Microbubble Generator

Abstract

To provide technique capable of excellently generating microbubbles with a simple structure.SOLUTION: A microbubble generator may include a first member having a first recessed portion that forms a part of a flow path, and a second member having a second recessed portion that forms another part of the flow path, where the first and second members are assembled such that the first and second recessed portions face each other. The first and second recessed portions may face each other in a direction perpendicular to the axial direction of the flow path, thereby forming the flow path. The flow path may include a diameter-reducing section that narrows from the upstream side toward the downstream side, and a diameter-expanding section that is downstream of the diameter-reducing section and widens from the upstream side toward the downstream side. The first member may include a first protrusion that protrudes from the inner surface of the first recessed portion into the flow path in the diameter-expanding section. The second member may include a second protrusion that protrudes from the inner surface of the second recessed portion into the flow path in the diameter-expanding section of the flow path.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a microbubble generator. [Background technology]

[0002] Patent Document 1 discloses a micro-bubble generator that generates micro-bubbles in a liquid flowing through a flow path. In the micro-bubble generator of Patent Document 1, the flow path through which the liquid flows includes a reduced diameter section whose diameter decreases from the upstream side to the downstream side, and an increased diameter section whose diameter increases from the upstream side to the downstream side downstream of the reduced diameter section. The micro-bubble generator of Patent Document 1 also includes an internal member that is arranged within the flow path from the reduced diameter section to the increased diameter section of the flow path. In the micro-bubble generator of Patent Document 1, micro-bubbles are generated by the internal member that is arranged within the flow path. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-147980 Summary of the Invention [Problem to be solved by the invention]

[0004] The micro-bubble generator of Patent Document 1 has a complicated configuration because an internal member is disposed within the flow path. Furthermore, in the micro-bubble generator of Patent Document 1, the internal member is inserted into the flow path from the expanded diameter portion of the flow path. However, if the expanded diameter portion is long, the internal member must be moved a long distance within the flow path to be positioned between the reduced diameter portion and the expanded diameter portion. This makes the process of inserting the internal member into the flow path complicated.

[0005] The present specification provides a technique that can effectively generate fine bubbles with a simple configuration. [Means for solving the problem]

[0006] A first aspect of the present technology relates to a micro-bubble generator that generates micro-bubbles in a liquid flowing through a flow path. The micro-bubble generator may include a first member having a first recess that constitutes a part of the flow path when viewed in a cross section perpendicular to the axial direction of the flow path, and a second member having a second recess that constitutes another part of the flow path, the second member being combined with the first member with the first recess and the second recess facing each other. The first recess and the second recess may constitute the flow path by facing each other in a direction perpendicular to the axial direction of the flow path. When viewed in a cross section parallel to the axial direction of the flow path, the flow path may include a reduced-diameter portion that decreases in diameter from the upstream side to the downstream side, and an expanded-diameter portion that increases in diameter from the upstream side to the downstream side downstream of the reduced-diameter portion. The first member may include a first convex portion that protrudes into the flow path from an inner surface of the first recess at the expanded-diameter portion of the flow path. The second member may include a second convex portion that protrudes into the flow path from an inner surface of the second recess at the expanded-diameter portion of the flow path.

[0007] With this configuration, a micro-bubble generator can be produced simply by combining the first member and the second member with the first recess and the second recess facing each other. In this micro-bubble generator, micro-bubbles are generated when the liquid flowing through the flow path hits the first convex portion or the second convex portion. With the above configuration, the first convex portion and the second convex portion protrude from the inner surfaces of the first recess and the second recess, respectively, which face each other, so that micro-bubbles can be generated on both the first recess side and the second recess side of the flow path. Therefore, micro-bubbles can be generated in a balanced manner on both the first recess side and the second recess side of the flow path. As described above, with the above configuration, micro-bubbles can be generated well with a simple configuration.

[0008] In a second aspect, in the first aspect, the first convex portion and the second convex portion may face each other across a center of the flow channel.

[0009] With this configuration, fine bubbles can be effectively generated near the center of the flow channel.

[0010] In a third aspect, in the first or second aspect, the first convex portion may extend in a first direction from an upstream side to a downstream side of the flow channel, and the second convex portion may extend in a second direction different from the first direction from the upstream side to a downstream side of the flow channel.

[0011] With this configuration, the micro-bubbles generated by the first convex portion and the micro-bubbles generated by the second convex portion spread in different directions toward the downstream side of the flow channel, thereby enabling the micro-bubbles to spread throughout the entire flow channel.

[0012] In a fourth aspect, in any one of the first to third aspects, the first convex portion may have a first side surface extending along the axial direction of the flow channel and a second side surface extending along a direction inclined with respect to the axial direction of the flow channel.

[0013] With this configuration, the first and second side surfaces can change the direction of the liquid flow, thereby agitating the liquid flowing through the flow path, or allowing the liquid to flow smoothly downstream of the flow path.

[0014] In a fifth aspect, in the fourth aspect, the first side surface and the second side surface may be configured to approach each other from the upstream side to the downstream side of the flow channel.

[0015] This configuration allows the liquid to flow smoothly downstream of the flow path.

[0016] In a sixth aspect, in any one of the first to fifth aspects, the first member or the second member may have a suction hole downstream of the reduced diameter portion of the flow path that sucks gas or liquid into the flow path.

[0017] With this configuration, by sucking gas into the flow path through the suction hole, microscopic bubbles can be generated in the liquid in the flow path. Also, by sucking liquid into the flow path through the suction hole, additional liquid can be added to the liquid in the flow path. The additional liquid may be the same liquid as the liquid in the flow path or a different liquid. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 2 is a side view of the micro-bubble generator according to the embodiment. [Figure 2] Cross-sectional view of II-II in Figure 1. [Figure 3] Cross-sectional view of III-III in Figure 2. [Figure 4] IV-IV cross section of Figure 1. [Figure 5] FIG. 4 is a diagram showing the relationship between a first convex portion and a second convex portion in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] A micro-bubble generator according to an embodiment will be described with reference to the drawings. As shown in Figs. 1 to 4, the micro-bubble generator 2 according to the embodiment comprises a first member 10 and a second member 40. The micro-bubble generator 2 is configured by combining the first member 10 and the second member 40. The first member 10 and the second member 40 are fastened together by a plurality of bolts 200 while facing each other. The facing surfaces (contact surfaces) of the first member 10 and the second member 40 are flat. The first member 10 and the second member 40 are made of, for example, metal.

[0020] The micro-bubble generator 2 also has a flow path 70 formed between the first member 10 and the second member 40. The flow path 70 is formed where the first member 10 and the second member 40 face each other. The micro-bubble generator 2 is a device that generates micro-bubbles in a liquid flowing through the flow path 70. The liquid flowing through the flow path 70 is, for example, water, but may be something other than water (for example, oil, etc.). The type of liquid is not particularly limited. The flow path 70 of the micro-bubble generator 2 functions as a Venturi tube. Since Venturi tubes are already known, a detailed description thereof will be omitted.

[0021] The micro-bubble generator 2 further includes an inlet-side connecting part 32 and an outlet-side connecting part 34. The inlet-side connecting part 32 is provided at one end (the upstream end of the flow path 70) of the first member 10 and the second member 40. The outlet-side connecting part 34 is provided at the other end (the downstream end of the flow path 70) of the first member 10 and the second member 40. The inlet-side connecting part 32 and the outlet-side connecting part 34 are formed, for example, by cutting the first member 10 and the second member 40. An introduction pipe 82 for introducing liquid into the flow path 70 is connected to the inlet-side connecting part 32. An outlet pipe 84 for guiding liquid from the flow path 70 is connected to the outlet-side connecting part 34.

[0022] The first member 10 and the second member 40 will be described in detail. The first member 10 has a first recess 12 that constitutes a part of the flow path 70. The first recess 12 is produced, for example, by cutting a metal member (the first member 10). When viewed in a cross section perpendicular to the axial direction of the flow path 70, the first recess 12 constitutes, for example, the upper half of the flow path 70 (see FIG. 4). When viewed in a cross section perpendicular to the axial direction of the flow path 70, the first recess 12 is configured, for example, in a semicircular shape. In a modified example, the first recess 12 may constitute more than half of the range of the flow path 70, or may constitute less than half of the range of the flow path 70.

[0023] The second member 40 has a configuration similar to that of the first member 10. Specifically, the second member 40 has a second recess 42 that constitutes a part of the flow path 70. The second recess 42 is produced, for example, by cutting a metal member (the second member 40). When viewed in a cross section perpendicular to the axial direction of the flow path 70, the second recess 42 constitutes, for example, the lower half of the flow path 70 (see FIG. 4). When viewed in a cross section perpendicular to the axial direction of the flow path 70, the second recess 42 is configured, for example, in a semicircular shape. In a modified example, the second recess 42 may constitute more than half of the range of the flow path 70, or may constitute less than half of the range of the flow path 70.

[0024] The flow path 70 is formed by combining the first recess 12 of the first member 10 and the second recess 42 of the second member 40. The first recess 12 and the second recess 42 face each other. The flow path 70 is formed, for example, in a circular shape when viewed in a cross section perpendicular to the axial direction of the flow path 70 (see FIG. 4). In a modified example, the shape of the flow path 70 may be elliptical or the like.

[0025] When viewed in a cross section parallel to the axial direction of the flow path 70, the flow path 70 includes a reduced diameter section 72, an intermediate section 76, an expanded diameter section 74, and an outlet section 78 (see FIGS. 2 and 3). The reduced diameter section 72, the intermediate section 76, the expanded diameter section 74, and the outlet section 78 are arranged in this order from the upstream side to the downstream side of the flow path 70.

[0026] The diameter of the reduced diameter section 72 decreases (the inner diameter decreases) from the upstream side to the downstream side of the flow path 70. The reduced diameter section 72 is configured in a cylindrical shape that is approximately frustum-shaped. The diameter of the expanded diameter section 74 increases (the inner diameter increases) from the upstream side to the downstream side of the flow path 70. The expanded diameter section 74 is configured in a cylindrical shape that is approximately frustum-shaped.

[0027] The intermediate section 76 is provided between the reduced diameter section 72 and the expanded diameter section 74. The intermediate section 76 is configured in a substantially cylindrical shape. The inner diameter of the intermediate section 76 is smaller than the inner diameter of the reduced diameter section 72 and smaller than the inner diameter of the expanded diameter section 74. The intermediate section 76 is sometimes called the constriction section of a Venturi tube. In the intermediate section 76, the flow velocity of the liquid flowing through the flow path 70 increases and the pressure decreases.

[0028] The outlet portion 78 is provided downstream of the expanded diameter portion 74 in the flow path 70. The outlet portion 78 is configured in a substantially cylindrical shape. The inner diameter of the outlet portion 78 is larger than the inner diameter of the expanded diameter portion 74.

[0029] The first member 10 further includes a suction hole 100 communicating with the intermediate portion 76 of the flow path 70. The suction hole 100 penetrates the first member 10 and extends, for example, in a direction perpendicular to the axial direction of the flow path 70. The inner diameter of the suction hole 100 is sufficiently smaller than the inner diameter of the intermediate portion 76 of the flow path 70. In the micro-bubble generator 2, when liquid flows through the intermediate portion 76 of the flow path 70, external gas (e.g., air) is sucked into the flow path 70 through the suction hole 100. This introduces the external gas into the liquid flowing through the flow path 70, generating microbubbles in the liquid flowing through the flow path 70. In a modified example, the suction hole 100 may be provided in the second member 40. In another modified example, the suction hole 100 may be provided in both the first member 10 and the second member 40.

[0030] The first member 10 of the micro-bubble generator 2 further includes a first protrusion 20. The first protrusion 20 protrudes from the inner surface of the first recess 12 into the flow path 70. The first protrusion 20 is provided in the expanded diameter section 74 of the flow path 70. The first protrusion 20 is provided at a position in the expanded diameter section 74 closer to the outlet section 78 than to the intermediate section 76. In a modified example, the first protrusion 20 may be provided at a position in the expanded diameter section 74 closer to the intermediate section 76 than to the outlet section 78. The first protrusion 20 extends toward the center of the flow path 70 when viewed in a cross section perpendicular to the axial direction of the flow path 70 (see FIG. 4). The first protrusion 20 extends from the upstream side to the downstream side of the flow path 70 when viewed in a cross section parallel to the axial direction of the flow path 70 (see FIGS. 2 and 3).

[0031] 5, the first protrusion 20 is configured to taper from the upstream side to the downstream side of the flow path 70. The first protrusion 20 extends in a first direction D1 from the upstream side to the downstream side of the flow path 70. The first protrusion 20 has an upstream end 22, a downstream end 24, a first side surface 26, and a second side surface 28.

[0032] The upstream end 22 is located further upstream in the flow path 70 than the downstream end 24, and is configured to be thicker than the downstream end 24. The downstream end 24 is located further downstream in the flow path 70 than the upstream end 22, and is configured to be thinner than the upstream end 22.

[0033] The first side surface 26 and the second side surface 28 are each provided between the upstream end 22 and the downstream end 24. The first side surface 26 and the second side surface 28 each extend from the upstream side to the downstream side of the flow channel 70. The first side surface 26 extends, for example, along the axial direction of the flow channel 70. In a modified example, the first side surface 26 may extend in a direction inclined with respect to the axial direction of the flow channel 70.

[0034] The second side surface 28 extends, for example, in a direction inclined with respect to the axial direction of the flow channel 70. The second side surface 28 extends in a direction inclined with respect to the first side surface 26. The second side surface 28 is configured to approach the first side surface 26 as it moves toward the downstream side of the flow channel 70. The second side surface 28 is provided to face the downstream side of the flow channel 70. The inclination angle of the second side surface 28 with respect to the axial direction of the flow channel 70 is greater than the inclination angle of the first side surface 26 with respect to the axial direction of the flow channel 70.

[0035] Like the first member 10, the second member 40 of the micro-bubble generator 2 has a second protrusion 50. The second protrusion 50 protrudes from the inner surface of the second recess 42 into the flow path 70. The second protrusion 50 is provided in the expanded diameter section 74 of the flow path 70. The second protrusion 50 is provided at a position in the expanded diameter section 74 closer to the outlet section 78 than to the intermediate section 76. In a modified example, the second protrusion 50 may be provided at a position in the expanded diameter section 74 closer to the intermediate section 76 than to the outlet section 78. The second protrusion 50 extends toward the center of the flow path 70 when viewed in a cross section perpendicular to the axial direction of the flow path 70 (see FIG. 4). The second protrusion 50 extends from the upstream side to the downstream side of the flow path 70 when viewed in a cross section parallel to the axial direction of the flow path 70 (see FIGS. 2 and 3).

[0036] 5, the second protrusion 50 is configured to taper from the upstream side toward the downstream side of the flow path 70. The second protrusion 50 extends in a second direction D2 from the upstream side toward the downstream side of the flow path 70. The second direction D2 is a direction different from the first direction D1 in which the first protrusion 20 extends and is a direction intersecting the first direction D1. The second protrusion 50 has an upstream end 52, a downstream end 54, a first side surface 56, and a second side surface 58.

[0037] The upstream end 52 is located further upstream in the flow path 70 than the downstream end 54, and is configured to be thicker than the downstream end 54. The downstream end 54 is located further downstream in the flow path 70 than the upstream end 52, and is configured to be thinner than the upstream end 52.

[0038] The first side surface 56 and the second side surface 58 are each provided between the upstream end 52 and the downstream end 54. The first side surface 56 and the second side surface 58 each extend from the upstream side to the downstream side of the flow channel 70. The first side surface 56 extends, for example, along the axial direction of the flow channel 70. In a modified example, the first side surface 56 may extend in a direction inclined with respect to the axial direction of the flow channel 70.

[0039] The second side surface 58 extends, for example, in a direction inclined with respect to the axial direction of the flow channel 70. The second side surface 58 extends in a direction inclined with respect to the first side surface 56. The second side surface 58 is configured to approach the first side surface 56 as it moves toward the downstream side of the flow channel 70. The second side surface 58 is provided to face the downstream side of the flow channel 70. The inclination angle of the second side surface 58 with respect to the axial direction of the flow channel 70 is greater than the inclination angle of the first side surface 56 with respect to the axial direction of the flow channel 70.

[0040] The first protrusion 20 of the first member 10 and the second protrusion 50 of the second member 40 face each other in the radial direction of the flow path 70 (see FIG. 4). The first protrusion 20 and the second protrusion 50 face each other across the center of the flow path 70. The first protrusion 20 extends toward the second protrusion 50, and the second protrusion 50 extends toward the first protrusion 20. The tip of the first protrusion 20 and the tip of the second protrusion 50 are in contact with each other.

[0041] Furthermore, the first side surface 26 of the first protrusion 20 and the first side surface 56 of the second protrusion 50 face in different directions (see FIG. 5). Similarly, the second side surface 28 (inclined surface) of the first protrusion 20 and the second side surface 58 (inclined surface) of the second protrusion 50 face in different directions. In the example shown in FIG. 5, the first side surface 26 of the first protrusion 20 faces in the clockwise direction, and the first side surface 56 of the second protrusion 50 faces in the counterclockwise direction. Furthermore, the second side surface 28 (inclined surface) of the first protrusion 20 faces in the counterclockwise direction, and the second side surface 58 (inclined surface) of the second protrusion 50 faces in the clockwise direction.

[0042] In the micro-bubble generator 2 having the above configuration, liquid is introduced from the introduction pipe 82 into the reduced diameter section 72 of the flow path 70. The liquid introduced into the reduced diameter section 72 flows from the reduced diameter section 72 through the intermediate section 76 to the expanded diameter section 74. At this time, the pressure of the liquid decreases as the liquid flows from the reduced diameter section 72 to the expanded diameter section 74, and gas is sucked into the flow path 70 through the suction holes 100. As a result, micro-bubbles are generated in the liquid flowing through the flow path 70. Furthermore, when the liquid flowing through the expanded diameter section 74 hits the first convex portion 20 or the second convex portion 50, micro-bubbles are generated in the liquid flowing through the expanded diameter section 74. The liquid containing the micro-bubbles is then discharged from the expanded diameter section 74 to the discharge pipe 84.

[0043] (effect) The above describes the embodiment. As is clear from the above description, the micro-bubble generator 2 of the embodiment includes a first member 10 having a first recess 12 that forms part of the flow path 70, and a second member 40 having a second recess 42 that forms another part of the flow path 70. The first member 10 and the second member 40 are combined with each other such that the first recess 12 and the second recess 42 face each other. The first recess 12 and the second recess 42 face each other in a direction perpendicular to the axial direction of the flow path 70, thereby forming the flow path 70. The first member 10 includes a first protrusion 20 that protrudes into the flow path 70 from the inner surface of the first recess 12 at the expanded diameter portion 74 of the flow path 70. The second member 40 includes a second protrusion 50 that protrudes into the flow path 70 from the inner surface of the second recess 42 at the expanded diameter portion 74 of the flow path 70.

[0044] With this configuration, the fine-bubble generator 2 can be produced simply by combining the first member 10 and the second member 40 with the first recess 12 and the second recess 42 facing each other. In this fine-bubble generator 2, fine bubbles are generated when the liquid flowing through the flow path 70 hits the first convex portion 20 or the second convex portion 50. With the above configuration, the first convex portion 20 and the second convex portion 50 protrude from the inner surfaces of the first recess 12 and the second recess 42, respectively, which face each other. This allows fine bubbles to be generated on both the first recess 12 side and the second recess 42 side of the flow path 70. Therefore, fine bubbles can be generated in a balanced manner on both the first recess 12 side and the second recess 42 side of the flow path 70. As described above, with the above configuration, fine bubbles can be generated well with a simple configuration.

[0045] The first protrusion 20 and the second protrusion 50 face each other across the center of the flow channel 70. With this configuration, fine bubbles can be generated effectively near the center of the flow channel 70.

[0046] The first convex portions 20 extend in a first direction D1 from the upstream side to the downstream side of the flow path 70. The second convex portions 50 extend in a second direction D2 different from the first direction D1 from the upstream side to the downstream side of the flow path 70. With this configuration, the micro-bubbles generated by the first convex portions 20 and the micro-bubbles generated by the second convex portions 50 spread in different directions toward the downstream side of the flow path 70. This allows the micro-bubbles to spread throughout the entire flow path 70.

[0047] The first protrusion 20 has a first side surface 26 extending along the axial direction of the flow channel 70 and a second side surface 28 extending along a direction inclined with respect to the axial direction of the flow channel 70. With this configuration, the first side surface 26 and the second side surface 28 can change the direction in which the liquid flows. This makes it possible to agitate the liquid flowing through the flow channel 70. Alternatively, it is possible to make the liquid flow smoothly toward the downstream side of the flow channel 70. The same is true for the second protrusion 50.

[0048] The first side surface 26 and the second side surface 28 of the first protrusion 20 are configured to approach each other from the upstream side to the downstream side of the flow path 70. This configuration allows the liquid to flow smoothly toward the downstream side of the flow path 70. The same applies to the second protrusion 50.

[0049] The first member 10 has a suction hole 100 that sucks gas into the flow path 70 downstream of the reduced diameter section 72 of the flow path 70. With this configuration, by sucking gas into the flow path 70 through the suction hole 100, it is possible to generate microscopic bubbles in the liquid in the flow path 70. In a modified example, the suction hole 100 may be provided in the second member 40.

[0050] (Variation) Although the embodiments have been described above, the aspects of the fine bubble generator 2 are not limited to the above embodiments. In the following description, detailed description of the same configuration as that described above may be omitted.

[0051] (1) In the above embodiment, gas is sucked into the flow path 70 through the suction hole 100, but the present invention is not limited to this configuration. In a modified example, a liquid may be sucked into the flow path 70 through the suction hole 100. The liquid sucked into the flow path 70 through the suction hole 100 may be the same liquid as the liquid already flowing through the flow path 70, or may be a different liquid. This allows additional liquid to be added to the liquid flowing through the flow path 70.

[0052] (2) When the suction holes 100 are not used, the suction holes 100 may be closed. Also, the suction holes 100 may not be provided.

[0053] (3) There are no particular limitations on the applications for which the fine-bubble generator 2 is used. For example, the fine-bubble generator 2 is used to wash an object to be washed. In this case, the object to be washed is washed with a liquid containing fine bubbles generated by the fine-bubble generator 2. The object to be washed is not particularly limited, and examples thereof include fresh food (fish, meat, vegetables, etc.). The object to be washed may also be something other than food.

[0054] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0055] 2: micro-bubble generator, 10: first member, 12: first recess, 20: first convex portion, 22: upstream end, 24: downstream end, 26: first side surface, 28: second side surface, 32: inlet connection portion, 34: outlet connection portion, 40: second member, 42: second recess, 50: second convex portion, 52: upstream end, 54: downstream end, 56: first side surface, 58: second side surface, 70: flow path, 72: reduced diameter portion, 74: expanded diameter portion, 76: intermediate portion, 78: outlet portion, 82: inlet pipe, 84: outlet pipe, 100: suction hole

Claims

1. A micro-bubble generator that generates micro-bubbles in a liquid flowing through a flow path, When viewed in a cross section perpendicular to the axial direction of the flow path, a first member including a first recess that forms a part of the flow path; a second member including a second recess that constitutes another part of the flow path, the second member being combined with the first member in a state where the first recess and the second recess face each other; the first recess and the second recess face each other in a direction perpendicular to an axial direction of the flow path, thereby constituting the flow path; When viewed in a cross section parallel to the axial direction of the flow path, the flow path includes a reduced diameter portion whose diameter decreases from the upstream side to the downstream side, and an expanded diameter portion whose diameter increases from the upstream side to the downstream side downstream of the reduced diameter portion, the first member includes a first protrusion protruding into the flow path from an inner surface of the first recess in the expanded diameter portion of the flow path, the second member includes a second protrusion protruding into the flow path from an inner surface of the second recess in the expanded diameter portion of the flow path, the first convex portion and the second convex portion are spaced apart in the circumferential direction of the flow channel, the first protrusion includes a first side surface extending along an axial direction of the flow channel and a second side surface extending along a direction inclined with respect to the axial direction of the flow channel, the first side surface and the second side surface of the first protrusion are configured to approach each other from the upstream side to the downstream side of the flow path, the second protrusion includes a first side surface extending along the axial direction of the flow channel and a second side surface extending along a direction inclined with respect to the axial direction of the flow channel, A micro-bubble generator, wherein the first side surface and the second side surface of the second convex portion are configured to approach each other as they move from the upstream side to the downstream side of the flow path.

2. The fine-bubble generator according to claim 1 , wherein the first convex portion and the second convex portion face each other across a center of the flow path.

3. the first convex portion extends in a first direction from an upstream side to a downstream side of the flow channel, The micro-bubble generator according to claim 1 or 2, wherein the second convex portion extends from the upstream side to the downstream side of the flow channel in a second direction different from the first direction.

4. 3. The micro-bubble generator according to claim 1, wherein the first member or the second member has a suction hole that draws gas or liquid into the flow path downstream of the reduced diameter portion of the flow path.

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