Ultrasonic atomizing device

• US 5,657,926 A
• Filed: 04/13/1995
• Issued: 08/19/1997
• Est. Priority Date: 04/13/1995
• Status: Expired due to Term

• Current Assignee: Toda, Kohji
• Original Assignee: Toda, Kohji
• Inventors: Toda, Kohji
• Primary Examiner(s): Oberleitner, Robert J.
• Assistant Examiner(s): Lipka, Pamela J.
• Application Number:
  US08/421,512
• Time in Patent Office: 859 Days
• Field of Search: 239/102.1, 239/102.2, 239/338
• US Class Current: 239/102.2
• CPC Class Codes: B05B 17/0646 Vibrating plates, i.e. plates being directly subjected to the vibrations, e.g. having a piezoelectric transducer attached thereto
• CPC Class Codes: B05B 17/0684 Wicks or the like

Abstract

An ultrasonic atomizing device comprising a piezoelectric vibrator, at least an interdigital transducer P comprising two parts P_D and P_F, at least an electrode G, electrode terminals T_D, T_F and T_G formed on the parts P_D, P_F and electrode G, respectively, a vibrating plate connected to the piezoelectric vibrator, a self-oscillator circuit, and means for dispensing a liquid to the vibrating plate. The interdigital transducer P and the electrode G are formed on two end surfaces of the piezoelectric vibrator, respectively. When an electric signal with a frequency substantially equal to one of the resonance frequencies of the piezoelectric vibrator is applied to the piezoelectric vibrator through the electrode terminals T_D and T_G, the piezoelectric vibrator is vibrated acoustically. The acoustic vibration is not only transmitted to the vibrating plate, but also transduced to an electric signal between the electrode terminals T_F and T_G. The acoustic vibration transmitted to the vibrating plate is consumed for liquid atomization effectively. The voltage between the electrode terminals T_F and T_G, that arises from the piezoelectricity of the piezoelectric vibrator is fedback, and again, applied to the electrode terminals T_D and T_G, which is essential for supplying the mechanical vibration energy for liquid atomization. The self-oscillator circuit is confirmed to work for continuous, stable liquid atomization without special compensation, for considerably large resonance frequency deviation of the piezoelectric vibrator.

Claims

1. An ultrasonic atomizing device comprising:

a piezoelectric vibrator having two end surfaces running perpendicular to the thickness direction of said piezoelectric vibrator;

at least an interdigital transducer (P) formed on one end surface of said piezoelectric vibrator, said interdigital transducer (P) comprising a first part (P_D), and a second part (P_F), said first of said parts (P_D) having about two times as large an area on said one end surface of said piezoelectric vibrator as the second of said parts (P_F);

at least an electrode (G), formed on the other end surface of said piezoelectric vibrator;

first and second electrode terminals (T_D and T_F) formed on said first and second parts (P_D and P_F), respectively;

an electrode terminal (T_G) formed on said electrode (G);

a vibrating plate having a plurality of holes and connected to said electrode (G);

a self-oscillator circuit; and

means for dispensing a liquid to said plurality of holes,

said piezoelectric vibrator, said vibrating plate, said interdigital transducer (P), and said electrode (G) forming a vibrating assembly,

said first electrode terminal (T_D) and said electrode terminal (T_G) receiving an electric signal with a frequency approximately equal to a resonance frequency of said vibrating assembly and causing said piezoelectric vibrator to vibrate acoustically,

said piezoelectric vibrator causing said vibrating plate to vibrate acoustically and generating an electric signal between said second electrode terminal (T_F) and said electrode terminal (T_G),

said second electrode terminal (T_F) and said electrode terminal (T_G) delivering said electric signal, generated between said second electrode terminal (T_F) and said electrode terminal (T_G) and having a frequency approximately equal to said resonance frequency of said vibrating assembly,

said vibrating plate atomizing a liquid dispensed to said plurality of holes by the acoustic vibration of said vibrating plate,

each of said plurality of holes having an inlet opening portion and an outlet opening portion, the liquid penetrating from said inlet opening portion to said outlet opening portion during atomizing the liquid, the circumference of said inlet opening portion being larger than that of said outlet opening portion,

said self-oscillator circuit comprising

a direct current power supply (V_dc),

a coil (L₁) connected between said direct current power supply (V_dc) and said first electrode terminal (T_D), and

a transistor (T_r1), output terminal thereof being connected to said first electrode terminal (T_D) and input terminal thereof being connected to said second electrode terminal (T_F), said vibrating assembly acting as a resonance element and said transistor (T_r1) acting as a feedback amplifier element,

said means for dispensing a liquid to said plurality of holes comprising

a supporting material upholding said piezoelectric vibrator and having a lower acoustic impedance compared with that of said piezoelectric vibrator,

a sponge-like liquid-keeping material having a lower acoustic impedance compared with that of said piezoelectric vibrator, and a large absorption ability for dispensing a liquid to said inlet opening portion of said plurality of holes, said inlet opening portion being in contact with said sponge-like liquid-keeping material, and

a liquid bath for accommodating said sponge-like liquid-keeping material and supplying said sponge-like liquid-keeping material with a liquid,

said piezoelectric vibrator having a rectangular plate-shaped body,

the ratio of length to width thereof being substantially equal to 1,

an area between said first and second parts (P_D and P_F) on said one end surface of said piezoelectric vibrator being located parallel to the length direction of said piezoelectric vibrator, and

said vibrating plate being mounted on an edge of said electrode (G) in parallel to the width direction of said piezoelectric vibrator.

2. An ultrasonic atomizing device comprising:

a piezoelectric vibrator having two end surfaces running perpendicular to the thickness direction of said piezoelectric vibrator;

at least an interdigital transducer (P) formed on one end surface of said piezoelectric vibrator, said interdigital transducer (P) comprising a first part (P_D), and a second part (P_F), said first of said parts (P_D) having about two times as large an area on said one end surface of said piezoelectric vibrator as the second of said parts (P_F);

at least an electrode (G), formed on the other end surface of said piezoelectric vibrator;

first and second electrode terminals (T_D and T_F) formed on said first and second parts (P_D and P_F), respectively;

an electrode terminal (T_G) formed on said electrode (G);

a vibrating plate having a plurality of holes and connected to said electrode (G);

a self-oscillator circuit; and

means for dispensing a liquid to said plurality of holes,

said piezoelectric vibrator, said vibrating plate, said interdigital transducer (P), and said electrode (G) forming a vibrating assembly,

said first electrode terminal (T_D) and said electrode terminal (T_G) receiving an electric signal with a frequency approximately equal to a resonance frequency of said vibrating assembly and causing said piezoelectric vibrator to vibrate acoustically,

said piezoelectric vibrator causing said vibrating plate to vibrate acoustically and generating an electric signal between said second electrode terminal (T_F) and said electrode terminal (T_G),

said second electrode terminal (T_F) and said electrode terminal (T_G) delivering said electric signal, generated between said second electrode terminal (T_F) and said electrode terminal (T_G) and having a frequency approximately equal to said resonance frequency of said vibrating assembly,

said vibrating plate atomizing a liquid dispensed to said plurality of holes by the acoustic vibration of said vibrating plate,

each of said plurality of holes having an inlet opening portion and an outlet opening portion, the liquid penetrating from said inlet opening portion to said outlet opening portion during atomizing the liquid, the circumference of said inlet opening portion being larger than that of said outlet opening portion,

said self-oscillator circuit comprising

a direct current power supply (V_dc),

a current pick up circuit comprising a first diode (D₁) connected in series to said second electrode terminal (T_F) and said electrode terminal (T_G), and a second diode (D₂) connected in parallel to said first diode (D₁) with the opposite polarity to said first diode (D₁), said current pick up circuit picking up a phase of a current between said second electrode terminal (T_F) and said electrode terminal (T_G),

a voltage amplifying circuit including an inverter (IC₁) and amplifying a weak voltage picked up by said current pick up circuit, and

a power amplification circuit including a transistor (T_r1) and a coil (L₁) for raising a voltage in a passage for applying said transistor (T_r1) with a direct current, an output power of said power amplification circuit being applied through said first electrode terminal (T_D) and said electrode terminal (T_G), said vibrating assembly acting as a resonance element and said transistor (T_r1) acting as a feedback amplifier element,

said means for dispensing a liquid to said plurality of holes comprising

a supporting material upholding said piezoelectric vibrator and having a lower acoustic impedance compared with that of said piezoelectric vibrator,

a sponge-like liquid-keeping material having a lower acoustic impedance compared with that of said piezoelectric vibrator, and a large absorption ability for dispensing a liquid to said inlet opening portion of said plurality of holes, said inlet opening portion being in contact with said sponge-like liquid-keeping material, and

a liquid bath for accommodating said sponge-like liquid-keeping material and supplying said sponge-like liquid-keeping material with a liquid,

said piezoelectric vibrator having a rectangular pillar-shaped body,

the ratio of length to width, length to thickness, or width to thickness thereof being substantially equal to 1,

an area between said first and second parts (P_D and P_F) on said one end surface of said piezoelectric vibrator being located parallel to the length direction of said piezoelectric vibrator, and

said vibrating plate being mounted on an edge of said electrode (G) in parallel to the width direction of said piezoelectric vibrator.

3. An ultrasonic atomizing device comprising:

a piezoelectric vibrator having two end surfaces running perpendicular to the thickness direction of said piezoelectric vibrator;

at least first and second electrodes (D) and (F), formed on one end surface of said piezoelectric vibrator with electrically separated condition each other;

at least one electrode (G) formed on the other end surface of said piezoelectric vibrator;

first and second electrode terminals (T_D and T_F) formed on said first and second electrodes (D and F), respectively;

an electrode terminal (T_G) formed on said electrode (G);

a vibrating plate having a plurality of holes and connected to said electrode (G);

a self-oscillator circuit; and

means for dispensing a liquid to said plurality of holes,

said piezoelectric vibrator, said vibrating plate, said first and second electrodes (D and F) and said electrode (G) forming a vibrating assembly,

said first electrode terminal (T_D) and said electrode terminal (T_G) receiving an electric signal with a frequency approximately equal to a resonance frequency of said vibrating assembly and causing said piezoelectric vibrator to vibrate acoustically,

said piezoelectric vibrator causing said vibrating plate to vibrate acoustically and generating an electric signal between said second electrode terminal (T_F) and said electrode terminal (T_G),

said second electrode terminal (T_F) and said electrode terminal (T_G) delivering said electric signal, generated between said second electrode terminal (T_F) and said electrode terminal (T_G) and having a frequency approximately equal to said resonance frequency of said vibrating assembly,

said vibrating plate atomizing a liquid dispensed to said plurality of holes by the acoustic vibration of said vibrating plate,

each of said plurality of holes having an inlet opening portion and an outlet opening portion, the liquid penetrating from said inlet opening portion to said outlet opening portion during atomizing the liquid, the circumference of said inlet opening portion being larger than that of said outlet opening portion,

said self-oscillator circuit comprising

a direct current power supply (V_dc),

a coil (L₁) connected between said direct current power supply (V_dc) and said first electrode terminal (T_D), and

a transistor (T_r1), output terminal thereof being connected to said first electrode terminal (T_D) and input terminal thereof being connected to said second electrode terminal (T_F), said vibrating assembly acting as a resonance element and said transistor (T_r1) acting as a feedback amplifier element,

said means for dispensing a liquid to said plurality of holes comprising

a supporting material upholding said piezoelectric vibrator and having a lower acoustic impedance compared with that of said piezoelectric vibrator,

a sponge-like liquid-keeping material having a lower acoustic impedance compared with that of said piezoelectric vibrator, and a large absorption ability for dispensing a liquid to said inlet opening portion of said plurality of holes, said inlet opening portion being in contact with said sponge-like liquid-keeping material, and

a liquid bath for accommodating said sponge-like liquid-keeping material and supplying said sponge-like liquid-keeping material with a liquid,

said piezoelectric vibrator having a rectangular plate-shaped body,

the ratio of length to width thereof being substantially equal to 1,

said first electrode (D) having about three to four times as large an area on said one end surface of said piezoelectric vibrator as said second electrode (F),

a linear area between said first and second electrodes (D and F) on said one end surface of said piezoelectric vibrator being located parallel to the length direction of said piezoelectric vibrator, and

said vibrating plate being mounted on an edge of said electrode (G) in parallel to the width direction of said piezoelectric vibrator.

4. An ultrasonic atomizing device comprising:

a piezoelectric vibrator having two end surfaces running perpendicular to the thickness direction of said piezoelectric vibrator;

at least first and second electrodes (D and F), formed on one end surface of said piezoelectric vibrator with electrically separated condition each other;

at least one electrode (G) formed on the other end surface of said piezoelectric vibrator;

first and second electrode terminals (T_D and T_F) formed on said first and second electrodes (D and F), respectively;

an electrode terminal (T_G) formed on said electrode (G);

a vibrating plate having a plurality of holes and connected to said electrode (G);

a self-oscillator circuit; and

means for dispensing a liquid to said plurality of holes,

said piezoelectric vibrator, said vibrating plate, said first and second electrodes (D and F) and said electrode (G) forming a vibrating assembly,

said first electrode terminal (T_D) and said electrode terminal (T_G) receiving an electric signal with a frequency approximately equal to a resonance frequency of said vibrating assembly and causing said piezoelectric vibrator to vibrate acoustically,

said piezoelectric vibrator causing said vibrating plate to vibrate acoustically and generating an electric signal between said second electrode terminal (T_F) and said electrode terminal (T_G),

said second electrode terminal (T_F) and said electrode terminal (T_G) delivering said electric signal, generated between said second electrode terminal (T_F) and said electrode terminal (T_G) and having a frequency approximately equal to said resonance frequency of said vibrating assembly,

said vibrating plate atomizing a liquid dispensed to said plurality of holes by the acoustic vibration of said vibrating plate,

each of said plurality of holes having an inlet opening portion and an outlet opening portion, the liquid penetrating from said inlet opening portion to said outlet opening portion during atomizing the liquid, the circumference of said inlet opening portion being larger than that of said outlet opening portion,

said self-oscillator circuit comprising

a direct current power supply (V_dc),

a current pick up circuit comprising a first diode (D₁) connected in series to said second electrode terminal (T_F) and said electrode terminal (T_G), and a second diode (D₂) connected in parallel to said first diode (D₁) with the opposite polarity to said first diode (D₁), said current pick up circuit picking up a phase of a current between said second electrode terminal (T_F) and said electrode terminal (T_G),

a voltage amplifying circuit including an inverter (IC₁) and amplifying a weak voltage picked up by said current pick up circuit, and

a power amplification circuit including a transistor (T_r1) and a coil (L₁) for raising a voltage in a passage for applying said transistor (T_r1) with a direct current, an output power of said power amplification circuit being applied through said first electrode terminal (T_D) and said electrode terminal (T_G), said vibrating assembly acting as a resonance element and said transistor (T_r1) acting as a feedback amplifier element,

said means for dispensing a liquid to said plurality of holes comprising

a supporting material upholding said piezoelectric vibrator and having a lower acoustic impedance compared with that of said piezoelectric vibrator,

a sponge-like liquid-keeping material having a lower acoustic impedance compared with that of said piezoelectric vibrator, and a large absorption ability for dispensing a liquid to said inlet opening portion of said plurality of holes, said inlet opening portion being in contact with said sponge-like liquid-keeping material, and

a liquid bath for accommodating said sponge-like liquid-keeping material and supplying said sponge-like liquid-keeping material with a liquid,

said piezoelectric vibrator having a pillar-shaped body with a pierced hole located parallel to the thickness direction of said piezoelectric vibrator,

the ratio of length in the thickness direction of said piezoelectric vibrator to the shortest distance between the outer edge and the inner edge of an end surface of said piezoelectric vibrator being approximately equal to 1,

said first electrode (D) having approximately the same area on said one end surface of said piezoelectric vibrator as said second electrode (F), or the area not only more than the same as said second electrode (F) but also less than five times said second electrode (F), and

said vibrating plate covering an opening of said pierced hole.