JPH0810660A - Method and apparatus for electrostatic coating - Google Patents

Abstract

PURPOSE:To provide a method and an apparatus for electrostatic coating wherein tracks of electrostatically charged coating particles can be controlled without using an air curtain and coating efficiency of a coating with good workability can be improved. CONSTITUTION:Tracks of electrostatically charged particles are controlled by a magnetic field formed by means of a coil 6 formed on the apex part of an electrostatic coating spray gun 1 to make coating particles head for an article P to be coated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to, for example, an electrostatic coating method which is used for coating automobile bodies and the like and which can enhance the coating efficiency of coating particles by the force of static electricity. The present invention relates to an electrostatic coating device.

[0002]

2. Description of the Related Art In electrostatic coating, a grounded object is used as an anode and a spray gun is used as a cathode to form an electrostatic field between both electrodes by applying a negative high voltage and atomized paint particles to a negative electrode. It is a coating method in which the anode is electrostatically charged and is suction-adhered to the object to be coated of the anode.Since the electrostatic effect is used, the coating efficiency of the paint is extremely superior compared to normal spray coating, and the front and back of the object to be coated can be simultaneously coated. Features such as painting.

As a spray gun used for electrostatic coating, an air atomization method in which compressed air is atomized, an airless atomization method in which liquid pressure is used, or a rotary atomization method in which atomization is performed by centrifugal force of a rotating cup or disk is used. Methods such as methods are known.

Each of these spray guns has an atomizing mechanism for atomizing a liquid paint at the tip of the gun and an electrode for charging the paint and forming an electrostatic field between the paint and the object to be coated. The electrode is disposed inside the atomizing mechanism or in front of the atomizing mechanism, that is, in a state of protruding from the atomizing mechanism toward the object to be coated.

This electrode is normally -30 with respect to the object to be coated.
A high voltage of 2 to 4 kV / cm is maintained between the electrode provided at the tip of the spray gun and the object to be coated in order to maintain a high negative voltage of about -90 kV and to impart a charge to the atomized paint particles. In many cases, a voltage is applied to form a corona discharge field, and the resulting ions are attached to the paint particles to increase the charge amount of the paint particles. Further, for the purpose of contact-charging the paint, the paint may come into contact with the electrodes immediately before leaving the gun.

In this case, it is general that the object to be coated is grounded and a negative high voltage is applied to the electrode to the object because the positive high voltage is applied to the electrode. This is because the stability of corona discharge is superior to that of (1) and the limit voltage can be set high.

In such an electrostatic coating apparatus, the spray gun main body is grounded and a high voltage is applied only to the voltage application electrode for the sake of simplicity of the apparatus and safety of the operator. As a result, the object to be coated and the gun body have the same potential, which causes a problem that some of the atomized charged paint particles adhere to the spray gun body without moving toward the object to be coated. Therefore, not only the coating efficiency of the paint is lowered, but also the paint adhered to the gun main body falls on the object to be coated, which deteriorates the coating quality. In rare cases, there is a risk of igniting the paint and piping due to the Joule heat due to the leak current flowing along the adhered paint, so it is necessary to clean the spray gun frequently, resulting in a significant increase in work efficiency. Will be reduced.

For this reason, among the spray guns, for example, in the rotary atomization type spray gun having the most remarkable tendency as described above, an air nozzle is provided at the tip of the spray gun to remove the atomized paint particles. By forming an air curtain on the periphery, the paint particles are directed to the object to be coated, or a plate-shaped or ring-shaped shield electrode having the same polarity as the electrode is provided around the voltage applying electrode, and the electrostatic repulsion effect is provided. Techniques such as avoiding adhesion of paint to the gun body are used.

[0009]

These methods are applied individually or in combination, but when an air curtain is used, the traces of paint particles are easily disturbed and formed near the surface of the object to be coated. As a result of the paint particles being carried away by the air flow parallel to the object to be coated, there is a problem that the coating efficiency decreases. Also, when a shield electrode for electrostatic repulsion is used, it is possible to prevent paint from adhering to the gun body, but it is effective if the potential of this shield electrode is not set to the same potential as or higher than the voltage application electrode. However, if a worker accidentally touches such a high-potential shield electrode, there is a high risk of electric shock, and there is a practical constraint that it can only be applied to automatic painting. It has been a problem in the conventional electrostatic coating method or apparatus to solve these problems.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems in the conventional electrostatic coating method or apparatus, and can control the traces of charged paint particles without using an air curtain or a shield electrode. An object of the present invention is to provide an electrostatic coating method and an apparatus therefor capable of improving the coating efficiency of coating material with good workability.

[0011]

The electrostatic coating method according to the present invention is an electrostatic coating in which charged coating particles are formed in electrostatic coating in which charged coating particles are attached to an object to be coated by using the force of static electricity. The electrostatic coating apparatus according to the present invention is characterized in that the electrostatic coating device according to the present invention is atomized to atomize the liquid coating material by controlling the tracks of the charged coating material particles by a magnetic field generated in the vicinity of the particle generating portion. An electrostatic coating spray gun having an electrode that forms an electrostatic field between the mechanism and an object to be coated and that gives an electric charge to atomized paint particles is provided, and at least one of the electrostatic coating spray gun has a tip. The present invention is characterized in that a coil is provided, and such an electrostatic coating method and apparatus configuration are means for solving the above-mentioned conventional problems.

[0012]

In the electrostatic coating method according to the first and second aspects of the present invention, for example, the track of the charged paint particles is controlled by the magnetic field formed by the coil provided in the vicinity of the portion where the charged paint particles are generated, Since the paint particles are directed toward the object to be coated, the paint particles do not adhere to the gun body, and no air curtain or shield electrode with high voltage is used, so the paint particles are carried away by the air flow. The coating efficiency is improved and the risk of electric shock due to the shield electrode is eliminated.

Further, in the electrostatic coating method according to the third aspect of the present invention, since the direct currents supplied to the plurality of coils arranged in the vicinity of the charged paint particle producing portion are controlled respectively, the charging is performed. The traces of paint particles are controlled more complicatedly, and the spray pattern can be easily shaped.

Since the electrostatic coating apparatus according to the present invention is provided with at least one coil at the tip of the electrostatic coating gun, an air curtain is used by the magnetic field generated by the current supply to the coil. Instead, the scattering direction of the charged particles is changed, and the structure is suitable for carrying out the electrostatic coating method.

Further, in the electrostatic coating apparatus according to the fifth aspect of the present invention, since the coil has a flexible structure, the shape of the spray pattern changes according to the deformation of the coil, and the pattern adjustment becomes easy. .

In the electrostatic coating method according to the present invention, as in the electrostatic coating apparatus according to the sixth aspect of the present invention, the electrostatic atomization method of the electrostatic atomization system, in which the problem of paint adhesion to the gun body is the most serious in view of the mechanism. The effect becomes remarkable when applied to a coating device.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic explanatory view showing the principle of an electrostatic coating method according to the present invention and an embodiment of an electrostatic coating apparatus according to the present invention.

The electrostatic coating spray gun 1 shown in the figure is of a rotary atomizing system, and has a motor 2 at the tip thereof,
The atomizing mechanism including the disk 3 rotated by the motor 2 is provided, and the liquid paint supplied by the paint pump 4 into the rotating disk 3 is radially scattered by the rotation of the disk 3 and atomized by the centrifugal force. It is a mechanism to operate.

The disk 3 is connected to the negative terminal of the high-voltage generator 5 and is attached to the object P to be coated.
The disk 3 is maintained at 30 to -90 kV, and the disk 3 functions as an electrode that forms an electrostatic field with the object P to be coated and gives a negative charge to the atomized paint particles. Is also equipped.

The spray gun 1 is provided with a charged paint particle generator for forming charged paint particles, that is, an annular coil 6 around the disk 3, and a DC current is supplied to the coil 6 from a controller 7. Thus, a magnetic field is formed around the disk 3.
The coil 6 is insulated from the spray gun and the disk 3 so that there is no risk of electric shock even if an operator touches the coil during manual painting.

In the spray gun 1 having such a structure, when the paint is supplied by the paint pump 4 into the disk 3 which is being rotated by the motor 2, the paint collides with the disk 3 and is scattered radially to be atomized. At the same time, the electric charge is received from the disk 3 and negatively charged. At this time, the atomized paint particles try to scatter in the direction of the arrow R indicated by the broken line in the figure due to the centrifugal force, but around the disk 3, the doughnut-shaped magnetic field is generated by the direct current flowing through the coil 6. Is formed, the Lorentz force acts on the charged paint particles that have jumped into the magnetic field in a direction perpendicular to the direction, and the paint particles flow in the direction of arrow D shown by the solid line in the figure and flow toward the object P to be coated. To form.

In this way, the paint particles separated from the disk 3 can be efficiently applied to the object P to be coated by the force of static electricity, and the paint can be prevented from adhering to the gun body, which is an indispensable spray in the past. Coupled with the elimination of paint loss due to pattern shaping air, it is possible to greatly improve the coating efficiency.

By the way, the coating efficiency of the spray gun 1 and the coating efficiency of the conventional rotary atomizing type spray gun using an air curtain are set at a distance of 30 cm.
As a result of comparison by coating on the m square object to be coated, the coating efficiency of the conventional air curtain type spray gun is 65%, whereas the coating efficiency of the spray gun 1 according to the present invention is 85%. Therefore, it was confirmed that the coating efficiency could be significantly improved.

In the spray gun 1, a circular or donut-shaped spray pattern can be obtained because the circular coil 6 is used. However, by making the coil elliptical, the spray pattern is shaped into an elliptical shape. It is also possible to do so. Further, the spray pattern of the paint can be adjusted by making the coil a flexible structure and deforming the shape of the coil.

Embodiment 2 FIGS. 2A and 2B are schematic explanatory views showing another embodiment of the electrostatic coating apparatus according to the present invention.

The electrostatic coating spray gun 10 shown in the figure is of the rotary atomizing system as in the above-mentioned embodiment, except that the electrostatic spray gun 10 has the same shape and number of coils provided at the tip thereof. The coating spray gun 1 has basically the same structure.

That is, the spray gun 10 is provided with a motor 2 as an atomizing mechanism and a disk 3, atomizes the liquid coating material supplied by a coating material pump 4 by the rotation of the disk 3, and at a high potential by a high voltage generator 5. The held disk 3 forms an electrostatic field with an object to be coated (not shown) and gives a negative charge to the atomized paint particles.

The spray gun 10 according to this embodiment is
As shown in FIG. 2B, a coil 11 having a circular shape and a coil 12 having an elliptical shape are provided around the charged paint particle generating unit, that is, the disk 3, and the coils 11 and 12 are provided to the controller 13, respectively. By adjusting the direct currents that are connected and supplied from the controller 13 to the respective coils, it is possible to control the strength of the magnetic field formed around the disk 3 and the direction of the lines of magnetic force.

In the spray gun 10 having such a structure, the negatively charged paint particles atomized by the rotating disk 3 can be directed toward the object to be coated by the magnetic field formed by the coils 11 and 12. It is possible to obtain the same effect as that of the above-mentioned embodiment, and the spray pattern of the paint can be freely changed by adjusting the balance of the direct currents supplied to the coils 11 and 12, which is optimal according to the object to be coated. Can be obtained.

In each of the above embodiments, various components as an electrostatic coating device, such as a safety device such as a high resistance for grounding and a concrete example of a high voltage generating circuit, are omitted. It can be used in combination with known devices and parts. Further, by using it in combination with an automatic machine such as a reciprocator, it is possible to further improve the coating efficiency.

Further, in each of the above embodiments, an example in which a coil is provided in a rotary atomizing type spray gun is shown, but the electrostatic coating method according to the present invention is not limited to the rotary atomizing type,
It can also be applied to other air atomization methods and airless atomization methods.

That is, in an air atomization type or airless atomization type spray gun, the flow of paint particles toward the object to be coated is formed by the compressed air or liquid pressure, and therefore, originally, Less paint adheres to the gun body than the rotary atomization method. However, by applying the present invention, the air for spray pattern shaping becomes unnecessary, and there is no paint particles carried away by the air flow flowing along the surface of the object to be coated. Therefore, the air atomizing method or the airless atomizing method is used. It is possible to greatly improve the coating efficiency even with this spray gun.

[0034]

As described above, in the electrostatic coating method according to the present invention, for example, by the coil disposed near the generating portion of the charged paint particles, the magnetic field formed near the generating portion causes the charged paint particles to be dispersed. Since the track is controlled, the charged paint particles can be directed to the object to be coated without using an air curtain or a shield electrode applied with a high voltage, preventing the paint from adhering to the gun body and adjusting the spray pattern. And the paint particles are not carried away by the air stream formed on the surface of the object to be coated,
The coating efficiency can be improved, and the extremely excellent effect of eliminating the risk of electric shock due to the shield electrode is brought about.

Further, in the electrostatic coating method according to the third aspect of the present invention, since the direct current supplied to the plurality of coils arranged in the vicinity of the charged paint particle generating portion is controlled, the charged paint is controlled. The particle tracks can be controlled intricately, and the shape of the spray pattern can be freely adjusted.

Since the electrostatic coating apparatus according to the present invention is provided with at least one magnetic field forming coil at the tip of the electrostatic coating gun, the air curtain is used by adjusting the current supplied to the coil. Without changing the scattering direction of the charged particles, the coating efficiency can be improved, the spray pattern can be easily adjusted, and the electrostatic coating method can be smoothly carried out.

Further, in the electrostatic coating apparatus according to the fifth aspect of the present invention, since the coil for forming the magnetic field has a flexible structure, the spray pattern can be easily adjusted by appropriately deforming it.

Further, the electrostatic coating apparatus according to claim 6 of the present invention is a rotary atomizing type electrostatic coating apparatus provided with a coil for forming a magnetic field. This brings about an excellent effect that it is possible to effectively solve the serious problems such as the adhesion of the paint to the gun body, the reduction of the coating efficiency and the work efficiency.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing the principle of an electrostatic coating method according to the present invention and an embodiment of an electrostatic coating apparatus according to the present invention.

FIG. 2 (a) is a schematic explanatory view showing another embodiment of the electrostatic coating method and apparatus according to the present invention. (B) It is a schematic explanatory drawing which shows the coil shape of the electrostatic coating apparatus shown to FIG.

[Explanation of symbols]

 1,10 Electrostatic coating spray gun 2 Motor (atomization mechanism) 3 Disc (atomization mechanism, electrode) 6,11,12 Coil P Object to be coated

Claims (6)

[Claims] 1. In electrostatic coating in which charged paint particles are attached to an object to be coated by using the force of static electricity, the charged paint is generated by a magnetic field generated in the vicinity of a charged paint particle generating portion where the charged paint particles are formed. An electrostatic coating method characterized by controlling the traces of particles for coating. 2. The static electricity according to claim 1, wherein a coil is provided in the vicinity of the charged paint particle generating portion, and the track of the charged paint particles is controlled by supplying a direct current to the coil. Electric coating method. 3. The spray pattern of the paint is adjusted by disposing a plurality of coils in the vicinity of the charged paint particle generating portion and controlling a direct current supplied to each coil. Alternatively, the electrostatic coating method according to claim 2. 4. An electrostatic coating spray gun comprising an atomizing mechanism for atomizing a liquid coating material, and an electrode for forming an electrostatic field between the liquid coating material and an object to give an electric charge to the atomized coating material particles. , An electrostatic coating device, wherein at least one coil is provided at the tip of the electrostatic coating spray gun. 5. The electrostatic coating apparatus according to claim 4, wherein the coil has a flexible structure. 6. The electrostatic coating device according to claim 4, wherein the atomizing mechanism is a rotary atomizing system which atomizes the liquid coating material by a centrifugal force generated by the rotation of the disk.