JPH04349961A - Ultrasonic atomizer - Google Patents

Abstract

PURPOSE:To carry out an efficient ultrasonic atomization of a small amount of liquid using a small electric power suitable for driving battery. CONSTITUTION:A method for ultrasonic atomization which is characterized by mounting a net-like thin plate 3 on a piezoelectric ceramics 1, supplying a liquid into a gap between the piezoelectric ceramics 1 and the net-like thin plate 3 using capillary phenomenon and atomizing the liquid by the ultrasonic vibration excited by resonance in the direction of the thickness of the piezoelectric ceramics 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic atomizer suitable for use as an inhaler or the like that requires low power and produces a small amount of atomization.

0002

2. Description of the Related Art Home-use atomizers for indoor humidification are conventionally known as ultrasonic atomizers that utilize ultrasonic vibrations caused by resonance in the thickness direction of piezoelectric ceramics. Such an atomizer for room humidification has a piezoelectric vibrator using a piezoelectric ceramic attached to the bottom of a container containing liquid, and the liquid is filled to a predetermined water level from the ultrasonic emission surface of the piezoelectric ceramic. in this case,
The amount of atomization is maximum when the water level from the ultrasonic emission surface is a sufficiently high constant liquid level. For example, when the frequency of 1.7 MHz is 1.7 MHz and the transducer diameter is about 20 mm, the maximum atomization point is reached at a water level of 30 to 40 mm. obtain. Furthermore, the driving conditions for the piezoelectric vibrator to maximize atomization were driving at a location higher than the resonance point fr in the thickness direction, that is, at a point where the piezoelectric vibrator becomes an inductive component. As a result, when a self-excited oscillation circuit is used, it is basically a Colpitts-type oscillation circuit using a piezoelectric vibrator as an inductive component, as shown in Japanese Patent Publication No. 56-40640, for example. In this way, an ultrasonic atomizer with a piezoelectric vibrator arranged at the bottom of a liquid storage container filled with liquid requires an input power of 30
With W, an atomization amount of about 500 to 600 cc/hour has been achieved.

However, recently, ultrasonic atomizers have been developed that can produce a small amount of atomization (approximately 1 cc/min) with a low power of 5 W or less, which is suitable for battery operation, while maintaining the particle size of the atomized particles. It is now required for applications such as inhalers for inhaling into the throat, trachea, lungs, etc.

[0004] Conventionally, as an inhaler, there is a
As shown in No. 950, a piezoelectric vibrator is attached to a modified conical horn, or a piezoelectric vibrator is attached to a λ/2 (λ: wavelength of ultrasonic wave) horn. , those that atomize the liquid at the tip of the horn have been put into practical use. An atomizer having this type of structure is shown in FIGS. 6 and 7 as a conventional example. In these figures, a piezoelectric vibrator 13 is attached to the large-diameter end face of an ultrasonic vibrator in which a resonance plate 12 is formed on the small-diameter end face side of a conical horn (coupler) 11. The liquid is atomized by ultrasonic vibration of the resonance plate 12.

FIG. 8 shows another conventional example, in which λ/2
A piezoelectric vibrator 16 is attached to the large diameter end face of the horn 15, and the liquid sucked up by the water absorption band 14 is atomized by ultrasonic vibration of the tip face of the horn 15.

[0006]

[Problems to be Solved by the Invention] In the conventional examples shown in FIGS. 6 to 8 above, (1) the atomization point (area that contributes to atomization) is limited to the area around the area where the water absorption band 14 is in contact; ■Since the amplitude of the ultrasonic vibration of the piezoelectric vibrator is amplified by the horns 11 and 15, which are metal blocks, there are problems with the machining accuracy of the horn and the adhesion between the piezoelectric vibrator and the metal horn. (The thermal expansion coefficients of metal horns and piezoelectric ceramics are quite different).

In view of the above points, the present invention has a wide atomization area that contributes to liquid atomization, can effectively utilize the ultrasonic vibration of a piezoelectric ceramic for atomization, and does not require a horn for amplitude expansion. The purpose is to provide an ultrasonic atomizer that does not.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the ultrasonic atomizer of the present invention includes a thin mesh plate placed on a piezoelectric ceramic, and a capillary tube formed in a gap between the piezoelectric ceramic and the thin mesh plate. The liquid is supplied using this phenomenon, and the liquid is atomized by ultrasonic vibration caused by resonance in the thickness direction of the piezoelectric ceramic.

[0009]

[Operation] In the ultrasonic atomizer of the present invention, the liquid to be atomized spreads on the piezoelectric ceramic by capillary action and enters each microscopic hole in the net-like thin plate to form a microscopic liquid column. The tip of the piezoelectric ceramic is atomized by ultrasonic vibration caused by resonance in the thickness direction, and is released into the air as atomized particles. Since such atomization is performed over almost the entire ultrasonic radiation surface of the piezoelectric ceramic, the ultrasonic vibrations of the piezoelectric ceramic can be effectively converted into atomization energy, resulting in good efficiency. Also,
There is no need to use a metal horn, it is suitable for reduction in size and weight, and there are no problems such as peeling of the piezoelectric ceramic from the horn.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the ultrasonic atomizer according to the present invention will be described below with reference to the drawings.

A first embodiment of the present invention will be explained with reference to FIGS. 1 and 2. In these figures, 1 is a disc-shaped piezoelectric ceramic, and an ultrasonic emission side electrode 2A is formed on this ultrasonic emission surface, and a counter electrode 2B is formed by plating or the like on the opposite surface facing the ultrasonic emission surface. and constitutes a piezoelectric vibrator TD. A large number of micro holes 6 are provided on the ultrasonic radiation surface side of the disc-shaped piezoelectric ceramic 1.
The net-like thin plates 3 having the same shape are placed one on top of the other, and are disposed together with the disc-shaped piezoelectric ceramic 1 in the insertion groove 5 of the elastic annular holder 4. What is important here is that as shown in Fig. 2, between the ultrasonic radiation surface of the piezoelectric ceramic 1 and the lower surface of the reticular thin plate 3, there is a microscopic gap between the ultrasonic wave emitting surface of the piezoelectric ceramic 1 and the lower surface of the reticular thin plate 3 so that the liquid W to be atomized, such as water or chemical solution, can spread through capillary action. This means that there is a gap G, and this minute gap G
is a mesh thin plate 3 with a slight play relative to the piezoelectric ceramic 1.
This can be achieved by holding it with the holder 4. The net-like thin plate 3 is made of stainless steel and has a wall thickness of several tens of micrometers, and the hole diameter D of the numerous microholes 6 formed therein is approximately 10 to 100 micrometers. Note that 7 is a water supply capillary tube through which an appropriate amount of liquid to be atomized is dropped onto the piezoelectric ceramic 1.

FIG. 3 shows a specific example of a drive circuit for driving the piezoelectric vibrator TD formed by forming the electrodes 2A and 2B on the piezoelectric ceramic 1 shown in the first embodiment. In this figure, Q is an oscillation transistor, T1 is a step-up transformer, T2 is a tuning transformer, and the primary winding N1 of the tuning transformer T2 is
is inserted in series with the piezoelectric vibrator TD, and a capacitor C1 is connected in parallel to the secondary winding N2 to form a tuned circuit (parallel resonant circuit) tuned to the resonant frequency in the thickness direction of the piezoelectric ceramic 1. There is. In addition, C2 is a DC blocking capacitor, R
is a base bias resistor, and E is a 6-12V DC power source (for example, a battery).

The drive circuit shown in FIG. 3 is a self-oscillation circuit, and in the configuration of the first embodiment, the atomization efficiency is higher when the piezoelectric vibrator TD is driven at a point closer to the resonance point fr in the thickness direction. In view of this, the circuit configuration is a current feedback type. When transistor Q is turned on in the circuit of FIG. (due to resonance) is fed back to transistor Q,
Transistor Q is turned on again. In this circuit, oscillation continues at a point where the vibrator current It is at its maximum, that is, close to the resonance point fr of the piezoelectric vibrator TD.

Now, a high frequency voltage (for example, 2.4 MHz) is applied between the electrodes 2A and 2B of the piezoelectric vibrator TD of the first embodiment of FIG. 1 using a drive circuit as shown in FIG. When ultrasonic vibration is caused by directional resonance and a liquid such as water or a chemical solution to be atomized is dripped onto the edge of the piezoelectric ceramic from the water supply capillary 7, the dropped liquid will form a piezoelectric ceramic due to capillary action as shown in Figure 2. The liquid enters the minute gap G between the ultrasonic wave emission surface of 1 and the lower surface of the net-like thin plate 3, spreads, and enters each of the minute holes 6 of the net-like thin plate 3 to form a minute liquid column. Then, the tip portions of a large number of micro liquid columns are atomized by ultrasonic vibration in the thickness direction of the piezoelectric ceramic 1 and released into the air as atomized particles.

In the case of this first embodiment, due to the presence of the thin mesh plate 3, a very thin and uniform liquid film is obtained between the ultrasonic emission surface of the piezoelectric ceramic 1 and the lower surface of the thin mesh plate, so that the area contributing to atomization is small. can efficiently convert the ultrasonic vibration of the piezoelectric ceramic 1 into atomization energy, and the input power 3 to the piezoelectric vibrator TD can be widely
．． An atomization amount of 2 cc/min was obtained at 5 W. moreover,
There is no need for a metal horn, making it suitable for smaller size and lighter weight.

FIG. 4 shows a second embodiment of the invention. In this case, instead of the water supply thin tube, a water absorption band 21 formed of a water absorption member in the form of a band is used to supply an appropriate amount of liquid such as water or chemical solution onto the edge portion of the net-like thin plate 3. The rest of the configuration is the same as the first embodiment described above.

FIG. 5 shows a third embodiment of the invention. In this case, the piezoelectric vibrator TD in which the electrodes 2A and 2B are formed on the piezoelectric ceramic 1 and the thin mesh plate 3 placed on top of this ultrasonic wave emitting surface are arranged so that the lower part thereof is immersed in a liquid W such as water or a chemical solution. Ru. However, in order to prevent liquid from entering the back side of the piezoelectric vibrator TD, it is desirable that the portion of the elastic annular holder 4 that is immersed in the liquid W has a waterproof structure. Note that the other structures are the same as those of the first embodiment described above.

In the third embodiment shown in FIG. 5, the liquid rises due to capillary action from a minute gap between the reticular thin plate 3 immersed in the liquid and the ultrasonic emission surface of the piezoelectric ceramic 1, and almost reaches the ultrasonic emission surface. It spreads over the entire area, and as in the first embodiment, efficient atomization can be achieved with a wide atomization area. Furthermore, there is also the advantage that there is no need to provide a separate water supply means.

Although FIG. 2 above shows a case where the microhole 6 in the net-like thin plate 3 is a tapered hole whose hole diameter widens toward the bottom, a straight hole whose diameter is the same from top to bottom is shown. A hole is also fine.

[0020]

[Effects of the Invention] As explained above, according to the present invention,
A highly efficient ultrasonic atomizer can be constructed that has a wide atomization area that contributes to liquid atomization and can effectively utilize the ultrasonic vibrations of the piezoelectric ceramic for atomization, and does not require a horn to increase the amplitude. It has the advantage of being small and lightweight, and is particularly effective when used in applications such as battery-powered inhalers.

[Brief explanation of drawings]

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

FIG. 2 is an enlarged sectional view of a main part for explaining the operation of the first embodiment.

FIG. 3 is a circuit diagram showing a specific example of a drive circuit for driving the piezoelectric vibrator used in the first embodiment.

FIG. 4 is a front sectional view showing a second embodiment of the present invention.

FIG. 5 is a front sectional view showing a third embodiment of the present invention.

FIG. 6 is a side view showing a conventional example of an ultrasonic atomizer.

FIG. 7 is a front view of the same.

FIG. 8 is a side view showing another conventional example.

[Explanation of symbols]

1 Disc-shaped piezoelectric ceramic 2A, 2B electrode 3. Reticulated thin plate 4 Elastic annular holder 5 Insertion groove 6 Microhole 7 Water supply tube 21 Water absorption band

Claims (1)

[Claims] 1. A thin mesh plate is placed on a piezoelectric ceramic, a liquid is supplied to a gap between the piezoelectric ceramic and the thin mesh plate using capillary phenomenon, and ultrasonic waves are generated by resonance in the thickness direction of the piezoelectric ceramic. An ultrasonic atomizer, characterized in that the liquid is atomized by vibration.