JPH0645016B2 - Air purifier - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air purifying device, and more particularly to an air purifying device having no mechanical driving part.

2. Related Art and Problems Thereof It is a well-known fact in the field of electrostatic precipitator that ionic wind is generated by electric discharge. Utilizing this phenomenon, an electronic air purifying device that does not have a mechanical drive part such as a blower is known. For example, Japanese Examined Patent Publication No. 54-23147 discloses an air purifying device in which an ionizing wire, a counter electrode and a dust collecting electrode are provided at predetermined positions. When a high voltage is applied between the ionizing wire and the dust collecting electrode to generate corona discharge, a large amount of ions are generated and the movement of the ions causes the air to fluidize. Further, during discharge, fine particles in the air are charged, and a Coulomb force is applied to the charged fine particles by an electric field formed between the dust collecting electrode and the counter electrode, and this force collects the charged fine particles to the dust collecting electrode. It is what is done. This type of device does not generate any noise or vibration because it has no mechanical drive parts, and has a high dust collection efficiency of about 99% even for fine particles of 0.3 microns or more such as cigarette smoke. Since it has many features such as compactness and easy maintenance because it does not require replacement of a filter such as an air filter, it is used for air purification in offices, restaurants or homes.

In recent years, attention has been paid to the characteristics of this type of device, and its application to a bioclean room such as an operating room or an LSI manufacturing space has been studied. HE is currently used in this type of application
A PA filter is used, and 99.97% or more of fine particles of 0.3 micron or more are removed by this filter. Recently, even higher cleanliness of air is required, and in this case, the dust collection efficiency must be 99.99% or more.

By the way, the dust collecting performance of the electronic air purifier depends on the amount of charge of the particles and the electrostatic force acting on the charged particles. Therefore, theoretically, the dust collection efficiency can be improved by increasing the charge amount or the electrostatic force. Since the fine particles are charged by the corona discharge formed between the ionization line and the dust collecting electrode, the charge of the fine particles is increased by increasing the discharge current, that is, increasing the potential difference between the ionization line and the dust collecting electrode. The quantity increases. However, along with this, the wind speed of the ion wind also increases, and the force acting on the particles in the flow direction of the air flow increases, and the dust collection efficiency is suppressed.

To increase the electrostatic force on the particles, the potential difference between the dust collecting electrode and the counter electrode may be increased, or the gap between the electrodes may be narrowed to increase the potential gradient. However, the former is naturally limited because it leads to an increase in operating costs and avoids discharge between both electrodes. Also, in the latter case, this gap leads to an increase in the flow resistance of the air flow, so this gap cannot be extremely narrowed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an air purification device having a high dust collection efficiency, which has been made to solve the above problems.

The present invention comprises a dust collecting electrode arranged in parallel at a predetermined interval; a counter electrode positioned in parallel between adjacent dust collecting electrodes; and an ionization line positioned upstream of these electrodes. That is, air is caused to flow by the discharge generated between the ionization line and the dust collecting electrode, and particles in the air are made to flow to the dust collecting electrode by an electric field formed between the dust collecting electrode and the counter electrode. In the air purifying apparatus for attracting and removing dust, at least one slit is formed in the dust collecting electrode in a direction perpendicular to the flow direction of the air flow.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of the device according to the present invention. The dust collecting electrodes 1 (details of which will be described later) are provided so that their upstream ends are on the same line and parallel to each other. A counter electrode 2 whose upstream end is located on the line connecting the upstream ends of the adjacent dust collecting electrodes is provided at approximately the center of the adjacent dust collecting electrodes. The width of the counter electrode 2 is the dust collecting electrode 1
Wider than. Therefore, the downstream end of the counter electrode 2 is located further downstream than the downstream end of the dust collecting electrode. The terms "upstream" or "downstream" as used herein are based on the airflow obtained by the practice of the inventive device.

That is, since the ion wind is generated from the ionization line 3 toward the electrode as described later, the air flow means a flow of the ion wind that is parallel to the electrode.

An ionization line 3 is provided on the upstream extension of the counter electrode 2. A predetermined voltage is applied from the power source 4 to the ionization line 3, the dust collecting electrode 1, and the counter electrode 2. A discharge (preferably a corona discharge) is formed between the ionization wire 3 and the dust collection electrode 1. When many ions generated by this discharge move to the dust collecting electrode 1, kinetic energy is given to oxygen molecules and nitrogen molecules which are neutral molecules to generate an air flow. Further, the particles in the air are charged by this discharge, and the charged particles obtain Coulomb force by the electric field formed between the dust collecting electrode 1 and the counter electrode 2, and move to the dust collecting electrode to remove dust.

Conductive screens 5 are provided on the upstream side of the ionization line 3 and the downstream side of the counter electrode 2, respectively. This conductive screen 5 can be, for example, a Hankham-shaped screen made of aluminum, and a voltage of the same potential as the ionization line is applied to this screen (ground in the figure) to ensure the safety of the device when the electrodes are short-circuited. To secure. The use of this screen is optional in the present invention.

In addition to the configuration shown in FIG. 1, as shown in Japanese Patent Publication No. 54-23147, the upstream end of the counter electrode is located downstream of the line connecting the upstream ends of the dust collecting electrodes and the width is narrower than that of the dust collecting electrodes. Counter electrodes can also be used.

Next, the structure of the dust collecting electrode, which is a feature of the present invention, will be described.

FIG. 2 is a plan view showing an example of the dust collecting electrode used in the present invention. Five slits 21 are formed on the plane of the dust collecting electrode 1 in a direction perpendicular to the flow direction of the air flow. The slit penetrates both surfaces of the dust collecting electrode 1 to form a space.
The width l ₁ of the slit can be appropriately determined, but it is preferable that it is substantially equal to or narrower than the gap between the dust collecting electrode 1 and the counter electrode 2. Particles are trapped at the electrode portion between two adjacent slits, but a large number of particles tend to be trapped upstream of this portion. The length l ₂ of this electrode portion can be appropriately set to, for example, approximately the same length as l ₁ to about 10 times the length. The number of slits 21 can be set appropriately according to the required level of purified air, but is, for example, several to several tens. The larger the number of slits, the higher the dust collection efficiency.

FIG. 3 shows another embodiment of the dust collecting electrode used in the present invention. In this figure, unlike FIG. 2, the dust collecting electrode is divided into dust collecting electrode pieces 31a to 31a, and these electrode pieces are arranged in parallel at a predetermined interval and the upper and lower ends thereof are fixed to the support 32. . The upper ends of these electrode pieces are connected to the power supply line 33, and a predetermined voltage is applied. In this case, different voltages can be applied to each electrode piece. For example, the applied voltage value can be gradually increased from the electrode piece 31a on the upstream side to the electrode piece 31 on the downstream side. If such a configuration is adopted, coarse particles are removed at a relatively low voltage on the upstream side, and fine particles are removed at a relatively high voltage on the downstream side, improving the dust collection efficiency per unit power consumption.

The edge portions of the dust collecting electrode pieces 31a to 31a may be formed in an arc shape having a predetermined radius of curvature (not shown). As a result, the region of the non-uniform electric field formed between the dust collecting electrode and the counter electrode expands, and the shapes and materials of the ionizing line, the dust collecting electrode and the counter electrode are not particularly limited, and known materials can be used. Conventionally known conditions can be applied to the applied voltage.
For example, 5 to 100 KV, preferably 10
Apply a voltage of 20 to 20 KV and apply 3 to 5 to the counter electrode.
A voltage of 0 KV, preferably 5 to 10 KV is applied. A voltage lower than that of the dust collecting electrode is applied to the counter electrode, preferably about half the voltage of the dust collecting electrode.

The distance between the dust collecting electrode and the counter electrode is usually 2.5 to 100.
mm, preferably 5 to 20 mm. The distance between the ionization line and the counter electrode is usually 5 to 100 mm, preferably 10 to 30 mm.

FIG. 4 is a modification of the apparatus shown in FIG. 1, in which an intermediate electrode 6 is provided between the dust collecting electrode 1 and the counter electrode 2. The upstream end of the intermediate electrode 6 is aligned with the upstream end of the adjacent electrode, and the downstream end is preferably located approximately halfway between both downstream ends of the adjacent electrodes. A voltage lower than the voltage applied to the dust collecting electrode 1 but higher than the voltage applied to the counter electrode is applied to the intermediate electrode 6. It is preferable to apply a voltage substantially in the middle of the voltage applied to both electrodes. When such a configuration is adopted, the intermediate electrode acts as a dust collecting electrode and the trapping capacity of particles increases, so that the operating time can be extended.

Action The action of the present invention will be described in comparison with a conventional device. FIG. 5 is an explanatory view showing a particle capturing action in the conventional apparatus. FIG. 6 is an explanatory view showing a particle capturing action in the device of the present invention. It should be noted that in these figures, the alternate long and short dash line indicates the isoelectric field lines.

Referring to FIG. 5, in the conventional device, the dust collecting electrode 1 '
Since there are no slits, equal electric field lines are formed at equal intervals between this electrode and the counter electrode 2, that is, an equal electric field is formed. The particles P'charged by corona discharge between the ionization line 3 and the dust collecting electrode 1'have an electric force F'acting on the dust collecting electrode 1'in the direction perpendicular to the electric field.

On the other hand, referring to FIG. 6, a slit is formed on the dust collecting electrode 1. Since the isoelectric field lines bend into the slit, it is considered that the electric field strength has a very large gradient in the vicinity of the slit. When the charged particles P pass near the slit, an electric force F acts on the dust collecting electrode 1-b perpendicularly to the equal electric field lines. Since this force F is proportional to the magnitude of the electric field gradient, it is considered that a larger force F acts on the particles P than in the conventional device and the collection efficiency increases.

Advantageous Effects of Invention According to the present invention, the dust collection efficiency can be dramatically improved,
In particular, the trapping performance has been remarkably improved for fine particles of 0.3 microns or more, and it is a class 10 required for LSI factories.
It is possible to obtain about 0 clean air. Moreover, the power consumption can be reduced by about 20% as compared with the conventional case.

Examples and Comparative Examples Dust collecting electrodes (the entire width was 100 mm) were installed in parallel on both sides of a counter electrode having a width of 120 mm at intervals of 10 mm. This dust collecting electrode is divided into four and has a slit width of 5 mm. Further, the upstream end of the dust collecting electrode was aligned with the upstream end of the counter electrode. The ionization line was installed on the upstream extension line of the counter electrode at a position 20 mm away from this upstream end. Ground the ionization line, apply a voltage of 9 to 15 KV to the dust collecting electrode,
A voltage of 5 to 8 KV was applied to the counter electrode.

On the other hand, the comparative example was carried out in the same manner as the above-mentioned example except that a slit-free dust collecting electrode having a width of 100 mm was used.

The results of Examples and Comparative Examples are shown in FIG. The number of particles in the air to be treated was 300,000 / cubic foot, and the number of particles was measured by a light scattering method.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the apparatus of the present invention. 2 and 3 are plan views showing an example of the dust collecting electrode used in the present invention. FIG. 4 is an electrode layout diagram showing a modification of FIG. 5 and 6 are explanatory views showing the trapping action of particles in the conventional device and the device of the present invention, respectively. FIG. 7 is a diagram showing the results of Examples and Comparative Examples. 1 ... Dust collecting electrode, 2 ... Counter electrode 3 ... Ionization line

Claims (8)

[Claims] 1. A dust collecting electrode arranged in parallel at a predetermined interval;
A counter electrode located in parallel between adjacent dust collecting electrodes; and an ionization line located upstream of these electrodes; and by an electric discharge generated between the ionization line and the dust collecting electrode. In an air purifying device that removes dust by attracting particles in the air to the dust collecting electrode by an electric field formed between the dust collecting electrode and the counter electrode while flowing air, a flow of air flow to the dust collecting electrode. An air purification device, wherein at least one slit is formed in a direction perpendicular to the direction. 2. The slit is formed by dividing the dust collecting electrode into a plurality of dust collecting electrode pieces and arranging the dust collecting electrode pieces in parallel with the air flow at a predetermined interval in the same plane. The device according to claim 1. 3. The device according to claim 1, wherein the width of the slit is equal to or shorter than the gap between the dust collecting electrode and the counter electrode adjacent thereto. 4. The upstream end of the counter electrode is located on a line connecting the upstream ends of the adjacent dust collection electrodes, and the downstream end of the counter electrode is located downstream of the downstream end of the adjacent dust collection electrodes. Apparatus according to claim 1. 5. The device according to claim 4, which forms a corona discharge between the ionizing wire and the dust collecting electrode. 6. An apparatus according to claim 4, wherein the ionization line is grounded. 7. The device according to claim 4, wherein the width of the counter electrode is 30% wider than that of the dust collecting electrode. 8. A conductive screen is provided upstream of the ionization line and downstream of the counter electrode, respectively.
The device according to claim 4.