CN118973695A - Bubble generating device and bubble generating system - Google Patents

Abstract

The present disclosure provides a bubble generating device and a bubble generating system that can realize miniaturization and cost reduction of the device. The bubble generating device (1) involved in the present disclosure is installed in a liquid tank (10) to generate tiny bubbles in the liquid in the liquid tank (10). The bubble generating device (1) comprises: a vibration plate (2) formed with a plurality of openings, a first surface in contact with the liquid in the liquid tank (10), and a second surface in contact with the gas; a vibration body (3) supporting the vibration plate (2); and a piezoelectric element (4) arranged on the vibration body (3) to vibrate the vibration plate (2). With respect to the shapes of the plurality of openings formed in the vibration plate (2), the opening diameter on the liquid side is larger than the opening diameter on the gas side.

Description

Bubble generating device and bubble generating system

Technical Field

The present disclosure relates to a bubble generating device and a bubble generating system.

Background Art

In recent years, microbubbles have been used for water purification, wastewater treatment, fish farming, etc., and in various fields. Therefore, a bubble generating device that generates microbubbles has been developed (Japanese Patent Publication No. 2016-209825 (Patent Document 1), Japanese Patent Publication No. 2014-150784 (Patent Document 2)). In addition, as for the bubble generating device, in addition to water, the development of the use of liquid fuel, disinfectant, cosmetic liquid, etc. to generate microbubbles is being promoted. For example, it has been reported that a bubble generating device is provided in a fuel injection device so that the liquid fuel injected into the piston contains microbubbles to improve fuel efficiency.

Patent Document 1: Japanese Patent Application Publication No. 2016-209825

Patent Document 2: Japanese Patent Application Publication No. 2014-150784

In the bubble generating device described in Japanese Patent Publication No. 2016-209825 (Patent Document 1), a supply unit for supplying gas is provided under a vibrating plate in order to generate tiny bubbles in a liquid. The supply unit is connected to a raw material supply pipe that supplies raw materials from the outside of the bubble generating device. The raw material container is connected to the raw material supply pipe via a pressure regulator that adjusts the pressure. When using a bubble generating device to make bubbles using gas as a raw material, a gas cylinder or the like is required as the raw material container.

In the bubble generating device described in Japanese Patent Publication No. 2014-150784 (Patent Document 2), a predetermined gas required for microbial culture is supplied from a compressor to a culture tank through a through hole of a vibration plate. At this time, in the bubble generating device, a piezoelectric vibration element to which a high-frequency voltage is applied from an oscillator applies vibrations of a predetermined frequency to the vibration plate, thereby generating tiny bubbles in the liquid.

Therefore, in any bubble generating device, in order to generate fine bubbles in liquid, it is necessary to forcibly supply gas from the lower side of the vibration plate using a gas cylinder, a compressor, etc., which hinders the miniaturization and cost reduction of the device.

Summary of the invention

Therefore, an object of the present disclosure is to provide a bubble generating device and a bubble generating system that can achieve miniaturization and cost reduction of the device.

A bubble generating device according to one embodiment of the present disclosure is a bubble generating device that is installed in a liquid tank and generates micro bubbles in the liquid in the liquid tank, and includes: a vibration plate having a plurality of openings formed thereon, a first surface in contact with the liquid in the liquid tank, and a second surface in contact with the gas; a vibration body that supports the vibration plate; and a piezoelectric element that is disposed on the vibration body and vibrates the vibration plate. The plurality of openings formed in the vibration plate each have a shape in which the opening diameter on the first surface side is larger than the opening diameter on the second surface side.

A bubble generation system according to another aspect of the present disclosure includes the above-mentioned bubble generation device and a liquid tank.

According to the present disclosure, in a bubble generating device, with respect to the shapes of the plurality of openings formed on the vibration plate, the opening diameter on the first surface side is larger than the opening diameter on the second surface side, thereby enabling tiny bubbles to be generated in the liquid through natural air intake. Since there is no need for a forced gas supply portion, the device can be miniaturized and cost-effective.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a bubble generating system using a bubble generating device according to an embodiment.

FIG. 2 is a cross-sectional perspective view of the bubble generating device according to the embodiment.

FIG. 3 is a cross-sectional view of a head portion of the bubble generating device according to the embodiment.

FIG. 4 is a schematic diagram for explaining a force generated near the opening of the bubble generating device according to the embodiment.

FIG. 5 is a cross-sectional view of the bubble generating device according to Modification 1. FIG.

FIG. 6 is a cross-sectional view of a bubble generating device according to Modification 2. FIG.

FIG. 7 is a schematic diagram of the bubble generating system for explaining the installation position of the bubble generating device.

FIG. 8 is a schematic diagram of the bubble generating system for explaining another installation position of the bubble generating device.

DETAILED DESCRIPTION

(Implementation Method)

Hereinafter, the bubble generating device and the bubble generating system according to the embodiment will be described in detail with reference to the accompanying drawings. In addition, the same reference numerals are attached to the same or corresponding parts in the drawings, and the description thereof will not be repeated.

First, FIG. 1 is a schematic diagram of a bubble generating system 100 using a bubble generating device 1 according to an embodiment. The bubble generating device 1 shown in FIG. 1 is, for example, a bubble generating system 100 that is disposed on the upper portion of a liquid tank 10 storing a liquid such as water, gasoline, or kerosene and is used to generate microbubbles 200 in the liquid in the liquid tank 10. In addition, the bubble generating system 100 can be applied to various systems such as a water purification device, a wastewater treatment device, a fish farming tank, and a fuel injection device.

In addition, the liquid tank 10 has different liquids introduced depending on the system used. If it is a water purification device, the introduced liquid is water, but if it is a fuel injection device, the introduced liquid is liquid fuel. In addition, the liquid tank 10 only needs to be able to temporarily store liquid, and also includes a structure in which the liquid is always flowing in the pipe for introducing the liquid.

The bubble generating device 1 includes a vibration plate 2, a vibration body 3, and a piezoelectric element 4. The bubble generating device 1 is inserted from a hole formed in a cover provided on the upper part of the liquid tank 10, and the bubble generating device 1 is fixed to the cover of the liquid tank 10 by a retaining flange 5 at a position of the vibration body 3 provided with the vibration plate 2 and provided with the liquid immersed. By vibrating the vibration plate 2 immersed in the liquid by the piezoelectric element 4, microbubbles 200 are generated from a plurality of pores (openings) formed in the vibration plate 2. In addition, the vibration plate 2 is provided so that one surface (first surface) contacts the liquid in the liquid tank 10, and the other surface (second surface) contacts the gas.

FIG2 is a cross-sectional perspective view of the bubble generating device 1 according to the embodiment. As shown in FIG2 , the bubble generating device 1 is composed of a vibration plate 2, a head 31 for fixing the peripheral portion of the vibration plate 2, and a cylindrical body 32 connected to the head 31. The cylindrical body 32 is a so-called Langevin type vibrator. The cylindrical body 32 is a structure in which two piezoelectric elements 4 are clamped by an upper metal ring 32a and a lower metal ring 32b and fixed by a fastening bolt 34.

The two piezoelectric elements 4 have a structure in which a first piezoelectric element 41 and a second piezoelectric element 42 having a polarization direction opposite to that of the first piezoelectric element 41 are overlapped. Terminals 43 and 44 for supplying power to the first piezoelectric element 41 and the second piezoelectric element 42 are drawn out from between the upper metal ring 32a, the lower metal ring 32b and the first piezoelectric element 41 and the second piezoelectric element 42, and are electrically connected to the controller 20 shown in FIG. 1 through wiring.

By supplying power from the controller 20 to the first piezoelectric element 41 and the second piezoelectric element 42, the cylindrical body 32 is driven at a resonance frequency depending on the length direction of the head 31 and the cylindrical body 32, thereby obtaining a large displacement at the vibration plate 2. Since there are multiple high-order vibration modes in the resonance of the cylindrical body 32, it is possible to select a resonance frequency from multiple resonance frequencies. In addition, by reducing the diameter of the portion connected to the head 31 from the upper metal ring 32a to be smaller than other portions, the displacement of the vibration plate 2 can be further amplified.

2, a through hole 35 is provided at the center of the upper metal ring 32a, the lower metal ring 32b, and the fastening bolt 34, and the through hole 35 serves as an inlet for introducing gas into the vibration plate 2. The upper metal ring 32a, the lower metal ring 32b, and the fastening bolt 34 are made of stainless steel, aluminum, etc. The first piezoelectric element 41 and the second piezoelectric element 42 are made of ceramics such as PZT (lead zirconate titanate), KNN ((K, Na) NbO ₃ ), and piezoelectric crystals such as lithium tantalate and lithium niobate.

Specifically, the cylindrical body 32 is formed of SUSU304 material, the diameter of the upper metal ring 32a is 16 mm, the height including the head is 46.5 mm, and the diameter of the lower metal ring 32b is 16 mm and the height is 10 mm. The diameters of the first piezoelectric element 41 and the second piezoelectric element 42 are 16 mm and 2.55 mm respectively. The total length of the vibrating body 3 is about 63 mm. The resonance frequency of the cylindrical body 32 also depends on the shape of the head 31, but in the case of half-wavelength resonance, it is about 45 kHz.

Since the cylindrical body 32 is structured such that the upper metal ring 32a and the lower metal ring 32b are fastened by the fastening bolts 34, a compressive bias is applied to the first piezoelectric element 41 and the second piezoelectric element 42. Therefore, the structure formed is that even if piezoelectric ceramics with low resistance to tensile stress are used for the first piezoelectric element 41 and the second piezoelectric element 42, and a large power is supplied to the first piezoelectric element 41 and the second piezoelectric element 42 to drive, the first piezoelectric element 41 and the second piezoelectric element 42 are not easily damaged. In addition, since the upper metal ring 32a and the lower metal ring 32b are at the same potential, it is necessary to sandwich an applied electrode between the two piezoelectric elements 4. The applied electrode is electrically connected to the terminal 43.

Furthermore, if it is not necessary to supply a large amount of power to the first piezoelectric element 41 and the second piezoelectric element 42 for driving, the cylindrical body 32 may be configured not to be fastened by the fastening bolts 34, but to have a structure in which one piezoelectric element 4 is sandwiched between the upper metal ring 32a and the lower metal ring 32b and bonded. Alternatively, the cylindrical body 32 may have only the upper metal ring 32a, and the piezoelectric element 4 may be bonded to the bottom surface of the upper metal ring 32a. Regardless of which structure the cylindrical body 32 adopts, the manufacturing cost can be reduced.

FIG3 is a cross-sectional view of a head 31 of the bubble generating device 1 according to the embodiment. The head 31 is disposed on the upper portion of the cylindrical body 32 and is in the shape of a truncated cone. In addition, the shape of the head 31 shown in FIG3 is an example and is not limited to a truncated cone shape, and may also be other shapes such as a cylindrical shape. In addition, the head 31 may be formed separately from the cylindrical body 32 and connected to the cylindrical body 32, or may be formed integrally with the cylindrical body 32.

The head 31 fixes the vibration plate 2 to the upper peripheral portion of the truncated cone shape by adhesive, welding, etc. The vibration plate 2 is formed of, for example, a resin plate, a metal plate, a Si or SOI (Silicon On Insulator) substrate, a porous ceramic plate, a glass plate, etc. Specifically, the outer diameter Rc of the vibration plate 2 is 9 mm, and the vibration plate 2 uses a plate whose thickness in the central portion is thinner than that in the peripheral portion, for example, the thickness in the peripheral portion is 0.15 mm, and the thickness in the central portion is 0.05 mm.

The vibration plate 2 is provided with 185 openings 2a in the central portion where the thickness becomes thinner. As shown in FIG3 , the cross-sectional shape of each opening 2a is a cone in which the opening diameter Ra of one side (liquid side) is larger than the opening diameter Rb of the other side (gas side) (Ra＞Rb). In addition, the cross-sectional shape of the opening 2a is not limited to a cone, and may be any shape such as a step shape as long as at least the opening diameter Ra of the liquid side is larger than the opening diameter Rb of the gas side. Specifically, the opening diameter Ra of the liquid side is about 70 μm, and the opening diameter Rb of the gas side is about 10 μm.

In the bubble generating device 1, the vibration plate 2 is mounted on the head 31 in such a manner that the opening diameter Ra with a large opening diameter is on the liquid side and the opening diameter Rb with a small opening diameter is on the gas side, and the vibration plate 2 is made to perform piston vibration that vibrates up and down, thereby enabling the liquid to generate fine bubbles 200 by natural air intake. On the contrary, when the vibration plate 2 is mounted on the head 31 in such a manner that the opening diameter Ra with a large opening diameter is on the gas side and the opening diameter Rb with a small opening diameter is on the liquid side, the liquid cannot generate fine bubbles 200 unless a gas pressure of 20 kPa to 40 kPa is applied. That is, in the opposite case, the bubble generating device 1 requires a compressor.

In the bubble generating device 1, it can be considered that when the vibration plate 2 is mounted on the head 31 in such a manner that the opening diameter Ra with a large opening diameter is the liquid side and the opening diameter Rb with a small opening diameter is the gas side, and when the vibration plate 2 is driven by a piston, a pumping effect of sending gas into the liquid by natural air intake is generated. This pumping effect can be explained based on Bernoulli's principle. Specifically, it can be considered that when the vibration plate 2 is mounted on the head 31 in such a manner that the opening diameter Ra with a large opening diameter is the liquid side and the opening diameter Rb with a small opening diameter is the gas side, and when the vibration plate 2 is driven by a piston, since the flow rate increases in the part with a small opening diameter, a part with a low pressure is formed, and a pumping effect of sucking gas up from the gas side is generated. In addition, it can also be considered that: when the vibration plate 2 is displaced in the downward direction due to the piston vibration, the gas entering from the opening portion 2a side with a small opening diameter diffuses along the cross-sectional shape of the opening portion 2a, and is pushed up by the tapered portion due to the displacement of the vibration plate 2 in the upward direction, thereby generating a pumping effect.

In the bubble generating device 1, in order to generate a pumping effect, it is preferred to perform piston vibration in which the vibration plate 2 vibrates up and down without bending. In the vibration plate 2 that is easy to bend, the longitudinal vibration is absorbed in the liquid, and it functions as a "soft spring", and the pumping effect is reduced. Therefore, it is preferred to perform piston vibration on the vibration plate 2 that is not easy to bend. The pumping effect generated in the bubble generating device 1 can be understood as a phenomenon caused by the flow of gas in a single direction from the gas side to the liquid side. In addition, the pumping effect generated in the bubble generating device 1 can be optimized by changing parameters such as the resonance frequency (vibration mode), the height of the head 31, the outer diameter Rc of the vibration plate 2, and the inner diameter Rd of the vibration plate 2.

As shown in Figure 1, when the bubble generating device 1 is set on the upper part of the liquid tank 10, liquid leakage from the opening portion 2a does not become a problem, but when the bubble generating device 1 is set on the bottom surface of the liquid tank 10, the vibration plate 2 is installed on the head 31 in such a manner that the opening diameter Ra with a larger opening diameter is on the liquid side and the opening diameter Rb with a smaller opening diameter is on the gas side, so liquid leakage from the opening portion 2a becomes a problem.

Therefore, the leakage of liquid from the opening 2a is studied. FIG4 is a schematic diagram for explaining the force generated near the opening 2a of the bubble generating device 1 according to the embodiment. FIG4(a) is a schematic diagram when the amount of liquid dripping from the opening 2a is small, and FIG4(b) is a schematic diagram when the amount of liquid dripping from the opening 2a is large.

First, let the opening diameter of an opening 2a on the gas side of the vibration plate 2 be Rb (m), let the depth of the liquid (here, water) be h (m), let the contact angle between the liquid and the interface of the opening 2a on the gas side be θ (°), and let the weight of the liquid dripping from the opening 2a be m (kg). Since the surface tension of the liquid (water) is γ = 0.728 N/m, an upward force F1 is generated in the figure. This force F1 is expressed as Formula 1.

F1＝2π×(Rb/2)×γ×cosθ

=0.728π(Rb)cosθ(N)···(Formula 1)

Since the pressure (water pressure) of the liquid applied to the opening 2a is 0.1 atmospheric pressure = 10130 N/ ^m2 relative to the depth 1m of the liquid and the cross-sectional area of the opening 2a is π×(Rb/2) ² ( ^m2 ), a force F2 is generated downward in the figure.

F2＝10130×h×π×(Rb/2) ² (N)···(Formula 2)

If the mass m of the dripping liquid is considered to be 4×π×(Rb/2) ² /3 (kg) even if it is a sphere with the largest opening diameter Rb, a downward gravity mg is generated in the figure. The gravity mg is expressed as Equation 3.

mg(max)＝9.8×π×(Rb) ² /3(N)···(Formula 3)

Therefore, as shown in FIG4 (a), as long as the relationship of F1>F2+mg holds, the liquid will not leak from the opening 2a of the vibration plate 2. Specifically, if the opening diameter of the opening 2a of the vibration plate 2 is considered to be a fine bubble (less than 100 μm) to an ultrafine bubble (less than 1 μm), the opening diameter Rb of the opening 2a becomes a region of 1× ^10-7 to 1× ^10-5 (m). If the contact angle is assumed to be 20°, the force F1 becomes a range of 2.15× ^10-7 to 2.15× ^10-5 (N), and even if the depth (h) of the liquid is assumed to be 1 m, the force F2 becomes a range of 7.96× ^10-11 to 7.96× ^10-7 (N). Since the gravity mg is in the range of 1.02× ^10-20 to 1.02× ^10-14 (N) when it is at its maximum, the relationship between the force F1 and the force F2 is generally used to determine whether the liquid leaks from the opening 2a of the vibration plate 2. In the case where the contact angle is 20°, as long as the opening diameter of the opening 2a is 26μm or less, the relationship of F1>F2+mg is satisfied, so the liquid will not leak from the opening 2a of the vibration plate 2. In addition, the result of making the opening diameter of the opening 2a 26μm or less is the case where the depth (h) of the liquid is 1m. If the depth (h) of the liquid is, for example, 0.1m (10cm), the liquid will not leak from the opening 2a of the vibration plate 2 even if the opening diameter of the opening 2a is 100μm.

Here, when the contact angle is 0°, when the relationship between the opening diameter Rb of the opening 2a, the depth h of the liquid, and the surface tension ratio γa of the liquid with the surface tension of water being 1 is obtained using Formulas 1 to 3, it can be obtained as in Formula 4.

Rb＜28×10 ^－6 ×(γa)/h···(Formula 4)

If the depth h of the liquid is 1m and the liquid is water (γa=1), the opening diameter Rb of the opening 2a is less than 28μm. That is, as long as the opening diameter Rb of the opening 2a is less than 28μm, the liquid will not leak from the opening 2a of the vibration plate 2, and a compressor for conveying air is not required, and the liquid can generate microbubbles 200.

In addition, even when the contact angle is assumed to be 80°, when using Formulas 1 to 3 to calculate the relationship between the opening diameter Rb of the opening 2a, the depth h of the liquid, and the surface tension ratio γa of the liquid where the surface tension of water is 1, it can also be calculated as in Formula 5.

Rb＜5× ^10-6 ×(γa)/h···(Formula 5)

If the depth h of the liquid is 1m and the liquid is water (γa=1), the opening diameter Rb of the opening 2a is less than 5μm. That is, as long as the opening diameter Rb of the opening 2a is less than 5μm, the liquid will not leak from the opening 2a of the vibration plate 2, and a compressor for conveying air is not required, and the liquid can generate microbubbles 200.

As for the vibration plate 2, as described above, a vibration plate with a thicker plate thickness and less prone to bending is more suitable. In addition, on the one hand, the opening diameter Rb of the opening portion 2a is related to the size of the generated microbubbles 200. In order to produce so-called microbubbles with a size of less than 100 μm that stay in the liquid for a long time, an opening diameter of less than 20 μm is preferred. On the other hand, the limit of the miniaturization and processing of the opening portion 2a is related to the aspect ratio obtained by the opening diameter Rb and the plate thickness of the vibration plate 2. In the processing with an aspect ratio exceeding 10, the manufacturing cost increases dramatically. Therefore, forming a small opening diameter Rb becomes a constraint on thickening the plate thickness of the vibration plate 2. In addition, by making the cross-sectional shape of the opening portion 2a conical, the constraint of thickening the plate thickness of the vibration plate 2 can be alleviated. However, by making the cross-sectional shape of the opening portion 2a conical, the spacing interval of the opening portion 2a, which is limited by the opening diameter Ra, becomes a new constraint during manufacturing.

Considering the manufacturing, it is simple to make the vibration plate 2 out of metal, but in the conventional etching technology, only an opening diameter of the same degree as the plate thickness can be formed, so it is necessary to use a special plating technology to form the vibration plate 2. Nevertheless, the aspect ratio obtained by the opening diameter Rb and the plate thickness of the vibration plate 2 is also limited to about 10, so if the opening diameter Rb is set to 10μm, the maximum thickness of the vibration plate 2 is also limited to 100μm. By using MEMS (Micro ElectroMechanical Systems) technology, in addition to making the cross-sectional shape of the opening 2a conical, the opening can also be processed by forming holes with different opening diameters from the front and back. In addition, if ceramics or glass are used as the material of the vibration plate 2, sandblasting technology and laser processing technology can be used for asymmetric hole processing. The opening diameter Rb of the opening 2a is preferably about 1μm to 20μm.

In the bubble generating device 1, in addition to the advantage that a compressor for conveying air is not required by realizing the pumping effect obtained by the vibration plate 2, there is also the advantage that the amount of gas in the generated micro-bubbles 200 can be controlled by the driving amount of the vibration plate 2. In particular, when a compressor is used, when the air pressure applied to the vibration plate 2 is high, the gas entering from the opening 2a is not separated and destroyed by the vibration plate 2 and is output as a larger bubble, which sometimes absorbs other micro-bubbles. In the bubble generating device 1, the pumping effect does not cause the situation where the gas is excessively supplied to the liquid, so there is also the advantage that complex control such as controlling the compressor is not required.

As described above, the bubble generating device 1 according to the embodiment is mounted on the liquid tank 10 and generates micro bubbles in the liquid in the liquid tank 10. The bubble generating device 1 includes: a vibration plate 2 having a plurality of openings 2a formed therein, a first surface of which is in contact with the liquid in the liquid tank 10 and a second surface of which is in contact with the gas; a vibration body 3 that supports the vibration plate 2; and a piezoelectric element 4 that is provided on the vibration body 3 and vibrates the vibration plate 2. The plurality of openings 2a formed in the vibration plate 2 each have a shape such that the opening diameter Ra on the liquid side is larger than the opening diameter Rb on the gas side.

Therefore, in the bubble generating device 1, with respect to the shapes of the plurality of opening portions 2a formed on the vibration plate 2, the opening diameter Ra on the liquid side is larger than the opening diameter Rb on the gas side. Therefore, it is possible to generate tiny bubbles in the liquid through natural air intake. Since there is no need for a compressor for forced supply of gas, the device can be miniaturized and cost-effective.

The bubble generation system 100 includes the bubble generation device 1 and the liquid tank 10. Thus, it is possible to achieve miniaturization and cost reduction of the bubble generation system.

(Variant 1)

In the bubble generating device 1 shown in FIG2 , the vibrating body 3 is described as a Langevin type vibrator, but it is not limited to this. As long as it is a vibrating body of piston vibration that causes the vibration plate 2 to vibrate up and down, it can be of any structure. FIG5 is a cross-sectional view of the bubble generating device 1A involved in the modification 1. In addition, the same reference numerals are marked for the same structure in the bubble generating device 1A shown in FIG5 as in the bubble generating device 1 shown in FIG2 , and the detailed description is not repeated. In addition, in the bubble generating device 1A shown in FIG5 , the illustration of the vibration plate 2 is omitted.

In the bubble generating device 1A, the vibration plate 2 is vibrated via the vibration body 3A by the piezoelectric element 4. The vibration body 3A shown in Fig. 5 includes a head portion 31, a spring portion 32c, a cylindrical body 33a, and a flange portion 34a.

The spring portion 32c is supported by the cylindrical body 33a at a position located outside the position of the support head 31. The cylindrical body 33a is cylindrical in shape. The cylindrical body 33a supports the spring portion 32c through one end. The end of the cylindrical body 33a on the side opposite to the spring portion 32c is supported by the flange portion 34a. The flange portion 34a is a plate-shaped member that supports the bottom surface of the cylindrical cylindrical body 33a and extends outward from the position supporting the cylindrical body 33a.

On the lower surface of the flange portion 34a, a hollow circular piezoelectric element 4 is provided to match the shape of the flange portion 34a. The piezoelectric element 4 vibrates in the through direction of the cylindrical body 33a (the up-down direction in the figure). The piezoelectric element 4 vibrates in the through direction of the cylindrical body 33a, thereby causing the spring portion 32c to vibrate in the through direction of the cylindrical body 33a, causing the head 31 to be displaced approximately uniformly in the up-down direction. In addition, the piezoelectric element 4 may also be provided on the upper surface of the flange portion 34a.

The inner side of the cylindrical body 33a is connected to the through hole 35 provided in the head 31, and the inner side of the cylindrical body 33a and the through hole 35 serve as an inlet portion for introducing gas into the vibration plate 2. A flange 36 is provided on the outer side of the cylindrical body 33a, and the bubble generating device 1A is fixed to the liquid tank 10 by the flange 36. The side surface of the cylindrical body 33a where the flange 36 is formed serves as a vibration node, and the vibration of the piezoelectric element 4 is not transmitted to the liquid tank 10, and the liquid side and the gas side can be separated by a support member joined to the flange 36.

(Variant 2)

FIG6 is a cross-sectional view of the bubble generating device 1B according to Modification 2. In addition, the same reference numerals are given to the same structures in the bubble generating device 1B shown in FIG6 as those in the bubble generating device 1 shown in FIG2 , and detailed descriptions thereof will not be repeated. In addition, in the bubble generating device 1B shown in FIG6 , the vibrating plate 2 is omitted from illustration.

In the bubble generating device 1B, the vibration plate 2 is vibrated via the vibration body 3B by the piezoelectric element 4. The vibration body 3B shown in Fig. 6 includes a head 31, a spring portion 32d, a cylindrical body 33b, and a weight portion 34b.

The spring portion 32d is supported by the cylindrical body 33b at a position located outside the position of the support head 31. The cylindrical body 33b is cylindrical in shape. The cylindrical body 33b supports the spring portion 32d through one end. The cylindrical body 33b has a counterweight portion 34b on the outside of the end portion on the side opposite to the spring portion 32d side. In addition, the cylindrical body 33b and the counterweight portion 34b are arranged at a position where the displacement of the side surface of the cylindrical body 33b is within a specified range when the spring portion 32d is vibrated by the piezoelectric element 4.

On the lower surface of the spring portion 32d, a hollow circular piezoelectric element 4 is provided to match the shape of the spring portion 32d. The piezoelectric element 4 vibrates in the through-hole 35 provided in the head portion 31 (the up-down direction in the figure). The piezoelectric element 4 vibrates in the through-hole 35, thereby vibrating the spring portion 32d in the through-hole 35, and displacing the head portion 31 substantially uniformly in the up-down direction.

The inner side of the cylindrical body 33b, the hole provided in the piezoelectric element 4, and the through hole 35 provided in the head 31 are connected to form an introduction portion for introducing gas from the inner side of the cylindrical body 33b through the through hole 35 to the vibration plate 2. Although not shown, a flange is provided on the outer side of the cylindrical body 33b, and the bubble generating device 1B is fixed to the liquid tank 10 by the flange. The side surface of the cylindrical body 33b formed with the flange becomes a node of vibration, and the vibration of the piezoelectric element 4 is not transmitted to the liquid tank 10, and the liquid side and the gas side can be separated by the support member connected to the flange.

The following describes a bubble generating system that fixes the bubble generating device 1B to the liquid tank 10. Fig. 7 is a schematic diagram of the bubble generating system for explaining the attachment position of the bubble generating device.

Fig. 8 is a schematic diagram of the bubble generating system for explaining another installation position of the bubble generating device. The same components of the bubble generating system shown in Figs. 7 and 8 as those of the bubble generating system 100 shown in Fig. 1 are denoted by the same reference numerals, and detailed description thereof will not be repeated.

In the bubble generating system 100A shown in FIG. 7( a ), the bubble generating device 1B is fixed to the bottom surface of the liquid tank 10 so that at least a portion of the vibrating body 3B supporting the vibrating plate 2 is immersed in the liquid of the liquid tank 10. In the bubble generating system 100B shown in FIG. 7( b ), the bubble generating device 1B is fixed to the side surface of the liquid tank 10 so that at least a portion of the vibrating body 3B supporting the vibrating plate 2 is immersed in the liquid of the liquid tank 10.

In the bubble generating system 100C shown in Figure 8, the installation position of the bubble generating device 1B is higher than the liquid surface of the liquid tank 10, and the bubble generating device 1B is fixed toward the bottom surface of the liquid tank 10 so that at least a portion of the vibrating body 3B supporting the vibration plate 2 is immersed in the liquid of the liquid tank 10.

7 and 8 illustrate the installation position of the bubble generating device 1B in the liquid tank 10, but the bubble generating device 1 and the bubble generating device 1A can also be installed in the same position relative to the liquid tank 10. In addition, compared with the bubble generating device 1 using the vibrating body 3 of the Langevin type vibrator, the bubble generating device 1A and the bubble generating device 1B can be easily installed on the bottom surface of the liquid tank 10 because the vibrating body 3A, 3B is less immersed in the liquid, and it is not necessary to select the surface of the liquid tank 10 for installation.

(Way)

(1) The bubble generating device disclosed in the present invention is a bubble generating device installed in a liquid tank and generates tiny bubbles in the liquid in the liquid tank, comprising: a vibration plate, which is formed with a plurality of openings, a first surface of which is in contact with the liquid in the liquid tank, and a second surface of which is in contact with the gas; a vibration body, which supports the vibration plate; and a piezoelectric element, which is arranged on the vibration body and causes the vibration plate to vibrate, wherein the opening diameter on the first surface side is larger than the opening diameter on the second surface side with respect to the shapes of the plurality of openings formed on the vibration plate.

According to the bubble generating device disclosed in the present invention, with respect to the shapes of the plurality of openings formed on the vibration plate, the opening diameter on the first surface side is larger than the opening diameter on the second surface side, so that tiny bubbles can be generated in the liquid through natural air intake. Since there is no need for a forced gas supply portion, the device can be miniaturized and cost-effective.

(2) According to the bubble generating device described in (1), each of the plurality of openings has a tapered cross-sectional shape. Thus, the bubble generating device can easily generate fine bubbles in the liquid by natural air intake.

(3) According to the bubble generating device described in (1) or (2), when the opening diameter of the first surface side is set to Rb, the distance from the vibration plate to the liquid surface of the liquid tank is set to h, and the surface tension ratio of the liquid whose surface tension is 1 is set to γa, the relationship of Rb<28× ^10-6 ×(γa)/h is satisfied. As a result, in the bubble generating device, the liquid does not leak from the opening of the vibration plate.

(4) According to the bubble generating device described in (1) or (2), when the opening diameter of the first surface side is set to Rb, the distance from the vibration plate to the liquid surface of the liquid tank is set to h, and the surface tension ratio of the liquid whose surface tension is 1 is set to γa, the relationship of Rb<5× ^10-6 ×(γa)/h is satisfied. As a result, in the bubble generating device, the liquid does not leak from the opening of the vibration plate.

(5) The bubble generating device according to any one of (1) to (4), wherein the vibrating body is formed of a Langevin type vibrator. This makes it easier for the bubble generating device to cause the vibrating plate to perform piston vibration in which the vibrating plate vibrates up and down.

(6) The bubble generating device according to any one of (1) to (4), wherein the vibrating body comprises: a head portion supporting the vibrating plate; a plate-shaped spring portion supporting the head portion; a cylindrical body supporting one end of the spring portion at a position located outside the position supporting the head portion; and a plate-shaped flange portion provided at the end of the cylindrical body and extending outward from the position of the cylindrical body, wherein the piezoelectric element is provided on a first surface of the flange portion on the cylindrical body side or on a second surface on the opposite side to the first surface. Thus, the bubble generating device can easily cause the vibrating plate to vibrate in a piston manner so as to vibrate up and down.

(7) The bubble generating device according to any one of (1) to (4), wherein the vibrating body includes: a head portion supporting the vibrating plate; a plate-shaped spring portion supporting the head portion; a cylindrical body supporting one end of the spring portion at a position located outside the position supporting the head portion; and a weight portion provided at an end of the cylindrical body, wherein the piezoelectric element is provided on a surface of the spring portion supported by the cylindrical body. Thus, the bubble generating device can easily cause the vibrating plate to vibrate in a piston manner so as to vibrate up and down.

(8) The bubble generation system of the present disclosure includes the bubble generation device described in any one of (1) to (7) and a liquid tank. Thus, the bubble generation system can achieve miniaturization and cost reduction of the device.

(9) According to the bubble generating system described in (8), the bubble generating device is fixed to the bottom surface or side surface of the liquid tank so that at least a part of the vibrating body supporting the vibrating plate is immersed in the liquid of the liquid tank. Thus, the bubble generating system can generate micro bubbles in the liquid from the bottom surface or side surface of the liquid tank.

(10) According to the bubble generating system described in (8), the bubble generating device is installed at a position higher than the liquid surface of the liquid tank and fixed toward the bottom surface of the liquid tank, so that at least a portion of the vibrating body supporting the vibrating plate is immersed in the liquid of the liquid tank. Thus, the bubble generating system can generate micro bubbles in the liquid from the upper surface of the liquid tank.

The embodiments disclosed herein are illustrative in all aspects and should not be construed as limiting the present invention. The scope of the present disclosure is indicated by the claims rather than the above description, and includes all modifications within the meaning and scope equivalent to the claims.

Description of Reference Numerals

1. 1A, 1B…bubble generating device; 2…vibrating plate; 2a…opening; 3. 3A, 3B…vibrating body; 4. 41, 42…piezoelectric element; 5…holding flange; 10…liquid tank; 20…controller; 31…head; 32. 33a, 33b…cylindrical body; 32a…upper metal ring; 32b…lower metal ring; 32c, 32d…spring part; 34…fastening bolt; 34a…flange; 34b…weight part; 35…through hole; 36…flange; 43, 44…terminals; 100, 100A~100C…bubble generating system; 200…bubble.

Claims (10)

1. A bubble generating device, which is installed in a liquid tank and generates micro bubbles in the liquid in the liquid tank, wherein: The bubble generating device comprises: a vibration plate having a plurality of openings formed therein, a first surface of the vibration plate being in contact with the liquid in the liquid tank, and a second surface of the vibration plate being in contact with the gas; a vibrating body supporting the vibrating plate; and A piezoelectric element is provided on the vibrating body to vibrate the vibrating plate. The plurality of openings formed in the vibration plate each have a shape in which an opening diameter on the first surface side is larger than an opening diameter on the second surface side. 2. The bubble generating device according to claim 1, wherein: Each of the plurality of openings has a tapered cross-sectional shape. 3. The bubble generating device according to claim 1 or 2, wherein: When the opening diameter of the first surface side is Rb, the distance from the vibration plate to the liquid surface of the liquid tank is h, and the surface tension ratio of the liquid whose surface tension is 1 is γa, the relationship of Rb<28×10 ⁻⁶ ×(γa)/h is satisfied. 4. The bubble generating device according to claim 1 or 2, wherein: When the opening diameter of the first surface side is Rb, the distance from the vibration plate to the liquid surface of the liquid tank is h, and the surface tension ratio of the liquid whose surface tension is 1 is γa, the relationship of Rb<5×10 ⁻⁶ ×(γa)/h is satisfied. 5. The bubble generating device according to any one of claims 1 to 4, wherein: The vibrating body is composed of a Langevin type vibrator. 6. The bubble generating device according to any one of claims 1 to 4, wherein: The vibrating body comprises: A head portion, supporting the vibration plate; a plate-shaped spring portion supporting the head; a cylindrical body that supports one end of the spring portion at a position located outside a position that supports the head portion; and The plate-shaped flange portion is provided at the end of the cylindrical body and extends outward from the position of the cylindrical body. The piezoelectric element is provided on a first surface of the flange portion on the cylindrical body side or a second surface on the opposite side to the first surface. 7. The bubble generating device according to any one of claims 1 to 4, wherein: The vibrating body comprises: A head portion, supporting the vibration plate; a plate-shaped spring portion supporting the head; a cylindrical body that supports one end of the spring portion at a position located outside a position that supports the head portion; and A counterweight portion is provided at the end of the cylindrical body, The piezoelectric element is provided on a surface of the spring portion supported by the cylindrical body. 8. A bubble generating system, comprising: The bubble generating device according to any one of claims 1 to 7; and The liquid tank. 9. The bubble generating system according to claim 8, wherein: The bubble generating device is fixed to the bottom surface or the side surface of the liquid tank so that at least a part of the vibrating body supporting the vibrating plate is immersed in the liquid of the liquid tank. 10. The bubble generating system according to claim 8, wherein: The bubble generating device is mounted above the liquid surface of the liquid tank and fixed toward the bottom surface of the liquid tank so that at least a portion of the vibrating body supporting the vibration plate is immersed in the liquid of the liquid tank.