JPH05277413A - Ultrasonic atomizing device - Google Patents

Abstract

PURPOSE:To atomize a liquid by small power and to variably control the particle size of atomized particles by providing an exciting circuit for intermittently exciting a piezoelectric vibrator in duty of 70% or less to atomize a liquid by the intermittent ultrasonic vibration of the piezoelectric vibrator and providing a control circuit making the intermittent frequency of the exciting circuit variable. CONSTITUTION:An ultrasonic atomizing device is constituted by arranging a perforated or reticulated thin plate on the atomizing action surface of a piezoelectric vibrator TD so as to form a fine gap between at least a part of the thin plate and the atomizing action surface. An intermittent oscillation circuit 1 is provided as an exciting circuit intermittently exciting the piezoelectric vibrator TD in duty of 70% or less and the liquid spreading throughout the fine gap between the atomizing action surface and the thin plate is atomized by the intermittent ultrasonic vibration of the piezoelectric vibrator and the intermittent frequency of the intermittent oscillation circuit 1 is made variable by a control circuit 3.

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 with a small amount of electric power and a small amount of atomization.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 5, a reticulated thin plate 31 is placed on the front end surface of a vibrating body (horn) 30 to form a vibrating body 30.
The liquid spread in the gap between the mesh plate 31 and the net-like thin plate 31 is atomized by ultrasonic vibration of the vibrating body 30, which is proposed by the applicant.
No. 15674. In this case, the vibration frequency of the vibrating body 30 is 20 to 200 kHz (because it has a structure similar to that of the Langevin type vibrator), and the theoretical generated particle diameter without the mesh thin plate 31 is about 20 to 40 μm. The net diameter of the holes 32 formed in the net-like thin plate 31 is set to 5 to 30 μm which is smaller than the theoretically generated particle size.
1 was used to reduce the size of the generated particles. The theoretical particle size d is expressed by the following equation (1). d = 0.34 × (8πT / ρF ² ) ^1/3 (1) (where T: surface tension of liquid, ρ: density of liquid, F: drive frequency)

[0003]

By the way, when the ultrasonic atomizer is used as a medical inhaler, the mist diameter that can be reached differs depending on the body part. Since the vibration frequency of the vibrating body or the hole diameter of the mesh thin plate is fixedly determined, it is necessary to change or replace the device when the required fog diameter is different.

In view of the above points, the present invention provides an ultrasonic atomizing device suitable for use as an inhaler, which is capable of atomizing a liquid with a small amount of electric power and variably controlling the particle size of atomized particles. The purpose is to provide.

[0005]

In order to achieve the above-mentioned object, an ultrasonic atomizing device of the present invention comprises a porous or reticulated thin plate,
An excitation for arranging the piezoelectric vibrator on the side of the atomizing surface so that a minute gap is formed at least between a part of the thin plate and the surface for atomizing, and exciting the piezoelectric vibrator intermittently at a duty of 70% or less. A circuit is provided to atomize the liquid spread in the minute gap between the atomizing surface and the thin plate by intermittent ultrasonic vibration of the piezoelectric vibrator, and to make the intermittent frequency of the excitation circuit variable. The circuit is provided.

[0006]

In the ultrasonic atomizing device of the present invention, since the piezoelectric vibrator is intermittently excited by the exciting circuit at a duty of 70% or less, the atomizing surface of the piezoelectric vibrator and a thin plate having a large number of small diameter holes opened. The piezoelectric vibrator can be driven with a high-frequency voltage having an amplitude necessary and sufficient for atomizing a liquid such as water spread in a minute gap between them. Further, since the driving is intermittent, it is possible to reduce the input power to the piezoelectric vibrator per unit time and avoid deterioration due to heat generation of the piezoelectric vibrator. Furthermore, the particle size of atomized particles can be changed by changing the intermittent frequency (for example, in the range of several Hz to several tens kHz) of the excitation circuit by the control circuit.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of an ultrasonic atomizing device according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit configuration of an embodiment of the present invention,
FIG. 2 shows the structure of the piezoelectric vibrator used in this embodiment.
In these figures, 1 is an intermittent oscillation circuit as an excitation circuit for intermittently exciting the piezoelectric vibrator TD, and 2 is DC-DC.
The DC-DC converter 2 is a converter, and the voltage of the DC power supply E, which is a battery power supply of about 3V to 6V, is several tens of
The voltage is boosted to about 30 V, for example, and is supplied to the intermittent oscillation circuit 1 via the positive side line P and the negative side line N. Reference numeral 3 is a control circuit for varying the intermittent frequency of the intermittent oscillation circuit.

The intermittent oscillating circuit 1 is a collector grounded transistor oscillating circuit, and includes an oscillating transistor Q1.
And a resistor R1 for flowing a base bias current of the transistor, a variable resistor VR, and a switching transistor Q.
2 and inductors L1 and L2 connecting the negative line N of the DC-DC converter 2 and the emitter of the transistor Q1.
A capacitor C1 connected between the positive and negative lines P and N, a connection point between the inductors L1 and L2 and the collector of the transistor Q1, a connection point between the inductors L1 and L2 and a transistor The piezoelectric vibrator TD is connected between the collector and the base of the transistor Q1 via the capacitor C4.

The control circuit 3 changes the frequency of the gate pulse generation circuit 4 for applying a square wave gate pulse GP to the switching transistor Q2, the duty variable circuit 5 for changing the duty of the gate pulse GP, and the gate pulse GP. The frequency variable circuit 6 is provided. The control circuit 3 can generate a gate pulse GP having a frequency of several Hz to several tens of Hz by changing the setting of the frequency variable circuit 6, and several% to 70% by changing the setting of the duty variable circuit 5. The duty of the gate pulse GP can be changed within the range.

The intermittent oscillation circuit 1 receives the gate pulse GP from the control circuit 3 and switches the switching transistor Q.
2 is conducting, the switching transistor Q
2, the base bias current flows to the oscillation transistor Q1 through the path of the variable resistor VR and the resistor R1, and the piezoelectric vibrator TD
The piezoelectric vibrator near the resonance point can self-oscillate at a frequency at which the piezoelectric vibrator becomes inductive (for example, 1.6 MHz or 2.4 MHz).

FIG. 3 shows an example of the intermittent oscillation waveform of the intermittent oscillation circuit 1. In this figure, when the ratio of the oscillation period Don to the intermittent cycle D is duty (Don / D), the intermittent frequency (1 / D) is f, and the oscillation amplitude is A,
The input power P to the piezoelectric vibrator TD is theoretically directly proportional to f · (Don / D) · A. Therefore, intermittent frequency f, duty
By appropriately setting (Don / D) and the input power P, the input power P can be reduced and the amplitude A required for atomization can be secured. The frequency of the gate pulse GP of the control circuit 3 becomes the intermittent frequency (1 / D) of the intermittent oscillation waveform of the intermittent oscillation circuit 1, and the duty of the gate pulse and Don / D match.

As shown in FIG. 2, the piezoelectric vibrator TD utilizes ultrasonic vibration due to resonance in the thickness direction of the piezoelectric ceramic. The piezoelectric vibrator TD has a main surface 11 and an opposite surface 12 of the disk-shaped piezoelectric ceramic 10. The electrodes 13 and 14 are formed, respectively.
The piezoelectric vibrator TD is elastically supported by an elastic annular support 16 fixed to the holder 15. A perforated or reticulated thin plate 21 having a large number of minute holes 23 is disposed on an atomization surface 20 (a surface on which an electrode is formed on the main surface) of the piezoelectric vibrator TD, and an end of the perforated or reticulated thin plate 21. The part is fixed to the holder 15 via a fixture 22. The porous or reticulated thin plate 21 having a large number of minute holes 23 is in contact with the atomizing action surface 20 of the piezoelectric vibrator TD at a portion curved at least partially so as to face the atomizing action surface 20 with a minute gap. ing.
Such a porous or mesh thin plate 21 is a thin metal plate such as stainless steel having a thickness of several tens of μm to 100 μm, and has a small hole 2
The hole diameter of 3 is several μm to 50 μm. The thin plate 21
If the thickness exceeds 200 μm, the processing of fine holes is troublesome and it is not desirable in terms of atomization efficiency. If the diameter of the fine holes 23 exceeds 80 μm, the atomization efficiency decreases and the atomization state becomes unstable, which is not preferable.

The atomizing surface 2 of the piezoelectric vibrator TD
0 and a small amount of liquid to be atomized into the minute gap between the porous or net-like thin plate 21 (a thin tube for dropping the liquid or a liquid absorbing member for sucking up and supplying the liquid by a capillary phenomenon).
25 are provided.

In the configuration of the above embodiment, the variable resistance VR of the base bias circuit of the intermittent oscillation circuit 1 is set to an appropriate value, and the DC output between the positive and negative lines P, N of the DC-DC converter 2 is set. Set the voltage to a value that can secure the amplitude A of the oscillation voltage waveform that enables atomization (Amplitude A
There is no atomization on the atomizing surface of the piezoelectric vibrator below a certain level). In this way, the operating state of the intermittent oscillation circuit 1 is set appropriately, and the control circuit 3 sets the duty 7
When the gate pulse GP of 0% or less is applied, the intermittent oscillation circuit 1 intermittently oscillates at the intermittent frequency and the duty specified by the gate pulse, whereby the piezoelectric ceramic 10 of the piezoelectric vibrator TD is superposed by resonance in the thickness direction. Sonic vibration is caused intermittently, and the atomizing surface 2 is supplied by the liquid supply means 25.
0 and the liquid that has spread into the minute gap between the porous or mesh thin plate 21 and has entered each minute hole 23 is atomized by the intermittent ultrasonic vibration of the atomizing surface 20 (becomes fine particles) and goes into the air. Is released.

At that time, the relationship between the intermittent frequency (1 / D) and the average particle size of the atomized particles emitted in the air was found to be as a result of experiments.
The results are shown in Table 1 below (however, the porous or reticulated thin plate 21
Thickness: 40 μm, hole diameter 30 μm).

[0017] In this way, the frequency of the gate pulse GP of the control circuit 3
Changing the intermittent frequency of the piezoelectric vibrator TD by changing it
Thus, the particle size of the atomized particles generated can be variably controlled.

FIG. 4 shows the relationship between the duty of the output waveform of the intermittent oscillation circuit 1 and the temperature of the piezoelectric vibrator TD during the atomizing operation. When the duty is 70% or less, the temperature of the piezoelectric vibrator TD always falls below 100 ° C., but when the duty exceeds 70%, it approaches or exceeds 100 ° C., and the piezoelectric vibrator TD deteriorates. There is a fear that a phenomenon will occur.

[0019]

As described above, according to the ultrasonic atomizing device of the present invention, the piezoelectric vibrator is intermittently excited by the exciting circuit at a duty of 70% or less, and the piezoelectric vibrator and the porous or mesh thin plate are separated. Since the liquid spread in the minute gap is atomized, the amplitude of the intermittent oscillation output voltage applied to the piezoelectric oscillator causes atomization even when the input power is small enough not to deteriorate the piezoelectric oscillator. Therefore, the size can be made sufficiently large, and the atomization operation can be efficiently performed with a small electric power. Further, by providing a control circuit for variably controlling the intermittent frequency of the intermittent oscillation of the excitation circuit and changing the intermittent frequency of the excitation circuit, the particle size of the atomized particles generated can be variably controlled. It is very effective when used as an inhaler.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a circuit configuration of an embodiment of an ultrasonic atomizing device according to the present invention.

FIG. 2 is a front sectional view showing the arrangement of a piezoelectric vibrator and a porous or net-like thin plate in an example.

FIG. 3 is an explanatory diagram showing an example of an intermittent oscillation waveform.

FIG. 4 is a graph showing the relationship between the duty of the intermittent oscillation waveform and the temperature of the piezoelectric vibrator during the atomizing operation.

FIG. 5 is a cross-sectional view showing a main configuration of a conventional ultrasonic atomizing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Intermittent oscillation circuit 2 DC-DC converter 3 Control circuit 4 Gate pulse generation circuit 5 Duty variable circuit 6 Frequency variable circuit 10 Piezoelectric ceramic 20 Atomizing action surface 21 Porous or mesh thin plate 23 Micro hole 25 Liquid supply means C1 to C4 Capacitor L1 , L2 inductor Q1, Q2 transistor R1 resistance VR variable resistance TD piezoelectric vibrator

Claims (1)

[Claims] 1. A piezoelectric or vibrator, wherein a porous or mesh thin plate is arranged on the atomizing surface side of a piezoelectric vibrator so that a minute gap is formed between at least a part of the thin plate and the atomizing surface. Is provided with an excitation circuit that excites intermittently at a duty of 70% or less to atomize the liquid spread in the minute gap between the atomizing surface and the thin plate by intermittent ultrasonic vibration of the piezoelectric vibrator, An ultrasonic atomizing device, comprising a control circuit for varying the intermittent frequency of the excitation circuit.