Microbubble generator

Abstract

To provide a technology that can generate a large amount of fine air bubbles.SOLUTION: A fine air bubble generator includes: an inflow part; an outflow part; a first fine air bubble generation part provided between the inflow part and the outflow part and including a first passage; and a second fine air bubble generation part provided between the first fine air bubble generation part and the outflow part and including a second passage. The first passage includes a diameter decreasing part and a diameter increasing part. The second passage includes a guide passage and a collision passage. The collision passage is provided with: a first bearing part; and a first impeller rotatably attached to the first bearing part. The first impeller includes: a circular disc part provided at a position, with which water that has passed through the guide passage collides, the circular disc part provided so as to be orthogonal to a passage axis of the second passage; a first rotary shaft part provided on a downstream side surface of the circular disc part and rotatably attached to the first bearing part; and a first impeller part provided on an upstream side surface of the circular disc part.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Patent Document 1 discloses a micro-bubble generator including an inflow section into which water containing dissolved gas flows, an outflow section from which the water containing dissolved gas flows out, and a micro-bubble generating section provided between the inflow section and the outflow section. The micro-bubble generating section includes a contracting flow passage whose diameter decreases from upstream to downstream, and an expanding flow passage provided downstream of the contracting flow passage and whose diameter increases from upstream to downstream. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-8193 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the micro-bubble generator of Patent Document 1, water in which gas is dissolved (hereinafter, sometimes referred to as "gas-dissolved water") flows into the narrowing flow passage of the micro-bubble generating section via the inflow section. The flow rate of the gas-dissolved water increases as it passes through the narrowing flow passage, and as a result, the pressure of the gas-dissolved water is reduced. The reduced pressure of the gas-dissolved water generates bubbles. Next, the pressure of the gas-dissolved water is gradually increased as it passes through the expanding flow passage. When the pressure of the gas-dissolved water after bubbles are generated by the reduced pressure is increased, the bubbles contained in the gas-dissolved water are split and become micro-bubbles. In this way, in the micro-bubble generating device of Patent Document 1, micro-bubbles are generated by the micro-bubble generating section. However, in the micro-bubble generating device of Patent Document 1, a situation occurs in which the amount of micro-bubbles generated by the micro-bubble generating device is insufficient.

[0005] This specification provides a technology capable of generating a large amount of fine bubbles. [Means for solving the problem]

[0006] The micro-bubble generating device disclosed in the present specification comprises an inflow section into which dissolved gas flows in, an outflow section from which dissolved gas flows out, a first micro-bubble generating section provided between the inflow section and the outflow section and having a first flow path, and a second micro-bubble generating section provided between the first micro-bubble generating section and the outflow section and having a second flow path, the first flow path comprises a reduced diameter flow path whose flow path diameter reduces from upstream to downstream, and an increased diameter flow path provided downstream of the reduced diameter flow path and whose flow path diameter increases from upstream to downstream, and the second flow path converts the dissolved gas flowing into the second flow path into the reduced diameter flow path. The second flow passage has a guide flow passage that guides water toward the center of a flow passage axis of the second flow passage, and a collision flow passage that is provided downstream of the guide flow passage and is defined by a collision flow passage wall portion, and the collision flow passage is provided with a first bearing portion and a first impeller rotatably attached to the first bearing portion, and the first impeller is provided at a position where the gas-dissolved water that has passed through the guide flow passage collides, and is provided with a disk portion provided perpendicular to the flow passage axis of the second flow passage, a first rotating shaft portion provided on the downstream surface of the disk portion and rotatably attached to the first bearing portion, and a first blade portion provided on the upstream surface of the disk portion.

[0007] According to the above configuration, the dissolved gas flows into the narrowed diameter flow passage of the first fine-bubble generating section through the inflow section. When the dissolved gas flows through the narrowed diameter flow passage, the flow rate increases, and the pressure is reduced. When the dissolved gas flows through the narrowed diameter flow passage, bubbles are generated. The dissolved gas flows through the widened diameter flow passage, and the pressure is gradually increased. When the dissolved gas flows through the widened diameter flow passage after the bubbles are generated through the reduced pressure, the bubbles contained in the dissolved gas break down and become fine bubbles. The dissolved gas flows through the first fine-bubble generating section and flows into the second fine-bubble generating section. The dissolved gas flows through the guide flow passage and flows into the collision flow passage, and collides with the disk of the first impeller provided in the collision flow passage. The dissolved gas flows through the guide flow passage and flows into the second fine-bubble generating section toward the center of the flow passage axis of the second flow passage, i.e., toward the center of the disk, so that most of the dissolved gas collides near the center of the disk. Since the first blade portion is provided on the upstream surface of the disk portion, the dissolved gas water that collides with the disk portion flows along the first blade portion, and the disk portion rotates with respect to the first bearing portion. As the disk portion rotates with respect to the first bearing portion, the dissolved gas water that flows along the first blade portion is pushed radially outward of the disk portion and collides with the collision flow path wall portion that defines the collision flow path. As the dissolved gas water collides with the collision flow path wall portion, the fine bubbles generated in the first fine bubble generating portion are split into finer bubbles and the amount of fine bubbles increases. Therefore, a large amount of fine bubbles can be generated.

[0008] In one or more embodiments, the micro-bubble generator may further include a third micro-bubble generating section provided between the first micro-bubble generating section and the outlet section and having a third flow path. The third flow path may include a second bearing section, a second rotating shaft section rotatably attached to the second bearing section and extending along the flow path axis of the third flow path, and a second impeller connected to the second rotating shaft section and having a second blade section extending radially outward from the second rotating shaft section.

[0009] According to the above configuration, the gas-dissolved water that has passed through the first micro-bubble generating unit flows into the third flow path of the third micro-bubble generating unit. The gas-dissolved water collides with the second blade of the second impeller provided in the third flow path, causing the second impeller to rotate relative to the second bearing. Then, the micro-bubbles in the gas-dissolved water passing through the second impeller are sheared by the rotating second blade when the gas-dissolved water passes through the second impeller. This causes the micro-bubbles in the gas-dissolved water to become finer and increases the amount of micro-bubbles.

[0010] In one or more embodiments, the third fine bubble generating section may further include a rib portion located downstream of the second blade portion and connecting the second bearing portion and the wall portion defining the third flow path.

[0011] According to the above configuration, when the gas-dissolved water that has passed through the second impeller passes through the rib portion, the micro-bubbles in the gas-dissolved water are sheared by the rib portion, which causes the micro-bubbles in the gas-dissolved water to become finer and the amount of the micro-bubbles to increase.

[0012] In one or more embodiments, the second fine bubble generating section may be provided between the third fine bubble generating section and the outlet section.

[0013] In the second fine-bubble generating section, the gas-dissolved water collides with the disk section and the collision flow path wall section, and the flow path direction of the gas-dissolved water changes significantly. On the other hand, in the third fine-bubble generating section, the flow path direction of the gas-dissolved water does not change significantly. Therefore, the pressure loss in the second flow path of the second fine-bubble generating section is larger than the pressure loss in the third flow path of the third fine-bubble generating section, and the flow of the gas-dissolved water is likely to stagnate. By causing the gas-dissolved water before the flow stagnates to flow into the third fine-bubble generating section, a large number of fine bubbles can be generated. According to the above configuration, the pressure loss before flowing into the third fine-bubble generating section can be reduced compared to the configuration in which the third fine-bubble generating section is provided between the second fine-bubble generating section and the outflow section, and the gas-dissolved water before the flow stagnates flows into the second fine-bubble generating section. Therefore, the gas dissolution is more easily sheared in the third fine-bubble generating section, and as a result, a large number of fine bubbles can be generated.

[0014] In one or more embodiments, the impingement channel may further include an axial extension portion disposed radially of the first rotating shaft portion between the impingement channel wall portion and the first impeller and extending along the axial direction of the first rotating shaft portion.

[0015] By increasing the number of collisions of the dissolved gas water, the micro-bubbles become finer and the amount of the micro-bubbles increases. According to the above configuration, a part of the dissolved gas water pushed out radially outward of the disk portion collides with the axial extension portion and then with the wall portion of the collision flow path. Therefore, the number of collisions of the dissolved gas water can be increased compared to a configuration in which the collision flow path does not have an axial extension portion. Therefore, the micro-bubbles in the dissolved gas water become finer and the amount of the micro-bubbles increases.

[0016] In one or more embodiments, the first blade portion has a first end portion on the inner side in the radial direction of the first rotating shaft portion, which is located on the first rotation direction side relative to the first rotating shaft portion relative to the outer second end portion, and the axial extension portion has a third end portion on the inner side in the radial direction, which is located on the second rotation direction side, which is opposite to the first rotation direction side, relative to the outer fourth end portion.

[0017] According to the above configuration, the gas-dissolved water that collides with the disk portion passes through the first blade portion, and the disk portion rotates in the first rotation direction relative to the first rotary bearing portion. The gas-dissolved water pushed outward in the radial direction from the first impeller is pushed outward in the radial direction while flowing in the second rotation direction that is the opposite direction to the first rotation direction. Since the third end of the axial extension portion is located closer to the second rotation direction than the fourth end, the gas-dissolved water pushed outward in the radial direction is likely to collide with the axial extension portion. The gas-dissolved water that collides with the axial extension portion flows radially outward, that is, toward the collision flow path wall portion. Therefore, the gas-dissolved water that collides with the axial extension portion can be caused to collide with the collision flow path wall portion. Therefore, the number of collisions of the gas-dissolved water can be increased, and the fine bubbles in the gas-dissolved water become finer and the amount of fine bubbles increases. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a hot water supply system 2 according to an embodiment. [Diagram 2] FIG. 2 is a perspective view of a fine bubble generating device 46 according to the embodiment. [Diagram 3] FIG. 2 is a cross-sectional view of a fine bubble generating device 46 according to an embodiment. [Figure 4] 1 is a perspective view of the fine-bubble generating device 46 according to the embodiment with the main body case 100 removed. FIG. [Diagram 5] FIG. 5 is an exploded view of FIG. [Figure 6] FIG. 2 is a view of the upstream fine bubble generating section 110 according to the embodiment, as viewed from the upstream side. [Figure 7] FIG. 2 is a view of the upstream fine bubble generating section 110 according to the embodiment as viewed from the downstream side. [Figure 8] FIG. 2 is an exploded view of the intermediate fine bubble generating section 112 according to the embodiment, as viewed from the upstream side. [Figure 9] FIG. 2 is an exploded view of the intermediate fine bubble generating section 112 according to the embodiment, as viewed from the downstream side. [Figure 10]FIG. 2 is an exploded view of the downstream fine bubble generating section 114 according to the embodiment, as viewed from the upstream side. [Figure 11] FIG. 2 is an exploded view of the downstream fine bubble generating section 114 according to the embodiment, as viewed from the downstream side. [Figure 12] FIG. 4 is a cross-sectional view taken along line XII-XII in FIG. [Figure 13] FIG. 4 is a cross-sectional view taken along line XIII-XIII in FIG. [Figure 14] FIG. 4 is a cross-sectional view taken along line XIV-XIV in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] (Example) (Configuration of hot water supply system 2; Figure 1) 1 can heat water supplied from a water supply source 4 such as a water supply system, and supply the water heated to a desired temperature to a faucet 6 installed in a kitchen or the like, or to a bathtub 8 in a bathroom. The hot water supply system 2 can also reheat the water in the bathtub 8.

[0020] The hot water supply system 2 includes a first heat source unit 10, a second heat source unit 12, and a combustion chamber 14. The first heat source unit 10 is a heat source unit used for supplying hot water to the faucet 6 and for filling the bathtub 8. The second heat source unit 12 is a heat source unit used for reheating the bathtub 8. The interior of the combustion chamber 14 is divided by a partition wall portion 16 into a first combustion chamber 18 and a second combustion chamber 20. The first combustion chamber 18 contains the first heat source unit 10, and the second combustion chamber 20 contains the second heat source unit 12.

[0021] The first heat source unit 10 includes a first burner 22 and a first heat exchanger 24. The second heat source unit 12 includes a second burner 26 and a second heat exchanger 28.

[0022] The upstream end of the first heat exchanger 24 of the first heat source unit 10 is connected to the downstream end of the water supply passage 30. Water is supplied from the water supply source 4 to the upstream end of the water supply passage 30. The downstream end of the first heat exchanger 24 is connected to the upstream end of the hot water supply passage 32. The water supply passage 30 and the hot water supply passage 32 are connected by a bypass passage 34. A bypass servo 36 is provided at the connection point between the water supply passage 30 and the bypass passage 34. The bypass servo 36 adjusts the ratio of the flow rate of water sent from the water supply passage 30 to the first heat source unit 10 to the flow rate of water sent from the water supply passage 30 to the bypass passage 34. At the connection point between the bypass passage 34 and the hot water supply passage 32, the low-temperature water passing through the water supply passage 30 and the bypass passage 34 and the high-temperature water passing through the water supply passage 30, the first heat source unit 10, and the hot water supply passage 32 are mixed. A water flow sensor 38 and a water flow servo 40 are provided in the water supply passage 30 upstream of the bypass servo 36. The water flow sensor 38 detects the flow rate of water flowing through the water supply passage 30. The water flow servo 40 adjusts the flow rate of water flowing through the water supply passage 30. A heat exchanger outlet thermistor 42 is provided in the hot water supply passage 32 upstream of the connection point with the bypass passage 34.

[0023] The upstream end of the water filling path 50 is connected to the hot water supply path 32 downstream of the connection point of the bypass path 34. A hot water supply thermistor 44 is provided at the connection point between the hot water supply path 32 and the hot water filling path 50. A fine bubble generator 46 is provided between the connection point between the hot water supply path 32 and the bypass path 34 and the connection point between the hot water supply path 32 and the hot water filling path 50. The fine bubble generator 46 will be described in detail later. In the following, the water path of the hot water supply path 32 upstream of the fine bubble generator 46 may be referred to as a first hot water supply path 32a, and the water path of the hot water supply path 32 downstream of the fine bubble generator 46 may be referred to as a second hot water supply path 32b.

[0024] The downstream end of the water filling path 50 is connected to the upstream end of the reheating outward path 60 and the downstream end of the first bathtub circulation path 62. The downstream end of the reheating outward path 60 is connected to the upstream end of the second heat exchanger 28. The upstream end of the first bathtub circulation path 62 is connected to the bathtub 8. The water filling path 50 is provided with a water filling control valve 52 and a check valve 54. The water filling control valve 52 opens and closes the water filling path 50. The check valve 54 allows water to flow from the upstream side of the water filling path 50 to the downstream side, and prohibits water to flow from the downstream side of the water filling path 50 to the upstream side. A bathtub return thermistor 64 is provided at the connection point of the water filling path 50, the reheating outward path 60, and the first bathtub circulation path 62. The reheating outward path 60 is provided with a circulation pump 66.

[0025] The downstream end of the second heat exchanger 28 of the second heat source unit 12 is connected to the upstream end of the second bathtub circulation path 68. The downstream end of the second bathtub circulation path 68 is connected to the bathtub 8. A bathtub forward thermistor 70 is provided in the second bathtub circulation path 68.

[0026] When the hot water supply system 2 supplies hot water to the faucet 6, the first burner 22 of the first heat source unit 10 is combusted with the hot water filling control valve 52 closed. In this case, water supplied from the water supply source 4 to the water supply path 30 is heated by heat exchange in the first heat exchanger 24, and then supplied to the faucet 6 from the hot water supply path 32. By adjusting the combustion amount of the first burner 22 of the first heat source unit 10 and the opening degree of the bypass servo 36, the temperature of the water flowing through the hot water supply path 32 can be adjusted to a desired temperature.

[0027] When the hot water supply system 2 fills the bathtub 8, the first burner 22 of the first heat source unit 10 is burned with the bath filling control valve 52 open. In this case, the water supplied from the water supply source 4 to the water supply path 30 is heated by heat exchange in the first heat exchanger 24, and then flows from the hot water supply path 32 into the bath filling path 50. The water adjusted to the desired temperature by adjusting the combustion amount of the first burner 22 of the first heat source unit 10 and adjusting the opening of the bypass servo 36 flows into the bath filling path 50. The water that flows into the bath filling path 50 flows into the bathtub 8 via the first bathtub circulation path 62, and also flows into the bathtub 8 via the reheating forward path 60 and the second bathtub circulation path 68.

[0028] When the hot water supply system 2 reheats the bathtub 8, the circulation pump 66 is driven and the second burner 26 of the second heat source unit 12 is combusted while the water filling control valve 52 is closed. In this case, the water in the bathtub 8 flows into the first bathtub circulation path 62 and is sent to the second heat source unit 12 via the reheating outward path 60. The water sent to the second heat source unit 12 is heated by heat exchange in the second heat exchanger 28 and then flows into the second bathtub circulation path 68. The water adjusted to the desired temperature by adjusting the combustion amount of the second burner 26 of the second heat source unit 12 flows into the second bathtub circulation path 68. The water that flows into the second bathtub circulation path 68 is returned to the bathtub 8.

[0029] (Configuration of the micro-bubble generating device 46; Figs. 2 to 14) Next, the micro-bubble generator 46 provided in the hot water supply passage 32 will be described with reference to Figs. 2 to 14. The "clockwise direction" and "counterclockwise direction" described below refer to the direction of the central axis A of the micro-bubble generator 46 when the micro-bubble generator 46 is viewed from the upstream side. Hereinafter, the central axis A of the micro-bubble generator 46 may be simply referred to as the "central axis A". As shown in Fig. 2, the micro-bubble generator 46 includes a main body case 100, an inlet portion 102, and an outlet portion 104. An outer wall portion 100a of the main body case 100 has a rectangular prism shape. The central axis of the main body case 100 coincides with the central axis A. As shown in Fig. 12, when the micro-bubble generator 46 is viewed in the central axis A direction, an inner wall portion 100b of the main body case 100 has a circular shape. The inlet portion 102 in FIG. 3 is fixed to the upstream end 100c of the main body case 100 by a screw (not shown). An inlet port 102a is formed in the inlet portion 102. The inlet portion 102 is connected to the downstream end of the first hot water supply path 32a (see FIG. 1). The outlet portion 104 is fixed to the downstream end 100d of the main body case 100 by a screw (not shown). An outlet port 104a is formed in the outlet portion 104. The outlet portion 104 is connected to the upstream end of the second hot water supply path 32b (see FIG. 1).

[0030] The main body case 100 accommodates an upstream fine bubble generating section 110, an intermediate fine bubble generating section 112, and a downstream fine bubble generating section 114. The upstream fine bubble generating section 110, the intermediate fine bubble generating section 112, and the downstream fine bubble generating section 114 are provided along the central axis A. The upstream fine bubble generating section 110, the intermediate fine bubble generating section 112, and the downstream fine bubble generating section 114 are provided from the upstream side to the downstream side in the following order: upstream fine bubble generating section 110, intermediate fine bubble generating section 112, downstream fine bubble generating section 114.

[0031] (Configuration of the upstream fine bubble generating section 110; Figs. 3 to 7) Next, the upstream fine bubble generating part 110 will be described with reference to Fig. 3 to Fig. 7. As shown in Fig. 3 and Fig. 4, the upstream fine bubble generating part 110 has a cylindrical shape. As shown in Fig. 3, the outer diameter of the upstream fine bubble generating part 110 and the inner diameter of the main body case 100 are the same. The central axis of the upstream fine bubble generating part 110 coincides with the central axis A.

[0032] As shown in Figs. 3, 6 and 7, the upstream fine-bubble generating section 110 is provided with eight venturi sections 120a to 120h. The venturi section 120a is provided in the center of the upstream fine-bubble generating section 110. The venturi section 120a is provided on the central axis A. As shown in Fig. 3, the upstream section of the venturi section 120a is provided with a reduced diameter flow passage 122a whose flow passage diameter decreases from upstream to downstream. The flow passage diameter of the upstream end of the reduced diameter flow passage 122a is smaller than the flow passage diameter of the inlet 102a of the inlet section 102. The downstream side of the reduced diameter flow passage 122a of the venturi section 120a is provided with an increased diameter flow passage 124a whose flow passage diameter increases from upstream to downstream.

[0033] As shown in Figs. 6 and 7, the venturi sections 120b to 120h are provided radially outward of the central axis A with respect to the venturi section 120a. The venturi sections 120b to 120h are arranged at equal intervals along the circumferential direction of the central axis A. The venturi sections 120b to 120h are provided with reduced diameter flow paths 122b to 122h (see Fig. 6) and expanded diameter flow paths 124b to 124h (see Fig. 7) in the same manner as the venturi section 120a. The reduced diameter flow paths 122a to 122h and the expanded diameter flow paths 124a to 124h define an upstream flow path 126 in the upstream fine-bubble generating section 110. The number of venturi sections 120 provided in the upstream fine-bubble generating section 110 is not limited to eight, and may be one to seven, or nine or more. As shown in FIG. 3, water flowing from the inlet 102 into the upstream fine-bubble generating section 110 passes through the upstream flow path 126 and flows into the intermediate fine-bubble generating section 112.

[0034] (Configuration of the intermediate fine bubble generating unit 112; Figs. 3 to 5, 8, and 9) Next, the intermediate fine bubble generating unit 112 will be described with reference to Fig. 3 to Fig. 5, Fig. 8 and Fig. 9. As shown in Fig. 8 and Fig. 9, the intermediate fine bubble generating unit 112 includes an intermediate fixed unit 130 and an intermediate rotating unit 132.

[0035] The intermediate fixing part 130 includes a first intermediate cylindrical part 140, an intermediate bearing part 142, and five intermediate rib parts 144. The first intermediate cylindrical part 140, the intermediate bearing part 142, and the five intermediate rib parts 144 are integrally formed. As shown in FIG. 3, the outer diameter of the first intermediate cylindrical part 140 and the inner diameter of the main body case 100 are the same. The central axes of the first intermediate cylindrical part 140 and the intermediate bearing part 142 coincide with the central axis A. The upstream end of the first intermediate cylindrical part 140 is connected to the downstream end of the upstream side fine bubble generating part 110. The intermediate bearing part 142 is provided at the downstream part of the intermediate fixing part 130. As shown in FIG. 8 and FIG. 9, the intermediate rib part 144 connects the inner wall part of the first intermediate cylindrical part 140 and the outer wall part of the intermediate bearing part 142. The intermediate rib part 144 extends perpendicular to the central axis A. The five intermediate rib portions 144 are disposed at equal intervals along the circumferential direction of the central axis A. As shown in FIG. 3, an intermediate flow path 146 in the intermediate fine bubble generating unit 112 is defined by the intermediate fixing portion 130 (specifically, the first intermediate cylindrical portion 140). The flow path axis of the intermediate flow path 146 coincides with the central axis A.

[0036] As shown in FIG. 8 and FIG. 9, the intermediate rotating part 132 includes a second intermediate cylindrical part 150, an intermediate rotating shaft part 152, and five intermediate blade parts 154. The second intermediate cylindrical part 150, the intermediate rotating shaft part 152, and the intermediate blade parts 154 are integrally formed. As shown in FIG. 3, the outer diameter of the second intermediate cylindrical part 150 is slightly smaller than the inner diameter of the first intermediate cylindrical part 140 of the intermediate fixed part 130. The central axes of the second intermediate cylindrical part 150 and the intermediate rotating shaft part 152 coincide with the central axis A. That is, the second intermediate cylindrical part 150 and the intermediate rotating shaft part 152 extend along the flow path axis of the intermediate flow path 146. The downstream end of the intermediate rotating shaft part 152 is attached to the intermediate bearing part 142 of the intermediate fixed part 130 so as to be rotatable around the central axis A. As shown in Fig. 8 and Fig. 9, the middle blade portion 154 is connected to the inner wall portion of the second middle cylindrical portion 150, extends radially outward from the inner wall portion of the second middle cylindrical portion 150, and is connected to the outer wall portion of the middle rotating shaft portion 152. As shown in Fig. 8, the middle blade portion 154 is inclined toward the downstream side as it moves in the clockwise direction along the central axis A when the middle rotating portion 132 is viewed from the upstream side. As shown in Fig. 3, the water flowing from the upstream side fine bubble generating portion 110 to the middle fine bubble generating portion 112 flows into the downstream side fine bubble generating portion 114 via the middle flow path 146.

[0037] (Configuration of the downstream fine bubble generating section 114; Figs. 3 to 5, 10, and 11) Next, the downstream fine bubble generating section 114 will be described with reference to Fig. 3 to Fig. 5, Fig. 10 and Fig. 11. As shown in Fig. 10 and Fig. 11, the downstream fine bubble generating section 114 includes a first downstream fixed section 160, a downstream rotating section 162, and a second downstream fixed section 164.

[0038] The first downstream fixing portion 160 includes a first downstream cylindrical portion 170, a downstream bearing portion 172, and four downstream ribs 174. The first downstream cylindrical portion 170, the downstream bearing portion 172, and the four downstream ribs 174 are integrally formed. As shown in FIG. 3, the outer diameter of the first downstream cylindrical portion 170 is the same as the inner diameter of the main body case 100. The central axes of the first downstream cylindrical portion 170 and the downstream bearing portion 172 coincide with the central axis A. The downstream end of the first downstream cylindrical portion 170 contacts the upstream end of the outflow portion 104. As shown in FIG. 10, two recesses 170a are provided at the upstream end of the first downstream cylindrical portion 170. The downstream ribs 174 connect the inner wall of the first downstream cylindrical portion 170 and the outer wall of the downstream bearing portion 172. The downstream rib portion 174 extends perpendicular to the central axis A. The four downstream rib portions 174 are disposed in the circumferential direction of the central axis A at equal intervals.

[0039] As shown in Figs. 10 and 11, the downstream rotating part 162 includes a disk part 180, a downstream rotating shaft part 182, a downstream blade part 184, and a flange part 186. As shown in Fig. 3, the disk part 180 is provided so as to be perpendicular to the flow path axis of the downstream flow path 222 described later. The flow path axis of the downstream flow path 222 coincides with the central axis A of the fine bubble generating device 46. The central axis of the disk part 180 coincides with the central axis A of the fine bubble generating device 46, i.e., the flow path axis of the downstream flow path 222. As shown in Fig. 11, the downstream rotating shaft part 182 extends downstream from the downstream surface 180a of the disk part 180. As shown in Fig. 3, the downstream end part of the downstream rotating shaft part 182 is attached to the downstream bearing part 172 of the first downstream fixing part 160 so as to be rotatable around the central axis A. The outer diameter of the disk portion 180 is smaller than the inner diameter of the first downstream cylindrical portion 170. The center of the upstream surface 180b of the disk portion 180 protrudes upstream. As shown in FIG. 10, the downstream blade portion 184 is provided on the upstream surface 180b of the disk portion 180. As shown in FIG. 14, when the downstream blade portion 184 is viewed from the upstream side along the central axis A, the downstream blade portion 184 is curved so that the inner end 184a on the radial inner side of the central axis A is located counterclockwise from the outer end 184b on the radial outer side of the central axis A. The center of the downstream blade portion 184 is located counterclockwise from the imaginary line connecting the inner end 184a and the outer end 184b. The outer end 184b of the downstream blade portion 184 extends outward from the disk portion 180. 10, the downstream blade portion 184 further includes an extension portion 184c extending upstream from the inner end portion 184a. The flange portion 186 is provided radially outward of the extension portion 184c. The flange portion 186 is provided on the upstream surface of the outer end portion 184b.

[0040] As shown in FIG. 10, the second downstream fixing part 164 includes a guide part 190 and an axial extension part 192. The guide part 190 has a cylindrical shape. As shown in FIG. 3, the outer diameter of the guide part 190 and the inner diameter of the main body case 100 are the same. The central axis of the guide part 190 coincides with the central axis A. The guide part 190 is provided with a guide flow channel 200 whose flow channel diameter decreases from the upstream to the downstream. The flow channel diameter on the upstream side of the guide flow channel 200 is the same as the flow channel diameter of the downstream end part of the first intermediate cylindrical part 140 of the intermediate fine bubble generating part 112. The flow channel diameter on the downstream side of the guide flow channel 200 is smaller than the outer diameter of the disk part 180.

[0041] As shown in FIG. 11, the axially extending portion 192 includes four first axially extending portions 210 and twelve second axially extending portions 212. The first axially extending portions 210 and the second axially extending portions 212 extend downstream from the downstream end of the guide portion 190. As shown in FIG. 14, the first axially extending portions 210 and the second axially extending portions 212 are disposed at equal intervals along the circumferential direction of the central axis A. The diameter of a circle formed by connecting the outer wall portion of the first axially extending portion 210 and the outer wall portion of the second axially extending portion 212 is the same as the inner diameter of the main body case 100. Three second axially extending portions 212 are provided between adjacent first axially extending portions 210 in the circumferential direction of the central axis A. When the micro-bubble generator 46 is viewed in the direction of the central axis A, the side wall 210a of the first axially extended portion 210 is parallel to an imaginary line connecting the central axis A and the circumferential center of the first axially extended portion 210. The side wall 212a of the second axially extended portion 212 is inclined so that an inner end 212b on the radially inner side of the central axis A is located further clockwise than an outer end 212c on the radially outer side.

[0042] As shown in FIG. 11, among the four first axial extension parts 210, two first axial extension parts 210 provided at positions corresponding to the recessed parts 170a (see FIG. 10) of the first downstream cylindrical part 170 of the first downstream fixing part 160 are provided at their downstream ends with protruding parts 210b protruding downstream. As shown in FIG. 3, the collision flow path 220 is defined by the inner wall part 100b of the main body case 100 located radially outward of the axial extension part 192. The downstream flow path 222 in the downstream fine bubble generating part 114 is defined by the guide flow path 200 and the collision flow path 220. Hereinafter, the part of the inner wall part 100b of the main body case 100 that defines the collision flow path 220 may be referred to as the "collision flow path wall part."

[0043] Next, the micro-bubbles generated by the micro-bubble generator 46 will be described with reference to FIG. 3 and FIG. 12 to FIG. 14. The solid arrows in FIG. 13, the solid arrows in FIG. 14, and the dashed arrows in FIG. 14 indicate the direction of water flow. The micro-bubble generator 46 of this embodiment generates micro-bubbles by using air contained in water supplied from a water supply source 4 such as a waterworks. Air (oxygen, carbon dioxide, nitrogen, etc.) is dissolved in the water supplied from the waterworks. In the following, water in which air is dissolved is referred to as "water dissolved in air." In addition, the following description is given assuming a situation in which the faucet 6 is operated by a user. As shown in FIG. 1, when the faucet 6 is operated by a user, the first burner 22 of the first heat source unit 10 is burned with the water filling control valve 52 closed. The air-dissolved water supplied from the water supply source 4 to the water supply passage 30 is heated by heat exchange in the first heat exchanger 24, and then flows into the fine bubble generator 46 via the first hot water supply passage 32a.

[0044] Before describing the fine bubbles generated by the fine bubble generator 46, the reason why the fine bubble generator 46 is provided in the first hot water supply path 32a will be described. The amount of dissolved air, which indicates the amount of air that can be dissolved in water, becomes smaller as the temperature of the water increases. The closer the amount of air dissolved in water is to the amount of dissolved air, the easier it is to generate bubbles. As will be described in detail later, the fine bubble generator 46 generates fine bubbles by generating bubbles in the air-dissolved water and making the bubbles finer. Therefore, the more bubbles generated in the air-dissolved water, the greater the amount of fine bubbles can be. For this reason, in this embodiment, the fine bubble generator 46 is provided in the first hot water supply path 32a through which the water heated by the first heat source unit 10 flows.

[0045] As shown in FIG. 3, the air-dissolved water that has flowed into the fine-bubble generating device 46 flows into the upstream flow passage 126 in the upstream fine-bubble generating section 110 via the inlet 102a of the inlet section 102. The air-dissolved water that has flowed into the upstream flow passage 126 flows into the venturi sections 120a to 120h. For example, the air-dissolved water that has flowed into the venturi section 120a flows into the reduced diameter flow passage 122a. The air-dissolved water that has flowed into the reduced diameter flow passage 122a increases in flow velocity by passing through the reduced diameter flow passage 122a, and as a result, the pressure is reduced. The reduced pressure of the air-dissolved water generates bubbles. The air-dissolved water that has passed through the reduced diameter flow passage 122a flows into the expanded diameter flow passage 124a. The air-dissolved water that has flowed into the expanded diameter flow passage 124a decreases in flow velocity by passing through the expanded diameter flow passage 124a, and as a result, the pressure is increased. When the pressure of the air-dissolved water after bubbles are generated by the reduction in pressure is increased, the air bubbles contained in the air-dissolved water break up and become fine bubbles. The water that has passed through the enlarged diameter flow path 124a flows into the intermediate flow path 146 of the intermediate fine bubble generating section 112. In this manner, fine bubbles are generated by the air-dissolved water passing through the venturi section 120a. As for the air-dissolved water that passes through the venturi sections 120b to 120h, fine bubbles are also generated by the air-dissolved water passing through the venturi sections 120b to 120h. The air-dissolved water that has passed through the upstream flow path 126 in the upstream fine bubble generating section 110 flows into the intermediate flow path 146 of the intermediate fine bubble generating section 112.

[0046] The air-dissolved water that has flowed into the intermediate flow passage 146 of the intermediate fine-bubble generating section 112 collides with the intermediate blade section 154 of the intermediate rotating section 132. As shown in Fig. 12, the air-dissolved water collides with the intermediate blade section 154, causing the intermediate blade section 154 to rotate in a counterclockwise direction. When the air-dissolved water passes through the intermediate blade section 154 rotating in the counterclockwise direction, the fine bubbles in the air-dissolved water are sheared, and as a result, the fine bubbles in the air-dissolved water become finer bubbles, and the amount of fine bubbles increases. The water that passes through the intermediate blade section 154 flows downstream while swirling in a clockwise direction.

[0047] Next, the air-dissolved water that has passed through the middle blade section 154 reaches the middle rib section 144 while swirling in a clockwise direction. Then, as shown in Fig. 13, when the air-dissolved water passes through the middle rib section 144, the middle rib section 144 shears the fine bubbles in the air-dissolved water, resulting in finer bubbles in the air-dissolved water and a greater amount of fine bubbles. As shown in Fig. 3, the air-dissolved water that has passed through the middle flow path 146 of the middle fine-bubble generating section 112 flows into the downstream flow path 222 of the downstream fine-bubble generating section 114.

[0048] The air-dissolved water that has flowed into the downstream flow passage 222 of the downstream fine-bubble generating section 114 flows into the guide flow passage 200. As described above, the flow passage axis of the guide flow passage 200 and the central axis of the disk section 180 coincide with each other. Therefore, the air-dissolved water that passes through the guide flow passage 200, which decreases in diameter from upstream to downstream, is guided toward the upstream side of the disk section 180 of the downstream rotating section 162 and toward the center of the flow passage axis of the downstream flow passage 222 (i.e., toward the center of the disk section 180). Therefore, most of the air-dissolved water that has passed through the guide flow passage 200 collides with the vicinity of the center of the disk section 180. When the air-dissolved water collides with the disk section 180, it flows along the upstream surface 180a of the disk section 180 and the downstream blade section 184. The air-dissolved water flows along the upstream surface 180a of the disk portion 180 and the downstream blade portion 184, causing the downstream rotating portion 162 to rotate in a counterclockwise direction. As shown in FIG. 14, the air-dissolved water flows in a clockwise direction and is pushed outward in the radial direction from the downstream rotating portion 162. The air-dissolved water pushed outward in the radial direction from the downstream rotating portion 162 collides with the impingement flow path wall portion (i.e., the inner wall portion 100b), the first axial extension portion 210, and the second axial extension portion 212. The air-dissolved water collides with the impingement flow path wall portion, the first axial extension portion 210, and the second axial extension portion 212, causing the fine bubbles in the air-dissolved water to split. As a result, the fine bubbles in the air-dissolved water become finer bubbles, and the amount of the fine bubbles increases. Furthermore, some of the dissolved air in the water collides with the side wall portion 212a of the second axial extension portion 212, and then collides with the collision flow path wall portion. Some of the dissolved air in the water collides with the side wall portion 212a of the second axial extension portion 212 and then with the collision flow path wall portion, and then collides with the dissolved air in the water pushed out from the disk portion 180. As the dissolved air in the water collides with the collision flow path wall portion, the first axial extension portion 210, the second axial extension portion 212, and the dissolved air in the water, the fine bubbles in the water become finer, and the amount of fine bubbles increases.

[0049] According to the above configuration, as shown in Fig. 2 to Fig. 5, the fine bubble generator 46 includes the inlet section 102, the outlet section 104, the upstream fine bubble generating section 110 provided between the inlet section 102 and the outlet section 104 and provided with the upstream flow path 126, and the downstream fine bubble generating section 114 provided between the upstream fine bubble generating section 110 and the outlet section 104 and provided with the downstream flow path 222. As shown in Figs. 3, 6 and 7, the upstream flow path 126 includes the narrowing flow paths 122a to 122f and the widening flow paths 124a to 124f provided downstream of the narrowing flow paths 122a to 122f. As shown in Figs. 3, 10 and 11, the downstream flow path 222 includes a guide flow path 200 that guides the air-dissolved water flowing into the downstream flow path 222 toward the center of the flow path axis of the downstream flow path 222, and a collision flow path 220 defined by a collision flow path wall portion. The collision flow passage 220 is provided with a downstream bearing 172 and a downstream rotating part 162 rotatably attached to the downstream bearing 172. The downstream rotating part 162 is provided at a position where the water passing through the guide flow passage 200 collides with the downstream flow passage 222. The collision flow passage 220 is provided with a disk part 180 provided perpendicular to the flow passage axis of the downstream flow passage 222, a downstream rotating shaft part 182 provided on the downstream surface of the disk part 180 and rotatably attached to the downstream bearing 172, and a downstream blade part 184 provided on the upstream surface of the disk part 180. As shown in FIG. 3, the air-dissolved water flows into the diameter-reducing flow passages 122a to 122f of the upstream fine bubble generating part 110 via the inflow part 102. When the air-dissolved water passes through the diameter-reducing flow passages 122a to 122f, the flow velocity increases, and as a result, the pressure is reduced. When the pressure of the air-dissolved water is reduced, air bubbles are generated. Next, the pressure of the air-dissolved water is gradually increased as it passes through the diameter-increasing flow paths 124a-124f. When the pressure of the air-dissolved water after bubbles have been generated by decompression is increased, the air bubbles contained in the air-dissolved water break down into fine bubbles. The air-dissolved water that has passed through the upstream fine bubble generating section 110 flows into the downstream fine bubble generating section 114. As shown in FIG. 14, the air-dissolved water that flows into the downstream fine bubble generating section 114 passes through the guide flow path 200 and collides with the disk portion 180 of the downstream rotating section 162 provided in the collision flow path 220.The guide flow passage 200 guides the air-dissolved water flowing into the downstream fine-bubble generating section 114 toward the center of the flow passage axis of the downstream flow passage 222, i.e., toward the center of the disk section 180, so that most of the air-dissolved water collides with the vicinity of the center of the disk section 180. Since the downstream blade section 184 is provided on the upstream surface 180a of the disk section 180, the water that collides with the disk section 180 flows along the downstream blade section 184, and the disk section 180 rotates relative to the downstream bearing section 172. By the rotation of the disk section 180 relative to the downstream bearing section 172, the water flowing along the downstream blade section 184 is pushed outward in the radial direction of the disk section 180 and collides with the collision flow passage wall section that defines the collision flow passage 220. When the air-dissolved water collides with the wall of the collision flow path, the microbubbles generated in the upstream microbubble generating section 110 are split into smaller bubbles and the amount of microbubbles increases. Therefore, a large amount of microbubbles can be generated.

[0050] As shown in Figs. 2 to 5, the micro-bubble generator 46 further includes an intermediate micro-bubble generating section 112 having an intermediate flow passage 146, which is provided between the upstream micro-bubble generating section 110 and the outlet section 104. As shown in Figs. 3, 8 and 9, the intermediate flow passage 146 includes an intermediate bearing section 142, an intermediate rotating shaft section 152 rotatably attached to the intermediate bearing section 142 and extending along the flow passage axis of the intermediate flow passage 146, and an intermediate rotating section 132 connected to the intermediate rotating shaft section 152 and having an intermediate blade section 154 extending radially outward from the intermediate rotating shaft section 152. According to the above configuration, the air-dissolved water that has passed through the upstream micro-bubble generating section 110 flows into the intermediate flow passage 146 of the intermediate micro-bubble generating section 112. 12, the air-dissolved water collides with the intermediate blade portion 154 of the intermediate rotation portion 132 provided in the intermediate flow passage 146, causing the intermediate blade portion 154 to rotate relative to the intermediate bearing portion 142. Then, the fine bubbles in the air-dissolved water passing through the intermediate blade portion 154 are sheared by the rotating intermediate blade portion 154 as the air-dissolved water passes through the intermediate rotation portion 132. As a result, the fine bubbles in the air-dissolved water become finer bubbles and the amount of fine bubbles increases.

[0051] 8 and 9, the intermediate fine-bubble generating section 112 is further provided downstream of the intermediate blade section 154 and includes an intermediate rib section 144 that connects the intermediate bearing section 142 and the first intermediate cylindrical section 140 that defines the intermediate flow path 146. According to the above configuration, as shown in Fig. 13, when the air-dissolved water that has passed through the intermediate rotating section 132 passes through the intermediate rib section 144, the fine bubbles in the air-dissolved water are sheared by the intermediate rib section 144. This causes the fine bubbles in the air-dissolved water to become finer and the amount of fine bubbles to increase.

[0052] As shown in FIG. 3, the downstream fine bubble generating section 114 is provided between the intermediate fine bubble generating section 112 and the outflow section 104. As shown in FIG. 14, in the downstream fine bubble generating section 114, the air-dissolved water collides with the disk section 180 and the collision flow path wall, so that the flow path direction of the air-dissolved water changes significantly. On the other hand, as shown in FIG. 12 and FIG. 13, in the intermediate fine bubble generating section 112, the flow path direction of the air-dissolved water does not change significantly. Therefore, the pressure loss in the downstream flow path 222 of the downstream fine bubble generating section 114 is larger than the pressure loss in the intermediate flow path 146 of the intermediate fine bubble generating section 112, so that the flow of the air-dissolved water is likely to stagnate. By flowing the air-dissolved water into the intermediate fine bubble generating section 112 before the flow stagnates, a large number of fine bubbles can be generated. According to the above configuration, the pressure loss before flowing into the intermediate fine bubble generating section 112 can be reduced compared to a configuration in which the intermediate fine bubble generating section 112 is provided between the downstream side fine bubble generating section 114 and the outflow section 104, and the gas-dissolved water before the flow stagnates flows into the intermediate fine bubble generating section 112. Therefore, in the intermediate fine bubble generating section 112, the dissolved air is more easily sheared, and as a result, more fine bubbles can be generated.

[0053] 3, 10, and 11, the collision flow passage 220 is further provided with an axial extension portion 192 extending along the axial direction of the downstream rotating shaft portion 182, which is provided between the collision flow passage wall portion and the downstream rotating portion 162 in the radial direction of the downstream rotating shaft portion 182. According to the above configuration, as shown in FIG. 14, a part of the air-dissolved water pushed outward in the radial direction of the disk portion 180 collides with the axial extension portion 192 and then with the collision flow passage wall portion. Therefore, the number of collisions of the air-dissolved water can be increased compared to a configuration in which the axial extension portion 192 is not provided in the collision flow passage 220. Therefore, the fine bubbles in the air-dissolved water become finer and the amount of the fine bubbles increases.

[0054] As shown in FIG. 14, the inner end 184a of the downstream blade 184 is located counterclockwise from the outer end 184b, and the inner end 212b of the second axial extension 212 is located clockwise from the outer end 212c. According to the above configuration, the air-dissolved water that collides with the disk portion 180 passes through the downstream blade 184, causing the disk portion 180 to rotate counterclockwise relative to the downstream bearing 172. The air-dissolved water pushed outward in the radial direction from the downstream rotating portion 162 flows in the clockwise direction and is pushed outward in the radial direction. As described above, the inner end 212b of the second axial extension 212 is located clockwise from the outer end 212c. If the inner end 212b of the second axially extending portion 212 is located counterclockwise from the outer end 212c, the dissolved air water pushed outward in the radial direction while flowing in the clockwise direction is likely to flow along the side wall 212a of the second axially extending portion 212. Therefore, the dissolved air water is unlikely to collide with the second axially extending portion 212 (specifically, the side wall 212a). On the other hand, in the present embodiment, the inner end 212b of the second axially extending portion 212 is located clockwise from the outer end 212c, so the dissolved air water pushed outward in the radial direction while flowing in the clockwise direction is likely to collide with the second axially extending portion 212 (specifically, the side wall 212a). Then, the dissolved air water that has collided with the second axially extending portion 212 (specifically, the side wall 212a) flows radially outward, that is, toward the collision flow path wall. Therefore, the air-dissolved water that collides with the second axially extending portion 212 (specifically, the side wall portion 212a) can be caused to collide with the wall portion of the collision flow path. This increases the number of collisions of the air-dissolved water, making the fine bubbles in the air-dissolved water finer and increasing the amount of the fine bubbles.

[0055] (Correspondence) The air-dissolved water is an example of "gas-dissolved water". The upstream fine bubble generating section 110 is an example of "first fine bubble generating section". The upstream flow path 126 is an example of "first flow path". The downstream fine bubble generating section 114 is an example of "second fine bubble generating section". The downstream flow path 222 is an example of "second flow path". A part of the inner wall section 100b of the main body case 100 that defines the collision flow path 220 is an example of "collision flow path wall section". The downstream bearing section 172 is an example of "first bearing section". The downstream rotating section 162 is an example of "first impeller". The downstream rotating shaft section 182 is an example of "first rotating shaft section". The downstream blade section 184 is an example of "first blade section". The intermediate fine bubble generating section 112 is an example of "third fine bubble generating section". The intermediate flow passage 146 is an example of a "third flow passage". The intermediate bearing portion 142 is an example of a "second bearing portion". The intermediate rotating portion 132 is an example of a "second impeller". The intermediate rotating shaft portion 152 is an example of a "second rotating shaft portion". The intermediate blade portion 154 is an example of a "second blade portion". The first intermediate cylindrical portion 140 is an example of a "cylindrical portion". The intermediate rib portion 144 is an example of a "rib portion". The axial extension portion 192, the first axial extension portion 210, and the second axial extension portion 212 are examples of an "axial extension portion". The inner end portion 184a and the outer end portion 184b of the downstream blade portion 184 are examples of a "first end portion" and a "second end portion", respectively. The inner end 212b and the outer end 212c of the second axially extending portion 212 are examples of a "third end" and a "fourth end", respectively. The counterclockwise direction and the clockwise direction in Fig. 14 are examples of a "first rotation direction" and a "second rotation direction", respectively.

[0056] Although each embodiment has been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples exemplified above.

[0057] (First Modification) The location where the micro-bubble generator 46 is provided is not limited to the first hot water supply passage 32a. The micro-bubble generator 46 may be provided in the water supply passage 30, the water filling passage 50, the reheating outward passage 60, the first bathtub circulation passage 62, or the second bathtub circulation passage 68.

[0058] (Second Modification) In the above-described hot water supply system 2, fine bubbles are generated by utilizing air contained in water supplied from a water supply source 4 such as a waterworks. In a modification, the hot water supply system 2 may include an air-dissolved water generating device that dissolves air taken in from the outside into water. The air-dissolved water generated by the air-dissolved water generating device may be supplied to the fine bubble generating device 46. In another modification, an air introduction passage that introduces air from the outside may be provided at a connection between the narrowing flow paths 122a-122f and the widening flow paths 124a-124f of the upstream fine bubble generating section 110. Also, instead of air, gas such as carbon dioxide, hydrogen, or oxygen may be dissolved in water.

[0059] (Third Modification) The fine bubble generating device 46 does not have to include the intermediate fine bubble generating section 112.

[0060] (Fourth Modification) The intermediate fine bubble generating section 112 does not have to include the first intermediate cylindrical section 140 of the intermediate fixing section 130. In this modification, the intermediate rib section 144 connects the inner wall section 100b of the main body case 100 and the outer wall section of the intermediate bearing section 142. In this modification, the intermediate flow path 146 is defined by a part of the inner wall section 100b of the main body case 100 (an example of a "wall section defining the third flow path").

[0061] (Fifth Modification) The number of the upstream fine bubble generating section 110, the intermediate fine bubble generating section 112 and the downstream fine bubble generating section 114 is not limited to one, and the fine bubble generating device 46 may be equipped with two or more upstream fine bubble generating sections 110, two or more intermediate fine bubble generating sections 112, or two or more downstream fine bubble generating sections 114.

[0062] (Sixth Modification) The upstream fine bubble generating section 110, the intermediate fine bubble generating section 112, and the downstream fine bubble generating section 114 may be arranged from the upstream side to the downstream side in the following order: upstream fine bubble generating section 110, downstream fine bubble generating section 114, intermediate fine bubble generating section 112.

[0063] (Seventh Modification) The intermediate fine bubble generating section 112 does not have to include the intermediate rib section 144.

[0064] (Eighth Modification) The downstream fine bubble generating section 114 does not have to have the axially extending section 192.

[0065] (Ninth Modification) The axially extending portion 192 may be composed of only the first axially extending portion 210, or may be composed of only the second axially extending portion 212.

[0066] The technical elements described in this specification or drawings have technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful. [Explanation of symbols]

[0067] 2: Hot water system 4: Water supply source 6: Karan 8: Bathtub 10: First heat source unit 12: Second heat source unit 14: Combustion chamber 16: Partition wall 18: First combustion chamber 20: Second combustion chamber 22: First burner 24: First heat exchanger 26: Second burner 28: Second heat exchanger 30: Water supply channel 32: Hot water supply line 32a: First hot water supply passage 32b: Second hot water supply passage 34: Bypass road 36: Bypass servo 38: Water level sensor 40: Water volume servo 42: Heat exchanger outlet thermistor 44: Hot water thermistor 46: Microbubble generator 50: Hot Springs Road 52: Water filling control valve 54: Check valve 60: Reheating outward journey 62: First bathtub circulation path 64: Bathtub return thermistor 66: Circulation pump 68: Second bathtub circulation path 70: Bathtub thermistor 100: Main unit case 100a: Exterior wall 100b:Inner wall 100c: Upstream end 100d: downstream end 102:Inflow part 102a: Inlet 104: Outflow section 104a: Outlet 110: Upstream fine bubble generating section 112: Medium fine bubble generating section 114: Downstream fine bubble generating section 120a-120h: Venturi section 122a-122h: Reduced diameter channel 124a-124h: Expanded diameter flow path 126: Upstream flow path 130: Intermediate fixed part 132: Intermediate rotating part 140: First intermediate cylindrical portion 142: Intermediate bearing part 144: Intermediate rib section 146: Intermediate channel 150: Second intermediate cylindrical section 152: Intermediate rotating shaft 154: Middle blade section 160: First downstream fixing part 162: Downstream rotating section 164: Second downstream fixing part 170: First downstream cylindrical portion 170a: recess 172: Downstream bearing section 174: Downstream rib section 180: Disc section 180a: Upstream side 180b: Downstream surface 182: Downstream rotating shaft 184: Downstream blade section 184a :Inner edge 184b: Outer edge 184c: Stretching part 186: Flange part 190: Information department 192: Axial extension part 200: Guide channel 210: First axial extension 210a: Side wall part 210b:Protrusion 212: Second axial extension 212a: Side wall part 212b :Inner edge 212c: Outer edge 220: Collision channel 222: Downstream flow path A: Central axis

Claims

1. A fine bubble generating device, comprising: an inlet portion into which gas-dissolved water flows; an outlet portion through which the gas-dissolved water flows out; a first fine-bubble generating unit provided between the inlet and the outlet and having a first flow path; a second fine-bubble generating section provided between the first fine-bubble generating section and the outflow section and having a second flow path; The first flow path is A flow path having a diameter that decreases from the upstream to the downstream; a diameter-increasing flow passage provided downstream of the diameter-increasing flow passage, the diameter of the diameter-increasing flow passage increasing from the upstream to the downstream, The second flow path is a guide flow path that guides the gas-dissolved water flowing into the second flow path toward a center of a flow path axis of the second flow path; an impingement channel provided downstream of the guide channel and defined by an impingement channel wall; The collision flow path includes: A first bearing portion; a first impeller rotatably mounted on the first bearing portion, The first impeller comprises: a circular plate portion provided at a position where the water that has passed through the guide flow path collides with the circular plate portion and is provided perpendicular to the flow path axis of the second flow path; a first rotating shaft portion provided on a downstream surface of the disk portion and rotatably attached to the first bearing portion; and a first blade portion provided on the upstream surface of the disk portion.

2. The fine bubble generating device further comprises: a third fine-bubble generating section provided between the first fine-bubble generating section and the outflow section and having a third flow path; The third flow path includes: A second bearing portion; 2. The fine-bubble generating device according to claim 1, further comprising: a second rotating shaft portion rotatably attached to the second bearing portion and extending along a flow path axis of the third flow path; and a second impeller connected to the second rotating shaft portion and having a second blade portion extending radially outward from the second rotating shaft portion.

3. The third fine bubble generating unit further includes:

3. The fine-bubble generating device according to claim 2, further comprising a rib portion provided downstream of the second blade portion and connecting the second bearing portion and a wall portion defining the third flow path.

4. The fine-bubble generating device according to claim 2 or 3, wherein the second fine-bubble generating section is provided between the third fine-bubble generating section and the outflow section.

5. The impingement channel further comprises:

5. The micro-bubble generating device according to claim 1, further comprising an axial extension portion disposed between the collision flow path wall portion and the first impeller in the radial direction of the first rotating shaft portion and extending along the axial direction of the first rotating shaft portion.

6. The first blade portion has a first end portion on an inner side in the radial direction of the first rotating shaft portion, the first end portion being located closer to a first rotation direction side with respect to the first rotating shaft portion than a second end portion on an outer side, 6. The micro-bubble generating device according to claim 5, wherein the axially extending portion has an inner third end portion in the radial direction that is located on the second rotation direction side, which is opposite to the first rotation direction side, relative to an outer fourth end portion.

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