JPS599728Y2 - Ultrasonic atomizer - Google Patents

Description

[Detailed description of the invention] This invention relates to an ultrasonic atomization device that atomizes liquid by making a piezoelectric vibrator vibrate at high frequency and emitting ultrasonic waves into liquid. An object of the present invention is to provide an ultrasonic atomization device that can prevent transient current from flowing through a piezoelectric vibrator and deteriorating the piezoelectric vibrator.

The ultrasonic atomizer drives a piezoelectric vibrator 2 attached to the bottom of a liquid 1 to be atomized by an oscillation circuit 3, as shown in Fig. 1 a, l), and directs ultrasonic waves 4 toward the liquid surface. The liquid 1 is atomized into fine particles by radiation.

As shown in FIG. 1a, when the drive oscillation circuit 3 of the piezoelectric vibrator 2 starts, the liquid level 6 is horizontal, and the first ultrasonic wave 4 emitted from the piezoelectric vibrator 2 is transmitted to the horizontal liquid level 6. The ultrasonic waves are totally reflected by the ultrasonic waves 5 and become reflected ultrasonic waves 5, which excite the piezoelectric vibrator 2 in the opposite direction.

If the reflected ultrasonic wave 5 generated at the moment of the start of this operation has large energy, a large transient current flows through the piezoelectric vibrator 2 due to the reflected ultrasonic wave 5.

FIG. 2 is a diagram showing the relationship between the time from the moment when the starting switch is turned on and the current flowing through the piezoelectric vibrator 2. At the moment when the starting switch is turned on, a transient current 9 as shown in FIG. It can be seen that the current flows through the piezoelectric vibrator 2.

Such a transient current 9 that is larger than the allowable current range of the piezoelectric vibrator 2 accelerates the deterioration of the piezoelectric vibrator 2.

On the other hand, once the atomization operation is started and a water column 7 is formed on the water surface 6 as shown in FIG. 6 is undulating, the liquid surface reflected wave of the ultrasonic wave 4 becomes a diffusely reflected wave 8, and even if the energy of the ultrasonic wave 4 emitted from the piezoelectric vibrator 2 is large, it hardly affects the piezoelectric vibrator 2.

That is, in FIG. 2, 10 indicates the current flowing through the piezoelectric vibrator 2 after a certain period of time has elapsed since the starting switch is turned on, and the magnitude is within the range of the allowable current flowing through the piezoelectric vibrator 2.

As shown below, if the energy of the ultrasonic waves 4 emitted from the piezoelectric vibrator 2 of the ultrasonic atomizer shown in FIG. This means that the deterioration of 2 can be prevented.

Next, the following phenomenon will be specifically explained with reference to FIG. 3, which shows the basic circuit of a conventional ultrasonic atomizer, and FIG. 4, which shows voltage waveforms at various parts of the circuit.

In FIG. 3, 11a and 1lb are AC power input terminals, 12a, 12b, 12c, 12d are diodes that constitute a rectifier circuit, 13 is a capacitor with a capacitance of about 0.02 μF for noise removal, and 14 is a capacitor with a capacitance of about 0.02 μF. The output terminal of the rectifier circuit, 15.16 is a voltage dividing resistor that provides a bias voltage to the base of the transistor 17, 18, 19.20 are capacitors, 21 is a resistor, and 22 is an oscillator, which constitute the Colpitts oscillation circuit. do.

23 is a choke coil, and 24 is a collector terminal of the transistor 17.

25 is a starting switch, and when this switch 25 is turned on, the piezoelectric vibrator 22 starts vibrating.

In the circuit of the ultrasonic atomizer having the above structure, a single-phase AC voltage as shown in FIG. The circuit converts the voltage into a rectified voltage as shown in FIG. 4b.

This voltage appears at the output terminal 14 of the rectifier circuit and resistor 15
．． 16 and becomes the base bias voltage of the transistor 17.

Further, the collector terminal 24 of the transistor 17 is connected to the transistor 17, capacitors 18, 19, 20, resistor 21,
The voltage waveform shown in FIG. 2C appears when the high frequency voltage generated by the oscillation circuit constituted by the piezoelectric vibrator 22 is modified by the power supply voltage shown in FIG. 2B.

Now, in the above state, the starting switch 25 is turned on, and the time is 11 (voltage waveform phase angle is O) shown in FIG. 4b.
(or an integer multiple of 180°), only a small voltage appears at the output terminal 14 of the rectifier circuit at first, so the oscillation output of the piezoelectric vibrator 22 in FIG. 3 is initially small;
Therefore, the overcurrent terminal 9 in FIG. 2 is relatively small.

However, the time it takes to turn on the starting switch 25 is shown in Fig. 4b.
Time t2 shown in (when the phase angle of the voltage waveform is 90' or 90')
(odd multiple of °), the ultrasonic wave 4 with large energy is emitted first in Figure 1a, so
The reflected ultrasonic wave 5 with strong energy hits the piezoelectric vibrator 22 (2 in FIG. 1), and the transient current 9 in FIG. 2 becomes very large.

In this way, if the time to turn on the starting switch 25 happens to be around time t1, the transient current 9 will be relatively small, but in most other cases, a large transient current exceeding the allowable current of the piezoelectric vibrator 22 will occur. flows, deteriorating the piezoelectric vibrator 22.

The present invention has been developed taking the above points into consideration.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 5 is a circuit diagram of an ultrasonic atomizer according to an embodiment of the present invention.

In the same figure, the part inside the broken line 26 is the main part in one embodiment of the present invention. Shows protection circuit.

Since the parts other than the protection circuit 26 are the same as those in FIG. 3 showing the basic circuit of a conventional ultrasonic atomizer, the same numbers as in FIG. 3 are given.

In the protection circuit 26 shown in FIG. 5, 27 is a starting switch, 28 is an I transistor, 29 is a resistor provided between the base of the I transistor 28 and the starting switch 27, and 30
is a diode, and 32 is a capacitor and a resistor provided between the cathode of the diode 30 and ground.

33 is a power supply voltage input terminal of the oscillation circuit. The collector of the transistor 28 is connected to the output terminal 14 of a rectifier circuit consisting of diodes 12a to 12d, and the emitter of the transistor 28 is connected to the output terminal 14 of the rectifier circuit consisting of the diodes 12a to 12d.
19, 20, a resistor 21, and a piezoelectric vibrator 22.

The base of the transistor 28 is connected to the output terminal 14 of the rectifier circuit through a resistor 29 and a starting switch 27.

Further, a diode 30, a capacitor 31, and a resistor 32 connected in parallel to the capacitor 31 are provided between the base of the transistor 28 and the ground.

Now consider the case where the starting switch 27 is turned on in the above circuit configuration.

When the starting switch 27 is turned on, a voltage shown in FIG.

At this time, if the resistance value of the resistor 29 is R29 and the capacitance of the capacitor 31 is 63, the time constant during charging is approximately R29, C3.
It becomes 1.

If this time constant is set large, the transistor 28
The base voltage of transistor 28 gradually increases, and current gradually begins to flow between the emitter and collector of transistor 28.

That is, at the moment when the switch 27 is turned on, the bias voltage of the transistor 17 is a very small value, and thereafter the bias voltage gradually increases.

Therefore, the reflected ultrasonic wave 5 shown in FIG. 1A that is generated when the switch 27 is turned on and the oscillation operation is started becomes extremely small, and almost no transient current flows through the piezoelectric vibrator 22.

FIG. 6 is a diagram showing the relationship between the time from the moment when the switch 27 is turned on and the current flowing through the piezoelectric vibrator 22 in the circuit of the ultrasonic atomizer which is an embodiment of the present invention.

In the figure, the transient current 34 flowing through the piezoelectric vibrator 22 at the moment the switch 27 is turned on is extremely small, and as time passes, the current increases in the order of 35 → 36 → 37-+38 and approaches a steady value. Recognize.

Note that the diode 30 has a capacitor 31 whose charge is connected to the resistor 2.
9, to prevent discharge through the switch 27 to the terminal 14 side.

The resistor 32 is for discharging the charge stored in the capacitor 31 when the switch 27 is opened.

In addition, in the above explanation, the cause of the large transient current that flows through the piezoelectric vibrator at the moment the starting switch is turned on is attributed to reflected ultrasonic waves, but in addition to this, the inductance of the circuit is also a cause of the transient current. It is thought that there are.

However, here, for convenience of explanation, the cause of the transient current is explained as being caused only by reflected ultrasound waves.

Regardless of the cause, the voltage applied to the oscillation circuit when the starting switch is turned on poses a problem, and the ultrasonic atomizer of the present invention solves this problem of the voltage applied to the oscillation circuit when the starting switch is turned on. It is something.

As explained above, the ultrasonic atomizer of the present invention can be realized by simply adding an extremely simple protection circuit consisting of transistors, resistors, capacitors, etc. to the basic circuit of a conventional ultrasonic atomizer. When the starting switch of the oscillation circuit is turned on, a high specified bias voltage is not applied instantaneously, but the bias voltage is gradually increased to suppress transient current and prevent deterioration of the piezoelectric vibrator.

[Brief explanation of the drawing]

Figure 1 a and l) are cross-sectional views of the ultrasonic atomizer when it is at rest and when it is in operation. Figure 2 shows the basic circuit of a conventional ultrasonic atomizer, showing the time from the moment the starting switch is turned on. A diagram showing the relationship between the current flowing through the piezoelectric vibrator, Figure 3 is a basic circuit diagram of a conventional ultrasonic atomizer, and Figure 4 a, l) and c are diagrams at various points in the circuit of the ultrasonic atomizer. Voltage waveform diagram, Figure 5 is a circuit diagram of an ultrasonic atomizer according to an embodiment of the present invention, Figure 6 is the time from the moment when the starting switch is turned on in the apparatus shown in Figure 5, and the voltage flowing through the piezoelectric vibrator. FIG. 3 is a diagram showing the relationship with electric current. 11a, 1lb...--AC power input terminal,
12a, 12b, 12 C, 12 d... Diode, 14... Output terminal of rectifier circuit, 22
...Piezoelectric vibrator, 27...Starting switch, 28...Transistor, 29...
・Resistance, 31... Condenser, 32...
...Resistor, 33...Power supply voltage input terminal to the oscillation circuit.

Claims (1)

[Scope of utility model registration request] An ultrasonic atomizer comprising a rectifier circuit that rectifies alternating current, and an oscillation circuit that uses the output voltage of the rectifier circuit as a power supply voltage, wherein an output terminal of the rectification circuit and a power supply voltage input terminal of the oscillation circuit The collector and emitter of a transistor are connected between the transistors, and a time constant circuit consisting of a capacitor and a resistor that supplies the base voltage is connected to the base of the transistor, and a starting switch is provided in the time constant circuit. conversion device.