Microbubble generator

Abstract

To provide a technology capable of stably and continuously generating fine bubbles in liquid of a liquid tank.SOLUTION: A control device of a fine bubble generation device can execute fine bubble generation operation for driving a booster pump, pressurizing and supplying liquid from a tank supply passage to a tank, and supplying the liquid with gas dissolved under pressure from the tank to a liquid tank through a tank exhaust passage. The control device can execute tank circulation operation for circulating the liquid in the tank with a tank circulation passage by a tank circulation pump during the execution of the fine bubble generation operation, and generating negative pressure in a decompression part of a gas introduction mechanism. The control device is configured so as to open a second gas introduction valve first, and then, open a first gas introduction valve in the case of opening both the first gas introduction valve and the second gas introduction valve from a closed state when the fine bubble generation operation is executed and the tank circulation operation is executed.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] Patent Document 1 discloses a fine bubble generator including a tank for pressurizing and dissolving a gas in a liquid, a tank supply path for supplying the liquid to the tank, a pressure pump provided in the tank supply path, a tank discharge path for discharging the liquid in which the gas has been pressurized and dissolved from the tank to a liquid tank, a fine bubble generating nozzle provided in the tank discharge path for reducing the pressure of the liquid in which the gas has been pressurized and dissolved to generate fine bubbles, a gas introduction mechanism provided in the tank, and a control device. The gas introduction mechanism includes a gas inlet for introducing the gas, a gas introduction path that communicates the tank and the gas inlet, and a gas introduction valve provided in the gas introduction path for opening and closing the gas introduction path. The control device alternately performs a gas introduction operation in which the gas is introduced into the tank by supplying the liquid from the tank to the liquid tank with the gas introduction valve open, and a fine bubble generation operation in which, with the gas introduction valve closed, the pressure pump is driven to pressurize and supply liquid from the tank supply path to the tank, and the liquid in which the gas has been pressurized and dissolved is supplied from the tank to the liquid tank via the tank discharge path. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-18118 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the micro-bubble generator of Patent Document 1, the gas introduction operation and the micro-bubble generation operation cannot be performed simultaneously, and the gas introduction operation supplies gas to the tank, and the micro-bubble generation operation consumes gas from the tank, so the gas introduction operation and the micro-bubble generation operation must be performed alternately. However, since micro-bubbles cannot be generated in the liquid supplied from the tank to the liquid vat during the gas introduction operation, the micro-bubbles generated in the liquid in the liquid vat during the micro-bubble generation operation disappear during the gas introduction operation, making it difficult to stably generate micro-bubbles in the liquid in the liquid vat. This specification provides a technology that can stably generate micro-bubbles in the liquid in the liquid vat. [Means for solving the problem]

[0005] The fine-bubble generating device disclosed in this specification includes a tank for pressurizing and dissolving a gas in a liquid, a tank supply path for supplying the liquid to the tank, a pressure pump provided in the tank supply path, a tank discharge path for discharging the liquid in which the gas has been pressurized and dissolved from the tank to a liquid tank, a fine-bubble generating nozzle provided in the tank discharge path for reducing the pressure of the liquid in which the gas has been pressurized and dissolved to generate fine bubbles, a tank circulation path provided separately from the tank discharge path for transporting the liquid from an outlet connected to the tank to an inlet connected to the tank, a tank circulation pump provided in the tank circulation path, a gas introduction mechanism provided in the tank circulation path, and a control device. The gas introduction mechanism includes a pressure reducing section that reduces the pressure of the liquid and passes the liquid through it, a gas inlet that introduces the gas by the negative pressure of the liquid in the pressure reducing section, a gas introduction passage that communicates the pressure reducing section and the gas inlet, a first gas introduction valve that is provided in the gas introduction passage and opens and closes the gas introduction passage, and a second gas introduction valve that is provided in the gas introduction passage between the first gas introduction valve and the gas inlet and opens and closes the gas introduction passage. The first gas introduction valve is configured to receive a force in a direction that opens the first gas introduction valve when the negative pressure of the liquid in the pressure reducing section acts on it. The second gas introduction valve is configured to receive a force in a direction that closes the second gas introduction valve when the negative pressure of the liquid in the pressure reducing section acts on it. The control device is capable of executing a fine bubble generating operation in which the pressurized liquid is pressurized and supplied from the tank supply path to the tank by driving the pressurizing pump, and the liquid in which the gas is pressurized and dissolved is supplied from the tank to the liquid tank via the tank discharge path. The control device is capable of executing a tank circulation operation in which the liquid in the tank is circulated through the tank circulation path by the tank circulation pump during the execution of the fine bubble generating operation, thereby generating a negative pressure in the pressure reducing section of the gas introduction mechanism. The control device is configured to open the second gas introduction valve first and then the first gas introduction valve when both the first gas introduction valve and the second gas introduction valve are changed from a closed state to an open state.

[0006] In the above-mentioned fine-bubble generator, even during the fine-bubble generation operation, the gas introduction mechanism can introduce gas and supply it to the tank by performing the tank circulation operation with the first gas introduction valve and the second gas introduction valve open. Therefore, there is no need to interrupt the fine-bubble generation operation to supply gas to the tank, and the fine-bubble generation operation can be performed continuously. With this configuration, fine bubbles can be stably generated continuously in the liquid in the liquid tank.

[0007] In the above-mentioned fine-bubble generator, the first gas introduction valve and the second gas introduction valve are provided in the gas introduction passage, the second gas introduction valve is provided between the first gas introduction valve and the gas introduction port, and when the negative pressure of the liquid in the pressure reduction section acts on the first gas introduction valve, a force acts in a direction to open the first gas introduction valve, and when the negative pressure of the liquid in the pressure reduction section acts on the second gas introduction valve, a force acts in a direction to close the second gas introduction valve. For this reason, for example, when the fine-bubble generating operation and the tank circulation operation are performed simultaneously, if the first gas introduction valve is opened first when both the first gas introduction valve and the second gas introduction valve are changed from a closed state to an open state, when the second gas introduction valve is opened thereafter, the negative pressure of the liquid in the pressure reduction section acts on the second gas introduction valve, which may cause the second gas introduction valve to not operate smoothly. As configured above, when both the first gas introduction valve and the second gas introduction valve are changed from a closed state to an open state, by opening the second gas introduction valve first, it is possible to prevent the negative pressure of the liquid in the pressure reduction section from acting on the second gas introduction valve, and the second gas introduction valve can be operated smoothly.

[0008] In the fine-bubble generating device, when the first gas introduction valve is changed from a closed state to an open state during execution of the fine-bubble generating operation, the control device may be configured to first reduce the flow rate of the pressure pump from a first flow rate to a second flow rate smaller than the first flow rate, and then open the first gas introduction valve.

[0009] During the execution of the fine bubble generating operation, if the flow rate of the pressurizing pump is large, the pressure in the tank increases, and the pressure of the liquid in the pressure reducing section of the gas introduction mechanism also increases. That is, the negative pressure of the liquid in the pressure reducing section decreases. Conversely, if the flow rate of the pressurizing pump is small, the pressure in the tank decreases, and the pressure of the liquid in the pressure reducing section of the gas introduction mechanism also decreases. That is, the negative pressure of the liquid in the pressure reducing section increases. Since a force in the direction of opening the first gas introduction valve is applied to the first gas introduction valve by the negative pressure of the liquid in the pressure reducing section, when the first gas introduction valve is opened, the lower the pressure of the liquid in the pressure reducing section, the smoother the operation of the first gas introduction valve can be. According to the above configuration, when the first gas introduction valve is changed from a closed state to an open state, the flow rate of the pressurizing pump is first reduced from the first flow rate to the second flow rate, thereby lowering the pressure of the liquid in the pressure reducing section of the gas introduction mechanism, and then the first gas introduction valve is opened, so that the first gas introduction valve can be operated smoothly. The first flow rate and the second flow rate can be set to any flow rate. For example, the first flow rate may be the flow rate of the pressurizing pump when the fine bubble generating operation is performed with the first gas introduction valve closed, and the second flow rate may be the flow rate of the pressurizing pump when both the fine bubble generating operation and the tank circulation operation are performed with the first gas introduction valve open. Alternatively, the first flow rate may be the flow rate of the pressurizing pump when the liquid level in the tank rises during the fine bubble generating operation, and the second flow rate may be the flow rate of the pressurizing pump when the liquid level in the tank falls during both the fine bubble generating operation and the tank circulation operation.

[0010] In the fine-bubble generating device, when the first gas introduction valve is changed from a closed state to an open state during execution of the tank circulation operation, the control device may be configured to first increase the flow rate of the tank circulation pump from a third flow rate to a fourth flow rate greater than the third flow rate, and then open the first gas introduction valve.

[0011] When the tank circulation operation is performed, if the flow rate of the tank circulation pump is small, the pressure of the liquid in the pressure reduction section of the gas introduction mechanism becomes high. That is, the negative pressure of the liquid in the pressure reduction section becomes small. Conversely, if the flow rate of the tank circulation pump is large, the pressure of the liquid in the pressure reduction section of the gas introduction mechanism becomes low. That is, the negative pressure of the liquid in the pressure reduction section becomes large. Since a force in the direction of opening the first gas introduction valve is applied to the first gas introduction valve by the negative pressure of the liquid in the pressure reduction section, when the first gas introduction valve is opened, the lower the pressure of the liquid in the pressure reduction section, the smoother the first gas introduction valve can be operated. According to the above configuration, when the first gas introduction valve is changed from a closed state to an open state, the flow rate of the tank circulation pump is first increased from the third flow rate to the fourth flow rate to lower the pressure of the liquid in the pressure reduction section of the gas introduction mechanism, and then the first gas introduction valve is opened, so that the first gas introduction valve can be operated smoothly. The third flow rate and the fourth flow rate can each be set to an arbitrary flow rate. For example, the third flow rate may be the flow rate of the tank circulation pump when the fine-bubble generating operation is performed with the first gas introduction valve closed (if the tank circulation operation is performed with the first gas introduction valve closed, the flow rate of the tank circulation pump at that time, and if the tank circulation operation is not performed with the first gas introduction valve closed, the flow rate is zero), and the fourth flow rate may be the flow rate of the tank circulation pump when both the fine-bubble generating operation and the tank circulation operation are performed with the first gas introduction valve open. Alternatively, the third flow rate may be the flow rate of the tank circulation pump when the liquid level in the tank rises during the fine-bubble generating operation, and the fourth flow rate may be the flow rate of the tank circulation pump when the liquid level in the tank falls during both the fine-bubble generating operation and the tank circulation operation.

[0012] In the fine bubble generating device, the control device may be configured to, when changing both the first gas introduction valve and the second gas introduction valve from an open state to a closed state, first close the first gas introduction valve and then close the second gas introduction valve.

[0013] In the above-mentioned fine-bubble generator, the first gas introduction valve and the second gas introduction valve are provided in the gas introduction passage, the second gas introduction valve is provided between the first gas introduction valve and the gas introduction port, and when the negative pressure of the liquid in the pressure reducing section acts on the first gas introduction valve, a force acts in a direction to open the first gas introduction valve, and when the negative pressure of the liquid in the pressure reducing section acts on the second gas introduction valve, a force acts in a direction to close the second gas introduction valve. For this reason, for example, when the fine-bubble generating operation and the tank circulation operation are performed simultaneously, if the first gas introduction valve and the second gas introduction valve are both changed from an open state to a closed state, if the second gas introduction valve is closed first, when the second gas introduction valve is closed, the negative pressure of the liquid in the pressure reducing section acts on the second gas introduction valve, causing the valve element of the second gas introduction valve to strongly hit the valve seat, which may cause noise generation and damage to the second gas introduction valve. As configured above, when both the first gas introduction valve and the second gas introduction valve are changed from an open state to a closed state, by closing the first gas introduction valve first, it is possible to prevent the negative pressure of the liquid in the pressure reduction section from acting on the second gas introduction valve when the second gas introduction valve is subsequently closed, and it is possible to prevent noise generation and damage to the second gas introduction valve caused by the valve body of the second gas introduction valve strongly colliding with the valve seat.

[0014] In the fine bubble generating device, the liquid may be water, and the liquid tank may be a bathtub used by a user for bathing.

[0015] According to the above configuration, fine bubbles can be stably generated continuously in the water of the bathtub used by the user for bathing. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a diagram showing a schematic configuration of a water heating device 2 of the embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing a state in which a first gas introduction valve 106 and a second gas introduction valve 108 are both closed in the gas introduction mechanism 96 of the water heating device 2 of the embodiment. [Diagram 3]FIG. 2 is a cross-sectional view showing a state in which a first gas introduction valve 106 and a second gas introduction valve 108 are both open in the gas introduction mechanism 96 of the water heating device 2 of the embodiment. [Figure 4] FIG. 2 is a cross-sectional view showing a state in which the first gas introduction valve 106 is open and the second gas introduction valve 108 is closed in the gas introduction mechanism 96 of the water heating device 2 of the embodiment. [Diagram 5] FIG. 2 is a cross-sectional view showing a state in which a first gas introduction valve 106 is closed and a second gas introduction valve 108 is open in the gas introduction mechanism 96 of the water heating device 2 of the embodiment. [Figure 6] 2 is a schematic cross-sectional view of a bathtub adaptor 132 of the hot water heater 2 of the embodiment. FIG. [Figure 7] 10 is a flowchart of the process executed by the control device 150 during the hot water filling operation of the hot water device 2 of the embodiment. [Figure 8] FIG. 2 is a diagram showing a schematic example of a water flow in the hot water device 2 of the embodiment. [Figure 9] 5 is a diagram showing a schematic diagram of another example of the water flow in the hot water device 2 of the embodiment. FIG. [Figure 10] 4 is a flowchart of a process executed by a control device 150 during a fine bubble generating operation of the hot water device 2 of the embodiment. [Figure 11] 10 is a flowchart of an air introduction amount adjustment process executed by a control device 150 during a fine bubble generating operation of the water heating device 2 of the embodiment. [Figure 12] FIG. 10 is a diagram showing a schematic diagram of still another example of the water flow in the hot water device 2 of the embodiment. [Figure 13] FIG. 10 is a diagram showing a schematic diagram of still another example of the water flow in the hot water device 2 of the embodiment. [Figure 14] 13 is a flowchart of an air introduction amount adjustment process executed by a control device 150 during a fine bubble generating operation of a water heating device 2 of a modified example. [Figure 15] FIG. 11 is a diagram showing a schematic configuration of a water heating device 2 according to another modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] (Example) 1, the hot water device 2 of this embodiment includes a heat source unit 10, an air pressurization dissolution unit 50, a bathtub adapter 132, and a control device 150. The hot water device 2 heats water supplied from a water supply source 200 such as a tap, and can supply the water heated to a desired temperature to a faucet 250 installed in a kitchen or the like, or to a bathtub 130 installed in a bathroom. The hot water device 2 can also generate fine air bubbles in the water in the bathtub 130 that a user uses for bathing.

[0018] (Configuration of heat source unit 10) The heat source unit 10 includes a first heat source unit 12, a second heat source unit 14, a water supply passage 16, a hot water outlet passage 18, a bypass passage 20, a bypass servo 22, a hot water inlet passage 24, a hot water filling valve 26, a water volume sensor 28, a forward circulation passage 30, a return circulation passage 32, a bathtub circulation pump 34, and a water flow switch 36.

[0019] The upstream end of the water supply passage 16 is connected to a water supply source 200, and the downstream end of the water supply passage 16 is connected to the first heat source unit 12. The upstream end of the hot water outlet passage 18 is connected to the first heat source unit 12, and the downstream end of the hot water outlet passage 18 is connected to a faucet 250. The first heat source unit 12 is a combustion heat source unit that heats water by, for example, burning gas. The first heat source unit 12 heats the water flowing in from the water supply passage 16 and sends the heated water to the hot water outlet passage 18.

[0020] The upstream end of the bypass passage 20 is connected to the water supply passage 16, and the downstream end of the bypass passage 20 is connected to the hot water outlet passage 18. The bypass servo 22 is provided at the point where the bypass passage 20 connects to the water supply passage 16. The bypass servo 22 can adjust the ratio of the flow rate of water flowing from the water supply passage 16 to the hot water outlet passage 18 via the first heat source unit 12 and the flow rate of water flowing from the water supply passage 16 to the hot water outlet passage 18 via the bypass passage 20 by adjusting the opening degree of the built-in valve body. By adjusting the opening degree of the bypass servo 22, the hot water outlet passage 18 downstream of the point where the bypass passage 20 is connected is supplied with water whose temperature has been adjusted to a desired temperature by mixing high-temperature water flowing from the first heat source unit 12 and low-temperature water flowing from the bypass passage 20 at a desired ratio. The hot water outlet passage 18 downstream of the point where the bypass passage 20 is connected is provided with an outlet hot water temperature thermistor 18a that detects the temperature of the water in the hot water outlet passage 18.

[0021] The upstream end of the molten metal pouring passage 24 is connected to the molten metal outlet passage 18 downstream of the point where the bypass passage 20 is connected, and the downstream end of the molten metal pouring passage 24 is connected to the return circulation passage 32. The molten metal filling valve 26 is provided in the molten metal pouring passage 24 and opens and closes the molten metal pouring passage 24. The molten metal filling valve 26 is normally kept closed. The water volume sensor 28 is provided in the molten metal pouring passage 24 and detects the amount of water flowing through the molten metal pouring passage 24.

[0022] The upstream end of the return circulation path 32 is connected to a heat source return path 60 (details will be described later) of the air pressurized dissolving unit 50, and the downstream end of the return circulation path 32 is connected to the second heat source device 14. The upstream end of the forward circulation path 30 is connected to the second heat source device 14, and the downstream end of the forward circulation path 30 is connected to a heat source forward path 68 (details will be described later) of the air pressurized dissolving unit 50. The second heat source device 14 is a combustion heat source device that heats water by, for example, burning gas. The second heat source device 14 heats the water flowing from the return circulation path 32 and sends the heated water to the forward circulation path 30. A return circulation thermistor 32a that detects the temperature of the water in the return circulation path 32 is provided near the upstream end of the return circulation path 32. A forward circulation thermistor 30a that detects the temperature of the water in the forward circulation path 30 is provided near the downstream end of the forward circulation path 30.

[0023] The bathtub circulation pump 34 is provided in the circulation return path 32 downstream of the connection point of the molten metal pouring path 24, and sends water in the circulation return path 32 toward the second heat source unit 14. The water flow switch 36 is provided in the circulation return path 32 between the bathtub circulation pump 34 and the second heat source unit 14, and detects whether water is flowing in the circulation return path 32.

[0024] (Configuration of the air pressure dissolving unit 50) The air pressurization dissolution unit 50 includes a tank 52, a heat source return path 60, a heat source outward path 68, a tank return path 74, a tank connection path 76, a tank outward path 64, a communicating path 66, a first three-way valve 80, a second three-way valve 82, a check valve 84, a tank supply valve 86, a first pressurization pump 88, a second pressurization pump 90, a tank suction path 92, a tank circulation pump 94, and a gas introduction mechanism 96.

[0025] The tank 52 can store water therein. A low water level electrode 52a, a high water level electrode 52b, and an earth electrode 52c are installed inside the tank 52 to detect the water level in the tank 52. The water level detected by the low water level electrode 52a (hereinafter also referred to as the lower limit water level) is lower than the water level detected by the high water level electrode 52b (hereinafter also referred to as the upper limit water level). When the low water level electrode 52a and the high water level electrode 52b come into contact with the water surface stored in the tank 52, a current flows between the low water level electrode 52a and the earth electrode 52c, and an ON signal is output to the control device 150. The tank 52 is used to generate air-dissolved water by pressurizing and dissolving air in water.

[0026] One end of the heat source return line 60 is connected to a communication passage 66, and the other end of the heat source return line 60 is connected to the circulation return line 32 of the heat source unit 10. The communication passage 66 connects the first three-way valve 80 and the second three-way valve 82. The first three-way valve 80 is connected to the communication passage 66, the first bathtub water passage 62, and the tank outward line 64. The first three-way valve 80 can be switched between a first communication state (see Figures 12 and 13) in which the tank outward line 64 and the first bathtub water passage 62 are connected, a second communication state (see Figure 1) in which the tank outward line 64 and the communication passage 66 are connected, and a third communication state (see Figures 8 and 9) in which the first bathtub water passage 62, the tank outward line 64, and the communication passage 66 are connected. The upstream end of the tank outgoing passage 64 is connected to the bottom of the tank 52, and the downstream end of the tank outgoing passage 64 is connected to the first three-way valve 80. The tank outgoing passage 64 is provided with a check valve 84 that allows water to flow from the tank 52 to the first three-way valve 80 and prohibits water from flowing from the first three-way valve 80 to the tank 52. One end of the first bathtub water passage 62 is connected to the first three-way valve 80, and the other end of the first bathtub water passage 62 is connected to the bathtub adapter 132.

[0027] One end of the heat source outgoing path 68 is connected to the circulation outgoing path 30 of the heat source unit 10, and the other end of the heat source outgoing path 68 is connected to the second three-way valve 82. The second three-way valve 82 is connected to the communication passage 66, the heat source outgoing path 68, and the second bathtub water passage 70. The second three-way valve 82 can switch between a fourth communication state (see Figures 12 and 13) in which the second bathtub water passage 70 and the communication passage 66 communicate with each other, and a fifth communication state (see Figures 1, 8, and 9) in which the heat source outgoing path 68 and the second bathtub water passage 70 communicate with each other. One end of the second bathtub water passage 70 is connected to the second three-way valve 82, and the other end of the second bathtub water passage 70 is connected to the bathtub adapter 132.

[0028] The upstream end of the tank return line 74 is connected to the heat source outward line 68, and the downstream end of the tank return line 74 is connected to the upstream end of the tank connection line 76. The downstream end of the tank connection line 76 (hereinafter also referred to as the inlet 76a) is connected to the top of the tank 52. The water level at the point where the inlet 76a of the tank connection line 76 is connected to the tank 52 is higher than the upper limit water level detected by the high water level electrode 52b. The tank water supply valve 86 is provided in the tank return line 74 and opens and closes the tank return line 74. The tank water supply valve 86 is normally closed. The first pressurizing pump 88 and the second pressurizing pump 90 are provided downstream of the tank water supply valve 86 in the tank return line 74. The first pressurizing pump 88 and the second pressurizing pump 90 pressurize the water in the tank return line 74 and send it toward the tank connection line 76. In the tank return line 74, the first pressurizing pump 88 is provided upstream of the second pressurizing pump 90. The water sent from the tank return line 74 to the tank connecting line 76 flows into the tank 52 via the inlet 76a.

[0029] An upstream end of the tank suction passage 92 (hereinafter also referred to as an outlet 92a) is connected to the bottom of the tank 52. The water level at the point where the outlet 92a of the tank suction passage 92 is connected to the tank 52 is lower than the lower limit water level detected by the low water level electrode 52a. A downstream end of the tank suction passage 92 is connected to the upstream end of the tank connection passage 76. A tank circulation pump 94 is provided in the tank suction passage 92. The tank circulation pump 94 sucks water from the tank 52 into the tank suction passage 92 through the outlet 92a, and sends water from the tank suction passage 92 toward the tank connection passage 76. The water sent from the tank suction passage 92 to the tank connection passage 76 flows into the tank 52 through the inlet 76a.

[0030] The gas introduction mechanism 96 is provided in the tank suction passage 92 upstream of the tank circulation pump 94. The gas introduction mechanism 96 includes a water inlet pipe 98, a water outlet pipe 100, a Venturi tube 102, a gas introduction passage 104, a first gas introduction valve 106, and a second gas introduction valve 108. Water flows into the water inlet pipe 98 from the upstream side of the tank suction passage 92. The water outlet pipe 100 causes water to flow out to the downstream side of the tank suction passage 92. The Venturi tube 102 connects the water inlet pipe 98 and the water outlet pipe 100. The diameter of the Venturi tube 102 is smaller than the diameters of the water inlet pipe 98 and the water outlet pipe 100. The water flowing through the gas introduction mechanism 96 is decompressed to a pressure lower than atmospheric pressure when it flows from the water inlet pipe 98 to the Venturi tube 102, and is boosted to its original pressure when it flows from the Venturi tube 102 to the water outlet pipe 100. The upstream end of the gas introduction passage 104 (hereinafter also referred to as the gas introduction port 110) is open to the atmosphere, and the downstream end is connected to the Venturi tube 102. The first gas introduction valve 106 and the second gas introduction valve 108 are provided in the gas introduction passage 104, and each opens and closes the gas introduction passage 104. In the gas introduction passage 104, the first gas introduction valve 106 is disposed downstream of the second gas introduction valve 108 (closer to the Venturi tube 102). When water flows through the gas introducing mechanism 96, if both the first gas introducing valve 106 and the second gas introducing valve 108 are open, air is drawn into the gas introducing passage 104 from the gas introducing port 110, and the air is mixed with the water flowing through the Venturi tube 102. The air introduced by the gas introducing mechanism 96 is mixed with the water flowing through the tank suction passage 92, and flows into the tank 52 via the tank connecting passage 76.

[0031] Even if the gas introduction mechanism 96 as described above is provided in the tank return line 74, air can be introduced by the gas introduction mechanism 96 when water is supplied from the tank return line 74 to the tank 52. However, with such a configuration, the pressure loss in the tank return line 74 increases, and the pressure of the water sent to the tank 52 by the first pressure pump 88 and the second pressure pump 90 decreases. Also, with such a configuration, if the amount of air introduced by the gas introduction mechanism 96 is increased, the pressure of the water sent to the tank 52 decreases, and if the pressure of the water sent to the tank 52 is increased, the amount of air introduced by the gas introduction mechanism 96 decreases. In contrast, in this embodiment, the gas introduction mechanism 96 is provided in the tank suction path 92 provided separately from the tank return line 74, so that the pressure loss in the tank return line 74 can be reduced. Also, a large amount of air can be introduced by the gas introduction mechanism 96 while sending water from the tank return line 74 to the tank 52 at high pressure.

[0032] (Configuration of gas introduction mechanism 96) 2, the first gas introduction valve 106 and the second gas introduction valve 108 are disposed to face each other. In the following description, in the gas introduction path 104, a portion between the Venturi tube 102 and the first gas introduction valve 106 is also referred to as a first gas introduction path 104a, a portion between the first gas introduction valve 106 and the second gas introduction valve 108 is also referred to as a second gas introduction path 104b, and a portion between the second gas introduction valve 108 and the gas introduction port 110 is also referred to as a third gas introduction path 104c.

[0033] The first gas introduction valve 106 includes a valve chamber 106a, a valve seat 106b, a valve body 106c, a plunger 106d, a coil 106e, and a spring 106f. The valve chamber 106a communicates with the first gas introduction passage 104a and communicates with the second gas introduction passage 104b via the valve seat 106b. The valve body 106c can be seated on the valve seat 106b, and when the valve body 106c is seated on the valve seat 106b, communication between the valve chamber 106a and the second gas introduction passage 104b is blocked. The valve body 106c is held at the tip of the plunger 106d. The plunger 106d incorporates a core (not shown) made of a magnetic material. When energized, the coil 106e exerts a magnetic attraction force on the core of the plunger 106d. That is, when the coil 106e is energized, a magnetic attraction force acts on the plunger 106d in a direction in which the valve body 106c moves away from the valve seat 106b. The spring 106f acts on the plunger 106d in a direction in which the valve body 106c seats on the valve seat 106b. As shown in FIG. 2, when the coil 106e is not energized, the spring 106f acts on the plunger 106d, so that the valve body 106c seats on the valve seat 106b, and the first gas introduction valve 106 is closed. As shown in FIG. 3, when the coil 106e is energized, a magnetic attraction force that exceeds the force acting on the plunger 106d from the spring 106f acts on the plunger 106d from the coil 106e, so that the valve body 106c moves away from the valve seat 106b, and the first gas introduction valve 106 is opened. In the first gas introduction valve 106, when the pressure in the first gas introduction passage 104a is lower than the pressure in the second gas introduction passage 104b, a force acts on the plunger 106d in a direction that moves the valve body 106c away from the valve seat 106b due to the pressure difference.

[0034] The second gas introduction valve 108 includes a valve chamber 108a, a valve seat 108b, a valve body 108c, a plunger 108d, a coil 108e, and a spring 108f. The valve chamber 108a communicates with the third gas introduction passage 104c, and communicates with the second gas introduction passage 104b via the valve seat 108b. The valve body 108c can be seated on the valve seat 108b, and when the valve body 108c is seated on the valve seat 108b, communication between the valve chamber 108a and the second gas introduction passage 104b is blocked. The valve body 108c is held at the tip of the plunger 108d. The plunger 108d incorporates a core (not shown) made of a magnetic material. When energized, the coil 108e exerts a magnetic attraction force on the core of the plunger 108d. That is, when the coil 108e is energized, a magnetic attraction force acts on the plunger 108d in a direction in which the valve body 108c moves away from the valve seat 108b. The spring 108f acts on the plunger 108d in a direction in which the valve body 108c seats on the valve seat 108b. As shown in FIG. 2, when the coil 108e is not energized, the spring 108f acts on the plunger 108d, so that the valve body 108c seats on the valve seat 108b, and the second gas introduction valve 108 is closed. As shown in FIG. 3, when the coil 108e is energized, a magnetic attraction force that exceeds the force acting on the plunger 108d from the spring 108f acts on the plunger 108d from the coil 108e, so that the valve body 108c moves away from the valve seat 108b, and the second gas introduction valve 108 is opened. In the second gas introduction valve 108, when the pressure in the second gas introduction passage 104b is lower than the pressure in the third gas introduction passage 104c, a force acts on the plunger 108d in a direction such that the valve body 108c seats on the valve seat 108b due to the pressure difference.

[0035] A case where the state where both the first gas introduction valve 106 and the second gas introduction valve 108 are closed (see FIG. 2) is switched to a state where both the first gas introduction valve 106 and the second gas introduction valve 108 are open (see FIG. 3) will be described. As shown in FIG. 4, when the first gas introduction valve 106 is opened first, the first gas introduction passage 104a and the second gas introduction passage 104b communicate with each other with the second gas introduction valve 108 closed. In this state, if the pressure of the water flowing through the Venturi tube 102 is low (i.e., the negative pressure of the water in the Venturi tube 102 is large), the pressure of the second gas introduction passage 104b becomes lower than the pressure of the third gas introduction passage 104c, and the pressure difference acts in a direction to close the second gas introduction valve 108. For this reason, it becomes difficult to smoothly open the second gas introduction valve 108. On the other hand, as shown in FIG. 5, when the second gas introduction valve 108 is opened first, the second gas introduction passage 104b is blocked from the first gas introduction passage 104a, so that a large pressure difference does not occur between the pressure of the second gas introduction passage 104b and the pressure of the third gas introduction passage 104c, and the second gas introduction valve 108 can be opened smoothly. In addition, in the state shown in FIG. 5, the second gas introduction passage 104b communicates with the third gas introduction passage 104c. In this state, when the pressure of the water flowing through the Venturi tube 102 is low (i.e., the negative pressure of the water in the Venturi tube 102 is large), the pressure of the first gas introduction passage 104a becomes lower than the pressure of the second gas introduction passage 104b, and the pressure difference acts in a direction to open the first gas introduction valve 106. Therefore, the first gas introduction valve 106 can be opened smoothly.

[0036] A case where the state where both the first gas introduction valve 106 and the second gas introduction valve 108 are open (see FIG. 3) is switched to a state where both the first gas introduction valve 106 and the second gas introduction valve 108 are closed (see FIG. 2) will be described. As shown in FIG. 4, when the second gas introduction valve 108 is closed first, the first gas introduction valve 106 is open, so that the first gas introduction passage 104a and the second gas introduction passage 104b communicate with each other. In this state, if the pressure of the water flowing through the Venturi tube 102 is low (i.e., the negative pressure of the water in the Venturi tube 102 is large), the pressure of the second gas introduction passage 104b becomes lower than the pressure of the third gas introduction passage 104c, and the pressure difference acts in a direction to close the second gas introduction valve 108. Therefore, when the second gas introduction valve 108 is closed, the valve body 108c may collide with the valve seat 108b with force, which may cause noise generation and damage to parts. In contrast, as shown in Fig. 5, when the first gas introduction valve 106 is closed first, the second gas introduction passage 104b is blocked from the first gas introduction passage 104a, so that no large pressure difference occurs between the pressure of the second gas introduction passage 104b and the pressure of the third gas introduction passage 104c. Therefore, it is possible to prevent the valve body 108c from colliding with the valve seat 108b with force when the second gas introduction valve 108 is closed, and it is possible to prevent noise generation and damage to parts.

[0037] (Configuration of bathtub adapter 132) Next, with reference to Figures 6(a) and (b), the bathtub adapter 132 provided on the wall 130a of the bathtub 130 will be described. Figure 6(a) shows the flow of water in the bathtub adapter 132 when water flows from the first bathtub water channel 62 toward the bathtub 130 and from the bathtub 130 toward the second bathtub water channel 70 (for example, the state of Figure 12). Figure 6(b) shows the flow of water in the bathtub adapter 132 when water flows from the bathtub 130 toward the first bathtub water channel 62 and from the second bathtub water channel 70 toward the bathtub 130 (for example, the state of Figure 9).

[0038] The bathtub adaptor 132 has a first water passage 136 and a second water passage 138. The first water passage 136 is connected to the first bathtub water passage 62, and the second water passage 138 is connected to the second bathtub water passage 70. The first water passage 136 branches into a first discharge passage 136a and a first suction passage 136b. The first discharge passage 136a is connected to a first discharge port 134a provided on the front surface 132a of the bathtub adaptor 132. The water discharged from the first discharge port 134a into the bathtub 130 is discharged in front of the wall portion 130a of the bathtub 130, that is, in a direction perpendicular to the wall portion 130a of the bathtub 130. The first discharge passage 136a is provided with a backflow prevention portion 140a that prevents water from flowing from the bathtub 130 toward the first bathtub water passage 62, and a fine bubble generating nozzle 142 that is arranged upstream of the backflow prevention portion 140a (on the first bathtub water passage 62 side). The fine bubble generating nozzle 142 reduces the pressure of the water passing through the fine bubble generating nozzle 142. The first suction passage 136b is connected to a first suction port 134b provided on the front surface 132a of the bathtub adapter 132. The first suction passage 136b is provided with a backflow prevention portion 140b that prevents water from flowing from the first bathtub water passage 62 toward the bathtub 130.

[0039] The second water passage 138 branches into a second discharge passage 138a and a second suction passage 138b. The second suction passage 138b is connected to a second suction port 134c provided on the front surface 132a of the bathtub adapter 132. The second suction passage 138b is provided with a check portion 140c that prevents water from flowing from the second bathtub water passage 70 toward the bathtub 130. The second discharge passage 138a is connected to a second discharge port 134d provided on the lower surface 132b of the bathtub adapter 132. Water discharged from the second discharge port 134d is discharged downward, that is, in a direction parallel to the wall portion 130a of the bathtub 130. The second discharge passage 138a is provided with a check portion 140d that prevents water from flowing from the bathtub 130 toward the second bathtub water passage 70.

[0040] (Configuration of control device 150) The control device 150 shown in Fig. 1 controls the operation of each component of the heat source unit 10 and the air pressurized dissolution unit 50. The control device 150 is configured to be able to communicate with a remote control 154 that can be operated by a user. The control device 150 includes a memory 152, and is capable of storing various settings input by the user, such as the set temperature and set water volume for the water filling operation, and the set temperature for the reheating operation. Through the remote control 154, the user can give instructions to start and end the water filling operation, the fine bubble generation operation, and the reheating operation, which will be described later.

[0041] (Bath filling operation) The water filling operation starts when the user issues a command to start the water filling operation on the remote control 154. Alternatively, the water filling operation may start when the user sets the start time of the water filling operation on the remote control 154 and the control device 150 determines that the start time of the water filling operation has arrived. When starting the water filling operation, the control device 150 sets the first three-way valve 80 and the second three-way valve 82 to the third communication state and the fifth communication state, respectively (see Figures 8 and 9). From this state, the control device 150 executes the processing shown in Figure 7.

[0042] In S2, the control device 150 executes the air removal process. Specifically, the control device 150 opens the water filling valve 26 and starts heating the water by the first heat source unit 12. As a result, as shown in FIG. 8, water adjusted to the set temperature flows from the hot water outlet path 18 through the hot water supply path 24 into the circulation return path 32. The water that flows into the circulation return path 32 branches into a flow toward the upstream side (i.e., the heat source return path 60) and a flow toward the downstream side (i.e., the second heat source unit 14). The water that flows from the circulation return path 32 to the heat source return path 60 flows into the bathtub 130 via the communication path 66, the first three-way valve 80, the first bathtub water path 62, and the bathtub adapter 132. The water that flows from the circulation return path 32 to the second heat source unit 14 flows into the bathtub 130 via the circulation outward path 30, the heat source outward path 68, the second three-way valve 82, the second bathtub water path 70, and the bathtub adapter 132. As a result, the first bathtub water channel 62 and the second bathtub water channel 70 are filled with water, and any air remaining inside the first bathtub water channel 62 and the second bathtub water channel 70 is expelled into the bathtub 130. When the accumulated water volume detected by the water volume sensor 28 reaches a predetermined value (e.g., 6 L), the control device 150 closes the water filling valve 26 and ends heating by the first heat source unit 12, thereby ending the air removal process.

[0043] In S4, the control device 150 executes a process for detecting remaining water in the bathtub 130. Specifically, as shown in FIG. 9, the control device 150 drives the bathtub circulation pump 34 and determines whether there is remaining water in the bathtub 130 based on whether the water flow switch 36 detects a water flow. If there is no remaining water in the bathtub 130 and the bathtub adapter 132 is not submerged in water, the water flow switch 36 does not detect a water flow even if the bathtub circulation pump 34 is driven. In contrast, if there is remaining water in the bathtub 130 and the bathtub adapter 132 is submerged in water, the water flow switch 36 detects a water flow when the bathtub circulation pump 34 is driven. If there is remaining water in the bathtub 130 in S4 (if YES), the process proceeds to S6. If there is no remaining water in the bathtub 130 in S4 (if NO), the process proceeds to S10.

[0044] In S6, the control device 150 performs a process to determine the amount of water remaining in the bathtub 130. Specifically, the control device 150 drives the bathtub circulation pump 34 and stores the temperature detected by the circulation return thermistor 32a as the pre-heating temperature. After that, the control device 150 starts heating the water by the second heat source unit 14. As a result, as shown in FIG. 9, the remaining water in the bathtub 130 is sent to the second heat source unit 14 via the bathtub adapter 132, the first bathtub water passage 62, the first three-way valve 80, the communication passage 66, the heat source return passage 60, and the circulation return passage 32. The remaining water heated by the second heat source unit 14 is returned to the bathtub 130 via the circulation outward passage 30, the heat source outward passage 68, the second three-way valve 82, the second bathtub water passage 70, and the bathtub adapter 132. When the temperature detected by the circulation return thermistor 32a becomes equal to or higher than the set temperature, the control device 150 stores the temperature detected by the circulation return thermistor 32a as the post-heating temperature, and then stops the bathtub circulation pump 34 and ends the heating of water by the second heat source unit 14. The control device 150 then calculates the amount of remaining water in the bathtub 130 from the temperature rise obtained by subtracting the pre-heating temperature from the post-heating temperature and the integrated amount of heat in the second heat source unit 14 in S6.

[0045] In S8, the control device 150 subtracts the amount of remaining water in the bathtub 130 determined in S6 from the set amount of water for the water filling operation to update the set amount of water for the water filling operation.

[0046] In S10, the control device 150 opens the water filling valve 26 and starts heating by the first heat source unit 12. As a result, as shown in Fig. 8, water adjusted to the set temperature flows from the hot water outlet path 18 through the hot water supply path 24 into the circulation return path 32. The water flowing into the circulation return path 32 branches into a flow toward the upstream side (i.e., the heat source return path 60) and a flow toward the downstream side (i.e., the second heat source unit 14). The water flowing from the circulation return path 32 to the heat source return path 60 flows into the bathtub 130 via the communication path 66, the first three-way valve 80, the first bathtub water path 62, and the bathtub adapter 132. The water flowing from the circulation return path 32 to the second heat source unit 14 flows into the bathtub 130 via the circulation outward path 30, the heat source outward path 68, the second three-way valve 82, the second bathtub water path 70, and the bathtub adapter 132.

[0047] In S12, control device 150 waits until the accumulated water volume detected by water volume sensor 28 reaches the set water volume for the water filling operation. Note that the accumulated water volume here is the sum of the accumulated water volume detected by water volume sensor 28 in the air removal process in S2 and the accumulated water volume since the start of filling bathtub 130 with water in S10. When the accumulated water volume reaches the set water volume (YES), processing proceeds to S14.

[0048] In S14, the control device 150 closes the water filling valve 26 and terminates the heating of water by the first heat source unit 12.

[0049] In S16, the control device 150 drives the bathtub circulation pump 34 and obtains the temperature detected by the circulation return thermistor 32a as the bathtub water temperature. The control device 150 then determines whether the bathtub water temperature is equal to or higher than the set temperature. If the bathtub water temperature is lower than the set temperature (NO), the process proceeds to S18. If the bathtub water temperature is equal to or higher than the set temperature (YES), the process proceeds to S20.

[0050] In S18, the control device 150 performs a reheating process for the water in the bathtub 130. Specifically, the control device 150 drives the bathtub circulation pump 34 and starts the heating of the water by the second heat source unit 14. As a result, as shown in FIG. 9, the water in the bathtub 130 is sent to the second heat source unit 14 via the bathtub adapter 132, the first bathtub water passage 62, the first three-way valve 80, the communication passage 66, the heat source return path 60, and the circulation return path 32. The water heated by the second heat source unit 14 is returned to the bathtub 130 via the circulation outward path 30, the heat source outward path 68, the second three-way valve 82, the second bathtub water passage 70, and the bathtub adapter 132. When the temperature detected by the circulation return thermistor 32a becomes equal to or higher than the set temperature, the control device 150 stops the bathtub circulation pump 34 and ends the heating of the water by the second heat source unit 14.

[0051] In S20, the control device 150 notifies the user that the water filling operation has been completed via the remote control 154. After S20, the processing in FIG.

[0052] (Fine bubble generation operation) The fine bubble generating operation is started when the user issues a command to start the fine bubble generating operation via the remote control 154. In the hot water heater 2 of this embodiment, the fine bubble generating operation is also started automatically after the above-mentioned water filling operation is completed. In other words, the fine bubble generating operation is executed in conjunction with the execution of the water filling operation. When starting the fine bubble generating operation, the control device 150 sets the first three-way valve 80 and the second three-way valve 82 to the third communication state and the fifth communication state, respectively (see Figures 8 and 9). From this state, the control device 150 executes the process shown in Figure 10.

[0053] In S32, the control device 150 executes a cold water reduction process. Specifically, when the temperature detected by the circulation forward thermistor 30a or the circulation return thermistor 32a is equal to or lower than a predetermined temperature, the control device 150 drives the bathtub circulation pump 34 and starts heating the water by the second heat source unit 14. When low-temperature water remains inside the circulation forward path 30 or the circulation return path 32 due to this cold water reduction process, as shown in FIG. 9, the low-temperature water flows into the bathtub adapter 132 via the heat source forward path 68, the second three-way valve 82, and the second bathtub water path 70, and is discharged from the second outlet 134d on the bottom surface 132b of the bathtub adapter 132 into the bathtub 130. Therefore, even if the user is taking a bath in the bathtub 130, it is possible to prevent low-temperature water from being discharged directly toward the user's body. When a predetermined time has elapsed since the start of the cold water mitigation process, the control device 150 stops the bathtub circulation pump 34 and terminates the heating of water by the second heat source unit 14, thereby terminating the cold water mitigation process.

[0054] In S34, the controller 150 opens the second gas introduction valve 108.

[0055] In S36, the control device 150 drives the tank circulation pump 94. This starts the circulation of water between the tank 52 and the tank suction path 92 and the tank connection path 76. When driving the tank circulation pump 94 in S34, the control device 150 controls the tank circulation pump 94 so that the rotation speed of the tank circulation pump 94 becomes higher than the standard rotation speed (for example, 120% of the standard rotation speed).

[0056] In S38, the control device 150 opens the first gas introduction valve 106. This causes air to be introduced into the water flowing through the gas introduction mechanism 96 of the tank suction passage 92.

[0057] In S40, the control device 150 controls the tank circulating pump 94 so that the rotation speed of the tank circulating pump 94 becomes the standard rotation speed, thereby reducing the flow rate of water pumped by the tank circulating pump 94.

[0058] In S42, the control device 150 starts supplying the air-dissolved water from the tank 52 to the bathtub 130. Specifically, as shown in FIG. 12, the control device 150 sets the first three-way valve 80 to the first communication state, sets the second three-way valve 82 to the fourth communication state, and drives the bathtub circulation pump 34, the first pressurizing pump 88, and the second pressurizing pump 90. As a result, the water in the bathtub 130 is supplied to the tank 52 via the bathtub adapter 132, the second bathtub water passage 70, the second three-way valve 82, the communication passage 66, the heat source return passage 60, the circulation return passage 32, the second heat source unit 14, the circulation outward passage 30, the heat source outward passage 68, the tank return passage 74, and the tank connection passage 76. At this time, the tank 52 is supplied with water pressurized by the first pressurizing pump 88 and the second pressurizing pump 90. As a result, air is pressurized and dissolved in the water inside the tank 52. The water in which the air has been pressurized and dissolved is then supplied to the bathtub 130 from the tank 52 via the tank outward path 64, the first three-way valve 80, the first bathtub water path 62, and the bathtub adapter 132. At this time, the water in which the air has been pressurized and dissolved is depressurized to below atmospheric pressure as it passes through the fine bubble generating nozzle 142 of the first discharge path 136a of the bathtub adapter 132, and is pressurized to atmospheric pressure as it is sprayed into the bathtub 130, generating fine bubbles in the water in the bathtub 130.

[0059] In S44 shown in FIG. 10, the control device 150 executes an air introduction amount adjustment process shown in FIG.

[0060] In S62 shown in FIG. 11, the control device 150 judges whether the water level of the tank 52 falls below the lower limit water level based on the detection signal from the low water level electrode 52a. In this embodiment, the amount of air introduced in the gas introduction mechanism 96 when the first gas introduction valve 106 and the second gas introduction valve 108 are open is greater than the amount of air in the fine bubbles generated in the water of the bathtub 130. Therefore, when the first gas introduction valve 106 and the second gas introduction valve 108 are open, the amount of air in the tank 52 increases, and the water level of the tank 52 falls. If the water level of the tank 52 falls below the lower limit water level (if YES), the process proceeds to S64. If the water level of the tank 52 is equal to or higher than the lower limit water level (if NO), the process proceeds to S68.

[0061] In S64, the control device 150 closes the first gas introduction valve 106. This stops the introduction of air into the water flowing through the gas introduction mechanism 96 of the tank suction passage 92. Note that in this embodiment, even while the first gas introduction valve 106 is closed, the tank circulation pump 94 continues to be driven. This promotes the flow of water in the tank 52, and promotes the pressurized dissolution of air into the water in the tank 52.

[0062] In S66, the controller 150 closes the second gas introduction valve .

[0063] In S68, the control device 150 judges whether the water level of the tank 52 is equal to or higher than the upper water level based on the detection signal from the high water level electrode 52b. With the first gas introduction valve 106 and the second gas introduction valve 108 closed, air is not supplied to the tank 52, so the amount of air in the tank 52 decreases and the water level of the tank 52 rises. If the water level of the tank 52 is equal to or higher than the upper water level (YES), the process proceeds to S70. If the water level of the tank 52 is below the upper water level (NO), the process of FIG. 11 ends and the process proceeds to S46 (see FIG. 10).

[0064] In S70, the controller 150 opens the second gas introduction valve 108.

[0065] In S72, the control device 150 stops the second pressurizing pump 90. This reduces the flow rate of water pumped by the first pressurizing pump 88 and the second pressurizing pump 90.

[0066] In S74, the control device 150 controls the tank circulating pump 94 so that the rotation speed of the tank circulating pump 94 becomes higher than the standard rotation speed (for example, 120% of the standard rotation speed). This increases the flow rate of water pumped by the tank circulating pump 94.

[0067] In S76, the control device 150 opens the first gas introduction valve 106. This restarts the introduction of air into the water flowing through the gas introduction mechanism 96 of the tank suction passage 92.

[0068] In S78, the control device 150 controls the tank circulating pump 94 so that the rotation speed of the tank circulating pump 94 becomes the standard rotation speed, thereby reducing the flow rate of water pumped by the tank circulating pump 94.

[0069] In S80, the control device 150 resumes driving the second pressurizing pump 90. This increases the flow rate of water pumped by the first pressurizing pump 88 and the second pressurizing pump 90. After S80, the process of FIG. 11 ends, and the process proceeds to S46 (see FIG. 10).

[0070] In S46 of FIG. 10, the control device 150 judges whether the operation time of the fine bubble generating operation has reached the set time. Here, the operation time of the fine bubble generating operation is the time elapsed since the start of the fine bubble generating operation. In the hot water device 2 of this embodiment, when the fine bubble generating operation is performed independently without being linked to the execution of the water filling operation, the set time is set to, for example, 10 minutes. In contrast, when the fine bubble generating operation is performed in conjunction with the execution of the water filling operation, the set time is set to, for example, 30 minutes. If the operation time has not reached the set time (if NO), the process returns to S44. If the operation time has reached the set time (if YES), the process proceeds to S48.

[0071] In S48, the control device 150 stops the bathtub circulating pump 34, the first pressurizing pump 88, and the second pressurizing pump 90, and ends the supply of air-dissolved water from the tank 52 to the bathtub 130.

[0072] In S50, if the first gas introduction valve 106 is open, the control device 150 closes the first gas introduction valve 106. This ends the introduction of air into the water flowing through the gas introduction mechanism 96 of the tank suction passage 92.

[0073] In S52, the controller 150 closes the second gas introduction valve 108 if the second gas introduction valve 108 is open.

[0074] In S54, the control device 150 executes a tank cleaning process. Specifically, the control device 150 opens the water filling valve 26 and starts heating the water by the first heat source unit 12. As a result, as shown in Fig. 13, water adjusted to the set temperature flows from the hot water outlet path 18 through the hot water supply path 24 into the circulation return path 32. The water that flows into the circulation return path 32 branches into a flow toward the upstream side (i.e., the heat source return path 60) and a flow toward the downstream side (i.e., the second heat source unit 14). The water that flows from the circulation return path 32 to the heat source return path 60 flows into the bathtub 130 via the communication path 66, the second three-way valve 82, the second bathtub water path 70, and the bathtub adapter 132. In addition, the water flowing from the circulation return path 32 to the second heat source unit 14 flows into the bathtub 130 via the circulation outward path 30, the heat source outward path 68, the tank return path 74, the tank connection path 76, the tank 52, the tank outward path 64, the first three-way valve 80, the first bathtub water path 62, and the bathtub adapter 132. This cleans the inside of the tank 52, the tank suction path 92, and the tank connection path 76.

[0075] In S56, the control device 150 stops the tank circulation pump 94. This ends the circulation of water between the tank 52 and the tank suction passage 92 and the tank connection passage 76. After S62, the processing in FIG. 10 ends.

[0076] (Reheating operation) The reheating operation starts when the user instructs the start of the reheating operation with the remote control 154. When starting the reheating operation, the control device 150 sets the first three-way valve 80 to the third communication state and the second three-way valve 82 to the fifth communication state (see Fig. 8 and Fig. 9). From this state, the control device 150 drives the bathtub circulation pump 34 and starts heating water by the second heat source unit 14. As a result, as shown in Fig. 9, the water in the bathtub 130 is sent to the second heat source unit 14 via the bathtub adapter 132, the first bathtub water passage 62, the first three-way valve 80, the communication passage 66, the heat source return path 60, and the circulation return path 32. The water heated by the second heat source unit 14 is returned to the bathtub 130 via the circulation outward path 30, the heat source outward path 68, the second three-way valve 82, the second bathtub water passage 70, and the bathtub adapter 132. When the temperature detected by the circulation return thermistor 32a becomes equal to or higher than the set temperature, the control device 150 stops the bathtub circulation pump 34 and ends the heating of water by the second heat source unit 14. The control device 150 then notifies the user via the remote control 154 that the reheating operation has been completed, and ends the reheating operation.

[0077] (Modification) In the above-described hot water device 2, when performing the fine bubble generating operation, the control device 150 may execute the process shown in Fig. 14 in the air introduction amount adjustment process of S44 in Fig. 10, instead of executing the process shown in Fig. 11. The following describes the process shown in Fig. 14 and the differences from the process shown in Fig. 11.

[0078] In the process shown in Fig. 14, first, in S82, the control device 150 waits until the elapsed time from opening the first gas introduction valve 106 in S38 (see Fig. 10) or S76 reaches a first predetermined time. The first predetermined time is an estimated time for the water level of the tank 52 to drop from the upper limit water level to the lower limit water level with the first gas introduction valve 106 and the second gas introduction valve 108 open, and is a time shorter than the set time in S46 (see Fig. 10). When the elapsed time from opening the first gas introduction valve 106 reaches the first predetermined time (YES), the process proceeds to S64.

[0079] 14, the process proceeds to S84 after S66. In S84, the control device 150 waits until the time that has elapsed since the first gas introduction valve 106 was closed in S64 reaches a second predetermined time. The second predetermined time is an estimated time for the water level of the tank 52 to rise from the lower limit water level to the upper limit water level with the first gas introduction valve 106 and / or the second gas introduction valve 108 closed, and is shorter than the set time of S46 (see FIG. 10). When the time that has elapsed since the first gas introduction valve 106 was closed reaches the second predetermined time (YES), the process proceeds to S70.

[0080] According to the process shown in FIG. 14, the first gas introduction valve 106 and the second gas introduction valve 108 can be switched between open and closed states without using detection signals from the low water level electrode 52a and the high water level electrode 52b.

[0081] (Other variations) In the above-described hot water device 2, in the fine bubble generating operation that is executed in conjunction with the execution of the hot water filling operation, the cold water reduction process of S32 in FIG. 10 may be omitted.

[0082] In the above-described hot water apparatus 2, the tank cleaning process in S54 in FIG. 10 may be omitted.

[0083] In the above-mentioned hot water device 2, even if the operating time reaches the set time in the operating time determination process of S46 in FIG. 10, the process may be configured to return to S44 and continue the fine bubble generating operation without proceeding to S48 until the user issues an instruction to end the fine bubble generating operation via the remote control 154.

[0084] In the above-described water heating device 2, the order of the processes of S34 and S36 in Fig. 10 may be reversed. That is, after the cold water reduction process of S32, the control device 150 may drive the tank circulating pump 94 in S36, and then open the second gas introduction valve 108 in S34.

[0085] In the hot water device 2 described above, after closing the first gas introduction valve 106 in S64 of Fig. 11 or 14, the control device 150 may stop the tank circulating pump 94. In this case, in the subsequent S74, the control device 150 drives the tank circulating pump 94 again and controls the tank circulating pump 94 so that the rotation speed of the tank circulating pump 94 becomes a rotation speed higher than the standard rotation speed (for example, a rotation speed that is 120% of the standard rotation speed).

[0086] In the above-described hot water device 2, the order of the processes of S70, S72, and S74 in Fig. 11 or Fig. 14 may be interchanged. For example, when the answer is YES in S68 in Fig. 11 or S84 in Fig. 14, the control device 150 may first stop the second pressurizing pump 90 in S72 and / or set the rotation speed of the tank circulating pump 94 to a speed higher than the standard rotation speed in S74, and then open the second gas introduction valve 108 in S70.

[0087] In the above-described hot water device 2, the control device 150 may control the rotation speed of the first pressurizing pump 88 and / or the second pressurizing pump 90 so that the rotation speed of the first pressurizing pump 88 and / or the second pressurizing pump 90 is lower than the standard rotation speed (for example, 80% of the standard rotation speed) instead of stopping the second pressurizing pump 90 in S72 of FIG. 11 or FIG. 14. Even in such a configuration, the flow rate of water pumped by the first pressurizing pump 88 and the second pressurizing pump 90 can be reduced by the process of S72. In this case, the control device 150 may control the rotation speed of the first pressurizing pump 88 and / or the second pressurizing pump 90 so that the rotation speed of the first pressurizing pump 88 and / or the second pressurizing pump 90 is the standard rotation speed instead of restarting the drive of the second pressurizing pump 90 in S80 of FIG. 11 or FIG. 14.

[0088] In the above hot water device 2, when the fine bubble generating operation is performed in conjunction with the execution of the water filling operation, the notification of the end of water filling in S20 of Fig. 7 may be performed while the fine bubble generating operation is being performed, rather than at the end of the water filling operation. More specifically, the notification of the end of water filling may be performed after the operation time of the fine bubble generating operation reaches a predetermined notification time (e.g., 2 minutes) that allows sufficient fine bubbles to be generated in the water of the bathtub 130. With this configuration, the user can delay the timing of entering the bathroom, and the user can be prevented from entering the bathroom before sufficient fine bubbles are generated in the water of the bathtub 130.

[0089] In the hot water apparatus 2 described above, the user may be able to switch, via the remote control 154, whether or not to execute the fine bubble generating operation in conjunction with the execution of the water filling operation.

[0090] In the above-described hot water device 2, air is introduced into the tank 52, but instead of air, gas such as carbon dioxide gas, hydrogen, oxygen, etc. may be introduced into the tank 52. In this case, a gas-filled tank (not shown) filled with gas may be connected to the gas inlet 110 of the gas introduction path 104.

[0091] In the above-described hot water heater 2, during the bath filling operation, a set amount of water is stored in bathtub 130 based on the accumulated water amount detected by water amount sensor 28. Alternatively, the hot water heater 2 may be configured to be provided with a water level sensor capable of detecting the water level of bathtub 130, and during the bath filling operation, water at the set water level is stored in bathtub 130 based on the water level of bathtub 130 detected by the water level sensor.

[0092] In the above-described hot water device 2, the heat source unit 10 is connected to the faucet 250, and the pressurized air dissolving unit 50 is connected to the bathtub 130. Alternatively, the heat source unit 10 may be connected to another heat utilization location, and the pressurized air dissolving unit 50 may be connected to another liquid tank.

[0093] In the above-described hot water device 2, a check valve (not shown) may be provided downstream of the tank circulation pump 94 in the tank suction passage 92 to allow water to flow from the upstream side to the downstream side of the tank suction passage 92 and to prohibit water from flowing from the downstream side to the upstream side of the tank suction passage 92. By providing a check valve in the tank suction passage 92, it is possible to prevent water pumped out from the tank return passage 74 by the first pressurizing pump 88 and the second pressurizing pump 90 from flowing back through the tank suction passage 92, even if the tank circulation pump 94 is stopped while the first pressurizing pump 88 and the second pressurizing pump 90 are being driven.

[0094] In the above-described hot water device 2, the gas introduction mechanism 96 is disposed in the tank suction passage 92 upstream of the tank circulation pump 94. Alternatively, the gas introduction mechanism 96 may be disposed in the tank suction passage 92 downstream of the tank circulation pump 94.

[0095] In the above-described hot water device 2, the downstream end of the tank return passage 74 and the downstream end of the tank suction passage 92 are connected to the tank 52 via a common tank connection passage 76. Alternatively, as shown in Fig. 15, the air pressurization dissolution unit 50 may not include the tank connection passage 76, and the downstream end of the tank return passage 74 (hereinafter also referred to as inlet 74a) and the downstream end of the tank suction passage 92 (hereinafter also referred to as inlet 92b) may be configured to be connected separately to the tank 52. In this case, the water flowing through the tank return passage 74 flows into the tank 52 via the inlet 74a, and the water flowing through the tank suction passage 92 flows into the tank 52 via the inlet 92b.

[0096] As described above, in one or more embodiments, the hot water device 2 (an example of a fine-bubble generating device) includes a tank 52 that pressurizes and dissolves air (an example of a gas) in water (an example of a liquid), a tank return path 74 that supplies water to the tank 52, a tank connection path 76 (an example of a tank supply path), a first pressure pump 88 and a second pressure pump 90 (an example of a pressure pump) provided in the tank return path 74, a tank outward path 64 that discharges the water in which air has been pressurized and dissolved from the tank 52 to a bathtub 130 (an example of a liquid tank), a first bathtub water path 62, and a bathtub adapter 132 (an example of a tank discharge path), The system is equipped with a fine bubble generating nozzle 142 provided in the bathtub adapter 132, which reduces the pressure in water in which air has been pressurized and dissolved to generate fine bubbles, a tank suction path 92 provided separately from the tank outflow path 64, the first bathtub water path 62, and the bathtub adapter 132, which sends water from an outlet 92a connected to the tank 52 to an inlet 76a connected to the tank 52, a tank connection path 76 (an example of a tank circulation path), a tank circulation pump 94 provided in the tank suction path 92, a gas introduction mechanism 96 provided in the tank suction path 92, and a control device 150. The gas introduction mechanism 96 includes a Venturi tube 102 (an example of a pressure reducing section) that reduces the pressure of water and passes it through, a gas inlet 110 that introduces air by the negative pressure of water in the Venturi tube 102, a gas introduction passage 104 that communicates the Venturi tube 102 and the gas inlet 110, a first gas introduction valve 106 that is provided in the gas introduction passage 104 and opens and closes the gas introduction passage 104, and a second gas introduction valve 108 that is provided in the gas introduction passage 104 between the first gas introduction valve 106 and the gas inlet 110 and opens and closes the gas introduction passage 104. The first gas introduction valve 106 is configured to receive a force in a direction that opens the first gas introduction valve 106 when the negative pressure of water in the Venturi tube 102 acts. The second gas introduction valve 108 is configured to receive a force in a direction to close the second gas introduction valve 108 when negative pressure of water is applied in the Venturi tube 102. The control device 150 is capable of executing a fine bubble generating operation in which the first pressurizing pump 88 and the second pressurizing pump 90 are driven to pressurize and supply water from the tank return line 74 and the tank connection line 76 to the tank 52, and water in which air has been pressurized and dissolved is supplied from the tank 52 to the bathtub 130 via the tank outgoing line 64, the first bathtub water line 62, and the bathtub adapter 132.The control device 150 can execute a tank circulation operation in which, during execution of a fine bubble generating operation, the tank circulation pump 94 circulates the water in the tank 52 through the tank suction passage 92 and the tank connection passage 76 to generate a negative pressure in the Venturi tube 102 of the gas introduction mechanism 96. When both the first gas introduction valve 106 and the second gas introduction valve 108 are changed from a closed state to an open state, the control device 150 is configured to open the second gas introduction valve 108 first, and then open the first gas introduction valve 106.

[0097] In the above-described hot water device 2, even when the fine bubble generating operation is being performed, the first gas introduction valve 106 and the second gas introduction valve 108 are opened while the tank circulation operation is being performed, so that air can be introduced by the gas introduction mechanism 96 and supplied to the tank 52. Therefore, there is no need to interrupt the fine bubble generating operation to supply air to the tank 52, and the fine bubble generating operation can be performed continuously. With this configuration, fine bubbles can be stably generated continuously in the water of the bathtub 130.

[0098] In the above-mentioned hot water device 2, a first gas introduction valve 106 and a second gas introduction valve 108 are provided in the gas introduction passage 104, and the second gas introduction valve 108 is provided between the first gas introduction valve 106 and the gas introduction port 110. When negative pressure of water in the Venturi tube 102 acts on the first gas introduction valve 106, a force acts in a direction to open the first gas introduction valve 106, and when negative pressure of water in the Venturi tube 102 acts on the second gas introduction valve 108, a force acts in a direction to close the second gas introduction valve 108. For this reason, for example, when the fine bubble generating operation and the tank circulation operation are being performed simultaneously, if the first gas introduction valve 106 is opened first when both the first gas introduction valve 106 and the second gas introduction valve 108 are changed from a closed state to an open state, the negative pressure of the water in the Venturi tube 102 acts on the second gas introduction valve 108 when the second gas introduction valve 108 is subsequently opened, and the second gas introduction valve 108 may not operate smoothly. As in the above configuration, when the fine bubble generating operation and the tank circulation operation are being performed simultaneously, if the first gas introduction valve 106 and the second gas introduction valve 108 are changed from a closed state to an open state, the negative pressure of the water in the Venturi tube 102 acts on the second gas introduction valve 108 by opening the second gas introduction valve 108 first, it is possible to suppress the negative pressure of the water in the Venturi tube 102 from acting on the second gas introduction valve 108, and the second gas introduction valve 108 can be operated smoothly.

[0099] In the hot water device 2, when the first gas introduction valve 106 is opened from a closed state during execution of the fine bubble generating operation, the control device 150 is configured to first reduce the flow rates of the first pressurizing pump 88 and the second pressurizing pump 90 from a first flow rate (for example, a flow rate when both the first pressurizing pump 88 and the second pressurizing pump 90 are driven) to a second flow rate (for example, a flow rate when the first pressurizing pump 88 is driven and the second pressurizing pump 90 is stopped) that is smaller than the first flow rate, and then open the first gas introduction valve 106. The first flow rate can also be referred to as the flow rate of the first pressurizing pump 88 and the second pressurizing pump 90 when the fine bubble generating operation is performed with the first gas introduction valve 106 closed, and the second flow rate can also be referred to as the flow rate of the first pressurizing pump 88 and the second pressurizing pump 90 when both the fine bubble generating operation and the tank circulation operation are performed with the first gas introduction valve 106 open. Alternatively, the first flow rate can be said to be the flow rate of the first pressurizing pump 88 and the second pressurizing pump 90 when the water level in the tank 52 is rising while the fine bubble generating operation is being performed, and the second flow rate can be said to be the flow rate of the first pressurizing pump 88 and the second pressurizing pump 90 when the water level in the tank 52 is falling while both the fine bubble generating operation and the tank circulation operation are being performed.

[0100] During the execution of the fine bubble generating operation, if the flow rates of the first pressurizing pump 88 and the second pressurizing pump 90 are large, the pressure in the tank 52 increases, and the water pressure in the Venturi tube 102 of the gas introduction mechanism 96 also increases. That is, the negative pressure of the water in the Venturi tube 102 decreases. Conversely, if the flow rates of the first pressurizing pump 88 and the second pressurizing pump 90 are small, the pressure in the tank 52 decreases, and the water pressure in the Venturi tube 102 of the gas introduction mechanism 96 also decreases. That is, the negative pressure of the water in the Venturi tube 102 increases. Since a force in the direction of opening the first gas introduction valve 106 acts on the first gas introduction valve 106 due to the negative pressure of the water in the Venturi tube 102, when the first gas introduction valve 106 is opened, the lower the water pressure in the Venturi tube 102, the smoother the first gas introduction valve 106 can be operated. According to the above configuration, when the first gas introduction valve 106 is changed from a closed state to an open state, the flow rates of the first pressurizing pump 88 and the second pressurizing pump 90 are first reduced from the first flow rate to the second flow rate to lower the water pressure in the Venturi tube 102 of the gas introduction mechanism 96, and then the first gas introduction valve 106 is opened, so that the first gas introduction valve 106 can be operated smoothly.

[0101] In the hot water device 2, when the first gas introduction valve 106 is changed from a closed state to an open state during tank circulation operation, the control device 150 is configured to first increase the flow rate of the tank circulation pump 94 from a third flow rate (e.g., the flow rate when the tank circulation pump 94 is driven at a standard rotation speed) to a fourth flow rate (e.g., the flow rate when the tank circulation pump 94 is driven at a high rotation speed) that is greater than the third flow rate, and then open the first gas introduction valve 106. The third flow rate can also be said to be the flow rate of the tank circulation pump 94 when the fine-bubble generating operation is performed with the first gas introduction valve 106 closed (if the tank circulation operation is performed with the first gas introduction valve 106 closed, it is the flow rate of the tank circulation pump 94 at that time, and if the tank circulation operation is not performed with the first gas introduction valve 106 closed, it is zero), and the fourth flow rate can also be said to be the flow rate of the tank circulation pump 94 when both the fine-bubble generating operation and the tank circulation operation are performed with the first gas introduction valve 106 open. Alternatively, the third flow rate can also be said to be the flow rate of the tank circulation pump 94 when the water level of the tank 52 rises during the fine-bubble generating operation, and the fourth flow rate can also be said to be the flow rate of the tank circulation pump 94 when the water level of the tank 52 falls during both the fine-bubble generating operation and the tank circulation operation.

[0102] When the tank circulation operation is performed, if the flow rate of the tank circulation pump 94 is small, the water pressure in the Venturi tube 102 of the gas introduction mechanism 96 becomes high. That is, the negative pressure of the water in the Venturi tube 102 becomes small. Conversely, if the flow rate of the tank circulation pump 94 is large, the water pressure in the Venturi tube 102 of the gas introduction mechanism 96 becomes low. That is, the negative pressure of the water in the Venturi tube 102 becomes large. A force acts on the first gas introduction valve 106 in a direction to open the first gas introduction valve 106 due to the negative pressure of the water in the Venturi tube 102, so that when the first gas introduction valve 106 is opened, the lower the water pressure in the Venturi tube 102, the smoother the first gas introduction valve 106 can be operated. According to the above configuration, when the first gas introduction valve 106 is changed from a closed state to an open state, the flow rate of the tank circulation pump 94 is first increased from the third flow rate to the fourth flow rate to lower the water pressure in the Venturi tube 102 of the gas introduction mechanism 96, and then the first gas introduction valve 106 is opened, so that the first gas introduction valve 106 can be operated smoothly.

[0103] In the hot water device 2, the control device 150 is configured to close the first gas introduction valve 106 first and then close the second gas introduction valve 108 when both the first gas introduction valve 106 and the second gas introduction valve 108 are changed from an open state to a closed state.

[0104] In the above-mentioned hot water device 2, a first gas introduction valve 106 and a second gas introduction valve 108 are provided in the gas introduction passage 104, and the second gas introduction valve 108 is provided between the first gas introduction valve 106 and the gas introduction port 110. When negative pressure of water in the Venturi tube 102 acts on the first gas introduction valve 106, a force acts in a direction to open the first gas introduction valve 106, and when negative pressure of water in the Venturi tube 102 acts on the second gas introduction valve 108, a force acts in a direction to close the second gas introduction valve 108. For this reason, for example, when the fine bubble generation operation and the tank circulation operation are being performed simultaneously, if the first gas introduction valve 106 and the second gas introduction valve 108 are both changed from an open state to a closed state, and the second gas introduction valve 108 is closed first, the negative pressure of the water in the Venturi tube 102 will act on the second gas introduction valve 108 when the second gas introduction valve 108 is closed, causing the valve body 108c of the second gas introduction valve 108 to strongly collide with the valve seat 108b, which may result in noise generation or damage to the second gas introduction valve 108. As configured above, when both the first gas introduction valve 106 and the second gas introduction valve 108 are changed from an open state to a closed state, by closing the first gas introduction valve 106 first, it is possible to prevent the negative pressure of the water in the Venturi tube 102 from acting on the second gas introduction valve 108 when the second gas introduction valve 108 is subsequently closed, and it is possible to prevent noise generation and damage to the second gas introduction valve 108 caused by the valve body 108c of the second gas introduction valve 108 strongly colliding with the valve seat 108b.

[0105] 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 variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful. [Explanation of symbols]

[0106] 2: Hot water device 10: Heat source unit 12: 1st heat source machine 14:Second heat source machine 16: Water supply channel 18: Hot water outlet 18a: Hot water outlet temperature thermistor 20: Bypass road 22: Bypass servo 24: Pouring channel 26: Bath valve 28: Water level sensor 30:Circulation route 30a: Circulation forward thermistor 32: Circulation return route 32a: Circulation return thermistor 34: Bathtub circulation pump 36: Water flow switch 50: Air pressure dissolving unit 52: Tank 52a: Low water level electrode 52b: High water level electrode 52c: Earth electrode 60: Return to heat source 62: First bathtub waterway 64:Tank outbound 66:Communication path 68:Heat source outward route 70: Second bathtub waterway 74: Tank Return 74a:Inlet 76: Tank connection 76a:Inlet 80: First three-way valve 82: 2nd three-way valve 84: Check valve 86: Tank water supply valve 88: First pressure pump 90: Second pressure pump 92: Tank suction passage 92a: Outlet 92b:Inlet 94: Tank Circulation Pump 96: Gas introduction mechanism 98: Water Inlet 100: Outlet pipe 102: Venturi tube 104: Gas inlet passage 104a: First gas introduction passage 104b: second gas introduction passage 104c: Third gas introduction passage 106: First gas introduction valve 106a: Valve chamber 106b: Valve seat 106c: Valve body 106d : Plunger 106e : Coil 106f: Spring 108: Second gas introduction valve 108a: Valve chamber 108b: Valve seat 108c: Valve body 108d : Plunger 108e : Coil 108f: Spring 110: Gas inlet 130: Bathtub 130a: Wall part 132: Bathtub adapter 132a:Front 132b: Bottom surface 134a: 1st discharge port 134b: First intake port 134c: Second intake port 134d: 2nd discharge port 136: 1st waterway 136a: 1st discharge path 136b: First intake passage 138: 2nd waterway 138a: Second discharge path 138b: Second intake passage 140a: Check valve 140b: Check valve 140c: Check valve 140d: Check valve 142: Microbubble generating nozzle 150: Control device 152: Memory 154: Remote control 200: Water source 250: Karan

Claims

1. A tank for dissolving gas under pressure in liquid; a tank supply line for supplying the liquid to the tank; a pressure pump provided in the tank supply line; a tank discharge passage for discharging the liquid in which the gas is pressurized and dissolved from the tank to a liquid tank; a fine bubble generating nozzle provided in the tank discharge path for generating fine bubbles by reducing the pressure of the liquid in which the gas is pressurized and dissolved; a tank circulation path that is provided separately from the tank discharge path and that sends the liquid from an outlet connected to the tank to an inlet connected to the tank; a tank circulation pump provided in the tank circulation path; a gas introduction mechanism provided in the tank circulation path; A control device is provided. The gas introduction mechanism includes: a pressure reducing section for reducing the pressure of the liquid and passing the liquid therethrough; a gas inlet port that introduces the gas by negative pressure of the liquid in the pressure reducing section; a gas introduction passage that communicates the pressure reducing section and the gas introduction port; a first gas introduction valve provided in the gas introduction path and configured to open and close the gas introduction path; a second gas introduction valve that is provided in the gas introduction path between the first gas introduction valve and the gas introduction port and opens and closes the gas introduction path, the first gas introduction valve is configured to receive a force in a direction to open the first gas introduction valve when a negative pressure of the liquid in the pressure reducing section acts, the second gas introduction valve is configured to receive a force in a direction to close the second gas introduction valve when a negative pressure of the liquid in the pressure reducing section acts, the control device is capable of executing a fine bubble generating operation in which the pressurizing pump is driven to pressurize and supply the liquid from the tank supply path to the tank, and the liquid in which the gas is pressurized and dissolved is supplied from the tank to the liquid tank via the tank discharge path, the control device is capable of executing a tank circulation operation in which, during execution of the fine bubble generating operation, the liquid in the tank is circulated through the tank circulation path by the tank circulation pump to generate a negative pressure in the pressure reducing section of the gas introducing mechanism; The control device is configured to open the second gas introduction valve first and then the first gas introduction valve when both the first gas introduction valve and the second gas introduction valve are changed from a closed state to an open state.

2. 2. The fine-bubble generating device of claim 1, wherein when the first gas introduction valve is changed from a closed state to an open state during execution of the fine-bubble generating operation, the control device is configured to first reduce the flow rate of the pressure pump from a first flow rate to a second flow rate smaller than the first flow rate, and then open the first gas introduction valve.

3. 3. The fine-bubble generating device of claim 1 or 2, wherein when the first gas introduction valve is changed from a closed state to an open state during execution of the tank circulation operation, the control device is configured to first increase the flow rate of the tank circulation pump from a third flow rate to a fourth flow rate greater than the third flow rate, and then open the first gas introduction valve.

4. 4. The fine-bubble generating device according to claim 1, wherein the control device is configured to close the first gas introduction valve first and then close the second gas introduction valve when both the first gas introduction valve and the second gas introduction valve are changed from an open state to a closed state.

5. the liquid is water, The fine bubble generating device according to claim 1 , wherein the liquid tank is a bathtub used by a user for bathing.

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