JPH09173913A - Spindle for electrostatic coating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep stable rotation supporting by restraining the occurrence of sputtering in the clearance of a static pressure gas bearing. SOLUTION: In a spindle for an electrostatic coating device in which a rotor 8 of a rotational force generator connected to a rotating shaft 7 and the rear end part of the rotating shaft is incorporated inside a housing 1 connected to a high voltage generator 2, and the rotating shaft 7 and the rotor 8 are freely rotatably supported though a beating clearance 6 of a static pressure gas being, and a coating material spray head is fitted to the front end part of the rotating shaft 7, a conducting layer projecting to the bearing clearance is formed on at least one surface of the rotating shaft 7, of the rotor 8, or the rotating shaft 7 of the housing 1 or the surface opposite to the rotor 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle incorporated in a rotary atomizing type electrostatic coating device.

[0002]

2. Description of the Related Art Conventionally, in the coating of automobile parts, electric parts, etc., electrostatic coating in which a negative charge is applied in a fog-like state and the electric attraction is used to adhere to the surface to be coated. Many machines are used.

In such an electrostatic coating machine, it is required to rotate the paint spraying head at a high speed in order to make the particle size of the atomized paint as small as possible to obtain a uniform coated surface. In order to deal with this, a structure is generally adopted in which the rotary shaft of the spindle to which the spray head is attached is supported by a static pressure gas bearing in a non-contact manner.

FIG. 5 shows the structure of this type of electrostatic coating machine. In this coating machine, a rotary shaft 33 is inserted into a housing 30 connected to a high voltage generator 31 via a bearing gap 32, and compressed air is supplied to the bearing gap 32 from a plurality of air supply nozzles 34 formed in the housing 30. By blowing out, the rotating shaft 33 is supported in a non-contact manner.

The rotating shaft 33 has a paint spraying head 35 fixed at its front end portion for spraying the paint to the surroundings by rotation of the rotating shaft 33, and a motor 36 having a stator and a rotor at its rear end portion. Therefore, it is held in an electrically insulated state with respect to the ground of the high voltage generator 31 while being levitationally supported via the bearing gap 32.

In the above structure, when a negative high voltage is applied to the housing 30 by the high voltage generator 31 with the ground of the high voltage generator 31 and the surface to be coated of the work set to the same potential, the housing 30 A discharge phenomenon occurs in the bearing gap 32 between the rotating shaft 33 rotating at high speed, and the paint spraying head 35 connected to the rotating shaft 33 is charged. Then, the paint is charged with a negative electric charge by the spraying head 35 and blown out in a mist state, and the paint is adhered to the surface to be coated by an electric suction action to form a uniform coated surface.

[0007]

In the above structure, a discharge phenomenon may occur in the bearing gap 32 due to the combination of the applied voltage, the bearing clearance, the material used, etc., and this discharge phenomenon may cause sputtering. .

When sputtering occurs in this way,
Since metal atoms forming the bearing surface of the housing 30 fly out and adhere to the surface of the rotating shaft 33, the bearing gap 32 decreases and the supporting state of the rotating shaft 33 becomes unstable, so that the rotating shaft 33 and the housing 30 are separated from each other. There was a case of contact.

Therefore, the object of the present invention is to suppress the occurrence of sputtering in the static pressure gas bearing gap and maintain stable rotation support without being significantly affected by the conditions such as the applied voltage, the material used, and the bearing clearance. It is to be.

[0010]

In order to solve the above-mentioned problems, the present invention incorporates a rotating shaft and a rotor of a rotational force generating device connected to the rear end of the rotating shaft into a housing, and In a spindle for an electrostatic coating machine, which rotatably supports a shaft and a rotor through a bearing gap of a static pressure gas bearing, and a paint spraying head is attached to a front end portion of the rotary shaft, the rotary shaft surface, the rotor surface, Alternatively, a conductive layer protruding into the bearing gap is provided on at least one of the surfaces of the housing facing the rotating shaft or the rotor.

Since a conductive layer protruding between the bearing gaps is provided on at least one of the surface of the rotating shaft, the surface of the rotor, or the surface of the housing facing the rotating shaft or the rotor, the conductive layer faces the conductive layer. The gap between the surfaces
It becomes narrower than the bearing gap of the other static pressure gas bearings. Therefore, the discharge phenomenon between the housing and the rotating shaft is
It is concentrated in the conductive layer and is not generated in other bearing gaps, so that it is possible to prevent the occurrence of sputtering in the bearing gaps.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIGS.

As shown in FIG. 1, a high voltage generator 2 for generating a high negative voltage is electrically connected to a housing 1, and an air passage 3 connected to a compressed air supply source (not shown) is provided therein. Is formed, and in the inner hole 1a of the housing 1,
A plurality of air supply nozzles 4, 5 connected to the air passage 3 are formed.

In the inner hole 1a of the housing 1, the rotor 8 of the rotating force generator (for example, turbine) for rotating the rotating shaft 7 and the rotating shaft 7 provided at the rear end of the rotating shaft.
Are inserted through the bearing gap 6. The rotating shaft 7
A radial air bearing 9 is formed between the periphery of the air supply nozzle 4 and the air supply nozzle 4, and a thrust air bearing 10 is formed between the rotor 8 and the air supply nozzle 5. When compressed air is supplied to the bearing gap 6 from the air supply nozzles 4 and 5,
The rotary shaft 7 and the rotor 8 are levitationally supported by the pressure of the air, and are brought into a non-contact state with the housing 1, and the function of the static pressure gas bearing including the radial air bearing 9 and the thrust air bearing 10 is exerted.

The material used for the rotating shaft 7 and the rotor 8 is not particularly limited, but for rust prevention,
It is preferable to use stainless steel. Further, the surface of the bearing may be subjected to a hardening treatment such as a hard chrome plating treatment in order to prevent galling at the time of contact with the bearing and suppress seizure.

The paint spray head 13 attached to the front end of the rotary shaft 7 has a cup-shaped metallic guide plate 14 which is screwed onto the rotary shaft 7, and an annular paint introducing space between the guide plate 14. Support plate 16 forming 15
And a paint injection nozzle 17 attached to the introduction space 15 so that the opening faces the guide space 14 and the support plate 16.
A large number of paint outflow holes 18 are formed between them.

In the spray head 13, the jet nozzle 17
The paint sprayed from is introduced into the inner peripheral surface of the cup-shaped guide plate 14 through the outflow hole 18 by the high-speed rotation of the spray head 13, and is blown to the surroundings while being atomized by the centrifugal force. In this case, when the guide plate 14 is in a charged state, the paint is charged with a negative charge while flowing on the inner peripheral surface thereof.

As the spray head 13, not only the spray head 13 shown in FIG. 1 but also another spray head 13 may be used. For example, the spray head 35 shown in FIG. 5 may be used. In the spray head 35 shown in FIG. 5, the paint injection nozzle 37 does not pass through the rotary shaft 17, but is directly introduced into the paint introduction space 38 from the outside. The paint sprayed into the paint introducing space 38 is introduced into the inner peripheral surface of the cup-shaped guide plate 40 through the outflow hole 39 by the high speed rotation of the spray head 35, and is blown to the surroundings while being atomized by the centrifugal force. Be done. The method of charging the paint is the same as in the case of FIG.

On the other hand, a plurality of turbine blades 19 are arranged around the rotor 8 at the rear end of the rotary shaft 7, and a compressed air jet hole 20 for blowing compressed air to the turbine blades 19 is formed in the housing 1. . Further, a compressor 21 is connected to the ejection hole 20. In this structure, when compressed air is blown from the compressor 21 to the turbine blades 19 through the ejection holes 20, a rotational force is applied to the turbine blades 19 and, as a result, the levitationally supported rotating shaft 7 is rotated at a high speed.

The means for generating a rotational force on the rotary shaft 7 may employ the structure using the motor shown in FIG.

The surface of the rotating shaft 7, the surface of the rotor 8, or the rotating shaft 7 or the rotor 8 of the housing 1.
The conductive layer 11 that protrudes into the bearing gap is provided on at least one of the surfaces facing the. That is, FIG.
When the conductive layer 11 is provided on the surface of the rotating shaft 7, as shown in FIG. 5, it is formed in a cylindrical shape on the outer peripheral surface of the rotating shaft 7 of the radial air bearing 9. As shown in FIG. 2, the conductive layer 11 is formed several μm higher than the outer peripheral surface of the rotating shaft 7, and a gap 12 between the conductive layer 11 and the housing 1 that is narrower than the bearing gap 6 is formed. . Further, the cylindrical conductive layer 11 may be provided on the inner peripheral surface of the inner hole 1 a of the housing 1 facing the outer peripheral surface of the rotating shaft 7. Even with this,
A gap 12 narrower than the bearing gap 6 is formed. Further, the cylindrical conductive layer 11 may be provided on both the outer peripheral surface of the rotating shaft 7 and the inner peripheral surface of the inner hole 1a of the housing 1 facing the outer peripheral surface.

The conductive layer may be provided on the end surface of the rotor 8. In this case, as shown in FIG. 3 and FIG. 4, an annular conductive layer 11 ′ centering on the rotation center of the rotor 8 is provided on the end surface of the rotor 8. In this way, a gap between the conductive layer 11 'and the housing 1 that is narrower than the bearing gap 6 is formed. Further, the annular conductive layer 11 ′ may be provided on the inner surface side of the housing 1 facing the end surface of the rotor 8. Even in this case, a gap narrower than the bearing gap 6 is formed.
Further, the annular conductive layer 11 ′ may be provided both on the end surface of the rotor 8 and on the inner surface side of the housing 1 facing the end surface of the rotor 8.

The conductive layers 11 and 11 'are made of a material having conductivity and a small friction coefficient, and are provided by forming a conductive film by a method such as painting or vapor deposition. For example, the conductive film can be formed by coating such as coating using a conductive resin based on molybdenum disulfide and graphite. The conductive film can also be formed by depositing titanium nitride or the like. Further, the conductive film can be formed by plating such as hard chrome plating.

When the conductive layer is provided on the rotary shaft 7 or the rotor 8, a conductive film may be formed by using the same material as the surface material when processing the rotary shaft 7 or the rotor 8. Good.

When the conductive layer 11 is provided on the radial air bearing 9 portion, that is, either the surface of the rotary shaft 7 or the surface of the housing 1 facing the rotary shaft 7, the radial air bearing 9 portion. Although the conductive layer 11 can be provided at any place in the above, when the rotating shaft 7 rotates, resonance occurs when it is tuned to a fixed frequency. Therefore, the conductive layer 11
And the rotating shaft 7 can easily come into contact with each other. From this, when the resonance occurs, it is preferable to provide the conductive layer 11 in a place where the amplitude of the rotary shaft 7 is small, and the conductive layer 11 is provided at a portion serving as a node of the amplitude, for example, substantially in the axial center of the rotary shaft 7. Is more preferable.

In the electrostatic coating machine having the above structure, when the housing 1 is applied with a negative high voltage by the high voltage generator 2, the gaps formed by the conductive layers 11 and 11 'and the surface facing the conductive layers 11 and 11'. Is the narrowest, so the dielectric strength of this part is the smallest. Therefore, a discharge phenomenon occurs in this portion, and the discharge phenomenon does not occur in the bearing gap 6 having a relatively large dielectric strength. Therefore, adhesion of molten metal due to sputtering is prevented. Moreover, since the dielectric strength is reduced, the energy during discharge in the gap formed by the conductive layers 11 and 11 ′ and the surface facing the conductive layers is reduced, and the influence of sputtering in this portion can be suppressed.

Therefore, the bearing gap 6 is formed by sputtering.
It is possible to prevent contact and the like that occur in the.

[0028]

According to the present invention, a conductive layer protruding into the bearing gap is provided on at least one of the surface of the rotating shaft, the surface of the rotor of the rotating force generator, the rotating shaft of the housing, and the surface facing the rotor. As a result, the gap of the surface facing the conductive layer becomes narrower than the bearing gaps of the other static pressure gas bearings. Therefore, the discharge phenomenon from the housing toward the rotary shaft or the rotor is concentrated in the conductive layer and does not occur in the other bearing gaps, so that the occurrence of sputtering in the bearing gaps can be prevented. Further, since the gap between the surfaces facing the conductive layer is narrower than the bearing gaps of the other static pressure gas bearings, the energy at the time of discharge becomes small, so that the influence of sputtering in this portion can be suppressed.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view showing an example of an electrostatic coating machine of the present invention.

2 is a partially enlarged sectional view of FIG.

FIG. 3 is a vertical sectional front view showing another example of the electrostatic coating machine of the present invention.

4 is a sectional view taken along line AA of FIG.

FIG. 5 is a vertical sectional front view showing a conventional electrostatic coating machine.

[Explanation of symbols]

 1 Housing 1a Internal Hole 2 High Voltage Generator 3 Air Passage 4 Air Supply Nozzle 5 Air Supply Nozzle 6 Bearing Gap 7 Rotating Shaft 8 Rotor 9 Radial Air Bearing 10 Thrust Air Bearing 11, 11 'Conductive Layer 12 Gap 13 Paint Spray Head 14 Guide plate 15 Paint introduction space 16 Support plate 17 Paint injection nozzle 18 Paint outflow hole 19 Turbine blade 20 Air injection hole 21 Compressor 30 Housing 31 High voltage generator 32 Bearing gap 33 Rotating shaft 34 Air supply nozzle 35 Paint spray head 36 Motor 37 Paint injection nozzle 38 Paint introduction space 39 Outflow hole 40 Guide plate

Claims (8)

[Claims] 1. A rotary shaft and a rotor of a rotational force generator connected to the rear end of the rotary shaft are incorporated in a housing, and the rotary shaft and the rotor are freely rotatable through a bearing gap of a static pressure gas bearing. In a spindle for an electrostatic coating machine having a paint spraying head attached to the front end of the rotating shaft, at least one of the rotating shaft surface, the rotor surface, or the rotating shaft of the housing or the surface facing the rotor. A spindle for an electrostatic coating machine, characterized in that a conductive layer protruding from the bearing gap is provided on the surface of the. 2. The spindle for an electrostatic coating machine according to claim 1, wherein the conductive layer is provided on an outer peripheral surface of a substantially central portion in the axial direction of the rotating shaft. 3. The electrostatic coating machine spindle according to claim 1, wherein the conductive layer is provided on an end surface of the rotor. 4. The conductive layer comprises a conductive coating formed on at least one of the surface of the rotating shaft, the surface of the rotor, or the surface of the housing facing the rotating shaft or the rotor. The spindle for an electrostatic coating machine according to any one of 1. 5. The electrostatic coating machine spindle according to claim 1, wherein the material of the conductive layer is the same as the material of the surface of the rotating shaft or the rotor. 6. The spindle for an electrostatic coating machine according to claim 4, wherein the conductive coating is a coating formed by a conductive resin coating. 7. The spindle for an electrostatic coating machine according to claim 4, wherein the conductive film is a film formed by plating. 8. The spindle for an electrostatic coating machine according to claim 4, wherein the conductive film is a film formed by vapor deposition.