JPS648587B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a liquid atomization device that atomizes liquid fuel such as kerosene or light oil, water, medicinal solution, recording liquid, etc. using an electric vibrator.

Configuration of conventional examples and their problems Various types of liquid atomization devices have been proposed in the past, and many ultrasonic atomization devices using electric vibrators such as piezoelectric elements are also seen. A means for efficiently driving a piezoelectric element near its mechanical resonance point has also been proposed.

First, Figure 1 shows the electrical equivalent circuit of a commonly used piezoelectric element, with an inductance of 1
It consists of a series circuit section consisting of L ₁ , 2 capacitance C ₁ , and 3 resistance R ₁ , and an equivalent parallel capacitance section consisting of 4 capacitance C ₀ . Figure 2 shows the reactance characteristics of a normal piezoelectric element with respect to frequency, and f
Capacitive for <fr, inductive for fr<f<far, far<
f also shows capacitance. fr and far are called the resonant frequency and anti-resonant frequency, respectively, and f
It can be seen that when = fr, the impedance becomes the pure resistance component R ₁ .

FIG. 3 shows a piezoelectric element having the basic characteristics as shown in FIG. 2, or a basic oscillation driving means for an atomizer incorporating a piezoelectric element. Figure a shows a prototype of the Colpitts oscillator circuit, which consists of a transistor 5, capacitors 6 and 7, and a coil 8. b is a diagram in which the coil 8 described above is replaced with a piezoelectric element 9, and the frequency range in which the piezoelectric element 9 acts as an inductance component, that is, fr<f in Fig. 2
Continue oscillation at <far. At this time, oscillation is performed almost at the mechanical resonance point, and oscillation is achieved with high efficiency and at the optimum driving frequency.

However, atomizers that use piezoelectric elements do not have a region that acts as an inductance and exhibit capacitive characteristics near the resonance point of actual atomization.
The basic Colpitts oscillator circuit as described above is not applicable. As a driving means for such an atomizer,
(1) Applying a predetermined drive frequency to the piezoelectric element using an external oscillator circuit and changing the frequency according to the temperature characteristics; (2) Using the capacitance component of the atomizer to resonate in series with this capacitance. Conventionally, a method has been proposed in which a resonant signal is extracted by disposing an inductance and fed back to an amplifier to form a self-oscillating string.

FIG. 4 is a block diagram showing the conventional example of (2) above, in which a signal is transmitted to the piezoelectric element 9 via an inductance 10. Reference numeral 11 denotes a resistor for detecting resonance current, and this detection signal is transmitted to an amplifier 13 via a capacitor 12 for cutting off DC, and the amplified signal is applied to the piezoelectric element via the inductor 10 described above. This self-excited oscillation system transmits a predetermined drive frequency signal to the atomizer to perform atomization.

However, the examples (1) and (2) above do not have a configuration that reliably tracks and oscillates the series resonance point (fr=1/2π√ _{1 1} ) of the piezoelectric element shown in Figure 1. First, it has the disadvantage that it cannot compensate for shifts in the mechanical resonance point due to environmental changes such as temperature or changes over time.

Purpose of the Invention The present invention eliminates such conventional drawbacks by canceling the equivalent capacitance of the atomizer that exhibits capacitance near the resonance point of use, extracting a series resonance signal, and constructing a self-oscillation system. The purpose of the present invention is to provide a simple atomization device that tracks mechanical resonance points that can maintain a stable atomization state and drive efficiently at all times by following resonance point changes due to changes in the external environment or changes over time. .

Structure of the Invention In order to achieve this object, the present invention includes a body provided with a pressurized chamber filled with a liquid as a load, a supply section for supplying liquid to the pressurized chamber, and a An atomizer comprising a nozzle part having a nozzle facing toward the user, an electric vibrator that energizes the nozzle part and vibrates the nozzle, and the electric vibrator is connected to a secondary side. The transformer includes a transformer, a current detection unit that detects a current flowing through the primary side of the transformer, and an amplification unit that amplifies a signal from the current detection unit and transmits the signal to an electric vibrator via the transformer. .

With this configuration, the equivalent parallel capacitance of the atomizer incorporating the electric vibrator can be canceled by the primary inductance of the transformer, and a self-oscillating circuit based on the internal series resonance signal can be constructed.

DESCRIPTION OF EMBODIMENTS An atomizer which is an embodiment of the present invention will be described with reference to FIG. A body 15 equipped with a pressurized chamber 14 filled with liquid is fixed to a mounting plate 17 with screws 16. The liquid enters the pressurizing chamber 14 through the supply pipe 18, and during the atomization operation, the gas discharge pipe 19 is filled halfway. 20 is the pressurized chamber 14
The nozzle part is arranged facing one side of the body 15, and its outer periphery is joined to the body 15. A spherical protrusion 21 having a fine hole for ejecting droplets is formed in the center of the nozzle portion 20 . Further, the nozzle portion 20 includes an annular electric vibrator, here a piezoelectric element 2.
2 is installed. This piezoelectric element 22 is a piezoelectric ceramic polarized in the thickness direction, and has electrodes on the surface to be joined to the nozzle and on the opposite surface. 23
is a lead wire for transmitting a drive signal to the piezoelectric element 22, one of which is soldered to one electrode surface of the piezoelectric element 22, and the other is connected to the body 15 with a screw 24. When the mechanical vibration of the piezoelectric element 22 is excited by the drive signal, the nozzle portion 20 is also energized and vibrates, and as a result, the liquid in the pressurizing chamber 14 is discharged as atomized particles 25.

By the way, the liquid supplied to the pressurizing chamber 14 may be filled halfway into the gas discharge pipe 19 in an atomizer installation configuration, but as an alternative, the pressurizing chamber is usually empty and liquid droplets are filled. Before entering the discharge sequence, negative pressure may be applied through the exhaust pipe 19 to fill the pressurized chamber 14 with liquid and to draw the liquid up to the middle of the exhaust pipe 19. According to the latter method, impurities in the liquid are assimilated in the nozzle hole and the problem that droplets cannot be ejected does not occur.

FIG. 6 is a diagram showing the relationship between frequency f and current of the atomizer of the present invention, with a maximum point at f = fr, and f = far
There is a minimum point in . Each point is a point where series resonance and parallel resonance occur in the electrical equivalent circuit shown in FIG. The actual spray amount reaches its maximum value at the midpoint between fr and far. That is, it is possible to spray most efficiently at the mechanical resonance point (frm).

FIG. 7 shows the leading phase of current with respect to voltage when the atomizer of the present invention is driven. Although the phase difference is minimized at the mechanical resonance point frm, all of the current leads the phase, that is, exhibits capacitive characteristics.

FIG. 8 shows how the signal from the external oscillator 26 is transferred to the amplifier 13.
This is a block configuration of a circuit in which an inductance 27 is connected in parallel with a piezoelectric element 9 through a circuit. 28 is a resistor for detecting the signal passing through the piezoelectric element 9 and the inductance 27, and V ₀ is its output signal. The value of the inductance 27 is selected so that it resonates in parallel with the equivalent parallel capacitance near the mechanical resonance point of the piezoelectric element.

FIG. 9 is a frequency characteristic diagram of the configuration shown in FIG. 8, with the horizontal axis representing the driving frequency and the vertical axis representing the output signal V ₀ . _A1 has a characteristic with the configuration as shown in FIG. 8, and there is a peak value at frm, but the output signal _V0 becomes large at frequencies both lower and higher than that. A ₂ is the output signal V ₀ in Figure 8
is passed through a bandpass filter (B.P.F.) with a center frequency near f=frm, and it can be seen that the signal near the resonance point shows a maximum value in a predetermined frequency region.

FIG. 10 shows a drive circuit for an atomizer according to an embodiment of the present invention. Parts with the same numbers as those in FIG. 8 are components having the same functions. 29 is a transformer, and the electric vibrator 9 is connected to the secondary side. The current flowing to the primary side of the transformer is detected by a current detection section 28 and transmitted to the amplification section 13 via a DC cut capacitor 30. Considering the impedance of the electrical oscillator 9 converted to the primary side of the transformer 29, the square of the turns ratio of the equivalent parallel capacitance C ₀ resonates in parallel with the primary inductance of the transformer and is canceled out. The self-excited oscillation circuit shown in FIG. 10 oscillates mainly due to the series resonance signal caused by L ₁ and C ₁ of the external oscillators.

With this circuit configuration, the self-excited oscillation circuit always continues oscillating near the mechanical resonance point of the electrical vibrator.
Further, since the electric vibrator is connected through the transformer, the drive circuit section and the electric vibrator are electrically insulated. That is, in the atomizer which is an embodiment of the present invention shown in FIG. 5, one of the electrodes of the electric vibrator has the same potential as the main body of the device, but as mentioned above, it is insulated from the drive circuit section. Therefore, there is no need for a complicated circuit configuration for signal processing for electrical parts (for example, frame rods) that are at the same potential as the main body of the device.

FIG. 11 is a diagram showing another embodiment of the present invention. 31 is a band pass filter that makes it easy to extract signals near the mechanical resonance point of the electric vibrator. Other parts with the same numbers as above are components having the same functions.

Effects of the Invention According to the atomizer of the present invention, the primary inductance of the transformer connected to the electric vibrator on the secondary side cancels out the equivalent parallel capacitance of the vibrator, so the mechanical resonance of the atomizer It becomes possible to construct a self-oscillation system with a simple configuration in which the point can be extracted and the resonance signal is fed back to the amplifier. This has the effect that it is possible to automatically track changes in the mechanical resonance point due to external environmental conditions or changes over time, and it is possible to always drive efficiently.
Furthermore, since the electrical vibrator is connected through the transformer, electrical isolation in relation to other circuit systems is simplified.

[Brief explanation of the drawing]

Figure 1 is an electrical equivalent circuit diagram of a piezoelectric element, Figure 2 is a diagram showing the reactance characteristics of a piezoelectric element with respect to frequency changes, Figure 3a is a basic circuit diagram of a Colpittz type oscillator circuit, and Figure 3b is a diagram of a piezoelectric element. 4 is a conventional oscillation circuit diagram, FIG. 5 is a sectional view of an atomizer according to an embodiment of the present invention, and FIG. 6 is a diagram of the incorporated Pierce circuit.
The figure is a characteristic diagram of driving frequency and current of the same atomizer, No. 7
The figure shows the phase relationship between the current and voltage of the same atomizer.
Figure 8 is a frequency characteristic measurement circuit diagram when an inductance is connected in parallel with the piezoelectric element of the same atomizer, Figure 9 is a frequency measurement diagram in the measurement circuit of Figure 8,
FIG. 10 is a circuit diagram of an atomizer showing one embodiment of the invention, and FIG. 11 is a circuit diagram of an atomizer showing another embodiment of the invention. DESCRIPTION OF SYMBOLS 13... Amplification part, 14... Pressurization chamber, 15... Body, 18... Supply part, 20... Nozzle part, 22... Electric vibrator, 28... Current detection part, 29... Transformer, 3
1...Band pass filter.

Claims (1)

[Claims] 1. A body equipped with a pressurized chamber filled with liquid;
a supply unit for supplying liquid to the pressurizing chamber; a nozzle unit having a nozzle facing the pressurizing chamber; and an electric vibrator that biases the nozzle unit and vibrates the nozzle. a transformer to which the electric vibrator is connected to the secondary side; a current detection unit that detects the current flowing to the primary side of the transformer; and a signal from the current detection unit that amplifies the signal of the current detection unit. and an amplifying section that transmits information to an electric vibrator via the transformer. 2. The atomization device according to claim 1, wherein the signal from the current detection section is transmitted to the amplification section via a predetermined bandpass filter. 3. Claim No. 3, wherein the parallel resonance frequency determined by the equivalent parallel capacitance of the electric vibrator and the self-inductance of the primary winding of the transformer is made to substantially match the mechanical resonance frequency of the electric vibrator. The atomization device according to item 1.