Edge of substrate l: Rotation axis 102: Edge pool of paint

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI B05D 7/14 B05D 7/14 L (56) References JP-A-63-258679 (JP, A) JP-A-63-178871 ( JP, A) (58) Fields studied (Int. Cl. ⁶ , DB name) B05D 1/00-3/14 B05C 13/00-13/02 B05C 9/14 B05D 7/14

Claims (2)

(57) [Claims] An object to be coated is coated with a coating material having a thickness not less than a sagging limit, and then the object is substantially cured until at least the coating surface of the object is cured until no dripping occurs. A coating method of rotating around a horizontal axis, wherein the spraying viscosity of the coating material sprayed on the object is 18 seconds or less (Ford cup # 4, 20 ° C), and the solvent contained in the coating material has a boiling point of 110 ° C or less. A coating method comprising a low-boiling solvent, wherein the low-boiling solvent is contained in an amount of 50% by weight or more of the total solvent. 2. The method according to claim 1, wherein the rotation speed of the object to be coated is earlier than a degree at which the surface of the object to be coated shifts from a substantially vertical state to a substantially horizontal state before the paint dripping occurs due to gravity. A coating method characterized by being set at a speed lower than a speed at which paint dripping occurs due to centrifugal force generated by rotation.