GENERATING METHOD AND GENERATOR FOR GENERATING MIST OR FINE-BUBBLE BY USING SURFACE ACOUSTIC WAVE
In a generating method and a generator of mist or fine-bubble, with a simple and small configuration, application into a wide range kind of liquid is enabled, and generating stably the mist or the fine-bubbles or both is enabled. The generator is provided with a piezoelectric substrate which equips two or more comb-like electrodes on a surface and arranged so that the surface may intersect the mutual interface of the gas and the liquid and a part of piezoelectric substrate is put in a liquid, and a surface acoustic wave excited on the surface with the electrode is made to propagate along the surface so that may exist in the upper and lower sides of an interface. The surface acoustic wave generates mist in the gas side which is above the interface, and generates fine-bubbles in the liquid side which is below the interface. Since the mist and the fine-bubbles are generated with the surface acoustic wave, without being based on mechanical operation for generating a turning stream, the mist and the fine-bubbles can be stably generated in the simple and small configuration.
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The present invention relates to method and generator which generate mist or fine-bubble of a micro-meter or nanometer order.
BACKGROUND ARTTo generate fine bubbles of diameter of a nanometer order below a micron, conventionally, a turning stream is generated in a gas and liquid mixing fluid, and the gas contained in the liquid is subdivided with a shear force produced in the liquid. For example, an equipment is known which supplies a gas and liquid mixing fluid into a cylinder from an inner circumference tangential direction with a vortex pump and then miniaturizes bubbles during revolutions within the cylinder (for example, refer to Japanese patent No. 4118939).
Moreover, a phenomenon is known that if a liquid is supplied to a surface, of a substrate consisting of the piezoelectric material etc., on which a surface acoustic wave is propagating, the liquid receives an energy of the surface acoustic wave, flows or vibrates, and flies as fine particles. Generators which atomize a liquid by using this phenomenon are proposed variously, and a method is known which atomizes a liquid drop by breathing out the drop from an ink jet unit and supplying the drop onto a surface where a surface acoustic wave is propagating (for example, refer to Japanese Laid-open Patent Publication Hei 11-114467).
However, a pump for highly pressurizing a liquid, and so on, are necessary in the generating method of the fine bubbles shown in the Japanese patent No. 4118939 mentioned above, and the miniaturization of apparatus is difficult. Moreover, in the generating method of mist shown in the Japanese Laid-open Patent Publication Hei 11-114467, it is necessary to stably supply the drop to be atomized with sufficient accuracy, and a constitution becomes complicated. Moreover, such a method or a generator is not known which can miniaturize the equipment and can simultaneously generate both of mist and fine-bubble of nanometer order or can generate only desired one.
DISCLOSURE OF THE INVENTIONThe present invention is to solve the above problem, and an object of the present invention is to provide a generating method and a generator of mist or fine-bubble, which can stably generate mist or fine-bubble, or both, with a simple and small configuration, by using surface acoustic wave.
A generating method for generating mist or fine-bubble, comprises the steps of: arranging in a liquid a part of a piezoelectric substrate having a surface, said surface intersecting a mutual interface of gas and the liquid and equipped thereon with an excitation means consisting of a plurality of electrodes to excite surface acoustic wave; exciting a surface acoustic wave on the surface with the excitation means; and propagating the excited surface acoustic wave along the surface so that the surface acoustic wave to exist in the upper and lower sides of the interface and the surface acoustic wave to generate mist in the gas side upon the wave being above the interface and to generate fine-bubbles in the liquid side upon the wave being below the interface.
According to such constitution, mist or a fine-bubble can be generated in space-saving and low cost by a simple and small configuration without being based on mechanical operation of generating a turning stream, since generating of mist and generating of a fine-bubble both of which are performed with the surface acoustic wave by using one piezoelectric substrate. Moreover, since the constitution is simple, it is applicable to a various kinds of liquid.
A generator for generating mist or fine-bubble at an interface of gas and a liquid or within the liquid, comprises: a piezoelectric substrate equipped with an excitation means on a surface thereof, the excitation means consisting of a plurality of electrodes to excite a surface acoustic wave; and a substrate-holder holding the substrate, dipping in the liquid a part of the substrate so that the surface to intersect the mutual interface of the gas and the liquid, and a surface acoustic wave excited on the surface of the piezoelectric substrate existing in the upper and lower sides of the interface and propagating along the surface from the gas side to the liquid side.
According to such constitution, since it is enough to provide a piezoelectric substrate so that the substrate intersects a gas-liquid interface, a generator for the mist or the fine-bubbles of a simple and small configuration can be offered. Moreover, since constitution and the principle are simple, there are few restrictions of liquid selection and it is applicable to a various kinds of liquid.
Hereafter, generating method and generator for generating mist or fine-bubble by using surface acoustic wave, according to the embodiments of the present invention, are described with reference to the drawings.
First EmbodimentThe piezoelectric substrate 2 is a rectangular plate, and is vertically held by a substrate-holder 20 so that the longitudinal direction of the plate is in up-and-down direction and a part of it is inserted into the liquid 10. The piezoelectric substrate 2 is a substrate which consists of a piezoelectric crystal itself like LiNbO3 (lithium niobate), for example. Moreover, the piezoelectric substrate 2 can be made of a non-piezoelectric substrate having a piezoelectric thin film, such as PZT thin film (lead, zirconium, titanium-alloy thin film), for example, on its surface, and the surface acoustic wave W is excited on a surface of the piezoelectric thin film covering the surface of the non-piezoelectric substrate. Consequently, the piezoelectric substrate 2 is enough to be a substrate having on its surface the piezoelectric part where the surface acoustic wave can be excited. Moreover, its form is not limited to a rectangle, and it may be arbitrary as the piezoelectric substrate 2 of the generator 1. Moreover, the surface S is not restricted to be flat, but can be made into a surface with arbitrary curved surfaces. The piezoelectric substrate 2 is not restricted to be a plate of constant thickness, but can be of an arbitrary form and is enough if it is equipped with the surface S which can propagate a surface acoustic wave W.
The comb-like electrodes 21 make up an electrode (an intersection finger electrode, IDT: interdigital transducer) by combining two comb shape electrodes each having an opposite polarity. Each of comb teeth of the electrodes 21 are adjacent mutually to belong to different electrodes of different polarity and are arranged at a pitch of half length of a wavelength of a surface acoustic wave W to be excited. By impressing high frequency (for example, MHz band) voltage from an electric circuit E which is dedicated to the high-frequency voltage impression between the electrodes of different polarity of the electrodes 21, an electrical energy is converted into a wave mechanical energy by the comb shape electrodes, and the surface acoustic wave W is excited on the surface S of the piezoelectric substrate 2. An amplitude of the excited surface acoustic wave W is decided by the size of the voltage impressed to the electrodes 21. A length of wave packet of the excited surface acoustic wave W corresponds to a length of time the voltage is impressed. The surface acoustic wave W excited by the electrodes 21 becomes a wave having a width corresponding to an overlap width of comb teeth in a pair of comb-like electrodes interdigitating with each other, and propagated in a direction-x perpendicular to the comb teeth. The above surface acoustic wave W has a feature forcing a liquid which exists on the surface S to move in a propagation direction of the surface acoustic wave W.
A surface acoustic wave W being propagated on a solid surface can be easily and stably excited as a wave of high frequency compared with the supersonic wave which generated with a piezoelectric element etc., and is propagated inside of a solid or fluid in three dimensions. The mist M containing fine particles of a diameter of micron order, or from a submicron to nanometer order can be generated in the gas side by propagating the surface acoustic wave W of short wave length and high frequency into the liquid 10, in the gas-liquid interface 10a where the surface acoustic wave W passes on, and moreover, the fine-bubbles B of a diameter of micron order, or from a submicron to nanometer order can be generated within the liquid 10 by the surface acoustic wave W propagated into the liquid side. According to the constitution of the generator 1, the mist M and the fine-bubbles B can be generated simultaneously.
It is thought that the fine-bubbles B is generated from the gas which is dissolved in the liquid 10. Then, it can be made easy to generate the fine-bubbles by dissolving beforehand the gas which serves as fine-bubbles into the liquid in a supersaturated state. It can be done also to maintain the temperature of the liquid 10 low by providing a cooler for cooling the liquid 10 in order to increase a dissolving capacity of the gas. Moreover, it is thought that the surface acoustic wave W, being propagated from the gas side to the liquid 10 side and passing through the gas-liquid interface 10a, makes involvement of the gas into the liquid from the gas side, and thus it is thought that the fine-bubbles B are generated also from the involved-in gas.
Water, such as tap water and pure water, and liquids such as organic solvents, for example alcohol, and other arbitrary liquid can be used for the liquid 10. However, when insulation protection has not fully been performed to the electrodes 21, the liquid 10 is restricted to the liquid of electrical insulation properties. Then, an insulating layer or a protective layer can be prepared on the surface of the piezoelectric substrate 2 for the electrical insulation of the electrodes 21 or for the corrosion prevention of the piezoelectric substrate 2. As for these, it is desirable not to cause the propagation loss of the surface acoustic wave W. Simple substance gas, such as oxygen and ozone, and desired arbitrary gas other than air in atmospheric air can be used for the gas.
As shown in
According to this embodiment, since generating of the mist M and generating of the fine-bubbles B both are performed by the one piezoelectric substrate 2, the mist M and the fine-bubbles B can be generated in simple and small configuration, space-saving, and at low cost. Moreover, since the constitution is simple, it is applicable to a various kinds of liquid.
Moreover, as shown in
According to this modification, since the transfer loss of the surface acoustic wave W, which occurs when the surface acoustic wave W propagates from the gas side into the liquid 10 side and passes through the interface 10a, can be suppressed with the cover 22, the fine-bubbles B can be generated with sufficient energy efficiency. Moreover, since the surface acoustic wave W comes into contacts with the liquid 10 inside of the liquid 10 away from the interface 10a, the fine-bubbles B can be generated selectively, without generating mist M. Moreover, since the fine-bubbles B are generated away from the interface 10a, their dissipation into the gas side is reduced.
Moreover, as shown in the modification of
The generation of the fine-bubbles B, towards the exterior (lower part) from a space between the piezoelectric substrate 2 and the plates 13, is stopped by arranging the plate 13 in front of the surface S with the gap d above-mentioned. This is based on the phenomenon that the fine-bubbles B stop appearing in the downward liquid 10, since each of the fine-bubbles B generated in the liquid of the space between the piezoelectric substrate 2 and the plate 13 combines together and comes up if the height H of the top hem of the plate 13 becomes beyond a certain constant value. Since the height H is set as upper height from the interface 10a, if the plate 13 is extended in a lower part from the interface 10a, the fine-bubbles B stops appearing below even if the height of the plate 13 is lower than above-mentioned height H.
According to this modification, the generation of the fine-bubbles B is suppressed inside of the liquid 10 and only the mist M can be generated to the exterior, since the movable space for the fine-bubbles B is limited in the gap d by making the gap d between the piezoelectric substrate 2 and the plate 13 narrow enough, and each of the fine-bubbles B combines and goes upwards. In such gap d, the mist M can be generated stably in a same height position to the piezoelectric substrate 2, since the height of the level rises than other portions and is kept with the surface tension of the liquid 10, even if the height of the level of other portions changes.
According to this modification, the mist M and the fine-bubbles B can be generated stably even if the liquid is conductive, since the electrodes 21 for constituting an excitation means is insulated. Moreover, since the electrodes 21 is equipped with the insulator 23, an unexpected situation of an accidental connection between the electrodes can be avoided, and the mist M and the fine-bubbles B can be easily generated with easy operation. Moreover, as shown in
Moreover, as shown in
Moreover, as shown in
In the generator 1, the liquid 10 containing the fine-bubbles B can be drawn from the center of the lower part of the liquid container 11, for example, as the arrow head OUT shows, and the liquid 10 can be used for a washing use, and so on. Moreover, resupply of the liquid can be supplied suitably from the upper part of the liquid container 11, as the arrow head IN shows, in order to compensate the outflow of the liquid 10. At this time, the quantity of the exciting power for the surface acoustic wave, an exciting frequency, the number of electrodes for excitation, propagation area in the piezoelectric substrate 2, and the number of the piezoelectric substrate itself, etc. which are the specifications in connection with the generation performance for the fine-bubbles B, can be set beforehand or changed while in use, so that the fine-bubbles B in the liquid 10 can have a suitable bubble number density according to its utilization object. Moreover, the flow volume of the liquid 10 to be drawn can be changed and adjusted, so that the fine-bubbles B can have a suitable bubble number density.
According to this modification, since it is possible to make the fine-bubbles B go off from vicinity of the piezoelectric substrate 2 and to separate and disperse each of the fine-bubbles B with the flow of the liquid 10 along the circumferencial direction of the circular liquid container 11, it is possible to prevent each of the fine-bubbles B from joining and to suppress an annihilation of the fine-bubbles B which is caused by their growth, and thus efficiently to generate the fine-bubbles B. In addition, it is good also to tilt the piezoelectric substrate 2 from the direction of the diameter of the liquid 10 in plan view and arrange it in the position where the rotational flow of the liquid is not disturbed.
According to this modification, by making an anion in the liquid 10 (for example, OH−) adhere to the surface of the piezoelectric substrate 2, the mist M, or the fine-bubbles B, and by using the repulsive force between the electric charges of the same kind, it is possible to make the mist M and the fine-bubbles B go off promptly from vicinity of the piezoelectric substrate 2, separate, and disperse the mist M or each of the fine-bubbles B, and thus the combination between the mist M or between each of the fine-bubbles B can be prevented. Therefore, annihilation of the mist M or the fine-bubbles B which is caused by combination growth is suppressed, and it is possible to efficiently generate the mist M or the fine-bubbles B, and to stably maintain the state of the mist M or the fine-bubbles B.
Moreover, as shown in
According to this modification, the propagation of the surface acoustic wave can be limited in the one direction, and the generation position of the mist M and the fine-bubbles B can be limited. Moreover, the energy of wave can be used effectively, when the piezoelectric substrate 2 is arranged with the electrodes 21 as an excitation means in the gas by reflecting the surface acoustic wave propagating toward the substrate edge in the gas which does not contribute to generating of mist or a fine-bubble at all, and making it go to the liquid 10 side with the reflector 24.
According to this modification, generating stabilization of the mist M and the fine-bubbles B can be attained by the physicochemical effect of the surface active substances. Moreover, for example, when using the mist M and the liquid 10 for washing, the surface active substances, which can improve a scavenging effect, can be made to adhere to the surface of the mist M and the fine-bubbles B efficiently in the minimum quantity.
According to this modification, since the fine-bubbles B can be made to go off from vicinity of the piezoelectric substrate 2 promptly and each of the fine-bubbles B can be made to separate by the flow of the liquid 10, combination between each of the fine-bubbles B can be prevented, and annihilation of the fine-bubbles B caused by combination grow can be suppressed, and the fine-bubbles B can be generated efficiently. Moreover, it is possible to generate the fine-bubbles B so that the density of the number of fine-bubbles in the liquid 10 becomes uniform. The liquid 10 containing such fine-bubbles B can be delivered to a desired place with the tubular structure 5 and can be used for processing of washing, and so on.
Moreover, as shown in
According to this embodiment, the fine-bubble of desired gas can be generated easily and efficiently. This is based on the fact that the fine-bubbles B is generated from the gas which is dissolving in the liquid 10. In addition, if the side wall 32 is extended from the interface 10a into the inside of liquid 10 without forming the opening 33, it is possible to use only the liquid 10 which contains the fine-bubbles B of the gas G without taking out the mist M and to prevent the consumption of the gas G made by dissipation. Moreover, it is possible to make a space-saving generator by using the container 3 which can localize the gas G and possible to make a further space-saving generator by making the container 3 is of the minimum volume which can contain the piezoelectric substrate 2 and its circumference in airtight. The gas G can be pressurized within the container 3 in order to promote its dissolution. The gas G can be generated within the container 3, without introducing from outside. For example, oxygen as the gas G can be generated by the oxygen permeable membrane which can make oxygen concentration high only by making air pass it.
According to this modification, a generating condition can be fixed and the mist M and the fine-bubbles B can be generated stably, since the position of the up and down direction of the piezoelectric substrate 2 can be maintained stably and automatically in a fixed height to the liquid 10 in which the height of the liquid level 10a changes. Moreover, since the piezoelectric substrate 2 is in the floating state, horizontal position changes and position keeping in the liquid level 10a are easy. In addition, the floating body 4 is not limited to the shape of C-type, but two or more floats of arbitrary shape can be combined and used for it. Moreover, an arbitrary shape component can be used for the support 41 which fixes the floating body 4 and the piezoelectric substrate 2, for example, a bar, a plate, and a lid-like component, etc., any of sealing and not sealing may be sufficient, and the floating body 4 and the support 41 can be combined to make an integral construction. Moreover, a moving guide, a latch, etc. can be provided to the liquid container in order to move the floating body 4 smoothly and the piezoelectric substrate 2 supported with it, vertically or horizontally relative to the liquid container.
Moreover, as shown in
According to such a modification, the influence of power loss or a noise can be minimized, since the close arrangement of the circuit substrate 42 and the piezoelectric substrate 2 can be carried out. Moreover, external wiring etc. become unnecessary by holding the power source 43 by the floating body 4, and the generator 1 can be constituted as an independent unit by including an apparatus required for generating the mist M or the fine-bubbles B in addition to the piezoelectric substrate 2, and an installation of the unit or the increase and decrease of the number of the unit are easy, and the mist M and the fine-bubbles B can be generated easily.
Moreover, as shown in
According to these modifications, the arbitrary gas G which is dissolved into the liquid 10 and made to be contained in the fine-bubbles B can be supplied adaptively to the liquid 10 according to the flow rate or the flow velocity of the liquid 10. Therefore, the gas G is not consumed in vain, and when it is expensive gas, the generator can be operated at low cost. A spring or a weight can be used so that the gas supply valve 51 can be closed when the liquid 10 is not flowing. Moreover, an area of the part which receives the suction force or the kinetic energy can be made wide so that open operation can be carried out and the gas G can be supplied even if the flow velocity is low or there are few flow rates. The gas supply valve 51 shown in
In addition, various modification is possible for the present invention, without being restricted to each above-mentioned embodiment and the constitution of each modification. For example, each embodiment mentioned above and constitution of each modification can be mutually combined to yield other constitutions. The method and generator of the present invention using a surface acoustic wave can generate, especially, mist or fine-bubble of submicron or nanometer order in diameter, and the gas or the liquid containing such a mist or fine-bubble can be conveniently used as various kinds of cleaning fluid, chemical reaction liquid for processing or reaction promotion, physiological function liquid, and so on. For example, it can be used for in-a-mist-washing of a machine part after processing, an electronic circuit substrate, various semiconductor substrates such as a silicon substrate, tableware, and so on. A plurality of piezoelectric substrates 2 can be combined and used. Moreover, it is effective to prevent combination growth between mist droplets or between fine-bubbles for the generation of the mist or the fine-bubbles of much smaller size more stably and effectively, and therefore, as mentioned above, means for generating a relative flow velocity between the piezoelectric substrate 2 and the liquid 10, and also means for charging the mist or the fine-bubbles are preferably used as the particle combination prevention means.
This application is based on the Japan patent application 2009-148112, and the contents should be united to the present application invention as a result by referring to the specification and figures of the above-mentioned patent application.
Claims
1. A generating method for generating mist or fine-bubble, comprising the steps of:
- arranging in a liquid a part of a piezoelectric substrate having a surface, said surface intersecting a mutual interface of gas and the liquid and equipped thereon with an excitation means consisting of a plurality of electrodes to excite surface acoustic wave;
- exciting a surface acoustic wave on the surface with the excitation means; and
- propagating the excited surface acoustic wave along the surface so that the surface acoustic wave to exist in the upper and lower sides of the interface and the surface acoustic wave to generate mist in the gas side upon the wave being above the interface and to generate fine-bubbles in the liquid side upon the wave being below the interface.
2. A generating method for generating mist or fine-bubble according to claim 1, further comprising:
- arranging the piezoelectric substrate so that the excitation means to be in the gas side;
- preparing a cover sticking on a region in the surface including at least a region intersecting the interface; and
- propagating the surface acoustic wave excited by the excitation means along the surface from the gas side to the liquid side to generate fine-bubbles inside the liquid away from the interface.
3. A generating method for generating mist or fine-bubble according to claim 2, wherein the cover being prepared further in a region for covering the excitation means.
4. A generating method for generating mist or fine-bubble according to claim 1, wherein providing a container wrapping a portion of the piezoelectric substrate in the gas side to confine the mist in a space formed with the container and the liquid.
5. A generating method for generating mist or fine-bubble according to claim 1, wherein providing a plate in a position intersecting the interface, said plate approaching and facing the surface.
6. A generating method for generating mist or fine-bubble according to claim 1, wherein changing a generation ratio of the mist or the fine-bubbles by changing an angle of intersection between the surface and the interface.
7. A generating method for generating mist or fine-bubble according to claim 1, wherein the surface being covered by an insulator to cover at least the excitation means.
8. A generating method for generating mist or fine-bubble according to claim 1, wherein a substrate-thickness of the piezoelectric substrate being made into the substrate-thickness so that the surface acoustic wave excited by the excitation means to propagate on a rear-surface countering the surface.
9. A generating method for generating mist or fine-bubble according to claim 1, wherein furthermore providing the excitation means on a rear-surface countering the surface, and exciting the surface acoustic waves on these both surfaces.
10. A generating method for generating mist or fine-bubble according to claim 9, wherein exciting the surface acoustic waves on the both surfaces so that a mutual phase to become in phase.
11. A generating method for generating mist or fine-bubble according to claim 1, wherein making finer bubbles by crushing the fine-bubbles generated with the surface acoustic wave by using a shock wave.
12. A generating method for generating mist or fine-bubble according to claim 1, wherein containing the liquid in a container of a circle configuration in plan view.
13. A generating method for generating mist or fine-bubble according to claim 1, wherein an area, the mist or fine-bubbles to be generated therein in the piezoelectric substrate, being made into positive potential to an ambience.
14. A generating method for generating mist or fine-bubble according to claim 1, wherein an area, the mist or fine-bubbles to be generated therein in the piezoelectric substrate, being made into negative potential to an ambience.
15. A generating method for generating mist or fine-bubble according to claim 1, wherein providing the surface with a reflective means for propagating the surface acoustic wave to one way.
16. A generating method for generating mist or fine-bubble according to claim 1, wherein dropping surface active substances in a domain the fine-bubbles being generated.
17. A generating method for generating mist or fine-bubble according to claim 1, wherein providing a container wrapping a portion of the piezoelectric substrate in the gas side, and filling an inside of a space formed by the container and the liquid with an arbitrary gas.
18. A generating method for generating mist or fine-bubble according to claim 1, wherein supporting the piezoelectric substrate in a position of a definite height from the liquid level by a floating body.
19. A generating method for generating mist or fine-bubble according to claim 18, wherein providing a circuit substrate, for controlling the excitation means, supported by the floating body.
20. A generating method for generating mist or fine-bubble according to claim 18, wherein providing a power source, for driving the excitation means, supported by the floating body.
21. A generating method for generating mist or fine-bubble according to claim 1, wherein generating the fine-bubbles in a liquid flowing through an inside of a tubular structure.
22. A generating method for generating mist or fine-bubble according to claim 1, wherein providing the piezoelectric substrate and the excitation means on an internal surface of a liquid container accommodating the liquid.
23. A generating method for generating mist or fine-bubble according to claim 1, wherein supplying an arbitrary gas into the liquid from the gas side along the surface.
24. A generating method for generating mist or fine-bubble according to claim 23, wherein supplying the gas being performed, by giving a flow-velocity to the liquid, through a valve opened by a suction force based on a pressure drop accompanying the flow-velocity rise of the liquid, or by a kinetic energy of the liquid increasing with the flow-velocity rise.
25. A generator for generating mist or fine-bubble at an interface of gas and a liquid or within the liquid, comprising:
- a piezoelectric substrate equipped with an excitation means on a surface thereof, the excitation means consisting of a plurality of electrodes to excite a surface acoustic wave; and
- a substrate-holder holding the substrate, dipping in the liquid a part of the substrate so that the surface to intersect the mutual interface of the gas and the liquid, and a surface acoustic wave excited on the surface of the piezoelectric substrate existing in the upper and lower sides of the interface and propagating along the surface from the gas side to the liquid side.
Type: Application
Filed: Jun 2, 2010
Publication Date: Apr 26, 2012
Applicant: PANASONIC ELECTRIC WORKS CO., LTD. (Osaka)
Inventors: Masanori Okano ( Osaka), Shigeki Fujiwara ( Nara), Youhei Ishigami ( Osaka)
Application Number: 13/379,358
International Classification: B05B 17/00 (20060101); B05B 1/08 (20060101);