Air conditioning system, control device, and control method

Abstract

An air conditioning system (1) comprises a plurality of outdoor units (10) and a control device (100). The plurality of outdoor units are configured such that a refrigerant circulates between the outdoor units and at least one indoor unit (20). The plurality of outdoor units are each provided with: a refrigerant circuit (3) that is provided with a compressor (30), a condenser (60), an expansion valve (65), and an evaporator (50) and that is configured to circulate a refrigerant; an accumulator (70) that is disposed between the compressor and the evaporator and that separates a refrigerant flowing through the refrigerant circuit into a liquid refrigerant and a gas refrigerant, and stores the liquid refrigerant; a first temperature sensor (91) that measures the temperature of a refrigerant flowing into the accumulator; and second temperature sensors (92 and 93) that measure the temperature of a refrigerant flowing out from the accumulator. The control device calculates the difference between a first measurement value of the first temperature sensor and a second measurement value of the second temperature sensor in each of the plurality of outdoor units, and, on the basis of the difference, adjusts the amount of the liquid refrigerant stored by the accumulator of each of the plurality of outdoor units.

Description

Technical Field

[0001] The present disclosure relates to an air conditioning system, a control device, and a control method.

Background Art

[0002] An air conditioning system is configured to cool or heat a room to be air-conditioned by circulating a refrigerant in a refrigerant circuit. Generally, the amount of refrigerant required during heating operation is less than the amount of refrigerant required during cooling operation. Therefore, the amount of refrigerant filled in the refrigerant circuit of an air conditioner is determined based on the amount of refrigerant required during cooling operation. Excess refrigerant not used during heating operation is stored by an accumulator provided between a compressor and an evaporator constituting the refrigerant circuit. An operator performing installation or inspection of the air conditioner can determine whether the amount of refrigerant circulating in the refrigerant circuit is appropriate by checking the amount of refrigerant stored in the accumulator.

[0003] WO 2019 / 065242 A1 (Patent Document 1) discloses a liquid level detection sensor for detecting the liquid level height of the refrigerant stored in an accumulator. This liquid level detection sensor is configured to heat the accumulator by a heater and measure the surface temperature of the accumulator by a plurality of temperature sensors provided in the height direction of the accumulator, and detect the liquid level height of the refrigerant stored in the accumulator based on the difference in temperature change according to the refrigerant state in the accumulator.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An air conditioning system may be configured such that multiple outdoor units are connected to at least one indoor unit, causing refrigerant to circulate between the multiple outdoor units and at least one indoor unit. In such an air conditioning system combining multiple outdoor units and at least one indoor unit, the refrigerant may be unevenly distributed among the multiple outdoor units depending on the operating status of each unit. For example, the amount of refrigerant stored in the accumulator of one outdoor unit may differ from that of the other outdoor units. If the amount of refrigerant stored in the accumulator becomes excessively large, a large amount of liquid refrigerant will flow into the compressor due to liquid back, which may increase the burden on workers inspecting the compressor. On the other hand, if the amount of refrigerant stored in the accumulator becomes excessively small, there will be insufficient refrigerant flowing through the refrigerant circuit, reducing the cooling or heating capacity, which may cause discomfort to the user. According to the liquid level detection sensor disclosed in International Publication No. 2019 / 065242, the amount of refrigerant stored in the accumulator can be detected, but it does not take into account the uneven distribution of refrigerant among multiple outdoor units as described above. Therefore, there is a need for technology to prevent the uneven distribution of refrigerant among multiple outdoor units.

[0006] This disclosure was made to solve the above-mentioned problems and aims to provide a technology that reduces the burden on workers and does not cause discomfort to users by preventing the uneven distribution of refrigerant among multiple outdoor units. [Means for solving the problem]

[0007] The air conditioning system according to this disclosure comprises a plurality of outdoor units and a control device. The plurality of outdoor units are configured to circulate a refrigerant between them and at least one indoor unit. Each of the plurality of outdoor units comprises a compressor, a condenser, an expansion valve, and an evaporator, and a refrigerant circuit configured to circulate the refrigerant; an accumulator positioned between the compressor and the evaporator, which separates the refrigerant flowing through the refrigerant circuit into liquid refrigerant and gaseous refrigerant and stores the liquid refrigerant; a first temperature sensor that measures the temperature of the refrigerant flowing into the accumulator; and a second temperature sensor that measures the temperature of the refrigerant flowing out of the accumulator. The control device calculates the difference between a first measurement value from the first temperature sensor and a second measurement value from the second temperature sensor in each of the plurality of outdoor units, and adjusts the amount of liquid refrigerant stored by the accumulator of each of the plurality of outdoor units based on the difference value.

[0008] The control device according to this disclosure controls a plurality of outdoor units. The plurality of outdoor units are configured to circulate a refrigerant between them and at least one indoor unit. The control device comprises a processor and a memory for storing a control program executed by the processor. Each of the plurality of outdoor units comprises a compressor, a condenser, an expansion valve, and an evaporator, and a refrigerant circuit configured to circulate a refrigerant; an accumulator positioned between the compressor and the evaporator, which separates the refrigerant flowing through the refrigerant circuit into liquid refrigerant and gaseous refrigerant and stores the liquid refrigerant; a first temperature sensor for measuring the temperature of the refrigerant flowing into the accumulator; and a second temperature sensor for measuring the temperature of the refrigerant flowing out of the accumulator. The processor calculates the difference between a first measurement of the first temperature sensor and a second measurement of the second temperature sensor in each of the plurality of outdoor units, and adjusts the amount of liquid refrigerant stored by the accumulator of each of the plurality of outdoor units based on the difference.

[0009] The control method relating to this disclosure is a method for controlling a plurality of outdoor units using a processor. The plurality of outdoor units are configured to circulate a refrigerant between them and at least one indoor unit. Each of the plurality of outdoor units includes a compressor, a condenser, an expansion valve, and an evaporator, and is configured to circulate a refrigerant; an accumulator positioned between the compressor and the evaporator, which separates the refrigerant flowing through the refrigerant circuit into liquid refrigerant and gaseous refrigerant and stores the liquid refrigerant; a first temperature sensor that measures the temperature of the refrigerant flowing into the accumulator; and a second temperature sensor that measures the temperature of the refrigerant flowing out of the accumulator. The control method includes, as a process executed by the processor, the steps of calculating the difference between a first measurement value of the first temperature sensor and a second measurement value of the second temperature sensor in each of the plurality of outdoor units; and adjusting the amount of liquid refrigerant stored by the accumulator of each of the plurality of outdoor units based on the difference value. [Effects of the Invention]

[0010] According to this disclosure, the control device calculates the difference between a first measurement of the temperature of the refrigerant flowing into the accumulator of each of the multiple outdoor units and a second measurement of the temperature of the refrigerant flowing out of the accumulator. Based on this difference, the control device can adjust the amount of liquid refrigerant stored in the accumulator of each of the multiple outdoor units, thereby preventing uneven distribution of refrigerant among the multiple outdoor units. This reduces the burden on workers and avoids causing discomfort to users. [Brief explanation of the drawing]

[0011] [Figure 1] This is a diagram showing the configuration of the air conditioning system according to Embodiment 1. [Figure 2] This diagram shows the configuration of the air conditioner according to Embodiment 1. [Figure 3] This is a diagram illustrating the internal configuration of the accumulator according to Embodiment 1. [Figure 4] This is a flowchart illustrating the refrigerant amount adjustment process performed by the control device according to Embodiment 1. [Modes for carrying out the invention]

[0012] The embodiments of this disclosure will be described in detail below with reference to the drawings. While multiple embodiments will be described below, it has been intended from the outset that the configurations described in each embodiment may be combined as appropriate. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0013] Embodiment 1. The air conditioning system 1 according to Embodiment 1 will now be described.

[0014] [Air Conditioning System Configuration] The configuration of the air conditioning system 1 according to Embodiment 1 will be described with reference to Figure 1. Figure 1 is a diagram showing the configuration of the air conditioning system 1 according to Embodiment 1.

[0015] As shown in Figure 1, the air conditioning system 1 comprises at least one indoor unit 20, a plurality of outdoor units 10A, 10B, 10C connected to at least one indoor unit 20, and control devices 100A, 100B, 100C that control outdoor units 10A, 10B, and 10C, respectively. Hereinafter, outdoor units 10A, 10B, and 10C will be collectively referred to as "outdoor unit 10". Also, control devices 100A, 100B, and 100C will be collectively referred to as "control device 100".

[0016] Multiple outdoor units 10 are configured to circulate refrigerant between them and at least one indoor unit 20. In the example in Figure 1, three outdoor units 10A, 10B, and 10C are shown as multiple outdoor units 10, but the multiple outdoor units 10 may include two or four, or other types of outdoor units 10. Also, in the example in Figure 1, one indoor unit 20 is connected to multiple outdoor units 10, but refrigerant may circulate between multiple outdoor units 10 and multiple indoor units 20 by connecting multiple indoor units 20 to multiple outdoor units 10. Alternatively, refrigerant may circulate between each outdoor unit 10 and multiple indoor units 20 by connecting multiple indoor units 20 to each outdoor unit 10. Furthermore, refrigerant may circulate between each outdoor unit 10 and one indoor unit 20 by connecting one indoor unit 20 to each outdoor unit 10.

[0017] An air conditioner 2 is composed of an outdoor unit 10 and an indoor unit 20. That is, the air conditioning system 1 includes multiple air conditioners 2, each consisting of an outdoor unit 10 and an indoor unit 20. In the example shown in Figure 1, the refrigerant circulates through the indoor unit 20, outdoor unit 10A, outdoor unit 10B, and outdoor unit 10C.

[0018] [Air conditioner configuration] The configuration of the air conditioner 2 according to Embodiment 1 will be described with reference to Figure 2. Figure 2 is a diagram showing the configuration of the air conditioner 2 according to Embodiment 1. Note that Figure 2 functionally shows the connection relationships and arrangement of each component in the air conditioner 2, and does not necessarily show the physical arrangement in space.

[0019] As shown in Fig. 2, the air conditioner 2 includes a refrigerant circuit 3 and a control device 100. The refrigerant circuit 3 includes an outdoor unit 10 and an indoor unit 20. The outdoor unit 10 and the indoor unit 20 are connected by extension pipes 21 and 22, and refrigerant circulates between the outdoor unit 10 and the indoor unit 20. In Fig. 2, a combination of the outdoor unit 10A and the indoor unit 20 is illustrated as the air conditioner 2. However, combinations of the outdoor unit 10B and the indoor unit 20, and the outdoor unit 10C and the indoor unit 20 also have the same configuration as the combination of the outdoor unit 10A and the indoor unit 20.

[0020] The outdoor unit 10 is generally installed outdoors where air conditioning is not the target, and includes a four-way valve 40, a compressor 30, an outdoor heat exchanger 50, an outdoor fan 51, and an expansion valve 65.

[0021] The four-way valve 40 includes a connection port 41, a connection port 42, a connection port 43, and a connection port 44. The connection port 41 of the four-way valve 40 is connected to the suction port 31 of the compressor 30 via pipes 18 and 19. The connection port 42 of the four-way valve 40 is connected to the outdoor heat exchanger 50 via pipe 17. The connection port ۴۳ of the four-way valve 40 is connected to the discharge port 32 of the compressor 30 via pipe 11. The connection port 44 of the four-way valve 40 is connected to the indoor unit 20 via pipes 12 and extension pipe 21. The four-way valve 40 is configured to switch its internal communication state according to the control of the control device 100.

[0022] The compressor 30 is configured to operate and stop, and further change the rotational speed during operation according to the control of the control device 100. The control device 100 controls the compressor 30 to arbitrarily change the drive frequency of the compressor 30. The compressor 30 changes the number of rotations per unit time, that is, the rotational speed, according to the change in the drive frequency, thereby changing the discharge amount of the refrigerant. Various types of compressors can be adopted for the compressor 30. For example, a scroll type, a rotary type, a screw type, etc. can be adopted as the compressor 30.

[0023] The outdoor heat exchanger 50 performs heat exchange between the air drawn in from outside by the outdoor fan 51 (i.e., outside air) and the refrigerant. One end of the outdoor heat exchanger 50 is connected to the connection port 42 of the four-way valve 40 via piping 17. The other end of the outdoor heat exchanger 50 is connected to the indoor unit 20 via piping 16, piping 15, and extension piping 22.

[0024] The outdoor fan 51 is configured to operate and stop, and to change its rotational speed during operation, according to the control of the control device 100. The control device 100 controls the outdoor fan 51 to arbitrarily change its drive frequency. The outdoor fan 51 changes its rotational speed, i.e., the number of rotations per unit time, in accordance with the change in drive frequency, thereby changing the amount of air sent to the outdoor heat exchanger 50.

[0025] The expansion valve 65 is an electronic expansion valve whose opening degree is adjusted according to the control of the control device 100, for example. The expansion valve 65 reduces the pressure of the incoming refrigerant and discharges the refrigerant obtained by the pressure reduction. The control device 100 can adjust the amount of refrigerant pressure reduction and the amount of refrigerant flowing through the expansion valve 65 by controlling the expansion valve 65. For example, the control device 100 can reduce the amount of refrigerant flowing through the expansion valve 65 by reducing its opening degree, and increase the amount of refrigerant flowing through the expansion valve 65 by increasing its opening degree. One end of the expansion valve 65 is connected to the outdoor heat exchanger 50 via piping 16. The other end of the expansion valve 65 is connected to the indoor unit 20 via piping 15 and extension piping 22.

[0026] The indoor unit 20 is generally installed in the indoor space that is to be air-conditioned, and includes an indoor heat exchanger 60 and an indoor fan 61.

[0027] The indoor heat exchanger 60 performs heat exchange between the air drawn in from the room by the indoor fan 61 and the refrigerant. One end of the indoor heat exchanger 60 is connected to the outdoor unit 10 via piping 13 and extension piping 21. The other end of the indoor heat exchanger 60 is connected to the outdoor unit 10 via piping 14 and extension piping 22.

[0028] The indoor fan 61 is configured to operate and stop, and to change its rotational speed during operation, according to the control of the control device 100. The control device 100 controls the indoor fan 61 to arbitrarily change its drive frequency. The indoor fan 61 changes its rotational speed, i.e., the number of rotations per unit time, in accordance with the change in drive frequency, thereby changing the amount of air supplied to the indoor heat exchanger 60.

[0029] The control device 100 comprises a processor 101 and a memory 102. The control device 100 is capable of communicating with each actuator of the refrigerant circuit 3 in order to control each actuator of the refrigerant circuit 3, such as the compressor 30, expansion valve 65, four-way valve 40, outdoor fan 51, and indoor fan 61. The control device 100 may be mounted on either the outdoor unit 10 or the indoor unit 20, or it may be a separate unit from the outdoor unit 10 and the indoor unit 20.

[0030] The processor 101 is a computing unit (computer) that controls each actuator of the refrigerant circuit 3 by executing various programs. The processor 101 is composed of, for example, a microcontroller, a CPU (central processing unit), or an MPU (micro-processing unit). Although the processor 101 has the function of executing various processes by executing programs, some or all of these functions may be implemented using dedicated hardware circuits such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field-Programmable Gate Array). The processor 101 is not limited to a processor in the narrow sense that executes processing in a stored-program manner, such as a CPU or MPU, but may also include hardwired circuits such as ASICs or FPGAs. For this reason, the processor 101 can also be read as a processing circuitry in which processing is predefined by computer-readable code and / or hardwired circuits. The processor 101 may consist of one chip or multiple chips. Furthermore, the processor 101 and associated processing circuits may consist of multiple computers interconnected by wire or wireless means via a local area network or wireless network. The processor 101 and associated processing circuits may also consist of a cloud computer that remotely performs calculations based on input data and outputs the calculation results to other devices located at a distance.

[0031] Memory 102 provides a storage area for storing program code or work memory when the processor 101 executes various programs. Memory 102 may be one or more non-transitory computer-readable media. Examples of memory 102 include volatile memory such as DRAM (dynamic random access memory) and SRAM (static random access memory), or non-volatile memory such as ROM (Read Only Memory) and flash memory. Memory 102 may also be one or more computer-readable storage media. Examples of memory 102 include storage devices such as HDD (Hard Disk Drive) and SSD (Solid State Drive). The processor 101 controls each actuator of the refrigerant circuit 3 by executing the control program 120 stored in memory 102.

[0032] The air conditioner 2 further includes a temperature sensor 91, a temperature sensor 92, a temperature sensor 93, and a pressure sensor 94.

[0033] The temperature sensor 91 is installed between the inlet side of the accumulator 70 and the evaporator, and measures the temperature of the refrigerant flowing into the accumulator 70. The refrigerant temperature T1 measured by the temperature sensor 91 is transmitted to the control device 100. In the air conditioning system 1 according to Embodiment 1, the temperature sensor 91 is an example of a "first temperature sensor". The refrigerant temperature T1 measured by the temperature sensor 91 is an example of a "first measured value".

[0034] The temperature sensor 92 is installed between the outlet side of the accumulator 70 and the inlet 31 of the compressor 30, and measures the temperature of the refrigerant flowing out of the accumulator 70. The refrigerant temperature T2 measured by the temperature sensor 92 is transmitted to the control device 100. In the air conditioning system 1 according to Embodiment 1, the temperature sensor 92 is an example of a "second temperature sensor". The refrigerant temperature T2 measured by the temperature sensor 92 is an example of a "second measured value".

[0035] The temperature sensor 93 is installed between the discharge port 32 of the compressor 30 and the condenser, and measures the temperature of the refrigerant discharged from the compressor 30. The refrigerant temperature T3 measured by the temperature sensor 93 is transmitted to the control device 100.

[0036] The pressure sensor 94 is installed between the discharge port 32 of the compressor 30 and the condenser, and measures the pressure of the refrigerant discharged from the compressor 30. The refrigerant pressure P1 measured by the pressure sensor 94 is transmitted to the control device 100.

[0037] The control device 100 calculates the refrigerant saturation temperature based on the refrigerant pressure P1 measured by the pressure sensor 94, and adjusts the amount of refrigerant flowing through the refrigerant circuit 3 by controlling the drive frequency of the compressor 30 and the opening degree of the expansion valve 65 based on the difference between the calculated refrigerant saturation temperature and the refrigerant temperature T3 measured by the temperature sensor 93.

[0038] As described above, the air conditioner 2 is controlled to one of several operating modes, including a heating mode for heating the indoor space and a cooling mode for cooling the indoor space.

[0039] First, let's explain the operation of the air conditioner 2 in heating mode. As shown by the solid line in Figure 1, in heating mode, the internal communication state of the four-way valve 40 is such that connection port 41 communicates with connection port 42, and connection port 43 communicates with connection port 44. In other words, in heating mode, the intake port 31 of the compressor 30 is connected to the outdoor heat exchanger 50, and the discharge port 32 of the compressor 30 is connected to the indoor heat exchanger 60.

[0040] The compressor 30 draws in low-temperature, low-pressure gaseous refrigerant flowing in from the outdoor heat exchanger 50 and increases the pressure of the gaseous refrigerant by compressing it. The compressor 30 then discharges the high-temperature, high-pressure gaseous refrigerant obtained by compression to the indoor heat exchanger 60.

[0041] In heating mode, the indoor heat exchanger 60 acts as a condenser. The indoor heat exchanger 60 exchanges heat between the high-temperature, high-pressure gaseous refrigerant from the compressor 30 and the air drawn in from the indoor space by the indoor fan 61. The gaseous refrigerant that has released heat into the air through this heat exchange condenses inside the indoor heat exchanger 60, changing into a high-temperature, high-pressure liquid refrigerant. The high-temperature, high-pressure liquid refrigerant obtained from the indoor heat exchanger 60 flows out to the expansion valve 65. The air that has absorbed heat from the gaseous refrigerant in the indoor heat exchanger 60 is sent back into the indoor space. This heats the indoor space.

[0042] The expansion valve 65 reduces the pressure of the high-temperature, high-pressure liquid refrigerant from the indoor heat exchanger 60. The low-temperature, low-pressure gaseous-liquid two-phase refrigerant obtained by the expansion valve 65 flows out to the outdoor heat exchanger 50. The amount of refrigerant flowing out from the expansion valve 65 to the outdoor heat exchanger 50 is regulated by the control device 100.

[0043] In heating mode, the outdoor heat exchanger 50 acts as an evaporator. The outdoor heat exchanger 50 exchanges heat between the low-temperature, low-pressure gaseous two-phase refrigerant from the expansion valve 65 and the air drawn in from outside by the outdoor fan 51. The gaseous two-phase refrigerant that has absorbed heat from the air through this heat exchange evaporates inside the outdoor heat exchanger 50, changing into a low-temperature, low-pressure gaseous refrigerant. The low-temperature, low-pressure gaseous refrigerant obtained from the outdoor heat exchanger 50 flows out to the compressor 30.

[0044] Thus, in heating operation mode, the refrigerant flows in the following order: compressor 30, indoor heat exchanger 60 (condenser), expansion valve 65, and outdoor heat exchanger 50 (evaporator).

[0045] Next, the operation of the air conditioner 2 in cooling mode will be explained. As shown by the dashed line in Figure 1, in cooling mode, the internal communication state of the four-way valve 40 is such that connection port 41 communicates with connection port 44, and connection port 42 communicates with connection port 43. In other words, in cooling mode, the intake port 31 of the compressor 30 is connected to the indoor heat exchanger 60 side, and the discharge port 32 of the compressor 30 is connected to the outdoor heat exchanger 50 side.

[0046] The compressor 30 draws in low-temperature, low-pressure gaseous refrigerant from the indoor heat exchanger 60 and increases the pressure of the gaseous refrigerant by compressing it. The compressor 30 then discharges the high-temperature, high-pressure gaseous refrigerant obtained by compression to the outdoor heat exchanger 50.

[0047] In cooling operation mode, the outdoor heat exchanger 50 acts as a condenser. The outdoor heat exchanger 50 exchanges heat between the high-temperature, high-pressure gaseous refrigerant from the compressor 30 and the air drawn in from outside by the outdoor fan 51. The gaseous refrigerant that has released heat into the air through this heat exchange condenses inside the outdoor heat exchanger 50, changing into a high-temperature, high-pressure liquid refrigerant. The high-temperature, high-pressure liquid refrigerant obtained by the outdoor heat exchanger 50 flows out to the expansion valve 65.

[0048] The expansion valve 65 reduces the pressure of the high-temperature, high-pressure liquid refrigerant from the outdoor heat exchanger 50. The low-temperature, low-pressure gaseous-liquid two-phase refrigerant obtained by the pressure reduction of the expansion valve 65 flows out into the indoor heat exchanger 60. The amount of refrigerant flowing out from the expansion valve 65 into the indoor heat exchanger 60 is regulated by the control device 100.

[0049] In cooling mode, the indoor heat exchanger 60 acts as an evaporator. The indoor heat exchanger 60 exchanges heat between the low-temperature, low-pressure gaseous two-phase refrigerant from the expansion valve 65 and the air drawn in from the room by the indoor fan 61. The gaseous two-phase refrigerant that has absorbed heat from the air through this heat exchange evaporates inside the indoor heat exchanger 60, changing into a low-temperature, low-pressure gaseous refrigerant. The low-temperature, low-pressure gaseous refrigerant obtained from the indoor heat exchanger 60 flows out to the compressor 30. The air that has absorbed heat from the gaseous refrigerant in the indoor heat exchanger 60 is then sent back into the room. This cools the room.

[0050] Thus, in cooling operation mode, the refrigerant flows in the following order: compressor 30, outdoor heat exchanger 50 (condenser), expansion valve 65, and indoor heat exchanger 60 (evaporator).

[0051] Generally, the amount of refrigerant required during heating operation is less than the amount required during cooling operation. Therefore, the amount of refrigerant filled into the refrigerant circuit 3 of the air conditioner 2 is determined based on the amount of refrigerant required during cooling operation, and during heating operation, excess refrigerant that is not used for heating operation may be generated. To address this, the air conditioner 2 is further equipped with an accumulator 70 between the compressor 30 and the evaporator, and is configured to store excess refrigerant using the accumulator 70. As shown in Figure 2, in heating operation mode, the accumulator 70 is located between the compressor 30 and the outdoor heat exchanger 50. In cooling operation mode, the accumulator 70 is located between the compressor 30 and the indoor heat exchanger 60.

[0052] [Accumulator Configuration] The configuration of the accumulator 70 according to Embodiment 1 will be described with reference to Figure 3. Figure 3 is a diagram illustrating the internal configuration of the accumulator 70 according to Embodiment 1. As shown in Figure 3, the accumulator 70 comprises a container 71, an inlet pipe 72, and an outlet pipe 73.

[0053] The inlet pipe 72 is configured to be connectable to the piping 18 connected to the evaporator, and introduces the refrigerant flowing from the evaporator into the container 71 via the piping 18. Of the refrigerant introduced by the inlet pipe 72, the liquid refrigerant is stored in the lower part of the container 71, and the gaseous refrigerant is retained in the upper part of the container 71.

[0054] The outlet pipe 73 is configured to be connectable to the piping 19 connected to the compressor 30, and introduces the refrigerant accumulated in the container 71 to the suction port 31 of the compressor 30 via the piping 19. The outlet pipe 73 is U-shaped and has a gas suction port 73a for drawing in gaseous refrigerant accumulated at the top of the container 71 and a liquid suction port 73b for drawing in liquid refrigerant accumulated at the bottom of the container 71. The gaseous refrigerant drawn in from the gas suction port 73a flows out through the outlet pipe 73 to the suction port 31 of the compressor 30. The liquid refrigerant drawn in from the liquid suction port 73b flows out through the outlet pipe 73 to the suction port 31 of the compressor 30. Since the diameter of the liquid suction port 73b is smaller than the diameter of the outlet pipe 73, only a very small amount of liquid refrigerant is drawn in from the liquid suction port 73b.

[0055] The accumulator 70, configured as described above, separates the refrigerant flowing through the refrigerant circuit 3 into liquid and gaseous refrigerant by accumulating the liquid refrigerant at the bottom of the container 71 while retaining the gaseous refrigerant at the top of the container 71, thereby allowing the liquid refrigerant to be stored in the container 71. The liquid refrigerant stored in the container 71 flows in very small amounts into the outlet pipe 73 through the liquid inlet 73b located in the liquid refrigerant, and is returned through the outlet pipe 73 to the inlet 31 of the compressor 30.

[0056] When installing an air conditioner 2, workers may fill the refrigerant circuit 3 with refrigerant, or they may add refrigerant to the refrigerant circuit 3 of an already installed air conditioner 2. At this time, workers can determine whether the appropriate amount of refrigerant has been filled into the refrigerant circuit 3 by checking the amount of liquid refrigerant stored in the accumulator 70. In addition, workers can determine whether there is a refrigerant leak in the refrigerant circuit 3 of an already installed air conditioner 2 by checking the amount of liquid refrigerant stored in the accumulator 70.

[0057] In an air conditioning system 1 that combines multiple outdoor units 10 and at least one indoor unit 20, the refrigerant may be unevenly distributed among the multiple outdoor units 10 depending on the operating status of each of the multiple outdoor units 10. For example, the amount of refrigerant stored in the accumulator 70 may differ between outdoor unit 10A and the other outdoor units 10B and 10C. If the amount of refrigerant stored in the accumulator 70 becomes excessively large, a large amount of liquid refrigerant will flow into the compressor 30 due to liquid back, which may increase the burden on the workers inspecting the compressor 30. On the other hand, if the amount of refrigerant stored in the accumulator 70 becomes excessively small, there will be insufficient refrigerant flowing through the refrigerant circuit, reducing the cooling or heating capacity, which may cause discomfort to users in the indoor space.

[0058] Therefore, the air conditioning system 1 according to Embodiment 1 is configured to adjust the amount of liquid refrigerant stored in each of the accumulators 70 of the multiple outdoor units 10 by performing a refrigerant amount adjustment process.

[0059] Specifically, in the air conditioning system 1, one of the control devices 100 that control each of the multiple outdoor units 10 functions as a central control device. For example, control device 100A, which controls outdoor unit 10A, can control not only outdoor unit 10A but also outdoor units 10B and 10C by communicating with control device 100B, which controls outdoor unit 10B, and control device 100C, which controls outdoor unit 10C. Note that the central control device is not limited to control device 100A, but may be control device 100B or control device 100C, or it may be a different control device (not shown) from control devices 100A, 100B, and 100C. Below, an example in which control device 100A functions as a central control device will be described.

[0060] During heating operation, when the amount of refrigerant stored in the accumulator 70 is greater than during cooling operation, the control device 100A adjusts the amount of liquid refrigerant stored in each of the multiple outdoor units 10 by performing a refrigerant amount adjustment process according to the control program 120. Specifically, for each of the multiple outdoor units 10A, 10B, and 10C, the control device 100A calculates the difference value dT between the refrigerant temperature T1 measured by the temperature sensor 91 and the refrigerant temperature T2 measured by the temperature sensor 92. The difference value dT between refrigerant temperature T1 and refrigerant temperature T2 is roughly proportional to the amount of refrigerant stored in the accumulator 70. Therefore, the control device 100A controls the multiple outdoor units 10A, 10B, and 10C so that the difference value dT for each of the multiple outdoor units 10A, 10B, and 10C is equal. The control device 100A may also control the multiple outdoor units 10A, 10B, and 10C so that the difference between the difference values ​​dT in each of the multiple outdoor units 10A, 10B, and 10C falls within a predetermined range.

[0061] For example, control device 100A obtains the refrigerant temperature T1 measured by temperature sensor 91 and the refrigerant temperature T2 measured by temperature sensor 92 at the outdoor unit 10A, and calculates the difference value dTA by subtracting the refrigerant temperature T2 from the refrigerant temperature T1. Control device 100B obtains the refrigerant temperature T1 measured by temperature sensor 91 and the refrigerant temperature T2 measured by temperature sensor 92 at the outdoor unit 10B, and calculates the difference value dTB by subtracting the refrigerant temperature T2 from the refrigerant temperature T1. Control device 100B transmits the calculated difference value dTB to control device 100A. Control device 100C obtains the refrigerant temperature T1 measured by temperature sensor 91 and the refrigerant temperature T2 measured by temperature sensor 92 at the outdoor unit 10C, and calculates the difference value dTC by subtracting the refrigerant temperature T2 from the refrigerant temperature T1. Control device 100C transmits the calculated difference value dTC to control device 100A. The control unit 100A, which is the central control unit, obtains the difference value dTB from control unit 100B and the difference value dTC from control unit 100C. Alternatively, control unit 100A may obtain the refrigerant temperature T1 and refrigerant temperature T2 at the outdoor unit 10B via control unit 100B and calculate the difference value dTB by subtracting refrigerant temperature T2 from refrigerant temperature T1. Alternatively, control unit 100A may obtain the refrigerant temperature T1 and refrigerant temperature T2 at the outdoor unit 10C via control unit 100C and calculate the difference value dTC by subtracting refrigerant temperature T2 from refrigerant temperature T1.

[0062] The control device 100A compares the difference value dTA in outdoor unit 10A, the difference value dTB in outdoor unit 10B, and the difference value dTC in outdoor unit 10C. If there is an uneven distribution of the difference value dT in each of the outdoor units 10A, 10B, and 10C, the control device 100A controls the multiple outdoor units 10A, 10B, and 10C so that the difference values ​​dTA, dTB, and dTC become equal.

[0063] Specifically, the control device 100A reduces the opening degree of the expansion valve 65 in at least one of the multiple outdoor units 10A, 10B, and 10C. For example, if the difference value dTA in outdoor unit 10A is 10°C, the difference value dTB in outdoor unit 10B is 2°C, and the difference value dTC in outdoor unit 10C is 2°C, the control device 100A assumes that the accumulator 70 of the outdoor unit 10 having a different difference value dT from the other outdoor units 10, in this example, the outdoor unit 10A having the largest difference value dT, stores more liquid refrigerant than the accumulator 70 of outdoor unit 10B and the accumulator 70 of outdoor unit 10C. Therefore, the control device 100A reduces the amount of refrigerant flowing through the refrigerant circuit 3 of outdoor unit 10A by reducing the opening degree of the expansion valve 65 in outdoor unit 10A.

[0064] The control device 100A may also reduce the amount of refrigerant flowing through the refrigerant circuit 3 of outdoor unit 10A by reducing the drive frequency of the compressor 30 in at least one of the multiple outdoor units 10A, 10B, and 10C.

[0065] As a result, the control device 100A can reduce the amount of refrigerant flowing into the accumulator 70 of the outdoor unit 10A to less than the amount of refrigerant stored in the accumulator 70 of the outdoor unit 10A and flowing out of the accumulator 70, thereby gradually reducing the amount of refrigerant stored in the accumulator 70 of the outdoor unit 10A. On the other hand, the refrigerant that flows out of the accumulator 70 of the outdoor unit 10A flows into the other outdoor units 10B and 10C and is stored in the respective accumulators 70 of the outdoor units 10B and 10C, thereby gradually increasing the amount of refrigerant stored in the respective accumulators 70 of the outdoor units 10B and 10C. As a result, the control device 100A can equalize the amount of liquid refrigerant stored in the respective accumulators 70 of the multiple outdoor units 10A, 10B, and 10C.

[0066] Thus, in the air conditioning system 1, in addition to controlling the drive frequency of the compressor 30 and the opening degree of the expansion valve 65 in each outdoor unit 10 based on the refrigerant saturation temperature and refrigerant temperature T3 calculated from the refrigerant pressure P1, the drive frequency of the compressor 30 and the opening degree of the expansion valve 65 are controlled based on a difference value dT that takes into account the entire set of multiple outdoor units 10 that are combined to circulate the refrigerant. This makes it possible to equalize the amount of refrigerant stored in each of the accumulators 70 of the multiple outdoor units 10A, 10B, and 10C, taking into account the balance of the total amount of refrigerant in the air conditioning system 1.

[0067] [Refrigerant quantity adjustment process] Referring to Figure 4, the specific flow of the refrigerant quantity adjustment process performed by the control device 100A, which is the central control device, will be explained. Figure 4 is a flowchart for explaining the refrigerant quantity adjustment process performed by the control device 100A according to Embodiment 1. The control device 100A performs the refrigerant quantity adjustment process shown in the flowchart of Figure 4 by, for example, having the processor 101 execute the control program 120 stored in the memory 102. In the figure, "S" is used as an abbreviation for "STEP".

[0068] As shown in Figure 4, the control device 100A determines whether or not heating operation is in progress (S1). If heating operation is not in progress (NO in S1), the control device 100A terminates the refrigerant amount adjustment process.

[0069] On the other hand, if heating operation is in progress (YES in S1), the control device 100A determines whether or not it has obtained the refrigerant temperature T1 measured by the temperature sensor 91 from one of the multiple outdoor units 10A, 10B, or 10C (S2).

[0070] If the control device 100A has not obtained the refrigerant temperature T1 measured by the temperature sensor 91 from any of the multiple outdoor units 10A, 10B, or 10C (NO in S2), it repeats the process in S2.

[0071] On the other hand, if the control device 100A obtains the refrigerant temperature T1 measured by the temperature sensor 91 from one of the multiple outdoor units 10A, 10B, or 10C (YES in S2), it stores the obtained refrigerant temperature T1 in the memory 102 (S3).

[0072] The control device 100A determines whether or not it has obtained the refrigerant temperature T2 measured by the temperature sensor 92 from one of the multiple outdoor units 10A, 10B, or 10C (S4). If the control device 100A has not obtained the refrigerant temperature T2 measured by the temperature sensor 92 from any of the multiple outdoor units 10A, 10B, or 10C (NO in S4), it repeats the process in S4.

[0073] On the other hand, if the control device 100A obtains the refrigerant temperature T2 measured by the temperature sensor 92 from one of the multiple outdoor units 10A, 10B, or 10C (YES in S4), it stores the obtained refrigerant temperature T2 in the memory 102 (S5).

[0074] The control device 100A calculates the difference value dT for each of the multiple outdoor units 10A, 10B, and 10C by subtracting the refrigerant temperature T2 from the refrigerant temperature T1 stored in the memory 102 (S6). The control device 100A determines whether or not the difference value dT has been calculated for all of the outdoor units 10A, 10B, and 10C (S7). If the control device 100A has not calculated the difference value dT for all of the outdoor units 10A, 10B, and 10C (NO in S7), it returns to the process in S2.

[0075] On the other hand, if the control device 100A calculates the difference value dT for all outdoor units 10A, 10B, and 10C (YES in S7), it compares the difference value dTA for outdoor unit 10A, the difference value dTB for outdoor unit 10B, and the difference value dTC for outdoor unit 10C (S8). For example, the control device 100A compares the difference value dTA, the difference value dTB, and the difference value dTC by calculating the difference between the difference value dTA and the difference value dTB, the difference between the difference value dTA and the difference value dTC, and the difference between the difference value dTB and the difference value dTC.

[0076] The control device 100A determines whether there is an imbalance between the difference values ​​dTA, dTB, and dTC (S9). That is, the control device 100A determines whether the difference values ​​dTA, dTB, and dTC are different. The control device 100A may also determine whether the difference between the difference values ​​dTA, dTB, and dTC exceeds a predetermined range. If there is no imbalance between the difference values ​​dTA, dTB, and dTC (NO in S9), the control device 100A assumes that there is no imbalance in the amount of refrigerant stored by the respective accumulators 70 of the outdoor units 10A, 10B, and 10C, and terminates the refrigerant amount adjustment process.

[0077] On the other hand, if there is an uneven distribution between the difference value dTA, the difference value dTB, and the difference value dTC (YES in S9), the control device 100A reduces the opening degree of the expansion valve 65 in at least one of the multiple outdoor units 10A, 10B, and 10C (S10).

[0078] The control device 100A gradually reduces the opening of the expansion valve 65 in at least one outdoor unit 10 until the opening of the expansion valve 65 is minimized (for example, fully closed, opening = 0), and then it determines again whether there is an imbalance between the difference values ​​dTA, dTB, and dTC (S11). When the opening of the expansion valve 65 is minimized, if there is no imbalance between the difference values ​​dTA, dTB, and dTC (NO in S11), the control device 100A assumes that there is no imbalance in the amount of refrigerant stored by the respective accumulators 70 of the outdoor units 10A, 10B, and 10C, and terminates the refrigerant amount adjustment process.

[0079] On the other hand, if the control device 100A finds that there is an imbalance between the difference values ​​dTA, dTB, and dTC even when the opening of the expansion valve 65 is minimized (YES in S11), it reduces the drive frequency of the compressor 30 in at least one outdoor unit 10 (S12).

[0080] After reducing the drive frequency of the compressor 30 in at least one outdoor unit 10, the control device 100A again determines whether there is an imbalance between the difference values ​​dTA, dTB, and dTC (S13). That is, the control device 100A determines whether the difference values ​​dTA, dTB, and dTC are different. The control device 100A may also determine whether the difference between the difference values ​​dTA, dTB, and dTC exceeds a predetermined range. If the control device 100A still finds an imbalance between the difference values ​​dTA, dTB, and dTC even after reducing the drive frequency of the compressor 30 in at least one outdoor unit 10 (YES in S13), it repeats the process in S12 to further reduce the drive frequency of the compressor 30 in at least one outdoor unit 10.

[0081] On the other hand, if the control device 100A reduces the drive frequency of the compressor 30 in at least one outdoor unit 10 and there is no longer any unevenness between the difference values ​​dTA, dTB, and dTC (NO in S13), it assumes that there is no unevenness in the amount of refrigerant stored by the respective accumulators 70 of the outdoor units 10A, 10B, and 10C, and terminates the refrigerant amount adjustment process.

[0082] As described above, according to the air conditioning system 1 of Embodiment 1, the control device 100A, which is the central control device, calculates the difference value dT between the refrigerant temperature T1 of the refrigerant flowing into the accumulator 70 of each of the multiple outdoor units 10A, 10B, and 10C and the refrigerant temperature T2 of the refrigerant flowing out of the accumulator. Based on the difference value dT, it can adjust the amount of liquid refrigerant stored in each of the multiple outdoor units 10A, 10B, and 10C's accumulator 70, thereby preventing uneven distribution of refrigerant among the multiple outdoor units 10A, 10B, and 10C. This prevents an excessive amount of refrigerant from being stored in the accumulator 70, which would cause a large amount of liquid refrigerant to flow into the compressor 30 due to liquid backflow, thus preventing an increased burden on workers inspecting the compressor 30. Furthermore, it prevents an excessive amount of refrigerant from being stored in the accumulator 70, which would result in insufficient refrigerant flowing through the refrigerant circuit 3 and a decrease in cooling or heating capacity, thus preventing discomfort to the user. This reduces the burden on workers and avoids causing discomfort to users.

[0083] Embodiment 2. The air conditioning system 1 according to Embodiment 2 will now be described. In the air conditioning system 1 according to Embodiment 1, a temperature sensor 92 was used as the "second temperature sensor" and the refrigerant temperature T2 was used as the "second measured value". However, in the air conditioning system 1 according to Embodiment 2, a temperature sensor 93 is used as the "second temperature sensor" and the refrigerant temperature T3 is used as the "second measured value".

[0084] Specifically, the control device 100A calculates the difference value dT between the refrigerant temperature T1 measured by the temperature sensor 91 and the refrigerant temperature T3 measured by the temperature sensor 93 in each of the multiple outdoor units 10A, 10B, and 10C. The difference value dT between the refrigerant temperature T1 and the refrigerant temperature T3 is roughly proportional to the amount of refrigerant stored in the accumulator 70. Therefore, the control device 100A adjusts the amount of liquid refrigerant stored in the accumulator 70 of each of the multiple outdoor units 10A, 10B, and 10C so that the difference value dT in each of the multiple outdoor units 10A, 10B, and 10C is equal.

[0085] For example, control device 100A acquires the refrigerant temperature T1 measured by temperature sensor 91 and the refrigerant temperature T3 measured by temperature sensor 93 at the outdoor unit 10A, and calculates the difference value dTA by subtracting the refrigerant temperature T3 from the refrigerant temperature T1. Control device 100B acquires the refrigerant temperature T1 measured by temperature sensor 91 and the refrigerant temperature T3 measured by temperature sensor 93 at the outdoor unit 10B, and calculates the difference value dTB by subtracting the refrigerant temperature T3 from the refrigerant temperature T1. Control device 100B transmits the calculated difference value dTB to control device 100A. Control device 100C acquires the refrigerant temperature T1 measured by temperature sensor 91 and the refrigerant temperature T3 measured by temperature sensor 92 at the outdoor unit 10C, and calculates the difference value dTC by subtracting the refrigerant temperature T3 from the refrigerant temperature T1. Control device 100C transmits the calculated difference value dTC to control device 100A. The control unit 100A, which is the central control unit, obtains the difference value dTB from control unit 100B and the difference value dTC from control unit 100C. Alternatively, control unit 100A may obtain the refrigerant temperature T1 and refrigerant temperature T3 at the outdoor unit 10B via control unit 100B and calculate the difference value dTB by subtracting refrigerant temperature T3 from refrigerant temperature T1. Alternatively, control unit 100A may obtain the refrigerant temperature T1 and refrigerant temperature T3 at the outdoor unit 10C via control unit 100C and calculate the difference value dTC by subtracting refrigerant temperature T3 from refrigerant temperature T1.

[0086] The control device 100A compares the difference value dTA in outdoor unit 10A, the difference value dTB in outdoor unit 10B, and the difference value dTC in outdoor unit 10C. If there is an uneven distribution of the difference values ​​dT in each of the outdoor units 10A, 10B, and 10C, the control device 100A reduces the opening degree of the expansion valve 65 in at least one outdoor unit 10 or reduces the drive frequency of the compressor 30 in at least one outdoor unit 10 so that the difference values ​​dTA, dTB, and dTC become equal.

[0087] For example, if the difference value dTA in outdoor unit 10A is 70°C, the difference value dTB in outdoor unit 10B is 60°C, and the difference value dTC in outdoor unit 10C is 70°C, the control device 100A determines that the accumulator 70 of outdoor unit 10 with a different difference value dT from the other outdoor units 10, in this example, outdoor unit 10B with the smallest difference value dT, has more liquid refrigerant stored in it than the accumulator 70 of outdoor unit 10A and the accumulator 70 of outdoor unit 10C. In this case, the control device 100A reduces the amount of refrigerant flowing through the refrigerant circuit 3 of outdoor unit 10B by reducing the opening of the expansion valve 65 in outdoor unit 10B or by reducing the drive frequency of the compressor 30 in outdoor unit 10B.

[0088] Even with the configuration described above, according to the air conditioning system 1 of Embodiment 2, the amount of liquid refrigerant stored by each accumulator 70 of the multiple outdoor units 10A, 10B, and 10C can be adjusted based on the difference value dT, thereby preventing uneven distribution of refrigerant among the multiple outdoor units 10A, 10B, and 10C.

[0089] [summary] The air conditioning system 1 according to this disclosure comprises a plurality of outdoor units 10 (10A, 10B, 10C) and a control device 100 (100A, 100B, 100C). The plurality of outdoor units 10 are configured to circulate a refrigerant between them and at least one indoor unit 20. Each of the plurality of outdoor units 10 comprises a compressor 30, a condenser (e.g., an indoor heat exchanger 60), an expansion valve 65, and an evaporator (e.g., an outdoor heat exchanger 50), and a refrigerant circuit 3 configured to circulate the refrigerant; an accumulator 70 positioned between the compressor 30 and the evaporator (e.g., the outdoor heat exchanger 50) which separates the refrigerant flowing through the refrigerant circuit 3 into liquid refrigerant and gaseous refrigerant and stores the liquid refrigerant; a temperature sensor 91 which measures the temperature of the refrigerant flowing into the accumulator 70; and temperature sensors 92, 93 which measure the temperature of the refrigerant flowing out of the accumulator 70. The control device 100 calculates the difference between the first measurement value of the temperature sensor 91 and the second measurement value of the temperature sensors 92 and 93 in each of the multiple outdoor units 10, and adjusts the amount of liquid refrigerant stored by the accumulator 70 of each of the multiple outdoor units 10 based on the difference value.

[0090] According to the above configuration, in the air conditioning system 1, the control device 100 calculates the difference between a first measurement of the temperature of the refrigerant flowing into the accumulator 70 of each of the multiple outdoor units 10 and a second measurement of the temperature of the refrigerant flowing out of the accumulator 70. Based on this difference, the control device can adjust the amount of liquid refrigerant stored in each of the multiple outdoor units 10's accumulators 70, thereby preventing uneven distribution of refrigerant among the multiple outdoor units 10. This reduces the burden on workers and avoids causing discomfort to users.

[0091] The control device 100 reduces the opening degree of the expansion valve 65 of at least one of the multiple outdoor units 10 so that the difference values ​​in each of the multiple outdoor units 10 are equal.

[0092] According to the above configuration, the control device 100 can equalize the amount of liquid refrigerant stored by the accumulator 70 of each of the multiple outdoor units 10 by reducing the opening degree of the expansion valve 65 of at least one of the multiple outdoor units 10 and making the difference value equal for each of the multiple outdoor units 10.

[0093] The control device 100 reduces the drive frequency of the compressor 30 of at least one of the multiple outdoor units 10 so that the difference values ​​in each of the multiple outdoor units 10 are equal.

[0094] According to the above configuration, the control device 100 can equalize the amount of liquid refrigerant stored by the accumulator 70 of each of the multiple outdoor units 10 by reducing the drive frequency of the compressor 30 of at least one of the multiple outdoor units 10 and making the difference value equal for each of the multiple outdoor units 10.

[0095] If the control device 100 finds that the difference values ​​differ for each of the multiple outdoor units 10 even when the opening degree of the expansion valve 65 of at least one outdoor unit 10 is set to the minimum, it reduces the drive frequency of the compressor 30 of at least one outdoor unit 10.

[0096] According to the above configuration, if the difference values ​​in each of the multiple outdoor units 10 are different even when the opening degree of the expansion valve 65 of at least one of the multiple outdoor units 10 is set to the minimum, the control device 100 can equalize the difference values ​​in each of the multiple outdoor units 10 by reducing the drive frequency of the compressor 30 of at least one of the multiple outdoor units 10.

[0097] During heating operation, the control device adjusts the amount of liquid refrigerant stored by each of the accumulators 70 of the multiple outdoor units 10 based on the difference value.

[0098] With the above configuration, the control device 100 can adjust the amount of liquid refrigerant stored in each of the accumulators 70 of the multiple outdoor units 10 during heating operation, when the amount of refrigerant stored in the accumulator 70 is greater than during cooling operation.

[0099] The temperature sensor 92 is located between the compressor 30 and the accumulator 70. According to the above configuration, the control device 100 can adjust the amount of liquid refrigerant stored in each of the accumulators 70 of the multiple outdoor units 10 based on the temperature difference of the refrigerant generated by the accumulators 70.

[0100] The temperature sensor 93 is located between the compressor 30 and the condenser (for example, the indoor heat exchanger 60).

[0101] According to the above configuration, the control device 100 can adjust the amount of liquid refrigerant stored in each of the accumulators 70 of the multiple outdoor units 10 based on the temperature difference of the refrigerant generated by the accumulator 70 and the compressor 30.

[0102] The control device 100 (100A, 100B, 100C) according to this disclosure comprises a processor 101 and a memory 102 for storing a control program 120 executed by the processor 101. The plurality of outdoor units 10 are configured to circulate a refrigerant between them and at least one indoor unit 20. Each of the plurality of outdoor units 10 comprises a compressor 30, a condenser (e.g., an indoor heat exchanger 60), an expansion valve 65, and an evaporator (e.g., an outdoor heat exchanger 50), and a refrigerant circuit 3 configured to circulate the refrigerant; an accumulator 70 positioned between the compressor 30 and the evaporator (e.g., the outdoor heat exchanger 50) which separates the refrigerant flowing through the refrigerant circuit 3 into liquid refrigerant and gaseous refrigerant and stores the liquid refrigerant; a temperature sensor 91 for measuring the temperature of the refrigerant flowing into the accumulator 70; and temperature sensors 92, 93 for measuring the temperature of the refrigerant flowing out of the accumulator 70. The processor 101 calculates the difference between the first measurement value of the temperature sensor 91 and the second measurement value of the temperature sensors 92 and 93 in each of the multiple outdoor units 10, and adjusts the amount of liquid refrigerant stored by the accumulator 70 in each of the multiple outdoor units 10 based on the difference value.

[0103] With the above configuration, the control device 100 calculates the difference between a first measurement of the temperature of the refrigerant flowing into the accumulator 70 of each of the multiple outdoor units 10 and a second measurement of the temperature of the refrigerant flowing out of the accumulator 70. Based on this difference, the control device 100 can adjust the amount of liquid refrigerant stored in each of the multiple outdoor units 10's accumulators 70, thereby preventing uneven distribution of refrigerant among the multiple outdoor units 10. This reduces the burden on workers and avoids causing discomfort to users.

[0104] The control method according to this disclosure is a method for controlling a plurality of outdoor units 10 by a processor 101. The plurality of outdoor units 10 are configured to circulate a refrigerant between at least one indoor unit 20. Each of the plurality of outdoor units 10 includes a compressor 30, a condenser (e.g., an indoor heat exchanger 60), an expansion valve 65, and an evaporator (e.g., an outdoor heat exchanger 50), and a refrigerant circuit 3 configured to circulate the refrigerant; an accumulator 70 positioned between the compressor 30 and the evaporator (e.g., the outdoor heat exchanger 50) which separates the refrigerant flowing through the refrigerant circuit 3 into liquid refrigerant and gaseous refrigerant and stores the liquid refrigerant; a temperature sensor 91 which measures the temperature of the refrigerant flowing into the accumulator 70; and temperature sensors 92, 93 which measure the temperature of the refrigerant flowing out of the accumulator 70. The control method includes the steps of: calculating the difference between a first measurement value from temperature sensor 91 and a second measurement value from temperature sensors 92 and 93 in each of the multiple outdoor units 10, as a process executed by the processor 101; and adjusting the amount of liquid refrigerant stored by the accumulator 70 of each of the multiple outdoor units 10 based on the difference value.

[0105] According to the above configuration, the processor 101 calculates the difference between a first measurement of the temperature of the refrigerant flowing into the accumulator 70 in each of the multiple outdoor units 10 and a second measurement of the temperature of the refrigerant flowing out of the accumulator 70. Based on this difference, the processor can adjust the amount of liquid refrigerant stored in each of the multiple outdoor units 10's accumulators 70, thereby preventing uneven distribution of refrigerant among the multiple outdoor units 10. This reduces the burden on workers and avoids causing discomfort to users.

[0106] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope of the claims are intended to be included. [Explanation of symbols]

[0107] 1 Air conditioning system, 2 Air conditioner, 3 Refrigerant circuit, 10, 10A, 10B, 10C Outdoor unit, 11, 12, 13, 14, 15, 16, 17, 18, 19 Piping, 20 Indoor unit, 21, 22 Extension piping, 30 Compressor, 31 Inlet, 32 Outlet, 40 Four-way valve, 41, 42, 43, 44 Connection port, 50 Outdoor heat exchanger, 51 Outdoor fan, 60 Indoor heat exchanger, 61 Indoor fan, 65 Expansion valve, 70 Accumulator, 71 Container, 72 Inlet pipe, 73 Outlet pipe, 73a Gas inlet, 73b Liquid inlet, 91, 92, 93 Temperature sensor, 94 Pressure sensor, 100, 100A, 100B, 100C Control device, 101 Processor, 102 Memory, 120 control programs.

Claims

1. It is an air conditioning system, Multiple outdoor units, Equipped with a control device, The aforementioned plurality of outdoor units are configured to circulate refrigerant between them and at least one indoor unit. Each of the aforementioned multiple outdoor units is A refrigerant circuit comprising a compressor, condenser, expansion valve, and evaporator, configured to circulate the refrigerant, An accumulator is positioned between the compressor and the evaporator, separating the refrigerant flowing through the refrigerant circuit into liquid refrigerant and gaseous refrigerant, and storing the liquid refrigerant. A first temperature sensor for measuring the temperature of the refrigerant flowing into the accumulator, The system includes a second temperature sensor for measuring the temperature of the refrigerant flowing out of the accumulator, The control device is The difference between the first measurement value of the first temperature sensor and the second measurement value of the second temperature sensor in each of the plurality of outdoor units is calculated. An air conditioning system that adjusts the amount of liquid refrigerant stored by the accumulator of each of the plurality of outdoor units so that the difference values ​​in each of the plurality of outdoor units are equal.

2. The air conditioning system according to claim 1, wherein the control device reduces the opening degree of the expansion valve of at least one of the plurality of outdoor units so that the difference values ​​in each of the plurality of outdoor units are equal.

3. The air conditioning system according to claim 1 or 2, wherein the control device reduces the drive frequency of the compressor of at least one of the plurality of outdoor units so that the difference values ​​in each of the plurality of outdoor units are equal.

4. The air conditioning system according to claim 2, wherein the control device reduces the drive frequency of the compressor of the at least one outdoor unit if the difference value differs in each of the plurality of outdoor units even when the opening degree of the expansion valve of the at least one outdoor unit is set to the minimum.

5. The air conditioning system according to any one of claims 1 to 4, wherein the control device adjusts the amount of liquid refrigerant stored by the accumulator of each of the plurality of outdoor units based on the difference value during heating operation.

6. The air conditioning system according to any one of claims 1 to 5, wherein the second temperature sensor is located between the compressor and the accumulator.

7. The air conditioning system according to any one of claims 1 to 5, wherein the second temperature sensor is located between the compressor and the condenser.

8. The air conditioning system according to claim 1, wherein the control device reduces the opening degree of the expansion valve of the outdoor unit having the largest difference value among the plurality of outdoor units, thereby making the difference values ​​equal in each of the plurality of outdoor units.

9. A control device for controlling multiple outdoor units, Processor and The system includes a memory for storing a control program executed by the processor, The aforementioned plurality of outdoor units are configured to circulate refrigerant between them and at least one indoor unit. Each of the aforementioned multiple outdoor units is A refrigerant circuit comprising a compressor, condenser, expansion valve, and evaporator, configured to circulate the refrigerant, An accumulator is positioned between the compressor and the evaporator, separating the refrigerant flowing through the refrigerant circuit into liquid refrigerant and gaseous refrigerant, and storing the liquid refrigerant. A first temperature sensor for measuring the temperature of the refrigerant flowing into the accumulator, The system includes a second temperature sensor for measuring the temperature of the refrigerant flowing out of the accumulator, The aforementioned processor, The difference between the first measurement value of the first temperature sensor and the second measurement value of the second temperature sensor in each of the plurality of outdoor units is calculated. A control device that adjusts the amount of liquid refrigerant stored by the accumulator of each of the plurality of outdoor units so that the difference values ​​in each of the plurality of outdoor units are equal.

10. A control method for controlling multiple outdoor units using a processor, The aforementioned plurality of outdoor units are configured to circulate refrigerant between them and at least one indoor unit. Each of the aforementioned multiple outdoor units is A refrigerant circuit comprising a compressor, condenser, expansion valve, and evaporator, configured to circulate the refrigerant, An accumulator is positioned between the compressor and the evaporator, separating the refrigerant flowing through the refrigerant circuit into liquid refrigerant and gaseous refrigerant, and storing the liquid refrigerant. A first temperature sensor for measuring the temperature of the refrigerant flowing into the accumulator, The system includes a second temperature sensor for measuring the temperature of the refrigerant flowing out of the accumulator, The control method described above is The process that the aforementioned processor will perform is as follows: The steps include calculating the difference between the first measurement value of the first temperature sensor and the second measurement value of the second temperature sensor in each of the plurality of outdoor units, A control method comprising the step of adjusting the amount of liquid refrigerant stored by the accumulator of each of the plurality of outdoor units so that the difference values ​​in each of the plurality of outdoor units are equal.

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