JP2656608B2 - Painting method - 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 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 article, a step of applying a paint to the article, and a drying step of drying the applied paint. This drying step is generally performed in two stages, a setting step and a baking step, and 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. It is performed in a temperature atmosphere of 60 ° C. (the baking temperature in the baking process 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 viewpoints described above, in the past, in order to obtain a painted surface with as large a smoothness as possible while preventing "sagging" of the paint, it has been attempted to apply the paint using a paint with low fluidity (small viscosity) as much as possible. I was The so-called "sagging limit" at which "sagging" of the paint occurs on the vertical surface was the maximum of about 40 [mu] m in the thickness of the coating film of the conventional paint. More specifically, the “sag” of the paint is likely to occur at the beginning of the setting process and at the beginning of the baking process, particularly at the beginning of the baking process. 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.

The present invention has been made in consideration of the above circumstances, and improves the smoothness on the vertical surface of the object to be coated while preventing the sagging of the paint, so that the vertical and horizontal surfaces of the object to be coated are improved. It is an object of the present invention to provide a coating method capable of setting the smoothness in the same manner as above.

(Means for Solving the Problems, Function) The present invention basically provides a method of appropriately changing the direction of gravity acting on a paint applied to a vertical surface of an object to be applied to the fluidity of the paint. By taking advantage of this fact, it is possible to obtain a painted surface having a greater smoothness if the thickness of the coating film is the same. Specifically, the configuration is as follows. That is, in a coating method comprising: a coating step of applying a coating material to an object to be coated; and a drying step of drying the coating material applied to the object to be coated, wherein the coating step includes a first stage and after the first stage. The second stage of the first stage, the coating of the coating on the vertical surface of the object to be coated is performed in both the first stage and the second stage, and finally the desired film thickness is obtained by applying the coating in the second stage. And the thickness of the coating is such that dripping occurs in the drying process. The coating of the paint on the lateral surface of the object is performed using the same paint as that applied on the vertical surface of the object in the second stage. First
The process is performed only in one of the stage and the second stage, and the final film thickness of the lateral surface is made smaller than the final film thickness of the vertical surface of the object to be coated. The coating object is rotated about a substantially horizontal axis until sagging does not occur.

Thus, in the present invention, even if the coating applied to the vertical surface is applied thickly so as to cause sagging, by rotating the object to be coated about a substantially horizontal axis in a subsequent drying step, the fluidity is called. A material having good smoothness can be obtained without causing sagging while sufficiently utilizing the material. Needless to say, the use of the fluidity of the paint does not significantly move the paint beyond 1 to 2 mm from the adhesion position at the time of spraying. More specifically, when the paint adheres to the object to be coated, it is inevitably affected by the surface tension when viewed in an enlarged manner, and is inevitably a high portion (a portion having a large thickness) and a low portion (a portion having a small thickness). Are in a continuous state. And
This high portion of the paint seeks to take advantage of the fluidity that fills the nearby low portion.

Therefore, if the thickness of the coating film is the same, considering that the smoothness is better on the horizontal surface than on the vertical surface, the smoothness of the vertical surface is increased by increasing the thickness of the vertical surface. Is improved, and the smoothness of the horizontal surface and the vertical surface can be made the same, whereby the difference in appearance between the horizontal surface and the receiving surface can be eliminated.

Of course, the thickness of the paint applied to the lateral surface may be a thickness that does not cause dripping, or may be a thickness that causes dripping.

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 overcoating an automobile body W as an object to be coated, and the steps are indicated by P1 to P5.

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 steps P2 and P3, a paint is sprayed on the body W. Then, the paint is dried in the setting step P4 and the baking step P5. Thereafter, the body W is conveyed 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 exchanged to the state described above, and stopped at this position, and dust is removed again. In this way, as shown in (c), (d)... (I) of FIG.
The dust is removed while intermittently rotating.

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 of paint Spraying of paint consists of the first stage in process P2 and the process P3
The second stage is performed in two stages.
In the process P2 as the first stage, the paint is sprayed only on the vertical surface of the body W, that is, the surface extending in the vertical direction such as the left and right side surfaces and the front and rear surfaces. The thickness of the paint sprayed in this step P2 is a desired final film thickness, for example, 60 mμ.
Thinner and less sagging, e.g. 20μ
m.

In the process P3 as the second stage, the vertical surface of the body W and the horizontal surfaces of the roof, hood, trunk lid, etc.
Paint is sprayed on both. On the vertical side,
Remaining thickness required for final film thickness of, for example, 60 mμ, that is, 40 μm because of the 20 μm coating on the previous stage
Paint is sprayed to a thickness of At the stage of newly applying the coating having a thickness of 40 μm, the thickness becomes such that at least the paint is dripped in the drying steps P4 and P5.

On the lateral surface of the body W, the paint is sprayed so as to have the final film thickness by only one spraying in this step P3. The paint sprayed on the horizontal surface is the same as the paint sprayed on the vertical surface, and the final film thickness is, for example,
It is made smaller than the final film thickness on the vertical surface such as 50 μm. The paint sprayed on the lateral surface may be in a range that does not cause dripping, but it is preferable that dripping occurs in the drying steps P4 and P5 so that the smoothness is further improved if the coating thickness is the same. Of course, even if the thickness is sufficiently thinner than the thickness which was conventionally regarded as the sag limit, the sagging in the drying steps P4 and P5 can be achieved by increasing the solvent to increase the fluidity or by reducing the content of the anti-sagging agent. Can be generated.

As described above, at least one of the drying steps P4 and P5 causes dripping of the paint, particularly the baking step.
It may be made to occur only at P5. The spraying of the paint on the lateral surface of the body W may be performed only in the process P2. However, spray the paint on the side
Performing in step P3 as a stage is preferable in order to minimize the influence of overspray when sprayed on the vertical surface in the process P3 on the horizontal surface.

The application of paint is performed by spraying because it is possible to control the thickness of the coating film as desired. The concept of spraying is electrostatic coating (electrostatic atomizing coating). ). On the other hand, in the case where the paint is applied by dipping, when the object to be coated is lifted from the dipping tank, the above-described visual movement of the paint far exceeding 1 to 2 mm occurs. And
If the coating is applied more than the sagging limit and is rotated after the sagging has occurred once, even after the subsequent rotation, the painted surface of the part where the sagging occurs once is as smooth as other painted surfaces where no sagging occurs You can't get sex.

Drying of Paint In the setting step P4, before dripping occurs on the surface of the body W that has been coated in the coating step P3, FIG.
As shown in (i), the body W is rotated in the horizontal direction. That is, the rotation axis l where the body W extends in the horizontal direction
, And in the embodiment, the rotation axis l
Extend in the front-rear direction of the body W.

The rotation speed of the body W changes 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. In other words, the lower limit of the rotation speed is the minimum value of the rotation speeds at which the coating surface can be changed from at least 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. 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 is at least in the drying step, from the time before the coating surface is sagged until it hardens until no sagging occurs. The object to be coated may be rotated throughout the drying process.

In addition, 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 P4 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 P5. Of course, this setting step P4 is to volatilize the low-boiling components in the paint in advance, so that pinholes are generated on the painted surface due to rapid volatilization of the low-boiling components in the next baking step P5. Is prevented.

In the baking step P5, for example, the paint is baked in a 140 ° C. temperature atmosphere. At P5, the body W is rotated in the horizontal direction as shown in FIGS. 2 (a) to 2 (i), similarly to the setting step of P4.

Due to the horizontal rotation of the body W at P4 and P5 described above, the paint is dried without dripping even if the paint is sprayed to a thickness greater than the sag limit at P3. 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 film thickness, sag limit, smoothness, and horizontal rotation FIG. 3 shows the effect of the film thickness on the 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 dripping limit is 1 to 3 in the drying process.
The value when 2 mm sag occurs (the paint surface is considered to be defective if sag of 2 mm or more occurs), but the maximum coating thickness obtained in the range below this sag limit is It is about 40 μm for paint.

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. A in FIG. 4 shows a state in which the body W is not rotated (conventional coating method). FIG. 4B shows a case where the body W is rotated by 90 ° and then reversed (forward and reverse rotation between FIGS. 2 (a) and (c)). FIG. 4C shows
The case where the body W is rotated by 135 ° and then reversely rotated (forward and reverse rotation between FIGS. 2 (a) and (d)) is shown. 4th
FIG. D shows a case in which the body W is rotated 180 ° and then reversed (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” (the lower limit of 0.7 in the PGD value) when the body W is not rotated. If you let the IG `` 6
8 "(lower limit of 0.8 in PGD value).

As is known, IG (image gloss) in the image sharpness indicates the ratio of the sharpness to the mirror surface (black glass) as 100, and the PGD indicates the degree of discrimination of the reflected image as 1.0. Is a value at which the smoothness of the painted surface decreases as the value decreases.

The test conditions of the data shown in FIG. 3 and FIG. 4 are as follows. These test conditions show the conditions when overcoating is performed at P2.

a. Paint: Melamine alkyd (black) Viscosity: 22 seconds / 20 ° C with Ford cup # 4 b. Coating machine: Minibell (16,000 rpm) Shaping air: 2, 0 kg / cm ₂ c. The first time: 100 cc / min The second time: 150-200 cc / min d. Setting time: 10 minutes × normal temperature e. Baking conditions: 140 ° C. × 25 minutes f. Substrate smoothness : 0.6 (PGD value) (intermediate coating, on PE tape) g.Rotating or reversing operation area: setting (10 minutes) to baking (10 minutes) h.Coating object: Painted on the side of a 30 cm square cylinder, center I. Rotation speed of the object to be coated: 6 rpm, 30 rpm, and 60 rpm, but there was virtually no difference due to the difference in rotation speed.

In the above-described paint, the cause of sagging in the setting step P4 and the baking step P5 is as follows. First, the dripping in the setting step P4 is because the paint applied in the coating step P3 has fluidity in a wet state, so the viscosity of the paint is thicker than the conventional film thickness that does not cause dripping. This is caused by the fact that the paint moves in the direction of gravity over the gravity applied by the paint. On the other hand, the sag in the baking process P5 is due to the temperature of the baking process P5, which causes the paint to have fluidity before the paint hardens (usually called thermal flow), and the gravity applied to the paint due to the viscosity of the paint. More specifically, the paint moves in the direction of gravity.

Variations of paint (FIGS. 16 and 17) The paint used in the present invention is preferably a coating process.
Immediately after completion of P3 and before rotation in the setting step P4 is started, a film thickness that is equal to or greater than the sag limit at which sag does not occur is appropriate. The coating film thickness defined in this manner is determined by the viscosity of the coating material, the rate of the anti-sagging agent, and the like, and is not a ratio.

FIG. 16 and FIG. 17 show examples of paint that causes dripping only in the setting step P4 and does not cause dripping in the baking step P5. FIG. 16 shows an example of a two-component curable paint, and FIG. 17 shows an example of a thermosetting paint.

The test conditions for the data shown in FIG. 16 are as follows.

a. Paint: Polyester urethane paint white (trade name: R-263, manufactured by Nippon Bee Chemical Co., Ltd.) Main resin: Polyester polyol white Curing agent: Hexamethylene diisocyanate Mixing ratio (weight ratio): Hardening agent for main resin 4 B. Coating machine: Pressurized air spray gun (Iwata Coating Machine Co., Ltd.)
Spray viscosity: 16 seconds / Ford cup # 4 d. Paint discharge amount: 350cc / min e. Atomization air pressure: 4.0kg / cm ² f. Spray distance: 30cm g. Number of superpositions: 2 (interval: 3 minutes) FIG. 17 is a view showing the sagging characteristics of the thermosetting paint when the thermosetting paint is used as the paint used in the process P2. The setting process should be performed at a temperature of 20 ° C.
10 minutes. Also, the baking process should be performed between 20 ℃ and 140 ℃
To 140 ° C for 8 minutes.
For a minute.

FIG. 17 shows a total of three test examples a to c, that is, examples of thermosetting paints that can be used in the present invention. The specific test conditions for obtaining such data are as follows. It is as follows. In the following description, Test Example a
Those that do not distinguish between c and c are common matters.

(1) Paints ・ Solvent diluted thermosetting melamine kid (hue black) ・ Diluted solvent Triol 4% (wt%) Solvesso 100 (manufactured by Esso) 3% (wt%) Solvent 200 (manufactured by Esso) 3% ( (% By weight)-Anti-sagging agent It is a cross-linked acrylic resin, and all numerical values indicating the amount of addition are shown in Table 1 together with the viscosity in terms of% by weight based on the nonvolatile content.

-Viscosity All numerical values are indicated by Ford Cup # 4/20 ° C and are shown in Table 1 together with the content of the anti-sagging agent.

(2) Coating conditions Table 2 shows the results of two-stage spraying.

The setting and baking are as described above.

(3) Test plate ・ Cold rolled steel sheet treated with zinc phosphate ・ Undercoat Cathodic electrodeposition 170 ° C × 25 minutes baking thickness 25μm ・ Intermediate coating 140 ° C × 25 minutes baking thickness 40μm ・ Intermediate water sharpening (4) Evaluation method With the test plate of (3) set vertically, the topcoat paint was applied with various changes in the paint viscosity and the content of the anti-sagging agent under the above-mentioned coating conditions. Paints that cause sagging in the subsequent setting step and do not cause sagging in the baking step are shown in FIG. 15 as Test Examples a to c. In addition,
For Test Examples a to c, the test plate was rotated around the horizontal axis by 10 rp until sagging did not occur during the setting process.
The PGD value when rotated at a speed of m was measured with a resolution gloss meter. Only the test example c obtained a good PGD value of "0.9". An extremely excellent result with a PGD value of "1.0" was obtained.

Here, as the paint used for painting the automobile body W, as shown in Table 3 below, the paint resin preferably has a number average molecular weight in the range of 2,000 to 20,000.

The reason why the number average molecular weight is preferably in the range of 2,000 to 20,000 as a paint for automobiles is that if it is less than 2,000, it is a paint that cures with an electron beam or ultraviolet light, and this paint has a high crosslinking density and is durable because of its brittleness (2 to 3 years), which is not very suitable for use in automobile outer panels. Also, 20000
If the viscosity exceeds the above, 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.Moreover, for latex polymers having a number average molecular weight of more than 20,000, the viscosity becomes high immediately after spraying, so that the It is not preferable because it is difficult to improve the properties.

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, at the rear end of the floor frame 13, a bumper mounting bracket is welded in advance because the bumper is generally mounted, so that the rear jig 1R is Mounting can also be performed.

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 This is a dolly that is used in at least P1, P4, and P5 and has a function of rotating 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 application of the rotational force to the body W is performed via the rotary shaft 5 of the front jig 1F.
(See also FIG. 5).

A stay 29 projects 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, the rotation shaft 37 and the connection shaft 40 are installed so as to be located on the rotation axis l. Of course, the painting process
In P2 and P3, the clutch 32A is disengaged, and the body W is maintained in the posture shown in FIG.

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.

In the coating processes P2 and P3, the engagement recess 40c and the connection portion 5b
And the body W is sprayed with the paint in the posture shown in FIG.

(Effects of the Invention) As is clear from the above description, the present invention improves the smoothness of the upper and lower surfaces of the object to be coated in the same manner as the smoothness of the lateral surface, and reduces the smoothness between the lateral surface and the upper and lower surfaces. Appearance can be almost or completely the same.

[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 between the thickness of the paint and the dripping, the smoothness of the painted surface and the 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 X99 of 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 and FIG. 17 are diagrams showing sagging characteristics of a paint suitable for use in the present invention. P1 to P5: Process W: Body l: Rotation axis D: Transport cart 1F, 1R: Rotating jig

Claims (1)

(57) [Claims] 1. A coating method comprising: a coating step of applying a coating material to an object to be coated; and a drying step of drying the coating material applied to the object to be coated, wherein the coating step includes a first stage and a second stage. It has two stages, one stage after and the second stage, and the first stage and the second stage
The coating is performed both on the stage and the coating is applied to the second stage so that the final thickness becomes a desired thickness and a dripping occurs in a drying process. Is performed only in one of the first stage and the second stage using the same paint as the paint applied to the vertical surface of the object to be coated in the second stage, and the final film thickness of the lateral surface is reduced. The thickness is made smaller than the final film thickness of the vertical surface of the object to be coated, and in the drying step, the object to be coated is rotated around a substantially horizontal axis until dripping of the paint does not occur. Painting method.