JP2013221633A - Ultrasonic atomizing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic atomizing device that can reduce the power consumption by improving the atomization efficiency, scatter a generated mist in a desired direction without using means such as a fan, and suppress generation of a liquid splash on an interface as much as possible.SOLUTION: An ultrasonic atomizing device that atomizes a liquid in a container by applying ultrasonic vibrations to the liquid to form a liquid column on the liquid surface includes: a perforated plate 4 having fine through holes 6 formed; and arrangement means 3 for arranging the perforated plate 4 at a predetermined position, wherein the perforated plate 4 is fitted to the arrangement means 3 through an elastic holding member 5, and also arranged by the arrangement means 3 so that an upper surface 42 is not in contact with the liquid and a lower surface 41 can contact the liquid in a propagation direction of the ultrasonic vibrations.

Description

  The present invention relates to an ultrasonic atomizer that atomizes a liquid in a container using ultrasonic vibration.

Conventionally, as an ultrasonic atomizer that atomizes a liquid using the ultrasonic vibration of an ultrasonic vibrator, an ultrasonic vibrator is disposed in the liquid in the container to emit the ultrasonic vibration into the liquid. And the apparatus which forms a liquid column in a liquid surface and generates atomization particle | grains is known (refer FIG. 6).
The principle of mist generation using this ultrasonic vibration is that the liquid level is generated by applying ultrasonic vibration to the liquid and generating capillary waves (capillary surface waves) and cavitation (cavity phenomenon) specific to the frequency and inside the liquid. It produces countless capillary surface waves and generates fog.

Atomization in the ultrasonic atomization apparatus as described above is performed by entrusting the directivity of the ultrasonic vibration emitted in the liquid, so not all of the ultrasonic vibration energy is used for atomization. In addition, since the capillary surface wave of the liquid is also generated spontaneously, the atomized particles generated from the liquid column formed on the liquid surface are obtained as an accidental product, and the atomization efficiency is high. It is bad.
In other words, in the conventional ultrasonic atomizer, in order to obtain a predetermined atomization amount, the ultrasonic vibration including the useless ultrasonic vibration component that does not contribute to the atomization is included. This means that the ultrasonic transducer must be operated so as to emit a large amount of power, and thus a large amount of driving power is required, and there is a problem that power is wasted.

In addition, as described above, the conventional ultrasonic atomizer has a large driving power for operating the ultrasonic vibrator, so the ultrasonic vibrator easily generates heat, and a cooling fan is required to cool the ultrasonic vibrator. It becomes.
In addition, when the liquid to be atomized disappears, such as when the water runs out, and there is no load, the ultrasonic vibrator may be damaged due to heat generation, and therefore, it is necessary to provide a damage prevention circuit.
For this reason, in the conventional ultrasonic atomizer, there exists a problem that a circuit and an apparatus will enlarge.

Furthermore, the atomized particles generated by the conventional ultrasonic atomizer are generated from the liquid column formed on the liquid surface by ultrasonic vibrations, and rise up as if it were steam. Therefore, in order to disperse the generated mist in a desired direction, it is necessary to provide a fan or the like to blow and convey the mist.
Further, since a liquid column is formed on the liquid surface, there is a problem that liquid droplets are likely to be generated at the interface and the liquid droplets are likely to be scattered.

In this regard, in Japanese Patent Application Laid-Open No. 2009-28582, a cylinder for concentrating ultrasonic vibrations propagating in a direction away from the ultrasonic transducer is disposed in the liquid facing the ultrasonic transducer. Therefore, an ultrasonic atomizing device that realizes a stable atomization amount by effectively using ultrasonic vibration energy and contributes to low power consumption and miniaturization has been proposed.
However, this invention improves the atomization efficiency by concentrating the ultrasonic vibration by using the cylindrical body and increasing the ultrasonic vibration energy. However, the liquid column is formed on the liquid surface and the atomized particles are naturally There is no difference from the conventional ultrasonic atomizer in terms of generation, and it is necessary to provide a fan to scatter the generated mist in the desired direction, or liquid splash at the interface However, the problem that the droplets are likely to scatter is not solved.
JP 2009-28582 A

  This invention improves atomization efficiency and reduces power consumption, and can generate the generated fog in a desired direction without using a means such as a fan, and can also generate liquid splashes at the interface. It is an object to obtain an ultrasonic atomizer that can be suppressed as much as possible.

  The ultrasonic atomizing device according to the present invention is an ultrasonic atomizing device in which a liquid column is formed on a liquid surface by applying ultrasonic vibration to a liquid in a container to atomize the liquid. A porous plate, and a disposing means for disposing the porous plate at a predetermined position, and the perforated plate is attached to the disposing means via an elastic holding member, and the ultrasonic vibration is provided by the disposing means. The upper surface is arranged so as not to come into contact with the liquid and the lower surface in contact with the liquid column in front of the propagation direction of the liquid.

The perforated plate may be formed by forming a large number of minute through holes penetrating in the vertical direction (thickness direction) on a thin metal plate having a thickness of about 0.02 mm to 0.05 mm. It is good also as a bowl shape.
The minute through-holes formed in the porous plate may be those having a hole diameter of about 0.003 mmΦ to 0.050 mmΦ, and are formed with a diameter-expanding portion that expands in a tapered shape on the lower surface side of the porous plate. (Claim 2).

The porous plate has an upper surface that is not in contact with the liquid in the container in front of the propagation direction of the ultrasonic vibration, and a lower surface of the liquid column that is formed on the liquid surface by the ultrasonic vibration when the ultrasonic vibration is oscillated. What is necessary is just to be arrange | positioned so that contact is possible. That is, the lower surface of the perforated plate does not need to be in contact with the liquid at all times, and may not be in contact with the liquid when the ultrasonic vibration is not oscillated.
Further, the perforated plate need not be disposed perpendicular to the traveling direction of the ultrasonic vibration propagating the liquid, and may be disposed so as to be inclined with respect to the traveling direction.

  An elastic holding member that is interposed between the perforated plate and the disposing means and attaches the perforated plate to the disposing means uses the elastic material to prevent the liquid from entering the upper surface of the perforated plate. Any plate can be used as long as it can hold the plate elastically and attach it to the disposing means. For example, it is formed into a donut plate shape having a thickness of about 1 mm with low-hardness silicon rubber, and the porous It is conceivable to attach the disposing means to the peripheral edge of the plate and the outer peripheral edge, but the present invention is not limited to this.

According to this invention, in the ultrasonic atomizing device that atomizes the liquid by applying ultrasonic vibration to the liquid in the container, the liquid column formed on the liquid surface by the ultrasonic vibration is elastically held by the elastic holding member. Since the held perforated plate is disposed so as to be in contact with the liquid, the lower surface of the perforated plate and the liquid can be brought into contact with each other so as not to lose the momentum of the liquid in the vigorously moving liquid column as much as possible. At this time, the liquid in the liquid column is in a state where the surface tension is easily sheared by the convergence of the ultrasonic vibration, and the shearing of the surface tension of the liquid is promoted by the perforated plate contacting the liquid in such a state. . The liquid whose surface tension has been sheared is released vigorously through the minute through hole into the atmosphere, but the lower surface side (the side in contact with the liquid column) and the upper surface side (the side in contact with air) of the through hole. Since there is a large pressure difference (water pressure and atmospheric pressure) between the two, the atomization occurs under the influence of a rapid pressure change.
Further, since the velocity of the liquid passing through the through hole is maintained as it is even when the atomized particles are formed, it is formed as a mist having a velocity.
In other words, since the conventional "natural shearing of the surface tension of the liquid" was promoted using a perforated plate held by an elastic holding member, when compared with a conventional ultrasonic atomizer, The amount of atomization can be increased under the same conditions.
Therefore, when it is going to obtain the same amount of atomization, since it can achieve with ultrasonic vibration energy smaller than the conventional apparatus, power saving is attained.

In addition, since the driving power of the ultrasonic vibrator required for obtaining the same atomization amount can be reduced as compared with the conventional case, heat generation of the ultrasonic vibrator can also be suppressed. For this reason, it is not necessary to provide a cooling fan for cooling the ultrasonic vibrator in the apparatus, and it is not necessary to provide a circuit for preventing damage to the ultrasonic vibrator in a no-load state such as when water runs out.
Thereby, power consumption can be further reduced and downsizing of circuits and devices can be realized.

Furthermore, since the mist ejected from the minute through-holes of the perforated plate is formed as having a momentum in the opening direction of the through-holes by ultrasonic vibration energy, the perforated plate with the upper surface of the perforated plate facing the desired direction By bringing the lower surface into contact with the liquid, the mist can be scattered in a desired direction. That is, there is no need to blow using a fan or the like to carry the generated mist in a desired direction.
In this sense as well, power consumption can be reduced and the apparatus can be downsized.

  Also, since the perforated plate is arranged in front of the propagation direction of the ultrasonic vibration radiated from the ultrasonic vibrator, the upper surface of the perforated plate is not in contact with the liquid and the lower surface is in contact with the liquid column, Formation of a large liquid column on the liquid surface is hindered, and generation of liquid splashes at the interface can be suppressed as much as possible.

  In addition, since the perforated plate is disposed at a position where it can come into contact with the liquid column formed on the liquid surface by ultrasonic vibration, the perforated plate comes into contact with a liquid containing a large amount of ultrasonic vibration energy. Atomization can be performed.

  According to the invention of claim 2, since the through-hole has a diameter-expanding portion that expands in a tapered shape on the lower surface side of the perforated plate, the liquid easily flows toward the through-hole, and the mist is more ejected. It becomes easy.

Overview of an embodiment of the present invention Schematic diagram of an embodiment using disposing means of different modes Expanded cross-sectional view of the through hole The figure which shows the Example which inclined the perforated panel The figure which shows the mode of atomization in the Example of this invention Outline diagram of conventional ultrasonic atomizer

FIG. 1 is a diagram showing an outline of the ultrasonic atomizer of the present invention.
An ultrasonic vibrator 2 is disposed at the bottom of the container 1 for storing the water W to be atomized, and disposed above the liquid surface in front of the propagation direction of the ultrasonic vibration emitted from the ultrasonic vibrator 2. Using the means 3, the perforated plate 4 is disposed at a height at which the water W through which ultrasonic vibration propagates and the lower surface 41 can come into contact with each other.
An elastic holding member 5 made of silicon rubber is attached to the periphery of the porous plate 4, and the porous plate 4 is attached to the disposing means 3 made of synthetic resin via the holding member 5.
The disposing means 3 includes an inner wall 31 for disposing the perforated plate 4 at the above position, and is detachably attached to the opening of the container 1. The inner wall 31 is formed so as to surround the periphery of the porous plate 4, thereby disposing the porous plate 4 at the above position and preventing water W from entering the upper surface 42 of the porous plate 4. In this embodiment, the disposing means 3 is constructed as a member such as a lid that closes the opening of the container 1, but is limited to this constitution as long as the perforated plate 4 can be disposed at the above position. Instead, for example, legs 32 may be provided outside the inner wall 31 so as to prevent the water W from entering and exiting, and may be erected on the bottom surface of the container 1 (see FIG. 2).

  The perforated plate 4 is formed in a disc shape having a thickness of about 0.05 mm using a SUS / nickel alloy, and minute through holes 6 having a diameter of 0.005 mmΦ penetrating in the thickness direction of the plate are staggered at a pitch of 0.06 mm. About 7000 are formed. The through-hole 6 formed in the porous plate 4 includes a diameter-expanding portion 61 that expands in a tapered shape on the lower surface side 41 of the porous plate 4 (see FIG. 3).

  The elastic holding member 5 made of silicon rubber interposed between the disposing means 3 and the perforated plate 4 is formed in a donut plate shape having a thickness of about 1 mm. However, the disposing means 3 is attached to each of the outer peripheral edge portions.

As the ultrasonic transducer 2, a known ultrasonic transducer can be used. In this embodiment, a piezoelectric ultrasonic transducer configured in a flat plate shape with the upper and lower surfaces of the piezoelectric ceramic sandwiched between electrodes is used. is there. An oscillation circuit 7 is connected to the ultrasonic vibrator 2, and by applying a high frequency voltage from the oscillation circuit 7 to the ultrasonic vibrator 2, ultrasonic vibration is generated in a direction perpendicular to the water W in the container 1. Is oscillated.
The ultrasonic transducer 2 may be disposed so that the vibration surface is in contact with the liquid so that the ultrasonic vibration is radiated to the water W in the container 1. In this embodiment, the bottom surface of the container 1 is used. However, the present invention is not limited to this.

Next, the operation of this ultrasonic atomizer will be described.
When a high frequency voltage is applied to the ultrasonic vibrator 2, ultrasonic vibration is oscillated from the ultrasonic vibrator 2 and propagates in the water W in the vertical direction. When the ultrasonic vibration reaches the water surface of the water W, most of the light is reflected and travels downward. The ultrasonic vibration strikes the vibration surface of the oscillating ultrasonic vibrator 2 and the bottom surface of the container 1 and travels upward again. By repeating such propagation of ultrasonic vibration, the ultrasonic vibration energy propagating in the water W gradually increases, and the water surface in the propagation direction is raised to form a water column.
Above the water surface in front of the propagation direction of the ultrasonic vibration, the perforated plate 4 having the minute through holes 6 is disposed so that the lower surface 41 can come into contact with the water W through which the ultrasonic vibration propagates. The water column raised by the energy contacts the lower surface 41 of the porous plate 4. At this time, although the water W in the water column is moving violently by ultrasonic vibration, the porous plate 4 is elastically held by the thin plate-like silicon rubber elastic holding member 5 and relatively free movement is allowed. It is possible to move corresponding to the movement of the water W to some extent, and it is possible to contact the water W without greatly impairing the intense movement of the water W.
At this time, in the raised water W, a capillary wave (capillary surface wave) and cavitation (cavity phenomenon) are generated on the liquid surface and inside the liquid due to ultrasonic vibration, and some shearing of the surface tension has already occurred. The water W is pushed out into the gas from the upper surface 42 side of the perforated plate 4 through the through-hole 6, is affected by a sudden pressure change from the water pressure to the atmospheric pressure, and is ejected as a vigorous mist.
Moreover, since the minute through-hole 6 is provided with the diameter-expanding part 61 which expands gradually in the taper shape on the lower surface side of the perforated plate 4, the water W easily flows into the through-hole 6 and mist is easily ejected. .

Here, when the porous plate 4 is not brought into contact with the water W, when the ultrasonic vibration radiated from the ultrasonic transducer 2 is focused, a water column is formed on the water surface, and a mist is spontaneously formed therefrom. However, if the ultrasonic atomizing device of the present invention is used, the porous plate 4 having the minute through holes 6 is closed to the water column so as to close the water column. Be blocked. That is, a vigorous mist can be ejected from the through-hole 6 of the perforated plate 4 using ultrasonic vibration energy while suppressing the generation of liquid splash at the interface as much as possible.
Further, if the upper surface 42 of the porous plate 4 is inclined so as to be directed in a desired direction and brought into contact with the water W, mist can be ejected in that direction (see FIG. 4).

  FIG. 5 is a diagram showing a state of an actual mist formed by using the ultrasonic atomizer of the present invention (the disposing means 3 is based on the example shown in FIG. 2), and the mist is ejected vigorously. Can be confirmed.

Below, the experiment example of atomization using the ultrasonic atomizer of this invention is shown.
In addition, when there was no special description in each experiment, it experimented on the following common conditions.
[Inside container size]: Height 100 mm, width 100 mm, depth 100 mm
[Ultrasonic vibrator]: Piezoelectric ultrasonic vibrator (disk shape with a diameter of 20 mm and a thickness of 0.2 mm)
[Perforated plate]: Made of SUS / nickel alloy, disk-shaped with a diameter of 5.5 mm and a plate thickness of 0.05 mm, the through-hole has a hole diameter of 0.005 mmΦ and a tapered enlarged portion on the lower surface side, and a pitch of 0.06 mm 7000 in a zigzag pattern [elastic holding member]: silicon rubber (hardness 20 °), outer shape 20 mm, inner diameter 5.0 mm, thickness 1.0 mm donut plate [atomizing liquid]: water [ Power supply]: Input AC100V50Hz, output DC15V700mA

<Experimental example 1>
In Experimental Example 1, the depth of the water W in the container 1 is 18 mm (the amount of water is 180 ml), the height of the lower surface 41 of the porous plate 41 is 6.2 mm, and the resonance frequency of the ultrasonic transducer 2 is 1.7 MHz and 2 The atomization amount when the frequency is 4 MHz is compared with the atomization amount when the porous plate 4 is not provided.
According to this experiment, when the water depth (water amount) of the water W in the container 1 and the height from the water surface of the porous plate 4 are the same, the fog when the porous plate 4 is disposed for any frequency. It can be confirmed that the amount of formation is greatly increased as compared with the case without the porous plate 4.

<Experimental example 2>
In Experimental Example 2, the frequency of the ultrasonic transducer applied to the water W in the container 1 is 1.7 MHz, the height from the water surface of the porous plate 4 is 6.2 mm, and the water depth of the water W in the container 1 is changed. The amount of atomization in the case where the perforated plate 4 is not disposed is compared with the amount of atomization in the case of the above.
According to this experiment, when the water depth (water amount) of the water W in the container 1 and the height from the water surface of the porous plate 4 are the same, the porous plate 4 is disposed even if the water depth (water amount) is varied. It can be confirmed that the amount of atomization in this case is greatly increased as compared with the case without the porous plate 4.
In this experiment, the frequency was 1.7 MHz, but it is expected that the same result can be obtained even when the frequency condition is changed.

  From the above experimental examples 1 and 2, when the porous plate 4 is arranged at a height of 6.2 mm from the water surface and brought into contact with the water W in which ultrasonic vibration has propagated, the frequency and water depth (water volume) conditions can be changed. It can be seen that the amount of atomization can be increased as compared with the conventional apparatus.

<Experimental example 3>
In Experimental Example 3, the depth of the water W in the container 1 is 23.0 mm (water volume 230 ml), and the amount of atomization when the height from the water surface of the porous plate 4 is changed for each frequency of the ultrasonic vibrator. This is an experiment to see changes.
According to this experiment, when the water depth (water amount) of the water W in the container 1 is set to the same condition (water depth 23.0 mm), the gap between the lower surface of the perforated plate 4 and the water surface is the frequency of any ultrasonic transducer. When the atomization is performed by bringing the lower surface 41 of the porous plate 4 into contact with the water column formed on the water surface with a gap in the surface, the amount of atomization can be greatly increased, and the height of the porous plate is 6.2 mm. It can be seen that the maximum atomization amount is obtained.

<Experimental example 4>
Experimental example 4 is an experiment for seeing changes in the amount of atomization when the water depth in the container 1 and the height from the water surface of the porous plate 4 are changed for each frequency of the ultrasonic transducer. is there.
According to this experiment, the porous plate 4 is not in contact with the water surface during normal times (when the ultrasonic vibration is not oscillated), but is contacted only when the ultrasonic vibration is oscillated (that is, the water column formed on the water surface by ultrasonic vibration is porous. When it is disposed at a position where the plate 4 is in contact, it can be seen that the atomization amount is greatly increased regardless of the water depth at any frequency.

<Experimental example 5>
Experimental Example 5 is an experiment for seeing a change in atomization amount when the hardness of the elastic holding member 5 made of silicon rubber is changed. The frequency of the ultrasonic vibrator is 1.7 MHz, the water depth of water W is 19 mm (water volume 190 ml), the thickness of the elastic holding member 5 is 1.0 mm, and the height of the porous plate 4 from the water surface is two ways. went.
According to this experiment, it can be seen that the amount of atomization can be increased regardless of the hardness of the silicon rubber.

<Experimental example 6>
Experimental Example 6 is an experiment for seeing the difference in the amount of atomization between the case where the porous plate 4 is held by the elastic holding member 5 made of silicon rubber and the case where the porous plate 4 is held directly by tweezers. The frequency of the ultrasonic vibrator was 1.7 MHz, the depth of water W was 18 mm (water volume 180 ml), the height of the porous plate 4 from the water surface was 6.2 mm, and the hardness of the silicon rubber was 5 °.
According to this experiment, it is understood that the amount of atomization can be greatly increased when the elastic holding member 5 made of silicon rubber is used.

  The present invention relates to an ultrasonic atomizing device that atomizes a liquid in a container using ultrasonic vibration, and has industrial applicability.

DESCRIPTION OF SYMBOLS 1 Container 2 Ultrasonic vibrator 3 Arrangement means 31 Inner wall 32 Leg 4 Porous plate 41 Porous plate lower surface 42 Porous plate upper surface 5 Elastic holding member 6 Through-hole 61 Lower surface side enlarged portion 7 Oscillation circuit W Water

Claims (2)

In an ultrasonic atomizing device that atomizes the liquid by applying ultrasonic vibration to the liquid in the container to form a liquid column on the liquid surface,
A perforated plate in which a large number of minute through-holes are formed, and a disposing means for disposing the perforated plate at a predetermined position,
The perforated plate is attached to the disposing means via an elastic holding member, and the disposing means allows the upper surface to not contact the liquid and the lower surface to contact the liquid column in front of the propagation direction of the ultrasonic vibration. Arranged,
Ultrasonic atomizer. The through hole was provided with a diameter-expanding portion that expands in a tapered shape on the lower surface side of the porous plate,
The ultrasonic atomizer of Claim 1.