Microbubble generator, water heater, and dishwasher

Abstract

This invention provides a technology that enables the generation of a larger number of microbubbles in a microbubble generating device. [Solution] The microbubble generating device comprises an inlet, an outlet, a first microbubble generation unit provided between the inlet and outlet, and a second microbubble generation unit provided between the first microbubble generation unit and the outlet. The first microbubble generation unit includes a venturi section having a narrowing channel whose diameter decreases as it moves from upstream to downstream, and an expanding channel whose diameter increases as it moves from upstream to downstream. The second microbubble generation unit includes a plurality of swirling flow generation units arranged in line along the downstream central axis direction of the second microbubble generation unit. Each of the plurality of swirling flow generation units includes a shaft portion extending in the downstream central axis direction, an outer periphery surrounding the shaft portion, and a plurality of blade portions provided between the shaft portion and the outer periphery, which generate a swirling flow that flows in a predetermined swirling direction relative to the shaft portion.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a fine bubble generator, a water heater, and a dishwasher.

Background Art

[0002] Patent Document 1 discloses a fine bubble generator including an inflow portion into which gas-dissolved water flows, an outflow portion from which the gas-dissolved water flows out, and a fine bubble generation portion provided between the inflow portion and the outflow portion. The fine bubble generation portion includes a reduced-diameter flow path whose flow path diameter decreases from upstream to downstream, and an enlarged-diameter flow path provided downstream of the reduced-diameter flow path and whose flow path diameter increases from upstream to downstream.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the fine bubble generator of Patent Document 1, water in which gas is dissolved (hereinafter sometimes referred to as "gas-dissolved water") flows into the reduced-diameter flow path of the fine bubble generation portion via the inflow portion. The gas-dissolved water passes through the reduced-diameter flow path, whereby the flow velocity increases and as a result, the pressure is reduced. When the gas-dissolved water is depressurized, bubbles are generated. Next, the gas-dissolved water passes through the enlarged-diameter flow path, whereby the pressure is gradually increased. When the gas-dissolved water after bubbles are generated by depressurization is pressurized, the bubbles contained in the gas-dissolved water split into fine bubbles. Thus, in the fine bubble generator of Patent Document 1, fine bubbles are generated by the fine bubble generation portion. However, in the fine bubble generator of Patent Document 1, a situation occurs in which the amount of fine bubbles generated by the fine bubble generator is insufficient.

[0005] This specification provides a technology that can generate a large quantity of microbubbles. [Means for solving the problem]

[0006] The microbubble generating device disclosed herein comprises an inlet into which gaseous dissolved water flows in, an outlet outlet into which the gaseous dissolved water flows out, a first microbubble generating unit provided between the inlet and the outlet outlet, and a second microbubble generating unit provided between the first microbubble generating unit and the outlet outlet, wherein the first microbubble generating unit comprises a venturi section having a diameter-reducing channel whose channel diameter decreases as it moves from upstream to downstream, and a diameter-expanding channel provided downstream of the diameter-reducing channel whose channel diameter increases as it moves from upstream to downstream, wherein the second microbubble generating unit comprises a plurality of swirling flow generating units arranged in line along the downstream central axis direction of the second microbubble generating unit, each of the plurality of swirling flow generating units comprises a shaft portion extending in the downstream central axis direction, an outer peripheral portion surrounding the shaft portion, and a plurality of blade portions provided between the shaft portion and the outer peripheral portion, which generate a swirling flow that flows in a predetermined swirling direction relative to the shaft portion.

[0007] According to the above configuration, the gaseous dissolved water flowing into the microbubble generator flows into the first microbubble generation section. The gaseous dissolved water flowing into the first microbubble generation section increases in flow velocity as it passes through the narrowed diameter channel, resulting in a decrease in pressure. Bubbles are generated as the gaseous dissolved water is reduced in pressure. Next, the gaseous dissolved water is gradually pressurized as it passes through the widened diameter channel. When the gaseous dissolved water, which has been pressurized after bubbles have been generated by the pressure reduction, is increased in pressure, the bubbles contained in the gaseous dissolved water split into microbubbles. Next, the gaseous dissolved water that has passed through the first microbubble generation section flows into the swirling flow generation section of the second microbubble generation section. The gaseous dissolved water that has flowed into the swirling flow generation section becomes a swirling flow that flows in a predetermined swirling direction. The microbubbles in the gaseous dissolved water become finer due to the shear force caused by the swirling flow, and the amount of microbubbles increases. By having the dissolved gaseous water pass through multiple swirling flow generation sections, the path through which the dissolved gaseous water flows as a swirling flow can be lengthened compared to a configuration where the dissolved gaseous water passes through a single swirling flow generation section. As a result, the microbubbles in the dissolved gaseous water become finer and their quantity increases. Consequently, a large amount of microbubbles can be generated.

[0008] In one or more embodiments, the direction opposite to a predetermined swirling direction is defined as the reverse swirling direction. For each of the plurality of blades in the swirling flow generating unit, the end of a particular blade among the plurality of blades on the swirling direction side may be positioned on the reverse swirling direction side of the end of the adjacent blade in the swirling direction. When the swirling flow generating unit is viewed in the direction of the downstream central axis axis, a plurality of first openings may be provided in the swirling flow generating unit. When the swirling flow generating unit is viewed in the direction of the downstream central axis axis, each of the plurality of first openings may be surrounded by the end of the particular blade on the swirling direction side, the end of the adjacent blade in the reverse swirling direction side, the shaft, and the outer circumference. When the second microbubble generating section is viewed in the direction of the downstream central axis, each of the multiple vanes of the downstream swirling flow generating section, which is different from the swirling flow generating section provided on the upstream side, may be arranged to overlap at least a portion of the corresponding first opening of the multiple first openings of the upstream swirling flow generating section adjacent to the downstream swirling flow generating section, on the upstream side of the downstream swirling flow generating section.

[0009] According to the above configuration, when the second microbubble generation unit is viewed in the direction of the downstream central axis, compared to a configuration in which each of the multiple blades of the downstream swirling flow generation unit does not overlap with the corresponding first opening among the multiple first openings of the upstream swirling flow generation unit, the amount of gas-dissolved water flowing out of the upstream swirling flow generation unit that passes through the downstream swirling flow generation unit without passing through the blades of the downstream swirling flow generation unit can be reduced. In other words, the amount of gas-dissolved water that reaches the blades of the downstream swirling flow generation unit can be increased. Therefore, the amount of gas-dissolved water flowing as a swirling flow can be increased. Consequently, a larger quantity of microbubbles can be generated.

[0010] In one or more embodiments, when the second microbubble generating unit is viewed in the direction of the downstream central axis, each of the plurality of blades of the downstream swirling flow generating unit may be arranged to overlap the entirety of the corresponding first opening among the plurality of first openings of the upstream swirling flow generating unit.

[0011] With the above configuration, much of the dissolved gaseous water flowing out from the upstream swirling flow generation section flows into the blades of the downstream swirling flow generation section. Therefore, the amount of dissolved gaseous water flowing as a swirling flow can be increased. Consequently, a larger quantity of fine bubbles can be generated.

[0012] In one or more embodiments, the downstream end of the swirling flow generation section may be provided with a plurality of second openings. Each of the plurality of second openings may be surrounded by the end of a particular blade section on the swirling direction side, the ends of adjacent blade sections on the swirling direction side, the shaft, and the outer circumference. When the second microbubble generation section is viewed in the direction of the downstream central axis, the ends of each of the plurality of blade sections of the downstream swirling flow generation section on the counter-swirling direction side may be located near the central portion in the swirling direction of the corresponding second opening among the plurality of second openings.

[0013] According to the above configuration, a portion of the gaseous dissolved water flowing out from the upstream swirling flow generation section collides with the end of the blade section of the downstream swirling flow generation section on the reverse-swirl direction side. When the gaseous dissolved water collides with the end of the blade section of the downstream swirling flow generation section on the reverse-swirl direction side, the microbubbles in the gaseous dissolved water split, becoming finer bubbles and increasing the quantity of microbubbles. In addition, a portion of the gaseous dissolved water flowing out from the upstream swirling flow generation section is sheared as it passes through the end of the blade section of the downstream swirling flow generation section on the reverse-swirl direction side. When the gaseous dissolved water is sheared, the microbubbles in the gaseous dissolved water become finer bubbles and the quantity of microbubbles increases. Therefore, a larger quantity of microbubbles can be generated.

[0014] In one or more embodiments, the first microbubble generating unit may comprise a plurality of venturi sections. The plurality of venturi sections may include a plurality of outer venturi sections arranged around an upstream central axis which is the central axis of the first microbubble generating unit. The number of the plurality of outer venturi sections may be the same as the number of vane sections of the upstreammost swirling flow generating unit, which is located at the upstream end of the plurality of swirling flow generating units. The downstream end of the enlarged diameter flow path of each of the plurality of outer venturi sections may face the corresponding vane section of the upstreammost swirling flow generating unit.

[0015] According to the above configuration, much of the dissolved gas water flowing out from the first microbubble generation section flows into the blades of the upstream swirling flow generation section. Therefore, the amount of dissolved gas water flowing as a swirling flow can be increased. Consequently, a larger quantity of microbubbles can be generated.

[0016] In one or more embodiments, the first microbubble generating unit may comprise a plurality of venturi sections. The plurality of venturi sections may include a plurality of outer venturi sections arranged around an upstream central axis which is the central axis of the first microbubble generating unit. The number of the plurality of outer venturi sections may be the same as the number of vane sections of the upstreammost swirling flow generating unit, which is located at the upstream end of the plurality of swirling flow generating units. The downstream end of the enlarged diameter flow path of each of the plurality of outer venturi sections may face the end of the corresponding vane section of the upstreammost swirling flow generating unit on the counter-swirling direction side.

[0017] According to the above configuration, a portion of the gas-dissolved water flowing out from the first microbubble generation unit collides with the end of the blade section of the upstream swirling flow generation unit on the reverse-swirl direction side. When the gas-dissolved water collides with the end of the blade section of the upstream swirling flow generation unit on the reverse-swirl direction side, the microbubbles in the gas-dissolved water split, becoming finer bubbles and increasing the quantity of microbubbles. In addition, a portion of the gas-dissolved water flowing out from the first microbubble generation unit is sheared as it passes through the end of the blade section of the upstream swirling flow generation unit on the reverse-swirl direction side. When the gas-dissolved water is sheared, the microbubbles in the gas-dissolved water become finer bubbles and the quantity of microbubbles increases. Therefore, a larger quantity of microbubbles can be generated.

[0018] In one or more embodiments, the microbubble generating device may further include a main body case housing the first microbubble generating unit and the second microbubble generating unit. The main body case may include a first positioning unit for positioning the first microbubble generating unit and the main body case, and a second positioning unit for positioning the second microbubble generating unit and the main body case.

[0019] According to the above configuration, the first microbubble generation unit and the main body case are positioned by the first positioning unit, and the second microbubble generation unit and the main body case are positioned by the second positioning unit, thereby positioning the multiple outer venturi sections of the first microbubble generation unit and the multiple blade sections of the uppermost swirling flow generation unit of the second microbubble generation unit. As a result, much of the gaseous dissolved water flowing out from the first microbubble generation unit can be directed into the blade section of the uppermost swirling flow generation unit, or collide with the end of the blade section of the uppermost swirling flow generation unit on the reverse swirling direction side, or be sheared as it passes through the end of the blade section of the uppermost swirling flow generation unit on the reverse swirling direction side. Consequently, a larger quantity of microbubbles can be generated.

[0020] In one or more embodiments, each of the plurality of swirling flow generating units is provided with an upstream convex portion projecting upstream or an upstream recessed portion recessing downstream at its upstream end, and at its downstream end, if the upstream convex portion is provided at the upstream end of the swirling flow generating unit, a downstream recessed portion recessing upstream is provided, and if the upstream recess is provided at the upstream end of the swirling flow generating unit, a downstream convex portion projecting downstream is provided. The upstream convex portion may have a shape corresponding to the second positioning portion and the downstream recess. The upstream recess may have a shape corresponding to the second positioning portion and the downstream convex portion.

[0021] According to the above configuration, the main body case and the uppermost swirling flow generation unit can be positioned using the upstream convex or upstream recess at the upstream end of the swirling flow generation unit, and two adjacent swirling flow generation units in the downstream central axis direction can also be positioned. In this case, it is not necessary to provide a structure different from the upstream convex or upstream recess at the upstream end of the uppermost swirling flow generation unit in order to position the main body case and the uppermost swirling flow generation unit. Therefore, the structure of multiple swirling flow generation units can be standardized.

[0022] In one or more embodiments, the plurality of venturi sections may further include inner venturi sections extending along the upstream central axis. The downstream end of the enlarged diameter flow path of the inner venturi section may face the shaft of the upstream swirling flow generator. The opening area of ​​the downstream end of the enlarged diameter flow path of the inner venturi section may be smaller than the area of ​​the shaft of the upstream swirling flow generator when viewed in the direction of the downstream central axis.

[0023] According to the above configuration, compared with a configuration where the opening area at the downstream end of the diffusion flow path of the inner Venturi portion is larger than the area of the shaft portion of the most upstream swirl flow generation portion, most of the gas-dissolved water flowing out from the inner Venturi portion can collide with the shaft portion of the most upstream swirl flow generation portion. When the gas-dissolved water collides with the shaft portion, the fine bubbles in the gas-dissolved water split into finer bubbles and the amount of fine bubbles increases. Therefore, a larger amount of fine bubbles can be generated.

[0024] In one or more embodiments, the opening area may be smaller than the area of the outer shape of the upstream end of the shaft portion of the most upstream swirl flow generation portion when viewed in the downstream central axis direction.

[0025] A part of the gas-dissolved water flowing out from the inner Venturi portion may flow in the outer direction of the shaft portion of the most upstream swirl flow generation portion. According to the above configuration, the amount of gas-dissolved water colliding with the shaft portion (specifically, the upstream end) of the most upstream swirl flow generation portion can be increased. Therefore, a larger amount of fine bubbles can be generated.

[0026] In one or more embodiments, a recess recessed downstream may be provided at the upstream end of the shaft portion of the most upstream swirl flow generation portion.

[0027] According to the above configuration, the gas-dissolved water flowing out from the inner Venturi portion collides with the recess. And the gas-dissolved water colliding with the recess flows toward the inner Venturi portion side. In this case, the gas-dissolved water flowing out from the inner Venturi portion and the gas-dissolved water colliding with the recess and flowing toward the inner Venturi portion side collide with each other. When the gas-dissolved waters collide with each other, the fine bubbles in the gas-dissolved water split into finer bubbles and the amount of fine bubbles increases. Therefore, a larger amount of fine bubbles can be generated.

[0028] In one or more embodiments, a protruding portion protruding upstream may be provided on the upstream side surface of the plurality of blade portions.

[0029] In the above configuration, the gaseous dissolved water flowing through multiple vane sections collides with the protruding parts. This collision causes the microbubbles within the gaseous dissolved water to split, becoming even finer bubbles, and increasing the overall quantity of microbubbles. Therefore, a larger volume of microbubbles can be generated.

[0030] In one or more embodiments, the downstream end of the widened flow path of each of the plurality of outer venturi sections may face the projection provided on the corresponding blade of the plurality of blades of the upstream swirling flow generating section.

[0031] With the above configuration, the dissolved gaseous water flowing out from the outer venturi section can be reliably brought into contact with the protruding section. Therefore, a larger quantity of fine bubbles can be generated.

[0032] In one or more embodiments, the microbubble generator may be provided between the second microbubble generation unit and the outlet unit and may include a flow rectifier that straightens the flow of gas-dissolved water discharged from the second microbubble generation unit from a swirling flow to a straight flow.

[0033] The flow of dissolved gaseous water flowing out of the second microbubble generation section is a swirling flow (i.e., turbulent flow). When the flow of dissolved gaseous water is a swirling flow, it is more likely to collide with the wall (hereinafter simply referred to as "wall") that defines the flow path of the dissolved gaseous water downstream of the rectifier, compared to when the flow of dissolved gaseous water is a straight flow (i.e., laminar flow). Therefore, if the flow of dissolved gaseous water flowing out of the second microbubble generation section is not rectified from a swirling flow to a straight flow, a relatively large amount of dissolved gaseous water will collide with the wall. In this case, the pressure loss within the microbubble generator will increase, and the amount of dissolved gaseous water flowing through the microbubble generator will decrease. With the above configuration, the flow of dissolved gaseous water flowing out of the second microbubble generation section is rectified from a swirling flow (i.e., turbulent flow) to a straight flow (i.e., laminar flow) by passing through the rectifier. Therefore, the amount of dissolved gaseous water that collides with the wall can be reduced, and the pressure loss within the microbubble generator can be reduced. Consequently, the amount of dissolved gaseous water flowing through the microbubble generator can be increased.

[0034] Furthermore, this specification discloses a water heater equipped with the above-described microbubble generating device.

[0035] According to the above configuration, gaseous dissolved water that has passed through the microbubble generator is supplied to the hot water supply point. In other words, gaseous dissolved water containing many microbubbles can be supplied to the hot water supply point. Because the gaseous dissolved water contains many microbubbles, the cleaning power is improved when the user washes their body. Therefore, the convenience of the user using the water heater can be improved.

[0036] Furthermore, this specification discloses a dishwasher equipped with the above-described microbubble generating device.

[0037] According to the above configuration, the gaseous dissolved water that has passed through the microbubble generator is supplied to the washing tank of the dishwasher. In other words, gaseous dissolved water containing many microbubbles can be supplied to the washing tank. The presence of many microbubbles in the gaseous dissolved water improves the cleaning power when washing dishes. Therefore, the convenience of the user of the dishwasher can be improved. [Brief explanation of the drawing]

[0038] [Figure 1] This is a perspective view of the microbubble generating device 2 according to the first embodiment. [Figure 2] This is a cross-sectional view of the microbubble generating device 2 according to the first embodiment. [Figure 3] This is a perspective view of the microbubble generator 2 according to the first embodiment with the main body case 10 removed. [Figure 4] This is a view of the first microbubble generation unit 20 according to the first embodiment, as seen from the upstream side. [Figure 5] This is a view of the first microbubble generation unit 20 according to the first embodiment, seen from the downstream side. [Figure 6] This is a view of the swirling flow generation section 50 of the second microbubble generation section 22 according to the first embodiment, as seen from the upstream side. [Figure 7] This is a perspective view of the swirling flow generation section 50 of the second microbubble generation section 22 according to the first embodiment, as seen from the upstream side. [Figure 8] This is a cross-sectional view along line VIII-VIII in Figure 2. [Figure 9] This is a view of the second microbubble generation unit 22 according to the first embodiment, as seen from the upstream side. [Figure 10] This is a cross-sectional view of the microbubble generating device 2 according to the second embodiment. [Figure 11] This is a cross-sectional view of the microbubble generating device 2 according to the third embodiment. [Figure 12] This is a view from the upstream side of the swirling flow generation section 350 of the second microbubble generation section 22 according to the fourth embodiment. [Figure 13] This is a cross-sectional view of the microbubble generating device 2 according to the fourth embodiment. [Figure 14] This is a perspective view of the swirling flow generation section 350 of the second microbubble generation section 22 according to the fourth embodiment, viewed from the downstream side. [Figure 15] This is a view of the swirling flow generation section 350 of the second microbubble generation section 22 according to the fourth embodiment, as seen from the downstream side. [Figure 16] This is a cross-sectional view along the line XIV-XIV in Figure 13. [Figure 17] This is a view of the second microbubble generation unit 22 according to the fourth embodiment, as seen from the upstream side. [Figure 18] This is a cross-sectional view along the line XVIII-XVIII in Figure 13. [Figure 19] This diagram schematically shows the configuration of the hot water supply system 402 according to the first embodiment. [Figure 20] This diagram schematically shows the configuration of the dishwasher 510 according to the second embodiment. [Figure 21] This is a cross-sectional view of the microbubble generating device 2 according to the fifth embodiment. [Figure 22] This is a view of the main body case 610 according to the fifth embodiment, seen from the upstream side. [Figure 23] This is a perspective view of the first microbubble generation unit 620 according to the fifth embodiment, viewed from the downstream side. [Figure 24] This is a perspective view of the swirling flow generation section 650 of the second microbubble generation section 622 according to the fifth embodiment, viewed from the upstream side. [Figure 25] This is a perspective view of the swirling flow generation section 650 of the second microbubble generation section 622 according to the fifth embodiment, viewed from the downstream side. [Figure 26] This is a cross-sectional view along the line XXVI-XXVI in Figure 21. [Figure 27] This is a perspective view of the second microbubble generation unit 622 according to the fifth embodiment, viewed from the upstream side. [Figure 28] This is a cross-sectional view of the microbubble generating device 2 according to the sixth embodiment. [Figure 29] This is a perspective view of the rectifier 770 according to the sixth embodiment, viewed from the upstream side. [Figure 30] This is a cross-sectional view of the microbubble generating device 2 according to the seventh embodiment. [Modes for carrying out the invention]

[0039] (First embodiment) As shown in Figure 1, the microbubble generator 2 comprises a main body case 10, an inlet 12, and an outlet 14. The main body case 10 has a substantially cylindrical shape. The inlet 12 is fixed to the upstream end 10a of the main body case 10 with screws. An inlet 12a is formed in the inlet 12. The outlet 14 is fixed to the downstream end 10b of the main body case 10 with screws. An outlet 14a is formed in the outlet 14. Hereafter, the central axis A of the microbubble generator 2 may be simply referred to as "central axis A".

[0040] As shown in Figure 2, the main body case 10 houses a first microbubble generation unit 20 and a second microbubble generation unit 22 located downstream of the first microbubble generation unit 20. The first microbubble generation unit 20 and the second microbubble generation unit 22 are arranged along the central axis A.

[0041] (Configuration of the first microbubble generation unit 20; Figures 2 to 5) As shown in Figure 3, the first microbubble generating unit 20 comprises a first main body 30 and a second main body 32 located downstream of the first main body 30. The outer diameter of the first main body 30 decreases as it extends downstream. The outer diameter of the second main body 32 increases as it extends downstream. The central axis of the first microbubble generating unit 20 coincides with the central axis A.

[0042] As shown in Figure 4, the first microbubble generation section 20 is provided with an inner venturi section 34 and six outer venturi sections 36. The inner venturi section 34 is located in the center of the first microbubble generation section 20. The inner venturi section 34 is located on the central axis A. As shown in Figure 2, the inner venturi section 34 includes a diameter-reducing channel 38 whose channel diameter decreases as it moves from upstream to downstream, and a diameter-expanding channel 40 located downstream of the diameter-reducing channel 38, whose channel diameter increases as it moves from upstream to downstream. The diameter-reducing channel 38 is located in the first main body section 30. The channel diameter at the upstream end of the diameter-reducing channel 38 is smaller than the channel diameter of the inlet 12a of the inlet section 12. The diameter-expanding channel 40 is located in the second main body section 32.

[0043] As shown in Figure 4, the six outer venturi sections 36 are located radially outward from the central axis A relative to the inner venturi section 34. The six outer venturi sections 36 are arranged at equal intervals along the circumferential direction of the central axis A. Each of the six outer venturi sections 36 is provided with a diameter-reducing channel 38 and a diameter-expanding channel 40 (see Figure 5), similar to the inner venturi section 34. As shown in Figure 2, the diameter-reducing channel 38 and the diameter-expanding channel 40 define the upstream channel 42 within the first microbubble generation section 20. Water flowing from the inlet 12 into the first microbubble generation section 20 flows into the second microbubble generation section 22 via the upstream channel 42.

[0044] (Configuration of the second microbubble generation section 22; Figures 2, 6-9) As shown in Figure 2, the second microbubble generation unit 22 is equipped with four swirling flow generation units 50. The four swirling flow generation units 50 are arranged in line along the central axis A. The central axis of the second microbubble generation unit 22 coincides with the central axis A. In the following, "clockwise direction" and "counterclockwise direction" refer to the direction when viewing the microbubble generator 2 from the upstream side along the central axis A.

[0045] As shown in Figure 6, the swirling flow generation unit 50 comprises a shaft portion 52, an outer peripheral portion 54 surrounding the shaft portion 52, and six blade portions 56 provided between the shaft portion 52 and the outer peripheral portion 54, which generate a swirling flow that flows clockwise relative to the shaft portion 52. The shaft portion 52 has a cylindrical shape. The outer peripheral portion 54 has a cylindrical shape. As shown in Figure 2, the outer diameter of the outer peripheral portion 54 is the same as the inner diameter of the main body case 10. The shaft portion 52 and the outer peripheral portion 54 are provided along the central axis A. Therefore, the central axis of the shaft portion 52 and the central axis of the outer peripheral portion 54 coincide with the central axis of the second microbubble generation unit 22. As shown in Figure 6, the blade portions 56 connect the outer wall of the shaft portion 52 and the inner wall of the outer peripheral portion 54. As shown in Figure 7, the blade portions 56 are inclined downstream as they move clockwise. The upstream surface of the blade portions 56 is provided with a projection 58 that protrudes upstream. When the swirling flow generation unit 50 is viewed in the direction of the central axis A, the protruding portion 58 has a hexagonal cross-sectional shape. In modified examples, the cross-sectional shape of the protruding portion 58 may be circular, fan-shaped, triangular, teardrop-shaped, etc. The blade portion 56 has an outlet end 60 on the clockwise side and an inflow end 62 on the counterclockwise side. As shown in Figure 6, when the swirling flow generation unit 50 is viewed in the direction of the central axis A, the swirling flow generation unit 50 is provided with six first openings 64 (thick lines in Figure 6). Each of the six first openings 64 is surrounded by the outlet end 60 of one of the six blade portions 56, the inflow end 62 of the blade portion 56 adjacent to the said blade portion 56 in the clockwise direction, a shaft portion 52, and an outer circumference portion 54. In the following, the four swirling flow generating units 50 may be referred to as "first swirling flow generating unit 50," "second swirling flow generating unit 50," "third swirling flow generating unit 50," and "fourth swirling flow generating unit 50," in the order they are arranged from upstream to downstream. Also, in Figure 3, for clarity, the reference numerals indicating the shaft portion 52, outer circumference portion 54, and blade portion 56 of the second to fourth swirling flow generating units 50 have been omitted.

[0046] As shown in Figure 8, the first swirling flow generation unit 50 (i.e., the upstreammost swirling flow generation unit 50) is positioned such that the downstream ends of the enlarged diameter flow channels 40 of the six outer venturi sections 36 of the first microbubble generation unit 20 face the protrusions 58 provided on the corresponding blade sections 56 of the six blade sections 56 of the first swirling flow generation unit 50. Furthermore, the downstream end of the enlarged diameter flow channel 40 of the inner venturi section 34 of the first swirling flow generation unit 50 is positioned so that it faces the shaft section 52 of the first swirling flow generation unit 50. The opening area of ​​the downstream end of the enlarged diameter flow channel 40 of the inner venturi section 34 is smaller than the outer area of ​​the upstream end 52a of the shaft section 52 of the first swirling flow generation unit 50 when viewed in the direction of the central axis A.

[0047] Referring to Figure 9, the relationship between two adjacent swirling flow generators 50 in the direction of the central axis A will be explained. Figure 9 shows the first swirling flow generator 50 and the second swirling flow generator 50, which is located downstream of the first swirling flow generator 50 and adjacent to it. In Figure 9, for ease of understanding, the six blades 56 of the second swirling flow generator 50 are shown in gray. Also, the first opening 64 is enclosed by a thick line. When the swirling flow generator 50 is viewed in the direction of the central axis A, each of the six blades 56 of the second swirling flow generator 50 is positioned to overlap the entirety of the corresponding first opening 64 of the first swirling flow generator 50. In other words, when the four swirling flow generating units 50 are viewed in the direction of the central axis A, each of the six blades 56 of the downstream swirling flow generating unit 50 of two adjacent swirling flow generating units 50 in the direction of the central axis A is arranged such that it overlaps with the entirety of the corresponding blade 56 of the six first openings 64 of the upstream swirling flow generating unit 50.

[0048] Next, the microbubbles generated by the microbubble generator 2 will be described. The microbubble generator 2 generates microbubbles using water in which air is dissolved (hereinafter referred to as "air-dissolved water"). The air-dissolved water may be water supplied from a water source such as a public water supply (so-called tap water), or it may be water produced by an air-dissolved water generator that dissolves air taken in from the outside into water. In the modified example, gases such as carbon dioxide, hydrogen, or oxygen may be dissolved in the water instead of air.

[0049] As shown in Figure 2, the air-dissolved water flowing into the microbubble generator 2 flows through the inlet 12a of the inlet section 12 into the upstream channel 42 in the first microbubble generation section 20. The air-dissolved water flowing into the upstream channel 42 flows into the inner venturi section 34 and the outer venturi section 36. The air-dissolved water flowing into the inner venturi section 34 flows into the narrowed-diameter channel 38. As the air-dissolved water flows into the narrowed-diameter channel 38, its flow velocity increases, and as a result, its pressure decreases. Bubbles are generated as the air-dissolved water is depressurized. The air-dissolved water that has passed through the narrowed-diameter channel 38 flows into the widened-diameter channel 40. As the air-dissolved water flows into the widened-diameter channel 40, its flow velocity decreases, and as a result, its pressure increases. When the air-dissolved water, which has generated bubbles due to the pressure decrease, is pressurized, the bubbles contained in the air-dissolved water split and become microbubbles. The water that has passed through the widened channel 40 flows into the second microbubble generation section 22. In this way, microbubbles are generated as the air-dissolved water passes through the inner venturi section 34. Similarly, microbubbles are generated as the air-dissolved water passes through the outer venturi section 36. The air-dissolved water that has passed through the upstream channel 42 in the first microbubble generation section 20 flows into the second microbubble generation section 22.

[0050] The air-dissolved water flowing out from the first microbubble generation unit 20 flows into the first swirling flow generation unit 50, which is located at the uppermost upstream side of the second microbubble generation unit 22. As shown in Figure 8, the air-dissolved water flowing out from the inner venturi section 34 of the first microbubble generation unit 20 collides with the upstream end 52a of the shaft section 52 of the first swirling flow generation unit 50. When the air-dissolved water collides with the upstream end 52a, the microbubbles in the air-dissolved water split, becoming finer bubbles and increasing the amount of microbubbles. In addition, the air-dissolved water flowing out from the outer venturi section 36 of the first microbubble generation unit 20 collides with the protruding section 58 of the blade section 56 of the first swirling flow generation unit 50. When the air-dissolved water collides with the protruding section 58, the microbubbles in the air-dissolved water split, becoming finer bubbles and increasing the amount of microbubbles. The air-dissolved water collides with the protrusion 58 and then passes through the blade section 56. As the air-dissolved water passes through the blade section 56, it becomes a swirling flow that flows in a clockwise direction. The fine bubbles in the air-dissolved water become finer due to the shear force caused by the swirling flow, and the amount of fine bubbles increases. As shown in Figure 9, the air-dissolved water flowing out from the outlet end 60 of the blade section 56 of the first swirling flow generation unit 50 flows into the blade section 56 of the second swirling flow generation unit 50. A portion of the air-dissolved water that flows into the blade section 56 of the second swirling flow generation unit 50 collides with the protrusion 58 of the blade section 56 of the second swirling flow generation unit 50. As the air-dissolved water flows continuously through the blade section 56 of the first swirling flow generation unit 50 and the blade section 56 of the second swirling flow generation unit 50, the amount of air-dissolved water sheared by the swirling flow increases. As a result, the microbubbles in the air-dissolved water become even finer, and the quantity of microbubbles increases. Subsequently, as shown in Figure 2, the air-dissolved water passes through the third swirling flow generation unit 50 and the fourth swirling flow generation unit 50, which are located downstream of the second swirling flow generation unit 50. As the air-dissolved water passes through a total of four swirling flow generation units 50, the microbubbles in the air-dissolved water are further refined, and a large quantity of microbubbles are generated. The air-dissolved water flowing in from the second microbubble generation unit 22 then flows out to the outside through the outlet 14a.

[0051] As described above, as shown in Figure 2, the microbubble generator 2 includes an inlet 12 into which air-dissolved water (an example of "gas-dissolved water") flows in, an outlet 14 into which air-dissolved water flows out, a first microbubble generation unit 20 provided between the inlet 12 and the outlet 14, and a second microbubble generation unit 22 provided between the first microbubble generation unit 20 and the outlet 14. The first microbubble generation unit 20 includes an outer venturi section 36 having a diameter-reducing channel 38 whose channel diameter decreases as it moves from upstream to downstream, and a diameter-expanding channel 40 provided downstream of the diameter-reducing channel 38 whose channel diameter increases as it moves from upstream to downstream. The second microbubble generation unit 22 includes four swirling flow generation units 50 arranged in line along the central axis A. Each of the four swirling flow generating units 50 comprises a shaft portion 52 extending in the direction of the central axis A, an outer peripheral portion 54 surrounding the shaft portion 52, and six blade portions 56 provided between the shaft portion 52 and the outer peripheral portion 54, which generate a swirling flow that flows clockwise relative to the shaft portion 52 (an example of a "predetermined swirling direction"). With this configuration, the air-dissolved water flowing into the microbubble generator 2 flows into the first microbubble generating unit 20. The air-dissolved water flowing into the first microbubble generating unit 20 increases in flow velocity as it passes through the narrowed diameter channel 38, and as a result, is depressurized. Bubbles are generated as the air-dissolved water is depressurized. Next, the air-dissolved water is gradually pressurized as it passes through the widened diameter channel 40. When the air-dissolved water, which has been pressurized after bubbles have been generated by depressurization, is pressurized, the bubbles contained in the air-dissolved water split and become microbubbles. Next, the air-dissolved water that has passed through the first microbubble generation unit 20 flows into the swirling flow generation unit 50 of the second microbubble generation unit 22. The air-dissolved water that flows into the swirling flow generation unit 50 becomes a swirling flow that flows in a clockwise direction. The microbubbles in the air-dissolved water become finer due to the shear force caused by the swirling flow, and the amount of microbubbles increases. By having the air-dissolved water pass through four swirling flow generation units 50, the path through which the air-dissolved water flows as a swirling flow can be made longer compared to a configuration in which the air-dissolved water passes through one swirling flow generation unit 50. As a result, the microbubbles in the air-dissolved water become finer, and the amount of microbubbles increases. Therefore, a large amount of microbubbles can be generated.

[0052] Furthermore, as shown in Figure 6, for each of the six blades 56 in the swirling flow generation unit 50, the outflow end 60 of one of the six blades 56 (an example of the "end on the swirling direction side") is positioned counterclockwise (an example of the "reverse swirling direction") than the inflow end 62 of the adjacent blade 56 (an example of the "end on the reverse swirling direction side") in the clockwise direction. When the swirling flow generation unit 50 is viewed in the direction of the central axis A, the swirling flow generation unit 50 is provided with six first openings 64 (thick lines in Figure 6). When the swirling flow generation unit 50 is viewed in the direction of the central axis A, each of the six first openings 64 is surrounded by the outflow end 60 of one blade 56, the inflow end 62 of the adjacent blade 56, the shaft 52, and the outer circumference 54. As shown in Figure 9, when the second microbubble generation unit 22 is viewed in the direction of the central axis A, each of the six blades 56 of the second swirling flow generation unit 50 (an example of a "downstream swirling flow generation unit") among the four swirling flow generation units 50 is positioned to overlap at least a portion of the corresponding first opening 64 of the six first openings 64 of the first swirling flow generation unit 50 (an example of an "upstream swirling flow generation unit"). With this configuration, compared to a configuration in which each of the six blades 56 of the second swirling flow generation unit 50 does not overlap with the corresponding first opening 64 of the six first openings 64 of the first swirling flow generation unit 50, the amount of air-dissolved water that flows out of the first swirling flow generation unit 50 and passes through the second swirling flow generation unit 50 without passing through the blades 56 of the second swirling flow generation unit 50 can be reduced. In other words, the amount of air-dissolved water reaching the blade portion 56 of the second swirling flow generation unit 50 can be increased. Therefore, the amount of air-dissolved water flowing as a swirling flow can be increased. Consequently, a larger quantity of fine bubbles can be generated.

[0053] In particular, in this embodiment, when the second microbubble generation unit 22 is viewed in the direction of the central axis A, each of the six blades 56 of the second swirling flow generation unit 50 is arranged to overlap the entirety of the corresponding first opening 64 of the six first openings 64 of the first swirling flow generation unit 50. With this configuration, a large amount of air-dissolved water flowing out from the first swirling flow generation unit 50 flows into the blades 56 of the second swirling flow generation unit 50. Therefore, the amount of air-dissolved water flowing as a swirling flow can be increased. Consequently, a larger quantity of microbubbles can be generated.

[0054] Furthermore, as shown in Figure 8, the first microbubble generation unit 20 is equipped with six outer venturi sections 36 arranged around the central axis A. The number of outer venturi sections 36 (i.e., 6) is the same as the number of blade sections 56 (i.e., 6) of the first swirling flow generation unit 50 (an example of the "upstreamest swirling flow generation unit"). The downstream end of each of the six enlarged flow channels 40 of the six outer venturi sections 36 faces the corresponding blade section 56 of the six blade sections 56 of the first swirling flow generation unit 50. With this configuration, much of the air-dissolved water flowing out of the first microbubble generation unit 20 flows into the blade section 56 of the first swirling flow generation unit 50. Therefore, the amount of air-dissolved water flowing as a swirling flow can be increased. Consequently, a larger quantity of microbubbles can be generated.

[0055] Furthermore, as shown in Figure 8, the first microbubble generation unit 20 is further equipped with an inner venturi section 34 extending along the central axis A. The downstream end of the enlarged diameter channel 40 of the inner venturi section 34 faces the shaft 52 of the first swirling flow generation unit 50. The opening area at the downstream end of the enlarged diameter channel 40 of the inner venturi section 34 is smaller than the area of ​​the shaft 52 of the first swirling flow generation unit 50 when viewed in the direction of the central axis A. With this configuration, compared to a configuration in which the opening area at the downstream end of the enlarged diameter channel 40 of the inner venturi section 34 is larger than the area of ​​the shaft 52 of the first swirling flow generation unit 50, a large portion of the air-dissolved water flowing out of the inner venturi section 34 can collide with the shaft 52 of the first swirling flow generation unit 50. When the air-dissolved water collides with the shaft 52, the microbubbles in the air-dissolved water split, becoming finer bubbles, and the amount of microbubbles increases. Therefore, a larger quantity of microbubbles can be generated. Furthermore, compared to a configuration where the opening area at the downstream end of the enlarged diameter channel 40 of the inner venturi section 34 is larger than the area of ​​the shaft 52 of the first swirling flow generation section 50 when viewed in the direction of the central axis A, the amount of air-dissolved water flowing out of the first swirling flow generation section 50 by passing through the first opening 64 without colliding with the shaft 52 of the first swirling flow generation section 50 can be reduced. In other words, the amount of air-dissolved water colliding with the shaft 52 of the first swirling flow generation section 50 can be increased. Therefore, a larger quantity of microbubbles can be generated.

[0056] Furthermore, as shown in Figure 8, the opening area at the downstream end of the enlarged diameter flow path 40 of the inner venturi section 34 is smaller than the outer area of ​​the upstream end 52a of the shaft 52 of the first swirling flow generation section 50 when viewed in the direction of the central axis A. A portion of the air-dissolved water flowing out from the inner venturi section 34 can flow outward from the shaft 52 of the first swirling flow generation section 50. With the above configuration, the amount of air-dissolved water that collides with the shaft 52 (specifically, the upstream end 52a) of the first swirling flow generation section 50 can be increased. Therefore, a larger amount of fine bubbles can be generated.

[0057] Furthermore, as shown in Figure 6, the upstream surfaces of the six blade sections 56 are provided with projections 58 that protrude upstream. With this configuration, the air-dissolved water flowing through the six blade sections 56 collides with the projections 58. When the air-dissolved water collides with the projections 58, the microbubbles in the air-dissolved water split, becoming even finer bubbles, and the amount of microbubbles increases. Therefore, a larger quantity of microbubbles can be generated.

[0058] Furthermore, as shown in Figure 8, the downstream end of each of the six outer venturi sections 36's enlarged flow channels 40 faces a projection 58 provided on the corresponding blade section 56 of the six blade sections 56 of the first swirling flow generation section 50. With this configuration, the air-dissolved water flowing out from the outer venturi section 36 can be reliably brought into contact with the projection 58. Therefore, a larger quantity of fine bubbles can be generated.

[0059] (Second example) Referring to Figure 10, the microbubble generator 2 of the second embodiment will be described. In the following, components common to both embodiments will be denoted by the same reference numerals, and their descriptions will be omitted.

[0060] The structure of the four swirling flow generation units 150 in the microbubble generator 2 of this embodiment differs from the structure of the four swirling flow generation units 50 (see Figure 2) of the first embodiment. In particular, the structure of the shaft portion 152 differs from the structure of the shaft portion 52 (see Figure 2) of the first embodiment. The upstream end 152a of the shaft portion 152 is provided with a recess 152b that is recessed on the downstream side. The recess 152b has a shape corresponding to a cylindrical shape. The diameter of the recess 152b is approximately the same as the flow path diameter at the downstream end of the inner venturi portion 34. In the modified example, the diameter of the recess 152b may be larger or smaller than the flow path diameter at the downstream end of the inner venturi portion 34.

[0061] As described above, as shown in Figure 10, the upstream end 152a of the shaft portion 152 of the first swirling flow generation unit 150 is provided with a recess 152b that is recessed on the downstream side. With this configuration, the air-dissolved water flowing out from the inner venturi portion 34 collides with the recess 152b. The air-dissolved water that collides with the recess 152b then flows towards the inner venturi portion 34. In this case, the air-dissolved water flowing out from the inner venturi portion 34 collides with the air-dissolved water that collides with the recess 152b and flows towards the inner venturi portion 34. As the air-dissolved water collides with each other, the microbubbles in the air-dissolved water split, becoming finer bubbles and increasing the amount of microbubbles. Therefore, a larger amount of microbubbles can be generated.

[0062] (Third embodiment) Referring to Figure 11, the microbubble generator 2 of the third embodiment will be described. The structure of the four swirling flow generation units 250 of the microbubble generator 2 of this embodiment differs from the structure of the four swirling flow generation units 150 (see Figure 10) of the second embodiment. In particular, the structure of the shaft portion 252 differs from the structure of the shaft portion 252 (see Figure 10) of the second embodiment. The upstream end 252a of the shaft portion 252 is provided with a recess 252b that is indented on the downstream side. The recess 252b has a shape corresponding to a hemispherical shape. With this configuration, similar to the configuration of the second embodiment, a larger amount of microbubbles can be generated by the collision of air-dissolved water with each other. Furthermore, compared to the configuration of the second embodiment, it is possible to suppress the stagnation of air-dissolved water passing through the recess 252b.

[0063] (Fourth embodiment) Referring to Figures 12 to 17, the microbubble generator 2 of the fourth embodiment will be described. The structure of the four swirling flow generation units 350 of the microbubble generator 2 of this embodiment differs from the structure of the four swirling flow generation units 50 (see Figure 2) of the first embodiment.

[0064] As shown in Figure 12, the swirling flow generation unit 350 comprises a shaft portion 352, an outer peripheral portion 354 surrounding the shaft portion 352, and six blade portions 356. The shaft portion 352 has a cylindrical shape. The outer peripheral portion 354 has a cylindrical shape. As shown in Figure 13, the outer diameter of the outer peripheral portion 354 is the same as the inner diameter of the main body case 10. The shaft portion 352 and the outer peripheral portion 354 are provided along the central axis A. The blade portions 356 connect the outer wall of the shaft portion 352 and the inner wall of the outer peripheral portion 354. The blade portions 356 are inclined downstream as they are directed clockwise. As shown in Figure 12, the blade portions 356 have an outflow end 360 on the clockwise side and an inflow end 362 on the counterclockwise side. When the swirling flow generation unit 350 is viewed in the direction of the central axis A, it is provided with six first openings 363 (thick lines in Figure 12). Each of the six first openings 363 is surrounded by the outflow end 360 of one of the six blades 356, the inflow end 362 of the blade adjacent to the said blade in a clockwise direction, the shaft 352, and the outer circumference 354. As shown in Figure 14, six second openings 364 are provided at the downstream end of the swirling flow generation unit 350. As shown by the thick lines in Figure 15, each of the six second openings 364 is surrounded by the outflow-side end 360 of one of the six blades 356, the outflow-side end 360 of the blade adjacent to that blade in a clockwise direction, the shaft 352, and the outer circumference 354.

[0065] As shown in Figure 16, the first swirling flow generation unit 350 (i.e., the upstreammost swirling flow generation unit 350) is positioned so that the downstream end of each of the six outer venturi sections 36's enlarged flow channels 40 is facing the inlet end 362 of the corresponding blade section 356 among the multiple blade sections 356 of the first swirling flow generation unit 350. Furthermore, the first swirling flow generation unit 350 is positioned so that the downstream end of the enlarged flow channel 40 of the inner venturi section 34 is facing the shaft section 352 of the first swirling flow generation unit 350. The opening area of ​​the downstream end of the enlarged flow channel 40 of the inner venturi section 34 is smaller than the outer area of ​​the upstream end 352a of the shaft section 352 of the first swirling flow generation unit 350 when viewed in the direction of the central axis A.

[0066] Referring to Figures 17 and 18, the relationship between two adjacent swirling flow generators 350 in the direction of the central axis A will be explained. Figures 17 and 18 show the first swirling flow generator 350 and the second swirling flow generator 350. In Figures 17 and 18, for ease of understanding, the six blades 356 of the second swirling flow generator 350 are shown in gray. As shown in Figure 17, when the swirling flow generator 350 is viewed in the direction of the central axis A, a portion of each of the six blades 356 of the second swirling flow generator 350 (specifically, a portion of the inlet end 362) is positioned to overlap the corresponding first opening 363 of the six first openings 363 of the first swirling flow generator 350. In other words, when the swirling flow generation unit 350 is viewed in the direction of the central axis A, the blade portion 356 of the second swirling flow generation unit 350 and the blade portion 356 of the first swirling flow generation unit 350 do not completely overlap. As shown in Figure 18, when the swirling flow generation unit 350 is viewed in the direction of the central axis A, the inlet end portion 362 of each of the multiple blade portions 356 of the second swirling flow generation unit 350 is positioned near the center in the clockwise direction of the corresponding second opening 364 (thick line portion in Figure 18) of the multiple second openings 364 of the first swirling flow generation unit 350. In other words, when the second swirling flow generating unit 350 is viewed in the direction of the central axis A, the inlet end 362 of each of the multiple blades 356 of the second swirling flow generating unit 350 is positioned near the central part in the clockwise direction between the outlet end 360 of one of the multiple blades 356 of the first swirling flow generating unit 350 and the outlet end 360 of the blade adjacent to that blade 356.

[0067] Next, the microbubbles generated by the microbubble generator 2 of this embodiment will be described. The flow of air-dissolved water passing through the first microbubble generation unit 20 is the same as in the first embodiment. Therefore, the flow of air-dissolved water passing through the second microbubble generation unit 22 of this embodiment will be described below.

[0068] As shown in Figure 13, the air-dissolved water flowing out from the first microbubble generation unit 20 flows into the first swirling flow generation unit 350, which is located at the uppermost upstream side of the second microbubble generation unit 22. As shown in Figure 16, the air-dissolved water flowing out from the inner venturi section 34 of the first microbubble generation unit 20 collides with the upstream end 352a of the shaft section 352 of the first swirling flow generation unit 350. This causes the microbubbles in the air-dissolved water to split, becoming finer bubbles and increasing the amount of microbubbles. In addition, the air-dissolved water flowing out from the outer venturi section 36 of the first microbubble generation unit 20 flows towards the inlet end 362 of the blade section 356 of the first swirling flow generation unit 350. A portion of the air-dissolved water flowing out from the outer venturi section 36 collides with the inlet end 362 of the blade section 356 of the first swirling flow generation unit 350. As a result, the microbubbles in the air-dissolved water split, becoming even finer, and the quantity of microbubbles increases. Also, as a portion of the air-dissolved water flowing out from the outer venturi section 36 passes near the inlet end 362 of the blade section 356 of the first swirling flow generation section 350, the microbubbles in the air-dissolved water are sheared. As a result, the microbubbles in the air-dissolved water become even finer, and the quantity of microbubbles increases. Then, a portion of the air-dissolved water passes through the blade section 356 of the first swirling flow generation section 350. As the air-dissolved water passes through the blade section 356, it becomes a swirling flow that flows in a clockwise direction. The microbubbles in the air-dissolved water become even finer, and the quantity of microbubbles increases, due to the shearing force caused by the swirling flow. Next, the air-dissolved water flowing out from the first swirling flow generation section 350 flows into the second swirling flow generation section 350. As shown in Figure 18, a portion of the air-dissolved water flowing out from the outlet end 360 of the blade 356 of the first swirling flow generation unit 350 collides with the inlet end 362 of the blade 356 of the second swirling flow generation unit 350. This causes the microbubbles in the air-dissolved water to split, becoming finer bubbles and increasing the quantity of microbubbles. Additionally, as a portion of the air-dissolved water flowing out from the outlet end 360 of the blade 356 of the first swirling flow generation unit 350 passes near the inlet end 362 of the blade 356 of the second swirling flow generation unit 350, the microbubbles in the air-dissolved water are sheared. This causes the microbubbles in the air-dissolved water to become even finer bubbles and increases the quantity of microbubbles.Then, a portion of the air-dissolved water passes through the blade portion 356 of the second swirling flow generation unit 350. After that, the air-dissolved water passes through the third swirling flow generation unit 350 and the fourth swirling flow generation unit 350, which are located downstream of the second swirling flow generation unit 350. As the air-dissolved water passes through a total of four swirling flow generation units 350, the microbubbles in the air-dissolved water are refined, and a large number of microbubbles are generated. Then, as shown in Figure 13, the air-dissolved water flowing in from the second microbubble generation unit 22 flows out to the outside from the outlet 14a.

[0069] As described above, as shown in Figure 15, six second openings 364 are provided at the downstream end of the swirling flow generation unit 350. Each of the six second openings 364 is surrounded by the outflow end 360 of one of the six blades 356, the outflow end 360 of the blade adjacent to the said blade, the shaft 352, and the outer circumference 354. As shown in Figure 18, when the second microbubble generation unit 22 is viewed in the direction of the central axis A, the inflow end 362 of each of the multiple blades 356 of the second swirling flow generation unit 350 is located near the center of the corresponding second opening 364 in the clockwise direction. With this configuration, a portion of the air-dissolved water flowing out of the first swirling flow generation unit 350 collides with the inlet end 362 of the blade portion 356 of the second swirling flow generation unit 350. When the air-dissolved water collides with the inlet end 362 of the blade portion 356 of the second swirling flow generation unit 350, the microbubbles in the air-dissolved water split, becoming finer bubbles and increasing the quantity of microbubbles. In addition, a portion of the air-dissolved water flowing out of the first swirling flow generation unit 350 is sheared as it passes through the inlet end 362 of the blade portion 356 of the second swirling flow generation unit 350. When the air-dissolved water is sheared, the microbubbles in the air-dissolved water become finer bubbles and the quantity of microbubbles increases. Therefore, a larger quantity of microbubbles can be generated.

[0070] Furthermore, as shown in Figure 16, the first microbubble generation unit 20 is equipped with six outer venturi sections 36 arranged around the central axis A. The number of outer venturi sections 36 (i.e., 6) is the same as the number of blade sections 356 (i.e., 6) of the first swirling flow generation unit 350 (an example of the "upstreamest swirling flow generation unit"). The downstream end of the widened flow channel 40 of each of the six outer venturi sections 36 faces the inlet end 362 of the corresponding blade section 356 of the six blade sections 356 of the first swirling flow generation unit 350. With the above configuration, a portion of the air-dissolved water flowing out of the first microbubble generation unit 20 collides with the inlet end 362 of the blade section 356 of the first swirling flow generation unit 350. When the air-dissolved water collides with the inlet end 362 of the blade portion 356 of the first swirling flow generation unit 350, the microbubbles in the air-dissolved water split, becoming finer bubbles and increasing in quantity. In addition, a portion of the air-dissolved water flowing out from the first microbubble generation unit 20 is sheared as it passes through the inlet end 362 of the blade portion 356 of the first swirling flow generation unit 350. When the air-dissolved water is sheared, the microbubbles in the air-dissolved water become even finer bubbles and increase in quantity. Therefore, a larger quantity of microbubbles can be generated.

[0071] The following describes useful embodiments utilizing the microbubble generator 2 of the first to fourth embodiments.

[0072] (First embodiment; configuration of a hot water supply system 402 using a microbubble generator 2) The hot water supply system 402 shown in Figure 19 can heat water supplied from a water source 404, such as a public water supply, and supply water heated to a desired temperature to faucets 406 installed in the kitchen, etc., or to a bathtub 408 located in the bathroom. The hot water supply system 402 can also reheat the water in the bathtub 408.

[0073] The hot water supply system 402 comprises a first heat source unit 410, a second heat source unit 412, and a combustion chamber 414. The first heat source unit 410 is used for supplying hot water to the faucet 406 and for filling the bathtub 408. The second heat source unit 412 is used for reheating the bathtub 408. The interior of the combustion chamber 414 is divided into a first combustion chamber 418 and a second combustion chamber 420 by a partition wall 416. The first heat source unit 410 is housed in the first combustion chamber 418, and the second heat source unit 412 is housed in the second combustion chamber 420.

[0074] The first heat source unit 410 includes a first burner 422 and a first heat exchanger 424. The second heat source unit 412 includes a second burner 426 and a second heat exchanger 428.

[0075] The upstream end of the first heat exchanger 424 of the first heat source unit 410 is connected to the downstream end of the water supply channel 430. Water is supplied to the upstream end of the water supply channel 430 from the water source 404. The downstream end of the first heat exchanger 424 is connected to the upstream end of the hot water supply channel 432. The water supply channel 430 and the hot water supply channel 432 are connected by a bypass channel 434. A bypass servo 436 is provided at the connection point between the water supply channel 430 and the bypass channel 434. The bypass servo 436 adjusts the ratio of the flow rate of water sent from the water supply channel 430 to the first heat source unit 410 and the flow rate of water sent from the water supply channel 430 to the bypass channel 434. At the connection point between the bypass channel 434 and the hot water supply channel 432, the low-temperature water passing through the water supply channel 430 and the bypass channel 434 is mixed with the high-temperature water passing through the water supply channel 430, the first heat source unit 410, and the hot water supply channel 432. Upstream of the bypass servo 436, the water supply channel 430 is equipped with a water flow sensor 438 and a water flow servo 440. The water flow sensor 438 detects the flow rate of water flowing through the water supply channel 430. The water flow servo 440 adjusts the flow rate of water flowing through the water supply channel 430. Upstream of the connection point with the bypass channel 434, the hot water supply channel 432 is equipped with a heat exchanger outlet thermistor 442.

[0076] The upstream end of the hot water supply channel 450 is connected to the hot water supply channel 432 downstream of the connection point of the bypass channel 434. A hot water thermistor 444 is provided at the connection point between the hot water supply channel 432 and the hot water supply channel 450. A microbubble generator 2 is provided between the connection point between the hot water supply channel 432 and the bypass channel 434, and the connection point between the hot water supply channel 432 and the hot water supply channel 450. In the following, the water channel of the hot water supply channel 432 upstream of the microbubble generator 2 may be referred to as the first hot water supply channel 432a, and the water channel of the hot water supply channel 432 downstream of the microbubble generator 2 may be referred to as the second hot water supply channel 432b.

[0077] The downstream end of the hot water supply path 450 is connected to the upstream end of the reheating supply path 460 and the downstream end of the first bathtub circulation path 462. The downstream end of the reheating supply path 460 is connected to the upstream end of the second heat exchanger 428. The upstream end of the first bathtub circulation path 462 is connected to the bathtub 408. The hot water supply path 450 is equipped with a hot water supply control valve 452 and a check valve 454. The hot water supply control valve 452 opens and closes the hot water supply path 450. The check valve 454 allows water to flow from the upstream side to the downstream side of the hot water supply path 450 and prohibits water to flow from the downstream side to the upstream side of the hot water supply path 450. A bathtub return thermistor 464 is provided at the connection point of the hot water supply path 450, the reheating supply path 460, and the first bathtub circulation path 462. A circulation pump 466 is provided in the reheating supply line 460.

[0078] The downstream end of the second heat exchanger 428 of the second heat source unit 412 is connected to the upstream end of the second bathtub circulation path 468. The downstream end of the second bathtub circulation path 468 is connected to the bathtub 408. The second bathtub circulation path 468 is provided with a bathtub supply thermistor 470.

[0079] When the hot water supply system 402 supplies hot water to the faucet 406, the hot water filling control valve 452 is closed and the first burner 422 of the first heat source unit 410 burns. In this case, the water supplied from the water source 404 to the water supply channel 430 is heated by heat exchange in the first heat exchanger 424 and then supplied to the faucet 406 from the hot water supply channel 432. By adjusting the combustion rate of the first burner 422 of the first heat source unit 410 and the opening degree of the bypass servo 436, the temperature of the water flowing through the hot water supply channel 432 can be adjusted to a desired temperature. As described above, the microbubble generator 2 is provided in the hot water supply channel 432. The water supplied from the water source 404 contains dissolved air (oxygen, carbon dioxide, nitrogen, etc.). Therefore, the water that passes through the microbubble generator 2 and is supplied to the faucet 406 contains many microbubbles.

[0080] When the hot water supply system 402 fills the bathtub 408 with hot water, the hot water filling control valve 452 is open and the first burner 422 of the first heat source unit 410 burns. In this case, the water supplied from the water source 404 to the water supply channel 430 is heated by heat exchange in the first heat exchanger 424 and then flows from the hot water supply channel 432 into the hot water filling channel 450. At this time, the water temperature is adjusted to the desired temperature by adjusting the combustion amount of the first burner 422 of the first heat source unit 410 and the opening degree of the bypass servo 436. The water that flows into the hot water filling channel 450 flows into the bathtub 408 via the first bathtub circulation channel 462, and also flows into the bathtub 408 via the reheating supply channel 460 and the second bathtub circulation channel 468. Because the microbubble generator 2 is installed in the hot water supply channel 432 (specifically, the first hot water supply channel 432a), the water supplied to the bathtub 408 contains many microbubbles.

[0081] When the hot water supply system 402 reheats the bathtub 408, the circulation pump 466 is driven with the hot water filling control valve 452 closed, and the second burner 426 of the second heat source unit 412 burns. In this case, the water from the bathtub 408 flows into the first bathtub circulation path 462, passes through the reheating supply path 460, and is sent to the second heat source unit 412. The water sent to the second heat source unit 412 is heated by heat exchange in the second heat exchanger 428, and then flows into the second bathtub circulation path 468. At this time, the water temperature is adjusted to the desired temperature by adjusting the combustion amount of the second burner 426 of the second heat source unit 412. The water that flows into the second bathtub circulation path 468 is returned to the bathtub 408.

[0082] As described above, as shown in Figure 19, the hot water supply system 402 (an example of a "water heater") is equipped with a microbubble generator 2. With this configuration, water that has passed through the microbubble generator 2 (an example of "water with dissolved gas") is supplied to the faucet 406 and the bathtub 408. In other words, water containing many microbubbles can be supplied to the faucet 406 and the bathtub 408. The inclusion of many microbubbles in the water improves the cleaning power when the user washes their body. Therefore, the convenience of the user using the hot water supply system 402 can be improved.

[0083] (Second embodiment; configuration of dishwasher 510 using microbubble generator 2) Figure 20 is a vertical cross-sectional view of the dishwasher 510. The dishwasher 510 is a drawer-type dishwasher. The dishwasher 510 comprises a main body 512, a washing tub 514, a door 515, and a controller 560.

[0084] The door 515 is provided with an operation panel 516 and an exhaust path 518. The operation panel 516 is equipped with various buttons such as a start button and lights. The exhaust path 518 extends from the inside to the outside of the washing tank 514.

[0085] The cleaning tank 514 is housed in the space formed by the main body 512 and the door 515. The cleaning tank 514 is slidably supported by the main body 512. The cleaning tank 514 is connected to the door 515. The cleaning tank 514 is formed in the shape of a box with an open top. A lid 556 is positioned above the cleaning tank 514. The lid 556 is connected to the cleaning tank 514 by a lifting mechanism (not shown).

[0086] The washing tank 514 houses a washing nozzle 520, a dish basket 561 for holding various dishes 519, a food residue filter 517, a heater 530, a thermistor 555, and the like. The washing nozzle 520 consists of a tower nozzle section 523 comprising an upper nozzle 521 and a lower nozzle 522, and a horizontal nozzle section 524. The washing nozzle 520 has multiple spray ports 521a, 522a, and 524a. An electric heater 530 for heating the washing water and the air inside the washing tank 514 is mounted near the bottom surface 539 of the washing tank 514. A thermistor 555 is mounted on the bottom surface 539 of the washing tank 514.

[0087] A water level detection unit 545 for detecting the water level inside the cleaning tank 514 is provided at the lower front outer part of the cleaning tank 514. The water level when cleaning water is supplied to the cleaning tank 514 normally (hereinafter referred to as "cleaning water level") is indicated by the dashed line of reference numeral 554. A pump 527 is provided below the bottom surface 539 of the cleaning tank 514. The pump 527 rotates an impeller 528 with a built-in electric motor. A cleaning nozzle 520 is rotatably mounted on the bottom surface 539 of the cleaning tank 514. The cleaning nozzle 520 and the first discharge port 511 of the pump 527 are in communication.

[0088] A suction recess 531 is formed at the bottom of the washing tank 514. The upper opening of the suction recess 531 is covered by a food residue filter 517. The water level detection unit 545 and the suction recess 531 are connected by a water level path 550. The pump 527 and the suction recess 531 are connected by a first suction passage 532. One end of a second suction passage 574 is connected to the first suction passage 532. The other end of the second suction passage 574 is connected to an opening 572 in the rear wall 551 of the washing tank 514. A flow path switching valve 576 is installed at the connection between the first suction passage 532 and the second suction passage 574.

[0089] A drying fan 552 is mounted on the outside of the rear wall 551 of the washing tank 514. The drying fan 552 rotates a fan 553 with its built-in motor. The drying fan 552 and the inside of the washing tank 514 are connected by a drying path 563. The drying fan 552 is positioned higher than the washing water level 554.

[0090] A drain hose 534 is connected to the rear wall 533 of the main body 512. The drain hose 534 and the second discharge port 535 of the pump 527 are connected by a drain passage 536. The middle of the drain passage 536 and the inside of the cleaning tank 514 are connected by an air vent passage 537. A drain check valve 538 is installed near the point where the drain passage 536 is connected to the drain hose 534.

[0091] A water supply hose 540 is connected to a stepped section horizontally formed in the middle of the rear wall 533 of the main body 512. Water supplied directly from a water source (not shown), such as a public water supply, or heated hot water may be supplied to the water supply hose 540. A water supply valve 541 is installed on the inside of the rear wall 533. The inlet 544 of the water supply valve 541 and the water supply hose 540 are connected by a first water supply channel 542. The outlet 564 of the water supply valve 541 and the inside of the washing tank 514 are connected by a second water supply channel 543. A microbubble generator 2 is installed in the middle of the second water supply channel 543.

[0092] The controller 560 is equipped with a CPU, ROM, RAM, etc., and controls the operation of the dishwasher 510. By controlling the operation of the dishwasher 510, the controller 560 performs a washing operation to wash the dishes 519 in the washing tank 514.

[0093] (Washing operation) When the controller 560 receives a command from the user to start the dishwashing operation via the control panel 516, it sequentially executes the washing, rinsing, and drying processes.

[0094] During the cleaning process, the controller 560 opens the water supply valve 541 to supply cleaning water from the water supply hose 540 to the cleaning tank 514. When the controller 560 determines that the required amount of cleaning water has been supplied to the cleaning tank 514 during the cleaning process, it closes the water supply valve 541. Next, the controller 560 drives the pump 527 to rotate the impeller 528 in the forward direction and turns on the heater 530. The cleaning water is drawn into the pump 527 from the suction recess 531. The cleaning water drawn into the pump 527 is sent to the cleaning nozzle 520 and forcefully ejected from the nozzles 521a, 522a, and 524a. The controller 560 terminates the cleaning process after a first predetermined time (for example, 5 minutes) has elapsed since the start of the cleaning process. The controller 560 also drives the pump 527 to rotate the impeller 528 in the reverse direction to drain the cleaning water from the cleaning tank 514. As described above, a microbubble generator 2 is installed in the middle of the second water supply channel 543. The water supplied from the water supply hose 540 contains dissolved air (oxygen, carbon dioxide, nitrogen, etc.). Therefore, the water supplied to the washing tank 514 after passing through the microbubble generator 2 contains many microbubbles. Dirt components attached to the dishes 519 are adsorbed onto the surface of the microbubbles contained in the washing water. By containing many microbubbles in the washing water, more dirt components can be adsorbed.

[0095] During the rinsing process, the controller 560 opens the water supply valve 541 to supply washing water from the water supply hose 540 to the washing tank 514. Once the required amount of washing water has been supplied to the washing tank 514, the controller 560 closes the water supply valve 541. The controller 560 drives the pump 527 to rotate the impeller 528 in the forward direction. This causes the washing water in the washing tank 514 to be sprayed from the washing nozzle 520 onto the dishes 519 contained in the dish basket 561, rinsing the dishes 519. The controller 560 terminates the rinsing process after a second predetermined time (for example, 5 minutes) has elapsed since the start of the rinsing process. The controller 560 also drives the pump 527 to rotate the impeller 528 in the reverse direction, thereby draining the washing water from the washing tank 514.

[0096] In the drying process, the controller 560 heats the air in the washing tank 514 with the heater 530 to dry the dishes 519. When the elapsed time since the start of drying the dishes 519 reaches a third predetermined time, the controller 560 terminates the heating by the heater 530 and ends the drying process.

[0097] As described above, as shown in Figure 20, the dishwasher 510 is equipped with a microbubble generator 2. With this configuration, the washing water (an example of "gas-dissolved water") that has passed through the microbubble generator 2 is supplied to the washing tank 514. That is, washing water containing many microbubbles can be supplied to the washing tank 514. The inclusion of many microbubbles in the washing water improves the washing power when washing dishes 519. Therefore, the convenience of the user using the dishwasher 510 can be improved.

[0098] The following describes the microbubble generator 2 according to the 5th to 7th embodiments.

[0099] (Fifth example) Referring to Figures 21 to 27, the microbubble generator 2 of the fifth embodiment will be described. The structure of the microbubble generator 2 of this embodiment differs from that of the microbubble generator 2 of the fourth embodiment (see Figure 13) in the main body case 610, the inlet 612, the first microbubble generation section 620, and the second microbubble generation section 622.

[0100] As shown in Figure 21, the inner wall 612b at the downstream end of the inlet 612 widens in diameter from upstream to downstream. The diameter D1 at the downstream end of the inlet 612 is larger than the diameter D2 of the circle formed by connecting the radially outer surfaces of the six outer venturi sections 36. With this configuration, the air-dissolved water flowing out of the inlet 612 can be distributed relatively evenly to the six outer venturi sections 36. In a modified example, the diameter D1 at the downstream end of the inlet 612 may be the same as the diameter D2 of the circle formed by connecting the radially outer surfaces of the six outer venturi sections 36.

[0101] As shown in Figure 22, the main body case 610 is provided with first to sixth protrusions 616a to 616f that project radially inward from the inner wall 610c of the main body case 610. As shown in Figure 21, the first to sixth protrusions 616a to 616f are located at the boundary between the first microbubble generating section 620 and the second microbubble generating section 622 in the direction of the central axis A. As shown in Figure 22, the first to sixth protrusions 616a to 616f are arranged along the circumferential direction. The circumferential widths of the first protrusion 616a, the third protrusion 616c, the fourth protrusion 616d, and the sixth protrusion 616f are smaller than the circumferential widths of the second protrusion 616b and the fifth protrusion 616e. A first positioning groove 618a is formed between the first protrusion 616a and the second protrusion 616b, between the second protrusion 616b and the third protrusion 616c, between the fourth protrusion 616d and the fifth protrusion 616e, and between the fifth protrusion 616e and the sixth protrusion 616f. A second positioning groove 618b is formed between the first protrusion 616a and the sixth protrusion 616f, and between the third protrusion 616c and the fourth protrusion 616d. The circumferential width of the first positioning groove 618a is smaller than the circumferential width of the second positioning groove 618b.

[0102] As shown in Figure 23, the downstream end of the first microbubble generation section 620 is provided with four positioning protrusions 620a that project downstream. The four positioning protrusions 620a are positioned to correspond to the four first positioning grooves 618a (see Figure 22) of the main body case 610, and have a shape that corresponds to the four first positioning grooves 618a.

[0103] As shown in Figure 24, the swirling flow generation unit 650 comprises a shaft portion 352, an outer peripheral portion 354 surrounding the shaft portion 352, and six blade portions 356. The upstream end of the outer peripheral portion 354 is provided with two upstream protrusions 654a that project upstream. The two upstream protrusions 654a are positioned to correspond to two second positioning grooves 618b (see Figure 22) of the main body case 610, and have a shape corresponding to the two second positioning grooves 618b. As shown in Figure 25, the downstream end of the outer peripheral portion 354 is provided with two downstream recesses 654b that recess upstream. The two downstream recesses 654b are positioned to correspond to the two upstream protrusions 654a, and have a shape corresponding to the two upstream protrusions 654a. In other words, the upstream protrusion 654a (see Figure 24) has a shape that corresponds to both the downstream recess 654b and the second positioning groove 618b of the main body case 610 (see Figure 22).

[0104] As shown in Figure 26, the four positioning protrusions 620a of the first microbubble generating unit 620 are fitted into the four first positioning grooves 618a of the main body case 10. That is, the first positioning grooves 618a and positioning protrusions 620a are a mechanism for positioning the first microbubble generating unit 620 relative to the main body case 610 in the direction of the central axis A and in the circumferential direction. The two upstream protrusions 654a of the second microbubble generating unit 622 (specifically, the uppermost swirling flow generating unit 650) are fitted into the two second positioning grooves 618b of the main body case 10. That is, the second positioning grooves 618b and upstream protrusions 654a are a mechanism for positioning the second microbubble generating unit 622 (specifically, the uppermost swirling flow generating unit 650) relative to the main body case 610 in the direction of the central axis A and in the circumferential direction. Furthermore, as shown in Figure 27, the upstream protrusion 654a of the downstream swirling flow generation unit 650 of the two adjacent swirling flow generation units 650 in the direction of the central axis A fits into the downstream recess 654b of the upstream swirling flow generation unit 650. In other words, the upstream protrusion 654a and the downstream recess 654b are a mechanism for positioning the two adjacent swirling flow generation units 650 in the direction of the central axis A and in the circumferential direction.

[0105] As described above, as shown in Figure 21, the microbubble generator 2 includes a main body case 610 that houses a first microbubble generation unit 620 and a second microbubble generation unit 622. As shown in Figure 26, the main body case 610 includes a first positioning groove 618a (an example of the "first positioning unit") for positioning the first microbubble generation unit 620 relative to the main body case 610, and a second positioning groove 618b (an example of the "second positioning unit") for positioning the second microbubble generation unit 622 relative to the main body case 610. With this configuration, the first microbubble generation unit 620 and the main body case 610 are positioned by the first positioning groove 618a, and the second microbubble generation unit 622 and the main body case 610 are positioned by the second positioning groove 618b, thereby positioning the six outer venturi sections 36 of the first microbubble generation unit 620 and the six blade sections 356 of the uppermost swirling flow generation unit 650 of the second microbubble generation unit 622. As a result, much of the dissolved gas water flowing out from the first microbubble generation unit 620 can be made to collide with the inlet end 362 of the blade section 356 of the uppermost swirling flow generation unit 650, or to be sheared as it passes through the inlet end 362 of the blade section 356 of the uppermost swirling flow generation unit 650. Consequently, a larger quantity of microbubbles can be generated.

[0106] In one or more embodiments, as shown in Figure 27, each of the multiple swirling flow generating units 650 is provided with an upstream projection 654a at its upstream end that protrudes upstream, and a downstream recess 654b at its downstream end that recesses upstream. The upstream projection 654a has a shape corresponding to the second positioning groove 618b and the downstream recess 654b. With the above configuration, the main body case 610 and the uppermost swirling flow generating unit 650 can be positioned using the upstream projection 654a of the swirling flow generating unit 650, and two adjacent swirling flow generating units 650 in the direction of the central axis A can be positioned. In this case, it is not necessary to provide a structure different from the upstream projection 654a at the upstream end of the uppermost swirling flow generating unit 650 in order to position the main body case 610 and the uppermost swirling flow generating unit 650. Therefore, the structure of multiple swirling flow generating units 650 can be standardized.

[0107] (Sixth embodiment) Referring to Figures 28 and 29, the microbubble generator 2 of the sixth embodiment will be described. The microbubble generator 2 of this embodiment differs from the microbubble generator 2 of the first embodiment (see Figure 2) in the structure inside the main body case 10.

[0108] As shown in Figure 28, the second microbubble generation unit 722 is equipped with three swirling flow generation units 50. A flow rectifier 770 is provided in the flow path 760 between the second microbubble generation unit 722 and the outflow unit 14. The flow path 760 is defined by the main body case 10. The flow path axis of the flow path 760 coincides with the central axis A. As shown in Figure 29, the flow rectifier 770 is equipped with a shaft portion 772, an outer peripheral portion 774 surrounding the shaft portion 772, six first flow rectifier walls 776, and six second flow rectifier walls 778. As shown in Figure 28, the outer diameter of the outer peripheral portion 774 is the same as the inner diameter of the main body case 10. The shaft portion 772 and the outer peripheral portion 774 are provided along the central axis A. As shown in Figure 29, the first flow rectifier walls 776 and the second flow rectifier walls 778 extend radially inward from the inner wall of the outer peripheral portion 774. The first rectifier wall 776 and the second rectifier wall 778 have a flat plate shape along the radial direction and the direction of the central axis A. The radially inner end of the first rectifier wall 776 is connected to the shaft portion 772. The six first rectifier walls 776 are arranged at equal intervals along the circumferential direction of the central axis A. The radially inner end of the second rectifier wall 778 is located radially outward from the outer wall of the shaft portion 772. The second rectifier wall 778 is provided between two adjacent first rectifier walls 776 in the circumferential direction. In a modified example, two or more rectifiers 770 may be provided inside the main body case 10.

[0109] As described above, as shown in Figure 28, the microbubble generator 2 is installed between the second microbubble generation unit 722 and the outlet unit 14, and includes a flow straightener 770 that straightens the flow of air-dissolved water flowing out from the second microbubble generation unit 722 from a swirling flow flowing clockwise to a straight flow. The flow of air-dissolved water flowing out from the second microbubble generation unit 722 to the flow straightener 770 is a swirling flow (i.e., turbulent flow) flowing clockwise. When the flow of air-dissolved water is turbulent, compared to when the flow of air-dissolved water is a straight flow (i.e., laminar flow), the air-dissolved water is more likely to collide with the inner wall 14b (an example of a "wall") of the outlet unit 14 that defines the flow path of the air-dissolved water downstream of the flow straightener 770. Therefore, if the flow of air-dissolved water flowing out of the second microbubble generation unit 722 is not rectified from a swirling flow to a straight flow, a relatively large amount of air-dissolved water will collide with the inner wall 14b of the outlet unit 14. In this case, the pressure loss inside the microbubble generator 2 will increase, and the amount of air-dissolved water flowing inside the microbubble generator 2 will decrease. With the above configuration, the flow of air-dissolved water flowing out of the second microbubble generation unit 722 is rectified from a swirling flow to a straight flow by passing through the rectifier 770. Therefore, the amount of air-dissolved water colliding with the inner wall 14b of the outlet unit 14 can be reduced, and the pressure loss inside the microbubble generator 2 can be reduced. Consequently, the amount of air-dissolved water flowing through the microbubble generator 2 can be increased.

[0110] (Seventh Example) Referring to Figure 30, the microbubble generator 2 of the seventh embodiment will be described. The microbubble generator 2 of this embodiment differs from the microbubble generator 2 of the first embodiment (see Figure 2) in the structure of the outflow section 814 and the structure of the first microbubble generation section 820.

[0111] As shown in Figure 30, the outlet section 814 includes a first outlet channel 816 and a second outlet channel 818. The first outlet channel 816 is a channel that extends along the central axis A. The second outlet channel 818 is a channel that extends along the direction of the second central axis A2, which is perpendicular to the central axis A. Hereafter, the left and right directions in Figure 30 may be referred to as the "first upstream direction" and the "first downstream direction," respectively, and the downward and upward directions in Figure 30 may be referred to as the "second upstream direction" and the "second downstream direction," respectively.

[0112] The upstream end of the first outflow channel 816 is connected to the downstream end of the second microbubble generation section 22, and the downstream end of the first outflow channel 816 is connected to the upstream end of the second outflow channel 818. An outlet 818a is formed at the downstream end of the second outflow channel 818. A stepped portion 819 protruding in the first downstream direction is provided at the connection between the downstream end of the first outflow channel 816 and the upstream end of the second outflow channel 818. With the above configuration, the flow of air-dissolved water flowing from the first outflow channel 816 toward the second outflow channel 818 is obstructed by the stepped portion 819. As a result, the flow of air-dissolved water becomes turbulent near the inner wall 816a of the first outflow channel 816.

[0113] The first microbubble generating section 820 comprises a first main body section 830 and a second main body section 832. The outer wall 830a of the first main body section 830 is tapered in diameter from the first upstream direction to the first downstream direction. An upstream flange section 834 is provided at the first upstream end of the outer wall 830a of the first main body section 830. The upstream flange section 834 extends radially outward from the first upstream end of the outer wall 830a of the first main body section 830 and is formed over the entire circumferential direction. The outer circumferential surface of the upstream flange section 834 abuts against the inner wall 10c of the main body case 10. The upstream flange section 834 is provided with a first recess 834a having a shape that is recessed radially inward. The first recess 834a is provided in the central part of the upstream flange section 834 in the direction of the central axis A and is formed over the entire circumferential direction. The outer wall 832a of the second main body 832 widens in diameter from the first upstream direction to the first downstream direction. A downstream flange portion 836 is provided at the first downstream end of the outer wall 832a of the second main body 832. The downstream flange portion 836 extends radially outward from the first downstream end of the outer wall 832a of the second main body 832 and is formed over the entire circumferential direction. The outer circumferential surface of the downstream flange portion 836 abuts against the inner wall 10c of the main body case 10. The downstream flange portion 836 is provided with a second recess 836a having an inwardly recessed shape. The second recess 836a is provided in the central part of the downstream flange portion 836 in the direction of the central axis A and is formed over the entire circumferential direction. A sealing member 838 is arranged in the first recess 834a and the second recess 836a. A space S is formed between the inner wall 10c of the main body case 10 and the outer wall 830a of the first main body section 830 and the outer wall 832a of the second main body section 832.

[0114] If the first microbubble generation unit 820 does not have a sealing member 838, the air-dissolved water flowing from the inlet 12 into the first microbubble generation unit 820 may enter the space S, and water may accumulate in the space S. If the air-dissolved water accumulated in the space S freezes, its volume will increase, which may damage the main body case 10. With the above configuration, it is possible to suppress the intrusion of water into the space S. Therefore, it is possible to suppress damage to the main body case 10.

[0115] Although each embodiment has been described in detail above, these are merely illustrative examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples illustrated above.

[0116] (First modified example) The number of swirling flow generating units 50, 150, 250, and 350 in the second microbubble generating unit 22 is not limited to four, but may be two, three, or five or more.

[0117] (Second modified example) The number of blades 56, 356 in the swirling flow generating sections 50, 150, 250, and 350 is not limited to 6, but may be 2 to 5, or 7 or more.

[0118] (Third Modification) The blades 56 and 356 of the swirling flow generating sections 50, 150, 250, and 350 may be inclined downstream as they move in a counterclockwise direction. In this modification, the counterclockwise direction and the clockwise direction are examples of the "predetermined swirling direction" and the "reverse swirling direction," respectively.

[0119] (Fourth modified example) The number of outer venturi portions 36 of the first microbubble generation portion 20 may be greater than or less than the number of blade portions 56 of the swirling flow generation portion 50 of the second microbubble generation portion 22.

[0120] (Fifth Modification) In the first embodiment, when the swirling flow generation unit 50 is viewed in the direction of the central axis A, the six blades 56 of the second swirling flow generation unit 50 and the six blades 56 of the first swirling flow generation unit 50 may completely overlap. The same applies to the second to fourth embodiments.

[0121] (Sixth Modification) The first microbubble generating unit 20 may not have six outer venturi sections 36, but only an inner venturi section 34. In another modification, the first microbubble generating unit 20 may not have an inner venturi section 34, but only one or more outer venturi sections 36.

[0122] (Seventh Modification) In the direction of the central axis A, the downstream ends of the six outer venturi sections 36 of the first microbubble generation section 20 may face the first opening 64 of the first swirling flow generation section 50 of the second microbubble generation section 22. In this case, the six outer venturi sections 36 may be inclined with respect to the direction of the central axis A.

[0123] (Eighth Modification) The area of ​​the upstream end 52a of the shaft portion 52 of the first swirling flow generation portion 50 of the second microbubble generation portion 22 may be smaller than the opening area of ​​the downstream end of the inner venturi portion 34 of the first microbubble generation portion 20. In this modification, it is preferable that the area of ​​the shaft portion 52 of the swirling flow generation portion 50, when viewed in the direction of the central axis A, is larger than the opening area of ​​the downstream end of the inner venturi portion 34 of the first microbubble generation portion 20. For example, the upstream end of the shaft portion 52 may have a hemispherical shape. Also, the shaft portion 52 may increase in diameter from upstream to downstream.

[0124] (9th Modification) In the hot water supply system 402 of the first embodiment, the microbubble generator 2 may be provided in the water supply passage 430, the hot water filling passage 450, the reheating supply passage 460, the first bathtub circulation passage 462, or the second bathtub circulation passage 468.

[0125] (Tenth Modification) In the dishwasher 510 of the first embodiment, the microbubble generator 2 may be provided in the first suction channel 532 or the second suction channel 574.

[0126] (11th Modification) In the fifth embodiment, the upstream end of the swirling flow generation unit 650 is provided with an upstream recess that is recessed downstream, and the downstream end is provided with a downstream convex portion that protrudes downstream. The upstream recess has a shape corresponding to the downstream convex portion. In this modification, the main body case 10 may have an annular portion that protrudes radially inward from the inner wall 610c of the main body case 610, instead of the first protrusions 616a to the sixth protrusions 616f. The downstream surface of the annular portion may be provided with a protrusion that protrudes downstream and has a shape corresponding to the upstream recess (an example of the "second positioning portion"). Even with this configuration, it is not necessary to provide a structure different from the upstream recess at the upstream end of the uppermost swirling flow generation unit 650 in order to position the main body case 610 and the uppermost swirling flow generation unit 650. Therefore, the structure of multiple swirling flow generation units 650 can be standardized.

[0127] (12th Modification) In the 5th embodiment, the upstream convex portion 654a of the uppermost swirling flow generating portion 650 among the multiple swirling flow generating portions 650 has a shape corresponding to the second positioning groove 618b of the main body case 610, but it does not have to have a shape corresponding to the downstream concave portion 654b of the swirling flow generating portion 650.

[0128] (13th Modification) The main body case 10 of the first embodiment (see Figure 2) may include a first positioning part for positioning the first microbubble generation unit 20 relative to the main body case 10, and a second positioning part for positioning the second microbubble generation unit 22 relative to the main body case 10. With this configuration, the first positioning part positions the first microbubble generation unit 20 and the main body case 10, and the second positioning part positions the second microbubble generation unit 22 and the main body case 10, thereby positioning the six outer venturi parts 36 of the first microbubble generation unit 20 and the six blade parts 56 of the uppermost swirling flow generation unit 50 of the second microbubble generation unit 22. As a result, a large amount of gaseous dissolved water flowing out from the first microbubble generation unit 20 can be directed into the blade parts 56 of the uppermost swirling flow generation unit 50. Consequently, a larger quantity of microbubbles can be generated.

[0129] The technical elements described herein or in the drawings demonstrate technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated herein or in the drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives constitutes technical usefulness in itself. [Explanation of symbols]

[0130] 2: Microbubble Generator 10: Main unit case 10a: Upstream end 10b: Downstream end 10c:Inner wall 12:Inflow part 12a:Inlet 14: Outlet 14a: Outlet 14b:Inner wall 22: Second microbubble generation section 30: First main body 32: Second main body 34: Inner Venturi section 36: Outer Venturi section 38: Reduced diameter flow path 40: Expanded diameter channel 42: Upstream flow path 50, 150, 250, 350: swirl flow generation section 52, 152, 252, 352: Shaft section 52a, 152a, 252a, 352a: Upstream end 152b, 252b: Recess 54, 354: Outer periphery 56, 356: Wing section 58: Protrusion 60, 360: Outlet end 62, 362: Inflow side end 64, 363: First opening 364: The second opening 402: Hot water supply system 404: Water supply source 406: Karan 408: Bathtub 410: First heat source unit 412: Second heat source unit 414: Combustion chamber 416: Partition wall section 418: First combustion chamber 420: Second combustion chamber 422: First Burner 424: First heat exchanger 426: The second burner 428: Second heat exchanger 430: Water supply channel 432: Hot water supply line 432a: First hot water supply line 432b: Second hot water supply channel 434: Bypass Road 436: Bypass Servo 438: Water volume sensor 440: Water volume servo 442: Heat exchanger outlet thermistor 444: Hot water thermistor 450: Hot Spring Path 452: Hot water filling control valve 454: Check valve 460: Reheating the bathwater (outbound journey) 462: First bathtub circulation path 464: Bathtub return thermistor 466: Circulation pump 468: Second bathtub circulation path 470: Bathtub-bound thermistor 510: Dishwasher 511: 1st discharge port 512: Main unit 514: Washing tank 515: Door 516: Control Panel 517: Leftover food filter 518: Exhaust path 519: Tableware 520: Cleaning nozzle 521: Upper nozzle 521a: Injection port 522: Lower nozzle 522a: Injection port 523: Tower nozzle section 524: Horizontal nozzle section 524a: Injection port 527: Pump 528: Impeller 530: Heater 531: Suction recess 532: First suction channel 533: Back wall 534: Drain hose 535:Second discharge port 536: Drainage channel 537: Air venting path 538: Drain check valve 539: Bottom 540: Water supply hose 541: Water supply valve 542: 1st water supply channel 543:Second water supply channel 544: Entrance 545: Water level detection unit 550: Water level path 551: Back wall 552: Drying fan 553: Fan 554: Washing water level 555: Thermistor 556: Lid 560: Controller 561: Dish basket 563: Drying route 564 :Exit 572 :Aperture 574: Second suction channel 576: Flow path switching valve A: Central axis 610: Main unit case 610c:Inner wall 612:Inflow section 612b :Inner wall 616a: First projection 616b: Second projection 616c: Third projection 616d: Fourth projection 616e: Fifth projection 616f: Sixth projection 618a: First positioning groove 618b: Second positioning groove 620: First microbubble generation section 620a: Positioning protrusion 622: Second microbubble generation section 650: Swirling flow generation section 654a: Upstream protrusion 654b: Downstream recess 722: Second microbubble generation section 760: Flow channel 770: Rectifier 772: Shaft 774: Outer perimeter 776: 1st rectifying wall 778:Second rectifying wall 814: Outlet 816: First outflow channel 816a :Inner wall 818: Second outflow channel 818a: Outlet 819: Stepped section 820: First microbubble generation section 830: First main body 830a: Exterior wall 832: Second main body 832a: Exterior wall 834: Upstream flange section 834a: First recess 836: Downstream flange section 836a: Second recess 838: Sealing material

Claims

1. A microbubble generator, The inlet into which the gaseous dissolved water flows, The outlet from which the gas-dissolved water flows out, A first microbubble generating section is provided between the inlet and outlet sections, It comprises a second microbubble generation section provided between the first microbubble generation section and the outflow section, The first microbubble generation section includes a venturi section having a diameter-reducing channel whose diameter decreases as it moves from upstream to downstream, and a diameter-expanding channel located downstream of the diameter-reducing channel whose diameter increases as it moves from upstream to downstream. The second microbubble generation unit is, The system comprises a plurality of swirling flow generating units arranged in line along the downstream central axis direction of the second microbubble generating unit, Each of the plurality of swirling flow generating units is The shaft portion extending in the direction of the downstream central axis, The outer circumference surrounding the aforementioned shaft portion, The system comprises a plurality of vane portions provided between the shaft portion and the outer circumference portion, which generate a swirling flow that flows in a predetermined swirling direction relative to the shaft portion. Microbubble generator.

2. When the direction opposite to the predetermined turning direction is defined as the reverse turning direction, In the swirling flow generating unit, for each of the plurality of blades, the end of a particular blade among the plurality of blades on the swirling direction side is positioned on the opposite side of the swirling direction to the end of the blade adjacent to the particular blade in the swirling direction. When the swirling flow generation unit is viewed in the direction of the downstream central axis, the swirling flow generation unit is provided with a plurality of first openings. When the swirling flow generating unit is viewed in the direction of the downstream central axis, each of the plurality of first openings is surrounded by the end of the specific blade portion on the swirling direction side, the end of the adjacent blade portion on the opposite swirling direction side, the shaft portion, and the outer circumference portion. The microbubble generating device according to claim 1, wherein, when the second microbubble generating unit is viewed in the direction of the downstream central axis, each of the plurality of blades of the downstream swirling flow generating unit, which is a downstream swirling flow generating unit among the plurality of swirling flow generating units and is different from the swirling flow generating unit provided on the uppermost side, is arranged to overlap with at least a portion of the corresponding first opening of the plurality of first openings of the upstream swirling flow generating unit adjacent to the downstream swirling flow generating unit, on the upstream side of the downstream swirling flow generating unit.

3. The microbubble generating apparatus according to claim 2, wherein, when the second microbubble generating section is viewed in the direction of the downstream central axis, each of the plurality of blades of the downstream swirling flow generating section is arranged to overlap the entirety of the corresponding first opening among the plurality of first openings of the upstream swirling flow generating section.

4. Multiple second openings are provided at the downstream end of the swirling flow generation section. Each of the plurality of second openings is surrounded by the end of the particular blade portion on the rotational direction side, the end of the adjacent blade portion on the rotational direction side, the shaft portion, and the outer circumference portion. The microbubble generating apparatus according to claim 2, wherein when the second microbubble generating section is viewed in the direction of the downstream central axis, the ends of each of the plurality of blades of the downstream swirling flow generating section on the reverse swirling direction are located near the central portion in the swirling direction of the corresponding second opening among the plurality of second openings.

5. The first microbubble generating unit comprises a plurality of the venturi units, The plurality of venturi sections include a plurality of outer venturi sections arranged around the upstream central axis, which is the central axis of the first microbubble generation section. The number of the multiple outer venturi sections is the same as the number of the multiple blade sections of the uppermost swirling flow generating section, which is located at the uppermost position among the multiple swirling flow generating sections. The microbubble generating apparatus according to any one of claims 1 to 4, wherein the downstream end of each of the enlarged diameter flow channels of the plurality of outer venturi sections faces the corresponding blade section of the plurality of blade sections of the upstream swirling flow generating section.

6. The first microbubble generating unit comprises a plurality of the venturi units, The plurality of venturi sections include a plurality of outer venturi sections arranged around the upstream central axis, which is the central axis of the first microbubble generation section. The number of the multiple outer venturi sections is the same as the number of the multiple blade sections of the uppermost swirling flow generating section, which is located at the uppermost position among the multiple swirling flow generating sections. The microbubble generating apparatus according to any one of claims 1 to 4, wherein the downstream end of the enlarged diameter flow path of each of the plurality of outer venturi portions faces the end of the corresponding blade portion of the plurality of blade portions of the upstreammost swirling flow generating portion on the reverse swirling direction side.

7. The aforementioned microbubble generating device further, The device comprises a first microbubble generating unit and a main body case that houses the second microbubble generating unit. The aforementioned main body case is A first positioning unit for positioning the first microbubble generation unit relative to the main body case, The microbubble generating apparatus according to claim 5 or 6, further comprising a second positioning unit for positioning the second microbubble generating unit relative to the main body case.

8. In each of the plurality of swirling flow generating units, The upstream end is provided with an upstream convex portion that protrudes upstream, or an upstream recess that recesses downstream. At the downstream end, If the upstream protrusion is provided at the upstream end of the swirling flow generating section, a downstream recess that is recessed on the upstream side is provided. If the upstream recess is provided at the upstream end of the swirling flow generating section, a downstream convex portion is provided that protrudes downstream. The upstream protrusion has a shape corresponding to the second positioning portion and the downstream recess, The microbubble generating apparatus according to claim 7, wherein the upstream recess has a shape corresponding to the second positioning portion and the downstream convex portion.

9. The plurality of venturi portions further include an inner venturi portion extending along the upstream central axis, The downstream end of the enlarged diameter flow channel of the inner venturi section faces the shaft of the uppermost swirling flow generation section. The microbubble generating apparatus according to any one of claims 5 to 8, wherein the opening area at the downstream end of the enlarged diameter flow channel of the inner venturi portion is smaller than the area of ​​the shaft portion of the upstream swirling flow generating portion when viewed in the direction of the downstream central axis.

10. The microbubble generating apparatus according to claim 9, wherein the opening area is smaller than the area of ​​the outer shape of the upstream end of the shaft of the uppermost swirling flow generating section when viewed in the direction of the downstream central axis.

11. The microbubble generating apparatus according to claim 10, wherein the upstream end of the shaft portion of the upstreammost swirling flow generating section is provided with a recess that is recessed on the downstream side.

12. The microbubble generating apparatus according to any one of claims 1 to 11, wherein the upstream surfaces of the plurality of blades are provided with protrusions that project upstream.

13. The microbubble generating device according to claim 12, which is dependent on any one of claims 5 to 11, wherein the downstream end of each of the enlarged diameter flow channels of the plurality of outer venturi sections faces the protruding portion provided on the corresponding blade among the plurality of blades of the upstream swirling flow generating section.

14. The aforementioned microbubble generating device further, The microbubble generating apparatus according to any one of claims 1 to 13, further comprising a flow rectifier provided between the second microbubble generating section and the outflow section, which rectifies the flow of gas-dissolved water discharged from the second microbubble generating section from a swirling flow to a straight flow.

15. A water heater equipped with a microbubble generating device according to any one of claims 1 to 14.

16. A dishwasher equipped with a microbubble generating device according to any one of claims 1 to 14.

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