Air conditioner and air conditioning system

Abstract

This air conditioner (1) comprises: a refrigerant circuit (200) that comprises a compressor (30), a condenser (60), at least one expansion valve (65), and an evaporator (50), and is configured so as to circulate a refrigerant; a control device (100) that controls the refrigerant circuit; an accumulator (70) that causes the refrigerant flowing through the refrigerant circuit to separate into a liquid refrigerant and a gas refrigerant, and stores the liquid refrigerant; a first temperature sensor (91) that measures the temperature of the refrigerant flowing into the accumulator; and a second temperature sensor (92) that measures the temperature of the refrigerant flowing out of the accumulator. The accumulator is disposed between the compressor and the evaporator. The control device calculates the amount of the liquid refrigerant stored in the accumulator on the basis of a first measurement result of the first temperature sensor and a second measurement result of the second temperature sensor.

Description

Air conditioners and air conditioning systems

[0001] The present disclosure relates to an air conditioner and an air conditioning system.

[0002] An air conditioner is configured to cool or heat a room by circulating a refrigerant through a refrigerant circuit. Generally, the amount of refrigerant required for heating operation is less than the amount required for cooling operation. Therefore, the amount of refrigerant charged into the refrigerant circuit of the air conditioner is determined based on the amount of refrigerant required for cooling operation. Excess refrigerant not used during heating operation is stored in an accumulator located between the compressor and evaporator that make up the refrigerant circuit. By checking the amount of refrigerant stored in the accumulator, a worker installing or inspecting the air conditioner can determine whether the amount of refrigerant circulating through the refrigerant circuit is appropriate.

[0003] International Publication No. 2019 / 065242 (Patent Document 1) discloses a liquid level detection sensor for detecting the liquid level of a refrigerant stored in an accumulator. This liquid level detection sensor is configured to heat the accumulator with a heater and measure the surface temperature of the accumulator with multiple temperature sensors provided in the height direction of the accumulator. The liquid level detection sensor detects the liquid level of the refrigerant stored in the accumulator based on differences in temperature changes according to the state of the refrigerant in the accumulator.

[0004] International Publication No. 2019 / 065242

[0005] While the liquid level detection sensor disclosed in International Publication No. 2019 / 065242 can detect the amount of refrigerant stored in the accumulator, it requires a heater and multiple temperature sensors to be specially installed in the accumulator, which increases costs. Therefore, there is a need for a technology that allows workers installing or inspecting air conditioners to check the amount of refrigerant stored in the accumulator more inexpensively.

[0006] The present disclosure has been made to solve the above-mentioned problem, and aims to provide a technology that allows workers to check the amount of refrigerant stored in an accumulator more inexpensively.

[0007] The air conditioner according to the present disclosure includes a refrigerant circuit including a compressor, a condenser, at least one expansion valve, and an evaporator and configured to circulate a refrigerant, a control device for controlling the refrigerant circuit, an accumulator for separating the refrigerant flowing through the refrigerant circuit into liquid refrigerant and gas refrigerant and storing 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 accumulator is disposed between the compressor and the evaporator. The control device calculates the amount of liquid refrigerant stored in the accumulator based on a first measurement result of the first temperature sensor and a second measurement result of the second temperature sensor.

[0008] An air conditioning system according to the present disclosure includes the air conditioner described above, and a user device that notifies the user of the amount of liquid refrigerant stored in the accumulator, the amount being calculated by the air conditioner.

[0009] According to the present disclosure, the air conditioner can calculate the amount of liquid refrigerant stored in the accumulator based on the temperature of the refrigerant flowing into the accumulator and the temperature of the refrigerant flowing out of the accumulator, allowing workers to more inexpensively check the amount of liquid refrigerant stored in the accumulator.

[0010] FIG. 1 is a diagram showing the configuration of an air conditioner and air conditioning system according to embodiment 1. FIG. 2 is a ph diagram of the refrigeration cycle in the air conditioner according to embodiment 1. FIG. 3 is a diagram for explaining the internal configuration of an accumulator according to embodiment 1. FIG. 4 is a timing chart for explaining changes in the state of the refrigeration cycle when the air conditioner according to embodiment 1 executes refrigerant amount detection processing. FIG. 5 is a graph showing changes in the liquid level height of liquid refrigerant in the accumulator relative to the difference between the degree of superheat of refrigerant flowing into the accumulator and the degree of superheat of refrigerant flowing out of the accumulator. FIG. 6 is a flowchart for explaining refrigerant amount detection processing executed by the air conditioner according to embodiment 1. FIG. 7 is a diagram showing the configuration of an air conditioner and air conditioning system according to embodiment 2.

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. While multiple embodiments will be described below, it is anticipated from the beginning that the configurations described in each embodiment will be appropriately combined. Note that identical or corresponding parts in the drawings will be designated by the same reference numerals, and their description will not be repeated.

[0012] Embodiment 1. An air conditioner 1 and an air conditioning system 1000 according to Embodiment 1 will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of the air conditioner 1 and the air conditioning system 1000 according to Embodiment 1. Note that Fig. 1 functionally shows the connection relationships and arrangement of the devices in the air conditioner 1, and does not necessarily show the physical arrangement in space.

[0013] As shown in FIG. 1 , the air conditioning system 1000 includes an air conditioner 1 and a user device 500 .

[0014] The air conditioner 1 includes a refrigerant circuit 200 and a control device 100. The refrigerant circuit 200 includes an outdoor unit 300 and an indoor unit 400. The outdoor unit 300 and the indoor unit 400 are connected by extension pipes 21 and 22, and a refrigerant circulates between the outdoor unit 300 and the indoor unit 400.

[0015] The outdoor unit 300 is generally installed outdoors in a location that is not the subject of air conditioning, and includes a four-way valve 40 , a compressor 30 , an outdoor heat exchanger 50 , and an outdoor fan 51 .

[0016] The four-way valve 40 includes connection ports 41, 42, 43, and 44. Connection port 41 of the four-way valve 40 is connected to the suction port 31 of the compressor 30 via piping 18 and 19. Connection port 42 of the four-way valve 40 is connected to the outdoor heat exchanger 50 via piping 17. Connection port 43 of the four-way valve 40 is connected to the discharge port 32 of the compressor 30 via piping 11. Connection port 44 of the four-way valve 40 is connected to the indoor unit 400 via piping 12 and extension piping 21. The four-way valve 40 is configured to switch its internal communication state under the control of the control device 100.

[0017] The compressor 30 is configured to operate and stop, and to change its rotational speed during operation, under 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, i.e., the rotational speed, in response to changes in the drive frequency, thereby changing the amount of refrigerant discharged. Various types of compressors can be used for the compressor 30, and for example, a scroll type, a rotary type, a screw type, etc. can be used as the compressor 30.

[0018] The outdoor heat exchanger 50 exchanges heat between the refrigerant and air drawn in from outdoors by an outdoor fan 51, i.e., outside air. One end of the outdoor heat exchanger 50 is connected to the connection port 42 of the four-way valve 40 via a pipe 17. The other end of the outdoor heat exchanger 50 is connected to the indoor unit 400 via a pipe 16 and an extension pipe 22.

[0019] The outdoor fan 51 is configured to operate and stop, and to change its rotation speed when operating, under the control of the control device 100. The control device 100 controls the outdoor fan 51 to arbitrarily change the drive frequency of the outdoor fan 51. The outdoor fan 51 changes the number of rotations per unit time, i.e., the rotation speed, in accordance with the change in drive frequency, thereby changing the amount of air sent to the outdoor heat exchanger 50.

[0020] The indoor unit 400 is generally installed in an indoor space to be air-conditioned, and includes an indoor heat exchanger 60 , an indoor fan 61 , and an indoor expansion valve 65 .

[0021] The indoor heat exchanger 60 exchanges heat between the refrigerant and air drawn in from the room by the indoor fan 61. One end of the indoor heat exchanger 60 is connected to the outdoor unit 300 via a pipe 13 and an extension pipe 21. The other end of the indoor heat exchanger 60 is connected to an indoor expansion valve 65 via a pipe 14.

[0022] The indoor fan 61 is configured to operate and stop, and to change its rotation speed when operating, under the control of the control device 100. The control device 100 controls the indoor fan 61 to arbitrarily change the drive frequency of the indoor fan 61. The indoor fan 61 changes the number of rotations per unit time, i.e., the rotation speed, in accordance with the change in drive frequency, thereby changing the amount of air sent to the indoor heat exchanger 60.

[0023] The indoor expansion valve 65 is, for example, an electronic expansion valve whose opening is adjusted under the control of the control device 100. The indoor expansion valve 65 reduces the pressure of the refrigerant that flows in and causes the refrigerant obtained by the reduced pressure to flow out. The control device 100 can adjust the amount of refrigerant pressure reduction by adjusting the opening of the indoor expansion valve 65. One end of the indoor expansion valve 65 is connected to the indoor heat exchanger 60 via piping 14. The other end of the indoor expansion valve 65 is connected to the outdoor unit 300 via piping 15 and extension piping 22.

[0024] The control device 100 includes a control unit 101 and a storage unit 102. The control device 100 is capable of communicating with each actuator of the refrigerant circuit 200 to control each actuator of the refrigerant circuit 200, such as the compressor 30, the indoor expansion valve 65, the four-way valve 40, the outdoor fan 51, and the indoor fan 61. The control device 100 may be mounted in either the outdoor unit 300 or the indoor unit 400, or may be separate from the outdoor unit 300 and the indoor unit 400.

[0025] The control unit 101 is a computing entity that controls each actuator of the refrigerant circuit 200 by executing various programs. The control unit 101 is configured as a computer such as a processor. The processor may be configured, for example, as a microcontroller, a central processing unit (CPU), or a micro-processing unit (MPU). The processor has the function of executing various processes by executing programs, but some or all of these functions may be implemented using dedicated hardware circuits such as an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA). The term "processor" is not limited to a processor in the narrow sense that executes processes using a stored program, such as a CPU or MPU, but may also include hardwired circuits such as an ASIC or FPGA. Therefore, the term "processor" can also be interpreted as a processing circuitry in which processes are predefined by computer-readable code and / or hardwired circuits. The processor may be configured as a single chip or multiple chips. Furthermore, the processor and associated processing circuitry may be comprised of multiple computers interconnected by wire or wirelessly, such as via a local area network or a wireless network. The processor and associated processing circuitry may also be comprised of a cloud computer that performs remote calculations based on input data and outputs the results of the calculations to other devices at remote locations.

[0026] The memory unit 102 provides a storage area for storing program code, work memory, etc., when the processor of the control unit 101 executes various programs. The memory unit 102 may be one or more non-transitory computer-readable media. Examples of the memory unit 102 include volatile memories such as dynamic random access memory (DRAM) and static random access memory (SRAM), and non-volatile memories such as read-only memory (ROM) and flash memory. The memory unit 102 may also be one or more computer-readable storage media. Examples of the memory unit 102 include storage devices such as hard disk drives (HDDs) and solid-state drives (SSDs). The control unit 101 controls each actuator of the refrigerant circuit 200 by executing the programs stored in the memory unit 102.

[0027] The user device 500 is configured to be able to communicate with the control device 100 via a network. The user device 500 is an information terminal used by a user such as a worker. The user device 500 may be implemented as a general-purpose computer or a computer dedicated to controlling the air conditioner 1. For example, the user device 500 may be an information terminal that executes predetermined information processing, such as a desktop personal computer (PC), a laptop PC, a smartphone, a smartwatch, a wearable device, a tablet PC, or a remote controller installed in a building. A user such as a worker may be able to control the air conditioner 1 using the user device 500, and may be able to view data acquired from the air conditioner 1 on a display (not shown) provided on the user device 500.

[0028] The air conditioner 1 further includes a pressure sensor 81 , a pressure sensor 82 , a temperature sensor 91 , a temperature sensor 92 , a temperature sensor 93 , a temperature sensor 94 , and a temperature sensor 95 .

[0029] The pressure sensor 81 is provided between the inlet side of the accumulator 70 and the evaporator, and measures the pressure of the refrigerant flowing out from the evaporator and into the accumulator 70. The refrigerant pressure P1 measured by the pressure sensor 81 is transmitted to the control device 100.

[0030] The pressure sensor 82 is provided 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 P2 measured by the pressure sensor 82 is transmitted to the control device 100.

[0031] The temperature sensor 91 is provided 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. 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 measurement result."

[0032] The temperature sensor 92 is provided between the outlet side of the accumulator 70 and the suction port 31 of the compressor 30, and measures the temperature of the refrigerant flowing out from the accumulator 70. The refrigerant temperature T2 measured by the temperature sensor 92 is transmitted to the control device 100. 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 measurement result."

[0033] The temperature sensor 93 is provided 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.

[0034] The temperature sensor 94 is provided between the indoor heat exchanger 60 and the indoor expansion valve 65, and measures the temperature of the refrigerant flowing out from the indoor heat exchanger 60. The refrigerant temperature T4 measured by the temperature sensor 94 is transmitted to the control device 100.

[0035] The temperature sensor 95 is provided at the outdoor heat exchanger 50 or in the vicinity of the outdoor heat exchanger 50, and measures the outdoor temperature. The outdoor air temperature T5 measured by the temperature sensor 95 is transmitted to the control device 100.

[0036] The air conditioner 1 configured as described above is controlled to one of a plurality of operation modes including a heating operation mode for heating an indoor space and a cooling operation mode for cooling an indoor space.

[0037] First, the operation of the air conditioner 1 in the heating operation mode will be described. As shown by the solid lines in Figure 1, in the heating operation mode, the internal communication state of the four-way valve 40 is such that connection port 41 is connected to connection port 42 and connection port 43 is connected to connection port 44. In other words, in the heating operation mode, the intake port 31 of the compressor 30 is connected to the outdoor heat exchanger 50 side and the discharge port 32 of the compressor 30 is connected to the indoor heat exchanger 60 side.

[0038] The compressor 30 draws in the low-temperature, low-pressure gas refrigerant that has flowed in from the outdoor heat exchanger 50 and compresses the drawn gas refrigerant to increase the pressure of the gas refrigerant. The compressor 30 discharges the high-temperature, high-pressure gas refrigerant obtained by the compression to the indoor heat exchanger 60.

[0039] In the heating operation mode, the indoor heat exchanger 60 functions as a condenser. The indoor heat exchanger 60 exchanges heat between the high-temperature, high-pressure gas refrigerant from the compressor 30 and air drawn in from the indoor space by the indoor fan 61. The gas refrigerant that has released heat to the air through this heat exchange condenses inside the indoor heat exchanger 60 and changes into a high-temperature, high-pressure liquid refrigerant. The high-temperature, high-pressure liquid refrigerant obtained by the indoor heat exchanger 60 flows out to the indoor expansion valve 65. The air that has absorbed heat from the gas refrigerant in the indoor heat exchanger 60 is sent back into the indoor space. This heats the indoor space.

[0040] The indoor 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 gas-liquid two-phase refrigerant obtained by the indoor expansion valve 65 flows out to the outdoor heat exchanger 50.

[0041] In the heating operation mode, the outdoor heat exchanger 50 functions as an evaporator. The outdoor heat exchanger 50 exchanges heat between the low-temperature, low-pressure gas-liquid two-phase refrigerant from the indoor expansion valve 65 and air drawn in from outdoors by the outdoor fan 51. The gas-liquid two-phase refrigerant absorbs heat from the air through this heat exchange, evaporating inside the outdoor heat exchanger 50 and changing into low-temperature, low-pressure gas refrigerant. The low-temperature, low-pressure gas refrigerant obtained by the outdoor heat exchanger 50 flows out to the compressor 30.

[0042] In this way, in the heating operation mode, the refrigerant flows through the compressor 30, the indoor heat exchanger 60 (condenser), the indoor expansion valve 65, and the outdoor heat exchanger 50 (evaporator) in this order.

[0043] Next, the operation of the air conditioner 1 in the cooling operation mode will be described. As shown by the dashed lines in Figure 1, in the cooling operation mode, the internal communication state of the four-way valve 40 is such that connection port 41 is connected to connection port 44, and connection port 42 is connected to connection port 43. In other words, in the cooling operation mode, the intake port 31 of the compressor 30 is connected to the indoor heat exchanger 60, and the discharge port 32 of the compressor 30 is connected to the outdoor heat exchanger 50.

[0044] The compressor 30 draws in the low-temperature, low-pressure gas refrigerant from the indoor heat exchanger 60 and compresses the drawn gas refrigerant to increase the pressure of the gas refrigerant. The compressor 30 discharges the high-temperature, high-pressure gas refrigerant obtained by the compression to the outdoor heat exchanger 50.

[0045] In the cooling operation mode, the outdoor heat exchanger 50 functions as a condenser. The outdoor heat exchanger 50 exchanges heat between the high-temperature, high-pressure gas refrigerant from the compressor 30 and air drawn in from the outdoors by the outdoor fan 51. The gas refrigerant that has released heat into the air through this heat exchange condenses inside the outdoor heat exchanger 50 and changes 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 indoor expansion valve 65.

[0046] The indoor 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 gas-liquid two-phase refrigerant obtained by the reduction in pressure in the indoor expansion valve 65 flows out to the indoor heat exchanger 60.

[0047] In the cooling operation mode, the indoor heat exchanger 60 functions as an evaporator. The indoor heat exchanger 60 exchanges heat between the low-temperature, low-pressure gas-liquid two-phase refrigerant from the indoor expansion valve 65 and air drawn in from the room by the indoor fan 61. The gas-liquid two-phase refrigerant absorbs heat from the air through this heat exchange, evaporating inside the indoor heat exchanger 60 and changing into low-temperature, low-pressure gas refrigerant. The low-temperature, low-pressure gas refrigerant obtained by the indoor heat exchanger 60 flows out to the compressor 30. The air whose heat has been absorbed by the gas refrigerant in the indoor heat exchanger 60 is sent back into the room. This cools the room.

[0048] In this way, in the cooling operation mode, the refrigerant flows through the compressor 30, the outdoor heat exchanger 50 (condenser), the indoor expansion valve 65, and the indoor heat exchanger 60 (evaporator) in this order.

[0049] Figure 2 is a ph diagram of the refrigeration cycle in the air conditioner 1 according to Embodiment 1. In the ph diagram of Figure 2, the vertical axis represents absolute pressure p, and the horizontal axis represents specific enthalpy h. In Figure 2, points a1, a2, and a3 indicate the state of the refrigerant between the discharge port 32 of the compressor 30 and the condenser. Point b indicates the state of the refrigerant between the condenser and the indoor expansion valve 65. Point c indicates the state of the refrigerant between the indoor expansion valve 65 and the evaporator. Points d1, d2, and d3 indicate the state of the refrigerant between the evaporator and the suction port 31 of the compressor 30.

[0050] In the refrigeration cycle, the changes in the state of the refrigerant from points d1, d2, and d3 to points a1, a2, and a3 represent the changes in the state of the refrigerant caused by the refrigerant flowing through the compressor 30. The changes in the state of the refrigerant from points a1, a2, and a3 to point b represent the changes in the state of the refrigerant caused by the refrigerant flowing through the condenser. The changes in the state of the refrigerant from point b to point c represent the changes in the state of the refrigerant caused by the refrigerant flowing through the indoor expansion valve 65. The changes in the state of the refrigerant from point c to points d1, d2, and d3 represent the changes in the state of the refrigerant caused by the refrigerant flowing through the evaporator.

[0051] Generally, in an air conditioner 1, the amount of refrigerant required during heating operation is less than the amount of refrigerant required during cooling operation. Therefore, the amount of refrigerant charged into the refrigerant circuit 200 of the air conditioner 1 is determined based on the amount of refrigerant required during cooling operation, and excess refrigerant not used during heating operation may be generated. Therefore, the air conditioner 1 further includes an accumulator 70 between the compressor 30 and the evaporator, and is configured to store the excess refrigerant. As shown in FIG. 1 , in the heating operation mode, the accumulator 70 is disposed between the compressor 30 and the outdoor heat exchanger 50. In the cooling operation mode, the accumulator 70 is disposed between the compressor 30 and the indoor heat exchanger 60.

[0052] 3 is a diagram illustrating the internal configuration of the accumulator 70 according to Embodiment 1. As shown in FIG. 3, the accumulator 70 includes a container 71, an inlet pipe 72, and an outlet pipe 73.

[0053] The inlet pipe 72 is configured to be connectable to the pipe 18 connected to the evaporator side, and introduces the refrigerant flowing from the evaporator via the pipe 18 into the container 71. Of the refrigerant introduced through the inlet pipe 72, liquid refrigerant accumulates in the lower part of the container 71, and gas refrigerant accumulates in the upper part of the container 71.

[0054] The outflow pipe 73 is configured to be connectable to the piping 19 connected to the compressor 30 side, and introduces the refrigerant accumulated in the container 71 into the suction port 31 of the compressor 30 via the piping 19. The outflow pipe 73 is U-shaped and includes a gas suction port 73a that draws in gas refrigerant accumulating in the upper part of the container 71, and a liquid suction port 73b that draws in liquid refrigerant accumulated in the lower part of the container 71. The gas refrigerant drawn through the gas suction port 73a flows out through the outflow pipe 73 to the suction port 31 of the compressor 30. The liquid refrigerant drawn through the liquid suction port 73b flows out through the outflow pipe 73 to the suction port 31 of the compressor 30. Because the diameter of the liquid suction port 73b is smaller than the diameter of the outflow pipe 73, only a very small amount of liquid refrigerant is drawn through the liquid suction port 73b.

[0055] The accumulator 70 configured as described above accumulates the liquid refrigerant in the lower part of the container 71, while allowing the gas refrigerant to remain in the upper part of the container 71, among the refrigerant flowing from the evaporator via the pipe 18, thereby separating the refrigerant flowing through the refrigerant circuit 200 into liquid refrigerant and gas refrigerant, and storing the liquid refrigerant in the container 71. The liquid refrigerant accumulated in the container 71 flows little by little into the outflow pipe 73 through the liquid suction port 73b disposed in the liquid refrigerant, and is returned to the suction port 31 of the compressor 30 through the outflow pipe 73.

[0056] Hereinafter, the accumulator 70 will also be referred to as "ACC" for short. The liquid level of the liquid refrigerant stored in the container 71 of the accumulator 70 will also be referred to as "ACC liquid level height." The amount of liquid refrigerant stored in the container 71 of the accumulator 70 will also be referred to as "ACC liquid refrigerant amount." Returning the liquid refrigerant stored in the container 71 to the outflow pipe 73 via the liquid suction port 73b will also be referred to as "liquid return."

[0057] A worker may charge refrigerant into the refrigerant circuit 200 when installing the air conditioner 1, or may charge additional refrigerant into the refrigerant circuit 200 of an air conditioner 1 that has already been installed. At this time, the worker can determine whether an appropriate amount of refrigerant has been charged into the refrigerant circuit 200 by checking the amount of liquid refrigerant stored in the accumulator 70. Furthermore, in an installed air conditioner 1, the worker can also determine whether a refrigerant leak has occurred in the refrigerant circuit 200 by checking the amount of liquid refrigerant stored in the accumulator 70. Thus, when installing or inspecting the air conditioner 1, the worker needs to check the amount of liquid refrigerant stored in the accumulator 70.

[0058] Here, one method for checking the amount of liquid refrigerant stored in the accumulator 70 is to heat the accumulator 70 with a heater (not shown) and measure the surface temperature of the accumulator 70 with multiple temperature sensors (not shown) provided in the height direction of the accumulator 70, thereby detecting the ACC liquid level based on differences in temperature changes according to the state of the refrigerant inside the accumulator 70. However, this method requires the accumulator 70 to be specially provided with a heater and multiple temperature sensors, which increases costs.

[0059] Therefore, the air conditioner 1 according to the first embodiment is configured to be able to check the amount of liquid refrigerant stored in the accumulator 70 at lower cost by executing a refrigerant amount detection process.

[0060] 4 is a timing chart for explaining the state change of the refrigeration cycle when the air conditioner 1 according to Embodiment 1 executes the refrigerant amount detection process. In FIG. 4, the state change of the refrigeration cycle when the refrigerant amount detection process is executed in the heating operation mode is shown.

[0061] As shown in FIG. 4, in the air conditioner 1, after startup, the control device 100 controls the refrigerant circuit 200 in the first operation mode, and then controls the refrigerant circuit 200 in the second operation mode.

[0062] 4A shows how the drive frequency of the compressor 30 (hereinafter also referred to as the "compressor frequency"), the number of rotations per unit time of the outdoor fan 51 (hereinafter also referred to as the "outdoor fan rotation speed"), and the opening degree of the indoor expansion valve 65 (hereinafter also referred to as the "LEV opening degree") change during startup, in the first operating mode, and in the second operating mode. The compressor frequency, the outdoor fan rotation speed, and the LEV opening degree are controlled by the control device 100.

[0063] Figure 4 (B) shows how the degree of subcooling at the condenser outlet (hereinafter also referred to as "condenser outlet SC"), the degree of superheat at the ACC inlet (hereinafter also referred to as "ACC inlet SH"), and the degree of superheat at the ACC outlet (hereinafter also referred to as "ACC outlet SH") change during startup, the first operating mode, and the second operating mode.

[0064] As shown in Fig. 2, the condenser outlet SC can be calculated by subtracting the refrigerant temperature at the condenser outlet from the condensing temperature. For example, the control device 100 obtains the pressure P2 of the refrigerant discharged from the compressor 30 from the pressure sensor 82 and calculates the saturation temperature of the refrigerant as the condensing temperature based on the obtained refrigerant pressure P2. Furthermore, the control device 100 obtains the temperature T4 of the refrigerant flowing out from the indoor heat exchanger 60, which serves as the condenser, from the temperature sensor 94. The control device 100 can calculate the condenser outlet SC by subtracting the refrigerant temperature T4 from the saturation temperature calculated as the condensing temperature.

[0065] As shown in FIG. 2 , the ACC inlet SH can be calculated by subtracting the evaporation temperature from the refrigerant temperature at the ACC inlet. For example, the control device 100 acquires the temperature T1 of the refrigerant flowing into the accumulator 70 from a temperature sensor 91. Furthermore, the control device 100 acquires the pressure P1 of the refrigerant flowing out from the outdoor heat exchanger 50, which serves as an evaporator, from a pressure sensor 81, and calculates the saturation temperature of the refrigerant as the evaporation temperature based on the acquired refrigerant pressure P1. The control device 100 can calculate the ACC inlet SH by subtracting the evaporation temperature calculated based on the refrigerant pressure P1 from the refrigerant temperature T1. The ACC inlet SH is an example of a "first degree of superheat."

[0066] As shown in FIG. 2 , the ACC outlet SH can be calculated by subtracting the evaporation temperature from the refrigerant temperature at the ACC outlet. For example, the control device 100 acquires the temperature T2 of the refrigerant flowing out of the accumulator 70 from the temperature sensor 92. Furthermore, the control device 100 acquires the pressure P1 of the refrigerant flowing out from the outdoor heat exchanger 50, which serves as an evaporator, from the pressure sensor 81, and calculates the saturation temperature of the refrigerant as the evaporation temperature based on the acquired refrigerant pressure P1. The control device 100 can calculate the ACC outlet SH by subtracting the evaporation temperature calculated based on the refrigerant pressure P1 from the refrigerant temperature T2. The ACC outlet SH is an example of a "second degree of superheat."

[0067] FIG. 4C shows how the evaporating temperature and condensing temperature change during startup, during the first operating mode, and during the second operating mode.

[0068] FIG. 4D shows how the amount of ACC liquid refrigerant changes during startup, during the first operation mode, and during the second operation mode.

[0069] In the air conditioner 1, when the control device 100 controls the refrigerant circuit 200 in the first operation mode, the refrigeration cycle enters a steady state. Specifically, as shown in FIG. 4A, in the first operation mode, the air conditioner 1 fixes the compressor frequency at a predetermined value so that the condensing temperature is constant, fixes the outdoor fan rotation speed at a predetermined value so that the evaporating temperature is constant, and fixes the LEV opening at a predetermined value so that the condenser outlet SC is constant. As shown in FIG. 4B, in this first operation mode, the difference between the ACC inlet SH and the ACC outlet SH (hereinafter also referred to as the "SH difference") is less than a predetermined value (e.g., a value greater than 0). More specifically, in the first operation mode, the SH difference is zero or approximately zero. In other words, in the first operation mode, the ACC inlet SH and the ACC outlet SH are the same or approximately the same. Furthermore, as shown in FIG. 4D, in the first operation mode, the amount of ACC liquid refrigerant also remains almost constant.

[0070] As described above, while the refrigeration cycle is in a steady state in the first operating mode, the SH difference and the amount of ACC liquid refrigerant are unlikely to change, and therefore the air conditioner 1 cannot detect the amount of ACC liquid refrigerant even if it uses the pressure and temperature of the refrigerant entering and leaving the accumulator 70, i.e., the refrigerant pressure P1 and the refrigerant temperatures T1 and T2.

[0071] Therefore, in the air conditioner 1, the control device 100 controls the refrigerant circuit 200 in the first operating mode to bring the refrigeration cycle into a steady state, and then controls the refrigerant circuit 200 in the second operating mode to deliberately change the state of the refrigeration cycle and bring it into a transient state.

[0072] Specifically, as shown in FIG. 4A , the air conditioner 1 changes the compressor frequency in the second operating mode, making the compressor frequency in the second operating mode lower than the compressor frequency in the first operating mode. For example, the air conditioner 1 minimizes the compressor frequency in the second operating mode. The air conditioner 1 changes the LEV opening in the second operating mode, making the LEV opening in the second operating mode lower than the LEV opening in the first operating mode. Meanwhile, the air conditioner 1 does not change the outdoor fan rotation speed in the second operating mode, making the airflow rate of the outdoor fan 51 in the second operating mode the same as the airflow rate of the outdoor fan 51 in the first operating mode. Note that the outdoor fan rotation speed in this case may be the maximum rotation speed.

[0073] As shown in Figure 4(B), when the air conditioner 1 is controlled to the second operation mode, the ACC inlet SH becomes larger than the ACC outlet SH, resulting in an SH difference. That is, when the air conditioner 1 is controlled to the second operation mode, the SH difference becomes equal to or greater than a predetermined value (for example, a value greater than 0). Furthermore, as shown in Figure 4(D), the amount of ACC liquid refrigerant decreases.

[0074] The reason why the above-mentioned SH difference occurs in the second operation mode will be explained. When the compressor frequency is reduced and the LEV opening is narrowed in the second operation mode from the steady state in the first operation mode, the amount of refrigerant flowing to the evaporator decreases. Because the outdoor fan rotation speed remains unchanged in the evaporator, gasification of the refrigerant in the evaporator is promoted more rapidly than in the first operation mode. Superheated gas generated by gasification in the evaporator flows into the accumulator 70. As a result, the refrigerant temperature at the ACC inlet temporarily rises. For example, as shown in FIG. 2 , if the refrigerant temperature at the ACC inlet in the first operation mode is near the evaporation temperature, the refrigerant temperature at the ACC inlet rises to a value corresponding to point d1 in the second operation mode.

[0075] Meanwhile, in the accumulator 70, the gas refrigerant drawn through the gas suction port 73a and the liquid refrigerant drawn through the liquid suction port 73b due to liquid return mix together, resulting in a mixed refrigerant that flows through the outflow pipe 73 and flows out to the compressor 30. The temperature of the mixed refrigerant decreases as the liquid refrigerant, which has a lower temperature than the gas refrigerant, mixes with the gas refrigerant. That is, the greater the amount of liquid refrigerant returning (kg / h), the lower the refrigerant temperature at the ACC outlet. The smaller the amount of liquid refrigerant returning, the higher the refrigerant temperature at the ACC outlet. Furthermore, the higher the ACC liquid level or the higher the refrigerant flow velocity in the outflow pipe 73, the greater the amount of liquid refrigerant returning. The lower the ACC liquid level or the lower the refrigerant flow velocity in the outflow pipe 73, the smaller the amount of liquid refrigerant returning. In other words, the higher the ACC liquid level or the higher the refrigerant flow velocity in the outflow pipe 73, the lower the refrigerant temperature at the ACC outlet. The lower the ACC liquid level or the lower the refrigerant flow velocity in the outflow pipe 73, the lower the refrigerant temperature at the ACC outlet. For example, as shown in FIG. 2, in the second operation mode, the refrigerant temperature at the ACC outlet drops from a value corresponding to point d1 to a value corresponding to point d2 or point d3 depending on the amount of liquid refrigerant returning.

[0076] In this way, by controlling the air conditioner 1 in the second operation mode, a difference can be created between the refrigerant temperature at the ACC inlet and the refrigerant temperature at the ACC outlet depending on the amount of liquid refrigerant returning, i.e., the ACC liquid level. As described above, the ACC inlet SH can be calculated by subtracting the evaporation temperature from the refrigerant temperature at the ACC inlet, and the ACC outlet SH can be calculated by subtracting the evaporation temperature from the refrigerant temperature at the ACC outlet. Given that the same evaporation temperature is used in the calculation of the ACC inlet SH and the ACC outlet SH, the SH difference between the ACC inlet SH and the ACC outlet SH is proportional to the difference between the refrigerant temperature T1 at the ACC inlet and the refrigerant temperature T2 at the ACC outlet. Therefore, as shown in FIG. 4B , when the air conditioner 1 is controlled in the second operation mode, the SH difference is created by the difference between the refrigerant temperature T1 at the ACC inlet and the refrigerant temperature T2 at the ACC outlet.

[0077] The relationship between the SH difference and the ACC liquid level will be described with reference to Fig. 5. Fig. 5 is a graph showing the change in the liquid level of the liquid refrigerant in the accumulator 70 (ACC liquid level) relative to the difference (SH difference) between the degree of superheat of the refrigerant flowing into the accumulator 70 (ACC inlet SH) and the degree of superheat of the refrigerant flowing out of the accumulator 70 (ACC outlet SH).

[0078] As shown in Fig. 5, the lower the ACC liquid level, the higher the refrigerant temperature at the ACC outlet, and therefore the smaller the SH difference. On the other hand, the higher the ACC liquid level, the lower the refrigerant temperature at the ACC outlet, and therefore the larger the SH difference.

[0079] Furthermore, such a change in the ACC liquid level relative to the SH difference differs depending on the compressor frequency. Specifically, the lower the compressor frequency, the smaller the change in the ACC liquid level relative to the SH difference. Since the ACC liquid level has an upper limit depending on the capacity of the container 71, the lower the compressor frequency, the more secure the detection width of the change in the ACC liquid level relative to the SH difference.

[0080] For example, as shown in Fig. 5, when the compressor frequency is f1, the change in the ACC liquid level relative to the SH difference is smaller than when the compressor frequency is f2, which is greater than f1. When the compressor frequency is f2, the ACC liquid level can only be detected when the SH difference is between 0 and 6°C, whereas when the compressor frequency is f1, the ACC liquid level can be detected when the SH difference is between 0 and 10°C.

[0081] Therefore, when the air conditioner 1 lowers the compressor frequency in the second operating mode, it can minimize the compressor frequency, thereby ensuring a wider detection range for the change in ACC liquid level height relative to the SH difference.

[0082] In this way, in the air conditioner 1, the control device 100 controls the refrigerant circuit 200 in the second operation mode to generate an SH difference, and then can detect the ACC liquid level from the SH difference by referring to data on changes in the ACC liquid level relative to the SH difference as shown in Figure 5. The control device 100 can calculate the amount of liquid refrigerant stored in the container 71 of the accumulator 70 based on the detected ACC liquid level and the shape or volume of the container 71 that is stored in advance in the memory unit 102.

[0083] Furthermore, when the condenser outlet SC is greater than 0, liquid refrigerant also remains in the condenser. Therefore, the control device 100 calculates the amount of liquid refrigerant remaining in the condenser other than the liquid refrigerant stored in the accumulator 70 based on the liquid phase area ratio A Ｌ It is configured to calculate based on %.

[0084] Liquid phase area ratio A Ｌ % is the liquid phase volume ratio in the total volume of the condenser, and is an index obtained by correcting the condenser outlet SC with the outside air temperature, the discharge enthalpy of the compressor 30, and the low-pressure liquid specific heat of the refrigerant. Specifically, the control device 100 calculates the liquid phase area ratio A using the following equation (1): Ｌ % is calculated. Ｌ %=-Ln(1-SC / dT ｃ ) * dT ｃ *C Ｐｒ / Δh ｃｏｎ ...(1) In equation (1), SC is the condenser outlet SC. dTｃ is the difference between the outside air temperature T5 measured by the temperature sensor 95 and the condensation temperature. Ｐｒ is the constant pressure liquid specific heat of the refrigerant. ｃｏｎ is the difference between the enthalpy of the refrigerant at the condenser inlet and the enthalpy of the refrigerant at the condenser outlet.

[0085] The control device 100 calculates the liquid phase area ratio A using the formula (1). Ｌ %, and the shape or volume of the condenser stored in advance in the storage unit 102. Ｌ For details about the percentage, please refer to Japanese Patent No. 5063346.

[0086] In this way, the control device 100 calculates the amount of liquid refrigerant stored in the accumulator 70, calculates the amount of liquid refrigerant stored in the condenser, and adds the amount of liquid refrigerant stored in the accumulator 70 and the amount of liquid refrigerant stored in the condenser, thereby being able to calculate the total amount of liquid refrigerant remaining in the refrigerant circuit 200. Note that in the evaporator, the refrigerant is gasified and flows into the accumulator 70, so no liquid refrigerant remains.

[0087] The control device 100 transmits liquid refrigerant amount data to the user device 500, which indicates the calculated amount of liquid refrigerant stored in the accumulator 70, the calculated amount of liquid refrigerant stored in the condenser, or the total amount of liquid refrigerant remaining in the refrigerant circuit 200. Based on the liquid refrigerant amount data acquired from the control device 100, the user device 500 notifies a user, such as an operator, of the calculated amount of liquid refrigerant stored in the accumulator 70, the calculated amount of liquid refrigerant stored in the condenser, or the total amount of liquid refrigerant remaining in the refrigerant circuit 200 using a display or the like.

[0088] In this way, the air conditioner 1 can calculate the amount of liquid refrigerant stored by the accumulator 70 based on the SH difference between the ACC inlet SH and the ACC outlet SH, and notify the worker of the calculated amount of liquid refrigerant, allowing the worker to check the amount of liquid refrigerant stored in the accumulator 70 more inexpensively.

[0089] A specific flow of the refrigerant amount detection process executed by the air conditioner 1 will be described with reference to Fig. 6. Fig. 6 is a flowchart for explaining the refrigerant amount detection process executed by the air conditioner 1 according to Embodiment 1. The control device 100 executes the refrigerant amount detection process of the flowchart shown in Fig. 6, for example, by executing a program stored in the storage unit 102. Note that in the figure, "S" is used as an abbreviation for "STEP."

[0090] 6 , the control device 100 starts up various devices included in the refrigerant circuit 200 of the air conditioner 1 (S1) and executes processing related to the first operation mode. Specifically, the control device 100 controls the compressor 30 to change the compressor frequency (S2). The control device 100 controls the outdoor fan 51 to change the outdoor fan rotation speed (S3). The control device 100 controls the indoor expansion valve 65 to change the LEV opening (S4).

[0091] The control device 100 determines whether the condenser outlet SC is at a predetermined value (S5). If the condenser outlet SC is not at the predetermined value (NO in S5), the control device 100 controls the indoor expansion valve 65 again to change the LEV opening degree (S4).

[0092] On the other hand, if the condenser outlet SC is at the predetermined value (YES in S5), the control device 100 determines whether the evaporation temperature is at the predetermined value (S6). If the evaporation temperature is not at the predetermined value (NO in S6), the control device 100 controls the outdoor fan 51 again to change the outdoor fan rotation speed (S3).

[0093] On the other hand, if the evaporation temperature is equal to the predetermined value (YES in S6), the control device 100 determines whether the condensation temperature is equal to the predetermined value (S7). If the condensation temperature is not equal to the predetermined value (NO in S7), the control device 100 controls the compressor 30 again to change the compressor frequency (S2). The control device 100 can bring the refrigeration cycle into a steady state as shown in FIG. 4 by the processing related to the first operation mode in S2 to S7 described above.

[0094] When the condensation temperature is the predetermined value (YES in S7), the control device 100 Ｌ% (S8). In this way, the control device 100 can calculate the amount of liquid refrigerant stored in the condenser.

[0095] Next, the control device 100 executes the process related to the second operation mode. Specifically, the control device 100 starts counting a predetermined time for executing the process related to the second operation mode (S9).

[0096] The control device 100 controls the indoor expansion valve 65 to change the LEV opening degree, and makes the LEV opening degree in the second operation mode smaller than the LEV opening degree in the first operation mode (S10).

[0097] The control device 100 controls the compressor 30 to change the compressor frequency, and makes the compressor frequency in the second operation mode lower than the compressor frequency in the first operation mode (S11). For example, the control device 100 controls the compressor 30 to minimize the compressor frequency.

[0098] The control device 100 fixes the outdoor fan rotation speed at a predetermined value, and sets the airflow rate of the outdoor fan 51 in the second operation mode to the same as the airflow rate of the outdoor fan 51 in the first operation mode (S12).

[0099] The control device 100 calculates the SH difference while the SH difference is generated as shown in Fig. 4 through the processing related to the second operation mode of S10 to S12 described above (S14). The control device 100 calculates the amount of liquid refrigerant stored in the accumulator 70 based on the calculated SH difference (S15). Specifically, the control device 100 stores in advance in the storage unit 102 data on the change in the ACC liquid level relative to the SH difference as shown in Fig. 5, and calculates the ACC liquid level based on this data and the calculated SH difference. Furthermore, the control device 100 calculates the amount of liquid refrigerant stored in the accumulator 70 based on the calculated ACC liquid level and the shape or volume of the container 71 stored in advance in the storage unit 102.

[0100] The control device 100 transmits liquid refrigerant amount data indicating the calculated amount of liquid refrigerant stored in the accumulator 70, the calculated amount of liquid refrigerant stored in the condenser, or the total amount of liquid refrigerant remaining in the refrigerant circuit 200 to the user device 500 (S16). This allows an operator to check the amount of liquid refrigerant stored in the accumulator 70 using the user device 500.

[0101] The control device 100 determines whether the time since counting started in S9 has passed a predetermined time (S17). If the time since counting started in S9 has not passed the predetermined time (NO in S17), the control device 100 returns to S14 and calculates the SH difference again (S14). On the other hand, if the time since counting started in S9 has passed the predetermined time (YES in S17), the control device 100 ends this process. Note that the control device 100 does not calculate the liquid phase area ratio A in S8. Ｌ %, for example, before S14 or after S15, Ｌ % may be calculated.

[0102] As described above, the air conditioner 1 according to embodiment 1 can calculate the amount of liquid refrigerant stored by the accumulator 70 based on the SH difference between the ACC inlet SH and the ACC outlet SH, and notify the worker of the calculated amount of liquid refrigerant, thereby enabling the worker to check the amount of liquid refrigerant stored in the accumulator 70 at a lower cost.

[0103] Embodiment 2 An air conditioner 1 according to embodiment 2 will be described with reference to Figure 7. In the following, the contents of the air conditioner 1 according to embodiment 2 will be described with the same components as those in the air conditioner 1 according to embodiment 1 being assigned the same reference numerals, and components different from those in the air conditioner 1 according to embodiment 1 being assigned different reference numerals.

[0104] Fig. 7 is a diagram showing the configuration of an air conditioner 1 and an air conditioning system 1000 according to Embodiment 2. As shown in Fig. 7, the air conditioner 1 according to Embodiment 2 further includes an outdoor expansion valve 55.

[0105] The outdoor expansion valve 55 is, for example, an electronic expansion valve whose opening is adjusted under the control of the control device 100. The outdoor expansion valve 55 reduces the pressure of the refrigerant that flows in and causes the refrigerant obtained by the reduced pressure to flow out. The control device 100 can adjust the amount of pressure reduction of the refrigerant by adjusting the opening of the outdoor expansion valve 55. One end of the outdoor expansion valve 55 is connected to the indoor unit 400 via piping 16 and extension piping 22. The other end of the outdoor expansion valve 55 is connected to the outdoor heat exchanger 50 via piping 20.

[0106] In the air conditioner 1 according to the second embodiment configured as described above, after the refrigeration cycle reaches a steady state in the first operation mode, the control device 100 controls the outdoor expansion valve 55 instead of the indoor expansion valve 65, thereby making the opening degree of the outdoor expansion valve 55 in the second operation mode smaller than the opening degree of the outdoor expansion valve 55 in the first operation mode. In this way, even when the opening degree of the outdoor expansion valve 55 is reduced, the control device 100 can reduce the amount of refrigerant flowing to the evaporator, and as a result, the ACC inlet SH can be made larger than the ACC outlet SH, thereby generating an SH difference.

[0107] In the second operation mode, the control device 100 only needs to reduce the opening degree of at least one of the indoor expansion valve 65 and the outdoor expansion valve 55. That is, in the second operation mode, the control device 100 may reduce the opening degree of only the indoor expansion valve 65, may reduce the opening degree of only the outdoor expansion valve 55, or may reduce the opening degrees of both the indoor expansion valve 65 and the outdoor expansion valve 55.

[0108] Embodiment 3 An air conditioner 1 according to Embodiment 3 will be described. In the air conditioner 1 according to Embodiment 1, the control device 100 fixes the outdoor fan rotation speed at a predetermined value in the second operation mode, and sets the airflow rate of the outdoor fan 51 in the second operation mode to the same as the airflow rate of the outdoor fan 51 in the first operation mode. In the air conditioner 1 according to Embodiment 3, the control device 100 may increase the outdoor fan rotation speed in the second operation mode, and make the airflow rate of the outdoor fan 51 in the second operation mode greater than the airflow rate of the outdoor fan 51 in the first operation mode.

[0109] In this way, when the control device 100 makes the airflow rate of the outdoor fan 51 in the second operating mode larger than the airflow rate of the outdoor fan 51 in the first operating mode, it can further promote the gasification of the refrigerant flowing into the evaporator, and as a result, it can make the ACC inlet SH larger than the ACC outlet SH, making it easier to create an SH difference.

[0110] Embodiment 4. An air conditioner 1 according to embodiment 4 will be described. In the air conditioner 1 according to embodiment 1, the control device 100 was configured to detect the ACC liquid level based on the SH difference that occurred in the second operation mode. Here, the ACC inlet SH can be calculated by subtracting the evaporation temperature from the refrigerant temperature at the ACC inlet, and the ACC outlet SH can be calculated by subtracting the evaporation temperature from the refrigerant temperature at the ACC outlet. Considering that the evaporation temperature used in the calculation is the same for the ACC inlet SH and the ACC outlet SH, the SH difference between the ACC inlet SH and the ACC outlet SH is proportional to the difference between the refrigerant temperature T1 at the ACC inlet and the refrigerant temperature T2 at the ACC outlet.

[0111] Therefore, in the air conditioner 1 according to Embodiment 4, the control device 100 may detect the ACC liquid level based on the difference between the refrigerant temperature T1 at the ACC inlet and the refrigerant temperature T2 at the ACC outlet. Specifically, by replacing the SH difference on the horizontal axis in the data shown in FIG. 5 with the difference between the refrigerant temperature T1 at the ACC inlet and the refrigerant temperature T2 at the ACC outlet, the control device 100 can obtain data on the change in the ACC liquid level relative to the difference between the refrigerant temperature T1 at the ACC inlet and the refrigerant temperature T2 at the ACC outlet. Using this data, the control device 100 may detect the ACC liquid level based on the difference between the refrigerant temperature T1 at the ACC inlet and the refrigerant temperature T2 at the ACC outlet.

[0112] The refrigerant amount detection process performed by the air conditioner 1 according to the first to fourth embodiments described above can be performed not only in the heating operation mode but also in the cooling operation mode. Furthermore, in the air conditioner 1 according to the first to fourth embodiments described above, the temperature sensor 92 is provided between the outlet side of the accumulator 70 and the intake port 31 of the compressor 30 as the "second temperature sensor" measuring the temperature of the refrigerant flowing out of the accumulator 70. However, a temperature sensor provided in another position may also be used as the "second temperature sensor." For example, because the refrigerant temperature T2 of the refrigerant flowing out of the accumulator 70 is uniquely linked to the refrigerant temperature T3 discharged from the compressor 30, the temperature sensor 93 may be used as the "second temperature sensor," and the refrigerant temperature T3 may be used as the "second measurement result." In this case, the temperature sensor 92 need not be provided. Furthermore, if the compressor 30 has a structure in which the compression mechanism is housed in a sealed container filled with intake or discharge refrigerant, a temperature sensor (not shown) that detects the surface temperature of the sealed container may be used as the "second temperature sensor," and the surface temperature of the sealed container may be used as the "second measurement result." Note that, since the sealed container of the compressor 30 is filled with the refrigerant flowing out from the accumulator 70, the surface temperature of the sealed container of the compressor 30 corresponds to the temperature of the refrigerant flowing out from the accumulator 70.

[0113] [Summary] The air conditioner 1 of the present disclosure includes a refrigerant circuit 200 including a compressor 30, a condenser (e.g., indoor heat exchanger 60), at least one expansion valve (e.g., indoor expansion valve 65, outdoor expansion valve 55), and an evaporator (e.g., outdoor heat exchanger 50) and configured to circulate a refrigerant; a control device 100 that controls the refrigerant circuit 200; an accumulator 70 that separates the refrigerant flowing through the refrigerant circuit 200 into liquid refrigerant and gas refrigerant and stores the liquid refrigerant; a temperature sensor 91 that measures a temperature T1 of the refrigerant flowing into the accumulator 70; and a temperature sensor 92 that measures a temperature T2 of the refrigerant flowing out of the accumulator 70. The accumulator 70 is disposed between the compressor 30 and the evaporator. The control device 100 calculates the amount of liquid refrigerant stored in the accumulator 70 based on the refrigerant temperature T1 measured by the temperature sensor 91 and the refrigerant temperature T2 measured by the temperature sensor 92.

[0114] With this configuration, the air conditioner 1 can calculate the amount of liquid refrigerant stored in the accumulator 70 based on the temperature T1 of the refrigerant flowing into the accumulator 70 and the temperature T2 of the refrigerant flowing out of the accumulator 70, allowing workers to more inexpensively check the amount of liquid refrigerant stored in the accumulator 70.

[0115] The control device 100 calculates the amount of liquid refrigerant stored by the accumulator 70 based on the difference between the temperature T1 of the refrigerant flowing into the accumulator 70 and the temperature T2 of the refrigerant flowing out of the accumulator 70 .

[0116] According to the above configuration, the air conditioner 1 can calculate the amount of liquid refrigerant stored in the accumulator 70 based on the difference between the temperature T1 of the refrigerant flowing into the accumulator 70 and the temperature T2 of the refrigerant flowing out of the accumulator 70, allowing workers to more inexpensively check the amount of liquid refrigerant stored in the accumulator 70.

[0117] The air conditioner 1 further includes a pressure sensor 81 that measures the pressure P1 of the refrigerant flowing into the accumulator 70. The control device 100 calculates the degree of superheat (ACC inlet SH) of the refrigerant flowing into the accumulator 70 based on the refrigerant pressure P1 measured by the pressure sensor 81 and the temperature T1 of the refrigerant flowing into the accumulator 70, calculates the degree of superheat (ACC outlet SH) of the refrigerant flowing out of the accumulator 70 based on the refrigerant pressure P1 measured by the pressure sensor 81 and the temperature T2 of the refrigerant flowing out of the accumulator 70, and calculates the amount of liquid refrigerant stored by the accumulator 70 based on the SH difference between the ACC inlet SH and the ACC outlet SH.

[0118] According to the above configuration, the air conditioner 1 can calculate the amount of liquid refrigerant stored in the accumulator 70 based on the SH difference between the ACC inlet SH and the ACC outlet SH, allowing workers to more inexpensively check the amount of liquid refrigerant stored in the accumulator 70.

[0119] The control device 100 controls the refrigerant circuit 200 in a first operating mode in which the SH difference between the ACC inlet SH and the ACC outlet SH is less than a predetermined value, and then controls the refrigerant circuit 200 in a second operating mode in which the SH difference between the ACC inlet SH and the ACC outlet SH is greater than or equal to a predetermined value, and calculates the amount of liquid refrigerant stored by the accumulator 70 in the second operating mode.

[0120] According to the above configuration, the air conditioner 1 can generate an SH difference between the ACC inlet SH and the ACC outlet SH by controlling the refrigerant circuit 200 in the second operation mode to put the refrigeration cycle into a transient state. This allows the air conditioner 1 to detect the amount of liquid refrigerant stored in the accumulator 70 using the SH difference generated in the second operation mode.

[0121] The control device 100 makes the opening degree of at least one expansion valve (e.g., the indoor expansion valve 65, the outdoor expansion valve 55) in the second operating mode smaller than the opening degree of at least one expansion valve (e.g., the indoor expansion valve 65, the outdoor expansion valve 55) in the first operating mode.

[0122] According to the above configuration, the air conditioner 1 can reduce the amount of refrigerant flowing to the evaporator by narrowing the opening of at least one expansion valve (for example, the indoor expansion valve 65, the outdoor expansion valve 55), and as a result, the ACC inlet SH can be made larger than the ACC outlet SH, thereby generating an SH difference.

[0123] At least one expansion valve is an indoor expansion valve 65 arranged in the indoor unit 400 or an outdoor expansion valve 55 arranged in the outdoor unit 300 .

[0124] According to the above configuration, the air conditioner 1 can reduce the amount of refrigerant flowing to the evaporator by narrowing the opening of at least one of the indoor expansion valve 65 and the outdoor expansion valve 55, and as a result, the ACC inlet SH can be made larger than the ACC outlet SH, thereby generating an SH difference.

[0125] The air conditioner 1 further includes a fan (for example, the outdoor fan 51) that sends air to the evaporator. The control device 100 sets the airflow rate of the fan in the second operation mode to the same as the airflow rate of the fan in the first operation mode.

[0126] According to the above configuration, the air conditioner 1 can reduce the amount of refrigerant flowing to the evaporator by narrowing the opening of at least one expansion valve (for example, the indoor expansion valve 65, the outdoor expansion valve 55) and maintaining the airflow rate of the fan (for example, the outdoor fan 51) that sends air to the evaporator, and as a result, the ACC inlet SH can be made larger than the ACC outlet SH, thereby generating an SH difference.

[0127] The air conditioner 1 further includes a fan (for example, the outdoor fan 51) that sends air to the evaporator. The control device 100 sets the airflow rate of the fan in the second operation mode to be greater than the airflow rate of the fan in the first operation mode.

[0128] According to the above configuration, the air conditioner 1 can reduce the amount of refrigerant flowing to the evaporator by narrowing the opening of at least one expansion valve (for example, the indoor expansion valve 65, the outdoor expansion valve 55) and increasing the airflow rate of the fan (for example, the outdoor fan 51) that sends air to the evaporator, and as a result, the ACC inlet SH can be made larger than the ACC outlet SH, thereby generating an SH difference.

[0129] The control device 100 sets the frequency of the compressor 30 in the second operation mode to be lower than the frequency of the compressor 30 in the first operation mode.

[0130] According to the above configuration, the air conditioner 1 can promote gasification of the refrigerant in the evaporator by making the frequency of the compressor 30 in the second operation mode lower than the frequency of the compressor 30 in the first operation mode, and as a result, the ACC inlet SH can be made higher than the ACC outlet SH to generate an SH difference. Furthermore, as shown in Figure 5, the air conditioner 1 can ensure a larger detection range for changes in the ACC liquid level height relative to the SH difference as the frequency of the compressor 30 in the second operation mode is made lower.

[0131] The air conditioning system 1000 of the present disclosure includes the air conditioner 1 described above, and a user device 500 that notifies the amount of liquid refrigerant stored in the accumulator 70 calculated by the air conditioner 1.

[0132] According to the above configuration, the air conditioning system 1000 can notify the worker of the amount of liquid refrigerant stored in the accumulator 70 calculated by the air conditioner 1 via the user device 500, thereby improving convenience for the worker.

[0133] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0134] 1 Air conditioner, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 Piping, 21, 22 Extension piping, 30 Compressor, 31 Intake port, 32 Discharge port, 40 Four-way valve, 41, 42, 43, 44 Connection port, 50 Outdoor heat exchanger, 51 Outdoor fan, 55 Outdoor expansion valve, 60 Indoor heat exchanger, 61 Indoor fan, 65 Indoor expansion valve, 70 Accumulator, 71 Container, 72 Inflow pipe, 73 Outflow pipe, 73a Gas intake port, 73b Liquid intake port, 81, 82 Pressure sensor, 91, 92, 93, 94, 95 Temperature sensor, 100 Control device, 101 Control unit, 102 Memory unit, 200 Refrigerant circuit, 300 Outdoor unit, 400 Indoor unit, 500 User device, 1000 air conditioning system.

Claims

1. A refrigerant circuit including a compressor, a condenser, at least one expansion valve, and an evaporator, configured to circulate a refrigerant; A control device for controlling the refrigerant circuit; An accumulator configured to separate the refrigerant flowing through the refrigerant circuit into a liquid refrigerant and a gas refrigerant and store the liquid refrigerant; A first temperature sensor configured to measure the temperature of the refrigerant flowing into the accumulator; A second temperature sensor configured to measure the temperature of the refrigerant flowing out of the accumulator, wherein the accumulator is disposed between the compressor and the evaporator; and the control device calculates the amount of the liquid refrigerant stored by the accumulator based on a first measurement result of the first temperature sensor and a second measurement result of the second temperature sensor. An air conditioner.

2. The air conditioner according to claim 1, wherein the control device calculates the amount of the liquid refrigerant stored by the accumulator based on a difference between the first measurement result and the second measurement result.

3. Further comprising a pressure sensor configured to measure the pressure of the refrigerant flowing into the accumulator, wherein the control device calculates a first superheat degree of the refrigerant flowing into the accumulator based on the measurement result of the pressure sensor and the first measurement result, calculates a second superheat degree of the refrigerant flowing out of the accumulator based on the measurement result of the pressure sensor and the second measurement result, and calculates the amount of the liquid refrigerant stored by the accumulator based on a difference between the first superheat degree and the second superheat degree. The air conditioner according to claim 2.

4. The control device controls the refrigerant circuit in a first operation mode in which a difference between the first superheat degree and the second superheat degree is less than a predetermined value, and then controls the refrigerant circuit in a second operation mode in which the difference between the first superheat degree and the second superheat degree is equal to or greater than the predetermined value, and calculates the amount of the liquid refrigerant stored by the accumulator in the second operation mode. The air conditioner according to claim 3.

5. The air conditioner according to claim 4, wherein the control device makes an opening degree of the at least one expansion valve in the second operation mode smaller than an opening degree of the at least one expansion valve in the first operation mode.

6. The air conditioner according to claim 5, wherein the at least one expansion valve is an indoor expansion valve disposed in an indoor unit or an outdoor expansion valve disposed in an outdoor unit.

7. Further comprising a fan configured to send air to the evaporator The air conditioner according to claim 5, wherein the control device makes the air volume of the fan in the second operation mode the same as the air volume of the fan in the first operation mode.

8. further comprising a fan that sends air to the evaporator, The air conditioner according to claim 5, wherein the control device makes the air volume of the fan in the second operation mode larger than the air volume of the fan in the first operation mode.

9. The air conditioner according to any one of claims 5 to 8, wherein the control device makes the frequency of the compressor in the second operation mode smaller than the frequency of the compressor in the first operation mode.

10. The air conditioner according to any one of claims 1 to 8, An air conditioning system comprising: a user device that notifies the amount of the liquid refrigerant stored by the accumulator calculated by the air conditioner.