JP6513020B2 - Sterilizer - Google Patents

Description

  The present invention relates to a sterilizer for sterilizing at least the surface of an object using plasma generated by discharge by high voltage pulses from a pulse power source.

  Recently, attempts have been made to sterilize agricultural crops and foods using active neutral particles in plasma (literature: IEEJ Journal, Vol. 132 No.10. 2012 p. 702-705 "Agriculture of Plasma" Application-from crop sterilization to plant growth control-").

  As an apparatus for generating radicals, in addition to the atmospheric pressure barrier discharge plasma torch described in the above-mentioned documents, the apparatuses described in WO 2011/065171 and WO 2012/120928 are known. There is.

  In the apparatus described in WO 2011/065171, an electrode assembly composed of a first electrode, a second electrode and a third electrode is disposed in the middle of a gas flow path, and the second electrode is It is installed upstream of the first electrode, and the third electrode is installed downstream of the first electrode. Then, one pole of the pulse power supply is connected to the first electrode, and the other pole of the pulse power supply is connected to the second electrode and the third electrode. Furthermore, the first electrode is disposed so as to cross the first gas passage surface and to occupy a part of the first gas passage surface, and the second electrode and the third electrode are respectively provided for the second The gas passage plane and the third gas passage plane are traversed, and the gas passage plane and the third gas passage plane are partially occupied. As a result, plasma is generated upstream and downstream of the first electrode. In addition, the respective ends of the first electrode, the second electrode and the third electrode do not become the starting point or the end point of the discharge, and the durability of the first electrode, the second electrode and the third electrode is improved. .

  In the device described in WO 2012/120928, a flow path forming member, a transformer, an electrode structure (anode rod and cathode plate), a feed path on the anode side, and a cathode side are provided in a housing made of a conductor. The power supply path of The extending direction of the anode bar is not parallel to the extending direction of the cathode plate, and the anode bar and the cathode plate cross the gas flow path. The anode bar and the cathode plate are spaced apart in the extending direction of the gas flow path. Electrically connect the feed end of the anode rod to the positive output end of the secondary winding of the pulse power supply, electrically connect the feed end of the cathode plate to the negative output end of the secondary winding, and And electrically connect the housing to the feed path on the cathode side. Thereby, the waveform of the pulse voltage is less likely to be disturbed.

  However, the documents mentioned above and WO 2011/065171 and WO 2012/120928 do not consider the mechanism for uniformly flowing the gas to the electrode assembly, and also the electrode assembly Since optimization of the parameters of the respective constituent members of the anode and the cathode that constitute the above has not been studied, it is difficult to efficiently generate plasma with the electrode assembly. Therefore, in the prior art, there is an inherent problem that the efficiency of plasma processing is limited when performing plasma processing such as sterilization, by indirectly applying an excited substance generated by plasma generation to an object to be treated.

  The present invention has been made in consideration of such problems, and it is possible to flow a fluid uniformly to the discharge electrode portion, to efficiently generate plasma in the discharge electrode portion, and to generate plasma. It is an object of the present invention to provide a sterilizing apparatus capable of achieving the efficiency of the sterilizing process when the sterilizing process is performed by indirectly applying the excited substance according to the above to the object to be treated.

[1] A sterilizing apparatus according to the first aspect of the present invention is a sterilizing apparatus for sterilizing at least the surface of an object using plasma generated by discharge by high voltage pulse from a pulse power source, comprising an anode and a cathode. A discharge electrode unit for generating a discharge between the anode and the cathode based on the supply of the high voltage pulse from the pulse power supply, a fluid guide unit for guiding a fluid to the discharge electrode unit, and the discharge electrode unit And a nozzle for outputting the fluid passing through toward the object, and introducing the fluid into the discharge electrode portion, generating a plasma by the discharge in the discharge electrode portion, and generating an excited matter thereof The fluid is applied to the object together with the fluid, and the supply direction of the fluid to the fluid guiding portion is different from the flowing direction of the fluid to the discharge electrode portion, and the fluid guiding portion has a flow area of the fluid Has a bellmouth portion of the bell mouth structure gradually becomes smaller toward the flow direction of the nozzle flow channel area have a gradually becomes smaller structure toward a direction of flow of the fluid, the fluid guide portion Has a rectifying structure for uniformly supplying the fluid to the discharge electrode part, and the rectifying structure includes the bell mouth part and one or more rectifying nets installed upstream of the bell mouth part A fluid inflow case installed on the upstream side of the rectifying network, and an angle formed by a supply direction of the fluid and a flow direction of the fluid is 80 ° to 100 ° .

  Thereby, the fluid can be uniformly flowed to the discharge electrode portion, and the plasma can be efficiently generated in the discharge electrode portion, and the excited substance by the generation of the plasma is indirectly applied to the object to be disinfected When performing a process, efficiency improvement of a sterilization process can be achieved.

[ 2 ] Furthermore, the aperture ratio of the rectification network may be 10 to 45%.

[ 3 ] Further, the inner dimension of the fluid inflow case in the fluid introduction direction to the bell mouth portion may be 20 mm to 100 mm at a fluid flow rate of 10 liters / min to 20 liters / min.

[ 4 ] In the first aspect of the present invention, the discharge electrode unit has a first discharge electrode to be the anode and a second discharge electrode to be the cathode, and a plurality of the first discharge electrodes are formed. When the first conductor and the plurality of second conductors that constitute the second discharge electrode are separated from each other and viewed from the flow direction of the fluid with respect to the discharge electrode portion, the first conductor and the second It may be in a positional relationship in which the conductor intersects.

[ 5 ] In the first aspect of the present invention, the discharge electrode portion has a first discharge electrode to be the anode and a second discharge electrode to be the cathode, and a plurality of first discharge electrodes constituting the first discharge electrode. One conductor and a plurality of second conductors constituting the second discharge electrode may be in a positional relationship of twist.

[ 6 ] A plurality of grids may be formed by the first conductor and the second conductor when viewed in the flow direction of the fluid with respect to the discharge electrode portion.

[ 7 ] The arrangement pitch of the intersection of the first conductor and the second conductor may be 5 to 50 mm.

[ 8 ] Further, when viewed in the flow direction of the fluid with respect to the discharge electrode portion, the aperture ratio of the discharge electrode portion may be 30 to 50%.

[ 9 ] The first discharge electrode includes the first conductor and a first ceramic layer covering the first conductor, and the second discharge electrode includes the second conductor and the second conductor. It may have a 2nd ceramic layer to coat.

[ 10 ] It is preferable that the first ceramic layer and the second ceramic layer do not have pores of 50 μm or more.

[ 11 ] In a cross section obtained by cutting the first conductor and the first ceramic layer in the direction orthogonal to the axial direction, the area of the first conductor is Aa1, the area of the first ceramic layer is Ab1, and the second In a cross section obtained by cutting the conductor and the second ceramic layer in the direction orthogonal to the axial direction, the area of the second conductor is Aa2, and the area of the second ceramic layer is Ab2,
0.1 <Aa1 / Ab1 <1.0
0.08 <Aa2 / Ab2 <2.0
Is preferred.

[ 12 ] In this case, each diameter of the first conductor and the second conductor is preferably 200 to 1000 μm.

[ 13 ] In the first aspect of the present invention, the pulse power supply generates a pulse so as to generate a discharge between the anode and the cathode, and a pulse generator for applying the high voltage pulse between the anode and the cathode. And a pulse control unit for controlling the unit, the pulse generation unit having a transformer and a switch serially connected at both ends of the DC power supply unit, and the on control to the switch of the pulse control unit is performed to the transformer. A pulse generation circuit may be provided which stores inductive energy and generates the high voltage pulse on the secondary side of the transformer by off control of the switch of the pulse control unit.

[ 14 ] A plasma processing apparatus according to a second aspect of the present invention is a plasma processing apparatus for processing at least the surface of an object using plasma generated by discharge by a high voltage pulse from a pulse power source. A discharge electrode unit for generating a discharge between the anode and the cathode based on the supply of the high voltage pulse from the pulse power supply, a fluid guide unit for guiding a fluid to the discharge electrode unit, and the discharge electrode A nozzle for outputting the fluid having passed through the part toward the target object, generating a plasma by the discharge in the discharge electrode unit while introducing the fluid into the discharge electrode unit, and generating an excited product thereof Together with the fluid, and at least one of the fluid guiding portion and the nozzle has a flow passage area gradually smaller in the flow direction of the fluid It characterized by having a made structure.

  Thus, the fluid can be uniformly flowed to the discharge electrode portion, and plasma can be efficiently generated in the discharge electrode portion, and an excited substance caused by the generation of the plasma is indirectly applied to the object to be treated, When at least the surface treatment of the object to be treated is performed, the surface treatment can be made more efficient. Of course, it can be applied to the sterilizer described above and other devices, and is versatile.

  As described above, according to the sterilizer according to the present invention, the fluid can be uniformly flowed to the discharge electrode portion, and plasma can be efficiently generated in the discharge electrode portion, and the generation of plasma is caused. In the case where the excited material is indirectly applied to the object to be subjected to the sterilization treatment, the efficiency of the sterilization treatment can be enhanced.

It is a block diagram which shows the sterilizer which concerns on this Embodiment. It is a perspective view which shows the structure of the discharge electrode part installed in a sterilizer, and the state which the plasma has generate | occur | produced between a 1st discharge electrode and a 2nd discharge electrode. It is a front view which shows an example of a structure of the 1st discharge electrode of a discharge electrode part, and a 2nd discharge electrode. 4A is a cross-sectional view taken along line IVA-IVA in FIG. 3, and FIG. 4B is a cross-sectional view taken along line IVB-IVB in FIG. It is a circuit diagram showing composition of pulse power supply. It is a disassembled perspective view which shows the structure of a sterilizer. It is a front view which shows the 1st modification of a structure of the 1st discharge electrode of a discharge electrode part, and a 2nd discharge electrode. It is a front view showing the 2nd modification of composition of the 1st electric discharge electrode of a electric discharge electrode part, and the 2nd electric discharge electrode. It is a front view which shows the 3rd modification of a structure of the 1st discharge electrode of a discharge electrode part, and a 2nd discharge electrode. Figure 10A is a nitrogen of the light emitting area (N ₂ emission region) represents a photographed image in the case of 100%, FIG. 10B shows the captured image when N ₂ emission region is 50%. It is a nondestructive observation image (by X-ray CT) which shows the state which the pore of 50 micrometers in diameter exists in a 1st ceramic layer.

  Hereinafter, an embodiment of a sterilizer according to the present invention will be described with reference to FIGS. In addition, "-" which shows a numerical range in this specification is used as a meaning which includes the numerical value described before and after that as a lower limit and an upper limit.

  The sterilizer 10 which concerns on this Embodiment applies the plasma processing apparatus 12 shown in FIG. 1 to the sterilizer 10. As shown in FIG. The plasma processing apparatus 12 has a pulse power supply 14 for generating high voltage pulses, and a reactor 16 for generating plasma by application of high voltage pulses from the pulse power supply 14.

  The reactor 16 has an anode and a cathode, and guides a fluid to the discharge electrode unit 18 which generates a discharge between the anode and the cathode based on the supply of high voltage pulses from the pulse power supply 14, and a fluid to the discharge electrode unit 18. And a nozzle 24 for outputting the fluid that has passed through the discharge electrode unit 18 toward the object 22 to be treated.

  Then, the plasma processing apparatus 12 generates a plasma by a discharge in the discharge electrode unit 18 while introducing the fluid into the discharge electrode unit 18, and applies the excited substance to the object to be processed 22 together with the fluid to process the object to be processed. Treat at least 22 surfaces. Therefore, the object to be treated 22 can be sterilized by applying the plasma processing device 12 to the sterilization treatment to form the sterilization device 10. At least one of the fluid guiding portion 20 and the nozzle 24 has a structure in which the flow passage area gradually decreases in the fluid flow direction. The “excitable substance” is a radical (chemically active species), an excited species (a molecule whose internal energy state has been changed (excited state) without changing its form by high-speed electron collision), an ion, a luminescent species, It refers to a molecule (eg, ozone) or the like generated by reaction of an exciter with a fluid molecule.

  As shown in FIG. 2, the discharge electrode unit 18 has a predetermined positional relationship between a first discharge electrode 26A serving as an anode, a second discharge electrode 26B serving as a cathode, and the first discharge electrode 26A and the second discharge electrode 26B. And a case 28 (see FIGS. 1 and 6) for holding the

  As shown in FIG. 3, the first discharge electrodes 26A extend in a first direction (x direction), and are arranged in a second direction (y direction) orthogonal to the first direction, and have a plurality of rod-like first conductors 30A. , A first common conductor 32A connecting the plurality of first conductors 30A, and a first ceramic layer 34A covering at least the first conductor 30A. The portion of the first conductor 30A and the portion of the first ceramic layer 34A covering the first conductor 30A will be referred to as a first electrode portion 36A.

  The second discharge electrode 26B extends in the second direction (y direction), and connects the plurality of rod-like second conductors 30B arranged in the first direction (x direction) with the plurality of second conductors 30B. It has a conductor 32B and a second ceramic layer 34B covering at least a second conductor 30B. The portion of the second conductor 30B and the portion of the second ceramic layer 34B covering the second conductor 30B will be referred to as a second electrode portion 36B.

  Copper, iron, tungsten, stainless steel, platinum or the like can be used as the first conductor 30A and the second conductor 30B. Alumina, silica, titania, zirconia or the like can be used as the first ceramic layer 34A and the second ceramic layer 34B.

  As shown in FIGS. 4A and 4B, the diameters d1 and d2 of the first conductor 30A and the second conductor 30B are 200 to 1000 μm. Further, the first ceramic layer 34A covering the first conductor 30A and the second ceramic layer 34B covering the second conductor 30B both have no pores of 50 μm or more inside. If the porosity is large enough to be expressed as a percentage, the voltage applied to the ceramic may cause dielectric breakdown immediately. If there is only one closed pore of 50 μm in total, dielectric breakdown may occur from the closed pore, resulting in arc plasma and melting of the ceramic. Ideally, closed pores do not exist, and it is desirable that the diameter of the closed pores dispersed in the material be all less than 10 μm.

In a cross section obtained by cutting the first electrode portion 36A in the direction orthogonal to the axial direction, the area of the first conductor 30A is Aa1, the area of the first ceramic layer 34A is Ab1, and the direction in which the second electrode portion 36B is orthogonal to the axial direction When the area of the second conductor 30B is Aa2 and the area of the second ceramic layer 34B is Ab2 in the cross section cut into
0.1 <Aa1 / Ab1 <1.0
0.08 <Aa2 / Ab2 <2.0
It is.

  When the first ceramic layer 34A and the second ceramic layer 34B are thick, the electric field strength is reduced, the energy given to the electrons is reduced, and the generation of radicals is reduced. This corresponds to an increase in the dielectric between the first conductor 30A and the second conductor 30B, so the capacitance component apparently increases, making it difficult to obtain a steep voltage increase rate (dV / dt). Then, it is desirable that it is the range mentioned above.

  The diameters d1 and d2 of the first conductor 30A and the second conductor 30B affect the electric field strength. In particular, the smaller the diameter d1, the higher the electric field strength of the surface of the anode (first conductor 30A) to which a high voltage is applied. Therefore, although it is preferable that the first conductor 30A and the second conductor 30B be thin, there is a limit to maintain the strength and the shape. Therefore, the diameter d1 of the first conductor 30A is preferably 0.2 to 0.5 mm, and the thickness t1 of the first ceramic layer 34A is preferably 0.25 to 0.65 mm. The diameter d2 of the second conductor 30B is preferably 0.5 to 1.0 mm, and the thickness t2 of the second ceramic layer 34B is preferably 0.25 to 1.25 mm.

  The case 28 is provided with, for example, a circular through hole through which fluid flows in the center, and the first common conductor 32A (see FIG. 3) and the positive side wiring 40A from the pulse power supply 14 (see FIG. 1) And a connection portion between the second common conductor 32B (see FIG. 3) and the negative electrode side wiring 40B (see FIG. 1) from the pulse power supply 14.

  When the first discharge electrode 26A and the second discharge electrode 26B are mounted in the case 28, the plurality of first electrode portions 36A and the plurality of second electrode portions 36B face each other, and the discharge electrode portion 18 When viewed in the flow direction of the fluid, the first electrode portion 36A and the second electrode portion 36B (see FIG. 3) are held in an intersecting positional relationship (positional relationship of twist). That is, the first conductor 30A and the second conductor 30B are held in a positional relationship (a positional relationship of twisting) in which the first conductor 30A and the second conductor 30B intersect. At this time, a portion where the first electrode portion 36A and the second electrode portion 36B intersect is exposed through the through hole of the case 28.

  When viewed from the flow direction of the fluid to the discharge electrode portion 18, as shown in FIG. 3, a plurality of grids are formed by the first electrode portion 36A (first conductor 30A) and the second electrode portion 36B (second conductor 30B) Is formed. In this case, the arrangement pitch of the intersection of the first electrode portion 36A (first conductor 30A) and the second electrode portion 36B (second conductor 30B) is 5 to 50 mm. Further, when viewed in the flow direction of the fluid with respect to the discharge electrode portion 18, the aperture ratio of the discharge electrode portion 18 is 30 to 50%.

  The arrangement pitch Pb of the second electrode portion 36B which is a cathode may be as small as, for example, 1 to 10 mm, but the arrangement pitch Pa of the first electrode portion 36A which is an anode is a distance dc from the second electrode portion 36B. The gap is preferably set to be positively correlated with (the gap: see FIGS. 4A and 4B). That is, as the separation distance dc from the second electrode portion 36B is increased, the arrangement pitch Pa of the first electrode portion 36A is widened. For example, when the separation distance dc is 5 mm, the array pitch Pa of the first electrode portions 36A is set to 5 mm or more, and when the separation distance dc is 40 mm, the array pitch Pa of the first electrode portions 36A is set to 30 mm or more, separation When the distance dc is 100 mm, the arrangement pitch Pa of the first electrode portion 36A is set to 50 mm or more. However, if the arrangement pitch Pa of the first electrode portions 36A is too far away, the discharge region is reduced, so the arrangement pitch Pa of the first electrode portions 36A is desirably 50 to 100% of the separation distance dc.

  Naturally, even if the aperture ratio of the discharge electrode portion 18 is smaller than 30%, the fluid molecules are sufficiently wide and hardly affected. However, the electric field strength of the surface of the anode and the rate of voltage rise (dV / dt) most affect the generation efficiency of radicals. As described above, the reason why the arrangement pitch Pa of the first electrode portion 36A which is the anode is expanded according to the separation distance dc is to maintain the electric field strength high.

  The positive electrode of the pulse power supply 14 is connected to the first discharge electrode 26A (anode), and the negative electrode of the pulse power supply 14 is connected to the second discharge electrode 26B (cathode). As a result, an electric field from the first discharge electrode 26A to the second discharge electrode 26B is applied to the gap between the first electrode portion 36A and the second electrode portion 36B. As a result, an ion sheath layer (in a state in which a large amount of ions are collected) is formed in the vicinity of the surface facing the first electrode portion 36A in the second electrode portion 36B, and the first electrode portion 36A and the second electrode portion 36B Plasma is generated in the gap between FIG. 2 shows a state in which plasma is generated between the first electrode portion 36A of the first discharge electrode 26A and the second electrode portion 36B of the second discharge electrode 26B.

  Here, the configuration of the pulse power supply 14 will be described with reference to FIG.

  As shown in FIG. 5, the pulse power supply 14 controls a pulse generator 41 that applies a high voltage pulse between the anode and the cathode, and a pulse controller that controls the pulse generator 41 to generate a discharge between the anode and the cathode. And 42.

  The pulse generation unit 41 has a pulse generation circuit 43 having the following configuration, for example. That is, this pulse generation circuit 43 includes a DC power supply unit 46 having a DC power supply 44 for supplying DC and a capacitor 45 for stabilizing the supply of DC from the DC power supply 44, a transformer 47 for storing inductive energy, and a transformer 47. DC supply path 50 to primary winding 48, MOSFET (metal oxide semiconductor field effect transistor) 52 and SI thyristor 54 for opening and closing supply path 50, bias application path 56 to the gate of SI thyristor 54, SI The diode 58 which suppresses the flow of current to the gate of the thyristor 54 and which allows the current to flow out of the gate of the SI thyristor 54, and the output path 62 of the pulse voltage from the secondary winding 60 of the transformer 47 Have. On the other hand, the pulse control unit 42 has a drive circuit 64 that drives the MOSFET 52.

  The SI thyristor 54 and the MOSFET 52 are inserted in series in the supply path 50 so as to close the supply path 50 when turned on and open the supply path 50 when turned off. One end 66a of primary winding 48 is connected to the positive electrode of DC power supply 44 and one end of capacitor 45, the anode of SI thyristor 54 is connected to the other end 66b of primary winding 48, and the cathode of SI thyristor 54 is the drain of MOSFET 52 The source of the MOSFET 52 is connected to the negative electrode of the DC power supply 44 and the other end of the capacitor 45. The gate of SI thyristor 54 is connected to one end 66 a of primary winding 48 via diode 58 by bias application path 56. The cathode of the diode 58 is connected to one end 66 a of the primary winding 48, and the anode of the diode 58 is connected to the gate of the SI thyristor 54. The diode 58 causes the SI thyristor 54 to be positively biased by voltage drive and negatively biased by current drive. Instead of the transformer 47, an inductor having a single winding may be used to output a pulse voltage directly from the inductor.

  Then, the input of the on signal from the drive circuit 64 to the MOSFET 52 starts, and when the MOSFET 52 is turned on, the gate of the SI thyristor 54 is positively biased, and the SI thyristor 54 is also turned on. Thereby, the supply path 50 is closed. When the supply path 50 is closed, direct current supply to the primary winding 48 is started, and accumulation of inductive energy in the transformer 47 is started.

  When the input of the on signal from the drive circuit 64 to the MOSFET 52 is finished and the MOSFET 52 is turned off, the induced electromotive force generated in the primary winding 48 negatively biases the gate of the SI thyristor 54 and the SI thyristor 54 is also rapidly turned off. Thus, the supply path 50 is rapidly opened. When supply path 50 is rapidly opened, an induced electromotive force is generated in secondary winding 60 due to mutual induction, and the rate of increase in time of voltage V at the time of rising between secondary winding 60 and positive electrode 68 and negative electrode 70 A pulse voltage with a significantly large dV / dt is output.

  The pulse width of the pulse voltage is preferably approximately 10 to 1000 ns in full width at half maximum (FWHM), and the time increase rate dV / dt of the voltage V at the time of rising is preferably approximately 30 to 3000 kV / μs The number of repetitions per unit time is preferably about 100 pps to several hundreds kpps. The desirable range is described as “generally” because the desirable range may be wider than the above range depending on the structure of the reactor 16, the material, the pressure of the fluid, and the flow rate of the fluid.

  A more detailed operation principle of the pulse power supply 14 is described in, for example, Katsuji Iida, Ken Sakuma: "Ultrashort pulse generation circuit (IES circuit) using SI thyristor", Proceedings of SI device symposium (2002).

  On the other hand, as shown in FIGS. 1 and 6, the fluid guiding portion 20 has a rectifying structure for uniformly supplying the fluid to the discharge electrode portion 18. The rectifying structure has a bell mouth portion 72, a rectifying mesh portion 74, and a fluid inflow case 76.

  The bell mouth portion 72 is disposed upstream of the discharge electrode portion 18 and has a bell mouth structure in which the flow passage area gradually decreases in the fluid flow direction.

  The rectifying mesh portion 74 is installed on the upstream side of the bell mouth portion 72, and has one or more rectifying mesh 78 and a pressing frame 80 for pressing the rectifying mesh 78 from both sides (upstream and downstream). The aperture ratio of the rectifying net 78 is desirably 10 to 45%, but depending on the aperture area of the bell mouth portion 72, the aperture ratio may be lower. The reason is that the rectifying mesh 74 functions to uniformly feed the fluid having various velocity vectors entering the fluid inflow case 76 to the bell mouth 72. It is desirable that the mesh number be large and the aperture ratio be low. However, when the opening diameter of the bell mouth portion 72 is as large as, for example, 30 mm, there is no problem no matter how low the opening ratio, as long as it is a commercially available mesh. If the inner diameter of the conduit 82 described later is 6 mm, for example, and the opening diameter of the bell mouth portion 72 is 30 mm, the opening area of the bell mouth portion 72 will be 25 times the opening area of the conduit 82. Therefore, no pressure loss occurs even if the aperture ratio is 4%.

  The fluid inflow case 76 is disposed on the upstream side of the rectifying net portion 74, and the inner dimension Da in the fluid lead-out direction to the bell mouth portion 72 has a positive correlation with the fluid flow rate. The inner dimension Da is 20 mm to 100 mm when the fluid flow rate is in the range of 10 to 20 liters / min.

  The fluid supply direction to the fluid inflow case 76 is different from the fluid discharge direction to the bell mouth portion 72. That is, the fluid supply to the fluid inflow case 76 is performed through the conduit 82 provided on one surface of the fluid inflow case 76, and the angle between the fluid supply direction m and the fluid discharge direction n is 80 ° to 100 °. ° In the example of FIG. 6, the conduit 82 is provided on a surface (for example, the upper surface) parallel to the fluid discharge direction n to the bell mouth portion 72 among the plurality of surfaces of the fluid inflow case 76, and the fluid supply direction m and the fluid discharge The angle with the direction n is approximately 90 °.

  The nozzle 24 may use a first nozzle 24A having a bell mouth structure in which the flow passage area gradually decreases in the flow direction of the fluid, or may use a rectangular cylindrical second nozzle 24B. By using the first nozzle 24A, the fluid containing the excited substance generated in the discharge electrode unit 18 can be uniformly applied to the object 22 (see FIG. 1).

  As described above, the plasma processing apparatus 12 according to the present embodiment has the anode and the cathode, and generates the discharge between the anode and the cathode based on the supply of the high voltage pulse from the pulse power supply 14. And a fluid guide portion 20 for guiding the fluid to the discharge electrode portion 18; and a nozzle 24 for jetting at least excited species generated in the fluid by the discharge in the discharge electrode portion 18 to the object 22; At least one of the guide portion 20 and the nozzle 24 has a structure in which the flow passage area gradually decreases in the fluid flow direction, so that the fluid flows uniformly to the discharge electrode portion 18 It is possible to generate plasma efficiently in the discharge electrode portion 18. Therefore, when performing the sterilizing process indirectly applying the excited substance by generation | occurrence | production of a plasma to the to-be-processed object 22, the efficiency improvement of a sterilizing process can be achieved.

  When the first discharge electrode 26A and the second discharge electrode 26B are manufactured, it is preferable to use a gel cast method. In the gel casting method, after the first conductor 30A is set in a mold and a slurry containing a ceramic powder, a dispersion medium, and a gelling agent is cast, the slurry is subjected to temperature conditions, addition of a crosslinking agent, etc. Is solidified to form a first discharge electrode 26A by firing and thereafter forming the first discharge electrode 26A. The second discharge electrode 26B can also be manufactured by the same method. According to this gel casting method, since the slurry is mixed with the first conductor 30A via the low viscosity state of the slurry, voids are unlikely to remain after mixing. Therefore, even if the first discharge electrode 26A is produced by firing after molding, the first ceramic layer 34A is maintained in a dense state. The same applies to the second ceramic layer 34B.

  In the above-mentioned example, although the example which made the 1st electrode part 36A and the 2nd electrode part 36B into the shape of a comb tooth was shown, in addition, as shown in the 1st modification of FIG. Both the conductor 30A and the second conductor 30B may be formed in a grid shape. In this case, the first electrode portion 36A (the first conductor 30A) and the second electrode portion 36B (the second conductor 30B) intersect when viewed from the flow direction of the fluid to the discharge electrode portion 18, ie, the first electrode portion 36A (the second conductor 30B). The intersection of the second electrode portion 36B is installed at the opening of the first electrode portion 36A.

  Further, as shown in the second modified example of FIG. 8, the first electrode portion 36A and the second electrode portion 36B are respectively formed in a lattice shape, and the first conductor 30A in the first electrode portion 36A and the second electrode portion 36B are formed. The second conductors 30B may be respectively in the form of teeth.

  That is, the first ceramic layer 34A of the first electrode portion 36A is formed in a lattice, and the first conductors 30A in the first ceramic layer 34A are extended, for example, in the x direction and arranged in the y direction. The second ceramic layer 34B of the second electrode portion 36B is formed in a lattice, and the second conductors 30B in the second ceramic layer 34B are extended, for example, in the y direction and arranged in the x direction.

  In this case, compared to the case where both the first conductor 30A and the second conductor 30B are formed in a lattice, the reduction in electric field strength can be suppressed.

  In the second modification described above, of the first ceramic layer 34A, the first portion 84A (a portion extending in the y direction and arranged in the x direction) in which the first conductor 30A is not inner layer is a first conductor It is sufficient that the strength between the first electrode portion 36A consisting of 30A and the first ceramic layer 34A can be maintained. Similarly, of the second ceramic layer 34B, the second portion 84B (a portion extending in the x direction and arranged in the y direction) in which the second conductor 30B is not inner layer is the second conductor 30B and the second ceramic It is sufficient to maintain the strength between the second electrode portion 36B composed of the layer 34B.

  Therefore, as shown in the third modification of FIG. 9, the first portion 84A of the first ceramic layer 34A not having the inner layer of the first conductor 30A is thinned out, and similarly, of the second ceramic layer 34B, You may thin-out the 2nd part 84B in which the 2nd conductor 30B is not inner layer. The example of FIG. 9 shows the case where one each of the first portion 84A and the second portion 84B described above is thinned out. Of course, as long as the strength between the first electrode portions 36A and the strength between the second electrode portions 36B can be maintained, thinning may be performed by two to several.

[First embodiment]
About Examples 1-6 and the reference examples 1 and 2, the change of the light emission area | region of nitrogen in the discharge electrode part 18 by the difference in the aperture ratio of the rectification | straightening mesh | network part 74 was confirmed.

<Measurement conditions>
The flow rate of the fluid (nitrogen N ₂ ) and the dimensions of the plasma processing apparatus 12 are as follows.
Supply flow rate of fluid (nitrogen N ₂ ): 10 liters / min
Dimensions of plasma processing apparatus 12 (see FIG. 6):
Inner diameter of conduit 82: 6 mm
Internal dimension Da of the fluid lead-out direction of the fluid inflow case 76: 100 mm
Number of rectifying networks 78: 2
Bellmouth 72:
Axial length La: 104 to 124 mm
Length Lb of one side of the opening on the rectifying mesh 74 side: 217 mm
Length Lc of one side of the opening on the nozzle 24 side: 61 mm
Pulse power supply 14:
Pulse waveform: DBD (dielectric barrier discharge) type
Pulse frequency: 2kpps
Peak voltage value: 16kV
Peak current value: 3A

<Confirmation of light emitting area>
In the confirmation of the light emitting area, a CCD camera was installed toward the nozzle 24 and an occurrence of discharge at the exposed discharge electrode portion 18 was imaged. Of the captured image to determine the ratio of the emission region of nitrogen to parts throughout the first electrode portion 36A and the second electrode portions 36B intersects (referred to as N ₂ emission region) in percentage. For comparison, FIG. 10A shows the state of 100% of the N ₂ light emitting region, and FIG. 10B shows the state of 50% of the N ₂ light emitting region.

(Examples 1 to 6)
In Examples 1, 2, 3, 4, 5, and 6, the aperture ratio of the rectifying mesh portion 74 was 16%, 21%, 23%, 28%, 37%, and 41%, respectively.

(Reference Examples 1 and 2)
In the reference examples 1 and 2, the aperture ratio of the rectifying mesh portion 74 was 5% and 52%, respectively.

<Evaluation>
The evaluation results are shown in Table 1 below.

From Table 1, the N ₂ light emitting region of Reference Examples 1 and 2 was 50%, but in each of Examples 1 to 6, the N 2 light emitting region was 70% or more and was good. In particular, in Examples 1 to 3, the N ₂ emission region was 100%. From this, it can be seen that as the aperture ratio of the rectifying net portion 74 is smaller, the rectifying property of the fluid is improved, and the discharge is stably performed over the entire area of the discharge electrode portion 18. However, as in the first embodiment, when the aperture ratio is extremely small, the flowability of the fluid is deteriorated, and the discharge becomes unstable. Therefore, it is understood that the preferable range of the aperture ratio of the rectifying net portion 74 is 16% to 41%, and more preferably 16% to 23%.

Second Embodiment
About Example 11-15 and the reference examples 11-13, the change of the light emission area | region of the nitrogen in the discharge electrode part 18 by the difference of the internal dimension Da of the fluid derivation | leading-out direction of the fluid inflow case 76 was confirmed.

  The measurement conditions and the confirmation of the light emitting area are the same as in the first embodiment described above, but the aperture ratio of the rectifying net portion 74 is 23%.

(Examples 11 to 13)
In Examples 11, 12, and 13, the inner dimensions Da in the fluid lead-out direction of the fluid inflow case 76 were 30 mm, 60 mm, and 100 mm, respectively, and the fluid flow rate was 10 (liter / min).

(Examples 14 and 15)
In Examples 14 and 15, the inner dimensions Da in the fluid lead-out direction of the fluid inflow case 76 were 60 mm and 100 mm, respectively, and the fluid flow rate was 20 (liters / min).

(Reference Examples 11, 12, 13)
In the reference examples 11, 12 and 13, the inner dimensions Da of the fluid inflow direction of the fluid inflow case 76 are 10 mm, 10 mm and 30 mm, respectively, and the fluid flow rates are 10 (liters / min), 20 (liters / min) and 20 (liters / min). Liter / min).

<Evaluation>
The evaluation results are shown in Table 2 below.

From Table 2, the N ₂ light emitting region of Reference Example 12 was 30%, and the N ₂ light emitting region of Reference Examples 11 and 13 was 50%, but in each of Examples 11 to 15, the N ₂ light emitting region was 100% It was good. From this, it can be understood that the larger the inner size Da in the fluid lead-out direction of the fluid inflow case 76, the better the fluid flowability, and the larger the flow size, the larger the inner size Da needs to be. Therefore, the lower limit value of the inner size Da in the fluid lead-out direction of the fluid inflow case 76 exists for each flow rate, and the lower limit value is 30 mm at 10 liters / min and 60 mm at 20 liters / min.

Third Embodiment
In Examples 21 to 28 and Reference Examples 21 to 24, changes in the light emission region of nitrogen at the discharge electrode portion 18 due to the difference in arrangement pitch Pa of the anodes (first electrode portion 36A) constituting the discharge electrode portion 18 were confirmed. .

  The measurement conditions and the confirmation of the light emitting area are the same as in the first embodiment described above, but the aperture ratio of the rectifying net portion 74 is 23%.

(Examples 21 to 23)
In Examples 21, 22 and 23, the arrangement pitch Pa of the anodes was 3 mm, 6 mm and 10 mm, respectively, and the distance dc between the anode and the cathode was 5 mm.

(Examples 24 to 26)
In Examples 24, 25 and 26, the arrangement pitch Pa of the anodes was 30 mm, 40 mm and 50 mm, respectively, and the distance dc between the anode and the cathode was 40 mm.

(Examples 27 and 28)
In Examples 27 and 28, the arrangement pitch Pa of the anodes was 50 mm and 80 mm, respectively, and the distance dc between the anode and the cathode was 100 mm.

(Reference Examples 21 to 24)
In Reference Examples 21, 22, 23, 24, the arrangement pitch Pa of the anodes was 2 mm, 20 mm, 40 mm, and 100 mm, respectively, and the distance dc between the anode and the cathode was 5 mm, 40 mm, 100 mm, and 100 mm.

<Evaluation>
The evaluation results are shown in Table 3 below.

From Table 3, N ₂ emission region of Reference Example 21, 22 and 24 is 50%, but N ₂ emission region of Reference Example 23 was 30% in Example 21 to 28 are all N ₂ emission region It was 80% or more and was good. In particular, in Examples 21, 22, 24, 25, and 27, the N ₂ emission region was 100%. From the experimental results, it has been found that the discharge in the central portion becomes weak unless the arrangement pitch Pa of the anodes is increased as the distance dc between the anodes and the cathodes is increased. On the other hand, it has been found that if the arrangement pitch Pa of the anodes is too wide, a cold spot region is formed in the plasma and the efficiency is lowered. Therefore, it is desirable that the arrangement pitch Pa of the anodes be 50% to 100% of the distance dc between the anodes and the cathodes.

Fourth Embodiment
About Example 31-36 and the reference examples 31 and 32, the endurance time of the discharge electrode part 18 by the difference in the pore size of the 1st ceramic layer 34A which comprises the discharge electrode part 18 was confirmed. The pores were confirmed by nondestructive observation images by X-ray CT (computed tomography). The endurance time is the time from the start of the experiment to the occurrence of dielectric breakdown. FIG. 11 shows a state in which pores with a diameter of 50 μm are present in the first ceramic layer 34A. This FIG. 11 is a nondestructive observation image by X-ray CT.

(Examples 31 to 36)
In Examples 31, 32, 33, 34, 35, and 36, the size of the pores present in the first ceramic layer 34A is 30 μm, 30 μm, 20 μm, 15 μm, 15 μm, and 10 μm.

(Reference Examples 31 and 32)
In the reference examples 31 and 32, the dimensions of the pores present in the first ceramic layer 34A are 50 μm and 70 μm.

<Evaluation>
The evaluation results are shown in Table 4 below.

  It can be seen from Table 4 that as the pore size decreases, the endurance time tends to increase. Also, from the experimental results, it was found that when there is even one large pore, dielectric breakdown occurs from there and breakage occurs even if the numerical porosity is 0%. In the case where the thickness of the ceramic layer is 200 μm, the presence of pores having a diameter of 40 μm corresponds to a reduction of the material thickness by 20%. Therefore, it is important to reduce the size of the pores as much as possible, and it is understood that it is desirable not to have pores of 50 μm or more inside the first ceramic layer 34A and the second ceramic layer 34B.

Fifth Embodiment
In Examples 41 to 46 and Reference Examples 41 and 42, the sectional area ratio of the first conductor 30A and the first ceramic layer 34A constituting the discharge electrode portion 18 (the sectional area Aa1 / the first ceramic layer 34A of the first conductor 30A) Changes in plasma emission intensity due to differences in cross-sectional area Ab1) were confirmed. The plasma emission intensity was measured by using an emission spectrometer (OES) to measure the emission (337.1 nm) intensity from N ₂ molecules in the vicinity of the electrode.

(Examples 41 to 46)
In Examples 41, 42, 43, 44, 45, 46, the cross-sectional area ratio (Aa1 / Ab1) is 0.15, 0.3, 0.5, 0.7, 0.8, 0.9, respectively. .

(Reference Examples 41 and 42)
The cross-sectional area ratio (Aa1 / Ab1) of the reference examples 41 and 42 is 0.05 and 1.5, respectively.

<Evaluation>
The evaluation results are shown in Table 5 below.

  From Table 5, the plasma emission intensity of Reference Example 41 was 0.1, but all of Examples 41 to 46 had a plasma emission intensity of 0.5 or more, and were good. In particular, the plasma emission intensities of Examples 44, 45 and 46 were 0.9, 0.9 and 1.0. On the other hand, in Reference Example 42, the plasma emission intensity was 1.0, but it was broken. From this, it is understood that the smaller the cross-sectional area of the first ceramic layer 34A, the higher the voltage applied to the surface of the first conductor 30A, and the higher the plasma emission intensity. However, if the thickness of the first ceramic layer 34A is too thin, dielectric breakdown is likely to occur, and even small pores may cause a large electric field concentration to be easily broken. Therefore, it is understood that the cross-sectional area ratio (Aa1 / Ab1) is 0.1 <Aa1 / Ab1 <1.0.

Sixth Embodiment
Similar to the fifth embodiment described above, the cross-sectional area ratio of the second conductor 30B and the second ceramic layer 34B which constitute the discharge electrode portion 18 in the embodiments 51 to 56 and the reference examples 51 and 52 (the second conductor 30B The change of the plasma emission intensity by the difference of cross-sectional area Ab2 of cross-sectional area Aa2 / 2nd ceramic layer 34B was confirmed.

(Examples 51 to 56)
Examples 51, 52, 53, 54, 55, 56 have cross-sectional area ratios (Aa2 / Ab2) of 0.1, 0.5, 1.0, 1.3, 1.5, 1.8, respectively. .

(Reference Examples 51 and 52)
The cross-sectional area ratio (Aa2 / Ab2) of the reference examples 51 and 52 is 0.05 and 2.5, respectively.

<Evaluation>
The evaluation results are shown in Table 6 below.

  From Table 6, the plasma emission intensity of Reference Example 51 was 0.3, but in all of Examples 51 to 56, the plasma emission intensity was 0.6 or more, which was good. In particular, Examples 53, 54, 55, 56 had plasma emission intensities of 0.9, 0.9, 0.9, 1.0. On the other hand, in Reference Example 52, although the plasma emission intensity was 1.0, it was broken. From this, it can be understood that the voltage applied to the surface of the second conductor 30B becomes higher and the plasma emission intensity becomes higher as the cross-sectional area of the second ceramic layer 34B becomes smaller, as in the fifth embodiment described above. However, if the thickness of the second ceramic layer 34B is too thin, dielectric breakdown is likely to occur, and even small pores cause large electric field concentration and become prone to breakage. Therefore, it is understood that the cross-sectional area ratio (Aa2 / Ab2) is 0.08 <Aa2 / Ab2 <2.0.

Seventh Embodiment
About Example 61-66 and the reference examples 61 and 62, the change of the plasma emission intensity by the difference in the diameter of the 1st conductor 30A (anode conductor) which comprises the discharge electrode part 18 was confirmed.

(Examples 61 to 66)
In Examples 61, 62, 63, 64, 65, 66, the diameter d1 of the first conductor 30A is 200 μm, 300 μm, 500 μm, 800 μm, 900 μm, and 1000 μm, respectively.

(Reference Examples 61 and 62)
In the reference examples 61 and 62, the diameter d1 of the first conductor 30A is 100 μm and 1200 μm, respectively.

<Evaluation>
The evaluation results are shown in Table 7 below.

  It is understood from Table 7 that as the diameter d1 of the first conductor 30A is smaller, higher electric field strength is applied, the ratio of high energy electrons is increased, and the number of active species generation from plasma is increased. On the other hand, the wire rod is easily cut and the reliability of the plasma processing apparatus is lowered. Reference Example 61 has a plasma emission intensity of 1.0, but is unreliable in terms of reliability. Accordingly, the diameter d1 of the first conductor 30A is preferably 200 to 1000 μm, and more preferably 300 to 500 μm.

  In addition, the sterilizer according to the present invention is not limited to the embodiment described above, and it goes without saying that various configurations can be adopted without departing from the scope of the present invention.

Claims (13)

In a sterilizer for sterilizing at least the surface of an object (22) using plasma generated by discharge by high voltage pulse from a pulse power source (14)
A discharge electrode unit (18) having an anode and a cathode and generating a discharge between the anode and the cathode based on the supply of the high voltage pulse from the pulse power supply (14);
A fluid guiding portion (20) for guiding a fluid to the discharge electrode portion (18);
A nozzle (24) for outputting the fluid having passed through the discharge electrode portion (18) toward the object (22);
The plasma is generated by the discharge in the discharge electrode portion (18) while introducing the fluid into the discharge electrode portion (18), and the excited substance is applied to the object (22) together with the fluid;
The supply direction of the fluid to the fluid guiding portion (20) is different from the flow direction of the fluid to the discharge electrode portion (18),
The fluid guiding portion (20) has a bell mouth portion (72) of a bell mouth structure in which a flow passage area gradually decreases in the flow direction of the fluid,
Said nozzle (24) has a passage area to have a gradually becomes smaller structure toward a direction of flow of the fluid,
The fluid guiding portion has a rectifying structure for uniformly supplying the fluid to the discharge electrode portion, and the rectifying structure includes the bell mouth portion and one or more installed upstream of the bell mouth portion And a fluid inflow case installed on the upstream side of the rectification network, and an angle between the supply direction of the fluid and the flow direction of the fluid is 80.degree. To 100.degree .. And sterilizer. In the sterilizer according to claim 1 ,
The sterilizer characterized in that the aperture ratio of the rectification net (78) is 10 to 45%. In the sterilizer according to claim 1 ,
An inside dimension in a fluid introduction direction to the bell mouth portion (72) of the fluid inflow case (76) is 20 mm to 100 mm at a fluid flow rate of 10 liters / min to 20 liters / min. In the sterilizer according to claim 1,
The discharge electrode portion (18) has a first discharge electrode (26A) to be the anode, and a second discharge electrode (26B) to be the cathode.
The plurality of first conductors (30A) constituting the first discharge electrode (26A) and the plurality of second conductors (30B) constituting the second discharge electrode (26B) are mutually separated from each other, and A sterilizer characterized in that the first conductor (30A) and the second conductor (30B) cross each other when viewed in the flow direction of the fluid with respect to the discharge electrode portion (18). In the sterilizer according to claim 1,
The discharge electrode portion (18) has a first discharge electrode (26A) to be the anode, and a second discharge electrode (26B) to be the cathode.
The plurality of first conductors (30A) constituting the first discharge electrode (26A) and the plurality of second conductors (30B) constituting the second discharge electrode (26B) are in a positional relationship of twist. A sterilizer characterized by In the sterilizer according to claim 5 ,
A plurality of grids are formed by the first conductor (30A) and the second conductor (30B) when viewed in the flow direction of the fluid with respect to the discharge electrode portion (18). . In the sterilizer according to claim 5 ,
The sterilizer characterized in that the arrangement pitch of the crossing part of said 1st conductor (30A) and said 2nd conductor (30B) is 5-50 mm. In the sterilizer according to claim 5 ,
The sterilizing apparatus characterized in that the aperture ratio of the discharge electrode portion (18) is 30 to 50% when viewed in the flow direction of the fluid with respect to the discharge electrode portion (18). In the sterilizer according to claim 5 ,
The first discharge electrode (26A) has the first conductor (30A) and a first ceramic layer (34A) covering the first conductor (30A),
The sterilizing apparatus characterized in that the second discharge electrode (26B) has the second conductor (30B) and a second ceramic layer (34B) covering the second conductor (30B). In the sterilizer according to claim 9 ,
A sterilizer characterized by having no pores of 50 μm or more inside the first ceramic layer (34A) and the second ceramic layer (34B). In the sterilizer according to claim 9 ,
In a cross section obtained by cutting the first conductor (30A) and the first ceramic layer (34A) in the direction orthogonal to the axial direction, the area of the first conductor (30A) is Aa1, and the first ceramic layer (34A) Let the area of be Ab1
In a cross section obtained by cutting the second conductor (30B) and the second ceramic layer (34B) in the direction orthogonal to the axial direction, the area of the second conductor (30B) is Aa2, and the second ceramic layer (34B) When the area of
0.1 <Aa1 / Ab1 <1.0
0.08 <Aa2 / Ab2 <2.0
A sterilizer characterized by being. In the sterilizer according to claim 11 ,
Each diameter of said 1st conductor (30A) and said 2nd conductor (30B) is 200-1000 micrometers, The sterilizer characterized by the above-mentioned. In the sterilizer according to claim 1,
The pulse power supply (14) is a pulse generation unit (41) for applying the high voltage pulse between the anode and the cathode, and the pulse generation unit (41) so as to generate a discharge between the anode and the cathode. And a pulse control unit (42) for controlling
The pulse generation unit (41) has a transformer (47) and a switch (54) connected in series at both ends of the DC power supply unit (46), and turns on the switch (54) of the pulse control unit (42). The induced energy is accumulated in the transformer (47) by control, and the high voltage pulse is generated on the secondary side of the transformer (47) by the off control of the switch (54) of the pulse control unit (42). And a pulse generating circuit (43) for performing the processing.

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