Microbubble Generator

Abstract

To generate favorable fine bubble regardless of a pipe diameter.SOLUTION: A fine bubble generator comprises: a first tapered portion 12 disposed on the inner surface of a flow passage forming space C and diametrically reduced toward a downstream side; a second tapered portion 15 diametrically enlarged toward its downstream side; an upstream side member 30 disposed facing the first tapered portion 12 the second tapered portion 15; and a downstream side member 40 disposed on the more downstream side than the upstream side member 30. The upstream side member 30 comprises on its outer surface, an upstream side outer periphery tapered portion 31 diametrically enlarged toward the downstream side, and constitutes a first flow passage portion 51 between the upstream side member 30 and the first tapered portion 12 and constitutes a second flow passage portion 52 between the upstream side member 30 and the second tapered portion 15. The downstream side member 40 comprises on its outer surface, a downstream side outer periphery tapered portion 43 diametrically enlarged toward the downstream side, and constitutes a fourth flow passage portion 54 between the downstream side member 40 and the second tapered portion 15. A third flow passage portion 53 having a large cross-sectional area and generating negative pressure in the flow passage is arranged between the second flow passage portion 52 and the fourth flow passage portion 54.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a micro-bubble generator for generating micro-bubbles in a liquid. [Background technology]

[0002] In recent years, there has been an increase in technologies that utilize microbubbles to purify water and promote the growth of organisms in aquaculture farms. Microbubbles are a collection of tiny bubbles present in a liquid, generally with a diameter of 100 μm or less. Microbubbles are also classified by their size; for example, bubbles with a diameter of 1 to 100 μm are called microbubbles, and even smaller bubbles are called micro-nanobubbles or nanobubbles.

[0003] As a device for generating fine bubbles, there are fine bubble generators described in Patent Documents 1 and 2, for example. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-28305 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-246441 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, conventional microbubble generators have the problem that the devices are large-scale. (1) Air supply is required. (2) Used only for small diameter pipes. There was a problem.

[0006] Patent Document 1 discloses a device having a jet nozzle, a cavitation generation chamber, and a discharge hole between the inlet and outlet of the device body. The inner diameter of the jet nozzle is narrowed to be smaller than the inner diameter of the inlet flow path, so that liquid introduced into the device body from the inlet flows forcefully from the jet nozzle into the cavitation generation chamber. This significantly reduces the static pressure in the cavitation generation chamber, causing cavitation and generating fine bubbles composed of air dissolved inside and vapor from the liquid. This technology does not require air supply, so it solves the problem (1) above. However, it cannot be used with large-diameter pipes, so it does not solve the problem (2) above.

[0007] Furthermore, Patent Document 2 discloses a technique in which a first acceleration member and a second acceleration member are provided within a pipe through which a liquid flows. The first acceleration member has an inclined surface on its outer circumferential surface that gradually narrows the internal cross-sectional area of ​​the pipe, thereby causing the liquid to flow at a high speed. The second acceleration member is located downstream of the first acceleration member and has a small-diameter constricted portion with a radial gap that generates negative pressure within the pipe. Negative pressure is generated as the high-speed liquid passes through the gap and the installation position of the terminal end of the second acceleration member, and this negative pressure is said to cause cavitation. However, this technique is also unable to be applied to large-diameter pipes, and the problem (2) above remains unresolved.

[0008] Therefore, an object of the present invention is to make it possible to generate good fine bubbles regardless of the pipe diameter. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides a casing having a flow path forming space connecting an upstream side and a downstream side, a first tapered portion provided on the inner surface of the flow path forming space and decreasing in diameter from the upstream side to the downstream side, a second tapered portion provided on the inner surface of the flow path forming space downstream of the first tapered portion and increasing in diameter from the upstream side to the downstream side, an upstream member arranged opposite the first tapered portion and the second tapered portion, and a downstream member arranged downstream of the upstream member, wherein the upstream member has a tapered portion on its outer surface. The micro-bubble generator employed has an upstream outer peripheral tapered section that expands in diameter from the upstream side toward the downstream side, and forms a first flow path section between itself and the first tapered section, and a second flow path section between itself and the second tapered section, and the downstream member has a downstream outer peripheral tapered section that expands in diameter from the upstream side toward the downstream side on its outer surface, and forms a fourth flow path section between itself and the second tapered section, and is provided with a third flow path section between the second flow path section and the fourth flow path section, which has a larger cross-sectional area of ​​the flow path than the second flow path section and the fourth flow path section and generates negative pressure within the flow path.

[0010] Here, a configuration can be adopted in which a connecting portion is provided that connects the upstream member and the downstream member, the outer surface of the connecting portion is located farther from the second tapered portion than the upstream outer peripheral tapered portion and the downstream outer peripheral tapered portion, and the third flow path portion is formed among the outer surface of the connecting portion, the second tapered portion, the downstream end face of the upstream member, and the upstream end face of the downstream member.

[0011] In this case, it is desirable that the angle formed between the downstream end face of the upstream member in the third flow path section and the generatrix of the upstream outer peripheral tapered section is an acute angle.

[0012] Furthermore, it is more desirable that the downstream end surface of the upstream member be an inclined surface that approaches the upstream side as it moves away from the second tapered portion.

[0013] Using a micro-bubble generator comprising any of these aspects or other micro-bubble generators, a valve device unit having any of the following configurations can be adopted: That is, a valve device unit with a micro-bubble generator, in which a first fluid passage is connected to the upstream side of the valve device and a second fluid passage is connected to the downstream side, the upstream end of a micro-bubble generator comprising any of the aspects described below is connected to an inlet pipe extending from the first fluid passage, and the downstream end of the micro-bubble generator is connected to an outlet pipe extending from the second fluid passage.

[0014] In the above aspect, further, in order to prevent the occurrence of cavitation downstream of the valve device, a configuration can be adopted in which a gas inlet pipe for introducing gas from the outside is connected to the second fluid passage.

[0015] In addition, a configuration can be adopted in which the connection position between the second fluid passage and the outflow pipe in the axial direction of the second fluid passage overlaps with the connection position between the second fluid passage and the gas introduction pipe in the axial direction of the second fluid passage. [Effects of the Invention]

[0016] The present invention can generate fine bubbles regardless of the pipe diameter. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention. [Figure 2] FIG. [Figure 3] FIG. 10 is a longitudinal sectional view showing a second embodiment of the present invention. [Figure 4] FIG. 4 is a perspective view showing the internal components of FIG. 3; [Figure 5] A perspective view of a valve device unit using a microbubble generator [Figure 6] Vertical cross-sectional view of the valve device DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment of the present invention will be described with reference to the drawings. Figures 1 and 2 show a first embodiment of the present invention, and Figures 3 and 4 show a second embodiment of the present invention.

[0019] The micro-bubble generator 10 can be easily installed by interposing a casing 11, which has a flow path forming space C connecting the upstream side and downstream side therein, between an upstream flow path 1 (inlet pipe 1) and a downstream flow path 2 (outlet pipe 2). The connection structure between the casing 11 and the upstream flow path and the downstream flow path 2 may be a press-fit structure as shown in Figure 1, or any other well-known structure may be used. A liquid such as water flows through the flow path forming space C.

[0020] The casing 11 has a first tapered section 12 that narrows in diameter from the upstream side to the downstream side along the flow path direction (hereinafter referred to as the axial direction of the flow path or simply the axial direction), and a second tapered section 15 that widens in diameter from the upstream side to the downstream side. The second tapered section 15 is located downstream of the first tapered section 12, and a ridge section 18 that protrudes at an obtuse angle toward the inner diameter side (toward the axial center of the flow path) between the first tapered section 12 and the second tapered section 15 is formed. The ridge section 18 has a smooth arc shape in any vertical cross section passing through the axial center. The first tapered section 12, the ridge section 18, and the second tapered section 15 form the inner surface of the flow path formation space C. The axial ends of the flow path formation space C are cylindrical surfaces 16, 17 that are continuous with the inner surfaces of the flow path spaces 3, 4 of the upstream flow path 1 and the downstream flow path 2, respectively.

[0021] The internal member 20 is disposed within this flow path forming space C. In this embodiment, the internal member 20 is molded as a separate member from the casing 11, and then the internal member 20 is fixed integrally to the casing 11 by a well-known method such as adhesion, but it may also be molded as a member integral with the casing 11.

[0022] The internal member 20 includes an upstream member 30 disposed opposite the first tapered portion 12 and the second tapered portion 15, and a downstream member 40 disposed downstream of the upstream member 30. The upstream member 30 is disposed opposite the first tapered portion 12 and the second tapered portion 15, while the downstream member 40 is disposed opposite only the second tapered portion 15. The upstream member 30 and the downstream member 40 are connected by a connecting portion 35. The connecting portion 35 is disposed opposite only the second tapered portion 15.

[0023] The upstream member 30 is a conical member having an upstream outer peripheral tapered portion 31 on its outer surface, the diameter of which increases from the upstream side to the downstream side, and a downstream end face 33 that closes the base of the upstream outer peripheral tapered portion 31. The tip (upstream end) 32 of the upstream outer peripheral tapered portion 31 has a sharp shape. However, the tip 32 may also have a smooth spherical shape. In this embodiment, the upstream outer peripheral tapered portion 31 has a single-gradient conical surface (tapered surface) that continues from the tip 32 of the upstream member 30 to the outer edge of the downstream end face 33. The upstream portion of the upstream outer peripheral tapered portion 31 forms a first flow path portion 51 with the opposing first tapered portion 12. The downstream portion of the upstream outer peripheral tapered portion 31 forms a second flow path portion 52 with the opposing second tapered portion 15. In this embodiment, the second tapered portion 15 and the second flow path portion 52 are configured so that their generatrixes are parallel to each other.

[0024] The first flow path section 51 has a configuration in which the cross-sectional area of ​​the flow path gradually decreases between the first tapered section 12, which gradually decreases in diameter along the flow direction of the flow path, and the upstream outer peripheral tapered section 31, which gradually increases in diameter along the flow direction of the flow path. The second flow path section 52 has a configuration in which the cross-sectional area of ​​the flow path slightly increases along the flow direction between the second tapered section 15, which gradually increases in diameter along the flow direction of the flow path, and the upstream outer peripheral tapered section 31, which gradually increases in diameter along the flow direction of the flow path. This is because the generatrix of the second tapered section 15 and the generatrix of the upstream outer peripheral tapered section 31 are parallel to each other, but the position of the space that constitutes the flow path therebetween gradually moves toward the outer diameter along the flow direction.

[0025] The downstream member 40 is a truncated cone-shaped member having a downstream outer peripheral tapered portion 43 on its outer surface, the diameter of which increases from the upstream side to the downstream side, a downstream end face 45 that closes the base of the downstream outer peripheral tapered portion 43, and an upstream end face 42 that is provided at the upstream end of the downstream outer peripheral tapered portion 43. In this embodiment, the downstream outer peripheral tapered portion 43 is a conical surface (tapered surface) with a single gradient that continues from the upstream end to the downstream end of the downstream member 40. A plurality of retaining portions 44 are intermittently provided along the circumferential direction of the downstream outer peripheral tapered portion 43. The downstream outer peripheral tapered portion 43 and the opposing second tapered portion 15 form a fourth flow path portion 54. The fourth flow path portion 54 has a shape in which the cross-sectional area of ​​the flow path increases slightly along the flow direction between the second tapered portion 15, which gradually increases in diameter along the flow direction of the flow path, and the downstream outer peripheral tapered portion 43, which gradually increases in diameter along the flow direction of the flow path. This is because, although the generatrix of the second tapered section 15 and the generatrix of the downstream outer peripheral tapered section 43 are parallel to each other, the position of the space that forms the flow path therebetween gradually moves toward the outer diameter side. However, the fourth flow path section 54 is divided into multiple flow path sections by multiple holding sections 44 that are provided intermittently along the circumferential direction.

[0026] As shown in Figures 1 and 2, the retaining portion 44 has a pair of side surfaces 44a that extend in an arc shape along the flow direction, and the upstream end 44c where the side surfaces 44a are connected forms a boat shape with an acute angle. This prevents the flow of fluid from being obstructed. In this embodiment, the downstream end of the retaining portion 44 also forms an acute angle. The top surface 44b of the retaining portion 44 abuts against the second tapered portion 15, holding the downstream member 40 so that its axis coincides with the axis of the casing 11. In this embodiment, the top surface 44b of the retaining portion 44 and the second tapered portion 15 are fixed by adhesive.

[0027] Between the second flow path section 52 and the fourth flow path section 54, there is provided a third flow path section 53, which has a larger cross-sectional area of ​​the flow path than the second flow path section 52 and the fourth flow path section 54, and generates negative pressure within the flow path by expanding the cross-sectional area.

[0028] The third flow path section 53 is formed between the outer surface 36 of the connecting section 35 connecting the upstream member 30 and the downstream member 40, the second tapered section 15, the downstream end face 33 of the upstream member 30, and the upstream end face 42 of the downstream member 40. The outer surface 36 of the connecting section 35 is located farther from the second tapered section 15 than the upstream outer peripheral tapered section 31 and the downstream outer peripheral tapered section 43. In other words, the outer surface 36 of the connecting section 35 is located closer to the axis of the flow path than the upstream outer peripheral tapered section 31 and the downstream outer peripheral tapered section 43. Therefore, when the fluid flows from the second flow path section 52 to the third flow path section 53, the cross-sectional area of ​​the flow path suddenly increases from the second flow path section 52 to the third flow path section 53, and this expansion of the cross section generates negative pressure within the flow path. This combination of features allows a large amount of cavitation to occur easily with a certain level of fluid pressure (water pressure), generating a large amount of fine bubbles made up of air dissolved inside and liquid vapor. In other words, it is possible to generate fine bubbles effectively in any diameter of flow path, not just in small diameter pipes as in the past.

[0029] Here, the cross-sectional area of ​​the first flow path section 51 gradually decreases along the flow direction of the fluid until the fluid reaches the third flow path section 53. This cross-sectional area decrease increases the force of the fluid flowing downstream. The subsequent second flow path section 52, although shorter in the axial direction of the flow path than the first flow path section 51, smoothly guides the fluid toward the third flow path section 53 by slightly expanding radially outward along the flow direction (slightly increasing the cross-sectional area of ​​the flow path). This configuration also contributes to the generation of a large amount of cavitation. In addition, the first tapered section 12 and the second tapered section 15, which are configured with opposite gradients, form a Venturi mechanism. The step that constitutes the third flow path section 53 (the step formed by the upstream outer peripheral tapered section 31 and downstream end face 33 of the upstream member 30 and the outer surface 36 of the connecting section 35, etc.) is provided immediately downstream of the Venturi mechanism, which also contributes to the generation of a large amount of cavitation.

[0030] Here, it is desirable that the angle formed between the downstream end face 33 of the upstream member 30 and the generatrix of the upstream outer peripheral tapered portion 31 in the third flow path section 53 be an acute angle. The flow path bends at an acute angle, which makes the generation of negative pressure more pronounced. Furthermore, in this first embodiment, the downstream end face 33 of the upstream member 30 is configured with an inclined surface 34 that approaches the upstream side as it moves away from the second tapered portion 15, thereby further reducing the acute angle (see acute angle α in FIG. 1 ), thereby increasing the degree of cavitation generation. In this embodiment, the inclined surface 34 is provided around the entire axis of the downstream end face 33, but the inclined surface 34 may be provided only in a partial direction around the axis of the downstream end face 33.

[0031] A second embodiment of the present invention will be described with reference to Figures 3 and 4. The main configuration of the device is the same as in the previous embodiment, so the following description will focus on the differences.

[0032] In the fine bubble generator 10 of this embodiment, the casing 11 and the downstream flow path 2 are connected via flanges 5 and 6. The flanges 5 and 6 are in surface contact with each other and fastened with bolts, nuts, etc. Furthermore, a packing is placed between the flanges 5 and 6, improving the liquid-tightness of the interior. The connection structure between the casing 11 and the upstream flow path 1 is the same as in the first embodiment, but the casing 11 and the upstream flow path 1 may also be connected by a flange similar to that on the downstream side.

[0033] The downstream member 40 of the internal member 20 has a downstream outer peripheral tapered portion 43 on its outer surface that expands in diameter from the upstream side to the downstream side, and an outer peripheral cylindrical surface 46 provided downstream of the downstream outer peripheral tapered portion 43. In addition, a plurality of retaining portions 44 are provided intermittently along the circumferential direction of the outer peripheral cylindrical surface 46. The retaining portions 44 fit into circumferential recesses 19 provided in the casing 11, thereby retaining the downstream member 40 to the casing 11.

[0034] Here, the angle formed by the downstream end face 33 of the upstream member 30 in the third flow path section 53 and the generatrix of the upstream outer peripheral tapered section 31 is an acute angle (see acute angle β in FIG. 3 ). However, unlike the first embodiment, the downstream end face 33 does not have the inclined surface 34. However, in this second embodiment, by providing the inclined surface 34 on the downstream end face 33, the acute angle β can be made even smaller, to an acute angle α (α<β).

[0035] In each of the above embodiments, the upstream member 30, downstream member 40, and connecting portion 35 that constitute the internal member 20 are molded as a single integrated member, but these may also be molded as separate members that are then connected to each other to form a single integrated member.

[0036] The configuration of a valve device unit using the fine bubble generator 10 according to the above embodiments will be described.

[0037] 5, a first fluid passage 74 is connected to the upstream side of the valve device 60, and a second fluid passage 77 is connected to the downstream side. From the upstream side to the downstream side, the first fluid passage 74, the valve device 60, and the second fluid passage 77 form part of the fluid passage. In this embodiment, the fluid passage is assumed to be a drainage channel for discharging water.

[0038] The upstream end of the fine-bubble generator 10 is connected to an inlet pipe 1 drawn out from the first fluid passage 74. The downstream end of the fine-bubble generator 10 is connected to an outlet pipe 2 drawn out from the second fluid passage 77. In other words, the fluid passage passing through the valve device 60 and the fluid passage passing through the fine-bubble generator 10 are arranged on separate routes, i.e., in parallel.

[0039] Here, the pipe diameters (diameters) of the inlet pipe 1 and the outlet pipe 2 are determined to be a size that allows the necessary amount of micro-bubbles to be introduced into the fluid (water in this embodiment) flowing downstream from the second fluid passage 77. Normally, the pipe diameters (diameters) of the inlet pipe 1 and the outlet pipe 2 are sufficiently smaller than the pipe diameters (diameters) of the first fluid passage 74 and the second fluid passage 77. In this embodiment, as shown in FIG. 5, two outlet pipes 2 are installed in parallel, so that the fluid containing micro-bubbles flowing out of the micro-bubble generator 10 is smoothly dispersed into the fluid in the second fluid passage 77. There may be one outlet pipe 2, or multiple outlet pipes, such as two or more, as in the embodiment, can be provided as needed.

[0040] 6 shows an example of a valve device 60. Here, a flow control valve, in particular a sleeve valve (link sleeve valve), is used as the valve device 60. However, various other valve devices 60, such as an eccentric butterfly valve, can also be used as the valve device 60.

[0041] As shown in Figure 6, the valve device 60, which is a sleeve valve, has a cylindrical valve box 61 with a first fluid passage 74, which is the inlet side, connected to one end and a second fluid passage 77, which is the outlet side, connected to the other end. A cylinder 62, the side of which is closed to the first fluid passage 74, is provided coaxially within the valve box 61. A sleeve valve element 63, the peripheral wall of which has multiple holes (multiple valve holes) 63c, is provided in the cylinder 62 so as to be movable coaxially. A valve shaft 65 is inserted into the valve box 61 perpendicular to the direction of fluid flow. The valve shaft 65 is rotated about its axis by a handle or driver (not shown).

[0042] The sleeve valve element 63 is cylindrical, with its upstream side being a guide portion 63a that fits and slides within the cylinder 62, and its downstream side being a porous portion 63b with multiple valve holes 63c arranged in a spiral around its outer periphery. The guide portion 63a has a slightly larger diameter than the porous portion 63b, and the boundary between them forms a step that slopes downward toward the downstream side. This step forms the valve seat 64a of the sleeve valve element 63. As the sleeve valve element 63 moves, the valve seat 64a comes into contact with the valve box valve seat 64b, which has the same inclined surface, thereby closing the sleeve valve.

[0043] A crank 67a is fixed to the valve stem 65 in the radial direction (around the axis), and a connecting rod 67b is rotatably connected to the tip of the crank 67a, constituting a link mechanism 67. The tip of the connecting rod 67b is rotatably connected to a boss 68 of the sleeve valve disc 63. Therefore, when the valve stem 65 rotates around its axis, the sleeve valve disc 63 moves along the flow direction of the flow passage (left and right in FIG. 6) via the link mechanism 67. As a result, the axial movement of the sleeve valve disc 63 sequentially opens and closes the valve holes 63c of the sleeve valve disc 63. In the open valve state, where the valve seat 64a and the valve box valve seat 64b are not in contact with each other, fluid from the first fluid passage 74 flows from the gap 66 between the inner circumferential surface of the valve box 61 and the outer circumferential surface of the cylinder 62 through the valve holes 63c into the sleeve valve disc 63 and then out to the second fluid passage 77. 6, the axis of the valve shaft 65, i.e., the fixing point (center of rotation) of the crank 67a to the valve shaft 65, is located on the piping center line c of the valve body 61, and the connection point a between the crank 67a and the connecting rod 67b and the connection point b between the connecting rod 67b and the connecting rod 68 are shifted (offset) in one direction from the piping center line c. The locations of the fixing point (center of rotation) of the crank 67a to the valve shaft 65, the connection point a, and the connection point b, or the configuration of the link mechanism 67 can be changed as appropriate.

[0044] In this embodiment, in order to prevent the occurrence of cavitation downstream of the valve device 60, a gas introduction pipe 78 that introduces gas from outside is connected to the second fluid passage 77. The gas introduction pipe 78 rises upward from the second fluid passage 77 and is connected to a gas supply source outside the pipe. In this embodiment, it is assumed that air will be introduced into the pipe, and the upstream side of the gas introduction pipe 78 is open to the atmosphere. Note that an on-off valve may be attached to the gas introduction pipe 78 as necessary.

[0045] Here, the connection position of the second fluid passage 77 and the outflow pipe 2 in the axial direction of the second fluid passage 77 and the connection position of the second fluid passage 77 and the gas introduction pipe 78 in the axial direction of the second fluid passage 77 are set to overlap with each other in the axial direction of the second fluid passage 77. In FIG. 5 , the pipe axis of the outflow pipe 2 at the connection portion to the second fluid passage 77 is indicated by the symbol x, and the pipe axis of the gas introduction pipe 78 at the connection portion to the second fluid passage 77 is indicated by the symbol y. In the embodiment of FIG. 5 , the pipe axis x of the outflow pipe 2 at the connection portion to the second fluid passage 77 and the pipe axis y of the gas introduction pipe 78 at the connection portion to the second fluid passage 77 are aligned with the axial direction of the second fluid passage 77. This further smoothes the dispersion of the fluid containing microbubbles into the fluid in the second fluid passage 77. However, even if the pipe axis x and the pipe axis y do not completely coincide, the above-mentioned effect of smooth dispersion can be expected as long as the opening range (connection position) of the outflow pipe 2 to the second fluid passage 77 and the opening range (connection position) of the gas introduction pipe 78 to the second fluid passage 77 overlap in the pipe axis direction of the second fluid passage 77. Note that if the valve device 60 is installed near the end of the flow path or if there is little risk of cavitation occurring, the installation of the gas introduction pipe 78 can be omitted. Here, the fine-bubble generator 10 is not limited to the embodiments and the aspects shown in Figures 1 to 4, and various other fine-bubble generating devices, fine-bubble generators, etc. can also be applied. [Explanation of symbols]

[0046] 1 Upstream flow path (inflow pipe) 2 Downstream flow path (outflow pipe) 10 Microbubble generator 11 Casing 12 First tapered section 15 Second tapered section 20 Internal components 30 Upstream member 31 Upstream outer tapered section 33 Downstream end face 34 Slope 35 Connecting part 36 Exterior 40 Downstream member 42 Upstream end face 43 Downstream outer tapered section 51 First flow path section 52 Second flow path section 53 Third flow path section 54 Fourth flow path section 60 Valve gear 74 1st fluid passage 77 Second fluid passage 78 Gas introduction pipe

Claims

1. A casing (11) having a flow path forming space (C) connecting the upstream side and the downstream side, Within the casing (11), there is provided a first tapered portion (12) provided on the inner surface of the flow path forming space (C) and having a diameter that decreases from the upstream side toward the downstream side; a second tapered portion (15) provided downstream of the first tapered portion (12) on the inner surface of the flow path forming space (C) and expanding in diameter from the upstream side toward the downstream side; an upstream member (30) disposed opposite the first tapered portion (12) and the second tapered portion (15); a downstream member (40) disposed downstream of the upstream member (30); Equipped with The upstream member (30) has an upstream outer peripheral tapered portion (31) on its outer surface, the diameter of which increases from the upstream side toward the downstream side, and forms a first flow path portion (51) between itself and the first tapered portion (12) and a second flow path portion (52) between itself and the second tapered portion (15), The downstream member (40) has a downstream outer peripheral tapered portion (43) on its outer surface, the diameter of which increases from the upstream side toward the downstream side, and forms a fourth flow path portion (54) between itself and the second tapered portion (15); a micro-bubble generator (10) including a third flow path section (53) between the second flow path section (52) and the fourth flow path section (54), the third flow path section (53) having a larger cross-sectional area of ​​the flow path than the second flow path section (52) and the fourth flow path section (54) and generating a negative pressure in the flow path, A first fluid passage (74) is connected to the upstream side of the valve device (60), and a second fluid passage (77) is connected to the downstream side thereof; The upstream end of the fine-bubble generator (10) is connected to an inlet pipe (1) drawn out from the first fluid passage (74), and the downstream end of the fine-bubble generator (10) is connected to an outlet pipe (2) drawn out from the second fluid passage (77).

2. A first fluid passage (74) is connected to the upstream side of the valve device (60), and a second fluid passage (77) is connected to the downstream side thereof; The upstream end of a fine-bubble generator (10) is connected to an inlet pipe (1) drawn out from the first fluid passage (74), and the downstream end of the fine-bubble generator (10) is connected to an outlet pipe (2) drawn out from the second fluid passage (77), A valve device unit with a fine bubble generator, in which a gas introduction pipe (78) for introducing gas from the outside is connected to the second fluid passage (77) in order to prevent the occurrence of cavitation downstream of the valve device (60).

3. 3. The valve device unit with a micro-bubble generator according to claim 2, wherein a connection position between the second fluid passage (77) and the outflow pipe (2) in the axial direction of the second fluid passage (77) overlaps with a connection position between the second fluid passage (77) and the gas introduction pipe (78) in the axial direction of the second fluid passage (77).

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