JPH04207799A - Ultrasonic atomizer - Google Patents

Abstract

PURPOSE:To improve atomization efficiency, atomization rate, the microcharacteristic of particles, uniformity, and to reduce the cost of a driving power source by providing an auxiliary plate which faces a tongue-shaped diaphragm apart a slight spacing therefrom and a means for supplying liquid into the slight spacing and boring many holes on the diaphragm thereby forming the diaphragm. CONSTITUTION:The AC signals having the frequency equal to the resonance frequency of the composite of a piezoelectric vibrator 1 and the diaphragm 2 are impressed to the piezoelectric vibrator 1 at the time of driving the ultrasonic atomizer. The liquid supplied from a liquid storage chamber 7 through a liquid supply tube 5 into the slight spacing is introduced by capillarity to the respective holes 22 as the vibrating part 20 vibrates elastically. The passage areas of the liquid in the respective holes 22 decreases from the inlet side thereof toward the outlet side at the time when the liquid passes the respective holes 22 and the liquid receives a throttling effect by the holes 22 and flows out to the upper part of the vibrating part 20. Consequently, the liquid flowing out of the holes 22 is efficiently atomized by the throttling effect, the effect of an increase in the liquid supplying rate, and the effect of limiting the liquid volume by a flow volume regulating valve.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an ultrasonic atomizer that atomizes liquid by using elastic vibrations generated by an ultrasonic exciter.

(Prior Art) Examples of conventional ultrasonic atomization devices include ultrasonic atomization devices and nebulizers that apply a bolted Langevin type vibrator. The atomization device using a bolted Langevin type vibrator uses ultrasonic waves with two frequencies of several tens of kilohertz, and has the advantage of being able to generate a large amount of mist, but the structure is complex and the device is large-scale. It also has the disadvantage of

On the other hand, nebulizers use ultrasonic waves in the MHz range, and although they have the advantage of having small particles and excellent uniformity, they have poor atomization efficiency (and have the disadvantages of being difficult to generate a large amount of mist with low power). have.

(Problems to be Solved by the Invention) Conventional ultrasonic atomizers have problems in either atomization efficiency, large amount of atomization, fineness and uniformity of particles, or cost of driving power source.

The objects of the present invention are atomization efficiency, large amount atomization, fineness of particles,
It is an object of the present invention to provide an ultrasonic atomizer that is satisfactory in terms of uniformity and drive power cost.

(Means for Solving the Problems) The ultrasonic atomizer according to claim 1 atomizes liquid by using elastic vibrations generated by an ultrasonic exciter including a tongue-shaped diaphragm fixed to a piezoelectric vibrator. The ultrasonic atomization device for atomizing includes an auxiliary plate facing the diaphragm with a small gap therebetween, and a means for supplying the liquid into the small gap, and the diaphragm includes: The ultrasonic atomizer according to claim 2, characterized in that a large number of holes are provided, and the ultrasonic atomizer according to claim 3, characterized in that the auxiliary plate is formed at an angle with respect to the horizontal direction. The ultrasonic atomizer according to claim 4, wherein the auxiliary plate is made of polystyrene foam or other material that has a lower acoustic impedance than the piezoelectric vibrator. The ultrasonic atomizer according to claim 5, wherein the piezoelectric vibrator and the auxiliary plate are held in a fixed positional relationship with each other by a clip that presses the piezoelectric vibrator and the auxiliary plate into contact with each other. 7. The ultrasonic atomizer according to claim 6, wherein the means includes a liquid storage chamber and a tube for supplying liquid from the liquid storage chamber into the gap. The ultrasonic atomizer according to claim 7, characterized in that the ultrasonic atomizer comprises a piezoelectric ceramic and electrodes formed on both surfaces perpendicular to the polarization axis of the piezoelectric ceramic, a vibrating portion that is integrally fixed to at least one surface of the piezoelectric vibrator and protrudes outward from the piezoelectric vibrator substantially parallel to the surface of the piezoelectric vibrator;
The ultrasonic atomizer according to claim 8, wherein the hole is provided in the vibrating section, and the opening area of one side of the diaphragm in the hole is different from the opening area of the other side of the diaphragm. The ultrasonic atomization device according to claim 9, wherein one of the resonant frequencies of the piezoelectric vibrator is approximately equal to one of the resonant frequencies of the composite of the piezoelectric vibrator and the diaphragm. is characterized in that the piezoelectric vibrator is a rectangular plate with a dimension ratio of length to width approximately equal to 1.

(Function) When the ultrasonic atomizer according to claim 1 is used, an alternating current signal having a frequency approximately equal to the resonant frequency of the composite of the piezoelectric vibrator and the diaphragm is applied to the piezoelectric vibrator, The piezoelectric vibrator is excited. The excitation of the piezoelectric vibrator causes the diaphragm to vibrate, and the liquid supplied into the minute gap between the diaphragm and the auxiliary plate is atomized through holes provided in the diaphragm. Atomization through holes promotes fineness and uniformity of particles, and the use of an auxiliary plate improves atomization efficiency, making it possible to achieve a large amount of atomization with low power consumption.
At the same time, the device can be easily downsized.

In the ultrasonic atomization device according to the second aspect, since the auxiliary plate is angled from the horizontal direction, supply of the liquid can be promoted and atomization efficiency can be increased.

In the ultrasonic atomization device according to claim 3, the auxiliary plate is made of polystyrene foam or other material that has a lower acoustic impedance than the piezoelectric vibrator, so that the excitation of the piezoelectric vibrator is propagated to the auxiliary plate. is suppressed, and the diaphragm can be vibrated efficiently. Therefore, efficient atomization can be achieved.

In the ultrasonic atomizer according to the fourth aspect, the piezoelectric vibrator and the auxiliary plate are pressed together with a clip. When the piezoelectric vibrator and the auxiliary plate are pressed together with the clip, they are stably held in a constant relationship with each other, and as a result, the small gap between the diaphragm and the auxiliary plate is stably held. Further, in the structure in which the two are pressed together with a clip, the vibration energy of the piezoelectric vibrator is unlikely to leak to the auxiliary plate, and the excitation of the piezoelectric vibrator is efficiently propagated to the diaphragm, thereby achieving efficient atomization.

In the ultrasonic atomization device according to claim 5, the liquid supply means includes the liquid storage chamber and the liquid supply tube, so that the liquid can be efficiently supplied without waste. can increase efficiency.

In the ultrasonic atomizer according to claim 6, the piezoelectric vibrator includes the piezoelectric ceramic and electrodes formed on both sides of the piezoelectric ceramic perpendicular to the polarization axis.

When an alternating current voltage is applied to the piezoelectric vibrator through the electrode, the vibrator is excited.

By employing a piezoelectric vibrator having such a simple structure, the ultrasonic atomization device can be downsized, and moreover, this device can atomize liquid with high efficiency.

In the ultrasonic atomization device according to claim 7, the vibrating plate is integrally fixed on at least one surface of the piezoelectric vibrator, so that the vibrating part connects the fixed part to a fixed end. Since it bends and vibrates in the form of a cantilever beam, the liquid within the minute gap is atomized by the elastic vibration and is dispersed as mist upward perpendicular to the diaphragm. Also,
Since the opening area of one of the holes is larger than the other opening area, by making one opening the inlet side and the other opening the outlet side, the liquid passing area of the hole is directed from the inlet side to the outlet side. Therefore, when the liquid passes through the hole, the liquid is subjected to a throttling action by the hole. As a result, the atomization of the liquid is promoted by the synergistic effect of the squeezing action and the vibration of the vibrating section, increasing the amount of mist generated and making the diameter of the particles uniform.

In the ultrasonic atomizer according to claim 8, one of the resonant frequencies of the piezoelectric vibrator is approximately equal to one of the resonant frequencies of a composite of the piezoelectric vibrator and the diaphragm'. By applying a voltage at the common resonant frequency to the piezoelectric vibrator, the diaphragm is efficiently excited,
Atomization efficiency is promoted and the amount of fog generated is further increased.

In the ultrasonic atomization device according to claim 9, the piezoelectric vibrator is a rectangular plate having a dimension ratio of length and width approximately equal to 1, so that a composite body of the piezoelectric vibrator and the diaphragm is formed. The coupled vibrations of are enhanced and the atomization efficiency is promoted.

(Example) Next, the present invention will be explained in more detail with reference to Examples.

FIG. 1(a) is a sectional view showing an embodiment of the ultrasonic atomization device of the present invention. This embodiment includes a piezoelectric vibrator 1 to which terminals P and Q made of copper foil are attached, a diaphragm 2, an auxiliary plate 3, a clip 4, a liquid supply tube 5, a flow rate adjustment valve 6, and a storage. It consists of a liquid chamber 7. However, Fig. 1 (
A) also shows a power supply circuit for supplying alternating current voltage to the piezoelectric vibrator 1, and the liquid storage chamber 7 is filled with an appropriate amount of liquid when in use. Terminals P and Q are fixed to piezoelectric vibrator 1 with adhesive.

FIG. 1(b) is a cross-sectional view of FIG. 1(a) with the liquid supply tube 5, flow rate adjustment valve 6, and liquid storage chamber 7 removed. An ultrasonic exciter consisting of a piezoelectric vibrator 1 and a diaphragm 2 is pressed against an auxiliary plate 3 with a clip 4. This is to efficiently propagate the excitation of the piezoelectric vibrator 1 to the diaphragm 2. Further, the ultrasonic exciter is fixed so as to maintain an angle of 30 degrees with respect to the horizontal plane. This is to increase the rate of supply of liquid into the minute gap between the diaphragm 2 and the auxiliary plate 3, and to perform atomization efficiently.

FIG. 1(C) is a perspective view of the clip 4, and FIG. 1(d) is a side view of the clip 4. The clip 4 is made of stainless steel and presses the piezoelectric vibrator 1 and the auxiliary plate 3 into contact with each other by elasticity.

The amount of liquid supplied from the liquid storage chamber 7 through the liquid supply tube 5 into the minute gap is limited by the liquid amount adjustment valve 6, and the amount of liquid that provides the highest atomization efficiency is set in the minute gap. Supplied.

FIG. 2(a) is a plan view showing the ultrasonic exciter in the embodiment shown in FIG. 1, and FIG. 2(b) is a partially enlarged plan view of the vibrating section 20 in FIG. Figure 2(a)
The shape, arrangement, and dimensions of the holes 22 are shown when viewed from the same direction.

FIG. 3(a) is a side view of the ultrasonic exciter of FIG. 2(a),
FIG. 3(b) is a diagram showing a cross section of the vibrating part 20 that appears when cut along a plane perpendicular to the plate surface.
) shows the longitudinal cross-sectional shape and dimensions of the hole 22.

The piezoelectric vibrator 1 has a rectangular plate-shaped piezoelectric ceramic 30, and the material of the piezoelectric ceramic 30 is TDK72A material (product name), and its length is 40 mm, width is 20 mm, and thickness is 1 mm. T.D.
K72A material is used in this example because it has a large electromechanical coupling coefficient. The direction of the polarization axis of the piezoelectric ceramic 30 coincides with the thickness direction, and Au electrodes 31 and Au electrodes 32 are formed on both surfaces perpendicular to the thickness direction.

The Au electrode 31 covers one side of the piezoelectric ceramic 30, and the Au electrode 31 covers one side of the piezoelectric ceramic 30.
The electrode 32 covers the other surface of the piezoelectric ceramic 30. A terminal P is attached to the Au electrode 31, and the Au electrode 3
A terminal Q is attached to 2. The terminal P and the terminal Q are arranged at one edge of the piezoelectric ceramic 30 along the width direction.

A tongue-shaped diaphragm 2 is attached to one surface of the piezoelectric vibrator 1. The diaphragm 2 is made of nickel, and is integrally fixed to the piezoelectric vibrator 1 at an elongated plate-shaped fixing part 21, and the part of the diaphragm 2 that protrudes from the piezoelectric vibrator 1 forms the vibrating part 20. ing. The fixed part 21 is made of Au
It is bonded to the piezoelectric vibrator 1 via an electrode 31 with an adhesive 33.

The diaphragm 2 has a length of 25 mm, a width of 20 mm, and a thickness of 0.05 m.
It is m. The fixed portion 21 has a length of 20 mm.

It has a width of 5 mm and a thickness of 0.05 mm.

The vibrating portion 20 extends parallel to the plate surface of the piezoelectric vibrator 1 and protrudes outward from the edge along the width direction of the piezoelectric vibrator 1 . The vibrating section 20 has a length of 20 mm.

It has a width of 2' Om m and a thickness of 0.05 mm. The vibrating section 20 is provided with a plurality of fine holes 22 penetrating through its thickness, and the holes 22 have a forest-like shape, with a diameter of 0.1 mm on the entrance side and a diameter of 0.1 mm on the exit side. is 0.02
It is mm. Each person 22 is arranged at equal pitch. When driving the ultrasonic atomizer shown in FIG. 1, an AC signal having a frequency equal to the resonant frequency of the composite of the piezoelectric vibrator 1 and the diaphragm 2 is applied to the piezoelectric vibrator 1 via the terminals P and Q. do. At this time, the frequency of the AC signal almost matches one of the resonance frequencies of the piezoelectric vibrator 1. The piezoelectric vibrator 1 is excited, and the diaphragm 2 is vibrated in the form of a cantilever beam with its fixed portion 21 as a fixed end. The vibration generated in the vibrating part 20 is a bending vibration, and the elastic vibration of the vibrating part 20 effectively functions to atomize the liquid.

As the vibrating section 20 vibrates, the liquid supplied from the liquid storage chamber 7 through the liquid supply tube 5 into the minute gap is guided to each person 22 by capillary action.

When the liquid passes through each person 22, the area through which the liquid passes through each person 22 decreases from the inlet side to the outlet side. leaks to. As a result, due to the throttling action, the vibration of the vibrating part 20, the action of increasing the liquid supply speed due to the angle of the ultrasonic exciter with respect to the horizontal plane, and the action of limiting the amount of liquid into the minute gap by the liquid amount adjustment valve 6. , the liquid flowing out from the holes 22 is efficiently atomized.

FIG. 4 is a characteristic diagram showing the relationship between admittance and phase of the piezoelectric vibrator 1 with respect to frequency. One frequency that operates effectively as an atomizer corresponds to a resonance around 100.8 KHz.

FIG. 5 is a characteristic diagram showing the relationship between applied voltage and atomization amount. The generation of fog cannot be observed until the applied voltage is around 0 to 30 V pp, but when the applied voltage exceeds 30 V pp, fog blows up from the vibrating section 20 . Resonance frequency 100.8KHz
In this case, the applied voltage at which the amount of atomization is maximum is 76V.
If the voltage is higher than that, the amount of atomization will be saturated. As shown in this figure, the amount of atomization increases rapidly in response to the applied voltage up to around 60V p -p.

Figure 6 shows the highest point and flight distance of the trajectory of the blown up mist,
FIG. 3 is a characteristic diagram showing the relationship with applied voltage.

The fog shows changes similar to those shown in FIG. 5, and the fog suddenly increases in force from around 40 Vp- and reaches saturation around 60 Vp-P.

The length in FIG. 7 is 20 mm instead of the example in FIG. 2.

Piezoelectric vibrator with width 20mm and thickness 1mm and length 2Qmm
, and a diaphragm having a vibrating part with a width of 20 mm and a thickness of 0.05 mm. FIG. If this example is used, the amount of atomization becomes maximum at a frequency of 1:14.6 KHz when the applied voltage is 9.8 V, and the power consumption at that time is 294 mW and the current is 30 mA. In addition, the power consumption of the entire device including the power supply is 588 m
W1 current is 60mA.

(Effects of the Invention) As explained in detail above, according to the ultrasonic atomization device of the present invention, since the liquid is atomized while passing through the holes provided in the vibrating part, the fineness of the mist particles can be reduced. , can promote uniformity. Furthermore, by adopting a structure in which the auxiliary plate is separated from the diaphragm by a small gap, the supplied liquid can be atomized efficiently, and a large amount of atomization can be achieved with low power consumption. It is also possible to easily reduce the size of the device.

By adopting a structure in which the auxiliary plate forms an angle with respect to the horizontal direction, it is possible to accelerate the liquid supply rate and increase the atomization efficiency.

By using a material with lower acoustic impedance than the piezoelectric vibrator, such as styrofoam, as the auxiliary plate, it is possible to suppress the propagation of the excitation of the piezoelectric vibrator to the auxiliary plate, allowing the diaphragm to vibrate efficiently. I can do it. Therefore, atomization efficiency can be increased.

By adopting a structure in which the ultrasonic exciter and the auxiliary plate are held in a fixed positional relationship with each other by a clip that presses the piezoelectric vibrator and the auxiliary plate, the excitation of the piezoelectric vibrator is efficiently propagated to the diaphragm. Therefore, efficient atomization can be achieved.

Since the liquid supply means includes the liquid storage chamber and the liquid supply tube, the liquid can be efficiently supplied without waste, and therefore the atomization efficiency can be increased.

By employing a simple structure consisting of a piezoelectric ceramic and an electrode as a piezoelectric vibrator, the device can be made smaller, and moreover, this device can atomize liquid with high efficiency.

By adopting a structure in which the diaphragm is integrally fixed to at least one surface of the piezoelectric vibrator, the vibrating part bends and vibrates in the form of a cantilever beam with the fixed part as the fixed end, so strong elastic vibrations can be avoided. The liquid in the minute gap is atomized vertically upward. In addition, since the opening area of one of the holes is larger than the other opening area, by adopting a structure in which one opening is the inlet side and the other opening is the outlet side, the area through which the liquid passes is from the inlet side of the hole. Since it decreases toward the outlet side, when the liquid passes through the hole, the liquid is subjected to a throttling effect by the hole. As a result, the synergistic effect of the squeezing action and the vibration of the vibrating section promotes the atomization action of the liquid, increasing the amount of mist generated and making the diameter of the oak particles uniform.

As the applied voltage increases, the amount of atomization also increases, so by changing the voltage depending on the purpose, the amount of atomization can be freely changed.

Atomization efficiency is improved by adopting a structure in which one of the resonant frequencies of the ultrasonic exciter as a composite of a piezoelectric vibrator and a diaphragm is approximately equal to one of the resonant frequencies of the piezoelectric vibrator. is promoted, and the amount of fog generated further increases.

By adopting a rectangular plate-like structure in which the dimension ratio of length and width is approximately equal to 1 as the piezoelectric vibrator, the combined vibration of the piezoelectric vibrator-diaphragm complex is enhanced, further promoting atomization efficiency. be done.

[Brief explanation of the drawing]

FIG. 1(a) is a sectional view showing one embodiment of the ultrasonic atomization device of the present invention, and FIG. 1(b) is a sectional view showing the liquid supply tube 5, flow rate adjustment valve 6, and storage FIG. 1(C) is a cross-sectional view drawn with the liquid chamber 7 removed, and FIG. 1(C) is a perspective view of the clip 4.
Figure 2(d) is a side view of the clip 4, Figure 2(a) is a plan view showing the ultrasonic exciter in the embodiment of Figure 1, and Figure 2(b) is a side view of the clip 4.
) is a partially enlarged plan view of the vibrating part 20 in FIG.
FIG. 3(a) is a side view of the ultrasonic exciter of FIG. 2(a),
FIG. 3(b) is a cross-sectional view of the vibrating part 20 that appears when cut along a plane perpendicular to the plate surface, and FIG. 4 is a characteristic diagram showing the relationship between admittance and phase with respect to frequency of the piezoelectric vibrator 1.
Figure 5 is a characteristic diagram showing the relationship between applied voltage and atomization amount;
The figure is a characteristic diagram showing the relationship between the highest point and flight distance of the locus of the blown-up mist and the applied voltage. Figure 7 is a plan view showing an example of an ultrasonic exciter shown in place of the example in Figure 2. It is. DESCRIPTION OF SYMBOLS 1... Piezoelectric vibrator, 2... Vibration plate, 3... Auxiliary plate, 4... Clip, 5... Liquid supply tube, 6...
...Liquid volume adjustment valve, 7...Liquid storage chamber, 20...Vibrating part, 21...Fixed part, 22...Hole, 30...Piezoelectric ceramic, 31.32...Au electrode , 33...adhesive.

Claims (9)

[Claims] (1) In an ultrasonic atomization device that atomizes liquid by using elastic vibrations generated by an ultrasonic exciter including a tongue-shaped diaphragm fixed to a piezoelectric vibrator, An ultrasonic atomization device comprising: an auxiliary plate facing each other; and means for supplying the liquid into the minute gap; and the vibration plate is provided with a large number of holes. (2) The ultrasonic atomization device according to claim 1, wherein the auxiliary plate is formed at an angle with respect to the horizontal direction. (3) The ultrasonic atomization device according to claim 1 or 2, wherein the auxiliary plate is made of polystyrene foam or other material that has a lower acoustic impedance than the piezoelectric vibrator. (4) The ultrasonic exciter and the auxiliary plate are held in a constant positional relationship with each other by a clip that presses the piezoelectric vibrator and the auxiliary plate into contact with each other. The ultrasonic atomization device described in . (5) The ultrasonic atomization device according to any one of claims 1 to 4, wherein the liquid supply means includes a liquid storage chamber and a tube for supplying liquid from the liquid storage chamber into the gap. . (6) The ultrasonic atomization device according to any one of claims 1 to 5, wherein the piezoelectric vibrator comprises a piezoelectric ceramic and electrodes formed on both surfaces of the piezoelectric ceramic perpendicular to the polarization axis. . (7) The diaphragm is integrally fixed to at least one surface of the piezoelectric vibrator, and extends substantially parallel to the surface of the piezoelectric vibrator toward the outside of the piezoelectric vibrator. Claims 1 to 6 have a protruding vibrating part, the hole is provided in the vibrating part, and the opening area of one side of the diaphragm in the hole is different from the opening area of the other side of the diaphragm. The ultrasonic atomization device described. (8) One of the resonant frequencies of the piezoelectric vibrator is approximately equal to one of the resonant frequencies of a composite body of the piezoelectric vibrator and the diaphragm. The ultrasonic atomization device described in . (9) Claims 1 to 8, wherein the piezoelectric vibrator is a rectangular plate with a length-to-width dimension ratio approximately equal to 1.
The ultrasonic atomization device described above.