JPS59209668A - Rotary atomizing electrostatic applicator - Google Patents

Abstract

PURPOSE:To hold an electrode at a low temp. for prolonging its life of use, by cooling the electrode existent in contact with the paint atomizing rotary shaft of a rotary atomizing electrostatic applicator at a low temp. caused by the expansion of compressed air for the rotation of said rotary shaft. CONSTITUTION:A rotary shaft 8 is supported with a couple of non-contact radial pneumatic bearings 22, 23 inside the front housing 2 of a rotary atomizing electrostatic applicator, a paint atomizer head 9 made of metal is attached to the front end 8b of said shaft 8, an electrode 66 is pressed onto the rear end 8c by a spring 67, and a turbine wheel 42 is further attached. Negative high voltage is impressed from a high-voltage power source 71 through the electrode 66 onto the rotary shaft 8 and the paint atomizer head 9. The rotary shaft 8 is rotated at a high speed with the turbine wheel 42 by compressed air from a compressor 56, and paint supplied through a nozzle 21 is charged with negative electricity and sprayed through the atomizer head 9. Although the electrode 66 driven in contact with the end part 68 of the rotary shaft 8 is heated at a high temp. by friction, it is cooled by low-temp. air formed by the expansion of the compressed air having passed through the turbine. Hence, the electrode 66 can be used over a long period while eliminating damage caused by high temp.

Description

[Detailed description of the invention] The present invention relates to a rotary atomization electrostatic coating device.

Traditionally, for example, vehicles? As a coating device for painting paint, a rotating shaft is supported by a ball bearing or roller bearing in the nozzle of the coating device, and a negative voltage is applied to a cup-shaped spray head fixed to the outer end of the rotating shaft. Supplying paint onto the inner peripheral surface of a cup-shaped spray head that is rotating at the same time as applying the paint,
Rotary atomization in which fine particles of paint charged with a negative voltage are ejected from a cup-shaped spray head and are attracted by electric force onto an electrically grounded surface to be painted, thereby painting the surface. Electrostatic coating devices are known.

In such a rotary atomizing electrostatic coating device, approximately 90'e-cents of the paint spray ejected from the spray head can be effectively used for painting the surface to be coated, so the amount of paint consumed is small, and therefore it is applicable to a wide range of industrial fields. It is used in

On the other hand, in the case of painting using a spray paint, it is necessary to make the particle size of the spray paint as small as possible in order to obtain a clean painted surface. When the above-mentioned rotary atomizing electrostatic coating device utilizes the centrifugal force generated by the rotation of the spray head to atomize the paint, the magnitude of the centrifugal force, i.e., the size of the spray head, is The rotational speed has a great effect on the particle size of the sprayed paint; the higher the rotational speed of the spray head, the smaller the particle size of the sprayed paint (/J). Therefore, in order to obtain a clean painted surface using such a rotary atomizing electrostatic coating device, it is necessary to increase the rotational speed of the spray head as much as possible. As mentioned above, conventional rotary atomizing electrostatic coating equipment uses ball bearings or roller bearings to support the rotating shaft, and these ball bearings or roller bearings are usually filled with a lubricant such as grease. There is. Bearings lubricated with such grease quickly deteriorate when the rotating shaft is rotated at high speeds. The number of rotations of the spray head should be at most 2000O.
It can only be raised to about r, p, and m. However, when the rotational speed of the spray head is around 2000 Or, p, m, the particle size of the sprayed paint is quite large, so it is difficult to finish a clean painted surface using such a rotary atomizing electrostatic coating device. It is. Therefore, the painting process for vehicle bodies normally consists of an undercoat by electrodeposition, then an intermediate coat, and then a top coat of Soji paint, but this rotary atomizing electrostatic coating f1 is used for the intermediate coat. , cannot be used to apply ten coats.

Therefore, in the present invention, the rotating shaft is supported by a non-contact type thrust bearing and a non-contact type thrust bearing to rotate the rotating shaft at high speed.

However, in a rotary atomizing electrostatic coating device, it is necessary to apply a high voltage to the spray head.Therefore, when the rotating shaft is supported by a non-contact type radial bearing and a non-contact type radial bearing, It is necessary to provide an electrode that contacts the rotating shaft. However, when an electrode is provided in contact with the rotating shaft as in the case of the above method, the rotating shaft is rotated at a high speed, which causes the electrode to overheat (1), leading to problems such as accelerated wear of the electrode and deterioration of the electrode.

In the present invention, the temperature of the compressed air passing through the turbine is
.

It is an object of the present invention to provide a rotary atomizing electrostatic coating device in which the stain electrode is cooled by the compressed air passing through the turbine by utilizing the lowering temperature, thereby extending the life of the electrode.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, a rotary atomizing electrostatic coating apparatus, generally designated 1, comprises a generally hollow cylindrical metal front housing 2 and a generally hollow cylindrical rear metal housing 3. The two housings 2.3 are firmly connected by bolts 4. A support rod 6 made of an electrically insulating material is fitted into the cylindrical hole 5 of the rear housing 30, and the rear housing 3 is fixed to the support rod 6 by a port 7.

This support rod 6 is supported by a base (not shown). On the other hand, inside the front housing 2 is a metal rotating shaft 8.
is inserted. This rotating shaft 8 has a hollow cylindrical part 8a located in the center thereof, a front end 'g [3b] integrally formed with the hollow cylindrical part 8a, and a rear end part 8c fixed to the hollow cylindrical part 8a.
A metal spray head 9 is fixed to the front end 8b of the rotating shaft 8 by a bolt 10. This spray head 9 has a spray head support 1 in which an annular space 11 is formed.
2 and a cup-shaped spray head main body 13 fixed on the support 12. As shown in FIGS. 1 and 2, the outer cylindrical portion 14 of the support 12 has an annular space 1
A large number of paint outlet holes 16 are formed which open into the inner wall 1 and smoothly connect to the inner wall surface 15 of the song head main body 13. on the other hand,
An end plate 17 is fixed to the front end of the front housing 2,
A paint spray nozzle 18 is mounted on this end plate 17.

This paint injection nozzle 18 is connected to a paint pump 20 via a paint supply pump 19, and is also connected to a paint injection nozzle 7]8.
The nozzle opening 21 is directed toward the cylindrical inner circumferential wall surface of the support outer cylinder 14.

As shown in FIG. 1, the front housing 2 is provided with a pair of non-contact radial bearings 22, 23 consisting of tilting pad air bearings.

The rotating shaft 8 is rotatably supported by the front housing 2 by 23. These tiltings<? The rad air bearings 2'2, 23 have the same construction, so only the construction of one tilting rad air bearing 22 will be described below. Referring to FIGS. 1 and 3, the tilting pad air bearing 22 includes three pads 24, 25, and 26 arranged with extremely small gaps from the outer peripheral surface of the rotating shaft hollow cylindrical portion 8a. Support bins 27°28 holding these pads 24, 25, 26 respectively
．． 29. Each of these support pins 27.28.
29 has a sphere 30°31.32 integrally formed at its inner end, and these spheres 30°31.32 are placed in a spherical recess formed on the back surface of each nograd 24, 25.26. engage. Therefore, each pad 24, 25, 26 can swing about the corresponding sphere 30, 31° 32 as a fulcrum. A bearing frame 33 is secured to the outer circumferential wall surface of the front opening 2 by, for example, bolts, and the support pins 28 and 29 are secured to this bearing frame 33 by screws 34 and 35, respectively. On the other hand, one end portion of the support arm 36 having the elastic plate-like portion 36a is fixed to the bearing frame 33 with a bolt 37, and -
A support pin 27 is attached to a nut 38 at the other end of the force support arm 36.
It is fixed by

Therefore, the nodule 24 is pressed onto the rotating shaft hollow cylindrical portion 8a by the elastic force of the support arm 36.

Referring again to FIG. 1, a pair of disc-shaped runners 39.40 are inserted into the rear end portion 8C of the rotating shaft 8, and these runners 39.40 are connected to the spacer 41 and the turbine wheel 4.
2 to the rear end portion 8c with a nut 43.

On the other hand, an annular plate 44 is disposed between these launches 39, 40, and the runners 39, 40 and the annular plate 44 constitute a non-contact type thrust air bearing. In addition, each runner is 39.4
0 is arranged so as to be separated from the annular plate 44 by a slight gap. The annular plate 44 is sealingly fixed to the front housing 2 via a pair of O-rings 45,46.

As shown in FIGS. 1 and 4, an annular groove 47 is formed in the front housing 2 along the outer peripheral surface of an annular plate 44.
This annular groove 47 is connected to an air supply pump f49 via a compressed air introduction hole 48 formed in the front housing 2. On the other hand, a large number of air passages 50 extending radially inward from the annular groove 47 are formed in the annular plate 44, and each air passage 50 has a runner 3 extending from the vicinity of the inner end thereof.
9 and an air outlet hole 51°5 extending toward the runner 40.
2 is formed.

On the other hand, a turbine nozzle holder 53 is fixed within the front housing 2 adjacent to the annular plate 44, and an annular air introduction chamber 54 is formed between the turbine nozzle holder 53 and the front housing 2. This air introduction chamber 54 is connected to a compressor 56 via a compressed air introduction hole 55. The air introduction chamber 54 has a compressed air jet nozzle 57 equipped with a large number of guide vanes (not shown), and the turbine blades 58 of the turbine wheel 42 are disposed facing the jet nozzle 57 . On the other hand, the turbine M wheel 42 is arranged in a compressed air exhaust chamber 59 formed in the housing, and this compressed air exhaust chamber 59 is connected to an exhaust hole 6 formed in the rear housing 3.
0 to the atmosphere. The compressed air introduced into the air introduction chamber 54 from the compressor 56 is discharged through the jet nozzle 57.
The compressed air is blown out into the compressed air discharge chamber 59 through the compressed air discharge chamber 59. At this time, the jetted compressed air applies rotational force to the turbine wheel 42, and the rotating shaft 8 is thus rotated at a high speed. On the other hand, the compressed air that has passed through the turbine wheel 42 is expanded in the compressed air discharge chamber 59, and the temperature of the compressed air is thus rapidly reduced. Next, the compressed air discharge chamber 59 whose temperature has decreased
The compressed air inside is exhausted to the atmosphere through the exhaust hole 60.

On the other hand, a through hole 62 is formed in the end wall 61 of the rear nozzle 3 defining the compressed air discharge chamber 59, and an electrode holder 63 passing through the through hole 62 is attached to the end wall 61 by a bolt 64. It is fixed. Inside this electrode holder 63, there is a cylindrical hole 65 formed coaxially with the rotation axis of the rotation shaft 8.
is formed, and an electrode 66 made of a wear-resistant conductive material such as carbon is movably inserted into this cylindrical hole 65. Furthermore, a compression spring 67 is inserted between the electrode 66 and the electrode holder 63, and the spring force of this compression spring 67 causes the electrode 66 to
The distal end surface 68 of is pressed onto the end surface of the rear end portion 8C of the rotating shaft. On the other hand, a terminal 69 is fixed on the outer wall surface of the rear housing 3 with a bolt 70, and this terminal 69 is -
It is connected to a high voltage generator 71 that generates a negative high voltage from 60 kV to -9 (lkV). Therefore, a negative high voltage is applied to the front housing 2 and the rear housing 3, and the spray head 9 is also supplied with a negative high voltage. A negative high voltage is applied to the electrode 66 and the rotating shaft 8.As shown in FIG.
Therefore, the front end of the electrode 66 is connected to the compressed air discharge chamber 59.
It is exposed within. Therefore, the electrode 66 is connected to the compressed air discharge chamber 5.
The electrodes 66 are cooled by the compressed air whose temperature has been reduced, thereby suppressing wear of the electrodes 66 and preventing deterioration of the electrodes 66.

The nozzle opening 21 of the paint injection nozzle 18 and the support outer cylinder 14
The paint sprayed onto the inner wall surface of the spray head body 13 flows out through the paint outlet hole 16 onto the inner wall surface 15 of the spray head body 13 due to the centrifugal force generated by the rotation of the spray head 9. Next, this paint becomes a thin liquid film on the inner wall surface 15 and spreads until it reaches the tip 13a of the spray head main body 13. As mentioned above, a negative high voltage is applied to the spray head 9, and therefore the spray head 9
Due to the centrifugal force generated by the rotation of the spray head body 13, the paint spreads out in a thin film from the tip 13a of the spray head body 13 is charged to a negative high voltage and becomes a spray. Normally, the surface to be painted is at zero potential, so the paint spray is attracted toward the surface by electric force, thereby painting the surface.

As mentioned above, the rotating shaft 8 is connected to the runners 39 and 40 and the annular plate 4.
4 and a pair of tilting pad radial air bearings 22 and 23. This tilting sonodo air bearing 22.23
When the rotating shaft 8 rotates, air is drawn into the minute gap between the rotating shaft hollow cylindrical portion 8a and each pad 24, 25° 26 (FIG. 3), and the rotating shaft hollow cylindrical portion 8a and each pad 24 The so-called air wedge action between the pads 24, 25 and 26 compresses the air and increases the pressure, thereby generating a force for each pad 24, 25, 26 to support the rotating shaft 8. On the other hand, in the above-mentioned thrust bearing, the compressed air introduced into the annular groove 47 from the air supply pump 49 passes through the air passage 50 and from the air outlet holes 51 and 52 to the annular plate 44 and the runner 3.
The pressure necessary to maintain the minute gap between the annular plate 44 and the runners 39 and 40 is generated within this gap. Therefore, the rotating shaft 8 is supported by a pair of radial bearings and a thrust bearing in a non-contact manner with a small air layer interposed therebetween. As is well known, the viscosity coefficient of air is approximately one tenth of the viscosity coefficient of lubricating oil. Therefore, an air bearing that uses air as a lubricant has extremely low friction loss, and since the heat generated by the friction loss is extremely small, it is possible to rotate at a very high speed. In the embodiment shown in FIG. 1, the rotating shaft 8 can be rotated at a high speed of about 80,000 r, p, m.

FIG. 7 shows the relationship between the size of paint particles and the rotational speed when a culm 9 with a diameter of 75 mm is used. In FIG. 7, the vertical axes S, M, and D indicate the particle size (μIT+) of the paint particles expressed in terms of the average particle diameter of Zaratar, and the horizontal axis N indicates the rotational speed of the spray head 9 (r
, p, m). As mentioned above, in the conventional rotary atomizing electrostatic coating device, the rotation speed N is at most 2000 Or, p-
Spray head 9 with a diameter of 75 liters and can only be raised to about m
When using
It can only be atomized to about m. On the other hand, in the present invention, the rotation speed can be increased to about 80,000 r, p, m, so the particle size of the spray paint can be reduced from 15 μm to 20 μm.
This means that the particles can be atomized by changing the process. Therefore, it can be seen that the rotary atomization electrostatic coating method according to the present invention can reduce the particle size of the sprayed paint to a diameter of 1 mm compared to the conventional method.

'Also, as mentioned above, the front and rear nozzles 2
, 3 and the rotating shaft 8, there is no risk of electrical discharge between these front and rear openings 2, 3 and the rotating shaft 8, since the same negative voltage is applied to them.

Another embodiment is shown in FIG. In addition, in Figure 5, the first
Components similar to those in the figures are designated by the same reference numerals.

In the embodiment shown in FIG. 5, a pair of porous radial air bearings 72, 73 and a porous thrust air bearing 74 are used to support the rotating shaft 8.

A pair of porous radial bearings 72 and 73 are the same 4j11
Therefore, the structure of only one porous type radial bearing 72 will be described. The porous type registration bearing 72 includes a porous bearing ring 75 made of a porous material facing the outer circumferential wall surface of the rotating shaft hollow cylindrical portion 8a, and a pair of support rings 76 and 77 that support the porous bearing ring 75. , a ring-shaped spacer 78 inserted between these holding rings 76 and 77, a porous bearing ring 75, and a spacer 3.
An annular air introduction chamber 79 and an annular air introduction chamber 79 formed between the support rings 76, 77 and 80.
81 into the front housing 2 in a sealed manner. Further, a ring-shaped spacer 82 is inserted between the porous radial bearings 72 and 73, and this ring-shaped spacer 8
An exhaust hole 84 is formed on the front housing 2 and is aligned with an exhaust hole 83 formed on the front housing 2 . The air introduction chamber 79 is connected to the air supply pump f49 via the air introduction holes 85, 86, so that the porous bearing ring 75 is
The rotating shaft 8 is supported in a non-contact state by the air jetted onto the outer circumferential wall surface of the rotating shaft hollow cylindrical portion 8a through the air. On the other hand, in the porous type thrust bearing 74, porous annular plates 87 and 88 made of a porous material are fixed to both sides of the annular plate 44 so as to cover the air outflow holes 51 and 52, respectively.

Therefore, from the air outflow hole 51.52, the porous annular plate 87°8
The porous annular plates 87 and 88 and the runners 39 and 40 are maintained in a non-contact state by the air blown to the runners 39 and 40 through the porous annular plates 87 and 88.

FIG. 6 shows another embodiment of a radial air bearing for supporting rotation 1118 (FIG. 1). In this embodiment, the radial air bearing consists of a hydrostatic air bearing. This static air bearing 89 is installed in the front housing 2 with O-rings 20, 9.
The annular air introduction chamber 93 formed between the bearing ring 92 and the front housing 2 is connected to the air supply pump 49 (the first Figure 5). On the other hand, a large number of air injection holes 95 communicating with the air introduction chamber 93 are connected to the bearing ring 9.
The rotary shaft 8 is supported in a non-contact manner by the air jetted from the air jet hole 95 formed on the inner circumferential wall surface of the rotor C.

As described above, according to the present invention, the rotation speed of the spray head is increased to 80
00 Or, p, m The atomization of the sprayed paint is very good with O which can be increased by about 1, and therefore an extremely clean painted surface can be obtained. It can be used as a final coat in the D painting process.

However, the stain electrode is cooled by the compressed air whose temperature decreases as it expands after passing through the turbine wheel, which prevents the electrode from overheating and thus prevents the electrode from wearing out. At the same time, deterioration of the electrode can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a rotary atomizing electrostatic coating device according to the present invention, viewed from above, and FIG. 2 is a cross-sectional view taken along line m-n in FIG. 1.
Fig. 3 is a sectional view taken along line ■-■ in Fig. 1, Fig. 4 is a sectional view taken along line It/-IV in Fig. 1, and Fig. 5 is a side sectional view of another embodiment. 6 is a side sectional view of another embodiment of the radial air bearing, and FIG. 7 is a graph showing the particle size of the sprayed paint. 2...Front housing, 3...Rear housing,
8...Rotating shaft, 9...14 Mist head, 18...Paint injection nozzle, 22.23...Tilting pad air bearing, 24.25.26...Nogud, 3 9
, 4 0... runner, 42... turbine blade wheel,
44... Annular plate, 5], 52... Air outflow hole, 5
7... Ejection nozzle, 58... Turbine blade, 5
9... Compressed air discharge chamber, 66... Evening, pole. Patent applicant Toyota Motor Corporation Patent agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney Yoshi 1) Masayuki Patent attorney Akira Yamaguchi Figure 2 Figure 3 Figure 4 Figure 6

Claims (1)

[Claims] A rotary atomizing electrostatic coating device has a rotating shaft rotatably supported in a housing, a spray head is fixed to a front end of the rotating shaft, and paint is supplied onto a cup-shaped inner wall surface of the spray head. In a rotary atomizing electrostatic coating device equipped with a paint supply device, the rotating shaft is supported by a non-contact type radial bearing and a non-contact type thrust bearing, and a turbine wheel is fixed to the rotating shaft, and the turbine wheel is fixed to the rotary shaft. A compressed air discharge chamber through which the compressed air that has passed through the impeller flows is formed in the housing, and a rear end of the rotating shaft is disposed within the compressed air discharge chamber, and the rotary shaft rotates in contact with the rear end of the rotary shaft. A rotary atomizing electrostatic coating device in which an electrode for applying a negative voltage to a shaft is disposed within the compressed air discharge chamber.