JP3082986B2 - Electrostatic 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 an electrostatic coating apparatus using a rotary atomizing head, and more particularly to an electrostatic coating apparatus suitable for applying a water-based paint or a metallic paint.

[0002]

2. Description of the Related Art Generally, paints used for electrostatic coating are roughly classified into solvent-based paints (oil-based paints) having relatively high electric resistance and water-based paints (water-based paints) having relatively small electric resistance. Further, there are metallic paints in which metal powder is dispersed in these solvent paints and water paints, and these metallic paints have relatively small electric resistance values like water paints. As described above, since the paints have different resistance values according to their types, the method of applying the high voltage differs according to the types of the paints.

[0003] That is, from the viewpoint of danger prevention, paint supply pipeline,
Paint tanks, color change valve devices, etc. are used by connecting them to ground, but solvent-based paints have a relatively large resistance value. There is no danger that the atomization head will be at ground potential via the paint supply line. Therefore, the electrostatic coating apparatus used for the solvent-based paint is configured to apply a high voltage directly to the rotary atomizing head and directly charge the paint particles.

On the other hand, since the water-based paint and the metallic paint have small electric resistance values, when a high voltage is directly applied to the rotary atomizing head, the rotary atomizing head is grounded via the paint in the paint supply pipe. It short-circuits to the electric potential, and the paint particles cannot be charged. Therefore, in the case of a water-based paint, an external electrode is provided at a position radially outside the rotary atomizing head,
By applying a high voltage to the external electrode to form a corona discharge region in front of the rotary atomizing head, paint particles sprayed from the rotary atomizing head are indirectly charged.

Therefore, a rotary atomizing head type electrostatic coating apparatus for water-based paint using an indirect charging system according to the prior art is described below.
This will be described with reference to FIGS.

In the drawing, reference numeral 1 denotes a coating machine main body. The coating machine main body 1 is provided with a housing 2 formed of a resin material in a cylindrical shape, and is provided so as to cover the housing 2. A resin cover 3 formed of a resin material (for example, polyethylene terephthalate) to be a shaping ring 3 </ b> A that sends shaping air toward the housing, and an air motor 4 with a built-in air bearing (not shown) provided in the housing 2. A rotary shaft 5 rotationally driven by the air motor 4; and a bell 6 as a rotary atomizing head, which is mounted on the rotary shaft 5 and located at the tip end of the housing 2.
And a paint feed tube 7 made of a metal pipe inserted through the rotary shaft 5 to supply paint to the bell 6.
At the rear end of the housing 2, an insulating support 8 attached to a reciprocator or the like is projected. The basic configuration of the air motor 4 and the like is described in Japanese Utility Model Application Publication No.
For example, in Japanese Patent Publication No. 259/259, the details are omitted because they are known.

9, 9, ... are radially outside the bell 6,
In addition, there are shown six electrode mounting brackets which are radially located and are uniformly spaced on the outer peripheral side of the resin cover 3, and each of the electrode mounting brackets 9 is supported at the rear end of the housing 2. Are external electrodes 11 described later.
A supporter as an electrode holding rod formed of a resin material (for example, polytetrafluoroethylene) covering
Each supporter 10 is provided on each of the electrode mounting brackets 9.

Reference numerals 11, 11,... Denote external electrodes held by being buried in the supporters 10 in the axial direction. The tips of the external electrodes 11 protrude from the supporters 10 and slightly extend from the bells 6. It is arranged rearward and radially outward.

Reference numeral 12 denotes a color changing valve device (also called "CCV") as a paint supply source provided outside, and the color changing valve device 12 includes an A color paint valve 12A, a B color paint valve 12B,
, And a cleaning air valve Ar and a thinner valve H are provided. The color changing valve device 12 supplies paint, air, and thinner to the bell 6 through a paint supply pipe 13 and a paint feed tube 7 according to a signal from a controller 17 described later. Further, the air motor 4 is connected to the ground 1.
4, the paint and the thinner are grounded.

Reference numeral 15 denotes a high voltage generator, which is composed of, for example, a Cockcroft circuit or the like, is electrically connected to each external electrode 11 through a high voltage cable 16, and applies a high voltage VH. It is supposed to.

Reference numeral 17 denotes a controller. The controller 17 controls the high voltage generator 15, the color changing valve device 12, and the air motor 4 based on a signal from an operation switch (not shown).

The electrostatic coating apparatus according to the prior art is constructed as described above. Next, referring to FIG. 4, the operation of each process of A-color coating, cleaning and B-color coating will be described.

First, the object 1 to be grounded by the earth 14
In the A-color coating process of applying the A-color paint to the coating machine 8, the air motor 4 of the coating machine main body 1 is rotated at a high speed,
Is rotated at a rotation speed NH (about 45000 rpm), and
Shaping air from bell shaping ring 3A to bell 6
Release to the side. The high voltage V is applied to each external electrode 11 by the high voltage generator 15 via the high voltage cable 16.
H (−60 kV) is applied to form a corona discharge region in front of the tip of each external electrode 11. Further, the A color paint valve 12A of the color changing valve device 12 is opened, and the A color paint is supplied to the bell 6 through the paint supply pipe 13 and the paint feed tube 7.

The A-color paint particles atomized by the bell 6 rotating at the rotation speed NH are charged while passing through the corona discharge region. Flying along the shaping air,
And apply a clear coating.

Next, in the cleaning step, the rotation speed of the bell 6 is reduced to NL (about 35,000 rpm), and the supply of the high voltage VH from the high voltage generator 15 is stopped. Further, the air valve Ar and the thinner valve H of the color changing valve device 12 are alternately opened, and the paint supply pipe 13 and the paint feed tube 7 are opened.
Air and thinner are supplied alternately to the bell 6 via the. Then, the remaining paint and thinner in the coating machine main body 1 are discharged from the bell 6 and discharged into a coating booth (not shown) by shaping air. Thereby, the paint supply pipe 13, the paint feed tube 7, and the bell 6 of the coating machine main body 1 are formed.
Is washed.

Further, in the B-color coating step of coating the B-color paint, the air motor 4 is again rotated at a high speed, the bell 6 is driven to rotate at a rotation speed NH (about 45000 rpm), and a high voltage is applied to each external electrode 11. Apply VH (−60 kV). Then, the B color paint valve 12B of the color changing valve device 12 is opened, the B color paint is supplied to the bell 6 through the paint supply pipe 13 and the paint feed tube 7, and the B color paint is applied to the object 18 to be coated. Paint.

[0017]

By the way, in the above-mentioned electrostatic coating apparatus according to the prior art, the high voltage VH is applied to each of the external electrodes 11 for safety in preventing an accident such as a fire during the cleaning process. Is stopped, and the bell 6 is rotated at about 70 to 80% of the rotation at the time of coating to wash the paint supply pipe 13, the paint feed tube 7, and the bell 6.

Further, since the resin cover 3 is made of a resin material having a high insulating property, the material is inevitably a material having a high dielectric constant. For this reason, at the time of coating, a current (electric field) is applied between each external electrode 11 having the high voltage VH and the bell 6 which is electrically grounded due to the potential difference, and the resin cover 3 is charged to a negative charge. (Charged).

On the other hand, at the time of cleaning, each external electrode 11
Since the application of the high voltage VH is stopped, negative charges are discharged from the negatively charged resin cover 3, and an electric field is generated between the resin cover 3 and the bell 6. The residual paint and thinner released from the bell 6 are sucked along the electric field by the resin cover 3 (particularly, the shaping ring 3A) against the shaping air from the shaping ring 3A, and are gradually deposited as deposits. I do.

Further, at the time of applying the next B-color paint, a current normally applied between the bell 6 and each of the external electrodes 11 causes a current between the attached matter (the shaping ring 3A of the resin cover 3) and each of the external electrodes 11. As a result, the electric field in the corona discharge region formed between the bell 6 and each of the external electrodes 11 becomes weak, so that the coating efficiency on the object 18 is significantly reduced, and There is a problem that the painted surface is stained.

Further, while repeating the coating step and the washing step, the deposits of the resin cover 3 (shea Epi <br/> ring ring 3A) that occurred during the washing step, the該付kimono in the next coating operation Discharge phenomenon (bridge phenomenon) between each external electrode 11
And acceleratively promote the deposition of the deposits. As a result, there is a problem that the high voltage generator 15 and the like are destroyed.

The present invention has been made in view of the problems of the prior art, and has as its object to provide an electrostatic coating apparatus capable of preventing deposits such as residual paint and cleaning liquid from being deposited on a resin cover. .

[0023]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention employs a high voltage generator.
High voltage adjustment means for adjusting the voltage value generated by
The high-voltage adjusting means applies the paint to the object at the time of painting.
To generate a predetermined high voltage necessary for
Controls the high voltage generator and generates it during painting during cleaning.
Generates a low-voltage high voltage that is lower than a predetermined high voltage
Thus, the high voltage generator is controlled .

[0024]

[Function] By adopting the above configuration, at the time of cleaning, at the time of painting
Low voltage, which is lower than the predetermined high voltage
Controlling a high voltage generator to generate, that you apply a low pressure high voltage between the rotary atomizing head and respective external electrodes
Can be. For this reason, even during cleaning, a higher electric field is generated between each external electrode and the rotary atomizing head than the electric field generated between the rotary atomizing head due to the discharge from the resin cover charged with negative charge. are allowed, it is possible residual paint and cleaning fluid is released from the rotary atomizing head is prevented from adhering to the resin cover.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. Note that the same components as those of the above-described related art are denoted by the same reference numerals, and description thereof will be omitted.

In the figure, reference numeral 21 denotes a controller including a high voltage adjusting means according to the present embodiment. Like the controller 17 described in the prior art, the controller 21 generates a high voltage based on a signal from an operation switch (not shown). Apparatus 1
5. Although the color changing valve device 12 and the air motor 4 are controlled, an internal program adjusts the high voltage VH during painting and washing.

Next, with reference to FIG. 2, the operation of each step of the A-color coating, the cleaning, and the B-color coating of the electrostatic coating apparatus according to the present embodiment will be described. In the A-color painting process and B color painting process, and <br/> Since this filtrate is not prior art vary a by painting steps is omitted.

In the cleaning step, the rotation speed of the bell 6 is set to N
L (approximately 35000 rpm) and high voltage generator 1
The power supply of the high voltage VH from 5 under reduced pressure to a voltage VL (-30 k V) based on a signal from the controller 21 is applied to each of the external electrodes 11. Further, thinner and air are alternately supplied from the color changing valve device 12 to the bell 6 through the paint supply pipe 13. Then, the paint supply pipe 13, the paint feed tube 7, and the bell 6 are washed.

Here, since the voltage VL is applied to each of the external electrodes 11, the resin cover 3 charged to a negative charge at the time of painting can discharge the negative charge even in the cleaning process. Instead, the charged state is maintained, and the residual paint and cleaning liquid released from the bell 6 are discharged into the coating booth and can be reliably prevented from adhering to the resin cover 3.

Thus, even during cleaning, by applying the voltage VL to each of the external electrodes 11, it is possible to prevent deposits such as residual paint and cleaning liquid from being deposited on the resin cover 3, and the following B color can be prevented. When applying the coating material, it is possible to effectively prevent unevenness of coating caused by a reduction in the coating efficiency on the object 18, which has conventionally occurred, and also to prevent the adhesion and the external electrodes 1 from being applied.
1 can be reliably prevented from being discharged (bridge phenomenon). In addition, it is possible to prevent the coating surface of the object 18 from being stained and to prevent the high voltage generator 15 and the like from being damaged, thereby effectively extending the life of the electrostatic coating apparatus.

In this embodiment, each external electrode 1
When the linear distance between the 1 and the bell 6 and about 10 cm, a high voltage VH during coating applies a -60 k V, but when flushing applying a voltage VL as -30 k V, the present invention is limited to this In addition, by increasing the voltage VL at the time of cleaning to a level at which a fire accident does not occur, residual coating on the resin cover 3 and adhesion of the cleaning liquid can be more reliably prevented.

The external electrodes 11 are not limited to the six needle electrodes, but may be ring-shaped external electrodes.
The number of 1 may be one or more.

[0033]

According to the present invention an electrostatic coating apparatus rather如described in detail above by, during coating at the time of cleaning by the high voltage regulator
Low voltage, which is lower than the predetermined high voltage
To control the high-voltage generator to generate
From even during washing, it is possible to apply a low-pressure high voltage to the external electrodes. Thus, also prevent discharge of charges from the resin cover charged during coating at the time of washing,
It can continue to maintain the charged state, the residual paint and cleaning fluid is released from the rotary atomizing head can be prevented from adhering to the resin cover when cleaning. In addition, it is possible to prevent a decrease in the efficiency of application to the object to be coated and to effectively extend the life of the high voltage generator.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an electrostatic coating apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing operations during painting and cleaning according to the embodiment.

FIG. 3 is an overall configuration diagram of a conventional electrostatic coating apparatus.

FIG. 4 is an explanatory view showing operations at the time of painting and cleaning according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coating machine main body 2 Housing 3 Resin cover 3A Shaping ring 4 Air motor 5 Rotating shaft 6 Bell 7 Paint feed tube 9 Electrode mounting bracket 11 External electrode 12 Color change valve device (paint supply source) 15 High voltage generator 21 Controller ( High voltage adjustment means)

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B05B 5/08 B05B 5/053

Claims (1)

(57) [Claims] A housing housing an air motor for driving a rotating shaft; a resin cover provided to cover the housing; a resin cover positioned at a tip end of the housing and attached to the rotating shaft, and rotated by the air motor. A rotating atomization head to be urged, a paint supply source provided at a position spaced apart from the rotation atomization head, and a communication between the paint supply source and the rotation atomization head; A paint supply flow path to be supplied, an external electrode disposed on the housing at a position radially outside the rotary atomizing head, and a high voltage cable for supplying a high voltage to the external electrode. in electrostatic painting apparatus comprising a high voltage generator which is connected to the external electrodes, adjusting the voltage value generated by the pre-Symbol high voltage generator
High voltage adjusting means is provided, and the high voltage adjusting means applies a predetermined high voltage necessary for applying a paint to an object to be coated during coating.
Controlling the high voltage generator to generate the
Is a low pressure lower than the specified high voltage generated during painting
Controlling the high voltage generator so as to generate a high voltage.
An electrostatic coating apparatus characterized by having a configuration as described above.