Discharge device and electrostatic precipitator

Abstract

To provide a discharge device capable of preventing an insulator covering a counter electrode from deteriorating, and an electrical dust collector.SOLUTION: A discharge device comprises a discharge electrode (310), a counter electrode (320) arranged opposite the discharge electrode (310), and a voltage application part applying a voltage to the discharge electrode (310). The counter electrode (310) has a conductive part (321) formed of a conductor, and a coating part (322) formed of a dielectric and covering a surface (321a) of the conductive part (321). The coating part (322) has a first member (323) formed of a dielectric including organic material and a second member (324) formed of inorganic material. The first member (323) comprises a hole part (325) exposing the surface (321a) of the conductive part (321), and the second member (324) covers an inner edge part (328), contacting an inner edge of the hole part (325) of the first member (323), of a contact surface (321a) between the conductive part (321) and first member (323).SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] Conventionally, an example of an electric dust collector is known that includes a discharge device having a discharge electrode and a counter electrode that is arranged in a pair with the discharge electrode, and the surface of the counter electrode in the discharge device is coated with an insulator (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2001 / 064349 [Patent Document 2] Japanese Patent Publication No. 2020-146605 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors of the present application have found that when a counter electrode coated with an insulator is used, if a voltage within a predetermined range is applied to the discharge electrode, pulsed discharge occurs intermittently from the counter electrode side (see Patent Document 2).

[0005] However, since pulsed discharge occurs 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 pulsed discharge with a high instantaneous energy density. Therefore, in order to utilize the phenomenon in which pulsed discharge occurs from the counter electrode side covered with an insulator in a discharge device or an electrostatic precipitator using the same, it was necessary to prevent deterioration of the insulator covering the counter electrode.

[0006] The disclosed technology has been made in view of the above, and aims to provide a discharge device and an electric dust collector that can prevent deterioration of the insulator that covers the counter electrode. [Means for solving the problem]

[0007] One aspect of the discharge device disclosed in the present application includes 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 includes 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 includes a first member formed of a dielectric containing an organic material and a second member formed of an inorganic material. The first member includes 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 of the first member. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to prevent deterioration of the insulator covering the counter electrode. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of an air purifier provided with a discharge device according to an embodiment and an electric dust collector equipped with the discharge device. [Figure 2] FIG. 2 is a configuration diagram of an electric dust collector according to an embodiment. [Figure 3] FIG. 3 is a schematic diagram showing a discharge electrode and a counter electrode of the charging unit according to the embodiment. [Figure 4] FIG. 4 is a diagram showing the waveform of the discharge current in the charge section according to the embodiment. [Figure 5] 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. [Figure 6] FIG. 6 is an enlarged cross-sectional view showing the configuration of the counter electrode in the reference example. [Figure 7] FIG. 7 is an enlarged cross-sectional view showing the configuration of the counter electrode according to the embodiment. [Figure 8] FIG. 8 is an enlarged cross-sectional view showing the configuration of a counter electrode according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the discharge device and the electrostatic precipitator disclosed in the present application will be described in detail with reference to the drawings. Note that the discharge device and the electrostatic precipitator disclosed in the present application are not limited to the following embodiments.

[0011] Furthermore, the components in the following description include those that are easily replaceable by those skilled in the art, or those that are substantially the same, or so-called equivalents. Note that the same elements will be denoted by the same reference numerals throughout the description of the embodiments.

[0012] In the following embodiment, the discharge device according to the disclosed technology is applied to an electric dust collector provided in an air purifier. However, the present invention 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.

[0013] <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.

[0014] As shown in Fig. 1, air purifier 1 includes a housing 10 that houses devices for purifying air. Housing 10 is formed, for example, in the shape of a rectangular parallelepiped and made of synthetic resin. Housing 10 is formed with an intake port 11 that draws in indoor air and an outlet port 12 that blows purified air into the room.

[0015] 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 collecting device. The pre-filter 14 removes large dust particles from the sucked air. The multiple electrostatic precipitators 2 collect dust particles in the air that has passed through the pre-filter 14 by electrostatic force. The deodorizing filter 5 deodorizes the air that has passed through the electrostatic precipitator 2.

[0016] 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.

[0017] 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 that passes through it. The dust collecting unit 4 collects the fine particles charged by the charging unit 3 using electrostatic force.

[0018] In this embodiment, three electrostatic precipitators 2 are arranged inside the housing 10, but the number of electrostatic precipitators to be arranged is not limited in any way.

[0019] The deodorizing filter 5 performs deodorizing treatment by using a catalytic filter to remove 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 pre-filter 14 and the electrostatic precipitator 2.

[0020] 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 disposed downstream of the deodorizing filter 5. The fan motor 61 rotates the fan 6.

[0021] The control board 7 controls the air purifier 1. The dust sensor 13 detects the dust concentration in the air sucked through the suction port 11. The operation and display board 15 performs, for example, an operation to start or stop the operation.

[0022] Also, the housing 10 is provided with a single constant voltage high-voltage power supply unit for the dust collection unit (hereinafter referred to as "high-voltage power supply 40 for dust collection unit") that supplies power to each dust collection unit 4 of each electric dust collector 2.

[0023] On the other hand, a constant current high voltage power supply unit for the charging unit (hereinafter referred to as "high voltage power supply for charging unit 30") that supplies power to the charging unit 3 is disposed in each of the three charging units 3. Such high voltage power supply for charging unit 30 is an example of a voltage application unit.

[0024] The air purifier 1 having such a configuration draws indoor air through the intake port 11 as shown by the arrow f by the rotation of the fan 6 driven by the fan motor 61, purifies the air as it passes through the pre-filter 14, the electrostatic precipitator 2 and the deodorizing filter 5, and blows the purified air into the room through the outlet port 12.

[0025] The air volume setting of 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 of the dust sensor 13, for example.

[0026] <Configuration of an electrostatic precipitator> Next, the configuration of an electric dust collector 2 equipped with 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.

[0027] 2, the electrostatic precipitator 2 includes a charging unit 3 and a dust collecting unit 4. The charging unit 3 includes a discharge electrode 310 and a counter electrode 320.

[0028] The discharge electrode 310 is a wire-like electrode. The counter electrode 320 is a flat electrode having a polarity different from that of the discharge electrode 310. In the charging unit 3, a plurality of discharge electrodes 310 and a plurality of counter electrodes 320 are alternately arranged at predetermined intervals.

[0029] The particulate 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 particulate collection unit 4, the electrode having the same polarity as the discharge electrode 310 is referred to as the "high-voltage electrode 410," and the electrode having the same polarity as the counter electrode 320 is referred to as the "collection electrode 420."

[0030] 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 is supplied with 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 FIG. 1) via the charging unit switches 301, 302, and 303. The counter electrode 320 of the charging unit 3 is grounded.

[0031] A high voltage is applied to the high-voltage electrode 410 of the dust collecting unit 4 by the dust collecting unit high-voltage power supply 40. Power is supplied to the dust collecting unit high-voltage power supply 40 from the power supply 50 via the power supply unit 55, and the dust collecting unit high-voltage power supply 40 is driven and controlled by the control unit 70 mounted on the control board 7 via the dust collecting unit switch 401. The collection electrode 420 of the dust collecting unit 4 is grounded (earthed).

[0032] 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 of the dust collecting units 4 are connected in parallel. Note that there is no particular limitation on the number of high-voltage power supplies 30 for the charging unit and the number of high-voltage power supplies 40 for the dust collecting unit.

[0033] <Charging section configuration> 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 a discharge electrode 310 and a counter electrode 320 of the charge unit 3 according to the embodiment.

[0034] The discharge electrode 310 is formed in a wire shape, and a cross section of the wire-shaped discharge electrode 310 is visible in Fig. 3. Note that the discharge electrode 310 may be formed in any shape as long as at least a portion thereof is thin or sharp, and may be formed in a needle shape instead of a wire shape, for example.

[0035] 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 of a conductor, for example, stainless steel such as SUS304.

[0036] Covering portion 322 is formed of a dielectric material and covers the entire surface 321a of conductive portion 321. Covering portion 322 also has a first member 323 and a second member 324.

[0037] The first member 323 is made of a dielectric material containing an organic substance. The first member 323 is made of, for example, 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, about 1 mm.

[0038] The second member 324 is made of an inorganic material, such as a ceramic material such as alumina.

[0039] The counter electrode 320, in which the surface 321a of the conductive portion 321 is covered with the covering portion 322 having such a configuration, can suppress the discharge current between the counter electrode 320 and the discharge electrode 310, and therefore can also suppress the generation of ozone.

[0040] 4 is a diagram showing the waveform of the discharge current in the charging unit 3 according to the embodiment. As shown in FIG. 4, it can be seen that intermittent pulses with large discharge current values appear among many continuous pulses with small discharge current values.

[0041] The continuous pulses with small discharge current values indicate discharge 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 caused by so-called burst pulse corona discharge.

[0042] On the other hand, a pulse with a large discharge current value indicates a discharge caused by a charge generated near the counter electrode 320 and having a polarity opposite to that of the voltage applied to the discharge electrode 310 (negative polarity in this embodiment).

[0043] From the results of this experiment, it was found 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.

[0044] Here, we will explain the mechanism by which a pulsed intermittent discharge current is generated from the counter electrode 320. Figure 5 is an explanatory diagram showing the process by which a pulsed current having a polarity opposite to that of the applied voltage is generated due to dielectric breakdown in the counter electrode 320 in the charging unit 3 according to this embodiment.

[0045] As shown in (a) of Figure 5, for example, when a positive DC voltage of a predetermined magnitude is applied to the discharge electrode 310, corona discharge causes positive ions (ions of positive polarity) to be generated near the discharge electrode 310 and attracted toward the counter electrode 320.

[0046] 5(b), positive ions are accumulated on the surface of the covering portion 322 of the counter electrode 320. At this time, electrons are unevenly distributed in the vicinity of the covering portion 322 of the conductive portion 321 of the counter electrode 320, and a potential difference (voltage) is generated between the surface of the covering portion 322 and the vicinity of the covering portion 322 of the conductive portion 321.

[0047] As the charge further accumulates, 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 counter electrode 320, as shown in Figure 5(c).

[0048] At this time, if a discharge path 327 (see FIG. 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.

[0049] That is, a phenomenon occurs in which a pulsed discharge current is intermittently generated from the counter electrode 320 due to the accumulation of charge on the surface of the covering portion 322. In this case, the discharge state is considered 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.

[0050] 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 (N2) that are present in abundance in the air. Then, as they collide with each nitrogen molecule (N2), the high-speed electrons repel the electrons from the nitrogen molecule (N2).

[0051] Nitrogen molecules (N2) that have lost electrons become positive ions (N2 + ) and are attracted to the counter electrode 320. + ) is unstable, so it steals an electron from a nearby water molecule and returns to a stable nitrogen molecule (N2).

[0052] On the other hand, the electrons that are ejected from the nitrogen molecules (N2) bond with nearby oxygen molecules (O2), as shown in Figure 5(d). The negative ions (O2 - ) are attracted along the electric field to the discharge electrode 310. These negative ions negatively charge fine particles such as dust.

[0053] As described above, in this embodiment, a voltage of a first polarity (e.g., "positive") is applied to the discharge electrode 310 to generate 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 covering portion 322 of the counter electrode 320, causing intermittent pulsed discharge accompanied by a large discharge current from the counter electrode 320.

[0054] This results in a large amount of ions of the second polarity (for example, "negative") being generated on the counter electrode 320 side.

[0055] Considering the above-mentioned experiments, it is possible to provide an electrostatic precipitator 2 that can improve the amount of charge applied to dust and charging efficiency (amount of charge obtained relative to the power consumed by the discharge device) compared to conventional devices by using ions generated near the counter electrode 320 of the charging unit 3. Moreover, it is expected that the generation of ozone will also be suppressed.

[0056] 6 is an enlarged cross-sectional view showing the configuration of a reference example of a counter electrode 320. 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 of a dielectric material containing an organic substance.

[0057] 6, hole 325 is formed in a predetermined location of first member 323. By not covering exposed surface 321b, which is part of surface 321a of conductive portion 321, hole 325 exposes exposed surface 321b to the air. For example, hole 325 is formed so as to penetrate first member 323 in the thickness direction, and in this reference example, functions as discharge path 327 for discharge accompanying dielectric breakdown of the air layer in covering portion 322. Note that there may be one or more hole 325 formed in first member 323.

[0058] Then, by forming the hole 325 in the first member 323, a triple boundary 326 is formed in the counter electrode 320, which is a boundary between the conductive portion 321, the dielectric covering portion 322 (first member 323), and the air layer present above the hole 325 (discharge path 327). Here, the triple boundary 326 refers to a boundary where three substances with different properties are adjacent to each other. For example, if the hole 325 of the first member 323 is formed in a cylindrical shape, 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 will be explained below.

[0059] As shown in (a) of Figure 5, for example, when a positive DC voltage of a predetermined magnitude is applied to the discharge electrode 310, corona discharge causes positive ions (ions of positive polarity, positive charge) to be generated near the discharge electrode 310 and attracted toward the counter electrode 320.

[0060] 6, positive ions are accumulated on surface 323a of covering portion 322 (first member 323) of counter electrode 320. At this time, electrons attracted by the positive ions are unevenly distributed in the vicinity of covering portion 322 of conductive portion 321 of counter electrode 320, and a potential difference (voltage) is generated between surface 323a of first member 323 and surface 321a of conductive portion 321.

[0061] When this potential difference reaches a certain level, dielectric breakdown occurs, and as shown in FIG. 5(c), a discharge phenomenon occurs in which electrons fly out at high speed from inside the conductive portion 321 of the counter electrode 320.

[0062] 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 FIG. 6, the flow of electrons accompanying 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 circumferential surface of the hole 325 of the first member 323). It is estimated 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).

[0063] 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 strongest at the triple boundary 326, which is the boundary between the air layer, the dielectric, and the conductor. Therefore, in the reference example of FIG. 6, it is considered that the discharge originates from the triple boundary 326, where the electric field is maximized. Therefore, there is a risk that the first member 323, which is made of a dielectric containing an organic substance, may deteriorate near the triple boundary 326, where the energy density becomes high and the temperature becomes high.

[0064] Therefore, in this embodiment, as shown in Fig. 7, the triple boundary 326, which is the starting point of discharge, is covered with a second member 324. Fig. 7 is an enlarged cross-sectional view showing the configuration of the counter electrode 320 according to this embodiment.

[0065] 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 to cover the triple boundary 326, and the other end reaches the surface 323a of the first member 323.

[0066] Furthermore, since the second member 324 is cylindrical, a columnar (for example, cylindrical) discharge path 327 is formed that penetrates the second member 324 between its upper and lower ends.

[0067] Here, because second member 324 is made of an inorganic dielectric (insulator) that does not contain carbon atoms, even if second member 324 arranged along discharge path 327 becomes hot due to discharge, second member 324 itself will not bond with oxygen atoms and be carbonized. In this way, by covering triple boundary 326, which is the starting point of discharge due to the electric field being maximized, with second member 324 made of an inorganic dielectric, even if ions are emitted with high energy near triple boundary 326 and become hot, it is possible to prevent the part of covering portion 322 that becomes the starting point of discharge from bonding with oxygen and changing its composition, and it is possible to prevent deterioration of covering portion 322.

[0068] Therefore, according to the 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, the inner edge portion 328 being in contact with 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, thereby preventing deterioration of the covering portion 322 that covers the counter electrode 320. Furthermore, by preventing deterioration of the covering portion 322, stable charging can be performed in the charging unit 3, and 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) can be suppressed.

[0069] Furthermore, in the embodiment, the covering portion 322 is composed of a second member 324 formed of an inorganic dielectric (insulator) and a first member 323 formed of a dielectric containing an organic substance, thereby making it possible to suppress increases in weight and cost compared to when the entire covering portion 322 is formed of an inorganic substance.

[0070] That is, according to the embodiment, by constructing the covering portion 322 from different types of dielectrics (insulators), that is, 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 due to the provision of such covering portion 322.

[0071] In addition, in the 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 over 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.

[0072] In addition, in the embodiment, it is preferable that the discharge path 327 is formed inside the second member 324. This allows the discharge phenomenon at the covering portion 322 of the counter electrode 320 shown in FIG. 5 and other figures to occur inside the second member 324 formed 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, and it is possible to further suppress deterioration of the covering portion 322.

[0073] In the above embodiment, an example has been described in which the second member 324 is cylindrical and the hole 325 (discharge path 327) of the first member 323 is columnar, but the present disclosure is not limited to such an example. For example, the hole 325 of the first member 323 may be a square pillar, and the second member 324 may be a square tube.

[0074] Preferably, first member 323 is made of resin, and second member 324 is 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 covering portion 322, while suppressing increases in weight and cost due to the provision of covering portion 322.

[0075] <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.

[0076] 8, in this modification, the shapes of hole 325 and second member 324 are different from those of the above-described embodiment. Specifically, hole 325 according to the modification has a shape in which the inner diameter is wider on the side of surface 321a of conductive portion 321 than on the side of surface 323a of first member 323.

[0077] In the modified example, an annular (for example, circular) second member 324 is disposed so as to be embedded in the widened portion of hole 325. That is, in the modified example, second member 324 is disposed only on the bottom side of the inner circumferential surface of hole 325.

[0078] Even with this configuration, as shown in Fig. 8, inner edge 328 (triple boundary 326) where the electric field is at its maximum can be covered by second member 324 made of an inorganic material. This prevents the location of the discharge starting point in covering portion 322 from bonding with oxygen and changing its composition, even if ions are emitted with high energy near triple boundary 326 and the temperature rises. This prevents deterioration of covering portion 322.

[0079] Therefore, according to this modification, deterioration of the covering portion 322 that covers the counter electrode 320 can be prevented.

[0080] Furthermore, in this modification, second member 324 is disposed only on the bottom side of the inner circumferential surface of hole 325, and therefore, increases in weight and costs due to the provision of second member 324 can be suppressed.

[0081] Although the embodiments of the present invention have been described above with reference to the drawings, they are merely examples, and various modifications and improvements can be made based on the knowledge of those skilled in the art.

[0082] The above-described embodiments can realize the following discharge device and electrostatic precipitator 2. The discharge device described below corresponds to the charging unit 3 in the electrostatic precipitator 2.

[0083] (1) A discharge device comprising: a discharge electrode (310); an opposing electrode (320) arranged opposite the discharge electrode (310); and a voltage application unit (high-voltage power supply (30) for a charging unit) 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 a surface (321 a) 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 (321 a) of the conductive portion (321); and the second member (324) covers at least an inner edge portion (328) of a contact surface (321 c) between the conductive portion (321) and the first member (323) that contacts the inner edge of the hole (325) of the first member (323).

[0084] With this configuration, deterioration of the covering portion 322 that covers the counter electrode 320 can be prevented.

[0085] (2) In the above (1), the second member 324 is a discharge device that is an annular member that is arranged along the inner circumferential surface of the hole 325 of the first member 323.

[0086] In addition to the effect (1) above, this configuration can further prevent deterioration of the covering portion 322 that covers the counter electrode 320.

[0087] (3) In the above (1) or (2), the second member (324) is arranged so as 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).

[0088] With this configuration, in addition to the above-mentioned effects (1) and (2), deterioration of the covering portion 322 that covers the counter electrode 320 can be more reliably prevented.

[0089] (4) In any one of the above (1) to (3), the second member (324) is formed with a discharge path (327) through which electric charges pass when an air layer in the covering portion (322) breaks down.

[0090] With this configuration, in addition to any one of the effects (1) to (3) above, the charging efficiency in the charging section 3 can be further improved.

[0091] (5) In any one of the above (1) to (4), the discharge device is such that the first member 323 is made of resin and the second member 324 is made of ceramic.

[0092] With this configuration, in addition to achieving any one of the effects (1) to (4) above, it is possible to suppress increases in weight and costs due to the provision of the covering portion 322.

[0093] (6) An electric dust collector 2 including a discharge device (charging unit 3) of any one of (1) to (5) above, and a dust collecting device (dust collecting unit 4) that collects dust in the air that has been charged by the discharge device (charging unit 3).

[0094] With this configuration, it is possible to provide an electrostatic precipitator 2 that achieves any one of the effects (1) to (5) above.

[0095] The above-described embodiment and the specific names, processes, controls, various data, etc. shown in the drawings are merely examples and may be changed as appropriate. For example, in the above-described embodiment, resin is used as the material for the first member 323, and ceramic is 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 such examples. The first member 323 may contain at least a portion of an organic material. In other words, the first member 323 is not limited to being formed using only organic materials, but may also be formed using a dielectric (insulator) that is a mixture of organic and inorganic materials. Furthermore, the second member 324 may be formed using an inorganic material that does not contain organic materials, or may be formed using a dielectric (insulator) that is a mixture of multiple inorganic materials.

[0096] 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 equivalents thereof. [Explanation of symbols]

[0097] 2. Electrostatic precipitator (an example of a dust collector) 3. Charging unit (an example of a discharge device) 4 Dust collection section 30 High-voltage power supply for charging unit (an example of a voltage application unit) 310 Discharge electrode 320 Counter electrode 321 Conductive part 321a surface 321c contact surface 322 Covering part 323 First member 324 Second member 325 Hole 326 Triple Boundary 327 Discharge Path 328 Inner edge

Claims

1. 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 portion of the first member. Discharge device.

2. The second member is an annular member that is disposed along the inner circumferential surface of the hole of the first member. The discharge device according to claim 1 .

3. The second member is disposed 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.

3. The discharge device according to claim 1 or 2.

4. The second member has a discharge path through which electric charges pass when an air layer in the covering portion breaks down. The discharge device according to any one of claims 1 to 3.

5. 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 4.

6. 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:

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