Plasma generating unit, plasma generating device and sterilization system

Abstract

To make it possible to take in fluid such as ambient air and efficiently perform sterilization treatment based on creation of atmospheric pressure low-temperature plasma on the fluid taken in.SOLUTION: A plasma generation unit 10 comprises a plasma creation section including a first electrode 16a obtained by forming a tabular conductive material into a cylindrical shape, a second electrode 16b obtained by forming a tabular conductive material into a cylindrical shape and disposed so as to surround the outer periphery of the first electrode with a predetermined gap, and a cylindrical dielectric layer 14 disposed so as to be interposed between the first electrode and the second electrode. The plasma generation unit generates atmospheric pressure low-temperature plasma between the first and second electrodes of the plasma creation section through the dielectric layer by applying predetermined AC voltage between the first and second electrodes of the plasma creation section.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a plasma generating unit, a plasma generating device, and a sterilization system. [Background technology]

[0002] With the global spread of the novel coronavirus, there is an increasing need for various sterilization treatments, including those for virus inactivation. In particular, droplet and aerosol infections are thought to be major routes of infection for the novel coronavirus, creating a demand for technologies that can effectively inactivate viruses suspended in the air. Conventional sterilization techniques involve irradiating the surface of an object with plasma gas. Environmental sterilization methods have also been proposed, in which ambient air is exposed to plasma gas to inactivate viruses and kill bacteria in the air.

[0003] For example, Patent Document 1 relates to an air purifying device that uses plasma, and proposes a configuration in which "a number of electrodes that create a turbulent air flow and generate dielectric barrier discharge narrow gap plasma are arranged in a matrix in a housing that has an air inlet and an air outlet for the plasma treatment target, and the plasma generated by the electrodes is efficiently brought into contact with and mixed with air containing viruses, pathogens, mycotoxins, etc." (abstract). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-171777 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the device described in Patent Document 1, plasma is generated around a rod-shaped electrode to mix with the surrounding air, so there is still insufficient contact and mixing between the plasma gas and the air flowing around the electrode, which could result in the problem of air that has not been plasma-treated being discharged downstream of the device.

[0006] The present invention has been made to solve the above and other problems, and one object of the present invention is to provide a plasma generating unit, a plasma generating device, and a sterilization system that can take in a fluid such as ambient air and perform a sterilization treatment on the taken-in fluid with high efficiency based on the generation of atmospheric pressure low-temperature plasma. [Means for solving the problem]

[0007] In order to achieve the above and other objects, one aspect of the present invention is a plasma generating unit comprising a plasma generating section having a first electrode formed from a flat conductive material in a cylindrical shape, a second electrode formed from a flat conductive material in a cylindrical shape and arranged to surround the outer periphery of the first electrode with a predetermined gap therebetween, and a cylindrical dielectric layer arranged to be interposed between the first electrode and the second electrode, and by applying a predetermined AC voltage between the first and second electrodes of the plasma generating section, atmospheric pressure low-temperature plasma is generated between the first and second electrodes of each of the plasma generating sections via the dielectric layer.

[0008] The present invention also provides a plasma generating unit comprising a first plasma generating unit and a second plasma generating unit each having the same configuration as the plasma generating unit, the first plasma generating unit and the second plasma generating unit being concentrically arranged such that a first electrode of the second plasma generating unit is spaced a predetermined distance from the second electrode of the first plasma generating unit, and applying a predetermined AC voltage between the first and second electrodes of the first and second plasma generating units to generate atmospheric pressure low-temperature plasma through the dielectric layer between the first and second electrodes of each plasma generating unit.

[0009] The first electrode may be formed of a punched metal plate having a plurality of fine holes formed in the metal plate, the second electrode may be formed of a metal mesh material made of braided thin metal wires, and a dielectric layer made of a dielectric material may be formed between the first electrode and the second electrode.

[0010] The present invention also encompasses a plasma generating device comprising a plasma generating unit according to the above aspect and a plasma power supply unit configured to apply a predetermined AC voltage between the first and second electrodes of each of the plasma generating sections of the plasma generating unit.

[0011] A sterilization system according to another aspect of the present invention includes the plasma generator, a blower unit arranged to face a gap in the plasma generation section of the plasma generator, and an ozone decomposition filter arranged between the gap and the blower unit.

[0012] A plasma generating unit according to yet another aspect of the present invention comprises a plasma generating unit including a first electrode formed from a cylindrical flat conductive material, a second electrode formed from a cylindrical flat conductive material and arranged to surround the outer periphery of the first electrode with a predetermined gap therebetween, and a cylindrical dielectric layer arranged to be interposed between the first electrode and the second electrode, and a communication passage that connects the gap between the first and second electrodes with the space inside the first electrode and the space outside the second electrode. By applying a predetermined AC voltage between the first and second electrodes of the plasma generating unit, atmospheric pressure low-temperature plasma is generated between the first and second electrodes of each of the plasma generating units through the dielectric layer, and a fluid introduced through the communication passage from the space outside the second electrode to the gap between the first and second electrodes is treated with the atmospheric pressure low-temperature plasma to generate a multi-plasma gas, and the multi-plasma gas is allowed to flow through the communication passage into the cylindrical space inside the first electrode.

[0013] The present invention also encompasses a plasma generating device comprising a plasma generating unit according to any one of the other aspects and a plasma power supply unit configured to apply a predetermined AC voltage between the first and second electrodes of each of the plasma generating sections of the plasma generating unit.

[0014] The plasma generating device may further include a fluid stirring means in the space inside the first electrode of the plasma generating unit. [Effects of the Invention]

[0015] According to the present invention, a plasma generating unit, a plasma generating device, and a sterilization system are provided that can take in a fluid such as ambient air and perform a sterilization treatment on the taken-in fluid with high efficiency based on the generation of atmospheric pressure low-temperature plasma. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is an exploded perspective view showing an example of the configuration of a plasma generating unit according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the main part of the plasma generating unit of FIG. [Figure 3] FIG. 3 is a cross-sectional view of a main part showing a modified example of the plasma generating unit of FIG. [Figure 4] FIG. 4 is a diagram showing an example of a circuit configuration of a plasma generating device using the plasma generating unit of FIG. [Figure 5] FIG. 5 is a diagram showing an example of the configuration of a sterilization system using the plasma generating unit of this embodiment. [Figure 6] FIG. 6 is a diagram showing an example of the configuration of a control circuit included in the sterilization system of FIG. [Figure 7] FIG. 7 is a diagram showing an example of the configuration of a tabletop air purifying device using the sterilization system of FIG. [Figure 8] FIG. 8 is an exploded perspective view showing an example of the configuration of a pipe-type plasma generating unit according to another embodiment of the present invention. [Figure 9]FIG. 9 is a cross-sectional view of the pipe-shaped plasma generating unit of FIG. [Figure 10] FIG. 10 is a schematic diagram showing the pipe-type plasma generating unit of FIG. 8 mounted on a pipe. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, the present invention will be described based on an embodiment thereof with reference to the drawings.

[0018] [Embodiment 1] 1 and 2 show an example of a plasma generating unit 10 according to an embodiment of the present invention. FIG. 1 is an exploded perspective view of the plasma generating unit 10 according to this embodiment, and FIG. 2 is a cross-sectional view of the main parts of the plasma generating unit 10. In FIG. 2, the configuration shown in FIG. 1 is shown excluding the outer casing 19 (the same applies to FIG. 3 showing a modified example). As shown in FIG. 1, the plasma generating unit 10 according to this embodiment is formed by concentrically combining multiple cylindrical members. These cylindrical members are, from the inside out, a first electrode 16a, a dielectric layer 14, a second electrode 16b, and an outer casing 19. Note that in FIG. 1, these cylindrical members are illustrated axially offset from one another for ease of viewing. However, the plasma generating unit 10 is actually a cylindrical device as a whole, with cylindrical members of the same length arranged concentrically. Because the cylindrical dielectric layer 14 is provided between the first electrode 16a and the second electrode 16b so as to contact the second electrode 16b, a dielectric barrier discharge can be induced by applying an AC voltage between the first electrode 16a and the second electrode 16b. This dielectric barrier discharge generates plasma in the gap between the first electrode 16a and the dielectric layer 14. Hereinafter, this gap will be referred to as the "plasma generation layer P." The plasma generating unit 10 of this embodiment can also be configured to have a cross-sectional shape other than circular.

[0019] The first electrode 16a is one of the electrodes used for generating plasma, and in this embodiment is configured as a cylindrical punched metal tube with a thickness of 0.5 to 1 mm. A conductive metal plate, such as a stainless steel plate, is preferably used as the material for the first electrode 16a. The holes provided in the punched metal plate can have a diameter of 1 mm, for example, and can be spaced approximately 5 mm apart, but this is not a particular limitation. The dimensions and arrangement of the holes should be such that plasma gas containing various active species, generated between the first electrode 16a and the second electrode 16b as described below, can be efficiently introduced into the punched metal tube through the holes.

[0020] The second electrode 16b can be made of a mesh-like metal material, such as a metal mesh material made by braiding thin stainless steel wires. As shown in Fig. 1, a glass tube that forms the dielectric layer 14 is placed inside the metal mesh material that serves as the second electrode 16b. In this embodiment, the thickness of the dielectric layer 14 is about 2 mm, and a gap of about 2 mm is provided between the dielectric layer 14 and the first electrode 16a to form the plasma generation layer P.

[0021] 1 and 2, the cylindrical plasma generating unit 10 can have an axial length of about 50 mm and a diameter of the second electrode 16b of about 45 mm. These dimensions are designed with application to a tabletop sterilization system, which will be described later, in mind, and do not particularly restrict the dimensions of the plasma generating unit 10.

[0022] Next, a modified example of the plasma generating unit 10 of this embodiment will be described. FIG. 3 illustrates a cross-sectional view of a main portion of the plasma generating unit 10 according to this modified example. The plasma generating unit 10 illustrated in FIG. 3 has the same overall cylindrical shape as those illustrated in FIGS. 1 and 2, but differs in that it includes another set of the same combination of first electrode 16a, dielectric layer 14, and second electrode 16b outside the combination of first electrode 16a, dielectric layer 14, and second electrode 16b shown in FIGS. 1 and 2. In other words, as shown in FIG. 3, a second set of first electrode 16a, dielectric layer 14, and second electrode 16b is provided outside the second electrode 16b belonging to the first set, separated by a gap 17. The gap 17 also serves as an electrical insulating layer between the first set of second electrode 16b and the second set of first electrode 16a.

[0023] A second plasma generation layer P is disposed in the gap between the second set of first electrodes 16a and the dielectric layer 14. The second set of first electrodes 16a, dielectric layer 14, and second electrodes 16b are configured similarly to the first set of first electrodes 16a, dielectric layer 14, and second electrodes 16b, respectively. Therefore, the multi-plasma gas containing various active species generated between the second set of first electrodes 16a and second electrodes 16b is efficiently introduced into the gap 17 through the pores of the first electrode 16a, which is a punched metal tube.

[0024] As will be described later, by applying a predetermined AC voltage between the first electrode 16a and the second electrode 16b, atmospheric pressure low-temperature plasma discharge occurs in the plasma generation layer P between the first electrode 16a and the second electrode 16b. This acts on the air and water vapor in the plasma generation layer P, and as is well known, produces, for example, singlet oxygen ( 1 O2), ozone (O3), hydroxyl radical (OH), superoxide anion radical (O2 -Active oxygen species, including various radicals such as oxygen radicals (O), hydroperoxy radicals (HO), and hydrogen peroxide (H2O2), are generated. Air passing through each plasma-generating layer P of the plasma generating unit 10 flows while coming into contact with the plasma discharge that is continuously generated in a planar shape within each plasma-generating layer P. Microorganisms such as viruses and bacteria contained in the ambient air drawn into each plasma-generating layer P are destroyed in an extremely short time, on the order of microseconds, by coming into contact with the plasma discharge within the plasma-generating layer P, and are then mixed with the multi-plasma gas containing the active oxygen species, thereby inactivating viruses and sterilizing the microorganisms.

[0025] Furthermore, by concentrically arranging two or more basic structural units each consisting of the first electrode 16a, the dielectric layer 14, and the second electrode 16b of the plasma generating unit 10 to form a nested stacked structure, the flow rate of the ambient air to be sterilized can be increased, and the required amount of sterilization can be flexibly accommodated according to the spatial volume of the object to be sterilized, etc.

[0026] FIG. 4 shows an example of the configuration of a plasma generation circuit applied to the plasma generation unit 10 according to the modified example of this embodiment shown in FIG. 3. For simplicity, FIG. 4 shows only a portion of the plasma generation unit 10 shown in FIG. 3. The plasma generation circuit includes a plasma power supply 20 having a booster 24 connected to each electrode pair consisting of a first electrode 16a and a second electrode 16b, and an inverter 22 that supplies AC current to the booster 24. A typical neon transformer used to light neon tubes can be used as the plasma power supply 20. The configuration of this plasma generation circuit is similar to that of the plasma generation unit 10 shown in FIG. 1.

[0027] DC 12V is input to inverter 22 of plasma power supply unit 20 from an external power source. Inverter 22 outputs an AC voltage controlled in accordance with the input DC voltage and supplies it to booster unit 24. The control method, type of switching element, and other factors of inverter 22 can be selected as appropriate, as long as the inverter 22 has a capacity appropriate for the power to be controlled. In this embodiment, inverter 22 functions to output an AC voltage in accordance with the input DC voltage. For example, inverter 22 can be configured to output an AC voltage proportional to the input voltage, such as outputting AC 1kV when DC 1V is applied and AC 9kV when DC 9V is applied. Specifically, the output voltage is controlled by parameters such as the distance between electrodes, the material, planar dimensions, and thickness of the electrodes. The AC frequency can be determined as appropriate.

[0028] This plasma generating unit 10 uses a dielectric barrier discharge, but if the inter-electrode voltage is low, no discharge occurs, and if the inter-electrode voltage is high, the discharge transitions to spark discharge or arc discharge, which reduces the efficiency of plasma generation of active species and leads to damage to the electrodes due to the discharge concentrating at specific locations. In this embodiment, a stable barrier discharge is maintained by controlling the AC voltage applied between the electrodes. In addition, by controlling the AC voltage applied between the electrodes, the unit is configured to efficiently generate a multi-plasma gas containing active oxygen species while suppressing the generation of harmful ozone (O3).

[0029] By applying a predetermined AC voltage between the first electrode 16a and the second electrode 16b of the plasma generating unit 10, a dielectric barrier discharge is generated between them via the dielectric layer 14, and the air and water vapor present in the plasma generating layer P between the first electrode 16a and the dielectric layer 14 are converted into plasma, generating various active species as exemplified above. The multi-plasma gas containing the generated active species flows into the cylindrical space A inside the first electrode 16a and the gap 17 through pores provided in the first electrode 16a.

[0030] Next, a sterilization system using the above-described plasma generating unit 10 will be described. Fig. 5 shows a configuration example of a sterilization system 100 using the plasma generating unit 10 of this embodiment. The sterilization system 100 in Fig. 5 is configured by coaxially arranging a cylindrical plasma generating unit 10, an ozone decomposition filter 130, an ozone sensor 140, and an electric fan 150. Fig. 5 simply shows a state in which these components are arranged along the flow path of ambient air, but the sterilization system 100 can be realized by housing these components in, for example, a cylindrical housing.

[0031] The ozone decomposition filter 130, located downstream of the plasma generating unit 10, is provided for the purpose of preventing ozone (O3), which is harmful to humans and has a distinctive odor, from escaping from the system 100, among the various active species generated by the plasma of the plasma generating unit 10. The ozone decomposition filter 130 can be appropriately selected from general-purpose ozone decomposition filters used in copy machines, etc. The shape and dimensions of the ozone decomposition filter 130 may also be determined according to the specifications of the sterilization system 100 to be applied. An ozone decomposition filter 130 may also be provided upstream of the plasma generating unit 10 to prevent ozone from flowing back through the flow path from the plasma generating unit 10 to the outside.

[0032] The ozone sensor 140 is a sensor device that measures the ozone concentration contained in the exhaust gas downstream of the ozone decomposition filter 130, which is located after the plasma generating unit 10. A highly sensitive semiconductor gas sensor can be suitably used as the ozone sensor 140, and by monitoring its output, the operation and shutdown of the plasma generating unit 10 can be controlled so that the ozone concentration is kept below 0.1 ppm, which is the permissible concentration in the working environment (Japan Society for Occupational Health, "Recommendations on Permissible Concentrations, etc. (2020)," Journal of Occupational Hygiene, 2020; 62(5): 198-230).

[0033] The electric fan 150 functions as an exhaust fan for the sterilization system 100 .

[0034] In the configuration example shown in FIG. 5, by operating the electric fan 150 in the exhaust direction, ambient air is introduced from the bottom of the plasma generating unit 10 into each plasma-generating layer P and the cylindrical space A and gap 17 inside the first electrode 16a (see FIG. 3). The air introduced into the plasma-generating layer P comes into contact with the generated plasma and is sterilized in a short time, on the order of microseconds. The introduced ambient air is mixed with the multi-plasma gas from the plasma-generating layer P in the cylindrical space A and gap 17 and is then discharged to the outside by the electric fan 150 via the ozone decomposition filter 130. During this process, the ambient air introduced into the cylindrical space inside the first electrode 16a is mixed with the multi-plasma gas containing active species, undergoes sterilization treatment, and is then discharged into the surrounding space by the electric fan 150. At this time, the active species contained in the multi-plasma gas are also discharged into the surrounding space, providing an even greater sterilization effect.

[0035] Figure 6 shows an example of the configuration of a control circuit in the sterilization system 100 of Figure 5. As shown in Figure 6, the control circuit is provided with a DC power supply unit 60, a plasma power supply unit 20, a control unit 70, and an input / output unit 80.

[0036] The sterilization system 100 is supplied with AC 100V, 50 / 60Hz commercial power, and first, a DC power supply unit 60 generates DC 24V and DC 5V as power supplies for the control circuit, and DC 12V as the operating power supply for the plasma generation unit 10. The control unit 70 is a functional unit that manages the overall operational control of the sterilization system 100, and can be configured using, for example, a microprocessor module. The input / output unit 80 can include input devices such as operation buttons and a touchpad, and output devices such as an LED lamp and a liquid crystal display.

[0037] The control contents of the control unit 70 may include the following items. On / off control of the plasma power supply unit 20 by an input signal from the input / output unit 80 On / off control of the plasma power supply unit 20 based on the concentration signal from the ozone sensor 140 Output voltage control of the plasma power supply unit 20 based on plasma current value detection Of course, it may be configured to perform control other than the above.

[0038] According to the sterilization system 100 of the embodiment described above, ambient air can be efficiently sterilized by the atmospheric pressure low-temperature plasma generated by the plasma generating unit 10. Furthermore, since the output voltage of the plasma power supply unit 20 is controlled according to the state of the generated plasma, stable atmospheric pressure low-temperature plasma can be continuously generated.

[0039] Figure 7 shows an example of a tabletop air purifier 1 that uses the sterilization system 100 whose configuration example is shown in Figure 5. The tabletop air purifier 1 is formed in a cylindrical shape as a whole, and the sterilization system 100 including the plasma generation unit 10 is housed in the upper half, and the plasma power supply unit 20, DC power supply unit 60, and control unit 70 are housed in the lower half.

[0040] The plasma generating unit 10 of the sterilization system 100 is placed on a partition plate 160 that separates the interior of the cylindrical housing. The partition plate 160 has an opening in a portion corresponding to the cylindrical space A and gap 17 inside the first electrode 16a of the plasma generating unit 10. A slit-shaped air intake port IN is provided in the outer panel of the housing along the circumferential direction at the middle of the tabletop air purifying device 1 in the height direction, and is internally connected to the cylindrical space A and gap 17 inside the first electrode 16a of the plasma generating unit 10.

[0041] Meanwhile, an opening OUT is provided on the top surface of the housing corresponding to the electric fan 150 at the top end of the sterilization system 100, and serves as a flow path for exhaust air from the electric fan 150. In the example of Fig. 7, this opening OUT is formed as a radial slit provided on the top panel of the tabletop air purifying device 1, but is not limited to this.

[0042] The plasma power supply unit 20, DC power supply unit 60, and control unit 70 have substantially the same configurations and functions as those of the sterilization system 100 of embodiment 1. A commercial power supply of 100V AC, 50 / 60 Hz is supplied to the DC power supply unit 60 via a power cord 40. The AC voltage applied between the first electrode 16a and the second electrode 16b by the plasma power supply unit 20 may be determined according to the plasma generating unit 10 having the configuration of this embodiment. Control of the AC voltage according to the properties of the generated plasma may also be customized to suit the plasma generating unit 10 of this embodiment.

[0043] An operation display panel corresponding to the input / output unit 80 of the first embodiment is provided at an appropriate location on the lower half of the peripheral surface of the tabletop air purifying device 1. In this embodiment, the operation display panel is provided with a power on / off switch and a power lamp for generating plasma. However, the operation display panel is not limited to these, and may also be provided with an operation display unit such as a liquid crystal display unit, a timer setting unit, or the like.

[0044] In the tabletop air purifier 1 having the above configuration, when power is turned on, an AC voltage is applied from the plasma power supply 20 between the first electrode 16a and the second electrode 16b of the plasma generating unit 10, generating plasma in the plasma generation layer P by dielectric barrier discharge. The multi-plasma gas containing various active species generated by the plasma is introduced into the inner cylindrical space A through the pores in the first electrode 16a, as shown in FIG. 2 . Meanwhile, the exhaust operation of the electric fan 150 draws ambient air into the housing of the tabletop air purifier 1 through the air inlet IN on the periphery of the tabletop air purifier 1, reaches the space inside the first electrode 16a, and mixes with the multi-plasma gas. The ambient air is thus sterilized in the cylindrical space A inside the first electrode 16a and is then discharged as clean air into the surrounding space by the electric fan 150 through the ozone decomposition filter 130. At the same time, a portion of the multi-plasma gas is also discharged into the surrounding space by the electric fan 150 along with the active species, thereby sterilizing the surrounding air.

[0045] As described above, the sterilization system 100 of this embodiment can efficiently and continuously generate atmospheric pressure low-temperature plasma by dielectric barrier discharge that occurs continuously in a plane between the concentrically opposed first electrode 16a and second electrode 16b. Furthermore, the plasma gas is introduced from the plasma generation layer P into the cylindrical space A or into the gap 17 through the pores of the first electrode 16a. The tabletop air purifier 1 using the sterilization system 100 can achieve efficient sterilization by bringing the ambient air into contact with plasma in the plasma generation layer P and mixing it with multiple plasma gases in the cylindrical space A.

[0046] 3, two sets of first electrode 16a, dielectric layer 14, and second electrode 16b are provided concentrically (nested), but three or more sets may be combined. The plasma generating unit 10 used in the tabletop air purifying device 1 may also be provided with two or more sets of first electrode 16a, dielectric layer 14, and second electrode 16b.

[0047] [Embodiment 2] Next, a sterilization system 100 according to a second embodiment of the present invention will be described. This sterilization system 100 has a similar configuration to the cylindrical sterilization system 100 of embodiment 1, but differs from embodiment 1 in that it is formed in a longer pipe shape. The electrode configuration for plasma generation also differs from embodiment 1. Below, differences and features of the sterilization system of this embodiment (hereinafter referred to as a "plasma pipe" for simplicity) will be described, keeping in mind the configuration of embodiment 1. Note that elements equivalent to those of embodiment 1 are given the same reference numerals.

[0048] Fig. 8 shows a partially exploded perspective view of the plasma pipe 100 of this embodiment, and Fig. 9 shows its cross-sectional view. This plasma pipe 100 can be installed in the middle of the flow path of various fluids to sterilize the fluid flowing through the flow path using atmospheric pressure low-temperature plasma.

[0049] As described above, the plasma pipe 100 is formed into a long pipe shape, with the first electrode 16a, dielectric layer 14, second electrode 16b, and outer casing 19, each of which is a pipe-shaped element, concentrically arranged from the inside. The first electrode 16a and second electrode 16b are each formed into a pipe shape using aluminum or stainless steel plates approximately 1 mm thick. A dielectric layer 14 approximately 3 mm thick is provided on the inner circumferential surface of the outer second electrode 16b. The dielectric layer 14 can be formed from an appropriate material, taking into consideration its workability and required dielectric constant, such as a glass layer. The inner circumferential surface of the dielectric layer 14 faces the outer circumferential surface of the first electrode 16a, with a gap of approximately 3 mm between them forming the plasma generating layer P. Ultrasonic oscillators SS are installed on the surface of the dielectric layer 14 facing the plasma generating layer P in a radially opposite position along the plasma pipe 100. In this embodiment, the ultrasonic oscillators SS are vibrators made of thin piezoelectric ceramics, but the type of vibrator is not particularly limited. By applying a high-frequency AC voltage to the ultrasonic oscillation element SS, ultrasonic waves are emitted into the plasma generation layer P. This emitted ultrasonic wave has the effect of promoting the active oxygen species generation process by plasma in the plasma generation layer P. The AC voltage supplied to the ultrasonic oscillation element SS can be configured to supply an AC voltage of an appropriate frequency to the ultrasonic oscillation element SS, for example, by providing a voltage supply control circuit to the ultrasonic oscillation element SS in the control unit 70 shown in FIG. 6 of the first embodiment. The amplitude and frequency of the AC voltage can be set according to the specifications for plasma generation in the plasma pipe 100. The installation position of the ultrasonic oscillation element SS is not limited to the above configuration example and can be changed.

[0050] An outer casing 19 is provided at an appropriate distance outside the second electrode 16b, forming the outer periphery of the plasma pipe 100. A circulator CR, which is a fluid agitation means for agitating the space inside the first electrode 16a, is installed in the center of the plasma pipe 100. The circulator CR is a cylindrical member extending along the axis of the plasma pipe 100, and is equipped inside with a rotating blade for the agitation and a drive mechanism for rotating the blade (not shown). The configuration of the circulator CR is not limited to a specific one, as long as it functions to agitate the fluid in the cylindrical space A surrounded by the first electrode 16a.

[0051] Between the outer periphery of the second electrode 16b and the plasma generation layer P, a long, thin, hollow duct D is provided, penetrating the second electrode 16b, the dielectric layer 14, and the first electrode 16a. The duct D, which serves as a communication path, is formed of a member such as a thin stainless steel tube and connects the annular space R between the second electrode 16b and the outer casing 19 to the plasma generation layer P, and the plasma generation layer P to the cylindrical space A. While only one duct D is shown in FIGS. 8 and 9 , any number of ducts D can be provided at appropriate intervals along the axial direction of the plasma pipe 100. The duct D functions as a flow path for the fluid in the annular space R to flow into the plasma generation layer P, where it is treated with plasma, and then into the cylindrical space A together with the various reactive oxygen species generated as a result. The cylindrical space A serves as a flow path for the fluid to be treated, which is taken in from outside the plasma pipe 100. The fluid to be treated flowing in the cylindrical space A is subjected to plasma treatment in the plasma generation layer P through the duct D, and the plasma-treated fluid containing various active oxygen species is introduced. In the cylindrical space A, the fluid to be treated and the fluid containing active oxygen species from the duct D are stirred and mixed by the circulator CR, and the fluid to be treated is sterilized by the active oxygen species.

[0052] The plasma power supply unit 20 described with reference to Figure 4 of the first embodiment is connected between the first electrode 16a and the second electrode 16b shown in the figure, and plasma is generated by dielectric barrier discharge in a plasma generation layer P formed between the first electrode 16a and the second electrode 16b, which are cylindrical members formed from a conductive material (aluminum plate, stainless steel plate, etc.), with a dielectric layer 14 interposed between them. The AC voltage applied by the plasma power supply unit 20 between the first electrode 16a and the second electrode 16b is controlled by the configuration of the control unit 70 described with reference to the first embodiment so that plasma generation is stable.

[0053] As described above, a fluid (e.g., air) in the annular space R is introduced through the duct D into the plasma generating layer P. The introduced fluid comes into contact with plasma in the plasma generating layer P and becomes a multi-plasma gas containing gas-phase active oxygen species. This multi-plasma gas generated in the plasma generating layer P is then introduced into the inner cylindrical space A through the duct D. In this embodiment, outside air taken into the plasma pipe 100 is guided into the cylindrical space A and, as it passes through the cylindrical space A, is mixed with the multi-plasma gas containing active oxygen species from the plasma generating layer P and sterilized. The circulator CR promotes mixing of the introduced outside air and the multi-plasma gas in the cylindrical space A by stirring, thereby accelerating the sterilization process. A portion of the outside air is diverted and enters the annular space R. However, since this outside air is introduced into the plasma generating layer P through the duct D as described above, the structure of any viruses, microorganisms, etc. contained therein is destroyed in a very short time by direct contact with the plasma generated throughout the plasma generating layer P.

[0054] As described above, according to the plasma pipe 100 of this embodiment, the introduced outside air comes into direct contact with the plasma in the plasma generation layer P and is mixed with the multi-plasma gas in the cylindrical space A, thereby enabling efficient sterilization treatment.

[0055] The above description focuses on the use of the plasma pipe 100 of this embodiment for sterilizing air (gas). However, the present invention is not limited to this application; the plasma pipe 100 of this embodiment can also be applied to sterilizing liquids. FIG. 10 schematically illustrates the plasma pipe 100, a sterilization system according to this embodiment, installed in the middle of a conduit constituting a fluid flow path. Although not shown, the plasma pipe 100 is also provided with a plasma power supply, a control unit, a power supply for driving the circulator CR, and other components, as described in the previous embodiment. As shown in FIG. 10, by installing the plasma pipe 100 in the middle of the flow path, various fluids flowing through the flow path can be continuously and efficiently sterilized by contact with the atmospheric-pressure low-temperature plasma continuously generated in the plasma generation layer P and the multi-plasma gas generated therein. In FIG. 10, when a liquid is introduced into the plasma pipe 100, the liquid to be treated is introduced into the cylindrical space A, but not into the plasma generation layer P. Outside air is first introduced into the annular space R, then passes through duct D into the plasma generation layer P and is subjected to plasma treatment, becoming a multi-plasma gas containing active oxygen species. This multi-plasma gas is then introduced through duct D into the liquid in the cylindrical space A, where it is mixed with the liquid to be treated and sterilized.

[0056] The material of the outer casing 19 can be determined depending on the shape of the flow path in which the plasma pipe 100 is installed and the type and properties of the fluid flowing through the flow path. For example, if the fluid is a liquid such as wastewater, a polyvinyl chloride pipe can be used, and if the fluid is a gas such as air, a metal pipe such as a stainless steel pipe can be used.

[0057] As described above, the plasma pipe 100, which is the sterilization system of this embodiment, enables efficient sterilization of the fluid by continuously contacting the fluid flowing through the flow path with plasma or a multi-plasma gas containing active oxygen species.

[0058] The technical scope of the present invention is not limited to the above-described embodiment, and other modifications, applications, etc. are also included within the scope of the claims. [Explanation of symbols]

[0059] 1. Tabletop air purifier 10 Plasma Generation Unit 14 Dielectric layer 16a 1st electrode 16b 2nd electrode 19 Exterior body 20 Plasma power supply unit 22 Inverter 24 Booster section 100 Plasma Generator 130 Ozone Decomposition Filter 140 Ozone Sensor 150 electric fan 60 DC power supply section 70 Control Unit 80 Input / output section 100 Sterilization System P plasma generation layer R-ring space A Cylindrical space D duct CR Circulator SS ultrasonic oscillator element

Claims

[Claim 1] a plasma generating section including a first electrode formed from a flat conductive material in a cylindrical shape; a second electrode formed from a flat conductive material in a cylindrical shape and arranged to surround the outer periphery of the first electrode with a predetermined gap therebetween; and a cylindrical dielectric layer arranged to be interposed between the first electrode and the second electrode; a communication passage that communicates a gap between the first electrode and the second electrode with a space inside the first electrode and a space outside the second electrode, applying a predetermined AC voltage between the first electrode and the second electrode of each plasma generating unit to generate atmospheric pressure low temperature plasma between the first electrode and the second electrode of each plasma generating unit through the dielectric layer; a plasma generating unit that processes a fluid introduced from the space outside the second electrode into the gap between the first electrode and the second electrode through the communication passage with atmospheric pressure low-temperature plasma to generate a multi-plasma gas, and causes the multi-plasma gas to flow into the cylindrical space inside the first electrode through the communication passage; a plasma power supply configured to apply a predetermined AC voltage between the first electrode and the second electrode of each of the plasma generating sections included in the plasma generating unit; Equipped with A fluid stirring means is provided in the space inside the first electrode of the plasma generating unit. Plasma generator.

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