JPH0824883B2 - Coating equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating apparatus for coating the surface of an article to be coated such as the body of an automobile.

[0002]

2. Description of the Related Art Conventionally, a method of applying a coating from the lateral direction to the surface of an object to be coated such as an automobile body, particularly a vertical surface, and performing the coating is disclosed in, for example, Japanese Patent Laid-Open No. 59-4471. Is known. It has also been proposed to change the amount of paint applied in accordance with the surface to be painted and to perform uniform painting.

On the other hand, when the coating amount of the coating is increased to increase the film thickness of the coating film, high smoothness of the surface is obtained and the quality is improved.

[0004]

However, when a large amount of paint is applied at one time when the film thickness of the paint film is increased to improve the quality of the paint as described above, the painted surface of the object to be coated If it is in the up-down direction or in an inclined state, the applied paint flows downward and "paint dripping" occurs, which creates irregularities on the painted surface and impairs smoothness and deteriorates the quality of the paint film. It will be.

Whether the coating dripping of the coating film occurs immediately during coating when the film thickness exceeds the limit value in the coating spraying process, or when a predetermined time elapses during the setting for volatilizing the solvent after spraying. In addition, since the coating film is baked, it is likely to occur when the temperature is raised in the initial stage of heating in the drying furnace.

[0006] Conventionally, since there is a problem of the above-mentioned paint dripping, there is a limit to apply a large amount of paint at one time to thicken the coating film, and the application and drying are repeated in several steps. Although it is possible to increase the final film thickness, there are problems that the coating time will be long in a complicated process and multiple coating facilities will be required, and a highly smooth coated surface can be obtained by increasing the coating sag limit film thickness. I couldn't do that.

In view of the above circumstances, therefore, the present invention has a simple structure to increase the coating sag limit film thickness so that a high film thickness can be applied once without causing paint sag on the upper and lower surfaces of an object to be coated. It is an object of the present invention to provide a coating apparatus which is obtained in step 1 above and can perform high smooth finish coating with an increase in film thickness.

[0008]

In order to achieve the above object, the coating apparatus of the present invention comprises a coating means for spray-coating a coating film having a film thickness of at least such that a coating dripping is generated on the surface of an object to be coated extending vertically. The transfer of the object to be coated from the coating step by the coating means to the drying step, and the drying of the object to be coated applied during any of the coating step to the drying step until the coating does not drip. And a rotation speed of the object to be coated by the object transfer device, the coating speed of the coating material of the part before the dripping of the paint is caused by gravity. It is characterized in that the speed is set to be higher than the speed at which the object surface changes from a substantially vertical state to a substantially horizontal state, and slower than the speed at which paint dripping occurs due to centrifugal force.

The coating means comprises, for example, a first spraying zone and a second spraying zone, and is provided with a coating machine for spray-coating the surface of the object to be coated with the coating material to a predetermined film thickness. When the coating surface is in the vertical direction, the coating film thickness is such that the coating film is usually thicker than the coating dripping. Further, the drying step following the coating means comprises a setting step of leaving the coating surface as it is after coating the coating material to volatilize the solvent, and a baking step of carrying it into a drying furnace and heating and baking it. .

An object-to-be-transferred device for transferring the object to be coated from the coating process by the coating means to the drying process is installed. The coating material conveying device is configured to rotate the coating object around a substantially horizontal axis during any of the coating process and the drying process.

In the coating and drying processes as described above, the first cause of the paint dripping is that the coating film drips in the coating process in a few seconds after the paint is applied beyond the coating dripping limit film thickness. It is a time, and the limit of the coating dripping film thickness is about 40 to 45 μm in the usual topcoating. If it does not occur during the above-mentioned painting, when the drying process is set, the dripping of the paint gradually starts after spraying, and
The state in which about 4 minutes have passed is the second generation time. Furthermore, immediately after heating the object to be coated in a furnace, that is, 20 to 30
The third generation time when the maximum sagging speed is reached is the state in which the temperature of the article to be coated has risen to, for example, about 60 ° C. after the lapse of seconds.

When at least the above-mentioned paint dripping occurs, the work to be coated is rotated around the horizontal axis by the above-mentioned object conveying device to prevent the paint dripping from occurring and to smooth the coated surface. To get sex. That is, when the film thickness of the coating film is much larger than the limit value, or when the viscosity of the coating material is low and the fluidity is large,
Since the paint drips from the timing of occurrence of the above, it is necessary to rotate the object to be coated at all of the first to third timings of occurrence in the coating process and the drying process. On the other hand, when the coating film thickness is not so large or the coating material has a high viscosity and a coating film having a predetermined film thickness is formed and paint dripping does not occur at the first generation time, in the setting zone and the baking zone. In the drying process of the second and third generation times, the object to be coated is installed so as to rotate.

The rotating mechanism may be a mechanism for continuously rotating, a mechanism for reversing by alternately repeating forward rotation and reverse rotation by a predetermined angle, and further, a continuous rotation or reversing operation for stopping at a constant angle. It is set in various rotation modes such as the one that is rotated. In addition, the rotation speed is such that the coating surface is in a horizontal state or an inverted state by the time the paint drips, and the speed at which the paint drips does not occur due to the centrifugal force accompanying the rotation,
That is, it is set to a speed that is faster than the speed at which the surface of the object to be coated of the applied paint shifts from a substantially vertical state to a substantially horizontal state before the paint drips due to gravity and is slower than the speed at which the paint drips due to centrifugal force. To be done.

[0014]

In the coating apparatus as described above, the object to be coated is coated in the coating step by the coating means, and is set and baked in the drying step. Concerning the transportation to the drying process, when the paint drips occur, the object to be coated is rotated around the horizontal axis at a predetermined speed to form a coating film having a film thickness not less than the paint dripping limit film thickness. Also, the coating dripping phenomenon is prevented from occurring in the coating film, and a coating film having a high surface smoothness due to a large film thickness is formed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of an article transfer device in a coating apparatus according to an embodiment, and FIG. 2 is a plan view of a bottom transfer mechanism.

The article 1 to be coated by the body of the automobile is rotatably mounted on the carriage 4 with its front and rear ends fastened to the horizontal shafts 2 and 3 of the article conveying device. This trolley 4 is provided so that it can travel on the floor 6 of the coating line by means of the wheels 5 at the bottom, and the trolley 4 is mounted on a rod 9 which is erected upward from a conveyor chain 8 installed in a pit 7 below the floor 6. Are engaged and conveyed along a coating line having a coating process and a drying process.

Further, a gear box 10 is provided on the horizontal shaft 2.
Bevel gear 11 inside is fixed and bevel gear that meshes with this bevel gear 11
The vertical shaft 13 is fixed to the upper end of the vertical shaft 13, the vertical shaft 13 is supported by the base 4a of the carriage 4, and the sprocket 14 is fixed to the lower end of the vertical shaft 13 which penetrates the carriage 4 and faces the pit 7. A drive chain 15 is arranged in the pit 7 in a region where the work 1 to be rotated is engaged with the sprocket 14.

In the coating process by the coating means, the vertical surface 1a (both side surfaces), the horizontal surface 1b (roof portion), etc. of the article 1 are coated, and each of the first zone and the second zone (not shown) is coated. A spray zone is provided, and a mini-bell, that is, a rotary atomizing electrostatic coating machine (not shown) is arranged above and on both sides of the article to be coated 1 in each zone and the coating material is sprayed to the article to be coated 1. In the second zone, the paint is sprayed to a film thickness exceeding the paint dripping limit film thickness.

On the other hand, the drying step following the coating step is a setting step of holding the coated object 1 for about 10 to 15 minutes, and heating the coated object 1 in a drying oven (not shown) to form a coating film. And a baking process for performing the baking process.

In this embodiment, a drive chain 15 for rotating the article 1 to be coated is arranged in the range from the second zone of the coating process to the middle of the baking zone of the drying process. The drive chain 15 has a drive system separately from the drive of the conveyor chain 8 for transporting the carriage 4, and is configured so that the rotation operation function of the article to be coated 1 can be obtained even when the transport is stopped. . This drive chain
The drive of 15 can be set arbitrarily such that it continuously drives in one direction to continuously rotate the article to be coated 1, or drives the article to be coated 1 in reverse by switching the driving rotation direction at predetermined intervals. Is. Also, the drive rotation speed can be arbitrarily set according to various conditions.

Next, when the coating object 1 (sample) is actually coated by the coating means and the coating material conveying device as described above, a mapping of the coating surface by the rotation operation about the horizontal axes 2 and 3 is performed. Experimental data for confirming the effect on the image clarity is shown in FIG.

The coating conditions in this data are: a. Paint melamine alkyd (black) Viscosity ... Ford cup # 4 22 seconds / 20 ° C b. Painting machine Minibell (16,000rpm) Shaping air ... 2.0kg / cm ² c. Discharge rate 1st zone: 100cc / min 2nd zone: 150-200cc / min d. Setting time 10 minutes e. Baking conditions 140 ° C x 25 minutes f. Ground smoothness (PGD value) 0.6 (intermediate coating, on PE tape) g. Rotation or reversal operating range Setting (10 minutes) to baking (10 minutes) h. Object to be coated Painted on the side of a 30 cm square tube, rotatably supported at the center As can be seen from Fig. 3, when the coating surface is in the vertical state, as shown in A, the top coating film thickness is about 45 µm. Paint dripping occurs and the smoothness is good.

On the other hand, when reversing at an angle of 90 °, 135 °, 180 ° (the reversing speed is equivalent to 6 rpm), B,
As shown in C and D, the larger the reversal angle, the larger the film thickness at which paint drips occur, and the smoothness is improved from good to excellent. It should be noted that when the reversal angle becomes large, the time for the paint flow to flow in the opposite direction due to reversal increases,
The effect of preventing paint dripping is further increased, and the film thickness can be increased.

On the other hand, when continuously rotated, the effect of preventing paint dripping is greatest as shown by E, and the smoothness is excellent due to the increase in the film thickness. The rotation speed in this continuous rotation was 6, 30, and 60 rpm, respectively, but there was no difference due to the speed, and good results were obtained even at 6 rpm. However, it is necessary to set a relatively high rotation speed depending on the type of paint, the film thickness, and the like.

The IG (image gloss) in the image clarity is a ratio of the image clarity to the mirror surface (black glass) of 100, and the PGD lowers the identification degree of the reflected image from 1.0. The value is such that the surface condition of the coating film decreases as

If the rotation speed of the object 1 to be continuously rotated or reversed is slow, the effect of preventing paint dripping is not obtained. On the other hand, if the speed of rotation is fast, the centrifugal force causes the coating film to flow to the outer side of rotation, which is similar to paint dripping. The above phenomenon occurs and is set according to the paint dripping speed of the coating film. In setting the rotation speed, for example, as shown in FIG. 4, the paint dripping speed in each zone is obtained, and the rotation speed is set so that the paint dripping does not occur even at the maximum speed.

That is, in FIG. 4, the result of measurement of the dripping speed in the course of the setting time (10 minutes) after coating is increased by increasing the film thickness in three stages by using the top coating material (viscosity Ford Cobb for about 20 seconds). , And the results of measuring the sagging speed during the elapse of the baking time due to heating after the above setting.

As a result of the above FIG. 4, the coating dripping limit film thickness is 40 to
It is 45 μm, and at a film thickness smaller than this, a large sag rate does not occur. Then, when the coating dripping exceeds the above-mentioned limit film thickness, it occurs after a few seconds and reaches the maximum dripping speed 3 to 4 minutes after coating. In addition, 20 to 30 seconds after starting the heating of the object to be coated 1 in a drying oven (object temperature of 60 ° C.)
The sagging speed becomes larger than that at the time of setting and reaches the maximum, and stops after 2 to 5 minutes.

With respect to the occurrence of paint dripping as described above, the paint dripping phenomenon which is easily found by visual observation is 1 to 2 mm, and if such paint dripping occurs, it becomes a defective product due to surface defects. In order to suppress the phenomenon, it is sufficient to rotate the coating surface from the vertical state to the horizontal state or the inverted state until the flow of the coating film starts to flow by 1 to 2 mm. On the other hand, when the article to be coated 1 is rotated at high speed, centrifugal force acts on the coating film to cause artificial paint dripping, which is the radius of 30
Since it occurred when reversing in 0.25 seconds in cm, the rotation speed is lower than this, but since the reversing or the rotation speed does not have to be constant, the tip speed should be 380 cm / sec or less. For example, it is possible to prevent paint dripping due to centrifugal force. Further, as the radius of rotation of the article to be coated 1 increases, the allowable rotation speed decreases.

From the above, in the case of FIG. 4, the object to be coated is 180 ° inverted or 90 ° to the horizontal state.
The time required for rotation should be set to 0.25 seconds to 10 minutes. In other words, if it is less than 0.25 seconds, the rotation will be too fast and paint dripping will occur due to centrifugal force. Also, in each time zone of about 10 minutes corresponding to a small dripping sag speed at the paint dripping limit film thickness (40 to 45 μm), You can set each by.

The rotating mechanism of the article to be coated 1 is not limited to the gear box structure using the bevel gear as in the above-mentioned embodiment, and a conventionally known drive mechanism is used depending on the size, weight, etc. of the article to be coated. Can be appropriately adopted.

[0032]

According to the present invention as described above, the coating means for spray-coating the coating material to a thickness greater than that which causes the coating material to drip on the surface of the coating material, and the coating material being conveyed from the coating step to the drying step. In addition, at the time when paint dripping occurs during any of the coating process and the drying process, the work transfer device rotates about a horizontal axis until the work is dried to a state where paint dripping does not occur. In addition, the rotation speed is higher than the speed at which the surface of the object to be coated moves from a substantially vertical state to a substantially horizontal state before paint dripping occurs due to gravity, and is slower than the speed at which paint dripping occurs due to centrifugal force. By setting the speed, it is possible to prevent the phenomenon of paint dripping during coating and drying, even when coating with a film thickness above the paint dripping limit film thickness, and it becomes possible to coat with a large film thickness. High surface smoothness Painting can be carried out with.

Since the coating sag limit film thickness of the object to be coated is greatly increased, it is possible to make the film thickness equal to that of the horizontal coating surface, and the vertical coating surface is mirror-finished like the horizontal coating surface. It can be applied to a highly smooth finished surface.

[Brief description of drawings]

FIG. 1 is a front view showing an article conveying device in a coating device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional plan view of an essential part showing the internal structure of a pit on the floor.

FIG. 3 is a graph showing the relationship between the coating film thickness on the coated surface and the image clarity as the coated object rotates.

FIG. 4 is a graph showing the relationship between the coating processing time and the paint dripping speed when the coating film thickness is changed.

[Explanation of symbols]

 1 Object to be coated 1a Vertical surface 2,3 Horizontal axis 4 Bogie 14 Sprocket 15 Drive chain

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tadamitsu Nakahama 3-1, Shinchi Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (72) Inventor Takakazu Yamane 3-3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Incorporated (56) Reference JP-A-53-110638 (JP, A) British patent 584432 (GB, A)

Claims (1)

[Claims] 1. A coating device for coating a surface of an article to be coated with a coating means for spray-applying the coating to a film thickness that causes a paint sag on at least the surface of the article to be vertically extended, The article to be coated is conveyed from the coating step to the drying step by the coating means, and the article to be coated coated between any one of the coating step to the drying step is substantially horizontal until it is dried in a state where no paint dripping occurs. And a rotation speed of an object to be coated by the above-mentioned object transport device, the coating material of the part being coated before the paint dripping occurs due to gravity. A coating device characterized in that the speed is set to be higher than the speed at which the surface changes from a substantially vertical state to a substantially horizontal state and slower than the speed at which paint drips due to centrifugal force.