Microbubble generating device, water heater, and dishwasher

Abstract

The microbubble generator disclosed in the present specification has a main body case having an inflow portion and an outflow portion, and a first microbubble generation portion housed in the main body case and provided between the inflow portion and the outflow portion. The first microbubble generation portion has one or a plurality of Venturi flow passages. The one or the plurality of Venturi flow passages have a reduced-diameter flow passage that has a flow passage diameter that is reduced toward a downstream side, and an enlarged-diameter flow passage that is provided at a position on the downstream side of the reduced-diameter flow passage and has a flow passage diameter that is enlarged toward the downstream side. A slit is formed in at least one of the one or the plurality of Venturi flow passages, and the slit is recessed from an inner side of the Venturi flow passage toward a radial direction outer side. The slit is continuously provided from a first end portion coinciding with a downstream end of the enlarged-diameter flow passage to a second end portion at a position on the upstream side of the downstream end.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a microbubble generator, a water heater, and a dishwasher. Background Technology

[0002] Japanese Patent Publication No. 2021-194625 discloses a microbubble generating device, which has a main body shell and a first microbubble generating unit. The main body shell has an inflow portion and an outflow portion. The first microbubble generating unit is housed in the main body shell and disposed between the inflow portion and the outflow portion. The first microbubble generating unit has one or more Venturi channels. The one or more Venturi channels each have a narrowing channel and an expanding channel. The diameter of the narrowing channel decreases as it moves from the upstream side to the downstream side. The expanding channel is disposed downstream of the narrowing channel and its diameter increases as it moves from the upstream side to the downstream side. Summary of the Invention

[0003] [The technical problem the invention aims to solve]

[0004] In the venturi flow channel of a microbubble generator, after the liquid is drained from the main body casing, a liquid film may sometimes form at the downstream end of the expanding flow channel due to the surface tension of the liquid. If the liquid film in the venturi flow channel is not eliminated, malfunctions such as blockage due to liquid film freezing may occur. Therefore, in a microbubble generator, it is necessary to eliminate the liquid film in at least one of the one or more venturi flow channels. This specification provides a technique for eliminating the liquid film in at least one of the one or more venturi flow channels.

[0005] [Technical solutions used to solve technical problems]

[0006] The microbubble generating device disclosed in this specification has a main body shell and a first microbubble generating unit, wherein the main body shell has an inlet and an outlet; the first microbubble generating unit is housed in the main body shell and disposed between the inlet and the outlet. The first microbubble generating unit has one or more Venturi channels. The one or more Venturi channels each have a narrowing channel and an expanding channel, wherein the narrowing channel has a narrowing diameter as it moves from the upstream side to the downstream side; the expanding channel is disposed downstream of the narrowing channel and has an expanding diameter as it moves from the upstream side to the downstream side. A slit is formed in at least one of the one or more Venturi channels, the slit being recessed radially outward from the inner surface of the Venturi channel. The slit is continuously disposed from a first end, which coincides with the downstream end of the expanding channel, to a second end located upstream of the downstream end.

[0007] According to the above structure, in a Venturi flow channel with a slit, when a liquid film forms in the expanding flow channel, the liquid film is attracted by the slit and thus moves upstream along the expanding flow channel. As the expanding flow channel narrows towards the upstream side, the surface area of ​​the liquid film decreases. At this point, the liquid film condenses as its surface area decreases, forming droplets or the like, and then disappears. Therefore, according to the above structure, a liquid film can be eliminated in at least one of one or more Venturi flow channels.

[0008] In one or more embodiments, the second end of the slit is located downstream of the downstream end of the narrowed flow channel.

[0009] The slit is recessed relative to the inner surface of the venturi channel, thus widening the depth of the slit in the portion where it is located. Here, in the venturi channel, the flow velocity of the liquid passing through the narrowed channel increases, depressurizing the liquid and generating bubbles. Therefore, for example, when the second end of the slit is located upstream of the downstream end of the narrowed channel, the narrowed channel is locally enlarged by the slit, potentially significantly reducing the amount of microbubbles generated. In contrast, according to the above structure, since the second end of the slit is located downstream of the downstream end of the narrowed channel, the narrowed channel does not enlarge even with the slit. By employing this structure, the reduction in the amount of microbubbles generated when the slit is present can be suppressed.

[0010] In one or more embodiments, the slit is arranged to extend in a generally straight line from the first end to the second end.

[0011] Based on the above structure, the slit extends in a roughly straight line from the downstream side to the upstream side. Therefore, the slit allows the liquid film to move smoothly upstream. Consequently, the liquid film can be eliminated more reliably.

[0012] In one or more embodiments, the microbubble generating device further includes a second microbubble generating section housed within the main body casing and disposed between the first microbubble generating section and the outflow section. The second microbubble generating section has a shaft portion, an outer peripheral portion, a plurality of blade portions, and a swirling flow channel, wherein the shaft portion extends in a direction from an upstream side to a downstream side; the outer peripheral portion surrounds the radially outer side of the shaft portion; the plurality of blade portions are disposed between the shaft portion and the outer peripheral portion for generating a swirling flow relative to the shaft portion in a predetermined swirling direction; the swirling flow channel passes through the gap between the shaft portion, the outer peripheral portion, and the plurality of blade portions. There are multiple Venturi flow channels, including an inner Venturi flow channel and a plurality of outer Venturi flow channels, the inner Venturi flow channel extending along the extension line of the shaft portion; the plurality of outer Venturi flow channels are arranged around the inner Venturi flow channel. The slit is located in the inner Venturi channel and is not located in any of the multiple outer Venturi channels.

[0013] According to the above structure, the liquid flowing into the swirling channel of the second microbubble generating section forms a swirling flow. The microbubbles generated by the first microbubble generating section are further reduced to smaller bubbles by the shear force of the swirling flow, increasing the number of microbubbles. At this time, the higher the flow velocity flowing into the swirling channel, the stronger the swirling flow, resulting in more microbubbles being generated. Here, the liquid flowing in the inner Venturi channel collides with the axis of the second microbubble generating section and is decelerated before flowing into the swirling channel. On the other hand, the liquid flowing in the multiple outer Venturi channels does not collide with the axis and flows into the swirling channel. Therefore, the liquid flowing in the inner Venturi channel has a smaller impact on the amount of microbubbles generated compared to the liquid flowing in the multiple outer Venturi channels. Generally, in a venturi channel with a slit, the amount of microbubbles generated is significantly reduced compared to a venturi channel without a slit. However, according to the above structure, the slit is only placed in the inner venturi channel where its impact on the amount of microbubbles generated is minimal. Therefore, in the above structure, the reduction in microbubbles when the slit is placed in the venturi channel can be minimized.

[0014] The water heater disclosed in this specification has the aforementioned microbubble generating device.

[0015] According to the above structure, liquid film can be eliminated in at least one of the one or more Venturi channels of the microbubble generating device in the water heater.

[0016] The dishwasher disclosed in this specification has the aforementioned microbubble generating device.

[0017] According to the above structure, liquid film can be eliminated in at least one of the venturi channels of one or more microbubble generating devices in the dishwasher. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the structure of the water heater 100 according to Embodiment 1.

[0019] Figure 2 This is an overall perspective view of the microbubble generating device 2 involved in Examples 1 and 2.

[0020] Figure 3 This is a cross-sectional view of the microbubble generating device 2 involved in Examples 1 and 2.

[0021] Figure 4 This is an overall perspective view of the first microbubble generating unit 3 of the microbubble generating device 2 involved in Embodiments 1 and 2.

[0022] Figure 5 yes Figure 3 VV sectional view.

[0023] Figure 6 yes Figure 3 Sectional view VI-VI.

[0024] Figure 7 This is a diagram showing the second microbubble generating section 5 of the microbubble generating device 2 described in Examples 1 and 2 from the upstream side.

[0025] Figure 8 This is a diagram showing the second microbubble generating section 5 of the microbubble generating device 2 involved in Embodiments 1 and 2, viewed from a direction orthogonal to the central axis A.

[0026] Figure 9 This is a diagram illustrating an example of the setup of the microbubble generating device 2 described in Embodiments 1 and 2.

[0027] Figure 10 This is a schematic diagram illustrating the structure of the dishwasher 510 according to Embodiment 2. Detailed Implementation

[0028] (Example 1: Water heater 100 with microbubble generator 2)

[0029] like Figure 1As shown, the water heater 100 includes a microbubble generator 2, a water supply pipe 104, a first drain plug 106, a water volume sensor 108, a water volume servo 110, a water heater controller 112, a heat exchanger 114, a gas burner 116, a combustion fan 118, a hot water supply pipe 122, a hot water supply thermistor 124, and a second drain plug 126.

[0030] The upstream end of the water supply pipe 104 is connected to a water source such as a waterworks. Along the water supply pipe 104, starting from the upstream side, a first drain plug 106, a water flow sensor 108, and a water flow servo 110 are sequentially installed. The water flow sensor 108 detects the flow rate of water flowing within the water supply pipe 104. The water flow servo 110 allows or disables water flow by switching between an open and closed state. The water flow rate of the water flow servo 110 in the open state varies depending on the opening degree of the water flow servo 110. In this embodiment, air (oxygen, carbon dioxide, nitrogen, etc.) is dissolved in the water supplied from the water source (e.g., tap water).

[0031] The upstream end of heat exchanger 114 is connected to the downstream end of water supply pipe 104. Gas burner 116 heats the water flowing within heat exchanger 114 by burning the supplied combustion gas. The downstream end of heat exchanger 114 is connected to the upstream end of hot water supply pipe 122. Along hot water supply pipe 122, a hot water supply thermistor 124, a microbubble generator 2, and a second drain plug 126 are sequentially arranged from the upstream side. Hot water supply thermistor 124 detects the temperature of the water flowing within hot water supply pipe 122. The downstream end of hot water supply pipe 122 is connected to a faucet, bathtub, or other hot water outlet. Hereinafter, the hot water supply pipe 122 connected to the upstream end of microbubble generator 2 is sometimes referred to as "first hot water supply pipe 122a", and the hot water supply pipe 122 connected to the downstream end of microbubble generator 2 is sometimes referred to as "second hot water supply pipe 122b".

[0032] The water heater controller 112 includes a CPU, ROM, RAM, etc. Information such as the water flow rate detected by the water flow sensor 108 and the water temperature detected by the hot water supply thermistor 124 is sent to the water heater controller 112. The water heater controller 112 can regulate the amount of water flowing from the water supply pipe 104 into the heat exchanger 114 by adjusting the opening degree of the water flow servo 110. Furthermore, the water heater controller 112 can regulate the heat output of the gas burner 116 by adjusting the amount of combustion gas supplied to the gas burner 116. The water heater controller 112 can regulate the temperature of the water flowing in the hot water supply pipe 122 to the desired temperature by controlling the operation of the water flow servo 110 and the gas burner 116 based on the information detected by the water flow sensor 108 and the hot water supply thermistor 124.

[0033] (Structure of microbubble generator 2)

[0034] like Figure 2 As shown, the microbubble generator 2 has a main housing 10, an inlet 12, and an outlet 14. The main housing 10 has a generally cylindrical shape centered on a central axis A. The inlet 12 and the outlet 14 are respectively threaded onto the main housing 10. A first hot water supply pipe 122a (see reference) is connected to the inlet 12. Figure 1 Downstream of the outlet 14. A second hot water supply pipe 122b is connected to the outlet 14 (see reference). Figure 1 The upstream end of the first hot water supply pipe 122a. Therefore, the water flowing in from the first hot water supply pipe 122a flows into the inlet section 12, passes through the main body casing 10, and then flows out from the outlet section 14 to the second hot water supply pipe 122b.

[0035] like Figure 3 As shown, a first microbubble generating unit 3 and a plurality of second microbubble generating units 5 are housed within the main body casing 10. The first microbubble generating unit 3 and the plurality of second microbubble generating units 5 are arranged along the central axis A. The plurality of second microbubble generating units 5 are arranged downstream of the first microbubble generating unit 3. In this embodiment, four plurality of second microbubble generating units 5 are provided. Furthermore, all of the plurality of second microbubble generating units 5 have the same shape.

[0036] (Structure of the first microbubble generation section 3)

[0037] like Figure 4 As shown, the first microbubble generating unit 3 has a generally rotating shape centered on the central axis A. The first microbubble generating unit 3 has a main body 30, an inner venturi channel 32, a plurality of outer venturi channels 34, an upstream fitting portion 36, and a downstream fitting portion 38. In this embodiment, the first microbubble generating unit 3 is integrally formed using a resin (e.g., polypropylene, polyphenylene sulfide, etc.) through injection molding. Therefore, the main body 30, the upstream fitting portion 36, and the downstream fitting portion 38 are seamlessly integrally formed. Figure 3 As shown, the main body 30 extends between the inflow portion 12 and the outflow portion 14, and has a narrowed outer surface 302 and an expanded outer surface 304. The narrowed outer surface 302 narrows along the central axis A as it moves from the upstream side to the downstream side; the expanded outer surface 304 is connected to the downstream end of the narrowed outer surface 302 and expands along the central axis A as it moves from the upstream side to the downstream side.

[0038] A first recess 306 and a second recess 308 are provided near the downstream end of the main body 30. The first recess 306 and the second recess 308 have a shape that is recessed inward in the radial direction from the outer side 304 of the enlarged diameter towards the central axis A. Figure 5As shown, the first recess 306 and the second recess 308 are provided at a depth that does not interfere with the plurality of outer Venturi channels 34. The first recess 306 and the second recess 308 are arranged at a circumferential interval of 180° from each other along the central axis A. The first recess 306 and the second recess 308 are provided to extend from the downstream end of the main body 30 to the upstream side.

[0039] like Figure 3 As shown, the first recess 306 has a first inclined portion 306a and a first bottom portion 306b. The first inclined portion 306a is inclined approximately to the central axis A as it moves from the upstream side to the downstream side. The first bottom portion 306b is connected to the first inclined portion 306a and extends along the central axis A. The first inclined portion 306a smoothly connects the expanded outer surface 304 and the first bottom portion 306b. The second recess 308 has a second inclined portion 308a and a second bottom portion 308b. The second inclined portion 308a is inclined approximately to the central axis A as it moves from the upstream side to the downstream side. The second bottom portion 308b is connected to the second inclined portion 308a and extends along the central axis A. The second inclined portion 308a smoothly connects the expanded outer surface 304 and the second bottom portion 308b.

[0040] The inner venturi flow channel 32 and multiple outer venturi flow channels 34 connect the inlet section 12 and the outlet section 14 through the interior of the main body 30. The inner venturi flow channel 32 extends along the central axis A. Figure 4 As shown, a plurality of outer Venturi channels 34 are arranged to surround the inner Venturi channel 32. In this embodiment, seven outer Venturi channels 34 are provided. The plurality of outer Venturi channels 34 are arranged at predetermined angular intervals (approximately 51° intervals in this embodiment) in the circumferential direction of the central axis A.

[0041] like Figure 3 As shown, the inner Venturi tube flow channel 32 has an inner diameter-reducing flow channel 322 and an inner diameter-expanding flow channel 324. The inner diameter-reducing flow channel 322 reduces its diameter along the central axis A from the upstream side to the downstream side. The inner diameter-expanding flow channel 324 is located downstream of the inner diameter-reducing flow channel 322, and its diameter expands along the central axis A from the upstream side to the downstream side.

[0042] like Figure 5As shown, a plurality of slits 4 are formed in the inner venturi channel 32, and the plurality of slits 4 are recessed radially outward from the inner surface of the inner venturi channel 32 toward the central axis A. In this embodiment, two plurality of slits 4 are provided. The plurality of slits 4 are arranged at predetermined angular intervals (180° intervals in this embodiment) in the circumferential direction of the central axis A. In other words, the plurality of slits 4 are arranged facing each other on the inner surface of the inner venturi channel 32. In addition, the plurality of slits 4 are continuously provided from a first end 42, which coincides with the downstream end of the inner venturi channel 324, to a second end 44 located upstream of the downstream end of the inner venturi channel 324. The plurality of slits 4 each have a substantially fixed width in a direction orthogonal to the recessed direction. The width of the plurality of slits 4 is, for example, in the range of 0.5 mm to 3.0 mm, and is 1.5 mm in this embodiment. In addition, multiple slits 4 are only provided in the inner Venturi flow channel 32, and multiple slits 4 are not provided in the multiple outer Venturi flow channels 34.

[0043] like Figure 3 As shown, the second end 44 is located downstream of the downstream end of the inner constricted flow channel 322. In this embodiment, the second end 44 coincides with the upstream end of the inner expanded flow channel 324. The plurality of slits 4 each have a substantially constant depth radially along the central axis A. The depth of the plurality of slits 4 is, for example, in the range of 0.5 mm to 3.0 mm, and in this embodiment, 1.8 mm. The plurality of slits 4 are arranged in a substantially linear manner extending from the first end 42 to the second end 44. Furthermore, as... Figure 4 As shown, the downstream end of the inner expansion channel 324 has a flared shape. Therefore, near the first end 42, the periphery of the plurality of slits 4 has a shape that curves along the flared shape of the inner expansion channel 324.

[0044] like Figure 3 As shown, the multiple outer Venturi channels 34 have an outer narrowing channel 342 and an outer widening channel 344. The outer narrowing channel 342 narrows in diameter as it moves from the upstream side to the downstream side; the outer widening channel 344 is positioned downstream of the outer narrowing channel 342 and widens in diameter as it moves from the upstream side to the downstream side. The downstream end of the outer widening channel 344 has a funnel shape. Furthermore, all the multiple outer Venturi channels 34 have the same shape.

[0045] like Figure 4 As shown, the upstream fitting portion 36 has a flange shape that protrudes radially outward from the upstream end of the main body portion 30 toward the central axis A. The upstream fitting portion 36 has an outer surface 36a that expands circumferentially toward the central axis A. Figure 6As shown, when the interior of the main housing 10 is viewed from the upstream side, the outer surface 36a of the upstream side fitting portion 36 is substantially fitted into the inner surface 10a of the main housing 10, covering the entire inner surface 10a of the main housing 10. Therefore, a mechanical seal is formed between the outer surface 36a of the upstream side fitting portion 36 and the inner surface 10a of the main housing 10.

[0046] like Figure 4 As shown, the downstream fitting portion 38 protrudes radially outward from the downstream end of the main body portion 30 towards the central axis A, and extends along the central axis A to a position further downstream than the downstream end of the main body portion 30. The downstream fitting portion 38 has a partially downstream-protruding engaging protrusion 382 at its downstream end. Furthermore, the first microbubble generating portion 3 is provided with a first notch portion 6 and a second notch portion 8, which are formed by creating a notch in a portion of the downstream fitting portion 38 from the downstream side towards the upstream side. The first notch portion 6 smoothly connects to the first recess 306 of the main body portion 30. The second notch portion 8 smoothly connects to the second recess 308 of the main body portion 30.

[0047] like Figure 5 As shown, when the interior of the main body shell 10 is viewed from the downstream side, the outer surface 38a of the downstream side fitting portion 38, except for the portion where the first notch 6 and the second notch 8 are formed, covers almost the entire inner surface 10a of the main body shell 10 and is substantially fitted with the inner surface 10a of the main body shell 10. Furthermore, the engaging protrusion 382 engages from the upstream side with the positioning member 10b protruding inward from the inner surface 10a of the main body shell 10. Accordingly, the first microbubble generating portion 3 is housed within the main body shell 10 in a state where it is positioned axially and circumferentially within the main body shell 10 along the central axis A.

[0048] like Figure 3 As shown, a gap space S is formed between the inner surface 10a of the main body shell 10 and the reduced-diameter outer surface 302 and expanded-diameter outer surface 304 of the main body portion 30, and between the upstream fitting portion 36 and the downstream fitting portion 38. The outer surface 36a of the upstream fitting portion 36 and the inner surface 10a of the main body shell 10 are mechanically sealed, thus suppressing the entry and exit of water on the upstream side of the gap space S. On the other hand, on the downstream side of the gap space S, water is allowed to enter and exit through a first drainage channel D1 formed by a first notch 6 and a first recess 306, and a second drainage channel D2 formed by a second notch 8 and a second recess 308. Therefore, the gap space S is connected to the outlet portion 14 through the first drainage channel D1 and the second drainage channel D2.

[0049] (Structure of the second microbubble generation section 5)

[0050] like Figure 7As shown, the second microbubble generating unit 5 includes: a shaft portion 52; an outer peripheral portion 54 surrounding the shaft portion 52; and a plurality of blade portions 56 disposed between the shaft portion 52 and the outer peripheral portion 54 for generating a swirling flow that flows clockwise relative to the shaft portion 52. Furthermore, the terms "clockwise direction" and "counterclockwise direction" used in this specification refer to the direction when viewing the microbubble generating device 2 from the upstream side along the central axis A. The second microbubble generating unit 5 is integrally formed using a resin (e.g., polypropylene, polyphenylene sulfide, etc.) by injection molding. Therefore, the shaft portion 52, the outer peripheral portion 54, and the plurality of blade portions 56 are seamlessly integrally formed.

[0051] The shaft portion 52 has a cylindrical shape. The outer peripheral portion 54 has a cylindrical shape. The outer peripheral portion 54 has an outer surface that substantially fits into the inner surface 10a of the main body housing 10. Furthermore, the shaft portion 52 and the outer peripheral portion 54 are arranged along the central axis A. A plurality of blade portions 56 connect the outer wall of the shaft portion 52 and the inner wall of the outer peripheral portion 54. The plurality of blade portions 56 are inclined downstream in a clockwise direction. In this embodiment, seven blade portions 56 are provided. The plurality of blade portions 56 are arranged at predetermined angular intervals (approximately 51° intervals in this embodiment) in the circumferential direction along the central axis A. Additionally, seven swirling flow channels 64 are provided in the second microbubble generating section 5. Figure 7 (The thicker part). Seven swirling channels 64 are respectively disposed in the gaps between the shaft portion 52, the outer peripheral portion 54, and multiple blade portions 56.

[0052] like Figure 8 As shown, the outer peripheral portion 54 has a partially protruding fitting protrusion 66 at its upstream end. The outer peripheral portion 54 has a partially recessed fitting recess 68 at its downstream end. The fitting protrusion 66 and the fitting recess 68 have shapes that allow them to fit together.

[0053] When considering two adjacent second microbubble generating units 5, the engaging protrusion 66 of the downstream second microbubble generating unit 5 engages with the engaging recess 68 of the upstream second microbubble generating unit 5. Accordingly, the plurality of second microbubble generating units 5 are positioned relative to each other. Furthermore, the engaging protrusion 66 of the upstream second microbubble generating unit 5 engages from the downstream side with the positioning member 10b of the main body housing 10 (see reference). Figure 5 Accordingly, the plurality of second microbubble generating units 5 are respectively positioned in the circumferential direction relative to the main body shell 10 on the central axis A and are housed in the main body shell 10.

[0054] (The principle of microbubble formation)

[0055] like Figure 1As shown, air is dissolved in the water supplied by the water source, and therefore air is also dissolved in the water flowing through the first hot water supply pipe 122a. Therefore, water containing dissolved air flows from the first hot water supply pipe 122a into the microbubble generator 2. Hereinafter, water containing dissolved air is sometimes referred to as "air-dissolved water".

[0056] like Figure 3 As shown, dissolved air water flowing from the inlet 12 into the main body casing 10 flows into the narrowed-diameter channels 322 and 342 of the venturi channels 32 and 34. The dissolved air water flowing into the narrowed-diameter channels 322 and 342 experiences an increased flow velocity, resulting in depressurization. Bubbles are generated by depressurizing the dissolved air water. The dissolved air water flowing through the narrowed-diameter channels 322 and 342 flows into the widened-diameter channels 324 and 344. The dissolved air water flowing into the widened-diameter channels 324 and 344 experiences a decreased flow velocity, resulting in pressurization. When the dissolved air water, after bubble generation through depressurization, is pressurized, the bubbles contained in the dissolved air water break down into microbubbles. In this specification, the inner venturi channel 32 and the multiple outer venturi channels 34 are sometimes collectively referred to as "venturi channels 32 and 34". Similarly, the inner narrowing channel 322 and the outer narrowing channel 342 are sometimes collectively referred to as "narrowing channels 322 and 342". Similarly, the inner widening channel 324 and the outer widening channel 344 are sometimes collectively referred to as "widening channels 324 and 344".

[0057] Air-dissolved water flowing from the first microbubble generating section 3 through the expansion channels 324 and 344 flows toward the upstream second microbubble generating section 5. At this time, air-dissolved water flowing from the inner Venturi channel 32 collides with the upstream end of the shaft portion 52 of the upstream second microbubble generating section 5, and is pushed radially outward from the central axis A, flowing into the swirling channel 64. On the other hand, air-dissolved water flowing from the multiple outer Venturi channels 34 does not collide with the shaft portion 52 and flows into the swirling channel 64. After this, the air-dissolved water passes from the upstream side to the downstream side in the respective swirling channels 64 of the multiple second microbubble generating sections 5. The air-dissolved water flowing through the swirling channel 64 flows along the blade portion 56, thus forming a clockwise swirling flow. The microbubbles within the air-dissolved water become even smaller bubbles due to the shear force of the swirling flow, and the number of microbubbles increases. Furthermore, the air-dissolved water flowing out from the swirling channel 64 of the second microbubble generating section 5 on the downstream side is guided to the outlet section 14. In this way, in the water heater 100 (refer to...) Figure 1 In this system, hot water containing a large number of tiny bubbles is supplied at the hot water outlet.

[0058] (Drainage mechanism of microbubble generator 2)

[0059] like Figure 1 As shown, by keeping the first drain plug 106 and the second drain plug 126 open, the microbubble generator 2 can be drained. When the first drain plug 106 and the second drain plug 126 are open, the water between the first drain plug 106 and the second drain plug 126 flows out from either the first drain plug 106 or the second drain plug 126 due to gravity. At this time, in the microbubble generator 2, water flows from the inlet 12 to the outlet 14 (see reference). Figure 3 )discharge.

[0060] like Figure 9 As shown, the microbubble generator 2 in this embodiment is configured such that it is vertically upward along the central axis A towards the upstream side and vertically downward along the central axis A towards the downstream side. Therefore, when the microbubble generator 2 drains water, the water inside the main body housing 10 (the water in the gap space S) is discharged downward due to gravity. In other words, as the water is discharged, the water level inside the main body housing 10 decreases downstream along the central axis A. Furthermore, in this specification, vertically upward is sometimes referred to as "above" and vertically downward is sometimes referred to as "below".

[0061] exist Figure 9 In the shown state, the first drainage channel D1 is connected to the vicinity of the lowest part of the gap space S. Similarly, the second drainage channel D2 is also connected to the vicinity of the lowest part of the gap space S. Therefore, when the microbubble generator 2 is draining water, almost all the water in the gap space S flows into either the first drainage channel D1 or the second drainage channel D2. Furthermore, in this specification, "vicinity of the lowest part of the gap space S" refers to the portion within L / 4 (mm) above the lowest part of the gap space S when viewed from the bottom, provided the vertical length from the lowest to the highest part of the gap space S is L (mm). In this embodiment, the vertical length from the lowest to the highest part of the gap space S is 40 mm; therefore, in this embodiment, "vicinity of the lowest part of the gap space S" refers to the portion within 10 mm above the lowest part of the gap space S when viewed from the bottom.

[0062] Furthermore, when draining the microbubble generator 2, a water film sometimes forms in the expanded flow channels 324 and 344 of the Venturi tubes 32 and 34 (especially near the downstream end of the expanded flow channels 324 and 344). Moreover, if the water film extending on the expanded flow channels 324 and 344 freezes instead of disappearing, even if water is subsequently passed through the microbubble generator 2, the frozen water film will prevent water from flowing immediately.

[0063] In the microbubble generator 2 of this embodiment, when the water film extends on the inner expansion channel 324 of the inner venturi channel 32, the water film is attracted by multiple slits 4 and moves upstream along the inner expansion channel 324. For example... Figure 3 As shown, the inner venturi channel 324 narrows as it moves upstream, thus reducing the surface area of ​​the water film. At this point, the water film condenses as its surface area decreases, forming droplets that then disappear. This eliminates the water film extending in the inner venturi channel 324. Therefore, even if the water film in the outer venturi channel 344 freezes after drainage, the water film in the inner venturi channel 324 is eliminated, preventing water flow obstruction at least in the inner venturi channel 324. Consequently, water can flow immediately even when the microbubble generator 2 is reused after drainage, improving the convenience of the microbubble generator 2.

[0064] (Example 2: Dishwasher 510 with microbubble generator 2)

[0065] Figure 10 This is a longitudinal sectional view of dishwasher 510. Dishwasher 510 is a pull-out dishwasher. Dishwasher 510 includes a microbubble generator 2, a main body 512, a washing tank 514, a door 515, and a dishwasher controller 560. The microbubble generator 2 in this embodiment is the same as the microbubble generator 2 in Embodiment 1. Therefore, the description of the structure of the microbubble generator 2 is omitted in this embodiment.

[0066] The door 515 is equipped 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 cleaning tank 514.

[0067] The cleaning tank 514 is housed within the space formed by the main body 512 and the door 515. The cleaning tank 514 is slidably supported on the main body 512. The cleaning tank 514 is connected to the door 515. The cleaning tank 514 is formed as a box shape with an open top. A cover 556 is disposed on top of the cleaning tank 514. The cover 556 is connected to the cleaning tank 514 via a lifting mechanism (not shown).

[0068] The cleaning tank 514 houses the following: a cleaning nozzle 520, a dish basket 561 for holding various tableware 519, a leftover food filter 517, a heater 530, and a thermistor 555. The cleaning nozzle 520 consists of a tower-type nozzle section 523 and a horizontal nozzle section 524. The tower-type nozzle section 523 consists of an upper nozzle 521 and a lower nozzle 522. Multiple spray nozzles 521a, 522a, and 524a are formed in the cleaning nozzle 520. An electric heater 530 for heating the cleaning water and the air inside the cleaning tank 514 is installed near the bottom surface 539 of the cleaning tank 514. A thermistor 555 is installed on the bottom surface 539 of the cleaning tank 514.

[0069] A water level detection unit 545 is installed on the lower part of the outer front side of the cleaning tank 514 to detect the water level inside the cleaning tank 514. The water level under normal water supply to the cleaning tank 514 is indicated by a double-dotted line (hereinafter referred to as "cleaning water level") using the attached reference numeral 554. A pump 527 is installed below the bottom surface 539 of the cleaning tank 514. The pump 527 rotates the impeller 528 via 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 is connected to the first outlet 511 of the pump 527.

[0070] 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 leftover food filter 517. A water level detection unit 545 is connected to the suction recess 531 via a water level path 550. A pump 527 is connected to the suction recess 531 via a first suction channel 532. One end of a second suction channel 574 is connected to the first suction channel 532. The other end of the second suction channel 574 is connected to an opening 572 in the rear wall 551 of the washing tank 514. A channel switching valve 576 is installed at the connection between the first suction channel 532 and the second suction channel 574.

[0071] A drying fan 552 is installed on the outer side of the rear wall 551 of the cleaning tank 514. The drying fan 552 is driven by a built-in motor to rotate the fan 553. The drying fan 552 is connected to the cleaning tank 514 via a drying path 563. The drying fan 552 is positioned higher than the cleaning water level 554.

[0072] A drain hose 534 is connected to the rear wall 533 of the main body 512. The drain hose 534 and the second outlet 535 of the pump 527 are connected through a drain channel 536. The drain channel 536 is connected to the cleaning tank 514 through an exhaust path 537. A drain check valve 538 is installed near the connection point of the drain channel 536 with the drain hose 534.

[0073] A water supply hose 540 is connected to a step formed horizontally in the middle of the rear wall 533 of the main body 512. Water supplied directly from a water source such as a waterworks (not shown) can be supplied to the water supply hose 540, and heated hot water can also be supplied to the water supply hose 540. A water supply valve 541 is installed on the inner side of the rear wall 533. The inlet 544 of the water supply valve 541 and the water supply hose 540 are connected through a first water supply channel 542. The outlet 564 of the water supply valve 541 and the cleaning tank 514 are connected through a second water supply channel 543. A microbubble generator 2 is installed along the second water supply channel 543.

[0074] The dishwasher controller 560 has a CPU, ROM, RAM, etc., and controls the operation of the dishwasher 510. The dishwasher controller 560 performs the cleaning operation, which means cleaning the tableware 519 in the cleaning tank 514 by controlling the operation of the dishwasher 510.

[0075] (Cleaning operation)

[0076] When the dishwasher controller 560 receives a user's command to start the dishwashing operation on the control panel 516, it sequentially executes the washing process, the rinsing process, and the drying process.

[0077] During the cleaning process, the dishwasher controller 560 opens the water supply valve 541, supplying cleaning water to the cleaning tank 514 from the water supply hose 540. When the dishwasher controller 560 determines that the required amount of cleaning water has been supplied to the cleaning tank 514 for the cleaning process, it closes the water supply valve 541. Next, the dishwasher controller 560 drives the pump 527, causing the impeller 528 to rotate forward, and activates the heater 530. Cleaning water is drawn into the pump 527 from the suction recess 531. The cleaning water drawn into the pump 527 is then fed into the cleaning nozzles 520 and forcefully sprayed out from the spray ports 521a, 522a, and 524a. The dishwasher controller 560 ends the cleaning process after a first predetermined time (e.g., 5 minutes) from the start of the cleaning process. Additionally, the dishwasher controller 560 drives the pump 527, causing the impeller 528 to rotate in the reverse direction, thereby discharging the cleaning water from the cleaning tank 514. As described above, a microbubble generator 2 is installed along the second water supply channel 543. Furthermore, air (oxygen, carbon dioxide, nitrogen, etc.) is dissolved in the water supplied from the water supply hose 540. Therefore, the water supplied to the washing tank 514 via the microbubble generator 2 contains many microbubbles. The contaminants adhering to the tableware 519 are adsorbed onto the surface of the microbubbles contained in the washing water. Because the washing water contains a large number of microbubbles, it can adsorb even more contaminants.

[0078] During the rinsing process, the dishwasher controller 560 opens the water supply valve 541, supplying cleaning water from the water supply hose 540 to the washing tank 514. When the required amount of cleaning water is supplied to the washing tank 514 during the rinsing process, the dishwasher controller 560 closes the water supply valve 541. The dishwasher controller 560 drives the pump 527, causing the impeller 528 to rotate forward. Accordingly, the cleaning water in the washing tank 514 is sprayed from the cleaning nozzle 520 onto the tableware 519 contained in the dish basket 561, rinsing the tableware 519. The dishwasher controller 560 ends the rinsing process after a second predetermined time (e.g., 5 minutes) from the start of the rinsing process. Additionally, the dishwasher controller 560 drives the pump 527, causing the impeller 528 to rotate in the reverse direction, discharging the cleaning water from the washing tank 514.

[0079] In the drying process, the dishwasher controller 560 heats the air in the washing tank 514 using the heater 530 to dry the tableware 519. When the elapsed time since the start of drying the tableware 519 reaches the third predetermined time, the dishwasher controller 560 stops the heating of the heater 530 and ends the drying process.

[0080] (Modified Example)

[0081] In the above embodiments, the microbubble generating device 2 is described as having a second microbubble generating unit 5 in addition to the first microbubble generating unit 3. In another embodiment, the microbubble generating device 2 may have only the first microbubble generating unit 3, or it may not have the second microbubble generating unit 5.

[0082] In the above embodiments, the inner surface 10a of the main housing 10 is described as having a generally cylindrical shape. In another embodiment, the inner surface 10a of the main housing 10 may not have a generally cylindrical shape. For example, the inner surface 10a of the main housing 10 may also have a square cylindrical shape. In this case, the upstream fitting portion 36, the downstream fitting portion 38, and the outer peripheral portion 54 may have the same square cylindrical shape as the inner surface 10a, and may also be generally fitted into the inner surface 10a.

[0083] In the above embodiments, the main body 30 is described as having a reduced-diameter outer surface 302 and an expanded-diameter outer surface 304. In another embodiment, the main body 30 may also have a cylindrical outer surface centered on the central axis A. Furthermore, the outer surface of the main body 30 may smoothly connect the outer surface 36a of the upstream fitting portion 36 and the outer surface 38a of the downstream fitting portion 38, or it may have a shape that substantially covers the inner surface 10a of the main body shell 10 and substantially fits into the inner surface 10a. In this case, the wall thickness of the main body 30 is increased, thereby improving the damage resistance of the first microbubble generating portion 3.

[0084] In the above embodiments, the structure of the first microbubble generating section 3 being formed of resin was described. In another embodiment, the first microbubble generating section 3 can also be formed of metal (e.g., aluminum, stainless steel, etc.). In this case, the first microbubble generating section 3 is composed of multiple parts, which can also be formed by welding the parts together.

[0085] In the above embodiments, a structure is described in which a plurality of slits 4 are arranged in a generally straight line from the first end 42 to the second end 44. In another embodiment, the plurality of slits 4 may also be arranged in a spiral shape centered on the central axis A from the first end 42 to the second end 44.

[0086] In the above embodiments, a structure is described in which the second end 44 of the plurality of slits 4 is located downstream of the downstream end of the inner narrowing channel 322 (the second end 44 coincides with the upstream end of the inner widening channel 324). In another embodiment, the second end 44 may also extend to a position upstream of the downstream end of the inner narrowing channel 322. For example, the second end 44 may also coincide with the upstream end of the inner narrowing channel 322. In this case, although the amount of microbubbles generated in the inner Venturi channel 32 is reduced, the water film can be eliminated more reliably. Furthermore, in another embodiment, the second end 44 may also be located downstream of the upstream end of the inner widening channel 324.

[0087] In the above embodiments, a structure is described in which multiple slits 4 are provided in the inner venturi flow channels 32, but not in the multiple outer venturi flow channels 34. In another embodiment, the multiple slits 4 may also be provided in the multiple outer venturi flow channels 34 instead of the inner venturi flow channels 32. In this case, the multiple slits 4 may also be provided in at least one of the multiple outer venturi flow channels 34. Furthermore, in another embodiment, the multiple slits 4 may be provided in both the inner venturi flow channels 32 and the multiple outer venturi flow channels 34.

[0088] In the above embodiments, a structure was described in which both the first notch 6 and the first recess 306 (or the second notch 8 and the second recess 308) function as the first drainage channel D1 (or the second drainage channel D2). In another embodiment, one of the first notch 6 and the first recess 306 (or the second notch 8 and the second recess 308) may not be provided. In this case, only the other of the first notch 6 and the first recess 306 (or the second notch 8 and the second recess 308) functions as the first drainage channel D1 (or the second drainage channel D2). Furthermore, in another embodiment, instead of providing the first notch 6 and the first recess 306 (or the second notch 8 and the second recess 308), a recess having a shape that recesses inward from the outer surface 38a of the downstream fitting portion 38 may be provided. In this case, the recess provided in the downstream fitting portion 38 can also function as the first drainage channel D1 (or the second drainage channel D2).

[0089] In the above embodiments, the structure of the first drainage channel D1 (or the second drainage channel D2) is described as being formed by creating a notch (or recess) in the first microbubble generating part 3. In another embodiment, the first drainage channel D1 (or the second drainage channel D2) may also be formed by recessing the main body shell 10 radially outward from the inner side surface 10a towards the central axis A.

[0090] In the above embodiments, the microbubble generator 2 is described as being arranged vertically upward along the central axis A towards the upstream side and vertically downward along the central axis A towards the downstream side. In another embodiment, the microbubble generator 2 may not be arranged in this way. For example, the microbubble generator 2 may be arranged such that it is inclined at an angle ranging from -90° to 90° relative to vertical upward along the central axis A towards the upstream side and inclined at an angle ranging from -90° to 90° relative to vertical downward along the central axis A towards the downstream side. In this case, either the first drainage channel D1 or the second drainage channel D2 may be arranged to be connected to the vicinity of the lowermost part of the gap space S. Even in this case, when the microbubble generator 2 drains water, almost all the water in the gap space S flows into the first drainage channel D1 or the second drainage channel D2.

[0091] In the above embodiments, a structure with two drainage channels was described. In another embodiment, three or more drainage channels may be provided. Alternatively, only one drainage channel may be provided.

[0092] In the above embodiments, the number of each of the plurality of second microbubble generating sections 5, the plurality of outer venturi channels 34, the plurality of slits 4, and the plurality of blade sections 56 can be suitably varied. Furthermore, although described as "a plurality of", it could also be one.

[0093] (Correspondence)

[0094] In one or more embodiments, the microbubble generating device 2 has a main body housing 10 and a first microbubble generating section 3. The main body housing 10 has an inlet section 12 and an outlet section 14. The first microbubble generating section 3 is housed in the main body housing 10 and is disposed between the inlet section 12 and the outlet section 14. The first microbubble generating section 3 has Venturi channels 32 and 34 (examples of one or more Venturi channels). The Venturi channels 32 and 34 have respectively a narrowing channel 322 and 342 and an expanding channel 324 and 344. The diameter of the narrowing channel 322 and 342 decreases as it moves from the upstream side to the downstream side. The expanding channel 324 and 344 are disposed downstream of the narrowing channel 322 and 342, and their diameters expand as they move from the upstream side to the downstream side. A plurality of slits 4 are formed in the inner Venturi channel 32 (an example of at least one Venturi channel among one or more Venturi channels), and the plurality of slits 4 are recessed radially outward from the inner surface of the inner Venturi channel 32. The plurality of slits 4 are continuously provided from a first end 42 that coincides with the downstream end of the inner expansion channel 324 to a second end 44 located upstream of the downstream end of the inner expansion channel 324.

[0095] According to the above structure, in the inner Venturi channel 32 provided with multiple slits 4, when a water film (an example of a liquid film) is formed in the inner widening channel 324, the water film is attracted by the multiple slits 4 and moves upstream along the inner widening channel 324. As the inner widening channel 324 moves upstream, its diameter narrows, and therefore, the surface area of ​​the water film decreases as it moves upstream. At this time, the water film condenses along with the decrease in surface area, forming water droplets or the like, and then disappears. Therefore, according to the above structure, a water film can be eliminated in the inner Venturi channel 32.

[0096] In one or more embodiments, the second end 44 of the plurality of slits 4 is located on the downstream side of the downstream end of the inner narrowing channel 322.

[0097] Multiple slits 4 are arranged in a recessed manner relative to the inner surface of the inner Venturi channel 32, thus expanding the depth of the slits 4 in the portion where they are provided. Here, in the Venturi channels 32 and 34, the flow velocity of the water passing through the narrowed channels 322 and 342 is increased, reducing water pressure and generating bubbles. Therefore, for example, when the second end 44 of the multiple slits 4 is located upstream of the downstream end of the inner narrowed channel 322, the local expansion of the inner narrowed channel 322 due to the multiple slits 4 may significantly reduce the amount of microbubbles generated. In contrast, according to the above structure, since the second end 44 of the multiple slits 4 is located downstream of the downstream end of the inner narrowed channel 322, the inner narrowed channel 322 does not expand even with the multiple slits 4 provided. By employing this structure, the reduction in the amount of microbubbles generated when multiple slits 4 are provided can be suppressed.

[0098] In one or more embodiments, the plurality of slits 4 are arranged in a generally straight line from the first end 42 to the second end 44.

[0099] According to the above structure, the multiple slits 4 extend in a roughly straight line from the downstream side to the upstream side. Therefore, the multiple slits 4 allow the water film to move smoothly upstream. Thus, the water film can be eliminated more reliably.

[0100] In one or more embodiments, the microbubble generating device 2 further includes a second microbubble generating section 5, which is housed in the main body housing 10 and disposed between the first microbubble generating section 3 and the outflow section 14. The second microbubble generating section 5 includes a shaft portion 52, an outer peripheral portion 54, a plurality of blade portions 56, and a swirling flow channel 64. The shaft portion 52 extends in a direction from the upstream side to the downstream side; the outer peripheral portion 54 surrounds the radially outer side of the shaft portion 52; the plurality of blade portions 56 are disposed between the shaft portion 52 and the outer peripheral portion 54 to generate a swirling flow that flows clockwise (an example of a specified swirling direction) relative to the shaft portion 52; the swirling flow channel 64 passes through the gap between the shaft portion 52, the outer peripheral portion 54, and the plurality of blade portions 56. There are multiple Venturi flow channels 32 and 34, including an inner Venturi flow channel 32 and multiple outer Venturi flow channels 34. The inner Venturi flow channel 32 extends along the extension line of the shaft portion 52; the multiple outer Venturi flow channels 34 are arranged around the inner Venturi flow channel 32. Multiple slits 4 are provided in the inner Venturi flow channel 32 but not in the multiple outer Venturi flow channels 34.

[0101] According to the above structure, the water flowing into the swirling channel 64 of the second microbubble generating section 5 forms a swirling flow. The microbubbles generated by the first microbubble generating section 3 are further reduced to smaller bubbles by the shear force of the swirling flow, and the number of microbubbles increases. At this time, the greater the flow velocity flowing into the swirling channel 64, the stronger the swirling flow, thus generating more microbubbles. Here, the water flowing in the inner Venturi channel 32 collides with the shaft portion 52 of the second microbubble generating section 5 and is decelerated before flowing into the swirling channel 64. On the other hand, the water flowing in the multiple outer Venturi channels 34 does not collide with the shaft portion 52 and flows into the swirling channel 64. Therefore, the water flowing in the inner Venturi channel 32 has a smaller impact on the amount of microbubbles generated compared to the water flowing in the multiple outer Venturi channels 34. Generally, in Venturi flow channels 32 and 34 with multiple slits 4, the amount of microbubbles generated is significantly reduced compared to Venturi flow channels 32 and 34 without multiple slits 4. However, according to the above structure, the multiple slits 4 are only provided in the inner Venturi flow channel 32, where the impact on the amount of microbubbles generated is minimal. Therefore, in the above structure, the reduction in microbubbles when multiple slits 4 are provided in the Venturi flow channels 32 and 34 can be minimized.

[0102] In one or more embodiments, the water heater 100 has a microbubble generating device 2.

[0103] According to the above structure, water film can be eliminated in the venturi channel 32 inside the microbubble generating device 2 of the water heater 100.

[0104] In one or more embodiments, the dishwasher 510 has a microbubble generating device 2.

[0105] According to the above structure, water film can be eliminated in the venturi channel 32 inside the microbubble generating device 2 of the dishwasher 510.

[0106] The technical elements described in this specification or drawings, individually or in various combinations, exert their technical usefulness and are not limited to the combinations described in the technical solution at the time of the application. Furthermore, the technology illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful.

Claims

1. A microbubble generating device, characterized in that, It has a main outer shell and a first microbubble generating section, wherein, The main outer shell has an inflow section and an outflow section; The first microbubble generating unit is housed within the main body casing and is disposed between the inlet and the outlet. The first microbubble generating section has one or more Venturi channels. One or more of the Venturi tube flow channels each have a narrowing flow channel and an expanding flow channel, wherein, The diameter of the narrowing flow channel decreases as it moves from the upstream side to the downstream side. The expanding flow channel is positioned downstream of the contracting flow channel, and its diameter increases as it moves from the upstream to the downstream side. A slit is formed in at least one of the one or more Venturi flow channels, the slit being recessed radially outward from the inner side of the Venturi flow channel. The slit is continuously provided from a first end, which coincides with the downstream end of the expansion channel, to a second end located upstream of the downstream end.

2. The microbubble generator according to claim 1, characterized in that, The size of the slit, i.e. the depth of the slit, in the concave direction is approximately constant from the first end to the second end. The size of the slit, i.e. the width of the slit, in the direction orthogonal to the recessed direction is approximately constant from the first end to the second end.

3. The microbubble generator according to claim 1 or 2, characterized in that, The slit depth in the concave direction is greater than the slit width in the direction orthogonal to the concave direction.

4. The microbubble generator according to claim 1 or 2, characterized in that, One or more of the Venturi channels include a first Venturi channel with the slit and a second Venturi channel without the slit.

5. The microbubble generator according to claim 1 or 2, characterized in that, The second end of the slit is located downstream of the downstream end of the narrowed flow channel.

6. The microbubble generator according to claim 1 or 2, characterized in that, The slit is arranged in a generally straight line from the first end to the second end.

7. The microbubble generator according to claim 1 or 2, characterized in that, It also has a second microbubble generating unit, which is housed within the main body casing and disposed between the first microbubble generating unit and the outflow portion. The second microbubble generating section has a shaft section, an outer peripheral section, multiple blade sections, and a swirling flow channel, wherein... The shaft extends in a direction from the upstream side to the downstream side; The outer peripheral portion surrounds the radial outer side of the shaft portion; A plurality of the blade portions are disposed between the shaft portion and the outer peripheral portion for generating a swirling flow relative to the shaft portion in a predetermined swirling direction; The swirling flow channel passes through the gap between the shaft portion, the outer peripheral portion, and the plurality of blade portions. The Venturi flow channels are multiple, including an inner Venturi flow channel and multiple outer Venturi flow channels, wherein... The inner Venturi flow channel extends along the extension line of the shaft portion; The plurality of said outer Venturi channels are arranged to surround the inner Venturi channels. The slit is located in the inner Venturi channel and is not located in the plurality of outer Venturi channels.

8. A water heater, characterized in that, A microbubble generating apparatus having any one of claims 1 to 7.

9. A dishwasher, characterized in that, A microbubble generating apparatus having any one of claims 1 to 7.

10. A microbubble generating device, characterized in that, It has a main outer shell and a first microbubble generating section, wherein, The main outer shell has an inflow section and an outflow section; The first microbubble generating unit is housed within the main body casing and is disposed between the inlet and the outlet. The first microbubble generating section has one or more expansion channels. The diameter of one or more of the aforementioned expansion channels increases as they move from the upstream side to the downstream side. A slit is formed in at least one of the expansion channels or a plurality of expansion channels, the slit being recessed radially outward from the inner side of the expansion channel. The slit is continuously provided from a first end, which coincides with the downstream end of the expansion channel, to a second end located upstream of the downstream end.

11. The microbubble generator according to claim 10, characterized in that, The size of the slit, i.e. the depth of the slit, in the concave direction is approximately constant from the first end to the second end. The size of the slit, i.e. the width of the slit, in the direction orthogonal to the recessed direction is approximately constant from the first end to the second end.

12. The microbubble generator according to claim 10 or 11, characterized in that, The slit depth in the concave direction is greater than the slit width in the direction orthogonal to the concave direction.

13. The microbubble generator according to claim 10 or 11, characterized in that, One or more of the enlarged flow channels include a first enlarged flow channel with the slit and a second enlarged flow channel without the slit.

14. The microbubble generator according to claim 10 or 11, characterized in that, The slit is arranged in a generally straight line from the first end to the second end.

15. The microbubble generator according to claim 10 or 11, characterized in that, It also has a second microbubble generating unit, which is housed within the main body casing and disposed between the first microbubble generating unit and the outflow portion. The second microbubble generating section has a shaft, multiple blade sections, and a swirling flow channel, wherein... The shaft extends in a direction from the upstream side to the downstream side; The plurality of blade portions extend from the shaft portion for generating a swirling flow relative to the shaft portion in a predetermined swirling direction; The swirling flow channel passes through the gaps between the multiple blade sections. The expansion channels are multiple, including inner expansion channels and multiple outer expansion channels, wherein... The inner diameter expansion channel extends along the extension line of the shaft portion; The plurality of said outer diameter expansion channels are arranged to surround the inner diameter expansion channels. The slit is located in the inner expansion channel and is not located in any of the multiple outer expansion channels.

16. A water heater, characterized in that, The microbubble generating apparatus has any one of claims 10 to 15.

17. A dishwasher, characterized in that, The microbubble generating apparatus has any one of claims 10 to 15.

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