Binary refrigeration cycle device and control method for binary refrigeration cycle device

Abstract

To shorten a boiling-up time while reducing a size of a high order-side refrigerant circuit for supplying hot water to a water heater.SOLUTION: A binary refrigeration cycle device includes: a low order-side refrigerant circuit LC in which a low order-side compressor 11, an indoor heat exchanger 21 and an outdoor heat exchanger 13 are connected, and a low order-side refrigerant circulates; cascade heat exchangers 31 and a low order-side refrigerant-water heat exchanger 32 that are connected to the indoor heat exchanger 21 in parallel; an opening / closing mechanism 5 that switches inflow / outflow of the low order-side refrigerant to / from the cascade heat exchanger 31 and the low order-side refrigerant-water heat exchanger 32; a high order-side refrigerant circuit HC in which a high order-side compressor 61, a high order-side refrigerant-water heat exchanger 62 and the cascade heat exchanger 31 are connected, and in which a high order-side refrigerant circulates; a hot water storage tank 41 that has therein the low order-side refrigerant-water heat exchanger 32 and the high order-side refrigerant-water heat exchanger 62; and a control device 7. During a hot water supply operation, the control device 7 controls the opening / closing mechanism 5 so that the low order-side refrigerant flows in at least one of the low order-side refrigerant-water heat exchanger 32 and the cascade heat exchanger 31.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a cascade refrigeration cycle apparatus and a control method for a cascade refrigeration cycle apparatus. [Background technology]

[0002] Some air conditioners are equipped with a hot water supply device in addition to the equipment required for air conditioning. In such air conditioners, the refrigerant temperature required for hot water supply (e.g., 80°C) is generally higher than the refrigerant temperature required for air conditioning (e.g., 50°C).

[0003] For this reason, a dual refrigeration cycle device may be used in which a cascade heat exchanger for hot water supply is added to a refrigerant circuit that combines an outdoor heat exchanger and an indoor heat exchanger, as in a general air conditioner (see Patent Document 1 below). In the case of a device using such a dual refrigeration cycle device, the high-side refrigerant circuit is used for hot water supply, and the low-side refrigerant circuit is used for air conditioning.

[0004] By using such a dual cascade refrigeration cycle device, the temperature of the refrigerant circulating through the refrigerant circuit in one heat pump system can be set to a plurality of different temperatures, making it possible to simultaneously perform air conditioning operation and supply operation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2009 / 122477 Summary of the Invention [Problem to be solved by the invention]

[0006] However, for the high-temperature side refrigerant circuit used for hot water supply operation, it is required to reduce the size of the entire high-temperature side refrigerant circuit, particularly the compressor, from the viewpoint of ease of installation. Furthermore, reducing the size of the entire high-temperature side refrigerant circuit also contributes to reducing the size of the entire cascade refrigeration cycle device.

[0007] On the other hand, if the refrigerant circuit on the high side is made smaller by downsizing the compressor, the capacity to heat water is limited by the amount of the compressor being made smaller than that of a general refrigeration cycle device used exclusively for hot water supply. If the capacity to heat water is limited, the time required to generate (boil) hot water becomes longer. Therefore, in order to shorten the boiling time from the viewpoint of the boiling time, it is necessary to enlarge the compressor of the refrigerant circuit on the high side, for example.

[0008] However, the increase in size of the compressor leads to a decrease in the ease of installation of the cascade refrigeration cycle device. Furthermore, if the enlarged compressor is operated at high speed in order to shorten the boiling time, it may cause problems such as increased noise and vibration during operation.

[0009] In this way, making the compressor larger or smaller directly affects the compressor's capacity (how long it takes to boil water), and also brings to light a variety of problems, including ease of installation.

[0010] The present invention is devised to solve the above-mentioned problems, and aims to provide a dual refrigeration cycle device and a control method for a dual refrigeration cycle device that can reduce the size of the high-side refrigerant circuit that supplies hot water to a hot water heater while shortening the boiling time. [Means for solving the problem]

[0011] A two-stage refrigeration cycle apparatus according to one aspect of the present invention includes a low stage side refrigerant circuit in which a low stage side compressor, an indoor heat exchanger, a low stage side expansion valve, and an outdoor heat exchanger are connected and in which a low stage side refrigerant circulates, a cascade heat exchanger and a low stage side refrigerant-water heat exchanger connected in parallel with the indoor heat exchanger, an opening / closing mechanism for switching the flow of the low stage side refrigerant to the cascade heat exchanger and the low stage side refrigerant-water heat exchanger, a high stage side compressor, a high stage side refrigerant-water heat exchanger, a high stage side expansion valve, and a cascade The system includes a high-stage side refrigerant circuit connected to a heat exchanger and through which a high-stage side refrigerant circulates, a hot water storage tank having a low-stage side refrigerant-water heat exchanger and a high-stage side refrigerant-water heat exchanger inside, in which water stored in the low-stage side refrigerant-water heat exchanger and the high-stage side refrigerant-water heat exchanger is heated, and a control device that controls the opening and closing mechanism, and during hot water supply operation, the control device controls the opening and closing mechanism so that the low-stage side refrigerant flows through at least one of the low-stage side refrigerant-water heat exchanger and the cascade heat exchanger.

[0012] A two-stage refrigeration cycle apparatus according to one aspect of the present invention includes a low stage side refrigerant circuit in which a low stage side compressor, an indoor heat exchanger, a low stage side expansion valve, and an outdoor heat exchanger are connected, and in which a low stage side refrigerant circulates, a cascade heat exchanger and a low stage side refrigerant-water heat exchanger connected in parallel with the indoor heat exchanger, an opening / closing mechanism for switching the flow of low stage side refrigerant to the cascade heat exchanger and the low stage side refrigerant-water heat exchanger, and a high stage side refrigerant circuit in which a high stage side refrigerant circulates, the high stage side compressor, the high stage side refrigerant-water heat exchanger, the high stage side expansion valve, and the cascade heat exchanger are connected, The hot water supply system includes a circuit, a hot water storage tank connected to the low-stage side refrigerant-water heat exchanger and the high-stage side refrigerant-water heat exchanger via piping, in which water stored in the low-stage side refrigerant-water heat exchanger and the high-stage side refrigerant-water heat exchanger is heated, a water temperature sensor provided in the hot water storage tank for detecting the temperature of the water stored in the hot water storage tank, and a control device for controlling the opening and closing mechanism, and during hot water supply operation, when the water temperature detected by the water temperature sensor is equal to or lower than a water temperature threshold value, the control device controls the opening and closing mechanism so that the low-stage side refrigerant flows to the low-stage side refrigerant-water heat exchanger.

[0013] Further, a control method for a two-stage refrigeration cycle apparatus according to one aspect of the present invention includes a low stage side refrigerant circuit in which a low stage side compressor, an indoor heat exchanger, a low stage side expansion valve, and an outdoor heat exchanger are connected, and in which a low stage side refrigerant circulates, a cascade heat exchanger and a low stage side refrigerant-water heat exchanger connected in parallel with the indoor heat exchanger, an opening and closing mechanism for switching a flow of low stage side refrigerant to the cascade heat exchanger and the low stage side refrigerant-water heat exchanger, a high stage side refrigerant circuit in which a high stage side refrigerant circulates, and a low stage side refrigerant-water heat exchanger and a high stage side refrigerant The hot water storage tank has a refrigerant-water heat exchanger therein or is connected via piping, and the water stored therein is heated by the low-side refrigerant-water heat exchanger and the high-side refrigerant-water heat exchanger, and a control device controls an opening and closing mechanism. During hot water supply operation, the hot water storage tank includes the steps of setting a water temperature threshold value to be compared with the temperature of the water stored in the hot water storage tank, comparing the water temperature with the water temperature threshold value, and controlling the opening and closing mechanism based on the comparison result of the water temperature with the water temperature threshold value so that the low-side refrigerant flows to at least one of the low-side refrigerant-water heat exchanger and the cascade heat exchanger. Effect of the Invention

[0014] According to the present invention, it is possible to reduce the size of a high-temperature side refrigerant circuit that supplies hot water to a hot water heater, while shortening the boiling time. [Brief description of the drawings]

[0015] [Figure 1] 1 is a refrigerant circuit diagram of a cascade refrigeration cycle device according to an embodiment of the present invention. [Diagram 2] FIG. 4 is a refrigerant circuit diagram of another aspect of a binary refrigeration cycle device according to an embodiment of the present invention. [Diagram 3] 1 is a block diagram showing an internal configuration of a control device of a cascade refrigeration cycle apparatus according to an embodiment of the present invention. [Figure 4] 4 is an explanatory diagram showing the relationship between the change in water temperature and time in a hot water storage tank according to an embodiment of the present invention. FIG. [Diagram 5]3 is a flowchart showing a control flow of the cascade refrigeration cycle device according to the embodiment of the present invention. [Figure 6] 3 is a flowchart showing a control flow of the cascade refrigeration cycle device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The structure of a cascade refrigeration cycle apparatus 100 according to an embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a refrigerant circuit diagram of the cascade refrigeration cycle apparatus 100 according to an embodiment of the present invention. The cascade refrigeration cycle apparatus 100 includes a low-stage refrigerant circuit LC used for air conditioning and a high-stage refrigerant circuit HC used for hot water supply.

[0017] A low-stage side compressor 11, a four-way valve 12, an indoor heat exchanger 21, a low-stage side expansion valve 22, and an outdoor heat exchanger 13 are connected to the low-stage side refrigerant circuit LC, and a low-stage side refrigerant circulates through the low-stage side refrigerant circuit LC. Of the devices connected to the low-stage side refrigerant circuit LC, the low-stage side compressor 11, the four-way valve 12, and the outdoor heat exchanger 13 are included in the outdoor unit 1. The outdoor unit 1 may further be provided with an outdoor fan 14. However, other devices that are normally provided in the outdoor unit 1 are not shown in FIG. 1.

[0018] The indoor unit 2 includes an indoor heat exchanger 21, a low-stage side expansion valve 22 that adjusts the overall flow rate of the low-stage side refrigerant flowing through the low-stage side refrigerant circuit LC, and an indoor fan 23. However, other devices that are normally included in the indoor unit 2 are not shown in FIG.

[0019] Furthermore, the indoor unit 2 is provided with an indoor heat exchanger temperature sensor 24 that detects the temperature of the low-stage side refrigerant flowing through the indoor heat exchanger 21. The indoor heat exchanger temperature sensor 24 is provided between the low-stage side compressor 11 and the indoor heat exchanger 21 in the low-stage side refrigerant circuit LC.

[0020] As described above, the low-temperature side refrigerant circuit LC is used for air conditioning. Here, a description will be given of heating operation and cooling operation using the outdoor unit 1 and the indoor unit 2. First, in the case of heating operation, the indoor heat exchanger 21 functions as a condenser, and the outdoor heat exchanger 13 functions as an evaporator.

[0021] When heating operation is performed in the two-stage refrigeration cycle apparatus 100, the low-stage side refrigerant circulates through the low-stage side refrigerant circuit LC in the order of the above-mentioned low-stage side compressor 11, four-way valve 12, indoor heat exchanger 21, low-stage side expansion valve 22, outdoor heat exchanger 13, four-way valve 12, and low-stage side compressor 11.

[0022] During heating operation, the low-stage refrigerant compressed in the low-stage compressor 11 of the outdoor unit 1 and put into a high-temperature, high-pressure gas phase state is supplied to the indoor heat exchanger 21. The high-temperature, high-pressure low-stage refrigerant in the gas phase state that flows through the indoor heat exchanger 21 releases heat and condenses into a liquid phase state by exchanging heat with indoor air taken in by the indoor fan 23 of the indoor unit 2. The air that has exchanged heat with the high-temperature, high-pressure low-stage refrigerant passing through the indoor heat exchanger 21 is warmed and supplied to the room.

[0023] The low-stage side refrigerant in liquid phase that has passed through indoor heat exchanger 21 passes through low-stage side expansion valve 22, where it is decompressed and becomes a low-temperature two-phase gas-liquid state. The low-stage side refrigerant in the decompressed two-phase gas-liquid state then flows into outdoor heat exchanger 13. The low-temperature low-stage side refrigerant flowing through outdoor heat exchanger 13 exchanges heat with the outside air taken in by outdoor fan 14, absorbing heat and evaporating to become a gas phase state. The low-stage side refrigerant in gas phase that has passed through outdoor heat exchanger 13 returns to low-stage side compressor 11 again, where it is compressed to a high temperature and high pressure.

[0024] Next, in the case of cooling operation, the indoor heat exchanger 21 functions as an evaporator, and the outdoor heat exchanger 13 functions as a condenser. That is, when cooling operation is performed in the two-stage refrigeration cycle apparatus 100, the low-stage side refrigerant circulates in the low-stage side refrigerant circuit LC in the order of the above-mentioned low-stage side compressor 11, four-way valve 12, outdoor heat exchanger 13, low-stage side expansion valve 22, indoor heat exchanger 21, four-way valve 12, and low-stage side compressor 11.

[0025] During cooling operation, the low-stage side refrigerant compressed in the low-stage side compressor 11 of the outdoor unit 1 and put into a high-temperature, high-pressure gas phase state is supplied to the outdoor heat exchanger 13. The low-stage side refrigerant in a high-temperature, high-pressure gas phase state flowing through the outdoor heat exchanger 13 exchanges heat with the outside air taken in by the outdoor fan 14 of the outdoor unit 1, thereby dissipating heat of the refrigerant to the outside air. The low-stage side refrigerant that has dissipated heat and condensed is put into a liquid phase state.

[0026] The low-side refrigerant in liquid phase that has passed through the outdoor heat exchanger 13 passes through the low-side expansion valve 22, where it is decompressed and becomes a low-temperature two-phase gas-liquid state. The low-side refrigerant that has been decompressed and becomes a two-phase gas-liquid state then flows into the indoor heat exchanger 21. The low-temperature low-side refrigerant flowing through the indoor heat exchanger 21 exchanges heat with the indoor air taken in by the indoor fan 23, absorbing heat and evaporating to become a gas phase state.

[0027] That is, the low-stage side refrigerant absorbs heat from the indoor air and evaporates due to heat exchange by the indoor heat exchanger 21, and the indoor air sucked into the indoor heat exchanger 21 is cooled. The low-stage side refrigerant is then supplied to the room by the indoor fan 23 to cool the room. The low-stage side refrigerant in the gas phase that has absorbed heat through heat exchange in the indoor heat exchanger 21 returns to the low-stage side compressor 11 and is compressed to a high temperature and high pressure.

[0028] The low stage side refrigerant circuit LC is further connected to a cascade heat exchanger 31 and a low stage side refrigerant-water heat exchanger 32 in parallel with the indoor heat exchanger 21. The cascade heat exchanger 31 is a heat exchanger that exchanges heat between the low stage side refrigerant and a high stage side refrigerant flowing in a high stage side refrigerant circuit HC described later.

[0029] On the other hand, the low stage side refrigerant-water heat exchanger 32 is a heat exchanger that exchanges heat between the low stage side refrigerant circulating in the low stage side refrigerant circuit LC and water stored in a hot water storage tank 41 described later. A low stage side refrigerant temperature sensor 33 that detects the temperature of the low stage side refrigerant flowing through the low stage side refrigerant-water heat exchanger 32 is provided between the low stage side refrigerant-water heat exchanger 32 and the low stage side compressor 11.

[0030] Water is stored inside the hot water storage tank 41. The water is heated by heat exchange with at least one of the low-stage side refrigerant-water heat exchanger 32 and the high-stage side refrigerant-water heat exchanger 62. The hot water storage tank 41 is also provided with a water temperature sensor 42 that detects the temperature of the water stored in the hot water storage tank 41.

[0031] When the hot water storage tank 41 is installed, the water temperature sensor 42 is disposed below the center in the vertical direction of the hot water storage tank 41. This is because the temperature of the water stored inside the hot water storage tank 41 is higher at the upper part than at the lower part, and therefore by detecting the low water temperature at the lower part inside the hot water storage tank 41, the low-side refrigerant-water heat exchanger 32 can be more effectively used for boiling the water in the hot water storage tank 41, as described later.

[0032] Furthermore, by arranging the water temperature sensor 42 at such a position, it is possible to make a determination to maximize the use of the low stage side refrigerant-water heat exchanger 32, particularly when the low stage side refrigerant-water heat exchanger 32 is arranged inside the hot water storage tank 41. That is, the water temperature sensor 42 makes it possible to more accurately grasp the temperature difference between the temperature of the low stage side refrigerant flowing inside the low stage side refrigerant-water heat exchanger 32 and the water temperature, so that it is possible to accurately determine whether or not to flow the low stage side refrigerant through the low stage side refrigerant-water heat exchanger 32.

[0033] The low-stage side refrigerant circuit LC is connected to an opening and closing mechanism 5 that switches the flow of low-stage side refrigerant to the cascade heat exchanger 31 and the low-stage side refrigerant-water heat exchanger 32. The opening and closing mechanism 5 includes a first opening and closing valve 51 connected between the low-stage side compressor 11 and the cascade heat exchanger 31, and a first expansion valve 52 connected between the cascade heat exchanger 31 and the outdoor heat exchanger 13.

[0034] The opening and closing mechanism 5 also includes a second opening and closing valve 53 connected between the low stage side compressor 11 and the low stage side refrigerant-water heat exchanger 32, and a second expansion valve 54 connected between the low stage side refrigerant-water heat exchanger 32 and the outdoor heat exchanger 13. Therefore, for example, by controlling to open the second opening and closing valve 53 and the second expansion valve 54, the low stage side refrigerant can be made to flow to the low stage side refrigerant-water heat exchanger 32.

[0035] The high-stage side refrigerant circuit HC is connected to a high-stage side compressor 61, a high-stage side refrigerant-water heat exchanger 62, a high-stage side expansion valve 63, and a cascade heat exchanger 31, and circulates the high-stage side refrigerant. As described above, the high-stage side refrigerant is heat exchanged with the low-stage side refrigerant in the cascade heat exchanger 31.

[0036] It is assumed that the low-stage side compressor 11 and the high-stage side compressor 61 in the embodiment of the present invention are variable capacity compressors whose rotation speeds can be variably controlled by an inverter.

[0037] Furthermore, when comparing the high stage side compressor 61 and the low stage side compressor 11, for example, the displacement volume of the high stage side compressor 61 is smaller than the displacement volume of the low stage side compressor 11. This is because, as described above, the high stage side compressor 61 is used only for hot water supply operation, and therefore a smaller capacity is sufficient than the low stage side compressor 11, and because a reduction in the size of the high stage side refrigerant circuit HC is required from the viewpoint of installation.

[0038] Furthermore, when the high stage side refrigerant-water heat exchanger 62 is compared with the low stage side refrigerant-water heat exchanger 32, the volume of the high stage side refrigerant-water heat exchanger 62 is smaller than that of the low stage side refrigerant-water heat exchanger 32. This is because the displacement volume of the high stage side compressor 61 is smaller than the displacement volume of the low stage side compressor 11, as described above.

[0039] As the low-stage side refrigerant, for example, R32 or the like is used. On the other hand, as the high-stage side refrigerant, the same refrigerant as the low-stage side refrigerant such as R32 or a different refrigerant such as R290 may be used. For example, when R290 is used as the high-stage side refrigerant, the critical temperature is higher than that of the low-stage side refrigerant, so that the water in the hot water storage tank 41 can be heated to a higher temperature.

[0040] 1, the cascade heat exchanger 31, the low stage side refrigerant-water heat exchanger 32, the hot water tank 41, the opening and closing mechanism 5, and the high stage side refrigerant circuit HC that constitute the low stage side refrigerant circuit LC are integrated into the hot water supply device 3. The hot water tank 41 is connected to a water circuit (not shown) via a pipe WP1. The heated water (hot water) in the hot water tank 41 is supplied to a room (for example, a bathroom or a kitchen) via the water circuit as appropriate.

[0041] 1, the low stage side refrigerant-water heat exchanger 32 and the high stage side refrigerant-water heat exchanger 62 are provided inside the hot water storage tank 41. Therefore, the water stored in the hot water storage tank 41 is directly heated in the hot water storage tank 41 by the low stage side refrigerant-water heat exchanger 32 and the high stage side refrigerant-water heat exchanger 62.

[0042] However, the connection relationship between the low-side refrigerant-water heat exchanger 32 and the high-side refrigerant-water heat exchanger 62 and the hot water storage tank 41 is not limited to the relationship shown in Figure 1, and the relationship shown in the two-stage refrigeration cycle apparatus 100A described next may also be adopted.

[0043] 1, the low stage side refrigerant-water heat exchanger 32 and the high stage side refrigerant-water heat exchanger 62 are provided inside the hot water storage tank 41, and are directly connected to each other. Here, "directly" means that no structure such as piping is interposed between the low stage side refrigerant-water heat exchanger 32 or the high stage side refrigerant-water heat exchanger 62 and the hot water storage tank 41.

[0044] In contrast, in the case of the cascade refrigeration cycle apparatus 100A shown in Fig. 2, the connection relationship between the low stage side refrigerant-water heat exchanger 32, the high stage side refrigerant-water heat exchanger 62, and the hot water tank 41 is different from that of the cascade refrigeration cycle apparatus 100 shown in Fig. 1. Here, Fig. 2 is a refrigerant circuit diagram of another aspect of the cascade refrigeration cycle apparatus 100A according to the embodiment of the present invention.

[0045] 2, the hot water storage tank 41 is connected to the low stage side refrigerant-water heat exchanger 32 and the high stage side refrigerant-water heat exchanger 62 via a pipe WP2. In other words, since the pipe WP2 is interposed between the hot water storage tank 41 and the low stage side refrigerant-water heat exchanger 32 and between the hot water storage tank 41 and the high stage side refrigerant-water heat exchanger 62, these are, so to speak, "indirectly" connected.

[0046] A pump 34 is connected between the hot water storage tank 41 and the low stage side refrigerant-water heat exchanger 32, and between the hot water storage tank 41 and the low stage side refrigerant-water heat exchanger 32 and the high stage side refrigerant-water heat exchanger 62. That is, the water stored in the hot water storage tank 41 is heated by the low stage side refrigerant-water heat exchanger 32 and the high stage side refrigerant-water heat exchanger 62 while circulating between the hot water storage tank 41 and the low stage side refrigerant-water heat exchanger 32 and the high stage side refrigerant-water heat exchanger 62 via the pipe WP2 by the operation of the pump 34.

[0047] In the cascade refrigeration cycle apparatus 100A in Fig. 2, since such a configuration is adopted, the hot water supply apparatus 4 includes only the hot water storage tank 41 and the water temperature sensor 42, as shown in Fig. 2. On the other hand, the other components, the cascade heat exchanger 31, the low stage side refrigerant-water heat exchanger 32, the opening and closing mechanism 5, and the high stage side refrigerant circuit HC, are collectively installed as a so-called intermediate unit U.

[0048] In addition, in both the two-stage refrigeration cycle apparatus 100 and the two-stage refrigeration cycle apparatus 100A, the high-stage side refrigerant-water heat exchanger 62 connected to the hot water storage tank 41 is positioned above the low-stage side refrigerant-water heat exchanger 32 when the hot water storage tank 41 is installed.

[0049] As described above, the temperature of the water stored inside the hot water storage tank 41 is higher in the upper part than in the lower part. Therefore, the high-stage side refrigerant-water heat exchanger 62, through which the high-stage side refrigerant with a higher temperature than the low-stage side refrigerant flows, is disposed in the upper part of the hot water storage tank 41, and the low-stage side refrigerant-water heat exchanger 32, through which the low-stage side refrigerant with a lower temperature than the high-stage side refrigerant flows, is disposed in the lower part of the hot water storage tank 41. As a result, the low-stage side refrigerant-water heat exchanger 32 exchanges heat with water with a lower temperature than the high-stage side refrigerant-water heat exchanger 62, and the water can be heated efficiently according to the respective refrigerant temperatures.

[0050] In addition, as in the two-stage refrigeration cycle apparatus 100A shown in Figure 2, when the low stage side refrigerant-water heat exchanger 32 and the high stage side refrigerant-water heat exchanger 62 are connected to the hot water storage tank 41 via piping WP2, the high stage side refrigerant-water heat exchanger 62 is positioned downstream of the low stage side refrigerant-water heat exchanger 32 in the direction of water flow.

[0051] Therefore, the low-temperature side refrigerant-water heat exchanger 32 heats the lower temperature water, and the high-temperature side refrigerant-water heat exchanger 62 heats the higher temperature water, thereby enabling efficient heating according to the respective refrigerant temperatures.

[0052] As described above, the only difference between the cascade refrigeration cycle apparatus 100 and the cascade refrigeration cycle apparatus 100A is the connection between the hot water storage tank 41 and the low-side refrigerant-water heat exchanger 32 and the high-side refrigerant-water heat exchanger 62. Therefore, in the following, the cascade refrigeration cycle apparatus 100 will be used as an example for explanation.

[0053] The control device 7 controls the opening degree of the opening and closing mechanisms 5. The control device 7 controls the opening degree of each opening and closing mechanism 5, thereby causing the low stage side refrigerant flowing through the low stage side refrigerant circuit LC to flow through the cascade heat exchanger 31 and the low stage side refrigerant-water heat exchanger 32.

[0054] By controlling the opening and closing mechanism 5 in this way, the control device 7 efficiently heats the water in the hot water storage tank 41 and shortens the boiling time. The control device 7 also controls, for example, the low-side compressor 11 and the high-side compressor 61.

[0055] Next, the contents of control by the control device 7 will be described in more detail. Fig. 3 is a block diagram showing the internal configuration of the control device 7 of the cascade refrigeration cycle apparatus 100 according to the embodiment of the present invention. The control device 7 is provided with a detection unit 71, a storage unit 72, a determination unit 73, and an opening / closing mechanism control unit 74, which are connected via a bus B.

[0056] The detection unit 71 acquires information on the temperature of the water stored inside the hot water storage tank 41, which is transmitted from the water temperature sensor 42. The detection unit 71 also acquires information on the temperature of the low-stage side refrigerant transmitted from the indoor heat exchanger temperature sensor 24 and the low-stage side refrigerant temperature sensor 33.

[0057] When the detection unit 71 obtains the water temperature or the low-side refrigerant temperature, the detection unit 71 may obtain temperature information by accessing each temperature sensor. Also, the detection unit 71 may obtain temperature information transmitted from each temperature sensor, whether at all times or at any time.

[0058] The storage unit 72 stores a water temperature threshold value required for controlling the opening and closing mechanism 5 described later. In addition, for example, information on the water temperature and the low-side refrigerant temperature transmitted from each temperature sensor at any time is stored. Furthermore, for example, a determination program or the like used when the determination unit 73 described later makes a determination to control the opening and closing mechanism 5 may be stored.

[0059] The determination unit 73 obtains information on the temperatures detected by each temperature sensor from the detection unit 71, and determines which opening / closing mechanism 5 to open or close when controlling the opening / closing mechanism 5. As described above, when performing hot water supply operation, heat is exchanged between the high-temperature side refrigerant circulating in the high-temperature side refrigerant circuit HC and the water in the hot water storage tank 41, thereby heating the water.

[0060] On the other hand, there is a demand for downsizing the entire high-stage side refrigerant circuit HC, which also includes downsizing the high-stage side compressor 61. If the high-stage side compressor 61 is downsized, the water heating capacity is limited, and as a result, the time required to generate (boil) hot water is extended. This has a large effect especially when the temperature of the water stored inside the hot water storage tank 41 is low.

[0061] Here, in the hot water supply operation, for example, when the water inside hot water storage tank 41 is heated to a water temperature (target temperature) set by the user, the change in water temperature versus time is considered as follows: Fig. 4 is an explanatory diagram showing the relationship between time and the change in water temperature inside hot water storage tank 41 according to the embodiment of the present invention.

[0062] In Fig. 4, the vertical axis indicates "water temperature" and the horizontal axis indicates "time." Furthermore, the change in water temperature is indicated by a solid line. Generally, when water stored inside hot water storage tank 41 is heated, the water temperature increases over time. Then, once the water temperature rises to the target temperature indicated by the dashed line, the water temperature is controlled to maintain the target temperature while the hot water supply operation is being performed, although the temperature may fluctuate slightly.

[0063] When the hot water supply operation is performed, the temperature of the water in the hot water storage tank 41 changes as shown by the solid line in Fig. 4. This change in water temperature occurs, for example, when the amount of hot water stored in the hot water storage tank 41 decreases as hot water is supplied to the room, and cold water is supplied to the hot water storage tank 41 to compensate for this decrease. However, as described above, if the hot water supply operation is performed using only the high temperature side refrigerant circuit HC, it takes time for the water temperature to reach the target temperature.

[0064] Therefore, in the dual cascade refrigeration cycle apparatus 100 according to the embodiment of the present invention, the heat exchanger to be used during hot water supply operation is selected based on information about the temperatures detected by each temperature sensor, and each part is controlled so that the target temperature is reached more quickly.

[0065] That is, during hot water supply operation, the control device 7 controls the opening and closing mechanism 5 so that the low stage side refrigerant flows through at least one of the cascade heat exchanger 31 and the low stage side refrigerant-water heat exchanger 32. Specifically, the control described below is performed.

[0066] First, a water temperature threshold value is set and stored in the memory unit 72. This "water temperature threshold value" is a threshold value used when the determination unit 73 determines whether or not to use the low-side refrigerant-water heat exchanger 32 in the hot water supply operation, and is indicated by a dashed line in the explanatory diagram of FIG.

[0067] In other words, when the temperature of the water stored in the hot water storage tank 41 is low and it takes a long time to boil the water if only the high-side refrigerant circuit HC is used for hot water supply operation, the time to boil the water is shortened by using the low-side refrigerant-water heat exchanger 32.

[0068] Here, since the low stage side refrigerant flowing to the low stage side refrigerant-water heat exchanger 32 flows through the low stage side refrigerant circuit LC, the temperature of the low stage side refrigerant depends on the load of the indoor unit 2, i.e., the temperature of the low stage side refrigerant flowing through the indoor heat exchanger 21. Also, when heat exchange is performed between the low stage side refrigerant and water in the low stage side refrigerant-water heat exchanger 32, the water cannot be heated to a temperature higher than the condensation temperature of the low stage side refrigerant.

[0069] From the above, the water temperature threshold is set based on the temperature of the low-source side refrigerant detected by the indoor heat exchanger temperature sensor 24. The water temperature threshold is not a fixed value, but is set each time the determination unit 73 determines whether or not to use the low-source side refrigerant-water heat exchanger 32 during hot water supply operation. Although the water temperature threshold is set each time in this manner, it is also possible to set the water temperature threshold to a value that is certainly lower than the condensation temperature during low-load operation of the indoor heat exchanger 21, for example, 30°C. By setting the water temperature threshold in this manner, the control performed by the control device 7 in the embodiment of the present invention can be executed even if the indoor heat exchanger temperature sensor 24 does not detect the temperature of the low-source side refrigerant.

[0070] The determination unit 73 acquires information about the temperature of the water inside the hot water storage tank 41 detected by the water temperature sensor 42 via the detection unit 71. Then, the determination unit 73 compares the acquired water temperature with a water temperature threshold. Then, when the water temperature detected by the water temperature sensor 42 is equal to or lower than the water temperature threshold, the determination unit 73 controls the opening and closing mechanism 5 so that the low stage side refrigerant flows into the low stage side refrigerant-water heat exchanger 32.

[0071] That is, when the determination unit 73 determines that the water temperature is equal to or lower than the water temperature threshold value (for example, the portion indicated by the symbol O in the explanatory diagram of FIG. 4), in the hot water supply operation, the water stored in the hot water storage tank 41 is heated using the low-stage side refrigerant-water heat exchanger 32. As described above, since the low-stage side compressor 11 has a larger displacement volume than the high-stage side compressor 61, the water in the hot water storage tank 41 can be heated using a compressor having a larger capacity.

[0072] When the determination unit 73 determines that the water temperature is equal to or lower than the water temperature threshold value as described above, it instructs the opening and closing mechanism control unit 74 to open the second opening and closing valve 53 and the second expansion valve 54 so as to flow the refrigerant to the low-temperature side refrigerant-water heat exchanger 32. The opening and closing mechanism control unit 74 opens the second opening and closing valve 53 and the second expansion valve 54 based on the instruction from the determination unit 73.

[0073] The opening and closing mechanisms 5 when the hot water supply operation is not performed and the opening and closing mechanisms 5 provided in flow paths not used for hot water supply are controlled by the opening and closing mechanism control section 74 to be in a closed state.

[0074] As described above, when the low stage side refrigerant is caused to flow through the low stage side refrigerant-water heat exchanger 32 to perform hot water supply operation, it is possible to arbitrarily set whether or not to use the high stage side refrigerant circuit HC. That is, when it is necessary to boil the water stored in the hot water storage tank 41 as soon as possible, the determination unit 73 instructs the opening / closing mechanism control unit 74 to open the first opening / closing valve 51 and the first expansion valve 52, for example.

[0075] Then, the low stage side refrigerant is caused to flow through the cascade heat exchanger 31, and the high stage side compressor 61 of the high stage side refrigerant circuit HC is also driven. By performing such control, not only the low stage side refrigerant circuit LC but also the high stage side refrigerant circuit HC is used during hot water supply operation, so that the stored water can be heated more quickly.

[0076] The flow of the low-stage refrigerant, particularly, during such hot water supply operation is the same as that during the heating operation described above. Explaining this with reference to Fig. 1, as shown by the arrows in Fig. 1, in the low-stage refrigerant circuit LC, the low-stage refrigerant discharged from the low-stage compressor 11 passes through the first on-off valve 51 and flows into the cascade heat exchanger 31.

[0077] Since the high-stage side refrigerant circulating in the high-stage side refrigerant circuit HC also flows into the cascade heat exchanger 31, heat exchange takes place between the low-stage side refrigerant and the high-stage side refrigerant in the cascade heat exchanger 31. The high-temperature, high-pressure low-stage side refrigerant dissipates heat in the cascade heat exchanger 31 and passes through the first expansion valve 52 to become a low-temperature, low-pressure refrigerant, which then flows into the low-stage side compressor 11 via the outdoor heat exchanger 13.

[0078] The high-stage side refrigerant absorbs heat from the low-stage side refrigerant in the cascade heat exchanger 31 and flows into the high-stage side compressor 61. The high-temperature, high-pressure high-stage side refrigerant discharged from the high-stage side compressor 61 flows into the high-stage side refrigerant-water heat exchanger 62 and exchanges heat with the water stored inside the hot water storage tank 41, heating the water. The high-stage side refrigerant that has been subjected to heat exchange then flows again into the cascade heat exchanger 31 via the high-stage side expansion valve 63.

[0079] The low stage side refrigerant discharged from the low stage side compressor 11 flows into the low stage side refrigerant-water heat exchanger 32 via the second on-off valve 53. In the low stage side refrigerant-water heat exchanger 32, heat is exchanged between the high temperature and high pressure low stage side refrigerant and the water stored inside the hot water storage tank 41, and the water is heated. The low stage side refrigerant flowing out from the low stage side refrigerant-water heat exchanger 32 flows into the low stage side compressor 11 via the second expansion valve 54 and the outdoor heat exchanger 13.

[0080] On the other hand, when the determination unit 73 compares the temperature of the water stored in the hot water storage tank 41 obtained from the water temperature sensor 42 with the water temperature threshold value and the result is that the water temperature exceeds the water temperature threshold value (for example, the part indicated by the symbol P in FIG. 4), it is considered that it is sufficient to heat the water using only the high stage side refrigerant circuit HC without heating the water using the low stage side refrigerant-water heat exchanger 32. Therefore, the opening and closing mechanism 5 is controlled so that the low stage side refrigerant flows only through the cascade heat exchanger 31.

[0081] Therefore, in this case, the determination unit 73 instructs the opening and closing mechanism control unit 74 to open the first opening and closing valve 51 and the first expansion valve 52. On the other hand, the determination unit 73 instructs the opening and closing mechanism control unit 74 to close both the second opening and closing valve 53 and the second expansion valve 54, so that the low-temperature side refrigerant does not flow to the low-temperature side refrigerant-water heat exchanger 32.

[0082] In addition, in the hot water supply operation, once the water is heated to the target temperature, the control device 7 controls the opening and closing mechanism 5 to maintain the target temperature as much as possible as long as the hot water supply operation continues. Since the target temperature is only to be maintained, as explained above, for example, as long as the water temperature exceeds the water temperature threshold, it is not necessary to boil water using the low-stage side refrigerant-water heat exchanger 32. Therefore, it is sufficient to use only the high-stage side refrigerant circuit HC.

[0083] 4, the determination unit 73 instructs the opening / closing mechanism control unit 74 to open the first opening / closing valve 51 and the first expansion valve 52, and to close the second opening / closing valve 53 and the second expansion valve 54. That is, in the low-stage side refrigerant circuit LC, the low-stage side refrigerant is caused to flow only through the cascade heat exchanger 31, and the temperature of the water in the hot water storage tank 41 is maintained at a target temperature using the high-stage side refrigerant circuit HC.

[0084] In the above description, an example has been given in which the determination unit 73 compares the temperature of the water stored in the hot water storage tank 41 detected by the water temperature sensor 42 with the water temperature threshold value in determining whether or not to use the low-temperature side refrigerant-water heat exchanger 32 in performing the hot water supply operation. However, in addition to the method of using the water temperature threshold value as the value used in the determination, for example, the following method can also be adopted.

[0085] In other words, when the judgment unit 73 determines that the temperature difference between the water temperature detected by the water temperature sensor 42 and the temperature of the low-side refrigerant detected by the low-side refrigerant temperature sensor 33 is less than the temperature difference threshold, it controls the opening and closing mechanism 5 via the opening and closing mechanism control unit 74 so that the low-side refrigerant flows only through the cascade heat exchanger 31.

[0086] For example, when the temperature of the water stored inside the hot water storage tank 41 is relatively high, that is, when there is little temperature difference between the water temperature and the temperature of the low-side refrigerant, efficient heating cannot be achieved even if the low-side refrigerant is flowed through the low-side refrigerant-water heat exchanger 32 to perform heat exchange.

[0087] Therefore, a preset temperature difference threshold is compared with the temperature difference between the water temperature and the temperature of the low stage side refrigerant, and if the latter is less than the former, the low stage side refrigerant is not caused to flow through the low stage side refrigerant-water heat exchanger 32. In this case, the low stage side refrigerant is caused to flow only through the cascade heat exchanger 31. The temperature difference threshold is a value obtained in advance by experiments or the like, and is stored in the storage unit 72.

[0088] On the other hand, when the temperature difference between the water temperature and the low stage side refrigerant temperature is compared with the temperature difference threshold, if the latter temperature difference is equal to or greater than the former, the low stage side refrigerant is made to flow to the low stage side refrigerant-water heat exchanger 32 to be boiled. After that, if the determination unit 73 determines that the latter temperature difference is less than the former, as described above, the opening and closing mechanism 5 is switched to perform control not to allow the low stage side refrigerant to flow to the low stage side refrigerant-water heat exchanger 32. In this case, whether or not to heat the water using the high stage side refrigerant-water heat exchanger 62 depends on the setting as described above.

[0089] As described above, when deciding whether to use the low stage side refrigerant-water heat exchanger 32, that is, when switching whether to flow the low stage side refrigerant to the low stage side refrigerant-water heat exchanger 32 or to the cascade heat exchanger 31 through the opening and closing of the opening and closing mechanism 5, information on the water temperature detected by the water temperature sensor 42 provided in the hot water storage tank 41 is used. The water temperature sensor 42 is disposed in the lower part of the hot water storage tank.

[0090] This is for detecting and using the lower water temperature among the temperatures of the water stored in the hot water storage tank 41 when determining whether or not to use the low stage side refrigerant-water heat exchanger 32. That is, by using such a water temperature and comparing it with the water temperature threshold value, or by comparing the temperature difference between the water temperature and the low stage side refrigerant temperature with the temperature difference threshold value, not only the high stage side refrigerant-water heat exchanger 62 but also the low stage side refrigerant-water heat exchanger 32 can be effectively used to the maximum extent when performing hot water supply operation. By effectively using the low stage side refrigerant-water heat exchanger 32, the water stored in the hot water storage tank 41 can be boiled up early.

[0091] [Operation] Next, the process of boiling up the water stored inside the hot water storage tank 41 in the cascade refrigeration cycle apparatus 100 in the embodiment of the present invention will be described with reference to Fig. 5 and Fig. 6. Fig. 5 and Fig. 6 are flowcharts showing the flow of control of the cascade refrigeration cycle apparatus 100 in the embodiment of the present invention. Note that the boiling process described below is premised on the fact that the indoor unit 2 is performing heating operation.

[0092] First, the control device 7 determines whether or not the hot water supply operation has started (ST1). The control device 7 waits until the hot water supply operation starts (NO in ST1). On the other hand, when the hot water supply operation starts (YES in ST1), the water temperature threshold value is first set (ST2).

[0093] As described above, the water temperature threshold is affected by the temperature of the low-stage side refrigerant. Therefore, the determination unit 73 acquires information on the temperature of the low-stage side refrigerant acquired by the indoor heat exchanger temperature sensor 24 via the detection unit 71. The determination unit 73 sets the water temperature threshold based on the temperature of the low-stage side refrigerant, and stores it in the storage unit 72.

[0094] Also, information on the temperature of the water stored in the hot water tank 41 is acquired from the water temperature sensor 42 via the detection unit 71 (ST3). Then, the determination unit 73 compares the acquired water temperature with a preset water temperature threshold value stored in the memory unit 72 (ST4).

[0095] If the comparison by the judgment unit 73 shows that the water temperature is below the water temperature threshold value (YES in ST4), the opening and closing mechanism control unit 74 is instructed to allow low-side refrigerant to flow at least through the low-side refrigerant-water heat exchanger 32, and the opening and closing mechanism 5 is opened and closed (ST5).

[0096] Specifically, the second on-off valve 53 and the second expansion valve 54 are opened so that the low stage side refrigerant flows to the low stage side refrigerant-water heat exchanger 32. On the other hand, since the low stage side refrigerant is not flowed to the cascade heat exchanger 31 which exchanges heat with the high stage side refrigerant, the on-off mechanism control unit 74 closes the first on-off valve 51 and the second expansion valve 52.

[0097] Furthermore, the determination unit 73 acquires the temperature of the low-stage side refrigerant acquired by the low-stage side refrigerant temperature sensor 33 via the detection unit 71 (ST6). Similarly, the determination unit 73 also acquires information on the water temperature from the water temperature sensor 42, and calculates the temperature difference between the low-stage side refrigerant temperature and the water temperature (ST7).

[0098] Then, the determination unit 73 compares the temperature difference with a temperature difference threshold value and determines whether the temperature difference is smaller than the temperature difference threshold value (ST8). As a result, if the temperature difference indicates a value equal to or larger than the temperature difference threshold value (NO in ST8), the low-side refrigerant continues to flow through the low-side refrigerant-water heat exchanger 32 and is used to heat water.

[0099] On the other hand, if the temperature difference is smaller than the temperature difference threshold (YES in ST8), the opening and closing mechanism 5 is switched so that the refrigerant flows only to the cascade heat exchanger 31 (ST9 in FIG. 6). This is because when the temperature difference between the water temperature and the low-side refrigerant temperature is small, effective heat exchange cannot be performed in the low-side refrigerant-water heat exchanger 32.

[0100] Therefore, in this case, the first on-off valve 51 and the first expansion valve 52 are opened, and the second on-off valve 53 and the second expansion valve 54 are closed so that the low-temperature side refrigerant flows only through the cascade heat exchanger 31.

[0101] While controlling the opening / closing mechanism 5 in this way, the water stored inside the hot water storage tank 41 is heated. The determination unit 73 further determines whether the temperature of the water in the hot water storage tank 41 has reached the target temperature based on the water temperature information from the water temperature sensor 42 (ST10). If the water temperature has not reached the target temperature (NO in ST10), the process returns to step ST2, where the water temperature threshold is set again, and the control described above is performed so that the water temperature reaches the target temperature.

[0102] On the other hand, when the determination unit 73 determines that the water temperature has reached the target temperature (YES in ST10), the control device 7 controls the water temperature to maintain the target temperature by using only the high-temperature side refrigerant-water heat exchanger 62 (ST11). Then, it is further determined whether the hot water supply operation has ended (ST12).

[0103] If the hot water supply operation has not ended (NO in ST12), control is continued to maintain the water temperature at the target temperature. On the other hand, if the hot water supply operation has ended (YES in ST12), control of the opening and closing mechanism 5 by the control device 7 ends.

[0104] After the hot water supply operation has started, when the judgment unit 73 compares the water temperature in the hot water storage tank 41 with the water temperature threshold value (ST4), if it judges that the water temperature exceeds the water temperature threshold value (NO in ST4), it instructs the opening and closing mechanism control unit 74 not to flow the low-side refrigerant through the low-side refrigerant-water heat exchanger 32, and to flow the low-side refrigerant only through the cascade heat exchanger 31 (ST13).

[0105] Specifically, the control unit 73 performs control to open the first on-off valve 51 and the first expansion valve 52, and close the second on-off valve 53 and the second expansion valve 54. After that, the determination unit 73 determines whether the water temperature has reached the target temperature (ST10).

[0106] By adopting the configuration described above and controlling the opening and closing mechanism, it is possible to provide a dual refrigeration cycle device and a control method for a dual refrigeration cycle device that can reduce the size of the high-side refrigerant circuit that supplies hot water to the hot water heater from the perspective of installation, while shortening the boiling time from the perspective of hot water supply capacity.

[0107] It should be noted that the present invention is not limited to the above-described embodiment, but is merely an example of the present invention. In the implementation stage, the components can be modified without departing from the gist of the invention, and various modifications and improvements can be made to the above-described embodiment. In addition, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiment.

[0108] For example, some of the components shown in the embodiment may be deleted. Furthermore, components from different embodiments may be appropriately combined, and such modified or improved forms may also be included in the present invention. Such embodiments and modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0109] In the explanation so far, the water temperature threshold value has been set based on the temperature of the low-stage side refrigerant detected by the indoor heat exchanger temperature sensor 24. This is on the premise that the indoor unit 2 is performing heating operation. Therefore, if the indoor unit is stopped, the judgment unit 73 sets the water temperature threshold value from the viewpoint of how much the low-stage side compressor 11 should operate (revolve) in order to perform the hot water supply operation most efficiently.

[0110] Furthermore, the techniques described in the embodiments of the present invention may also employ the following configurations. (1) a low-stage side refrigerant circuit in which a low-stage side compressor, an indoor heat exchanger, a low-stage side expansion valve, and an outdoor heat exchanger are connected and in which a low-stage side refrigerant circulates; A cascade heat exchanger connected in parallel to the indoor heat exchanger, and a low-temperature side refrigerant-water heat exchanger; an opening / closing mechanism for switching the flow of the low-temperature side refrigerant to the cascade heat exchanger and the low-temperature side refrigerant-water heat exchanger; a high-stage side refrigerant circuit in which a high-stage side compressor, a high-stage side refrigerant-water heat exchanger, a high-stage side expansion valve, and the cascade heat exchanger are connected and in which a high-stage side refrigerant circulates; a hot water storage tank including the low stage side refrigerant-water heat exchanger and the high stage side refrigerant-water heat exchanger therein, in which water stored therein is heated by the low stage side refrigerant-water heat exchanger and the high stage side refrigerant-water heat exchanger; A control device for controlling the opening and closing mechanism, The control device controls the opening and closing mechanism so that the low-side refrigerant flows through at least one of the low-side refrigerant-water heat exchanger and the cascade heat exchanger during hot water supply operation. (2) The hot water storage tank is provided with a water temperature sensor that detects the temperature of the water stored in the hot water storage tank; The control device is characterized in that, when the water temperature detected by the water temperature sensor is equal to or lower than a water temperature threshold value, the control device controls the opening and closing mechanism so that the low-side refrigerant flows through the low-side refrigerant-water heat exchanger. (3) a low-stage side refrigerant circuit in which a low-stage side compressor, an indoor heat exchanger, a low-stage side expansion valve, and an outdoor heat exchanger are connected and in which a low-stage side refrigerant circulates; A cascade heat exchanger connected in parallel to the indoor heat exchanger, and a low-temperature side refrigerant-water heat exchanger; an opening / closing mechanism for switching the flow of the low-temperature side refrigerant to the cascade heat exchanger and the low-temperature side refrigerant-water heat exchanger; a high-stage side refrigerant circuit in which a high-stage side compressor, a high-stage side refrigerant-water heat exchanger, a high-stage side expansion valve, and the cascade heat exchanger are connected and in which a high-stage side refrigerant circulates; a hot water storage tank connected to the low stage side refrigerant-water heat exchanger and the high stage side refrigerant-water heat exchanger via piping, in which water stored therein is heated by the low stage side refrigerant-water heat exchanger and the high stage side refrigerant-water heat exchanger; a water temperature sensor provided in the hot water storage tank for detecting a temperature of the water stored in the hot water storage tank; A control device for controlling the opening and closing mechanism, The control device is characterized in that, during hot water supply operation, when the water temperature detected by the water temperature sensor is equal to or lower than a water temperature threshold value, the control device controls the opening and closing mechanism so that the low-side refrigerant flows into the low-side refrigerant-water heat exchanger. (4) The control device is characterized in that, when the water temperature detected by the water temperature sensor is equal to or lower than the water temperature threshold value, the control device controls the opening and closing mechanism so that the low-side refrigerant flows to the cascade heat exchanger in addition to the low-side refrigerant-water heat exchanger. (5) The dual refrigeration cycle apparatus described in (2) or (3) above, characterized in that when the water temperature detected by the water temperature sensor exceeds the water temperature threshold value, the control device controls the opening and closing mechanism so that the low-side refrigerant flows only through the cascade heat exchanger. (6) A low-temperature side refrigerant temperature sensor is provided to detect the temperature of the low-temperature side refrigerant flowing through the low-temperature side refrigerant-water heat exchanger, The control device is characterized in that, when a temperature difference between the water temperature detected by the water temperature sensor and the temperature of the low-stage side refrigerant detected by the low-stage side refrigerant temperature sensor is less than a temperature difference threshold, the control device controls the opening and closing mechanism so that the low-stage side refrigerant flows only through the cascade heat exchanger. (7) An indoor heat exchanger temperature sensor is provided to detect the temperature of the low-temperature side refrigerant flowing through the indoor heat exchanger, The cascade refrigeration cycle device according to any one of (2) to (6) above, characterized in that the water temperature threshold is set based on the temperature of the low-side refrigerant detected by the indoor heat exchanger temperature sensor. (8) A binary refrigeration cycle apparatus as described in (1) or (2) above, characterized in that the high-side refrigerant-water heat exchanger connected to the hot water storage tank is positioned above the low-side refrigerant-water heat exchanger when the hot water storage tank is installed. (9) A dual refrigeration cycle device as described in any of (1) to (8) above, characterized in that the water temperature sensor is positioned below the vertical center of the hot water storage tank when the hot water storage tank is installed. (10) The cascade refrigeration cycle apparatus according to any one of (1) to (9) above, wherein the displacement volume of the high-stage side compressor is smaller than the displacement volume of the low-stage side compressor. (11) The cascade refrigeration cycle apparatus according to any one of (1) to (10) above, wherein the high-side refrigerant used in the high-side refrigeration cycle is an R290 refrigerant. (12) a low-stage side refrigerant circuit in which a low-stage side compressor, an indoor heat exchanger, a low-stage side expansion valve, and an outdoor heat exchanger are connected and in which a low-stage side refrigerant circulates; A cascade heat exchanger connected in parallel to the indoor heat exchanger, and a low-temperature side refrigerant-water heat exchanger; an opening / closing mechanism for switching the inflow and outflow of the low-temperature side refrigerant to the cascade heat exchanger and the low-temperature side refrigerant-water heat exchanger; a high-stage side refrigerant circuit in which a high-stage side compressor, a high-stage side refrigerant-water heat exchanger, a high-stage side expansion valve, and the cascade heat exchanger are connected and in which a high-stage side refrigerant circulates; a hot water storage tank that includes the low stage side refrigerant-water heat exchanger and the high stage side refrigerant-water heat exchanger therein or is connected via piping, and in which water stored therein is heated by the low stage side refrigerant-water heat exchanger and the high stage side refrigerant-water heat exchanger; A control device for controlling the opening and closing mechanism, During hot water supply operation, setting a water temperature threshold value to be compared with the temperature of the water stored in the hot water storage tank; comparing the water temperature with the water temperature threshold; based on a comparison result between the water temperature and the water temperature threshold value, controlling the opening and closing mechanism so that the low-temperature side refrigerant flows through at least one of the low-temperature side refrigerant-water heat exchanger and the cascade heat exchanger; A control method for a binary refrigeration cycle apparatus comprising: (13) In the step of controlling the opening and closing mechanism, The control method for a binary refrigeration cycle apparatus described in (12) above, characterized in that, when the result of comparing the water temperature with the water temperature threshold value indicates that the water temperature is equal to or lower than the water temperature threshold value, the opening and closing mechanism is controlled so that the low-side refrigerant flows into the low-side refrigerant-water heat exchanger. (14) In the step of controlling the opening and closing mechanism, The control method for a binary refrigeration cycle apparatus described in (13) above, characterized in that when the water temperature is equal to or lower than the water temperature threshold value, the opening and closing mechanism is controlled so that the low-side refrigerant flows to the cascade heat exchanger in addition to the low-side refrigerant-water heat exchanger. (15) In the step of controlling the opening and closing mechanism, The binary refrigeration cycle apparatus according to (12) above, characterized in that when the water temperature exceeds the water temperature threshold value, the opening and closing mechanism is controlled so that the low-temperature side refrigerant flows only through the cascade heat exchanger. (16) In the step of controlling the opening and closing mechanism, The control method for a binary refrigeration cycle apparatus described in (12) above, characterized in that when a temperature difference between the water temperature and the temperature of the low-stage side refrigerant flowing through the low-stage side refrigerant-water heat exchanger is less than a temperature difference threshold, the opening and closing mechanism is controlled so that the low-stage side refrigerant flows only through the cascade heat exchanger. (17) A method for controlling a cascade refrigeration cycle apparatus according to any one of (12) to (16) above, characterized in that the water temperature threshold is set based on the temperature of the low-side refrigerant flowing through the indoor heat exchanger. [Explanation of symbols]

[0111] 1 outdoor unit, 2 indoor unit, 3 hot water supply device, 4 hot water supply device, 5 opening / closing mechanism, 7 control device, 11 low-temperature side compressor, 12 four-way valve, 13 outdoor heat exchanger, 14 outdoor fan, 21 indoor unit heat exchanger, 22 low-temperature side expansion valve, 23 indoor fan, 24 indoor heat exchanger temperature sensor, 31 cascade heat exchanger, 32 low-temperature side refrigerant-water heat exchanger, 33 low-temperature side refrigerant temperature sensor, 34 pot pump, 41...hot water storage tank, 42...water temperature sensor, 51...first on-off valve, 52...first expansion valve, 53...second on-off valve, 54...second expansion valve, 61...high-stage side compressor, 62...high-stage side refrigerant-water heat exchanger, 63...high-stage side expansion valve, 71...detection unit, 72...storage unit, 73...determination unit, 74...on-off mechanism control unit, 100, 100A...cascade refrigeration cycle device, HC...high-stage side refrigerant circuit, LC...low-stage side refrigerant circuit

Claims

1. a low-stage side refrigerant circuit in which a low-stage side compressor, an indoor heat exchanger, a low-stage side expansion valve, and an outdoor heat exchanger are connected and in which a low-stage side refrigerant circulates; A cascade heat exchanger connected in parallel to the indoor heat exchanger, and a low-temperature side refrigerant-water heat exchanger; an opening / closing mechanism for switching the flow of the low-temperature side refrigerant to the cascade heat exchanger and the low-temperature side refrigerant-water heat exchanger; a high-stage side refrigerant circuit in which a high-stage side compressor, a high-stage side refrigerant-water heat exchanger, a high-stage side expansion valve, and the cascade heat exchanger are connected and in which a high-stage side refrigerant circulates; A hot water storage tank including the low-stage refrigerant-water heat exchanger and the high-stage refrigerant-water heat exchanger therein, in which water stored therein is heated by the low-stage refrigerant-water heat exchanger and the high-stage refrigerant-water heat exchanger; A control device for controlling the opening and closing mechanism, The control device controls the opening and closing mechanism so that the low-side refrigerant flows through at least one of the low-side refrigerant-water heat exchanger and the cascade heat exchanger during hot water supply operation.

2. The hot water storage tank is provided with a water temperature sensor for detecting the temperature of the water stored in the hot water storage tank; The control device controls the opening and closing mechanism so that the low-side refrigerant flows into the low-side refrigerant-water heat exchanger when the water temperature detected by the water temperature sensor is equal to or lower than a water temperature threshold value. The binary refrigeration cycle device according to claim 1,

3. a low-stage side refrigerant circuit in which a low-stage side compressor, an indoor heat exchanger, a low-stage side expansion valve, and an outdoor heat exchanger are connected and in which a low-stage side refrigerant circulates; A cascade heat exchanger connected in parallel with the indoor heat exchanger, and a low-temperature side refrigerant-water heat exchanger; an opening / closing mechanism for switching the flow of the low-temperature side refrigerant to the cascade heat exchanger and the low-temperature side refrigerant-water heat exchanger; a high-stage side refrigerant circuit in which a high-stage side compressor, a high-stage side refrigerant-water heat exchanger, a high-stage side expansion valve, and the cascade heat exchanger are connected and in which a high-stage side refrigerant circulates; A hot water storage tank connected to the low stage side refrigerant-water heat exchanger and the high stage side refrigerant-water heat exchanger via piping, in which water stored therein is heated by the low stage side refrigerant-water heat exchanger and the high stage side refrigerant-water heat exchanger; a water temperature sensor provided in the hot water storage tank for detecting a temperature of the water stored in the hot water storage tank; A control device for controlling the opening and closing mechanism, The control device is characterized in that, during hot water supply operation, when the water temperature detected by the water temperature sensor is below a water temperature threshold value, the control device controls the opening and closing mechanism so that the low-side refrigerant flows into the low-side refrigerant-water heat exchanger.

4. The control device controls the opening and closing mechanism so that the low-side refrigerant flows to the cascade heat exchanger in addition to the low-side refrigerant-water heat exchanger when the water temperature detected by the water temperature sensor is equal to or lower than the water temperature threshold value. The binary refrigeration cycle device according to claim 2 or 3,

5. 4. The dual refrigeration cycle apparatus according to claim 2, wherein the control device controls the opening and closing mechanism so that the low-side refrigerant flows only through the cascade heat exchanger when the water temperature detected by the water temperature sensor exceeds the water temperature threshold value.

6. a low-temperature side refrigerant temperature sensor for detecting the temperature of the low-temperature side refrigerant flowing through the low-temperature side refrigerant-water heat exchanger; 4. The dual refrigeration cycle apparatus according to claim 2, wherein the control device controls the opening and closing mechanism so that the low-stage side refrigerant flows only through the cascade heat exchanger when a temperature difference between the water temperature detected by the water temperature sensor and the temperature of the low-stage side refrigerant detected by the low-stage side refrigerant temperature sensor is less than a temperature difference threshold.

7. an indoor heat exchanger temperature sensor for detecting a temperature of the low-temperature side refrigerant flowing through the indoor heat exchanger; 4. The cascade refrigeration cycle apparatus according to claim 2, wherein the water temperature threshold value is set based on a temperature of the low-temperature side refrigerant detected by the indoor heat exchanger temperature sensor.

8. A binary refrigeration cycle apparatus as described in either claim 1 or claim 2, characterized in that the high-side refrigerant-water heat exchanger connected to the hot water storage tank is positioned above the low-side refrigerant-water heat exchanger when the hot water storage tank is installed.

9. 4. A dual refrigeration cycle apparatus as described in claim 1, wherein the water temperature sensor is arranged below the vertical center of the hot water storage tank when the hot water storage tank is installed.

10. 4. The cascade refrigeration cycle apparatus according to claim 1, wherein a displacement volume of the high-stage side compressor is smaller than a displacement volume of the low-stage side compressor.

11. 4. The cascade refrigeration cycle apparatus according to claim 1, wherein the high-stage refrigerant used in the high-stage refrigerant circuit is an R290 refrigerant.

12. a low-stage side refrigerant circuit in which a low-stage side compressor, an indoor heat exchanger, a low-stage side expansion valve, and an outdoor heat exchanger are connected and in which a low-stage side refrigerant circulates; A cascade heat exchanger connected in parallel with the indoor heat exchanger, and a low-temperature side refrigerant-water heat exchanger; An opening / closing mechanism for switching the inflow and outflow of the low-temperature side refrigerant to the cascade heat exchanger and the low-temperature side refrigerant-water heat exchanger; a high-stage side refrigerant circuit in which a high-stage side compressor, a high-stage side refrigerant-water heat exchanger, a high-stage side expansion valve, and the cascade heat exchanger are connected and in which a high-stage side refrigerant circulates; A hot water storage tank that includes the low-stage side refrigerant-water heat exchanger and the high-stage side refrigerant-water heat exchanger or is connected via piping, and water stored therein is heated by the low-stage side refrigerant-water heat exchanger and the high-stage side refrigerant-water heat exchanger; A control device for controlling the opening and closing mechanism, During hot water supply operation, setting a water temperature threshold value to be compared with the temperature of the water stored in the hot water storage tank; comparing the water temperature with the water temperature threshold; Based on a comparison result between the water temperature and the water temperature threshold value, controlling the opening and closing mechanism so that the low-temperature side refrigerant flows into at least one of the low-temperature side refrigerant-water heat exchanger and the cascade heat exchanger; A control method for a binary refrigeration cycle apparatus comprising:

13. In the step of controlling the opening and closing mechanism, The control method for a binary refrigeration cycle apparatus according to claim 12, characterized in that, when the result of comparing the water temperature with the water temperature threshold value indicates that the water temperature is equal to or lower than the water temperature threshold value, the opening and closing mechanism is controlled so that the low-stage side refrigerant flows into the low-stage side refrigerant-water heat exchanger.

14. In the step of controlling the opening and closing mechanism, The control method for a binary refrigeration cycle apparatus according to claim 13, characterized in that, when the water temperature is equal to or lower than the water temperature threshold value, the opening and closing mechanism is controlled so that the low-side refrigerant flows into the cascade heat exchanger in addition to the low-side refrigerant-water heat exchanger.

15. In the step of controlling the opening and closing mechanism, The cascade refrigeration cycle apparatus according to claim 12, characterized in that, when the water temperature exceeds the water temperature threshold value, the opening and closing mechanism is controlled so that the low-temperature side refrigerant flows only through the cascade heat exchanger.

16. In the step of controlling the opening and closing mechanism, The control method for a binary refrigeration cycle apparatus according to claim 12, characterized in that, when a temperature difference between the water temperature and the temperature of the low-stage side refrigerant flowing through the low-stage side refrigerant-water heat exchanger is less than a temperature difference threshold, the opening and closing mechanism is controlled so that the low-stage side refrigerant flows only through the cascade heat exchanger.

17. 17. The method for controlling a cascade refrigeration cycle apparatus according to claim 12, wherein the water temperature threshold value is set based on a temperature of the low-stage refrigerant flowing through the indoor heat exchanger.

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