JP7718241B2 - Discharge device and electrostatic precipitator - Google Patents

Description

The present invention relates to a discharge device and an electrostatic precipitator.

One example of a conventional electrostatic precipitator is one that includes a discharge device having a discharge electrode and a counter electrode that is paired with the discharge electrode, and in which the surface of the counter electrode in the discharge device is coated with an insulator (see, for example, Patent Document 1).

International Publication No. 2001/064349 Japanese Patent Application Laid-Open No. 2020-146605

The inventors of this application discovered that when an insulator-coated counter electrode is used, if the voltage applied to the discharge electrode is within a predetermined range, pulsed discharges occur intermittently from the counter electrode side (see Patent Document 2).

However, because pulsed discharges occur by suddenly consuming the charge accumulated on the surface of the insulator, there is a risk that the insulator covering the surface of the counter electrode may deteriorate due to the high instantaneous energy density of the pulsed discharge. Therefore, in order to utilize the phenomenon of pulsed discharges occurring from the insulator-covered counter electrode in discharge devices and electrostatic precipitators using such devices, it was necessary to prevent deterioration of the insulator covering the counter electrode.

The disclosed technology was developed in light of the above, and aims to provide a discharge device and an electrostatic precipitator that can prevent deterioration of the insulator that covers the counter electrode.

One aspect of the discharge device disclosed in this application comprises a discharge electrode, a counter electrode disposed opposite the discharge electrode, and a voltage application unit that applies a voltage to the discharge electrode. The counter electrode also has a conductive portion formed of a conductor and a covering portion formed of a dielectric and covering the surface of the conductive portion. The covering portion also has a first member formed of a dielectric containing an organic substance, and a second member formed of an inorganic substance. The first member has a hole that exposes the surface of the conductive portion, and the second member covers at least the inner edge portion of the contact surface between the conductive portion and the first member that contacts the inner edge of the hole in the first member.

This disclosure makes it possible to prevent deterioration of the insulator covering the counter electrode.

FIG. 1 is a schematic diagram of an air purifier provided with a discharge device according to an embodiment and an electric dust collector including the discharge device. FIG. 2 is a configuration diagram of an electric dust collector according to an embodiment. FIG. 3 is a schematic diagram showing a discharge electrode and a counter electrode of the charging unit according to the embodiment. FIG. 4 is a diagram showing the waveform of the discharge current in the charging unit according to the embodiment. FIG. 5 is an explanatory diagram showing a process in which a pulse current having a polarity opposite to that of an applied voltage is generated due to dielectric breakdown in the counter electrode in the charging unit according to the embodiment. FIG. 6 is an enlarged cross-sectional view showing the configuration of the counter electrode in the reference example. FIG. 7 is an enlarged cross-sectional view showing the configuration of the counter electrode according to the embodiment. FIG. 8 is an enlarged cross-sectional view showing the configuration of a counter electrode according to a modified example of the embodiment.

Embodiments of the discharge device and electrostatic precipitator disclosed in this application are described in detail below with reference to the drawings. Note that the discharge device and electrostatic precipitator disclosed in this application are not limited to the following embodiments.

Furthermore, the components described below include those that are easily replaceable by those skilled in the art, or those that are substantially identical, or so-called equivalents. Note that throughout the description of the embodiments, the same elements will be denoted by the same reference numerals.

Furthermore, in the following embodiment, a discharge device according to the disclosed technology is applied to an electric dust collector provided in an air purifier. However, this is not limited to this, and the discharge device according to the disclosed technology can also be applied to various devices that can generate ions by electrical charging, for example.

<Air purifier configuration>
First, the configuration of an air purifier 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram of the air purifier 1 provided with a discharge device according to an embodiment and an electrostatic precipitator 2 including the discharge device.

As shown in FIG. 1, the air purifier 1 includes a housing 10 that houses devices for purifying the air. The housing 10 is formed, for example, from a synthetic resin material in a rectangular parallelepiped shape. The housing 10 is formed with an intake port 11 that draws in air from the room and an outlet port 12 that blows purified air into the room.

Also provided within the housing 10 are a pre-filter 14, multiple electrostatic precipitators 2, and a deodorizing filter 5. The electrostatic precipitator 2 is an example of a dust collector. The pre-filter 14 removes large dust particles from the sucked air. The multiple electrostatic precipitators 2 use electrostatic force to collect dust particles in the air that has passed through the pre-filter 14. The deodorizing filter 5 deodorizes the air that has passed through the electrostatic precipitator 2.

The pre-filter 14 has a mesh structure made of woven polyethylene terephthalate (PET) threads, and is held in place by a resin frame (not shown). The pre-filter 14 captures relatively large dust particles contained in the air drawn into the housing 10.

Each of the multiple electrostatic precipitators 2 includes a charging unit 3 and a dust collecting unit 4. The charging unit 3 is an example of a discharge device and charges fine particles such as dust contained in the air passing through it. The dust collecting unit 4 uses electrostatic force to capture the fine particles charged by the charging unit 3.

In this embodiment, three electrostatic precipitators 2 are arranged inside the housing 10, but the number that can be arranged is not limited in any way.

The deodorizing filter 5 uses a catalytic filter to perform deodorizing processing, removing odorous components such as ammonia and methyl mercaptan, and harmful components such as formaldehyde, from the air from which dust has been removed by the prefilter 14 and electrostatic precipitator 2.

Also provided within the housing 10 are a fan 6, a fan motor 61, a control board 7, a dust sensor 13, and an operation and display board 15. The fan 6 is located downstream of the deodorizing filter 5. The fan motor 61 rotates the fan 6.

The control board 7 controls the air purifier 1. The dust sensor 13 detects the dust concentration in the air sucked in through the suction port 11. The operation and display board 15 performs, for example, operations to start and stop operation.

In addition, the housing 10 is equipped with a single constant-voltage high-voltage power supply unit for the dust collection unit (hereinafter referred to as the "high-voltage power supply 40 for the dust collection unit") that supplies power to each dust collection unit 4 of each electric dust collector 2.

On the other hand, a constant current high-voltage power supply unit for the charging unit (hereinafter referred to as the "high-voltage power supply for the charging unit 30") that supplies power to the charging unit 3 is disposed in each of the three charging units 3. Such a high-voltage power supply for the charging unit 30 is an example of a voltage application unit.

The air purifier 1 configured as described above draws indoor air through the intake port 11 as shown by arrow f, using the rotation of the fan 6 driven by the fan motor 61. The air is purified as it passes through the pre-filter 14, electrostatic precipitator 2, and deodorizing filter 5, and the purified air is then blown out into the room through the outlet port 12.

The air volume setting for the air purifier 1 can be changed manually by operating the operation display board 15, but it is also possible to provide an automatic air volume mode setting that automatically switches to an appropriate air volume based on the detection signal from the dust sensor 13, for example.

<Configuration of electrostatic precipitator>
Next, the configuration of an electric dust collector 2 including a discharge device according to an embodiment will be described with reference to Fig. 2. Fig. 2 is a configuration diagram of the electric dust collector 2 according to an embodiment.

As shown in Figure 2, the electrostatic precipitator 2 includes a charging unit 3 and a dust collecting unit 4. The charging unit 3 has a discharge electrode 310 and a counter electrode 320.

The discharge electrode 310 is a wire-shaped electrode. The counter electrode 320 is a flat electrode with a polarity different from that of the discharge electrode 310. In the charging unit 3, multiple discharge electrodes 310 and multiple counter electrodes 320 are arranged alternately at predetermined intervals.

The dust collection unit 4 has a structure in which a large number of flat plate electrodes are arranged in parallel and electrically connected so that a high voltage is applied between adjacent electrodes. In this embodiment, of the two types of electrodes that make up the dust collection unit 4, the electrode with the same polarity as the discharge electrode 310 is referred to as the "high-voltage electrode 410," and the electrode with the same polarity as the counter electrode 320 is referred to as the "collection electrode 420."

A high voltage is applied to the discharge electrode 310 of the charging unit 3 by the charging unit high-voltage power supply 30. The charging unit high-voltage power supply 30 receives power from the power supply 50 via the power supply unit 55, and is driven and controlled by the control unit 70 mounted on the control board 7 (see Figure 1) via the charging unit switches 301, 302, and 303. The counter electrode 320 of the charging unit 3 is grounded.

A high voltage is applied to the high-voltage electrode 410 of the dust collection unit 4 by the dust collection unit high-voltage power supply 40. The dust collection unit high-voltage power supply 40 receives power from the power supply 50 via the power supply unit 55, and is driven and controlled by the control unit 70 mounted on the control board 7 via the dust collection unit switch 401. The collection electrode 420 of the dust collection unit 4 is grounded.

The number of high-voltage power supplies 30 for the charging unit is the same as the number of charging units 3 built into the electrostatic precipitator 2 (three in this example), and they are connected in a one-to-one correspondence to the charging units 3 of each electrostatic precipitator 2. There is only one high-voltage power supply 40 for the dust collecting unit, regardless of the number of dust collecting units 4 built into the electrostatic precipitator 2, and all dust collecting units 4 are connected in parallel. There is no particular limit to the number of high-voltage power supplies 30 for the charging unit or the number of high-voltage power supplies 40 for the dust collecting unit.

<Configuration of charging section>
Next, the configuration of the charge unit 3 according to the embodiment will be described with reference to Figures 3 to 7. Figure 3 is a schematic diagram showing the discharge electrode 310 and the counter electrode 320 of the charge unit 3 according to the embodiment.

The discharge electrode 310 is formed in a wire shape, and Figure 3 shows a cross section of the wire-shaped discharge electrode 310. Note that the discharge electrode 310 may be formed in any shape as long as at least a portion of it is thin or sharp, and instead of being wire-shaped, it may be, for example, needle-shaped.

On the other hand, the counter electrode 320 is formed in a flat plate shape and has a conductive portion 321 and a covering portion 322. The conductive portion 321 is formed from a conductor, for example, stainless steel such as SUS304.

The covering portion 322 is formed of a dielectric material and covers the entire surface 321a of the conductive portion 321. The covering portion 322 also has a first member 323 and a second member 324.

The first member 323 is formed of a dielectric material containing an organic substance. The first member 323 is formed, for example, of an insulating material containing an organic substance (for example, a resin such as vinyl chloride resin or fluororesin). The thickness of the first member 323 is, for example, approximately 1 mm.

The second member 324 is formed from an inorganic material. The second member 324 is formed from a ceramic such as alumina, for example.

The counter electrode 320, in which the surface 321a of the conductive portion 321 is covered with the covering portion 322 having this configuration, can suppress the discharge current between it and the discharge electrode 310, and therefore the generation of ozone.

Figure 4 shows the waveform of the discharge current in the charging unit 3 according to the embodiment. As shown in Figure 4, intermittent pulses with large discharge current values appear among many continuous pulses with small discharge current values.

The continuous pulses with small discharge current values indicate discharges caused by charges of the same polarity (positive polarity in this embodiment) as the voltage applied to the discharge electrode 310, which are generated near the discharge electrode 310, and are the result of so-called burst pulse corona discharges.

On the other hand, pulses with large discharge current values indicate discharge due to charges generated near the counter electrode 320 and having the opposite polarity (negative polarity in this embodiment) to the voltage applied to the discharge electrode 310.

The results of this experiment showed that when the conductive portion 321 of the counter electrode 320 is covered with the covering portion 322 and a limited range of DC voltage is applied to the discharge electrode 310, a pulsed discharge current is intermittently generated from the vicinity of the counter electrode 320 due to charges of opposite polarity to the voltage applied to the discharge electrode 310.

Here, we will explain the mechanism by which a pulsed, intermittent discharge current is generated from the opposing electrode 320. Figure 5 is an explanatory diagram showing the process by which a pulsed current of opposite polarity to the applied voltage is generated due to dielectric breakdown in the opposing electrode 320 in the charging unit 3 according to this embodiment.

As shown in Figure 5(a), for example, when a positive DC voltage of a predetermined magnitude is applied to the discharge electrode 310, a corona discharge occurs, generating positive ions (ions of positive polarity) near the discharge electrode 310, which are attracted toward the counter electrode 320.

As a result, as shown in Figure 5(b), positive ions accumulate on the surface of the coating 322 of the counter electrode 320. At this time, electrons become unevenly distributed near the coating 322 of the conductive portion 321 of the counter electrode 320, and a potential difference (voltage) occurs between the surface of the coating 322 and the area near the coating 322 of the conductive portion 321.

As charge accumulates further, the potential difference increases, and when it reaches a certain potential difference, insulation breakdown occurs in the air layer, causing electrons to fly out at high speed from inside the conductive portion 321 of the opposing electrode 320, as shown in Figure 5(c).

In this case, if a discharge path 327 (see Figure 6) is present within the covering portion 322, a discharge will occur that penetrates the interior of the covering portion 322 through the interface between the air layer within the discharge path 327 and the covering portion 322 facing the discharge path 327.

In other words, the accumulation of charge on the surface of the covering portion 322 causes a phenomenon in which a pulsed discharge current is intermittently generated from the opposing electrode 320. In this case, the discharge state is thought to be an intermittent pulsed discharge when the electrical resistance formed by the covering portion 322, where the charge accumulates, and the discharge path 327 is appropriate.

The electrons that fly out at high speed from near the counter electrode 320 due to the dielectric breakdown have a large amount of energy, so they collide one after another with nitrogen molecules (N ₂ ) that are present in abundance in the air. Then, as they collide with each nitrogen molecule (N ₂ ), the high-speed electrons repel the electrons from the nitrogen molecule (N ₂ ).

The nitrogen molecules (N ₂ ) that have lost electrons become positive ions (N ₂ ⁺ ) and are attracted toward the counter electrode 320. Note that, because the positive ions (N ₂ ⁺ ) are unstable, they steal electrons from nearby water molecules and return to stable nitrogen molecules (N ₂ ).

Meanwhile, the electrons ejected from the nitrogen molecules (N ₂ ) bond with nearby oxygen molecules (O ₂ ), as shown in (d) of Figure 5. The negative ions (O ₂ ^- ) generated by bonding with the electrons are attracted to the discharge electrode 310 along the electric field. These negative ions negatively charge fine particles such as dust.

In this manner, in this embodiment, a voltage of a first polarity (e.g., "positive") is applied to the discharge electrode 310, causing a corona discharge near the discharge electrode 310. As a result, ions of the first polarity are generated near the discharge electrode 310, and dielectric breakdown occurs in the coating portion 322 of the counter electrode 320, causing intermittent pulsed discharges accompanied by a large discharge current from the counter electrode 320.

This results in a large amount of ions of the second polarity (e.g., "negative") being generated on the side of the opposing electrode 320.

Based on the above experiments and other considerations, it has been found that by using ions generated near the counter electrode 320 of the charging unit 3, it is possible to provide an electrostatic precipitator 2 that can improve the amount of charge applied to dust and charging efficiency (the amount of charge obtained relative to the power consumed by the discharge device) compared to conventional devices. Furthermore, it is expected that ozone generation will also be suppressed.

Figure 6 is an enlarged cross-sectional view showing the configuration of the counter electrode 320 in a reference example. In this reference example, the counter electrode 320 does not have a second member 324, and the covering portion 322 is composed only of a first member 323 formed from a dielectric material containing an organic substance.

As shown in FIG. 6 , a hole 325 is formed in a predetermined location on the first member 323. This hole 325 exposes the exposed surface 321b, which is part of the surface 321a of the conductive portion 321, to the air by not covering the exposed surface 321b. For example, the hole 325 is formed so as to penetrate the first member 323 in the thickness direction, and in this example, functions as a discharge path 327 for discharge caused by dielectric breakdown of the air layer in the covering portion 322. The first member 323 may have one or more holes 325 formed.

The formation of the hole 325 in the first member 323 forms a triple boundary 326 in the opposing electrode 320, which is the boundary between the conductive portion 321, the dielectric covering portion 322 (first member 323), and the air layer above the hole 325 (discharge path 327). The triple boundary 326 here refers to the boundary where three materials with different properties are adjacent to each other. For example, if the hole 325 in the first member 323 is cylindrical, the triple boundary 326 is formed in a circular shape along the inner periphery of the hole 325. The covering portion 322 (first member 323) is prone to deterioration near this triple boundary 326. The reason for this is explained below.

As shown in Figure 5(a), for example, when a positive DC voltage of a predetermined magnitude is applied to the discharge electrode 310, corona discharge generates positive ions (positively charged ions) near the discharge electrode 310, which are attracted toward the counter electrode 320.

As a result, as shown in Figure 6, positive ions accumulate on the surface 323a of the covering portion 322 (first member 323) of the counter electrode 320. At this time, electrons attracted by the positive ions are unevenly distributed near the covering portion 322 of the conductive portion 321 of the counter electrode 320, and a potential difference (voltage) occurs between the surface 323a of the first member 323 and the surface 321a of the conductive portion 321.

When this potential difference reaches a certain level, dielectric breakdown occurs, and as shown in Figure 5(c), a discharge phenomenon occurs in which electrons fly out at high speed from inside the conductive portion 321 of the opposing electrode 320.

In this discharge phenomenon, electrons unevenly distributed near the surface 321a of the conductive portion 321 move at high speed toward the surface 323a of the covering portion 322 (first member 323) via the discharge path 327. In Figure 6, the flow of electrons associated with the discharge is represented by arrows. The discharge path P of this discharge occurs along the interface between the air in the discharge path 327 and the covering portion 322 facing the discharge path 327 (the inner surface of the hole 325 of the first member 323). It is presumed that this discharge originates from the triple boundary 326, which is the boundary between the exposed surface 321b of the conductive portion 321, which is a conductor, the first member 323, which is a dielectric, and the air layer present above the hole 325 (discharge path 327).

Electrons (negative charges) unevenly distributed on the surface 321a of the conductive portion 321 are accelerated by the electric field near the discharge path 327, causing a discharge accompanied by dielectric breakdown of the air layer in the hole 325 (discharge path 327). The strength of the electric field accelerating the charges is greatest at the triple boundary 326, which is the boundary between the air layer, the dielectric, and the conductor. Therefore, in the reference example of Figure 6, it is believed that the discharge originates from the triple boundary 326, where the electric field is at its maximum. As a result, there is a risk that the first member 323, which is made of a dielectric containing organic matter, will deteriorate near the triple boundary 326, where the energy density becomes high and the temperature becomes high.

In this embodiment, therefore, as shown in Figure 7, the triple boundary 326, which is the starting point of discharge, is covered with a second member 324. Figure 7 is an enlarged cross-sectional view showing the configuration of the opposing electrode 320 according to this embodiment.

The second member 324 is arranged in a tubular (e.g., cylindrical) shape along the inner circumferential surface of the columnar (e.g., cylindrical) hole 325. That is, one end of the second member 324 reaches the surface 321a of the conductive portion 321 and covers the triple boundary 326, and the other end reaches the surface 323a of the first member 323.

Furthermore, since the second member 324 is cylindrical, a columnar (e.g., cylindrical) discharge path 327 is formed that penetrates between the upper and lower ends of the second member 324.

Here, because the second member 324 is made of an inorganic dielectric (insulator) that does not contain carbon atoms, even if the second member 324 arranged along the discharge path 327 becomes hot due to discharge, the second member 324 itself will not bond with oxygen atoms and become carbonized. In this way, by covering the triple boundary 326, which is the starting point of discharge due to the electric field being maximized, with the second member 324 made of an inorganic dielectric, even if ions are emitted with high energy near the triple boundary 326 and become hot, the part of the coating 322 that becomes the starting point of discharge will not bond with oxygen and change its composition, and deterioration of the coating 322 can be prevented.

According to this embodiment, the second member 324 covers at least the inner edge portion 328 of the contact surface 321c between the conductive portion 321 and the first member 323, which contacts the inner edge of the hole 325 of the first member 323. This prevents the triple boundary 326, where the electric field is maximized, from being exposed on the discharge path 327, preventing deterioration of the covering portion 322 that covers the opposing electrode 320. Furthermore, preventing deterioration of the covering portion 322 allows stable charging in the charging unit 3, and suppresses deterioration over time in the charging efficiency of the charging unit 3 (the amount of charge obtained relative to the power consumed by the discharge device).

Furthermore, in the embodiment, the covering portion 322 is composed of a second member 324 formed from an inorganic dielectric (insulator) and a first member 323 formed from a dielectric containing an organic material, thereby suppressing increases in weight and cost compared to when the entire covering portion 322 is formed from an inorganic material.

In other words, according to this embodiment, by configuring the covering portion 322 using different types of dielectrics (insulators), namely the first member 323 and the second member 324, it is possible to prevent deterioration of the covering portion 322 while suppressing increases in weight and cost that would otherwise be caused by providing such a covering portion 322.

In addition, in an embodiment, the second member 324 may be formed as an annular (cylindrical) member that is arranged along the inner circumferential surface of the hole 325. This prevents the first member 323 from being exposed across the entire inner circumferential surface of the hole 325, thereby more effectively preventing deterioration of the covering portion 322 that covers the counter electrode 320.

In addition, in the embodiment, the discharge path 327 is preferably formed inside the second member 324. This allows the discharge phenomenon at the covering portion 322 of the opposing electrode 320 shown in Figure 5 and other figures to occur inside the second member 324, which is made of an inorganic material. Therefore, according to the embodiment, it is possible to prevent the triple boundary 326 from being located on the discharge path P between the conductive portion 321 and the surface 323a of the covering portion 322, further suppressing deterioration of the covering portion 322.

In the above embodiment, an example was shown in which the second member 324 was cylindrical and the hole 325 (discharge path 327) of the first member 323 was columnar, but the present disclosure is not limited to this example. For example, the hole 325 of the first member 323 may be a square prism, and the second member 324 may be a square tube.

It is also preferable that the first member 323 be made of resin and the second member 324 be made of ceramic. Generally, the specific gravity of resin is smaller than that of ceramic, and resin is also cheaper than ceramic. This effectively prevents deterioration of the covering portion 322 while minimizing the increase in weight and cost that would result from providing such a covering portion 322.

<Modification>
Next, a modified example of the embodiment will be described with reference to Fig. 8. Fig. 8 is an enlarged cross-sectional view showing the configuration of a counter electrode 320 according to the modified example of the embodiment, and corresponds to Fig. 7 of the embodiment.

As shown in Figure 8, in this modified example, the shapes of the hole 325 and the second member 324 differ from those of the above-described embodiment. Specifically, the hole 325 in this modified example has a shape in which the inner diameter is wider on the surface 321a side of the conductive portion 321 than on the surface 323a side of the first member 323.

In this modified example, an annular (e.g., circular) second member 324 is disposed so as to be embedded in the widened portion of the hole 325. In other words, in this modified example, the second member 324 is disposed only on the bottom side of the inner circumferential surface of the hole 325.

Even with this configuration, as shown in Figure 8, the inner edge 328 (triple boundary 326) where the electric field is at its maximum can be covered by the second member 324 made of an inorganic material. This prevents the location of the discharge initiation point in the covering portion 322 from combining with oxygen and changing its composition, even if ions are emitted with high energy near the triple boundary 326, resulting in high temperatures, and prevents deterioration of the covering portion 322.

Therefore, according to this modified example, deterioration of the covering portion 322 that covers the counter electrode 320 can be prevented.

In addition, in this modified example, the second member 324 is positioned only on the bottom side of the inner circumferential surface of the hole 325, thereby minimizing the increase in weight and cost that would result from providing this second member 324.

The above describes the embodiments of the present application based on the drawings, but these are merely examples, and various modifications and improvements can be made based on the knowledge of those skilled in the art.

The above-described embodiments can realize the discharge device and electrostatic precipitator 2 shown below. Note that the discharge device described below corresponds to the charging unit 3 in the electrostatic precipitator 2.

(1) A discharge device comprising: a discharge electrode (310); an opposing electrode (320) disposed opposite the discharge electrode (310); and a voltage application unit (high-voltage power supply for charging unit (30)) that applies a voltage to the discharge electrode (310). The opposing electrode (320) has a conductive portion (321) formed of a conductor and a covering portion (322) formed of a dielectric and covering the surface (321a) of the conductive portion (321). The covering portion (322) has a first member (323) formed of a dielectric containing an organic substance and a second member (324) formed of an inorganic substance. The first member (323) has a hole (325) that exposes the surface (321a) of the conductive portion (321). The second member (324) covers at least an inner edge (328) of the contact surface (321c) between the conductive portion (321) and the first member (323) that contacts the inner edge of the hole (325) of the first member (323).

This configuration prevents deterioration of the covering portion 322 that covers the counter electrode 320.

(2) In the above (1), the second member 324 is a discharge device that is an annular member arranged along the inner circumferential surface of the hole 325 of the first member 323.

In addition to the effect of (1) above, this configuration further prevents deterioration of the covering portion 322 that covers the counter electrode 320.

(3) In the above (1) or (2), the second member 324 is a discharge device arranged to cover the triple boundary 326, which is the boundary between the conductive portion 321, the first member 323, and the air layer present in the hole 325.

In addition to the effects (1) and (2) above, this configuration more reliably prevents deterioration of the covering portion 322 that covers the counter electrode 320.

(4) In any one of (1) to (3) above, the second member 324 is formed with a discharge path 327 through which electric charge passes when insulation breaks down in the air layer in the covering portion 322.

This configuration not only achieves one of the effects (1) to (3) above, but also further improves the charging efficiency in the charging unit 3.

(5) In any one of (1) to (4) above, the discharge device is such that the first member 323 is made of resin and the second member 324 is made of ceramic.

This configuration not only achieves one of the effects (1) to (4) above, but also reduces the increase in weight and cost that would otherwise be caused by providing the covering portion 322.

(6) An electrostatic precipitator (2) comprising a discharge device (charging unit (3)) according to any one of (1) to (5) above, and a dust collector (dust collection unit (4)) that collects dust in the air that has been charged by the discharge device (charging unit (3)).

This configuration makes it possible to provide an electrostatic precipitator 2 that achieves any one of the effects (1) to (5) above.

The above-described embodiment and the specific names, processes, controls, and various data shown in the figures are merely examples and may be changed as appropriate. For example, in the above-described embodiment, resin was used as the material for the first member 323, and ceramic was used as the material for the second member 324. However, the materials for the first member 323 and the second member 324 are not limited to this example. The first member 323 may be made of any material as long as at least a portion of the material contains an organic substance. In other words, the first member 323 does not have to be made solely from organic substances, but may also be made of a dielectric (insulator) that is a mixture of organic and inorganic substances. Furthermore, the second member 324 may be made of an inorganic substance that does not contain organic substances, or may be made of a dielectric (insulator) that is a mixture of multiple inorganic substances.

Furthermore, the broader aspects of the above-described embodiments are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general invention as defined by the appended claims and their equivalents.

2. Electrostatic precipitator (an example of a dust collector)
3. Charging unit (an example of a discharge device)
4 Dust collection unit 30 High-voltage power supply for charging unit (an example of a voltage application unit)
310 Discharge electrode 320 Counter electrode 321 Conductive portion 321a Surface 321c Contact surface 322 Covering portion 323 First member 324 Second member 325 Hole portion 326 Triple boundary 327 Discharge path 328 Inner edge portion

Claims (6)

A discharge electrode;
a counter electrode disposed opposite the discharge electrode;
a voltage application unit that applies a voltage to the discharge electrode;
Equipped with
The counter electrode is
a conductive portion formed of a conductor;
a covering portion formed of a dielectric material and covering a surface of the conductive portion;
and
The covering portion is
a first member formed of a dielectric material containing an organic substance;
a second member formed of an inorganic material;
and
the first member has a hole that exposes a surface of the conductive portion,
The second member covers at least an inner edge portion of a contact surface between the conductive portion and the first member, the inner edge portion contacting an inner edge of a hole of the first member. The discharge device according to claim 1 , wherein the second member is an annular member that is disposed along an inner circumferential surface of the hole of the first member. The discharge device according to claim 1 or 2, wherein the second member is arranged so as to cover a triple boundary which is a boundary between the conductive portion, the first member, and an air layer present in the hole. The discharge device according to any one of claims 1 to 3, wherein the second member is formed with a discharge path through which electric charges pass when an air layer in the covering portion breaks down. 5. The discharge device according to claim 1, wherein the first member is made of resin, and the second member is made of ceramic. The discharge device according to any one of claims 1 to 5,
a dust collector that collects dust in the air that has been charged by the discharge device;
An electrostatic precipitator comprising: