JP2559761B2 - Painting method - Google Patents

Description

The present invention relates to a coating method using a powder coating material.

(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 object to be coated, a step of applying a coating material to the object to be coated, and a drying step of drying (curing) the applied coating material. When the coating material is powder coating material, this drying step is performed in only one step of baking step. 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 sagging is caused by the downward flow of the applied coating due to the gravity, and the larger the thickness of the coating applied at one time, the more easily the “sag” will occur. Since the cause of this "sag" is, after all, the effect of gravity, it tends to occur on the vertically extending surface of the article, that is, the so-called vertical surface.

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.

On the other hand, recently, powder paints are often used as paints. In the powder coating material, the above-mentioned sagging occurs in the baking process. That is,
When the powder coating material receives heat during the baking process, it becomes fluid so-called heat flow, which causes sagging. Therefore, in this powder coating material, the thickness of the coating material applied in the coating step is restricted so that sagging does not occur in the baking step.

Since the powder coating material does not contain a solvent, it does not have a setting step of volatilizing the solvent in a low temperature atmosphere before the baking step.

(Object of the Invention) The present invention has been made in consideration of the above circumstances, and in the case of using a powder coating, a coated surface having a larger smoothness can be obtained if the coating film has the same thickness. It is intended to provide a coating method adapted to the above.

(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, the coating step of applying the powder coating material to the article to be transported by the first transporting means to a thickness that causes paint dripping on the surface that normally extends in the vertical direction during baking and drying, and after the coating step. A transfer step of transferring the object to be coated from the first transfer means to a second transfer means provided with a rotating device, and rotating the object to be transferred transferred to the second transport means around a horizontal axis by the rotating device. And a baking step of baking and drying the coating material applied to the object to be coated while rotating the coating material. Is rotated at least at such a speed that 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 paint due to gravity, and is slower than the speed at which the paint sags due to centrifugal force due to the rotation. Rotated at speed A configuration equipped with Rukoto.

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 baking process. It will be dried and cured 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.

In addition to the above, in the present invention, since the conveying means of the article to be coated is changed between the coating step and the baking step,
In this baking step, the generation of dust caused by the paint is prevented, and a clean painted surface free from dirt can be obtained. Explaining this point in detail, when coating and fixing, powder coating material is applied not only to the object to be coated but also to the conveying means thereof. On the other hand, if the transport means to which the paint adheres is used as it is in the baking step, the transport means necessarily has a sliding portion, and therefore the paint adhered to the sliding portion of the transport means is separated from the transport means as it is cured. As a result, they become suspended dust and adhere to the surface of the object to be coated. However, in the present invention, since the baking step is performed by using the second transporting means separately without using the first transporting means used in the coating step, the above-mentioned coating agent causes dust adhesion to the surface of the article to be coated. Such a situation is prevented.

Since the powder coating material does not sag until it is subjected to a high temperature in the baking process, it is possible to secure a sufficient margin time for transferring the object to be coated from the first transfer means to the second transfer means. .

(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 P1.

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'as the first transfer means. In this embodiment, the carriage D'is the same as that used conventionally. In the preparation process P1, dust inside and outside the body W is removed by, for example, air blow or vacuum suction.
Next, in step P2, the powder coating material is sprayed onto the body W by, for example, an electrostatic coating method, and thereafter, in the transfer step P3, the body W moves from the dolly D ′ to the rotating device as the second transfer means. It is transferred to the trolley D provided. Then, the coating material is dried or hardened in the baking step P4 while rotating the body W around the horizontal axis.

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 powder coating material generally used, the maximum thickness of the coating material that does not cause "sag", that is, the sag limit value is about 80 μm, but in the process P2, it is much thicker than the sagging limit of 80 μm. The paint is sprayed so as to form a coating film (for example, 100 μm).

In the baking process P4, as shown in FIGS. 2 (a) to (i),
The body W is rotated horizontally. That is, the body W
Is rotated about a rotation axis l extending in the horizontal direction,
In the embodiment, the rotation axis l extends in the front-back direction of the body W. The temperature atmosphere in this baking step P4 is, eg, 150 ° C. At the time of this baking, the powder coating material has fluidity due to heat, but the fluidity becomes small due to the acceleration of curing, and eventually it is completely cured. The rotation of the body W is performed only while the powder coating material has fluidity (it is not necessary to rotate the body W for the entire baking process).

Due to the horizontal rotation of the body W in the baking process P3 described above, even if the paint is sprayed to a thickness exceeding the sagging 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.

Further, since the paint is not attached to the dolly D as the second conveying means, the paint does not peel off from the dolly D during baking and drying. Therefore, the finally obtained coated surface of the body W is obtained. Will be clean.

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 10
Two cases of 0 μm and 120 μm are shown. It is understood that in any of these thicknesses, heat flow occurs within 5 to 10 minutes after the start of baking. The sagging limit is a value at which a sagging of 1 to 2 mm is usually generated in 1 minute (when the sagging of 2 mm / min or more is visually observed, the coated surface is considered defective).

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.

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

Paint: Acrylic powder paint (Nippon Paint Co., Ltd., product name: Powdax A) b. Coating machine: Electrostatic powder coating device (Onoda Cement Co., Ltd.)
Product name: GX101) c. Applied voltage: −60 KV d. Paint discharge rate: 180 gr / min e. Paint transfer air pressure: 2.0 kg / cm ² f. Spraying distance: 25 cm Rotating jig Next, body W A specific example of a jig used to rotatably support the carriage D in the horizontal direction will be 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, 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.

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 D 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.
Accordingly, 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.

A trolley changing device (transfer device) is a device for changing the trolley by P3, and one example thereof is shown in FIGS. 15 to 17. As shown in FIG. 17, this trolley changing device is installed in the transfer station S1 where the trolley movement locus R1 in the previous process and the trolley movement locus R2 in the subsequent process are close to each other. The trolley changing device installed at the transfer station S1 is substantially constituted by a lifter 51 as shown in FIGS. 15 and 16. 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 move up and down, and support legs driven by the bases 53 so that they can be expanded and contracted. 54,
Have. Each of the support legs 54 has a pair of front and rear support portions 54a separated in the moving direction of the carriage D.

In the above-described structure, the carriage supporting the body W from the previous step (the carriage D as the second transfer means is shown in FIGS. 15 and 16) is stopped at the transfer station S1. When the carriage is stopped, the support legs 54 are extended from the base 53 located at the bottom, and then the base 53 is moved upward. Thus, as shown in FIGS. 15 and 16, the body W on the bogie is lifted from the bogie while being supported on the side sill or the floor frame portion of the body W by the support portion 54a of the support leg 54. Is raised to. After this,
The trolley for the previous process is separated from the transfer station S1, and the trolley for the subsequent process is newly located at the transfer station S1. Thereafter, the base 53 is lowered, and the body W is transferred to the carriage D. Then, the supporting leg 54 is shortened in preparation for the next transfer (see the alternate long and short dash line in FIG. 16). In this way, the body W is transferred from the trolley D ′ for the front end process to the trolley D for the rear end process.

Of course, at the time of transfer of the body W, it is preferable to firmly fix the trolley to a predetermined position in an immovable state by a positioning device or the like that clamps the trolley in the front-rear and left-right directions.

As a transfer device for the carriage, it is assumed that it has a hanger that is intermittently fed to a high place, and the lifter 51 temporarily transfers it to the hanger, and then the hanger moves the body W above the carriage for the post-process. At this position, the body may be transferred from the hanger to the truck for the subsequent process by using the lifter again.

Although the embodiment has been described above, the present invention is not limited to this, and includes the following cases, for example.

To rotate the body W, an air motor or the like separately provided on the carriage D may be used.

The dolly D ′ as the first carrying means may be of the same type as the dolly D as the second carrying means. In this case, dust removal can be performed more effectively by rotating the body W in the preparation step P1, for example. Further, in the coating process P2, the number of additional coating guns can be reduced by changing the rotational posture position of the surface of the body W facing the coating gun.
However, if an existing one having no rotating device is used as the carriage D'as the first transporting means, there is an advantage that the number of newly provided carriages D can be small.

(Effects of the Invention) As is apparent from the above description, the present invention utilizes the coating of a coating having a thickness not less than the sagging limit and the rotation of an object to be coated when coating with a powder coating. With the same paint thickness, it is possible to obtain a high-quality coated surface with higher smoothness than before.

Further, since the conveying means is changed between the coating process and the baking process, it is possible to eliminate the generation of dust caused by the paint in the baking process, and the finally obtained coated surface is clean and clean. Can be one. Of course, since the powder coating material does not sag in the previous stage of the baking process, it is possible to change the above-mentioned conveying means with a sufficient margin.

[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 side view showing an example of the transfer device. FIG. 16 is a right side view of FIG. FIG. 17 is a simplified plan view showing the loci of movement of the first transfer means and the second transfer means. P1 to P4: Process W: Body (object to be coated) l: Rotation axis D ': Truck (first transport means) D: Truck (second transport means) 1F, 1R: Rotating jig 33: Sprocket (rotary drive) 34) Chain (for rotary drive) 32, 37, 40: Shaft (for rotary drive) 38, 39: Gear (for rotary drive) 51: Lifter (transfer device)

Claims (1)

(57) [Claims] 1. A coating step of applying a powder coating material to an object to be conveyed by a first conveying means to a thickness that causes a coating sag to occur on a surface that normally extends in the vertical direction during baking and drying, and the coating step. After that, a transfer step of transferring the object to be coated from the first transfer means to the second transfer means provided with a rotation device, and the object to be transferred transferred to the second transfer means is horizontally moved by the rotation device. A baking step of baking and drying the paint applied to the object to be coated while rotating it about the axis, and starting to rotate the paint applied to the surface of the object to be applied before the paint drip occurs due to gravity, and The rotation in this case is at least such a speed that 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 paint due to gravity, and the speed at which the paint sags occurs due to the centrifugal force due to the rotation. Rotate at a slower speed Coating method for causing.