JP2004249171A - Method and apparatus for electrostatic atomization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic atomization method which increases the electrification efficiency of an atomized coating material etc., and makes improved application efficiency be obtained easily and an apparatus for the method. <P>SOLUTION: The electrostatic atomization apparatus has a discharge opening 22 for atomization, a discharged substance supply means for supplying the discharged substance from the discharge opening 22, an air ejection port 30, an air supply means for supplying air from the air ejection port 30, an electrode 40 for electrification for electrifying the atomized discharged substance, and a voltage supply means for supplying a high voltage to the electrode 40 for electrification and is provided with a supplementary electrode 50 for attraction which is protruded in the discharge direction of the discharged substance from the discharge opening 22 and attracts charged electrons released from the electrode 40. The charged electrons released from the electrode 40 are attracted to a place where the atomized discharged substance exists by the supplementary electrode 50, so that the atomized discharged substance can be electrified efficiently. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrostatic atomizing device and an electrostatic atomizing method that can be used for a coating device or the like that applies a charged atomized paint to an object to be coated.
[0002]
[Prior art]
As a method of performing electrostatic coating using a paint having a low electric resistance such as a water-based paint, there is a coating method of atomizing with compressed air or the like and simultaneously applying a negatively charged paint to a grounded workpiece. is there. As a method of charging the paint with a negative charge, there are a method by internal application and a method by external application.
[0003]
In the internal application method, high voltage power is supplied to the electrostatic charging electrode provided in the coating device, the charging electrode is brought into contact with the paint inside the coating device, and high voltage is applied to the entire coating to charge. The paint in the state is discharged from the apparatus.
[0004]
In this method, since the paint path forms an electric circuit, if a part of the path is grounded, a current may leak and a high voltage may not be applied. In order to prevent this, it is necessary to electrically insulate the paint path from the paint tank to the paint discharge port of the coating apparatus. Therefore, when changing the color of the paint, first discharge the paint equipment and the paint tank connected to it to ground, disconnect the paint equipment from the paint tank and connect it to another paint tank, and then A step of switching the connected paint tank to a state of being electrically insulated from the ground is required. Therefore, there is a disadvantage in that the number of steps is increased and the efficiency is low for the setup change.
[0005]
Therefore, when the efficiency of the color changing operation of the paint is required, a method using external application is often used. An example is disclosed in Japanese Patent Application Laid-Open No. 7-328493 (Patent Document 1). In this method, air near the coating device is ionized by a charging electrode provided in a form exposed to the outside of the coating device, and the atomized paint discharged from the coating device in the form of a mist is contacted with ionized air to be charged. It is made to be in a state. According to such a method, since the flow path of the paint can be always kept in the ground state, the work of switching between the insulating state and the discharge state at the time of the setup change becomes unnecessary.
[0006]
However, in the conventional electrostatic atomizing apparatus and the electrostatic atomizing method as described in the above-mentioned literature, since the atomized paint does not directly contact the charging electrode, the ions emitted from the charging electrode are atomized. It was difficult to make sufficient contact with the paint, and there were many ions that could not reach the atomized paint. In addition, among the ions that have reached the atomized paint, there are quite a few ions that go out of the atomized paint atmosphere without being charged. Therefore, the charging efficiency of the paint is not always sufficiently high, and as a result, there is a problem that it is difficult to obtain a sufficiently high coating efficiency at the time of painting.
[0007]
[Patent Document 1]
JP-A-7-328493
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and has a higher charging efficiency of atomized paint and the like than conventional electrostatic atomizers and electrostatic atomization methods, and a higher coating efficiency in coating of paint and the like. It is an object of the present invention to provide an electrostatic atomizing device and an electrostatic atomizing method capable of easily obtaining the following.
[0009]
[Means for Solving the Problems]
An electrostatic atomizer according to the present invention that solves the above-mentioned problems includes a discharge port for atomization, a discharge supply unit that supplies a discharge from the discharge port, an air outlet, and supplying air from the air outlet. An electrostatic atomizer comprising: an air supply unit for supplying; a charging electrode for charging the atomized discharge; and a voltage supply unit for supplying a high voltage to the charging electrode. It has an attracting auxiliary electrode that protrudes from the discharge port in the discharge direction of the discharge material and attracts valence electrons discharged from the charging electrode.
[0010]
The electrostatic atomization method of the present invention that solves the above-mentioned problems includes a discharge port for atomization, a discharge supply unit that supplies a discharge from the discharge port, an air outlet, and supplying air from the air outlet. An air supply means for supplying, a charging electrode for charging the atomized discharge material, and a voltage supply means for supplying a high voltage to the charging electrode, for charging the atomized discharge material. An electromigration method, comprising: providing an invitation auxiliary electrode for attracting valence electrons emitted from the charging electrode by projecting from the ejection port in the ejection direction of the ejected material, and attracted by the invitation auxiliary electrode. It is characterized in that the atomized discharge is charged by the charged electrons.
[0011]
In any of the means, the charged electrons include at least one of electrons, negative ions, and cluster-like particles charged to a negative charge.
[0012]
According to this means, the charged electrons emitted from the charging electrode are attracted to the place where the atomized discharge exists by the attracting auxiliary electrode. As a result, in the conventional electrostatic atomizing device and the conventional electrostatic atomizing method, the valence electrons that could not reach the discharge material can be brought into contact with the discharge material and charged by being attracted to the attracting auxiliary electrode. Become like In addition, even if it is possible to reach the atomized discharge, charged electrons that try to exit the atmosphere of the atomized discharge without charging it even if they reach the atomized discharge are attracted by the attracting auxiliary electrode. It stays in the atmosphere and comes into contact with the atomized discharge to charge it. Therefore, the charging efficiency of the ejected material can be improved as compared with the conventional electrostatic atomizing device and the conventional electrostatic atomizing method.
[0013]
Therefore, if this means is used in, for example, a coating apparatus, a sufficiently high coating efficiency can be obtained at the time of coating. As a result, the amount of paint used can be reduced, and the painting cost can be reduced.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a discharge port for atomization, a discharge supply means for supplying discharge from the discharge port, an air outlet, an air supply means for supplying air from the air discharge, The charging electrode for charging the discharged material and the voltage supply means for supplying a high voltage to the charging electrode are not particularly limited, and those having the same form as the conventional one may be used. Can be.
[0015]
In the present invention, the type of the ejected material is not limited, and if it is used for a coating apparatus, it can be used for any of a water-based paint and an oil-based paint. This is particularly effective when using a discharged material.
[0016]
The charging electrode may be provided in or near the flow path of the air jetted from the air jet port. However, as in an air cap used in an embodiment described later, air charged from the outside and communicated with the air jet port may be used. What is provided in the channel is preferred.
[0017]
The attracting auxiliary electrode is not particularly limited in shape, material, installation method and the like as long as it can attract valence electrons emitted from the charging electrode, but the following forms are preferable.
[0018]
As a method for causing the attracting auxiliary electrode to attract valence electrons, a method of grounding the attracting auxiliary electrode or a method of applying a voltage having a potential (positive potential) opposite to that of the valence electrons to the attracting auxiliary electrode is used. Is mentioned. Note that the latter method requires a voltage supply means for supplying a voltage to the invitation auxiliary electrode.
[0019]
Examples of the inviting auxiliary electrode include an electrode that protrudes from or near the ejection port for atomization, and an electrode that projects in the ejection direction of the ejected material from the ejection port for atomization is discharged from the charging electrode. It is easy to attract charged electrons to a place where atomized discharge is present, which is desirable in terms of the attraction efficiency and the like. In any case, if at least the electrode tip is in the atmosphere of the atomized discharge, the charged electrons emitted from the charging electrode can be easily attracted to the location of the atomized discharge. Further, it is preferable that the attraction assisting electrode has a needle-like electrode tip having a sharp tip.
[0020]
As the invitation assisting electrode, an electrode composed of an electrode base provided at the discharge port and an electrode tip protruding from the electrode base in the discharge direction of the discharged material is exemplified. As a specific example, an electrode base composed of a frame portion extending along the peripheral portion of the discharge port and installed at the peripheral portion of the discharge port, and a bridging portion extending from the frame portion and cross-linking on the discharge port has stability. It is preferable from the point of view. In addition, since the discharge ports for atomization are often circular, FIG. 5 shows a form of an electrode base suitable for the atomization, in which a ring-shaped frame portion and a frame portion (ring) are bridged in the diameter direction. The cross-linking portion is shown as an example. In this case, only one cross-linking portion may be used, but it is more preferable to have a plurality of cross-linking portions as shown in FIG. 5 because the stability is further improved. Furthermore, it is preferable to use a material having a net-like cross-linking portion, because the effect of promoting atomization of the discharged material is expected. Preferably, the electrode base is included in an insulating resin or the like.
[0021]
In particular, the inviting auxiliary electrode in the present invention includes a column-shaped electrode base that is housed in a discharge channel that communicates with the discharge port for atomization and extends in the direction of the discharge port, and extends from the electrode base and protrudes from the discharge port. And a needle-like electrode tip. Such an invitation assisting electrode is excellent in that it does not take up space and does not hinder the ejection of the ejected material and the ejection of the air.
[0022]
In this case, it is preferable that the electrode base extends in the center of the discharge passage that communicates with the discharge port. Since the discharge channel is often cylindrical or cylindrical, the electrode base preferably extends along the central axis of the discharge channel. On the other hand, it is preferable that the tip protrudes from the center of the discharge port. If the discharge port is also circular or annular, it is preferable to project from the center.
[0023]
In addition, as the above-mentioned inviting auxiliary electrode, an electrode in which the tip of the electrode tip portion is accommodated in the ejection port is also mentioned, but it is considered that the attraction efficiency of the charged electrons is reduced by being blocked by the liquid ejected material before being atomized. .
[0024]
The material of the invitation auxiliary electrode is not particularly limited, and may be formed of any of a metal material and a conductive resin.
[0025]
On the other hand, it is preferable that a resistance member is provided between the charging electrode and the charging auxiliary electrode. With this resistance member, it is possible to prevent a short circuit or interference between the charging electrode and the invitation auxiliary electrode during the atomization charging of the discharged material, and to eliminate the possibility that the electrode is damaged.
[0026]
【Example】
Examples of the electrostatic atomizing apparatus and the electrostatic atomizing method of the present invention include an electrostatic coating apparatus that atomizes a paint with compressed air and simultaneously charges the paint, and a coating method using the same. Hereinafter, as an embodiment of the present invention, a hand-gun type electrostatic coating gun that is gripped and handled by an operator will be described with reference to FIGS. In the following, for the sake of simplicity, the direction in which the paint is discharged from the discharge port is referred to as the front, and the opposite direction is referred to as the rear. Further, an upward direction toward the drawing is referred to as upward, and an opposite direction is referred to as downward.
[0027]
As shown in FIG. 1, the main part of the electrostatic coating gun of this embodiment is a gun main body 10 (partially shown) made of an insulating resin material, and is provided at the front end of the gun main body 10. A nozzle 20 for discharging and jetting compressed air (air).
[0028]
The electrostatic coating gun includes a paint discharge port 22 for atomization, and a discharge supply unit that supplies a paint (discharge) from the paint discharge port 22. The discharged material supply means includes a paint nozzle 24, a needle valve 12, and a paint hose (not shown). The center hole of the paint nozzle 24 is a paint flow path 24a. Here, when the normally closed needle valve 12 that opens and closes in response to the operation of a trigger (not shown) opens, the paint pumped through a paint hose connected to the rear of the gun body 10 is directed toward the paint nozzle 24. The ink is supplied and discharged in a mist form from the paint discharge port 22 through the paint flow path 24a.
[0029]
The nozzle 20 includes a plurality of components (a paint nozzle 24, an air cap 26, a fixing member 27, and the like) attached to the front end of the gun body 10. At the front end of the gun body 10, a circular mounting recess 10a is formed in which the center of the front end face is cut off. A paint nozzle 24 made of an insulating material is fixedly provided on the inner periphery of the mounting recess 10a in such a manner that its front end protrudes forward from the mounting recess 10a by screwing its rear end. Around the outer peripheral surface of the paint nozzle 24, a cylindrical portion 14 made of an insulating resin is provided coaxially with a cylindrical gap therebetween. An air flow path for supplying air to the pattern air ejection port 34 is provided in the cylindrical gap as described later.
[0030]
The air cap 26 includes a cylindrical portion 26a, a front portion 26b, a corner portion 26c protruding forward from upper and lower ends of the front surface of the front portion 26b, and a partitioning cylindrical portion extending rearward from both ends of the rear surface of the front portion 26b. 26d, and are integrally formed of insulating resin.
[0031]
A nut-like fixing member 27 is screwed onto the outer periphery of the distal end of the gun body 10 and the outer periphery of the rear end of the cylindrical portion 26a of the air cap 26. The air cap 26 is fixed by the fixing member 27 in a state where the partitioning cylindrical portion 26 d is applied to the front end face of the paint nozzle 24 at a position in front of the paint nozzle 24.
[0032]
The center hole of the paint nozzle 24, that is, the paint flow path 24a, is formed in a form in which a plurality of cylindrical cavities whose diameter gradually decreases in the paint flowing direction are coaxially arranged in series. The rear end of the paint flow path 24 a is connected to the needle valve 12.
[0033]
The front end of the paint nozzle 24 is inserted into the center hole of the air cap 26, and a substantially cylindrical gap is formed between the inner peripheral surface of the center hole of the air cap 26 and the outer peripheral surface of the front end of the paint nozzle 24. ing. This substantially cylindrical gap serves as an atomizing air jet port 30 for jetting air for atomizing the paint discharged from the paint discharge port 22. The front end of the paint nozzle 24 is open to the outside of the electrostatic coating gun as a paint discharge port 22 facing the front end face of the nozzle 20.
[0034]
On the front surface 26b of the air cap 26, a sub-pattern air outlet 32 is provided in addition to the atomized air outlet 30 described above. A pattern air outlet 34 is provided on the inner side surface of the corner 26c.
[0035]
The supply means for supplying air to the atomizing air jet port 30 and the sub-pattern air jet port 32 is constituted by atomizing air flow paths 36a to 36d. That is, in the paint nozzle 24, a plurality of atomizing air flow paths 36c arranged concentrically with the paint flow path 24a are formed in a hole shape penetrating between both front and rear end faces of the paint nozzle 24. The rear ends of these atomizing air passages 36c communicate with an annular atomizing air passage 36b formed at the inner end of the mounting recess 10a. The annular atomizing flow path 36b is communicated with an atomizing air flow path 36a formed inside the gun body 10.
[0036]
The front end of the atomizing air flow path 36 c of the paint nozzle 24 is an annular mist surrounded by the outer periphery of the front end of the paint nozzle 24, the inner periphery of the partitioning cylindrical portion 26 d of the air cap 26, and the rear surface of the air cap 26. It communicates with the air passage 36d. The annular atomizing air flow path 36d is formed in a gap between the inner periphery of the center hole of the air cap 26 and the outer periphery of the front end of the paint nozzle 24 so as to surround the paint discharge port 22. The nozzle 20 is opened at the front end face of the nozzle 20 through a sub-pattern air jet port 32 formed in the upper and lower sides of the atomizing air jet port 30 in the air cap 26.
[0037]
On the other hand, supply means for supplying air to the pattern air ejection port 34 is constituted by pattern air flow paths 38a to 38e. The pattern air flow path 38a has a hole-shaped flow path formed inside the gun body 10 as a separate flow path independent of the atomization air flow paths 36a to 36d. The front end of the pattern air flow path 38a communicates with an annular pattern air flow path 38b formed in a groove shape on the inner periphery of the mounting recess 10a. The pattern air flow path 38 b is formed by a plurality of pattern air flow paths 38 c penetrating in the front-rear direction, and is formed by an annular pattern air flow formed between the outer peripheral surface of the paint nozzle 24 and the inner peripheral surface of the cylindrical portion 14. It is communicated with the road 38d. The pattern air flow path 38d is communicated with a pair of upper and lower pattern air flow paths 38e formed inside the corner 26c of the air cap 26. The pattern air flow path 38e is opened to the outside of the nozzle 20 via the pattern air ejection port 34 formed at the corner 26c.
[0038]
A metal charging electrode 40 is attached to the tip of the cylindrical portion 14. The charging electrode 40 may be made of a conductive resin. The charging electrode 40 includes an arc-shaped ring portion 40a having a partially cut-out shape, and two pin portions projecting forward (in a direction parallel to the central axis of the ring portion 40a) from the ring portion 40a. 40b. The pin portion 40b is fixed to the ring portion 40b by welding or the like. The charging electrode 40 is embedded in the distal end of the cylindrical portion 14 with the distal end of the pin portion 40b protruding into the pattern air flow path 38e.
[0039]
A voltage supply means for supplying a high voltage to the charging electrode 40 for charging the paint is provided inside the gun body 10. The voltage supply means includes a high-voltage generator (not shown), and a conductive member 42 (partially shown) that connects the high-voltage generator and the charging electrode 40 in a conductive manner. The high voltage generator is housed inside the gun body 10 in a state of being longer in the front-rear direction and positioned above the needle valve 12. The conductive member 42 is also buried in the cylindrical portion 14, and the front end is connected to the ring 40a, and the rear end is connected to the high voltage generator. The conductive member 42 may be made of a metal or a conductive resin.
[0040]
The inviting auxiliary electrode 50 includes a column-shaped (circular cross-section) electrode base 50 a extending in the direction of the discharge port 22 from the rear end of the discharge path 24 a along the central axis of the discharge path 24 a, and the center of the discharge port 22. And a needle-like electrode tip portion 50b protruding therefrom. The electrode base 50a and the electrode tip 50b are integrally formed of the same metal material.
[0041]
The rear end of the electrode base 50a is included in a protective portion 52 made of an insulating resin. On the outer peripheral surface of the protective portion 52, projecting portions 54 projecting in four directions in the radially increasing direction are integrally formed like bow and arrow blades. Is formed. The rear end of the electrode base 50a is provided on the front end of the needle valve 12 in a state where the front end surface 54a of the protruding portion 54 is abutted against the inner peripheral surface of the rear end of the center hole of the paint nozzle 24. Into the mounting recess 12a. The protruding portion 54 assists in stably fixing and holding the inviting auxiliary electrode 50 in the center hole of the paint nozzle 24, just like a projection. Further, the paint supplied from the two-dollar valve 12 can flow through the center hole of the paint nozzle 24 through a gap formed between the protrusions 54.
[0042]
A positive voltage supply means for supplying a positive voltage to the invitation auxiliary electrode 50 is also provided inside the gun body 10 so that the invitation auxiliary electrode 50 has a positive potential. The positive voltage supply means includes a positive voltage generator (not shown), and a conductive member (not shown) that connects the positive voltage generator and the invitation auxiliary electrode 50 to be conductive.
[0043]
The paint discharge control means includes a hand gun trigger and a needle valve 12. When the trigger is operated, the needle valve 12 is opened, and the paint is discharged forward from the paint discharge port 22 of the nozzle 20. The air supply control means includes a trigger (not shown) and an air valve (not shown). The air valve is opened simultaneously with the operation of the trigger, and the air supply means is activated.
[0044]
At this time, air at a predetermined pressure supplied from the atomizing air jet port 30 and the sub-pattern air jet port 32 of the nozzle 20 through the atomizing air flow paths 36a to 36d respectively becomes the atomizing air Aa and the sub-pattern air Ab. It is gushing. The discharged paint becomes a paint flow P atomized by the atomizing air Aa. Also, from the pattern air jet port 34, air at a predetermined pressure supplied through the pattern air flow paths 38a to 38e is jetted toward the atomized paint flow P as pattern air Ac. The atomized paint flow P is formed into a pattern having a substantially elliptical cross section by the pattern air Ac. The sub-pattern air Ab is blown toward the pattern air Ac, and the division of the atomized paint flow P due to the pattern air Ac being locally concentrated and blown against the atomized paint flow P is performed. Has been prevented.
[0045]
When the air supply is started by operating the trigger, at the same time, the charging control means operates and the voltage supply means operates. That is, the air flowing in the pattern air flow paths 38a to 38e comes into contact with the charging electrode 40 arranged in the pattern air flow path 38e, so that the air including the ionized valence electrons is emitted from the pattern air ejection port 34. It is jetted out of the nozzle 20. In this way, the pattern air Ac containing the charged electrons is sprayed on the atomized paint flow P, and most of the charged electrons reaching the atomized paint flow P charge the atomized paint.
[0046]
On the other hand, the positive voltage supply means also operates at the same time when the charging control means operates, and a positive voltage is supplied to the invitation auxiliary electrode 50, so that the invitation auxiliary electrode 50 becomes a positive potential. As a result, the charge electrons that have not reached the atomized paint flow P are attracted to the quote assisting electrode 50 and contact the atomized paint to charge it. Furthermore, even if the atomized paint stream P can reach the atomized paint stream P, the charged electrons which are going to go out of the atomized paint stream P without being charged are also attracted to the attracting auxiliary electrode 50, and thereby the atomized paint stream is attracted. It stays in P and contacts the atomized paint and charges it. In this way, the atomized paint is mostly charged, and is applied to an object (not shown) that is grounded.
[0047]
Therefore, according to the present electrostatic coating gun, it is possible to increase the number of charged electrons that come into contact with and atomize the atomized paint by operating the attracting auxiliary electrode 50, thereby easily improving the charging efficiency of the paint. Can be. Therefore, a sufficiently high coating efficiency can be obtained at the time of coating, and the amount of paint to be discharged can be reduced. As a result, painting costs can be reduced.
[Brief description of the drawings]
FIG. 1 is a partial sectional view of an electrostatic coating gun according to an embodiment.
FIG. 2 is a view showing an invitation assisting electrode used in the electrostatic coating gun in the embodiment. (A) is a sectional view. (B) is a diagram showing a state viewed from behind.
FIG. 3 is a partially enlarged view of a nozzle portion of the electrostatic coating gun in the embodiment.
FIG. 4 is a partially enlarged perspective view of an air cap and a charging electrode used in the electrostatic coating gun in the embodiment. .
FIG. 5 is a partially enlarged perspective view of an invitation assisting electrode that can be used in the present invention.
[Explanation of symbols]
20: Nozzle 22: Paint outlet 26: Air cap 30: Atomized air jet (air jet) 34: Pattern air jet 38e: Pattern air flow path 40: Charging electrode 50: Inviting auxiliary electrode

Claims (4)

A discharge port for atomization, discharge supply means for supplying discharge from the discharge port, an air outlet, air supply means for supplying air from the air discharge, and charging the atomized discharge And a voltage supply unit for supplying a high voltage to the charging electrode, comprising:
An electrostatic atomizer, comprising: an attraction assisting electrode that projects from the ejection port in the ejection direction of the ejected material to attract valence electrons emitted from the charging electrode. The attraction assisting electrode includes a column-shaped electrode base that is housed in a discharge channel that communicates with the discharge port and extends in the direction of the discharge port, and a needle-like electrode tip that extends from the electrode base and protrudes from the discharge port. The electrostatic atomizer according to claim 1, comprising: a unit. The electrostatic atomizer according to claim 1, wherein a resistance member is provided between the charging electrode and the charging auxiliary electrode. A discharge port for atomization, discharge supply means for supplying discharge from the discharge port, an air outlet, air supply means for supplying air from the air discharge, and charging the atomized discharge A charging electrode for performing, and a voltage supply means for supplying a high voltage to the charging electrode, an electrostatic atomization method for charging the atomized discharge,
Providing an invitation auxiliary electrode for attracting charged electrons emitted from the charging electrode by projecting from the ejection port in the ejection direction of the ejected material, and atomizing the ejected material by the charged electrons attracted by the invitation auxiliary electrode. An electrostatic atomization method characterized by being charged.

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