Air conditioning device
Patent Information
- Application Number
- JP2025514985
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Filing Date
- 2025-05-19
- Publication Date
- 2025-07-30
Abstract
Description
air conditioning equipment
[0001] The present disclosure relates to an air conditioning apparatus.
[0002] Conventionally, air conditioners are known that perform a pump-down operation to recover refrigerant remaining in the indoor unit or piping to the outdoor unit when the unit is shut down (see, for example, Patent Document 1). Patent Document 1 discloses a method for performing a pump-down operation, in which the upstream shut-off valve of the indoor unit is closed and then the downstream shut-off valve is closed after a delay, thereby reducing the amount of refrigerant remaining in the indoor unit.
[0003] Japanese Patent Application Laid-Open No. 2020-134059
[0004] However, if the temperature in the room where the indoor unit is installed is low, liquid refrigerant may accumulate in the indoor unit, causing so-called stagnation. In this case, a large amount of refrigerant accumulates in the indoor unit, requiring a long time for pump-down operation.
[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to reduce the time required for pump-down operation in an air conditioning apparatus.
[0006] The air conditioning apparatus of the present disclosure comprises an outdoor unit having a compressor, an outdoor heat exchanger, and an outdoor heat exchanger temperature sensor that measures the outdoor heat exchanger temperature, which is the temperature of the outdoor heat exchanger; an indoor unit having an indoor heat exchanger and an indoor heat exchanger temperature sensor that measures the indoor heat exchanger temperature, which is the temperature of the indoor heat exchanger; a first on-off valve that has the function of switching between an open state that allows refrigerant to flow between the compressor and the indoor heat exchanger and a closed state that blocks refrigerant from flowing between the compressor and the indoor heat exchanger; a second on-off valve that has the function of switching between an open state that allows refrigerant to flow between the outdoor heat exchanger and the indoor heat exchanger and a closed state that blocks refrigerant from flowing between the outdoor heat exchanger and the indoor heat exchanger; and a control device that controls the on-off states of the first on-off valve and the second on-off valve based on the comparison result between the outdoor heat exchanger temperature and the indoor heat exchanger temperature.
[0007] In the air conditioner according to the present disclosure, after the compressor operation is stopped, the open / close states of the first and second on-off valves are controlled based on the comparison result between the outdoor heat exchanger temperature and the indoor heat exchanger temperature. This prevents refrigerant from accumulating in the indoor unit, which has a lower temperature than the outdoor unit. Therefore, the air conditioner can shorten the time required for pump-down operation.
[0008] Fig. 1 is a circuit diagram showing an air conditioning apparatus according to embodiment 1. Fig. 2 is a hardware configuration diagram showing a control device according to embodiment 1. Fig. 3 is a hardware configuration diagram showing a control device according to embodiment 1. Fig. 4 is a block diagram showing a control device according to embodiment 1. Fig. 5 is a flowchart showing the operation of the control device according to embodiment 1. Fig. 6 is a circuit diagram showing an air conditioning apparatus according to embodiment 2. Fig. 7 is a flowchart showing the operation of the control device according to embodiment 2.
[0009] Embodiment 1 An air conditioning apparatus 1 according to embodiment 1 will now be described with reference to the drawings. Fig. 1 is a circuit diagram showing the air conditioning apparatus 1 according to embodiment 1. As shown in Fig. 1, the air conditioning apparatus 1 has an outdoor unit 10 and an indoor unit 20. The air conditioning apparatus 1 according to embodiment 1 is capable of operating in cooling and heating modes.
[0010] The outdoor unit 10 is a device that supplies hot or cold heat to the indoor unit 20. The outdoor unit 10 has a compressor 101, a flow path switching device 102, and an outdoor heat exchanger 103. The indoor unit 20 is a device that conditions the air-conditioned space in which the indoor unit 20 is installed. The indoor unit 20 has an indoor heat exchanger 201 and an expansion valve 202. The outdoor unit 10 and the indoor unit 20 are connected by a first connecting pipe 31 and a second connecting pipe 32, thereby forming a refrigeration cycle. The first connecting pipe 31 is a pipe through which a gas refrigerant flows. The second connecting pipe 32 is a pipe through which a liquid refrigerant flows. For example, a refrigerant such as hydrocarbon, ammonia, or R32 is used as the refrigerant.
[0011] The compressor 101 draws in a low-temperature, low-pressure refrigerant, compresses it, and discharges it as a high-temperature, high-pressure refrigerant. The flow path switching device 102, which is, for example, a four-way valve, switches the flow direction of the refrigerant in the refrigerant circuit. The outdoor heat exchanger 103, which is, for example, a fin-and-tube heat exchanger, exchanges heat between the refrigerant and the outdoor air. The outdoor heat exchanger 103 functions as a condenser during cooling operation and as an evaporator during heating operation.
[0012] The indoor heat exchanger 201 exchanges heat between the indoor air and the refrigerant. The indoor heat exchanger 201 acts as an evaporator during cooling operation and as a condenser during heating operation. The expansion valve 202 reduces the pressure of the refrigerant to expand it, and is, for example, an electronic expansion valve.
[0013] A first on-off valve 33 is provided in the first connecting pipe 31. The first on-off valve 33 has a function of switching between an open state, which allows refrigerant to flow between the compressor 101 and the indoor heat exchanger 201, and a closed state, which blocks refrigerant from flowing between the compressor 101 and the indoor heat exchanger 201. The first on-off valve 33 is, for example, a so-called normally closed solenoid valve that is open when energized and closed when deenergized. Note that the refrigerant flow between the compressor 101 and the indoor heat exchanger 201 here refers to the refrigerant flow in the first connecting pipe 31, and does not refer to the refrigerant flowing between the compressor 101 and the indoor heat exchanger 201 via the second connecting pipe 32. In other words, the first on-off valve 33 is provided between the outlet side of the indoor heat exchanger 201 and the inlet side of the outdoor heat exchanger 103, based on cooling operation. When the heating operation is taken as a reference, the first on-off valve 33 is provided between the outlet side of the outdoor heat exchanger 103 and the inlet side of the indoor heat exchanger 201 .
[0014] A second on-off valve 34 is provided in the second connecting pipe 32. The second on-off valve 34 has a function of switching between an open state, which allows refrigerant to flow between the outdoor heat exchanger 103 and the indoor heat exchanger 201, and a closed state, which blocks refrigerant from flowing between the outdoor heat exchanger 103 and the indoor heat exchanger 201. The second on-off valve 34 is, for example, a so-called normally closed solenoid valve that is open when energized and closed when deenergized. Note that the refrigerant flow between the outdoor heat exchanger 103 and the indoor heat exchanger 201 here refers to the refrigerant flow in the second connecting pipe 32, and does not refer to the refrigerant flowing between the outdoor heat exchanger 103 and the indoor heat exchanger 201 via the first connecting pipe 31. In other words, the second on-off valve 34 is provided between the outlet side of the outdoor heat exchanger 103 and the inlet side of the indoor heat exchanger 201, based on cooling operation. In addition, in heating operation, the second on-off valve 34 is provided between the outlet side of the indoor heat exchanger 201 and the inlet side of the outdoor heat exchanger 103. Furthermore, as shown in Fig. 1, the flow of refrigerant between the outdoor heat exchanger 103 and the indoor heat exchanger 201 via the expansion valve 202 can also be considered to be one form of refrigerant flow between the outdoor heat exchanger 103 and the indoor heat exchanger 201.
[0015] The air conditioner 1 includes a control device 51. The control device 51 controls each device included in the air conditioner 1. As will be described in detail later, the control device 51 is characterized by performing a pump-down auxiliary operation to shorten the time required for pump-down operation after the compressor 101 is stopped. The pump-down operation is performed in the event of a refrigerant leak or when the air conditioner 1 is relocated, and is an operation to recover refrigerant to the outdoor unit 10. The pump-down operation itself is similar to a conventional method. For example, a valve (not shown) connecting the outdoor unit 10 and the second connecting pipe 32 is closed, and the flow path switching device 102 is switched to the direction for cooling operation, and the compressor 101 is operated at a relatively low operating frequency. During pump-down operation, the first on-off valve 33 and the second on-off valve 34 are controlled to an open state. Furthermore, during normal operating modes other than the pump-down auxiliary operation, i.e., cooling operation and heating operation, the first on-off valve 33 and the second on-off valve 34 are always controlled to an open state.
[0016] FIG. 2 is a hardware configuration diagram showing the control device 51 according to the first embodiment. As shown in FIG. 2, the control device 51 is configured with a processing circuit 71 such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). FIG. 3 is a hardware configuration diagram showing the control device 51 according to the first embodiment. When the functions of the control device 51 are performed by software, the control device 51 may be configured with a processor 72 such as a CPU and a memory 73, as shown in FIG. 3. FIG. 3 shows that the processor 72 and the memory 73 are communicatively connected to each other via a bus 74. The functions of the control device 51 are realized by the processor 72 reading and executing a program stored in the memory 73. The memory 73 may be a non-volatile or volatile semiconductor memory or a removable recording medium.
[0017] Returning to FIG. 1 , the air conditioning apparatus 1 has an operation and display device 52. The operation and display device 52 is, for example, a remote control or an operation panel, and has an operation unit and a display unit. The operation unit is, for example, buttons provided on the remote control or operation panel, and is used by the user to input settings such as starting or stopping air conditioning, temperature, air volume, or air direction. The display unit is, for example, a display, and displays settings input via the operation unit or information related to the operation of the air conditioning apparatus 1, such as the current indoor temperature. The operation and display device 52 is connected to the control device 51 by wire or wirelessly. Note that the operation and display device 52 may be provided integrally as a touch panel.
[0018] The outdoor unit 10 has an outdoor heat exchanger temperature sensor 104. The outdoor heat exchanger temperature sensor 104 is a sensor, such as a thermistor, that detects the temperature of a heat transfer tube (not shown) of the outdoor heat exchanger 103. The outdoor heat exchanger temperature sensor 104 is provided, for example, on the heat transfer tube with the lowest temperature among the multiple heat transfer tubes of the outdoor heat exchanger 103. Hereinafter, the temperature of the heat transfer tube of the outdoor heat exchanger 103 may be referred to as the outdoor heat exchanger temperature. The outdoor heat exchanger temperature sensor 104 transmits the detected outdoor heat exchanger temperature to the control device 51.
[0019] The indoor unit 20 has an indoor heat exchanger temperature sensor 203 and an indoor temperature sensor 204. The indoor heat exchanger temperature sensor 203 is a sensor, such as a thermistor, that detects the temperature of a heat transfer tube (not shown) of the indoor heat exchanger 201. The indoor heat exchanger temperature sensor 203 is provided, for example, on the heat transfer tube with the lowest temperature among the multiple heat transfer tubes of the indoor heat exchanger 201. Hereinafter, the temperature of the heat transfer tube of the indoor heat exchanger 201 may be referred to as the indoor heat exchanger temperature. The indoor heat exchanger temperature sensor 203 transmits the detected indoor heat exchanger temperature to the control device 51.
[0020] The indoor temperature sensor 204 detects the air temperature in the air-conditioned space in which the indoor unit 20 is installed. The indoor temperature sensor 204 is installed, for example, at an air intake port (not shown) through which air passes to be drawn into the indoor unit 20. Hereinafter, the air temperature in the air-conditioned space may be referred to as the indoor temperature. The indoor temperature sensor 204 communicates the detected indoor temperature to the control device 51.
[0021] (Cooling Operation) Here, the operation of the air conditioner 1 will be described. First, cooling operation will be described. In FIG. 1 , the flow of refrigerant during cooling operation is indicated by arrow F1. The air conditioner 1 performs cooling operation by switching the flow path switching device 102 so that the discharge side of the compressor 101 is connected to the outdoor heat exchanger 103. During cooling operation, the refrigerant drawn into the compressor 101 is compressed by the compressor 101 and discharged in a high-temperature, high-pressure gas state. The high-temperature, high-pressure gas refrigerant discharged from the compressor 101 passes through the flow path switching device 102 and flows into the outdoor heat exchanger 103, which functions as a condenser. The refrigerant that flows into the outdoor heat exchanger 103 exchanges heat with outdoor air, condenses, and liquefies. The liquid refrigerant passes through the open second on-off valve 34 and flows into the expansion valve 202, where it is decompressed and expanded to become a low-temperature, low-pressure, two-phase gas-liquid refrigerant. The refrigerant in a gas-liquid two-phase state flows into the indoor heat exchanger 201, which functions as an evaporator. The refrigerant that flows into the indoor heat exchanger 201 exchanges heat with the indoor air and evaporates, becoming gasified. At this time, the indoor air is cooled, thereby cooling the room. The evaporated refrigerant in a low-temperature, low-pressure gas state then passes through the first on-off valve 33, which is in an open state, and the flow switching device 102, and is drawn into the compressor 101.
[0022] (Heating Operation) Next, the heating operation will be described. In FIG. 1 , the flow of refrigerant during heating operation is indicated by arrow F2. The air conditioning apparatus 1 performs heating operation by switching the flow path switching device 102 so that the discharge side of the compressor 101 is connected to the indoor heat exchanger 201. During heating operation, the refrigerant drawn into the compressor 101 is compressed by the compressor 101 and discharged in a high-temperature, high-pressure gas state. The high-temperature, high-pressure gas refrigerant discharged from the compressor 101 passes through the flow path switching device 102 and the first on-off valve 33 in an open state and flows into the indoor heat exchanger 201, which functions as a condenser. The refrigerant that flows into the indoor heat exchanger 201 exchanges heat with the indoor air, condenses, and liquefies. At this time, the indoor air is heated, thereby heating the room. The liquid refrigerant flows into the expansion valve 202, where it is decompressed and expanded to become a low-temperature, low-pressure, two-phase gas-liquid refrigerant. The refrigerant in a gas-liquid two-phase state passes through the open second on-off valve 34 and flows into the outdoor heat exchanger 103, which functions as an evaporator. The refrigerant that flows into the outdoor heat exchanger 103 exchanges heat with the outdoor air and evaporates, becoming a gas. The evaporated refrigerant then passes through the flow switching device 102 and is drawn into the compressor 101.
[0023] Fig. 4 is a block diagram showing the control device 51 according to the first embodiment. As shown in Fig. 4, the control device 51 controls the operation or stop of the compressor 101, the operating frequency during operation, and the opening degree of the expansion valve 202 so that the indoor temperature detected by the indoor temperature sensor 204 becomes the temperature set by the user via the operation display device 52. The control device 51 also controls the connection direction of the flow path switching device 102 to switch the operation mode.
[0024] The control device 51 then performs the pump-down auxiliary operation after the compressor 101 has stopped and the standby time has elapsed. During the pump-down auxiliary operation, the control device 51 controls the open / close states of the first on-off valve 33 and the second on-off valve 34 based on the outdoor heat exchanger temperature detected by the outdoor heat exchanger temperature sensor 104, the indoor heat exchanger temperature detected by the indoor heat exchanger temperature sensor 203, and the indoor temperature detected by the indoor temperature sensor 204. The compressor 101 may be stopped either because a user instructs the compressor to stop operation or because temperature control automatically stops when the indoor temperature reaches a set temperature (so-called thermo-off). The standby time is set to, for example, 10 minutes, to limit the execution of the pump-down auxiliary operation to cases where the compressor 101 has been stopped for a relatively long period of time. The standby time may be omitted. The pump-down auxiliary operation may be performed only when a user instructs the compressor to stop operation or when the compressor 101 is in thermo-off mode, or both.
[0025] During pump-down assist operation, the control device 51 controls the open / close states of the first on-off valve 33 and the second on-off valve 34 as follows: First, the control device 51 compares the indoor heat exchanger temperature with the outdoor heat exchanger temperature. If the comparison results in the outdoor heat exchanger temperature being lower than the indoor heat exchanger temperature and the temperature difference between the indoor heat exchanger temperature and the outdoor heat exchanger temperature being greater than a first temperature, the control device 51 performs open control. The first temperature is set to prevent frequent changes in the open / close states of the first on-off valve 33 and the second on-off valve 34 (so-called hunting), and is set in the range of 0°C to 2°C, for example. The temperature difference between the indoor heat exchanger temperature and the outdoor heat exchanger temperature is the absolute value obtained by subtracting the outdoor heat exchanger temperature from the indoor heat exchanger temperature.
[0026] The opening control consists of two stages. In the first stage, the control device 51 opens the first on-off valve 33 and the second on-off valve 34. Generally, after the compressor 101 is stopped, if the outdoor heat exchanger temperature is lower than the indoor heat exchanger temperature, the refrigerant stagnating in the indoor unit 20 moves to the outdoor unit 10. In the first embodiment, the first stage of the opening control prevents this refrigerant movement. That is, the refrigerant can be collected in the outdoor unit 10. The refrigerant movement occurs during the process of pressure equilibration between the high-pressure and low-pressure portions of the refrigeration cycle after the compressor 101 is stopped. That is, the refrigerant moves from the high-pressure portion to the low-pressure portion. Since the high and low pressures and the high and low temperatures generally coincide after the compressor 101 is stopped, the direction of refrigerant movement can be determined by comparing the indoor heat exchanger temperature and the outdoor heat exchanger temperature.
[0027] Next, the control device 51 compares the indoor heat exchanger temperature with the indoor temperature. If the temperature difference between the indoor heat exchanger temperature and the indoor temperature becomes equal to or less than a second temperature, the control device 51 closes the first and second on-off valves 33 and 34 as a second stage of control. Alternatively, if the temperature difference between the indoor heat exchanger temperature and the indoor temperature remains equal to or less than the second temperature for a first period of time or longer, the control device 51 may close the first and second on-off valves 33 and 34. The second temperature is set to determine whether refrigerant transfer to the outdoor unit 10 is complete, and is, for example, between 0°C and 2°C. In other words, as refrigerant transfer to the outdoor unit 10 progresses, the indoor heat exchanger temperature decreases, and when the transfer is complete, the indoor heat exchanger temperature and the indoor temperature become approximately equal. The second temperature is set with this in mind. The first period of time is set to stabilize the comparison result between the indoor heat exchanger temperature and the indoor temperature, and is, for example, 5 minutes. The temperature difference between the indoor heat exchanger temperature and the indoor temperature is the absolute value obtained by subtracting the indoor temperature from the indoor heat exchanger temperature. By performing the second stage of the opening control, the first on-off valve 33 and the second on-off valve 34 continue to be open even after the refrigerant has moved to the outdoor unit 10, and it is possible to suppress excessive power consumption when the solenoid valve is of the normally closed type.
[0028] On the other hand, if a comparison of the outdoor heat exchanger temperature and the indoor heat exchanger temperature reveals that the outdoor heat exchanger temperature is higher than the indoor heat exchanger temperature and that the temperature difference between the outdoor heat exchanger temperature and the indoor heat exchanger temperature is greater than a third temperature, the first on-off valve 33 and the second on-off valve 34 are closed. This control is referred to as closed control in contrast to the open control described above. The third temperature is set to prevent frequent changes in the open / closed states of the first on-off valve 33 and the second on-off valve 34, and is set, for example, in the range of 0°C to 2°C. Note that the temperature difference between the outdoor heat exchanger temperature and the indoor heat exchanger temperature is the absolute value obtained by subtracting the indoor heat exchanger temperature from the outdoor heat exchanger temperature. Generally, after the compressor 101 is stopped, if the indoor heat exchanger temperature is lower than the outdoor heat exchanger temperature, the refrigerant stagnating in the outdoor unit 10 moves to the indoor unit 20. However, in the first embodiment, this refrigerant movement can be suppressed by performing closed control. In other words, the refrigerant can be stored in the outdoor unit 10.
[0029] The above-described open / close states refer to the open / close states during pump-down assist operation. For example, if the first on-off valve 33 and the second on-off valve 34 are normally closed solenoid valves, they may be closed by de-energizing them after the compressor 101 has stopped and before the standby time has elapsed. Also, if the first on-off valve 33 and the second on-off valve 34 are normally open solenoid valves, they may be open by de-energizing them. However, these open / close states do not represent the open / close states of the first on-off valve 33 and the second on-off valve 34 during pump-down assist operation.
[0030] That is, in the first stage of opening control during pump-down assist operation, opening the first on-off valve 33 and the second on-off valve 34 means the following two cases. In the first case, the first on-off valve 33 and the second on-off valve 34 are open before the start of pump-down assist operation and continue to be maintained in the open state after the start of pump-down assist operation. In the second case, the first on-off valve 33 and the second on-off valve 34 are closed before the start of pump-down assist operation and are changed to the open state after the start of pump-down assist operation.
[0031] The same applies to closing the first on-off valve 33 and the second on-off valve 34 in the closing control during the pump-down assist operation.
[0032] The operation of the control device 51 will be described using FIG. 5 . FIG. 5 is a flowchart showing the operation of the control device 51 according to the first embodiment. First, the control device 51 determines whether a standby time has elapsed since the compressor 101 stopped operating (step S1). If the compressor 101 has not stopped operating or if the standby time has not elapsed (step S1: NO), the control device 51 waits until the condition of step S1 is satisfied. If the standby time has elapsed since the compressor 101 stopped operating (step S1: YES), the control device 51 acquires the outdoor heat exchanger temperature and the indoor heat exchanger temperature from the outdoor heat exchanger temperature sensor 104 and the indoor heat exchanger temperature sensor 203 (step S2). Then, the control device 51 determines whether the indoor heat exchanger temperature is greater than the value obtained by adding the first temperature α to the outdoor heat exchanger temperature (step S3).
[0033] If the indoor heat exchanger temperature is greater than the sum of the outdoor heat exchanger temperature and the first temperature α (step S3: YES), the control device 51 performs the first stage of the opening control. That is, the first on-off valve 33 and the second on-off valve 34 are opened (step S4). Next, the control device 51 acquires the indoor temperature (step S5) and determines whether the value obtained by subtracting the indoor temperature from the indoor heat exchanger temperature is equal to or less than the second temperature β (step S6). If the value obtained by subtracting the indoor temperature from the indoor heat exchanger temperature is greater than the second temperature β (step S6: NO), the control device 51 repeats the processes of steps S5 and S6 until the condition of step S6 is satisfied. If the value obtained by subtracting the indoor temperature from the indoor heat exchanger temperature is equal to or less than the second temperature β (step S6: YES), the control device 51 acquires the indoor heat exchanger temperature and the indoor temperature again after the first time has elapsed (step S7). Then, the control device 51 determines whether the value obtained by subtracting the indoor temperature from the indoor heat exchanger temperature continues to be equal to or less than the second temperature β (step S8). If the value obtained by subtracting the indoor temperature from the indoor heat exchanger temperature exceeds the second temperature β (step S8: NO), the control device 51 repeats the processes of steps S5 to S8 until the condition of step S8 is satisfied.
[0034] If the value obtained by subtracting the indoor temperature from the indoor heat exchanger temperature is equal to or lower than the second temperature β (step S8: YES), the control device 51 performs the second stage of the opening control, i.e., closes the first on-off valve 33 and the second on-off valve 34 (step S9).
[0035] If the indoor heat exchanger temperature is equal to or lower than the sum of the outdoor heat exchanger temperature and the first temperature α (step S3: NO), the control device 51 determines whether the outdoor heat exchanger temperature is equal to or higher than the sum of the indoor heat exchanger temperature and the third temperature γ (step S10). If the outdoor heat exchanger temperature is lower than the sum of the indoor heat exchanger temperature and the third temperature γ (step S10: NO), the control device 51 does not change the open / close state. If the outdoor heat exchanger temperature is equal to or higher than the sum of the indoor heat exchanger temperature and the third temperature γ (step S10: YES), the control device 51 performs a closing control. That is, the first opening / closing valve 33 and the second opening / closing valve 34 are closed (step S11).
[0036] The control device 51 then determines whether the operation start condition for the compressor 101 is satisfied (step S12). The operation start condition for the compressor 101 may be satisfied, for example, when a user issues a command to start operation or when temperature control is automatically initiated because the indoor temperature deviates from the set temperature (so-called thermo-on). The state in which the operation start condition for the compressor 101 is satisfied here refers to the state before the compressor 101 actually starts operating. If the operation start condition for the compressor 101 is not satisfied (step S12: NO), the control device 51 repeatedly executes steps S2 to S11 until the condition of step S12 is satisfied. If the operation start condition for the compressor 101 is satisfied (step S12: YES), the control device 51 terminates the process. After completing the above process, the control device 51 opens the first on-off valve 33 and the second on-off valve 34 and then starts the normal operation mode. The control device 51 periodically executes the determination of step S1. During the processing of steps S2 to S9, the control device 51 starts the pump-down operation if a command to perform the pump-down operation is input to the operation display device 52 or the control device 51. At this time, the time required for the pump-down operation is shortened because the refrigerant has been collected in the outdoor unit 10 by the pump-down auxiliary operation.
[0037] The above-described flowchart is an example of control. For example, the comparison formulas are not limited to those described in the flowchart, and modified formulas may be used. Furthermore, the order of the process of step S3 relating to the opening control and the process of step S10 relating to the closing control may be reversed.
[0038] According to the air conditioner 1 of Embodiment 1, after the compressor operation is stopped, the open / close states of the first on-off valve 33 and the second on-off valve 34 are controlled based on the comparison result between the outdoor heat exchanger temperature and the indoor heat exchanger temperature. This prevents refrigerant from accumulating in the indoor unit 20, which has become colder than the outdoor unit 10. Therefore, in the air conditioner 1, the time required for pump-down operation can be shortened.
[0039] Furthermore, in recent years, some refrigerants known as chlorofluorocarbon alternatives used in air conditioners 1 are slightly flammable or flammable. When a slightly flammable or flammable refrigerant leaks, it is necessary to suppress the amount of refrigerant leakage so that the refrigerant concentration in the air-conditioned space of the indoor unit 20 does not reach the lower flammability limit (LFL). In particular, it is desirable to suppress the amount of refrigerant leakage from the indoor unit 20 installed in the air-conditioned space. According to the first embodiment, when a pump-down operation is performed in the event of a refrigerant leak, the amount of refrigerant leakage from the indoor unit 20 can be suppressed by shortening the time required for pump-down.
[0040] Furthermore, generally, if the pump-down auxiliary operation is performed between the establishment of a condition for stopping the operation of the compressor 101 (for example, a stop instruction from a user) and the actual stopping of the operation of the compressor 101, it may take a long time for the operation of the compressor 101 to actually stop. According to the first embodiment, the pump-down auxiliary operation is performed after the operation of the compressor 101 has stopped, so the compressor 101 can be stopped immediately after the establishment of the condition for stopping the operation of the compressor 101. This makes it possible to reduce power consumption related to the operation of the compressor 101.
[0041] Embodiment 2. Figure 6 is a circuit diagram showing an air conditioning apparatus 1A according to embodiment 2. As shown in Figure 6, embodiment 2 differs from embodiment 1 in that the air conditioning apparatus 1A has a plurality of indoor units 20. In embodiment 2, the same parts as in embodiment 1 are given the same reference numerals and their description will be omitted, and the description will focus on the differences from embodiment 1.
[0042] The air conditioning apparatus 1A has indoor units 20a, 20b, and 20c. The indoor units 20a, 20b, and 20c are arranged in parallel. The indoor units 20a, 20b, and 20c are provided in the same room, for example. However, the indoor units 20a, 20b, and 20c may also be provided in different rooms.
[0043] In the air conditioning apparatus 1A, the first connection pipe 31 branches into a first connection pipe 31a corresponding to the indoor unit 20a, a first connection pipe 31b corresponding to the indoor unit 20b, and a first connection pipe 31c corresponding to the indoor unit 20c. The second connection pipe 32 branches into a second connection pipe 32a corresponding to the indoor unit 20a, a second connection pipe 32b corresponding to the indoor unit 20b, and a second connection pipe 32c corresponding to the indoor unit 20c.
[0044] The indoor unit 20a has an indoor heat exchanger 201a, an expansion valve 202a, an indoor heat exchanger temperature sensor 203a, and an indoor temperature sensor 204a. The indoor unit 20b has an indoor heat exchanger 201b, an expansion valve 202b, an indoor heat exchanger temperature sensor 203b, and an indoor temperature sensor 204b. The indoor unit 20c has an indoor heat exchanger 201c, an expansion valve 202c, an indoor heat exchanger temperature sensor 203c, and an indoor temperature sensor 204c. The devices included in the indoor units 20a, 20b, and 20c have the same configuration and operation as the devices in the indoor unit 20 described in embodiment 1, so detailed description will be omitted. Note that, hereinafter, when there is no need to distinguish between the indoor units 20a, 20b, and 20c and the devices included in each, the suffixes "a," "b," and "c" will be omitted in the description.
[0045] The first on-off valve 33 is provided at a location other than the branching portion of the first connection pipe 31. The second on-off valve 34 is provided at a location other than the branching portion of the second connection pipe.
[0046] The only difference from the first embodiment is that the refrigerant flows in parallel through the indoor heat exchanger 201a and expansion valve 202a of the indoor unit 20a, the indoor heat exchanger 201b and expansion valve 202b of the indoor unit 20b, and the indoor heat exchanger 201c and expansion valve 202c of the indoor unit 20c during cooling and heating operations. Therefore, a detailed description of the refrigerant flow will be omitted.
[0047] During pump-down assist operation, the control device 51 controls the open / close states of the first on-off valve 33 and the second on-off valve 34 as follows: First, the control device 51 compares the reference indoor heat exchanger temperature with the outdoor heat exchanger temperature. Here, the reference indoor heat exchanger temperature is the minimum value of the multiple indoor heat exchanger temperatures measured by the multiple indoor heat exchanger temperature sensors 203 of the multiple indoor units 20. If the comparison shows that the outdoor heat exchanger temperature is lower than the reference indoor heat exchanger temperature and the temperature difference between the reference indoor heat exchanger temperature and the outdoor heat exchanger temperature is greater than the first temperature, the control device 51 performs opening control.
[0048] The opening control is composed of two stages. In the first stage, the control device 51 opens the first on-off valve 33 and the second on-off valve 34. In the second embodiment, the first stage of the opening control is performed so that the movement of the refrigerant from the indoor unit 20 to the outdoor unit 10 is not impeded. In other words, the refrigerant can be collected in the outdoor unit 10.
[0049] Next, the control device 51 compares the reference indoor heat exchanger temperature with the indoor temperature. If the temperature difference between the reference indoor heat exchanger temperature and the indoor temperature becomes equal to or less than a second temperature, the control device 51 closes the first on-off valve 33 and the second on-off valve 34 as a second-stage control. Here, the indoor temperature compared with the reference indoor heat exchanger temperature is detected by the indoor temperature sensor 204 of the indoor unit 20 that detected the reference indoor heat exchanger temperature. Alternatively, if the temperature difference between the reference indoor heat exchanger temperature and the indoor temperature remains equal to or less than the second temperature for a first period of time, the control device 51 may close the first on-off valve 33 and the second on-off valve 34. By performing the second-stage open control, the first on-off valve 33 and the second on-off valve 34 remain open even after the refrigerant has moved to the outdoor unit 10, thereby suppressing excessive power consumption when the solenoid valves are normally closed.
[0050] On the other hand, if the comparison result indicates that the outdoor heat exchanger temperature is higher than the reference indoor heat exchanger temperature and the temperature difference between the outdoor heat exchanger temperature and the reference indoor heat exchanger temperature is greater than a third temperature, the first on-off valve 33 and the second on-off valve 34 are closed as a closing control. In the third embodiment, by performing the closing control, it is possible to suppress the movement of refrigerant from the outdoor unit 10 to the indoor unit 20. In other words, it is possible to accumulate refrigerant in the outdoor unit 10.
[0051] The operation of the control device 51 will be described using FIG. 7 . FIG. 7 is a flowchart illustrating the operation of the control device 51 according to the second embodiment. The processes of steps S21, S22, and S24 to S33 in the second embodiment are similar to or correspond to the processes of steps S1 to S12 in the first embodiment. Here, differences between the processes of the second embodiment and the first embodiment will be described. First, the control device 51 acquires the outdoor heat exchanger temperature and the indoor heat exchanger temperature (step S22), and then sets the minimum value of the multiple indoor heat exchanger temperatures as the reference indoor heat exchanger temperature (step S23). Furthermore, in subsequent steps S26 and S28, the control device 51 acquires the reference indoor heat exchanger temperature instead of the indoor heat exchanger temperature. The acquired reference indoor heat exchanger temperature may be detected by the indoor heat exchanger temperature sensor 203 that detected the reference indoor heat exchanger temperature acquired in step S23. Alternatively, the control device 51 may acquire indoor heat exchanger temperatures from all indoor heat exchanger temperature sensors 203 again, and the minimum value of all indoor heat exchanger temperatures may be set as the reference indoor heat exchanger temperature. Then, in the comparison processes in steps S24, S27, S29, and S31, the reference indoor heat exchanger temperature is used instead of the indoor heat exchanger temperature.
[0052] As described above, according to the air conditioning apparatus 1A of the second embodiment, the open / close states of the first on-off valve 33 and the second on-off valve 34 are controlled based on the comparison result between the outdoor heat exchanger temperature and the reference indoor heat exchanger temperature. Therefore, the air conditioning apparatus 1A of the second embodiment can also achieve the same effects as the air conditioning apparatus 1A of the first embodiment.
[0053] Although the above is a description of the embodiments of the present disclosure, the present disclosure is not limited to the configurations of the above embodiments, and various modifications and combinations are possible within the scope of the technical concept. For example, in the first and second embodiments, the indoor unit has the expansion valve 202, but the expansion valve 202 may be provided outside the indoor unit as long as it is provided between the indoor heat exchanger 201 and the outdoor heat exchanger 103. In the second embodiment, one expansion valve 202 may be provided inside the second connecting pipe 32 or the outdoor unit 10.
[0054] Furthermore, if the expansion valve 202 has the function of shutting off the refrigerant in the same manner as the second on-off valve 34 is closed, the expansion valve 202 may be used instead of the second on-off valve 34. In this case, the second on-off valve 34 can be omitted from the air conditioning apparatus 1. When the second on-off valve 34 is omitted, the expansion valve 202 corresponds to the "second on-off valve" of the present disclosure. Note that in the case of the second embodiment, the second on-off valve 34 may be provided in each of the second connection pipes 32a, 32b, and 32c corresponding to the indoor units 20a, 20b, and 20c. In this case, the control device 51 controls all of the second on-off valves 34 to be closed simultaneously.
[0055] The air conditioner 1 of the first and second embodiments may be a dedicated cooling unit or a dedicated heating unit, in which case the flow path switching device 102 may be omitted.
[0056] 1, 1A Air conditioning apparatus, 10 Outdoor unit, 20, 20a, 20b, 20c Indoor unit, 31, 31a, 31b, 31c First connecting pipe, 32, 32a, 32b, 32c Second connecting pipe, 33 First opening / closing valve, 34 Second opening / closing valve, 51 Control device, 52 Operation display device, 71 Processing circuit, 72 Processor, 73 Memory, 74 Bus, 101 Compressor, 102 Flow path switching device, 103 Outdoor heat exchanger, 104 Outdoor heat exchanger temperature sensor, 201, 201a, 201b, 201c Indoor heat exchanger, 202, 202a, 202b, 202c Expansion valve, 203, 203a, 203b, 203c Indoor heat exchanger temperature sensor, 204, 204a, 204b, 204c Indoor temperature sensor.
Claims
1. An outdoor unit having a compressor, an outdoor heat exchanger, and an outdoor heat exchange temperature sensor that measures the outdoor heat exchange temperature which is the temperature of the outdoor heat exchanger; An indoor unit having an indoor heat exchanger and an indoor heat exchange temperature sensor that measures the indoor heat exchange temperature which is the temperature of the indoor heat exchanger; A first on-off valve having a function of switching between an open state that allows the refrigerant to flow between the compressor and the indoor heat exchanger and a closed state that blocks the flow of the refrigerant between the compressor and the indoor heat exchanger; A second on-off valve having a function of switching between an open state that allows the refrigerant to flow between the outdoor heat exchanger and the indoor heat exchanger and a closed state that blocks the flow of the refrigerant between the outdoor heat exchanger and the indoor heat exchanger; A control device that sets the first on-off valve and the second on-off valve to the open state when the outdoor heat exchange temperature is lower than the indoor heat exchange temperature and the temperature difference between the indoor heat exchange temperature and the outdoor heat exchange temperature is greater than a first temperature; An indoor temperature sensor that measures the indoor temperature where the indoor unit is installed, and After setting the first on-off valve and the second on-off valve to the open state, the control device sets the first on-off valve and the second on-off valve to the closed state when the temperature difference between the indoor heat exchange temperature and the indoor temperature is equal to or less than a second temperature. An air conditioner.
2. The control device Sets the first on-off valve and the second on-off valve to the closed state when the state where the temperature difference between the indoor heat exchange temperature and the indoor temperature is equal to or less than the second temperature continues for a first time or longer, And leaves the first on-off valve and the second on-off valve in the open state when the state where the temperature difference between the indoor heat exchange temperature and the indoor temperature is equal to or less than the second temperature continues for less than the first time. The air conditioner according to Claim 1.
3. A plurality of indoor units are provided, The plurality of indoor units are connected in parallel to the outdoor unit, The control device sets the first on-off valve and the second on-off valve to the open state when the outdoor heat exchange temperature is lower than a reference indoor heat exchange temperature and the temperature difference between the outdoor heat exchange temperature and the reference indoor heat exchange temperature is greater than the first temperature, The reference indoor heat exchange temperature is the minimum value of a plurality of indoor heat exchange temperatures measured by a plurality of indoor heat exchange temperature sensors that the plurality of indoor units have. The air conditioner according to any one of Claims 1 or 2.
4. When the outdoor heat exchanger temperature is higher than the indoor heat exchanger temperature and the temperature difference between the outdoor heat exchanger temperature and the indoor heat exchanger temperature is equal to or higher than a third temperature, the control device closes the first on-off valve and the second on-off valve. The air conditioner according to claim 1 or 2. **Claim 5** A plurality of indoor units are provided. The plurality of indoor units are connected in parallel to the outdoor unit. When the outdoor heat exchanger temperature is higher than the reference indoor heat exchanger temperature and the temperature difference between the outdoor heat exchanger temperature and the reference indoor heat exchanger temperature is equal to or higher than the third temperature, the control device closes the first on-off valve and the second on-off valve. The reference indoor heat exchanger temperature is the minimum value of a plurality of indoor heat exchanger temperatures measured by a plurality of indoor heat exchanger temperature sensors provided in the plurality of indoor units. The air conditioner according to claim 4. **Claim 6** After the compressor stops, the control device switches the opening and closing states of the first on-off valve and the second on-off valve. The air conditioner according to claim 1 or 2.