JPH019659Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic humidifier with a noise reduction structure having a structure for reducing noise terminal voltage and radiation noise.

Generally, humidifiers are often installed in living rooms due to their intended use, and are often placed near television receivers, radio receivers, and the like. For this reason, ultrasonic humidifiers that atomize water using ultrasonic waves may cause noise interference to these devices. The reason for this is that in ultrasonic humidifiers that use piezoelectric vibrators to atomize water, the driving frequency of the piezoelectric vibrators is 1MHz.
I use something with a band of about 2MHz to 2MHz.
Due to the non-linearity of the elements of the excitation circuit that drives the piezoelectric vibrator, the excitation waveform is distorted as shown in FIG. As a result, subharmonics and harmonics of the fundamental wave are generated, and these subharmonics and harmonics enter TV receivers and radio receivers through power lines, or are radiated into space from wiring parts such as excitation circuits. caused noise interference to television and radio receivers.

Therefore, as shown in FIG. 2, measures such as surrounding the entire excitation circuit 2 that drives the piezoelectric vibrator 1 with a metal body 3 or inserting a noise filter 4 on the power source side are being considered. However, the whole excitation circuit 2 is connected to the metal body 3.
If the noise filter 4 is surrounded by a radiated noise, the structure becomes complicated and impractical, and the noise filter 4 is not effective against radiated noise.

FIG. 3 shows an ultrasonic humidifier previously proposed by the present applicant, which has a structure in which an ultrasonic humidifying unit 11 as shown in FIG. 4 is attached to the bottom of a water storage container 10 having an opening at the bottom. There is. In this case, the ultrasonic humidification unit 11 includes a piezoelectric vibrator 13 mounted on a chamber base 12, a printed circuit board 14 mounted thereon, an excitation circuit 15 assembled on the printed circuit board 14, and the printed circuit board 14 and the excitation circuit 15 arranged in a ring shape. A shield ring 16 is provided so as to surround it. As the excitation circuit 15, a transistor oscillation circuit in which the water side electrode 13a of the piezoelectric vibrator 13 is connected to the base of the output transistor 20 as shown in FIG. The shield ring 16 has a structure insulated from the potential of the excitation circuit 15 and the power source.

In this case, the shield ring 16 is connected to the excitation circuit 15.
Since the ultrasonic humidifier 11 is insulated from the potential of the power source and the like, it has the disadvantage that although it has the effect of reducing radiation noise, it does not have the effect of reducing the noise terminal voltage appearing between the power connection terminals of the ultrasonic humidifier 11. In addition, the excitation circuit 15 in FIG.
are the electrode 13a on the water side of the piezoelectric vibrator 13 and the chamber base 12 (the electrode 13a to prevent electrolytic corrosion).
(same potential as a) is connected to the base of the transistor 20, and is floating above the virtual ground (not grounded to the earth, but equipment ground), which has the disadvantage that the virtual ground area cannot be increased.

In view of the above points, the present invention aims to reduce noise terminal voltage and radiation noise by connecting the water side electrode of the piezoelectric vibrator, the collector of the output transistor, and the shield ring so that they have the same potential. The present invention aims to provide an ultrasonic humidifier with a reduction structure.

Embodiments of the ultrasonic humidifier with a noise reduction structure according to the present invention will be described below with reference to the drawings.

FIG. 6 shows the structure of the ultrasonic humidifying unit in the embodiment, and FIG. 7 shows the wiring of the excitation circuit. In these figures, the chamber base 30
A piezoelectric vibrator 31 is mounted approximately at the center of the chamber base 30, and a printed circuit board 33 on which an excitation circuit 32 is assembled is mounted at the end of the chamber base 30. For the shield ring 34, a material with good high frequency conductivity is selected, such as aluminum, copper, zinc coated or galvanized iron plate. The shield ring 34 is formed to annularly surround the excitation circuit 32 and the printed circuit board 33.
5 or the like so that sufficient contact can be obtained with the chamber base 30. In addition, shield ring 3
An insulating sheet 36 is provided inside 4 for insulation from the substrate.

The excitation circuit 32 is a transistor oscillation circuit with a grounded collector, and includes an output transistor 40, capacitors 41 to 45, and inductors 46, 47, 4.
8, resistors 52 to 55 and a rectifier 56 are provided, and the piezoelectric vibrator 31 oscillates at its own frequency. Here, the water side electrode 31a of the piezoelectric vibrator 31 and the collector of the output transistor 40 are connected to the positive side line P (ground side line),
Furthermore, it is connected to the shield ring 34 via the chamber base 30. As a result, when the chamber base 30 is attached to the water storage container, the water, the chamber base 30, the shield ring 34, the electrode 31a, and the collector of the transistor 40 have the same potential, and these are considered as virtual ground. It functions effectively, and the virtual ground area can be increased significantly compared to the conventional configurations shown in FIGS. 4 and 5. By increasing the virtual ground area, it is possible to lower the high frequency impedance between the ground and reduce the noise terminal voltage and radiation noise.

FIG. 8 is a graph illustrating the effects of the embodiment of the present invention, where the solid line shows the case without the shield ring 34 and the chain line shows the case of the embodiment. It can be seen from this figure that considerable noise reduction is possible.

As described above, according to the present invention, in an ultrasonic humidifier that atomizes water by providing a piezoelectric vibrator at the bottom of a water storage container, a shield ring that annularly surrounds an excitation circuit and an output transistor of the excitation circuit are used. By connecting the collector and the water-side electrode of the piezoelectric vibrator with sufficient conductivity, the noise terminal voltage and radiation noise can be effectively reduced.

[Brief explanation of the drawing]

Fig. 1 is a waveform diagram showing an example of the excitation waveform of a piezoelectric vibrator in an ultrasonic humidifier, Fig. 2 is a block diagram showing an ultrasonic humidifier considering conventional noise countermeasures,
FIG. 3 is a schematic cross-sectional view showing an ultrasonic humidifier with a noise prevention structure previously proposed by the applicant;
The figure is a perspective view showing the ultrasonic atomization unit in that case, FIG. 5 is a circuit diagram showing the excitation circuit, and FIG. 6 is an embodiment of the ultrasonic humidifier with noise reduction structure according to the present invention. FIG. 7 is an exploded perspective view showing the ultrasonic atomization unit, FIG. 7 is a circuit diagram of an excitation circuit used in the embodiment, and FIG. 8 is a graph for explaining the effects of the embodiment. 1, 13, 31...Piezoelectric vibrator, 2, 15, 3
2...Excitation circuit, 10...Water storage container, 14,3
3... Printed circuit board, 16, 34... Shield ring, 20, 40... Output transistor, 17,
36...Insulating sheet.

Claims (1)

[Scope of utility model registration request] A piezoelectric vibrator is attached to a chamber base, a printed circuit board on which an excitation circuit for driving the piezoelectric vibrator is assembled is attached to the chamber base, and the piezoelectric vibrator is arranged at the bottom of a water storage container to atomize water. In the ultrasonic humidifier, the excitation circuit is composed of a transistor oscillation circuit with a grounded collector, a shield ring is connected and fixed to the chamber base so as to surround the transistor oscillation circuit and the printed circuit board in an annular shape, and the shield ring and An ultrasonic humidifier with a noise reduction structure, characterized in that the collector of the transistor of the transistor oscillation circuit and the water side electrode of the piezoelectric vibrator are connected with sufficient conductivity.