JPH07256156A - Rotating atomizing electrostatic coating device - Google Patents

Abstract

(57) [Summary] [Purpose] Prevents stains on the external electrodes by paint. A rotary atomization electrostatic coating device in which a tip of an external electrode 10 is located in front of a paint atomizing head 3 provided at a tip of a rotary shaft 2, and a rotary atomizing electrostatic coating device for an inner air outlet 4 and an external electrode 10 is provided. An outer air outlet 11 arranged to inject air along the inner side. On the outer periphery of the external electrode 10,
A concentric air outlet 112 may be further provided for the rotating shaft 2.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a rotary atomizing electrostatic coating apparatus having external electrodes.

[0002]

2. Description of the Related Art In recent years, the use of water-based paints has been expanding for the purpose of reducing VOC (volatile organic compound) emissions.
However, since most of the solvent of the water-based paint is water, the water-based paint is electrically conductive, and when the electrostatic coating method is applied, there is a problem that a high voltage leaks to the ground through the paint. As means for dealing with this, a method of separating the paint supply from the ground using a relay tank or the like and an external charging method (for example, Japanese Laid-Open Patent Publication No.
No. 20078). The former can be achieved relatively easily with a painting system that does not require color change, but it is extremely difficult to put it into practical use when painting a large number of paints of different colors with a single painting machine, such as top coating of automobiles. is there. The latter is usually used in rotary atomizing electrostatic coating machines (commonly called bell coating machines). This is a method in which a high voltage is not applied directly to the bell coater, but a high voltage is applied to electrodes provided outside the bell coater. With the external charging method, high voltage does not have the drawback of leaking through the paint, and is being widely put into practical use mainly in the waterborne topcoating line of automobiles.

[0003]

However, the external charging method also has the following problems. That is, when the external electrode is located in front of the paint atomizing head, the paint splashing outward from the paint atomizing head by centrifugal force is likely to hit the external electrode, and when the external electrode hits the external electrode, the external electrode is soiled and the external electrode If the paint drops on the object to be coated, the quality of the coating will be NG. On the contrary, when the external electrode is located behind the paint atomizing head as in Japanese Patent Laid-Open No. 4-200858, dirt on the electrode is suppressed, but the distance between the external electrode and the object to be coated becomes large. As a result, the strength of the electric field formed between the external electrode and the object to be coated weakens, and the charged paint particles are electrically attracted to the object to be coated by the electric field between the external electrode and the object to be coated. The efficiency of electrocoating is poor, that is, the coating efficiency is poor. SUMMARY OF THE INVENTION It is an object of the present invention to provide an external charging type rotary atomizing electrostatic coating device capable of suppressing contamination of the external electrode by the paint even if the external electrode is brought forward of the paint atomizing head.

[0004]

To achieve the above object, a rotary atomizing electrostatic coating device of the present invention comprises the following devices. (1) A paint atomizing head rotatable about an axis, an external electrode whose tip is located in front of the paint atomizing head, and an inner air outlet provided behind the tip of the paint atomizing head. A rotary atomization electrostatic coating device having an outer air outlet provided outside the inner air outlet and having a position set so as to blow out air along the inner side of the outer electrode. (2) The rotary atomizing electrostatic coating device according to (1), further including an air blowout port arranged coaxially with the paint atomizing head outside the external electrode. (3) The rotary atomizing electrostatic coating device according to (1), wherein the air blowing direction of the inner air outlet is twisted with respect to the axis of the paint atomizing head.

[0005]

In the device of the above (1), even if the external electrode is provided in front of the paint atomizing head, the outer air outlet blows air along the inner side of the outer electrode, so that it is scattered to the outer electrode. It is suppressed that the coating material adheres, and the contamination of the external electrode by the coating particles is suppressed. Further, since the tip of the external electrode is located in front of the tip of the paint atomizing head, the external electrode approaches the object to be coated, and the strength of the electric field formed between the external electrode and the object to be coated is large. Wearing efficiency is high. The device of (2) above is the device of (1) above in which air outlets are arranged outside the external electrodes. Therefore, in addition to the effect of the above (1), the contamination by the paint particles from the outside of the external electrode is suppressed. In the device of (3) above, since the air blowing direction is twisted, the pattern width becomes wider toward the front.

[0006]

1 and 2 show a first embodiment of the present invention, and FIGS. 3 and 4 show a second embodiment of the present invention. In the figure, components common to all the embodiments are given the same reference numerals in all the embodiments. First, a configuration common to all the embodiments is shown in FIG. 1 and FIG.
Will be described with reference to. As shown in FIGS. 1 and 2, the bell-shaped paint atomizing head 3 has an axis and is rotatable around the axis. The paint atomizing head 3 is attached to the tip of the rotary shaft 2 of the air motor (air turbine) 1,
It is driven to rotate by. In the paint atomizing head 3, the paint from the paint tank 17 is filled with the paint hose (including the paint supply pipe) 1
The paint supplied via 8 and supplied into the paint atomizing head 3 is sent to the tip edge portion of the paint atomizing head 3 by centrifugal force when the paint atomizing head 3 is rotated, and is almost discharged from the edge portion. The paint atomizes in a direction orthogonal to the head axis, and can be turned to the object side by shaping air, which will be described later.

Outside the paint atomizing head 3, the paint atomizing head 3
The external electrode 10 is disposed so as to be electrically insulated from the external electrode. The tip of the external electrode 10 is in front of the tip of the paint atomizing head 3 (on the side of the object to be coated). The external electrode 10 includes, for example, a plurality of pin-shaped electrodes 10A arranged on a circle centered on the paint atomizing head axis core, or a single ring-shaped electrode 10B concentric with the paint atomizing head axis core. Become. The external electrode 10 is given a positive or negative high voltage to emit ions by corona discharge, and when paint particles scattered in this discharge region pass through, the paint particles are charged to charge the paint particles with the same sign as the electrode 10. (The coating particles do not hit the external electrode 10), and the charged coating particles are coated by the electric field formed between the external electrode 10 and the grounded coating object (not shown) located in front of the electrode. And apply electrostatically. In this case, the paint atomizing head 3 is a conductive paint, such as a metallic paint, a water-based paint,
Grounded through.

The external electrode 10 is electrically insulated and supported by the resin housing 7. External electrode 10
Is a high resistance 16 for current control via the high voltage cable 15.
The high resistance 16 for current control is connected to the high voltage cable 1
Connected to the high voltage generator 8 via the high voltage generator 8
Is connected to a low voltage power supply 13 via a low voltage cable 14. Since the low-voltage power supply 13 is grounded and the object to be coated is also grounded, the external electrode 10 has a relatively high potential (applied voltage is about 10 to 60 KV) with respect to the object to be coated.

Inside the external electrode 10, two rows of air outlets are provided concentrically with the paint atomizing head 3, and the inside row of air outlets is a large number of air outlets (hereinafter referred to as the inner side). The outer air outlet row has a large number of air outlets (hereinafter referred to as outer air outlets) 11. The inner air outlet 4 is located behind the tip (edge portion) of the paint atomizing head 3. The inner air outlet 4 blows out the air supplied to the annular air chamber 5. The air blowing direction of the inner air blowing port 4 is a direction twisted with respect to the paint atomizing head axis (preferably, a twist angle of 20 to 50 degrees). As a result, the streamline of the blown air after being blown out is the inner air outlet 4
The diameter of the paint spray pattern (the diameter increases) as it moves away from the paint spray pattern, and the paint spray pattern (annular) scattered from the paint atomizing head 3 is not contracted (due to the negative pressure on the inside). When it is done, it becomes the coating width) and the coating film thickness is made uniform.

The outer air outlet 11 blows out the air supplied to the annular air chamber 12 on the outer peripheral side of the annular air chamber 5. The position of the outer air outlet 11 is set so as to eject the air along the inner side of the outer electrode 10. The air blowing direction of the outer air outlet 11 is parallel to the paint atomizing head axis or intersects with the paint atomizing head axis (the blowing direction may intersect either forward or backward).
Alternatively, it is twisted with respect to the paint atomizing head axis, and controls the diameter of the paint spray pattern by the air blown from the inner air outlet 4 and thus the spread of the paint width on the suppressing side. As a result, the coating width is 100 to 400 m.
It is variable at about m. In addition to the function of controlling the spread of the paint spray pattern, the air blown from the outer air outlet 11 prevents the paint from adhering to the outer electrode 10 from the inside by being ejected and flowing along the outer electrode 10. It is possible to prevent the external electrode 10 from being contaminated by the spray paint particles, and to prevent the paint from falling off the external electrode 10 onto the object to be coated. Further, since the external electrode 10 is prevented from becoming dirty, there is no problem even if the tip of the external electrode 10 is brought forward (on the side of the object to be coated) from the tip of the paint atomizing head 3, and the external electrode 10 is prevented.
By approaching the object to be coated, the strength of the electric field formed between the external electrode 10 and the object to be coated can be increased, thereby improving the coating efficiency.

Air from the air supply device 19 is supplied to the air chamber 5 via an air hose 23, and an air regulator 2 for controlling the air supply amount is provided in the middle of the air hose 23.
1 is provided. Similarly, air from the air supply device 19 is supplied to the air chamber 12 via the air hose 22, and an air regulator 20 for controlling the air supply amount is provided in the middle of the air hose 22. The air regulators 20 and 21 can be controlled independently of each other, and the coating pattern can be changed to about 100 to 400 mm.

Next, the structure peculiar to each embodiment will be described. In the first embodiment, as shown in FIGS. 1 and 2, the external electrodes 10 are plural (preferably 4 to 10) pin-shaped electrodes 1.
It consists of 0A. The pin-shaped external electrode 10 is provided such that the outer peripheral portion of the resin housing 7 projects forward in an annular shape, and the pin-shaped external electrode 10 projects forward from the front surface of the annular resin portion 9. An outer air outlet 11 is provided inside the annular resin portion 9,
Air is blown out along the inner surface of the annular resin portion.

In the second embodiment, as shown in FIGS. 3 and 4, the external electrode 10 is composed of an annular electrode 10B which is concentric with the paint atomizing head 3, and protrudes forward from the resin housing 7. ing. The outer air outlet 1 is provided inside the annular electrode 10.
1 is provided, and air is blown out along the inner surface of the annular electrode 10. Further, on the outer rear side of the external electrode 10, a large number of air outlets 112 are provided which are arranged concentrically with the paint atomizing head axis. The air outlet 112 blows air from the air chamber 113 along the outer peripheral surface of the external electrode 10. The air outlet 112 blows air in a direction parallel to, crossing, or twisting the paint atomizing head axis.
The air from the air outlet 112 prevents the spray paint from adhering to the outer peripheral surface of the external electrode 10 and prevents the external electrode 10 from becoming dirty. The air from the air outlet 112 has a function of controlling the spread of the paint spray pattern due to the air blown from the inner peripheral air outlet 4 to the suppression side, like the air blown from the outer air outlet 11. The air chamber 113 is provided with an air supply device 1 via an air hose 126.
9, an air regulator 123 for controlling the air supply amount is provided in the middle of the air hose 126.

Next, the operation will be described. First, the operation common to all the embodiments will be described. The paint is supplied from the paint tank 17 into the paint atomizing head 3 via the paint supply hose 18. The paint can be applied at high speed (1 to 60,000 r by the air motor 1).
by the centrifugal force from the paint atomizing head 3 rotated at
It is scattered outward in a direction almost orthogonal to the rotary atomizing head axis and can be turned by shaping air. On the other hand, the high voltage generated by the high voltage generator 8 is applied to the external electrode 10, and the ions emitted by the corona discharge from the external electrode 10 charge the paint particles scattered from the rotary atomizing head 3. Thus, the paint particles are charged with the same sign as the external electrode 10. The object to be coated is grounded and the electric field formed between the external electrode 10 and the object to be coated causes the charged paint particles to fly toward the object to be coated and electrostatically coat the object to be coated.

The air blown out from the inner air outlet 4 promotes atomization of the paint, and maintains a uniform coating pattern without being contracted along the paint atomization head axis. Then, the atomized paint is charged by the external electrode 10 and electrostatically applied, whereby a trapezoidal pattern having a uniform coating film cross section (painting width of about 100 to 400 mm) can be applied. When metallic coating is applied, the metallic brightness is high and the coating is spotless along the coating path. In addition to this, air blown out from the outer air outlet 11 is added to prevent paint stains on the external electrode 10, and the pressures of the air regulators 20 and 21 are independently controlled to make the coating pattern 100 to 400 mm. It is possible to change the degree, and it becomes possible to paint a trapezoidal pattern with a uniform coating cross section, the brightness of the metallic coating is high and the coating can be maintained without spots, and it can be used for narrow parts such as pillars of automobile bodies and door inner plate parts. Even with painting, it is possible to paint with high coating efficiency with little overspray and save paint.

With respect to the operation peculiar to each embodiment, since the external electrode 10 is pin-shaped in comparison with the first embodiment, corona discharge is easy, and in the second embodiment, the external electrode 10 is different. The ring shape makes it easy to manufacture, and the external electrode 1
Since the air outlet 112 is provided outside 0, the stain on the external electrode 10 due to the paint can be further reduced.

[0017]

According to the first aspect of the present invention, since the position of the inner air outlet is set so that the air is blown out to the inside of the external electrode, it is possible to prevent the external electrode from being contaminated due to the adhered paint. Further, since the tip of the external electrode is located in front of the tip of the paint atomizing head, the external electrode approaches the object to be coated, the strength of the electric field is increased, and the coating efficiency is improved. According to the second aspect, since the air outlet is also provided outside the external electrode, the external electrode can be further prevented from being contaminated. According to the third aspect, since the air blowing direction is twisted, the pattern width can be expanded toward the front.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a rotary atomizing electrostatic coating apparatus according to a first embodiment of the present invention.

2 is a front view of the device of FIG. 1. FIG.

FIG. 3 is a schematic sectional view of a rotary atomizing electrostatic coating device according to a second embodiment of the present invention.

FIG. 4 is a front view of the device of FIG.

[Explanation of symbols]

 1 Air Motor 2 Rotating Shaft 3 Paint Atomizing Head 4 Inner Air Outlet 5 Air Chamber 7 Resin Housing 8 High Voltage Generator 9 Annular Resin Part 10 External Electrode 11 Outside Air Outlet 12 Air Chamber 13 Low Voltage Power Supply 14 Low Voltage Cable 15 High-voltage cable 16 High resistance for current control 17 Paint tank 18 Paint supply hose 19 Air supply device 20 Air regulator 21 Air regulator 22 Air hose 23 Air hose 112 Air outlet 113 Air chamber 123 Air regulator 126 Air hose

Claims (3)

[Claims] 1. A paint atomizing head rotatable about an axis, an external electrode whose tip is located in front of the paint atomizing head, and an inner air blower provided behind the tip of the paint atomizing head. A rotary atomization static valve, comprising: an outlet; and an outer air outlet provided outside the inner air outlet and having a position set so as to blow out air along the inner side of the outer electrode. Electro-painting equipment. 2. The rotary atomizing electrostatic coating device according to claim 1, further comprising an air outlet arranged coaxially with the paint atomizing head outside the external electrode. 3. The rotary atomizing electrostatic coating device according to claim 1, wherein the air blowing direction of the inner air outlet is a direction twisted with respect to the axis of the paint atomizing head.