JP2545435B2 - Painting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) 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 steps, a setting step and a baking step. The setting step is performed before the baking step at a temperature lower than this baking step, for example, at room temperature or 40 ° so that it is also called calcination. It is performed to slowly volatilize the solvent in the paint in a 60 ° C temperature atmosphere (preventing pinholes due to rapid evaporation of the solvent during the baking process in high temperature atmosphere).

Then, the article to be coated usually goes through the above-mentioned preparation step, coating step and drying step while being transported by a transporting means such as a carriage, but the posture of the article to be coated maintains a predetermined posture in each step. It is still done.

By the way, smoothness (flatness) is one of the criteria for evaluating the quality of the coated surface. The higher the smoothness, the smaller the degree of unevenness of the coated surface, and the better the coated surface. It is already known that in order to improve the smoothness of the coated surface, the thickness of the coating film, that is, the thickness of the applied coating material may be increased.

On the other hand, there is "drip" of the paint that hinders the quality of the painted surface. This dripping occurs when the applied paint flows downward due to gravity and causes 1
The greater the film thickness of the coating applied at a time, the more easily “sagging” occurs. Since the cause of “sagging” is ultimately the effect of gravity, the so-called vertical surface of the object to be coated extends vertically. It is likely to occur.

Therefore, the horizontal surface of the object to be coated, which is a so-called horizontal surface, in which the "drip" of the coating material does not cause a problem, can be made thicker than the vertical surface. Even if the thickness of the coating film on the horizontal surface is the same as the thickness of the coating film on the vertical surface, the unevenness is reduced by the slight flow of the paint that does not cause sagging on the horizontal surface, resulting in smoothness on the vertical surface. The smoothness is better than the degree.

In view of the above, conventionally, in order to obtain a painted surface with as large a smoothness as possible while preventing "sagging" of the paint, painting has been performed using a paint with as low fluidity as possible. In other words, in order to obtain a coated surface with even greater smoothness, in the conventional coating method, for example, a series of steps from the coating step to the baking step, such as two-time coating, is repeated multiple times. I had to do it.

The above-mentioned sagging tends to occur in both the setting process and the baking process in the commonly used thermosetting paint, and in the setting process in the two-component curing paint that uses the main resin and the curing agent. It was supposed to happen.

(Object of the Invention) The present invention has been made in consideration of the above circumstances, and provides a coating method that can obtain a coated surface with even greater smoothness with the same coating thickness. The purpose is to do.

(Means for Solving the Problems, Function) The present invention basically relates to the fluidity of the paint by appropriately changing the direction of gravity acting on the paint applied to the object to be coated. Is positively utilized so as to obtain a painted surface having a higher smoothness if the film thickness is the same. Specifically, it has the following configuration. That is, a coating method including a coating step of applying a coating material to an object to be coated, a setting step of volatilizing a solvent in the applied coating material in a low temperature atmosphere, and a coating material curing step of curing the coating material after the setting step. In, the article to be coated is rotatably supported around a substantially horizontal axis, and in the coating step, paint sagging occurs on a surface extending in the vertical direction of the article only in the setting step of the setting step and the paint curing step. Such a coating material is applied to the object to be coated, and in the setting step, the object to be coated starts to rotate about a horizontal axis before the paint drip of the coating material applied to the object to be generated due to gravity. The rotation is performed at a speed such that the surface of the object to be coated shifts from a substantially vertical state to a substantially horizontal state at least before the paint sags of the applied paint due to gravity, and is rotated by the rotation. It is configured so that it is rotated at a speed slower than the speed at which paint drips due to centrifugal force.

As described above, in the present invention, the direction of gravity acting on the coating material applied to the object to be coated is changed by rotating the object to be coated in the horizontal direction, so that the coating material "drips" during the setting process. Will be dried without causing.

According to the present invention, it is possible to obtain a very good painted surface whose smoothness far exceeds the level which has been conventionally regarded as the limit by making the thickness of the coating applied at one time much thicker than before. it can.

Also, even when the thickness of the coating film is the same as the conventional one,
By utilizing the fluidity of the coating material, it is possible to obtain an excellent coated surface having a smaller unevenness, that is, a higher 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.

Of course, in the present invention, the paint is used so that the sagging does not occur any more during the setting process in the low temperature atmosphere. Therefore, in the paint curing process after the setting process, the coated object is rotated to prevent sagging. It is not necessary.

(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

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

First, the body W, whose undercoating has been completed by known electrodeposition coating, is sent to the preparatory step P1 while being held by the carriage D. In this preparation step P1, dust inside and outside the body W is removed by, for example, air blow or vacuum suction. Next, in step P2, after the body W is sprayed with a paint that causes sag only in the setting step P3 of the next setting step P3 and P4 as the paint curing step, for example, a two-component curing type paint. The paint is dried in the setting process P3 and the baking process P4.

Dust Removal The dust removal in the process P1 may be performed while rotating the body W around the horizontal axis l, as shown in FIG. (That is, first, for example, in the state shown in FIG.
After the rotation of is stopped to remove dust, the posture of the body W is changed to the state of FIG. 2 (b) and stopped at this position, and dust is removed again. In this way,
As shown in (c), (d), (i) of FIG. 2, dust is removed while the body W is intermittently rotated.

In this way, by removing dust while rotating the body W, for example, dust that adheres to the inner surface corners of the body W or the closed cross section of the side sill, 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 at P2 is performed so that the thickness of the coating film is equal to or greater than the sag limit. That is, in the conventional two-component curing type paint that is generally used, the maximum thickness of the paint that does not cause "sagging", that is, the sag limit value is about 40 μm, but in process P2, it is much less than the sagging limit of 40 μm. The paint is sprayed so as to form a thick coating film (for example, 65 μm).

After this P2, it will be immediately transferred to the setting process of P3. In this setting process P3, FIG.
As shown in (i), the body W is rotated in the horizontal direction. That is, the rotation axis core 1 in which 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. Although the temperature atmosphere in this setting step P3 is room temperature in the embodiment, it is the next baking step P4 such as 40 ° -60 ° C.
The temperature can be set to an appropriate temperature in a range lower than the temperature atmosphere. Of course, this setting step P3 is for volatilizing the low-boiling point component in the paint beforehand, which causes pinholes on the painted surface due to the rapid volatilization of the low-boiling point component in the next baking step P4. To be prevented. Also,
The rotation of the body W is performed until the paint is sufficiently cured until the sagging no longer occurs in the natural state.

In the baking process P4, for example, the paint is baked in a temperature atmosphere of 90 ° C. In this P4, the paint is sufficiently hardened in the setting process of P3 and sagging no longer occurs, so that the body W is not rotated to prevent sagging.

Due to the horizontal rotation of the body W in the setting process P3 described above, even if the paint is sprayed to a thickness exceeding the sag limit in P2, the paint is dried without sagging. As a result, a high-quality coated surface with extremely high smoothness, which cannot be obtained by the conventional coating method, can be obtained.

Relationship between coating thickness, sag limit and horizontal rotation FIG. 3 shows the influence of the coating thickness on the sagging limit. In Fig. 3, the coating thickness is 55
Three cases of μm, 65 μm, and 75 μm are shown. For both of these thicknesses, in the middle of the setting process,
It is understood that a "drip" peak occurs and no sagging occurs in the baking process (acceptable range). The sag limit is a value when a sagging of 1 to 2 mm is usually generated in 1 minute (a sagging of 2 mm / min or more is visually observed to indicate that the coated surface is defective). The maximum coating thickness obtained in the range is about 40 μm with the conventional paint.

The rotation of the body W may be continuously rotated in the same direction, or may be reversed at a predetermined angle. Further, the rotation speed is, for example, 3 rpm to 60 rpm, which causes sagging due to centrifugal force. It may be appropriately set in a range in which the direction of gravity acting on the paint is reversed before the sagging occurs without causing the sag. Further, the rotation axis of the body W may be inclined about 10 ° with respect to the horizontal axis.

The test conditions for the data shown in FIG. 3 are as follows.

Paint: Polyester urethane paint white (Nippon Bikemiral Co., Ltd., trade name R-263) Main resin: Polyester polyol white Curing agent: Hexalmethylene diisocyanate Mixing ratio (weight ratio): Curing agent 1 to main resin 4 B. Coating machine: Pressure feed type air spray gun (Iwata Coating Machine Co., Ltd.)
Product name: Wider W71) c. Spraying viscosity: 16 seconds / Ford cup # 4 d. Paint discharge rate: 350 cc / min e. Atomizing air pressure: 4.0 kg / cm ² f. Spraying distance: 30 cm g. Number of overlaps: 2 times (interval 3 minutes) FIG. 15 is a diagram showing the sag characteristic 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 ℃
After raising the temperature for 8 minutes to 140 ° C,
For a minute.

FIG. 15 shows a total of three test examples a to c, that is, examples of thermosetting paints that can be used in the present invention. Specific test conditions for obtaining such data are as follows. Is the street. In the following description, Test Example a
Those that do not distinguish between c and c are common matters.

(1) Paint ・ 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 after 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.

In each of the above test examples, [viscosity, anti-sagging agent] is [2
[2,3] is the standard one used in the conventional coating method. (Both the first stage and the second stage) In each of the test examples a to c, sagging occurs in the setting process (dripping speed is 2 mm / min or more), and sagging does not occur in the printing process.

It should be noted that while the standard for two stages is [22,3], the one stage is [22,3], [15,3], [30,3],
Each of [15,6], [22,6], and [30,6] was tested, and in each case, sagging occurred in the baking process.
As a result of conducting tests on [15,0] and [22,0] for one stage, sagging occurred in the setting process and did not occur in the baking process. However, the sagging occurred immediately after the setting process was started. It was quite rapid, within minutes. Therefore, if it is possible to move to the setting process immediately after the completion of painting, it is possible to use paints with the above conditions, but it is true if manual correction painting etc. is performed between the painting process and setting process. It is unusable.

In addition, the standard [22,3] for the 1st stage, while [22,3], [30,0], and [30,3] for the 2nd stage, caused sagging in the baking process. In addition, the tests [15,6], [22,6] and [30,6] did not cause sagging in the setting process.

Further, the tests were conducted in the following two cases for the first stage and the second stage, but in both cases, sagging occurred in the baking process.

First stage Second stage [15,0] [30,3] [15,3] [22,3] Rotating jig Next, in order to support the body W rotatably in the horizontal direction with respect to the carriage D. A specific example of the jig used for is described.

FIG. 4 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. It has the integrated rotating shaft 5. Such a jig 1F, the bracket 2 part,
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 part of the body W
Is shown in FIG. The rear jig 1R has the same structure as the front jig 1F, and the components corresponding to the front jig 1F are designated by the same reference numerals. This rear jig
1R is attached to the body W by mounting the bracket 2 on the floor frame 13 as a strength member at the rear end of the body W.
It is carried out 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.

The front and rear jigs 1F and 1R are arranged such that the rotating shafts 5 of the front and rear jigs 1F and 1R are located on the same straight line extending in the front-rear direction of the body W when mounted on the body W. This collinear line serves as the rotation axis l of the body W, and this rotation axis l is preferably the center of gravity G of the body W (see FIG. 6).
It is supposed to pass through. Since the rotation axis l passes through the center of gravity G, when the body W rotates, large fluctuations in the rotation speed are prevented. As a result, it is possible to prevent the body W from being impacted by the rotation fluctuation, which is more preferable in terms of preventing sagging.

In addition, the front and rear jigs 1F and 1R are for vehicle type (type of body W)
Special items are prepared in advance according to the requirements.

Truck A truck having a function of rotating the body W.

In FIG. 6, the dolly D has a base 21, and the base 21
Wheels 22 attached to the vehicle are run on a road surface 23. The base 21 is a front support column that extends upward from the front side to the rear side (from the right side to the left side in FIG. 6) in the traveling direction.
24, two intermediate columns 25 and 26, and one rear column 27 are provided, and a space between the intermediate columns 25 and 26 and the rear column 27 is a support space 28 that is largely spaced in the front-rear direction. .

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

The front and rear jigs 1F and 1R (rotating shaft 5 thereof) can be engaged with and disengaged from the columns 26 and 27 in the vertical direction, and the rear jigs
1R is immovably engaged in the direction of the rotation axis l. For this reason, the middle strut 26 is formed with a notch 26a opening at its upper end surface (see FIGS. 9 to 11), while the rear strut 27 is formed with a notch 27a opening at its upper end surface. (See FIGS. 9, 13 and 14). These two notches 26a, 27a
Is sized so that the rotary shaft 5 of the jigs 1F and 1R can be fitted therein. Then, the flange 5a is provided on the rotary shaft 5 of the rear jig 1R.
On the other hand, the rear strut 27 is formed with a notch 27b having a shape corresponding to the flange portion 5a communicating with the notch 27a. As a result, the rear jig 1R is notched in the rear strut 27.
It is engaged with and disengaged from the vertical direction with respect to 27a and 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 rotational force is applied to the body W via the rotary shaft 5 of the front jig 1F. Therefore, the tip of the rotary shaft 5 of the front jig 1F has a connecting portion 5b to be described later.
(See also FIG. 4) are formed.

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

The rotation of the body W is performed by using the movement of the carriage D, that is, the displacement of the carriage D with respect to the traveling road surface 23. A rotation take-out mechanism 31 for taking out the displacement of the carriage D as a rotation is configured as follows. That is, the rotary take-out mechanism 31 includes a rotary shaft 32 that is vertically extended on the base 21 and is rotatably supported, a sprocket 33 fixed to a lower end of the rotary shaft 32, and a chain 34 that is meshed with the sprocket 33. It consists of and. This chain 34
Are arranged in parallel with the wire 30 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 column 24 and a rotation shaft 37 rotatably supported on the casing 36 by extending in the lateral direction (front-back direction).
A pair of bevel gears 38 and 39 that interlock the rotating shaft 37 and the upper rotating shaft 32, and a connecting shaft 40 that is held rotatably and slidably in the front-rear direction with respect to the intermediate column 25. Have. The connecting shaft 40 is spline-connected to the rotating shaft 37 (this engaging portion is shown by reference numeral 41 in FIG. 6), and when the rotating shaft 32 is rotated by this, the connecting shaft 40 is also rotated. become. Of course, the rotary shaft 37 and the connecting shaft 40 are installed so as to be located on the rotary axis l.

The connecting shaft 40 is engaged with and disengaged from the rotary shaft 5 of the front jig 1F. That is, as shown in FIGS. 9 to 11, a cross-shaped connecting portion 5b is formed at the tip of the rotary shaft 5 for the front jig 1F, while at the end of the connecting shaft 40, As shown in FIGS. 9 and 12, a box portion 40a having an engaging recess 40c into which the connecting portion 5b is fitted without rattling is formed. Thus, for example, a pneumatic cylinder 42 may provide a rod 43
By sliding the connecting shaft 40 via the box part 40a (engaging recess 40c) and the connecting part 5b, the connecting shaft 40 and the rotary shaft 5 can be integrally rotated when engaged. It is said that The rod 43 is fitted in an annular groove 40b formed on the outer periphery of the box portion 40a so as not to hinder the rotation of the connecting shaft 40, as shown in FIG.

With the above configuration, the body W is lowered with respect to the carriage D in a state where the connecting shaft 40 is displaced to the right in FIG. 6, so that the rotary shafts 5 of the front and rear jigs 1F and 1R are moved to the middle. The columns 26 and 27 are rotatably supported in the front-rear direction in an immovable state. Then, the connecting shaft 40 (locking recess 40c) is engaged with (the connecting portion 5b of) the rotating shaft 5 in the front jig 1F.
As a result, when the carriage D is pulled through the wire 30, the body W is rotated about the predetermined horizontal axis l. It should be noted that the body W can be removed from the dolly D in the reverse order of the procedure described above.

Supplementary explanation Regardless of whether the carriage D is running or stopped, the body W can be switched between rotation and stop, and the rotation direction can be changed by using a separate dedicated actuator such as an air motor. Can be done. First, in the example of FIG. 6, the sprocket 33 is provided with a pair of first and second chains (corresponding to the chain 34) that mesh with each other from the radial opposite sides, and each chain can be driven appropriately. I will do so. With such a configuration, the rotation of the body W is controlled according to the following driving mode.

The first chain is stopped and the second chain is free: In this case, the body W is rotated in one direction as the bogie D travels.

First chain free and second chain stop: In this case, the body W is rotated in the opposite direction as the carriage D travels.

Both chains are free: in this case, the body W is not rotated with the movement of the truck D.

Driving the first chain in one direction and freeing the second chain: In this case, the body W is rotated in one direction even when the carriage D is stopped.

Driving the first chain in the other direction and freeing the second chain (the same applies when the first chain is free and the second chain is driven in the other direction): In this case, even if the bogie D is stopped,
The body W is rotated in the direction opposite to the above case.

Note that the above is the same even when a rack bar is used instead of the chain. When the rack bar is always arranged in a fixed state (in this case, the traveling of the bogie D is a prerequisite for the rotation of the body W), the rack bar is intermittently arranged, or the position at which the rack bar is arranged is left and right By setting arbitrarily, the body W can be rotated in an arbitrary direction according to the traveling position of the cart D, and the rotation of the body W can be stopped at an arbitrary position.

(Effects of the Invention) As is clear from the above description, the present invention makes it possible to obtain a high-quality coated surface having a higher smoothness than conventional ones if the same coating thickness is used.

Further, the rotation of the coated object for preventing paint dripping only needs to be performed in the settling step, and rotation is not required in the paint curing step, which is also preferable in suppressing energy consumption required for rotation.

[Brief description of drawings]

FIG. 1 is an overall process diagram showing an embodiment of the present invention. FIG. 2 is a view showing a state in which the posture of the automobile body as an object to be coated is changed as the automobile body rotates. FIG. 3 is a graph showing the relationship between paint thickness and sag. 4 and 5 are perspective views showing an example of a jig used for rotating the body. FIG. 6 is a side view showing an example of a trolley for carrying a body in which the body is rotated. FIG. 7 is a partially cutaway plan view showing a state below the traveling path of the carriage. FIG. 8 is a sectional view taken along line X9-X9 in FIG. FIG. 9 is a side sectional view showing a connecting portion between the rotating jig and the carriage. FIG. 10 is a sectional view taken along line X11-X11 of FIG. FIG. 11 is a plan view of FIG. FIG. 12 is a sectional view taken along line X13-X13 of FIG. 13 is a sectional view taken along line X14-X14 in FIG. FIG. 14 is a plan view of FIG. FIG. 15 is a diagram showing the dripping characteristics of the thermosetting paint that can be used in the present invention. P1 to P4: Process W: Body (substrate to be coated) l: Rotation axis D: Transport cart 1F, 1R: Rotating jig

Claims (1)

(57) [Claims] 1. A coating step of applying a coating material to an object to be coated, a setting step of volatilizing a solvent in the applied coating material in a low temperature atmosphere, and a coating material curing step of curing the coating material after the setting step. In the coating method, the article to be coated is rotatably supported about a substantially horizontal axis, and in the coating step, the coating is applied to a surface extending in the vertical direction only in the setting step of the setting step and the coating curing step. A paint that causes sagging is applied to the object to be coated, and in the setting step, before the paint sagging of the paint applied to the object to be started is caused by gravity, the object is started to rotate about a substantially horizontal axis, and In this case, the rotation should be performed at such a speed that at least the surface of the object to be coated shifts from a substantially vertical state to a substantially horizontal state before the paint sags of the applied coating due to gravity. That the centrifugal force is rotated operated at a slower rate than the coating sagging occurs, coating wherein the.