Surface acoustic wave atomizer

The present invention relates to an atomizer using surface acoustic waves.

Conventionally, when a liquid is supplied to the surface of a substrate such as a piezoelectric material in which surface acoustic waves are propagating, it is known that the liquid receives the energy of the surface acoustic waves and flows or vibrates to become fine particles and fly. Has been done. Various devices have been proposed for atomizing a liquid by utilizing this phenomenon. As a principle of atomization, for example, a surface acoustic wave (Rayleigh wave) propagating on the substrate surface becomes a surface tension wave (capillary wave) propagating inside the liquid and propagating on the surface, and as a result, the surface of the liquid. It is explained that fog is generated from.

Surface acoustic waves in such an atomizer are excited by applying high-frequency power to the crossed finger electrodes formed on the surface of the piezoelectric substrate. The cross-finger electrode is an electrical component, and it is necessary to protect the cross-finger electrode from defects such as short-circuiting or rusting and deterioration due to liquid. Further, in order to efficiently and stably atomize the liquid, it is necessary to stably induce (convey) and supply a fixed amount of the liquid to a predetermined atomization region. As one method of supplying such a liquid, it is conceivable to utilize the surface tension of the liquid and the capillary phenomenon.

For example, a spray head that does not use surface acoustic waves but supplies a liquid to the surface of a disc-shaped diaphragm that vibrates ultrasonic waves in a longitudinal vibration mode to atomize it is known (for example, Patent Documents). 1). The liquid in the spray head is supplied from the annular gap formed by arranging the bent portions of the cylindrical tube in close proximity to the peripheral portion of the diaphragm, and the liquid film thickness is maintained by the surface tension of the liquid.

Further, the piezoelectric substrate having a piezoelectric substrate having a surface acoustic wave-exciting cross finger electrode, a spacer disposed on the surface peripheral portion of the piezoelectric substrate, and a mist discharge port sandwiching the spacer. An atomizer is known in which a space for holding a liquid is formed by a liquid supply plate arranged to face the surface (see, for example, Patent Document 2). This atomizer supplies the liquid to the space by a capillary phenomenon in the liquid conduction path communicating with the space.

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2003-71343</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2008-104966</text></patcit></p>

<p> However, the spray head having a configuration as shown in Patent Document 1 described above does not include a cross-finger electrode or the like to be protected from contact with a liquid, and has problems such as protection of a cross-finger electrode in a surface acoustic wave atomizer. It does not suggest a solution. Further, in the atomizing device as shown in Patent Document 2 described above, a space for holding the liquid exists at the surface position where the crossed finger electrodes exist, and the entire surface of the crossed finger electrodes is an insulating protective film. Alternatively, it is always adjacent to the liquid via an insulating positivity membrane. That is, the protection of the crossed finger electrodes depends solely on the reliability of the insulating film, and cannot be said to be a preferable structure.</p><p> The present invention solves the above-mentioned problems, and can stably guide the liquid to the atomized region on the substrate surface by a fixed amount and limit the distribution of the liquid on the substrate surface by a simple configuration, and is stable. It is an object of the present invention to provide a surface acoustic wave atomizer capable of efficiently atomizing and suppressing deterioration of crossed finger electrodes and the like.</p>

<p> In order to achieve the above object, the present invention includes a piezoelectric substrate having a patterned electrode on the surface that excites a surface acoustic wave by applying a high frequency voltage, and a liquid supply means for supplying a liquid to the surface of the piezoelectric substrate. In an elastic surface acoustic wave atomizer that atomizes the liquid supplied to the surface of the piezoelectric substrate by the liquid supply means by surface acoustic waves generated on the surface, the liquid supply means is applied to the surface of the piezoelectric substrate. It has a liquid supply member arranged so as to face each other, and a minute gap is provided in a region between the liquid supply member and the surface of the piezoelectric substrate where the liquid is to be held and guided, and the liquid is not supplied. A gap larger than the minute gap is provided in the region, and the liquid is transferred to the atomized region in the region separated from the pattern electrode on the surface of the piezoelectric substrate by utilizing the difference in surface tension of the liquid depending on the size of the gap between the members. It is what we supply.</p><p> In one preferred embodiment, the microgap is formed by irregularities formed by roughening the surface of the liquid supply member facing the surface of the piezoelectric substrate.</p><p> In one preferred embodiment, the microgap is formed on the surface of the piezoelectric substrate in a region where surface acoustic waves are not excited.</p><p> In one preferred embodiment, the support plate is provided to support the piezoelectric substrate from the back surface, and the support plate is formed on the surface of the piezoelectric substrate in a region where the pattern electrode is formed and a region where a gap between the members is formed. It is provided so as to form a gap on the back surface of the region that separates the two from each other.</p><p> In one preferred embodiment, a contact jig having an electrode pin for applying a voltage to the pattern electrode and mounted on the piezoelectric substrate is provided, and the contact jig is attached to the surface of the piezoelectric substrate. A large gap is formed on the side closer to the pattern electrode and a gap smaller than this large gap is formed on the far side when viewed from the pattern electrode side, and the pattern electrode and the atomized region are separated from each other.</p>

<p> According to the present invention, the liquid is stably conveyed to the atomized region on the surface of the piezoelectric substrate by a substantially constant holding force due to the surface tension in the minute gap, and the distribution of the liquid on the surface of the piezoelectric substrate is restricted by the large gap. It is possible to realize stable and efficient atomization and suppression of deterioration of the crossed finger electrodes and the like.</p><p> When the minute gap is formed by the unevenness formed by roughening the surface of the liquid supply member facing the surface of the piezoelectric substrate, the formation of the minute gap may be formed by roughening the surface of the liquid supply member, and the large gap may be formed. Since it may be sufficiently large, the dimensional accuracy required for processing the liquid supply member is relaxed.</p><p> When the minute gap is formed on the surface of the piezoelectric substrate in a region where the surface acoustic wave is not excited, the liquid is atomized as calculated without receiving resistance from the surface acoustic wave trying to push the liquid back. It can be guided to the chemical region.</p><p> When the support plate is provided on the front surface of the piezoelectric substrate so as to form a gap on the back surface of a region where the pattern electrode is formed and the region where the gap between the members is formed are separated from each other. Since the gap on the back surface blocks the induction of the liquid due to the capillary phenomenon, even if the liquid leaks to the back surface of the piezoelectric substrate, the liquid does not travel along the back surface and reach the region where the pattern electrode is formed. Problems such as short circuit and deterioration of the pattern electrode can be prevented.</p><p> The contact jig is configured such that a large gap is formed on the side closer to the pattern electrode and a gap smaller than the large gap is formed on the far side of the surface of the piezoelectric substrate when viewed from the pattern electrode side. When the pattern electrode and the atomized region are separated from each other, the large and small gaps in front of the pattern electrode can prevent the liquid from approaching the pattern electrode, so that problems such as short circuit and deterioration of the pattern electrode can be prevented.</p>

<figref num="1">(a) is a perspective view of the surface acoustic wave atomizer according to the first embodiment of the present invention, and (b) is a sectional view of (a).</figref><figref num="2">The same as above. An exploded perspective view of the device partially broken.</figref><figref num="3">The perspective view which shows the modification of the said apparatus.</figref><figref num="4">The cross-sectional exploded view of the surface acoustic wave atomizing apparatus which concerns on 2nd Embodiment.</figref><figref num="5">A partially exploded perspective view of the surface acoustic wave atomizer according to the third embodiment.</figref><figref num="6">(a) is a plan view of the same device, and (b) is a sectional view taken along line BB of (a).</figref><figref num="7">Partially exploded perspective view of the surface acoustic wave atomizer according to the fourth embodiment.</figref><figref num="8">(a) is a cross-sectional view of the same device, and (b) is the same plane.</figref><figref num="9">The perspective view of the surface acoustic wave atomizing apparatus which concerns on 5th Embodiment.</figref><figref num="10">Same as above Cross-sectional view of the device.</figref>

(First Embodiment) Hereinafter, the surface acoustic wave atomizer according to the embodiment of the present invention will be described with reference to the drawings. FIGS. 1 (a) and 1 (b) and 2 show the surface acoustic wave atomizer according to the first embodiment. The surface acoustic wave atomizer 1 supplies a liquid M to a piezoelectric substrate 3 having a pattern electrode 2 on the surface S that excites a surface acoustic wave W by applying a high-frequency voltage, and an atomized region 30 on the surface S of the piezoelectric substrate 3. A contact jig 5 having a liquid supply member 4 for applying a voltage to the pattern electrode 2 and an electrode pin 51 for applying a voltage to the pattern electrode 2 and mounted on the piezoelectric substrate 3 from above the pattern electrode 2, and a piezoelectric substrate 3 A support plate 6 which is a basic member for supporting from below is provided, and the liquid M supplied to the surface S of the piezoelectric substrate 3 by the liquid supply member 4 is atomized by the surface acoustic wave W generated on the surface S. The liquid supply member 4 constitutes a liquid supply means together with a liquid container (not shown) or the like. The liquid supply member 4 supplies the liquid M to the atomization region 30 by forming a gap between the members that holds and guides the liquid M by the capillary phenomenon on the surface S of the piezoelectric substrate 3. Hereinafter, each configuration will be described in detail.

The pattern electrode 2 is an electrode (crossed finger electrode, IDT: inter-digital transducer) formed by meshing two comb-shaped electrodes on the surface S of the piezoelectric substrate 3. The comb teeth of the pattern electrodes 2 adjacent to each other belong to different electrodes and are arranged at a pitch of half the wavelength of the surface acoustic wave W to be excited. By applying a high frequency (for example, MHz band) voltage from the electric circuit E for applying a high frequency voltage to the two comb electrodes of the pattern electrode 2, the electric energy is converted into the mechanical energy of the wave by the comb electrode, and the piezoelectricity is obtained. An elastic surface wave W called a Rayleigh wave is excited on the surface S of the substrate 3. The amplitude of the excited surface acoustic wave W is determined by the magnitude of the voltage applied to the pattern electrode 2. The length of the wave packet of the excited surface acoustic wave W corresponds to the length of the voltage application time. The surface acoustic wave W excited by the pattern electrode 2 becomes a wave having a width corresponding to the width at which the teeth of the pair of comb electrodes intersect, and propagates in the direction x perpendicular to the teeth of the comb. Such a surface acoustic wave W has a property of exerting a force on the liquid existing on the surface S so as to move the surface acoustic wave W in the propagation direction. Further, since the comb-shaped electrode generates a surface acoustic wave propagating in both the positive and negative directions of the direction x, a reflector may be provided which totally reflects the surface acoustic wave in the negative direction and effectively utilizes it.

The piezoelectric substrate 3 is a substrate made of a piezoelectric material itself such as LiNbO3 (lithium niobate). Further, the piezoelectric substrate 3 may be a piezoelectric thin film, for example, a PZT thin film (lead, zirconate, titanium alloy thin film) formed on the surface of the non-piezoelectric substrate. Surface acoustic waves W are excited at the surface portion of the piezoelectric thin film on the surface. Therefore, the piezoelectric substrate 3 may be a substrate provided with a piezoelectric portion on the surface on which surface acoustic waves are excited.

The piezoelectric substrate 3 in this embodiment is formed in the shape of a rectangular plate. The pattern electrode 2 is formed on one end side (right side in the figure) of the piezoelectric substrate 3 in the longitudinal direction, and the liquid M is guided from the other end side toward the center along the direction y. An atomization region 30 in which the liquid M becomes fine particles and scatters is set near the central portion of the piezoelectric substrate 3. That is, the supply position of the liquid M and the atomization region 30 on the piezoelectric substrate 3 are set at positions separated from the position of the pattern electrode 2 that excites the surface acoustic wave W in the propagation direction (direction x) side of the surface acoustic wave W. Has been done. Further, the piezoelectric substrate 3 is placed in a recess formed in the support plate 6 so that the surfaces of the piezoelectric substrates 3 are flush with each other. The mounted piezoelectric substrate 3 is fixed to the support plate 6 by a contact jig 5 fixed to the support plate 6 using two screws (not shown). A recess 50 is formed on the surface of the contact jig 5 facing the piezoelectric substrate 3 so as not to hinder the excitation and propagation of the surface acoustic wave W.

The liquid supply member 4 is a substantially rectangular parallelepiped member, is arranged so as to face the surface S of the piezoelectric substrate 3 from above the piezoelectric substrate 3, and is fixed to the support plate 6 using two screws (not shown). ing. Two grooves 42 are formed on the lower surface 40 (the surface facing the piezoelectric substrate 3) of the liquid supply member 4 along the longitudinal direction (direction y) of the piezoelectric substrate 3, and the surface of the region sandwiched between the grooves 42. 41 is a surface recessed from the lower surface 40. By arranging such a liquid supply member 4 on the support plate 6, a minute gap 11 is formed by the surface 41 and the surface S of the piezoelectric substrate 3, and a large gap 12 is formed by the groove 42 and the surface S of the piezoelectric substrate 3. Is formed. The region A1 (FIG. 2) on the surface S of the piezoelectric substrate 3 where the minute gap 11 is formed is the region where the liquid M is held and guided, and the region A2 where the large gap 12 is formed does not induce the liquid M. The area. The minute gap 11 is, for example, a gap of about 0.1 to 0.3 μm. The large gap 12 is, for example, a gap of about 300 to 500 μm.

The supply of the liquid M to the region A1 is performed from the end P on the side opposite to the direction y side of the region A1. The liquid M can be supplied to the end portion P by dropping the liquid M, microgaps formed by a separate member, or a capillary phenomenon caused by a porous material or a fiber material.

In other words, the liquid supply member 4 described above is provided with a minute gap 11 in the region where the liquid M is to be held and guided, and a large gap 12 is provided in the region where the liquid M is not desired to be supplied, depending on the size of the gap between the members. The liquid M is supplied to the atomized region 30 in the region separated from the pattern electrode 2 on the surface S of the piezoelectric substrate 3 by utilizing the surface tension difference of the liquid M. The liquid M will come out at the end of the region A1 on the direction y side, and the region in front of the region y will be the atomization region 30. The liquid M keeps its shape around the front of the region A1 by surface tension to expose the liquid surface, but since it is consumed by atomization on the atomization region 30 side, the liquid M is supplied one after another. Become.

According to the surface acoustic wave atomizing device 1 of the present embodiment, the liquid is stably conveyed to the atomized region 30 of the piezoelectric substrate surface S by a substantially constant holding force due to the surface tension in the minute gap 11, and is large. The gap 12 can limit the distribution of the liquid M on the surface S of the piezoelectric substrate, and can realize stable and efficient atomization and suppression of deterioration of the crossed finger electrodes and the like. If a liquid M that is not atomized exists on the surface S of the piezoelectric substrate, such as a droplet, the energy of the surface acoustic wave W is generated by the droplet in the case of atomization by low power, regardless of the atomization by high power. Is absorbed and atomization stops or the operation becomes unstable. The surface acoustic wave atomizing device 1 of the present embodiment prevents the generation of droplets by the effect of the minute gap 11, and can stably atomize even at low power consumption. The retention and induction of liquid M by the microgap 11 is similar to the concept of waveguides by microstrip lines in high frequency electrical circuits. That is, by forming a line having a minute gap 11 (a line due to the region A1) on the surface S of the piezoelectric substrate 3 in a desired shape, the liquid M can be guided to a desired position without leaking from the line.

FIG. 3 shows a modified example of the surface acoustic wave atomizer 1 of the present embodiment. In this modification, the piezoelectric substrate 3 is fixed by placing the portion on the pattern electrode 2 side in the recess in the support plate 6, and the end on the side where the minute gap 11 is formed is a piece from the support plate 6. It is said to be in a state of being projected like a beam. Therefore, the region in which the minute gap 11 is formed (not shown, see region A1 in FIG. 8B described later) has a structure in which there is no joint line between members (gap between members). Here, the joining line between the members is, for example, a line formed by exposing the joining surface between the region A1 side end surface of the piezoelectric substrate 3 in FIG. 2 and the opening wall surface of the recess in the support plate 6. In the structure of FIG. 2, the region A1 passes through this joint line, and the liquid M enters the gap between the members in this joint line. In that respect, in the surface acoustic wave atomizing device 1 of this modified example, there is no bonding line in the region where the liquid M is induced, and the liquid is suppressed from wrapping around the back surface of the piezoelectric substrate 3.

Further, the prevention of the liquid M from wrapping around (entering) in such a gap between the members is also performed by, for example, the large gap 12 shown in FIGS. 1 (a) and 3. Here, the relationship with the ingress of liquid in a general gap between members will be described. Generally, there is a gap between the members, and when the liquid comes into contact with the gap, the liquid enters the gap remarkably. In order to prevent the liquid from entering by the structure, there are means of "zeroing the gap" or "reducing the surface tension generated in the liquid". However, it is difficult to make the gap zero from the viewpoint of dimensional accuracy and structure. Therefore, in the present embodiment, a large gap 12 is provided by a groove 42 between the region A1 for inducing the liquid M and the portion to be prevented from entering, a portion where the surface tension is reduced is arranged, and a joint line between the members is arranged. The liquid is prevented from entering the (gap between members). Further, in the modified example of FIG. 3, a slope is formed on the end surface of the liquid supply member 4 on the atomization region 30 side. This slope is provided so as not to hinder the flight and adhesion of the atomized liquid particles in the atomized region 30.

The surface acoustic wave atomizer 1 is used, for example, as a medical atomizer driven by a low-power dry cell. In this case, the liquid M to be atomized is water, a chemical solution in which a chemical is dissolved in water, or the like. When the surface acoustic wave atomizer 1 is driven by a relatively large amount of electric power, it is used as, for example, a humidity control device for preventing drying.

(Second embodiment) The surface acoustic wave atomizer according to the second embodiment will be described with reference to FIG. Elastic table of this embodiment The surface wave atomizer 1 is different from the first embodiment in the method of forming the minute gap 11, and is the same in other respects. That is, the surface 41 of the region sandwiched between the two groove portions 42 on the lower surface 40 of the liquid supply member 4 is formed with irregularities formed by roughening the lower surface 40 instead of forming a surface recessed from the lower surface 40. ing. The surface 41 on which the unevenness is formed due to such roughening comes into contact with the surface S of the piezoelectric substrate 3 to obtain the same effect as the above-mentioned minute gap 11.

Since the minute gap 11 in the first embodiment described above is as fine as about 0.1 to 0.3 μm, it may be affected by processing accuracy and mounting error. Further, it is known that when two members are fixed by screws, the liquid enters the gap between the members due to the presence of the surface roughness of the facing surfaces of the members. The liquid supply member 4 of the present embodiment is configured based on such a background.

According to the surface acoustic wave atomizing device 1 of the present embodiment, the formation of the minute gap 11 may be performed by roughening the surface of the liquid supply member 4, and the large gap may be sufficiently large. The dimensional accuracy required for is relaxed. That is, in guiding the liquid M, it is not necessary to perform highly accurate processing to form the minute gap 11, and the liquid M can be guided to the place to be guided by utilizing the surface roughness. In this case, grooves 42 for inducing the liquid M are formed on both sides of the line for inducing the liquid M. Further, the unevenness due to the roughening may be formed not only on the surface 41 but also on the entire surface of the lower surface 40, and the guide line can be set by the groove 42.

(Third embodiment) 5 and 6 show the surface acoustic wave atomizer according to the third embodiment. The surface acoustic wave atomizer 1 of the present embodiment is different from the first and second embodiments in the place where the minute gap 11 is formed on the piezoelectric substrate 3, and is the same in other respects. That is, the minute gap 11 is formed on the surface of the piezoelectric substrate 3 in a region where the surface acoustic wave W is not excited. The central region 31 along the longitudinal direction of the piezoelectric substrate 3 is a region where the surface acoustic wave W propagates, and the surface acoustic wave W does not exist in the regions on both sides of the region 31. A region A1 that holds and guides the liquid M is formed in a region on one side where the surface acoustic wave W does not exist. Further, a protrusion toward the center line of the piezoelectric substrate 3 is formed at the end of the liquid supply member 4 on the atomization region 30 side, and a minute gap 11 is continuously formed on the lower surface of the protrusion. There is. That is, the minute gap 11 is formed in the region where the surface acoustic wave W propagates only in the vicinity of the atomization region 30. Note that FIG. 6A shows the liquid container 7. The liquid M is supplied from the liquid container 7 to the region A1 by the member hanging from the end P side of the liquid supply member 4.

According to the surface acoustic wave atomizer 1 of the present embodiment, the liquid M can be guided to the atomization region 30 as calculated without receiving resistance from the surface acoustic wave W trying to push the liquid M back. As described above, the surface acoustic wave W exerts a force on the liquid existing on the surface so as to move it in the propagation direction of the surface acoustic wave W. However, according to the minute gap 11 of the present embodiment, it is efficient. The liquid M can be guided to the atomization region 30 and the atomization region 30 can be localized. On the contrary, a plurality of atomized regions 30 can be distributed by providing a plurality of protrusions of the liquid supply member 4 toward the center line of the piezoelectric substrate 3 in the longitudinal direction of the piezoelectric substrate 3. Further, in the present embodiment, the example in which the liquid supply member 4 is arranged on one side of the piezoelectric substrate 3 is shown, but the liquid supply member 4 may be arranged on both sides of the piezoelectric substrate 3.

(Fourth Embodiment) 7 and 8 show the surface acoustic wave atomizer according to the fourth embodiment. The surface acoustic wave atomizer 1 of the present embodiment is different from the first to third embodiments in the structure of the support plate 6, and is the same in other respects. That is, the support plate 6 of the present embodiment has a gap 60 on the back surface of the surface of the piezoelectric substrate 3 where the region where the pattern electrode 2 is formed and the regions A1 and A2 where the gap between the members is formed are separated from each other. Is provided to form. The gap 60 is formed by a groove 61 formed in the support plate 6.

According to the surface acoustic wave atomizing device 1 of the present embodiment, the gap 60 on the back surface of the piezoelectric substrate 3 blocks the induction of the liquid due to the capillary phenomenon, so that even if the liquid M leaks to the back surface of the piezoelectric substrate 3. The liquid M does not travel along the back surface to reach the region where the pattern electrode 2 is formed, and problems such as short circuit and deterioration of the pattern electrode 2 can be prevented.

(Fifth Embodiment) 9 and 10 show the surface acoustic wave atomizer according to the fifth embodiment. The surface acoustic wave atomizer 1 of the present embodiment is different from the first to fourth embodiments in the structure of the contact jig 5, and is the same in other respects. That is, in the contact jig 5 of the present embodiment, a large gap 53 is formed on the side closer to the pattern electrode 2 and a small gap 52 is formed on the far side when viewed from the pattern electrode 2 side with respect to the surface of the piezoelectric substrate 3. These gaps 52 and 53 separate the pattern electrode 2 from the atomized region 30.

According to the surface acoustic wave atomizer 1 of the present embodiment, the large and small gaps 52 and 53 on the atomization region 30 side of the pattern electrode 2 can prevent the liquid from approaching the pattern electrode 2, so that the pattern electrode 2 can be prevented from approaching. It is possible to prevent problems such as short circuit and deterioration.

Although each embodiment has been described above, the present invention is not limited to the above configuration and can be modified in various ways. For example, the configurations of the above-described embodiments can be combined with each other.

1 Surface acoustic wave atomizer 2 pattern electrodes 3 Piezoelectric substrate 4 Liquid supply member 5 Contact jig 6 Support plate 11 Micro gap 12 big gap 30 Atomized area 51 Electrode pin 60 gap S surface M liquid W surface acoustic wave