JP2673647B2 - 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 an ultrasonic atomizer suitable for applications such as an inhaler with a small amount of electric power and a small amount of atomization, an aroma device, a pseudo smoke generating toy, and the like.

[0002]

2. Description of the Related Art Conventionally, a household atomizer for indoor humidification has been known as an ultrasonic atomizer utilizing ultrasonic vibration caused by resonance in the thickness direction of a piezoelectric ceramic. As shown in FIG. 7, such an indoor humidifying atomizer has a piezoelectric vibrator TD ′ attached to the bottom of a water tank 1 for containing water W, and has a Colpitts-type self-exciting circuit of FIG. 8 as an excitation circuit. It used an oscillator circuit.

The Colpitts type self-oscillation circuit shown in FIG. 8 is a common-collector type transistor oscillation circuit, which includes a direct current power source E, an oscillation transistor Q, and a resistor R1 for flowing a base bias current of the transistor Q. R2 and a variable resistor VR, an inductor L1 connecting the negative side line N of the DC power source E and the emitter of the transistor Q, a capacitor C1 connected between the positive and negative side lines P and N, an emitter of the transistor Q, A capacitor C2 connected between collectors and a capacitor C3 connected between the emitter and base of the transistor Q are provided, and the piezoelectric vibrator TD 'is connected between the collector and base of the transistor Q via a capacitor C4. . The resistor R3 is a shunt resistor for stabilizing the base bias of the transistor Q, and the inductor L2 and the capacitor C5 are noise filters to prevent noise radiation when the wiring to the variable resistor VR becomes long.

The Colpitts type self-oscillation circuit shown in FIG.
Since the impedance of the piezoelectric vibrator TD 'oscillates stably in a region where the impedance is inductive, the piezoelectric vibrator TD' is actually shifted at a point higher than the resonance frequency of the piezoelectric vibrator TD '.
Is driving. For example, when the resonance frequency of the piezoelectric vibrator TD 'is 2.38 MHz, it is driven at about 2.45 MHz.

FIG. 9 shows the frequency characteristics of the impedance of the piezoelectric vibrator TD 'and the atomization amount in the case of the indoor humidifying atomizer of FIG. From FIG. 9, the maximum atomization amount point does not coincide with the resonance frequency fr of the piezoelectric vibrator TD ′, but is in a frequency region slightly higher than the resonance frequency fr.
D'is a frequency region in which it is inductive. Therefore,
Even with the simple Colpitts type self-oscillation circuit of FIG. 8 in which the piezoelectric oscillator oscillates in the inductive region, a substantial maximum atomization amount could be realized.

On the other hand, a porous or net-like thin plate is placed on the atomizing surface of the piezoelectric vibrator, and the thin film between the atomizing surface of the piezoelectric vibrator and the porous or net-like thin plate is made thin and wide and uniform by capillary action. An atomization structure for shaping water (or a liquid medicine, perfume, etc.) has been considered (proposed by the applicant in Japanese Patent Application No. 3-149252).

FIG. 10 shows an example of such an atomizing structure. In this figure, the piezoelectric vibrator TD uses ultrasonic vibration due to resonance in the thickness direction of the piezoelectric ceramic, and electrodes 13 and 14 are formed on the main surface 11 and the opposite surface 12 of the disk-shaped piezoelectric ceramic 10, respectively. It was done. The piezoelectric vibrator TD
Is elastically supported by an elastic annular support 16 fixed to the holder 15. A perforated or net-like thin plate 21 having a large number of minute holes opened is disposed on the atomizing surface 20 (the surface where electrodes are formed on the main surface) of the piezoelectric vibrator TD.
The end portion of is fixed to the holder 15 via a fixture 22. The porous or net-like thin plate 21 having a large number of minute holes 23 is at least partially in contact with the atomizing action surface 20 of the piezoelectric vibrator TD at a curved portion facing the atomizing action surface 20 with a minute gap. ing. Such a porous or net-like thin plate 21 is a thin metal plate such as stainless steel having a thickness of several tens to 200 μm, and the diameter of the minute holes 23 is several μm to 100 μm. The thin plate 21 has a thickness of 200 μm.
If it exceeds, the processing of the micro holes is troublesome and it is not desirable in terms of atomization efficiency. In addition, the diameter of the micro holes 23 is 100μ.
When it exceeds m, the atomization efficiency is lowered and the particles generated are not uniform, which is not preferable.

The atomizing surface 2 of the piezoelectric vibrator TD
Liquid supply means for supplying an appropriate amount of liquid to be atomized to the minute gap between the zero and the porous or net-like thin plate 21 (a thin tube for dropping the liquid, a liquid absorbing member for sucking and supplying the liquid by capillary action, etc.)
25 are provided.

FIG. 11 shows the atomization structure of FIG. 10 in which water (or chemical solution, perfume, etc.) is formed into a thin and wide uniform shape by a capillary phenomenon between the atomization surface of the piezoelectric vibrator and a thin plate having a porous or mesh shape. 4 shows the frequency characteristics of the impedance and atomization amount of the piezoelectric vibrator TD when using. It can be seen from FIG. 11 that the maximum atomization amount point is considerably close to (substantially matches) the resonance frequency fr of the piezoelectric vibrator TD.

[0010]

As described above, FIG.
In the case of the atomization structure of 0, the maximum atomization amount point substantially coincides with the resonance frequency of the piezoelectric vibrator TD, so that the piezoelectric vibrator TD oscillates in the inductive frequency range. Although the excited oscillation circuit is a circuit that is very simple and capable of stable oscillation, as can be seen from FIG. 11, the piezoelectric vibrator T is at a frequency at which the atomization amount is considerably lower than the maximum atomization amount point.
It was supposed to be a circuit with poor atomization efficiency because it would excite D. Therefore, in order to realize the maximum efficiency, it was considered necessary to study other circuit systems such as a complicated and expensive separately excited excitation circuit.

In view of the above points, the present invention is a Colpitts type when an atomization structure in which a thin and wide uniform liquid is interposed between an atomization surface of a piezoelectric vibrator and a porous or net-like thin plate is used. By devising the circuit configuration of the self-excited oscillation circuit, it is possible to excite the piezoelectric vibrator at a frequency that is approximately equal to or close to the resonance frequency of the piezoelectric vibrator, and ultrasonic atomization that can improve atomization efficiency The purpose is to provide a pesticide.

[0012]

In order to achieve the above object, an ultrasonic atomizer of the present invention has a porous or mesh thin plate disposed on the atomizing surface side of a piezoelectric vibrator, and at least the thin plate A minute gap is formed between a portion and the atomizing action surface, and the piezoelectric vibrator excites the piezoelectric vibrator with an exciting circuit to spread the liquid spread in the minute gap between the atomizing action surface and the thin plate to the piezoelectric vibration. In the case of atomizing by ultrasonic vibration of the child, the excitation circuit is configured by a Colpitts type self-excited oscillation circuit, and the piezoelectric vibrator connected between the collector and the base of the oscillation transistor of the self-excited oscillation circuit The inductor is inserted in series.

[0013]

In the ultrasonic atomizer of the present invention, the conventional Colpitts type self-excited oscillation circuit can oscillate only in the frequency region where the piezoelectric vibrator is inductive. By inserting, it is possible to enable self-excited oscillation in a frequency region that substantially matches or is close to the resonance frequency of the piezoelectric vibrator. Therefore, even in the case of the atomization structure as shown in FIG. 10 in which a liquid such as water is uniformly and thinly interposed between the atomization surface of the piezoelectric vibrator and the porous or net-like thin plate, it is complicated and expensive. The maximum atomization amount can be realized by a Colpitts type self-excited oscillation circuit having a simple and inexpensive circuit configuration without using an excitation type excitation circuit.

[0014]

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

FIG. 1 shows a first embodiment of the ultrasonic atomizer according to the present invention. In this case, the excitation circuit used in the ultrasonic atomizer is a collector-grounded transistor oscillation circuit that constitutes a Colpitts-type self-excited oscillation circuit and executes intermittent oscillation. In this figure, a common-collector type transistor oscillating circuit includes a DC power source E and an oscillating transistor Q.
1 and resistors R1 and R2 for flowing a base bias current of the transistor Q1 and a variable resistor VR, and a switch transistor Q2 for turning on / off the base bias current.
An inductor L1 connecting the negative side line N of the DC power source E and the emitter of the transistor Q1, a capacitor C1 connected between the positive and negative side lines P and N, and an emitter and a collector of the transistor Q1. Capacitor C
2 and a capacitor C3 connected between the emitter and base of the transistor Q1. The piezoelectric vibrator TD is connected between the collector and base of the transistor Q1 via a frequency adjusting inductor L3 and a DC blocking capacitor C4. There is. The switching transistor Q2 has a base of several Hz from a gate pulse generating circuit (not shown).
A square wave gate pulse GP having a frequency of several tens of Hz is applied. The duty of the gate pulse GP is set in the range of several% to 70%. The inductor L2 and the capacitor C5 are noise filters and prevent noise radiation when the wiring to the variable resistor VR becomes long. Further, the mechanism of the piezoelectric vibrator TD and its surroundings is the same as the atomization structure of FIG.

In the oscillation circuit of FIG. 1, during the period in which the switching transistor Q2 is conducting by the gate pulse GP,
A base bias current flows to the oscillation transistor Q1 through the path of the switching transistor Q2, the variable resistor VR and the resistor R1, the inductor L2, and the resistor R2, and the piezoelectric vibrator T
The series circuit of the piezoelectric vibrator TD near the resonance point of D and the frequency adjustment inductor L3 self-excitedly oscillates at a frequency at which the piezoelectric vibrator TD excites the piezoelectric vibrator TD. As a result, the atomizing surface 20 and the porous or mesh thin plate 21 of the piezoelectric vibrator TD of FIG.
The liquid such as water spread in the minute gap between the piezoelectric vibrator T
It can be atomized by ultrasonic vibration due to resonance in the thickness direction of D.

Here, the constant of each circuit element when the resonance frequency in the thickness direction of the piezoelectric vibrator TD is set to 2.42 MHz (the frequency of self-excited oscillation is also in this vicinity) will be exemplified below.

C1: 10 × 10 ⁴ pF, C2: 20 × 1
0 ² pF, C3, C4: 75 × 10 ³ pF, R1: 3.3
kΩ, VR: 5 kΩ, L3: 0.4 μH, DC power supply E:
30V

FIG. 2 shows how the oscillation frequency changes when the frequency adjusting inductor L3 is changed in the oscillation circuit of FIG. By setting the inductance value of the frequency adjusting inductor L3 to 0.4 μH, it can be seen that the oscillation frequency of the oscillation circuit can be made substantially equal to the resonance frequency 2.42 MHz of the piezoelectric vibrator TD.

FIG. 3 shows the impedance and atomization amount of the piezoelectric vibrator TD when the oscillation frequency is changed by adjusting the frequency adjustment inductor L3 of the oscillation circuit of FIG. 1 in the range of 0 to 1.5 μH. Frequency characteristics are shown (however, the switching transistor Q2 is turned on and off to intermittently drive the power consumption to be 2 W constant). From FIG. 3, the piezoelectric vibrator T
It can be seen that the maximum atomization amount can be obtained by exciting the piezoelectric vibrator TD at an oscillation frequency that substantially matches the resonance frequency fr of D.

FIG. 4 is a frequency adjustment inductor L of FIG.
8 shows the relationship between the power consumption and the atomization amount of the oscillation circuit having the circuit No. 3 and the conventional circuit of FIG. 8. The oscillation circuit of the first embodiment of FIG. 1 is much more fogged than the conventional circuit of FIG. It can be seen that the conversion efficiency is excellent. However, the resonance frequency of the piezoelectric vibrator TD is 2.42 MHz in both FIGS. 1 and 8, the frequency adjustment inductor L3 in FIG. 1 is 0.4 μH, and the oscillation frequency is 2.418.
MHz, intermittent duty (ratio of oscillation period Don to intermittent cycle D = Don / D) is 12 to 17%, and intermittent frequency is 1.2 kHz. The oscillation frequency in the case of FIG. 8 is 2.
452 MHz, the intermittent duty was 12 to 17%, and the intermittent frequency was 1.2 kHz.

As described above, in the case of the first embodiment, by inserting the frequency adjusting inductor L3 in series relation with the piezoelectric vibrator TD, the resonance frequency of the piezoelectric vibrator TD substantially matches.
Alternatively, the Colpitts type self-oscillation circuit can be made to be able to self-oscillate in a close frequency range. Therefore, even in the case of the atomization structure as shown in FIG. 10 in which a liquid such as water is uniformly and thinly formed between the atomization surface of the piezoelectric vibrator TD and the porous or mesh thin plate, it is complicated and expensive. It is possible to realize the maximum atomization amount by a Colpitts type self-excited oscillation circuit having a simple and inexpensive circuit configuration without using a separate excitation type excitation circuit.

FIG. 5 shows a second embodiment of the present invention. In this case as well, the excitation circuit used in the ultrasonic atomizer is a collector-grounded transistor oscillation circuit that forms a Colpitts-type self-excited oscillation circuit and executes intermittent oscillation. It is transformer-coupled with the oscillator TD. That is, the primary winding of the transformer T1 is connected between the collector and the base of the oscillating transistor Q1 via the capacitor C4, and the series winding of the piezoelectric vibrator TD and the frequency adjusting inductor L3 'is connected to the secondary winding of the transformer T1. It is connected. The other circuit configuration is the same as that of the first embodiment.

In the second embodiment, when the leakage inductance of the transformer T1 is also taken into consideration, the sum of the leakage inductance component of the transformer T1 and the frequency adjusting inductor L3 'which are connected in series with the piezoelectric vibrator TD is shown in the figure. The inductance value of the frequency adjusting inductor L3 having the maximum atomization amount in 1 may be set so as to match the value converted to the secondary side of the transformer T1.

FIG. 6 shows a third embodiment of the present invention. In this case as well, the excitation circuit used in the ultrasonic atomizer is a collector-grounded transistor oscillation circuit that forms a Colpitts-type self-excited oscillation circuit and executes intermittent oscillation. It is transformer-coupled with the oscillator TD. Further, the leakage inductance of the transformer is used as the frequency adjustment inductor. That is, the primary winding of the transformer T2 having an appropriate leakage inductance is connected between the collector and base of the oscillation transistor Q1 via the capacitor C4, and the piezoelectric oscillator TD is directly connected to the secondary winding of the transformer T2. There is. Since the leakage inductance of the transformer T2 is used as the frequency adjustment inductor,
No external frequency adjustment inductor is required. In addition,
Other circuit configurations are the same as those of the first embodiment.

In the case of the third embodiment, of the leakage inductance of the transformer T2, the leakage inductance component L of the transformer T2 that is connected in series with the piezoelectric vibrator TD.
3 ″ is used, that is, the leakage inductance component L3 ″ is the inductance value of the frequency adjusting inductor L3 having the maximum atomization amount in FIG.
It may be set so as to match the value converted to the secondary side of 2.

The configuration in which the piezoelectric vibrator TD is connected by transformer coupling between the collector and the base of the oscillation transistor Q1 as in the second and third embodiments is used even when a low DC power supply voltage is used. The advantage is that impedance matching with the piezoelectric vibrator TD can be improved.

Although the embodiment of the present invention has been described above, it is obvious to those skilled in the art that the present invention is not limited to this and various modifications and changes can be made within the scope of the claims. Let's do it.

[0029]

As described above, according to the ultrasonic atomizer of the present invention, by inserting the inductor in series relation with the piezoelectric vibrator, the resonance frequency of the piezoelectric vibrator is substantially matched or approached. A Colpitts type self-oscillation circuit can be oscillated in the frequency domain. Therefore, even in the case of the atomization structure in which a liquid such as water is uniformly and thinly formed between the atomization surface of the piezoelectric vibrator and the porous or net-like thin plate, a complicated and expensive separately excited excitation circuit. The maximum atomization amount can be realized by a Colpitts-type self-excited oscillation circuit having a simple and inexpensive circuit configuration without using.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of an ultrasonic atomizer according to the present invention.

FIG. 2 is a graph showing a relationship between a frequency adjustment inductor and an oscillation frequency in the circuit of the first embodiment.

FIG. 3 is a graph showing frequency characteristics of impedance and atomization amount of the piezoelectric vibrator when the oscillation frequency is changed by changing the frequency adjustment inductor in the circuit of the first embodiment.

FIG. 4 is a graph showing the relationship between power consumption and atomization amount in the case of the circuit of the first embodiment and the conventional circuit of FIG.

FIG. 5 is a circuit diagram showing a second embodiment of the present invention.

FIG. 6 is a circuit diagram showing a third embodiment of the present invention.

FIG. 7 is a schematic explanatory view of a conventional atomizer provided with a piezoelectric vibrator on the bottom of a water tank.

FIG. 8 is a circuit diagram showing a Colpitts type self-oscillation circuit which is a conventional excitation circuit.

9 is a graph showing frequency characteristics of impedance and amount of atomization of the piezoelectric vibrator in the case of the atomizer of FIG.

FIG. 10 is a front cross-sectional view showing an atomization structure for uniformly and thinly forming a liquid between the atomization surface of the piezoelectric vibrator and the porous or net-like thin plate.

11 is a graph showing frequency characteristics of impedance and atomization amount of the piezoelectric vibrator in the case of the atomization structure of FIG.

[Explanation of symbols]

 10 Piezoelectric Ceramic 20 Atomizing Action Surface 21 Perforated or Reticulated Thin Plate C1 to C5 Capacitors L1, L2, L3, L3 'Inductors Q, Q1, Q2 Transistors R1, R2 Resistance VR Variable resistance TD, TD' Piezoelectric vibrator T1, T2 Transformer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area B06B 1/06 B06B 1/06 A

Claims (3)

(57) [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 at least between a part of the thin plate and the atomizing surface. In an ultrasonic atomizer that excites a liquid spread in the minute gap between the atomizing surface and the thin plate by ultrasonic vibration of the piezoelectric vibrator, the excitation circuit is a Colpitts type It consists of the self-excited oscillation circuit of
An ultrasonic atomizer characterized in that an inductor is inserted in series with the piezoelectric vibrator connected between the collector and the base of the oscillation transistor of the self-excited oscillation circuit. 2. The ultrasonic atomizer according to claim 1, wherein the piezoelectric vibrator is connected between a collector and a base of the oscillation transistor via a transformer. 3. The ultrasonic atomizer according to claim 2, wherein the inductor is composed of a leakage inductance component of the transformer in series with the piezoelectric vibrator.