JP2005149983A - Ion generation element and ion generating device having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ion generating element which can generate ion by field emission and an ion generating device having the same. <P>SOLUTION: The device is provided with an ion generating element 5 using carbon nanotubes 12 and a voltage level setting circuit 2 for outputting an impressing voltage to impress on the ion generating element 5. Based on the impressing voltage given by the voltage level setting circuit 2, a high electric field is generated by the carbon nanotubes 12. Based on the collision and ionization of the electrons with water molecules emitted by the carbon nanotubes 12 by field emission in this high electric field, the ion is generated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ion generating element that generates ions, and more particularly to an ion generating element that generates negative ions and positive ions by field emission, and an ion generating apparatus including the same.

  In recent years, development of a technology for realizing a clean and comfortable living space, particularly a technology for purifying the air in the living space, has been eagerly desired with the high airtightness of the living space. For such air purification, air conditioning in which air in a target space has been conventionally sucked in, and a circulating airflow that is appropriately discharged through a filter is generated, and floating substances present in the circulating airflow are sequentially captured by the filter. The machine was widely used.

  However, in this type of air conditioner, there is a problem that the removal of suspended matters is only performed on the air sucked into the main body and it is difficult to exert a cleaning effect on the entire living space. It was. For example, there is a problem that air stagnation is likely to occur on the back side of furniture arranged in a room, each part of a living room, and a sufficient effect cannot be expected in places where cleaning is required. Further, in order to maintain the original performance, it is indispensable to clean and replace the filter, and there is a problem that complicated maintenance work including these is required. Furthermore, the suspended | floating matter in living space contains bacteria, such as mold | fungi and Escherichia coli, with microparticles, such as dust and smoke. In the air conditioner using the filter described above, fine particles can be effectively removed. However, bacteria harmful to the human body are propagated under the trapping of the filter, and enter the living space along with the circulating airflow. There is a problem that a sufficient sterilization effect, that is, a removal effect cannot be obtained because it is returned. In recent years, an air conditioner using a filter made of an antibacterial material to enhance the effect of removing bacteria has been put into practical use, but the actual situation is that satisfactory performance has not been obtained.

In order to solve such problems, Japanese Patent Application Laid-Open No. 2003-123940 proposes a cleaning method based on a new idea of purifying air in the space by releasing ions into the space. ing. In this method, an ion generator that generates approximately the same amount of positive ions and negative ions is arranged in the middle of an air passage that discharges airflow to the target space, and discharges it into the target space together with the airflow. Is. The positive ions and negative ions are generated by ionizing water vapor in the air by a discharge phenomenon, and a plurality of water molecules are attached around hydrogen ions (H ⁺ ) or oxygen ions (O ₂ ⁻ ). It is in the form of so-called cluster ions.

These ions released into the air are aggregated into suspended particles and chemically react with each other to form hydrogen peroxide (H ₂ O ₂ ) or hydroxyl radical (.OH) as an active substance and extract hydrogen from the suspended particles. It inactivates suspended particles by an oxidation reaction and sterilizes suspended bacteria. This air purification is performed by ion action that is released into the target space and spreads throughout the space.

In addition, these ions act on airborne bacteria, sterilize them, and also act on odorous molecules and harmful molecules, making them non-bromide and harmless. Can get to. The cluster ions released into the space are ions existing in the natural world and do not affect the human body.
JP 2003-123940 A

  However, the conventional ion generator employs a method of generating ions by a discharge phenomenon, and it is necessary to apply a high voltage between the electrodes. Therefore, it is difficult to reduce the size of an ion generating element for generating ions, and there is a problem that power consumption is large. In addition, there is a problem that ions and radicals and a large amount of ozone that are not required in practice are generated due to the discharge phenomenon.

  The present invention has been made to solve such problems, and it is an object of the present invention to provide an ion generation element capable of generating ions by field emission and an ion generation apparatus including the ion generation element. .

  The present invention provides an ion generating element that generates ions based on impact ionization of water molecules and electrons existing in air, and includes one of a first electrode element and a second electrode part. And an electron-emitting device for emitting electrons by generating a high electric field between the first and second electrode elements based on an applied voltage applied to the first and second electrode elements. Is provided.

  The ion generator of the present invention includes an ion generator that generates ions based on impact ionization of water molecules present in air and electrons emitted by field emission based on an applied voltage, and an applied voltage that is applied to the ion generator. And a voltage setting unit for adjusting. The applied voltage is set to a frequency at which the generated ions are captured, and is set to a voltage level of attenuation amplitude.

  With the ion generating element of the present invention, ions based on impact ionization of water molecules and electrons can be generated, so that desired ions can be generated without generating unnecessary ions.

  Since the generated ions can be captured by the ion generator of the present invention, the sputtering phenomenon can be suppressed and desired ions can be generated.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol in a figure shall show the same or an equivalent part.

  FIG. 1 is a schematic configuration diagram of a main part of an ion generator 1 according to an embodiment of the present invention.

  Referring to FIG. 1, ion generator 1 according to an embodiment of the present invention includes an ion generating element 5 that generates ions, a voltage level setting circuit 2 that sets a voltage level of an applied voltage for generating ions, and The control circuit 4 for controlling the voltage level setting circuit 2 and the oscillator 3 used for timing control in the control circuit 4 are provided. The voltage level setting circuit 2, the control circuit 4, and the oscillator 3 constitute a voltage setting unit.

  The voltage level setting circuit 2 outputs the voltage Vout using the voltage Vin (−5 V) as a drive voltage. The voltage level setting circuit 2 includes a step-down circuit 6 that steps down and outputs the voltage level of the voltage Vin (−20 V), a step-up circuit 7 that steps up and outputs the voltage level of the voltage Vin (10 V), and transistors NT1 to NT3. Including. The transistor NT1 is connected to the voltage Vin via the step-down circuit 6, and outputs the output voltage of the step-down circuit 6 to the ion generating element 5 as the voltage Vout in response to the control signal n1 from the control circuit 4. The transistor NT2 is connected to the voltage Vin, and outputs the voltage Vin as the voltage Vout to the ion generating element 5 in response to the control signal n3 from the control circuit 4. The transistor NT3 is connected to the voltage Vin via the booster circuit 7, and outputs the output voltage of the booster circuit 7 to the ion generating element 5 as the voltage Vout in response to the control signal n2 from the control circuit 4.

  FIG. 2 is a schematic configuration diagram of ion generating element 5 according to the embodiment of the present invention.

  Referring to FIG. 2, ion generating element 5 includes an anode plate 10, a cathode plate 11, and a carbon nanotube 12 that is an electron-emitting device provided attached to cathode plate 11. This configuration is a so-called paste-type carbon nanotube configuration.

  Here, ion generation based on field emission will be described.

In the field emission, when the electric field strength immediately before the electrode becomes about 10 ⁹ [V / m], the external potential drops rapidly, the potential barrier on the electrode surface becomes very thin, and the internal electrons are blocked by the tunnel effect. It is a phenomenon that it has a probability of being released to the outside (vacuum or in the atmosphere) through the. In order to obtain a very large electric field strength of 10 ⁹ [V / m], carbon nanotubes are used in the embodiment of the present invention.

  In general, carbon nanotubes (hereinafter referred to as CNTs) have a fibrous structure in which one or a plurality of cylinders with rounded graphite-like carbon atomic surfaces are arranged in a nested manner, and the diameter thereof is nano. It is composed of metric order and extremely fine substances.

  CNTs have a wide range of electrical properties from metals to semiconductors depending on their structure, and are very small, have a large surface area, and reach a length on the order of micrometers, so they have a very large aspect ratio (length / diameter ratio) and are hollow. Has a unique shape. In particular, the tip of the CNTs is formed in a hemispherical shape having a diameter on the order of nanometers, and electric field concentration due to the applied voltage can be easily obtained, and field emission can be realized with a low applied voltage.

  The following formula shows the electric field strength E in the ion generating element 5 using the carbon nanotube 12 shown in FIG.

By setting the distance d between the electrodes to 10 to 50 μm, the radius of curvature of the tip of the carbon nanotube to 40 to 50 nm, and the applied voltage | V | to 15 to 21 V, the electric field strength should be about 10 ⁹ [V / m]. Can do. Therefore, as described above, a high electric field strength necessary for field emission can be obtained. In addition, a high electric field that generates field emission at a low voltage can be generated, and power consumption can be reduced. In addition, the characteristics of carbon nanotubes are different from metals used for normal electrodes, and there is an experimental result that field emission occurs when the electric field strength is about 10 ⁷ [V / m] lower than about 10 ⁹ [V / m]. Has been obtained. Therefore, more effective field emission can be performed by using carbon nanotubes. In addition, since the voltage is low, ions can be generated using a small battery or the like (including a solar battery), and the apparatus can be miniaturized and portable. Further, desired cluster ions can be generated without generating unnecessary ions and radicals and a large amount of ozone.

  As described above, the present invention generates ions using CNTs that are electron-emitting devices having electron emission at a low voltage, chemical stability, and physical toughness.

Specifically, electrons emitted from the tips of CNTs attached to the negative electrode collide with water molecules. O ₂ ⁻ (H ₂ O) _m (m: natural number) as negative ions and H ⁺ (H ₂ O) _n (positive ions as positive ions based on impact ionization (dissociation) of water molecules due to electrons. n: natural number) is generated. In this respect, positive ions H ⁺ (H ₂ O) _n are generated based on collisions between water molecules and electrons having high energy (about 5 [eV]). On the other hand, the negative ions O ₂ ⁻ (H ₂ O) _m are generated even in collisions with electrons having a low energy (about 1 [eV]), because the electron affinity of oxygen is large and electron attachment is likely to occur.

On the other hand, positive ions H ⁺ (H ₂ O) _n generated by impact ionization are attracted to the carbon nanotubes of the negative electrode according to the electric field. At this time, the generated positive ions H ⁺ (H ₂ O) _n are high-energy particles, and when they collide with the carbon nanotube and the negative electrode, there is a possibility that a so-called sputtering phenomenon occurs in which breakage occurs in the vicinity of the contact.

Therefore, in the present embodiment, ions are trapped between the electrodes so that the carbon nanotube and the negative electrode are not destroyed by the sputtering phenomenon caused by the generated positive ions H ⁺ (H ₂ O) _n .

  This ion trapping will be explained. When charged particles move in a high-frequency electric field in a high-frequency electric field, if the frequency increases, the polarity of the voltage is reversed before the charged particles reach the opposite electrode, and the direction of the electric field is reversed. Thus, the charged particles may be pulled back. Therefore, depending on the position of the first charged particle, a phenomenon may occur in which the electrode always continues to reciprocate without reaching the opposing electrode. This state is called trapping of charged particles.

  In the present invention, by capturing these positive ions between the electrodes, the sputtering phenomenon is suppressed and desired ions are generated.

  Specifically, the sputtering phenomenon is suppressed by applying a desired high-frequency electric field.

  FIG. 3 is a diagram illustrating the free path distribution probability of electrons according to the embodiment of the present invention.

  With reference to FIG. 3, the vertical axis indicates the distribution probability P. The horizontal axis indicates the coefficient of the free stroke λ when the mean free stroke is set as a reference (1.00). As shown in the distribution probability diagram, the proportion of electrons below the mean free path is about 63%. Further, the ratio of electrons above the mean free path is about 37%.

When the electric field strength is about 10 ⁸ [V / m], the energy of electrons in this mean free path is about 3 eV. Therefore, it can be seen that about 37% of the electrons have an energy of 3 eV or more. Among them, in particular, in order to generate positive ions H ⁺ (H ₂ O) _n , the number of electrons must be equal to or greater than the mean free path. Note that there are several tens of% of the electrons having energy of about 5 eV or more.

  FIG. 4 is a diagram for explaining the movement of charged particles in an electric field.

As shown in FIG. 4A, the electrons e emitted from the carbon nanotubes 12 travel with a free path λ and collide with water molecules. By this impact ionization, negative ions O ₂ ⁻ (H ₂ O) _m and positive ions H ⁺ (H ₂ O) _n are generated. In this example, positive ions H ⁺ (H ₂ O) _n will be mainly described.

FIG. 4B is a diagram for explaining the movement of the generated positive ions H ⁺ (H ₂ O) _n according to the direction of the electric field.

As shown in FIG. 4B, the positive ions H ⁺ (H ₂ O) _n move toward the cathode plate 11. Therefore, as described above, a sputtering phenomenon may occur in the vicinity of the cathode plate 11.

Here, a diagram is shown in which positive ions H ⁺ (H ₂ O) _n advance x. Before the positive ions reach the cathode plate 11, the direction of the electric field is reversed, that is, the polarity is changed, so that the positive ions H ⁺ (H ₂ O) _n are attracted to the opposing anode plate 10 before reaching the cathode plate 11. The above-described ion trapping can be performed.

  FIG. 5 is a diagram illustrating generation of a high-frequency electric field according to the embodiment of the present invention.

  In FIG. 5A, the control circuit 4 outputs control signals n1 to n3 in response to the oscillation signal of the oscillator 3. Specifically, the control signal n1 is set to the “H” level at time t1. At time t2, control signal n1 is set to “L” level, and control signal n2 is set to “H” level. At time t3, the control signal n2 is set to the “L” level, and the control signal n3 is set to the “H” level. At time t4, the control signal n3 is set to the “L” level.

  FIG. 5B shows the applied voltage Vout output according to the control signals n1 to n3. Specifically, the applied voltage Vout having an attenuation waveform is output according to the control signals n1 to n3.

  FIG. 5C shows the electric field E generated according to the applied voltage Vout.

As shown in FIG. 5B, a high electric field is generated by the carbon nanotube, and an electric field E having a decay waveform is generated according to the applied voltage. At time t1a when the maximum high electric field −Em is reached, field emission is performed. Specifically, electrons are emitted from the tip of the carbon nanotube, and ions, that is, positive ions H ⁺ (H ₂ O) _n and negative ions O ₂ ⁻ (H ₂ O) _m are generated. During the period from time t1a to time t2, the generated ions move according to the direction of the electric field. Since the direction of the electric field is opposite in the section from time t2 to time t3, the positive ions move according to the direction of the electric field. In addition, the direction of the electric field changes again from the time t3 to the time t4, and the positive ions H ⁺ (H ₂ O) _n move according to the direction of the electric field. Therefore, positive ions H ⁺ (H ₂ O) _n can be trapped between the electrodes in accordance with such a high frequency high electric field.

  When the free path of electrons emitted from the carbon nanotube is λx, ions can be trapped without causing a sputtering phenomenon if the following equation is established.

λx ≧ x (x is the maximum distance that positive ions move according to the direction of the electric field)
In the present embodiment, as described above, the electrons in the mean free path have energy of about 3 eV. Therefore, as described above, electrons that collide with water molecules and generate positive ions H ⁺ (H ₂ O) _n have an energy of 5 eV or more and therefore have a free path greater than the mean free path.

  Therefore, in this example, as an example, the frequency of a high frequency high electric field to be applied is calculated by using λx as the mean free path of electrons.

Here, Ey indicates the electric field strength at a position advanced by the mean free path of electrons. Further, the integration interval is T / 4 to T / 2 in the interval of the period T of the high frequency high electric field, and is expressed as π / 2ω to π / ω in terms of the angular velocity ω. The mean free path is 0.44 × 10 ⁻⁶ m. Further, the mobility μ is set to 3 × 10 ⁻⁴ m ² / (V · t).

  When calculated based on the above formulas (1) and (2), ions can be captured without generating a sputtering phenomenon by generating a high electric field having a frequency of f = about 80 MHz.

  FIG. 6 is a schematic view of an ion generator according to the embodiment of the present invention.

  Referring to FIG. 6, here, a cover main body 51 that covers the inside of the apparatus, a blower 52, and a support portion 53 that supports the blower 52 and is connected to the cover main body are provided.

  The blower 52 generates and discharges an air flow. Therefore, by this structure, the ion between the produced | generated electrodes is discharge | released outside with the air blower 52, For example, air cleaning can be performed by the ion effect which spreads the whole circumference | surroundings of a room.

  FIG. 7 is a diagram illustrating the structure of the carbon nanotube according to the embodiment of the present invention.

  Referring to FIG. 7 (a), single-wall carbon nanotubes (SWCNT) are shown here. Here, a collection of one by one is shown.

  Referring to FIG. 7B, here, a multi-wall carbon nanotube (MWCNT) is shown. The upper layer tube has a multilayer structure in which the lower layer tube is covered.

  FIG. 8 is a structural diagram of another ion generating element.

  FIG. 8A shows another ion generating element 5a different from FIG. The ion generating element 5 a includes a substrate electrode 22, a gate electrode 20, an insulating layer 21, and a carbon nanotube 12.

  Carbon nanotube 12 is electrically coupled to substrate electrode 22.

  FIG. 8B is a diagram illustrating the structure of the ion generating element 5a.

  As shown in FIG. 8B, the substrate electrode 22 and the gate electrode 20 are provided to face each other with the insulating layer 21 therebetween. Near the center of the gate electrode 20 and the insulating layer 21, a space is provided in a columnar shape, and the carbon nanotube 12 is disposed in the center. That is, this is a so-called Spindt type structure in which the gate electrode 20 and the insulating layer 21 are provided so as to surround the carbon nanotube 12. In this configuration, electrons are emitted from the tip of the carbon nanotube 12 to the gate electrode 20 that surrounds the periphery.

  The following equation shows the electric field strength E in the ion generating element 5 using the carbon nanotube 12 shown in FIG.

  Also in this configuration, ions can be trapped without causing a sputtering phenomenon according to the same method as described in FIG.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic block diagram of the principal part of the ion generator 1 according to embodiment of this invention. It is a schematic block diagram of the ion generating element 5 according to embodiment of this invention. It is a figure explaining the free stroke distribution probability of the electron according to embodiment of this invention. It is a figure explaining the movement of the charged particle in an electric field. It is a figure explaining the production | generation of the high frequency electric field according to embodiment of this invention. It is a general-view figure of the ion generator according to embodiment of this invention. It is a figure explaining the structure of the carbon nanotube according to embodiment of this invention. It is a structural diagram of another ion generating element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Ion generator, 2 Voltage level setting circuit, 3 Oscillator, 4 Control circuit, 5, 5a Ion generating element, 6 Buck circuit, 7 Boost circuit, 10 Anode plate, 11 Cathode plate, 12 Carbon nanotube, 20 Gate electrode, 21 Insulating layer, 22 substrate electrode, 51 cover body, 52 blower, 53 support part.

Claims (10)

An ion generating element that generates ions based on impact ionization of water molecules and electrons existing in air,
First and second electrode elements;
A high electric field is applied between the first and second electrode elements based on an applied voltage applied to the first and second electrode elements, corresponding to one of the first and second electrode portions. An ion generating device comprising: an electron emitting device for generating and emitting the electrons.   The ion generating element according to claim 1, wherein the electron-emitting element corresponds to a carbon nanotube.   The ion generating element according to claim 2, wherein the carbon nanotube has a single-layer structure.   The ion generating element according to claim 2, wherein the carbon nanotube has a multilayer structure. The high electric field is a high frequency high electric field,
The frequency of the high-frequency high electric field is set so that the maximum distance that the generated ions move according to the high-frequency high electric field is shorter than the distance of the mean free path of the electrons emitted from the electron-emitting device. The ion generating element according to claim 1. The ion according to claim 1, wherein the ions include O ₂ ⁻ (H ₂ O) _m (m: natural number) as negative ions and H ⁺ (H ₂ O) _n (n: natural number) as positive ions. Generating element. An ion generator that generates ions based on impact ionization between water molecules present in the air and electrons emitted by field emission based on an applied voltage;
A voltage setting unit for adjusting the applied voltage applied to the ion generation unit,
The ion generator is set to a frequency at which the generated ions are captured and set to a voltage level of an attenuation amplitude. The voltage setting unit includes:
An oscillation circuit for oscillating a high-frequency signal;
A control circuit that outputs a control signal in response to the high-frequency signal output from the oscillation circuit;
The ion generator of Claim 7 including the voltage level setting circuit which adjusts the voltage level output according to the control signal output from the said control circuit.   The ion generator of Claim 7 further equipped with the air blower for distributing the said ion produced | generated by the said ion production | generation part.   The ion generator according to claim 7, wherein the voltage setting unit is driven by a battery.

Images