Refrigeration Cycle Equipment

Abstract

In a refrigeration cycle device equipped with a heat storage heat exchanger, the capacity of the refrigeration cycle device is prevented from decreasing by preventing refrigerant from stagnating inside the heat storage heat exchanger and minimizing the reduction in the amount of refrigerant circulating through the refrigerant circuit. [Solution] The system comprises a refrigerant circuit C having a compressor 1 that compresses the refrigerant, an indoor heat exchanger 2 that exchanges heat between the refrigerant and indoor air, an outdoor heat exchanger 3 that exchanges heat between the refrigerant and outdoor air, a heat storage heat exchanger 4 that exchanges heat between a heat storage material and the refrigerant, and an expansion valve 5 whose opening is adjustable, a heat storage temperature sensor HS that detects the heat storage temperature, which is the temperature of the heat storage heat exchanger 4, and a control device 7 that controls the expansion valve 5, and during heating operation, the control device 7 performs stagnation prevention control by adjusting the opening of the expansion valve based on the heat storage temperature so that refrigerant stagnating inside the heat storage heat exchanger 4 flows out of the heat storage heat exchanger 4.

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a refrigeration cycle device. [Background technology]

[0002] Generally, when an air conditioner is in heating operation, the indoor heat exchanger functions as a condenser, and the outdoor heat exchanger functions as an evaporator. In this case, a refrigerant with a temperature lower than the outdoor air temperature flows through the outdoor heat exchanger. Therefore, for example, when the outdoor air temperature is below freezing, if the refrigerant temperature falls below the dew point of the outdoor air, frost will form on the outdoor heat exchanger, making it difficult to exchange heat with the outdoor air. Therefore, when the air conditioner is in heating operation, a defrosting operation is periodically performed to remove frost from the outdoor heat exchanger.

[0003] Such defrosting operation is necessary for operating an air conditioner, and is typically performed by interrupting heating operation. Specifically, when starting defrosting operation, the refrigerant circuit is switched so that refrigerant discharged from the compressor is directly supplied to the outdoor heat exchanger. That is, defrosting is performed by making the indoor heat exchanger function as an evaporator and the outdoor heat exchanger function as a condenser. In defrosting operation, the high-temperature refrigerant supplied to the outdoor heat exchanger for defrosting melts the frost, drops in temperature, and then passes through an expansion valve to reduce its pressure and become a low-temperature refrigerant, which then flows into the indoor heat exchanger.

[0004] When such a defrosting operation is performed, heating operation is stopped and the indoor temperature gradually drops during the defrosting operation, reducing user comfort. Therefore, a possible method is to place a heat storage tank (heat storage device) separate from the indoor heat exchanger in the refrigerant circuit, as in the heat storage air conditioner shown in Patent Document 1 below, and use the heat stored in the heat storage material of the heat storage device for defrosting during the defrosting operation, thereby allowing heating operation to continue even during the defrosting operation. This method prevents the indoor temperature from dropping due to the temporary stop of heating operation for the defrosting operation, thereby maintaining user comfort.

[0005] When a heat storage device is provided in the refrigerant circuit, for example, during heating operation, the refrigerant discharged from the compressor is condensed in the indoor heat exchanger. That is, the indoor exchanger functions as a condenser, exchanging heat between the refrigerant and the indoor air to supply warm air to the room. The refrigerant flowing out of the indoor heat exchanger flows into the outdoor heat exchanger via an expansion valve and then into the compressor.

[0006] In such heating operation, when there is no need to exchange heat between the refrigerant and the heat storage material in the heat storage device, there is no need to flow the refrigerant from the compressor to the heat storage device. Therefore, by closing the expansion valve provided between the compressor and the heat storage device, the refrigerant discharged from the compressor is prevented from flowing into the heat storage device. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-017738 Summary of the Invention [Problem to be solved by the invention]

[0008] When the heating operation is performed in this way, the expansion valve is closed to prevent the refrigerant from flowing into the heat storage device, but the expansion valve is designed to allow a small amount of refrigerant to flow even when fully closed, so the flow of refrigerant cannot be completely blocked. In other words, even during heating operation, a small amount of refrigerant flows from the compressor into the heat storage device through the closed expansion valve.

[0009] In many cases, heat storage devices are installed outdoors. When the outdoor temperature is low, the refrigerant that flows into the heat storage device, exposed to the outside air and cooled to a low temperature, condenses and liquefies inside the heat storage device. This means that the liquid-phase refrigerant remains inside the heat storage device. Furthermore, the density of the liquid-phase refrigerant is high, so the amount of refrigerant circulating through the refrigerant circuit decreases. This decrease in the amount of refrigerant circulating through the refrigerant circuit can lead to a decrease in the capacity of the refrigeration cycle device.

[0010] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a refrigeration cycle device equipped with a heat storage heat exchanger, which can prevent refrigerant from stagnating inside the heat storage heat exchanger and minimize the reduction in the amount of refrigerant circulating through the refrigerant circuit, thereby suppressing a decrease in the capacity of the refrigeration cycle device. [Means for solving the problem]

[0011] A refrigeration cycle device according to one aspect of the present invention includes a refrigerant circuit having a compressor that compresses a refrigerant, an indoor heat exchanger that exchanges heat between indoor air and the refrigerant, an outdoor heat exchanger that exchanges heat between outdoor air and the refrigerant, a heat storage heat exchanger that exchanges heat between a heat storage material and the refrigerant, and an expansion valve whose opening is adjustable; a heat storage temperature sensor that detects a heat storage temperature, which is the temperature of the heat storage heat exchanger; and a control device that controls the expansion valve, wherein the control device, during heating operation, When it is determined that there is a possibility that the refrigerant may be stagnating inside the heat storage heat exchanger based on the heat storage temperature, Based on the heat storage temperature, stagnation prevention control is performed to adjust the opening of the expansion valve so that the refrigerant stagnated inside the heat storage heat exchanger flows out of the heat storage heat exchanger. In addition, a refrigeration cycle device according to one embodiment of the present invention includes a refrigerant circuit having a compressor that compresses a refrigerant, an indoor heat exchanger that exchanges heat between the refrigerant and indoor air, an outdoor heat exchanger that exchanges heat between the refrigerant and outdoor air, a heat storage heat exchanger that exchanges heat between a heat storage material and the refrigerant, an expansion valve with an adjustable opening, a heat storage temperature sensor that detects the heat storage temperature, which is the temperature of the heat storage heat exchanger, an outdoor air temperature detection sensor that detects the outdoor air temperature, and a control device that controls the expansion valve, and when the control device determines that the outdoor air temperature detected by the outdoor air temperature detection sensor is equal to or higher than a predetermined value set as a frost formation condition during heating operation, the control device performs retention prevention control that adjusts the opening of the expansion valve based on the heat storage temperature so as to allow the refrigerant remaining inside the heat storage heat exchanger to flow out of the heat storage heat exchanger. Furthermore, a refrigeration cycle device according to one aspect of the present invention includes a refrigerant circuit having a compressor that compresses a refrigerant, an indoor heat exchanger that exchanges heat between indoor air and the refrigerant, an outdoor heat exchanger that exchanges heat between outdoor air and the refrigerant, a heat storage heat exchanger that exchanges heat between a heat storage material and the refrigerant, and an expansion valve whose opening is adjustable; a heat storage temperature sensor that detects a heat storage temperature that is the temperature of the heat storage heat exchanger; and a control device that controls the expansion valve, wherein the control device executes a stagnation prevention control that adjusts the opening of the expansion valve based on the heat storage temperature so that refrigerant stagnated inside the heat storage heat exchanger flows out of the heat storage heat exchanger, and a normal heating control, and when the stagnation prevention control is executed by the control device, the indoor heat exchanger and the heat storage heat exchanger function as condensers. The expansion valve is controlled so that the outdoor heat exchanger functions as an evaporator, and the outdoor heat exchanger functions as an evaporator. When normal heating control is performed by the control device, only the outdoor heat exchanger and the indoor heat exchanger function, the indoor heat exchanger functions as a condenser, and the outdoor heat exchanger functions as an evaporator. The control device compares the heat storage temperature with an end judgment value for determining whether to end the retention prevention control. If the control device determines that the heat storage temperature is equal to or greater than the end judgment value, the control device transitions from retention prevention control to normal heating control. The end judgment value is lower than the value of the heat storage temperature in the heat storage completion condition that is preset and used to determine whether to end the heat storage heating control, which stores heat to be used during defrosting operation performed by the control device during heating operation. [Effects of the Invention]

[0012] According to the present invention, in a refrigeration cycle device equipped with a heat storage heat exchanger, it is possible to prevent refrigerant from stagnating inside the heat storage device and minimize the reduction in the amount of refrigerant circulating through the refrigerant circuit, thereby suppressing a decrease in the capacity of the refrigeration cycle device. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a refrigerant circuit diagram of a refrigeration cycle device according to an embodiment of the present invention. [Figure 2] 1 is a refrigerant circuit diagram showing the flow of refrigerant when a refrigeration cycle device according to an embodiment of the present invention performs cooling operation. [Figure 3]3 is a refrigerant circuit diagram showing the flow of refrigerant when the refrigeration cycle device according to the embodiment of the present invention performs heating operation based on normal heating control. FIG. [Figure 4] 3 is a refrigerant circuit diagram showing the flow of refrigerant when the refrigeration cycle device according to the embodiment of the present invention performs heating operation based on stagnation prevention control. FIG. [Figure 5] 1 is a block diagram showing an internal configuration of a control device in a refrigeration cycle apparatus according to an embodiment of the present invention. [Figure 6] 4 is a flowchart showing a flow of retention prevention control in the refrigeration cycle device according to the embodiment of the present invention. [Figure 7] 5 is a flowchart showing a control flow in a first modified example of retention prevention control in the refrigeration cycle device according to the embodiment of the present invention. [Figure 8] 10 is a flowchart showing a control flow in a second modified example of retention prevention control in the refrigeration cycle device according to the embodiment of the present invention. [Figure 9] 4 is a flowchart showing a flow of selecting between retention prevention control and thermal heating control in the refrigeration cycle apparatus according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The structure of a refrigeration cycle apparatus S 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 refrigeration cycle apparatus S according to the embodiment of the present invention. The refrigeration cycle apparatus S includes a refrigerant circuit C that connects a compressor 1, an indoor heat exchanger 2, an outdoor heat exchanger 3, a heat storage heat exchanger 4, expansion valves 5 (51, 52, 53), and switching valves 6 (61, 62) and circulates a refrigerant. The refrigeration cycle apparatus S also includes a control device 7 that controls the expansion valve 5 and the switching valve 6.

[0015] In addition, when the stagnation prevention operation described below is performed, the connection point between the pipe through which the refrigerant flows when it flows out of the indoor heat exchanger 2 and into the outdoor heat exchanger 3 via the third expansion valve 53, and the pipe midway along the pipe through which the refrigerant flows when it flows out of the heat storage heat exchanger 4 and into the outdoor heat exchanger 3 via the second expansion valve 52, will be referred to as connection point C1 below.

[0016] The compressor 1 compresses the refrigerant circulating through the refrigerant circuit C. The indoor heat exchanger 2 exchanges heat between the indoor air and the refrigerant. The outdoor heat exchanger 3 exchanges heat between the outdoor air and the refrigerant. Although a detailed description of the types of the compressor 1, indoor heat exchanger 2, and outdoor heat exchanger 3 will be omitted here, various types of equipment can be used.

[0017] An evaporation temperature detection sensor ES is provided in the outdoor heat exchanger 3. The evaporation temperature detection sensor ES detects the evaporation temperature of the refrigerant when the outdoor unit functions as an evaporator. Therefore, in the embodiment of the present invention, the evaporation temperature detection sensor ES is disposed in a position as shown in Fig. 1, for example, but is not limited to the above position as long as it can detect the evaporation temperature of the refrigerant.

[0018] The evaporation temperature of the refrigerant in the outdoor unit detected by the evaporation temperature detection sensor ES is used to determine whether the refrigerant will flow into the heat storage heat exchanger 4 through the second expansion valve 52 and condense and stagnate inside the heat storage heat exchanger 4, i.e., whether the control device 7 described later will perform stagnation prevention control.

[0019] The outdoor unit is also provided with an outdoor air temperature detection sensor OS. The outdoor air temperature detection sensor OS detects the outdoor air temperature, which is the temperature outside where the outdoor unit is installed. The location of the outdoor air temperature detection sensor OS is not limited to the location shown in FIG. 1. Information about the outdoor air temperature detected by the outdoor air temperature detection sensor OS is used when determining whether or not to execute the above-mentioned retention prevention control.

[0020] The thermal storage heat exchanger 4 is a heat exchanger that performs heat exchange between a thermal storage material and a refrigerant that passes through the thermal storage heat exchanger 4. The thermal storage heat exchanger 4 has a structure in which, for example, a heat transfer tube with fins on the outside of the tube and a thermal storage material are housed in a container, and heat exchange between the thermal storage material and the refrigerant occurs as the refrigerant passes through the inside of the heat transfer tube.

[0021] The heat storage material may be liquid or solid, as long as it can store heat by exchanging heat with the refrigerant flowing inside the heat storage heat exchanger 4. The heat storage material stores the heat supplied from the refrigerant.

[0022] The heat stored in the heat storage heat exchanger 4 is used, for example, during defrosting operation. By using the heat stored in the heat storage heat exchanger 4 for defrosting operation, it is possible to perform defrosting heating operation without stopping heating operation during defrosting operation. In addition, the heat stored in the heat storage heat exchanger 4 is used by retention prevention control, which will be described later, to cause the refrigerant retained in the heat storage heat exchanger 4 to flow from the inside to the outside of the heat storage heat exchanger.

[0023] The heat storage heat exchanger 4 is also provided with a heat storage temperature sensor HS that detects the heat storage temperature, which is the temperature of the heat storage heat exchanger 4. That is, in the refrigeration cycle apparatus S according to the embodiment of the present invention, control is performed to prevent the refrigerant from accumulating inside the heat storage heat exchanger 4, and at that time, whether or not to perform the control is determined based on the temperature of the refrigerant accumulating inside the heat storage heat exchanger 4.

[0024] Therefore, the heat-storage temperature sensor HS detects the temperature of the refrigerant accumulating inside the heat-storage heat exchanger 4. More specifically, it detects the temperature of the heat storage material provided inside the heat-storage heat exchanger 4.

[0025] The heat storage temperature sensor HS may be only one or may be multiple. When multiple heat storage temperature sensors HS are provided, the detected temperature of the heat storage material may be calculated, for example, by taking the average value of the values ​​detected by the respective heat storage temperature sensors HS as the temperature of the heat storage material, and used for control, which will be described later.

[0026] The opening degree of the expansion valve 5 can be adjusted based on an instruction from a control device 7, which will be described later, and a plurality of expansion valves are provided in the refrigeration cycle apparatus S in the embodiment of the present invention. Specifically, three expansion valves are provided, and the first expansion valve 51 is provided upstream in the refrigerant flow direction when the thermal storage heat exchanger 4 functions as a condenser.

[0027] The second expansion valve 52 is provided between the heat storage heat exchanger 4 and the outdoor heat exchanger 3. That is, it is provided downstream in the direction of refrigerant flow when the heat storage heat exchanger 4 functions as a condenser. The third expansion valve 53 is provided between the indoor heat exchanger 2 and the outdoor heat exchanger 3. That is, it is provided downstream in the direction of refrigerant flow when the indoor heat exchanger 2 functions as a condenser.

[0028] The switching valve 6 switches the refrigerant circulation path in the refrigerant circuit C between, for example, normal heating operation in which the indoor heat exchanger 2 functions as a condenser and the outdoor heat exchanger 3 functions as an evaporator, and cooling operation in which the indoor heat exchanger 2 functions as an evaporator and the outdoor heat exchanger 3 functions as a condenser.

[0029] Furthermore, the refrigeration cycle apparatus S according to the embodiment of the present invention is provided with two switching valves 6. That is, a first switching valve 61 is provided between the compressor 1 and the indoor heat exchanger 2. A second switching valve 62 is provided between the compressor 1 and the outdoor heat exchanger 3 and between the compressor 1 and the heat storage heat exchanger 4. The second switching valve 62 is provided so as to be able to switch the connection between the compressor 1 and the outdoor heat exchanger 3 or the heat storage heat exchanger 4.

[0030] In the following description, the first expansion valve 51 to the third expansion valve 53 will be referred to as "expansion valve 5" when collectively describing them, and will be referred to by their respective names when describing each individual expansion valve. Similarly, the first switching valve 61 and the second switching valve 62 will be referred to as "switching valve 6" when collectively describing them, and will be referred to by their respective names when describing each individual switching valve.

[0031] Next, a refrigerant circuit C of the refrigeration cycle apparatus S according to the embodiment of the present invention shown in Fig. 1 will be described. The refrigerant circuit C is composed of each device, such as the compressor 1, and flow paths connecting these devices. These flow paths are formed by refrigerant piping, and a refrigerant flows through the inside of the flow path. A first switching valve 61 is provided in the flow path connecting the compressor 1 and the indoor heat exchanger 2. A second switching valve 62 is provided in the flow path connected to the flow path between the compressor 1 and the first switching valve 61, and causes the refrigerant discharged from the compressor 1 to flow to the outdoor heat exchanger 3 or the heat storage heat exchanger 4.

[0032] Furthermore, in the refrigeration cycle apparatus S according to the embodiment of the present invention, a bypass path B is provided between the first switching valve 61 and the second switching valve 62. The bypass path B is provided with a check valve or the like so that the refrigerant flows only in the direction of the arrow as shown in Fig. 1. That is, as will be described later, when cooling operation is performed, the refrigerant flows from the first switching valve 61 toward the second switching valve 62.

[0033] The control device 7 controls the apertures of the multiple expansion valves 5. The control device 7 controls the apertures of each expansion valve, thereby adjusting the flow rate of the refrigerant flowing through the refrigerant circuit C. As described above, the control device 7 switches the flow of the refrigerant circulating through the refrigerant circuit C by switching the multiple switching valves 6. By controlling the multiple expansion valves 5 and the multiple switching valves 6 in this manner, the control device 7 switches the operating mode between, for example, a heating operation and a retention prevention operation that prevents the refrigerant from accumulating in the heat storage heat exchanger 4.

[0034] As described above, the general heating operation in which refrigerant flows only through the indoor heat exchanger 2 and the outdoor heat exchanger 3 as heat exchangers, with the indoor heat exchanger 2 functioning as a condenser and the outdoor heat exchanger 3 functioning as an evaporator, is referred to as normal heating operation, and the control by the control device 7 is referred to as normal heating control.

[0035] As described above, the refrigeration cycle apparatus S according to the embodiment of the present invention is provided with the heat storage heat exchanger 4 in addition to the indoor heat exchanger 2 and the outdoor heat exchanger 3. However, when the normal heating operation is performed, the heat storage heat exchanger 4 does not function as a condenser or an evaporator.

[0036] During normal heating operation, the second expansion valve 52 is controlled to be slightly open so that the refrigerant does not accumulate inside the heat storage heat exchanger 4. However, depending on the pressure difference of the refrigerant, some of the refrigerant flowing from the indoor heat exchanger 2 to the outdoor heat exchanger 3 may flow into the heat storage heat exchanger 4 via the second expansion valve 52 (details will be described later). Furthermore, even if the second expansion valve 52 is controlled to be fully closed, the refrigerant may still flow into the heat storage heat exchanger 4 via the second expansion valve 52 due to the structure of the expansion valve.

[0037] The refrigerant that flows into the heat storage heat exchanger 4 exchanges heat with the heat storage material provided in the heat storage heat exchanger 4, and in this case, if the temperature of the heat storage material is lower than that of the flowing refrigerant, the refrigerant will condense and liquefy. This phenomenon is particularly likely to occur when the heat storage heat exchanger 4 is disposed in, for example, an outdoor unit and the temperature outside the room where the outdoor unit is installed is very low.

[0038] When the refrigerant that has flowed into the heat-storage heat exchanger 4 reaches this liquid phase, as described above, the refrigerant accumulates inside the heat storage device, and since the density of the refrigerant in liquid phase is high, the amount of refrigerant circulating through the refrigerant circuit decreases. This decrease in the amount of refrigerant circulating through the refrigerant circuit may lead to a decrease in the capacity of the refrigeration cycle device.

[0039] Therefore, in the refrigeration cycle apparatus S according to the embodiment of the present invention, a retention prevention operation is performed during normal heating operation to prevent refrigerant from accumulating inside the heat storage heat exchanger 4. The retention prevention operation is an operating mode in which the heat storage heat exchanger 4 and the indoor heat exchanger 2 function as condensers, and the outdoor heat exchanger 3 functions as an evaporator. Note that the control by the control device 7 to perform such retention prevention operation is referred to as retention prevention control as appropriate.

[0040] Furthermore, in the refrigeration cycle apparatus S according to the embodiment of the present invention, when the normal heating operation is being performed, the retention prevention operation is started as necessary as described below, and after the retention prevention operation is completed, the normal heating operation is performed again. However, in view of the purpose of the retention prevention operation described above, the heating operation is not stopped even when the retention prevention operation for the heat storage heat exchanger 4 is being performed.

[0041] In this way, the control device 7 performs control such as switching the operation mode in the refrigeration cycle apparatus S. Therefore, before describing the functions of each part of the control device 7 of the refrigeration cycle apparatus S in the embodiment of the present invention, the operation modes performed in the refrigeration cycle apparatus S will first be described in order using the circuit diagrams of the refrigeration cycle apparatus S in the embodiment of the present invention shown in Figures 2 to 4.

[0042] 2 to 4, refrigerant circuits C through which refrigerant actually flows are indicated by solid lines. On the other hand, refrigerant circuits C through which refrigerant does not flow are indicated by dashed lines. The direction of the refrigerant flowing in the refrigerant circuit C is indicated by arrows.

[0043] First, the cooling operation will be described. Fig. 2 is a refrigerant circuit diagram showing the flow of refrigerant when the refrigeration cycle apparatus S according to the embodiment of the present invention performs cooling operation. During cooling operation, the indoor heat exchanger 2 functions as an evaporator, and the outdoor heat exchanger 3 functions as a condenser.

[0044] That is, the refrigerant compressed in the compressor 1 and discharged in a high-temperature, high-pressure state flows into the outdoor heat exchanger 3 via the first switching valve 61, the bypass path B, and the second switching valve 62, as shown by the arrows in Figure 2.

[0045] The second switching valve 62 is switched so that the refrigerant discharged from the compressor 1 and passing through the first switching valve 61 and the bypass path B flows toward the outdoor heat exchanger 3. Therefore, the refrigerant does not flow into the thermal storage heat exchanger 4.

[0046] The refrigerant discharged from the compressor 1 also flows through the first expansion valve 51. The refrigerant that has passed through the first expansion valve 51 flows into the outdoor heat exchanger 3 through the second switching valve 62. At this time, the first expansion valve 51 is fully open.

[0047] The refrigerant that has flowed into the outdoor heat exchanger 3 is cooled by outdoor air that is supplied by the rotation of an outdoor fan (not shown), and dissipates heat into the outdoor air, causing a part or all of the refrigerant to condense.

[0048] The refrigerant that has released heat to the outside air in this way flows out of the outdoor heat exchanger 3 and is reduced in pressure to become a low-temperature, low-pressure two-phase refrigerant by passing through the third expansion valve 53. The low-temperature, low-pressure two-phase refrigerant then flows into the indoor heat exchanger 2, where it exchanges heat with the indoor air.

[0049] The refrigerant absorbs heat from the indoor air and evaporates through heat exchange in the indoor heat exchanger 2, and the indoor air drawn into the indoor heat exchanger 2 by the indoor fan is cooled and then supplied to the room to cool the room. The refrigerant that has absorbed heat through heat exchange then flows into the compressor 1 via the first switching valve 61.

[0050] During cooling operation, the third expansion valve 53 is controlled so that the refrigerant drawn into the compressor 1 is in gas phase. On the other hand, the second expansion valve 52 is controlled to be fully closed so that the refrigerant flowing out from the outdoor heat exchanger 3 does not flow into the heat storage heat exchanger 4.

[0051] Next, the flow of the refrigerant when the refrigeration cycle apparatus S performs normal heating operation is as shown in Fig. 3. Fig. 3 is a refrigerant circuit diagram showing the flow of the refrigerant when the refrigeration cycle apparatus S according to the embodiment of the present invention performs heating operation based on normal heating control.

[0052] 3, the refrigerant discharged from the compressor 1 flows into the indoor heat exchanger 2 via the first switching valve 61. Therefore, the refrigerant flowing to the indoor heat exchanger 2 side does not flow from the first switching valve 61 through the bypass path B to the outdoor heat exchanger 3 as in the cooling operation described above.

[0053] On the other hand, the first expansion valve 51 provided in the flow path connected to the flow path between the compressor 1 and the first switching valve 61 is controlled to be fully closed. Also, as for the second switching valve 62, as will be described later, the refrigerant flowing out from the outdoor heat exchanger 3 is switched to flow into the compressor 1 via the second switching valve 62, so that the refrigerant does not flow into the thermal storage heat exchanger 4.

[0054] The indoor heat exchanger 2 exchanges heat between the refrigerant and the air flowing into the indoor unit, absorbs heat from the refrigerant, and supplies the heated air to the indoor space. Therefore, the indoor heat exchanger 2 functions as a condenser.

[0055] The refrigerant flowing out of the indoor heat exchanger 2 is decompressed through the third expansion valve 53 and flows into the outdoor heat exchanger 3. The outdoor heat exchanger 3 functions as an evaporator, and heat is exchanged between the refrigerant and the outdoor air. The refrigerant flowing out of the outdoor heat exchanger 3 flows into the compressor 1 through the second switching valve 62.

[0056] In the normal heating operation, the second expansion valve 52 is, for example, slightly open. However, if the temperature of the heat storage material in the heat storage heat exchanger 4 is sufficiently high, and the temperature of the refrigerant flowing out of the third expansion valve 53 and flowing into the outdoor heat exchanger 3 is lower, the pressure of the refrigerant flowing from the third expansion valve 53 toward the outdoor heat exchanger 3 is lower than the pressure of the refrigerant inside the heat storage heat exchanger 4. Therefore, even if the second expansion valve 52 is controlled to be slightly open, the refrigerant flowing out of the indoor heat exchanger 2 does not flow into the heat storage heat exchanger 4 while flowing into the outdoor heat exchanger 3.

[0057] On the other hand, if the temperature of the heat storage material in the heat storage heat exchanger 4 is lower than the temperature of the refrigerant flowing out from the third expansion valve 53 and flowing into the outdoor heat exchanger 3, the pressure of the refrigerant flowing from the third expansion valve 53 toward the outdoor heat exchanger 3 will be higher than the pressure of the refrigerant inside the heat storage heat exchanger 4. Therefore, there is a possibility that the refrigerant will flow into the heat storage heat exchanger 4 via the second expansion valve 52, which is controlled to be slightly open.

[0058] When the refrigerant flows into the heat storage heat exchanger 4, liquefies, and accumulates therein, the amount of refrigerant flowing through the refrigerant circuit C of the refrigeration cycle apparatus S decreases. This condition leads to a decrease in the capacity of the refrigeration cycle apparatus S.

[0059] Therefore, as described below, the control device 7 compares the temperature of the heat storage material with the evaporation temperature of the refrigerant flowing into the outdoor heat exchanger 3 during heating operation, and if it determines that the former temperature is lower than the latter temperature, it switches the operating mode from normal heating operation to retention prevention operation.

[0060] The flow of refrigerant during the stagnation prevention operation will be described with reference to Fig. 4. Fig. 4 is a refrigerant circuit diagram showing the flow of refrigerant when the refrigeration cycle apparatus S according to the embodiment of the present invention performs heating operation while executing stagnation prevention control.

[0061] The purpose of the retention prevention operation is to prevent the refrigerant that has flowed into the heat storage heat exchanger 4 from condensing and liquefying. Therefore, in order to raise the temperature of the heat storage material, the high-temperature refrigerant that has been discharged from the compressor 1 is caused to flow into the heat storage heat exchanger 4 to exchange heat with the heat storage material, thereby storing heat in the heat storage material.

[0062] That is, the refrigerant compressed in the compressor 1 and discharged in a high-temperature, high-pressure state flows into the thermal storage heat exchanger 4 via the first expansion valve 51 and the second switching valve 62, as shown by the arrows in Fig. 4. At this time, the opening of the first expansion valve 51 is preset, for example, fully open.

[0063] In the heat storage heat exchanger 4, the refrigerant that has flowed in exchanges heat with the heat storage material, releasing heat to the heat storage material and condensing, and the heat storage material absorbs heat from the refrigerant. That is, the heat of the refrigerant is stored in the heat storage material. Therefore, at this time, the heat storage heat exchanger 4 functions as a condenser.

[0064] The refrigerant flowing out of the heat storage heat exchanger 4 is reduced in pressure by passing through the second expansion valve 52, becoming a low-temperature, low-pressure two-phase refrigerant. The refrigerant flowing out of the heat storage heat exchanger 4 then flows into the outdoor heat exchanger 3 via the second expansion valve 52, and then flows out of the outdoor heat exchanger 3 and into the compressor 1 via the second switching valve 62.

[0065] The opening degree of the second expansion valve 52 during retention prevention operation is set in advance and is controlled to be sufficiently smaller than the opening degree of the first expansion valve 51, for example. In this way, the amount of pressure reduction when the high-temperature refrigerant discharged from the compressor 1 passes through the first expansion valve 51 is smaller than the amount of pressure reduction when the refrigerant passes through the second expansion valve 52, and the refrigerant maintains a high temperature, making it possible to warm the heat storage material.

[0066] On the other hand, the refrigerant discharged from the compressor 1 also flows through the first switching valve 61 and into the indoor heat exchanger 2. The refrigerant that has flowed into the indoor heat exchanger 2 exchanges heat with the indoor air in the indoor heat exchanger 2.

[0067] That is, through heat exchange by the indoor heat exchanger 2, the indoor air absorbs heat from the refrigerant and condenses, and the indoor air drawn into the indoor heat exchanger 2 by the indoor fan is heated and then supplied to the room. The refrigerant that has released heat through heat exchange then flows into the outdoor heat exchanger 3, which functions as an evaporator, via the third expansion valve 53. The refrigerant that flows out of the outdoor heat exchanger 3 also flows into the compressor 1 via the second switching valve 62.

[0068] Next, the control contents by the control device 7 will be described in more detail. Fig. 5 is a block diagram showing the internal configuration of the control device 7 in the refrigeration cycle apparatus S according to the embodiment of the present invention. The control device 7 includes a temperature detection unit 71, a setting unit 72, a determination unit 73, and a switching control unit 74.

[0069] The temperature detection unit 71 acquires the temperature of the heat storage material detected by the heat storage temperature sensor HS provided in the heat storage heat exchanger 4. The temperature of the heat storage material detected by the heat storage temperature sensor HS is, for example, a heat storage temperature, which is the temperature of the heat storage heat exchanger 4 when normal heating operation is being performed.

[0070] The temperature detection unit 71 also acquires the evaporation temperature of the refrigerant detected by an evaporation temperature detection sensor ES provided in the outdoor unit. The evaporation temperature of the refrigerant detected by the evaporation temperature detection sensor ES is the temperature of the refrigerant that flows into the outdoor heat exchanger 3 during normal heating operation.

[0071] Furthermore, the temperature detection unit 71 acquires the outdoor air temperature detected by an outdoor air temperature detection sensor OS provided in the outdoor unit. The outdoor air temperature detected by the outdoor air temperature detection sensor OS is the outdoor air temperature during normal heating operation. The temperature of the heat storage material, the evaporation temperature of the refrigerant, or the outdoor air temperature is used when performing retention prevention control for the heat storage heat exchanger 4.

[0072] The temperature of the heat storage material detected by the heat storage temperature sensor HS, the evaporation temperature of the refrigerant in the outdoor unit detected by the evaporation temperature detection sensor ES, and the outdoor air temperature detected by the outdoor air temperature detection sensor OS may be constantly transmitted from each temperature sensor to the temperature detection unit 71. Alternatively, they may be transmitted from each temperature sensor to the temperature detection unit 71 in response to a request from the temperature detection unit 71.

[0073] The setting unit 72 sets, for example, a start determination value for the retention prevention operation used when the control device 7 switches the operation mode from normal heating operation to retention prevention operation, and also sets an end determination value for the retention prevention operation used when the control device 7 switches the operation mode from retention prevention operation to normal heating operation.

[0074] Here, the start determination value can be set to a temperature obtained by adding 10°C to the evaporation temperature of the outdoor heat exchanger 3 detected by the evaporation temperature detection sensor ES. The retention prevention control is performed to avoid the adverse effects caused by the refrigerant retention inside the heat storage heat exchanger 4 as described above.

[0075] That is, during normal heating operation, the refrigerant that flows out from the third expansion valve 53 may flow into the heat storage heat exchanger 4 via the second expansion valve 52 as it flows to the outdoor heat exchanger 3. Whether the refrigerant flows into the heat storage heat exchanger 4 depends on the pressure difference between the pressure of the refrigerant present inside the heat storage heat exchanger 4 and the pressure of the refrigerant flowing from the indoor heat exchanger 2 toward the outdoor heat exchanger 3.

[0076] More specifically, it is the difference between the pressure of the refrigerant present inside the thermal storage heat exchanger 4 and the pressure at the connection point C1 of the refrigerant flowing from the indoor heat exchanger 2 to the outdoor heat exchanger 3. Although it is difficult to directly measure the pressures of these refrigerants, the pressures of the refrigerants can be considered as temperatures. Therefore, the pressure difference of the refrigerants can be considered as a temperature difference of the refrigerants.

[0077] That is, by comparing the temperature of the refrigerant inside the heat storage heat exchanger 4 with the evaporation temperature in the outdoor heat exchanger 3, it is possible to determine whether or not there is a possibility that the refrigerant will stagnate inside the heat storage heat exchanger 4. In this case, the temperature of the refrigerant present inside the heat storage heat exchanger 4 can be determined from the temperature of the heat storage material detected by the heat storage temperature sensor HS.

[0078] On the other hand, the temperature of the refrigerant flowing from the indoor heat exchanger 2 to the outdoor heat exchanger 3 can be determined from the evaporation temperature of the refrigerant in the outdoor heat exchanger 3, which is detected by the evaporation temperature detection sensor ES. However, this evaporation temperature is lower than the temperature at the connection point C1 due to the pressure loss of the refrigerant flowing from the indoor heat exchanger 2 to the outdoor heat exchanger 3, specifically, from the connection point C1 to the evaporation temperature detection sensor ES.

[0079] Therefore, if the temperature of the heat storage material is compared with the evaporation temperature itself detected by the evaporation temperature detection sensor ES, the control device 7 may determine that it is not yet necessary to transition to stagnation prevention control, even though the temperature of the heat storage material has dropped to the point where refrigerant is flowing into the heat storage heat exchanger 4.

[0080] Therefore, in order to prevent refrigerant from accumulating inside the thermal storage heat exchanger 4 without executing the stagnation prevention control, the temperature to be compared with the temperature of the thermal storage material, i.e., the start judgment value, is set by adding a temperature corresponding to the pressure loss to the evaporation temperature. By performing this processing, it is possible to set an accurate refrigerant temperature at the connection point C1 to be compared based on the evaporation temperature detected by the evaporation temperature detection sensor ES. Then, the control device 7 compares this start judgment value with the temperature of the thermal storage material.

[0081] As described above, in the embodiment of the present invention, the start determination value to be compared with the temperature of the heat storage material is set to a temperature obtained by adding, for example, 10°C to the evaporation temperature. This 10°C is a value obtained, for example, by experiment.

[0082] Strictly speaking, the pressure loss varies depending on the amount of refrigerant circulating per unit time through the refrigerant circuit C. Therefore, the temperature corresponding to the pressure loss may be set based on the amount of refrigerant circulating per unit time, and the start determination value may be set each time.

[0083] On the other hand, the setting unit 72 also sets an end determination value used when determining whether or not to end the retention prevention control. Whether or not to end the retention prevention control is determined based on whether or not the heat storage material of the thermal storage heat exchanger 4 is in a sufficiently warmed state in relation to the evaporation temperature of the outdoor heat exchanger 3.

[0084] When the heat storage temperature has reached a sufficient level, the temperature of the refrigerant present inside the heat storage heat exchanger 4 is sufficiently higher than the temperature at the connection point C1 of the refrigerant flowing from the indoor heat exchanger 2 to the outdoor heat exchanger 3, and the pressure of the refrigerant is also high. Therefore, the refrigerant flowing from the indoor heat exchanger 2 to the outdoor heat exchanger 3 does not flow into the heat storage heat exchanger 4 via the second expansion valve 52 and stagnate there.

[0085] From this perspective, the setting unit 72 sets the end determination value to a temperature that is sufficiently higher than the start determination value, for example, a temperature that is 20°C higher than the evaporation temperature. The end determination value is also set taking into account the temperature corresponding to the pressure loss. Furthermore, the temperature of 20°C is derived through experimentation, and may be a fixed value, or the temperature corresponding to the pressure loss may be set based on the amount of refrigerant circulating per unit time.

[0086] In this way, the setting unit 72 sets the termination determination value. However, the termination determination value is set taking into consideration the viewpoints described below. That is, in the refrigeration cycle apparatus S according to the embodiment of the present invention, when a defrosting condition for determining that an allowable amount of frost or more has adhered to the outdoor heat exchanger 3 is satisfied, the operation mode is shifted from normal heating operation to defrosting operation in order to remove the frost adhered to the outdoor heat exchanger 3. In the defrosting operation, high-temperature, high-pressure refrigerant is supplied from the compressor to the outdoor heat exchanger 3 to remove the frost.

[0087] In a typical defrosting operation, the switching valve 6 is switched to switch from heating operation to cooling operation, causing the refrigerant discharged from the compressor 1 to flow into the outdoor heat exchanger 3. Therefore, when the operation switches from heating operation to defrosting operation, the heating operation is stopped during the defrosting operation. As a result, the indoor temperature gradually drops, which may cause discomfort to the user.

[0088] Therefore, in order to continue heating operation even during defrosting operation, the refrigerant discharged from the compressor 1 during heating operation before starting defrosting operation is supplied to the indoor heat exchanger 2, and the expansion valve 5 is controlled so that a portion of the refrigerant is also supplied to the heat storage heat exchanger 4 (heat storage heating control). By supplying the refrigerant from the compressor 1 to the heat storage heat exchanger 4, heat exchange occurs between the refrigerant that has flowed into the heat storage heat exchanger 4 and the heat storage material, and heat is stored in the heat storage material.

[0089] During defrosting operation, the heat storage heat exchanger 4 is used as an evaporator, and the indoor heat exchanger 2 and the outdoor heat exchanger 3 are used as condensers, and the expansion valve 5 and the switching valve are controlled so that heating operation is performed while defrosting the outdoor heat exchanger 3 (defrosting heating control).

[0090] From the above perspective, when the heat storage heating control is executed and heat is stored in the heat storage heat exchanger, the temperature of the heat storage material (heat storage temperature), which is the criterion for determining whether sufficient heat has been stored in the heat storage heat exchanger (heat storage completion condition), must be high enough to be usable for defrosting operation.

[0091] In contrast to this, the retention prevention control executed by the refrigeration cycle apparatus S in the embodiments of the present invention described so far is control aimed at causing the refrigerant retained inside the heat storage heat exchanger 4 to flow out of the heat storage heat exchanger 4. Therefore, in order to terminate the retention prevention control, it is sufficient if the heat storage temperature reaches a level at which the retained refrigerant can be caused to flow out from inside the heat storage heat exchanger 4 to the outside.

[0092] Therefore, the heat storage temperature at the end of the retention prevention control is lower than the value of the heat storage temperature in the heat storage completion condition that is set in advance and used to determine whether or not to terminate the heat storage heating control that stores heat to be used in the defrosting operation executed by the control device 7 during normal heating operation. In other words, the termination determination value for the retention prevention control is lower than the value of the heat storage temperature in the heat storage completion condition.

[0093] As explained above, the setting unit 72 sets the termination determination value lower than the value of the heat storage temperature in the heat storage completion condition that is preset to determine whether or not to terminate the heat storage heating control. By setting the termination determination value in this manner, the time during which the retention prevention control is performed can be made shorter than the time during which the heat storage heating control is performed. Therefore, as will be described later, by shortening the time for retention prevention operation, which consumes more power than normal heating operation, the power consumption in the refrigeration cycle apparatus S can be reduced.

[0094] The determination unit 73 determines, for example, whether to switch the operation mode to retention prevention operation during normal heating operation. Specifically, first, the temperature detection unit 71 acquires the temperature of the heat storage material in the heat storage heat exchanger 4 (heat storage temperature) from the heat storage temperature sensor HS. The determination unit 73 also acquires a start determination value from the setting unit 72. Then, the determination unit 73 uses the heat storage temperature and the start determination value to determine whether to cause the refrigerant to flow into the heat storage heat exchanger 4 and perform retention prevention control.

[0095] If the determination unit 73 determines, as a result of comparing the heat storage temperature with the start determination value, that the heat storage temperature is less than the start determination value, the refrigeration cycle apparatus S ends the normal heating operation and transitions to the retention prevention operation. Specifically, the determination unit 73 instructs the switching control unit 74, which will be described later, to open the first expansion valve 51, which is fully closed in the normal heating operation. Similarly, the determination unit 73 instructs the switching control unit 74 to open the second expansion valve 52.

[0096] As a result of the first expansion valve 51 being opened in this manner, the gas phase refrigerant discharged from the compressor 1 flows into the heat storage heat exchanger 4 where the liquid phase refrigerant had been accumulating. Since the refrigerant is in a high temperature and high pressure state, it flows into the heat storage heat exchanger 4 and exchanges heat with the heat storage material.

[0097] When gas-phase refrigerant flows into the heat-storage heat exchanger 4 while liquid-phase refrigerant is accumulating inside, a region of gas-phase refrigerant is created inside the heat-storage heat exchanger 4. In other words, a difference in density occurs between the region of gas-phase refrigerant and the region of liquid-phase refrigerant throughout the heat-storage heat exchanger 4. Therefore, the amount of refrigerant in the entire heat-storage heat exchanger 4 decreases.

[0098] In other words, when gas phase refrigerant flows into the heat storage heat exchanger 4 where a large amount of liquid phase refrigerant exists, the liquid phase refrigerant that was originally stagnating there is pushed out of the heat storage heat exchanger 4.

[0099] As described above, the second expansion valve 52 is also controlled to an open state by the switching control unit 74, so that the refrigerant that has been accumulating inside the heat-storage heat exchanger 4 and that has changed from a liquid phase to a partial gas phase flows out of the heat-storage heat exchanger 4. This increases the amount of refrigerant circulating through the refrigerant circuit C. The refrigerant that has flowed out of the heat-storage heat exchanger 4 passes through the second expansion valve 52, the connection point C1, and flows into the outdoor heat exchanger 3.

[0100] If, as a result of comparing the heat storage temperature with the start judgment value, the judgment unit 73 judges that the heat storage temperature is equal to or higher than the start judgment value, the refrigeration cycle device S does not transition to the retention prevention operation, but continues the normal heating operation.

[0101] On the other hand, the determination unit 73 determines, for example, whether or not to switch the operation mode to normal heating operation during retention prevention operation. Specifically, the determination unit 73 first acquires the temperature of the heat storage material in the heat storage heat exchanger 4 (heat storage temperature) from the heat storage temperature sensor HS acquired by the temperature detection unit 71. The determination unit 73 also acquires an end determination value from the setting unit 72. Then, the determination unit 73 uses the heat storage temperature and the end determination value to determine whether or not to stop retention prevention control and perform normal heating control.

[0102] If the determination unit 73 determines, as a result of comparing the heat storage temperature with the termination determination value, that the heat storage temperature is equal to or higher than the termination determination value, the retention prevention operation is terminated and the operation transitions to normal heating operation. Specifically, the determination unit 73 instructs the switching control unit 74 (described later) to fully close the first expansion valve 51, which was fully open during the retention prevention operation. Furthermore, the determination unit 73 instructs the switching control unit 74 to control the opening of the second expansion valve 52 so that it is slightly open, for example, as described above.

[0103] By controlling the first expansion valve 51 to be fully closed in this manner, the refrigerant that had previously flowed from the compressor 1 into the heat storage heat exchanger 4 during the stagnation prevention operation will no longer flow into the heat storage heat exchanger 4.

[0104] However, because high-temperature, high-pressure refrigerant has flowed from the compressor 1 into the heat storage heat exchanger 4 due to the retention prevention control, the refrigerant that had been stagnating inside the heat storage heat exchanger 4 has now flowed out of the heat storage heat exchanger 4. The heat storage material has also become warmed. As a result, the temperature of the heat storage heat exchanger 4 (heat storage temperature) is higher than the temperature of the refrigerant at the connection point C1 where the refrigerant flows from the indoor heat exchanger 2 to the outdoor heat exchanger 3.

[0105] Therefore, the pressure of the refrigerant present inside the heat-storage heat exchanger 4 is higher than the pressure of the refrigerant at the connection point C1 where the refrigerant flows out from the indoor heat exchanger 2 and into the outdoor heat exchanger 3. Therefore, even if the second expansion valve 52 is in the open state, it is possible to prevent the refrigerant that has flowed out from the indoor heat exchanger 2 from the connection point C1 through the second expansion valve 52 and into the heat-storage heat exchanger 4.

[0106] The switching control unit 74 controls the opening degree of the expansion valve 5 and the switching of the switching valve 6 based on the determination of the start or end of the retention prevention control by the determination unit 73. Specifically, as described above, when transitioning from normal heating operation to retention prevention operation, the first expansion valve 51 is changed from a closed state to an open state, and the second expansion valve 52 is also controlled to have a preset opening degree.

[0107] Furthermore, even when the operating mode shifts from normal heating operation to retention prevention operation, the refrigerant discharged from the compressor 1 is supplied to the indoor heat exchanger 2. Therefore, the switching control unit 74 does not control the switching of the first switching valve 61. On the other hand, in retention prevention control, the refrigerant that has been discharged from the compressor 1 must be supplied not only to the indoor heat exchanger 2 but also to the heat storage heat exchanger 4, so the switching control unit 74 switches the second switching valve 62 so that the refrigerant is supplied to the heat storage heat exchanger 4.

[0108] On the other hand, when the retention prevention operation is completed and the operation shifts to normal heating operation, the switching control unit 74 controls the first expansion valve 51 to change from an open state to a closed state. Also, the second expansion valve 52 is controlled to be slightly open. Then, the second switching valve 62 is switched so that the refrigerant discharged from the compressor 1 is not supplied to the thermal storage heat exchanger 4. Note that the first switching valve 61 is not controlled to be switched.

[0109] [Operation] Next, the flow of control of the refrigeration cycle apparatus S by the control device 7 in the normal heating operation and the retention prevention operation described above will be described with reference to Fig. 6. Fig. 6 is a flowchart showing the flow of retention prevention control in the refrigeration cycle apparatus S according to the embodiment of the present invention.

[0110] First, normal heating operation is started (ST1). The flow of refrigerant and the switching control of the expansion valve 5 and the switching valve 6 performed by the control device 7 during normal heating operation are as described using the circuit diagram in FIG.

[0111] The control device 7 also checks whether the normal heating operation in the refrigeration cycle device S has stabilized (ST2). This is because the various parts of the refrigeration cycle device S have not yet reached a stable state immediately after the normal heating operation has started, and it is not appropriate to determine whether to transition to retention prevention operation in this state.

[0112] Note that various determination conditions can be used to determine whether the normal heating operation is stable. For example, a determination can be made using a time, such as whether 300 seconds have passed since the normal heating operation started. Specifically, for example, the determination unit 73 determines whether the time set in the setting unit 72 has passed, and if the set time has not passed (NO in ST2), the determination continues.

[0113] On the other hand, if the determination unit 73 determines that the set time has elapsed (YES in ST2), it then determines whether or not to execute the retention prevention control (retention prevention control determination). When the control device 7 performs the retention prevention control determination, it determines whether or not the heat storage temperature is below the start determination value, as described above (ST3).

[0114] That is, the determination unit 73 obtains the heat storage temperature, which is the temperature of the heat storage heat exchanger 4 detected by the heat storage temperature sensor HS, from the temperature detection unit 71. The determination unit 73 also obtains a preset start determination value from the setting unit 72. The start determination value is set based on the evaporation temperature in the outdoor heat exchanger 3, which is detected by the evaporation temperature detection sensor ES as described above and obtained by the setting unit 72 via the temperature detection unit 71.

[0115] However, if the evaporation temperature is used as the start determination value as is, it is not possible to take into account the pressure loss that occurs when the refrigerant flows into the outdoor heat exchanger 3. Therefore, a temperature that takes into account the pressure loss of the refrigerant from the connection point C1 to the evaporation temperature detection sensor ES based on the evaporation temperature, for example, a temperature obtained by adding 10°C to the evaporation temperature, is set as the start determination value. In the flowchart shown in FIG. 6, the start determination value is indicated as "evaporation temperature + 10°C."

[0116] The determination unit 73 acquires the start determination value thus set from the setting unit 72. Then, it determines whether or not the heat storage temperature is lower than the start determination value. If the determination unit 73 determines that the heat storage temperature is equal to or higher than the start determination value (NO in ST3), this means that there is little risk of refrigerant stagnation inside the heat storage heat exchanger 4 at this time. Therefore, in this case, the determination unit 73 continues to execute the stagnation prevention control determination.

[0117] On the other hand, if the determination unit 73 determines that the heat storage temperature is lower than the start determination value (YES in ST3), the control device 7 starts the retention prevention control. Therefore, at this point, the normal heating operation is switched to the retention prevention operation.

[0118] That is, the determination unit 73 instructs the switching control unit 74 to adjust the opening degree of the expansion valve 5 (ST4). More specifically, the first expansion valve 51, which has been controlled to a closed state during normal heating operation, is controlled to be fully open at a preset opening degree.

[0119] On the other hand, the second expansion valve 52 is also controlled to a preset opening degree by the switching control unit 74. Therefore, for example, in normal heating operation, since the opening degree is controlled to be, for example, slightly open as described above, the opening degree of the second expansion valve 52 may also be controlled to be slightly open.

[0120] As a result of this control, the high-temperature, high-pressure refrigerant discharged from the compressor 1 flows into the heat storage heat exchanger 4. As this refrigerant flows into the heat storage heat exchanger 4, heat exchange occurs between the heat storage material and the refrigerant. As a result of the heat exchange, the heat storage temperature rises, and the refrigerant that had been stagnating inside the heat storage heat exchanger 4 flows out.

[0121] Note that no switching control is performed on the switching valve 6. Therefore, the refrigerant discharged from the compressor 1 continues to flow into the indoor heat exchanger 2 and exchanges heat with the indoor air, thereby continuing the heating operation and supplying warm air to the room.

[0122] The determination unit 73 checks the heat storage temperature while the retention prevention control is being executed. That is, it determines whether the refrigerant has been heated to a temperature at which the refrigerant will not flow into the heat storage heat exchanger 4 even when normal heating operation is performed.

[0123] Specifically, the determination unit 73 determines whether the heat storage temperature is equal to or greater than the termination determination value (ST5). As described above, the termination determination value is set to a value obtained by adding 20°C to the evaporation temperature detected by the evaporation temperature detection sensor ES. Therefore, in the flowchart shown in FIG. 6, the termination determination value is indicated as "evaporation temperature + 20°C."

[0124] As mentioned above, when the termination judgment value is set, it is a value lower than the heat storage temperature in the heat storage completion condition for determining whether or not to terminate the heat storage heating control when using the heat stored in the heat storage heat exchanger 4 during defrosting operation.

[0125] If the determination unit 73 determines that the heat storage temperature is less than the termination determination value (NO in ST5), the retention prevention control continues to be executed, and the process described in step ST5 is repeated. On the other hand, if the determination unit 73 determines that the heat storage temperature is equal to or greater than the termination determination value (YES in ST5), the retention prevention control is terminated.

[0126] Then, the operation shifts from the retention prevention operation to the normal heating operation. In addition, with the shift to the normal heating operation, the determination unit 73 instructs the switching control unit 74 to adjust the opening of the expansion valve 5 (ST6).

[0127] Specifically, the determination unit 73 instructs the switching control unit 74 to adjust the opening degree of the first expansion valve 51 so that it changes from an open state to a closed state. In accordance with the instruction, the switching control unit 74 adjusts the opening degree of the first expansion valve 51. On the other hand, with regard to the second expansion valve 52, the switching control unit 74 adjusts the opening degree so that the opening degree becomes the opening degree set for normal heating operation, for example.

[0128] As described above, during normal heating operation, by performing retention prevention control to adjust the opening of the expansion valve 5 based on the heat storage temperature of the heat storage heat exchanger, the refrigerant retained inside the heat storage heat exchanger 4 can be caused to flow out of the heat storage heat exchanger 4, thereby preventing the refrigerant from retaining inside the heat storage heat exchanger 4.

[0129] By executing such retention prevention control, the refrigerant does not flow into the heat storage heat exchanger 4, thereby maintaining the amount of refrigerant circulating in the refrigerant circuit C. Therefore, it is possible to suppress a decrease in the capacity of the refrigeration cycle apparatus S due to a decrease in the amount of refrigerant.

[0130] (First Modification) Next, modified examples of the retention prevention control that have been described so far will be described below using flowcharts. First, the first modified example. Fig. 7 is a flowchart showing the control flow in the first modified example of the retention prevention control in the refrigeration cycle apparatus S according to the embodiment of the present invention.

[0131] In the first variant, either the start judgment value or the end judgment value, or both, are set based on the outside air temperature, rather than being set based on the evaporation temperature of the refrigerant in the outdoor heat exchanger 3 as in the past, which differs from the above-mentioned stagnation prevention control.

[0132] That is, the evaporation temperature is correlated with the outside air temperature. Therefore, even if the outside air temperature detected by the outside air temperature detection sensor OS is used, it is possible to perform the retention prevention control.

[0133] First, when the normal heating operation is started (ST21), the determination unit 73 executes the retention prevention control determination. Here, unlike the retention prevention control described above, the determination as to whether the normal heating operation is stable or not is not performed because whether the various parts of the refrigeration cycle apparatus S are stable or not is not directly related to the outside air temperature.

[0134] Therefore, when the start determination value is set based on the outside air temperature, the determination process of whether the normal heating operation has stabilized is not performed, and the determination unit 73 immediately performs the retention prevention control determination.

[0135] In the first modified example, the start determination value is set based on the outside air temperature. Because the pressure at the connection point C1 is correlated with the outside air temperature, the start determination value can be set in advance by experiment or the like based on the outside air temperature. That is, the setting unit 72 sets the start determination value to, for example, a temperature obtained by adding 5°C to the outside air temperature. Therefore, in the flowchart shown in FIG. 7, the start determination value is indicated as "outside air temperature + 5°C."

[0136] Then, the determination unit 73 compares the start determination value thus set with the heat storage temperature (ST22). As a result, if the determination unit 73 determines that the heat storage temperature is equal to or higher than the start determination value (NO in ST22), it determines whether or not to continue the retention prevention control.

[0137] On the other hand, if the determination unit 73 determines that the heat storage temperature is less than the start determination value (YES in ST22), the operation shifts from normal heating operation to retention prevention operation, and retention prevention control is started. The determination unit 73 instructs the switching control unit 74 to adjust the opening of the expansion valve 5, and the switching control unit 74 adjusts the opening of the expansion valve 5 based on the instruction from the determination unit 73 (ST23).

[0138] The determination unit 73 continues to check the heat storage temperature and then compares it with the end determination value (ST24). The end determination value used here is a temperature that is sufficiently higher than the start determination value, for example, a value obtained by adding 15°C to the outside air temperature. Therefore, the end determination value is shown as "outside air temperature + 15°C" in the flowchart shown in FIG. 7.

[0139] If the determination unit 73 determines that the heat storage temperature remains below the termination determination value thus set (NO in ST24), the retention prevention control continues. On the other hand, if the determination unit 73 determines that the heat storage temperature is equal to or greater than the termination determination value (YES in ST24), the retention prevention control ends.

[0140] That is, the operation shifts from retention prevention operation to normal heating operation. The determination unit 73 instructs the switching control unit 74 to adjust the opening of the expansion valve 5, and the switching control unit 74 adjusts the opening of the expansion valve 5 based on the instruction from the determination unit 73 (ST25). This completes the description of the first modified example in which the outside air temperature is used for either or both of the start determination value and the end determination value.

[0141] (Second Modification) Next, a second modified example will be described with reference to Fig. 8. Fig. 8 is a flowchart showing a control flow in a second modified example of the retention prevention control in the refrigeration cycle apparatus S according to the embodiment of the present invention.

[0142] In the first modification, the start and end determination values ​​are set based on the outside air temperature detected by the outside air temperature detection sensor OS. In the second modification, the start and end determination values ​​are set based on experimental values.

[0143] That is, as explained above, in consideration of the fact that a low heat storage temperature of the heat storage heat exchanger 4 causes refrigerant to stagnate inside the heat storage heat exchanger 4, a start determination value based on the evaporation temperature or the outside air temperature is set, and the set start determination value is compared with the heat storage temperature to determine whether or not to start stagnation prevention control. However, in the second modified example, the start determination value and the end determination value are set using only the heat storage temperature itself, without using the evaporation temperature or outside air temperature explained above.

[0144] That is, when the normal heating operation is started (ST31), the determination unit 73 executes the retention prevention control determination. Here, unlike the retention prevention control described above, the determination as to whether the normal heating operation is stable or not is not performed because in the second modified example, control is performed focusing on the heat storage temperature itself, and therefore whether each part of the refrigeration cycle apparatus S has been stably started or not is not directly related.

[0145] In the second modified example, the start determination value is set based on the heat storage temperature. That is, the setting unit 72 sets the reference heat storage temperature when determining whether to start retention prevention control to, for example, 10°C. Therefore, this "10°C" becomes the start determination value. Therefore, the start determination value is shown as "10°C" in the flowchart shown in FIG. 8.

[0146] Then, the determination unit 73 compares the start determination value thus set with the heat storage temperature (ST32). As a result, if the determination unit 73 determines that the heat storage temperature is equal to or higher than the start determination value (NO in ST32), it determines whether or not to continue the retention prevention control.

[0147] On the other hand, if the determination unit 73 determines that the heat storage temperature is less than the start determination value (YES in ST32), the operation shifts from normal heating operation to retention prevention operation, and retention prevention control is started. The determination unit 73 instructs the switching control unit 74 to adjust the opening of the expansion valve 5, and the switching control unit 74 adjusts the opening of the expansion valve 5 based on the instruction from the determination unit 73 (ST33).

[0148] The determination unit 73 continues to check the heat storage temperature and then compares it with the termination determination value (ST34). Like the start determination value, the termination determination value used here is based on the heat storage temperature when determining whether or not to terminate the retention prevention control, and is set to, for example, 20°C. Note that the termination determination value is shown as "20°C" in the flowchart shown in FIG. 8.

[0149] If the determination unit 73 determines that the heat storage temperature remains below the termination determination value thus set (NO in ST34), the retention prevention control continues to be performed.

[0150] On the other hand, if the determination unit 73 determines that the heat storage temperature is equal to or higher than the termination determination value (YES in ST34), the retention prevention control is terminated. That is, the operation shifts from retention prevention to normal heating operation. The determination unit 73 instructs the switching control unit 74 to adjust the opening of the expansion valve 5, and the switching control unit 74 adjusts the opening of the expansion valve 5 based on the instruction from the determination unit 73 (ST35). This concludes the description of the second modified example in which the heat storage temperature itself is used as the start determination value and the termination determination value.

[0151] As described above, the control device 7 starts the stagnation prevention control by comparing the heat storage temperature of the heat storage heat exchanger 4 with the start judgment value, and ends the stagnation prevention control by comparing the heat storage temperature with the end judgment value. By increasing the heat storage temperature in this way, the refrigerant stagnating inside the heat storage heat exchanger 4 can be caused to flow out of the heat storage heat exchanger 4.

[0152] By performing such retention prevention control, in a refrigeration cycle device equipped with a heat storage heat exchanger, it is possible to prevent refrigerant from stagnating inside the heat storage heat exchanger and to minimize the reduction in the amount of refrigerant circulating through the refrigerant circuit.

[0153] Furthermore, after the retention prevention control has started, by appropriately comparing the heat storage temperature with the termination judgment value, the retention prevention control can be terminated when the heat storage heat exchanger 4 is warmed and the refrigerant that has been retained inside the heat storage heat exchanger 4 flows out of the heat storage heat exchanger 4. As explained above, when retention prevention operation is performed, refrigerant is caused to flow from the compressor 1 not only into the indoor heat exchanger 2 but also into the heat storage heat exchanger 4. Therefore, the amount of refrigerant flowing into the indoor heat exchanger 2 decreases relatively.

[0154] In such a case, to maintain the heating capacity during normal heating operation, the same amount of refrigerant needs to be supplied to the indoor heat exchanger 2, which results in an increase in the rotation speed of the compressor 1 and an increase in power consumption. Therefore, by appropriately determining the end of the retention prevention control, the power consumption in the refrigeration cycle apparatus S can be reduced.

[0155] 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 and embodied without departing from the spirit of the invention, and various changes and improvements can be made to the above-described embodiment. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiment.

[0156] For example, some components may be deleted from all of the components shown in the embodiments. Furthermore, components from different embodiments may be combined as appropriate, and such modified or improved forms may also be included in the present invention. Such embodiments and their modifications are included in the scope and spirit of the inventions, and are also included in the scope of the inventions and their equivalents as defined in the claims.

[0157] For example, in the above examples, the start and end determination values ​​used to determine the start and end of the retention prevention operation, which are compared with the heat storage temperature, are set based on the evaporation temperature, the outside air temperature, or the heat storage temperature. In each of these examples, it has been assumed that the start and end determination values ​​are set using the same criteria.

[0158] That is, for example, if the start determination value is set based on the evaporation temperature, it is assumed that the end determination value is also set based on the evaporation temperature. However, it is not necessary to assume that the start determination value and the end determination value are set using the same criteria.

[0159] For example, when determining whether to transition from normal heating operation to retention prevention operation, a start determination value set based on the evaporation temperature is used, whereas when determining whether to transition from retention prevention operation to normal heating operation, an end determination value set based on the outside air temperature may be used.

[0160] Alternatively, for example, the normal heating operation may be switched to the retention prevention operation when a predetermined time has elapsed since the start of the normal heating operation, or the retention prevention operation may be switched to the normal heating operation when a predetermined time has elapsed since the start of the retention prevention operation. In this case, the start determination value and the end determination value are the predetermined times.

[0161] As described above, the start judgment value and end judgment value may be set based on the evaporation temperature, etc., as explained above, or may be set based on other criteria rather than these three criteria.

[0162] The start and end determination values ​​can be arbitrarily combined and set in any way, so that the start and end determination values ​​may be set based on the same criteria, or alternatively, the start and end determination values ​​may be set based on different criteria and then appropriately selected.

[0163] As explained above, either the start determination value or the end determination value, or both, can be set based on the evaporation temperature, the outside air temperature, or the heat storage temperature itself. The retention prevention control is then executed based on the start determination value or the end determination value set in this way. Meanwhile, the heat storage heating control described above can also be considered as a control for storing heat by causing the refrigerant discharged from the compressor 1 to flow into the heat storage heat exchanger 4.

[0164] The heat storage heating control is executed for the purpose of using the heat stored in the heat storage heat exchanger 4 when performing defrosting operation. Therefore, the heat storage heating control executes control to store heat in the heat storage heat exchanger 4 while heating operation is being performed.

[0165] Therefore, the control device 7 determines whether to execute the heat storage heating control using the frosting conditions, which are conditions for determining whether the operating environment is one in which frost may form on the outdoor unit. That is, when the outdoor air temperature is, for example, 5°C or higher, there may be an environment in which frost is unlikely to form on the outdoor unit, such as when the evaporation temperature is below freezing and below the dew point. In such an environment in which frost is unlikely to form on the outdoor unit, executing the heat storage heating control may result in unnecessary power consumption.

[0166] Therefore, in an environment where the possibility of frost forming on the outdoor unit is low, the heat storage heating control is not executed. On the other hand, in an environment where the possibility of frost forming on the outdoor unit is high, such as when the outdoor air temperature is below 5°C, the control device 7 executes the heat storage heating control to store heat in the heat storage heat exchanger 4.

[0167] When the heat storage heating control is executed, heat is stored in the heat storage heat exchanger 4, so there is little concern about the refrigerant stagnation inside the heat storage heat exchanger 4. Therefore, there is little need to execute the stagnation prevention control in such a situation.

[0168] In other words, it is necessary to execute the retention prevention control when the frosting conditions are not satisfied. Therefore, in the embodiment of the present invention, the retention prevention control and the heat storage heating control are selected by the process described below. Figure 9 is a flowchart showing the flow of executing the selection between the retention prevention control and the heat storage heating control in the refrigeration cycle apparatus S according to the embodiment of the present invention.

[0169] First, normal heating operation is started (ST21). Whether it is retention prevention control or heat storage heating control, it is a control that is executed when normal heating operation is being performed. Then, the determination unit 73 determines whether the frost formation condition is met while normal heating operation is being performed (ST41).

[0170] Whether or not the frosting condition is met can be determined, for example, using the outdoor air temperature detected by the outdoor air temperature detection sensor OS. The flowchart shown in FIG. 9 illustrates an example in which it is determined whether or not the outdoor air temperature is equal to or higher than a predetermined value. Therefore, the "predetermined value" here is a value set based on the temperature at which frost may form on the outdoor unit. The above-mentioned "5°C" is one example.

[0171] If the judgment unit 73 determines that the outdoor air temperature is lower than a predetermined value (NO in ST41), it is determined that there is a possibility of frost forming on the outdoor unit, and so starts heat storage heating control to store heat in the heat storage heat exchanger 4 in advance before frost actually forms (ST42).

[0172] When actually starting the heat storage heating control, various conditions can be considered in addition to the condition of whether or not the frost formation condition is met. However, details of the heat storage heating control will be omitted here. Therefore, the processing after the heat storage heating control is started will be omitted from the flowchart in Figure 9.

[0173] On the other hand, if the determination unit 73 determines that the outside air temperature is equal to or higher than the predetermined value (YES in ST41), retention prevention control is initiated. As explained above, retention prevention control in the embodiment of the present invention is performed in a temperature range in which heat storage heating control is not performed. Therefore, in any temperature range, refrigerant retention inside the heat storage heat exchanger 4 is prevented and the amount of refrigerant circulating in the refrigerant circuit is prevented from decreasing as much as possible, thereby suppressing a decrease in the capacity of the refrigeration cycle device.

[0174] One of the various conditions for starting the heat storage heating control described above may be that the outside air temperature is equal to or higher than a second predetermined value that is lower than the above predetermined value. The second predetermined value is set to an extremely low outside air temperature (for example, -15°C).

[0175] Under extremely low temperature conditions, where the outdoor air temperature is below the second predetermined value, the absolute humidity is low, resulting in a smaller amount of frost formation than when the outdoor air temperature is equal to or higher than the second predetermined value. Furthermore, under extremely low temperature conditions, the compressor suction pressure decreases, reducing the amount of refrigerant circulating, and therefore the heating capacity also decreases. Therefore, while the benefits of performing the heat storage heating operation are small, the disadvantage of performing the heat storage heating operation is significant: the heating capacity is further reduced. Furthermore, if the heat storage heating operation is performed assuming defrost heating operation even under extremely low temperature conditions, the capacity of the heat storage material must be increased.

[0176] Therefore, as described above, it is conceivable to perform the heat storage heating control when the outside air temperature is equal to or higher than the second predetermined value. In this case, it is desirable to perform the stagnation prevention control not only when the outside air temperature is equal to or higher than the predetermined value, but also when the outside air temperature is lower than the second predetermined value.

[0177] The flowchart shown in Fig. 9 illustrates an example in which either the start determination value or the end determination value, or both, are set based on the outdoor air temperature, which is the first modified example described above. Therefore, the processing flow in the retention prevention control is as described using Fig. 7. Therefore, in Fig. 9, the step numbers indicating the processing flow, including the step number at which the normal heating operation described above is started, conform to those in Fig. 7.

[0178] Furthermore, with regard to the processing flow of the stagnation prevention control, the start judgment value or the end judgment value, or both, may be set based on the outside air temperature, or the stagnation prevention control may be performed by setting them based on the evaporation temperature or the heat storage temperature.

[0179] The techniques described in the embodiments of the present invention may also be configured as follows. (1) a compressor that compresses a refrigerant; an indoor heat exchanger that exchanges heat between indoor air and the refrigerant; an outdoor heat exchanger that exchanges heat between outdoor air and the refrigerant; a heat storage heat exchanger that exchanges heat between a heat storage material and the refrigerant; an expansion valve whose opening degree is adjustable; a refrigerant circuit having a a heat storage temperature sensor for detecting a heat storage temperature, which is the temperature of the heat storage heat exchanger; a control device for controlling the expansion valve, The control device, during heating operation, When it is determined that there is a possibility that the refrigerant may be stagnating inside the heat storage heat exchanger based on the heat storage temperature, The refrigerant remaining inside the heat-storage heat exchanger is caused to flow out of the heat-storage heat exchanger. ,before The refrigeration cycle device is characterized by performing retention prevention control by adjusting the opening degree of the expansion valve. (2) The control executed by the control device during the heating operation is at least the retention prevention control and the normal heating control, When the retention prevention control is executed by the control device, the expansion valve is controlled so that the indoor heat exchanger and the heat storage heat exchanger function as condensers, and the outdoor heat exchanger functions as an evaporator, The refrigeration cycle device described in (1) above is characterized in that when the normal heating control is executed by the control device, only the outdoor heat exchanger and the indoor heat exchanger function, the indoor heat exchanger functions as a condenser, and the outdoor heat exchanger functions as an evaporator, and the expansion valve is controlled so that. (3) The refrigeration cycle device according to (2) above, characterized in that the control device compares the heat storage temperature with a start judgment value for determining whether or not to start the retention prevention control, and when it is determined that the heat storage temperature is less than the start judgment value, the control device transitions from the normal heating control to the retention prevention control. (4) The refrigeration cycle device according to (2) above, characterized in that the control device compares the heat storage temperature with a termination judgment value for determining whether or not to terminate the retention prevention control, and when it is determined that the heat storage temperature is equal to or greater than the termination judgment value, the control device transitions from the retention prevention control to the normal heating control. (5) The refrigeration cycle device further includes an evaporation temperature detection sensor that detects an evaporation temperature of the refrigerant in the outdoor heat exchanger, The refrigeration cycle device described in (3) or (4) above is characterized in that the control device sets either a start judgment value for determining whether to start the retention prevention control or an end judgment value for determining whether to end the retention prevention control, or both, based on the evaporation temperature detected by the evaporation temperature detection sensor. (6) The refrigeration cycle device further includes an outside air temperature detection sensor for detecting an outside air temperature, The refrigeration cycle device described in (3) or (4) above is characterized in that the control device sets either a start judgment value for determining whether to start the retention prevention control or an end judgment value for determining whether to end the retention prevention control, or both, based on the outside air temperature detected by the outside air temperature detection sensor. (7) a compressor that compresses a refrigerant; an indoor heat exchanger that exchanges heat between indoor air and the refrigerant; an outdoor heat exchanger that exchanges heat between outdoor air and the refrigerant; a heat storage heat exchanger that exchanges heat between a heat storage material and the refrigerant; an expansion valve whose opening degree is adjustable; a refrigerant circuit having a a heat storage temperature sensor for detecting a heat storage temperature, which is the temperature of the heat storage heat exchanger; outside Outside air temperature detection sensor and , a control device for controlling the expansion valve, The control device, during heating operation, before When it is determined that the outside air temperature detected by the outside air temperature detection sensor is equal to or higher than a predetermined value set as a frosting condition, and adjusting the opening degree of the expansion valve based on the heat storage temperature so that the refrigerant remaining inside the heat storage heat exchanger flows out of the heat storage heat exchanger. The method is characterized by executing a control to prevent congestion. Ru cold Freezing cycle device. (8) a compressor that compresses a refrigerant; an indoor heat exchanger that exchanges heat between indoor air and the refrigerant; an outdoor heat exchanger that exchanges heat between outdoor air and the refrigerant; a heat storage heat exchanger that exchanges heat between a heat storage material and the refrigerant; an expansion valve whose opening degree is adjustable; a refrigerant circuit having a a heat storage temperature sensor for detecting a heat storage temperature, which is the temperature of the heat storage heat exchanger; a control device for controlling the expansion valve, The control performed by the control device during heating operation is a retention prevention control that adjusts an opening degree of the expansion valve based on the heat storage temperature so that at least the refrigerant retained inside the heat storage heat exchanger flows out to the outside of the heat storage heat exchanger, and a normal heating control; When the retention prevention control is executed by the control device, the expansion valve is controlled so that the indoor heat exchanger and the heat storage heat exchanger function as condensers, and the outdoor heat exchanger functions as an evaporator, When the normal heating control is executed by the control device, only the outdoor heat exchanger and the indoor heat exchanger function, the expansion valve is controlled so that the indoor heat exchanger functions as a condenser and the outdoor heat exchanger functions as an evaporator, The control device compares the heat storage temperature with a termination determination value for determining whether to terminate the retention prevention control, and when it is determined that the heat storage temperature is equal to or greater than the termination determination value, the control device transitions from the retention prevention control to the normal heating control, before The termination determination value is lower than a value of a heat storage temperature in a heat storage completion condition that is set in advance and used to determine whether or not to terminate the heat storage heating control, in heat storage heating control that stores heat to be used in a defrosting operation executed by the control device during heating operation. Ru cold Freezing cycle device. [Explanation of symbols]

[0180] REFRIGERATION SYSTEM, ES, EVAPORATION TEMPERATURE DETECTION SENSOR, HS, HEAT STORAGE TEMPERATURE DETECTION SENSOR, OS, OUTDOOR TEMPERATURE DETECTION SENSOR, S, REFRIGERATION CYCLE DEVICE

Claims

1. a compressor that compresses a refrigerant; an indoor heat exchanger that exchanges heat between indoor air and the refrigerant; an outdoor heat exchanger that exchanges heat between outdoor air and the refrigerant; a heat storage heat exchanger that exchanges heat between a heat storage material and the refrigerant; an expansion valve whose opening degree is adjustable; a refrigerant circuit having a a heat storage temperature sensor for detecting a heat storage temperature, which is the temperature of the heat storage heat exchanger; a control device for controlling the expansion valve, The control device, during heating operation, A refrigeration cycle device characterized in that, when it is determined based on the heat storage temperature that the refrigerant may be stagnating inside the heat storage heat exchanger, stagnation prevention control is performed to adjust the opening degree of the expansion valve so that the refrigerant stagnating inside the heat storage heat exchanger flows out of the heat storage heat exchanger.

2. The control executed by the control device during the heating operation includes at least the retention prevention control and normal heating control, When the retention prevention control is executed by the control device, the expansion valve is controlled so that the indoor heat exchanger and the heat storage heat exchanger function as condensers, and the outdoor heat exchanger functions as an evaporator, 2. The refrigeration cycle device according to claim 1, wherein when the normal heating control is executed by the control device, the expansion valve is controlled so that only the outdoor heat exchanger and the indoor heat exchanger function, the indoor heat exchanger functions as a condenser, and the outdoor heat exchanger functions as an evaporator.

3. 3. The refrigeration cycle apparatus according to claim 2, wherein the control device compares the heat storage temperature with a start determination value for determining whether to start the retention prevention control, and when it is determined that the heat storage temperature is less than the start determination value, the control device shifts from the normal heating control to the retention prevention control.

4. 3. The refrigeration cycle apparatus according to claim 2, wherein the control device compares the heat storage temperature with a termination determination value for determining whether to terminate the retention prevention control, and when it is determined that the heat storage temperature is equal to or greater than the termination determination value, the control device transitions from the retention prevention control to the normal heating control.

5. The refrigeration cycle device further includes an evaporation temperature detection sensor that detects an evaporation temperature of the refrigerant in the outdoor heat exchanger, 5. The refrigeration cycle device according to claim 3, wherein the control device sets either a start judgment value for determining whether to start the stagnation prevention control or an end judgment value for determining whether to end the stagnation prevention control, or both, based on the evaporation temperature detected by the evaporation temperature detection sensor.

6. The refrigeration cycle device further includes an outside air temperature detection sensor for detecting an outside air temperature, 5. The refrigeration cycle device according to claim 3, wherein the control device sets either a start judgment value for determining whether to start the retention prevention control or an end judgment value for determining whether to end the retention prevention control, or both, based on the outside air temperature detected by the outside air temperature detection sensor.

7. A compressor for compressing a refrigerant; an indoor heat exchanger that exchanges heat between indoor air and the refrigerant; an outdoor heat exchanger that exchanges heat between outdoor air and the refrigerant; a heat storage heat exchanger that exchanges heat between a heat storage material and the refrigerant; an expansion valve whose opening degree is adjustable; a refrigerant circuit having a a heat storage temperature sensor for detecting a heat storage temperature, which is the temperature of the heat storage heat exchanger; an outside air temperature detection sensor for detecting an outside air temperature; a control device for controlling the expansion valve, The control device, during heating operation, A refrigeration cycle device characterized in that, when it is determined that the outside air temperature detected by the outside air temperature detection sensor is equal to or higher than a predetermined value set as a frosting condition, a retention prevention control is executed to adjust the opening degree of the expansion valve based on the heat storage temperature so that the refrigerant stagnating inside the heat storage heat exchanger flows out of the heat storage heat exchanger.

8. A compressor for compressing a refrigerant; an indoor heat exchanger that exchanges heat between indoor air and the refrigerant; an outdoor heat exchanger that exchanges heat between outdoor air and the refrigerant; a heat storage heat exchanger that exchanges heat between a heat storage material and the refrigerant; an expansion valve whose opening degree is adjustable; a refrigerant circuit having a a heat storage temperature sensor for detecting a heat storage temperature, which is the temperature of the heat storage heat exchanger; a control device for controlling the expansion valve, The control performed by the control device during heating operation is a retention prevention control that adjusts an opening degree of the expansion valve based on the heat storage temperature so that at least the refrigerant retained inside the heat storage heat exchanger flows out to the outside of the heat storage heat exchanger, and a normal heating control; When the retention prevention control is executed by the control device, the expansion valve is controlled so that the indoor heat exchanger and the heat storage heat exchanger function as condensers, and the outdoor heat exchanger functions as an evaporator, When the normal heating control is executed by the control device, only the outdoor heat exchanger and the indoor heat exchanger function, the expansion valve is controlled so that the indoor heat exchanger functions as a condenser and the outdoor heat exchanger functions as an evaporator, The control device compares the heat storage temperature with a termination determination value for determining whether to terminate the retention prevention control, and when it is determined that the heat storage temperature is equal to or greater than the termination determination value, the control device transitions from the retention prevention control to the normal heating control, The refrigeration cycle apparatus is characterized in that the termination judgment value is lower than a value of a heat storage temperature in a heat storage completion condition that is set in advance and used to determine whether or not to terminate the heat storage heating control, in which heat is stored to be used in a defrosting operation performed by the control device during heating operation.

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