JPH07265739A - Apparatus and method for electrostatic classification - Google Patents

Abstract

PURPOSE:To classify simply with high precision and stability into many grades as the need arises. CONSTITUTION:Linear cross electrodes 34a, 34b, 34c and linear cross electrodes 34x, 34y, 34z are arranged to cross at right angles correspondingly. When low voltage with two or more phases is applied only to the linear cross electrodes 34a, 34b, 34c, the lightest powder moves to be extracted. When higher voltage with two or more phases is applied to the linear cross electrodes 34a, 34b, 34c and the linear cross electrodes 34x, 34y, 34z, the second lightest powder moves in the direction other than that of the lightest powder to be extracted. When a still higher voltage is applied with two or more phases is applied to only the linear cross electrodes 34x, 34y, 34z, the third lightest powder moves in the direction other than those of the previous powder to be extracted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic classifying apparatus and an electrostatic classifying method suitable as means for separating powder into, for example, a predetermined particle size range.

[0002]

2. Description of the Related Art Conventionally, as a device of this type, a "traveling wave alternating electric field curtain" (Japanese Patent Publication No. 54-12667) produced by applying a multiphase AC voltage to an electrode array consisting of a plurality of linear electrodes in a phase order. Japanese Patent Laid-Open Publication No. 62-53753 and Japanese Patent Laid-Open Publication No. Sho 60-37553, in which powder is separated and extracted for each predetermined particle size range by utilizing the electrodynamic levitation conveying force (see Japanese Patent Publication No.
An electrostatic classification device described in Japanese Patent Publication No. 156568 is known. The electrostatic classification device described in JP-A-62-53753 includes a plurality of linear electrodes stretched in a mesh shape (matrix), and a three-phase AC voltage is applied to these linear electrodes in order of phase, Traveling wave alternating electric field curtain (electric field matrix)
Is a device for performing classification by supplying particles to be classified to this traveling wave alternating electric field curtain, and particles having a small particle size among the particles to be classified are easily subjected to the action of an electrostatic force, Levitated along the alternating electric field curtain, on the other hand, particles with a large particle size are less susceptible to the influence of electrostatic force and fall through the mesh, so classification is performed. .

On the other hand, the electrostatic classification device described in Japanese Patent Laid-Open No. 60-156568 discloses an inclined classification plate, a supply means for supplying the powder to be treated to the upper surface of the classification plate, and a vibration for the classification plate. A vibrating means for mechanically moving the powder to be treated supplied on the classifying plate to the downstream side along the inclined surface, and moving along the plate surface of the classifying plate in a direction substantially perpendicular to the direction of inclination. The powder having a small particle size is conveyed along the moving electric field in a direction substantially perpendicular to the direction of the inclination, whereas the powder having a large particle size is formed by a moving electric field generating means for generating an electric field. Since it can be mechanically slid to the downstream side along the slope, classification is performed.

[0004]

However, in the electrostatic classification device described in Japanese Patent Laid-Open No. 62-53753, when the device is repeatedly used, small meshes are clogged and particles having a large particle size are generated. Cannot pass through the mesh, leading to a reduction in classification ability. Further, in order to form a traveling wave alternating electric field curtain (electric field matrix) sufficient for levitating and transporting the particles to be classified, a high frequency high voltage power source is necessary, and such a high frequency high voltage is likely to become unstable and If the wave alternating electric field curtain is disturbed as much as possible, particles with a small particle size may pass through the mesh and fall. In addition, there is also a drawback that classification cannot be performed on particles having a large particle size that cannot pass through the mesh.

On the other hand, in the electrostatic classifier described in Japanese Patent Laid-Open No. 60-156568, when the inclination of the classifying plate becomes steep as much as possible, it is mixed with powder having a large particle size and powder having a small particle size. There is a risk that the body will also slide down along the inclined surface,
This will lead to a decline in classification ability. On the other hand, if the inclination of the classifying plate becomes even gentler, the powder with a large particle size stays on the classifying plate, which hinders the movement of the powder with a small particle size, which also reduces the classification ability. The inconvenience of causing In addition, the optimum tilt angle of the classifying plate varies depending on the material of the powder to be treated, temperature and humidity conditions, changes over time, etc., so that there is a problem that its adjustment is very difficult.

The present invention has been made in view of the above circumstances, and can perform classification processing with high accuracy and stability with simple operation and adjustment, and is limited to two types of classification, large and small. First, it is an object of the present invention to provide an electrostatic classification device and an electrostatic classification method capable of finely classifying into any number of grades as needed.

[0007]

In order to solve the above problems, the invention according to claim 1 provides at least a striped electrode array in which a plurality of linear electrodes are repeatedly arranged in one direction and in sequence. The one side is covered with an insulating layer, the surface of the insulating layer is a treatment surface for performing the classification treatment of the powder to be treated, and a predetermined cycle or timing with respect to the plurality of linear electrodes. And a voltage applying means for applying a voltage of a plurality of phases that fluctuate in, when an electrostatic force of a predetermined strength is applied to the powder to be processed placed at a predetermined initial position on the processing surface, An electrostatic classification device that utilizes the fact that it is divided into a powder group having a small particle size that is moved by the electrostatic force and a group having a large particle size that is left without moving, wherein the voltage applying means is a control unit or Predetermined boosting signal supplied from the operating unit Based on, it is characterized by outputting a voltage of said plurality of linear electrodes on the plurality of phases to be applied by a predetermined amount boosting. In the present invention, the term “powder” is a concept including particles, fiber scraps, minute pieces, and the like.

The invention according to claim 2 is the electrostatic classifying device according to claim 1, wherein the classifying stator includes a conductive wire to be the linear electrode and an insulating fiber. It is characterized by comprising an electrode fabric woven into each other as warp yarns and weft yarns, and the insulating layer covering at least the surface of the electrode fabric.

According to a third aspect of the present invention, a plurality of linear electrodes are repeatedly arranged in one direction and in a phase order, and a plurality of linear bias electrodes are arranged in a direction orthogonal to these linear electrodes. At least one side of the grid-like electrode array thus formed is covered with an insulating layer, and the surface of the insulating layer serves as a treated surface for classifying the powder to be treated. Voltage applying means for applying voltages of a plurality of phases that fluctuate at a predetermined cycle or timing to the electrode electrode, and a predetermined value for the powder to be processed placed at a predetermined initial position on the processing surface. The electrostatic classification device utilizes the fact that when an electrostatic force of strength is applied, it is divided into a powder group with a small particle size that moves due to the electrostatic force and a group with a large particle size that remains without moving. Then, the voltage applying means, The plurality of linear phases to be applied to the plurality of linear electrodes based on a predetermined boosting signal supplied from the control unit or the operation unit while applying a constant bias DC voltage to the plurality of linear bias electrodes. It is characterized by boosting the voltage of a predetermined amount and outputting it.

The invention according to claim 4 is a grid-shaped electrode array in which a plurality of first linear electrodes and a plurality of second linear electrodes that are orthogonal to each other are arranged in sequence in order. At least one side of the body is covered with an insulating layer, and the surface of the insulating layer serves as a treated surface for classifying the powder to be treated, and a plurality of the first or / and second wires. Voltage-applying means for applying a voltage of a plurality of phases that fluctuate at a predetermined cycle or timing to the electrode electrode,
When an electrostatic force having a predetermined strength is applied to the powder to be processed placed at a predetermined initial position on the processing surface, the powder group having a small particle size and moved by the electrostatic force are moved. In the electrostatic classification device, the voltage applying means utilizes the fact that the particle size is divided into a large particle size group that is left behind, and the plurality of voltage applying means are based on a predetermined boosting signal supplied from a control unit or an operation unit. It is characterized in that the voltages of a plurality of phases to be applied to the linear electrodes are boosted by a predetermined amount and output.

The invention according to claim 5 is the electrostatic classification device according to claim 3 or 4, wherein the classification stator is the linear electrode or the first linear electrode. And a second conductive wire that becomes the linear bias electrode or the second linear electrode are woven as warp yarns and weft yarns into each other, and at least the surface of the electrode fabric. The insulating layer for coating, and the first
At least one of the second conductive wire and the second conductive wire is coated with an insulating material.

Further, the invention according to claim 6 is based on claim 1,
3. The electrostatic classification device according to 3 or 4, wherein at least a part of the processing surface of the stator for classification is a curved surface, and the position of the predetermined destination of the powder to be processed is on the inclined surface. Or
Or, it is characterized by being set upside down.

The invention according to claim 7 is an electrostatic classification method for separating and extracting a powder to be treated in a predetermined particle size range by using the electrostatic classification device according to claim 1 or 3. By controlling the voltage applying means, the powder to be processed placed at a predetermined initial position on the processing surface, an electrostatic force of a predetermined strength is applied, and further, each time a predetermined processing period elapses, It is characterized in that the electrostatic force is gradually strengthened in a stepwise manner so that the groups having a small particle size are sequentially electrostatically moved to be separated and extracted.

Furthermore, the invention according to claim 8 is the electrostatic classification method for separating and extracting the powder to be treated for each predetermined particle size range by using the electrostatic classification device according to claim 4. The voltage applying means is controlled to apply an electrostatic force having a predetermined strength and a predetermined direction to the powder to be processed placed at a predetermined initial position on the processing surface, and further, for a predetermined processing period. By increasing the electrostatic force stepwise with each passage, and changing the direction of the electrostatic force, from the group of small particle size,
It is characterized in that it is sequentially electrostatically moved in different directions and separated and extracted.

[0015]

In the structure of claim 1, the voltage applying means applies the voltages of the plurality of phases to be applied to the plurality of linear electrodes on the basis of a predetermined boosting signal supplied from the control section or the operating section. It boosts a predetermined amount and outputs. In order to separate the powder to be processed into predetermined particle size ranges, the voltages of the multiple phases to be applied to the linear electrodes are initially set to low voltages. Then, the lightest group (powder) with the smallest particle size (which easily moves even with weak electrostatic force) starts to move. When the first classification process is completed, this time, the voltage of the plurality of phases to be applied to the linear electrode is set and changed to be higher by a predetermined amount. The electrostatic force is strengthened, and the next smaller group of particles starts to move. After that, if the voltage of the plurality of phases to be applied to the linear electrode is stepwise increased, the groups having a smaller particle size are sequentially separated and extracted from the group having a smaller particle size (claim 7). Therefore, if the pressurization is repeated repeatedly, it is possible to finely classify into several grades accordingly.

Further, a conductive wire having a circular cross section is used as the linear electrode, and the conductive wire and the insulating fiber are mutually warped and
By weaving at a predetermined pitch as a weft and making it into a form of an electrode woven fabric, the wiring of the linear electrodes can be formed.
A long classifier can be easily obtained, and since the peripheral edge of the linear electrode is smooth, dielectric breakdown can be avoided (claim 2). Further, it is possible to freely set the processing surface to a curved surface and set the position of the movement destination of the powder to be processed to an inclined surface or an inverted surface.
In such a curved surface configuration, when the powder to be processed reaches the destination on the inclined surface or upside down, if the action of the electrostatic force is interrupted or terminated, the powder to be processed easily slips or falls. Therefore, the collection becomes easy (claim 6).

According to the third aspect of the invention, the first aspect of the invention is as follows.
In addition to the described structure, a linear bias electrode is provided in a direction orthogonal to the linear electrode, and a bias DC voltage is applied to the linear bias electrode. Therefore, the moving powder to be processed is continuously subjected to the electrostatic attraction force from the linear bias electrode, and thus moves straight along the linear bias electrode. The linear electrodes wired in the form of electrode fabric are woven in a state where they cross up and down alternately with the orthogonal threads one by one, so the powder to be treated tends to bend and bend. Is. Therefore, the configuration according to claim 3 is particularly useful when the linear electrode is wired in the form of an electrode fabric and applied to the orthogonal thread thereof.

In the structure of claim 4, the plurality of first linear electrodes and the plurality of second linear electrodes are arranged in a state of being orthogonal to each other, so that the powder to be processed is two-dimensionally moved. Is possible. In order to classify the powder to be treated in a predetermined particle size range, the voltage applying means is controlled so that, for example, first, low voltages of a plurality of phases are applied only to the plurality of first linear electrodes. Then, the lightest group (which easily moves even with a weak electrostatic force) first starts to move in a direction, for example, the right side orthogonal to the length direction of the first linear electrode, and is separated and extracted. Next, a further increased voltage of a plurality of phases is applied to both the plurality of first linear electrodes and the plurality of second linear electrodes. Then, the second lightest group starts to move in the direction of 45 degrees with respect to each of the first and second linear electrodes and is extracted. Then the second
The voltage of a plurality of phases further boosted is applied to the linear electrode of. Then, the group with the third lightest particle size moves in the direction along the first linear electrode and is extracted. Hereinafter, if the voltage of a plurality of phases is repeatedly stepped up, and the control is performed to change the direction of the moving destination two-dimensionally every time the voltage is stepped up, the particles are moved in order from the smaller particle size group. Separation and extraction are performed while changing the destination (claim 8). Therefore, if the pressurization is repeated repeatedly, it is possible to finely classify into several grades accordingly. Moreover, since the destinations of movement are different from each other, recovery after separation and extraction is much easier.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. First Embodiment FIG. 1 is a perspective view showing the configuration of an induction charge type electrostatic classification device according to a first embodiment of the present invention. The electrostatic classification device of this example is applied to powder to be treated. It is roughly composed of a classification stator 1 that generates an electrostatic carrying force, and an electric circuit unit 2 that applies a three-phase voltage to the classification stator 1 in a variable level.
FIG. 2 is a plan view showing an electrode structure of the classification stator 1, and FIG.
Is an exploded perspective view showing an exploded configuration of the stator 1 for classification,
FIG. 4 is a sectional view of the stator 1 for classification. First,
The classification stator 1 will be described first. The classification stator 1 is
An electrode array body 3 in which three-phase linear electrodes 31a, 31b, 31c, ... Are repeatedly arranged in one direction and in phase order, and a pair of insulating films 4 and 4 sandwiching the electrode array body 3 from the upper and lower surfaces. , And the inter-film filling material 5.
The electrode array 3 includes a plurality of conductive wires (in this example,
Use copper wire with wire diameter 40μm) 31'a, 31'b, 31 '
c, ... Are warp threads or weft threads, and insulating fibers (in this example,
Polyester fiber with a wire diameter of 40 μm is used) 32, 32,
.. are formed by alternately weaving one by one with a predetermined pitch and using a plurality of conductive wires 31 '.
The a, 31'b, 31'c, ... Are woven in this way to form the linear electrodes 31a, 31b, 31c, ... With a predetermined pitch (80 μm in this example). These linear electrodes 31a, 31b, 31c, ...
As shown in FIG. 1, every two lines are connected in series or in parallel to form a stator electrode group for each phase. That is, the linear electrodes 31a, 31a, ... Are connected to each other to form the A-phase stator electrode group, and the linear electrodes 31b, 31b, ... Are connected to each other to form the B-phase stator electrode group. Linear electrode 3
, 1c, 31c, ... Are connected to each other to form a C-phase stator electrode group.

As the insulating films 4 and 4, for example, a PET (polyethylene terephthalate) film having a surface resistivity of 10 ¹⁵ Ω / □ or more and a thickness of 1 μm to 200 μm, which is non-charged, is used. Insulation film 4
The surface is a processing surface 4a that carries the powders 6, 6, ...
Used as. In addition, the inter-film filler (in this example, Nissili epoxy resin "Plastic" is used) 5 fills the texture generated in the electrode array 3 to fix the electrode pitch, and It is used to bond a pair of insulating films 4 and 4 which are opposed to each other by sandwiching them.

In order to produce the classification stator 1 having the above-mentioned structure, first, a weaving machine (not shown) is used to weave the electrode array 3 and the woven electrode array 3 (this electrostatic classification device After cutting into a predetermined size (depending on the device and the scale of the system to be incorporated), it is placed on one of the insulating films 4 in an overlapping manner. Next, the inter-film filler 5 in a fluid state is applied from above the electrode array 3 on the insulating film 4. The applied inter-film filler 5 reaches the inner surface of the insulating film 4 below from the texture of the electrode array 3. Then, the other insulating film 4 is placed on the electrode array body 3 in an overlapping manner. Finally, using a pressure bonding machine, pressure is applied from both sides of the pair of insulating films 4 and 4 to bring the insulating films 4 and the electrode array 3 into close contact with each other to cure the inter-film filler 5 for classification. Complete the stator 1.

Next, the electrical configuration of the electric circuit section 2 will be described. FIG. 5 is a block diagram showing the electrical configuration of the electric circuit section. As shown in the figure, the electric circuit unit 2 of this example includes a power supply circuit 21 that variably outputs a plurality of DC voltages.
And switching elements 22a, 22 interposed between the power supply circuit 21 and the stator electrode group of each phase of the electrode array 3.
b, 22c and a control circuit 23. The power supply circuit 21 includes an AC / DC converter that converts commercial alternating current into direct current, a voltage variable circuit, and the like, and outputs three types of voltages (positive voltage + V, negative voltage −V, zero voltage 0V). The voltage variable circuit sets / changes the level of the output voltage based on the level setting signal supplied from the control circuit 23. The switching elements 22a, 22b, 22c have three types of voltages (positive voltage + V, negative voltage -V) supplied from the power supply circuit 21 based on a three-phase voltage generation signal sent from the control circuit 23 at a predetermined timing. , Zero voltage 0V) by selecting one by one in a predetermined order,
Three-phase voltage (rectangular wave pulse voltage) is generated and applied to the stator electrode group of each phase. Further, the control circuit 23 is a CPU
(Central processing unit), ROM, RAM, etc., and the above-mentioned power supply circuit 21 and switching elements 22a, 22b, 2
The control of each part of the apparatus including the control of 2c is performed. The linear electrodes 31a, 31b, 31 forming the stator electrode group
For c, ..., Switching elements 22a, 22b, 2
When a voltage of three phases from 2c is applied, a traveling wave electric field is formed in the space near the processing surface 4a, and powder having a predetermined particle size range is selected from the powders 6, 6, ... An electrostatic transport force is generated on the body.

Next, the principle of electrostatic movement (conveyance) of powder will be described with reference to FIGS. 6 and 7. For convenience of explanation, only two large and small powders (aluminum powders) 61a and 61b are handled, and two large and small powders 6 are provided on the processing surface 4a.
It is assumed that 1a and 61b are placed in contact with each other. The particle size of the large powder 61a is 300 μm, and the particle size of the small powder 61b is 100 μm. First, the control circuit 23
Sends a predetermined level setting signal to the power supply circuit 21 and sends a three-phase voltage generation signal to the switching elements 22a, 2
2b, 22c, and as shown in FIG.
Low-voltage positive voltage + V to the phase stator electrode group (linear electrodes 31a, 31a, ...) And the B-phase stator electrode group (linear electrode 31
b, 31b, ...) With a zero voltage of 0 V, and a C-phase stator electrode group (linear electrodes 31c, 31c, ...) With a low negative voltage -V.
Is applied. Then, as shown in (b) of the figure, a weak current flows between the powders 61a and 61b that initially had no charge, and the powder 61a on the left side of the figure (the linear electrode 3
Negative charge (inverse polarity of 1a) is induced, while positive charge (inverse polarity of charge of the linear electrode 31c) is induced (charged) in the powder 61b on the right side in the figure, resulting in an equilibrium state. become. As a result, the electrostatic attraction force is applied in the direction of the linear electrode 31a closest to the left powder 61a, and to the linear electrode 31c of the nearest powder 61b in the right direction. work. However, since the electrostatic attraction is weak, both powders 61
a and 61b still do not move in the direction of the electrostatic attraction force. Here, once the supply of the three-phase voltage to each linear electrode is cut off, a current in the opposite direction to the above flows through the powders 61a and 61b, and the positive and negative induced charges disappear.

Next, the control circuit 23 sends a predetermined level signal to the power supply circuit 21 to raise the output voltage by one step above the initial set value. Then, the switching element 22
Send a three-phase voltage generation signal to a, 22b, and 22c, and
A positive voltage + V boosted by one step compared to the phase stator electrode group (linear electrodes 31a, 31a, ...) First, zero voltage 0V to the B phase stator electrode group (linear electrodes 31b, 31b, ...), C
The negative voltage -V boosted by one step is applied again to the phase stator electrode group (linear electrodes 31c, 31c, ...). Then, an electric current that is one step larger than that at the beginning flows between the powders 61a and 61b, and more negative charges are induced in the powder 61a on the left side,
On the other hand, more positive charges are induced in the powder 61b on the right side. The electrostatic field in the space near the processing surface 4a also becomes stronger.
As a result, the static electricity becomes stronger toward the linear electrode 31a closest to the left powder 61a, and toward the linear electrode 31c closest to the right powder 61b. Electric attraction works. The large powder 61a on the right side is heavy, so it still does not move. However, the small powder 61b on the left side is light, so as shown in FIG. It moves to just above the linear electrode 31c. At this time, the two powders 61a and 61b separate from each other while having induced charges of opposite polarities to each other, so that the powder 61a on the right side is charged to the negative electrode and the powder on the left side is charged to the positive electrode.

Next, as shown in FIG. 3D, the linear electrode to which a voltage is applied is shifted to the right in the figure, for example. That is, the voltage is switched and the A-phase stator electrode group (the linear electrodes 31a,
31a, ...) to a negative voltage −V, a B-phase stator electrode group (linear electrodes 31b, 31b, ...) To a positive voltage + V, a C-phase stator electrode group (linear electrodes 31c, 31c, ...) Zero voltage 0V
, The electric charges of the linear electrodes 31a, 31b, 31c, ... Are exchanged, but the electric charges of the powders 61a, 61b are charged, so that the original electric charge state is maintained. At this time, due to the electrostatic force between the charges of the classification stator 7 and the small powder 61b, a rightward conveying force is generated with respect to the powder 61b charged to the positive electrode. As a result, the powder 61b quickly moves to the right as shown in FIG. On the other hand, the electrostatic force in the right direction acts on the large powder 61a charged in the negative electrode, but it is heavy and cannot be the carrying force.

Next, as shown in FIG. 6 (f), the linear electrode for applying a voltage is further shifted to the right.
By the electrostatic force between the electric charges of the small powder 61b and the small powder 61b, the powder 61b charged to the positive electrode moves further to the right as shown in FIG. Hereinafter, each time the voltage switching operation of shifting the linear electrode to which the voltage is applied to the right is repeated, the powder 61a
Sequentially move one electrode to the right by one pitch, and finally fall from the right end surface of the processing surface 4a in the figure and are collected in a collection container (not shown), as shown in FIG. On the other hand, the large powder 61a charged in the negative electrode remains left at the initial position.

After collecting (collecting) the powder 61b, next,
The control circuit 23 controls the power supply circuit 21 to further boost the output voltage by one stage. Then, the switching element 22
By controlling a, 22b, 22c, as shown in FIG. 7 (i), the A-phase stator electrode group (the linear electrodes 31a, 31a,
...) with a further positive voltage + V, zero voltage 0V applied to the B-phase stator electrode group (linear electrodes 31b, 31b, ...).
The negative voltage -V further boosted by one step is applied again to the C-phase stator electrode group (linear electrodes 31c, 31c, ...). As a result, the electrostatic field in the space near the processing surface 4a becomes even stronger. At this point, the large powder 61a charged in the negative electrode
Also, as shown in (j) of the same figure, it moves to just above the linear electrode 31a. Next, as described above, each time the voltage switching operation of shifting the linear electrode applying the voltage to the right is repeated,
As shown in (k) to (n) of the figure, the powder 61a sequentially moves to the right by one pitch of the electrode, and as shown in (o) of the figure,
Finally, it falls from the right end surface of the processing surface 4a in the figure and is collected in a collection container (not shown).

In the electrostatic transfer principle described above, the case where there are only two powders to be processed has been described as an example, but in reality, a large number of powders of various particle sizes are mixed in the powder to be processed. It is a thing. However, when a large number of powders to be treated are mixed, each powder is inevitably in contact with any of a large number of other powders, or is highly likely to be in contact with one another due to collision or the like. When a voltage is applied to the stator electrode group in this state, an induced current flows (that is, charges are exchanged) between the many powder particles that are in contact with each other, and the powder particles that are close to the linear electrodes are generated. Causes an induced charge having a polarity opposite to that of the charge of the linear electrode. Therefore, since electrostatic attraction works between the linear electrode and the powder, there is a very high chance that the powders are separated from each other and charged.

In order to classify a large amount of powder to be processed into a predetermined particle size range, the control circuit 23 controls the power supply circuit 21 and the switching elements 22a, 22b, 22c to form the linear electrodes 31a, 31b ,. The three-phase voltages to be applied to 31c, ... Are initially set to low voltages. Then, the voltage switching operation of shifting the linear electrode to which the voltage is applied, for example, to the right is repeated.
Then, the group (powder) with the smallest particle size (which easily moves even with a weak electrostatic force) starts to move, falls from a predetermined end surface of the processing surface 4a, and is collected in a collection container (not shown). Next, the voltages of the plurality of phases to be applied to the linear electrode are set and changed one step higher. Then, the voltage switching operation of shifting the linear electrode to which the voltage is applied, for example, to the right is repeated. Then, the charge amount of the powder is further increased and the electrostatic field is further strengthened.
This time, a group next to the particle size starts to move, falls from a predetermined end surface of the processing surface 4a, and is collected in a collection container (not shown). Hereinafter, by stepwise increasing the voltage of a plurality of phases to be applied to the linear electrode, the groups having a small particle size to the group having a large particle size are separated and extracted in order.

Modification of First Embodiment In the above-mentioned first embodiment, the electrode array 3 made by plain weaving the conductive wire and the insulating fiber is used, but the electrode array is a woven fabric body. Not limited. For example, a metal film such as copper or aluminum is formed on an electric circuit substrate such as phenol resin or glass epoxy resin, a photosensitive resin is applied on the metal film, and the strip electrode pattern is baked to etch the metal film. By doing so, an electrode array may be obtained.

Further, the processing surface 4 in the first embodiment described above.
a may be a flat surface shape, a bent surface shape, a curved surface shape, a spherical surface shape, or other various surface shapes. For example, by setting the processing surface to a curved surface, the preset target position (end point) of the moving powder is set to be directly above the capture container, and when the powder reaches the target position, the line If the application of the voltage to the electrode is cut off, the powder easily slides or falls, and the collection becomes easy. On the other hand, the processing surface 4a remains flat, and after the powder reaches the target position and accumulates, all or part of the processing surface is inclined or inverted, and the voltage application to the linear electrode is cut off. However, this may be configured so that the powder slides or falls.

Second Embodiment FIG. 8 is a perspective view showing the configuration of an induction charge type electrostatic classification device according to a second embodiment of the present invention, and FIG. 9 is a classification stator of the electrostatic classification device. 1a is a plan view showing the electrode structure of FIG. 1a, FIG. 10 is an exploded perspective view showing the structure of the stator 1a for classification in an exploded manner, and FIG. 11 is an electrical structure of an electric circuit section 2a in the electrostatic classification device. It is a block diagram showing. The electrostatic classification device of the second embodiment is largely different from the structure of the first embodiment in that it has a plurality of linear electrodes 31a, 31.
The electrode array 3a is configured by using a plurality of linear bias electrodes 33, 33, 33, ... Instead of the insulating fibers 32, 32, ... Of the electrode array 3 woven orthogonally to b, 31c ,. This is the point I chose to do. That is, as shown in FIGS. 9 and 10, the electrode array 3a of this example includes a plurality of conductive wire members (copper wires having a wire diameter of 40 μm in this example) 31 ′.
a, 31'b, 31'c, ... are warp threads or weft threads, and conductive wire material with insulation coating (in this example, a Teflon-coated copper wire with a wire diameter of 40 µm) 33 ', 33', ... is orthogonal thread As one of the conductive wires 31'a, 31'b, 3
1'c, ... are woven in this way,
The wiring of the three-phase linear electrodes 31a, 31b, 31c, ... Has a predetermined pitch (80 μm in this example), and the conductive wires 33 ′, 33 ′ ,. By a predetermined pitch (80 in this example)
(.mu.m) linear bias electrodes 33, 33, ... Are wired. Here, the three-phase linear electrodes 31a, 31b, 3
1c, ... Are repeatedly wired in the order of phases, but the linear bias electrodes 33, 33, ... Are directly connected in series or in parallel to each other so that all of them have the same potential (however, they are not necessarily the same. It does not have to be a potential). Note that FIG.
In FIG. 1, the same components as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

The electric circuit portion 2a of this example includes an electrode array 3
Since a includes the linear bias electrodes 33, 33, ..., As shown in FIG. 11, in addition to variably outputting a plurality of DC voltages (the same as in the eleventh embodiment), a constant bias DC voltage is provided. A power supply circuit 21 for applying DC to the linear bias electrodes 33, 33, ..., Switching elements 22a, 22b, 22c having the same configuration as the first embodiment, and a control circuit 23a for controlling each part of the apparatus. There is.

Next, the classification operation of this example will be described. In order to classify a large amount of powder to be processed in a predetermined particle size range, the control circuit 23a controls the power supply circuit 21a and the switching elements 22a, 22b, 22c to cause the linear bias electrodes 33, 32 ,. With a predetermined bias DC voltage DC applied, the three-phase voltages to be applied to the linear electrodes 31a, 31b, 31c, ... Are initially set to low voltages. Then, the voltage switching operation of shifting the linear electrode to which the voltage is applied, for example, to the right is repeated. Then, the group (powder) with the smallest particle size (which easily moves even with weak electrostatic force)
By the "rail effect (electrostatic attraction force)" of the linear bias electrodes 33, 33, ..., The linear bias electrodes 33, 33, ... Start moving along the linear bias electrodes 33, 33 ,. Collected in a collection container.

Next, the voltages of the plurality of phases to be applied to the linear electrodes are set and changed one step higher. Then, the voltage switching operation of shifting the linear electrode to which the voltage is applied, for example, to the right is repeated. Then, since the charge amount of the powder is further increased and the electrostatic field is further strengthened, the group next to the particle size is the rail effect (electrostatic attraction force) of the linear bias electrodes 33, 33 ,. ) ”, The linear bias electrodes 33, 33,
.. starts to move, falls from a predetermined end surface of the processing surface 4b, and is collected in a collection container (not shown). Less than,
By repeating stepwise boosting of the voltages of a plurality of phases to be applied to the linear electrode, it is possible to separate and extract several grades from a group having a small particle size to a group having a large particle size in order.

"Rail effect" on each linear bias electrode 33
The reason is that the non-uniform electric field generated by the application of the bias DC voltage always acts on the moving powder 6, so that electric charges of the opposite polarity to the linear bias electrode 33 are induced in the powder 6. . Therefore, under the unequal electric field, the electrostatic attraction force acts between the charges of the powder 6 and the linear bias electrode 33 as a whole. Therefore, the powder 6 travels along the linear bias electrode 33 so as to be guided to the rail. As shown in FIG. 12, even when the powder 6b having a large particle diameter obstructs the path, the electrostatic attraction force constantly acting in the direction of the linear bias electrode 33 causes the large powder to wrap around, You can return to the original rail.

Therefore, according to the configuration of this example, it is possible to improve the traveling straightness of the powder 6 by the "rail effect" of the linear bias electrodes 33, 33, .... The linear electrodes wired in the form of electrode fabric are woven in a state where they cross up and down alternately with the orthogonal threads one by one, so the powder to be treated tends to bend and bend. Is. Therefore, when wiring the linear electrodes in the form of the electrode fabric, it is extremely effective to use the linear bias electrodes 33, 33, ... As the orthogonal threads of the linear electrodes.

Third Embodiment FIG. 13 is a perspective view showing the structure of an induction charge type electrostatic classifier according to a third embodiment of the present invention, and FIG. 14 is an electric circuit of the electrostatic classifier. It is a block diagram which shows the electric constitution of the part 2a. In the third embodiment, the classification stator 1b includes a plurality of linear lateral electrodes 34 which are orthogonal to each other.
a, 34b, 34b, 34c, ... And a plurality of linear vertical electrodes 3
4x, 34y, 34z, ... And each of the linear horizontal electrodes 34a, 34b, 3 is provided with a grid-shaped electrode array 3b which is repeatedly arranged in order of phase.
4c, ... And the linear vertical electrodes 34x, 34y, 34z, ... Simultaneously apply three-phase voltages so that the powder to be processed can be two-dimensionally transferred (extracted).

That is, the electrode array 3b of this example is composed of a plurality of insulating coated conductive wires (wire diameter 60 in this example).
Uses Teflon-coated copper wire of μm) 34'a, 34'b, 3
4'c, 34'x, 34'y, 34'z, ... are warp yarns and weft yarns, and are alternately woven one by one, so that they are linearly arranged at a predetermined pitch (100 µm) and in phase order. The horizontal electrodes 34a, 34b, 34c, ... And the linear vertical electrodes 34x, 34y, 34z ,.

In the electric circuit portion 2b of this example, the three-phase linear horizontal electrodes 34a, 34b, 34c, ... And the three-phase linear vertical electrodes 34x, 34y, 34z ,. Then, as shown in FIG.
a, 22b, 22c, 22x, 22y, 22z are added. The control circuit 23b controls the switching elements 22a, 22b, 22c, 22x, 22y, 22z.
To control only the linear horizontal electrodes 34a, 34b, 34c, ..., Only the linear vertical electrodes 34x, 34y, 34z, ... Or the linear horizontal electrodes 34a, 34b, 34c ,. Power is supplied to both 34x, 34y, 34z, ....

Next, the operation of this example will be described with reference to FIG. The case where the powder to be processed (aluminum powder) placed on the central portion (initial position) of the processing surface 4c is classified into 8 grades for each particle size range will be described as an example. Here, of the 8 grades, the lightest particle, the second lightest particle, the third lightest particle, the fourth lightest particle, the fourth heavyest particle, and the third heavyest particle in order from the smallest particle size (lightest mass). We will call them heavy particles, second heavy particles, and first heavy particles. Separation and extraction are performed in order from the lightest one.

Separation and extraction of the lightest particles The control circuit 23b controls the power supply circuit 21b to output an output voltage other than 0V (among eight predetermined levels).
Set to the lowest level voltage. Then, the switching elements 22a, 22b, 22c are drive-controlled and the switching elements 22x, 22y, 22z are cut off to apply a three-phase voltage only to the linear lateral electrodes 34a, 34b, 34c, .... Then, positive voltage + V, negative voltage -V,
Linear horizontal electrodes 34a, 34 for applying a zero voltage of 0V
The voltage switching operation of shifting b, 34c, ... Up in the figure is repeated. Then, the lightest particles first move upward in the figure, fall from the end surface of the processing surface 4c shown by A in the figure, and are collected in a collection container (not shown).

Separation and Extraction of Second Light Particle Next, the control circuit 23b controls the power supply circuit 21b to make it 0.
The output voltage other than V is set to the second lowest level voltage, and the switching elements 22a, 22b, 22c,
By driving and controlling 22x, 22y, and 22z, the linear horizontal electrodes 34a, 34b, 34c, ...
Three-phase voltages are applied to both 4x, 34y, 34z, .... Then, the linear lateral electrodes 34a, 34b, 34c, ... To which the positive voltage + V, the negative voltage −V, and the zero voltage 0V are applied.
Voltage switching operation to shift the above in the figure, and positive voltage + V,
The voltage switching operation of shifting the linear vertical electrodes 34x, 34y, 34z, ... To which a voltage of negative voltage −V and zero voltage 0V is applied to the left in the drawing is repeated. Then, this time, the second lightest particles start moving toward the upper left of the drawing, fall from the corner of the processing surface 4c shown by B in the drawing, and are collected in a collection container (not shown).

Separation and Extraction of Third Light Particle Next, the control circuit 23b controls the power supply circuit 21b to set 0.
By increasing the output voltage other than V by one step, controlling the switching elements 22x, 22y, 22z and controlling the switching elements 22a, 22b, 22c to be cut off, only the linear vertical electrodes 34x, 34y, 34z ,. Apply phase voltage. Then, the voltage switching operation of shifting the linear horizontal electrodes 34x, 34y, 34z, ... To which the voltage is applied to the left in the drawing is repeated. Then, the third light particles start moving to the left in the drawing, fall from the end surface of the processing surface 4c indicated by C in the drawing, and are collected in a collection container (not shown).

Separation and Extraction of Fourth Light Particle Next, the control circuit 23b controls the power supply circuit 21b to make it 0.
The output voltage other than V is further boosted by one step, and the switching elements 22a, 22b, 22c, 22x, 22y,
By controlling the drive of 22z, the linear lateral electrodes 34a,
34b, 34c, ... And linear vertical electrodes 34x, 34y, 3
Three-phase voltage is applied to both 4z ,. Then, the voltage switching operation for shifting the linear horizontal electrodes 34a, 34b, 34c, ... Applying the voltage to the lower side in the figure, and the voltage for shifting the linear vertical electrodes 34x, 34y, 34z ,. Repeat the switching operation. Then, this time, the fourth light particles start moving toward the lower left in the figure, fall from the corner indicated by D in the figure of the treated surface 4c, and are collected in a collection container (not shown).

After that, the control circuit 23b controls the power supply circuit 21b to boost the output voltage other than 0V to the level of the next stage, and drives the switching elements 22a, 22b, 22c. By controlling and cutting off the switching elements 22x, 22y, 22z, the linear lateral electrodes 34a, 34b, 34 are formed.
A three-phase voltage is applied only to c, .... Then, the voltage switching operation of shifting the linear horizontal electrodes 34a, 34b, 34c, ... Then, the fourth heavy particle started to move downward in the figure and the treated surface 4
It falls from the end surface indicated by E in the figure of c and is collected in a collection container (not shown). Separation and Extraction of Third Heavy Particle Next, the control circuit 23b controls the power supply circuit 21b to make it 0.
The output voltage other than V is further boosted by one step, and the switching elements 22a, 22b, 22c, 22x, 22y,
By controlling the drive of 22z, the linear lateral electrodes 34a,
34b, 34c, ... And linear vertical electrodes 34x, 34y, 3
Three-phase voltage is applied to both 4z ,. Then, the voltage switching operation for shifting the linear horizontal electrodes 34a, 34b, 34c, ... To which the voltage is applied downward in the figure, and the voltage for shifting the linear vertical electrodes 34x, 34y, 34z, ... Repeat the switching operation. Then, this time, the third light particles start moving toward the lower left of the drawing, fall from the corner of the processing surface 4c indicated by F in the drawing, and are collected in a collection container (not shown).

Separation and Extraction of Duplex Particles Next, the control circuit 23b controls the power supply circuit 21b to make it 0.
By increasing the output voltage other than V by one step, controlling the switching elements 22x, 22y, 22z and controlling the switching elements 22a, 22b, 22c to be cut off, only the linear vertical electrodes 34x, 34y, 34z ,. Apply phase voltage. Then, the voltage switching operation of shifting the linear lateral electrodes 34x, 34y, 34z, ... To which the voltage is applied to the right in the drawing is repeated. Then, this time, the second heavy particles start moving toward the right in the figure, fall from the end surface of the processing surface 4c indicated by G in the figure, and are collected in a collection container (not shown).

Separation and Extraction of the Most Heavy Particle Finally, the control circuit 23b controls the power supply circuit 21b to set the output voltage other than 0V to the highest voltage, and
Switching elements 22a, 22b, 22c, 22x, 2
By controlling the drive of 2y and 22z, the linear lateral electrodes 3
4a, 34b, 34c, ... And linear vertical electrodes 34x, 34
Three-phase voltages are applied to both y, 34z, .... Then, the linear horizontal electrodes 34a, 34b, 34 for applying a voltage
The voltage switching operation of shifting c, ... To the upper side in the figure and the voltage switching operation of shifting the linear vertical electrodes 34x, 34y, 34z ,. Then, this time, the most heavy particles start moving toward the upper right in the figure, fall from the corner of the processing surface 4c shown by H in the figure, and are collected in a collection container (not shown). This completes the 8th grade classification,
The "remains" that are heavier than the heaviest particles are left in the center of the processing surface 4c.

Modification of Third Embodiment In the above-described third embodiment, as shown in FIG. 14, the linear horizontal electrodes 34a, 34b, 34c, ...
4x, 34y, 34z, ..., The same voltage is applied to the A-phases, the B-phases, and the C-phases, respectively, but the linear horizontal electrodes 34a, 34b, 34c,
, And the linear vertical electrodes 34x, 34y, 34z, ... Are provided with different power supply circuits, it is possible to classify into eight or more grades.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific structure is not limited to this embodiment, and there are design changes and the like within a range not departing from the gist of the present invention. Also included in the present invention. For example, the conductive wire used as a linear electrode is not limited to a copper wire, a gold wire,
A silver wire, a stainless wire, a nichrome wire, an aluminum wire or the like may be used. Further, not limited to the bare conductive wire, a wire covered with an insulating material such as Teflon, polyimide, polyamide, polyester, polyurethane, or polyvinyl chloride may be used. Further, the insulating fiber is not limited to polyester fiber, for example, soft polyvinyl chloride fiber,
Synthetic fibers such as polyethylene fibers, polypropylene fibers, polyimide fibers, polyamide fibers, polyurethane fibers, polyacrylonitrile fibers, polyvinyl alcohol fibers, polyvinylidene chloride fibers, and polyfluorinated ethylene fibers may be used. Further, the wire diameters of various wire materials are not limited to those in the embodiment, and various thick wire and thin wire can be used as necessary.

The electrode pitch is not limited to 80 μm,
By changing the wire diameter and weave, the thickness of the wire is ~ 2mm
It is set arbitrarily in the range of μm. Note that theoretically, the smaller the electrode pitch, the greater the force and power density obtained. Further, the insulating film is not limited to the PET film,
For example, a polymer film such as a polypropylene film, a polyimide film, or a soft polyvinyl chloride film may be used. The inter-film filler is not limited to the epoxy resin, but may be synthetic rubber such as butyl rubber or butadiene-styrene rubber, natural rubber, acrylic adhesive, epoxy adhesive, vinyl chloride resin, or the like. Further, the powder to be treated is not limited to aluminum spheres, and may be, for example, iron powder, copper powder, zirconia powder, etc., not limited to metal powder, semiconductor powder,
Resistor powder may be used, and further, dielectric powder such as glass, polyethylene, polycarbonate, acrylic and ceramics may be used.

In the above-mentioned embodiments, the case where the insulating films are provided on both surfaces of the electrode array body which is the electrode woven fabric has been described. However, when the linear electrodes are arranged by the electrically conductive wire covered with the insulation, The insulating film can be omitted.

[0053]

As described above, according to the configuration of the present invention, since there is no clogging, no high frequency, and the shape of the processing surface is flexible, highly accurate and stable classification processing can be performed by a simple operation. be able to. In addition, it is not limited to two types of classification, large or small, and can be finely classified to any number of grades as needed. Further, according to the structure of the third aspect, since the linear bias electrode is provided in the direction orthogonal to the linear electrode, it is possible to prevent the deviation of the traveling of the powder. Further, according to the configuration of the fourth aspect, since the moving direction can be specified for each particle size range, recovery after separation and extraction becomes much easier.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing a configuration of an induction charge type electrostatic classification device according to a first embodiment of the present invention.

FIG. 2 is a plan view showing an electrode structure of a classification stator in the electrostatic classification device.

FIG. 3 is an exploded perspective view showing an exploded configuration of a stator for classification.

FIG. 4 is a cross-sectional view showing the structure of the same classification stator.

FIG. 5 is a block diagram showing an electrical configuration of an electric circuit section.

FIG. 6 is a principle diagram for explaining a principle of electrostatic transfer of powder in the embodiment.

FIG. 7 is a principle diagram for explaining the electrostatic transport principle of powder in the same example.

FIG. 8 is a perspective view showing a schematic configuration of an induction charge type electrostatic classification device according to a second embodiment of the present invention.

FIG. 9 is a plan view showing an electrode structure of a classification stator in the same electrostatic classification device.

FIG. 10 is an exploded perspective view showing an exploded configuration of the same classification stator.

FIG. 11 is a block diagram showing an electrical configuration of an electric circuit section in the electrostatic classification device.

FIG. 12 is a diagram for explaining the operation of the embodiment.

FIG. 13 is a perspective view showing a configuration of an induction charge type electrostatic classification device according to a third embodiment of the present invention.

FIG. 14 is a block diagram showing an electrical configuration of an electric circuit unit in the electrostatic classification device.

FIG. 15 is an explanatory diagram for explaining a classification operation of the same example.

[Explanation of symbols]

1, 1a, 1b Classification stator 2, 2a, 2b Electric circuit unit (voltage applying unit and control unit) 21, 21a, 21b Power supply circuit (part of voltage applying unit) 22a, 22b, 22c Switching element (voltage applying unit) Part of means 22x, 22y, 22z Switching element (part of voltage applying means) 23, 23a, 23b Control circuit (part of voltage applying means) 3,3a Electrode array (electrode fabric) 31a, 31b, 31c Linear electrodes 31'a, 31'b, 31'c Conductive wire 32 Insulating fibers 34a, 34b, 34c Linear horizontal electrodes (first linear electrodes) 34x, 34y, 34z Linear vertical electrodes (second) Linear electrode) 34'a, 34'b, 34'c conductive wire (first conductive wire) 34'x, 34'y, 34'z conductive wire (second conductive wire) 4 Insulating film (insulating layer) 4a, 4b, c treated surface 6 to be treated powder 6a large flour 33 linear bias electrode 33 having a particle size of 'conductive wires (second conductive wires)

Claims (8)

[Claims] 1. A striped electrode array in which a plurality of linear electrodes are repeatedly arrayed in one direction and in a phase order is coated with an insulating layer on at least one side, and the surface of the insulating layer classifies powder to be treated. A classification stator, which is the processing surface for processing,
A powder applying unit that applies a voltage of a plurality of phases that fluctuates at a predetermined cycle or timing to the plurality of linear electrodes, and the powder to be processed placed at a predetermined initial position on the processing surface. When an electrostatic force of a predetermined strength is applied to, a powder group having a small particle size that is moved by the electrostatic force,
An electrostatic classification device that utilizes the fact that it is divided into a large particle size group that is left without moving, and the voltage applying unit is based on a predetermined boosting signal supplied from a control unit or an operation unit. An electrostatic classification device, wherein the voltages of the plurality of phases to be applied to the plurality of linear electrodes are boosted by a predetermined amount and output. 2. The classification stator is an electrode woven fabric in which a conductive wire material to be the linear electrode and an insulating fiber are woven as warp yarns and weft yarns, and at least the surface of the electrode woven fabric. The electrostatic classification device according to claim 1, further comprising: the insulating layer that covers the insulating layer. 3. A grid-shaped electrode array in which a plurality of linear electrodes are repeatedly arranged in one direction and in a phase order, and a plurality of linear bias electrodes are wired in a direction orthogonal to these linear electrodes. At least one side of the body is covered with an insulating layer, and the surface of the insulating layer serves as a processing surface for classifying the powder to be treated. A voltage applying unit for applying a voltage of a plurality of phases that fluctuates in a cycle or timing, and applies an electrostatic force of a predetermined strength to the powder to be processed placed at a predetermined initial position on the processing surface. If so, an electrostatic classification device that utilizes the fact that it is divided into a powder group having a small particle size that moves due to the electrostatic force and a group having a large particle size that is left without moving, the voltage applying unit comprising: The plurality of linear bias electrodes It applies a constant bias DC voltage for, based on a predetermined boost signal supplied from the control unit or the operation unit,
An electrostatic classification device, wherein the voltages of the plurality of phases to be applied to the plurality of linear electrodes are boosted by a predetermined amount and output. 4. At least one side of a grid-like electrode array body in which a plurality of first linear electrodes and a plurality of second linear electrodes that are orthogonal to each other are repeatedly arranged in sequence are covered with an insulating layer. A predetermined cycle of the classifying stator having the surface of the insulating layer serving as a processing surface for classifying the powder to be processed and the plurality of first or / and second linear electrodes; Voltage applying means for applying a voltage of a plurality of phases that fluctuate with timing, and when an electrostatic force of a predetermined strength is applied to the powder to be processed placed at a predetermined initial position on the processing surface. And an electrostatic classification device that utilizes the fact that it is divided into a powder group having a small particle size that moves by the electrostatic force and a group having a large particle size that remains without moving, wherein the voltage applying unit is a control unit. Or a predetermined boost signal supplied from the operation unit Based on electrostatic classifying device and outputs a voltage of the plurality of phases to be applied to said plurality of linear electrodes by a predetermined amount boosting. 5. The classifying stator includes a first conductive wire serving as the linear electrode or the first linear electrode, and a second conductive wire serving as the linear bias electrode or the second linear electrode. The conductive wire comprises an electrode woven fabric woven as warp and weft yarns, and the insulating layer covering at least the surface of the electrode woven fabric, and the first and second conductive materials 5. The electrostatic classification device according to claim 3, wherein at least one of the wire rods is coated with insulation. 6. The classification stator is such that at least a part of the processing surface is a curved surface, and the target position of the moving powder is set on an inclined surface or an upside down surface. 5. The electrostatic classification device according to claim 1, 3 or 4. 7. An electrostatic classification method for separating and extracting a powder to be treated in a predetermined particle size range by using the electrostatic classification device according to claim 1 or 3, wherein the voltage applying means is controlled. , To the powder to be processed placed at a predetermined initial position on the processing surface,
By applying an electrostatic force of a predetermined strength, and further increasing the electrostatic force stepwise every time a predetermined processing period elapses,
An electrostatic classification method characterized in that a group having a small particle size is sequentially electrostatically moved for separation and extraction. 8. An electrostatic classification method for separating and extracting a powder to be treated for each predetermined particle size range by using the electrostatic classification device according to claim 4, wherein the voltage applying means is controlled to An electrostatic force having a predetermined strength and a predetermined direction is applied to the powder to be processed placed at a predetermined initial position on the processing surface, and the electrostatic force is stepped every time a predetermined processing period elapses. The electrostatic classification method is characterized in that the electrostatic force is changed and the direction of the electrostatic force is changed to sequentially electrostatically move the particles having a small particle diameter in different directions to perform separation and extraction.