JP2020151654A - Charging device, and air cleaner provided with the charging device - Google Patents

Abstract

To provide a charging device which suppresses an increase in the size of the device while simultaneously achieving both a charging function and an ozone generating function, and can increase a concentration of generated ozone.SOLUTION: A charging device includes: a discharge electrode having a passive-state film formed thereon; a charging part having a counter electrode arranged so as to face the discharge electrode; a control part which controls energization to the discharge electrode; and a humidity detection part which detects the humidity. The control part performs such a control that when the humidity detected by the humidity detection part is equal to or lower than a predetermined humidity, a temperature of the discharge electrode is set to be equal to or higher than a predetermined temperature by energization to the discharge electrode.SELECTED DRAWING: Figure 5

Description

The present invention relates to a charging device and an air purifier including the charging device.

Conventionally, there is known an electrostatic precipitator capable of having both a charging function of charging fine particles such as dust by discharging from a discharge electrode and an ozone generating function of generating ozone (see, for example, Patent Document 1). .. In addition, in order to obtain high charge efficiency and high ozone generation efficiency with one device, a positive high voltage is applied to the discharge electrode when charging, while a negative high voltage is applied to the discharge electrode when generating ozone. Some are designed to apply a voltage (see, for example, Patent Document 2). Further, there is a case in which an ozone generating part that generates ozone by applying a negative voltage and a charged part that is charged by applying a positive high voltage are arranged in one unit (for example, Patent Document 3). reference).

JP-A-2002-286240 Japanese Unexamined Patent Publication No. 4-78456 Japanese Unexamined Patent Publication No. 2008-284412

However, in Patent Document 1, ozone is generated as a by-product of electric discharge for charging dust, and the generated ozone concentration is lowered. Further, since the apparatus of Patent Document 2 can apply only a high voltage of one of the polarities at a time, the charging efficiency and the ozone generation efficiency cannot be increased at the same time. Further, in Patent Document 3, although both the charging efficiency and the ozone generation efficiency can be increased at the same time, an ozone generating part, a charging part, a positive voltage supply part and a negative voltage supply part are required, and the device is large. It invites the change.

The disclosed technique has been made in view of the above, and provides an air purifier including a charging device and a charging device capable of suppressing an increase in size of the device while simultaneously increasing the charging efficiency and the ozone generation efficiency. The purpose is.

One aspect of the charging device disclosed in the present application is a control that controls energization of a discharge electrode having a static coating formed on its surface, a charged portion having a counter electrode arranged to face the discharge electrode, and energization of the discharge electrode. A unit and a humidity detection unit for detecting humidity are provided. When the humidity detected by the humidity detection unit is equal to or lower than the predetermined humidity, the control unit controls the discharge electrode so as to raise the temperature of the discharge electrode to the predetermined temperature or higher by energizing the discharge electrode.

According to the charging device and one aspect of the air purifier including the charging device disclosed in the present application, it is possible to suppress the increase in size of the device while simultaneously increasing the charging efficiency and the ozone generation efficiency.

FIG. 1 is a schematic configuration diagram of an air purifier provided with an electrostatic precipitator including the charging device according to the embodiment. FIG. 2 is a block diagram of the same electrostatic precipitator. FIG. 3A is a front view of a discharge electrode plate of a charging device according to an embodiment of the same electrostatic precipitator. FIG. 3B is a plan view of the discharge electrode plate of the charged portion of the same. FIG. 3C is a side view of the same discharge electrode plate. FIG. 3D is an explanatory view showing the tip end portion of the discharge electrode of the same discharge electrode plate in a cross-sectional view. FIG. 4 is a block diagram mainly composed of a control unit included in the same electrostatic precipitator. FIG. 5 is a flowchart showing the control procedure of the electrostatic precipitator as described above. FIG. 6 is a graph showing the relationship between the shape of the discharge electrode and the ozone concentration in the charged portion of the electrostatic precipitator according to the embodiment. FIG. 7 is a graph showing the shape of the discharge electrode and the relationship between the relative humidity and the amount of ozone produced. FIG. 8 is a graph showing the relationship between relative humidity and ozone concentration over time. FIG. 9 is a graph showing the time change of the ozone concentration when the number of needles of the discharge electrode is 117. FIG. 10 is a graph showing the time change of the ozone concentration when the number of needles of the discharge electrode is 58. FIG. 11 is a graph showing the ozone concentration and humidity characteristics of the discharge electrode according to the reference example. FIG. 12 is a graph showing the relationship between the polarity of the high voltage applied to the discharge electrode and the amount of ozone generated over time.

Hereinafter, embodiments of the charging device and the air purifier disclosed in the present application will be described in detail with reference to the drawings. It should be noted that the following embodiments do not limit the structure and control method of the charging device and the air purifier disclosed in the present application. In addition, the components according to the following description include those that can be easily replaced by those skilled in the art, or those that are substantially the same, that is, those having a so-called equal range. The same elements will be described with the same reference numerals throughout the description of the embodiment. In the following embodiment, the case where the charging device according to the disclosed technique is applied to the electrostatic precipitator provided in the air purifier is shown. However, the present invention is not limited to this, and the charging device according to the disclosed technology can be applied to, for example, various devices capable of generating ozone by electric discharge.

FIG. 1 is a schematic configuration diagram of an air purifier provided with an electrostatic precipitator including the charging device according to the embodiment, and FIG. 2 is a configuration diagram of the electrostatic precipitator. As shown in FIG. 1, the air purifier 1 includes a housing 10 for accommodating devices for purifying air. The housing 10 is made of a synthetic resin material and is formed in a substantially rectangular parallelepiped shape, and a suction port 11 for sucking indoor air and an air outlet 12 for blowing clean air into the room are formed.

As shown in FIGS. 1 and 2, a prefilter 14 that removes large dust from the sucked air and a plurality of prefilters 14 that collect dust in the air that has passed through the prefilter 14 by electrostatic force are contained in the housing 10. The electrostatic precipitator 2 and the deodorizing filter 5 for deodorizing the air that has passed through the electrostatic precipitator 2 are provided.

The electrostatic precipitator 2 includes a charged unit 3 and a dust collecting unit 4, respectively. In this embodiment, the charging unit 3 functions as a charging device. In the present embodiment, the three electrostatic precipitators 2 are arranged in the housing 10, but the number of the three electrostatic precipitators 2 is not limited in any way.

The pre-filter 14 has, for example, a mesh structure in which a thread-like PET material is woven, and is held by a resin frame (not shown). The pre-filter 14 collects relatively large dust contained in the air sucked into the housing 10. The deodorizing filter 5 performs a deodorizing treatment for removing odorous components such as ammonia and methyl mercaptan and harmful components such as formaldehyde from the air from which the dust has been removed by the pre-filter 14 and the electrostatic precipitator 2.

Further, in the housing 10, a fan 6 arranged on the downstream side of the deodorizing filter 5, a fan motor 61 for rotating the fan 6, and a control board 7 for controlling the air purifier 1 are provided.

Further, inside the housing 10, a dust sensor 13 for detecting the dust concentration of the air sucked from the suction port 11 and an operation display board 15 for performing an operation start operation, an operation stop operation, and the like are provided.

Further, the housing 10 has a constant voltage high-voltage power supply unit for a single dust collector that supplies power to each dust collector 4 of each electric dust collector 2 (hereinafter referred to as “high-voltage power supply 40 for dust collector”). Is placed. On the other hand, the constant current high-voltage power supply unit (hereinafter referred to as "high-voltage power supply 30 for the charged unit") for the charged unit that supplies power to the charged unit 3 is arranged in each of the three charged units 3.

With this configuration, the air purifier 1 sucks indoor air from the suction port 11 by the rotation of the fan 6 driven by the fan motor 61, as shown by the arrow f, and the pre-filter 14, the electrostatic precipitator 2, and the deodorizing filter. The air is purified while passing through 5, and the purified air is blown into the room from the outlet 12.

The air volume setting of the air purifier 1 can be manually switched based on the operation of the operation display board 15, but for example, it is automatically switched to an appropriate air volume based on the detection signal of the dust sensor 13. An automatic air volume mode setting can also be provided.

Here, the electrostatic precipitator 2 including the charging device according to the embodiment will be described with reference to FIG. As shown in FIG. 2, the electrostatic precipitator 2 includes a charged unit 3 and a dust collecting unit 4. The charging unit 3 charges fine particles such as dust contained in the passing air. The dust collecting unit 4 collects the fine particles charged by the charged unit 3 by electrostatic force. The charged portion 3 that functions as a charging device includes a charged portion discharge electrode having a sawtooth shape with a sharp tip (hereinafter referred to as “discharge electrode 310”) and a charged portion facing electrode having a polarity different from that of the discharge electrode 310 (hereinafter “discharge electrode 310”). Opposite electrodes 320 ”) are alternately arranged at predetermined intervals. Further, the counter electrode 320 is composed of a flat plate electrode.

The dust collecting unit 4 has a structure in which a large number of flat plate electrodes are arranged in parallel and electrically connected so that voltages of different polarities are alternately applied. In the present embodiment, the dust collecting unit 4 has the same polarity as the discharge electrode 310. Is referred to as a dust collecting portion high-voltage electrode (hereinafter referred to as “high-voltage electrode 410”), and an electrode having the same polarity as the counter electrode 320 is referred to as a dust collecting portion collecting electrode (hereinafter referred to as “collecting electrode 420”).

A high voltage is applied between the discharge electrode 310 and the counter electrode 320 of the charged portion 3 from the power supply 50 via the power supply portion 55 by the high voltage power supply 30 for the charged portion. The high-voltage power supply 30 for the charged unit is driven and controlled by the control unit 70 mounted on the control board 7 via the charged unit switches 301, 302, and 303.

A high voltage is applied between the dust collecting electrode 420 and the high voltage electrode 410 of the dust collecting section 4 from the power source 50 via the power supply section 55 by the high voltage power source 40 for the dust collecting section. The high-voltage power supply 40 for the dust collecting unit is driven and controlled by the control unit 70 mounted on the control board 7 via the dust collecting unit switch 401.

The high-voltage power supply 30 for the charged part is provided with the same number (three in this case) as the number of charged parts 3 built in the electrostatic precipitator 2, and is connected to the charged part 3 of each electrostatic precipitator 2 in a one-to-one correspondence. Will be done. The high-voltage power supply 40 for the dust collector is one regardless of the number of the dust collectors 4 built in the electric dust collector 2, and all the dust collectors 4 are connected in parallel.

Further, as shown in the figure, the electrostatic precipitator 2 according to the present embodiment includes a humidity sensor 210 as a humidity detection unit, a temperature sensor 220, and a dehumidification unit 230, each of which is electrically connected to the control unit 70. There is. The humidity sensor 210 is a sensor for acquiring the relative humidity around the air purifier 1 or the electrostatic precipitator 2, and thereby can detect the relative humidity around the charged portion 3. The temperature sensor 220 can detect the surface temperature of the discharge electrode 310. Further, the dehumidifying unit 230 may be at least capable of lowering the relative humidity around the charged unit 3. The dehumidifying unit 230 may be, for example, one capable of dehumidifying the room in which the air purifier 1 is installed, or one capable of dehumidifying the periphery of the air purifier 1 or the electrostatic precipitator 2. In this case, by dehumidifying the air taken into the air purifier 1 or the electrostatic precipitator 2, the relative humidity around the charged portion 3 arranged inside the air purifier 1 or the electrostatic precipitator 2 can be lowered. Alternatively, the relative humidity around the charged portion 3 may be lowered by warming the air taken into the air purifier 1.

Here, the discharge electrode 310 included in the charged unit 3 will be described with reference to FIGS. 3A to 3D. 3A is a front view of the discharge electrode plate of the charging device according to the embodiment, FIG. 3B is a plan view of the discharge electrode plate, FIG. 3C is a side view of the discharge electrode plate, and FIG. 3D is a side view of the discharge electrode plate. It is explanatory drawing which shows the tip part in the cross-sectional view. As shown in FIG. 3B, the discharge electrode 310 is formed in a sharp sawtooth shape in which a plurality of protrusions 315 are formed at the tip. Then, as shown in FIGS. 3A and 3C, a plurality of discharge electrodes 310 are connected to the frame portion 311 at predetermined intervals. Here, the plurality of discharge electrodes 310 are formed by cutting up a rectangular plate-shaped discharge electrode plate 31 made of stainless steel (for example, SUS304).

Further, in the present embodiment, each protrusion 315 of the discharge electrode 310 is formed with a passivation film 316 as shown in FIG. 3D.

Passivation film 316 in this embodiment is a trivalent chromium, for example, formed by chromium oxide _{(III) (Cr 2 0 3} ). That is, as shown in FIG. 3D, the protrusions 315 formed at the tip of the discharge electrode 310, a passivation film 316 is formed of stainless steel substrates 315a to chromium oxide _{(III) (Cr 2 0 3} ) ing.

Next, the dust collecting action in the electrostatic precipitator 2 will be briefly described. When a high voltage of the positive electrode is applied to the discharge electrode 310 of the charged portion 3 and the counter electrode 320 is connected to the ground electrode (earth) of the high-voltage power supply 30 for the charged portion, a corona discharge occurs, and electrons and air are between the electrodes. The positively charged ions of the molecule are filled. Of these, the electrons reach the discharge electrode 310 and flow toward the high-voltage power supply 30 for the charged portion. Assuming that the current of the entire charged portion 3 at this time is 0.25 mA, ions are generated between the electrodes corresponding to this current value.

When dust passes through a space filled with positive ions, charge transfer occurs due to collision between ions and dust, depending on the passage time and the strength of the electric field created by the discharge electrode 310 and the counter electrode 320. The dust is positively charged.

On the other hand, when, for example, 5 kV is applied to the high-pressure electrode 410 of the dust collecting portion 4 and the collecting electrode 420 is connected to the ground electrode (earth) of the high-pressure power supply 40 for the dust collecting portion, 25 kV if the distance between the two electrodes is 2 mm. An electrostatic field of / cm is formed. When the dust positively charged by the charged unit 3 moves to the dust collecting unit 4, it receives a force in the direction of being attracted to the collecting electrode 420 having the opposite polarity to the dust by the electrostatic field.

Dust floating in the air immediately reaches the terminal velocity due to air resistance, and becomes a constant velocity motion having velocity components in the flow direction and the collection electrode 420 direction. The velocity component in the direction of the collection electrode 420 is proportional to the amount of electric charge of the dust and the strength of the electrostatic field (electric field strength) between the high-voltage electrode 410 and the collection electrode 420, and the velocity in the flow direction and the dust collection unit 4 The dust that has reached the collection electrode 420 is collected within the passage time of the dust collection unit 4 determined by the depth of the above.

The dust floating in the air is sufficiently small, and some of them move in a direction away from the collection electrode 420, and not all dust is collected while passing through the dust collection unit 4. However, during the operation of the air purifier 1, the dust that has not been collected is repeatedly taken into the air purifier 1 and passes through the electrostatic precipitator 2, so that the dust passes through the dust collecting unit 4 without being collected. The amount of dust gradually decreases with the lapse of time from the start of operation of the air purifier 1.

The air purifier 1 according to the present embodiment uses ozone generated by the charged portion 3 of the electrostatic precipitator 2 while executing the above-mentioned dust collecting action to disinfect the inside of the air purifier 1, for example. It can even sterilize indoor air.

That is, it has been found that in the charging unit 3 provided as a charging device in the electrostatic precipitator 2, a phenomenon occurs in which the ozone concentration generated by the corona discharge from the discharge electrode 310 rapidly increases when predetermined conditions are met. By utilizing such a phenomenon, the air purifier 1 according to the present embodiment can fulfill a sufficient dust collecting function and an ozone generating function (and a sterilizing function) even though it is a compact device.

The conditions for obtaining a sufficient ozone concentration, that is, the conditions under which the ozone concentration rapidly increases (predetermined conditions) are shown below. As the material of the discharge electrode 310, stainless steel containing chromium (for example, SUS304) is used, and the shape thereof is a shape (for example, serrated) in which the current is concentrated on the needle tip (projection 315) and the power density is high. Then, for example, in a low humidity atmosphere where the relative humidity (RH: Relative Humidity) is RH 35% or less, the needle tip (projection portion 315), which is the tip end portion of the discharge electrode 310, is heated to a high temperature by continuous energization. Here, the temperature of the needle tip is preferably 470 K or higher. The 470K, the projection portion 315 formed passive film 316 in which chromium oxide of the discharge electrodes _{310 (III) (Cr 2 0} 3) Some react with ozone chromium oxide (VI) _(Cr0 3) It is the temperature at which it reacts with oxygen molecules to act as a catalyst to generate ozone.

Certainly, in general, the concentration of ozone generated tends to increase as the relative humidity decreases, but when the charged unit 3 is continuously operated so as to satisfy the above-mentioned predetermined conditions, ozone increases rapidly. The phenomenon of Moreover, a concentration several to ten times higher than the ozone concentration generally assumed in the case of low humidity is detected.

In the present embodiment, the discharge electrode 310 of the charged portion 3 is formed by using SUS304, which is an inexpensive and durable stainless steel material, having a thickness of 0.1 mm and a sawtooth shape (see FIG. 3B). It was adopted. The passivation film is formed on the surface of SUS304 without any special treatment. As the stainless steel material having the passivation film formed on the surface, austenitic materials such as SUS303 and SUS316 can be used in addition to SUS304. Further, the counter electrode 320 at this time had a thickness of 0.5 mm, a flat plate shape, and was formed by using SUS304 as the material like the discharge electrode 310.

Further, a passivation film 316 made of trivalent chromium was formed on the protrusion 315 of the saw-toothed discharge electrode 310. Here, trivalent is one chromium oxide chromium _{(III) (Cr 2 0 3} ) is reacted before and after ozone and 470K produced by corona discharge from the discharge electrode 310, a portion of strong oxidizing It has been found to vary in chromium oxide hexavalent chromium _(VI) (Cr0 3) is agent. The reaction at this time is represented by the following chemical reaction formula.

Cr ₂ 0 ₃ +0 ₃ → ₂ Cr0 ₃

Such chromium oxide _(VI) (Cr0 3) is unstable under high humidity atmosphere, immediately returned to the chromium oxide (III), as a catalyst has been found that not act. Therefore, the phenomenon of sudden increase in ozone does not occur in a high humidity atmosphere. On the other hand, chromium oxide _(VI) (Cr0 3) is stable at a low humidity atmosphere, is predicted to surge the amount of ozone generated by acting as a catalyst. The reaction at this time is represented by the following chemical reaction formula.

30 ₂ → 20 ₃

That is, the temperature of the discharge electrodes 310 in the low-humidity atmosphere, the passivation film formed on the surface of the discharge electrode 310 (chromium oxide _{(III) (Cr 2 0 3} )) is reacted with ozone, a passivation film hexavalent compounds of metal elements forming (chromium oxide _(VI) (Cr0 3)) to become a made temperature (470K) or as produced, by controlling the energization, to generate a high concentration of ozone be able to.

Then, under the above-mentioned conditions, by performing the following energization control, it is possible to charge with high efficiency while generating high-concentration ozone in one charged unit 3. Further, in the present embodiment, a dehumidifying unit 230 is provided in the front stage portion of the charged unit 3 (see FIGS. 2 and 4) so that the relative humidity can be controlled to a desired humidity. That is, in order to increase the amount of ozone generated, it is desirable to have a low humidity atmosphere. Therefore, in the air purifier 1 of the present embodiment, ozone is provided depending on the presence or absence of dehumidification by providing the dehumidifying unit 230 in the front stage of the charged unit 3. It is possible to control the amount of production of.

Here, the control unit 70 will be mainly described with reference to FIG. FIG. 4 is a block diagram mainly composed of a control unit 70 included in the electrostatic precipitator 2 of the present embodiment. The control board 7 also includes a control unit that controls a high-voltage power supply 30 for the charged unit, a high-voltage power supply 40 for the dust collecting unit, a dehumidifying unit 230, and a fan motor power supply (not shown) that supplies electric power to the fan motor 61. However, in FIG. 4, illustrations other than the control unit 70 that controls the dehumidifying unit 230 and the high-voltage power supply 30 for the charged unit are omitted.

The control unit 70 includes a humidity control unit 710, an energization control unit 720, and a determination unit 730. The control unit 70 has, for example, a microcomputer such as a CPU or a memory, and functions as a humidity control unit 710, an energization control unit 720, and a determination unit 730 by reading and processing a predetermined program. The humidity control unit 710 is connected to the dehumidification unit 230, the energization control unit 720 is connected to the high-voltage power supply 30 for the charging unit, and the determination unit 730 is connected to the humidity sensor 210 and the temperature sensor 220.

In this way, the control unit 70 determines whether or not the determination unit 730 starts the energization control for controlling the temperature of the discharge electrode 310 of the charge unit 3 based on the relative humidity detected by the humidity sensor 210. That is, when the humidity detected by the humidity sensor 210 is equal to or lower than a predetermined humidity (for example, RH35%) that is a boundary for whether or not a rapid increase of ozone occurs, energization control is executed and the energization control unit 720 is used for the charged unit. controls the high voltage power supply 30, for example by increasing the current while the voltage was maintained constant, the temperature of the discharge electrode 310, a passivation film (chromium oxide _{(III) (Cr 2 0 3} )) that reacts with ozone , hexavalent compounds of metal elements constituting the passivation film (chromium oxide _(VI) (Cr0 3)) is increased to a predetermined temperature to be generated (e.g., 470K) or more.

Here, values such as RH35%, which is a predetermined humidity, and 470K, which is a predetermined temperature, are stored in a storage unit 700 provided on the control board 7. That is, the storage unit 700 is, for example, an internal storage device using a volatile semiconductor storage device as an example, a non-volatile external storage device using a semiconductor as a storage medium, or the like.

The storage unit 700 can store various measured values, acquired values, calculated values, various threshold values, and the like, and various measured values, acquired values, and calculated values are stored at each measurement timing, acquisition timing, and calculation timing. It is stored in the storage unit 700 in series.

FIG. 5 is a flowchart showing a control procedure of the electrostatic precipitator 2 according to the embodiment. The control procedure of the electrostatic precipitator 2 is executed triggered by the start of operation of the air purifier 1.

As shown in FIG. 5, the control unit 70 starts the operation of the electrostatic precipitator 2 in response to the start of the operation of the air purifier 1 (step S11). Next, the control unit 70 determines whether the relative humidity around the charged unit 3 is equal to or less than a predetermined humidity (RH35%), which is a boundary for whether or not a rapid increase phenomenon of ozone occurs (step S12). That is, the control unit 70 determines the relative humidity of the charged unit 3 based on the detection result of the humidity sensor 210 by the determination unit 730, and the relative humidity around the charged unit 3 serves as a boundary for whether or not a rapid increase phenomenon of ozone occurs. If it exceeds the predetermined humidity (RH35%), it waits until the RH is 35% or less.

At this time, when the relative humidity around the charged unit 3 exceeds RH35% (step S12: No), the humidity control unit 710 of the control unit 70 drives the dehumidifying unit 230 to lower the relative humidity. Then, when it is determined from the detection result of the humidity sensor 210 that the relative humidity around the charged unit 3 is RH 35% or less (step S12: Yes), the energization control unit 720 of the control unit 70 executes the energization control and the charged unit. High voltage power supply 30 is controlled (step S13).

Then, the control unit 70 determines whether or not the surface temperature of the discharge electrode 310 has reached, for example, 470 K (predetermined temperature) (step S14). At this time, if the surface temperature of the discharge electrode 310 is 470 K or less (step S14: No), the energization control unit 720 of the control unit 70 controls the high-voltage power supply 30 for the charged unit to reduce the amount of energization to the discharge electrode 310. When it is determined that the surface temperature of the discharge electrode 310 has reached 470 K or higher based on the detection result of the temperature sensor 220 (step S14: Yes), this control procedure ends.

As described above, in the present embodiment, when the relative humidity detected by the humidity sensor 210 is RH 35% or less, the control unit 70 controls the high-voltage power supply 30 for the charged unit, and the surface temperature of the discharge electrode 310 is 470 K or more. The amount of electricity supplied to the discharge electrode 310 is controlled so as to be.

As described above, in the charging unit 3 according to the present embodiment, the discharge electrode 310 can also function as an ozonizer for generating high-concentration ozone while maintaining the original function of charging dust.

Therefore, since it is not necessary to separately provide the charging device and the ozonizer, it is possible to realize a high-performance electrostatic precipitator 2 having both a charging function and a sterilization function by ozone without increasing the size. Then, by using the electrostatic precipitator 2, it is possible to provide a high-performance air purifier 1 having both functions of dust collection and sterilization while also suppressing the increase in size.

Further, for example, it is conceivable to apply a high voltage of the positive electrode (plus) to the discharge electrode when charging, and to apply a high voltage of the negative electrode (minus) to the discharge electrode when generating ozone. However, in the charged unit 3 according to the present embodiment, the ozone concentration can be made higher by applying a positive high voltage to the discharge electrode 310 than by applying a negative high voltage to the discharge electrode 310. it can.

By the way, when the electrostatic precipitator 2 or the air purifier 1 equipped with the electrostatic precipitator 2 is used for home use, the odor component can be decomposed by the high concentration ozone generated in the charged unit 3, for example, in the charged unit 3. It is desirable to arrange an ozone decomposition catalyst or the like on the downstream side so that high-concentration ozone is not released into the room as it is.

Here, the ozone rapid increase phenomenon of the charged portion 3 in the present embodiment described above will be described with reference to FIGS. 6 to 12.

First, the temporal change of the ozone concentration is compared between the case where the shape of the discharge electrode 310 is serrated and the case where the shape is linear formed by a wire. FIG. 6 is a graph showing the relationship between the shape of the discharge electrode 310 and the ozone concentration in the charged portion 3 included in the electrostatic precipitator 2 according to the embodiment. The relative humidity in the charged portion 3 at this time is 28%, and the wind speed is 1.1 m / s.

As can be seen from the graph of FIG. 6, when the discharge electrode is a linear electrode formed of wires, the ozone concentration does not change even if the energization time of the discharge electrode exceeds 120 minutes, but the discharge electrode It was found that when the 310 was serrated, the ozone concentration sharply increased after the energization time of the discharge electrode 310 exceeded 60 minutes. That is, when the discharge electrode 310 is serrated, the ozone concentration rapidly increases from a concentration of about 40 ppb to a concentration exceeding 110 ppb in about 40 minutes from 60 minutes to 100 minutes.

This difference is because whether or not the temperature of the passivation coating 316 formed on the surface of the discharge electrode 310 reaches the temperature (470K) at which the ozone rapid increase phenomenon occurs depends on the difference in the shape of the discharge electrode 310. Conceivable. That is, when the discharge electrode 310 has a serrated shape, since the discharge electrode 310 has a protrusion 315, the current tends to concentrate on the protrusion 315, the temperature of the passivation coating 316 rises locally, and an ozone rapid increase phenomenon occurs. It is probable that the temperature (470K) has been reached. On the other hand, when the discharge electrode 310 is linear formed of wires, the temperature rises uniformly as a whole because it does not have a protrusion, and the temperature of the passivation coating does not rise locally, and ozone It is probable that the temperature (470K) at which the rapid increase phenomenon occurred was not reached.

Next, the humidity, which is a condition for abrupt changes in ozone concentration, will be described. FIG. 7 is a graph showing the relationship between the shape of the discharge electrode 310 and the relative humidity and the amount of ozone generated with respect to the energization time. Since the ozone production amount here is proportional to the ozone concentration, there is a strong correlation between the increase in the ozone production amount and the increase in the ozone concentration. As shown in FIG. 7, even in a low humidity atmosphere of RH 30%, if the discharge electrode is a linear electrode formed of wire, the amount of ozone generated even if the energization time exceeds 180 minutes. There is no change in (ozone concentration). On the other hand, when the discharge electrode 310 is serrated, there is almost no change in the amount of ozone generated even if the energization time exceeds 180 minutes in an atmosphere of RH 50%, but the energization time is 60 in a low humidity atmosphere of RH 30%. After a minute, it was found that the amount of ozone produced sharply increased to about three times the amount of ozone produced immediately after the start of energization.

This is part of the chromium oxide constituting the passive film 316 formed on the surface of the projecting portion 315 of the discharge electrodes _{310 (III) (Cr 2 0} 3) is reacted with ozone at temperatures above 470K, oxide despite changes in chromium (VI) (Cr0 _3), not stable under RH 50% atmosphere, immediately because it did not act as a catalyst to return to the chromium oxide _{(III) (Cr 2 0 3} ), surge phenomenon of ozone generated It is presumed that it did not. On the other hand, chromium oxide _(VI) (Cr0 3) is stable under low humidity atmosphere Rh30%, is estimated to cause by rapidly increasing the amount of ozone generated by acting as a catalyst. Therefore, next, we searched for the humidity condition that is the boundary of whether or not the ozone rapid increase phenomenon occurs.

FIG. 8 is a graph showing the experimental results of observing how the ozone concentration fluctuates with the energization time by changing the relative humidity around the charged portion 3 during energization. Specifically, the energizing time is 0 to 250 min. During that time, the relative humidity was maintained at approximately RH 30%, and the energizing time was 250 min. After that, the relative humidity was increased and the energizing time was 350 min. Until, the RH was kept at about 40%, and the energizing time was 350 min. After that, the ozone concentration was measured under the condition that the relative humidity was further increased to RH 50%. The black circles (●) in the graph represent the ozone concentration at each time point of the energization time, and the white circles (○) represent the relative humidity at each time point of the energization time. At this time, the wind speed in the charged portion 3 is 1.1 m / s, and the current flowing through the discharge electrode 310 is constant at 150 μA.

As can be seen from the graph, the energizing time at which the relative humidity is almost constant at RH 30% is 0 to 250 min. In the case of, the ozone concentration starts to increase sharply from the concentration of about 0.05 ppm immediately after the start of energization after the energization time exceeds 30 minutes. Then, when the energization time exceeds 80 minutes, the ozone concentration increases until it exceeds 0.2 ppm, and thereafter it is stable between 0.18 and 0.22 ppm. After that, when the relative humidity is gradually increased and the relative humidity is increased to about RH 40%, it can be seen that the ozone concentration decreases sharply. After that, when the relative humidity is further increased and the relative humidity rises to about RH 50%, the ozone concentration further decreases and returns to around 0.05 ppm immediately after the start of energization. In this example, in consideration of the above results, the condition under which a rapid increase in ozone concentration occurs is a low humidity atmosphere with an RH of 35% or less.

Further, FIG. 9 shows the time change of the ozone concentration when the wind speed in the charged portion 3 is 0.06 m / s, the relative humidity is RH 20%, and the number of needles (the number of protrusions 315) of the discharge electrode 310 is 117. In the graph and FIG. 10, the wind speed in the charged portion 3 is 0.06 m / s, the relative humidity is RH 20%, and the number of needles (the number of protrusions 315) of the discharge electrode 310 is 58 (about half that in the case of FIG. 9). It is a graph which shows the time change of the ozone concentration in the case of (the number of stitches). At this time, although the current flowing through the entire discharge electrode 310 is constant at 150 μA, the current flowing through each of the protrusions 315 changes depending on whether the number of protrusions 315 is 117 or 58. There is a difference in the power density (power per unit area) in the protrusion 315. That is, the power density when the number of protrusions 315 is 58 is about twice the power density when the number of protrusions 315 is 117.

When the number of needles (the number of protrusions 315) of the discharge electrode 310 in the charged portion 3 is 117, the ozone concentration is about 0.05 ppm immediately after the start of energization, as shown in FIG. 9, but 30 from the start of energization. It can be seen that the ozone concentration suddenly increases in about a minute, and after 60 minutes have passed since the start of energization, the ozone concentration has increased to 4 to 7 ppm with the passage of time.

On the other hand, when the number of needles (the number of protrusions 315) of the discharge electrode 310 in the charged portion 3 is 58, the ozone concentration is about 0.05 ppm immediately after the start of energization, as shown in FIG. It can be seen that the ozone concentration suddenly increased in about 15 minutes, and that the ozone concentration remained at 6 to 9 ppm after 30 minutes had passed from the start of energization. From the comparison between FIGS. 9 and 10, the smaller the number of needles (the number of protrusions 315) of the discharge electrode 310, that is, the larger the current (power density) flowing through each protrusion 315, the more the ozone rapid increase phenomenon occurs. It turns out that it happens in a shorter time.

As can be seen from the comparison between FIGS. 9 and 10, when the conditions such as the shape of the discharge electrode 310, the presence or absence of the passivation coating 316, and the relative humidity around the charged portion 3 are the same, the smaller the number of the protrusions 315 ( It can be seen that the current flowing through each protrusion 315, that is, the larger the power density), the shorter the time from the start of energization to the occurrence of the phenomenon of rapid increase in ozone concentration. It is estimated that this is because the larger the current (power density) flowing through each protrusion 315, the shorter the time required for the temperature of the passivation coating 316 formed on the surface of the discharge electrode 310 to reach 470K. Will be done.

Further, from the graphs of FIGS. 6 and 7, a rapid increase in ozone concentration in the case of low humidity may occur when the shape of the discharge electrode 310 is not a linear shape like a wire but a flat sawtooth shape. It was found, as shown in the reference example shown in FIG. 11, it is known that even in a discharge electrode made of a linear wire, the ozone concentration generated increases as the relative humidity decreases. FIG. 11 is a graph showing the ozone concentration and humidity characteristics of the discharge electrode according to the reference example.

As shown in FIG. 11, it is true that the ozone concentration is higher when the relative humidity is lower than when the relative humidity is high, but the ozone concentration in this case is only increased from 0.025 ppm to 0.029 ppm, and also. Even if the relative humidity changes by about 10%, the amount of change in ozone concentration is only about 5%.

In that respect, in the charged portion 3 according to the present embodiment, as can be seen from FIGS. 6 to 10, the concentration may be several to several tens of times higher than the ozone concentration in the reference example shown in FIG. I understand.

FIG. 12 is a graph showing the relationship between the polarity (positive electrode and negative electrode) of the voltage applied to the discharge electrode 310 of the charged portion 3 and the amount of ozone generated over time. At this time, the relative humidity in the charged portion 3 is RH 30%, the wind speed is 1.1 m / s, and the current flowing through the discharge electrode 310 is constant at 150 μA. As shown in the figure, when the polarity of the high voltage applied to the discharge electrode 310 is the negative electrode, the amount of ozone generated (ozone concentration) is 0.15 to 0.2 ppm from the start of energization until the energization time exceeds 180 minutes. There is almost no change over time. On the other hand, when the polarity of the high voltage applied to the discharge electrode 310 is the positive electrode, it can be seen that the amount of ozone generated, which was 0.02 ppm at the start of energization, begins to increase rapidly after the energization time of 30 minutes. That is, when the energization time exceeds 30 minutes, the amount of ozone produced, which was about 0.02 ppm, increases to exceed 0.25 ppm within about 30 minutes, and then between 0.25 to 0.33 ppm. It is stable. This result suggests that the phenomenon of rapid increase in ozone does not occur when a high voltage of the negative electrode is applied to the discharge electrode 310, but may occur only when a high voltage of the positive electrode is applied to the discharge electrode 310. are doing.

Further, from the start of energization until the energization time exceeds 60 minutes, ozone is applied when the high voltage polarity applied to the discharge electrode 310 is used as the negative electrode than when the high voltage polarity applied is used as the negative electrode. The amount of production is large. On the other hand, after the energization time exceeds 60 minutes (that is, after the sudden increase of ozone occurs), the polarity of the high voltage applied to the discharge electrode 310 is the positive electrode as compared with the case where the polarity of the high voltage applied to the discharge electrode 310 is the negative electrode. If it is set to, the amount of ozone generated will be larger. Therefore, in the charged unit 3 according to the present embodiment, by controlling the discharge electrode 310 to apply the high voltage of the positive electrode, the ozone concentration is further higher than that in the case of controlling to apply the high voltage of the negative electrode. It will be possible to make the concentration.

Although the examples of the present application have been described above based on the drawings, they are merely examples, and various modifications and improvements can be made based on the knowledge of those skilled in the art.

From the above-described embodiment, the following charging device and air purifier 1 can be realized. The following charging device corresponds to the charging unit 3 in the electrostatic precipitator 2.

(1) A charged unit 3 having a discharge electrode 310 on which a dynamic coating 316 is formed on the surface, a counter electrode 320 arranged to face the discharge electrode 310, and a control unit 70 that controls energization of the discharge electrode 310. When the relative humidity detected by the humidity sensor 210 is equal to or lower than the predetermined humidity, the control unit 70 sets the temperature of the discharge electrode 310 to a predetermined temperature by energizing the discharge electrode 310. A charging device that controls to increase to the above.

With such a configuration, sufficient ozone generation can be expected in one charging device. Therefore, it is possible to increase the charging efficiency and the ozone generation efficiency at the same time while suppressing the increase in size of the apparatus. Further, by applying such a charging device to, for example, an electrostatic precipitator 2 or an air purifier 1, it is possible to suppress the increase in size of these.

(2) In the above (1), the predetermined humidity is a humidity that is a boundary as to whether or not a rapid increase phenomenon of ozone occurs.

With such a configuration, the effect of the above (1) can be more reliably achieved.

(3) In the above (1) or (2), the discharge electrode 310 has a protrusion 315, and a passivation coating 316 is formed on the protrusion 315.

With such a configuration, the effect of the above (1) or (2) can be more reliably achieved.

(4) In any of the above (1) to (3), the discharge electrode 310 is a charging device made of stainless steel.

With such a configuration, the above effects (1) to (3) can be obtained at low cost.

(5) In the above (4), passive film 316 is a chromium oxide (III) _(Cr 2 _{0 3)} charging device.

With such a configuration, the effect of the above (4) can be more reliably achieved.

(6) In the above (4) or (5), the charging device having a predetermined humidity of RH 35%.

With such a configuration, the effect of (4) or (5) can be more reliably achieved.

(7) In any one of (1) to (6), a predetermined temperature, metal passivation film (chromium oxide _{(III) (Cr 2 0} 3)) is reacted with ozone to form a passive film hexavalent compound of an element is the temperature at which (chromic acid _(VI) (Cr0 3)) is generated charging device.

With such a configuration, the effects of (1) to (6) can be more reliably achieved.

(8) A charging device having a predetermined temperature of 470 K in any of the above (1) to (7).

With such a configuration, the effect of any one of (1) to (7) can be more reliably achieved.

(9) In the air purifier 1 provided with any of the charging devices (1) to (8) above, the air purifier 1 further provided with a dehumidifying unit 230.

With such a configuration, it is possible to control the amount of ozone produced depending on the presence or absence of dehumidification. Further, for example, the effect of any one of (1) to (8) above can be reliably achieved regardless of the humidity in the usage environment of the electrostatic precipitator 2 having a charging device and the air purifier 1 equipped with the electrostatic precipitator 2. it can.

(10) In (9) above, when the humidity detected by the humidity sensor 210 exceeds the predetermined humidity, the control unit 70 drives the dehumidifying unit 230 to control the humidity of the charged unit 3 to the predetermined humidity or less. Air purifier 1.

With such a configuration, it is possible to control the amount of ozone produced depending on the presence or absence of dehumidification. Further, for example, the effect of (9) above can be reliably achieved regardless of the humidity in the usage environment of the electrostatic precipitator 2 having a charging device and the air purifier 1 equipped with the electrostatic precipitator 2.

The above-described embodiment and the specific names, processes, controls, various data, and the like shown are merely examples and may be changed as appropriate. For example, in the above-described embodiment, the discharge electrode 310 is formed in a serrated shape using SUS304 as a material. Thus, the protrusion 315 which is formed at the tip of the discharge electrode 310 was assumed that trivalent is one chromium oxide chromium _{(III) (Cr 2 0 3} ) passive film 316 made of is formed .. However, even if the shape of the discharge electrode 310 is not necessarily a sawtooth shape, a shape having a protrusion 315 where the current concentrates on the passivation coating 316 and the power density becomes high (for example, a thorned wire, a thorny cylinder, a needled rod, etc.) If it is (shape), it is presumed that a phenomenon in which the ozone concentration rises sharply occurs in a low humidity atmosphere. Further, as a formation easily metals passivation film except chromium, aluminum, nickel, titanium and the like, are passive film 316 is formed on the discharge electrodes 310 chromium oxide _{(III) (Cr 2 0 3} ) It is presumed that the same phenomenon occurs even when the passivation film of these metals is replaced.

Also, the broader aspects of the above embodiments are not limited to the particular details and representative embodiments expressed and described as described above. Therefore, various modifications can be made without departing from the general concept or scope of the invention as defined by the appended claims and their equivalents.

1 Air purifier 2 Electrostatic precipitator 3 Charged part (charging device)
70 Control unit 210 Humidity sensor (humidity detection unit)
230 Dehumidifying part 310 Discharge electrode 315 Projection part 316 Passivation coating 320 Opposite electrode

Claims (10)

A charged portion having a discharge electrode on which a passivation film is formed on the surface and a counter electrode arranged to face the discharge electrode,
A control unit that controls energization of the discharge electrode and
Equipped with a humidity detector that detects humidity,
The control unit
A charging device that controls the temperature of the discharge electrode to rise to the predetermined temperature or higher by energizing the discharge electrode when the humidity detected by the humidity detection unit is equal to or lower than the predetermined humidity. The charging device according to claim 1, wherein the predetermined humidity is a humidity that serves as a boundary for whether or not a rapid increase phenomenon of ozone occurs. The charging device according to claim 1 or 2, wherein the discharge electrode has a protrusion, and the passivation film is formed on the protrusion. The charging device according to any one of claims 1 to 3, wherein the discharge electrode is made of stainless steel. The passive film is a chromium oxide _{(III) (Cr 2 0 3} ), charging device according to claim 4. The charging device according to claim 4 or 5, wherein the predetermined humidity is RH 35%. The predetermined temperature is the temperature at which the passivation film reacts with ozone to form a hexavalent compound of a metal element constituting the passivation film, according to any one of claims 1 to 6. Charging device. The charging device according to any one of claims 1 to 7, wherein the predetermined temperature is 470 K. An air purifier including the charging device according to any one of claims 1 to 8.
An air purifier with a dehumidifying section. The air purifier according to claim 9.
The control unit
An air purifier that drives the dehumidifying unit to control the humidity of the charged unit to or less than the predetermined humidity when the humidity detected by the humidity detecting unit exceeds a predetermined humidity.

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