JP2025126009A - Refrigeration cycle device and control method for refrigeration cycle device - Google Patents

Abstract

[Problem] Even when cooling operation is performed 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 an indoor heat exchanger 2, an outdoor heat exchanger 3, a heat storage heat exchanger 4 that exchanges heat between a heat storage material and a refrigerant, a switching valve 6, and a control device 7 that controls the switching valve 6. The switching valve 6 switches the flow path between cooling operation in which the outdoor heat exchanger 3 functions as a condenser and the indoor heat exchanger 2 functions as an evaporator, and heat storage cooling operation in which at least the indoor heat exchanger 2 functions as an evaporator when the heat storage heat exchanger 4 functions as a condenser. When the detection value of a heat storage temperature sensor HS that detects the temperature of the heat storage material during cooling operation becomes lower than a first predetermined temperature, the control device 7 controls the switching valve 6 so that the system switches from cooling operation to heat storage cooling operation.
[Selected Figure] Figure 1

Description

Embodiments of the present invention relate to a refrigeration cycle device and a control method for a refrigeration cycle device.

Generally, when an air conditioner is in heating operation, a low-temperature refrigerant flows through the outdoor heat exchanger. Therefore, for example, when the outdoor 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.

This type of 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 supplied directly to the outdoor heat exchanger. In other words, defrosting is performed by making the outdoor heat exchanger function as a condenser. During defrosting operation, the high-temperature refrigerant supplied to the outdoor heat exchanger for defrosting melts the frost, causing the low-temperature refrigerant to flow into the indoor heat exchanger.

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, one 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 in the heat storage device for defrosting during defrosting, thereby allowing heating operation to continue even during defrosting. This method prevents the indoor temperature from dropping when heating operation is temporarily stopped for defrosting, thereby maintaining user comfort.

When a heat storage device is installed in the refrigerant circuit and cooling operation is performed, the refrigerant discharged from the compressor is condensed in the outdoor heat exchanger and then flows into the indoor heat exchanger via an expansion valve. The indoor exchanger functions as an evaporator, exchanging heat between the refrigerant and the indoor air, thereby supplying cool air to the room. The refrigerant that flows out of the indoor heat exchanger then flows into the compressor.

During this type of cooling operation, there is no need to exchange heat between the refrigerant and the heat storage material in the heat storage device, so the expansion valve located between the outdoor heat exchanger and the heat storage device is closed to prevent refrigerant from flowing into the heat storage device from the outdoor heat exchanger.

JP 2016-017738 A

When cooling is performed in this way, the expansion valve is closed to prevent refrigerant from flowing into the heat storage device. However, because the expansion valve is designed to allow a small amount of refrigerant to flow even when fully closed, the flow of refrigerant cannot be completely blocked. In other words, even during cooling operation, a small amount of refrigerant flows from the outdoor heat exchanger into the heat storage device via the closed expansion valve.

Heating devices are often installed outdoors, and especially when the heat storage material is cooled by outside air, the refrigerant that flows into the device condenses inside the device and becomes liquid-phase refrigerant. This means that liquid-phase refrigerant accumulates inside the device, and because the density of liquid-phase refrigerant is high, the amount of refrigerant circulating through the refrigerant circuit decreases. A decrease in the amount of refrigerant circulating through the refrigerant circuit can lead to a decrease in the capacity of the refrigeration cycle device.

The present invention was made in consideration of the above-mentioned problems, and aims to provide a refrigeration cycle device and a control method for a refrigeration cycle device that can prevent a decrease in the capacity of the refrigeration cycle device by preventing refrigerant from accumulating inside the heat storage heat exchanger and minimizing a decrease in the amount of refrigerant circulating through the refrigerant circuit, even when cooling operation is performed in the refrigeration cycle device equipped with a heat storage heat exchanger.

A refrigeration cycle device according to one aspect of the present invention includes 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 the refrigerant and a heat storage material, a refrigerant circuit having an expansion valve with an adjustable opening and a switching valve that switches the flow path when the refrigerant circulates, a heat storage temperature sensor that detects the temperature of the heat storage material, and a control device that controls the switching valve and the expansion valve. The switching valve switches the flow path between cooling operation, in which the outdoor heat exchanger functions as a condenser and the indoor heat exchanger functions as an evaporator, and heat storage cooling operation, in which at least the indoor heat exchanger functions as an evaporator when the heat storage heat exchanger functions as a condenser. When the control device determines that the detected value of the heat storage temperature sensor has fallen below a first predetermined temperature during cooling operation, the control device controls the switching valve to switch from cooling operation to heat storage cooling operation.

In another aspect of the present invention, a refrigeration cycle device includes 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 the refrigerant and a heat storage material, a refrigerant circuit having an expansion valve with an adjustable opening and a switching valve that switches the flow path when the refrigerant circulates, a heat storage temperature sensor that detects the temperature of the heat storage material, and a control device that controls the switching valve and the expansion valve.During cooling operation in which the outdoor heat exchanger functions as a condenser and the indoor heat exchanger functions as an evaporator, if the control device determines that the detected value of the heat storage temperature sensor has fallen below a first predetermined temperature, the control device opens a second expansion valve located between the outdoor heat exchanger and the heat storage heat exchanger so that the refrigerant flowing out of the outdoor heat exchanger flows into the heat storage heat exchanger.

A control method for a refrigeration cycle device according to one aspect of the present invention is a refrigeration cycle device including 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, a refrigerant circuit having an expansion valve with an adjustable opening and a switching valve that switches the flow path when the refrigerant circulates, a heat-storage temperature sensor that detects the temperature of the heat storage material, and a control device that controls the switching valve and the expansion valve. The control device includes the steps of: performing cooling operation in which the outdoor heat exchanger functions as a condenser and the indoor heat exchanger functions as an evaporator; comparing the detected value of the heat-storage temperature sensor with a first predetermined temperature during cooling operation by the control device; and, when the control device determines that the detected value of the heat-storage temperature sensor has fallen below the first predetermined temperature, controlling the switching valve by the control device to switch from cooling operation to heat-storage cooling operation in which at least the indoor heat exchanger functions as an evaporator when the heat-storage heat exchanger functions as a condenser.

A control method for a refrigeration cycle device according to one aspect of the present invention is a refrigeration cycle device including 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, a refrigerant circuit having an expansion valve with an adjustable opening and a switching valve that switches the flow path when the refrigerant circulates, a heat storage temperature sensor that detects the temperature of the heat storage material, and a control device that controls the switching valve and the expansion valve, in which the control device controls the outdoor heat exchanger. the outdoor heat exchanger functions as a condenser and the indoor heat exchanger functions as an evaporator, the control device compares the detected value of the heat storage temperature sensor with a first predetermined temperature during the cooling operation, and when the control device determines that the detected value of the heat storage temperature sensor has become lower than the first predetermined temperature, the control device opens a second expansion valve disposed between the outdoor heat exchanger and the heat storage heat exchanger so that the refrigerant flowing out of the outdoor heat exchanger flows into the heat storage heat exchanger.

According to the present invention, even when cooling operation is performed in a refrigeration cycle device equipped with a heat storage heat exchanger, the refrigerant is prevented from accumulating inside the heat storage device and the amount of refrigerant circulating through the refrigerant circuit is kept as low as possible, thereby preventing a decrease in the capacity of the refrigeration cycle device.

1 is a refrigerant circuit diagram of a refrigeration cycle device according to an embodiment of the present invention. 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. 1 is a refrigerant circuit diagram showing the flow of refrigerant when the refrigeration cycle device according to an embodiment of the present invention performs heating operation. 2 is a refrigerant circuit diagram showing the flow of refrigerant when the refrigeration cycle device according to the first embodiment of the present invention performs a heat-storage cooling operation. FIG. 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. 3 is a flowchart showing a control flow when performing a cooling operation in the refrigeration cycle device according to the first embodiment of the present invention. 4 is a flowchart showing a control flow when a heat-storage cooling operation is performed in the refrigeration cycle device according to the first embodiment of the present invention. FIG. 6 is a refrigerant circuit diagram showing the flow of refrigerant when a refrigeration cycle device according to a second embodiment of the present invention performs cooling operation. 10 is a flowchart showing a control flow when a cooling operation is performed in a refrigeration cycle device according to a second embodiment of the present invention.

(First embodiment)
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.

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

The thermal storage heat exchanger 4 is a heat exchanger in which heat is exchanged between the thermal storage material and the refrigerant passing through the thermal storage heat exchanger 4. The thermal storage heat exchanger 4 is, for example, a fin-and-tube type heat exchanger. The thermal storage heat exchanger 4 is placed inside a thermal storage container filled with thermal storage material.

The heat storage material may be liquid or solid, as long as it can exchange heat with the refrigerant flowing inside the heat storage heat exchanger 4 and store heat. This heat storage material stores heat supplied from the refrigerant, and the stored heat is used, for example, during defrosting operation of the outdoor heat exchanger 3. As will be described later, in the first embodiment of the present invention, the heat storage material is used to prevent the refrigerant flowing into the heat storage heat exchanger 4 from condensing and remaining in the heat storage heat exchanger 4 during cooling operation.

The heat storage heat exchanger 4 is also provided with a heat storage temperature sensor HS that measures the temperature of the heat storage material. There may be only one heat storage temperature sensor HS, or multiple sensors may be provided. For example, if multiple heat storage temperature sensors HS are provided, the detected temperature of the heat storage material may be calculated and used for the control described below, such as by taking the average of the values detected by each sensor HS as the temperature of the heat storage material.

Furthermore, a refrigerant temperature sensor RS is provided between the heat storage heat exchanger 4 and the second expansion valve 52. The refrigerant temperature sensor RS detects the temperature of the refrigerant flowing into the heat storage heat exchanger 4. This temperature is correlated with the saturation temperature of the refrigerant in the indoor heat exchanger 2, which functions as an evaporator during cooling operation.

The refrigerant temperature detected by the refrigerant temperature sensor RS is used to determine whether the refrigerant flowing into the heat storage heat exchanger 4 during cooling operation will condense inside the heat storage heat exchanger 4, i.e., whether or not to perform the heat storage cooling operation described below. Hereinafter, the refrigerant temperature detected by the refrigerant temperature sensor RS will be referred to as the "first predetermined temperature."

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

The second expansion valve 52 is located between the heat storage heat exchanger 4 and the outdoor heat exchanger 3. That is, it is located downstream in the direction of refrigerant flow when the heat storage heat exchanger 4 functions as a condenser. Specifically, the second expansion valve 52 is located on a refrigerant pipe connected at one end to the refrigerant pipe connecting the indoor heat exchanger 2 and the outdoor heat exchanger 3, and at the other end to the heat storage heat exchanger 4. The third expansion valve 53 is located between the indoor heat exchanger 2 and the outdoor heat exchanger 3. That is, it is located downstream in the direction of refrigerant flow when the indoor heat exchanger 2 functions as a condenser. Specifically, the third expansion valve 53 is located on a refrigerant pipe connected at one end to the refrigerant pipe connecting the outdoor heat exchanger 3 and the second expansion valve 52, and at the other end to the indoor heat exchanger 2.

The switching valve 6 switches the refrigerant circulation path in the refrigerant circuit C between, for example, normal cooling operation, in which the outdoor heat exchanger 3 functions as a condenser and the indoor heat exchanger 2 functions as an evaporator, and heat storage cooling operation (described below), in which the heat storage heat exchanger 4 functions as a condenser and the indoor heat exchanger 2 and outdoor heat exchanger 3 function as evaporators.

Furthermore, in the refrigeration cycle apparatus S according to the embodiment of the present invention, two switching valves 6 are provided. Specifically, a first switching valve 61 is provided between the compressor 1 and the indoor heat exchanger 2. Furthermore, a second switching valve 62 is provided between the compressor 1 and the outdoor heat exchanger 3 or the thermal storage heat exchanger 4.

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

Furthermore, in the refrigeration cycle apparatus S according to an embodiment of the present invention, cooling operation is not stopped even when heat storage operation is performed on the heat storage heat exchanger 4, and heat storage cooling operation is performed in parallel with the heat storage operation.

Next, the refrigerant circuit C of the refrigeration cycle apparatus S in the embodiment of the present invention shown in Figure 1 will be described. The refrigerant circuit C is composed of each device, such as the compressor 1 described above, and refrigerant piping connecting these devices through which refrigerant flows. Here, a first switching valve 61 is provided in the refrigerant piping connecting the compressor 1 and the indoor heat exchanger 2. In addition, a second switching valve 62 is provided in the refrigerant piping between the compressor 1 and the first switching valve 61, which directs the refrigerant discharged from the compressor 1 to the outdoor heat exchanger 3 or the thermal storage heat exchanger 4.

Furthermore, in the refrigeration cycle apparatus S according to an embodiment of the present invention, a bypass circuit B is provided between the first switching valve 61 and the second switching valve 62. The bypass circuit B is provided with a check valve or the like so that the refrigerant flows only in the direction of the arrow 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 to the second switching valve 62.

The control device 7 controls the opening degrees of the multiple expansion valves 5. By controlling the opening degree of each expansion valve, the control device 7 can adjust the flow rate of refrigerant circulating through the refrigerant circuit C. As described above, the control device 7 also switches the flow of refrigerant circulating through the refrigerant circuit C by switching the multiple switching valves 6. By controlling the multiple expansion valves 5 and multiple switching valves 6 in this way, the control device 7 can switch the operating mode, for example, between cooling operation and heat storage cooling operation in which heat storage operation is performed in parallel with the heat storage heat exchanger 4.

In this way, the control device 7 performs control such as switching the operating mode of the refrigeration cycle apparatus S. Therefore, before explaining the functions of each part of the control device 7 of the refrigeration cycle apparatus S in this embodiment of the present invention, the operating modes performed in the refrigeration cycle apparatus S will first be explained in order using the circuit diagram of the refrigeration cycle apparatus S in this embodiment of the present invention shown in Figures 2 to 4.

In the circuit diagrams shown in Figures 2 to 4, the refrigerant circuits C through which the refrigerant actually flows are indicated by solid lines. On the other hand, the refrigerant circuits C through which the refrigerant does not flow are indicated by dashed lines. Furthermore, the direction of the refrigerant circulating within the refrigerant circuit C is indicated by arrows.

First, we will explain normal cooling operation. Figure 2 is a refrigerant circuit diagram showing the flow of refrigerant when the refrigeration cycle device S according to an 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.

That is, the refrigerant compressed by compressor 1 and discharged in a high-temperature, high-pressure state flows into outdoor heat exchanger 3 via first expansion valve 51 and second switching valve 62, as shown by the arrows in Figure 2. At this time, first expansion valve 51 is fully open. Refrigerant discharged from compressor 1 also flows through first switching valve 61, but also passes through bypass circuit B and flows into outdoor heat exchanger 3 via second switching valve 62.

The refrigerant that flows into the outdoor heat exchanger 3 is cooled by outside air supplied by the rotation of an outdoor fan (not shown), and dissipates heat into the outside air. Some or all of the refrigerant then condenses.

The refrigerant that has released heat to the outside air in this way flows out of the outdoor heat exchanger 3 and passes through the third expansion valve 53, where it is decompressed and becomes a low-temperature, low-pressure refrigerant. The low-temperature, low-pressure refrigerant then flows into the indoor heat exchanger 2, where it exchanges heat with the indoor air.

Through heat exchange in the indoor heat exchanger 2, the refrigerant absorbs heat from the indoor air and evaporates. The indoor air drawn into the indoor heat exchanger 21 is cooled and supplied to the room by the indoor fan, cooling the room. The refrigerant that has absorbed heat through heat exchange then flows into the compressor 1 via the first switching valve 61.

During cooling operation, the third expansion valve 53, through which the refrigerant condensed in the outdoor heat exchanger 3 passes, is controlled to an opening angle according to the user's request. Meanwhile, the second expansion valve 52 is controlled to be fully closed, so that the refrigerant flowing out of the outdoor heat exchanger 3 does not flow into the thermal storage heat exchanger 4.

Next, the flow of refrigerant when the refrigeration cycle device S is performing heating operation is as shown in Figure 3. Figure 3 is a refrigerant circuit diagram showing the flow of refrigerant when the refrigeration cycle device S according to an embodiment of the present invention is performing heating operation.

As shown in Figure 3, the refrigerant discharged from compressor 1 flows into indoor heat exchanger 2 via first switching valve 61. Meanwhile, the first expansion valve 51, located between compressor 1 and first switching valve 61, is controlled to be fully closed, so refrigerant does not flow to outdoor heat exchanger 3 via second switching valve 62, as in the cooling operation described above.

The indoor heat exchanger 2 exchanges heat between the refrigerant and the air flowing into the indoor unit, absorbing heat from the refrigerant and supplying warmed air to the indoor space. Therefore, the indoor heat exchanger 2 functions as a condenser.

The refrigerant flowing out of the indoor heat exchanger 2 passes through the third expansion valve 53, where it is reduced in pressure and becomes a low-temperature, low-pressure refrigerant, which then 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 via the second switching valve 62.

As described above, the refrigeration cycle apparatus S in this embodiment of the present invention is provided with a heat storage heat exchanger 4 in addition to the indoor heat exchanger 2 and the outdoor heat exchanger 3. However, when the normal cooling operation or heating operation described above is performed, the heat storage heat exchanger 4 does not function as a condenser or evaporator. Therefore, for example, during cooling operation, the second expansion valve 52 is fully closed to prevent refrigerant flowing out of the outdoor heat exchanger 3 from flowing into the heat storage heat exchanger 4.

However, as mentioned above, even when the second expansion valve 52 is fully closed, due to the structure of the expansion valve, a small amount of the refrigerant flowing from the outdoor heat exchanger 3 to the indoor heat exchanger 2 flows into the thermal storage heat exchanger 4 via the second expansion valve 52.

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. In this case, if the temperature of the heat storage material is lower than that of the flowing refrigerant, the refrigerant may condense and become a liquid-phase refrigerant. This phenomenon is particularly likely to occur if the heat storage heat exchanger 4 is located in, for example, an outdoor unit and the temperature outside the outdoor unit is very low.

When the refrigerant that flows into the heat storage heat exchanger 4 reaches this liquid phase, as mentioned above, the refrigerant accumulates inside the heat storage device. Furthermore, because the density of refrigerant in liquid phase is high, the amount of refrigerant circulating through the refrigerant circuit decreases. A decrease in the amount of refrigerant circulating through the refrigerant circuit can lead to a decrease in the capacity of the refrigeration cycle device.

As described below, the control device 7 compares the temperature of the heat storage material with the (evaporation) temperature of the refrigerant that flows into the heat storage heat exchanger 4 during cooling operation, and if it determines that the former temperature is lower than the latter temperature, it switches the operating mode from cooling operation to heat storage cooling operation.

The flow of refrigerant during the heat storage cooling operation will now be explained using Figure 4. Figure 4 is a refrigerant circuit diagram showing the flow of refrigerant when the refrigeration cycle device S according to the first embodiment of the present invention is performing heat storage cooling operation.

The reason for performing the heat storage cooling operation is to prevent the refrigerant that flows into the heat storage heat exchanger 4 from condensing and becoming a liquid-phase refrigerant. Therefore, in order to raise the temperature of the heat storage material, high-temperature refrigerant immediately after being discharged from the compressor 1 flows into the heat storage heat exchanger 4 and exchanges heat with the heat storage material, thereby storing heat in the heat storage material.

That is, the refrigerant compressed by compressor 1 and discharged in a high-temperature, high-pressure state flows into the heat storage heat exchanger 4 via the first expansion valve 51 and the second switching valve 62, as shown by the arrows in Figure 4. At this time, the first expansion valve 51 is fully open. The refrigerant discharged from compressor 1 also flows through the first switching valve 61, but also passes through bypass circuit B and flows into the heat storage heat exchanger 4 from the second switching valve 62.

In the heat storage heat exchanger 4, the refrigerant that flows in exchanges heat with the heat storage material, causing the heat of the refrigerant to be stored in the heat storage material. Therefore, the heat storage heat exchanger 4 at this time functions as a condenser.

The refrigerant flowing out of the thermal storage heat exchanger 4 is decompressed as it passes through the second expansion valve 52 and the third expansion valve 53, becoming a low-temperature, low-pressure refrigerant. The low-temperature, low-pressure refrigerant then flows into the indoor heat exchanger 2, where it exchanges heat with the indoor air.

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

The refrigerant flowing out of the thermal storage heat exchanger 4 flows further 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.

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

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, the temperature of the heat storage material when heat exchange occurs with the refrigerant discharged from the compressor 1 and flowing into the heat storage heat exchanger 4 during heat storage cooling operation.

The temperature of the heat storage material detected by the heat storage temperature sensor HS may be constantly transmitted from the heat storage temperature sensor HS to the temperature detection unit 71. Alternatively, conversely, the temperature detection unit 71 may obtain the temperature from the heat storage temperature sensor HS as needed.

The temperature detection unit 71 also acquires the refrigerant temperature (first predetermined temperature) detected by the refrigerant temperature sensor RS. The refrigerant temperature detected by the refrigerant temperature sensor RS is the temperature of the refrigerant flowing from the outdoor heat exchanger 3 to the indoor heat exchanger 2 that has flowed into the heat storage heat exchanger 4 via the fully closed second expansion valve 52. Because the second expansion valve 52 is fully closed, the amount of refrigerant at this time is small compared to the amount of refrigerant flowing from the outdoor heat exchanger 3 to the indoor heat exchanger 2. The evaporating temperature may also be constantly transmitted from the refrigerant temperature sensor RS to the temperature detection unit 71, or the temperature detection unit 71 may acquire it from the refrigerant temperature sensor RS as needed.

In this embodiment, the first predetermined temperature is determined by a refrigerant temperature sensor that detects the temperature of the refrigerant flowing into the heat storage heat exchanger 4, but this is not limiting. For example, because the temperature of the refrigerant flowing into the heat storage heat exchanger 4 is correlated with the saturation temperature of the refrigerant in the indoor heat exchanger 2, the first predetermined temperature may be set based on the detection value of an intermediate temperature sensor (not shown) that detects the temperature of the refrigerant flowing into the indoor heat exchanger 2. In this case, there is a difference in pressure loss between the path from the branching point to the inlet position of the heat storage heat exchanger 4 and the path from the branching point to the position detected by the intermediate temperature sensor in the indoor heat exchanger. Therefore, by correcting the predetermined value to take pressure loss into account, refrigerant stagnation in the heat storage heat exchanger can be more accurately prevented.

Furthermore, the indoor temperature (room temperature) detected by a temperature sensor (not shown) provided in the indoor heat exchanger 2 is also acquired by the temperature detection unit 71. These temperatures of the heat storage material and the refrigerant are used to control the storage of heat in the heat storage heat exchanger 4.

The memory unit 72 is composed of, for example, a semiconductor or a magnetic disk. The memory unit 72 stores, for example, the set temperature, the first predetermined temperature, and the second predetermined temperature set in the indoor unit equipped with the indoor heat exchanger 2 that constitutes the refrigeration cycle apparatus S.

The determination unit 73 determines, for example, whether to switch the operating mode to heat storage cooling operation during cooling operation. Specifically, it uses the temperature of the heat storage material in the heat storage heat exchanger 4 and the saturation temperature of the refrigerant (first predetermined temperature) to determine whether to allow the refrigerant to flow into the heat storage heat exchanger 4 and store heat in the heat storage material.

That is, when the refrigeration cycle device S is performing cooling operation, as explained using Figure 2, the high-temperature, high-pressure refrigerant discharged from the compressor 1 flows into the outdoor heat exchanger 3 and is condensed. The refrigerant then flows out of the outdoor heat exchanger 3 and becomes low-temperature, low-pressure refrigerant as it passes through an expansion valve (here, the third expansion valve 53 as shown in Figure 1), and flows into the indoor heat exchanger 2.

The indoor heat exchanger 2 functions as an evaporator, supplying cool air to the room. The refrigerant that leaves the indoor heat exchanger 2 then flows into the compressor 1. During this cooling operation, the second expansion valve 52 is closed, and the refrigerant that leaves the outdoor heat exchanger 3 does not generally flow into the thermal storage heat exchanger 4.

However, as mentioned above, due to the structure of the second expansion valve 52, a small amount of refrigerant flows even when it is fully closed, so it is inevitable that the refrigerant flowing out of the outdoor heat exchanger 3 will flow into the heat storage heat exchanger 4. When refrigerant flows into the heat storage heat exchanger 4 in this way, if the temperature outside the outdoor unit where the outdoor unit is installed is very low and the heat storage material is cooled by the outside air, the refrigerant will condense inside the heat storage heat exchanger 4 and become a liquid-phase refrigerant.

When the refrigerant reaches a liquid phase in this way, it accumulates inside the thermal storage heat exchanger 4, and combined with its high density, the amount of refrigerant circulating through the refrigerant circuit C decreases. This can potentially lead to a decrease in the capacity of the refrigeration cycle device S.

Therefore, in the refrigeration cycle apparatus S according to the first embodiment of the present invention, a heat storage cooling operation is performed as described using Figure 4. In other words, heat storage cooling operation is an operating mode in which heat is stored in the heat storage material provided inside the heat storage heat exchanger 4 during cooling operation. By performing this heat storage cooling operation, heat is stored in the heat storage material of the heat storage heat exchanger 4, and condensation of the refrigerant that has flowed into the heat storage heat exchanger 4 during cooling operation is prevented inside the heat storage heat exchanger 4.

Specifically, when the refrigeration cycle device S is performing cooling operation, the determination unit 73 obtains the temperature of the heat storage material from the heat storage temperature sensor HS via the temperature detection unit 71. At the same time, the determination unit 73 obtains the temperature of the refrigerant flowing out of the second expansion valve 52 (first predetermined temperature) from the refrigerant temperature sensor RS. The determination unit 73 then compares the temperature of the heat storage material with the first predetermined temperature.

If the determination unit 73 determines, as a result of the comparison, that the temperature of the heat storage material is lower than the first predetermined temperature, it switches the operating mode from air conditioning operation to heat-storage air conditioning operation and starts heat-storage air conditioning operation. That is, the determination unit 73 issues an instruction to the switching control unit 74 to switch the operating mode to heat-storage air conditioning operation. The switching control unit 74 switches the expansion valve 5 and the switching valve 6 based on the instruction from the determination unit 73.

As described above, during cooling operation, the refrigerant discharged from the compressor 1 flows into the outdoor heat exchanger 3 via the first expansion valve 51 and the second switching valve 62. On the other hand, when the determination unit 73 determines that the operating mode should be switched from cooling operation to heat-storage cooling operation, the switching control unit 74 controls the second switching valve 62 based on the instruction of the determination unit 73 to switch the refrigerant flow path.

The opening of the second expansion valve 52 is controlled from a fully closed state to a preset initial opening, and then the opening is controlled so that the temperature of the refrigerant discharged from the compressor 1 (discharge temperature) becomes the target discharge temperature. The initial opening is set based on the evaporation pressure, compressor 1 rotation speed, etc. The target discharge temperature is set based on the condensation pressure, evaporation pressure, and compressor 1 rotation speed, and is the target value for the discharge temperature at which the refrigerant drawn into the compressor is in an optimal state.

When the second switching valve 62 is switched by the switching control unit 74, the high-temperature refrigerant discharged from the compressor 1 flows directly into the heat storage heat exchanger 4 rather than into the outdoor heat exchanger 3 (heat storage cooling operation). In the heat storage heat exchanger 4 into which the refrigerant from the compressor 1 flows, heat exchange occurs between the high-temperature refrigerant and the heat storage material, and the heat of the refrigerant is transferred to the heat storage material and stored in the heat storage material.

In this case, the heat storage heat exchanger 4 functions as a condenser, and the refrigerant that has exchanged heat in the heat storage heat exchanger 4 passes through the second expansion valve 52 and flows into the indoor heat exchanger 2. The indoor heat exchanger 2 functions as an evaporator, exchanging heat between the refrigerant that has flowed in and the indoor air to supply cool air into the room. In this way, during heat storage cooling operation, heat is stored in the heat storage heat exchanger 4 and the indoor heat exchanger 2 is used as an evaporator, so cooling operation can be performed simultaneously.

The refrigerant flowing out of the thermal storage heat exchanger 4 also flows into the outdoor heat exchanger 3 via the second expansion valve 52. In this case, the outdoor heat exchanger 3 also functions as an evaporator, just like the indoor heat exchanger 2. The refrigerant flowing out of the outdoor heat exchanger 3 flows into the compressor 1 via the second switching valve 62.

As described above, during heat storage cooling operation, the refrigerant flowing out of the heat storage heat exchanger 4 flows into the indoor heat exchanger 2, but cooling operation continues. The determination unit 73 also compares the current indoor temperature (room temperature) with the temperature set by the user. This is to determine the opening degree of the third expansion valve 53, and how much of the refrigerant flowing out of the heat storage heat exchanger 4 should be allowed to flow into the indoor heat exchanger 2 depending on the current situation.

Specifically, the determination unit 73 obtains information about the room temperature via the temperature detection unit 71, and also obtains information about the temperature set by the user from the memory unit 72. It then compares the room temperature with the set temperature.

If the comparison shows that the room temperature is lower than the set temperature, the room is sufficiently cooled, and further operation of the indoor unit may actually reduce user comfort. Therefore, there is no need to lower the temperature any further, and it is sufficient not to flow refrigerant through the indoor heat exchanger 2.

The determination unit 73 then instructs the switching control unit 74 to fully close the third expansion valve 53. Based on the instruction from the determination unit 73, the switching control unit 74 fully closes the third expansion valve 53. In this case, the refrigerant flowing out of the heat storage heat exchanger 4 does not flow into the indoor heat exchanger 2, but only into the outdoor heat exchanger 3. In other words, the circuit to which the outdoor heat exchanger 3 is connected can be used as a bypass circuit. Therefore, in cases where sufficient heat storage is required in the heat storage heat exchanger 4 but such capacity is not required in the indoor heat exchanger 2, a place for the refrigerant to go can be secured, and both requirements can be met.

On the other hand, if the determination unit 73 determines that the room temperature is higher than the set temperature, it is necessary to continue supplying cool air to the room. Therefore, the determination unit 73 instructs the switching control unit 74 to fully open the third expansion valve 53. Based on the instruction from the determination unit 73, the switching control unit 74 fully opens the third expansion valve 53.

The determination unit 73 compares the temperature of the heat storage material measured by the heat storage temperature sensor HS with a second predetermined temperature pre-stored in the memory unit 72 to determine whether to terminate the heat storage cooling operation and switch the operating mode to normal cooling operation.

The reason for performing heat storage cooling operation is, as explained above, to store heat in the heat storage material to prevent the refrigerant flowing into the heat storage heat exchanger 4 from the second expansion valve 52, which is fully closed during cooling operation, from condensing and becoming a liquid-phase refrigerant through heat exchange with the heat storage material in the heat storage heat exchanger 4.

For this reason, even if refrigerant flows from the outdoor heat exchanger 3 into the heat storage heat exchanger 4 during cooling operation, it is sufficient that heat is stored in the heat storage material to the extent that condensation does not occur. On the other hand, frequent switching between cooling operation and heat storage cooling operation could ultimately result in a loss of user comfort. Also, during heat storage cooling operation, the higher the rotation speed of the compressor 1, the higher the temperature of the refrigerant supplied to the heat storage heat exchanger 4. However, if the rotation speed is increased too much, the high-pressure will rise excessively, triggering protection control and shutting down the compressor 1.

In this way, it is necessary to reduce the frequency of switching from cooling operation to heat storage cooling operation while still storing heat in the heat storage material, and a balance must be struck between these two.

Therefore, the "second predetermined temperature" is set to a temperature at which the compressor 1 can be driven at a rotation speed during heat storage cooling operation that does not activate protection control and allows heat to be stored in the heat storage material. Specifically, this is, for example, 50°C.

If the determination unit 73 determines that the temperature of the heat storage material is lower than the second predetermined temperature, the amount of heat stored in the heat storage material is still insufficient, and heat storage cooling operation continues. On the other hand, if the determination unit 73 determines that the temperature of the heat storage material is equal to or higher than the second predetermined temperature, the determination unit 73 instructs the switching control unit 74 to end heat storage cooling operation and switch the operating mode to normal cooling operation.

[Operation]
Next, the control flow of the refrigeration cycle apparatus S by the control device 7 in the above-mentioned cooling operation and heat-storage cooling operation will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is a flowchart showing the control flow when the refrigeration cycle apparatus S according to the first embodiment of the present invention performs the cooling operation. Fig. 7 is a flowchart showing the control flow when the refrigeration cycle apparatus S according to the first embodiment of the present invention performs the heat-storage cooling operation.

First, normal cooling operation is initiated in the refrigeration cycle device S (ST1). The conditions for initiating cooling operation are set in advance, and the control device 7 determines whether these conditions are met. A possible condition for initiating cooling operation is, for example, the user setting a set temperature and initiating cooling operation.

When cooling operation begins, as described above, the refrigerant discharged from the compressor 1 flows into the outdoor heat exchanger 3 via the first expansion valve 51, the second switching valve 62, and the first switching valve 61. The refrigerant condensed in the outdoor heat exchanger 3 flows into the indoor heat exchanger 2 via the third expansion valve 53. In the indoor heat exchanger 2, heat is exchanged between the refrigerant and the indoor air, and cool air is supplied to the room. The refrigerant that flows out of the indoor heat exchanger 2 flows into the compressor 1 via the first switching valve 61.

During cooling operation, the second expansion valve 52 is controlled by the switching control unit 74 to be fully closed. This prevents the refrigerant flowing out of the outdoor heat exchanger 3 from flowing into the heat storage heat exchanger 4. However, as mentioned above, a small amount of the refrigerant flowing from the outdoor heat exchanger 3 to the indoor heat exchanger 2 flows into the heat storage heat exchanger 4.

The control device 7 therefore acquires information regarding the temperature of the heat storage material during cooling operation and information regarding the saturation temperature of the refrigerant flowing from the outdoor heat exchanger 3 to the heat storage heat exchanger 4. Specifically, information regarding the temperature of the heat storage material detected by the heat storage temperature sensor HS and information regarding the temperature of the refrigerant detected by the refrigerant temperature sensor RS are acquired via the temperature detection unit 71.

Then, the determination unit 73 compares the temperature of the heat storage material with the temperature of the refrigerant (first predetermined temperature) (ST2). As a result, if it is determined that the temperature of the heat storage material is a high temperature equal to or higher than the first predetermined temperature (NO in ST3), the process returns to step ST2, and the temperature of the heat storage material is again compared with the first predetermined temperature. In this case, even if some of the refrigerant flows from the outdoor heat exchanger 3 into the heat storage heat exchanger 4, it is unlikely to condense into liquid-phase refrigerant, so there is no need to switch to heat storage cooling operation.

On the other hand, if the judgment unit 73 determines that the temperature of the heat storage material is lower than the first predetermined temperature (YES in ST3), there is a possibility that the refrigerant flowing into the heat storage heat exchanger 4 will condense and become a liquid-phase refrigerant, so the operating mode is switched from normal cooling operation to heat storage cooling operation, and heat storage cooling operation is started (ST4).

In this case, after compressor 1 is temporarily stopped, based on the determination result of determination unit 73 as described above, switching control unit 74 controls second switching valve 62 to switch the refrigerant flow path so that the refrigerant discharged from compressor 1 flows into heat storage heat exchanger 4 rather than into outdoor heat exchanger 3.

As a result, the operating mode switches to heat storage cooling operation (ST41 in Figure 7), and the judgment unit 73 compares the indoor temperature with the set temperature for cooling operation set by the user (ST42). This is because in heat storage cooling operation, the heat storage heat exchanger 4 acts as a condenser, and the opening degree of the third expansion valve 53 is determined to determine how much of the refrigerant flowing out of the heat storage heat exchanger 4 should flow into the indoor heat exchanger 2 depending on the current situation.

Therefore, the determination unit 73 compares the indoor temperature with the set temperature to allow the refrigerant corresponding to the capacity required by the indoor unit to flow into the indoor heat exchanger 2. As a result, if it is determined that the room temperature is lower than the set temperature (YES in ST43), the third expansion valve 53 is controlled to be fully closed (ST44).

In other words, in this case, there is no need to flow the refrigerant flowing out of the heat storage heat exchanger 4 to the indoor heat exchanger 2, and the refrigerant flows only to the outdoor heat exchanger 3. On the other hand, if the judgment unit 73 determines that the room temperature is above the set temperature (NO in ST43), the third expansion valve 53 is controlled to be fully open, and cool air continues to be supplied to the room (ST45).

While heat storage cooling operation is being performed, the determination unit 73 determines whether sufficient heat has been stored in the heat storage material. Specifically, it compares the temperature of the heat storage material with a second predetermined temperature (ST5). The temperature of the heat storage material is obtained from the heat storage temperature sensor HS, and the second predetermined temperature is obtained from the memory unit 72.

As a result, if the temperature of the heat storage material is lower than the second predetermined temperature (NO in ST5), there is still a possibility that the refrigerant flowing into the heat storage heat exchanger 4 will condense and become liquid-phase refrigerant, so heat storage cooling operation will continue.

On the other hand, if the judgment unit 73 judges that the temperature of the heat storage material is equal to or higher than the second predetermined temperature (NO in ST5), even if refrigerant flows into the heat storage heat exchanger 4, it is unlikely to condense into a liquid-phase refrigerant, so the operating mode is switched from heat storage cooling operation to cooling operation (ST6).

As explained above, by performing heat storage cooling operation, even when cooling operation is performed in a refrigeration cycle device equipped with a heat storage heat exchanger, it is possible to prevent refrigerant from accumulating inside the heat storage device and minimize the reduction in the amount of refrigerant circulating through the refrigerant circuit.

Furthermore, if refrigerant flows into the heat storage heat exchanger during cooling operation, condenses, and becomes liquid-phase refrigerant, causing the refrigerant to accumulate inside the heat storage heat exchanger, reducing the amount of refrigerant circulating through the refrigeration cycle unit's refrigerant circuit. When cooling operation is performed in this case, the enthalpy difference becomes smaller when the amount of refrigerant is low, resulting in greater power consumption in compressor 1 compared to normal cooling operation, and reducing the energy-saving performance of the entire refrigeration cycle unit.

However, by performing the heat storage cooling operation in the first embodiment of the present invention as described above, the amount of refrigerant remaining in the heat storage heat exchanger can be reduced. This avoids a significant reduction in the total amount of refrigerant circulating through the refrigerant circuit, and as a result, it is possible to avoid a decrease in the energy-saving performance of the entire refrigeration cycle device.

In the first embodiment, it was explained that the operating mode is switched from cooling operation to heat-storage cooling operation when it is determined that the temperature of the heat storage material has become lower than the first predetermined temperature during cooling operation. However, the timing of switching the operating mode from cooling operation to heat-storage cooling operation is not limited to this timing.

For example, during cooling operation, the refrigeration cycle device S may enter a so-called thermo-off state. Because the thermo-off state occurs, heat exchange between the indoor air and the refrigerant does not occur in the indoor heat exchanger 2. Therefore, when the determination unit 73 determines that the thermo-off state has occurred during such cooling operation, it performs control to switch the operating mode from cooling operation to heat-storage cooling operation.

Then, heat is stored in the heat storage material by flowing high-temperature refrigerant from the compressor 1 into the heat storage heat exchanger 4. In addition, the third expansion valve 53 is controlled to be in a closed state so that the refrigerant flowing out of the heat storage heat exchanger 4 does not flow into the indoor heat exchanger 2, but only into the outdoor heat exchanger 3.
By performing such control, the indoor unit actively performs heat storage cooling operation when cooling capacity is not required, and by storing heat in the heat storage material, it is possible to prevent the refrigerant flowing into the heat storage heat exchanger 4 from condensing and becoming a liquid phase refrigerant during cooling operation.

In particular, by effectively utilizing the thermo-off state, the frequency of switching from cooling operation to heat storage cooling operation can be reduced, thereby reducing the possibility of compromising user comfort.

Furthermore, when heat storage cooling operation is performed, the refrigerant that flows out of the heat storage heat exchanger 4 flows not only into the indoor heat exchanger 2 but also into the outdoor heat exchanger 3. As a result, the amount of refrigerant flowing into the indoor heat exchanger 2 decreases, which may result in a corresponding decrease in the capacity of the indoor unit.

For example, an on-off valve can be provided between the second expansion valve 52 and the outdoor heat exchanger 3. By providing this on-off valve, it is possible to prevent refrigerant flowing out of the heat storage heat exchanger 4 from flowing into the outdoor heat exchanger 3 during heat storage cooling operation. Since no refrigerant flows into the outdoor heat exchanger 3, almost all of the refrigerant flowing out of the heat storage heat exchanger 4 flows into the indoor heat exchanger 2. This prevents any loss of capacity in the indoor unit.

Furthermore, during heat storage cooling operation, the above explanation has been given using an example in which the third expansion valve 53 is fully closed or fully open when the refrigerant flowing out of the heat storage heat exchanger 4 flows into the indoor heat exchanger 2. However, this control is not limited to this.

In other words, depending on the temperature set by the user in the indoor unit, there may be cases where a large cooling capacity is not required from the indoor unit. In such cases, the control device 7 can address this by setting the opening degree of the third expansion valve 53 to match the user's requirements.

That is, for example, during cooling operation, if the difference between room temperature and the set temperature is small and not much capacity is required of the indoor unit, control is performed to throttle the third expansion valve 53. On the other hand, if the difference between room temperature and the set temperature is large, a heavy load is placed on the indoor unit, so control is performed to increase the opening of the third expansion valve 53. In other words, during heat storage cooling operation, the amount of refrigerant flowing into the indoor heat exchanger 2 can be adjusted according to the cooling capacity of the indoor unit.

Even when control is performed according to the capacity of the indoor unit in this way, the refrigerant that flows out of the heat storage heat exchanger 4 during heat storage cooling operation also flows into the outdoor heat exchanger 3. In other words, the circuit to which the outdoor heat exchanger 3 is connected can be used as a bypass circuit, so in cases where sufficient heat storage is required in the heat storage heat exchanger 4 but such capacity is not required in the indoor heat exchanger 2, a place for the refrigerant to go can be secured, and both requirements can be met.

Second Embodiment
Next, a second embodiment of the present invention will be described. In the second embodiment, the same components as those described in the first embodiment are designated by the same reference numerals, and redundant descriptions of the same components will be omitted.

In the first embodiment described so far, in order to prevent the refrigerant flowing in from the outdoor heat exchanger 3 from condensing in the heat storage heat exchanger 4 during cooling operation and becoming a liquid-phase refrigerant, the operating mode is switched from cooling operation to heat storage cooling operation, and control is performed to store heat in the heat storage material.

In contrast, in the control of the second embodiment, heat storage cooling operation is not performed, and the refrigerant flowing out from the outdoor heat exchanger 3 is also circulated to the heat storage heat exchanger 4 while the cooling operation is performed. By performing this control, the refrigerant stagnating inside the heat storage heat exchanger 4 can be pushed out and flow into the compressor 1.

Figure 8 is a refrigerant circuit diagram showing the flow of refrigerant when the refrigeration cycle apparatus S1 according to the second embodiment of the present invention is performing cooling operation. The components that make up the refrigeration cycle apparatus S1 are the same and are arranged in the same way. However, the flow of refrigerant discharged from compressor 1 differs from that in heat storage cooling operation.

That is, the basic flow is the same as that of refrigerant in normal cooling operation, as explained using Figure 2. As shown by the arrows in Figure 8, refrigerant discharged from compressor 1 flows into outdoor heat exchanger 3 via first expansion valve 51 and second switching valve 62. Refrigerant condensed in outdoor heat exchanger 3 flows into indoor heat exchanger 2 via third expansion valve 53, where heat exchange occurs between the refrigerant and indoor air, supplying cool air to the room. Refrigerant flowing out of indoor heat exchanger 2 flows into compressor 1 via first switching valve 61.

In this type of refrigerant flow during cooling operation, in the second embodiment, the second expansion valve 52 is controlled to be open. Because the second expansion valve 52 is controlled to be open, the refrigerant flowing out of the outdoor heat exchanger 3 not only flows into the indoor heat exchanger 2, but also into the heat storage heat exchanger 4. The refrigerant flowing out of the heat storage heat exchanger 4 then flows into the compressor 1 via the second switching valve 62.

However, when controlling the second expansion valve 52 to be open in this manner, the determination unit 73 of the control device 7 determines whether or not to perform this control. That is, the determination unit 73 compares the temperature of the heat storage material in the heat storage heat exchanger 4 with the temperature of the refrigerant flowing into the heat storage heat exchanger 4 (first predetermined temperature). This comparison is the same as the control in the first embodiment described above.

If the determination unit 73 compares the temperature of the heat storage material with the temperature of the refrigerant and determines that the temperature of the heat storage material is higher than the first predetermined temperature, normal cooling operation continues. Therefore, control to open the second expansion valve 52 is not performed. In this case, even if some of the refrigerant flows from the outdoor heat exchanger 3 into the thermal storage heat exchanger 4 when the second expansion valve 52 is fully closed, it is unlikely to condense into liquid-phase refrigerant.

On the other hand, if the determination unit 73 determines that the temperature of the heat storage material is lower than the first predetermined temperature, the determination unit 73 instructs the switching control unit 74 to open the second expansion valve 52. Based on the instruction from the determination unit 73, the switching control unit 74 controls the second expansion valve 52 to open.

When the second expansion valve 52 is open, a small amount of the refrigerant flowing out of the outdoor heat exchanger 3 flows into the heat storage heat exchanger 4. In other words, the gas-liquid two-phase refrigerant flowing out of the outdoor heat exchanger 3 flows into the heat storage heat exchanger 4, which is filled with liquid-phase refrigerant.

When liquid-phase refrigerant accumulates inside the heat storage heat exchanger 4 during cooling operation, the entire heat storage circuit, including the heat storage heat exchanger 4, is filled with liquid-phase refrigerant. When gas-liquid two-phase refrigerant flows into the heat storage heat exchanger 4 in this state, a region of gas-phase refrigerant is created in the heat storage circuit. In other words, throughout the heat storage heat exchanger 4, a difference in density occurs between the region of gas-phase refrigerant and the region of liquid-phase refrigerant. Therefore, the amount of refrigerant in the entire heat storage heat exchanger 4 decreases. As a result, the amount of refrigerant used during cooling operation increases.

In other words, when gas-phase refrigerant flows into a heat storage circuit that is filled with liquid-phase refrigerant, the liquid-phase refrigerant that was originally stagnating there is pushed out of the heat storage heat exchanger 4.

The liquid-phase refrigerant that is pushed out then mixes with the gas-phase refrigerant that has flowed out of the indoor heat exchanger 2. Because the gas-phase refrigerant that has flowed out of the indoor heat exchanger 2 has been warmed, some of the liquid-phase refrigerant evaporates. This refrigerant returns to the compressor 1.

As described above, the switching control unit 74 controls the second expansion valve 52 to be open, but the opening degree of the second expansion valve 52 in this case is controlled as follows. That is, if the second expansion valve 52 is controlled to be fully open, there is a possibility that much of the refrigerant flowing out of the outdoor heat exchanger 3 will flow to the thermal storage heat exchanger 4 via the second expansion valve 52.

If a large amount of refrigerant flows into the heat storage heat exchanger 4 in this way, the amount of refrigerant flowing from the outdoor heat exchanger 3 into the indoor heat exchanger 2 will decrease. A decrease in the amount of refrigerant flowing into the indoor heat exchanger 2 will lead to a decrease in the capacity of the indoor heat exchanger 2, which may reduce user comfort.

Consider that this control is only for cooling operation, and it is therefore preferable to control the amount of refrigerant that flows out of the outdoor heat exchanger 3 and flows into the indoor heat exchanger 2 and the heat storage heat exchanger 4 so that the amount of refrigerant flowing into the indoor heat exchanger 2 is greater than the amount of refrigerant flowing into the heat storage heat exchanger 4.

In other words, when comparing the opening degrees of the second expansion valve 52 and the third expansion valve 53, the switching control unit 74 controls the opening degrees of the second expansion valve 52 and the third expansion valve 53 so that the opening degree of the latter is greater than the opening degree of the former. Note that the opening degree is defined as a ratio to when the expansion valves are fully open. In other words, the opening degrees of the second expansion valve 52 and the third expansion valve 53 are controlled so that the flow rate of refrigerant passing through the third expansion valve 53 is greater than the flow rate of refrigerant passing through the second expansion valve 52.

The opening degree of the second expansion valve 52 has the relationship described above with respect to the opening degree of the third expansion valve 53, but the actual opening degree can be determined by referring to the opening degree of the third expansion valve 53. Alternatively, it is also possible to control the opening degree to be set to a value obtained, for example, through experiments.

When the switching control unit 74 controls the second expansion valve 52 to be in an open state, refrigerant flows from the outdoor heat exchanger 3 into the heat storage heat exchanger 4. In this state, the determination unit 73 checks the temperature difference between the heat storage material temperature and the refrigerant temperature. That is, the determination unit 73 obtains information regarding the heat storage material temperature and the refrigerant saturation temperature obtained by the heat storage temperature sensor HS and the refrigerant temperature sensor RS, respectively, via the temperature detection unit 71.

The temperature difference to be compared is preset and stored in the memory unit 72. Therefore, when making the comparison, the determination unit 73 accesses the memory unit 72 to obtain information about the temperature difference. As a result, if the temperature difference between the temperature of the heat storage material and the temperature of the refrigerant is within the preset temperature difference range, control is continued to keep the second expansion valve 52 open.

On the other hand, if the temperature difference between the heat storage material temperature and the refrigerant temperature is outside the preset temperature difference range, it is considered unlikely that the refrigerant will condense into liquid-phase refrigerant even if it flows into the heat storage heat exchanger 4 from the outdoor heat exchanger 3. Therefore, in this case, the determination unit 73 controls the second expansion valve 52 to close via the switching control unit 74.

[Operation]
Next, the flow of control of the refrigeration cycle apparatus S by the control device 7 in the cooling operation of the second embodiment will be described with reference to Fig. 9. Fig. 9 is a flowchart showing the flow of control when the refrigeration cycle apparatus S1 according to the second embodiment of the present invention performs the cooling operation.

When cooling operation is started (ST71), the determination unit 73 compares the temperature of the heat storage material with the temperature of the refrigerant (first predetermined temperature) (ST72). As described above, this is to determine whether or not to control the second expansion valve 52 to an open state.

If the comparison by the determination unit 73 determines that the temperature of the heat storage material is equal to or higher than the first predetermined temperature (NO in ST73), even if the refrigerant flowing out from the outdoor heat exchanger 3 flows into the heat storage heat exchanger 4 in this state, it is unlikely to condense into liquid-phase refrigerant. Therefore, the second expansion valve 52 remains fully closed, and cooling operation continues.

On the other hand, if the comparison by the determination unit 73 determines that the temperature of the heat storage material is lower than the first predetermined temperature (YES in ST73), control is performed via the switching control unit 74 to open the second expansion valve 52 (ST74). Note that, as described above, the opening degree of the second expansion valve 52 is smaller than the opening degree of the third expansion valve 53.

The determination unit 73 also determines whether there is a predetermined temperature difference between the temperature of the heat storage material and the temperature of the refrigerant (ST75). If the determination results in a predetermined temperature difference (YES in ST75), the temperature rise of the heat storage material due to heat absorption from the refrigerant is insufficient, and even if refrigerant from the outdoor heat exchanger 3 flows into the heat storage heat exchanger 4, there is a high possibility that the refrigerant will condense and become liquid-phase refrigerant inside the heat storage heat exchanger 4. Therefore, in this case, the second expansion valve 52 continues to remain open.

In contrast, if the determination unit 73 determines that the temperature difference between the two does not meet the specified temperature difference (NO in ST75), the temperature of the heat storage material has risen due to heat absorption from the refrigerant, and when the refrigerant from the outdoor heat exchanger 3 flows into the heat storage heat exchanger 4, it is unlikely to condense in the heat storage heat exchanger 4 and become a liquid-phase refrigerant. Therefore, the second expansion valve 52 is controlled to be fully closed, preventing any further refrigerant from flowing into the heat storage heat exchanger 4 (ST76).

As explained above, by performing heat storage cooling operation, even when cooling operation is performed in a refrigeration cycle device equipped with a heat storage heat exchanger, it is possible to prevent refrigerant from accumulating inside the heat storage device and minimize the reduction in the amount of refrigerant circulating through the refrigerant circuit.

Furthermore, by performing the control in the second embodiment, the amount of refrigerant remaining inside the thermal storage heat exchanger can be reduced, so the total amount of refrigerant circulating through the refrigerant circuit does not need to be significantly reduced. This prevents a decrease in the energy-saving performance of the refrigeration cycle device when operating in cooling mode.

Furthermore, in the control of the second embodiment, there is no need to switch the second switching valve 62 to change the refrigerant flow path from the outdoor heat exchanger 3 to the heat storage heat exchanger 4; instead, control is simply performed to open the second expansion valve 52. Therefore, with simpler control, it is possible to prevent refrigerant that has become liquid phase refrigerant from accumulating inside the heat storage heat exchanger 4.

The present invention is not limited to the above-described embodiment, which merely shows one example of the present invention. In the implementation stage, the components can be modified to achieve specific embodiments 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.

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. These embodiments and their variations are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims.

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 switching valve for switching a flow path when the refrigerant circulates; and
a heat storage temperature sensor for detecting the temperature of the heat storage material;
a control device that controls the switching valve and the expansion valve,
The switching valve is
a cooling operation in which the outdoor heat exchanger functions as a condenser and the indoor heat exchanger functions as an evaporator; and a heat-storage cooling operation in which at least the indoor heat exchanger functions as an evaporator when the heat-storage heat exchanger functions as a condenser.
The flow path is switched by
A refrigeration cycle device characterized in that, when the control device determines that the detection value of the heat storage temperature sensor has become lower than a first predetermined temperature during the cooling operation, the control device controls the switching valve to switch from the cooling operation to the heat storage cooling operation.
(2) The refrigeration cycle device described in (1) above, characterized in that the control device controls the switching valve to switch from the heat storage cooling operation to the cooling operation when it determines that the temperature of the heat storage material detected by the heat storage temperature sensor has reached a second predetermined temperature or higher.
(3) The refrigeration cycle device described in (1) or (2) above, characterized in that the expansion valve is arranged between the outdoor heat exchanger and the indoor heat exchanger, and the amount of the refrigerant flowing into the indoor heat exchanger is adjusted by the control device during the heat storage cooling operation.
(4) A refrigeration cycle device described in any one of (1) to (3) above, characterized in that the control device controls the switching valve to switch from the air conditioning operation to the heat storage air conditioning operation when the thermostat is off during the air conditioning operation.
(5) The refrigeration cycle device according to any one of (1) to (4) above, wherein the first predetermined temperature is a value detected by a refrigerant temperature sensor.
(6) 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 switching valve for switching a flow path when the refrigerant circulates; and
a heat storage temperature sensor for detecting the temperature of the heat storage material;
a control device that controls the switching valve and the expansion valve,
When the control device determines that the detected value of the heat storage temperature sensor is lower than a first predetermined temperature during cooling operation in which the control device causes the outdoor heat exchanger to function as a condenser and the indoor heat exchanger to function as an evaporator,
The control device is characterized in that a second expansion valve arranged between the outdoor heat exchanger and the heat storage heat exchanger is opened so that the refrigerant flowing out of the outdoor heat exchanger flows into the heat storage heat exchanger.
(7) When the control device controls the second expansion valve to an open state,
The refrigeration cycle device described in (6) above, characterized in that the opening degree of the second expansion valve is controlled to be smaller than the opening degree of the first expansion valve arranged between the outdoor heat exchanger and the indoor heat exchanger.
(8) The refrigeration cycle device according to (6) or (7), wherein the first predetermined temperature is a value detected by a refrigerant temperature sensor.
(9) The refrigeration cycle device described in (8) above, characterized in that the control device controls the second expansion valve to a closed state when it determines that the difference between the detection value of the heat storage temperature sensor and the detection value of the refrigerant temperature sensor has reached a predetermined value.
(10) 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 switching valve for switching a flow path when the refrigerant circulates; and
a heat storage temperature sensor for detecting the temperature of the heat storage material;
A refrigeration cycle apparatus including a control device that controls the switching valve and the expansion valve,
performing a cooling operation in which the outdoor heat exchanger functions as a condenser and the indoor heat exchanger functions as an evaporator;
a step in which the control device compares the detected value of the heat storage temperature sensor with a first predetermined temperature during the cooling operation;
When it is determined by the control device that the detected value of the heat storage temperature sensor has become lower than the first predetermined temperature, the control device controls the switching valve to switch from the cooling operation to a heat storage cooling operation in which at least the indoor heat exchanger functions as an evaporator when the heat storage heat exchanger functions as a condenser;
A control method for a refrigeration cycle device, comprising:
(11) After the step of comparing the detected value of the heat storage temperature sensor with the detected value of the refrigerant temperature sensor by the control device during the cooling operation,
The control method for a refrigeration cycle device described in (10) above, characterized in that when the control device determines that the temperature of the heat storage material detected by the heat storage temperature sensor has reached a predetermined temperature or higher, the control device controls the switching valve to switch from the heat storage cooling operation to the cooling operation.
(12) When the thermostat is off during the cooling operation,
The method for controlling a refrigeration cycle device according to (10) or (11) above, wherein the control device controls the switching valve so as to switch from the cooling operation to the heat-storage cooling operation.
(13) The method for controlling a refrigeration cycle device according to any one of (10) to (12) above, wherein the first predetermined temperature is a value detected by a refrigerant temperature sensor.
(14)
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 switching valve for switching a flow path when the refrigerant circulates; and
a heat storage temperature sensor for detecting the temperature of the heat storage material;
A refrigeration cycle apparatus including a control device that controls the switching valve and the expansion valve,
a step of performing a cooling operation in which the control device causes the outdoor heat exchanger to function as a condenser and the indoor heat exchanger to function as an evaporator;
a step in which the control device compares the detected value of the heat storage temperature sensor with a first predetermined temperature during the cooling operation;
When the control device determines that the detected value of the heat storage temperature sensor has become lower than the first predetermined temperature, the control device controls a second expansion valve disposed between the outdoor heat exchanger and the heat storage heat exchanger to an open state so that the refrigerant flowing out of the outdoor heat exchanger flows into the heat storage heat exchanger;
A control method for a refrigeration cycle device, comprising:
(15) When the control device controls the second expansion valve to an open state,
A control method for a refrigeration cycle device described in (14) above, characterized in that the opening degree of the second expansion valve is controlled to be smaller than the opening degree of the first expansion valve arranged between the outdoor heat exchanger and the indoor heat exchanger.
(16) The method for controlling a refrigeration cycle device according to (14) or (15) above, wherein the first predetermined temperature is a value detected by a refrigerant temperature sensor.
(17) After the step of comparing the detected value of the heat storage temperature sensor with the detected value of the refrigerant temperature sensor by the control device during the cooling operation,
The control method for a refrigeration cycle device described in (16) above is characterized in that when the control device determines that the difference between the detection value of the heat storage temperature sensor and the detection value of the refrigerant temperature sensor has reached a predetermined value, the control device controls the second expansion valve to a closed state.

1: Compressor, 2: Indoor heat exchanger, 3: Outdoor heat exchanger, 4: Heat storage heat exchanger, 5: Expansion valve, 51: First expansion valve, 52: Second expansion valve, 53: Third expansion valve, 6: Switching valve, 61: First switching valve, 62: Second switching valve, 7: Control device, 71: Temperature detection unit, 72: Memory unit, 72: Determination unit, 74: Switching control unit, C: Refrigerant circuit, HS: Heat storage temperature sensor, RS: Refrigerant temperature sensor, S: Refrigeration cycle device

Claims (17)

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 switching valve for switching a flow path when the refrigerant circulates; and
a heat storage temperature sensor for detecting the temperature of the heat storage material;
a control device that controls the switching valve and the expansion valve,
The switching valve is
The flow path is switched between a cooling operation in which the outdoor heat exchanger functions as a condenser and the indoor heat exchanger functions as an evaporator, and a heat-storage cooling operation in which at least the indoor heat exchanger functions as an evaporator when the heat-storage heat exchanger functions as a condenser,
A refrigeration cycle device characterized in that, when the control device determines that the detection value of the heat storage temperature sensor has become lower than a first predetermined temperature during the cooling operation, the control device controls the switching valve to switch from the cooling operation to the heat storage cooling operation. The refrigeration cycle device of claim 1, characterized in that the control device controls the switching valve to switch from the heat storage cooling operation to the cooling operation when it determines that the temperature of the heat storage material detected by the heat storage temperature sensor has reached or exceeded a second predetermined temperature. The refrigeration cycle device of claim 1, characterized in that the expansion valve is disposed between the outdoor heat exchanger and the indoor heat exchanger, and the amount of refrigerant flowing into the indoor heat exchanger is adjusted by the control device during the heat storage cooling operation. The refrigeration cycle device of claim 1, characterized in that the control device controls the switching valve to switch from the cooling operation to the heat-storage cooling operation when the thermostat is off during the cooling operation. A refrigeration cycle device according to any one of claims 1 to 4, characterized in that the first predetermined temperature is a value detected by a refrigerant temperature sensor. 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 switching valve for switching a flow path when the refrigerant circulates; and
a heat storage temperature sensor for detecting the temperature of the heat storage material;
a control device that controls the switching valve and the expansion valve,
When the control device determines that the detected value of the heat storage temperature sensor is lower than a first predetermined temperature during cooling operation in which the control device causes the outdoor heat exchanger to function as a condenser and the indoor heat exchanger to function as an evaporator,
The control device is characterized in that a second expansion valve arranged between the outdoor heat exchanger and the heat storage heat exchanger is opened so that the refrigerant flowing out of the outdoor heat exchanger flows into the heat storage heat exchanger. When the control device controls the second expansion valve to an open state,
7. The refrigeration cycle device according to claim 6, wherein the opening degree of the second expansion valve is controlled to be smaller than the opening degree of a first expansion valve disposed between the outdoor heat exchanger and the indoor heat exchanger. The refrigeration cycle device of claim 6 or 7, characterized in that the first predetermined temperature is a value detected by a refrigerant temperature sensor. The refrigeration cycle device described in claim 8, characterized in that the control device controls the second expansion valve to a closed state when it determines that the difference between the detected value of the heat storage temperature sensor and the detected value of the refrigerant temperature sensor has reached a predetermined value. 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 switching valve for switching a flow path when the refrigerant circulates; and
a heat storage temperature sensor for detecting the temperature of the heat storage material;
A refrigeration cycle apparatus including a control device that controls the switching valve and the expansion valve,
performing a cooling operation in which the outdoor heat exchanger functions as a condenser and the indoor heat exchanger functions as an evaporator;
a step in which the control device compares the detected value of the heat storage temperature sensor with a first predetermined temperature during the cooling operation;
When it is determined by the control device that the detected value of the heat storage temperature sensor has become lower than the first predetermined temperature, the control device controls the switching valve to switch from the cooling operation to a heat storage cooling operation in which at least the indoor heat exchanger functions as an evaporator when the heat storage heat exchanger functions as a condenser;
A control method for a refrigeration cycle device, comprising: After the step of comparing the detected value of the heat storage temperature sensor with the first predetermined temperature during the cooling operation by the control device,
11. The control method for a refrigeration cycle device according to claim 10, wherein when the control device determines that the temperature of the heat storage material detected by the heat storage temperature sensor has reached a second predetermined temperature or higher, the control device controls the switching valve to switch from the heat storage cooling operation to the cooling operation. During the cooling operation, when the thermostat is off,
The method for controlling a refrigeration cycle apparatus according to claim 10, wherein the control device controls the switching valve to switch from the cooling operation to the heat-storage cooling operation. A method for controlling a refrigeration cycle device according to any one of claims 10 to 12, characterized in that the first predetermined temperature is a value detected by a refrigerant temperature sensor. 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 switching valve for switching a flow path when the refrigerant circulates; and
a heat storage temperature sensor for detecting the temperature of the heat storage material;
A refrigeration cycle apparatus including a control device that controls the switching valve and the expansion valve,
a step of performing a cooling operation in which the control device causes the outdoor heat exchanger to function as a condenser and the indoor heat exchanger to function as an evaporator;
a step in which the control device compares the detected value of the heat storage temperature sensor with a first predetermined temperature during the cooling operation;
When the control device determines that the detected value of the heat storage temperature sensor has become lower than the first predetermined temperature, the control device controls a second expansion valve disposed between the outdoor heat exchanger and the heat storage heat exchanger to an open state so that the refrigerant flowing out of the outdoor heat exchanger flows into the heat storage heat exchanger;
A control method for a refrigeration cycle device, comprising: When the control device controls the second expansion valve to an open state,
15. The control method for a refrigeration cycle apparatus according to claim 14, wherein the opening degree of the second expansion valve is controlled to be smaller than the opening degree of a first expansion valve disposed between the outdoor heat exchanger and the indoor heat exchanger. The refrigeration cycle device control method described in claim 14 or 15, characterized in that the first predetermined temperature is a value detected by a refrigerant temperature sensor. After the step of comparing the detected value of the heat storage temperature sensor with the detected value of the refrigerant temperature sensor by the control device during the cooling operation,
17. The control method for a refrigeration cycle device according to claim 16, further comprising a step in which the control device controls the second expansion valve to a closed state when the control device determines that the difference between the detected value of the heat storage temperature sensor and the detected value of the refrigerant temperature sensor has reached a predetermined value.