JPS63197582A - Method for painting car body - Google Patents

Abstract

PURPOSE:To obtain a good painting surface generating no dripping, by rotating a car body, which is coated with paint in a thickness equal to or more than a dripping limit, around the horizontal axis passing the center of gravity of the body and extending in a forward and rearward direction. CONSTITUTION:A car body W is sent into a painting process while held on a truck D and the spray for intermediate or to coating is performed so that the thickness of a paint film becomes a dripping limit or more. In the drying process after painting, the body W is rotated in the horizontal direction through the jigs 1F, 1R on the truck D. That is, the front and rear jigs 1F, 1R are set in the mount state to the body W so that the rotary axis 5 thereof is positioned on the same straight line extending in the forward and rearward direction of the body W. This same straight line becomes the rotary axis (l) of the body W and, by setting said straight line so as to pass the center of gravity of the body W, rotational variation is suppressed and the dripping of the paint is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of painting an automobile body.

(Prior art and its problems) When painting the outer surface of an automobile body, there are a step of applying paint to the body 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.
It is carried out in a temperature atmosphere of 0° to 60°C (the baking temperature in the baking process is usually around 140°C).

By the way, one of the criteria for evaluating the quality of painted surfaces is:
It has smoothness (flatness), and the higher the smoothness, the smaller the degree of unevenness on the painted surface, resulting in a better painted surface. It is already known that in order to improve the smoothness of the painted surface, it is sufficient to increase the thickness of the paint film, that is, the film thickness of the applied paint.

On the other hand, something that impedes the quality of the painted surface is "sagging" of the paint. This sagging occurs when the applied paint flows downward under the influence of gravity. The larger the thickness, the more likely ``sagging'' will occur.The cause of this ``sagging'' is ultimately the effect of gravity, so it is more likely to occur on the vertically extending surface of the body, that is, the so-called vertical surface.

Therefore, the horizontally extending surfaces of the body, the so-called lateral surfaces, are not as problematic as the amount of paint ``sagging''! !
! It is possible to make the thickness of the paint applied to the cloth larger than on the vertical sides. Furthermore, 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 on the vertical surface will be smooth. This means that better smoothness can be obtained than the average degree of smoothness.

From the above-mentioned point of view, conventionally, in order to prevent the paint from "sagging" and obtain a painted surface with as much smoothness as possible, painting was done using a paint with as little fluidity (low viscosity) as possible. was. The so-called "sag limit" at which paint sag occurs on the vertical surface is a maximum coating film thickness of about 40 pm for conventional paints. More specifically, paint sag tends to occur at the beginning of the setting process and at the beginning of the baking process, especially at the beginning of the baking process. The thickness is determined, and the maximum value of the determined thickness, ie, the sagging limit value, is approximately 401 Lm. Therefore, in order to obtain a painted surface with even greater absolute smoothness, conventional painting methods require repeating the series of steps from the painting process to the baking process multiple times, such as applying two coats to each individual. It was necessary to do it.

The present invention has been made in consideration of the above-mentioned circumstances, and provides a method for painting an automobile body that allows a coated surface with greater smoothness to be obtained with the same coating thickness. The purpose is to

(Means for solving the problem 1) The present invention basically improves the fluidity of the paint by appropriately changing the direction of gravity acting on the paint applied to the car body. By taking advantage of this, you can obtain a coated surface with greater smoothness for the same coating thickness. Specifically, the configuration is as follows. That is, in a method for painting an automobile body, which includes a painting process of applying the paint for the car body, and a drying process of drying the applied paint, in the painting process, the paint is applied to a thickness that exceeds the sag limit. Apply.

In the drying step, the automobile body is rotated around a horizontal axis passing through the center of gravity of the automobile body and extending in the longitudinal direction of the automobile body.

In this way, in the present invention, the direction of gravity acting on the paint applied to the car body is changed by rotating the body in the horizontal direction, so the paint is
It will dry without causing any sag.

According to the present invention, the film thickness of the paint applied per coat can be made much thicker than before, and an extremely good painted surface with smoothness that far exceeds the level conventionally considered to be the limit can be obtained. can.

Further, even when the thickness of the coating film is the same as that of the conventional coating, the fluidity of the coating material can be utilized to obtain an excellent coated surface with smaller irregularities, that is, greater smoothness.

Furthermore, if you try to obtain a painted surface with the same smoothness, for example, the same level of smoothness as that obtained with conventional painting methods,
The film thickness of the paint to be applied can be made thinner than in the conventional method, and the amount of paint used can be reduced by the amount that can be made thinner.

Of course, paints that cause "sagging" even in thin coatings can be obtained by reducing the components that inhibit fluidity in conventional paints by a predetermined percentage. (A hybrid agent is mixed in to reduce fluidity.)

Additionally, in the present invention, the axis of rotation of the body is set to pass through the center of gravity of the body and extend in the longitudinal direction of the body, so that the centrifugal force acting on the paint applied to the body is minimized. At the same time, rotation fluctuations are prevented, which is even more advantageous in preventing paint from sagging. That is, by extending the rotational axis in the front-rear direction of the body, the distance of the portion away from the rotational axis can be reduced. Furthermore, since the rotational axis passes through the center of gravity of the body, rotational fluctuations are suppressed, and paint sagging due to shocks accompanying these rotational fluctuations is effectively prevented. Incidentally, if the axis of rotation and the center of gravity are offset, the rotation of the body will be faster when the center of gravity moves downward with rotation, and slower when the center of gravity moves upward.

(Example) Hereinafter, an example of the present invention will be described based on the attached drawings.

Money transfer ヱ) [l! FIG. 1 shows the entire process for painting an automobile body Wt, and each process is indicated by Pi-P5.

First, the body W, which has been undercoated by electrodeposition coating in a known manner, is sent to the preparation step Pi while being held on a trolley. In this preparatory step P1, dust inside and outside the body W is removed by, for example, vacuum suction. After that, in step P2, paint is sprayed onto the body W. The body W onto which the paint has been sprayed is changed to a different carriage in step P3, and then the paint is dried in setting step P4 and baking step P5.

If the step Pi-P5 is for intermediate coating, the body W is sent to the top coating step after P5. Also, P
If the step L-P5 is for topcoating, the body W is transported to an assembly line in a known manner.

Preparation First, the paint (for top coat) is sprayed in P2 so that the thickness of the paint film is greater than the sag limit. In other words, with conventionally commonly used paints, the maximum thickness of the paint that does not cause 'sag', that is, the sag limit value, is about 40 pm, but in process P2, this sag limit of 40 pm is used.
m (e.g. 85p)
The paint is sprayed so that it becomes m).

After this P2, the carriage is quickly changed in P3, and then the process moves to the setting step of P4. In this setting step P4, 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 about a rotation axis 6 extending in the horizontal direction.

The temperature atmosphere in this setting step P4 is set to room temperature in the example, but it may be set to an appropriate temperature within a temperature range lower than the temperature atmosphere in the next baking step P5, such as 40° to 60@C. It is possible. Of course, this setting process P4
This is to volatilize the low boiling point components in the paint in advance, thereby preventing the generation of pinholes on the painted surface due to the rapid volatilization of the low boiling point components in the primary baking step P5.

In the baking step P5, the paint is baked in an atmosphere at a temperature of, for example, 1406C. Even in this P5, P
Same as setting step 4.

As shown in FIGS. 2(a) to 2(i), the body W is rotated in the horizontal direction.

Due to the horizontal rotation of the body W at P4 and P5 described above, even if the paint is sprayed to a thickness exceeding the sag limit at P2, the paint dries without sagging. As a result, a high-quality coated surface with extremely high smoothness that could not be obtained with conventional coating methods can be obtained.

In addition, the bogies are changed at P3 in P4, P5,
This is to prevent paint from adhering to the trolley used in the drying process. That is, in P2,
A considerable amount of paint will be sprayed on the trolley,
If the cart with this paint adhered to it is used as is and transferred to the drying process, a considerable amount of the paint adhering to the cart will peel off as the contacting cart moves and become dust.
This is because there is a possibility that the quality of the painted surface will be impaired.

Relationship between film thickness, sag limit, smoothness, and horizontal rotation Figure 3 shows the influence of coating film thickness on the sag limit. In this Figure 3, the coating film thickness is 407 zm,
Three cases are shown: 53#Lm and 65pm. 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 1 usually 1 per minute.
It refers to the value when dropping a sag of ~2 mm (visually 2 mm).
If sagging of more than mm/min occurs, the painted surface is considered defective.)
The maximum coating thickness that can be obtained within the range below this sag limit is about 40 pm with conventional paints.

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 shows the state in which the body W is not rotated (conventional painting method), and Fig. 4 B shows the state in which the body W is not rotated.
Figure 4C shows the case of rotating 90° and then reversing it (forward and reverse rotation between Figure 2 (a) and (C)).
This shows the case where the body W is rotated by 135° and then reversed (forward and reverse rotation between FIG. 2 (IL) and (d)).
The fourth diagram shows the case where the body W is rotated by 180 degrees and then reversed (forward and reverse rotation between Figure 2 (a) and (e)), and Figure 4 E shows the case where the body W is rotated 180 degrees and then reversed. This shows the case of continuous rotation in the same direction (Fig. 2 (a), (b),
Take the posture of (C), pleasure, (i), and then return to (a)).

As is clear from Fig. 4, if the thickness of the coating is the same, it is better to rotate the body W (Fig. 4 B, C, D, E).
), thicker smoothness can be obtained than in the case of no rotation (FIG. 4A). 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 the smoothness. Of course, if the body W does not rotate,
Since there is a limit to the thickness of the coating film, there is a limit to how much smoothness can be increased.

By the way, assuming the thickness of the paint film is 651Lm, the body W is 3
When rotated by 60 degrees, the obtained smoothness is equal to the image sharpness of 1. G is r87J (lower limit of 1.0 in PGD value). Also, when the coating thickness is 40gm, when the body W does not rotate, it is 1. r58J in G (
The lower limit of PGD value is 0.7), while the body W
When rotated by 360@, 1. r68J in G (P
The lower limit of GD value is 0.8).

As is known, IC (Image Gloss °) in image sharpness indicates the ratio of sharpness to a specular surface (black glass) as 100, and PGD indicates the degree of discrimination of reflected images. This is a value at which the smoothness of the painted surface decreases as it decreases from 1.0.

The test conditions for the data shown in FIGS. 3 and 4 are as follows, and these test conditions indicate 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 (1B, 000 rpm) Shaping air 0.2.0 kg 7 cm2 C8 Discharge amount: divided into 2 times The first spraying...
100cc/min 2nd time, 150~200cc/min, Setting time: 10 minutes x room temperature e, Baking conditions = 140°C x 25 molecules, Base smoothness: 0.6 (PGD value) (Intermediate coating, (on PE tape) g0 Rotation or reversal operating range: Setting (10 minutes) - Baking (10 minutes) h, Painted on the side of a rectangular cylinder with a knee side of 30 cm, rotatably supported at the center 1, coated Object rotation speed: 6 rpm, 30 rpm.

The rotation was performed at three different rotational speeds of 60 rpm, but there were no differences due to the different rotational speeds (see the margin below).Rin Kei ■L side A Next, the body W was supported so that it could rotate horizontally relative to the trolley. A specific example of a jig used for this purpose will be explained.

Figure 5 shows the front jig I attached to the front of the body W.
This jig IF 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, and a connecting bar 4 that connects the left and right pair of stays 3. , and a rotating shaft 5 integrated with the connecting bar 4. The bracket 2 portion of such a jig IF is fixed to the front end portion of the front strength member 1, for example, the front side frame 11 of the body W. That is, since a bracket 12 for mounting a bumper (as shown) is normally welded to the front side frame 11, this body W
The bracket 2 is fixed to the side bracket 12 using bolts (as shown).

On the other hand, the rear jig IR attached to the rear part of the body W is shown in FIG. The rear jig IR has a similar configuration to the front jig IF, and the same reference numerals are given to the components corresponding to the front jig IF. The rear jig IR is attached to the body W by fixing the bracket 2 to the floor frame 13 as a strength member at the rear end of the body W with bolts. Of course, at the rear end of the floor frame 13,
Since the bumper mounting bracket is generally welded for mounting the bumper, the rear jig IH can also be mounted using this bumper mounting bracket.

When the front and rear jigs IF and IR 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 rotation axis edge of the body W, and this rotation axis edge is set to pass through the center of gravity G of the body W (see FIG. 7).

In other words, the current automobile body painting line is a mixed flow line where many car models flow together, but by keeping the front and rear jigs dedicated to each car, it is possible to reduce the number of bogies that will be described later. The body W of all vehicle types is supported by a common truck so that it can be rotated around a horizontal axis that sends its center of gravity.

friend! At least P4. It is a trolley that is used in 'P5 and has the function of rotating the body W.

In FIG. 7, the trolley has a base 21, and this base 2
Wheels 22 attached to the vehicle 1 are run on a road surface 23. This base 21 consists of one front support 24, two wooden intermediate supports 25, 26, and one rear support that extend upward in sequence from the front side in the running direction to the rear side (from the right side to the left side in FIG. 7). It has a support column 27, and a support space 28 is provided between the intermediate column 25, 26 and the rear column 27 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 IF, while its rear part is supported using the rear jig IR. It is rotatably supported by the rear support 27. Of course, this support space 28 is formed to correspond to the largest body W.

The front and rear jigs IF and IR (rotary shafts 5 of them) can be freely engaged with and disengaged from the columns 26 and 27 from the vertical direction, and the rear jig IR is immovably engaged in the vertical direction of the rotation axis. Ru.

For this reason, a notch 26a that opens on the upper end surface of the intermediate support 2B is formed (see FIGS. 10 to 12).
, a notch 27a that opens on the upper end surface of the rear support 27 is formed (see Fig. 1θ, Fig. 14, and Fig. 15).
Both notches g26a and 27a are sized to fit the rotating shafts 5 of the jigs IF and IR. A flange portion 5a is formed on the rotating shaft 5 of the rear jig IR, while a notch 27b having a shape corresponding to the flange portion 5a communicating with the notch 27a is formed in the rear support 27. ing. As a result, the rear jig IR is engaged with and disengaged from the notches 27a and 27b of the rear column 27 from above and below, and the rear column 2
7, it is immobile in the front and back direction. Note that the rotational force is applied to the body W via the rotation shaft 5 of the front jig IF, and therefore, the tip of the rotation shaft 5 of the front jig IF has a
A connecting portion 5b (see also FIG. 5), which will be described later, is formed.

A stay 29 is provided to protrude downward from the base 21,
A traction wire 30 is connected to the lower end of this stay 29. This wire 30 is of an endless type,
It is driven in one direction by a motor (not shown), and thereby the trolley is driven 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 is performed by using the movement of one truck, that is, by using the displacement of the truck with respect to the running road surface 23. A rotation extraction mechanism 31 for extracting the displacement of the truck as rotation is configured in a first-order manner. That is, the rotation take-out mechanism 31 includes a rotation shaft 32 extended vertically and rotatably supported on the base 21, a sprocket 33 fixed to the lower end of the rotation shaft 32, and a sprocket 33 fixed to the lower end of the rotation 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 running road surface 23. This results in
When the trolley is pulled through the wire 30, the chain 3
Because 4 is immovable.

The sprocket 33 that meshes with the chain 34 rotates the rotating shaft 32.

The rotation of the rotation shaft 32 is controlled by the rotation shaft 5 of the front jig IF.
The transmission mechanism 35 for transmitting the signal is configured as follows. That is, the transmission mechanism 35
The casing 36 fixed to the rear surface of 4 and the casing 3
6, a rotating shaft 37 extending laterally (back and forth) and rotatably supported, a pair of bevel gears 38 and 39 that interlock this rotating shaft 37 and the upper rotating shaft 32, and The connecting shaft 40 is held rotatably and slidably in the front-rear direction. This connecting shaft 40 is
It is spline-coupled to the rotating shaft 37 (this retaining portion is indicated by material number 41 in FIG. 7), so that when the rotating shaft 32 is rotated, the connecting shaft 40 is also rotated. Of course, the rotating shaft 37 and the connecting shaft 40 are installed so as to be located above the rotating axis.

The connecting shaft 40 is connected to the rotating shaft 5 of the front jig IF.
be disengaged. That is, as shown in Figures 1θ to 12H, 1. A cross-shaped connecting portion 5b is formed at the tip of the rotating shaft 5 for the front jig IF.

The end of the connecting shaft 40 has an engaging recess 4 into which the connecting portion 5b is fitted without play, as shown in FIGS. 1θ and 13.
A box portion 40a having a diameter of 0c is formed. Therefore, for example, by sliding the connecting shaft 40 via the rod 43 by a pneumatic cylinder 42, the box portion 40a (engaging recess 40C) and the connection @5b are engaged and disengaged, and when they are engaged, they are connected. The shaft 40 and the rotating shaft 5 are allowed to rotate together. Note that the rod 43 is the tenth rod.
As shown in the figure, it 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, by lowering the body W relative to the trolley while the connecting shaft 40 is displaced to the right in FIG.

Each rotating shaft 5 of the IR is rotatably and immovably supported in the front-rear direction by intermediate struts 26 and 27. 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 IF. As a result, when the single carriage is towed via the wire 30, the body W is rotated around a predetermined horizontal axis. In addition, the removal of the body W from the trolley may be performed in the reverse order to the above-described procedure.

FIGS. 16, 17, 18, and 19 each show a modification of the connecting portion between the rotating shaft 5 of the front jig IF and the connecting shaft 40. FIG.

In the case of FIGS. 16 and 17, first.

The notch J26a of the intermediate support 26 is formed in a semicircular shape so as to be able to rotatably support the box portion 40a. Further, while the connecting portion 5b-1 of the rotating shaft 5 is formed in an L-shape, the engaging recess 40cm1 formed in the box portion 40a
However, the L-shaped connecting portion 5b-i is of a shape that is engaged in a relatively non-rotatable manner, and the engaging recess is 40 cm1.
is opened on one side of the box portion 40a, and when this opening portion faces upward, the connecting portion 5b-1 is engaged with and disengaged from the engagement recess 40cm1 from above and below. (no need for sliding of the connecting shaft 40).

In FIGS. 18 and 19, as in FIGS. 17 and 18, only when the engagement recess 40 cm2 formed in the box part 40a faces upward, the rotating shaft 5 of the front jig IF
The connecting portion 5b-2 formed in the shape can be connected and disconnected, and the connecting portion 5cm2 has a rectangular cross section,
The difference from the cases shown in FIGS. 16 and 17 is that the engaging recess 40 cm2 has a shape corresponding to this square.

Of course, in the cases shown in FIGS. 16 to 19, the connecting shaft 4
0 and the front jig IF can be engaged and detached (engagement recess 40c
m1.40cm2 facing upward), the body W
is in the upright position (the roof panel of the body W is facing upward as shown in FIG. 7).

This is a device for changing the trolley in the blood train P3, and examples thereof are shown in FIGS. 20 to 22.

As shown in FIG. 22, this truck changing device is installed at a transfer stage St where the truck movement trajectory R1 in the previous process and the truck movement trajectory R2 in the post process are close to each other. The trolley changing device installed at this transfer station Sl is the 20th
As shown in FIGS. 21 and 21, it is substantially composed of a lifter 51.

The lifter 51 includes a pair of left and right guide posts 52, a base 53 attached to each guide post 52 so as to be driven up and down, and support legs that are driven by the bases 53 so as to be able to expand and contract. 54. Each of the support legs 54 has a pair of front and rear support portions 54a spaced apart from each other in the moving direction of the truck.

In the above configuration, the trolley supporting the body W from the previous process is stopped at the transfer station S1.
When the trolley is stopped, the support legs 54 are extended from the base 53 located at the lowest position, and then the base 53 is moved upward. As a result, as shown in FIGS. 20 and 21, the body W on the one carriage is supported by the side sill or floor sill part of the body W by the support portions 54a of the support legs 54, and is lifted up from the carriage to a high height. be lifted into position. After this, the cart for the previous process moves away from the transfer stage St, and the cart for the post process moves to the new transfer station S.
1. After this, the base 53 is lowered and the body W is transferred to the trolley. Then, in preparation for the first transfer, the support legs 54 are retracted (see the dashed line in FIG. 21).
In this way, the body W is transferred from the front-process truck to the rear-process truck.

Of course, when transferring the body W, it is preferable to firmly fix the dolly in a predetermined position in an immovable state using a positioning device or the like that clamps the dolly from the front, back, left and right directions.

The transfer device for the trolley is assumed to have a hanger that is intermittently fed to a high place, and after the body W is transferred to the hanger by the lifter 51, this hanger moves the body W above the trolley for post-processing. The body may be moved, and at this position, the lifter may be used again to transfer the body from the hanger to a cart for post-processing.

(The following is a blank space) Supplementary Explanation and Modified Examples Next, supplementary explanations related to the present invention will be sequentially explained.

■First, when removing dust in step Pi, it is recommended to rotate the body W around the rotating shaft edge stand (second
(see Figures (2) to (i)), as a result, the dust that has adhered to the inner surface of the body W, especially the surface that faces downward in the upright position, falls downward due to gravity, so that the dust can be removed more reliably. It is possible to perform the removal. This prevents dust from falling during the rotation of the body W during the setting process and baking process, which is important in obtaining a high-quality painted surface.

■When applying the top coat after the intermediate coat, it is possible to eliminate the hydroponic bath after the intermediate coat baking process. In this case, the body W may be rotated only during either the intermediate coating process or the top coating process.In other words, the quality of the final painted surface obtained after the top coating is determined by the quality of the intermediate coating. However, when the body W is rotated during the intermediate coating, the finishing level of the intermediate coating can be increased, so that the conventional hydroponic method is no longer necessary. Furthermore, by rotating the body W during the top coat, the poor finish of the middle coat can be compensated for by the quality of the top coat, without the need for hydroponic treatment during the middle coat.

■When rotating the body W with the top coat and forming a thin coating film with a top coat with a small sag limit, it is recommended to use a so-called color intermediate coat, which allows the intermediate coat to show through the top coat. Even if you can see it, it will be completely unreliable in terms of color.

(2) Switching between rotating and stopping the body W and changing the direction of one rotation regardless of whether the trolley is running or stopping can be performed, for example, as follows. First, in the example shown in Fig. JJ7, a pair of first and second chains (chain 34
If the structure is such that each chain can be driven as appropriate, the rotation of the body W can be controlled according to the following drive mode. become.

■Stopping the first chain and freeing the second chain: In this case, the body W is rotated in one direction as the trolley moves.

■First chain free and second chain stopped: In this case, the body W is rotated in the opposite direction to the above (■) as the trolley moves.

■Both chains are free: In this case, the body W is not rotated as the trolley moves.

- Drive the first chain in one direction and free the second chain: In this case, even if the truck is stopped, the body W is rotated in one direction.

■Drive the first chain in the other direction and make the second chain free (same as if the first chain is free and the second chain is driven in the other direction): In this case, even if the bogie is stopped,
The body W is rotated in the opposite direction to that in the case (2) above.

Note that the above description also applies when a rack bar is used instead of the chain. If this rack bar is always placed in a fixed state (in this case, the traveling of the trolley 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 changed from left to right. By setting it arbitrarily, the body W can be rotated in any direction depending on the traveling position of the single carriage, and the rotation of the body W can be stopped at an arbitrary position.

In the above embodiments, a case has been described in which the body W is rotated even in the setting step P4 of the drying step, but it may also be rotated only in the baking step P5.

(Effects of the Invention) As is clear from the above description, the present invention utilizes the application of paint with a thickness exceeding the sag limit and the rotation of the automobile body to achieve a coating thickness that is higher than that of the conventional paint for the same paint thickness. A high-quality painted surface with high smoothness can be obtained.

In particular, the rotation of the body during the drying process is set so that its axis of rotation, which extends in the horizontal direction, passes through the center of gravity of the body and extends in the front and back direction of the body, so it acts on the paint applied to the body. It is extremely effective in minimizing centrifugal force and preventing shock to the paint due to rotational fluctuations, and reliably prevents paint from sagging caused by the rotation of the car body itself. be done.

[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. Figures 3 and 4 are graphs showing the relationship between paint thickness, blurring, smoothness of the painted surface, and rotation. FIGS. 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 transport 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. FIG. 10 is a side cross-sectional view showing the joint portion between the rotating jig and the truck. FIG. 11 is a sectional view taken along the line X1l-Xll in FIG. 10. FIG. 12 is a plan view of FIG. 11. FIG. 13 is a cross-sectional view taken along the line X13-X13 in FIG. 1θ (7). FIG. 14 is a sectional view taken along the line X14-X14 in FIG. io (7). FIG. 15 is a plan view of FIG. 14. 16 and 17 show modified examples of the connection part with the rotation jig, and FIG. 16 shows the X16-X16 in FIG.
A line sectional view, and FIG. 17 is a side sectional view. Figures 18 and 19 show still another modification of the joint portion between the rotating jig and the cart, in which Figure 18 is a cross-sectional view taken along the line X18-X18 in Figure 19, and Figure 19 is a side cross-sectional view. figure. FIG. 20 is a side view showing an example of a device for changing the truck. FIG. 21 is a front view of FIG. 20. FIG. 22 is a simplified plan view showing an example of the traveling route of the bogie and the arrangement position of the bogie changing device. P1 to P13: Process W: Body fL = Rotation axis D: Transport trolley G: Center of gravity 1F, IR: Rotation jig J: Skin fL (, L1ml

Claims (1)

[Claims] (1) In a method for painting an automobile body, which comprises a painting process of applying the paint for the car body and a drying process of drying the applied paint, in the painting process, the paint is coated to a thickness exceeding the sag limit. A method for coating an automobile body, characterized in that, in the drying step, the automobile body is rotated around a horizontal axis passing through the center of gravity of the automobile body and extending in the longitudinal direction of the automobile body.