Air conditioner

Abstract

To appropriately determine whether a refrigerant stays in a heat exchanger of a stopped indoor unit.SOLUTION: An air conditioning apparatus according to an embodiment of the present invention includes a refrigerant circuit and a control unit. The refrigerant circuit has a heat source unit having a heat source-side heat exchanger and an outdoor heat exchange temperature sensor, a usage-side unit having a usage-side heat exchanger and an indoor heat exchange temperature sensor, a connecting pipe including a liquid pipe and a gas pipe that connect the heat source unit and the usage-side unit, and a valve that controls the amount of refrigerant flowing through the connecting pipe. The utilization side unit includes at least two indoor units. The control unit determines whether or not refrigerant is retained in the use-side heat exchanger of the operation-stopped indoor unit by using any one of a temperature detected by the outdoor heat exchange temperature sensor and a temperature detected by the indoor heat exchange temperature sensor of the operation-performed indoor unit, and a temperature detected by the indoor heat exchange temperature sensor of the operation-stopped indoor unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an air conditioner and a heat source unit in which a plurality of indoor units are connected in parallel to one outdoor unit. [Background technology]

[0002] For example, Patent Document 1 discloses an air conditioner in which an indoor unit equipped with a water-refrigerant heat exchanger that exchanges heat between a refrigerant and water and at least one indoor unit (direct expansion indoor unit) equipped with an air-refrigerant heat exchanger that exchanges heat between a refrigerant and air are connected in parallel to an outdoor unit. Each indoor unit is equipped with an expansion valve disposed in a liquid refrigerant pipe connected to one end of the heat exchanger, and an on-off valve disposed in a gas refrigerant pipe connected to the other end of the heat exchanger. For example, when only one of the indoor units is operating in heating mode, the on-off valve on the indoor unit that is stopped is closed to prevent refrigerant from flowing into that indoor unit.

[0003] Furthermore, when the air conditioning system described in Patent Document 1 operates in heating mode on only one of the indoor units, it closes the on-off valve on the stopped indoor unit to prevent refrigerant from flowing into that stopped indoor unit, and opens the expansion valve on the stopped indoor unit to prevent refrigerant from accumulating in the stopped indoor unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 189942 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the inventor discovered that when the expansion valve on the stopped indoor unit side is left open, as in the air conditioning device described in Patent Document 1, there is a risk that refrigerant may flow into the indoor heat exchanger of the stopped indoor unit due to temperature changes in the indoor heat exchanger of the stopped indoor unit.

[0006] For example, during heating cycle operation, if the temperature of the heat exchanger of the stopped indoor unit is lower than the temperature of the outdoor heat exchanger functioning as an evaporator, some of the gas refrigerant flowing out of the operating indoor unit and toward the outdoor unit will likely flow into the heat exchanger of the stopped indoor unit through the open expansion valve on the stopped indoor unit. Also, during cooling cycle operation, if the temperature of the heat exchanger of the stopped indoor unit is lower than the temperature of the heat exchanger of the operating indoor unit functioning as an evaporator, some of the gas refrigerant flowing out of the operating indoor unit and toward the outdoor unit will likely flow into the heat exchanger of the stopped indoor unit through the open on-off valve on the stopped indoor unit. The refrigerant that flows into the heat exchanger of the stopped indoor unit condenses and reduces in volume, causing additional gas refrigerant to flow in to fill the space equivalent to the reduced volume.

[0007] In view of the above circumstances, an object of the present invention is to provide an air conditioning system that can appropriately determine whether or not refrigerant is stagnating in the heat exchanger of a stopped indoor unit, and that can eliminate the refrigerant stagnation when it is determined that refrigerant is stagnating. [Means for solving the problem]

[0008] An air conditioner according to one aspect of the present invention includes a refrigerant circuit and a control unit. The refrigerant circuit includes a heat source unit having a compressor, a heat source side heat exchanger, and an outdoor heat exchanger temperature sensor that detects the temperature of the heat source side heat exchanger, a user side unit having a user side heat exchanger and an indoor heat exchanger temperature sensor that detects the temperature of the user side heat exchanger, connecting piping including a liquid pipe and a gas pipe that connects the heat source unit and the user side unit, and a valve that controls the amount of refrigerant flowing through the connecting piping. The control unit controls the compressor and the valve. The user side units include at least two indoor units. When the indoor unit that is to be operated is designated as the operating indoor unit and the indoor unit that is to be stopped is designated as the stopped indoor unit, the control unit determines whether refrigerant is stagnating in the user side heat exchanger of the stopped indoor unit using either the detected temperature of the outdoor heat exchanger temperature sensor or the detected temperature of the indoor heat exchanger temperature sensor of the operating indoor unit, and the detected temperature of the indoor heat exchanger temperature sensor of the stopped indoor unit. [Effects of the Invention]

[0009] According to the present invention, it is possible to appropriately determine whether or not refrigerant is stagnating in the heat exchanger of a stopped indoor unit, and when it is determined that refrigerant is stagnating, the refrigerant stagnation can be eliminated. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a refrigerant circuit diagram showing an example of the configuration of an air conditioning apparatus according to an embodiment of the present invention. [Figure 2] 1 is a system diagram showing an example of the configuration of a water heater; [Figure 3] FIG. 2 is a block diagram showing the configuration of a control unit. [Figure 4] FIG. 10 is a diagram showing the relationship between the volumetric circulation amount of refrigerant and the rotation speed of the outdoor fan during heating operation. [Figure 5] FIG. 10 is a diagram showing the relationship between the rotation speed of the compressor and the rotation speed of the outdoor fan during hot water supply operation. [Figure 6] FIG. 10 is a diagram showing an example of a rotation speed table for controlling an outdoor fan for elimination of stagnation during heating operation. [Figure 7] FIG. 10 is a diagram showing the relationship between the rotation speed of a compressor for stagnation elimination control and the rotation speed of an outdoor fan during hot water supply operation. [Figure 8] 10 is a flowchart illustrating an example of a procedure for a retention elimination control process executed by a control unit. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] 1 is a refrigerant circuit diagram showing an example of the configuration of an air conditioner 100 according to one embodiment of the present invention. The entire air conditioner 100 of this embodiment will be described briefly below with reference to FIG.

[0013] [Overall configuration of air conditioning equipment] As shown in Fig. 1, the air conditioner 100 includes a refrigerant circuit 10. The refrigerant circuit 10 includes a heat source unit 1, a plurality of user-side units 2, connecting pipes (liquid pipe 3 and gas pipe 4 in Fig. 1) that connect an outdoor heat exchanger 13 in the heat source unit 1 to the user-side units 2, an expansion valve 5 connected to the liquid pipe 3, and an on-off valve 6 connected to the gas pipe 4. The expansion valve 5 and the on-off valve 6 each correspond to valves that control the amount of refrigerant flowing through the connecting pipes.

[0014] The heat source unit 1 corresponds to an outdoor unit. The user-side unit 2 corresponds to an indoor unit. In this embodiment, the user-side unit 2 includes a first indoor unit 2A having a first indoor heat exchanger 21A as a user-side heat exchanger, and a second indoor unit 2B having a second indoor heat exchanger 21B as a user-side heat exchanger. The number of user-side units 2 may be one or three or more.

[0015] The heat source unit 1 has a compressor 11, a four-way valve 12, an outdoor heat exchanger 13 as a heat source side heat exchanger, an outdoor fan 13F, an accumulator 14, a first liquid pipe connection part 311, a second liquid pipe connection part 312, a first gas pipe connection part 411, and a second gas pipe connection part 412.

[0016] The compressor 11 is a variable capacity compressor with a variable operating capacity driven by a motor (not shown) whose rotation speed is controlled by an inverter. The refrigerant discharge side of the compressor 11 is connected to port a of the four-way valve 12 via a discharge pipe 15. The refrigerant suction side of the compressor 11 is connected to the refrigerant outflow side of the accumulator 14 via a suction pipe 18.

[0017] The four-way valve 12 is a flow path switching valve that switches the flow direction of the refrigerant in the refrigerant circuit 10, and has four ports a, b, c, and d. As described above, port a is connected to the refrigerant discharge side of the compressor 11 by discharge piping 15. Port b is connected to one refrigerant inlet / outlet that is one end of the outdoor heat exchanger 13 by refrigerant piping 16. Port c is connected to the refrigerant inlet / outlet side of the accumulator 14 by refrigerant piping 17. Port d is connected to one refrigerant inlet / outlet that is one end of the first indoor heat exchanger 21A by a first gas pipe 4A that is part of the gas pipe 4, and is also connected to one refrigerant inlet / outlet that is one end of the second indoor heat exchanger 21B by a second gas pipe 4B that is part of the gas pipe 4.

[0018] The outdoor heat exchanger 13 exchanges heat between the refrigerant and the outside air that has been drawn into the heat source unit 1 by the rotation of the outdoor fan 13F. As described above, one end of the outdoor heat exchanger 13 is connected to port b of the four-way valve 12 by refrigerant piping 16. The other end of the outdoor heat exchanger 13 is connected to the other refrigerant inlet / outlet that is the other end of the first indoor heat exchanger 21A by a first liquid pipe 3A that is part of the liquid pipe 3, and is also connected to the other refrigerant inlet / outlet that is the other end of the second indoor heat exchanger 21B by a second liquid pipe 3B that is part of the liquid pipe 3.

[0019] The outdoor fan 13F is disposed near the outdoor heat exchanger 13. The outdoor fan 13F is rotated by a fan motor (not shown) to cause outdoor air taken in through an air inlet (not shown) of the heat source unit 1 to flow into the outdoor heat exchanger 13, and the outdoor air that has exchanged heat with the refrigerant in the outdoor heat exchanger 13 is discharged to the outside of the heat source unit 1 through an air outlet (not shown) of the heat source unit 1.

[0020] The liquid pipe 3 and the gas pipe 4 are refrigerant pipes that connect the outdoor heat exchanger 13 to the first indoor heat exchanger 21A and the second indoor heat exchanger 21B.

[0021] The liquid pipe 3 includes a first liquid pipe 3A and a second liquid pipe 3B. As described above, the first liquid pipe 3A connects the other end of the outdoor heat exchanger 13 to the other end of the first indoor heat exchanger 21A. As described above, the second liquid pipe 3B connects the other end of the outdoor heat exchanger 13 to the other end of the second indoor heat exchanger 21B.

[0022] The first liquid pipe 3A has an outdoor unit liquid pipe 31, a first outdoor unit liquid branch pipe 31A, and a first liquid refrigerant pipe 32A. The outdoor unit liquid pipe 31 is connected to the other end of the outdoor heat exchanger 13, and has a branch point C1 of the first outdoor unit liquid branch pipe 31A and the second outdoor unit liquid branch pipe 31B. The first outdoor unit liquid branch pipe 31A connects the branch point C1 of the outdoor unit liquid pipe 31 and the first liquid pipe connection part 311. The first liquid refrigerant pipe 32A connects the first liquid pipe connection part 311 and the other end of the first indoor heat exchanger 21A.

[0023] The second liquid pipe 3B has an outdoor unit liquid pipe 31, a second outdoor unit liquid branch pipe 31B, and a second liquid refrigerant pipe 32B. The second outdoor unit liquid branch pipe 31B connects the branch point C1 of the outdoor unit liquid pipe 31 and the second liquid pipe connection part 312. The second liquid refrigerant pipe 32B connects the second liquid pipe connection part 312 and the other end of the second indoor heat exchanger 21B.

[0024] The gas pipe 4 includes a first gas pipe 4A and a second gas pipe 4B. The first gas pipe 4A connects the one end of the outdoor heat exchanger 13 to the one end of the first indoor heat exchanger 21A. The second gas pipe 4B connects the one end of the outdoor heat exchanger 13 to the one end of the second indoor heat exchanger 21B.

[0025] The first gas pipe 4A has an outdoor unit gas pipe 41, a first outdoor unit gas branch pipe 41A, and a first gas refrigerant pipe 42A. The outdoor unit gas pipe 41 is connected to the one end of the outdoor heat exchanger 13 via the four-way valve 12 and the refrigerant pipe 16, and has a branch point C2 of the first outdoor unit gas branch pipe 41A and the second outdoor unit gas branch pipe 41B. The first outdoor unit gas branch pipe 41A connects the branch point C2 of the outdoor unit gas pipe 41 to a first gas pipe connection part 411. The first gas refrigerant pipe 42A connects the first gas pipe connection part 411 to the one end of the first indoor heat exchanger 21A.

[0026] The second gas pipe 4B has an outdoor unit gas pipe 41, a second outdoor unit gas branch pipe 41B, and a second gas refrigerant pipe 42B. The second outdoor unit gas branch pipe 41B connects the branch point C2 of the outdoor unit gas pipe 41 and the second gas pipe connection part 412. The second gas refrigerant pipe 42B connects the second gas pipe connection part 412 and the one end of the second indoor heat exchanger 21B.

[0027] The expansion valve 5 includes a first expansion valve 5A and a second expansion valve 5B. The first expansion valve 5A is disposed in the first liquid pipe 3A, and the second expansion valve 5B is disposed in the second liquid pipe 3B. In this embodiment, the first expansion valve 5A is disposed in the first outdoor unit liquid branch pipe 31A, and the second expansion valve 5B is disposed in the second outdoor unit liquid branch pipe 31B.

[0028] The first expansion valve 5A and the second expansion valve 5B are electronic expansion valves whose openings are adjusted by applying a DC voltage, for example. The openings of the first expansion valve 5A and the second expansion valve 5B are controlled based on the number of pulses applied to a stepping motor (not shown), for example.

[0029] The first expansion valve 5A reduces the pressure of the refrigerant flowing through the first liquid pipe 3A. The opening degree of the first expansion valve 5A is adjusted according to the operating capacity required by the first indoor unit 2A. The second expansion valve 5B reduces the pressure of the refrigerant flowing through the second liquid pipe 3B. The opening degree of the second expansion valve 5B is adjusted according to the operating capacity required by the second indoor unit 2B.

[0030] The on-off valve 6 includes a first on-off valve 6A and a second on-off valve 6B. The first on-off valve 6A is arranged in the first gas pipe 4A, and the second on-off valve 6B is arranged in the second gas pipe 4B. In this embodiment, the first on-off valve 6A is arranged in the first outdoor unit gas branch pipe 41A, and the second on-off valve 6B is arranged in the second outdoor unit gas branch pipe 41B.

[0031] The first on-off valve 6A is an on-off valve that can block the flow of refrigerant in the first gas pipe 4A. The first on-off valve 6A is open when the first indoor unit 2A is operating, and closed when the first indoor unit 2A is stopped. The second on-off valve 6B is an on-off valve that can block the flow of refrigerant in the second gas pipe 4B. The second on-off valve 6B is open when the second indoor unit 2B is operating, and closed when the indoor unit 2B is stopped.

[0032] The first on-off valve 6A and the second on-off valve 6B are, for example, DC solenoid valves that open and close when a direct current is passed through them. In this embodiment, the first on-off valve 6A and the second on-off valve 6B are normally open solenoid valves that close when current is passed through them. Alternatively, the first on-off valve 6A and the second on-off valve 6B may be AC ​​solenoid valves that open and close when current is passed through them, or may be normally closed solenoid valves that open when current is passed through them.

[0033] The first indoor unit 2A has a first indoor heat exchanger 21A, an indoor fan 21FA, and a first heating section 22A. The second indoor unit 2B has a second indoor heat exchanger 21B and a second heating section 22B.

[0034] In this embodiment, the first indoor heat exchanger 21A is an air-refrigerant heat exchanger that exchanges heat between the air (indoor air) in the indoor space where the first indoor unit 2A is installed and a refrigerant. On the other hand, the second indoor unit 2B is, for example, the water heater 500 shown in Fig. 2, and the second indoor heat exchanger 21B is a water-refrigerant heat exchanger that exchanges heat between the water circulating through the water heater 500 and a refrigerant.

[0035] 2 is a system diagram showing an example of the configuration when the second indoor unit 2B is used as a hot water heater 500. The hot water heater 500 has a hot water storage tank 51, a water pipe 52 that supplies city water to the hot water storage tank 51, a water circuit 50 including a pump 53 that circulates water between the hot water storage tank 51 and the second indoor heat exchanger (water-refrigerant heat exchanger) 21B, and a hot water supply pipe 54 that supplies hot water in the hot water storage tank 51 to the outside. A mixing valve 55 is provided in the hot water supply pipe 54 to mix the hot water flowing out of the hot water storage tank 51 with water in the water pipe 52.

[0036] The second indoor unit 2B is not limited to the above example, and may be a panel heater for floor heating instead of the hot water storage tank 51, or may be a fan coil unit (FCU) further equipped with a water-air heat exchanger that exchanges heat between the water circulating through the water circuit and the indoor air.

[0037] Furthermore, the second indoor heat exchanger 21B may be an air-refrigerant heat exchanger like the first indoor heat exchanger 21A. That is, both the first indoor heat exchanger 21A and the second indoor heat exchanger 21B may be air-refrigerant heat exchangers, or at least one of the first indoor heat exchanger 21A and the second indoor heat exchanger 21B may be a water-refrigerant heat exchanger.

[0038] The indoor fan 21FA is disposed near the first indoor heat exchanger 21A. The indoor fan 21FA is rotated by a fan motor (not shown) to take in indoor air through an intake port (not shown) of the first indoor unit 2A, exchange heat with the refrigerant in the first indoor heat exchanger 21A, and release the indoor air into the room through an outlet port (not shown) of the first indoor unit 2A.

[0039] The first heating unit 22A is capable of heating the first indoor heat exchanger 21A to a predetermined temperature and is, for example, an electric heater. The second heating unit 22B is capable of heating the second indoor heat exchanger 21B or the water stored in the hot water tank 51 to a predetermined temperature and is, for example, an electric heater. The details of the heating units 22A and 22B will be described later.

[0040] The air conditioner 100 is provided with various sensors. For example, in the heat source unit 1, the discharge piping 15 is provided with a high-pressure sensor 71 that detects the pressure of the refrigerant discharged from the compressor 11, and a discharge temperature sensor 72 that detects the temperature of the refrigerant discharged from the compressor 11. The suction piping 18 is provided with a low-pressure sensor 73 that detects the pressure of the refrigerant drawn into the compressor 11, and a suction temperature sensor 74 that detects the temperature of the refrigerant drawn into the compressor 11. The outdoor heat exchanger 13 is also provided with an outdoor heat exchanger temperature sensor (heat source-side heat exchanger temperature sensor) 75 that detects the temperature of the refrigerant flowing through the outdoor heat exchanger 13. An outdoor air temperature sensor 76 that detects the temperature of the outdoor air flowing into the heat source unit 1, i.e., the outdoor air temperature, is provided near an air inlet (not shown) of the heat source unit 1. The outdoor heat exchanger temperature sensor 75 is positioned so that it can detect a temperature equivalent to the evaporation temperature of the refrigerant flowing through the outdoor heat exchanger, which functions as an evaporator when the refrigerant circuit 10 is in the heating cycle.

[0041] The first indoor unit 2A is provided with a first indoor heat exchanger temperature sensor (first use-side heat exchanger temperature sensor) 77A for detecting the temperature of the refrigerant flowing through the first indoor heat exchanger 21A, and a room temperature sensor 78 for detecting the indoor temperature. The second indoor unit 2B is provided with a second indoor heat exchanger temperature sensor (second use-side heat exchanger temperature sensor) 77B for detecting the temperature of the refrigerant flowing through the second indoor heat exchanger 21B, as well as a water temperature sensor 79a for detecting the temperature of water flowing into the second indoor heat exchanger 21B, a water temperature sensor 79b for detecting the temperature of water flowing out of the indoor heat exchanger 21B, and a hot water storage tank temperature sensor 79c for detecting the temperature of water stored in the hot water storage tank 51, as shown in Fig. 2. The first indoor heat exchanger temperature sensor 77A is positioned so as to detect a temperature equivalent to the evaporation temperature of the refrigerant flowing through the first indoor heat exchanger 21A, which functions as an evaporator when the refrigerant circuit 10 is in the cooling cycle.

[0042] The air conditioning apparatus 100 further includes a control unit 90. The control unit 90 is a heat source unit control device provided in the heat source unit 1, and is mounted on a control board stored in an electrical component box (not shown) of the heat source unit 1. FIG. 3 is a block diagram showing the configuration of the control unit 90. As shown in the figure, the control unit 90 includes a CPU (Central Processing Unit) 91, a memory unit 92, a communication unit 93, a sensor input unit 94, and a rotation speed detection unit 95.

[0043] The memory unit 92 is a non-volatile memory such as a flash memory, and stores the control program and control parameters of the heat source unit 1, detection values ​​corresponding to detection signals from various sensors, the control status of each device provided in the heat source unit 1 such as the compressor 11 and the outdoor fan 13F, and the control status of the first indoor unit 2A and the second indoor unit 2B obtained via the communication unit 93.

[0044] The communication unit 93 is an interface that communicates with the first indoor unit 2A and the second indoor unit 2B. The sensor input unit 94 takes in detection results from various sensors in the heat source unit 1 and outputs them to the CPU 91. The rotation speed detection unit 95 detects the rotation speed of the motor of the compressor 11 and outputs it to the CPU 91. The rotation speed detection unit 95 may be configured to directly detect the rotation speed of the motor using an encoder or the like attached to the drive shaft of the motor, or may be configured to detect the rotation speed of the motor from the drive current supplied to the motor. In the following description, the rotation speed of the compressor 11 refers to the rotation speed of the motor.

[0045] The CPU 91 is a control unit that controls each device of the heat source unit 1, including the compressor 11, by executing a program stored in the storage unit 92. The program is installed in advance in the control unit 90. Alternatively, the program may be installed via the Internet or the like.

[0046] The CPU 91 receives the detection results of the sensors in the heat source unit 1 described above via the sensor input unit 94. Furthermore, the CPU 91 receives control signals transmitted from the first indoor unit 2A and the second indoor unit 2B via the communication unit 93. The control signals transmitted from the first indoor unit 2A and the second indoor unit 2B include the operating capacities required by the first indoor unit 2A and the second indoor unit 2B. Based on the received detection results and control signals, the CPU 91 controls the drive of the compressor 11, the outdoor fan 13F, and the like, for example, by setting the command rotation speed, which is the rotation speed to be applied when driving these. Furthermore, the CPU 91 controls the switching of the four-way valve 12 based on the received detection results and control signals.

[0047] Furthermore, the CPU 91 issues opening / closing operation commands to control the opening degrees of the first expansion valve 5A and the second expansion valve 5B and the opening and closing of the first on-off valve 6A and the second on-off valve 6B, respectively, based on the captured detection results and control signals. Particularly in this embodiment, when the CPU 91 operates either the first indoor unit 2A or the second indoor unit 2B, it stops the other. In other words, the first indoor unit 2A and the second indoor unit 2B are not operated simultaneously; only one of them is operated. Hereinafter, an indoor unit that is operating will be referred to as an operating indoor unit, and an indoor unit that is not operating will be referred to as a stopped indoor unit.

[0048] [Basic operation of air conditioning equipment] Next, we will explain the basic operations of the air conditioner 100. Here, we will explain the cooling operation, heating operation, and hot water supply operation.

[0049] (Cooling operation) When the air conditioning apparatus 100 performs cooling operation using the first indoor unit 2A, for example, the four-way valve 12 is placed in the state shown by the solid lines in Fig. 1, i.e., state 2 in which ports a and b are connected and ports c and d are connected, thereby switching the refrigerant circuit 10 to the cooling cycle. The second expansion valve 5B is fully closed, and both the first on-off valve 6A and the second on-off valve 6B are open. Adjusting the opening of the first expansion valve 5A will be described later.

[0050] In this state, driving the compressor 11 causes refrigerant to circulate through the refrigerant circuit 10. At this time, the outdoor heat exchanger 13 functions as a condenser, and the first indoor heat exchanger 21A functions as an evaporator. Here, the second expansion valve 5B is fully closed to prevent refrigerant from flowing into the second indoor heat exchanger 21B of the second indoor unit 2B, which is stopped. In addition, by opening the second on-off valve 6B, the refrigerant remaining between the second indoor heat exchanger 21B of the second indoor unit 2B, which is the stopped indoor unit, and the second on-off valve 6B flows out to the outdoor unit gas pipe 41 side as the compressor 11 is driven, thereby preventing refrigerant from accumulating between the second indoor heat exchanger 21B and the second on-off valve 6B.

[0051] The high-temperature, high-pressure refrigerant discharged from the compressor 11 flows into the four-way valve 12 through the discharge pipe 15, and then flows from the four-way valve 12 through the refrigerant pipe 16 into the outdoor heat exchanger 13. The refrigerant that has flowed into the outdoor heat exchanger 13 exchanges heat with outside air that has been drawn into the heat source unit 1 by the rotation of the outdoor fan 13F, and is condensed.

[0052] The refrigerant flowing out of the outdoor heat exchanger 13 flows through the outdoor unit liquid pipe 31 and the first outdoor unit liquid branch pipe 31A and is reduced in pressure as it passes through the first expansion valve 5A. The opening degree of the first expansion valve 5A is set so that the discharge temperature of the compressor 11 becomes the target discharge temperature. The refrigerant that has passed through the first expansion valve 5A flows through the first liquid refrigerant pipe 32A into the first indoor heat exchanger 21A, where it exchanges heat with the indoor air and evaporates. The refrigerant flowing out of the first indoor heat exchanger 21A flows through the first gas refrigerant pipe 42A, the first outdoor unit gas branch pipe 41A, and the first on-off valve 6A in the open state to the outdoor unit gas pipe 41. The refrigerant that has flowed into the outdoor unit gas pipe 41 flows through the four-way valve 12, refrigerant pipe 17, accumulator 14, and suction pipe 18, and is drawn into the compressor 11 and compressed again.

[0053] (Heating operation) When the air conditioning apparatus 100 performs heating operation with the first indoor unit 2A, the four-way valve 12 is set to the state shown by the dashed lines in Fig. 1, i.e., state 1 in which port a and port d are connected and port b and port c are connected, thereby switching the refrigerant circuit 10 to a heating cycle. Also, the second on-off valve 6B is closed, the second expansion valve 5B is fully opened, and the first on-off valve 6A is opened. Adjusting the opening of the first expansion valve 5A will be described later.

[0054] In this state, driving the compressor 11 causes refrigerant to circulate through the refrigerant circuit 10. At this time, the outdoor heat exchanger 13 functions as an evaporator, and the first indoor heat exchanger 21A functions as a condenser. Here, closing the second on-off valve 6B prevents refrigerant from flowing into the second indoor heat exchanger 21B of the stopped second indoor unit 2B. Furthermore, fully opening the second expansion valve 5B causes the refrigerant remaining between the second indoor heat exchanger 21B of the stopped second indoor unit 2B and the second expansion valve 5B to flow out to the outdoor unit liquid pipe 31 as the compressor 11 is driven, thereby preventing refrigerant from accumulating between the second indoor heat exchanger 21B and the second expansion valve 5B.

[0055] The high-temperature, high-pressure refrigerant discharged from the compressor 11 flows through the discharge pipe 15 into the four-way valve 12, and then flows from the four-way valve 12 through the outdoor unit gas pipe 41, the first outdoor unit gas branch pipe 41A, the first on-off valve 6A in the fully open state, and the first gas refrigerant pipe 42A into the first indoor heat exchanger 21A. The refrigerant that has flowed into the first indoor heat exchanger 21A exchanges heat with the indoor air and condenses.

[0056] The refrigerant flowing out of the first indoor heat exchanger 21A flows through the first liquid refrigerant pipe 32A and the first outdoor unit liquid branch pipe 31A, and is reduced in pressure when passing through the first expansion valve 5A. The opening degree of the first expansion valve 5A is set so that the discharge temperature of the compressor 11 becomes the target discharge temperature. The refrigerant that has passed through the first expansion valve 5A flows through the outdoor unit liquid pipe 31 into the outdoor heat exchanger 13, where it exchanges heat with outside air and evaporates. The refrigerant that flows out of the outdoor heat exchanger 13 flows into the refrigerant pipe 16, flows through the four-way valve 12, refrigerant pipe 17, accumulator 14, and suction pipe 18, and is drawn into the compressor 11 and compressed again.

[0057] (Hot water operation) When the air conditioning apparatus 100 performs hot water supply operation in the second indoor unit 2B, the four-way valve 12 is set to the state shown by the dashed lines in Fig. 1, i.e., state 1 in which port a and port d are connected and port b and port c are connected, thereby switching the refrigerant circuit 10 to the heating cycle. Also, the first on-off valve 6A is set to a closed state, the first expansion valve 5A is set to a fully opened state, and the second on-off valve 6B is set to an open state. Adjustment of the opening of the second expansion valve 5B will be described later.

[0058] In this state, driving the compressor 11 circulates refrigerant through the refrigerant circuit 10, and driving the pump 53 circulates water through the water circuit 50. At this time, the outdoor heat exchanger 13 functions as an evaporator, and the second indoor heat exchanger 21B functions as a condenser. Here, closing the first on-off valve 6A prevents refrigerant from flowing into the first indoor heat exchanger 21A of the stopped first indoor unit 2A. Fully opening the first expansion valve 5A also causes the refrigerant remaining between the first indoor heat exchanger 21A of the stopped first indoor unit 2A and the first expansion valve 5A to flow out to the outdoor unit liquid pipe 31 by driving the compressor 11, thereby preventing refrigerant from accumulating between the first indoor heat exchanger 21A and the first expansion valve 5A.

[0059] The high-temperature, high-pressure refrigerant discharged from the compressor 11 flows into the four-way valve 12 through the discharge pipe 15, and then flows from the four-way valve 12 through the outdoor unit gas pipe 41, the second outdoor unit gas branch pipe 41B, the second on-off valve 6B in the fully open state, and the second gas refrigerant pipe 42B into the second indoor heat exchanger 21B. The refrigerant that flows into the second indoor heat exchanger 21B exchanges heat with water delivered by the pump 53 from the hot water storage tank 51 and condenses. The water delivered by the pump 53 from the hot water storage tank 51 is heated by heat exchange with the refrigerant in the second indoor heat exchanger 21B and then returns to the hot water storage tank 51. As a result, the hot water heated in the second indoor heat exchanger 21B is stored in the hot water storage tank 51.

[0060] Meanwhile, the refrigerant flowing out of the second indoor heat exchanger 21B flows through the second liquid refrigerant pipe 32B and the second outdoor unit liquid branch pipe 31B, and is reduced in pressure when passing through the second expansion valve 5B. The opening degree of the second expansion valve 5B is set so that the discharge temperature of the compressor 11 becomes the target discharge temperature. The refrigerant that has passed through the second expansion valve 5B flows through the outdoor unit liquid pipe 31 into the outdoor heat exchanger 13, where it exchanges heat with outside air and evaporates. The refrigerant that has flowed out of the outdoor heat exchanger 13 flows into the refrigerant pipe 16, flows through the four-way valve 12, refrigerant pipe 17, accumulator 14, and suction pipe 18, and is drawn into the compressor 11 and compressed again.

[0061] [Expansion valves and on-off valves] In recent years, in this type of air conditioner, there has been a demand to minimize the amount of refrigerant charged into the refrigerant circuit in consideration of cost reduction and environmental impact. In this embodiment, as described above, the first expansion valve 5A is arranged in the first outdoor unit liquid pipe 31A, the second expansion valve 5B is arranged in the second outdoor unit liquid pipe 31B, the first on-off valve 6A is arranged in the first outdoor unit gas pipe 41A, and the second on-off valve 6B is arranged in the second outdoor unit gas pipe 41B. That is, the first expansion valve 5A, the second expansion valve 5B, the first on-off valve 6A, and the second on-off valve 6B are all arranged inside the heat source unit 1. Furthermore, when operating one of the indoor units 2A, 2B and stopping the other, the control unit 90 is configured to close the valve located upstream in the refrigerant flow direction among the valves corresponding to the stopped indoor unit (the second expansion valve 5B during the cooling cycle, and the first on-off valve 6A or the second on-off valve 6B during the heating cycle).

[0062] For example, when the refrigerant circuit 10 is in a cooling cycle (during cooling operation) and the second indoor unit 2B is a stopped indoor unit, the valve located upstream in the refrigerant flow direction among the corresponding valves is the second expansion valve 5B, which is the expansion valve corresponding to the second indoor unit 2B. Refrigerant that flows into the second liquid pipe 3B connecting the outdoor heat exchanger 13 and the second indoor unit 2B, which is a stopped indoor unit, accumulates between the branch point C1 of the outdoor unit liquid pipe 31 and the second expansion valve 5B, which is in a closed state, on the second outdoor unit liquid pipe 31B (see the shaded area R1 in FIG. 1). According to this embodiment, because the second expansion valve 5B is located inside the heat source unit 1, the pipe length indicated by the area R1 is shorter than when the second expansion valve 5B is located in the second liquid refrigerant pipe 32B or the second indoor unit 2B. This reduces the amount of refrigerant that accumulates in the region R1, and therefore reduces the amount of refrigerant that is charged into the refrigerant circuit 10 in anticipation of the amount of refrigerant that will accumulate in the region R1.

[0063] On the other hand, when the refrigerant circuit 10 is in the heating cycle (heating operation or hot water supply operation), the valve corresponding to the stopped indoor unit that is located upstream in the refrigerant flow direction is the second on-off valve 6B corresponding to the second indoor unit 2B during heating operation, and the first on-off valve 6A corresponding to the first indoor unit 2A during hot water supply operation. Refrigerant that flows into the gas pipe (the second gas pipe 4B during heating operation and the first gas pipe 4A during hot water supply operation) connecting the outdoor heat exchanger 13 to the stopped indoor unit (the second indoor unit 2B during heating operation and the first indoor unit 2A during hot water supply operation) accumulates between the branch point C2 of the outdoor unit gas pipe 41 and the second on-off valve 6B, which is in a closed state (see the shaded area R2 in FIG. 1 ), during heating operation, and between the branch point C2 of the outdoor unit gas pipe 41 and the first on-off valve 6A, which is in a closed state (see the shaded area R3 in FIG. 1 ). According to the present embodiment, because the on-off valves 6A, 6B are disposed inside the heat source unit 1, the pipe lengths indicated by the regions R2, R3 are shorter than when the on-off valves 6A, 6B are disposed in the gas refrigerant pipes 42A, 42B or the first indoor unit 2A and second indoor unit 2B. This reduces the amount of refrigerant accumulating in the regions R2, R3, and therefore reduces the amount of refrigerant charged into the refrigerant circuit 10 in anticipation of the amount of refrigerant accumulating in the regions R2, R3.

[0064] In addition, in this embodiment, the control unit 90 is configured to open the valve corresponding to the stopped indoor unit that is located downstream in the refrigerant flow direction (the second opening / closing valve 6B during the cooling cycle, and the first expansion valve 5A or the second expansion valve 5B during the heating cycle).

[0065] For example, when the refrigerant circuit 10 is in a cooling cycle (during cooling operation) and the second indoor unit 2B is set as a stopped indoor unit, the valve located downstream in the refrigerant flow direction among the corresponding valves is the second on-off valve 6B, which is the on-off valve corresponding to the second indoor unit 2B. By fully opening the second on-off valve 6B during cooling operation, the second indoor heat exchanger 21B communicates with the outdoor unit gas pipe 41, which is the low-pressure side of the refrigerant circuit 10, and refrigerant flows from the second indoor heat exchanger 21B to the outdoor unit gas pipe 41. This prevents refrigerant from accumulating between the second indoor heat exchanger 21B and the second on-off valve 6B (see the shaded area R4 in FIG. 1 ). This reduces the amount of refrigerant charged into the refrigerant circuit 10, thereby reducing the amount of refrigerant charged into the refrigerant circuit 10.

[0066] On the other hand, when the refrigerant circuit 10 is in a heating cycle (during heating operation or hot water supply operation), the valve corresponding to the stopped indoor unit that is located downstream in the refrigerant flow direction is the second expansion valve 5B, which is the expansion valve corresponding to the second indoor unit 2B, during heating operation, and the first expansion valve 5A, which is the expansion valve corresponding to the first indoor unit 2A, during hot water supply operation. Therefore, by opening the second expansion valve 5B during heating operation, the second indoor heat exchanger 21B communicates with the outdoor unit liquid pipe 31, which is the low-pressure side of the refrigerant circuit 10, and the refrigerant flows out from the second indoor heat exchanger 21B to the outdoor unit liquid pipe 31, thereby suppressing refrigerant accumulation between the second indoor heat exchanger 21B and the second expansion valve 5B (see the shaded area R5 in FIG. 1). Furthermore, by opening the first expansion valve 5A during hot water supply operation, the first indoor heat exchanger 21A communicates with the outdoor unit liquid pipe 31, which is the low-pressure side of the refrigerant circuit 10, and the refrigerant flows out from the first indoor heat exchanger 21A to the outdoor unit liquid pipe 31, thereby preventing refrigerant from accumulating between the first indoor heat exchanger 21A and the first expansion valve 5A (see the shaded area R6 in FIG. 1). This makes it possible to reduce the amount of refrigerant filled in the refrigerant circuit 10.

[0067] [Compressor and outdoor fan speeds] However, the inventors have discovered that when the on-off valve and expansion valve on the stopped indoor unit are left open as described above, there is a risk that refrigerant may flow into the indoor heat exchanger of the stopped indoor unit due to temperature changes in the indoor heat exchanger of the stopped indoor unit.

[0068] For example, if the stopped indoor unit is the second indoor unit 2B during the heating cycle, refrigerant of the same pressure accumulates in the flow path from the closed second on-off valve 6B to the branch point C1 of the outdoor unit liquid pipe 31 (the flow path corresponding to region R4, the second indoor heat exchanger 21B, region R5, and region R1 in FIG. 1). If the temperature of the second indoor heat exchanger 21B of the second indoor unit 2B, which is the stopped indoor unit, is lower than the temperature of the outdoor heat exchanger 13, which functions as an evaporator, the gas refrigerant accumulating in the second indoor heat exchanger 21B condenses. The flow path from the second on-off valve 6B to the branch point C1 of the outdoor unit liquid pipe 31 is at approximately the same pressure (although a slight difference occurs due to pressure loss). The temperature of the outdoor heat exchanger 13 (=evaporation temperature) is the same as the temperature of the refrigerant in the outdoor heat exchanger 13 and is also approximately the same as the temperature of the refrigerant in the second indoor heat exchanger 21B. In other words, the fact that the temperature of the second indoor heat exchanger 21B of the second indoor unit 2B, which is the stopped indoor unit, is lower than the temperature of the outdoor heat exchanger 13 means that the ambient temperature of the indoor heat exchanger 21B is lower than the temperature of the refrigerant in the indoor heat exchanger 21B, causing the refrigerant to condense in the indoor heat exchanger 21B. When the gas refrigerant in the second indoor heat exchanger 21B condenses to liquid refrigerant, the volume of the refrigerant decreases, and gas refrigerant flows from regions R4 and R5 into the second indoor heat exchanger 21B into the space equivalent to this decreased volume. Then, some of the gas refrigerant that flows from the first indoor unit 2A, which is the operating indoor unit, and into the heat source unit 1 flows into these empty spaces in regions R4 and R5 via branch point C2, region R1, and the second expansion valve 5B in an open state, further increasing the amount of refrigerant flowing into the second indoor heat exchanger 21B.

[0069] Furthermore, during the cooling cycle, if the stopped indoor unit is the second indoor unit 2B, refrigerant at the same pressure accumulates in the flow path from the closed second expansion valve 5B to branch point C2 of the outdoor unit gas pipe 41 (the flow path corresponding to region R5, the second indoor heat exchanger 21B, region R4, and region R2 in FIG. 1). In this case, if the temperature of the second indoor heat exchanger 21B of the second indoor unit 2B, which is the stopped indoor unit, is lower than the temperature of the first indoor heat exchanger 21A of the first indoor unit 2A, which is the operating indoor unit functioning as an evaporator, the gas refrigerant condenses into liquid refrigerant in the second indoor heat exchanger 21B for the same reason as during heating operation described above. As a result, the gas refrigerant in the second indoor heat exchanger 21B condenses into liquid refrigerant, reducing the refrigerant volume, and liquid refrigerant flows from regions R4 and R5 into the second indoor heat exchanger 21B in the space corresponding to the reduced volume. Furthermore, some of the gas refrigerant flowing out from the first indoor unit 2A, which is the driver's indoor unit, and flowing to the heat source unit 1 flows into the empty spaces in these areas R4 and R5 via branch point C1, area R2, and the second opening / closing valve 6B, which is in an open state, thereby further increasing the amount of refrigerant flowing into the second indoor heat exchanger 21B.

[0070] As explained above, when the refrigerant that has flowed into the heat exchanger of the stopped indoor unit condenses and its volume decreases, gas refrigerant flows into the space in the heat exchanger of the stopped indoor unit that corresponds to the decreased volume. As the refrigerant flows into the indoor heat exchanger of the stopped indoor unit, the amount of refrigerant remaining in the indoor heat exchanger of the stopped indoor unit increases over time, causing a shortage of refrigerant circulating in the refrigerant circuit, preventing the operating indoor unit from achieving its desired performance.

[0071] If the amount of refrigerant remaining in the heat exchanger of the stopped indoor unit increases, the amount of refrigerant circulating through the refrigerant circuit decreases, preventing the desired operating capacity (heating capacity, hot water supply capacity, cooling capacity) from being fully achieved. In recent years, particularly in light of cost reductions and environmental considerations, it has become necessary to minimize the amount of refrigerant charged into the refrigerant circuit. However, as described above, if the temperature of the heat exchanger of the stopped indoor unit is lower than the evaporation temperature of the refrigerant, the refrigerant is likely to remain in the heat exchanger of the stopped indoor unit. Therefore, if the amount of refrigerant to be charged into the refrigerant circuit is determined taking into account the amount of refrigerant remaining in the indoor unit that is stopped to achieve the desired heating or cooling capacity, the amount of refrigerant to be charged cannot be reduced.

[0072] Therefore, in the air conditioning device 100 of this embodiment, when the refrigerant circuit 10 is in the heating cycle, the control unit 90 controls the compressor 11 and the outdoor fan 13F so that the detected temperature of the utilization side heat exchanger temperature sensor of the stopped indoor unit (the second indoor heat exchanger temperature sensor 77B during heating operation, and the first indoor heat exchanger temperature sensor 77A during hot water supply operation) does not become lower than the detected temperature of the heat source side heat exchanger temperature sensor (the outdoor heat exchanger temperature sensor 75).

[0073] The rotation speed of the compressor 11 is typically determined according to the capacity required by the operating indoor units (the first indoor unit 2A during heating operation and the second indoor unit 2B during hot water supply operation). The required capacity refers to the thermal load of the indoor heat exchanger, and corresponds to the difference between the set temperature and the indoor temperature if the indoor heat exchanger is an air-refrigerant heat exchanger (the first indoor heat exchanger 21A), or corresponds to the difference between the set water temperature and the temperature of the water stored in the hot water storage tank 51 if the indoor heat exchanger is a water-refrigerant heat exchanger (the second indoor heat exchanger 21B). The required capacity is included in a control signal sent from each indoor unit 2A, 2B to the control unit 90.

[0074] On the other hand, during heating operation, the rotation speed of the outdoor fan 13F is determined according to the rotation speed (amount of refrigerant circulating) of the compressor 11. During hot water supply operation, the rotation speed of the outdoor fan 13F is determined according to the rotation speed (amount of refrigerant circulating) of the compressor 11 and the outside air temperature.

[0075] As an example, FIG. 4 shows the relationship between the refrigerant displacement (correlated with the refrigerant flow rate per unit time in the outdoor heat exchanger 13) during heating operation and the fan step indicating the rotation speed of the outdoor fan 13F. (A) is a table showing the relationship between the volumetric circulation rate and the fan rotation speed, and (B) is a table showing the relationship between the fan step and the fan rotation speed. Here, the displacement indicates how much refrigerant the compressor 11 can displace (discharge) per unit time and can be calculated by multiplying the displacement volume of the compressor 11 by the rotation speed of the compressor 11. In the table of FIG. 4, if the density of the refrigerant drawn into the compressor 11 is available, the mass flow rate (= displacement × refrigerant density) may be used instead of the displacement. The tables shown in FIGS. 4(A) and (B) are stored in the memory unit 92 of the control unit 90. Here, the volumetric circulation rate corresponds to the thermal load of the indoor heat exchanger of the indoor driver's unit, and the greater the thermal load, the greater the amount of refrigerant required in the indoor driver's unit, so the greater the displacement. Also, the fan step is set to 10 stages, from STEP 1 to STEP 10, with the rotation speed of the outdoor fan 13F increasing in order. STEPs 1 to 10 are assigned as follows according to the displacement of the refrigerant:

[0076] For example, when the displacement increases (when the rotation speed of compressor 11 increases), if the displacement (cc / sec) is greater than the minimum circulation volume and less than 100, STEP 1 is assigned; if it is greater than 100 and less than 150, STEP 2 is assigned; if it is greater than 150 and less than 250, STEP 3 is assigned; if it is greater than 250 and less than 400, STEP 4 is assigned; if it is greater than 400 and less than 500, STEP 5 is assigned; if it is greater than 500 and less than 700, STEP 6 is assigned; if it is greater than 700 and less than 1000, STEP 7 is assigned; if it is greater than 1000 and less than 1400, STEP 8 is assigned; if it is greater than 1400 and less than 2000, STEP 9 is assigned; and if it is greater than 2000 and less than the maximum circulation volume, STEP 10 is assigned.

[0077] On the other hand, when the displacement decreases (when the rotation speed of compressor 11 decreases), if the volumetric circulation rate (cc / sec) is 1800 or more but less than the maximum circulation rate, STEP 10 is assigned; if it is less than 1800 but 1250 or more, STEP 9 is assigned; if it is less than 1250 but 900 or more, STEP 8 is assigned; if it is less than 900 but 600 or more, STEP 7 is assigned; if it is less than 600 but 450 or more, STEP 6 is assigned; if it is less than 450 but 350 or more, STEP 5 is assigned; if it is less than 350 but 200 or more, STEP 4 is assigned; if it is less than 200 but 130 or more, STEP 3 is assigned; if it is less than 130 but 100 or more, STEP 2 is assigned; and if it is less than 100 but greater than the minimum circulation rate, STEP 1 is assigned.

[0078] Here, the boundary of the volumetric circulation amount for switching each fan step can be set arbitrarily depending on the type and specifications of the compressor 11. The boundary of each step is different when the rotation speed of the compressor 11 is increasing and decreasing in order to prevent hunting in control. The set values ​​of each of steps 1 to 10 of the outdoor fan 13F are set depending on the type and specifications of the outdoor fan 13F and the desired heating capacity. In this embodiment, when the refrigerant circuit 10 is in the heating cycle, the rotation speeds of the compressor 11 and the outdoor fan 13F are set so that the detected temperature of the use-side heat exchanger temperature sensor of the stopped indoor unit (second indoor heat exchanger temperature sensor 77B during heating operation, first indoor heat exchanger temperature sensor 77A during hot water supply operation) does not become lower than the detected temperature of the heat source-side heat exchanger temperature sensor (outdoor heat exchanger temperature sensor 75).

[0079] During heating operation, under normal operating conditions, the temperature of the indoor heat exchanger of the stopped indoor unit is maintained higher than the temperature of the outdoor heat exchanger. However, under overload conditions, such as when the outdoor temperature is high, the evaporation temperature of the refrigerant flowing through outdoor heat exchanger 13, which functions as an evaporator, may rise and become higher than the temperature of second indoor heat exchanger 21B of second indoor unit 2B, which is the stopped indoor unit. In this case, as described above, as the refrigerant volume decreases due to condensation in second indoor heat exchanger 21B, some of the refrigerant that flows from first indoor heat exchanger 21A to outdoor heat exchanger 13 flows from branch point C1 of outdoor unit liquid pipe 31 through second expansion valve 5B, which is in the open state, into the space created by the decrease in refrigerant volume in second indoor heat exchanger 21B, and the refrigerant tends to stagnate in second indoor heat exchanger 21B. To prevent such refrigerant accumulation, it is preferable to set the rotation speed of the outdoor fan 13F low so that the evaporation temperature of the refrigerant in the outdoor heat exchanger 13 can be maintained lower than the temperature of the second indoor heat exchanger 21B even under harsh operating conditions with high outdoor air temperatures, as long as the capacity required by the operating indoor unit can be realized. In this embodiment, the rotation speeds of steps 1 to 10 of the outdoor fan 13F are set as shown in FIG. 4(B) based on the case where the outdoor air temperature is 24°C. Note that the volumetric circulation amount in FIG. 4(A) is a value when the compressor 11 is operating at a rotation speed that allows stable driving of the compressor 11 and does not result in a pressure so low that the refrigerant accumulates in the stopped indoor unit.

[0080] FIG. 5(A) shows the relationship between the rotation speed F (rps) of the compressor 11, the outdoor air temperature Ta, and the rotation speed (rpm) of the outdoor fan 13F during hot water supply operation, and FIG. 5(B) shows the relationship between the fan STEP and the fan rotation speed. The tables shown in FIGS. 5(A) and (B) are stored in the memory unit 92 of the control unit 90. In FIG. 5(A), the rotation speed F (rps) of the compressor 11 is shown in the row direction, and the outdoor air temperature Ta (°C) is shown in the column direction. Here, the rotation speed of the outdoor fan 13F is set in seven steps, from STEP 1 to STEP 7, with the rotation speed of the outdoor fan 13F increasing in order. STEPs 1 to 7 are assigned as follows according to the rotation speed of the compressor 11 and the outdoor air temperature:

[0081] For example, when the rotation speed of the compressor 11 increases, the rotation speed F is divided into five categories: 16 rps or more but less than 30 rps, 30 rps or more but less than 42 rps, 42 rps or more but less than 47 rps, 47 rps or more but less than 70 rps, and 70 rps or more but less than the maximum rotation speed.When the rotation speed decreases, the rotation speed F is divided into five categories: 43 rps or more but less than 65 rps, 35 rps or more but less than 43 rps, 26 rps or more but less than 35 rps, 16 rps or more but less than 26 rps, and 16 rps or more but less than the minimum rotation speed.For each of the above categories of rotation speed F, the outside air temperature Ta is divided into seven categories: less than 5°C, 5°C or more but less than 12°C, 12°C or more but less than 16°C, 16°C or more but less than 20°C, 20°C or more but less than 24°C, 24°C or more but less than 30°C, and 30°C or more. The rotation speeds STEP1 to STEP7 of the outdoor fan 13F are assigned according to the rotation speed F and the outdoor air temperature Ta.

[0082] The rotation speed of the outdoor fan 13F is set to a lower value as the rotation speed F of the compressor 11 is lower and as the outdoor air temperature is higher. Furthermore, the rotation speed of the outdoor fan 13F is set to a lower value during hot water supply operation than during heating operation, even for the same STEP. This is because hot water supply operation may be performed even in summer, in which case the outdoor air temperature is higher than the outdoor air temperature during heating operation, and therefore the evaporation temperature of the refrigerant flowing through the outdoor heat exchanger 13, which functions as an evaporator, is more likely to rise than during heating operation. For this reason, the rotation speed of the outdoor fan 13F at each STEP is set lower during hot water supply operation than during heating operation, so that the evaporation temperature is maintained at a target temperature.

[0083] Furthermore, during hot water supply operation, if the evaporation temperature of the refrigerant becomes higher than the temperature of the first indoor heat exchanger 21A, which is the heat exchanger of the stopped indoor unit, some of the refrigerant flowing from the second indoor heat exchanger 21B to the outdoor heat exchanger 13 side flows into the first indoor heat exchanger 21A through the first expansion valve 5A, which is in the open state, and the refrigerant is likely to stagnate in the first indoor heat exchanger 21A. To prevent such refrigerant stagnation, it is preferable to set the rotation speed of the outdoor fan 13F low so that the evaporation temperature of the refrigerant in the outdoor heat exchanger 13 can be kept lower than the temperature of the first indoor heat exchanger 21A even under operating conditions with high outdoor air temperatures, as long as the required capacity from the operating indoor unit can be realized. In this embodiment, the rotation speeds of steps 1 to 7 of the outdoor fan 13F are set as shown in FIG. 5(B) based on the case where the outdoor air temperature is 37°C.

[0084] [Measures to prevent refrigerant accumulation] Even if the rotation speeds of the compressor 11 and the outdoor fan 13F are set to the conditions shown in Figures 4 and 5 during heating or hot water supply operation as described above, the evaporation temperature of the refrigerant may not be lowered below the temperature of the heat exchanger of the stopped indoor unit when the outdoor air temperature is excessively high. Furthermore, during cooling operation, increasing the rotation speed of the compressor 11 to lower the evaporation temperature may result in excessive cooling capacity in the operating indoor unit, reducing user comfort. Therefore, even during cooling operation, the temperature of the heat exchanger of the operating indoor unit, which functions as an evaporator, may not be lowered below the temperature of the heat exchanger of the stopped indoor unit. Therefore, the control unit 90 may be configured to determine whether refrigerant is stagnating in the heat exchanger of the stopped indoor unit and, if it is determined that refrigerant is stagnating, to execute stagnation elimination control to eliminate the stagnation of the refrigerant. Details of this control are described below.

[0085] (Refrigerant accumulation determination) When determining whether refrigerant is stagnating, the control unit 90 uses either the detected temperature of the outdoor heat exchanger temperature sensor or the detected temperature of the indoor heat exchanger temperature sensor of the operating indoor unit, and the detected temperature of the indoor heat exchanger temperature sensor of the stopped indoor unit to determine whether refrigerant is stagnating in the heat exchanger of the stopped indoor unit.

[0086] For example, when the refrigerant circuit 10 is in a heating cycle, the control unit 90 determines whether refrigerant is stagnating in the heat exchanger of the stopped indoor unit using the detected temperature of the outdoor heat exchanger temperature sensor 75, which functions as an evaporator, and the detected temperature of the indoor heat exchanger temperature sensor of the stopped indoor unit.

[0087] More specifically, during heating operation, the control unit 90 determines whether refrigerant is accumulating in the second indoor heat exchanger 21B, which is the stopped side, using the detected temperature of the outdoor heat exchanger temperature sensor 75 and the detected temperature of the second indoor heat exchanger temperature sensor 77B. When the detected temperature of the outdoor heat exchanger temperature sensor 75 is higher than the detected temperature of the second indoor heat exchanger temperature sensor 77B, the control unit 90 determines that refrigerant is accumulating in the second indoor heat exchanger 21B.

[0088] During hot water supply operation, the control unit 90 determines whether refrigerant is accumulating in the stopped first indoor heat exchanger 21A, using the detected temperature of the outdoor heat exchanger temperature sensor 75 and the detected temperature of the first indoor heat exchanger temperature sensor 77A. When the detected temperature of the outdoor heat exchanger temperature sensor 75 is higher than the detected temperature of the first indoor heat exchanger temperature sensor 77A, the control unit 90 determines that refrigerant is accumulating in the first indoor heat exchanger 21A.

[0089] On the other hand, when the refrigerant circuit 10 is in the cooling cycle, the control unit 90 determines whether refrigerant is accumulating in the heat exchanger of the stopped indoor unit using the temperature detected by the indoor heat exchanger temperature sensor of the operating indoor unit functioning as an evaporator and the temperature detected by the indoor heat exchanger temperature sensor of the stopped indoor unit. More specifically, during cooling operation, the control unit 90 determines whether refrigerant is accumulating in the stopped second indoor heat exchanger 21B using the temperature detected by the first indoor heat exchanger temperature sensor 77A and the temperature detected by the second indoor heat exchanger temperature sensor 77B. The control unit 90 determines that refrigerant is accumulating in the second indoor heat exchanger 21B when the temperature detected by the first indoor heat exchanger temperature sensor 77A is higher than the temperature detected by the second indoor heat exchanger temperature sensor 77B.

[0090] As described above, when the temperature (evaporation temperature) of the first indoor heat exchanger 21A functioning as an evaporator is higher than the temperature of the second indoor heat exchanger 21B, which is the heat exchanger of the stopped indoor unit, the gas refrigerant condenses in the second indoor heat exchanger 21B, reducing its volume, and some of the gas refrigerant flowing from the operating indoor unit 2A to the heat source unit 1 flows into the second indoor heat exchanger 21B from branch point C2 of the outdoor unit gas pipe 41 via the second on-off valve 6B in the open state into the space in the second indoor heat exchanger 21B corresponding to the reduced volume, making it easier for the refrigerant to stagnate in the second indoor heat exchanger 21B. In this embodiment, whether the refrigerant circuit 10 is in the heating cycle or the cooling cycle, the detected temperature of the heat exchanger temperature sensor that detects a temperature corresponding to the evaporation temperature of the refrigerant is compared with the detected temperature of the heat exchanger temperature sensor of the stopped indoor unit, making it possible to properly determine whether refrigerant is stagnating in the heat exchanger of the stopped indoor unit.

[0091] (Removal of congestion control) Next, the stagnation elimination control for causing refrigerant to flow out of the heat exchanger of the stopped indoor unit in which it has been determined that refrigerant is stagnating will be described.

[0092] ((Control Example 1)) When the refrigerant circuit 10 is in a heating cycle (during heating operation or hot water supply operation), if the control unit 90 determines that refrigerant is stagnating in the indoor heat exchanger of the stopped indoor unit, it performs stagnation elimination control by adjusting the compressor 11 and the outdoor fan 13F to their respective preset control rotation speeds, thereby lowering the detected temperature of the outdoor heat exchanger temperature sensor 13 below the detected temperature of the indoor heat exchanger temperature sensor of the stopped indoor unit.

[0093] FIG. 6 shows an example of a control rotation speed table for the outdoor fan 13F during heating operation. The control rotation speed table for the outdoor fan 13F shown in FIG. 6 is stored in the memory unit 92 of the control unit 90, and when stagnation elimination control is executed, it is applied as the rotation speed for each of steps 1 to 10 shown in FIG. 4(A) instead of the normal rotation speed table for the outdoor fan 13F shown in FIG. 4(B). In other words, FIG. 4(A) is a table that determines the fan step for the outdoor fan 13F during heating operation according to the volumetric circulation amount of refrigerant, and FIG. 4(B) is a table that determines the rotation speed for each fan step in FIG. 4(A) and is used when refrigerant stagnation occurs in the heat exchanger of a stopped indoor unit. And FIG. 6 is a table that determines the rotation speed for each fan step in FIG. 4(A) and is used when refrigerant stagnation occurs in the heat exchanger of a stopped indoor unit.

[0094] The control rotation speed of the outdoor fan 13F is set to a value lower than the normal rotation speed in all steps. Note that the control rotation speed of the outdoor fan 13F shown in Fig. 6 is merely an example, and can be set arbitrarily depending on the specifications of the air conditioning apparatus 100, etc.

[0095] In this way, by adjusting the rotation speed of the outdoor fan 13F to a lower rotation speed than normal during retention elimination control, the increase in the evaporation temperature of the refrigerant flowing through the outdoor heat exchanger 13, which functions as an evaporator, is further suppressed. This promotes a decrease in the temperature of the outdoor heat exchanger 13, making it possible to make the temperature detected by the outdoor heat exchanger temperature sensor 75 lower than the temperature detected by the second indoor heat exchanger temperature sensor 77B on the stopped indoor unit side.

[0096] By setting the temperature of the outdoor heat exchanger 13 lower than the temperature of the second indoor heat exchanger 21B, it is possible to eliminate refrigerant stagnation in the second indoor heat exchanger 21B. Furthermore, since the amount of refrigerant circulating through the refrigerant circuit 10 increases when refrigerant stagnation is eliminated, the amount of refrigerant flowing into the outdoor heat exchanger 13, which functions as an evaporator, also increases, resulting in a predetermined heating capacity being achieved.

[0097] Similarly, during hot water supply operation, the outdoor fan 13F is adjusted to a lower rotation speed than normal during retention elimination control. Figures 7(A) and 7(B) show the relationship between the rotation speed F (rps) of the compressor 11, the outdoor air temperature Ta, and the rotation speed (rpm) of the outdoor fan 13F used during retention elimination control performed during hot water supply operation. The control rotation speed table for the outdoor fan 13F shown in these figures is stored in the memory unit 92 of the control unit 90 and is applied during retention elimination control in place of the normal rotation speed table shown in Figures 5(A) and 5(B). In other words, Figure 5(A) is a table that determines the fan step of the outdoor fan 13F during hot water supply operation depending on the rotation speed of the compressor 11 and the outdoor air temperature, and Figure 5(B) is a table that determines the rotation speed of each fan step in Figure 5(A). Each table is used when no refrigerant is stagnating in the heat exchanger of the stopped indoor unit. On the other hand, Figure 7(A) is a table that determines the fan step of the outdoor fan 13F during hot water supply operation depending on the rotation speed of the compressor 11 and the outdoor air temperature, and Figure 7(B) is a table that determines the rotation speed of each fan step in Figure 7(A), but each table is used when refrigerant stagnation occurs in the heat exchanger of a stopped indoor unit.

[0098] As shown in Fig. 7(A), the control rotation speed of the outdoor fan 13F, which is determined by the rotation speed F of the compressor 11 and the outdoor air temperature Ta, is set to a rotation speed for a step number that is one step lower than the rotation speed of the outdoor fan 13F shown in Fig. 5(A) for all ranges of compressor rotation speed and outdoor air temperature. Furthermore, the control rotation speed for each step number of the outdoor fan 13F is set to a lower value for the control rotation speed during hot water supply operation, even for the same step, compared to the control rotation speed of the outdoor fan 13F under retention elimination control in heating operation shown in Fig. 6. Because a higher condensing temperature may be required during hot water supply operation than during heating operation, the high pressure tends to increase and the discharge temperature also increases during hot water supply operation. If the rotation speed of the outdoor fan 13F is too high, the evaporation capacity will be high and the discharge temperature will also be high. Therefore, in this embodiment, the rotation speed of the outdoor fan 13F during hot water supply operation is set to a lower value than the rotation speed of the outdoor fan 13F during heating operation. In this way, by differentiating the control rotation speed of the outdoor fan 13F (or the relationship between the compressor rotation speed and the outdoor fan rotation speed) when the stopped indoor unit is the first indoor unit 2A and when it is the second indoor unit 2B, it is possible to adjust the rotation speed of the outdoor fan 13F to a rotation speed optimized for the individual operating conditions of heating operation and hot water supply operation. Note that the control rotation speed of the outdoor fan 13F shown in Figure 7 is merely an example, and can be set arbitrarily depending on the specifications of the air conditioning apparatus 100, etc.

[0099] In this way, by adjusting the rotation speed of the outdoor fan 13F during the retention elimination control to a rotation speed lower than the rotation speed before the retention elimination control was executed, the increase in the evaporation temperature of the refrigerant flowing through the outdoor heat exchanger 13, which functions as an evaporator, is further suppressed. This promotes a decrease in the temperature of the outdoor heat exchanger 13, making it possible to make the temperature detected by the outdoor heat exchanger temperature sensor 75 lower than the temperature detected by the first indoor heat exchanger temperature sensor 77A on the stopped indoor unit side.

[0100] By setting the temperature of the outdoor heat exchanger 13 lower than the temperature of the first indoor heat exchanger 21A, it is possible to eliminate refrigerant stagnation in the first indoor heat exchanger 21A. Furthermore, since the amount of refrigerant circulating through the refrigerant circuit 10 increases when refrigerant stagnation is eliminated, the amount of refrigerant flowing into the outdoor heat exchanger 13, which functions as an evaporator, also increases, resulting in a predetermined hot water supply capacity being achieved.

[0101] ((Control Example 2)) As described above, simply adjusting the relationship between the compressor rotation speed and the outdoor fan rotation speed during retention elimination control may not be enough to lower the temperature of the outdoor heat exchanger 13 below the temperature of the heat exchanger on the stopped indoor unit under conditions where low pressure is likely to increase (for example, when the refrigerant charge amount is greater than a specified value or when the length of the refrigerant piping 32A, 32B, 42A, 42B is extremely short). Alternatively, it may take a long time to lower the temperature of the outdoor heat exchanger 13 below the temperature of the heat exchanger on the stopped indoor unit. Similarly, when the indoor heat exchanger 13 is exposed to direct sunlight, the amount of heat the refrigerant receives increases compared to when it is not exposed to direct sunlight, and the evaporating temperature may increase (low pressure may increase). In particular, because the control rotation speed of the outdoor fan 13F described above is lower than the normal rotation speed, driving the outdoor fan 13F at this control rotation speed for a long period of time may not be able to fulfill the capacity required by the operating indoor unit, resulting in a risk of a decrease in heating capacity or hot water supply capacity.

[0102] In this case, the heating unit of the stopped indoor unit (second heating unit 22B during heating operation, first heating unit 22A during hot water supply operation) may be activated to heat the heat exchanger of the stopped indoor unit to a predetermined temperature. This allows the temperature of the outdoor heat exchanger 13 to be lower than the temperature of the heat exchanger of the stopped indoor unit even when the temperature of the outdoor heat exchanger 13 cannot be lowered below that of the heat exchanger of the stopped indoor unit by simply adjusting the relationship between the compressor rotation speed and the outdoor fan rotation speed during heating operation and hot water supply operation, or when the temperature of the heat exchanger of the operating indoor unit cannot be lowered below that of the heat exchanger of the stopped indoor unit during cooling operation. This allows refrigerant stagnating in the heat exchanger of the stopped indoor unit to quickly flow to the outdoor heat exchanger 13 side. The predetermined temperature is not particularly limited as long as it is higher than the temperature detected by the outdoor heat exchanger temperature sensor 75 (the evaporation temperature of the refrigerant), and is, for example, the temperature detected by the outdoor heat exchanger temperature sensor 75 + 4°C (a margin).

[0103] The second heating section 22B arranged in the second indoor unit 2B is not limited to heating the second indoor heat exchanger 21B, and may also be configured to heat water stored in the hot water storage tank 51. Because the water stored in the hot water storage tank 51 circulates through the second indoor heat exchanger 21B, the second indoor heat exchanger 21B can be indirectly heated via the water heated by the second heating section 22B. The second heating section 22B can be used as an auxiliary heater when the heat pump (refrigerant circuit 10) alone is insufficient to achieve the target hot water temperature.

[0104] This control example is also applicable when the refrigerant circuit 10 is in the cooling cycle. That is, when the refrigerant circuit 10 is in the cooling cycle, if the control unit 90 determines that refrigerant is stagnating in the second indoor heat exchanger 21B on the stopped indoor unit side, the control unit 90 may perform stagnation elimination control by heating the water stored in the second indoor heat exchanger 21B or the hot water storage tank 51 by the second heating unit 22B to a temperature higher than the temperature detected by the first indoor heat exchanger temperature sensor 77A on the operating indoor unit side.

[0105] The temperature of the first indoor heat exchanger 21A becomes lower than the temperature of the second indoor heat exchanger 21B, thereby eliminating refrigerant stagnation in the second indoor heat exchanger 21B. Furthermore, since the amount of refrigerant circulating through the refrigerant circuit 10 increases when the temperature of the first indoor heat exchanger 21A becomes lower than the temperature of the second indoor heat exchanger 21B, the amount of refrigerant flowing into the first indoor heat exchanger 21A, which functions as an evaporator, also increases, resulting in a predetermined cooling capacity being achieved.

[0106] [Processing procedure by the control unit] 8 is a flowchart showing an example of the processing procedure for retention elimination control executed by the control unit 90. In the following explanation, the detected temperature of the outdoor heat exchanger temperature sensor 75 is defined as T0, the detected temperature of the first indoor heat exchanger temperature sensor 77A is defined as TA, the detected temperature of the second indoor heat exchanger temperature sensor 77B is defined as TB, and the temperature of the indoor heat exchanger on the stopped indoor unit side during the heating cycle (the second indoor heat exchanger 21B during heating operation and the first indoor heat exchanger 21A during hot water supply operation) is defined as T1.

[0107] When the air conditioner 100 starts operating, if the refrigerant circuit 10 is in the heating cycle (Yes in ST101), the control unit 90 acquires the temperature T0 of the outdoor heat exchanger 13, which functions as an evaporator, and the temperature T1 of the indoor heat exchanger on the stopped indoor unit side. During heating operation, T1 corresponds to TB, and during hot water supply operation, T1 corresponds to TA. The control unit 90 then determines whether a predetermined time has elapsed since the start of heating operation (ST102), and if the predetermined time has elapsed, determines whether the temperature T0 of the outdoor heat exchanger 13 is lower than the temperature T1 of the indoor heat exchanger of the stopped indoor unit (ST103). The predetermined time is not particularly limited as long as it is the time required for the heating cycle to stabilize, and is, for example, 30 minutes.

[0108] When the temperature T0 of the outdoor heat exchanger 13 is lower than the temperature T1 of the indoor heat exchanger of the stopped indoor unit (Yes in ST103), the control unit 90 determines that no refrigerant is stagnating in the indoor heat exchanger, and returns the processing to ST101 without performing stagnation elimination control.

[0109] On the other hand, when the temperature T0 of the outdoor heat exchanger 13 is equal to or higher than the temperature T1 of the indoor heat exchanger of the stopped indoor unit (No in ST103), the control unit 90 determines that refrigerant is stagnating in the indoor heat exchanger, and changes the rotation speed table of the compressor 11 and the outdoor fan 13F from the rotation speed table shown in Fig. 4 to the control rotation speed table shown in Fig. 6 during heating operation, and changes the rotation speed table of the compressor 11 and the outdoor fan 13F from the rotation speed table shown in Fig. 5 to the control rotation speed table shown in Fig. 7 during hot water supply operation (ST104). As a result, the rotation speed of the outdoor fan 13F is adjusted to be lower than the rotation speed before the change, and the evaporation temperature of the refrigerant flowing through the outdoor heat exchanger 13 decreases.

[0110] Next, when a predetermined time has elapsed since the change to the control rotation speed table (Yes in ST105), the control unit 90 again determines whether the temperature T0 of the outdoor heat exchanger 13 is lower than the temperature T1 of the indoor heat exchanger of the stopped indoor unit (ST106). The predetermined time can be set to any time long enough for the change to the rotation speed table to take effect, for example, 60 minutes.

[0111] When the temperature T0 of the outdoor heat exchanger 13 is lower than the temperature T1 of the indoor heat exchanger of the stopped indoor unit (Yes in ST106), the control unit 90 determines that the refrigerant accumulation in that indoor heat exchanger has been eliminated, and changes the rotation speed table of the compressor 11 and the outdoor fan 13F from the control rotation speed table shown in Fig. 6 to the rotation speed table shown in Fig. 4 during heating operation, and from the control rotation speed table shown in Fig. 7 to the rotation speed table shown in Fig. 5 during hot water supply operation (ST107). This makes it possible to prevent refrigerant accumulation in the indoor heat exchanger of the stopped indoor unit, while also preventing a decrease in heating capacity or hot water supply capacity that occurs over a long period of use of the control rotation speed table.

[0112] On the other hand, if the temperature T0 of the outdoor heat exchanger 13 is still equal to or higher than the temperature T1 of the indoor heat exchanger of the stopped indoor unit (No in ST106), the control unit 90 heats the indoor heat exchanger of the stopped indoor unit to the predetermined temperature for a certain period of time using the heating unit on the stopped indoor unit (the second heating unit 22B during heating operation, and the first heating unit 22A during hot water supply operation) (ST108). The certain period of time is not particularly limited and may be, for example, 10 minutes. Thereafter, the control unit 90 repeats the processing of ST106 and ST108 until the temperature T0 of the outdoor heat exchanger 13 becomes lower than the temperature T1 of the indoor heat exchanger of the stopped indoor unit. Thereafter, the control unit 90 changes the rotation speed table of the compressor 11 and the outdoor fan 13F to the rotation speed table shown in FIG. 4 during heating operation and to the rotation speed table shown in FIG. 5 during hot water supply operation, and then repeats the processing of ST101 to ST108 until the heating cycle operation ends (ST109).

[0113] Next, when the refrigerant circuit 10 is in the cooling cycle (No in ST101), the control unit 90 acquires the temperature TA of the first indoor heat exchanger 21A, which functions as an evaporator, and the temperature TB of the second indoor heat exchanger 21B, which is on the stopped indoor unit side. The control unit 90 then determines whether a predetermined time has elapsed since the start of the cooling operation (ST110), and if the predetermined time has elapsed, determines whether the temperature TA of the first indoor heat exchanger 21A is lower than the temperature TB of the second indoor heat exchanger 21B (ST111). The predetermined time is not particularly limited as long as it is the time required for the cooling cycle to stabilize, and is, for example, 30 minutes.

[0114] When the temperature TA of the first indoor heat exchanger 21A is lower than the temperature TB of the second indoor heat exchanger 21B (Yes in ST111), the control unit 90 determines that no refrigerant is stagnating in the second indoor heat exchanger 21B, and returns the processing to ST101 without performing stagnation elimination control.

[0115] On the other hand, when the temperature TA of the first indoor heat exchanger 21A is equal to or higher than the temperature TB of the second indoor heat exchanger 21B (No in ST111), the control unit 90 determines that refrigerant is stagnating in the second indoor heat exchanger 21B, and causes the second heating unit 22B on the second indoor unit 2B side to heat the second indoor heat exchanger 21B to the above-mentioned predetermined temperature for a certain period of time (ST112). The above-mentioned certain period of time is not particularly limited, and is, for example, 10 minutes. Thereafter, the control unit 90 again determines whether the temperature TA of the first indoor heat exchanger 21A is lower than the temperature TB of the second indoor heat exchanger 21B (ST113).

[0116] When the temperature TA of the first indoor heat exchanger 21A is lower than the temperature TB of the second indoor heat exchanger 21B (Yes in ST113), the control unit 90 assumes that the refrigerant stagnation in the second indoor heat exchanger 21B has been eliminated, and continues the cooling operation. On the other hand, when the temperature TA of the first indoor heat exchanger 21A is still equal to or higher than the temperature TB of the second indoor heat exchanger 21B (No in ST113), the control unit 90 causes the second heating unit 22B to reheat the second outdoor heat exchanger 21B to a predetermined temperature for a certain period of time (ST112). The control unit 90 repeats the processes of ST112 and ST113 described above until the temperature TA of the first indoor heat exchanger 21A becomes lower than the temperature TB of the second indoor heat exchanger 21B. The control unit 90 then repeats the processes of ST111 to ST113 described above until the operation of the cooling cycle is completed (ST109).

[0117] [Variations] In the above embodiment, the first expansion valve 5A and the second expansion valve 5B are both arranged inside the heat source unit 1 (first outdoor unit liquid pipe 31A and second outdoor unit liquid pipe 31B), but this is not limited thereto and they may also be arranged in the first liquid refrigerant pipe 32A and the second liquid refrigerant pipe 32B, respectively. Similarly, the first on-off valve 6A and the second on-off valve 6B may also be arranged in the first gas refrigerant pipe 42A and the second gas refrigerant pipe 42B, respectively. [Explanation of symbols]

[0118] 1...Heat source unit 2A: First indoor unit (user unit) 2B: Second indoor unit (user unit) 3A…1st liquid pipe 3B…Second liquid pipe 4A...First gas pipe 4B...Second gas pipe 5A...First expansion valve 5B...Second expansion valve 6A...First shut-off valve 6B...Second on-off valve 10...Refrigerant circuit 11...Compressor 12...Four-way valve (flow path switching valve) 13...Outdoor heat exchanger (heat source side heat exchanger) 13F...Outdoor fan 21A…1st indoor heat exchanger (user side heat exchanger) 21B…Second indoor heat exchanger (user side heat exchanger) 22A…1st heating section 22B…Second heating section 41A...1st outdoor unit gas branch pipe 41B...Second outdoor unit gas branch pipe 75...Outdoor heat exchanger temperature sensor (heat source side heat exchanger temperature sensor) 77A...First indoor heat exchanger temperature sensor (use side heat exchanger temperature sensor) 77B...Second indoor heat exchanger temperature sensor (use side heat exchanger temperature sensor) 90...Control unit 100...Air conditioning equipment

Claims

1. a heat source unit having a compressor, a heat source side heat exchanger, and an outdoor heat exchanger temperature sensor that detects the temperature of the heat source side heat exchanger; a user side unit having a user side heat exchanger and an indoor heat exchanger temperature sensor that detects the temperature of the user side heat exchanger; a connecting pipe including a liquid pipe and a gas pipe that connects the heat source unit and the user side unit; and a refrigerant circuit having a valve that controls the amount of refrigerant flowing through the connecting pipe; a control unit that controls the compressor and the valve; Equipped with The user side unit includes at least two indoor units, When the indoor unit to be operated is designated as an operating indoor unit and the indoor unit to be stopped is designated as a stopped indoor unit, the control unit determines whether or not refrigerant is stagnating in the stopped indoor unit using either the detected temperature of the outdoor heat exchanger temperature sensor or the detected temperature of the indoor heat exchanger temperature sensor of the operating indoor unit, and the detected temperature of the indoor heat exchanger temperature sensor of the stopped indoor unit. Air conditioning equipment.

2. The air conditioning apparatus according to claim 1, the connecting pipes include liquid pipes and gas pipes corresponding to the indoor operation unit and the indoor stop unit, respectively; the valve includes an expansion valve disposed in the liquid pipe and an on-off valve disposed in the gas pipe, The control unit When the refrigerant circuit is in a heating cycle, the on-off valve corresponding to the stopped indoor unit is closed and the expansion valve corresponding to the stopped indoor unit is opened, and whether or not refrigerant is stagnating in the utilization side heat exchanger of the stopped indoor unit is determined using the detected temperature of the outdoor heat exchanger temperature sensor and the detected temperature of the indoor heat exchanger temperature sensor of the stopped indoor unit; When the refrigerant circuit is in a cooling cycle, the expansion valve corresponding to the stopped indoor unit is closed and the on-off valve corresponding to the stopped indoor unit is opened, and the temperature detected by the indoor heat exchanger temperature sensor of the operating indoor unit and the temperature detected by the indoor heat exchanger temperature sensor of the stopped indoor unit are used to determine whether refrigerant is stagnating in the user-side heat exchanger of the stopped indoor unit. Air conditioning equipment.

3. The air conditioning apparatus according to claim 2, When the refrigerant circuit is in a heating cycle, if the detected temperature of the outdoor heat exchanger temperature sensor is higher than the detected temperature of the indoor heat exchanger temperature sensor of the stopped indoor unit, the control unit determines that refrigerant is stagnating in the user-side heat exchanger of the stopped indoor unit. Air conditioning equipment.

4. The air conditioning apparatus according to claim 2, When the refrigerant circuit is in a cooling cycle, if the detected temperature of the indoor heat exchanger temperature sensor of the operating indoor unit is higher than the detected temperature of the indoor heat exchanger temperature sensor of the stopped indoor unit, the control unit determines that refrigerant is stagnating in the user-side heat exchanger of the stopped indoor unit. Air conditioning equipment.

5. The air conditioning apparatus according to claim 3 or 4, When it is determined that refrigerant is stagnating in the use-side heat exchanger of the stopped indoor unit, the control unit executes stagnation elimination control, which is control for causing the refrigerant stagnating in the use-side heat exchanger of the stopped indoor unit to flow out. Air conditioning equipment.

6. The air conditioning apparatus according to claim 5, The heat source unit further includes an outdoor fan, When the control unit determines that refrigerant is stagnating in the use-side heat exchanger of the stopped indoor unit when the refrigerant circuit is in a heating cycle, the control unit adjusts the compressor and the outdoor fan to respective preset rotation speeds to lower the detected temperature of the outdoor heat exchanger temperature sensor below the detected temperature of the indoor heat exchanger temperature sensor of the stopped indoor unit as the stagnation elimination control. Air conditioning equipment.

7. The air conditioning apparatus according to claim 6, The stopped indoor unit further includes a heating unit that heats the user-side heat exchanger of the stopped indoor unit, When the temperature detected by the outdoor heat exchanger temperature sensor does not become lower than the temperature detected by the indoor heat exchanger temperature sensor of the stopped indoor unit despite the compressor and the outdoor fan being adjusted to their respective preset rotational speeds, the control unit heats the utilization side heat exchanger of the stopped indoor unit to a temperature higher than the temperature detected by the outdoor heat exchanger temperature sensor by the heating unit. Air conditioning equipment.

8. The air conditioning apparatus according to claim 6, The stopped indoor unit further includes a heating unit that heats the user-side heat exchanger of the stopped indoor unit, When the control unit determines that refrigerant is stagnating in the use-side heat exchanger of the stopped indoor unit when the refrigerant circuit is in a cooling cycle, the control unit performs the stagnation elimination control by heating the use-side heat exchanger of the stopped indoor unit to a temperature higher than the detected temperature of the outdoor heat exchanger temperature sensor. Air conditioning equipment.

9. The air conditioning apparatus according to claim 6, The plurality of indoor units include a first indoor unit having an air-refrigerant heat exchanger that exchanges heat between a refrigerant and air as the use-side heat exchanger, and a second indoor unit having a water-refrigerant heat exchanger that exchanges heat between a refrigerant and water as the use-side heat exchanger, The preset rotation speeds of the compressor and the outdoor heat exchanger differ depending on whether the stopped indoor unit is the first indoor unit or the second indoor unit. Air conditioning equipment.

10. The air conditioning apparatus according to claim 8, The stopped indoor unit has a water-refrigerant heat exchanger that exchanges heat between a refrigerant and water as the use-side heat exchanger, and a tank that stores the water heated by the water-refrigerant heat exchanger, The heating unit heats the water stored in the tank. Air conditioning equipment.

11. The air conditioning apparatus according to claim 1, The liquid pipes include outdoor unit liquid pipes that are provided in the heat source unit and correspond to each of the indoor units, The gas pipe includes an outdoor gas pipe that is provided in the heat source unit and corresponds to each of the indoor units, The expansion valve is disposed in the outdoor unit liquid pipe, The on-off valve is disposed in the outdoor unit gas pipe. Air conditioning equipment.

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