air conditioner

Abstract

To provide an air conditioner capable of maintaining comfort during defrosting and heating operation. [Solution] A refrigerant circuit C that circulates refrigerant is connected to an indoor heat exchanger 2, an outdoor heat exchanger 3, a heat storage heat exchanger 4, multiple expansion valves with adjustable opening, and switching valves 61, 62 that switch the flow path of the refrigerant circuit between heat storage heating operation in which the indoor heat exchanger and the heat storage heat exchanger function as condensers and the outdoor heat exchanger as an evaporator, and defrost heating operation in which the indoor heat exchanger and the outdoor heat exchanger function as condensers and the heat storage heat exchanger as an evaporator.The system is equipped with a heating capacity estimation means that estimates the heating capacity during defrost heating operation, and a control device 7 that controls the multiple expansion valves and switching valves.The multiple expansion valves include a first expansion valve 51 that is located upstream of the outdoor heat exchanger during defrost heating operation, and the control device controls the opening of the first expansion valve during defrost heating operation based on the heating capacity estimated by the heating capacity estimation means.

Description

Technical Field

[0001] The present invention relates to an air conditioner.

Background Art

[0002] In an air conditioner provided with a heat storage heat exchanger that exchanges heat between a part of the refrigerant discharged from a compressor and a heat storage material, when performing a defrosting operation, there is a technique of continuing the heating operation even during the defrosting operation by using the heat stored in the heat storage material as a heat source (hereinafter, also referred to as a defrosting heating operation). In such an air conditioner, during the defrosting heating operation, the room temperature, the condensation temperature, the temperature of the outdoor heat exchanger, and the discharge temperature are detected, and by operating an expansion valve arranged on the outlet side of the indoor heat exchanger and the outdoor heat exchanger, there is a technique of suppressing the shortage of heating capacity and defrosting capacity and the occurrence of liquid backflow in which liquid refrigerant returns from the heat storage heat exchanger to the compressor (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, when the building load is small (for example, when the building volume is small and the outside temperature is high during heating operation, meaning the energy required for the building's air conditioning operation is small), the required heating capacity will be small. Generally, during defrosting operation, the control prioritizes removing frost from the outdoor heat exchanger, and the finer control of heating capacity is not performed compared to normal heating operation. As a result, the room temperature may rise or fall too much relative to the set temperature, reducing comfort. Therefore, when the building load is small, the heating capacity during defrosting heating operation is often excessive. The air conditioner in Patent Document 1 does not anticipate cases where the heating capacity is excessive, and if the heating capacity is reduced by decreasing the opening of the expansion valve on the outlet side of the indoor heat exchanger, the condensation temperature of the indoor heat exchanger will rise, which may actually result in excessive heating capacity and a decrease in comfort. Another method to reduce heating capacity is to lower the rotation speed of the compressor, but this also reduces the defrosting capacity, so the defrosting time will be longer, which may reduce comfort.

[0005] Therefore, the present invention has been made to solve these problems and aims to provide an air conditioner that can maintain comfort during defrost heating operation. [Means for solving the problem]

[0006] An air conditioner according to one aspect of the present invention includes, connected to a refrigerant circuit for circulating a refrigerant, a compressor for compressing the refrigerant, an indoor heat exchanger for exchanging heat between indoor air and the refrigerant, an outdoor heat exchanger for exchanging heat between outdoor air and the refrigerant, a heat storage heat exchanger for exchanging heat between a heat storage material and the refrigerant, a plurality of expansion valves whose opening degree can be adjusted, a switching valve for switching the flow path of the refrigerant circuit to a heat storage heating operation in which the indoor heat exchanger and the heat storage heat exchanger function as a condenser and the outdoor heat exchanger function as an evaporator, and a defrosting heating operation in which the indoor heat exchanger and the outdoor heat exchanger function as a condenser and the heat storage heat exchanger function as an evaporator, a heating capacity estimation means for estimating the heating capacity during defrosting heating operation, and a control device for controlling the plurality of expansion valves and the switching valve, wherein the plurality of expansion valves include a first expansion valve provided on the upstream side of the outdoor heat exchanger during defrosting heating operation, and the control device controls the opening degree of the first expansion valve based on the heating capacity estimated by the heating capacity estimation means during defrosting heating operation. [Effects of the Invention]

[0007] According to the air conditioner of the present invention, comfort can be maintained during defrost heating operation. [Brief explanation of the drawing]

[0008] [Figure 1] This is a refrigerant circuit diagram of an air conditioner according to an embodiment of the present invention. [Figure 2] This figure shows a specific configuration of an indoor heat exchanger constituting an air conditioner in an embodiment of the present invention. [Figure 3] This is a refrigerant circuit diagram showing the flow of refrigerant when an air conditioner according to an embodiment of the present invention performs cooling operation. [Figure 4] This is a refrigerant circuit diagram showing the flow of refrigerant when an air conditioner according to an embodiment of the present invention is performing heating operation. [Figure 5] This is a refrigerant circuit diagram showing the flow of refrigerant when an air conditioner according to an embodiment of the present invention performs thermal storage heating operation. [Figure 6] This is a refrigerant circuit diagram showing the flow of refrigerant when an air conditioner according to an embodiment of the present invention performs defrost heating operation. [Figure 7]This is a block diagram showing the internal configuration of a control device in an air conditioner according to an embodiment of the present invention. [Figure 8] This flowchart shows the control flow for the defrost heating operation according to the first embodiment of the present invention. [Figure 9] This flowchart shows the process for estimating heating capacity in the defrost heating operation of the first embodiment of the present invention. [Figure 10] This flowchart shows the control flow for defrost heating operation according to the second embodiment of the present invention. [Figure 11] This flowchart shows the flow for estimating heating capacity in the defrost heating operation of the second embodiment of the present invention. [Figure 12] This flowchart shows the control flow for defrost heating operation according to the third embodiment of the present invention. [Figure 13] This flowchart shows the process for estimating heating capacity in the defrost heating operation of the third embodiment according to the present invention. [Modes for carrying out the invention]

[0009] [First Embodiment] The structure of the air conditioner S according to the first embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a refrigerant circuit diagram of the air conditioner S. The air conditioner S is equipped with a refrigerant circuit C that circulates the refrigerant, connecting 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). It is also equipped with a control device 7 that controls the expansion valves 5 and the switching valves 6.

[0010] Compressor 1 compresses the refrigerant circulating in refrigerant circuit C. Indoor heat exchanger 2 exchanges heat between indoor air and the refrigerant. Outdoor heat exchanger 3 exchanges heat between outdoor air and the refrigerant. The types of compressor 1, indoor heat exchanger 2, and outdoor heat exchanger 3 are not explained here, but various types of equipment can be used.

[0011] The heat storage heat exchanger 4 is a heat exchanger in which a heat storage material and a refrigerant passing through the heat storage heat exchanger 4 exchange heat. The heat storage heat exchanger 4 is, for example, a fin-and-tube type heat exchanger. And this heat storage heat exchanger 4 is arranged in a heat storage container filled with a heat storage material inside. As the heat storage material, for example, regardless of whether it is a liquid or a solid, it is sufficient if it can exchange heat with the refrigerant flowing inside the heat storage heat exchanger 4 and store heat.

[0012] The switching valve 6 switches the circulation path of the refrigerant in the refrigerant circuit C between, for example, a heat storage heating operation in which the indoor heat exchanger 2 and the heat storage heat exchanger 4 function as condensers and the outdoor heat exchanger 3 functions as an evaporator, and a defrosting heating operation in which the indoor heat exchanger 2 and the outdoor heat exchanger 3 function as condensers and the heat storage heat exchanger 4 functions as an evaporator. The air conditioner S of the present embodiment is provided with two switching valves 6 that switch the flow of the refrigerant based on an instruction from a control device 7 described later. That is, a first switching valve 61 is provided between the compressor 1 and the indoor heat exchanger 2. Also, the second switching valve 62 is provided between the compressor 1 and the outdoor heat exchanger 3 or the heat storage heat exchanger 4. The second switching valve 62 causes the refrigerant discharged from the compressor 1 to flow to the outdoor heat exchanger 3 or the heat storage heat exchanger 4.

[0013] The expansion valve 5 can adjust its opening degree based on an instruction from a control device 7 described later, and a plurality of expansion valves 5 are provided in the air conditioner S of the present embodiment. Specifically, a first expansion valve 51, a second expansion valve 52, and a third expansion valve 53 are provided. The first expansion valve 51 is provided on the upstream side of the outdoor heat exchanger 3 in the direction in which the refrigerant flows during the defrosting heating operation.

[0014] The second expansion valve 52 is provided between the indoor heat exchanger 2 and the outdoor heat exchanger 3. That is, it is provided on the downstream side of the indoor heat exchanger 2 in the direction in which the refrigerant flows during the defrosting heating operation. Specifically, the second expansion valve 52 is provided in the refrigerant pipe connecting the outdoor heat exchanger 3 and the indoor heat exchanger 2.

[0015] The third expansion valve 53 is provided between the heat storage heat exchanger 4 and the outdoor heat exchanger 3. That is, it is provided on the upstream side of the heat storage heat exchanger 4 in the direction in which the refrigerant flows during the defrost heating operation. Specifically, the third expansion valve 53 is provided in the refrigerant pipe connecting the refrigerant pipe connecting the indoor heat exchanger 2 and the outdoor heat exchanger 3 and the heat storage heat exchanger 4.

[0016] In the following, when these first expansion valve 51 to third expansion valve 53 are collectively described, they are referred to as "expansion valve 5", and when each expansion valve is described, they are represented by their respective names. Also, regarding the switching valve 6, when these first switching valve 61 and second switching valve 62 are collectively described, they are referred to as "switching valve 6", and when each switching valve is described, they are represented by their respective names.

[0017] The indoor heat exchanger 2 is provided with a refrigerant temperature sensor 22 for detecting the temperature of the refrigerant in the indoor heat exchanger 2. Here, FIG. 2 shows the indoor heat exchanger 2 provided inside the indoor unit 10. Inside the indoor unit 10, there are further provided a room temperature sensor 21 for detecting the indoor temperature and an indoor fan 11 for blowing the air heat-exchanged with the refrigerant in the indoor heat exchanger 2 into the room. Also, between the switching valve 61 and the indoor heat exchanger 2, a gas-side refrigerant temperature sensor 23 for detecting the temperature of the refrigerant flowing into the indoor heat exchanger 2 during the defrost heating operation is provided, and between the indoor heat exchanger 2 and the second expansion valve 52, a liquid-side refrigerant temperature sensor 24 for detecting the temperature of the refrigerant flowing out of the indoor heat exchanger 2 during the defrost heating operation is provided.

[0018] Next, the refrigerant circuit C of the air conditioner S will be described. The refrigerant circuit C is composed of each device such as the compressor 1 described above and the refrigerant pipes connecting these devices through which the refrigerant flows. Here, a first switching valve 61 is provided in the refrigerant pipe connecting the compressor 1 and the indoor heat exchanger 2. Also, in the refrigerant pipe between the compressor 1 and the first switching valve 61, a second switching valve 62 for flowing the refrigerant discharged from the compressor 1 to the outdoor heat exchanger 3 or the heat storage heat exchanger 4 is provided.

[0019] Furthermore, in the air conditioner S according to the 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 equipped with a check valve and the like so that the refrigerant flows only in the direction of the arrow shown in Figure 1.

[0020] The control device 7 can control the opening degree of multiple expansion valves 5 and adjust the flow rate of refrigerant circulating in the refrigerant circuit C. It can also switch the flow of refrigerant circulating in the refrigerant circuit C by switching multiple switching valves 6.

[0021] Next, before explaining the functions of each part of the control device 7, the operating modes of the air conditioner S will be explained in order using the circuit diagrams of the air conditioner S shown in Figures 3 to 6. In these circuit diagrams, the refrigerant circulation paths through which the refrigerant actually flows are shown with solid lines. On the other hand, the refrigerant circulation paths that constitute the refrigerant circuit C but through which the refrigerant does not flow, and the bypass circuit B are shown with dashed lines. The direction of the refrigerant circulating within the refrigerant circuit C is indicated by arrows.

[0022] First, Figure 3 is a refrigerant circuit diagram showing the flow of refrigerant when the air conditioner S of the first embodiment is performing cooling operation. In cooling operation, the indoor heat exchanger 2 functions as an evaporator and the outdoor heat exchanger 3 functions as a condenser.

[0023] The refrigerant, compressed in compressor 1 and discharged in a high-temperature, high-pressure state, flows into the outdoor heat exchanger 3 via the first expansion valve 51 and the second switching valve 62, as shown by the arrows in Figure 3. 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 then flows through the bypass circuit B and into the outdoor heat exchanger 3 via the second switching valve 62.

[0024] The refrigerant flowing into the outdoor heat exchanger 3 is cooled by the outside air supplied by the rotation of an outdoor fan (not shown), and the heat is released into the outside air. Then, some or all of the refrigerant condenses.

[0025] The refrigerant that has released heat into the outside air in this manner flows out of the outdoor heat exchanger 3 and passes through the second expansion valve 52, where it is depressurized and becomes a low-temperature, low-pressure refrigerant. Subsequently, the low-temperature, low-pressure refrigerant flows into the indoor heat exchanger 2, where heat exchange takes place between it and the indoor air.

[0026] Through heat exchange by the indoor heat exchanger 2, the refrigerant absorbs heat from the indoor air and evaporates, while the indoor air drawn into the indoor heat exchanger 2 is cooled and supplied to the room by the indoor fan 11 to cool the room. The refrigerant that has absorbed heat through heat exchange then flows into the compressor 1 via the first switching valve 61.

[0027] During cooling operation, the second expansion valve 52, through which the condensed refrigerant in the outdoor heat exchanger 3 passes, is controlled to open to an degree corresponding to the required air conditioning capacity of the air conditioner S. On the other hand, the third expansion valve 53 is controlled to be fully closed, preventing the refrigerant that has flowed out of the outdoor heat exchanger 3 from flowing into the thermal storage heat exchanger 4.

[0028] Next, Figure 4 is a refrigerant circuit diagram showing the flow of refrigerant when the air conditioner S of the first embodiment is performing heating operation. As shown in Figure 4, the refrigerant discharged from the compressor 1 flows into the indoor heat exchanger 2 via the first switching valve 61. On the other hand, since the first expansion valve 51 is controlled to be completely closed, the refrigerant does not flow to the outdoor heat exchanger 3 via the second switching valve 62, as in the cooling operation described above. In the indoor heat exchanger 2, heat exchange takes place between the refrigerant and the air flowing into the indoor unit, and air warmed by absorbing heat from the refrigerant is supplied to the indoor space, thereby heating the room. Therefore, the indoor heat exchanger 2 functions as a condenser.

[0029] The refrigerant flowing out of the indoor heat exchanger 2 is depressurized by passing through the second expansion valve 52, becoming a low-temperature, low-pressure refrigerant before flowing into the outdoor heat exchanger 3. The outdoor heat exchanger 3 functions as an evaporator, and heat exchange takes place 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.

[0030] In the air conditioner S according to the present invention, when the above-described normal cooling or heating operation is performed, the thermal storage heat exchanger 4 does not function as a condenser or evaporator.

[0031] Next, Figure 5 is a refrigerant circuit diagram showing the flow of refrigerant when the air conditioner S of the first embodiment performs thermal storage heating operation. Thermal storage heating operation is an operation in which heat is stored in the thermal storage heat exchanger 4 by opening the first expansion valve 51 during heating operation and allowing a portion of the refrigerant discharged from the compressor 1 to flow into the thermal storage heat exchanger 4. As shown in Figure 5, the refrigerant discharged from the compressor 1 flows into the indoor heat exchanger 2 via the first switching valve 61. Then, heat exchange takes place between the refrigerant and the air flowing into the indoor unit in the indoor heat exchanger 2, and the air that has been heated by absorbing heat from the refrigerant is supplied to the room. Therefore, the indoor heat exchanger 2 functions as a condenser. The refrigerant that flows out of the indoor heat exchanger 2 flows into the outdoor heat exchanger 3 via the second expansion valve 52. The outdoor heat exchanger 3 functions as an evaporator, and heat exchange takes place between the refrigerant and the outdoor air. The refrigerant that flows out of the outdoor heat exchanger 3 flows into the compressor 1 via the second switching valve 62.

[0032] In thermal storage heating operation, the refrigerant discharged from the compressor 1 branches off before reaching the first switching valve 61 and flows into the thermal storage heat exchanger 4 via the first expansion valve 51 and the second switching valve 62. The refrigerant that flows into the thermal storage heat exchanger 4 exchanges heat with the heat storage material, and the heat of the refrigerant is stored in the heat storage material. The refrigerant that flows out of the thermal storage heat exchanger 4 flows into the outdoor heat exchanger 3 via the third expansion valve 53.

[0033] Next, Figure 6 is a refrigerant circuit diagram showing the flow of refrigerant when the air conditioner S of the first embodiment performs defrost heating operation. Defrost heating operation is an operation in which the first expansion valve 51 is opened during heating operation, and a portion of the refrigerant discharged from the compressor 1 flows into the outdoor heat exchanger 3, thereby melting the frost attached to the outdoor heat exchanger 3. As shown in Figure 6, the refrigerant discharged from the compressor 1 flows into the indoor heat exchanger 2 via the first switching valve 61. Since this is heating operation, the indoor heat exchanger 2 functions as a condenser, and heat exchange is performed between the refrigerant and the air flowing into the indoor unit in the indoor heat exchanger 2, and the air that has been heated by absorbing heat from the refrigerant is supplied to the indoor space.

[0034] Furthermore, the refrigerant discharged from the compressor 1 branches off before reaching the first switching valve 61 and flows into the outdoor heat exchanger 3 via the first expansion valve 51 and the second switching valve 62. At this time, the opening degree of the first expansion valve 51 is adjusted based on the control described later.

[0035] When high-temperature refrigerant from compressor 1 flows into the outdoor heat exchanger 3, a defrosting and heating operation is performed to melt the frost accumulated on the outdoor heat exchanger 3. The refrigerant flowing out from the indoor heat exchanger 2 flows into the thermal storage heat exchanger 4 via the second expansion valve 52 and the third expansion valve 53. Similarly, the refrigerant flowing out from the outdoor heat exchanger 3 flows into the thermal storage heat exchanger 4 via the third expansion valve 53. In the thermal storage heat exchanger 4, heat exchange takes place between the incoming refrigerant and the heat storage material, and the refrigerant evaporates by absorbing heat from the heat stored in the heat storage material. The refrigerant flowing out from the thermal storage heat exchanger 4 flows into compressor 1 via the second switching valve 62. Here, the opening degree of the second expansion valve 52 is set to such an opening degree that the refrigerant flowing out from the indoor heat exchanger 2, which is functioning as a condenser, becomes supercooled. This makes it possible to simultaneously adjust the heating capacity of the indoor heat exchanger 2 and the defrosting capacity of the outdoor heat exchanger 3 during defrosting heating operation simply by controlling the opening degree of the first expansion valve 51, without requiring complex control.

[0036] Next, Figure 7 is a block diagram showing the functions of each part of the control device 7 of the first embodiment. The control device 7 includes a temperature detection unit 71, a storage unit 72, a determination unit 73, and a switching control unit 74.

[0037] The temperature detection unit 71 acquires the room temperature detected by the room temperature sensor 21 installed in the indoor unit 10. The temperature detection unit 71 also acquires the refrigerant temperature detected by the refrigerant temperature sensor 22 installed in the indoor heat exchanger 2. During defrost heating operation, the refrigerant temperature detected by the refrigerant temperature sensor 22 is the condensation temperature of the indoor heat exchanger 2, which functions as a condenser. The temperature detection unit 71 also acquires the refrigerant temperature detected by the gas-side refrigerant temperature sensor 23. During defrost heating operation, the temperature detected by the gas-side refrigerant temperature sensor 23 is the temperature of the refrigerant flowing into the indoor heat exchanger 2. Furthermore, the temperature detection unit 71 acquires the refrigerant temperature detected by the liquid-side refrigerant temperature sensor 24. During defrost heating operation, the temperature detected by the liquid-side refrigerant temperature sensor 24 is the temperature of the refrigerant flowing out of the indoor heat exchanger 2.

[0038] The memory unit 72 is composed of, for example, a semiconductor or a magnetic disk, and in the first embodiment described later, it stores the amount of refrigerant circulated during defrost heating operation based on the change in the rotational speed of the compressor 1. That is, the amount of refrigerant circulated can be determined by the rotational speed of the compressor 1 × the exhaust volume × the suction density, so the memory unit 72 stores the amount of refrigerant circulated corresponding to the rotational speed of the compressor 1 during defrost heating operation in a storage table. Furthermore, in the first embodiment described later, the storage unit 72 stores the heating capacity at the start of defrost heating operation, which is obtained by multiplying the refrigerant circulation amount at the start of defrost heating operation by the enthalpy difference between the inlet and outlet of the indoor heat exchanger 2 at the start of defrost heating operation. This heating capacity at the start of defrost heating operation is the initial heating capacity value in the first embodiment described later.

[0039] Furthermore, the memory unit 72 stores the opening degrees of the first expansion valve 51 and the second expansion valve 52, which are determined according to the required capacity. The opening degree of the first expansion valve 51 is the opening degree required for defrost heating operation, and the opening degree of the second expansion valve 52 is the opening degree at which the refrigerant flowing out from the indoor heat exchanger 2, which functions as a condenser during defrost heating operation, becomes supercooled.

[0040] The determination unit 73 estimates the heating capacity during defrost heating operation. In the first embodiment described later, the specific process involves calculating the enthalpy difference between the inlet and outlet of the indoor heat exchanger 2 based on the temperature of the refrigerant flowing into the indoor heat exchanger 2 (gas-side refrigerant temperature) and the temperature of the refrigerant flowing out of the indoor heat exchanger 2 (liquid-side refrigerant temperature) during defrost heating operation. Next, the refrigerant circulation amount corresponding to the currently driven compressor 1 is obtained from the storage table of compressor 1 rotation speed and refrigerant circulation amount stored in the storage unit 72. Then, the heating capacity is calculated by multiplying the enthalpy difference between the inlet and outlet of the indoor heat exchanger 2 by the refrigerant circulation amount corresponding to the currently driven compressor 1 rotation speed. This heating capacity is the estimated heating capacity value in the first embodiment described later.

[0041] Furthermore, in the first embodiment described later, the determination unit 73 compares the initial heating capacity value stored in the storage unit 72 with the estimated heating capacity value, and determines, based on the comparison result, whether the indoor heating capacity is excessive, insufficient, or appropriate.

[0042] The switching control unit 74 controls the opening degree of the first expansion valve 51 and the second expansion valve 52 according to the determination result received from the determination unit 73, and performs switching control of the first switching valve 61 and the second switching valve 62. [Control of defrost heating operation in the first embodiment]

[0043] Next, the control flow of the defrost heating operation in the first embodiment will be explained using the flowcharts shown in Figures 8 and 9. The control of the defrost heating operation in the first embodiment is characterized by estimating the heating capacity based on the enthalpy difference between the inlet and outlet of the indoor heat exchanger 2.

[0044] First, the defrost heating operation is started in the air conditioner S (ST1). At this time, the switching control unit 74 controls the first expansion valve 51 and the second expansion valve 52 to a predetermined opening degree so that the refrigerant circuit is as shown in Figure 6, and performs switching control of the first switching valve 61 and the second switching valve 61, thereby executing the defrost heating operation.

[0045] Next, the determination unit 73 estimates the heating capacity during defrost heating operation (ST2).

[0046] The specific process for estimating the heating capacity during this defrost heating operation is as follows, as shown in Figure 9: the temperature detection unit 71 acquires the temperature of the refrigerant flowing into the indoor heat exchanger 2 during defrost heating operation (gas-side refrigerant temperature) and the temperature of the refrigerant flowing out of the indoor heat exchanger 2 (liquid-side refrigerant temperature) (ST11). Next, the determination unit 73 calculates the enthalpy difference between the inlet and outlet of the indoor heat exchanger 2 based on the acquired gas-side refrigerant temperature and liquid-side refrigerant temperature (ST12). Next, the determination unit 73 acquires the refrigerant circulation amount corresponding to the currently driven compressor 1 rotation speed from the storage table of compressor 1 rotation speed and refrigerant circulation amount stored in the storage unit 72 (ST13). Next, the determination unit 73 calculates the estimated heating capacity by multiplying the enthalpy difference between the inlet and outlet of the indoor heat exchanger 2 by the refrigerant circulation amount corresponding to the currently driven compressor 1 rotation speed.

[0047] Next, returning to Figure 8, the determination unit 73 compares the initial heating capacity value at the start of defrost heating operation, which is stored in the memory unit 72, with the calculated estimated heating capacity value (ST3 in Figure 8).

[0048] The determination unit 73 compares the estimated heating capacity with the initial heating capacity (ST4). If the estimated heating capacity is greater than the initial heating capacity (YES in ST4), the determination unit 73 determines that the indoor heating capacity is excessive, causing the room temperature to rise and reducing indoor comfort. It then calculates the difference between the estimated heating capacity and the initial heating capacity and calculates an opening control amount corresponding to this difference. The switching control unit 74 then controls the opening of the first expansion valve 51 by the opening control amount (ST5).

[0049] On the other hand, if the initial heating capacity is greater than the estimated heating capacity, or if the initial heating capacity is equal to the estimated heating capacity (NO in ST4), then it is determined whether the initial heating capacity and the estimated heating capacity are equal (ST6).

[0050] If the determination unit 73 determines that the initial heating capacity value and the estimated heating capacity value are equal (YES in ST6), the switching control unit 74 controls the opening of the first expansion valve 51 (ST7). On the other hand, if it determines that the initial heating capacity value and the estimated heating capacity value are not equal (NO in ST6), it corresponds to the case where the estimated heating capacity value is smaller than the initial heating capacity value. In this case, it is determined that the indoor heating capacity is insufficient, the room temperature will drop, and the indoor comfort will decrease, so the difference between the initial heating capacity value and the estimated heating capacity value is calculated, and an opening control amount corresponding to that difference is calculated. Then, the switching control unit 74 controls the opening of the first expansion valve 51 by the opening control amount (ST8).

[0051] Then, while the defrost heating operation is being performed, the determination unit 73 determines, based on the pre-set termination conditions, whether the frost on the outdoor heat exchanger 3 has melted and the defrost heating operation can be terminated (ST9). If the determination unit 73 determines that the frost on the outdoor heat exchanger 3 has not melted and the defrost heating operation cannot be terminated yet (NO in ST9), the defrost heating operation that is currently running continues (progresses to ST2). On the other hand, if the determination determines that the defrost heating operation can be terminated (YES in ST9), the defrost heating operation is terminated (ST10).

[0052] Next, the effects and advantages of the defrost heating operation in the first embodiment will be described.

[0053] During defrost heating operation, the control system prioritizes removing frost from the outdoor heat exchanger 3, resulting in less precise control of the heating capacity relative to the set temperature compared to normal thermal storage heating operation. This can easily lead to excessively high or low room temperatures, reducing comfort. Therefore, in high outdoor temperatures and with a small building volume and low building load, the heating capacity during defrost heating operation may become excessive.

[0054] Therefore, the control device 7 of this embodiment calculates an estimated heating capacity based on the enthalpy difference between the inlet and outlet of the indoor heat exchanger 2 and the refrigerant circulation rate during defrost heating operation. It then compares this estimated heating capacity with a preset initial heating capacity value and controls the opening of the first expansion valve 51 to be increased if it determines that the estimated heating capacity is excessive, and to be decreased if it determines that the estimated heating capacity is insufficient.

[0055] Therefore, when it is determined that the estimated heating capacity is excessive, the control is performed to increase the opening of the first expansion valve 51. This causes a portion of the refrigerant flowing through the indoor heat exchanger 2 to flow to the outdoor heat exchanger 3, reducing the indoor heating capacity and lowering the room temperature. As a result, even when the building load is small, a decrease in indoor comfort can be suppressed. In addition, the defrosting time can be shortened because a portion of the refrigerant flowing through the indoor heat exchanger 2 flows to the outdoor heat exchanger 3.

[0056] Furthermore, if it is determined that the estimated heating capacity is insufficient, the control system reduces the opening of the first expansion valve 51. This causes the refrigerant flowing through the outdoor heat exchanger 3 to flow into the indoor heat exchanger 2, increasing the indoor heating capacity and raising the room temperature, thereby suppressing a decrease in indoor comfort.

[0057] Furthermore, by controlling the opening degree of the first expansion valve 51 based on the enthalpy difference between the inlet and outlet of the indoor heat exchanger 2, it is possible to simultaneously control the adjustment between the heating capacity of the indoor heat exchanger 2 and the defrosting capacity of the outdoor heat exchanger 3 during defrost heating operation.

[0058] Furthermore, the second expansion valve 52, located downstream of the refrigerant in the indoor heat exchanger 2, is fixed at an opening such that the refrigerant flowing out of the indoor heat exchanger 2, which functions as a condenser during defrosting and heating operation, becomes supercooled. Therefore, complex control is not required, and the heating capacity of the indoor heat exchanger 2 and the defrosting capacity of the outdoor heat exchanger 3 can be adjusted simultaneously during defrosting and heating operation simply by controlling the opening of the first expansion valve 51. [Control of defrost heating operation in the second embodiment]

[0059] Next, the control flow of the defrost heating operation in the second embodiment of the present invention will be explained using the flowcharts shown in Figures 10 and 11. The control of the defrost heating operation in the second embodiment is characterized by estimating the heating capacity based on the room temperature.

[0060] In the second embodiment, the control device 7 has the same configuration as the control device 7 of the first embodiment, specifically the temperature detection unit 71 and the switching control unit 74.

[0061] The storage unit 72 of the control device 7 in the second embodiment stores a first threshold temperature and a second threshold temperature. The first threshold temperature is, for example, 2°C higher than the room temperature (24°C) set for defrost heating operation, and the second threshold temperature is, for example, 2°C lower than the room temperature (24°C) set for defrost heating operation. Furthermore, the storage unit 72 of the control device 7 in the second embodiment stores an estimated heating capacity value for the first threshold temperature estimated from the first threshold temperature, and an estimated heating capacity value for the second threshold temperature estimated from the second threshold temperature. Furthermore, the memory unit 72 of the control device 7 in the second embodiment stores the opening degrees of the first expansion valve 51 and the second expansion valve 52, which are determined according to the required capacity. The opening degree of the first expansion valve 51 is the opening degree required for defrost heating operation, and the opening degree of the second expansion valve 52 is the opening degree at which the refrigerant flowing out from the indoor heat exchanger 2, which functions as a condenser during defrost heating operation, becomes supercooled. Furthermore, the storage unit 72 of the control device 7 in the second embodiment is set to the opening degree of the second expansion valve 52, which causes the refrigerant flowing out from the indoor heat exchanger 2, which functions as a condenser during defrosting and heating operation, to become subcooled. The storage unit 72 of the control device 7 in the second embodiment also stores data of estimated heating capacity corresponding to changes in indoor temperature.

[0062] As shown in Figure 10, the control of the defrost heating operation in the second embodiment begins with the start of the defrost heating operation in the air conditioner S (ST21). At that time, when the switching control unit 74 controls the first expansion valve 51 and the second expansion valve 52 to a predetermined opening degree, the refrigerant discharged from the compressor 1 via the first switching valve 61 flows into the indoor heat exchanger 2, and the high-temperature refrigerant from the compressor 1 flows into the outdoor heat exchanger 3, thereby performing a defrost operation to melt the frost attached to the outdoor heat exchanger 3.

[0063] Next, the determination unit 73 estimates the heating capacity during defrost heating operation (ST22).

[0064] The specific process for estimating the heating capacity during defrost heating operation is as shown in Figure 11: the temperature detection unit 71 obtains the current room temperature detected by the room temperature sensor 21 installed on the indoor unit 10 (ST41). Next, the determination unit 73 obtains a heating capacity estimate corresponding to the current room temperature from the data of heating capacity estimates corresponding to changes in indoor temperature stored in the storage unit 72 (ST42).

[0065] Next, returning to Figure 10, the determination unit 73 compares the current room temperature with the first threshold temperature (ST23 in Figure 10).

[0066] The determination unit 73 compares the current room temperature with the first threshold temperature (ST24). If the current room temperature is above the first threshold temperature (YES in ST24), it determines that the indoor heating capacity is excessive, causing the room temperature to rise and reducing indoor comfort. It then calculates the difference between the estimated heating capacity and the estimated heating capacity at the first threshold temperature, and calculates an opening control amount corresponding to this difference. The switching control unit 74 then controls the opening of the first expansion valve 51 by the opening control amount (ST25).

[0067] On the other hand, if the current room temperature falls below the first threshold temperature (NO in ST24), The determination unit 73 compares the current room temperature with the second threshold temperature (ST26).

[0068] The determination unit 73 compares the current room temperature with the second threshold temperature (ST27). If the current room temperature is below the second threshold temperature (YES in ST27), it determines that the indoor heating capacity is insufficient, causing the room temperature to drop and reducing indoor comfort. It then calculates the difference between the estimated heating capacity and the estimated heating capacity at the second threshold temperature, and calculates an opening control amount corresponding to this difference. The switching control unit 74 then controls the opening of the first expansion valve 51 by the opening control amount (ST28). If the current room temperature is above the second threshold temperature (NO in ST27), the switching control unit 74 maintains the opening of the first expansion valve 51 (ST29).

[0069] While the defrost heating operation is in progress, the determination unit 73 determines, based on pre-set termination conditions, whether the frost on the outdoor heat exchanger 3 has melted and the defrost heating operation can be terminated (ST30). If the determination unit 73 determines that the frost on the outdoor heat exchanger 3 has not melted sufficiently and the defrost heating operation cannot be terminated yet (NO in ST30), the ongoing defrost heating operation continues (proceeds to ST22). On the other hand, if the determination determines that the defrost heating operation can be terminated (YES in ST30), the defrost heating operation is terminated (ST31).

[0070] The effects and advantages of the defrost heating operation in the second embodiment will be explained.

[0071] In the second embodiment, the control device 7 determines that the estimated heating capacity is excessive when it determines that the room temperature during defrost heating operation is above the first threshold temperature, and controls the opening of the first expansion valve 51 to be increased. When it determines that the room temperature during defrost heating operation is below the second threshold temperature, it determines that the estimated heating capacity is insufficient, and controls the opening of the first expansion valve 51 to be decreased.

[0072] Therefore, by controlling the first expansion valve 51 to increase its size when it is determined that the estimated heating capacity is excessive, a portion of the refrigerant flowing through the indoor heat exchanger 2 flows to the outdoor heat exchanger 3, reducing the indoor heating capacity and lowering the room temperature. This suppresses a decrease in indoor comfort even when the building load is small. In addition, by having a portion of the refrigerant flowing through the indoor heat exchanger 2 flow to the outdoor heat exchanger 3, the defrosting time can be shortened.

[0073] Furthermore, if it is determined that the estimated heating capacity is insufficient, the control system reduces the size of the first expansion valve 51. This causes the refrigerant flowing through the outdoor heat exchanger 3 to flow into the indoor heat exchanger 2, increasing the indoor heating capacity and raising the room temperature, thereby suppressing a decrease in indoor comfort.

[0074] Furthermore, the second embodiment controls the opening degree of the first expansion valve 51 based on the room temperature during defrost heating operation, thereby simultaneously controlling the adjustment between the heating capacity of the indoor heat exchanger 2 and the defrosting capacity of the outdoor heat exchanger 3 during defrost heating operation.

[0075] Furthermore, the second expansion valve 52, located downstream of the refrigerant in the indoor heat exchanger 2, is set to a fixed opening value such that the refrigerant flowing out of the indoor heat exchanger 2, which functions as a condenser during defrosting and heating operation, becomes supercooled. Therefore, complex control is not required, and the heating capacity of the indoor heat exchanger 2 and the defrosting capacity of the outdoor heat exchanger 3 during defrosting and heating operation can be adjusted simultaneously by controlling only the opening of the first expansion valve 51. [Control of defrost heating operation in the third embodiment]

[0076] Next, the control flow of the defrost heating operation according to the third embodiment of the present invention will be explained using the flowcharts shown in Figures 11 and 12. The control of the defrost heating operation in the third embodiment is characterized by estimating the heating capacity based on the condensation temperature of the indoor heat exchanger 2.

[0077] In the third embodiment, the storage unit 72 of the control device 7 stores the condensation temperature of the indoor heat exchanger 2, which functions as a condenser during defrost heating operation, at the start of the defrost heating operation, and the initial heating capacity value of the defrost heating operation based on this condensation temperature. Furthermore, the storage unit 72 of the control device 7 in the third embodiment stores the opening degrees of the first expansion valve 51 and the second expansion valve 52, which are determined according to the required capacity, similar to the first and second embodiments.

[0078] Furthermore, the storage unit 72 of the third embodiment stores data of estimated heating capacity corresponding to the condensation temperature of the indoor heat exchanger 2, which functions as a condenser during defrosting and heating operation.

[0079] In the third embodiment, the determination unit 73 estimates the heating capacity during defrost heating operation. Specifically, this process involves obtaining a heating capacity estimate corresponding to the refrigerant temperature (condensation temperature) detected by the refrigerant temperature sensor 22 from the heating capacity estimate data stored in the storage unit 72.

[0080] Furthermore, the determination unit 73 compares whether the temperature difference between the current room temperature and the room temperature a predetermined time ago (for example, 1 minute ago) is within a predetermined temperature range (for example, 2°C). The determination unit 73 also compares the current refrigerant temperature with the refrigerant temperature (condensation temperature) at the start of the defrost heating operation.

[0081] As shown in Figure 12, the control of the defrost heating operation in the third embodiment begins with the air conditioner S starting the defrost heating operation (ST51). At that time, when the switching control unit 74 controls the first expansion valve 51 and the second expansion valve 52 to a predetermined opening degree, the refrigerant discharged from the compressor 1 via the first switching valve 61 flows into the indoor heat exchanger 2, and high-temperature refrigerant from the compressor 1 flows into the outdoor heat exchanger 3, thereby performing a defrost operation to melt the frost attached to the outdoor heat exchanger 3.

[0082] Next, the determination unit 73 estimates the heating capacity during defrost heating operation (ST52).

[0083] The specific process for estimating the heating capacity during defrost heating operation is as shown in Figure 13: the temperature detection unit 71 acquires the current condensation temperature detected by the refrigerant temperature sensor 22 (ST71). Next, the determination unit 73 acquires a heating capacity estimate corresponding to the current condensation temperature from the heating capacity estimate data stored in the storage unit 72 (ST72).

[0084] Next, returning to Figure 12, the determination unit 73 calculates the temperature difference between the current room temperature and the room temperature from a predetermined time ago (ST53).

[0085] Next, the determination unit 73 compares the temperature difference in the room temperature with a predetermined temperature range (for example, 2°C). If the temperature difference in the room temperature is less than or equal to the predetermined temperature range (YES in ST54), it compares the current condensation temperature with the condensation temperature at the start of the defrost heating operation (ST55). If the current condensation temperature is greater than the condensation temperature at the start of the defrost heating operation (YES in ST56), the determination unit 73 determines that the heating capacity in the room is excessive, causing the room temperature to rise and reducing the comfort level in the room. It then calculates the difference between the estimated heating capacity and the initial heating capacity and calculates an opening control amount corresponding to this difference. The switching control unit 74 then controls the opening of the first expansion valve 51 by the opening control amount (ST57).

[0086] If the current condensation temperature is less than or equal to the condensation temperature at the start of the defrost heating operation (ST56 NO), and the current condensation temperature is lower than the condensation temperature at the start of the defrost heating operation (ST58 YES), the determination unit 73 determines that the indoor heating capacity is insufficient, the room temperature will drop, and the indoor comfort will decrease. It calculates the difference between the estimated heating capacity and the initial heating capacity and calculates an opening control amount corresponding to this difference. The switching control unit 74 then controls the opening of the first expansion valve 51 by the opening control amount (ST59). If the current condensation temperature and the condensation temperature at the start of the defrost heating operation are equal (ST58 NO), the switching control unit 74 controls the opening of the first expansion valve 51 to be maintained (ST60).

[0087] While the defrost heating operation is in progress, the determination unit 73 determines, based on pre-set termination conditions, whether the frost on the outdoor heat exchanger 3 has melted and the defrost heating operation can be terminated (ST61). If the determination unit 73 determines that the frost on the outdoor heat exchanger 3 has not melted sufficiently and the defrost heating operation cannot be terminated yet (NO in ST61), the ongoing defrost heating operation continues (proceeds to ST52). On the other hand, if the determination determines that the defrost heating operation can be terminated (YES in ST61), the defrost heating operation is terminated (ST62).

[0088] The effects and advantages of the defrost heating operation in the third embodiment will be explained.

[0089] Assume the current room temperature during defrost heating operation is 24°C, and the room temperature a predetermined time ago was 23°C. There is not much temperature difference between the current room temperature and the room temperature a predetermined time ago. However, if the current condensation temperature of the indoor heat exchanger 2 is higher than the condensation temperature at the start of the defrost heating operation, the system determines that the estimated heating capacity is excessive and controls the first expansion valve 51 to be larger. If the current condensation temperature of the indoor heat exchanger 2 is lower than the condensation temperature at the start of the defrost heating operation, the system determines that the estimated heating capacity is insufficient and controls the first expansion valve 51 to be smaller.

[0090] Therefore, in the third embodiment, by monitoring the change in the condensation temperature of the indoor heat exchanger 2, even when the temperature change in the room temperature is small, it is possible to estimate whether the heating capacity is excessive or insufficient from the condensation capacity, thereby suppressing a decrease in indoor comfort due to the room temperature rising too high or falling too low.

[0091] Furthermore, similar to the first and second embodiments, by controlling the opening degree of the first expansion valve 51 based on the room temperature during defrost heating operation, it is possible to simultaneously control the heating capacity of the indoor heat exchanger 2 and the defrosting capacity of the outdoor heat exchanger 3 during defrost heating operation. In addition, the second expansion valve 52, which is located downstream of the refrigerant in the indoor heat exchanger 2, is set to a fixed opening degree such that the refrigerant flowing out of the indoor heat exchanger 2, which functions as a condenser during defrost heating operation, becomes supercooled. Therefore, complex control is not required, and the heating capacity of the indoor heat exchanger 2 and the defrosting capacity of the outdoor heat exchanger 3 during defrost heating operation can be simultaneously adjusted by controlling only the opening degree of the first expansion valve 51.

[0092] [Means for estimating heating capacity in the fourth embodiment]

[0093] In the first to third embodiments, the estimated heating capacity was calculated based on the enthalpy difference and refrigerant circulation rate at the inlet and outlet of the indoor heat exchanger 2 during defrost heating operation, the estimated heating capacity was calculated based on the room temperature detected by the room temperature sensor 21, or the estimated heating capacity was calculated based on the condensation temperature of the indoor heat exchanger 2 and the room temperature.

[0094] As shown in Figure 2, the heating capacity during defrost heating operation may be estimated based on the airflow rate from the indoor fan 11 that blows air that has been heat-exchanged with the refrigerant in the indoor heat exchanger 2 into the room. In other words, the estimated heating capacity during defrost heating operation can be calculated based on the temperature difference between the room temperature detected by the room temperature sensor 21 installed in the indoor unit 10 and the refrigerant temperature detected by the refrigerant temperature sensor 22, and the airflow rate of the indoor fan 11.

[0095] By calculating an estimated heating capacity based on the airflow rate from the indoor fan 11 and using this to control the defrost heating operation in the first to third embodiments, more precise and rapid control of the defrost heating operation can be achieved compared to calculating the estimated heating capacity based solely on the room temperature and the refrigerant temperature flowing through the indoor heat exchanger 2.

[0096] It should be noted that this invention is not limited to the embodiments described above, but rather represents an example of the present invention. In the implementation stage, the components can be modified and materialized without departing from the spirit of the invention, and various changes or improvements can be made to the above embodiments. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above embodiments.

[0097] For example, some components may be removed from all the components shown in the embodiment. 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 in the scope and essence of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0098] S Air conditioner 1. Compressor 2 Indoor heat exchanger 3 Outdoor heat exchanger 4 Regenerative heat exchanger 5. Expansion valve 10 Indoor unit 11 Indoor fan 51 First expansion valve 52 Second expansion valve 53 Third expansion valve 6. Switching valve 61 First switching valve 62 Second switching valve 21 Room temperature sensor 22 Refrigerant temperature sensor 23. Gas-side refrigerant temperature sensor 24 Liquid-side refrigerant temperature sensor B Bypass Circuit C Refrigerant circuit

Claims

1. In the refrigerant circuit that circulates the refrigerant, A compressor for compressing the aforementioned refrigerant, An indoor heat exchanger that exchanges heat between indoor air and the aforementioned refrigerant, An outdoor heat exchanger that exchanges heat between the outdoor air and the refrigerant, A heat storage heat exchanger that exchanges heat between a heat storage material and the refrigerant, Multiple expansion valves with adjustable opening degrees, A switching valve is connected to switch the flow path of the refrigerant circuit between a thermal storage heating operation in which the indoor heat exchanger and the thermal storage heat exchanger function as condensers and the outdoor heat exchanger function as an evaporator, and a defrosting heating operation in which the indoor heat exchanger and the outdoor heat exchanger function as condensers and the thermal storage heat exchanger function as an evaporator. A heating capacity estimation means for estimating the heating capacity during the defrost heating operation, The system comprises a control device for controlling the plurality of expansion valves and the switching valve, The plurality of expansion valves include a first expansion valve provided on the upstream side of the outdoor heat exchanger during the defrost heating operation. The control device controls the opening degree of the first expansion valve based on the heating capacity estimated by the heating capacity estimation means during the defrost heating operation, and increases the opening degree of the first expansion valve when the heating capacity estimation means determines that the estimated heating capacity is excessive.

2. The air conditioner according to claim 1, characterized in that the control device reduces the opening of the first expansion valve when it determines that the heating capacity estimated by the heating capacity estimation means is insufficient.

3. The system includes an enthalpy difference calculation means that calculates the enthalpy difference based on the enthalpy on the inlet side and the enthalpy on the outlet side of the indoor heat exchanger. The air conditioner according to claim 1, characterized in that the heating capacity estimation means estimates the heating capacity based on the enthalpy difference calculated by the enthalpy difference calculation means.

4. Equipped with a room temperature sensor to detect the indoor temperature, The air conditioner according to claim 1, characterized in that the heating capacity estimation means estimates the heating capacity based on the room temperature detected by the room temperature sensor.

5. The air conditioner according to claim 4, characterized in that the control device determines that the heating capacity estimated by the heating capacity estimation means is excessive when the room temperature detected by the room temperature sensor exceeds a predetermined first threshold, and increases the opening of the first expansion valve when it is determined that the heating capacity is excessive.

6. The control device is characterized in that, when the room temperature detected by the room temperature sensor falls below a predetermined second threshold, it determines that the heating capacity estimated by the heating capacity estimation means is insufficient, and when it determines that the heating capacity is insufficient, it reduces the opening of the first expansion valve, as described in claim 4.

7. A room temperature sensor that detects the indoor temperature, The system includes an indoor heat exchanger temperature sensor for detecting the temperature of the indoor heat exchanger, The air conditioner according to claim 1, characterized in that the heating capacity estimation means estimates the heating capacity based on the temperature of the indoor heat exchanger detected by the indoor heat exchanger temperature sensor.

8. The control device determines that the heating capacity estimated by the heating capacity estimation means is excessive if the temperature difference between the current room temperature detected by the room temperature sensor and the room temperature a predetermined time ago is within a predetermined range, and the temperature of the indoor heat exchanger detected by the indoor heat exchanger temperature sensor is higher than the temperature at the start of the defrost heating operation, and increases the opening of the first expansion valve when it is determined that the heating capacity is excessive, as described in claim 7.

9. The control device determines that the heating capacity estimated by the heating capacity estimation means is insufficient when the temperature difference between the current room temperature detected by the room temperature sensor and the room temperature a predetermined time ago is within a predetermined range, and the temperature of the indoor heat exchanger detected by the indoor heat exchanger temperature sensor is lower than the temperature at the start of the defrost heating operation, and when it determines that the heating capacity is insufficient, it reduces the opening of the first expansion valve, as described in claim 7.

10. The system includes an airflow calculation means for calculating the airflow volume discharged from an indoor fan that blows air, which has had its heat exchanged with the refrigerant in the indoor heat exchanger, into the room. The air conditioner according to claim 7, characterized in that the heating capacity estimation means estimates the heating capacity based on the temperature difference between the room temperature detected by the room temperature sensor and the temperature of the indoor heat exchanger detected by the indoor heat exchanger temperature sensor, and the airflow calculated by the airflow calculation means.

11. The air conditioner according to any one of claims 1 to 10, characterized in that the plurality of expansion valves are provided downstream of the indoor heat exchanger during the defrost heating operation and include a second expansion valve whose opening degree is set to a fixed value during the defrost heating operation.

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