JP5861121B2 - Surface acoustic wave atomizer - Google Patents

Description

  The present invention relates to a surface acoustic wave atomizer.

  Conventionally, it is made of a piezoelectric material in which a pair of comb-shaped electrodes is formed, and includes a substrate on which surface acoustic waves are generated by the comb-shaped electrodes, and the elasticity that atomizes the liquid supplied to the surface of the substrate by the liquid supply means by the surface acoustic waves A surface wave atomizer is known (see, for example, Patent Document 1). This surface acoustic wave atomizer suppresses the presence of liquids that are not involved in atomization by forming a slender liquid distribution along the surface of the surface acoustic wave by surface tension to maintain the balance between the liquid supply amount and the atomization amount. In addition, it is intended to stably spray a large amount of fine particles with less power consumption.

JP 2008-104974 A

  However, in the surface acoustic wave atomization apparatus as described above, although the supply of liquid is taken into consideration, it is considered that there is still room for improvement in the configuration of the surface acoustic wave generation side, that is, the comb electrode side. .

  The present invention solves the above-mentioned problems, and generates and propagates a surface acoustic wave having a large wave amplitude and a small spread with a simple configuration, and stably atomizes with high energy efficiency. It is an object of the present invention to provide a surface acoustic wave atomization device capable of performing the above.

In order to achieve the above object, a surface acoustic wave atomization apparatus according to the present invention includes a substrate made of a piezoelectric material, a pair of comb electrodes provided on the substrate to generate surface acoustic waves on the surface of the substrate, and a substrate. A liquid supply unit that supplies a liquid atomized by surface acoustic waves generated on the surface of the substrate to the substrate, and the liquid supply unit is disposed to face the surface of the substrate and is supplied to the substrate And a supply member for distributing the film in a film shape by the surface tension of the liquid, the supply member is opposed to the surface of the substrate at a uniform height from the surface of the substrate, and a gap space is formed between the surface and the surface of the substrate. The pair of comb electrodes are meshed with each other, and the meshing length of the comb teeth is not more than 10 times the wavelength of the surface acoustic wave generated by the comb electrodes. is, the supply member, the surface acoustic wave generated on the surface of the substrate Wherein the length of the surface to form a clearance space in the direction perpendicular to the traveling direction is configured to be equal to or less than the length meshing of each other of the comb teeth.

  In this surface acoustic wave atomization device, it is preferable that the meshing length of the comb teeth is 5 times or more the wavelength of the surface acoustic wave generated by the comb electrode.

In this surface acoustic wave atomizer supply member, so as not that a comb-shaped electrode in the liquid distributed in a film shape is normally to exposure, it is preferable that provided at a distance from the comb-shaped electrode.
In this surface acoustic wave atomization device, it is preferable that the meshing length of the comb teeth is constant in each comb tooth of the pair of comb-shaped electrodes.
In this surface acoustic wave atomizer, the pair of comb electrodes preferably include a reflective electrode for constituting a unidirectional electrode.

  According to the surface acoustic wave atomization device of the present invention, by making the opening width appropriate, the surface acoustic waves generated by the comb-shaped electrode are not spread and a large amplitude is maintained. The region can be limited and atomization can be performed efficiently.

Fig.1 (a) is a top view about the surface acoustic wave atomizer based on one Embodiment of this invention, FIG.1 (b) is the side view, FIG.1 (c) is atomization of the apparatus It is principal part sectional drawing of an area | region. FIG. 2A is a plan view of a pair of comb-shaped electrodes when the meshing length of comb teeth is long (opening width is wide), and FIG. 2B is a plan view when the meshing length is short (opening width is narrow). FIG. FIG. 3 is a graph showing the relationship between the amplitude of the surface acoustic wave and the opening width of the comb electrode at three points with different distances from the comb electrode in the surface acoustic wave atomizer. 4A is a distribution diagram of amplitudes obtained by actually measuring surface acoustic waves when the aperture width D = 2.5λ, and FIG. 4B is a distribution diagram when the aperture width D = 5λ. FIG. 4C is a distribution diagram when the opening width D = 10λ, and FIG. 4D is a distribution diagram when the opening width D = 20λ.

  Hereinafter, a surface acoustic wave atomization apparatus according to an embodiment of the present invention will be described with reference to the drawings. 1A, 1B, and 1C show a surface acoustic wave atomizer 1. FIG. The surface acoustic wave atomization apparatus 1 is generated on a surface 2 of a substrate 2 made of a piezoelectric material, a pair of comb electrodes 21 provided on the substrate 2 to generate a surface acoustic wave W on the surface S of the substrate 2, and the surface S. And a liquid supply unit 3 for supplying the liquid atomized by the surface acoustic wave W to the substrate 2. The surface acoustic wave W is generated by applying a high frequency voltage to the comb electrode 21. The substrate 2 provided with a pair of comb-shaped electrodes 21 constitutes a vibrator that generates a surface acoustic wave W. Further, on the surface S, a reflective comb electrode 22 is disposed adjacent to the comb electrode 21. Here, for the sake of explanation, the longitudinal direction of the comb teeth of the comb-shaped electrode 21 is defined as direction Y, the direction perpendicular to the comb teeth is defined as direction X (right direction), and the origin X = 0 in the direction X is set to the maximum on the direction X side. The outermost position of the outer comb teeth.

The substrate 2 is made of a piezoelectric material made of a piezoelectric body itself such as LiNbO ₃ (lithium niobate), for example. This piezoelectric material may be one in which a piezoelectric thin film, for example, a PZT thin film (lead, zirconium, titanium alloy thin film) is formed on the surface of a non-piezoelectric substrate. A surface acoustic wave is excited in the surface portion of the piezoelectric thin film on the surface. The pair of comb-shaped electrodes 21 are electrodes (IDT: inter-digital transducer) formed by meshing each comb-tooth portion of two comb-shaped electrodes on the surface of the piezoelectric material. Comb teeth adjacent to each other of the comb-shaped electrode 21 belong to different electrodes, and are arranged at a pitch having a length half the wavelength λ of the surface acoustic wave W to be excited.

  The mutual meshing length of the comb teeth of the pair of comb-shaped electrodes 21, that is, the width at which the comb teeth intersect is a dimension that defines the width of the surface acoustic wave W generated by the comb-shaped electrode 21. The opening width D of the comb electrode 21 is defined. The opening width D (engagement length) is 5 to 10 times the wavelength λ of the surface acoustic wave generated by the comb electrode 21. The comb teeth of the comb-shaped electrode 21 have the same length, and the meshing length of the comb teeth is constant in each comb tooth. The opening width D will be described in detail later (see FIGS. 2, 3, and 4).

  The liquid supply unit 3 is disposed opposite to the liquid container 31, the liquid deriving member 32 for deriving the liquid 4 from the liquid container 31 and supplying the liquid 4 to the surface S, and the surface S of the substrate 2. The supply member 30 is provided. The supply member 30 forms a gap space G for distributing the liquid 4 supplied onto the substrate 2 on the surface S of the substrate 2 in a film shape by the surface tension of the liquid 4. The supply member 30 is an elongated member and has a surface that forms a gap space G with the surface S of the substrate 2, and the surface is spaced from the surface S of the substrate 2 by a uniform height g, Opposite the surface S. Further, the supply member 30 has its longitudinal direction directed in a direction Y orthogonal to the traveling direction X of the surface acoustic wave W generated on the surface S of the substrate 2, and the length in the direction Y (the gap space G is formed). The length of the surface is equal to or smaller than the opening width D. In other words, the gap space G is formed such that the width in the width direction Y orthogonal to the traveling direction X of the surface acoustic wave W is equal to or less than the opening width D. Further, the supply member 30 is disposed so that the entire width of the gap space G in the direction Y is substantially within the opening width D desired from the comb-shaped electrode 21. The liquid 4 is distributed in the form of a film on the surface S by being held in the gap space G by its own surface tension. Accordingly, the distribution of the liquid 4 in the direction Y is approximately within the opening width D. The supply member 30 is configured using a pipe having pores through which the liquid 4 leaks, or a member that has a fine structure on the surface and transports the liquid 4 by capillary action, such as a bar or plate. You can do it.

  Next, the operation of the surface acoustic wave atomizer 1 will be described. By applying a high-frequency (for example, MHz band) voltage from the electric circuit 23 for applying a high-frequency voltage to the comb-shaped electrode 21, the electrical energy is converted into wave mechanical energy by the comb-shaped electrode 21, and is applied to the surface of the substrate 2. A surface acoustic wave W called a Rayleigh wave is excited. The surface acoustic wave W excited by the comb-shaped electrode 21 is generated with a width based on the opening width D and propagates in both directions of the comb-shaped electrode 21, that is, the direction X and the opposite direction (left direction). The amplitude of the excited surface acoustic wave W is determined by the magnitude of the voltage applied to the comb electrode 21. The surface acoustic wave propagating in the left direction is reflected and returned by the reflective comb electrode 22 provided on the left side of the comb electrode 21. The reflective comb electrode 22 constitutes a so-called reflector that totally reflects the surface acoustic wave. The comb-shaped electrode 21 is combined with the reflective comb-shaped electrode 22 to form a so-called unidirectional electrode that generates a surface acoustic wave W that propagates only in the X direction. The configuration of the unidirectional electrode is not limited to that shown in this embodiment.

  The liquid 4 is supplied to the surface S of the substrate 2 by the liquid supply unit 3, atomized by the surface acoustic wave W that has propagated through the surface S, and fly as fine particles 41. When the liquid 4 held by the surface tension is consumed by atomization, it is automatically replenished via the liquid lead-out member 32 by the action of the surface tension. Atomization by the surface acoustic wave W is performed by the droplets leaving and flying from the surface of the liquid 4 by surface tension waves (capillary waves) propagating on the surface of the liquid 4. Therefore, if the film thickness of the liquid 4 is thick, the energy of the surface acoustic wave is attenuated before reaching the surface of the liquid 4 and cannot be atomized. Therefore, it is necessary to increase the amplitude of the surface acoustic wave as much as possible, concentrate and supply energy to the liquid 4, and make the liquid 4 as thin as possible. Concentration of high energy on the liquid 4 can be performed by an appropriate design of the opening width D, and the film thickness of the liquid 4 can be further adjusted by adjusting the above-described height g, and further by adjusting the roughness of the surface S and the liquid. It can be optimized by adjusting affinity and the like.

  The surface acoustic wave atomizer 1 is used as, for example, a medical atomizer that is driven by a low-power dry battery. In this case, the atomized liquid 4 is water or a chemical solution in which a chemical is dissolved in water. Moreover, when driving the surface acoustic wave atomizer 1 with comparatively high electric power, it is used as a humidity adjusting device for preventing drying, for example.

  Next, description will be made on setting the aperture width D to 5 to 10 times the wavelength λ. The optimization of the opening width D is performed together with the optimization of the position of the atomization region on the surface S of the substrate 2, that is, the region where the liquid 4 is present and atomization is performed. That is, when the comb-shaped electrode 21 is normally exposed to the liquid 4, the deterioration of the electrode proceeds. Therefore, the atomization region needs to be set apart from the comb-shaped electrode 21 to some extent. If the atomization region is too far from the comb-shaped electrode 21, the efficiency of atomization deteriorates due to the spread or attenuation of the surface acoustic wave. On the premise of setting the atomization region in this way, the opening width D is set as follows. The atomization region is set by the shape and arrangement of the gap space G formed by the supply member 30.

  As shown in FIGS. 2 (a) and 2 (b), a substrate 2 having a different opening width D by changing the meshing length of the comb teeth of the comb electrode 21 is prepared, and the direction X of the comb electrode 21 is measured by a laser Doppler vibrometer. The distribution of the amplitude A of the surface acoustic wave on the side was measured, and the measurement results shown in FIGS. 3 and 4 were obtained. The substrate 2 used for the measurement has the opening width D changed to five stages of D = 1λ, 2.5λ, 5λ, 10λ, and 20λ. The amplitude A graph shown in FIG. 3 shows measured values at three points of X = 0λ, 25λ, and 50λ on the central axis of the pair of comb-shaped electrodes 21 in arbitrary units. Here, the amplitude A at X = 0λ, that is, X = 0, is displayed for comparison. As described above, from the viewpoint of protecting the comb-shaped electrode 21, the vicinity region of X = 0 is determined. The atomization area is not used. 4A, 4B, 4C, and 4D show the surface distribution of the amplitude A for D = 2.5λ, 5λ, 10λ, and 20λ, respectively, for the measurement areas having the same width. . The size of the measurement area is 70λ in the direction X and 20λ in the direction Y. The frequency of the high-frequency voltage applied to the comb-shaped electrode 21 is in the MHz band, and similar measurement results are obtained from 20 MHz to 400 MHz.

  When attention is paid to the measured values at two points of X = 25λ and 50λ, the amplitude A shown in FIG. 3 shows a change in a mountain shape that increases and decreases as the aperture width D increases, and decreases as the position in the direction X increases. It shows a tendency to become. When an average curve of two curves at two points of X = 25λ and 50λ is obtained, a smoother mountain shape is seen. Such a change in the amplitude A is understood as a result of the surface acoustic waves generated at each point within the range of the opening width D in the comb electrode 21 interfering with each other when propagating in the direction X while spreading. The Further, FIG. 4 shows that the amplitude A increases due to wave interference, and that the amplitude A attenuates as the wave propagates and spreads. In FIG. 3, the amplitude A monotonously decreases in the region where the opening width D exceeds 10λ. In addition, as shown in FIG. 4D, when the opening width D is too wide, the surface acoustic wave propagates and transitions with a small amplitude value generated in a spread state. On the other hand, when the opening width D is 10λ or less, generally a large amplitude value is obtained. From these measurement results, it is concluded that the aperture width D is preferably not more than 10 times the wavelength λ, that is, D ≦ 10λ.

  When the opening width D is narrower than 5λ, a large amplitude value is obtained in the vicinity of X = 0, that is, in the vicinity of the outermost comb teeth, as shown in FIGS. Since it is large, it is concluded that it is more preferable to set the aperture width D to 5 times the wavelength λ or more. When the spread due to propagation is large in this way, it is conceivable to use a surface acoustic wave in a spread state. However, if the energy density of the source is increased to sufficiently increase the amplitude A in the atomization region, the comb-shaped electrode 21 is used. This is not preferable because the load on the battery becomes excessive. The above is summarized as follows. In order to efficiently perform the surface acoustic wave atomization, it is necessary to maintain the amplitude A large. By narrowing the opening width D, the amplitude A of the wave is increased, and the spread of the wave generated by narrowing the opening width D is defined as the opening width. This can be avoided by setting it to an appropriate lower limit value or more for D. That is, the amplitude A of the wave is increased by setting the opening width D to D ≦ 10λ, and the spread of the wave can be avoided by setting 5λ ≦ D. Thereby, the surface acoustic wave atomization apparatus 1 can be atomized efficiently and efficiently. Further, by forming the gap space G so that the length in the width direction orthogonal to the traveling direction of the surface acoustic wave W generated on the surface S of the substrate 2 is equal to or less than the opening width D, the surface acoustic wave The liquid 4 distributed with a width commensurate with the spread of W can be atomized, and the liquid 4 can be effectively used. The range of the aperture width D is preferably 5 to 10 times the wavelength λ, but it may be wider than this range by several wavelengths.

  The present invention is not limited to the above-described configuration, and various modifications can be made. For example, the length of the wave packet of the excited surface acoustic wave W corresponds to the length of voltage application time, so that the comb-shaped electrode 21 is intermittently excited to generate a pulsed surface acoustic wave W. Then, it can be atomized in a pulse shape. By the pulse operation, the power can be concentrated and a dense fog can be generated. Further, the supply of the liquid 4 is performed by dropping the liquid 4 on the surface S instead of using the supply member 30, or by immersing a part of the substrate 2 in the liquid and the surface at the interface between the liquid surface and the surface S. You may carry out by using the creeping phenomenon by tension.

  This application is based on the Japan patent application 2010-165379, The content should be united with this invention as a result by referring the specification and drawing of the said patent application.

DESCRIPTION OF SYMBOLS 1 Surface acoustic wave atomizer 2 Substrate 21 Comb electrode 22 Comb electrode (reflection electrode)
3 Liquid supply part 30 Supply member g Height D Opening width (engagement length)
G Gap space S Surface W Surface acoustic wave λ Wavelength

Claims (5)

In the surface acoustic wave atomizer,
A substrate made of piezoelectric material;
A pair of comb electrodes provided on the substrate to generate surface acoustic waves on the surface of the substrate;
A liquid supply unit for supplying a liquid to be atomized by the surface acoustic wave generated on the surface of the substrate onto the substrate;
The liquid supply unit includes a supply member that is disposed to face the surface of the substrate and distributes the liquid supplied onto the substrate in a film shape by the surface tension of the liquid,
The supply member is opposed to the surface of the substrate with a uniform height from the surface of the substrate, and has a surface that forms a gap space with the surface of the substrate,
The pair of comb electrodes have comb teeth meshed with each other, and the meshing length of the comb teeth is set to be 10 times or less the wavelength of the surface acoustic wave generated by the comb electrodes ;
In the supply member, the length of the surface forming the gap space in the direction orthogonal to the traveling direction of the surface acoustic wave generated on the surface of the substrate is equal to or less than the meshing length of the comb teeth. A surface acoustic wave atomization device characterized by comprising:   2. The surface acoustic wave atomization device according to claim 1, wherein the meshing length of the comb teeth is at least five times the wavelength of the surface acoustic wave generated by the comb electrode. The supply member, so as not to have the comb-shaped electrode in the liquid distributed in a film shape is normally to exposure, claim 1 or claim, characterized in that provided at a distance from the comb-shaped electrode 2. The surface acoustic wave atomization apparatus according to 2. The mutual interdigitated length of the comb teeth, the surface acoustic wave atomizer according to any one of claims 1 to 3 characterized in that it is a constant in the comb teeth of the pair of comb-shaped electrodes . The pair of comb-shaped electrodes, the surface acoustic wave atomizer according to any one of claims 1 to 4, characterized in that it comprises an electrode for reflection for constituting the unidirectional electrode .

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