JPH078848A - Electrostatic atomizing type coater - Google Patents

Abstract

PURPOSE:To stably perform application with uniform film thickness in a device where while high voltage is applied to a spray head, a coating material is atomized by electrostatic action to coat the surface of a work with it by intermittently applying ultra-high voltage to superimpose it on the high voltage of the spray head. CONSTITUTION:High voltage is applied to a spray head 1 installed adjacent to a strip S as a work, and also a coating material is fed to the spray head 1. And the coating material is applied to the surface of the strip S while it is atomized by electrostatic action. In this case, an ultra-high voltage generating device 100 equipped with an ultra-high voltage generator 111 generating ultra- high voltage much higher than the high voltage is arranged, and also an intermittent superimposed applying means 20 for intermittently applying the ultra-high voltage superimposed on the high voltage to the spray head 1 is installed there. That is, when plural sliding switches 250, 251 constituting the intermittent superimposed applying means 20 are, for example, in contact with an insulating disc 23 apart from a conductor 22, the ultra-high voltage is applied to the spray head 1 through a voltage adjusting resistance 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic atomization type coating apparatus for atomizing a coating material by electrostatic action and coating it on a work surface.

[0002]

2. Description of the Related Art An electrostatic atomization type coating apparatus for atomizing oil, rust preventive material, wax, paint, etc. by an electrostatic action and coating the surface of a work is widely used.

In FIGS. 6 and 7, an electrostatic atomization type oil coating device in which the coating material is oil, for example, is a strip (continuously fed in the X direction from a spray head 1 having a slit (spray port) 2). Work) S is disposed close to the surface of S, and the high voltage Vb generated from the high voltage generator 10 is applied to the spray head 1 and oil is supplied, and the oil is utilized by utilizing the electrostatic action. As shown in FIG. 8A, the strip (work) surface is uniformly applied with oil while atomizing. d is the distance between the poles.

The longitudinal dimension of the spray head 1 is the same as the width dimension W of the strip S shown in FIG. Also,
The high voltage generator 10 has a configuration in which a current limiting resistor 15, a high voltage generator 11, and a safety device (for example, SCR type) 13 shown in FIG. 7 are connected in series. 14 is an ammeter. Also, a voltmeter 17 is provided via the resistor 16. The slit 2 of the spray head 1 is as narrow as several tens of μm, and the high voltage Vb is selected to be 100 kV, for example.

[0005]

By the way, the above-mentioned conventional electrostatic atomization type oil coating device is a system for atomizing oil by utilizing electrostatic action as described above, and therefore atomized oil particles are relatively small. Roughly, it is difficult to follow load changes. On the other hand, nowadays due to the diversification, it is often operated in various usage modes including light load. Due to these relationships, the oil coating film thickness may vary in the width direction of the strip surface as shown in FIG. 8B depending on the use / operation mode. That is, there are cases where there are variations Pa to Pc where the oil cannot be atomized and ejected.

Conventionally, in order to prevent the occurrence of the variation, the shape of the spray head 1 is finely finished and carefully assembled so that the distance d between the strip S and the gap S is constant in any longitudinal direction.・ Although it is adjusted, variations may still occur even if this measure is taken. Therefore, not only the quality is deteriorated, but also the entire strip may be defective.

The above problems similarly occur even when the coating material is a rust preventive material, wax, paint, or the like, and even when the spray head 1 is not in the form shown in FIGS.

An object of the present invention is to provide an electrostatic atomization type coating device which eliminates variations in the work surface and can stably coat the entire surface with a uniform film thickness.

[0009]

In order to clarify the above-mentioned variation problem, that is, the cause of variation points Pa, Pb, Pc where atomization does not occur in the longitudinal direction of the spray head 1 as shown in FIG. 8 (B). Although it is analyzed through many actual machines, for example, surface tension of oil etc. and spray port (slit 2)
We are conducting testing and research by selectively changing the size and other factors, but the cause is still unclear. Moreover, the irregularity has an irregular property that it does not occur at the start of operation and may occur in the middle of it, and in some cases, it may disappear after restart. Further, it is a delicate technical matter that the mechanical vibration is applied to the spray head 1 at the time of occurrence of the variation regardless of positive or negative, and the variation is eliminated.

Attention is paid to the fact that the variation may be eliminated by mechanical vibration, that is, if the mechanical vibration induces a variation in the inter-electrode distance d, and as a result, the defective discharge at the variation point Pi is corrected. Based on the experience, the present invention is configured to intermittently apply an ultrahigh voltage, which is much higher than the normal high voltage, to the spraying head while keeping the distance d between the electrodes constant, thereby achieving the above object. It is the one.

That is, in the electrostatic atomization type coating apparatus according to the present invention, the spraying head is arranged close to the work, and a high voltage is applied to the spraying head and the coating material is supplied to perform electrostatic action. In the electrostatic atomization type coating device that coats the work surface while atomizing the coating material by using the ultra high voltage generation device that generates an ultra high voltage that is much higher than the high voltage, the ultra high voltage An intermittent superimposition applying means for superimposing an ultra-high voltage generated from a generator on the high voltage and intermittently applying it to the high voltage is provided.

[0012]

In the case of the present invention having the above-mentioned structure, the intermittent superimposition applying means intermittently superimposes the ultrahigh voltage generated from the ultrahigh voltage generator on the normal high voltage and applies it. Therefore, even if there is a defective spraying portion or a non-spraying portion of the spraying head under the constant distance between the electrodes, the electric shock due to the ultrahigh voltage accelerates the discharge. Therefore, since the spraying can be smoothly performed by starting the discharge, it is possible to eliminate the variation and stably form a uniform coating film thickness on the work surface. Further, if it is set such that the superimposed application is intermittently performed at appropriate intervals, the occurrence of variations can be prevented.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) As shown in FIGS. 1 and 2, the electrostatic atomization type coating apparatus of the first embodiment has the same basic structure as that of the conventional example (FIGS. 6 and 7). Although it is a type oil coating device, the ultra-high voltage generator 100 and the intermittent superimposition applying means 20 are provided, and the ultra-high voltage Vp is intermittently superposed and applied to the normal high voltage Vb to discharge a defective discharge location. It is configured so that the start (restart) can be promoted to eliminate the variation in the oil film thickness and prevent the variation from occurring.

The same parts as those of the conventional example (FIGS. 6 and 7) are designated by the same reference numerals, and the description thereof will be simplified or omitted.

In FIG. 1, an ultrahigh voltage generator 100 is shown.
Is structurally the same as the conventional example (FIG. 7), but the ultra-high voltage generator 111 has a DC 15 voltage as shown by the dotted line in FIG.
It can continuously output an ultra-high voltage Vp of 0 kV and has a current capacity of 0.5 mA. Therefore, the withstand voltage characteristics of the safety device 113, the current limiting resistor 115, and the resistor 116 are the same as those of the conventional example (13, 1).
It is higher than 5, 16). In addition, 114 is an ammeter and 117 is a voltmeter.

This ultra-high voltage generator 111 is constructed so as to serve also as the high-voltage generator (11), paying attention to the fact that the current capacity may be small. That is, the voltage adjustment resistor 2
1 to the spray head 1. By the way,
The resistance value of the voltage adjusting resistor 21 is 100 MΩ. Therefore, when the load current I is 0.5 mA, 50
It causes a voltage drop of kV. That is, the normal high voltage Vb (10
0 kV) can be applied.

Next, the intermittent superimposition applying means 20 is means for intermittently applying the super high voltage Vp generated from the ultra high voltage generator 100 to the normal high voltage Vb to intermittently apply it. In the case of, the structure is mechanical.

That is, the electric conductor 22 having a predetermined length is fixed to the peripheral surface of the electrically insulating disk 23 which is rotated at a constant speed by the motor 24, and the limit switch type is provided on the input side and the output side of the voltage adjusting resistor 21. Sliding switches 25I and 2
5O is provided, and the super-high voltage Vp is superposed on the normal high voltage Vb in a state where both the sliding switches 25I and 25O slide on the conductor 22. That is, by passing the voltage adjustment resistor 21, the ultra high voltage Vp can be applied in a pulse shape as shown in FIG. The substantial voltage applied in superposition is (Vp-Vb).

The intermittent superimposition applying means 20 (2
1, 22, 23, 25I and 25O) are immersed in insulating oil (for example, silicone oil) in the tank 29 to prevent sparks.

In the present invention, the high voltage Vb (1
Superimposing a super-high voltage Vp (150 kV) on (00 kV) does not mean switching from the high voltage Vb to the super-high voltage Vp, but a normal high voltage Vb at a predetermined voltage of 50 kV.
This means that the pressure is further increased by (= 150-100). This is because switching from the high voltage Vb to the ultrahigh voltage Vp to the high voltage Vb in this order causes a voltage cutoff even for a moment. This is because this adversely affects the good spray location of the spray head 1.

The pulse width of this ultrahigh voltage Vp is determined by the number of revolutions (rpm) of the insulating disk 23 and the length of the conductor 22.
In the case of this embodiment, the insulating disc 23 has a diameter of 300 mm,
The rotational speed of the motor 24 is a variable speed type of 250 to 2500 rpm, and the pulse width is set to be changeable within the range of 1/5 to 1/50 sec. 1/3 in this first embodiment
It is set to 0 sec.

If the voltage adjusting resistor 21 is formed in a clip selection system in which the resistance elements 21A to 24G shown in FIG. 3 are connected in series, for example, the ultrahigh voltage Vp and the normal high voltage Vp can be obtained.
The ratio with b can be variably adjusted.

The resistance 25 connected between the voltage adjusting resistance 21 and the spray head 1 is set to 500 KΩ. Also,
A voltmeter 17 connected via the resistor 16 monitors the voltage (Vb or Vp) applied to the spray head 1. A resistor 16A is detachably provided for level adjustment.

Next, the operation of this embodiment will be described. Sliding switches 25I, 25 forming the intermittent superposition applying means 20
When both or one of O is separated by the conductor 22 and is in sliding contact with the peripheral surface of the insulating disk 23, the ultra high voltage generator 1
The ultrahigh voltage Vp generated from 00 (111) is applied to the spray head 1 through the voltage adjusting resistor 21.

That is, when the load current I is 0.5 mA, a voltage drop of 50 kV occurs in the voltage adjusting resistor 21, so that the spray head 1 has a normal high voltage Vb (100 kV).
Is applied. Therefore, from the spray head 1 to FIG.
As shown in (A), the oil is atomized and can be applied to the surface of the strip S.

If, for some reason, variation points Pa, Pb, Pc as shown in FIG. 8 (B) occur in the longitudinal direction (strip width direction) of the spray head 1, a uniform film thickness is obtained on the strip surface. The oil cannot be formed. However, in the case of the first embodiment, both the sliding switches 25I and 25O are simultaneously in sliding contact with the conductor 22 on the peripheral surface of the insulating disk 23 every 1/30 sec.

Then, since the voltage adjusting resistor 21 is passed, the ultrahigh voltage Vp is applied to the spray head 1 as it is. That is, instead of the normal high voltage Vb (100 kV), the pulsed ultra high voltage Vp (150 kV) is intermittently applied as shown in FIG. Specifically, the high voltage Vb (1
50 kV is superposed on (00 kV).

Therefore, the strip S and the spray head 1
Even if the inter-electrode distance d is constant, it is possible to start or restart the discharge at the variation points Pa, Pb, Pc where the complete discharge has not been performed yet by the electric shock. That is, a high voltage trigger for starting discharge is added to accelerate the electrostatic atomization action.

Therefore, even if there is a possibility that the variation points Pa, Pb, and Pc may occur at the intervals of 1/30 sec or more, the atomization may be interrupted due to the fact that the discharge is not completed or the discharge is defective. Since this can be prevented in advance, it is possible to stably form a coating oil having a uniform film thickness in the width direction.

Therefore, according to the first embodiment, the ultra high voltage generator 100 for generating the ultra high voltage Vp which is much higher than the high voltage Vb is provided, and the ultra high voltage generator 100 generates the ultra high voltage Vp. The spray head 1 is provided with an intermittent superimposition applying means 20 for intermittently applying the super high voltage Vp to the high voltage Vb to intermittently apply the pulse-shaped super high voltage Vp to the spray head 1 during the oiling operation. Since the configuration is such that the spraying is applied in a superimposed manner, it is possible to eliminate the conventional atomization variation problem due to discharge incompleteness or discharge failure in the longitudinal direction of the spray head 1. Therefore, it is possible to stably apply the oil having a uniform film thickness over the entire width of the strip S.

The ultra high voltage generator 100 (111)
Is configured to also serve as the normal high voltage generator 10 (11), the structure is simple. Further, the intermittent superposition applying means 20 is formed so as to apply the ultra high voltage Vp (150 kV) instead of the normal high voltage Vb (100 kV) without voltage interruption by passing the voltage adjusting resistor 21. Therefore, it is possible to prevent the occurrence of the spray variation part without giving any trouble to the smooth spraying part of the spray head 1.

Further, the insulating disc 2 of the intermittent superimposition applying means 20.
The motor 24 for rotating 3 (conductor 22) is of a variable speed type, and is configured to apply the ultra-high voltage Vp in a pulse shape at every set period within the range of 1/5 to 1/50 sec. ing. Therefore, if the application cycle of the ultra-high voltage Vp is set in advance to a cycle corresponding to the timing of occurrence of spray variation that can occur randomly, it is possible to completely prevent the occurrence of spray variation.

Since the intermittent superimposition applying means 20 has a mechanical structure (22, 23, 24, 25I, 25O), the cost is low and reliable and stable operation can be performed for a long period of time.

Further, by applying a pulsed ultra-high voltage Vp to the spray head 1, that is, by adding a discharge start trigger, the spray variation is eliminated and the application cycle is appropriately set. Since this can be prevented, the finishing and assembling adjustment of the spray head 1 can be greatly simplified as compared with the conventional example. Therefore, cost reduction can also be achieved.

(Second Embodiment) This second embodiment is shown in FIG.
As shown in FIG. The high voltage generator 10 is exactly the same as the case of the conventional example (FIG. 7), and the ultra high voltage generator 100
Are separately provided as shown in FIG. That is,
The ultra high voltage generator 100 has an ultra high voltage Vp (150 k
V) is formed by an ultra-high voltage generator 111 and a ballast 113 that continuously generate and output V) as shown by the one-dot chain line in FIG.

Here, the intermittent superposition applying means 20 comprises a timing signal generating circuit 22E and a switching circuit 21E which is ON / OFF controlled by a timing signal output from the circuit 22E. The diode D
1, D2 are provided to prevent backflow.

Therefore, in addition to the normal high voltage Vb (100 kV) shown in FIG. 5A, the pulse-shaped super high voltage Vp shown by the solid line in FIG.
(150 kV) can be applied in a superimposed manner. That is, the spraying head 1 is superimposedly applied as shown in FIG. The application period of the ultra high voltage Vp is determined by the generation timing of the timing signal.

However, in the case of the second embodiment as well, in addition to the same effects as in the case of the first embodiment, the intermittent superimposition applying means 20 has an electrical structure (21E, 22E). It has a wide applicability that can be downsized and can be easily attached to an existing device. Moreover, the high voltage Vb
It is possible to lower the voltage of, for example, 80 kV compared to the conventional example (100 kV).

In the above embodiments, the electrostatic atomization type oil coating device has been described, but the device is not limited to the oil coating device as long as it is a device for atomizing and applying the coating material by electrostatic action.
For example, an electrostatic atomization type coating device.

[0040]

According to the present invention, an ultra-high voltage generator for generating an ultra-high voltage much higher than the high voltage is provided, and the ultra-high voltage generated by the ultra-high voltage generator is applied to the spray head. Since intermittent superimposition applying means for superimposing a high voltage and applying intermittently is provided, and a pulsed ultra-high voltage is intermittently superposed and applied to the spray head during the coating operation, the spray head discharges. It is possible to eliminate the conventional atomization variation problem due to incompleteness or defective discharge. Therefore, it is possible to stably apply a film having a uniform thickness over the entire surface of the work.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a super high voltage superposition application state.

FIG. 3 is also a diagram for explaining a modification of the voltage adjustment resistor.

FIG. 4 is an overall configuration diagram showing a second embodiment.

FIG. 5 is also a diagram for explaining a super high voltage superposition application state.

FIG. 6 is a schematic view showing a conventional example.

FIG. 7 is likewise an overall configuration diagram.

FIG. 8 is a diagram for explaining the problems of the conventional example.

[Explanation of symbols]

 1 Spray Head 2 Slit 10 High Voltage Generator 11 High Voltage Generator 15 Current Limiting Resistance 20 Intermittent Superimposition Applying Means 21 Voltage Adjustment Resistor 21E Switching Circuit 22 Conductor 22E Timing Signal Generating Circuit 23 Insulating Disc 24 Motor 100 Ultra High Voltage Generation Device 111 Ultra high voltage generator Vb High voltage Vp Ultra high voltage S Strip (work) d Distance between poles

Claims (1)

[Claims] 1. A spray head is disposed close to a work, a high voltage is applied to the spray head and a coating material is supplied, and the coating material is atomized by using an electrostatic action to coat the surface of the work. In the electrostatic atomization type coating device to be provided, an ultra-high voltage generator that generates an ultra-high voltage that is much higher than the high voltage is provided, and the ultra-high voltage generated from the ultra-high voltage generator is applied to the spray head. An electrostatic atomization type coating device, characterized in that an intermittent superimposition applying means for superimposing it on the high voltage and applying it intermittently is provided.