JP4275965B2 - Electrostatic atomizer and electrostatic atomizing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrostatic atomizing apparatus and an electrostatic atomizing method that can be used in a coating apparatus that applies a charged atomized paint to an object to be coated.
[0002]
[Prior art]
As a method of electrostatic coating using a paint with low electrical resistance, such as a water-based paint, there is a painting method in which a paint charged to a negative charge at the same time as atomizing with compressed air is applied to an object to be grounded. is there. As a method of charging a paint with a negative charge, there are a method by internal application and a method by external application.
[0003]
In the internal application method, a high voltage power supply 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 charging is performed by applying a high voltage to the entire paint. The paint in a state is discharged from the apparatus.
[0004]
In this method, since the paint path constitutes an electric circuit, if a part of the path is grounded, current may leak and 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 painting apparatus. Therefore, when changing the color of paint, first discharge the paint device and the paint tank connected to it to ground, disconnect the paint device from the paint tank and connect it to another paint tank, A process of switching the connected paint tank to a state where it is electrically insulated from the ground is required. Therefore, there is a disadvantage that the number of steps is increased and the efficiency is poor with respect to the setup change.
[0005]
Therefore, when the efficiency of the color changing operation of the paint is required, a method by external application is often used. One example is disclosed in Japanese Patent Application Laid-Open No. 7-328493 (Patent Document 1). In this method, charging is performed by ionizing the air in the vicinity of the coating device with a charging electrode provided in a form exposed to the outside of the coating device, and bringing the atomized paint discharged from the coating device in a mist form into contact with the ionized air. It is intended to be in a state. With such a method, the paint flow path can always be in a grounded state, and therefore, switching work between the insulating state and the discharging state is not required at the time of setup change.
[0006]
However, in the conventional electrostatic atomizer and electrostatic atomization method as in the method of the above document, since the atomized paint and the charging electrode are not in direct contact, the ions released 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, there are not a few ions that have reached the atomized paint and go out of the atmosphere of the atomized paint without charging the atomized paint. 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 the charging efficiency of the atomized paint and the like is higher than that of the conventional electrostatic atomizing apparatus and electrostatic atomizing method, and higher application efficiency in the coating of the paint and the like. It is an object of the present invention to provide an electrostatic atomizing apparatus and an electrostatic atomizing method that can easily obtain the above.
[0009]
[Means for Solving the Problems]
The electrostatic atomizer of the present invention that solves the above problems includes an atomizing discharge port, discharged material supply means for supplying discharged material from the discharge port, an air outlet, and air from the air outlet. An air supply means for supplying, a charging electrode provided inside the air supply means for discharging valence electrons into the air before being ejected from the air outlet, and supplying a high voltage to the charging electrode an electrostatic atomizer comprising: a voltage supply means, and in that it has attracted auxiliary electrode to attract the valence emitted from the discharge direction projecting the charging electrode of the discharged product from the discharge port Features.
[0010]
The electrostatic atomization method of the present invention that solves the above problems includes an atomizing discharge port, discharged material supply means for supplying discharged material from the discharge port, an air outlet, and air from the air outlet. An air supply means for supplying, a charging electrode provided inside the air supply means for discharging valence electrons into the air before being ejected from the air outlet, and supplying a high voltage to the charging electrode An electrostatic atomization method for charging an atomized discharge by a voltage supply means,
Attractants auxiliary electrode to attract the valence emitted from the discharge direction projecting the charging electrode of the discharged product from the discharge port provided atomized the valence, which is attracted by the dielectric cited auxiliary electrode It is characterized by being charged by bringing it into contact with the discharged material .
[0011]
In any means, the valence electrons include at least one of electrons, negative ions, and cluster-like particles charged to a negative charge.
[0012]
According to this means, the valence electrons emitted from the charging electrode are attracted to the place where the ejected material atomized by the reference auxiliary electrode exists. As a result, in the conventional electrostatic atomizer and electrostatic atomization method, the charged electrons that could not reach the discharged material can be charged by contacting the discharged material by being attracted to the reference auxiliary electrode. It becomes like this. In addition, even if the atomized discharge can reach the atomized discharge, it is not charged, and the charged electrons that are going to go out of the atmosphere of the atomized discharge are attracted to the reference auxiliary electrode. It stays in the atmosphere and can be charged by contact with the atomized discharge. Therefore, the charging efficiency of the discharged material can be improved as compared with the conventional electrostatic atomizer and electrostatic atomization method.
[0013]
Therefore, if this means is used in, for example, a coating apparatus, a sufficiently high coating efficiency can be obtained during coating. As a result, the amount of paint used can be reduced, and the coating cost can be reduced.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a discharge port for atomizing the discharged product supply means for supplying a discharged material from the discharge port, and the air spout, and air supply means for supplying air from the air ejection ports, for a static- The voltage supply means for supplying a high voltage to the electrodes is not particularly limited, and those having the same form as conventional can be used.
[0015]
In the present invention, the type of ejected material is not limited, and can be used for both water-based paints and oil-based paints as long as they are used in a coating apparatus. This is particularly effective when a discharge product is used.
[0016]
The charging electrode is provided inside the air supply means and emits valence electrons into the air before being ejected from the air ejection port, and is partitioned from the outside like an air cap used in an embodiment described later. What is provided in the air flow path connected to the air outlet is preferable.
[0017]
The reference 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 citation auxiliary electrode to attract the valence electron, a method of grounding the citation auxiliary electrode, a method of applying a voltage (positive potential) opposite to the valence electron to the reference auxiliary electrode, etc. Is mentioned. In the latter method, voltage supply means for supplying a voltage to the reference auxiliary electrode is required. In the present invention, in particular, it is preferable that a positive voltage supply unit that supplies a positive voltage to the reference auxiliary electrode is provided, and the voltage supply unit supplies a negative voltage to the charging electrode.
[0019]
Examples of the auxiliary auxiliary electrode include those that protrude from the atomizing discharge port or the vicinity thereof, but those that protrude in the discharge direction of the discharged material from the atomizing discharge port are discharged from the charging electrode. It is desirable from the viewpoint of attracting efficiency because it is easy to attract the charged electrons to the place where the atomized discharge is present. In any case, if at least the tip of the electrode is in the atomized discharge atmosphere, it is easy to attract the charged electrons emitted from the charging electrode to the atomized discharge. In addition, it is desirable that the reference auxiliary electrode has a needle-like electrode tip having a sharp tip.
[0020]
Examples of the reference auxiliary electrode include an electrode base portion installed at the discharge port and an electrode tip portion protruding from the electrode base portion in the discharge direction of the discharged material. As a specific example, an electrode base composed of a frame portion that extends along the peripheral portion of the discharge port and is installed at the peripheral portion of the discharge port and a bridging portion that extends from the frame portion and crosslinks on the discharge port has stability and the like. From the point of view, it is preferable. In addition, since the discharge outlet for atomization is often circular, in FIG. 5, as a suitable electrode base configuration, a ring-shaped frame portion and a frame portion (ring) are bridged in the diameter direction. A cross-linking part 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 stability is further improved. Furthermore, it is preferable to use a material having a net-like cross-linked portion because an effect of promoting atomization of the discharged material is expected. Note that the electrode base is preferably encapsulated in an insulating resin or the like.
[0021]
In particular, the citation auxiliary electrode in the present invention is housed in a discharge flow passage communicating 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. It is desirable that the needle-shaped electrode tip portion has a bow-and-blade blade-like protruding portion that protrudes in the diameter-expanding direction from the outer peripheral surface of the electrode base portion and abuts against the inner peripheral surface of the discharge material channel . Such a reference auxiliary electrode is excellent in that it does not take up space and does not hinder the discharge of discharged matter or the ejection of air.
[0022]
In this case, it is preferable that the electrode base portion extends in the central portion in the discharge material flow path communicating with the discharge port. In many cases, the discharge passage is columnar or cylindrical. In this case, the electrode base preferably extends along the central axis of the discharge passage. On the other hand, it is preferable that the front-end | tip part protrudes from the center part of a discharge outlet. If the discharge port is also circular or annular, it preferably protrudes from the center. In addition, the reference auxiliary electrode can be stably fixed and held in the central hole of the discharge material flow path by the protrusion.
[0023]
In addition, as the above-mentioned reference auxiliary electrode, there may be cited one in which the tip of the electrode tip is contained in the discharge port, but it is considered that the attracting efficiency of valence electrons is lowered by being blocked by the liquid discharge before being atomized. .
[0024]
The material of the reference auxiliary electrode is not particularly limited, and may be formed from any of a metal material and a conductive resin.
[0025]
On the other hand, it is desirable that a resistance member is provided between the charging electrode and the auxiliary charging electrode. With this resistance member, it is possible to prevent a short circuit or interference between the charging electrode and the reference auxiliary electrode during the atomization charging of the discharged material, and it is possible to eliminate the possibility of the electrode being damaged.
[0026]
【Example】
Examples of the electrostatic atomizing apparatus and the electrostatic atomizing method of the present invention include an electrostatic coating apparatus that charges a paint at the same time as atomizing with a compressed air and a coating method using the same. Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 4, taking as an example a hand gun type electrostatic coating gun to be gripped and handled by an operator. In the following, for ease of explanation, 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, the upward direction is referred to as the upper direction and the opposite direction is referred to as the downward direction.
[0027]
As shown in FIG. 1, the electrostatic coating gun of this embodiment is provided at a gun body 10 (partially shown) made of an insulating resin material and a front end portion of the gun body 10, The nozzle 20 is configured to discharge and eject compressed air (air).
[0028]
The electrostatic coating gun has an atomizing paint discharge port 22 and a discharge material supply means for supplying paint (discharged material) from the paint discharge port 22. The discharge material supply means is composed of a paint nozzle 24, a needle valve 12, and a paint hose (not shown). The central hole of the paint nozzle 24 is a paint flow path 24a. Here, when the normally-closed needle valve 12 that is opened and closed in conjunction with a trigger operation (not shown) is opened, the paint pressure-fed through the paint hose connected to the rear portion of the gun body 10 is directed toward the paint nozzle 24. Supplied and discharged from the paint discharge port 22 in the form of a mist through the paint flow path 24a.
[0029]
The nozzle 20 is composed of a plurality of components (such as a paint nozzle 24, an air cap 26, and a fixing member 27) attached to the front end portion of the gun body 10. At the front end of the gun body 10, a circular mounting recess 10 a is formed in a form in which the center of the front end surface is cut out. A coating nozzle 24 made of an insulating material is fixed to the inner periphery of the mounting recess 10a in such a manner that the front end protrudes forward from the mounting recess 10a by screwing the 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 outlet 34 is provided in the cylindrical gap as will be described later.
[0030]
The air cap 26 includes a cylindrical portion 26a, a front surface portion 26b, corner portions 26c protruding forward from both upper and lower end portions of the front surface of the front surface portion 26b, and a partitioning cylindrical portion extending rearward from both end portions of the rear surface of the front surface portion 26b. 26d, and is made up of an insulating resin.
[0031]
A nut-like fixing member 27 is screwed onto the outer periphery of the distal end portion of the gun body 10 and the outer periphery of the rear end portion of the cylindrical portion 26 a of the air cap 26. By this fixing member 27, the air cap 26 is fixed in a state where the partitioning cylindrical portion 26 d is in contact with the front end surface of the paint nozzle 24 at a position in front of the paint nozzle 24.
[0032]
The central 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 direction in which the paint flows are coaxially connected in series. The rear end of the paint flow path 24 a communicates with the needle valve 12.
[0033]
The front end portion 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 portion of the paint nozzle 24. ing. The substantially cylindrical gap serves as an atomizing air outlet 30 that ejects air for atomizing the paint discharged from the paint discharge port 22. Further, the front end portion of the paint nozzle 24 is opened to the outside of the electrostatic paint gun as a paint discharge port 22 facing the front end surface of the nozzle 20.
[0034]
In addition to the atomizing air jet 30 described above, a sub-pattern air jet 32 is provided on the front surface portion 26 b of the air cap 26. A pattern air jet 34 is provided on the inner side surface of the corner portion 26c.
[0035]
The supply means for supplying air to the atomizing air ejection port 30 and the sub-pattern air ejection port 32 is composed of atomizing air flow paths 36a to 36d. That is, the paint nozzle 24 is formed with a plurality of atomizing air flow paths 36 c concentrically arranged with the paint flow path 24 a so as to penetrate between the front and rear end faces of the paint nozzle 24. The rear ends of these atomizing air flow paths 36c are communicated with an annular atomizing air flow path 36b formed at the back end of the mounting recess 10a. The annular atomizing flow path 36 b communicates with an atomizing air flow path 36 a 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. The communication air channel 36d communicates. The annular atomizing air flow path 36d is an annular atomizing air outlet formed so as to surround the paint discharge port 22 in the 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. 30 and a sub-pattern air jet 32 formed in the upper and lower sides of the atomizing air jet 30 in the air cap 26 and opened in the front end face of the nozzle 20.
[0037]
On the other hand, the supply means for supplying air to the pattern air outlet 34 is constituted by pattern air flow paths 38a to 38e. The pattern air flow path 38 a is formed with a hole-shaped flow path as a separate flow path independent of the atomizing air flow paths 36 a to 36 d inside the gun body 10. The front end portion 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. This pattern air flow path 38b is 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 via a plurality of pattern air flow paths 38c penetrating in the front-rear direction. It communicates with the road 38d. The pattern air flow path 38d communicates with a pair of upper and lower pattern air flow paths 38e formed inside the corner portion 26c of the air cap 26. The pattern air flow path 38e is opened to the outside of the nozzle 20 via a pattern air jet port 34 formed in the corner portion 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 that is partially cut away, and two pin portions that protrude forward from the ring portion 40a (in a direction parallel to the central axis of 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 portion of the cylindrical portion 14 with the distal end portion of the pin portion 40b protruding into the pattern air flow path 38e.
[0039]
Inside the gun body 10 is provided voltage supply means for supplying a high voltage to the charging electrode 40 for charging the paint. 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 accommodated in the gun body 10 so as to be longer than the needle valve 12 in the longitudinal direction. The conductive member 42 is also embedded in the cylindrical portion 14, and the front end portion thereof is connected to the ring portion 40a, and the rear end portion thereof is connected to the high voltage generator. The conductive member 42 may be made of metal or made of conductive resin.
[0040]
The reference auxiliary electrode 50 includes a columnar (circular cross-sectional shape) electrode base 50a extending in the direction of the discharge port 22 from the rear end of the discharge flow channel 24a along the central axis of the discharge flow channel 24a, and the center of the discharge port 22. And a needle-like electrode tip portion 50b projecting from the tip. The electrode base portion 50a and the electrode tip portion 50b are formed of the same metal material in the same body.
[0041]
The rear end portion of the electrode base portion 50a is enclosed in a protective portion 52 made of an insulating resin. On the outer peripheral surface of the protective portion 52, a protruding portion 54 protruding in the four directions in the diameter increasing direction is integrated like a blade of a bow and arrow. Is formed. The rear end portion of the electrode base portion 50a is provided on the front end surface of the needle valve 12 with the front end surface 54a of the projecting portion 54 being in contact with the inner peripheral surface of the rear end portion of the center hole of the paint nozzle 24. It is inserted in the mounting recess 12a. As described above, the protrusion 54 helps the reference auxiliary electrode 50 to be stably fixed and held in the center hole of the paint nozzle 24. In addition, the paint supplied from the dollar valve 12 can flow through the central 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 reference auxiliary electrode 50 is also provided inside the gun body 10 so that the reference 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 reference auxiliary electrode 50 in a conductive manner.
[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). Simultaneously with the operation of the trigger, the air valve opens, and the air supply means is activated.
[0044]
At this time, air of a predetermined pressure supplied from the atomizing air outlet 30 and the sub-pattern air outlet 32 of the nozzle 20 through the atomizing air passages 36a to 36d is respectively atomized air Aa and sub-pattern air Ab. Erupted. The discharged paint becomes a paint flow P atomized by the atomizing air Aa. In addition, air of a predetermined pressure supplied through the pattern air flow paths 38a to 38e is also ejected from the pattern air ejection port 34 toward the atomized paint flow P as pattern air Ac. By this pattern air Ac, the atomized paint flow P is formed into a pattern having a substantially elliptical cross section. The sub-pattern air Ab is blown toward the pattern air Ac, and the atomized paint flow P is divided due to the pattern air Ac being locally concentrated on the atomized paint flow P. It is prevented.
[0045]
When the air supply is started by operating the trigger, the charging control means is activated at the same time and the voltage supply means is activated. That is, the air flowing in the pattern air flow paths 38a to 38e comes into contact with the charging electrode 40 disposed in the pattern air flow path 38e, so that the ionized charge electrons are included and the air is discharged from the pattern air outlet 34. It is ejected to the outside of the nozzle 20. The pattern air Ac including the charged electrons is thus sprayed onto the atomized paint flow P, and most of the charged electrons that have reached the atomized paint flow P charge the atomized paint.
[0046]
On the other hand, the positive voltage supply means is activated simultaneously with the operation of the charging control means, the positive voltage is supplied to the citation auxiliary electrode 50, and the citation auxiliary electrode 50 becomes positive potential. As a result, the charged electrons that have not been able to reach the atomized paint flow P are attracted to the citation auxiliary electrode 50 to contact the atomized paint and charge it. In addition, even if the atomized paint flow P can be reached, a valence electron that tries to go out of the atomized paint flow P without being charged is also attracted to the reference auxiliary electrode 50, so that the atomized paint flow P Stays in P and contacts the atomized paint to charge it. Thus, most of the atomized paint becomes charged and is applied to an object to be coated (not shown) in a grounded state.
[0047]
Therefore, according to the present electrostatic coating gun, by using the reference auxiliary electrode 50, it is possible to increase the number of charged electrons that come into contact with and charge the atomized paint, and the charging efficiency of the paint can be easily improved. Can do. Therefore, it is possible to obtain a sufficiently high coating efficiency at the time of painting, and to reduce the number of paints to be discharged. As a result, the coating cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view of an electrostatic coating gun in an embodiment.
FIG. 2 is a view showing a reference auxiliary electrode used in the electrostatic coating gun in the embodiment. (A) is sectional drawing. (B) is a figure which shows a mode seen from back.
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 for the electrostatic coating gun in the embodiment. .
FIG. 5 is a partially enlarged perspective view of a reference auxiliary electrode that can be used in the present invention.
[Explanation of symbols]
20: Nozzle 22: Paint outlet 26: Air cap 30: Atomizing air outlet (air outlet) 34: Pattern air outlet 38e: Pattern air flow path 40: Electrode for charging 50: Auxiliary auxiliary electrode

Claims (6)

An atomizing discharge port, a discharge material supply means for supplying discharge material from the discharge port, an air outlet, an air supply means for supplying air from the air outlet, and an interior of the air supply means An electrostatic atomizer comprising: a charging electrode that discharges valence electrons into the air before being ejected from the air ejection port; and a voltage supply unit that supplies a high voltage to the charging electrode. ,
The electrostatic atomization apparatus characterized by having attractive auxiliary electrode to attract the valence emitted from the discharge direction projecting the charging electrode of the discharged product from the discharge port. The electrostatic atomizer according to claim 1, further comprising a positive voltage supply unit that supplies a positive voltage to the reference auxiliary electrode, wherein the voltage supply unit supplies a negative voltage to the charging electrode. The reference auxiliary electrode includes a columnar electrode base that is housed in a discharge flow passage communicating with the discharge port and extends in the direction of the discharge port, and a needle-shaped electrode tip that extends from the electrode base and protrudes from the discharge port The electrostatic discharge according to claim 1 or 2, comprising a portion and a blade-like protrusion of a bow and arrow that protrudes from the outer peripheral surface of the electrode base in the diameter-expanding direction and abuts against the inner peripheral surface of the discharge material channel. Atomization device. The attraction auxiliary electrode, the discharge direction of the a discharge port electrode base comprising a crosslinked part crosslinking with the discharge Prompt extending from the frame portion and the frame portion are placed on the periphery of the discharged product from the electrode base The electrostatic atomizer of Claim 1 or 2 which consists of an electrode front-end | tip part which protrudes to. The electrostatic atomizer as described in any one of Claims 1-4 with which the resistance member is provided between the said electrode for charging, and the said reference auxiliary electrode. An atomizing discharge port, a discharge material supply means for supplying discharge material from the discharge port, an air outlet, an air supply means for supplying air from the air outlet, and an interior of the air supply means The charged atomized material is charged by a charging electrode that discharges valence electrons into the air before being ejected from the air ejection port, and a voltage supply means that supplies a high voltage to the charging electrode. An electrostatic atomization method for
Attractants auxiliary electrode to attract the valence emitted from the discharge direction projecting the charging electrode of the discharged product from the discharge port provided atomized the valence, which is attracted by the dielectric cited auxiliary electrode An electrostatic atomizing method, wherein the discharged material is charged by being brought into contact therewith .

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