JP3111202B2 - Ultrasonic atomizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small and lightweight ultrasonic atomizer for atomizing a liquid by applying a high-frequency voltage to a composite comprising a piezoelectric vibrator and a diaphragm.

[0002]

2. Description of the Related Art An elastic vibration of ultrasonic waves is generated in a composite body including a piezoelectric vibrator in which electrodes are provided on a plate-shaped piezoelectric ceramic and a vibrating plate partially fixed to the piezoelectric vibrator.
An ultrasonic atomizer that makes a liquid come into contact with the diaphragm to atomize the liquid has been disclosed by the present inventors in Japanese Patent Application No. 2-339181.
It has been filed as 3-84730. The piezoelectric vibrator used in these ultrasonic atomizing devices has a prismatic or rectangular plate shape, and the vibrating plate is fixed to the piezoelectric vibrator as a beam.

[0003] By the way, despite the small size of the ultrasonic atomizing device formed by providing the liquid supply means on the composite body composed of the piezoelectric vibrator and the vibrating plate,
Driving the complex required a relatively complicated circuit configuration and a high DC voltage power supply. Furthermore, there was a problem in terms of efficiency regarding power consumption. In addition, there are also problems with the number of parts constituting the circuit, the weight of the parts, and the price of the parts. In other words, the smaller the composite is and the better its performance is, the more the circuit for driving the composite needs to be small and have high performance.

Further, the driving circuit of the ultrasonic atomizing device needs to generate a high-frequency high voltage and track the resonance frequency of the complex. This is because the resonance frequency of the composite varies according to the temperature of the composite. Therefore, a means for changing the frequency following the resonance frequency of the complex is required for the drive circuit. In other words, the driving circuit has a resonance frequency,
It must have the function of automatically tracking the resonance frequency of the complex while satisfying the specifications such as voltage and power.

There are two types of driving circuits capable of automatically tracking the output frequency to the resonance frequency of the composite with respect to the principle of automatic frequency tracking. The first method is an automatic tracking oscillation method. The automatic tracking oscillation method is a method of detecting the resonance frequency of the complex and automatically shifting the frequency of the oscillator to match the resonance frequency.
(Phase Locked Loop) method is often used. The second method is a self-excited oscillation method. The self-excited oscillation method adopts a circuit configuration in which oscillation and voltage / power amplification are integrated.
This is a method of oscillating using the resonance of the complex without having its own oscillation circuit inside, and FIGS. 12 to 14 show examples of conventional circuits.

[0006]

FIG. 12 shows a case where a piezoelectric vibrator is driven by a CR coupling amplifier circuit. The CR-coupled amplifier circuit has a problem that the DC voltage drop at the resistor R1 is large, and the utilization of the power supply is poor. Further, since the power supply voltage is directly used as the drive voltage of the piezoelectric vibrator, there is a disadvantage that a high DC voltage power supply is required.

FIG. 13 shows a case where a piezoelectric vibrator is driven by a DC-AC inverter circuit often used for a switching power supply circuit or a power supply for ultrasonic equipment. DC-
The AC inverter circuit has the advantage that it can be driven at a low voltage (the piezoelectric vibrator can be driven with a power supply voltage of 2 V), but the loss in the transformer is large compared to the power consumption of the piezoelectric vibrator, and there is a problem in efficiency. There is.

FIG. 14 shows a case where a piezoelectric vibrator is driven by a transformer coupled amplifier circuit. The transformer-coupled amplifier circuit has poor high-frequency characteristics, and has problems with the price and weight of the transformer T1.

The above-mentioned automatic tracking oscillation system using the PLL has a disadvantage that a complicated and expensive circuit is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a piezoelectric vibrator capable of receiving power from a power supply having a voltage lower than a required driving voltage and outputting high-frequency AC power having the required driving voltage, and having excellent power efficiency and a simple circuit configuration. Another object of the present invention is to provide a small, lightweight, and compact ultrasonic atomizer.

[0011]

An ultrasonic atomizing device according to the present invention comprises a piezoelectric vibrator having electrodes A and B provided on both ends of a piezoelectric ceramic in parallel with each other, and a piezoelectric vibrator comprising: a piezoelectric vibrator; An ultrasonic atomizing device that atomizes the liquid by bringing the liquid into contact with the diaphragm, wherein the resonance frequency of the piezoelectric vibrator is set between the electrodes A and B. A circuit for driving the piezoelectric vibrator by applying a voltage having substantially the same frequency, the driving circuit comprising: means for detecting a phase of a current flowing between the electrodes A and B; Power amplifying means for applying high-frequency power obtained by amplifying the output signal of the phase detecting means between the electrodes A and B, wherein the high-frequency signal output from the power amplifying means is provided by the current phase detecting means. Return to power amplification means Is, the final stage amplifying element of the power amplifier means comprises a transistor, wherein the coil for boosting the flow path for supplying power to the transistor has been inserted.

An ultrasonic atomizer according to a second aspect is characterized in that at least the electrode A among the electrodes A and B is divided into electrodes A1 and A2 which are insulated from each other.

According to a third aspect of the present invention, in the ultrasonic atomizing apparatus, the driving circuit outputs an AC pulse voltage as a voltage to be supplied to the piezoelectric vibrator, and adjusts a voltage value of the AC pulse voltage; Means for adjusting the pulse width and pulse repetition frequency of the AC pulse voltage.

According to a fourth aspect of the present invention, in the ultrasonic atomizing apparatus, the current phase detecting means includes a first diode connected in series to the piezoelectric vibrator and the first diode connected in parallel to the first diode. And a second diode connected to the opposite polarity to the diode.

According to a fifth aspect of the present invention, in the ultrasonic atomizing device, one of the resonance frequencies of the piezoelectric vibrator is set to one of the resonance frequencies of a composite body including the piezoelectric vibrator and the vibration plate. It is characterized by being substantially equal.

According to a sixth aspect of the present invention, in the ultrasonic atomizing apparatus, the piezoelectric vibrator is a rectangular plate whose dimensional ratio between length and width is close to 1 and not equal to 1.

According to a seventh aspect of the present invention, in the ultrasonic atomizing apparatus, the piezoelectric vibrator is a rectangular prism having a dimensional ratio of two sides of three sides close to and not equal to one. And

An ultrasonic atomizer according to claim 8 is characterized in that the diaphragm has a large number of holes.

An ultrasonic atomizer according to a ninth aspect of the present invention is characterized in that one opening area and the other opening area of the diaphragm in the hole are different from each other.

[0020] In the ultrasonic atomizing device according to the tenth aspect, the hole in at least one end surface of the diaphragm is provided in:
There are at least two types of opening areas.

12. The ultrasonic atomizer according to claim 11, wherein the means for bringing the liquid into contact with the vibration plate includes: a support for supporting a composite comprising the piezoelectric vibrator and the vibration plate; And a liquid retaining material made of a substance having a large liquid absorbing capacity having a large number of through holes and absorbing the liquid, wherein the support holds the complex at a predetermined position with respect to a fixed object. Alternatively, the composite is floated in the liquid by buoyancy, and at least a portion of the support that comes into contact with the composite is made of Styrofoam or another substance having a lower acoustic impedance than the piezoelectric vibrator. The plate is always or intermittently in contact with the liquid retaining material,
The liquid absorbed in the liquid retaining material is atomized.

An ultrasonic atomizer according to a twelfth aspect is characterized in that the liquid contact means includes a tube for supplying the liquid from the liquid storage chamber to the diaphragm.

The ultrasonic atomizer of the present invention employs a two-terminal self-excited oscillation system.

The two-terminal system is a system having two terminals for connection with a piezoelectric vibrator. Two electrodes A and B provided on both end faces of the piezoelectric vibrator
The system of the drive circuit to which each of the two terminals is connected is a two-terminal system.

In the present invention, by employing a self-excited oscillation type driving circuit (hereinafter abbreviated as a self-excited circuit), fluctuations in the resonance frequency of the composite (substantially equal to the resonance frequency of the piezoelectric vibrator) are suppressed. The piezoelectric vibrator is excited at the tracked frequency, and the excitation is propagated to the diaphragm.

FIG. 11 shows a current detector 11 and a voltage amplifier 12
FIG. 2 is a block diagram showing a two-terminal type self-excited circuit configured by a power amplifier 13 and a power amplifier 13; The current detector 11 is for detecting the phase of the current flowing through the piezoelectric vibrator,
It is connected in series to the piezoelectric vibrator. The voltage amplifier 12 amplifies the minute voltage signal detected by the current detector 11 and generates a signal for driving the power amplifier 13 in the next stage. One electrode (the above-described electrode A1 or A2) of the piezoelectric vibrator is used as a drive electrode D for applying a voltage, and the other electrode (the above-described electrode B) is a ground electrode G.
As ground.

When a voltage is applied from the power amplifying unit 13, the piezoelectric vibrator operates as a resonator. Current detector 11
Detects the resonance frequency component of the applied voltage.
The detected voltage is supplied to the voltage amplifier 12 and the power amplifier 13
And the same-phase voltage is applied to the piezoelectric vibrator. As a result, a positive feedback loop is formed and self-excited oscillation occurs.

In the configuration of the oscillation circuit, as is clear from the operation principle, self-excited oscillation is performed at a frequency at which the current and the voltage flowing through the piezoelectric vibrator have the same phase. There are many frequencies at which the phase difference between the current and the voltage becomes zero in the piezoelectric vibrator, including the first resonance frequency and the axially antisymmetric primary vibration mode, but the first resonance having the lowest frequency and the large electromechanical coupling coefficient. Self-excited oscillation at the frequency.

[0029]

FIG. 1 is a perspective view showing an embodiment of an ultrasonic atomizer according to the present invention. In this embodiment, a composite 1 formed by joining a vibration plate 3 to a prism-shaped piezoelectric vibrator 2 in a cantilever manner, a liquid retaining material 4 used as liquid retaining means,
And a circuit 5 for driving the composite 1. However, in FIG.
The drive circuit 5 is not shown. The upper end of the liquid retaining material 4 is in contact with the lower end surface of the diaphragm 3, and the liquid sucked up by the liquid retaining material 4 is supplied to the diaphragm 3 and atomized above the diaphragm 3.

FIG. 2 is an exploded perspective view of the composite 1, and FIG.
Is an enlarged plan view of the diaphragm 3 in the composite 1, and FIG. 4 is a cross-sectional view of the diaphragm 3 taken along the line AA. The prism-shaped piezoelectric ceramic 6 has a polarization axis in the thickness direction, and is a 5 × 10 × 6 mm ³ rectangular parallelepiped. As shown in the figure, electrodes are provided on both upper and lower end surfaces, and the upper electrode is divided into electrodes D and F having the same area. Diaphragm 3
Is composed of a beam 3A and a joint 3B. As shown in FIGS. 3 and 4, the beam 3A has high-density fine holes 7 and a thickness of 50 μm. The diameter of the hole 7 is about 7 μm on the upper surface side and 80 μm on the lower surface side, and has a truncated cone shape. The diaphragm 3 is 1
A plate of 2 × 5 mm ^2, the width of the joint portion 3B of the piezoelectric vibrator 2 and the diaphragm 3 is 1.5 mm, the adhesive 8 of the joint portion 3B is an epoxy resin Araldite.

When the ultrasonic atomizing apparatus shown in FIG. 1 is driven, the piezoelectric vibrator 2 is excited and the vibrating plate 2 is excited with the excitation of the piezoelectric vibrator 2.
Is vibrated in the form of a cantilever having the joint 3B as a fixed end. The elastic vibration of the beam 3A functions effectively for atomizing the liquid. The liquid sucked up by the liquid retaining material 4 is guided to each hole 7 by capillary action. When the liquid passes through each hole 7, the passage area of the liquid in each hole 7 decreases from the inlet side to the outlet side. And flows out to the upper part of the beam 3A. As a result, the liquid flowing out of the hole 7 is efficiently atomized by the restricting action and the elastic vibration of the beam 3A.

FIG. 5 shows a driving circuit 5 of the ultrasonic atomizing apparatus shown in FIG.
FIG. 3 is a diagram showing one embodiment of the present invention. In the present embodiment, the current detection unit 1
1, a voltage amplifier 12 and a power amplifier 13. In the two-terminal self-excited circuit, the electrodes of the piezoelectric vibrator
In the self-exciting circuit of the two-terminal type shown in this embodiment, one electrode of the piezoelectric vibrator 2 is connected to the drive electrode D.
And a feedback electrode F, and the feedback electrode F and the ground electrode G are short-circuited. The other electrode G of the piezoelectric vibrator 2 is grounded.

The power amplifier 13 is a back electromotive voltage circuit composed of Q1, L1, C3 and R3. The transistor Q1 is for switching, and a power MOS FET is used in consideration of switching speed and simple driving. L1 is for generating a back electromotive voltage and supplying power of a voltage higher than the power supply voltage Vcc to the piezoelectric vibrator 2, and C3 is for adjusting the time constant of the back electromotive voltage. C3
As the time constant increases, the time constant increases, but the maximum voltage decreases. When C3 is reduced, the opposite is true.

The current detecting section 11 has a detection rectifying diode D
1 and D2, and aims to detect the phase of the current flowing through the piezoelectric vibrator 2. As shown in the circuit diagram, the current detecting unit 11 is connected in series with the piezoelectric vibrator 2, and the voltage divided into the piezoelectric vibrator 2 decreases as the impedance of the current detecting unit 11 increases. Therefore, the condition of the current detection unit 11 is preferably that the impedance is low. However, if the impedance is too low, the detected voltage is also small, and the self-excitation rise time is delayed.

In the driving circuit 5 of the ultrasonic atomizing apparatus according to the present invention, a diode is used for the current detecting section 11. As is apparent from the current-voltage characteristics, the diode operates as a high resistance when the voltage at the rise of the self-excited oscillation is low, and operates as a low resistance when the self-excitation is stable and the voltage is high. This is convenient as an element.

The voltage amplifying unit 12 comprises IC1, C1, C2, R1
And R2. The purpose is to amplify the minute voltage signal detected by the current detection unit 11 and drive the power amplification unit 13 at the next stage. In order to obtain high-frequency power sufficient for driving the piezoelectric vibrator 2, if the power amplifying means is composed of a transistor or the like, a voltage amplifying unit composed of a plurality of voltage amplifiers must be used in order to obtain a large gain at high speed. No. In this embodiment, an inverter IC1 composed of a CMOS logic IC is used for the voltage amplifier 12. The voltage amplifying unit 12 utilizes the fact that when feedback is applied to the inverter IC1 of the CMOS IC by the resistor R1, the voltage amplifying unit 12 stops near the threshold and operates as an analog amplifier. Although the circuit of the voltage amplifying unit 12 has a feature that the gain is high and the gain is large, the voltage of the power supply is limited. Therefore, in this circuit, a predetermined voltage is obtained in the inverter IC1 by using the Zener diode ZD1. .
C1 and C2 are DC cut capacitors.

In the embodiment shown in FIG. 5, a driving voltage of 50 Vp-p was obtained when the power supply voltage was 12 V. Thus, the piezoelectric vibrator 2 can be driven with a peak voltage four times the power supply voltage. The minimum voltage that can drive the piezoelectric vibrator 2 is 20 V
Since it is pp, the piezoelectric vibrator 2 can be driven if the power supply voltage is 5 V or more. The ability to drive the piezoelectric vibrator with a low power supply voltage is extremely effective in widening the application of the ultrasonic atomizer.

In the drive circuit 5 of the ultrasonic atomizing apparatus according to the present invention, a switching transistor Q1 and a coil L1 are used as boosting means for enabling the above-mentioned low voltage driving. There is also a transformer as shown in FIGS. 13 and 14 as the boosting means. However, comparing the combination of a transistor and a coil with a transformer to boost the voltage to the same extent, the transistor and the coil are smaller, lighter, and less expensive than the transformer. Since the piezoelectric vibrator in the ultrasonic atomizer of the present invention is extremely small, it is practically essential that the drive circuit 5 is also small. In this regard, the drive circuit of the ultrasonic atomizing apparatus according to the present invention uses the transformer as the boosting means.
Is much more practical than conventional circuits.

Further, in the driving circuit 5 of the ultrasonic atomizing apparatus according to the present invention, the load circuit of the power amplifying unit 13 includes the coil L1 and the capacitor C3 and does not include a resistor. The power use efficiency of the power supply, that is, the power efficiency is excellent.

FIG. 6 shows the result of measuring the change in the resonance frequency in the operating state of the piezoelectric vibrator 2. It can be seen that the resonance frequency changes with time. However, in the ultrasonic atomizing apparatus of the present invention, the piezoelectric vibrator can be excited at a frequency that follows the fluctuation of the resonance frequency of the composite (substantially equal to the resonance frequency of the piezoelectric vibrator), so that the stable atomization is always achieved. Can be realized.

FIG. 7 shows the relationship between the beam length and the amount of atomization. The reason why the length of the beam 3A is limited to the range of 5.0 to 6.5 mm is that particularly good atomizing operation is obtained in the beam length in this range. FIG. 8 shows the relationship between beam length and power consumption in this range, and FIG. 9 shows the amount of atomization per unit power consumption, that is, the atomization efficiency. From the above results, the maximum atomization amount was obtained when the beam length was 5.5 mm. In the frequency characteristics of the admittance phase, the maximum amount of atomization was obtained when the characteristics of the piezoelectric vibrator alone and the characteristics of the composite vibrator matched well.

FIG. 10 shows the results of measuring the frequency dependence of the insertion loss and the phase difference due to the composite 1 (beam length 5.5 mm).
Is shown. The solid line indicates the phase difference, and the broken line indicates the input loss.
HP 4195A NETWORK / SPECTRUM ANALYZER was used for the measurement. Since the phase inversion occurs at the atomization frequency and the insertion loss is the smallest, it is clear that the frequency stability in the drive circuit 5 is sufficiently high.

As described above, in the ultrasonic atomizing apparatus of the present invention, the maximum atomizing efficiency can be obtained with the beam length of 5.5 mm.
The amount of atomization was 72 cc / h · W. In the frequency characteristics of admittance, good matching between the characteristics of the piezoelectric vibrator and the composite vibrator is the optimal condition for the maximum atomization by self-excited drive. Could be explained based on the good correspondence.

From the consideration of the operation principle and operation characteristics of the circuit, the drive circuit used in this embodiment has a small number of parts and
It is a low power consumption type using a DC power supply, and can be said to have features such as downsizing is possible and operation stability due to the atomization frequency being in a stable region.

[0045]

As described above in detail with reference to the embodiments, according to the present invention, DC power is supplied from a power supply having a voltage lower than the required driving voltage of the piezoelectric vibrator, and high-frequency AC power of the required driving voltage is received. Output and power efficiency,
It is possible to provide an inexpensive, compact and lightweight ultrasonic atomizer having a simple circuit configuration. Moreover, the drive circuit is a drive circuit that can cope with environmental changes such as an external temperature.

A means for outputting an AC pulse voltage as an excitation voltage to be supplied to the piezoelectric vibrator and adjusting the voltage value of the AC pulse voltage, and a means for adjusting the pulse width and pulse repetition frequency of the AC pulse voltage Is provided in the drive circuit, so that the atomization operation can be very accurately controlled stepwise, and stable atomization can be realized.

The drive circuit of the ultrasonic atomizing apparatus according to the present invention is not only compact and lightweight and can be driven with low power consumption, but also can realize a further reduction in size and weight of the apparatus. Therefore,
Because it is convenient to carry, it has a wide range of use.

According to the drive circuit of the ultrasonic atomizing apparatus of the present invention, a rectangular prism-shaped piezoelectric vibrator can be driven. In addition, a rectangular plate-shaped piezoelectric vibrator or a through-hole at the center is provided. It is clear that the columnar piezoelectric vibrator can also be driven.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of an ultrasonic atomizer according to the present invention.

FIG. 2 is an exploded perspective view of the composite 1.

FIG. 3 is an enlarged plan view of a diaphragm 3 in the composite 1.

FIG. 4 is a cross-sectional view of the diaphragm 3 taken along the line AA.

FIG. 5 is a diagram showing one embodiment of a drive circuit 5 of the ultrasonic atomizing device of FIG.

FIG. 6 is a diagram showing a change over time of a resonance frequency in the piezoelectric vibrator 2.

FIG. 7 is a diagram showing the relationship between the beam length and the amount of atomization in the embodiment of FIG.

FIG. 8 is a diagram showing a relationship between beam length and power consumption in the embodiment of FIG. 1;

FIG. 9 is a diagram showing a relationship between beam length and atomization efficiency in the embodiment of FIG. 1;

FIG. 10 is a diagram illustrating frequency characteristics of an insertion loss and a phase difference caused by the composite vibrator.

FIG. 11 is a diagram illustrating a basic configuration of a drive circuit that performs self-excited oscillation in a two-terminal system.

FIG. 12 is a diagram showing an example of a conventional self-excited drive circuit.

FIG. 13 is a diagram showing an example of a conventional self-excited drive circuit.

FIG. 14 is a diagram showing an example of a conventional self-excited drive circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 composite 2 piezoelectric vibrator 3 diaphragm 3A joint 3B beam 4 liquid retaining material 5 drive circuit 6 piezoelectric ceramic 7 hole 8 adhesive 11 current detector 12 voltage amplifier 13 power amplifier D, F, G electrode IC1 CMOS IC Inverter Vcc Power supply voltage L1 Boost coil Q1 Transistor ZD1 Zener diode D1, D2 Diode C1, C2, C3 Capacitor R1, R2, Q3, Q4 Resistance

Claims (12)

(57) [Claims] 1. A piezoelectric vibrator comprising electrodes A and B provided on both ends of a piezoelectric ceramic in parallel with each other, and a vibrating plate partially fixed to the piezoelectric vibrator,
In an ultrasonic atomization device that atomizes the liquid by bringing the liquid into contact with the vibration plate, by applying a voltage having a frequency substantially equal to the resonance frequency of the piezoelectric vibrator between the electrodes A and B, A circuit for driving the piezoelectric vibrator, wherein the drive circuit detects a phase of a current flowing between the electrodes A and B, and amplifies an output signal of the current phase detection means. Power amplifying means for applying the obtained high-frequency power between the electrodes A and B, wherein a high-frequency signal output from the power amplifying means is positively fed back to the power amplifying means by the current phase detecting means, An ultrasonic atomizing device, wherein a final-stage amplifying element of the amplifying means is a transistor, and a step-up coil is inserted in a flow path for supplying power to the transistor. 2. The ultrasonic atomizer according to claim 1, wherein at least the electrode A among the electrodes A and B is divided into electrodes A1 and A2 which are insulated from each other. 3. The drive circuit outputs an AC pulse voltage as a voltage to be supplied to the piezoelectric vibrator, and adjusts a voltage value of the AC pulse voltage; and a pulse width and a pulse repetition frequency of the AC pulse voltage. The ultrasonic atomizing device according to claim 1 or 2, further comprising: means for adjusting the pressure. 4. The current phase detecting means includes a first diode connected in series to the piezoelectric vibrator, and a first diode connected in parallel to the first diode and having a polarity opposite to that of the first diode. 4. The ultrasonic atomizing device according to claim 1, comprising two diodes. 5. One of the resonance frequencies of the piezoelectric vibrator.
The ultrasonic atomizer according to claim 1, 2, 3, or 4, wherein one of the two is substantially equal to one of resonance frequencies of a composite body including the piezoelectric vibrator and the diaphragm. 6. The ultrasonic atomizer according to claim 5, wherein the piezoelectric vibrator is a rectangular plate having a length-to-width dimension ratio close to 1 and not equal to 1. 7. The ultrasonic fog according to claim 5, wherein the piezoelectric vibrator is a rectangular prism having a dimensional ratio of two sides of three sides close to and not equal to one. Device. 8. The ultrasonic atomizer according to claim 1, wherein the diaphragm has a large number of holes. 9. The ultrasonic atomizer according to claim 8, wherein one opening area of the diaphragm and the other opening area of the diaphragm in the hole are different from each other. 10. The ultrasonic atomizing apparatus according to claim 9, wherein the holes in at least one end face of the diaphragm have at least two types with respect to an opening area. 11. A means for bringing the liquid into contact with the vibration plate includes a support for supporting a complex comprising the piezoelectric vibrator and the vibration plate, a liquid storage chamber for storing the liquid, and a plurality of through-holes. A liquid retaining material made of a substance having a large liquid absorbing ability having holes and absorbing the liquid, wherein the support holds the composite at a predetermined position with respect to a fixed object, or holds the composite by buoyancy. Floating in a liquid, at least a portion of the support that comes into contact with the composite is made of styrene foam or another substance having a lower acoustic impedance than the piezoelectric vibrator, and the diaphragm is always or intermittently the liquid retaining material. The ultrasonic atomizing device according to claim 1, wherein the ultrasonic atomizing device is configured to atomize the liquid absorbed by the liquid retaining material in contact with the liquid retaining material. 12. The ultrasonic atomizer according to claim 11, wherein the liquid contacting means includes a tube for supplying the liquid from the liquid storage chamber to the diaphragm.