WO2010110488A1

WO2010110488A1 - Electrostatic atomization apparatus

Info

Publication number: WO2010110488A1
Application number: PCT/JP2010/055982
Authority: WO
Inventors: Takayuki Nakada; Takafumi Omori; Hiroshi Suda; Junpei Ohe
Original assignee: Panasonic Electric Works Co., Ltd.
Priority date: 2009-03-26
Filing date: 2010-03-25
Publication date: 2010-09-30
Also published as: TW201039923A; JP2010227807A

Abstract

An electrostatic atomization apparatus includes a discharge electrode (1), a cooling device (2) that cools the discharge electrode and condenses moisture in air on the discharge electrode to supply the discharge electrode with water, and a high voltage application device (3) that applies high voltage t the water supplied to the discharge electrode to perform electrostatic atomization and generate charged micro-particle water. A vacuum area (5) surrounds the cooling device.

Description

DESCRIPTION

ELECTROSTATIC ATOMIZATION APPARATUS

TECHNICAL FIELD

The present invention relates to an electrostatic atomization apparatus that that performs electrostatic atomization to generate charged micro-particle water of nanometer size and supplies the micro-particle water to an atomization area.

BACKGROUND ART

Fig. 1 shows an electrostatic atomization apparatus 4 of the prior art which is described in Japanese Laid-Open Patent Publication No. 2006-826. The electrostatic atomization apparatus 4 cools a discharge electrode 1 with a cooling means 2 and condenses the moisture in air on the discharge electrode 1. A high voltage application means 3 applies high voltage to the water supplied to the discharge electrode 1 by the cooling means 2. This results in electrostatic atomization that generates charged micro-particle water. The cooling means 2 is formed by a Peltier unit 6.

The Peltier unit 6 includes two Peltier circuit boards 10 and a plurality of thermoelectric elements 11 arranged between the two Peltier circuit boards 10. Each Peltier circuit board 10 includes an insulative plate and a circuit section located on one side of the insulative plate. The insulative plate is formed from alumina or aluminum nitride, which have high thermal conductance. The thermoelectric elements 11 are held between the circuit sections of the two Peltier circuit boards 10 that face toward each other to electrically couple between the adjacent thermoelectric elements 11. When current flows through a Peltier input line 12 to the thermoelectric elements 11, heat is conveyed from one of the Peltier circuit boards 10 to the other one of the Peltier circuit boards 10.

One of the Peltier circuit boards 10 functions as a cooling side of the Peltier unit 6. This cooling Peltier circuit board 10 has an outer side coupled to a cooling insulative plate 13, which has high thermal conductance and withstands high voltages. Further, the insulative plate 13 is formed from alumina or aluminum nitride. The insulative plate of the Peltier circuit board 10 and the cooling insulative plate 13 form a cooling portion 7. The other one of the Peltier circuit boards 10 functions as a heat radiating side. This heat radiating Peltier circuit board 10 has an outer side coupled to a heat radiation portion 14, which has high thermal conductance and is formed from a metal such as aluminum.

A housing 8 is formed from an insulative material such as polybutylene terephthalate (PBT) resin, polycarbonate, or polyphenylene sulfide (PPS) resin. The housing 8 includes a tubular wall having openings (right side and left side in Fig. 1) . Further, the housing 8 includes an intermediate portion in which a partition 15 partitions the housing 8 into an accommodation chamber 9 and a discharge chamber 16. The accommodation chamber 9 has an open rear side (lower side as viewed in Fig. 1) and a flange 25, which is coupled to the heat radiation portion 14 and extends from the entire circumference of the open rear end. The discharge chamber 16 has an open front side (upper side as viewed in Fig. 1) . A ring- shaped opposing electrode 17 is arranged on the open front end.

The Peltier unit 6 is accommodated in the accommodation chamber 9 with the heat radiation portion 14 located outside the accommodation chamber 9. In this state, the peripheral portion of the heat radiation portion 14 is fixed to the flange 25 to accommodate the Peltier unit 6 in the housing 8.

When the housing 8 is coupled to the Peltier unit 6, the discharge electrode 1 is fitted into a hole extending through the partition 15. The discharge electrode 1 includes a basal portion arranged in the accommodation chamber 9. The remaining part of the discharge electrode 1 is arranged in the discharge chamber 16. The basal portion of the discharge electrode 1 is held between the partition 15 of the housing 8 and the cooling portion 7 of the Peltier unit 6. This holds the discharge electrode 1 in a state pressed against the cooling portion 7 of the Peltier unit 6.

In the prior art described above, the heat radiation portion 14 is fixed to the flange 25 to seal the accommodation chamber 9 of the housing 8. Nevertheless, air is present in the accommodation chamber 9.

Accordingly, when the cooling portion 7 in the accommodation chamber 9 is cooled, the cooling portion 7 further cools the air in the accommodation chamber 9. This condenses moisture in the air and forms condensed water on the cooling portion 7. When the condensed water enters the Peltier circuit, a problem such as short circuiting may occur. Moreover, the Peltier circuit may be electrically conducted to the discharge electrode 1 due to the condensed water produced in the accommodation chamber 9. This would destabilize the electrostatic atomization operation.

Further, in the prior art described above, cooling energy is conducted from the cooling portion 7 to the housing 8 through the surrounding air, through parts contacting the cooling portion 7, or through parts contacting the cooling portion 7 by means of an adhesive agent. This results in heat loss that lowers the cooling efficiency of the discharge electrode 1.

SUMMARY OF THE INVENTION

The present invention provides an electrostatic atomization apparatus that efficiently cools the discharge electrode with a cooling device, reduces heat loss during cooling, prevents condensed water from being formed around the cooling device, and stably performs electrostatic atomization.

One aspect of the present invention is an electrostatic atomization apparatus including a discharge electrode. A cooling device cools the discharge electrode and condenses moisture in air on the discharge electrode to supply the discharge electrode with water. A high voltage application device applies high voltage to the water supplied to the discharge electrode to perform electrostatic atomization and generate charged micro- particle water. A vacuum area surrounds the cooling device .

In this structure, since the cooling device is surrounded by the vacuum area, the condensed water does not form on the cooling device. Thus, an electrical problem such as short circuiting is prevented from occurring. Further, an air layer is not present around the cooling device. This prevents cooling energy from being emitted from the cooling device through the surrounding air. Thus, heat loss is reduced, and electrostatic atomization is stably performed.

Preferably, the cooling device is a Peltier unit including a cooling portion that cools the discharge electrode. The Peltier unit is arranged in a housing of the electrostatic atomization device. Preferably, the housing includes an accommodation chamber that accommodates at least the cooling portion of the Peltier unit. The cooling portion is arranged in non-contact with the housing. The discharge electrode extends through the housing and projects out of the accommodation chamber. In this case, the vacuum area is formed in the accommodation chamber.

This structure reduces loss of cooling energy from the cooling portion of the Peltier unit and effectively cools the discharge electrode.

Preferably, the discharge electrode is generally rod- shaped and includes a basal portion that is in contact with the cooling portion of the Peltier unit. The cooling portion of the Peltier unit is in contact with only the basal portion of the discharge electrode in the vacuum area. In this structure, the cooling portion is in contact with only the basal portion of the discharge electrode. Thus, there is no unnecessary cooling heat loss .

Preferably, the electrostatic atomization apparatus further includes a housing that accommodates the discharge electrode and the cooling device, and a heat radiation portion that supports the cooling device. The vacuum area is formed by the housing and the heat radiation portion. In this structure, only the area surrounded by the housing and the heat radiation portion may be vacuum. This facilitates the formation of a vacuum area .

Preferably, the discharge electrode includes a basal portion arranged between the housing and the cooling device. The housing and the cooling device are separated from each other by the vacuum area. In this structure, the housing and the cooling device are not in contact with each other. This prevents the loss of cooling energy through the housing. Further, the housing and the cooling device are separated from each other by the vacuum area. Thus, there is no cooling energy loss that would occur through an air layer.

Preferably, the electrostatic atomization apparatus further includes a housing that accommodates the discharge electrode and the cooling device. The cooling device includes first and second circuit boards arranged facing toward each other, with each of the first and second circuit boards including an insulative plate and a circuit section. A plurality of electrically connected thermoelectric elements are held between the circuit sections of the first and second circuit boards. When current flows through the thermoelectric elements, the first circuit board functions as a cooling circuit board and the second circuit board functions as a heat radiating circuit board. The insulative plate of the first circuit board is coupled to the discharge electrode in non-contact with the housing. This structure prevents the loss of cooling energy through the housing from the insulative plate of the first circuit board.

Preferably, the insulative plate of the first circuit board is connected to the discharge electrode via a further insulative plate, and the insulative plate of the first circuit board and the further insulative plate are both arranged to be in non-contact with the housing. This structure increases the cooling effect, while preventing loss of cooling energy.

Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

Fig. 1 is a schematic diagram showing a prior art example of an electrostatic atomization apparatus; and

Fig. 2 is a schematic diagram showing an electrostatic atomization apparatus according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

One embodiment of the present invention will now be discussed with reference to the drawings. Fig. 2 is a schematic diagram showing an electrostatic atomization apparatus 4. The electrostatic atomization apparatus 4 includes a discharge electrode 1, a cooling device 2, and a high voltage application device 3. The cooling device cools the discharge electrode 1 and condenses the moisture in air on the discharge electrode 1 to supply the discharge electrode 1 with water. The high voltage application device 3 applies high voltage to the water on the discharge electrode 1. The cooling device 2 is formed by, for example, a Peltier unit 6.

In the embodiment of Fig. 2, the insulative plate that forms the main part of the cooling Peltier circuit board 10 defines a cooling portion 7. The heat radiating Peltier circuit board 10 has an outer side coupled to a heat radiation portion 14, which has high thermal conductance and is formed from a metal such as aluminum.

In the embodiment shown in Fig. 2, the cooling Peltier circuit board 10 (upper side as viewed in Fig. 2) may be further coupled to a cooling insulative plate

(refer to Fig. 1), which has high thermal conductance, withstands high voltages, and is formed from alumina or aluminum nitride. In this manner, the cooling portion 7 may be formed by the insulative plate of the Peltier circuit board 10 and the cooling insulative plate 13.

A housing 8 is formed from an insulative material such as polybutylene terephthalate (PBT) resin, polycarbonate, or polyphenylene sulfide (PPS) resin. The housing 8 includes a tubular wall having openings (right side and left side in Fig. 2) . Further, the housing 8 includes an intermediate portion in which a partition 15 partitions the housing 8 into an accommodation chamber 9 and a discharge chamber 16. The accommodation chamber 9 has an open rear side (lower side as viewed in Fig. 2) and a flange 25, which is coupled to the heat radiation portion 14 and extends from the entire circumference of the open rear end. The discharge chamber 16 has an open front side (upper side as viewed in Fig. 1) . A ring- shaped opposing electrode 17 is arranged on the open front end.

When the housing 8 is coupled to the Peltier unit 6, the discharge electrode 1 is fitted into a hole 18 extending through the partition 15. The discharge electrode 1 includes a basal portion (large diameter portion) arranged in the accommodation chamber 9. The remaining part of the discharge electrode 1 is arranged in the discharge chamber 16. The basal portion (large diameter portion) of the discharge electrode 1 is held between the partition 15 of the housing 8 and the cooling portion 7 of the Peltier unit 6. This holds the discharge electrode 1 in a state pressed against the cooling portion 7 of the Peltier unit 6. The cooling portion 7 of the Peltier unit 6 and the basal portion of the discharge electrode 1 may be adhered together by an adhesive agent having superior thermal conductivity. The hole 18, into which the discharge electrode 1 is fitted, may be sealed by a seal 19.

The cooling portion 7 of the Peltier unit 6 is in contact with or fixed to only the basal portion of the discharge electrode 1. The cooling portion 7 is not in contact with the housing 8. Thus, the cooling energy of the cooling portion 7 is thermally conducted to only the basal portion of the discharge electrode 1. When forming the cooling portion 7 with the insulative plate of the Peltier circuit board 10 and the cooling insulative plate 13 (refer to Fig. 1), the insulative plate of the Peltier circuit board 10 and the cooling insulative plate 13 are both arranged in non-contact with the housing 8, while only the cooling insulative plate 13 is held in contact with the discharge electrode 1.

After accommodating the Peltier unit 6, excluding the heat radiation portion 14, and the basal portion of the discharge electrode 1 in the accommodation chamber 9 of the housing 8, the accommodation chamber 9 is vacuumed to form a vacuum area 5 in the accommodation chamber 9. To vacuum the accommodation chamber 9, a communication passage (not shown) , which is in communication with the accommodation chamber 9, is formed in the housing 8 or the heat radiation portion 14. A vacuum pump is coupled to the communication passage to vacuum the accommodation chamber 9. Then, the communication passage is sealed by a seal. In this manner, by forming the vacuum area 5 in the accommodation chamber 9, the cooling portion 7 of the Peltier unit 6 is surrounded by the vacuum area 5.

The discharge electrode 1, which is coupled to the cooling portion 7 of the Peltier unit 6, is generally rod-shaped and formed from a material having high thermal conductance and electrical conductance. The discharge electrode 1 produces condensed water when cooled by the

Peltier unit 6. The ring-shaped opposing electrode 17 has a center lying along an extension of the distal end of the discharge electrode 1. As shown in Fig. 2, a high voltage application plate 20 is coupled to the discharge electrode 1 near the basal portion. The high voltage application plate 20 and the opposing electrode 17 are connected by a high voltage lead line 21 to the high voltage application device 3. The high voltage application device 3 applies high voltage between the discharge electrode 1 and the opposing electrode 17.

In the electrostatic atoraization apparatus 4, when current flows to the thermoelectric elements 11, each thermoelectric element 11 conveys heat in the same direction (upper side to lower side as viewed in Fig. 2) . This cools the cooling portion 7 of the Peltier unit 6, which, in turn, cools the discharge electrode 1 coupled to the cooling portion 7. As a result, the air around the discharge electrode 1 is cooled, and the moisture in the air is condensed and liquefied. This forms condensed water on the distal portion of the discharge electrode 1.

In a state in which the discharge electrode 1 is cooled and condensed water is formed on the distal portion of the discharge electrode 1, the high voltage application device 3 applies high voltage to the water on the distal portion of the discharge electrode 1. For example, the high voltage application device 3 applies a high voltage of approximately 5 kV between the discharge electrode 1 and the opposing electrode 17. This concentrates charge at the distal portion of the discharge electrode 1, which functions as a negative electrode. Thus, the water on the distal portion of the discharge electrode 1 is charged, and Coulomb force acts on the charged water. As a result, the surface level of the water locally rises and forms a conical shape (Taylor cone) . The concentration of charge at the distal end of the conical water increases the charge density at the distal end. The repulsive force of the high density- charge fragments and scatters the water (Rayleigh fission) . Electrostatic atomization is performed in this manner to generate charged micro-particle water (negative ion mist) having nanometer size and including radicals.

The cooling portion 7 of the Peltier unit 6 (cooling device 2) is surrounded by the vacuum area 5. Accordingly, air is either not present or subtly present around the cooling portion 7. This differs from the prior art in which an air layer surrounds the cooling device 2. As a result, condensed water does not form on the cooling portion 7 even when cooling the cooling portion 7. This prevents electrical problems that would occur when condensed water forms on the cooling portion 7.

Further, since the cooling portion 7 of the Peltier unit 6 (cooling device 2) is surrounded by the vacuum area 5, the cooling energy is prevented from being conducted to the housing 8 through the surrounding air. This differs from the prior art in which an air layer surrounds the cooling device 2. Accordingly, cooling energy of the cooling portion 7 is efficiently conducted to the discharge electrode 1. Thus, the heat loss is small, and the Peltier unit 6, which has a small capacity, effectively cools the discharge electrode 1 and forms condensed water on the discharge electrode 1. This allows for the electrostatic atomization apparatus 4 to be reduced in size. Particularly, in the embodiment shown in Fig. 2, the cooling portion 7 of the Peltier unit 6 is not in contact with the housing 8. Thus, cooling energy is conducted from the cooling portion 7 to only the basal portion of the discharge electrode 1. Such a structure further suppresses heat loss.

In the embodiment discussed above, the cooling device 2 is not limited to only the Peltier unit 6. For example, any one of various types of heat transfer means known in the prior art may be used as a cooling device.

It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.

Claims

CLAIMS :

1. An electrostatic atomization apparatus comprising: a discharge electrode; a cooling device that cools the discharge electrode and condenses moisture in air on the discharge electrode to supply the discharge electrode with water; a high voltage application device that applies high voltage to the water supplied to the discharge electrode to perform electrostatic atomization and generate charged micro-particle water; and a vacuum area surrounding the cooling device.

2. The electrostatic atomization apparatus according to claim 1, wherein the cooling device is a Peltier unit including a cooling portion that cools the discharge electrode, the electrostatic atomization apparatus further comprising: a housing including an accommodation chamber that accommodates at least the cooling portion of the Peltier unit, wherein the cooling portion is arranged in non- contact with the housing, the discharge electrode is arranged to extend through the housing and project out of the accommodation chamber, and the vacuum area is formed in the accommodation chamber.

3. The electrostatic atomization apparatus according to claim 2, wherein the discharge electrode is generally rod-shaped and includes a basal portion that is in contact with the cooling portion of the Peltier unit, and the cooling portion of the Peltier unit is in contact with only the basal portion of the discharge electrode in the vacuum area.

4. The electrostatic atomization apparatus according to claim 1, further comprising: a housing that accommodates the discharge electrode and the cooling device; and a heat radiation portion that supports the cooling device; wherein the vacuum area is formed by the housing and the heat radiation portion.

5. The electrostatic atomization apparatus according to claim 4, wherein the discharge electrode includes a basal portion arranged between the housing and the cooling device; and the housing and the cooling device are separated from each other by the vacuum area.

6. The electrostatic atomization apparatus according to claim 1, further comprising: a housing that accommodates the discharge electrode and the cooling device, the cooling device including: first and second circuit boards arranged facing toward each other, with each of the first and second circuit boards including an insulative plate and a circuit section; and a plurality of electrically coupled thermoelectric elements held between the circuit sections of the first and second circuit boards, wherein when current flows through the thermoelectric elements, the first circuit board functions as a cooling circuit board and the second circuit board functions as a heat radiating circuit board; wherein the insulative plate of the first circuit board is coupled to the discharge electrode in non- contact with the housing.

7. The electrostatic atomization apparatus according to claim 6, wherein the insulative plate of the first circuit board is coupled to the discharge electrode via a further insulative plate, and the insulative plate of the first circuit board and the further insulative plate are both arranged to be in non-contact with the housing.