Charging device and electric dust collector

Abstract

To suppress charge-up to a peripheral member, without requiring a wide ion diffusion space.SOLUTION: A charging device includes: a discharge electrode to which a high voltage for generating ions by corona discharge is applied; a grounding electrode kept at a grounding potential; and an auxiliary electrode which is installed to a direction approximately vertical to a treatment air flow, on the upstream side of the discharge electrode in the treatment air flow, and releases ions generated by corona discharge.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a charging device and an electrostatic precipitator. [Background technology]

[0002] Patent Document 1 describes an ionizer that includes a discharge section for emitting ions toward an object to be neutralized, and a capture means for capturing the ions released from the discharge section, the capture means including a capture section that captures ions, and a capture control section that adjusts the amount of ions captured by the capture section. Patent Document 2 describes an electronic device used in the vicinity of an object to be neutralized, which includes an electric component, a wiring section for transmitting electric power from a high-voltage power supply to the electric component, and a housing for accommodating the electric component and the wiring section, and a cover section for covering at least a part of the electric component, and the surface resistivity of the cover section is 10 4 Ω / □ or more 10 11 Ω / □ or less, and the surface resistivity of the housing is 10 4 Ω / □ or more 10 11 The present invention describes an electronic device having at least one of the following configurations: a resistance of Ω / □ or less; [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-345199 [Patent Document 2] Japanese Patent Publication No. 2023-030053 Summary of the Invention [Problem to be solved by the invention]

[0004] If a configuration is adopted in which an auxiliary electrode for discharging ions generated by corona discharge is not installed upstream of the discharge electrode in the treatment airflow, a large ion diffusion space is required to prevent charging of surrounding components.

[0005] An object of the present invention is to suppress charge buildup on peripheral members without requiring a large ion diffusion space. [Means for solving the problem]

[0006] To this end, the present invention provides a charging device comprising: a discharge electrode to which a high voltage is applied to generate ions by corona discharge; a ground electrode maintained at ground potential; and an auxiliary electrode that is installed upstream of the discharge electrode in the process airflow, facing in a direction approximately perpendicular to the process airflow, and that allows ions generated by corona discharge to escape.

[0007] The auxiliary electrode may have a structure that quickly decays even if it is charged with ions generated by corona discharge. In this case, the auxiliary electrode may have a structure that prevents ions generated by corona discharge from being emitted upstream of the auxiliary electrode in the treatment airflow. In this case, the auxiliary electrode may have a structure in which the surface of a conductive member other than the end portion is treated with an insulating member and the end portion is connected to a ground potential. Also, in this case, the insulating member may be made of a static electricity dissipative material. Furthermore, in this case, the static electricity dissipative material may have a porous surface. The auxiliary electrode may be installed at the most upstream position in the processing airflow within the apparatus itself. The auxiliary electrode may be a flat electrode having an opening or a plurality of rod-shaped electrodes. The ground electrode may be formed of a plate-shaped or rod-shaped conductive member. The discharge electrode may be formed of a wire, a needle-shaped or sawtooth-shaped conductive member, or a plurality of fibrous conductors.

[0008] The present invention also provides an electrostatic precipitator comprising any one of the charging devices described above and a dust collector that collects dust by attaching suspended fine particles in a process airflow that have been charged by the charging device. [Effects of the Invention]

[0009] According to the present invention, it is possible to suppress charging up of peripheral members without requiring a large ion diffusion space. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view showing an example of the overall configuration of an electric dust collector according to an embodiment of the present invention. [Figure 2] 2 is a diagram showing an example of the configuration of a charging unit and a dust collecting unit of an electric dust collector according to the present embodiment. FIG. [Figure 3] 4A and 4B are diagrams illustrating the operation of the electric dust collector according to the present embodiment. [Figure 4A] FIG. 4 is a diagram showing a method for measuring a surface potential of the electric dust collector according to the present embodiment. [Figure 4B] FIG. 4 is a diagram showing a method for measuring the amount of ions related to the electric dust collector in the present embodiment. [Figure 5] 10 is a graph showing the measurement results of the surface potential of an auxiliary electrode or a prefilter for the electrostatic precipitator according to the present embodiment. [Figure 6A] 4 is a graph showing the measurement results of the amount of ions related to the electric dust collector of the present embodiment. [Figure 6B] 4 is a graph showing the measurement results of the amount of ions related to the electric dust collector of the present embodiment. [Figure 7] FIG. 10 is a diagram showing an electrode configuration when a white anodized aluminum mesh is used as an auxiliary electrode in the electric dust collector of the present embodiment. [Figure 8A] FIG. 10 is a diagram showing the measurement results of the surface potential when "only a white anodized aluminum mesh (10 μm) is present." [Figure 8B] FIG. 10 is a diagram showing the measurement results of the surface potential when "only a white anodized aluminum mesh (20 μm) is present." [Figure 9] FIG. 10 is a diagram showing the performance in terms of the cleaning area when a white anodized aluminum mesh is used as the auxiliary electrode of the electric dust collector according to the present embodiment. [Figure 10]10 is a diagram showing an electrode configuration when a hard anodized aluminum rod is used as an auxiliary electrode in the electric dust collector of the present embodiment. FIG. [Figure 11A] FIG. 10 is a diagram showing the measurement results of the surface potential when "only a hard anodized aluminum rod (20 μm) is used." [Figure 11B] FIG. 10 is a diagram showing the measurement results of the surface potential in the case of "with hard anodized aluminum rod (20 μm) and pre-filter." [Figure 12] FIG. 10 is a diagram showing the performance in terms of the cleaning area when a hard anodized aluminum rod is used as the auxiliary electrode of the electric dust collector according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0012] [Background and Overview of the Present Embodiment] An electrostatic precipitator, which collects airborne particles by charging them with an electric discharge, is an environmentally friendly dust collection technology that does not require disposal or replacement. An electrostatic precipitator consists of a charging section that charges airborne particles with an electric discharge, and a dust collection section that captures the charged particles using Coulomb force. By incorporating two charging methods, diffusion charging and electric field charging, in the charging section at the front stage to improve charging efficiency, the charged particles can be dispersed over a wide space. However, the scattered charged particles can charge up the surrounding pre-filter, grill, etc., causing the problem of unstable charging. Therefore, in this embodiment, we provide a charging device that uses an auxiliary electrode (third electrode) that can stabilize charging performance without degrading it in the limited space of products such as air purifiers and air conditioners, and an electric dust collector that uses this charging device.

[0013] [Configuration of the electric dust collector according to the present embodiment] FIG. 1 is a perspective view showing an example of the overall configuration of an electric dust collector 1 according to the present embodiment. As shown in the figure, the electrostatic precipitator 1 includes a charging unit 10, a dust collecting unit 20, a fan 40, a housing 50 that houses these components, and a high-voltage power supply 60 that supplies high voltage to the charging unit 10 and the dust collecting unit 20. Here, the housing 50 is indicated by a dashed line, allowing the configuration of the charging unit 10 and the dust collecting unit 20 provided inside the housing 50 to be seen. This electrostatic precipitator 1 is a two-stage electrostatic precipitator in which the charging unit 10 and the dust collecting unit 20 are functionally separate. The charging unit 10 and the dust collecting unit 20 may be configured as a detachable unit. Here, the direction of the processing airflow (ventilation) (ventilation direction) is set in the direction indicated by the arrow. The ventilation is performed by a fan 40 provided downstream (downwind side) of the dust collecting unit 20 in the ventilation direction.

[0014] The charging unit 10 charges particles suspended in the air. The charging unit 10 includes a plurality of discharge electrodes 11, a ground electrode 12, an auxiliary electrode 13, and a power supply member 14 for supplying a high voltage supplied from a high-voltage power supply 60 to the plurality of discharge electrodes 11. The discharge electrodes 11, the ground electrode 12, and the auxiliary electrode 13 will be described in detail later. The charging unit 10 is an example of a charging device.

[0015] The dust collecting unit 20 collects dust by attaching airborne fine particles charged by the charging unit 10 to the dust collecting unit 20. The dust collecting unit 20 includes alternately stacked plate-shaped high-voltage electrodes 21, the surfaces of which are coated with a film of insulating material, and plate-shaped conductive collecting electrodes 22. Alternatively, the dust collecting unit 20 may be made of a dust collecting film. In the following, the dust collecting unit 20 will be described using a dust collecting film as an example. The dust collecting unit 20 is an example of a dust collecting device.

[0016] The housing 50 has an inlet 51 on the charging unit 10 side, which is on the upstream side (windward side) in the direction of airflow, and an outlet 52 on the dust collection unit 20 side, which is on the downstream side (downwind side) in the direction of airflow. The inlet 51 may be provided with a mesh (net, lattice) or the like. The mesh (net, lattice) or the like provided in the inlet 51 is preferably provided so as to reduce resistance to airflow while preventing the user from coming into contact with the charging unit 10. The inlet 51 may also be provided with a pre-filter that prevents large particles from entering. The housing 50 is made of a resin material such as ABS (acrylonitrile butadiene styrene copolymer).

[0017] The fan 40 is provided at an outlet 52 on the leeward side of the housing 50. The air flow (ventilation) enters the housing 50 from an inlet 51 on the charging unit 10 side, passes through the charging unit 10 and the dust collecting unit 20, and exits the housing 50 from an outlet 52 where the fan 40 is provided. As long as ventilation is not obstructed, the electric dust collector 1 may be placed in any orientation.

[0018] The high-voltage power supply 60 applies a high direct current (DC) voltage between the discharge electrode 11 and the ground electrode 12, thereby generating a corona discharge (discharge) between the discharge electrode 11 and the ground electrode 12. Ions generated by the generated corona discharge then attach to the airborne particles, thereby charging the airborne particles. Note that the high-voltage power supply 60, which applies a high voltage between the discharge electrode 11 and the ground electrode 12 in this manner, can also be considered as part of the charging unit 10. The high-voltage power supply 60 also applies a high direct current (DC) voltage between the high-voltage electrode 21 and the collecting electrode 22. As a result, the airborne particles charged by the charging unit 10 adhere to the surface of the collecting electrode 22 due to electrostatic force (Coulomb force). This causes the airborne particles to be collected. The high-voltage power supply 60, which applies a high voltage between the high-voltage electrode 21 and the collecting electrode 22 in this manner, can also be considered as part of the collecting unit 20.

[0019] Fig. 2 is a diagram showing an example of the configuration of the charging unit 10 and the dust collecting unit 20 in Fig. 1. Fig. 2 shows a cross-sectional view of the charging unit 10 and the dust collecting unit 20 in Fig. 1 when viewed from viewpoint V. Therefore, in Fig. 2, the ventilation direction is set from top to bottom as shown by the arrow. As shown in the figure, the charging unit 10 includes a discharge electrode 11 , a ground electrode 12 , and an auxiliary electrode 13 .

[0020] The discharge electrode 11 is an electrode that generates ions by corona discharge in order to charge suspended particles in the air. A high voltage is applied to the discharge electrode 11 for this purpose. The discharge electrode 11 may be formed of a wire, a needle-shaped or sawtooth conductive member, or a plurality of fibrous conductors. The discharge electrode 11 is an example of a discharge electrode to which a high voltage is applied to generate ions by corona discharge.

[0021] The ground electrode 12 is an electrode for defining a ground potential in the charged region. The ground electrode 12 is preferably formed of a flat or rod-shaped conductive member. The ground electrode 12 is an example of a ground electrode that is maintained at a ground potential.

[0022] The auxiliary electrode 13 is installed on the windward side of the discharge electrode 11 in a direction approximately perpendicular to the treatment airflow, and is an electrode for discharging the ion current that has diffused in the area on the windward side of the discharge electrode 11. In this sense, the auxiliary electrode 13 is an example of an electrode that is installed on the upstream side of the discharge electrode in the treatment airflow, in a direction approximately perpendicular to the treatment airflow, and dissipates ions generated by corona discharge. The auxiliary electrode 13 has a structure that quickly decays the ions generated by the corona discharge even if the ions are charged, so that the auxiliary electrode 13 does not release the ions generated by the corona discharge to the upstream side of the auxiliary electrode 13 in the treatment airflow.

[0023] The auxiliary electrode 13 may be a mesh electrode or multiple rod-shaped electrodes. In this sense, the auxiliary electrode 13 is an example of a flat electrode or multiple rod-shaped electrodes having openings. Here, the mesh electrode or multiple rod-shaped electrodes may have their ends formed of a conductive material, and the remaining portions formed of an insulating material. Forming the remaining portions of the electrodes of an insulating material may mean forming the remaining portions of the electrodes of an electrically conductive material and surface-treating the conductive material with an insulating material. The ends may also be grounded. In this sense, the auxiliary electrode 13 is an example of an electrode having a structure in which the remaining portions of the electrodes of an electrically conductive material are surface-treated with an insulating material, and the remaining portions are connected to ground potential.

[0024] Here, it is desirable that the insulating member is made of a static electricity dissipative material. A static electricity dissipative material is a material that is difficult to charge and, even if it does charge, can dissipate the charge relatively quickly. Furthermore, a static electricity dissipative material does not cause a strong static discharge even when a charged object comes into contact with it. The surface resistivity of a static electricity dissipative material is, for example, 10 4 ~10 12 [Ω / sq.]. Examples of such static-dissipative materials include anodized aluminum (hereinafter referred to as "anodized aluminum"), zirconia, cationic polymers, semiconductive silicone rubber, extruded polyethylene foam, and cross-linked polyethylene. Furthermore, it is more desirable for the static-dissipative material to have a porous surface structure. Typically, anodized aluminum has such a porous surface structure. Experiments have confirmed that anodized aluminum is hardly charged. This is presumably due to the porous structure of anodized aluminum. Anodized aluminum has a two-layer structure consisting of a barrier layer and a porous coating layer formed by a reaction at the interface between the electrolyte and the aluminum base. The micropores in the porous coating layer are usually sealed, but because they are not completely blocked, electric charges escape through the micropores, preventing electric charges from accumulating on the surface.

[0025] The dust collecting section 20 also includes a dust collecting film 200 . The figure also shows a pre-filter 30 that prevents large particles from entering, although it is not a component of the charging unit 10 or the dust collecting unit 20. Therefore, it can be said that the auxiliary electrode 13 is installed at the most upstream position in the treatment airflow within the charging unit 10.

[0026] [Action of the electric dust collector in this embodiment] FIG. 3 is a diagram showing the operation of the electric dust collector 1 in this embodiment. As shown in the figure, in the electrostatic precipitator 1 of this embodiment, in the charging section 10, a discharge electrode 11 generates ions by corona discharge between itself and a ground electrode 12, and the ions charge suspended particles P in the treatment airflow through electric field charging and diffusion charging. Then, the charged suspended particles CP flow downstream in the ion diffusion space S due to a fountain flow (a flow like a water fountain) indicated by arrow FF. On the other hand, the generated ions are allowed to escape by the auxiliary electrode 13, and therefore do not diffuse upstream of the auxiliary electrode 13, thereby suppressing charging of the pre-filter 30 and objects outside it.

[0027] [Charge-up Suppression Effect of the Auxiliary Electrode in the Present Embodiment] First, the results of measurements of the surface potential and the amount of ions regarding the electric dust collector 1 of this embodiment will be described.

[0028] 4A is a diagram showing a method for measuring the surface potential in this case, and FIG. 4B is a diagram showing a method for measuring the amount of ions in this case. Here, a discharge electrode 11 and a ground electrode 12 are arranged as charging electrodes of the charging unit 10, and a dust collection film 200 is arranged as the dust collection unit 20, so that the charging electrode of the charging unit 10 and the dust collection unit 20 have a two-stage configuration. In addition, an auxiliary electrode 13 with a thickness of 10 μm and a surface resistivity of 10 is arranged at a position 20 mm from the charging electrode of the charging unit 10. 9 ~10 11 An anodized aluminum mesh 130 of [Ω / sq.] was installed, and a pre-filter 30 was installed just outside of it. Fig. 4A shows how the surface potential is measured by a static electricity measuring device 70, and Fig. 4B shows how the amount of ions is measured by an ion amount measuring device 80.

[0029] Figure 5 is a graph showing the results of measuring the surface potential. Here, the surface potential in the case of "only anodized aluminum mesh present" is the surface potential of the anodized aluminum mesh 130 measured from the outside using the static electricity meter 70 with the prefilter 30 removed from Figure 4A. The surface potential in the case of "prefilter and anodized aluminum mesh present" is the surface potential of the prefilter 30 outside the anodized aluminum mesh 130 measured from the outside using the static electricity meter 70 in the state of Figure 4B. Figure 5 shows that the charge-up voltage is low at all current values, indicating that the effect of charge-up is small.

[0030] 6A and 6B are graphs showing the results of measuring the amount of ions. Fig. 6A shows the results of measuring the amount of ions using the ion amount measuring device 80 when the anodized aluminum mesh 130 is not installed, and Fig. 6B shows the results of measuring the amount of ions using the ion amount measuring device 80 when the anodized aluminum mesh 130 is installed. Both graphs show the results of measuring the amount of ions at a position a certain distance away from the anodized aluminum mesh 130 or the pre-filter 30.

[0031] FIG. 6A shows that the amount of ions is very large when there is no pre-filter, and the amount of ions when there is a pre-filter is also small when the current value is small, but increases as the current value increases.

[0032] On the other hand, in FIG. 6B, the amount of ions in the case of "without pre-filter" is very large as in FIG. 6A, but the amount of ions in the cases of "with only anodized aluminum mesh" and "with pre-filter and anodized aluminum mesh" is small at all current values. That is, it can be seen from FIGS. 6A and 6B that when the auxiliary electrode 13 is installed, the amount of ions released outside the system is significantly reduced compared to when only the pre-filter 30 is installed.

[0033] Next, a description will be given of the results of measurements of the effect of thickness on performance when a white anodized aluminum mesh 131 is used as the auxiliary electrode 13 in the electrostatic precipitator 1 of this embodiment.

[0034] FIG. 7 shows the electrode configuration in this case. Here, a discharge electrode 11 and a ground electrode 12 are arranged as the charging electrodes of the charging unit 10, and a dust collection film 200 is arranged as the dust collection unit 20. The charging electrodes and dust collection unit 20 of the charging unit 10 are configured in a single layer. A 10 μm- or 20 μm-thick white anodized aluminum mesh 131 is arranged 20 mm from the charging electrode of the charging unit 10 as the auxiliary electrode 13, and a prefilter 30 is arranged immediately outside of it. However, depending on the measurement content, the white anodized aluminum mesh 131 or the prefilter 30 may not be arranged. Hereinafter, the case where the prefilter 30 is arranged but the white anodized aluminum mesh 131 is not arranged is referred to as "prefilter only." Furthermore, the cases where the 10 μm-thick or 20 μm-thick white anodized aluminum mesh 131 is arranged without the prefilter 30 are referred to as "white anodized aluminum mesh (10 μm) only" and "white anodized aluminum mesh (20 μm) only," respectively.

[0035] 8A is a diagram showing the measurement results of the surface potential when "only a white anodized aluminum mesh (10 μm) is present." Here, the surface potential when "only a white anodized aluminum mesh (10 μm) is present" is the surface potential of the white anodized aluminum mesh 131 during discharge at -6 kV, measured from a position 25 mm outside with a static electricity meter with the pre-filter 30 removed from FIG. 7.

[0036] 8B is a diagram showing the measurement results of the surface potential when "only the white anodized aluminum mesh (20 μm) is present." Here, the surface potential when "only the white anodized aluminum mesh (20 μm) is present" is the surface potential of the white anodized aluminum mesh 131 during discharge at -6 kV, measured from a position 25 mm outside with a static electricity meter with the pre-filter 30 removed from FIG. 7.

[0037] Specifically, the surface of the white anodized aluminum mesh 131 was divided into nine regions, three vertically and three horizontally, and the surface potential was measured for each region. In Figures 8A and 8B, the horizontal direction corresponds to the horizontal direction of the white anodized aluminum mesh 131 in Figure 7, and the vertical direction corresponds to the depth direction of the white anodized aluminum mesh 131 in Figure 7. Figures 8A and 8B show that the surface potential of the white anodized aluminum mesh 131 is very low. In particular, the surface potential of the 20 μm thick white anodized aluminum mesh 131 is lower than that of the 10 μm thick white anodized aluminum mesh 131.

[0038] 9 is a diagram showing the performance in terms of the cleaning area of ​​the electrostatic precipitator 1. In the diagram, the single unit specific performance indicates the ratio of the cleaning area when the cleaning area of ​​the single unit is taken as 100%. In the case of "pre-filter only", the performance ratio of the single unit is less than 14.5%, which is very poor.

[0039] On the other hand, in the case of "only white anodized aluminum mesh (10 μm)", the surface potential of the white anodized aluminum mesh 131 is very low as shown in FIG. 8A, and the single unit specific performance is 71.0%, which is significantly better than the case of "only pre-filter". Furthermore, in the case of "only white anodized aluminum mesh (20 μm) present," the surface potential of the white anodized aluminum mesh 131 becomes very low as shown in FIG. 8B, and the single unit specific performance is 72.5%, which is significantly better than the case of "only pre-filter present."

[0040] Next, the results of measurements on the effect on performance of using the hard anodized aluminum rod 132 as the auxiliary electrode 13 in the electrostatic precipitator 1 of this embodiment will be described.

[0041] FIG. 10 shows the electrode configuration in this case. Here, too, a discharge electrode 11 and a ground electrode 12 are arranged as the charging electrodes of the charging unit 10, and a dust collection film 200 is arranged as the dust collection unit 20. The charging electrode and dust collection unit 20 of the charging unit 10 are configured in a single layer. A 20 μm-thick hard anodized aluminum rod 132 is installed 20 mm from the charging electrode of the charging unit 10 as the auxiliary electrode 13, and a prefilter 30 is installed just outside of it. However, depending on the measurement content, the hard anodized aluminum rod 132 or the prefilter 30 may not be installed. Hereinafter, the case where the prefilter 30 is installed but the hard anodized aluminum rod 132 is not installed is referred to as "prefilter only." The case where the hard anodized aluminum rod 132 is installed without the prefilter 30 is referred to as "hard anodized aluminum rod (20 μm) only." Furthermore, the case where both the pre-filter 30 and the hard anodized aluminum rod 132 are installed is referred to as "with hard anodized aluminum rod (20 μm) and pre-filter."

[0042] 11A is a diagram showing the measurement results of the surface potential when "only the hard anodized aluminum rod (20 μm) is present." Here, the surface potential when "only the hard anodized aluminum rod (20 μm) is present" is the surface potential of the hard anodized aluminum rod 132 during discharge at -6 kV, measured with a static electricity meter from a position 25 mm outside with the pre-filter 30 removed from FIG. 10.

[0043] 11B is a diagram showing the measurement results of the surface potential when "hard anodized aluminum rod (20 μm) and pre-filter are used." Here, the surface potential when "hard anodized aluminum rod (20 μm) and pre-filter are used" is the surface potential of the pre-filter 30 on the outside of the hard anodized aluminum rod 132 during discharge at -6 kV, measured from a position 25 mm outside using a static electricity meter in the state shown in FIG.

[0044] Specifically, the area in which the hard anodized aluminum rod 132 was arranged was divided into 10 regions, 2 vertically and 5 horizontally, and the surface potential was measured for each region. In Figures 11A and 11B, the horizontal direction corresponds to the horizontal direction of the hard anodized aluminum rod 132 in Figure 10, and the vertical direction corresponds to the depth direction of the hard anodized aluminum rod 132 in Figure 10. It can be seen from Figures 11A and 11B that the surface potential of the hard anodized aluminum rod 132 or the prefilter 30 outside the hard anodized aluminum rod 132 is very low.

[0045] 12 is a diagram showing the performance in terms of the cleaning area of ​​the electrostatic precipitator 1. In the diagram, the single unit specific performance indicates the ratio of the cleaning area when the cleaning area of ​​the single unit is taken as 100%. In the case of "pre-filter only", the performance ratio of the single unit is less than 21.4%, which is very poor.

[0046] On the other hand, in the case of "only hard anodized aluminum rod (20 μm) present," the surface potential of the hard anodized aluminum rod 132 becomes very low as shown in FIG. 11A, and the single unit specific performance is 109.0%, which is significantly better than the case of "only pre-filter present." Furthermore, in the case of "with hard anodized aluminum rod (20 μm) and pre-filter," the surface potential of the pre-filter 30 becomes very low as shown in FIG. 11B, and the single unit specific performance is 98.9%, which is significantly better than the case of "with pre-filter only."

[0047] [Advantages of this embodiment] In this embodiment, a charging device applies a high voltage between a discharge electrode 11 and a ground electrode 12 to generate a discharge, and charges suspended particles in the air with ions generated by the discharge. An auxiliary electrode 13 is installed in the ion diffusion space to suppress charge buildup. Generally, in order to prevent charging of an object, it is necessary to provide a wide ion diffusion space, but in this embodiment, it is possible to prevent charging of an object with a narrow ion diffusion space. Furthermore, the auxiliary electrode 13 plays a role in dissipating electric charges, making it possible to prevent ions from leaking outside the ion diffusion space. Furthermore, since the surface of the auxiliary electrode 13 is insulated, it is possible to prevent sparks from occurring between the discharge electrode 11 and the auxiliary electrode 13. [Explanation of symbols]

[0048] 1...electrostatic precipitator, 10...charging section, 11...discharge electrode, 12...ground electrode, 13...auxiliary electrode, 14...power supply member, 20...dust collection section, 21...high voltage electrode, 22...collecting electrode, 30...prefilter, 40...fan, 50...casing, 60...high voltage power supply

Claims

1. a discharge electrode to which a high voltage is applied for generating ions by corona discharge; a ground electrode maintained at ground potential; an auxiliary electrode that is installed upstream of the discharge electrode in the treatment airflow, facing in a direction substantially perpendicular to the treatment airflow, and that allows ions generated by the corona discharge to escape; A charging device is provided.

2. 2. The charging device according to claim 1, wherein the auxiliary electrode has a structure that quickly attenuates ions generated by the corona discharge even when the ions are charged.

3. 3. The charging device according to claim 2, wherein the auxiliary electrode has the structure, so that the ions generated by the corona discharge are not emitted upstream of the auxiliary electrode in the processing airflow.

4. 3. The charging device according to claim 2, wherein the auxiliary electrode has a structure in which the surface of the conductive member is treated with an insulating member except for the end portion, and the end portion is connected to a ground potential.

5. 5. The charging device according to claim 4, wherein the insulating member is made of a static electricity dissipative material.

6. The charging device according to claim 5 , wherein the static electricity dissipative material has a surface with a porous structure.

7. The charging device according to claim 1 , wherein the auxiliary electrode is installed at the most upstream position in the processing airflow within the device itself.

8. The charging device according to claim 1 , wherein the auxiliary electrode is a flat electrode having an opening or a plurality of rod-shaped electrodes.

9. 2. The charging device according to claim 1, wherein the ground electrode is formed of a conductive member having a flat plate shape or a rod shape.

10. 2. The charging device according to claim 1, wherein the discharge electrode is formed by a wire, a needle-shaped or sawtooth-shaped conductive member, or a plurality of fibrous conductors.

11. The charging device according to any one of claims 1 to 10, a dust collector that collects dust by attaching the floating fine particles in the treatment airflow that have been charged by the charging device; An electrostatic precipitator comprising:

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