JPH0436749B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an atomizer of the type in which the atomized charged paint particles are directed toward the object to be coated along the lines of electric force by rotating the rotary atomizer head at high speed and are applied by flight. This invention relates to an electrostatic spray device.

Conventionally, this type of electrostatic spraying device has a rotating shaft supported via a bearing such as a ball bearing or a roller bearing, an air-driven turbine is attached to one end of the rotating shaft, and a rotating atomizer is attached to the other end. The rotary atomizing head is attached, and the rotary atomizing head is rotated at high speed by the turbine while applying a high voltage to atomize the paint supplied to the rotary atomizing head. To atomize the paint, the rotating atomizer head is rotated at high speed, and the paint supplied to the liquid contact surface is made to flow down to the discharge edge as a thin film-like liquid stream by centrifugal force. The paint is discharged from the discharge edge as liquid threads (cusps), and the liquid threads are further electrostatically atomized to form charged paint particles.

By the way, liquid paint is atomized into paint particles,
When coating an object to be coated, the quality of the paint film formed on the painted surface is determined by the maximum particle size and average particle size of the paint particles, and when the maximum particle size is large, the quality of the paint film is is known to significantly reduce Therefore, the rotation speed of the rotating atomizing head has a large effect on the particle size, and the higher the rotation speed of the rotating atomizing head, the smaller the particle size can be, which improves the quality of the coating film. can be done.

However, since the above conventional technology uses ball bearings or roller bearings as a means to support the rotating shaft, the rotation tolerance is limited to 25,000 to 40,000 rpm in order to prevent seizure of these bearings. .
However, when the rotational speed of the rotary atomizing head is about 40,000 rpm or less, the average particle size of the paint becomes considerably large, and there is a problem that good paint film quality cannot be obtained.

To solve these problems, we used a static air bearing to support the rotating shaft without contact.
Those configured to increase the rotational speed of the rotating atomizing head to about 60,000 to 100,000 rpm, for example, JP-A-56-
An electrostatic spraying device as shown in Japanese Patent No. 115652 is known.

That is, the electrostatic spraying device according to the above-mentioned prior art includes a housing in which a shaft hole is formed in the axial direction and a turbine chamber is formed in the radial direction on one end side of the shaft hole, and a housing in which a shaft hole is formed in the shaft hole of the housing. a rotating shaft fitted into the housing; a turbine loosely fitted into a turbine chamber of the housing and fixed to one end of the rotating shaft;
a rotating atomizing head located outside the housing and fixed to the other end of the rotating shaft; and a rotating atomizing head located around the rotating shaft and provided on the housing to support the rotating shaft in a non-contact state. The turbine is generally comprised of a radial air bearing and a thrust air bearing that is located on both sides of the turbine and provided in the housing to support the turbine in a non-contact manner, and is capable of supplying high pressure air to the turbine. Therefore, the rotating shaft is rotated at high speed, and high-pressure air is supplied to the radial and thrust bearings to support the rotating shaft in a non-contact manner.On the other hand, paint is supplied to the rotating atomizing head and paint particles are removed from the discharge edge. It is designed to spray.

In this way, an electrostatic spraying device using a hydrostatic air bearing can obtain a high rotation speed that is more than twice as high as that using a ball bearing, a roller bearing, or the like.

By the way, such electrostatic spraying devices usually
A high voltage of -60 to -120 [KV] is applied to the rotating atomizing head, and the liquid threads released from the discharge edge of the rotating atomizing head are electrostatically atomized into charged paint particles. Particles are applied by flying along an electrostatic field (lines of electric force) formed between a rotating atomizer head and the object to be coated, toward the object at ground potential.

Therefore, if the rotating shaft is directly supported by ball bearings, roller bearings, etc., applying a high voltage from a high voltage generator to the conductive housing will cause the rotating shaft to move through the bearings. Contact charging allows high voltage to be applied to the rotating atomizing head. Also,
Power can also be supplied directly by attaching a brush to the rotating shaft.

However, when a static pressure air bearing is used as a means for supporting the rotating shaft, even if a high voltage is applied to the housing, there is an air layer between the air bearing and the rotating shaft. It was believed that it was not possible to apply high voltage directly to the

Therefore, in the above-mentioned Japanese Patent Application Laid-open No. 56-115652, a cylindrical hole is formed in the housing side at the rear end side of the rotating shaft, and an electrode made of a conductive material can be moved into the cylindrical hole. A compression spring is inserted between the housing and the electrode to press the electrode against the rear end surface of the rotating shaft.By applying a high voltage to the housing, the electrode is pressed against the rotating shaft by the spring. It is designed so that power can be directly supplied while being in sliding contact with.

However, the prior art described above has a drawback in that a compression spring acts on the rotating shaft, making it impossible to manage the axial clearance with high precision using the thrust air bearing. Therefore, it is necessary to increase the gap between the thrust air bearing and the turbine, or to make the high pressure air supplied to the thrust air bearing extremely high pressure, which not only complicates the structure but also increases the play of the rotating shaft. The disadvantage is that it gets old and shortens its lifespan. Furthermore, there is a drawback that the rotational speed cannot be controlled with high precision due to the sliding resistance.

The present invention was made in view of the shortcomings of the conventional technology which adopts a method of directly feeding power to the rotating shaft as described above, and merely applies a high voltage to the air bearing, thereby causing a discharge phenomenon to occur in the air bearing. It is an object of the present invention to provide an electrostatic spraying device that can apply a high voltage to a rotating shaft in a non-contact state.

In order to achieve the above object, an electrostatic spraying device according to the present invention includes a housing having a shaft hole formed therein in the axial direction and a turbine chamber formed in the radial direction at one end of the shaft hole, and the housing. a rotating shaft loosely fitted into a shaft hole of the housing; a turbine loosely fitted into a turbine chamber of the housing and fixed to one end of the rotating shaft; and a turbine located outside the housing and fixed to the other end of the rotating shaft. A rotary atomizing head is provided in the housing around the rotating shaft to support the rotating shaft in a non-contact manner, and directs high-pressure air toward the space between the rotary atomizing head and the rotating shaft. a radial air bearing equipped with a multi-hole bearing that ejects air; and a radial air bearing provided in the housing on both sides of the turbine to support the turbine in a non-contact manner, and extending toward the bottom between the bearing and the turbine. The thrust air bearing includes a porous bearing that blows out high-pressure air.

The structure adopted by the present invention is characterized in that the housing, the turbine, the rotating shaft, the rotating atomizing head, and the porous bearings of each air bearing are formed of a conductive material, and the housing is provided with a high voltage generator. A high voltage cable that applies a high voltage to the housing is connected, and the high voltage applied from the high voltage cable to the housing is transmitted between the porous bearing of the radial air bearing and the rotating shaft and between the porous bearing of the thrust bearing. Between the bearing and the turbine
The reason is that the voltage is applied to the rotating shaft through a discharge phenomenon.

With this configuration, when a high voltage is applied from the high voltage generator to the high voltage cable, the porous bearing of each air bearing is charged to a high voltage through the housing, and the porous bearing of the radial air bearing and the rotation An air layer interposed between the shaft and the porous bearing of the thrust bearing and the turbine causes dielectric breakdown due to a discharge phenomenon, and a high voltage is applied to the rotating shaft and the turbine made of a conductive material. The rotating atomizing head is also charged to a high voltage. At this time, since each of the porous bearings has minute irregularities, it acts like a needle-like electrode, and the discharge phenomenon can be carried out reliably.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

In the drawings, reference numeral 1 denotes a cylindrical housing made of a conductive metal body and composed of a main body part 1A and a front part 1B.A shaft hole 2 is bored in the housing 1 in the axial direction. A circular turbine chamber 3 is formed in the radial direction on one end side, and the shaft hole 2
The other end is an opening 2A. 4 is the shaft hole 2
A rotary shaft 5 made of a metal material such as SUS is loosely fitted into the shaft hole 2 with a small gap in the radial direction; A disk-shaped turbine made of a metal material such as aluminum, which is loosely fitted with a
is fixed to one end side 4A of the rotating shaft 4 by means such as welding or bolts, and a large number of blades 5A, 5A, . . . are provided on the outer peripheral surface of the turbine 5 at equal intervals. Reference numeral 6 denotes a rotating atomizing head located outside the housing 1 and fixed to the other end 4B of the rotating shaft 4. In this embodiment, the rotating atomizing head 6 is a bell-shaped atomizing head. The rotary atomizing head 6 consists of a hub member 7 fixed to the rotating shaft 4 and an atomizing head main body 8 attached to the hub member 7, and the hub member 7 is formed with a liquid contact surface 7A. At the same time, a plurality of paint passages 7B, 7B... are formed, and an atomizing head main body 8
A liquid contact surface 8A is formed that thins the paint from each paint passage 7B into a thin film, and the tip thereof becomes a discharge edge 8B, and a large number of grooves are carved in the discharge edge 8B as necessary. It is set up.

9, 9 are radial air bearings located around the rotating shaft 4 and disposed in the housing 1 in order to support the rotating shaft 4 in a non-contact state with respect to the shaft hole 2; A sleeve-shaped porous bearing 10 made of a porous metal material made of cemented carbide and fixed to the housing 1 so as to surround the outer periphery of the rotating shaft 4, and the shaft hole 10.
The air chamber 11 is located on the outer peripheral surface of the housing 1 and is formed concentrically with the shaft hole 2. Each of the air bearings 9 is a porous bearing 10.
and the air chamber 11 constitute a static pressure air bearing,
As will be described later, by blowing out high-pressure air supplied to the air chamber 11 from the porous bearing 10 as shown by the arrow in the figure, the rotating shaft 4 can be supported in a non-contact manner. In the case of this embodiment, two radial air bearings 9 are arranged at a predetermined interval in the axial direction, but the number of air bearings 9 may be one, or three or more may be arranged. It is okay to do so.

Reference numerals 12 and 12 designate thrust air bearings that are located on both sides of the turbine 5 and disposed in the housing 1 in order to support the turbine 5 in a non-contact state with respect to the turbine chamber 3. is an annular porous bearing 13 made of a porous metal material made of cemented carbide fixed to the housing 1 so as to sandwich both sides of the turbine 5; It is composed of an air chamber 14. Each of the air bearings 12 also constitutes a static pressure air bearing with a porous bearing 13 and an air chamber 14,
The high pressure air supplied to the air chamber 14 is transferred to the porous bearing 1.
3 in the direction of the arrow in the figure, the turbine 5 can be supported in a non-contact manner.

Next, reference numeral 15 denotes a turbine driving air passage formed in the housing 1, and one end 15 of the air passage 15
A is connected to a pressure source, and the other end 15B is a nozzle opening that opens toward the front surface of the blade 5A of the turbine 5 in the turbine chamber 3. By injecting the high pressure air supplied to the turbine drive air passage 15 from the other end 15B to the front surface of the blades 5A of the turbine 5, the turbine 5 is moved in the direction of arrow A together with the rotating shaft 4 and the rotating atomizing head 6. , 60000～
It can rotate at high speed of 100000rpm. Further, 16 is a bearing air passage formed in the housing 1, one end 16A of the air passage 16 is connected to a pressure air source, and the other ends 16B, 16B, . . . are branched and connected to the air chambers 11, 14, respectively. ing. 17 is an exhaust passage, and one end 17A, 17A of the exhaust passage 17 is branched to connect between each radial air bearing 9, 9, and between the radial air bearing 9 on the left side in the figure and the thrust air bearing 12 on the right side in the figure. The other end 17B is located in between and opens into the shaft hole 2, and the other end 17B is connected to an exhaust muffler 18 provided in the housing 1.

Next, 19 is a brake air passage formed in the housing 1, one end 19A of the air passage 19 is connected to a pressure air source via a pressure reducing regulator, and the other end 19B is connected to the back surface of the blade 5A of the turbine 5. The nozzle opening is oriented towards the target. The regulator then reduces the pressure of the high-pressure air to a predetermined pressure lower than the pressure of the turbine drive air to obtain brake air, which is then injected from the other end 19B of the brake air passage 19 onto the back surface of the blade 5A of the turbine 5. By doing so, the rotation speed of the turbine 5 can be reduced to 5,000 to 10,000 rpm.

On the other hand, 20 is a paint tube provided on the front part 1B of the housing 1, one end 20A of the paint tube 20 serves as a joint to be connected to a paint source, and the other end 20B is connected to the liquid contact surface 7A of the rotary atomizing head 6. It serves as a paint discharge port that supplies paint. Reference numeral 21 denotes an air ring provided in the aforementioned front section 1B, in which an annular groove 21A is formed, and a large number of jet holes 21B for jetting shaping air from the back side of the rotary atomizing head 6. 21B,... are bored at equal intervals. The annular groove 21A of the air ring 21 is connected to a pressurized air source via an air passage 22 formed in the front surface 1B.

Note that 23 is a male thread for promoting exhaust gas carved on the outer peripheral surface of the other end side 4B of the rotating shaft 4, and the male thread 23 is a male thread for promoting exhaust gas. from the opening 2A toward the rotating atomizing head 6 through the annular minute gap between the other end of the shaft hole 2 and the rotating shaft 4, as indicated by the arrow B in the figure.
When the rotary shaft 4 rotates in the direction of the arrow A, its pumping action promotes the exhaust in a swirling manner to prevent paint from adhering.

Further, reference numeral 24 in the figure denotes a metal mounting member fixed to one end face of the housing 1 via bolts 25, 25, . . . , and an insulating support member 26 made of synthetic resin is attached to the mounting member 24. 27 is a high voltage cable, one end of the high voltage cable 27 is connected to a high voltage generator that generates a high voltage of, for example, -30 to -120 [KV], and the other end is attached via a connector 27A and a bolt 25. It is fixed to the housing 1 together with the member 24, so that a high voltage can be directly applied to the housing 1.

The present invention is constructed as described above, and its operation will now be described.

First, from the shaft air passage 16 to each air bearing 9,
High-pressure air is supplied to the twelve air chambers 11 and 14, and the high-pressure air is ejected from the porous bearings 10 and 13 in the direction indicated by the arrow in the figure. As a result, the rotating shaft 4 is held in a non-contact state in the radial direction by the radial air bearing 9, and the turbine 5 is held in a non-contact state in the axial direction by the thrust air bearing 12.

In this state, when high pressure air is supplied from the turbine drive air passage 15 toward the front surface of the blades 5A of the turbine 5, the turbine 5 rotates at high speed in the direction of arrow A in the figure together with the rotating shaft 4 and the rotating atomizing head 6. During this time, most of the exhaust from each of the air bearings 9 and 12 and the turbine 5 is discharged into the atmosphere from the exhaust passage 17 via the muffler 18.

On the other hand, from the high voltage generator to the high voltage cable 27
For example, if you supply a high voltage of -90 [KV] to
The housing 1 made of metal is charged to -90 [KV] together with the mounting member 24. On the other hand, each air bearing 9,
Since the twelve porous bearings 10 and 13 are also made of metal, each of these bearings 10 and 13 is charged to the same potential as the housing 1. On the other hand, the rotating shaft 4 and the turbine 5 are in a non-contact state with respect to the housing 1, but the rotating shaft 4 is loosely fitted into the porous bearing 10 and the shaft hole 2 with a small gap, and the turbine 5 is only loosely fitted into the porous bearing 13 and the turbine chamber 3 with a small gap.

As a result, a high voltage is applied to each porous bearing 10, 13 via the housing 1, so that
A microscopic air layer interposed between the rotating shaft 4 and the porous bearing 10 and between the turbine 5 and the porous bearing 13 causes dielectric breakdown due to an electrical discharge phenomenon, and the rotating shaft 4 made of a metal material , −90 [KV] is applied to the turbine 5. Thus, the rotating atomizing head 6 is also charged to this high voltage via the rotating shaft 4.

At this time, in the present invention, each air bearing 9, 1
Porous bearings 10 and 13 are used as porous bearings 10 and 13, but the inner peripheral surface of each of the porous bearings 10 and 13 has an extremely minute uneven shape when viewed microscopically, and the tip of the protrusion of this uneven shape looks like It acts like a needle-like electrode and can reliably perform the discharge phenomenon.
At this time, electrostatic induction due to an electrostatic field is also performed in addition to the discharge phenomenon. Moreover, since the high voltage is applied directly to the housing 1, the discharge phenomenon occurs in both the rotating shaft 4 and the turbine 5, so the charging area (discharging area) can be increased, and the high voltage applied to the rotating shaft 4 can be increased. Application becomes more reliable.

Next, when paint is supplied from the paint tube 20, this paint is supplied to the hub member 7 of the rotary atomizing head 6, and from the liquid contacting surface 7A to the liquid contacting surface 8A of the atomizing head main body 8 via the paint passage 7B. The centrifugal force generated when rotating at high speed makes the film extremely thin, and the discharge edge 8B
It is atomized as liquid threads and electrostatically atomized into charged paint particles. These paint particles fly along the electric lines of force formed between the rotating atomizing head 6 and the object to be coated,
Apply to the object to be coated which is at ground potential. During this time, in order to form a spray pattern, air is supplied from the air passage 22 to the air ring 21, and its ejection holes 21B
Shaping air is blown out from.

Further, in order to spray the next color paint, thinner and air are sequentially supplied from the color change valve through the rotary atomizing head 6 and the paint tube 20 to clean the paint of the previous color adhering to the interior of the paint tube 20, etc. Supply and wash until clean. At this time, if the rotation of the rotary atomizing head 6 is too fast, waste liquid will scatter around, so brake air is supplied from the brake air passage 19 and the rotational speed of the rotary atomizing head 6 is set at 5000 to 10000 rpm.
to slow down. Once the cleaning process is complete, prepare for the next color painting process.

Note that since the rotating shaft 4 is provided with a male thread 23, when the rotating shaft 4 rotates in the direction of arrow A, the pumping action of the male thread 23 promotes the swirling exhaust in the direction of arrow B. be able to. As a result,
Paint particles that flow backward in the direction of arrow C due to the air pumping phenomenon etc. are constantly pushed back by the exhaust gas ejected from the annular gap in the direction of arrow B, causing paint to adhere to the inside of the shaft hole 2 or to the radial air bearing 9. It is possible to reliably prevent a situation in which the porous bearing 10 of the air bearing 9 is clogged due to adhesion.

In addition, in the above-mentioned embodiment, the mounting member 24 and the housing 1 are formed of metal material, and the high voltage cable 2
7 is applied to the porous bearings 10 and 13 of each air bearing 9 and 12 through the housing 1, but for safety reasons, the high voltage from the housing 1
A cover made of an insulating material such as synthetic resin may be fitted onto the outside of the cover. Further, although the rotary atomizing head 6 has been described as having a bell shape, it may also have a so-called disk shape or a disk shape. Furthermore, the object to which the present invention is applied is not limited to a paint spraying device, but may also be a spray granulation device or an emulsion manufacturing device.

The electrostatic coating device according to the present invention, as described in detail above, applies a high voltage to the porous bearings constituting the radial air bearing and the thrust air bearing through the housing, and rotates the porous bearings. A high voltage is applied to the rotary shaft and the turbine through a gap formed between the shaft and the turbine by a discharge phenomenon, and the high voltage from the rotary shaft is charged to the rotary atomizing head. Electricity can be supplied from the housing to the rotating atomizing head in the contact state. At this time, the inner circumferential surface of the porous bearing constituting each air bearing has minute irregularities and acts like a needle-like electrode, so that the discharge phenomenon can be reliably performed. Moreover, since high voltage is applied directly to the housing, high voltage can be applied to both the rotating shaft and the turbine, and the charged area can be increased. Furthermore, since high voltage is applied to the rotating shaft through non-contact power supply, it is not only possible to strictly control the distance between the air bearings compared to conventional technology that supplies power through contact. , rotation speed control,
High pressure air for bearings can be controlled accurately.

[Brief explanation of drawings]

The figure is a longitudinal sectional view of an electrostatic spraying device according to the present invention. DESCRIPTION OF SYMBOLS 1... Housing, 2... Shaft hole, 3... Turbine chamber, 4... Rotating shaft, 5... Turbine, 6... Rotating atomization head, 9... Radial air bearing, 12... Thrust air bearing, 15...Air passage for turbine drive, 16...Air passage for bearing, 17...Exhaust passage, 19...Air passage for brake, 20...Paint tube, 21...Air ring, 23...Male thread, 27... …High voltage cable.

Claims (1)

[Claims] 1. A housing in which a shaft hole is formed in the axial direction and a turbine chamber is formed in the radial direction at one end of the shaft hole, a rotating shaft loosely fitted in the shaft hole of the housing, and a turbine in the housing. A turbine loosely fitted into the chamber and fixed to one end of the rotating shaft, a rotating atomizing head located outside the housing and fixed to the other end of the rotating shaft, and the rotating shaft in a non-contact state. the turbine; Thrust air bearings are provided in the housing on both sides of the turbine to support the turbine in a non-contact manner, and include porous bearings that blow out high-pressure air toward the space between the turbine and the turbine. In this electrostatic spraying device, the housing, the turbine, the rotary shaft, the rotary atomizing head, and the porous bearings of each air bearing are formed of a conductive material, and the high voltage from the high voltage generator is applied to the housing. A high voltage cable is connected to the housing, and the high voltage applied from the high voltage cable to the housing is applied between the porous bearing of the radial air bearing and the rotating shaft and between the porous bearing of the thrust bearing and the turbine. An electrostatic spraying device characterized in that the electrostatic spraying device is configured to apply an electric current to the rotating shaft by a discharge phenomenon through a gap formed between the two.