JPS6338950Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an acoustic transducer suitable for use in ultrasonic atomizers for kerosene burners and the like.

A piezoelectric vibrator was fixed to the large end face of a conical truncated coupler whose length was less than 1/2 wavelength, and a resonant plate was attached to the small end face of the coupler, and the resonant plate was bent. Acoustic transducers that vibrate have been proposed. This acoustic transducer constitutes an ultrasonic vibrating body, and the bending resonance frequency of the resonance plate becomes the resonance frequency of the entire ultrasonic vibration system, and
Both the large end surface and the resonant plate perform coaxial bending vibration. Atomization of the liquid is performed by supplying the liquid from the liquid introduction pipe to the working surface of the resonance plate on the side opposite to the coupler. At this time, if the surface tension or viscosity of the liquid is low, a portion of the liquid will drop downward before it is atomized, making it impossible to obtain liquid particles with a uniform particle size. In other words, normally when using such an acoustic transducer, the atomized particles that are atomized on the acting surface of the resonant plate are sent out in a predetermined direction by forced air blowing, but there are some particles that are not atomized and are sent out from the resonant plate. This is because the dropped particles are also scattered by the blast of air. Particularly when used in a kerosene combustor, droplets falling from the resonance plate may enter the combustion chamber, causing incomplete combustion.

An example of a conventional acoustic transducer that takes the above points into consideration is shown in FIGS. 1 and 2. In these figures,
The acoustic transducer 1 includes a truncated conical coupler 2 having a large end face and a small end face on its central axis, a resonance plate 3 integrally provided on the small end face of the coupler 2, and a piezoelectric vibrator bonded to the large end face. 4, and a recess 5 is formed on the working surface of the resonator plate 3 to prevent liquid from dripping. A liquid to be atomized is supplied to the working surface of the resonance plate 3 from a liquid introduction pipe 6 to such an acoustic transducer 1 . In this case, the liquid is atomized mainly at the lower part of the recess 5 formed on the working surface, but this is not sufficient to prevent the liquid from dripping. Particularly in the case of a liquid having a high surface tension, a ball 7 of the liquid will adhere to the recess 5 as shown in FIG. In this case, the resonant frequency of the resonant plate 3 changes, and when the acoustic transducer 1 is driven by a self-excited oscillation circuit, it sometimes deviates from the bending vibration mode and is drawn into radial resonance.

FIG. 4 shows another example of a conventional acoustic transducer. In this figure, the acoustic transducer 1A has a convex portion 8 on the working surface of the resonator plate 3 to prevent liquid from dripping, and the other configurations are the same as those shown in FIGS. 1 and 2. It is becoming. In the case of the acoustic transducer 1A shown in FIG. 4 as well, the convex portion 8 was not sufficient to prevent the liquid from dripping, and a similar problem occurred.

In view of the above points, the present invention has been developed by forming the working surface of the resonator plate into a rough surface with countless unevenness, so that the liquid to be atomized can be uniformly distributed in a film form on the working surface. It is an object of the present invention to provide an acoustic transducer that can uniformly atomize the entire working surface and prevent liquid from dripping.

Embodiments of the acoustic transducer according to the present invention will be described below with reference to the drawings.

In FIGS. 5 and 6, acoustic transducer 1B
is composed of a conical truncated coupler 2, a resonant plate 3 integrally formed on the small end face of the coupler 2, and a piezoelectric vibrator 4 bonded to the large end face of the coupler 2.
Numerous irregularities are formed on the working surface 10 by thermal spraying or sandblasting of metal or ceramic, and the working surface 10 is a rough surface.
Note that the liquid to be atomized is supplied to the working surface 10 through the liquid introduction pipe 6, and the coupler 2
has a large end face and a small end face on its central axis, and has a length of 1/2
This is set shorter than the wavelength, and the resonant frequency of the bending of the resonator plate 3 becomes the resonant frequency of the entire ultrasonic vibration system of the acoustic transducer 1B, and the large end face and the resonator plate 3 both perform coaxial bending vibrations, which is the basic principle of the conventional technology. It is the same as a typical acoustic transducer.

According to the configuration of the above embodiment, since the working surface 10 of the resonant plate 3 is a rough surface having countless unevenness, the liquid to be atomized is instantaneously uniformly spread over the working surface 10 of the resonating plate 3 due to the capillary phenomenon. It can be maintained in a thin film form, and the atomization pattern is such that the atomization is uniformly performed from the working surface 10 of the resonance plate 3 as shown in FIG. 7, and dripping of the liquid can be effectively prevented. . Furthermore, the design of the bending resonance frequency of the resonance plate 3 is simplified compared to the conventional case, and it is possible to design it almost theoretically. When a disk shape is adopted as the resonance plate 3, the resonance frequency of the disk is or However, h: Thickness (cm) = 0.1 a: Radius (cm) = 0.5 σ: Poisson's ratio of metal ≒ 0.3 (when using stainless steel) c: Sound velocity ≒ 3230 x 10 ² cm/sec α _np : Normative constant (σ = 0.3 and the first mode ≒ 3.00), and substituting the above values, the resonant frequency ≒
It becomes 112kHz. However, in reality, the disk is not supported by a point at the center, but by about 5 mm from the small end of the coupler.
Since the surface is fixed, α _np is not 3 but is considered to be around 2.2, which is actually lower than 112kHz.

Note that aluminum, celmic, etc. can be used as the material for thermal spraying.

As explained above, according to the present invention, the liquid to be atomized can be distributed almost evenly in a film over the entire working surface of the resonating plate by making the working surface of the resonating plate a rough surface with innumerable irregularities. Thus, it is possible to obtain an acoustic transducer that can uniformize the atomization pattern and prevent liquid from dripping.

[Brief explanation of the drawing]

Figure 1 is a side sectional view showing an example of a conventional acoustic transducer, Figure 2 is a rear view of the same, Figure 3 is a side sectional view showing a state in which a liquid ball is generated, and Figure 4 is a conventional acoustic transducer. FIG. 5 is a side sectional view showing an embodiment of the acoustic transducer according to the present invention, FIG. 6 is a rear view of the same, and FIG. 7 is an atomization pattern according to the embodiment. FIG. 1, 1A, 1B...acoustic transducer, 2...conical truncated coupler, 3...resonance plate, 4...piezoelectric vibrator, 10...working surface.

Claims (1)

[Scope of utility model registration request] The length of the large end face and the small end face on its central axis is 1/
An ultrasonic vibrating body is constructed by using a coupler smaller than two wavelengths, fixing a transducer to the large end face of the coupler, and providing a resonating plate on the small end face, and the bending resonance frequency of the resonating plate is equal to the ultrasonic vibration system. In an acoustic transducer in which the large end face and the resonant plate both vibrate coaxially in a coaxial manner, the coupler of the resonant plate has a rough surface with countless irregularities formed on the working surface on the reflection side. An acoustic transducer characterized in that it is formed as follows.