JP7622818B2 - Air bubble generating device and air bubble generating system - Google Patents

Description

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

In recent years, microscopic bubbles have been used in a variety of fields, including water purification, wastewater treatment, and fish farming. For this reason, a bubble generator that generates microscopic bubbles has been developed (Patent Publication No. 6108526: Patent Document 1).

The bubble generator described in Patent Document 1 uses a piezoelectric element to generate fine bubbles. In this bubble generator, the up and down vibrations at the center of a flexurally vibrating vibration plate are used to break up and miniaturize bubbles generated in pores formed in the vibration plate.

Patent No. 6108526

One application of the bubble generator is, for example, in an on-board vehicle where it generates bubbles in diesel fuel to improve combustion in diesel engines. For on-board applications, high reliability is required, and the bubble generator needs to take measures to prevent the liquid (diesel) in the liquid tank from leaking from the joint between the liquid tank and the bubble generator.

Therefore, the object of the present disclosure is to provide a bubble generating device and a bubble generating system in which liquid in the liquid tank is less likely to leak from the connecting parts between the liquid tank and the bubble generating device.

A bubble generating device according to one aspect of the present disclosure is a bubble generating device that is attached to a liquid tank and generates fine bubbles in the liquid in the liquid tank, and includes a vibration plate having a plurality of openings formed therein and disposed at a position where one surface is in contact with the liquid in the liquid tank and the other surface is in contact with gas, a first cylindrical body that supports one end of the vibration plate, a plate-shaped spring portion that supports the other end of the first cylindrical body, a second cylindrical body that supports one end of the spring portion at a position outside the position that supports the first cylindrical body, and a spring portion that supports the other end of the second cylindrical body. The spring portion has a plate-shaped flange portion that supports the second cylindrical body and extends outward from the position of the second cylindrical body, a third cylindrical body that supports one end of the flange portion at a position outer than the position supporting the second cylindrical body, a weight portion provided at the other end of the third cylindrical body, and a piezoelectric element provided on the surface of the spring portion supported by the second cylindrical body and vibrating the spring portion, and the length from the central axis of the first cylindrical body to a position outside the third cylindrical body is within a range in which the amount of displacement of the second cylindrical body in the penetration direction is half compared to a configuration in which the third cylindrical body is not provided .

A bubble generating system according to another embodiment of the present disclosure comprises the aforementioned bubble generating device and a liquid tank.

According to the present disclosure, the bubble generating device is provided with a third cylindrical body and a weight portion, so that the amount of displacement of the joint with the liquid tank can be adjusted to be within a predetermined range, making it less likely for liquid in the liquid tank to leak from the joint between the liquid tank and the bubble generating device.

1 is a schematic diagram of an air bubble generating system in which an air bubble generating device according to an embodiment of the present invention is used. FIG. 1 is a perspective view of an air bubble generation device according to an embodiment of the present invention. 1 is a cross-sectional view of an air bubble generating device according to an embodiment of the present invention. FIG. 2 is a half cross-sectional view of the air bubble generation device according to the present embodiment. 11 is a half cross-sectional view of a type of air bubble generation device in which the position of the weight portion provided at the other end of the third cylindrical body is different. FIG. 13 is a graph showing the displacement in the Z direction of a target side surface of type A of the air bubble generation device according to the present embodiment. 13 is a graph showing the displacement in the X direction of a target side surface of type A of the air bubble generation device according to the present embodiment. 13 is a graph showing the change in average displacement amount with respect to the length of position D. 13 is a graph showing the change in the average displacement amount in the Z direction relative to the length of the position D for each type. 13 is a graph showing the change in moment of inertia with respect to the length of position D. 13 is a graph showing the displacement in the Z direction versus the density of the weight portion. 13A and 13B are diagrams showing an example in which the end of a spring portion is processed into a tapered shape.

(Embodiment)
Hereinafter, an air bubble generating device and an air bubble generating system according to the present embodiment will be described in detail with reference to the drawings. Note that the same or corresponding parts in the drawings are given the same reference characters and the description thereof will not be repeated.

First, Fig. 1 is a schematic diagram of a bubble generation system 100 in which the bubble generation device 1 according to the present embodiment is used. The bubble generation device 1 shown in Fig. 1 is provided at the bottom of a liquid tank 10 that stores liquid such as water, gasoline, or diesel, and is used in the bubble generation system 100 that generates fine bubbles 200 in the liquid in the liquid tank 10. The bubble generation system 100 can be applied to various systems, such as water purification devices, wastewater treatment devices, fish farming tanks, and fuel injection devices.

The liquid introduced into the liquid tank 10 varies depending on the system to which it is applied: for example, if it is a water purification device, the liquid will be water, but if it is a fuel injection device, the liquid will be liquid fuel. Furthermore, the liquid tank 10 only needs to be able to temporarily store liquid, and it also includes a pipe through which the liquid is introduced and through which the liquid always flows.

The bubble generating device 1 comprises a vibration plate 2, a cylindrical body 3, and a piezoelectric element 4. The bubble generating device 1 is provided in a hole opened in a part of the bottom of the liquid tank 10, and generates fine bubbles 200 from a plurality of pores (openings) formed in the vibration plate 2 by vibrating the vibration plate 2 protruding from the hole into the liquid side using the piezoelectric element 4.

The vibration plate 2 is formed, for example, from a resin plate, a metal plate, a Si or SOI (Silicon On Insulator) substrate, a porous ceramic plate, a glass plate, or the like. When the vibration plate 2 is formed from a glass plate, it may be formed, for example, from a glass plate that transmits ultraviolet light and deep ultraviolet light with a wavelength of 200 nm to 380 nm. By forming the vibration plate 2 from a glass plate that transmits ultraviolet light and deep ultraviolet light, a light source that emits ultraviolet light from the other side of the vibration plate 2 toward the liquid in the liquid tank 10 can be provided, and sterilization by ozone generation and sterilization by ultraviolet light irradiation can be performed simultaneously.

The vibration plate 2 has multiple pores formed, one side of which is in contact with the liquid (e.g., water) in the liquid tank 10, and the other side of which is in contact with the gas (e.g., air). In other words, in the bubble generator 1, the vibration plate 2 separates the liquid from the air, and by applying back pressure to the other side (in the direction of the arrow shown in Figure 1), the gas is sent through the multiple pores into the liquid in the liquid tank 10. The bubble generator 1 generates fine bubbles 200 by tearing off the gas sent through the multiple pores using the vibration of the vibration plate 2.

To explain in more detail, when gas tries to escape from the multiple pores, the surface tension of the liquid prevents the gas from entering the liquid, while the buoyancy of the gas acts to break that surface tension. The diameter of the bubbles 200 is determined by this balance, but the vibration of the diaphragm 2 creates a pulling effect from the walls of the pores, creating a state as if the surface tension had become smaller. As a result, in the early stage when the gas tries to escape from the multiple pores, the vibration of the diaphragm 2 tears the gas apart, and it is possible to generate fine bubbles 200 with a diameter that is about 1/10 of that when the vibration of the diaphragm 2 is not applied.

Although not shown, for example, multiple pores are formed in a 5 mm x 5 mm area provided in the center of a diaphragm 2 with a diameter of 14 mm. If the pore diameter is 1 μm and the spacing between pores is 0.25 mm, 441 pores can be formed in a 5 mm x 5 mm area.

In the bubble generating device 1, the vibration plate 2 is vibrated by the piezoelectric element 4 via the cylindrical body 3. FIG. 2 is an oblique view of the bubble generating device 1 according to this embodiment. FIG. 3 is a cross-sectional view of the bubble generating device according to this embodiment. The cylindrical body 3 shown in FIG. 1 includes a first cylindrical body 31, a spring portion 32, a second cylindrical body 33, a flange portion 34, a third cylindrical body 35, and a weight portion 36 as shown in FIG. 3. The bubble generating device 1 in FIG. 3 is a cross-sectional view cut at the center in the penetration direction of the second cylindrical body 33 (the vertical direction in the figure).

The end of the vibration plate 2 is held by the end of the cylindrical first cylindrical body 31. The vibration plate 2 is supported by the first cylindrical body 31 at a position where the penetration direction of the multiple pores formed in the vibration plate 2 is parallel to the vibration direction of the first cylindrical body 31. The end of the first cylindrical body 31 opposite the vibration plate 2 side is supported by the spring part 32. The spring part 32 is an elastically deformable plate-like member that supports the bottom surface of the cylindrical first cylindrical body 31 and extends toward the outside of the first cylindrical body 31. The spring part 32 does not have a hole penetrating the first cylindrical body 31 and the second cylindrical body 33, and has at least one communication part 320 that allows gas to flow into the first cylindrical body 31 from the side. By not providing a hole penetrating the first cylindrical body 31 and the second cylindrical body 33 in the spring portion 32, liquid leaking from the multiple pores formed in the vibration plate 2 does not leak below the second cylindrical body 33, and the piezoelectric element 4 can be protected from the liquid. Of course, the spring portion 32 may be hollow and circular and have a hole penetrating the first cylindrical body 31 and the second cylindrical body 33. Also, the communicating portion 320 does not have to be provided in the spring portion 32.

The spring portion 32 is supported by the second cylindrical body 33 at a position outside the position where the first cylindrical body 31 is supported. The second cylindrical body 33 has a cylindrical shape. The second cylindrical body 33 supports the spring portion 32 at one end. The end of the second cylindrical body 33 opposite the spring portion 32 side is supported by the flange portion 34. The flange portion 34 is a plate-shaped member that supports the bottom surface of the cylindrical second cylindrical body 33 and extends outward from the position where the second cylindrical body 33 is supported.

The flange portion 34 is supported by the third cylindrical body 35 at a position outside the position where the second cylindrical body 33 is supported. The third cylindrical body 35 has a cylindrical shape. The third cylindrical body 35 supports the flange portion 34 at one end. The other end of the third cylindrical body 35 has a cylindrical weight portion 36 on the outside. The third cylindrical body 35 and the weight portion 36 are provided at a position where the displacement of the side surface of the second cylindrical body 33 is within a predetermined range when the spring portion 32 is vibrated by the piezoelectric element 4.

A circular piezoelectric element 4 is provided on the underside of the spring portion 32 to match the shape of the spring portion 32. The piezoelectric element 4 vibrates in the penetration direction of the first cylindrical body 31 (up and down direction in the figure). When the piezoelectric element 4 vibrates in the penetration direction of the first cylindrical body 31, the spring portion 32 is vibrated in the penetration direction of the first cylindrical body 31, causing the first cylindrical body 31 to be displaced in the up and down direction approximately uniformly. Note that the piezoelectric element 4 may be a hollow circle with a hole in the center, rather than a circle that covers the entire inner diameter of the second cylindrical body 33.

The first cylindrical body 31, the spring portion 32, the second cylindrical body 33, the flange portion 34, the third cylindrical body 35, and the weight portion 36 are integrally formed. The first cylindrical body 31, the spring portion 32, the second cylindrical body 33, the flange portion 34, the third cylindrical body 35, and the weight portion 36 are made of, for example, a metal such as stainless steel or a synthetic resin. Preferably, a metal with high rigidity such as stainless steel is desirable. Note that the first cylindrical body 31, the spring portion 32, the second cylindrical body 33, the flange portion 34, the third cylindrical body 35, and the weight portion 36 may be formed as separate bodies or as separate members. There is no particular limit to the method of joining the diaphragm 2 and the first cylindrical body 31. The diaphragm 2 and the first cylindrical body 31 may be joined by adhesive, welding, fitting, press-fitting, or the like.

1, the bubble generator 1 is connected to a hole opened in a part of the bottom of the liquid tank 10 at the outer end of the spring part 32 or the outer surface of the second cylindrical body 33. By providing a third cylindrical body 35 and a weight part 36 as described below, the outer end of the spring part 32 or the outer surface of the second cylindrical body 33 is almost vibration-free even when the vibration plate 2 is vibrated by the piezoelectric element 4. Therefore, it is possible to vibrate only the vibration plate 2 without transmitting the vibration of the piezoelectric element 4 to the liquid tank 10. Furthermore, it is possible to make it difficult for the liquid in the liquid tank 10 to leak from the joint between the bubble generator 1 and the liquid tank 10.

The piezoelectric element 4 vibrates, for example, by polarization in the thickness direction. The piezoelectric element 4 is made of lead zirconate titanate piezoelectric ceramics. However, other piezoelectric ceramics such as (K,Na)NbO3 may also be used. Furthermore, a piezoelectric single crystal such as LiTaO3 may also be used. The piezoelectric element 4 vibrates in the penetration direction of the first cylindrical body 31 based on a drive signal from the controller 20 (see Figure 1).

In the bubble generating device 1, the vibration plate 2 in contact with the liquid is made of, for example, a glass plate, and the vibration plate 2 is vibrated by the piezoelectric element 4 via the cylindrical body 3, thereby completely separating the space into which the gas is introduced and the liquid. By completely separating the space into which the gas is introduced and the liquid, it is possible to prevent the electrical wiring of the piezoelectric element 4 from being immersed in the liquid. Furthermore, in the bubble generating device 1, even if a light source that emits ultraviolet light is provided for the liquid in the liquid tank 10, the light source can be provided in the space into which the gas is introduced, so that the electrical wiring of the light source can be prevented from being immersed in the liquid.

Next, the adjustment of the displacement amount of the outer surface of the second cylindrical body 33 (the joint part with the liquid tank 10) by providing the third cylindrical body 35 and the weight part 36 in the bubble generating device 1 will be described in detail. FIG. 4 is a half cross-sectional view of the bubble generating device according to this embodiment. The dashed line shown in FIG. 4 is a part passing through the central axis of the first cylindrical body 31. The inner position of the first cylindrical body 31 is position A, the inner position of the second cylindrical body 33 is position B, the outer position of the second cylindrical body 33 is position C, and the outer position of the third cylindrical body 35 is position D. The outer end of the spring part 32 or the outer surface of the second cylindrical body 33 is the side that joins with the liquid tank 10 and is the target side that suppresses the displacement amount within a predetermined range. The penetration direction of the second cylindrical body 33 (the up-down direction in the figure) is the Z direction, and the left-right direction in the figure is the X direction.

Figure 5 is a half cross-sectional view of a bubble generator 1 of a different type in which the position of the weight 36 provided at the other end of the third cylindrical body 35 is different. Figure 5(a) illustrates a type A bubble generator 1 in which the length from the central axis to the outside of the weight 36 is 7.0 mm. Figure 5(b) illustrates a type B bubble generator 1 in which the length from the central axis to the outside of the weight 36 is 7.5 mm. In Figures 5(a) and 5(b), the length from the central axis to the inside of the weight 36 changes according to the length from the central axis to the inside of the third cylindrical body 35. Figure 5(c) illustrates a type C bubble generator 1 in which the length from the central axis to the outside of the weight 36 is 7.0 mm and the inside position of the weight 36 is fixed at position B.

A simulation was performed in which the vibration plate 2 was vibrated by the piezoelectric element 4 for each of types A to C of bubble generator 1 shown in Figures 5(a) to 5(c), and the change in the amount of displacement of the target side surface was determined. Figure 6 is a graph showing the amount of displacement in the Z direction of the target side surface of type A of bubble generator 1. Figure 7 is a graph showing the amount of displacement in the X direction of the target side surface of type A of bubble generator 1. In Figures 6 and 7, the vertical axis represents the amount of displacement (unit: μm), and the horizontal axis represents the position on the target side surface (the position on the side surface of the second cylindrical body 33 from the spring portion 32 to the flange portion 34) (unit: mm). Furthermore, Figures 6 and 7 show the amount of displacement of the target side when the length from the central axis to position D (hereinafter simply referred to as the length of position D) is changed to 4.5 mm (D1), 5.25 mm (D2), 5.75 mm (D3), 6.0 mm (D4), 6.25 mm (D5), 6.5 mm (D6), 6.75 mm (D7), and 7.0 mm (D8).

Figure 8 is a graph showing the change in average displacement amount versus the length of position D. In Figure 8, the vertical axis represents the average displacement amount (unit: μm) and the horizontal axis represents the length of position D (unit: mm). Figure 8 is a graph in which the displacement amounts shown in Figures 6 and 7 are averaged for each length from the central axis to position D and plotted. As can be seen from Figure 8, in type A of bubble generating device 1, the displacement amounts in the X and Z directions become nearly 0 (zero) when the length of position D is 6.5 mm.

A similar simulation was performed for types B and C of bubble generator 1, and by performing the processing shown in Figures 6 to 8, it was found that, like type A, the amount of displacement in the X direction was smaller than the amount of displacement in the Z direction, and the longer the length of position D, the smaller the amount of displacement in the X direction. For type B of bubble generator 1, the amount of displacement in the X direction and the Z direction becomes nearly 0 (zero) when the length of position D is 6.3 mm. For type C of bubble generator 1, the amount of displacement in the X direction and the Z direction becomes nearly 0 (zero) when the length of position D is 6.1 mm.

Figure 9 is a graph showing the change in the average displacement in the Z direction with respect to the length of position D for each type. In Figure 9, the vertical axis is the average displacement in the Z direction (unit: μm), and the horizontal axis is the length of position D (unit: mm). Furthermore, Figure 9 illustrates a predetermined range S. The displacement of the displacement target range (side surface of the second cylindrical body 33) falling within the predetermined range S means, for example, that the average displacement falls within about half of the initial value. Specifically, in the example shown in Figure 9, the range of absolute values (approximately ±0.03 μm) of the average displacement in the Z direction, which is half the initial value (approximately +0.06 μm), is set as the predetermined range S. The range of position D that satisfies this predetermined range S is approximately ±0.4 mm = approximately ±3% for the strictest type C, and approximately ±0.7 mm = approximately ±5% for type A. The specified range S is set to a range that is half the amount of displacement when the third cylindrical body 35 is not present, but is not limited to this and may be any range that makes it difficult for the liquid in the liquid tank 10 to leak from, for example, the connection between the liquid tank 10 and the bubble generating device 1.

The positions at which the third cylindrical body 35 and the weight section 36 are provided can also be defined from the viewpoint of the moment of inertia. The moment of inertia Ia between positions A and B is the first moment of inertia occurring at one end of the second cylindrical body 33, and can be calculated as Ia=Ma(B ² -A ² )×(1/2). Here, Ma is the equivalent mass including the masses of the diaphragm 2, the first cylindrical body 31, and the spring section 32, taking into account the surface density, and A and B are the coordinates of positions A and B. On the other hand, the moment of inertia Ib between positions C and D is the second moment of inertia occurring at the other end of the second cylindrical body 33, and can be calculated as Ib=Mb(D ² -C ² )×(1/2). Here, Mb is the equivalent mass including the masses of the third cylindrical body 35 and the weight section 36, taking into account the surface density, and C and D are the coordinates of positions C and D.

The moment of inertia Ia between positions A and B does not depend on the type of bubble generator 1, but the moment of inertia Ib between positions C and D depends on the type of bubble generator 1. Figure 10 is a graph showing the change in moment of inertia with respect to the length of position D. In Figure 10, the vertical axis represents the moment of inertia (arbitrary units ARB) and the horizontal axis represents the length of position D (units mm). The moment of inertia Ia is a constant value (= 83565) since it does not depend on the type of bubble generator 1. On the other hand, the moment of inertia Ib depends on the type of bubble generator 1, so a graph is shown for each type.

As can be seen from Figure 10, the length of position D where the moment of inertia Ia and the moment of inertia Ib of each type coincide is close to the length of position D where the displacement in the Z direction shown in Figure 9 is nearly 0 (zero). Specifically, the length of position D where the moment of inertia Ia and the moment of inertia Ib coincide is approximately 6.6 mm for type A of bubble generating device 1, approximately 6.2 mm for type B, and approximately 5.9 mm for type C. Therefore, if the difference between the moment of inertia Ia and the moment of inertia Ib is within ±3%, the displacement amount of the displacement target range (side surface of second cylindrical body 33) will be within the specified range S as shown in Figure 9.

In addition, since the change in the graph of the moment of inertia Ib of type A is gradual, it can be seen that the tolerance of the range of position D is also wide, which is the same as the tendency of the range of position D of type A shown in Figure 9.

It will be explained that the displacement amount of the target side surface changes depending on the density of the weight portion 36. FIG. 11 is a graph showing the displacement amount in the Z direction versus the density of the weight portion 36. In FIG. 11, the vertical axis represents the displacement amount in the Z direction (unit: μm), and the horizontal axis represents the position on the target side surface (the position on the side surface of the second cylindrical body 33 from the spring portion 32 to the flange portion 34) (unit: mm). Furthermore, FIG. 11 illustrates the displacement amount of the target side surface when the weight portion 36 is Cu (density: 8.93 g/cm ³ ), the weight portion 36 is SUS (Steel Use Stainless) (density: 7.75 g/cm ³ ), and the weight portion 36 is duralumin (density: 2.79 g/cm ³ ). From FIG. 11, it can be seen that even if the positions of the third cylindrical body 35 and the weight portion 36 are the same, if the density is small, the displacement amount of the target side surface increases.

As described above, the bubble generating device 1 according to this embodiment is attached to the liquid tank 10 and generates fine bubbles in the liquid in the liquid tank 10. The bubble generating device 1 includes a vibration plate 2, a first cylindrical body 31, a spring portion 32, a second cylindrical body 33, a flange portion 34, a third cylindrical body 35, a weight portion 36, and a piezoelectric element 4. The vibration plate 2 has a plurality of openings formed therein, and is provided at a position where one surface is in contact with the liquid in the liquid tank 10 and the other surface is in contact with the gas. The first cylindrical body 31 supports the vibration plate 2 at one end. The spring portion 32 is plate-shaped and supports the other end of the first cylindrical body 31. The second cylindrical body 33 supports the spring portion 32 at one end at a position outside the position where the first cylindrical body 31 is supported. The flange portion 34 is plate-shaped, supports the other end of the second cylindrical body 33, and extends outward from the position of the second cylindrical body 33. The third cylindrical body 35 supports one end of the flange portion 34 at a position outside the position supporting the second cylindrical body 33. The weight portion 36 is provided at the other end of the third cylindrical body 35. The piezoelectric element 4 vibrates the spring portion 32. The third cylindrical body 35 and the weight portion 36 are provided at positions where the displacement amount of the side surface of the second cylindrical body 33 is within a predetermined range S when the spring portion 32 is vibrated by the piezoelectric element 4.

As a result, in the bubble generating device 1, by providing the third cylindrical body 35 and the weight portion 36, the amount of displacement of the joint with the liquid tank 10 can be adjusted to be within a predetermined range S, making it less likely for the liquid in the liquid tank 10 to leak from the joint between the liquid tank 10 and the bubble generating device 1, etc.

In addition, in the air bubble generating device 1, in the case where light oil leaks from the pores of the vibration plate 2 into the inside of the first cylindrical body 31, the spring part 32 does not have a hole penetrating from the first cylindrical body 31 to the second cylindrical body 33 so that the leaked light oil does not get on the piezoelectric element 4 and corrode it. Instead, as shown in FIG. 3, the spring part 32 has a communication part 320 that allows gas to flow into the first cylindrical body 31 from the side. In order to allow gas to flow in from the opening of this communication part 320, it is necessary to keep the displacement amount of the second cylindrical body 33 including the spring part 32 within a predetermined range S. Furthermore, when a structure is adopted in which the light oil accumulated at the bottom of the first cylindrical body 31 is released to the outside using the communication part 320, it is also necessary to keep the displacement amount of the second cylindrical body 33 including the spring part 32 within a predetermined range S in order to make the joint between the structure and the opening of the communication part 320 less susceptible to the vibration of the piezoelectric element 4.

It is preferable that the third cylindrical body 35 and the weight portion 36 are provided at a position where the difference between the first moment of inertia (Ia) generated at one end of the second cylindrical body 33 and the second moment of inertia (Ib) generated at the other end of the second cylindrical body 33 becomes a predetermined difference when the spring portion 32 is vibrated by the piezoelectric element 4. This allows the bubble generating device 1 to adjust the amount of displacement of the side surface of the second cylindrical body 33 to be within a predetermined range S when the spring portion 32 is vibrated by the piezoelectric element 4. In particular, it is preferable that the predetermined difference is within ±3%.

It is preferable that the piezoelectric element 4 is provided on the surface of the spring portion 32 on the side supported by the second cylindrical body 33, inside the position supported by the second cylindrical body 33. This allows the bubble generating device 1 to efficiently transmit vibrations caused by the piezoelectric element 4 to the first cylindrical body 31, and to vibrate the first cylindrical body 31 and the vibration plate 2 up and down in parallel.

It is preferable that the piezoelectric element 4 is provided on the surface of the spring portion 32 supported by the second cylindrical body 33, over the entire inner diameter of the second cylindrical body 33. This makes it possible to generate fine bubbles more effectively.

(Variation 1)
In the bubble generating device 1 according to the embodiment described above, the spring portion 32 is described as being plate-shaped, but the end of the spring portion 32 may be processed into a tapered shape. This is because the edge portion often has a large inclination of displacement, and by tapering, it is possible to form a holding plate in a portion where the inclination of the internal displacement amount is small. When two holding portions are provided on the side portion to increase the holding strength and to double prevent liquid leakage or to introduce gas into the space, it is possible to provide one plate on this tapered portion. Figure 12 is a diagram showing an example in which the end of the spring portion is processed into a tapered shape. Note that, in the bubble generating device 1a shown in Figure 12, the same components as those of the bubble generating device 1 shown in Figure 3 are assigned the same reference numerals and detailed description will not be repeated.

As shown in Fig. 12, the end of the spring portion 32a is processed into a tapered shape 32b. As shown in Fig. 12, by processing the corner of the end of the spring portion 32a closer to the vibration plate 2 into a tapered shape 32b, it is possible to make it difficult for the spring portion 32a to damp the vibration of the piezoelectric element 4.

(Variation 2)
1, the second cylindrical body 33 may be provided with a flange portion 33a, and the liquid tank 10 may be coupled to the second cylindrical body 33 via the flange portion 33a. This increases the airtightness between the bubble generator 1 and the liquid tank 10 in the bubble generation system 100 including the bubble generator 1 and the liquid tank 10.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

1, 1a: bubble generating device, 2: vibration plate, 3: cylindrical body, 4: piezoelectric element, 10: liquid tank, 20: controller, 31: first cylindrical body, 32: spring portion, 33: second cylindrical body, 33a: flange portion, 34: flange portion, 35: third cylindrical body, 36: weight portion, 100: bubble generating system, 200: bubbles.

Claims (6)

A bubble generating device that is attached to a liquid tank and generates fine bubbles in the liquid in the liquid tank,
a vibration plate having a plurality of openings formed therein, one surface of the vibration plate being in contact with the liquid in the liquid tank and the other surface of the vibration plate being in contact with the gas;
A first cylindrical body supporting one end of the diaphragm;
A plate-shaped spring portion supporting the other end of the first cylindrical body;
a second cylindrical body supporting one end of the spring portion at a position outside the position supporting the first cylindrical body;
a plate-shaped flange portion supporting the other end of the second cylindrical body and extending outward from the position of the second cylindrical body;
a third cylindrical body supporting one end of the flange portion at a position outside the position supporting the second cylindrical body;
A weight portion provided at the other end of the third cylindrical body;
a piezoelectric element provided on a surface of the spring portion supported by the second cylindrical body and vibrating the spring portion;
A bubble generating device, wherein the length from the central axis of the first cylindrical body to an outer position of the third cylindrical body is within a range in which the amount of displacement of the second cylindrical body in the penetration direction is half compared to a configuration in which the third cylindrical body is not provided . The bubble generating device described in claim 1, wherein the third cylindrical body and the weight portion are positioned such that when the spring portion is vibrated by the piezoelectric element, the difference between a first moment of inertia generated at one end of the second cylindrical body and a second moment of inertia generated at the other end of the second cylindrical body is within ±3% . The bubble generating device according to claim 1 or claim 2 , wherein the piezoelectric element is provided on the surface of the spring portion on the side supported by the second cylindrical body, further inward than the position supported by the second cylindrical body. 3. The air bubble generation device according to claim 1 , wherein the piezoelectric element is provided over the entire inner diameter of the second cylindrical body on a surface of the spring portion that is supported by the second cylindrical body. The air bubble generating device according to any one of claims 1 to 4 ,
The liquid tank. The bubble generation system according to claim 5 , wherein the bubble generation device is coupled to the liquid tank at a side surface of the second cylindrical body.

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