Refrigeration cycle device and refrigeration cycle device control method

Abstract

A refrigeration cycle device (101) comprises a compressor (1), an indoor heat exchanger (2), an expansion valve (3), an outdoor heat exchanger (4), a pipe (20), a first bypass pipe (31), a first valve (11), and a control device (50). The pipe (20) connects the compressor (1), the indoor heat exchanger (2), the expansion valve (3), and the outdoor heat exchanger (4). The first valve (11) guides a refrigerant from the compressor (1) to the first bypass pipe (31). The control device (50) controls the first valve (11). One end (31A) of the first bypass pipe (31) is connected to a pipe (20A) that connects the indoor heat exchanger (4) and the expansion valve (3). The other end (31B) of the first bypass pipe (31) is connected to a pipe on the discharge side (1A) of the compressor (1). The control device (50) opens the first valve (11) when operation of the refrigeration cycle device (101) stops.

Description

Refrigeration cycle device and method for controlling the refrigeration cycle device

[0001] The present disclosure relates to a refrigeration cycle device and a control method for a refrigeration cycle device.

[0002] BACKGROUND ART A refrigeration cycle apparatus including a compressor that compresses and discharges a refrigerant has been known. Generally, when the refrigeration cycle apparatus is started, if the difference between the pressure value of the refrigerant on the suction side of the compressor and the pressure value of the refrigerant on the discharge side of the compressor is large, the compressor may fail.

[0003] In anticipation of such a case, Patent Document 1 (JP 2000-55484 A) discloses a refrigeration cycle apparatus that performs pressure equalization to equalize the pressure value of the refrigerant on the suction side and the pressure value of the refrigerant on the discharge side of a compressor. This refrigeration cycle apparatus includes a bypass path and a regulating valve that opens and closes the bypass path. One end of the bypass path is connected to a pipe on the suction side of the compressor, and the other end of the bypass path is connected to a pipe on the discharge side of the compressor. When the refrigeration cycle apparatus stops operation of the compressor, the regulating valve is opened. Opening the regulating valve establishes communication between the discharge side and the suction side of the compressor, thereby performing the above-mentioned pressure equalization.

[0004] Japanese Patent Application Laid-Open No. 2000-55484

[0005] In the above-described refrigeration cycle apparatus, if the compressor stops while not operating sufficiently, liquid refrigerant that has not traveled through the bypass path remains near the compressor. Therefore, if the compressor stops while not operating sufficiently and the control valve is opened, the remaining liquid refrigerant may enter the compressor through the compressor suction port via the one end of the bypass path. In this case, the liquid refrigerant that has entered the compressor may reduce the concentration of refrigeration oil inside the compressor, causing a problem of compressor failure when the compressor is started.

[0006] The present disclosure has been made to solve such problems, and its purpose is to equalize the pressure of the refrigerant on the suction side and the refrigerant on the discharge side of the compressor while suppressing the intrusion of liquid refrigerant from the suction side of the compressor.

[0007] The refrigeration cycle apparatus of the present disclosure includes a compressor, a condenser, an expansion valve, an evaporator, a piping, a first bypass piping, a first valve, and a control device. The piping connects the compressor, the condenser, the expansion valve, and the evaporator. The first valve is a valve for directing refrigerant from the compressor to the first bypass piping. The control device controls the first valve. One end of the first bypass piping is connected to a piping connecting the evaporator and the expansion valve. The other end of the first bypass piping is connected to a piping on the discharge side of the compressor. The control device opens the first valve when operation of the refrigeration cycle apparatus stops.

[0008] The disclosed method is a control method for a refrigeration cycle apparatus. The refrigeration cycle apparatus includes a compressor, a condenser, an expansion valve, an evaporator, the compressor, the condenser, the expansion valve, a pipe, a first bypass pipe, and a first valve. The pipe connects the compressor, the condenser, the expansion valve, and the evaporator. The first valve is a valve for directing refrigerant from the compressor to the first bypass pipe. One end of the first bypass pipe is connected to a pipe connecting the evaporator and the expansion valve. The other end of the first bypass pipe is connected to a pipe on the discharge side of the compressor. The control method opens the first valve when operation of the refrigeration cycle apparatus stops.

[0009] According to the present disclosure, it is possible to suppress the intrusion of liquid refrigerant from the suction side of the compressor while equalizing the pressure between the suction side and the discharge side of the compressor.

[0010] Fig. 1 is a diagram showing a configuration example of a refrigeration cycle device of embodiment 1. Fig. 2 is a flowchart showing processing of a control device of embodiment 1. Fig. 3 is a diagram showing a configuration example of a refrigeration cycle device of embodiment 2. Fig. 4 is a diagram for explaining a method of identifying whether or not the operating state of the refrigeration cycle device is stable. Fig. 5 is a flowchart showing processing of a control device of an embodiment.

[0011] Hereinafter, the present embodiment will be described in detail with reference to the drawings, in which the same or corresponding parts are designated by the same reference numerals and description thereof will not be repeated.

[0012] Embodiment 1. [Configuration example of refrigeration cycle device] Fig. 1 is a diagram showing a configuration example of a refrigeration cycle device 101 according to embodiment 1. The refrigeration cycle device 101 functions as, for example, an air conditioning device. The configuration of the refrigeration cycle device 101 according to this embodiment will be described with reference to Fig. 1 .

[0013] The refrigeration cycle apparatus 101 performs at least one of a cooling operation and a heating operation. FIG. 1 is a diagram illustrating a case in which the refrigeration cycle apparatus 101 performs a heating operation. As shown in FIG. 1 , the refrigeration cycle apparatus 101 includes an outdoor unit 201 and an indoor unit 202. The outdoor unit 201 and the indoor unit 202 are connected by piping. The outdoor unit 201 mainly includes a compressor 1, an expansion valve 3, an outdoor heat exchanger 4, a first valve 11, and a first bypass piping 31. The indoor unit 202 mainly includes an indoor heat exchanger 2. In FIG. 1 , the first bypass piping 31 is indicated by a bold line.

[0014] The compressor 1, the indoor heat exchanger 2, the expansion valve 3, and the outdoor heat exchanger 4 are connected by a pipe 20. In Fig. 1, the pipe connecting the outdoor heat exchanger 4 and the expansion valve 3 is shown as a pipe 20A.

[0015] The refrigerant is used in a refrigeration cycle that transports heat between the outdoor unit 201 and the indoor unit 202. The refrigerant is, for example, a non-azeotropic refrigerant mixture. A non-azeotropic refrigerant mixture is a refrigerant mixture in which two or more refrigerants with different boiling points are mixed. An example of a non-azeotropic refrigerant mixture is R454C. The non-azeotropic refrigerant mixture may be another refrigerant. Furthermore, the non-azeotropic refrigerant mixture may be a mixture of three or more types of refrigerants.

[0016] Furthermore, when the heating operation is in progress and the first valve 11 is closed, the refrigerant is configured to circulate through the compressor 1, the indoor heat exchanger 2, the expansion valve 3, the outdoor heat exchanger 4, and the compressor 1 in that order.

[0017] The compressor 1 is configured to compress and discharge the sucked refrigerant. During heating operation, the refrigerant discharged from the compressor 1 flows to the indoor heat exchanger 2. The indoor heat exchanger 2 exchanges heat between the refrigerant flowing inside the indoor heat exchanger 2 and the air in a first space (e.g., an indoor space) in which the indoor unit 202 is installed. The indoor heat exchanger 2 is configured to function as an evaporator that evaporates the refrigerant during cooling operation, and as a condenser that condenses the refrigerant during heating operation. The evaporator is also referred to as a low-pressure side heat exchanger, and the condenser is also referred to as a high-pressure side heat exchanger.

[0018] The refrigerant from the indoor heat exchanger 2 flows to the expansion valve 3. The expansion valve 3 is configured to reduce the pressure of the refrigerant condensed in the condenser (indoor heat exchanger 2) by expanding it. The expansion valve 3 is, for example, an electromagnetic expansion valve.

[0019] The outdoor heat exchanger 4 exchanges heat between the refrigerant flowing inside the outdoor heat exchanger 4 and the air in the second space (outdoor space) where the outdoor unit 201 is installed. The outdoor heat exchanger 4 is configured to function as a condenser that condenses the refrigerant during cooling operation, and to function as an evaporator that evaporates the refrigerant during heating operation.

[0020] The control device 50 is configured to control each device of the refrigeration cycle device 101. The control device 50 is electrically connected to the compressor 1, the expansion valve 3, the first valve 11, etc., and is configured to control the operations of these devices.

[0021] The control device 50 controls the compressor 1 and other components based on the set temperature and the indoor temperature. The set temperature is set, for example, by a user. The indoor temperature is the temperature of the space (room) in which the indoor unit 202 is installed. The control device 50 controls the compressor 1 and other components, for example, so that the indoor temperature approaches the set temperature. Specifically, the control device 50 controls the operating parameters of the motor of the compressor 1 in accordance with the thermal load (air conditioning load). The operating parameters are, for example, the operating frequency or rotation speed of the motor. In this embodiment, the operating parameter is the operating frequency of the motor. For example, the control device 50 controls the operating frequency in accordance with the thermal load required to set the indoor temperature to the set temperature (to cool or heat the indoor temperature).

[0022] The control device 50 has, as its main components, a CPU (Central Processing Unit) 51 and a memory 52. ​​The CPU 51 executes various processes and calculations. The components are interconnected by a data bus. The memory 52 includes a ROM (Read Only Memory) and a RAM (Random Access Memory). The CPU 51 is also referred to as "at least one processor" or "control circuit."

[0023] The ROM stores programs executed by the CPU 51. The RAM temporarily stores data generated by the execution of the programs in the CPU 51. The RAM can function as a temporary data memory used as a work area. The control device 50 stores a mode flag indicating the operation mode in the RAM. When performing cooling operation, the control device 50 stores a cooling operation flag (mode flag) indicating the cooling operation in the RAM. When performing heating operation, the control device 50 stores a heating operation flag (mode flag) indicating the heating operation in the RAM.

[0024] In addition, the refrigeration cycle apparatus 101 may be configured to include a four-way valve when both cooling and heating operations are possible. By switching the four-way valve, the refrigerant circulates in the order of the compressor 1, condenser, expansion valve 3, evaporator, and compressor 1 when the first valve 11 is closed, regardless of whether the operation is cooling or heating.

[0025] [Pressure Equalization] Next, the pressure equalization process will be described. If the refrigerant pressure on the discharge side 1A of the compressor 1 differs significantly from the refrigerant pressure on the suction side 1B of the compressor 1, the compressor 1 may malfunction due to reasons such as an increased drive torque at startup. Therefore, the refrigeration cycle apparatus 101 of this embodiment executes a pressure equalization process. The pressure equalization process is a process for equalizing the refrigerant pressure on the discharge side 1A of the compressor 1 and the refrigerant pressure on the suction side 1B of the compressor 1. Equalizing the refrigerant pressure on the discharge side 1A of the compressor 1 and the refrigerant pressure on the suction side 1B of the compressor 1 can prevent malfunction of the compressor 1. Note that the pressure equalization process may be a process for approximately equalizing the refrigerant pressure on the discharge side 1A of the compressor 1 and the refrigerant pressure on the suction side 1B of the compressor 1. "Approximately the same" means that the difference between the refrigerant pressure on the discharge side 1A of the compressor 1 and the refrigerant pressure on the suction side 1B of the compressor 1 is a value that can prevent breakdown of the compressor 1. The pressure equalization process may also be expressed as "processing that reduces the difference between the refrigerant pressure on the discharge side 1A of the compressor 1 and the refrigerant pressure on the suction side 1B of the compressor 1."

[0026] A conventional refrigeration cycle apparatus includes a bypass path and a control valve that opens and closes the bypass path to perform a pressure equalization process. One end of the bypass path is connected to the suction side of a compressor, and the other end of the bypass path is connected to the discharge side of the compressor. When the refrigeration cycle apparatus stops operating the compressor, the control valve is opened. Opening the control valve connects the discharge side and suction side of the compressor, allowing the pressure equalization process to be performed.

[0027] However, in the above-described refrigeration cycle apparatus, if the compressor stops while not operating sufficiently (for example, if the compressor is repeatedly turned on and off in a short period of time), liquid refrigerant that has not completely migrated through the bypass path remains near the compressor. Therefore, if the regulating valve is opened when the compressor stops while not operating sufficiently, the remaining liquid refrigerant may enter the compressor through the compressor suction port via the one end of the bypass path. In this case, the liquid refrigerant that has entered the compressor may reduce the concentration of refrigeration oil inside the compressor, causing a problem of compressor failure when the compressor is started.

[0028] In contrast, in the present embodiment, one end 31A of the first bypass pipe 31 is not connected to the suction side of the compressor 1, but is connected to a pipe 20A that connects the outdoor heat exchanger 4 (evaporator) and the expansion valve 3. The first valve 11 is provided midway along the first bypass pipe 31. The first valve 11 is, for example, an expansion valve, more typically an electromagnetic expansion valve. The other end 31B of the first bypass pipe 31 is connected to a pipe on the discharge side 1A of the compressor 1.

[0029] When the operation of the refrigeration cycle apparatus 101 (or the compressor 1) is stopped, the control device 50 executes a process of opening the first valve 11 (increasing the opening degree of the first valve 11). This process of opening the first valve 11 is a pressure equalization process (first pressure equalization process). In addition to opening the first valve 11, the control device 50 also opens the expansion valve 3.

[0030] This first pressure equalization process connects all of the pipes 20 and the first bypass pipe 31. The connected pipes are collectively referred to as "first connecting pipes." In particular, the pressure is equalized between the pipe on the discharge side 1A of the compressor 1 and the pipe on the outdoor heat exchanger 4.

[0031] Furthermore, the first valve 11 guides the refrigerant (or at least a portion of the refrigerant) from the indoor heat exchanger 2 to the first bypass pipe 31. When the operation of the refrigeration cycle apparatus 101 (or the compressor 1) is stopped (when the first valve 11 is opened), the refrigerant (liquid refrigerant) discharged from the compressor 1 flows from the other end 31B to the first bypass pipe 31. At least a portion of the refrigerant (liquid refrigerant) flows to the outdoor heat exchanger 4 (evaporator). Then, the liquid refrigerant that has flowed to the outdoor heat exchanger 4 (evaporator) is evaporated to become gas refrigerant.

[0032] Furthermore, as a method for the control device 50 to determine that the operation of the refrigeration cycle apparatus 101 has been stopped, for example, when the operating frequency of the compressor 1 becomes zero, the compressor 1 outputs a stop signal to the control device 50. When the control device 50 receives the stop signal, it determines that the operation of the refrigeration cycle apparatus 101 has been stopped.

[0033] As described above, when the operation of the refrigeration cycle apparatus 101 is stopped, the refrigeration cycle apparatus 101 opens the first communication pipe by opening the first valve 11. Therefore, while the operation of the refrigeration cycle apparatus 101 is stopped, the refrigeration cycle apparatus 101 can equalize the refrigerant pressure on the discharge side 1A of the compressor 1 and the refrigerant pressure on the suction side 1B of the compressor 1, and can prevent liquid refrigerant from entering through the suction side 1B of the compressor 1. Therefore, it is possible to prevent a malfunction of the compressor 1 due to a difference between the refrigerant pressure on the discharge side 1A and the refrigerant pressure on the suction side 1B of the compressor 1.

[0034] Furthermore, at least a portion of the refrigerant (liquid refrigerant) that has flowed through the first bypass pipe 31 flows to the outdoor heat exchanger 4 (evaporator). Therefore, the liquid refrigerant that has flowed through the outdoor heat exchanger 4 (evaporator) is evaporated to become gas refrigerant, and it is possible to prevent the liquid refrigerant from entering the compressor 1 (so-called liquid backflow).

[0035] [Flowchart] Fig. 2 is a flowchart showing the processing of the control device 50. The processing of Fig. 2 is processing that the control device 50 executes at predetermined intervals (for example, every second). First, in step S2, the control device 50 detects the operation mode. The operation mode is a mode that indicates whether the refrigeration cycle apparatus 101 (or the compressor 1) is operating or not.

[0036] Next, in step S4, the control device 50 determines whether operation has been stopped. If operation has been stopped (YES in step S4), the control device 50 opens the first valve 11 in step S6. Then, the processing in Fig. 2 ends. On the other hand, if operation has not been stopped in step S4 (NO in step S4), the processing in Fig. 2 ends.

[0037] 3 is a diagram showing a configuration example of a refrigeration cycle apparatus 102 according to Embodiment 2. In addition to the components of the refrigeration cycle apparatus 101, the refrigeration cycle apparatus 102 includes a second bypass pipe 32, a second valve 12, a first pressure sensor 61, and a second pressure sensor 62. The second valve 12 is, for example, an expansion valve, and more typically, an electromagnetic expansion valve.

[0038] One end 32A of the second bypass pipe 32 is connected to a pipe on the discharge side 1A of the compressor 1. The other end 32B of the second bypass pipe 32 is connected to a pipe on the suction side 1B of the compressor 1. In the example of Fig. 3, the other end 31B and the other end 32B are connected. Also, in the example of Fig. 3, the other end 31B and the one end 32A are located at the same end. However, as a modified example, the other end 31B and the one end 32A may be located at different positions.

[0039] When the operation of the refrigeration cycle apparatus 102 (or the compressor 1) is stopped, the control device 50 executes a process of closing the first valve 11 and opening the second valve 12 (increasing the opening degree of the second valve 12). This process of opening the second valve 12 (increasing the opening degree of the second valve 12) is a pressure equalization process (second pressure equalization process). This second pressure equalization process establishes communication between the piping from the discharge side 1A of the compressor 1 to one end 32A of the second bypass piping 32, the piping from the one end 32A to the other end 32B, and the piping from the other end 32B to the suction side 1B of the compressor 1. All of these connected piping (the piping from the discharge side 1A of the compressor 1 to one end 32A of the second bypass piping 32, the piping from the one end 32A to the other end 32B, and the piping from the other end 32B to the suction side 1B of the compressor 1) are collectively referred to as the "second communication piping."

[0040] Furthermore, the second valve 12 guides the refrigerant (or at least a portion of the refrigerant) discharged from the compressor 1 to the second bypass pipe 32. Therefore, when the second pressure equalization process is performed, the refrigerant discharged from the compressor 1 flows through the compressor 1 and the second bypass pipe 32 (one end 32A, the second valve 12, the other end 32B).

[0041] The length of the second communicating pipe is shorter than the length of the first communicating pipe (see the description of the first embodiment). Therefore, when the second communicating pipe is formed (when the first valve 11 is closed and the second valve 12 is open), the pressure equalization speed is faster than when the first communicating pipe is formed (when the first valve 11 is open and the second valve 12 is closed). In other words, the pressure equalization speed is faster in the second pressure equalization process than in the first pressure equalization process. The pressure equalization speed refers to the amount of decrease per unit time of the difference between the refrigerant pressure on the discharge side 1A of the compressor 1 and the refrigerant pressure on the suction side 1B of the compressor 1. Note that in the first pressure equalization process, pressure loss due to the expansion valve 3 can also be a factor in slowing the pressure equalization speed.

[0042] While the provision of the second communicating pipe can increase the pressure equalization speed, the short length of the second communicating pipe raises concerns about refrigerant intrusion from the discharge side 1A or suction side 1B of the compressor 1. Here, when the refrigeration cycle apparatus 102 (or the compressor 1) is operating in a stable state, the refrigerant is in a gaseous state. Even if the gaseous refrigerant intrudes into the compressor 1 from the discharge side 1A, the oil concentration of the refrigeration oil does not decrease, so no particular problem occurs. The refrigeration cycle apparatus 102 also includes a storage unit (e.g., a receiver, an accumulator, etc.) for storing liquid refrigerant. The storage unit is not illustrated in FIG. 3 . When the refrigeration cycle apparatus 102 is operating in a stable state, the liquid refrigerant is stored in the storage unit. Therefore, when the refrigeration cycle apparatus 102 is operating in a stable state, liquid refrigerant is prevented from intruding into the compressor 1 from the discharge side 1A.

[0043] Therefore, when the operation of the refrigeration cycle apparatus 102 is stopped, if the operating state of the refrigeration cycle apparatus 102 is stable, the second pressure equalization process (processing of closing the first valve 11 and opening the second valve 12) is performed. This allows the refrigeration cycle apparatus 102 to achieve pressure equalization at a high pressure equalization speed while suppressing a decrease in the oil concentration of the refrigeration oil. On the other hand, when the operation of the refrigeration cycle apparatus 102 is stopped, if the operating state of the refrigeration cycle apparatus 102 is not stable (unstable), the refrigerant is likely to be liquid refrigerant. Therefore, in this case, the refrigeration cycle apparatus 102 performs the first pressure equalization process (processing of opening the first valve 11 and closing the second valve 12). This allows the refrigeration cycle apparatus 102 to achieve pressure equalization while suppressing the intrusion of liquid refrigerant from the discharge side 1A of the compressor 1.

[0044] Next, a method for determining whether the operating state of the refrigeration cycle apparatus 102 is stable will be described. Fig. 4 is a diagram for explaining a method for determining whether the operating state of the refrigeration cycle apparatus 102 is stable. Fig. 4 shows first to fourth examples of this method. In this second embodiment, the first example is applied. The second to fourth examples will be described later.

[0045] The refrigeration cycle apparatus 102 includes a sensor that detects an operating parameter related to the operation of the refrigeration cycle apparatus 102. The control device 50 determines that the operating state of the refrigeration cycle apparatus 102 is stable when the detected operating parameter is greater than a threshold value corresponding to the operating parameter.

[0046] In the second embodiment, the sensors are a first pressure sensor 61 and a second pressure sensor 62. The first pressure sensor 61 detects the refrigerant pressure (first pressure value) on the discharge side 1A of the compressor 1. The second pressure sensor 62 detects the refrigerant pressure (second pressure value) on the suction side 1B of the compressor 1. The operating parameters include a difference value between the first pressure value and the second pressure value.

[0047] The control device 50 acquires a first pressure value from the first pressure sensor 61 and a second pressure value from the second pressure sensor 62. The control device 50 then calculates a difference between the first pressure value and the second pressure value as an operating parameter. For example, the control device 50 calculates the difference by subtracting the second pressure value from the first pressure value. Alternatively, the control device 50 may calculate the absolute value of the difference between the first pressure value and the second pressure value as the difference.

[0048] The control device 50 compares the difference value with a threshold value (first threshold value) corresponding to the difference value, and if the difference value is greater than the first threshold value, determines that the operating state of the refrigeration cycle apparatus 102 is stable. On the other hand, if the difference value is smaller than the first threshold value, the control device 50 determines that the operating state of the refrigeration cycle apparatus 102 is unstable. Note that if the difference value is the same as the first threshold value, the control device 50 may determine that the operating state of the refrigeration cycle apparatus 102 is stable or unstable.

[0049] 5 is a flowchart showing the processing of the control device according to embodiment 2. After the processing of step S2, in step S104, the control device 50 detects the operating state (stable state or unstable state) of the refrigeration cycle device 102. This detection of the operating state is performed based on the above-mentioned operating parameters.

[0050] If it is determined in step S4 that the operation of the refrigeration cycle apparatus 102 has been stopped, then in step S108, the control device 50 determines whether the operating state of the refrigeration cycle apparatus 102 is stable based on the detection result of step S104. If the operating state is stable in step S108 (YES in step S108), the control device 50 executes the second pressure equalization process (i.e., a process of opening the second valve 12 and closing the first valve 11) in step S110. Then, the process of FIG. 5 ends.

[0051] On the other hand, if the operating state is unstable in step S108 (NO in step S108), the control device 50 executes the first pressure equalization process (i.e., process of closing the second valve 12 and opening the first valve 11) in step S112, and the process in FIG. 5 then ends.

[0052] As described above, the refrigeration cycle apparatus 102 of this embodiment includes the second bypass pipe 32 and the second valve 12. The refrigeration cycle apparatus 102 performs the second pressure equalization process using the second bypass pipe 32 and the second valve 12. The refrigeration cycle apparatus 102 performs either the first pressure equalization process or the second pressure equalization process depending on whether the operating state of the refrigeration cycle apparatus 102 is stable or unstable when the operation of the refrigeration cycle apparatus 102 is stopped. Specifically, when the operation of the refrigeration cycle apparatus 102 is stopped, the refrigeration cycle apparatus 102 performs the second pressure equalization process (process of opening the second valve 12) if the operating state of the refrigeration cycle apparatus 102 is stable. This allows the refrigeration cycle apparatus 102 to achieve pressure equalization at a high speed.

[0053] The second pressure equalization process is a process of opening the second valve 12 and closing the first valve 11. Therefore, the refrigeration cycle apparatus 102 can appropriately perform the second pressure equalization process.

[0054] Furthermore, when the operation of the refrigeration cycle apparatus 102 is stopped and the operating state of the refrigeration cycle apparatus 102 is unstable, the refrigeration cycle apparatus 102 executes the first pressure equalization process (processing of opening the first valve 11). This allows the refrigeration cycle apparatus 102 to achieve pressure equalization while suppressing the intrusion of liquid refrigerant from the discharge side 1A of the compressor 1.

[0055] Furthermore, the first pressure equalization process is a process of closing the second valve 12 and opening the first valve 11. Therefore, the refrigeration cycle apparatus 102 can appropriately perform the first pressure equalization process.

[0056] Furthermore, the refrigeration cycle apparatus 102 determines that the operating state of the refrigeration cycle apparatus 102 is stable when the operating parameter is greater than a threshold value corresponding to the operating parameter. Therefore, the refrigeration cycle apparatus 102 can appropriately determine that the operating state of the refrigeration cycle apparatus 102 is stable.

[0057] The refrigeration cycle apparatus 102 also has, as the sensors, a first pressure sensor 61 that detects a first pressure value and a second pressure sensor 62 that detects a second pressure value. The control device 50 uses the difference between the first pressure value and the second pressure value as an operating parameter. This allows the refrigeration cycle apparatus 102 to appropriately determine whether the operating state of the refrigeration cycle apparatus 102 is stable, with a relatively simple configuration.

[0058] Next, second to fourth examples of Fig. 4 will be described. The control device 50 to which the second example is applied includes a timer 151 (see the dashed line in Fig. 3) that detects the operation time of the refrigeration cycle device 102 as the sensor. The operation time is, for example, the time from when the operation of the refrigeration cycle device 102 starts to when the operation of the refrigeration cycle device 102 ends. The operation parameters of the refrigeration cycle device 102 to which the second example is applied include the operation time detected by the timer 151.

[0059] The refrigeration cycle apparatus 102 determines that the operating state of the refrigeration cycle apparatus 102 is stable when the operating time is greater than a second threshold value corresponding to the operating time. On the other hand, the refrigeration cycle apparatus 102 determines that the operating state of the refrigeration cycle apparatus 102 is unstable when the operating time is less than the second threshold value. In the refrigeration cycle apparatus 102 to which the second example is applied, the operating state of the refrigeration cycle apparatus 102 can be determined with a relatively simple configuration.

[0060] The refrigeration cycle apparatus 102 to which the third example is applied includes a superheat sensor 152 (see the dashed line in FIG. 3 ) that detects the superheat degree of the refrigerant on the discharge side of the compressor 1. The superheat degree is the difference between the temperature of the refrigerant on the discharge side 1A and the saturation temperature of the refrigerant at its pressure. The operating parameters of the refrigeration cycle apparatus 102 to which the third example is applied include the superheat degree of the refrigerant detected by the superheat sensor 152. The control device 50 acquires the superheat degree from the superheat sensor 152.

[0061] The refrigeration cycle apparatus 102 determines that the operating state of the refrigeration cycle apparatus 102 is stable when the degree of superheat of the refrigerant is greater than a third threshold value corresponding to the degree of superheat. On the other hand, the refrigeration cycle apparatus 102 determines that the operating state of the refrigeration cycle apparatus 102 is unstable when the degree of superheat is less than the third threshold value. In the refrigeration cycle apparatus 102 to which the third example is applied, the operating state of the refrigeration cycle apparatus 102 can be determined with a relatively simple configuration.

[0062] The refrigeration cycle apparatus 102 to which the fourth example is applied includes a subcooling degree sensor 153 (see dashed line in FIG. 3 ) that detects the degree of subcooling of the refrigerant on the discharge side of the indoor heat exchanger 2 (condenser). The degree of subcooling is the difference between the temperature of the refrigerant on the outlet side of the indoor heat exchanger 2 and the saturation temperature of the refrigerant. The operating parameters of the refrigeration cycle apparatus 102 to which the fourth example is applied include the degree of subcooling of the refrigerant detected by the subcooling degree sensor 153. The control device 50 acquires the degree of subcooling from the subcooling degree sensor 153.

[0063] The refrigeration cycle apparatus 102 determines that the operating state of the refrigeration cycle apparatus 102 is stable when the degree of subcooling of the refrigerant is greater than a fourth threshold value corresponding to the degree of subcooling. On the other hand, the refrigeration cycle apparatus 102 determines that the operating state of the refrigeration cycle apparatus 102 is unstable when the degree of subcooling is less than the fourth threshold value. In the refrigeration cycle apparatus 102 to which the fourth example is applied, the operating state of the refrigeration cycle apparatus 102 can be determined with a relatively simple configuration.

[0064] [Summary] (Section 1) The refrigeration cycle device of the present disclosure includes a compressor, a condenser, an expansion valve, an evaporator, a piping, a first bypass piping, a first valve, and a control device. The piping connects the compressor, the condenser, the expansion valve, and the evaporator. The first valve is a valve for directing refrigerant from the compressor to the first bypass piping. The control device controls the first valve. One end of the first bypass piping is connected to a piping that connects the evaporator and the expansion valve. The other end of the first bypass piping is connected to a piping on the discharge side of the compressor. The control device opens the first valve when operation of the refrigeration cycle device stops.

[0065] (Item 2) The refrigeration cycle apparatus according to item 1, further comprising a second bypass pipe and a second valve for guiding refrigerant discharged from the compressor to the second bypass pipe. One end of the second bypass pipe is connected to a pipe on the discharge side of the compressor. The other end of the second bypass pipe is connected to a pipe on the suction side of the compressor. When operation of the refrigeration cycle apparatus is stopped, the control device opens the second valve if the operating state of the refrigeration cycle apparatus is stable.

[0066] (Clause 3) In the refrigeration cycle device described in clause 2, when operation of the refrigeration cycle device is stopped, the control device opens the second valve and closes the first valve when the operating state of the refrigeration cycle device is stable.

[0067] (4) In the refrigeration cycle device described in paragraph 2 or 3, when operation of the refrigeration cycle device is stopped, the control device opens the first valve if the operating state of the refrigeration cycle device is not stable.

[0068] (5) In the refrigeration cycle device described in 4, when the operation of the refrigeration cycle device is stopped, the control device opens the first valve and closes the second valve if the operating state of the refrigeration cycle device is not stable.

[0069] (Item 6) The refrigeration cycle apparatus according to any one of Items 2 to 5, further comprising a sensor for detecting a parameter related to operation of the refrigeration cycle apparatus, and the control device determines that the operation state of the refrigeration cycle apparatus is stable when the parameter is greater than a threshold value corresponding to the parameter.

[0070] (Item 7) In the refrigeration cycle apparatus according to item 6, the sensor includes a first pressure sensor that detects a first pressure value of the refrigerant on a discharge side of the compressor, and a second pressure sensor that detects a second pressure value of the refrigerant on a suction side of the compressor, and the parameter includes a differential value between the first pressure value and the second pressure value.

[0071] (Item 8) In the refrigeration cycle device according to item 6 or 7, the sensor includes a timer that detects an operation time of the refrigeration cycle device, and the parameters include the operation time.

[0072] (Item 9) In the refrigeration cycle apparatus according to any one of Items 6 to 8, the sensor includes a superheat sensor that detects a degree of superheat of the refrigerant on the discharge side of the compressor. The parameter includes the degree of superheat.

[0073] (Item 10) In the refrigeration cycle apparatus according to any one of Items 6 to 9, the sensor includes a subcooling degree sensor that detects the subcooling degree of the refrigerant on the outlet side of the condenser. The parameter includes the subcooling degree.

[0074] (11) In the refrigeration cycle device according to any one of the first to tenth aspects, the refrigerant introduced by the first valve flows into the evaporator.

[0075] (Item 12) A method disclosed herein is a control method for a refrigeration cycle apparatus. The refrigeration cycle apparatus includes a compressor, a condenser, an expansion valve, an evaporator, the compressor, the condenser, the expansion valve, a pipe, a first bypass pipe, and a first valve. The pipe connects the compressor, the condenser, the expansion valve, and the evaporator. The first valve is a valve for directing refrigerant from the compressor to the first bypass pipe. One end of the first bypass pipe is connected to a pipe connecting the evaporator and the expansion valve. The other end of the first bypass pipe is connected to a pipe on the discharge side of the compressor. The control method opens the first valve when operation of the refrigeration cycle apparatus stops.

[0076] 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 the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0077] 1 Compressor, 1A Discharge side, 1B Suction side, 2 Indoor heat exchanger, 3 Expansion valve, 4 Outdoor heat exchanger, 11 First valve, 12 Second valve, 20, 20A Pipe, 31 First bypass pipe, 31A, 32A One end, 31B, 32B Other end, 32 Second bypass pipe, 50 Control device, 52 Memory, 61 First pressure sensor, 62 Second pressure sensor, 101, 102 Refrigeration cycle device, 151 Timer, 152 Superheat sensor, 153 Subcool sensor, 201 Outdoor unit, 202 Indoor unit.

Claims

1. A refrigeration cycle device comprising: a compressor, a condenser, an expansion valve, an evaporator; piping connecting the compressor, the condenser, the expansion valve, and the evaporator; a first bypass piping; a first valve for guiding refrigerant from the compressor to the first bypass piping; and a control device for controlling the first valve, wherein one end of the first bypass piping is connected to a piping connecting the evaporator and the expansion valve, and the other end of the first bypass piping is connected to a piping on the discharge side of the compressor, and the control device opens the first valve when operation of the refrigeration cycle device stops.

2. The refrigeration cycle device according to claim 1, further comprising a second bypass pipe and a second valve for guiding refrigerant discharged from the compressor to the second bypass pipe, one end of the second bypass pipe being connected to a pipe on the discharge side of the compressor and the other end of the second bypass pipe being connected to a pipe on the suction side of the compressor, and the control device opening the second valve when the operation of the refrigeration cycle device is stopped and the operating state of the refrigeration cycle device is stable.

3. A refrigeration cycle device as described in claim 2, wherein the control device opens the second valve and closes the first valve when the operation state of the refrigeration cycle device is in the stable state when operation of the refrigeration cycle device is stopped.

4. A refrigeration cycle device as described in claim 2 or claim 3, wherein the control device opens the first valve when the operating state of the refrigeration cycle device is not in the stable state when operation of the refrigeration cycle device is stopped.

5. A refrigeration cycle device as described in claim 4, wherein the control device opens the first valve and closes the second valve when the operation state of the refrigeration cycle device is not in the stable state when operation of the refrigeration cycle device is stopped.

6. A refrigeration cycle device according to any one of claims 2 to 5, further comprising a sensor for detecting a parameter relating to the operation of the refrigeration cycle device, and the control device determines that the operating state of the refrigeration cycle device is in the stable state when the parameter is greater than a threshold value corresponding to the parameter.

7. A refrigeration cycle device as described in claim 6, wherein the sensor includes a first pressure sensor that detects a first pressure value of the refrigerant on the discharge side of the compressor, and a second pressure sensor that detects a second pressure value of the refrigerant on the suction side of the compressor, and the parameter includes a difference value between the first pressure value and the second pressure value.

8. The refrigeration cycle device according to claim 6 or 7, wherein the sensor includes a timer that detects an operating time of the refrigeration cycle device, and the parameters include the operating time.

9. A refrigeration cycle device according to any one of claims 6 to 8, wherein the sensor includes a superheat sensor that detects the degree of superheat of the refrigerant on the discharge side of the compressor, and the parameter includes the degree of superheat.

10. A refrigeration cycle device according to any one of claims 6 to 9, wherein the sensor includes a subcooling degree sensor that detects the degree of subcooling of the refrigerant on the outlet side of the condenser, and the parameter includes the degree of subcooling.

11. A refrigeration cycle device according to any one of claims 1 to 10, wherein the refrigerant guided by the first valve flows into the evaporator.

12. A control method for a refrigeration cycle device, the refrigeration cycle device comprising: a compressor, a condenser, an expansion valve, an evaporator; piping connecting the compressor, the condenser, the expansion valve, and the evaporator; a first bypass piping; and a first valve for directing refrigerant from the compressor to the first bypass piping, one end of the first bypass piping being connected to a piping connecting the evaporator and the expansion valve, and the other end of the first bypass piping being connected to a piping on the discharge side of the compressor, the control method opening the first valve when operation of the refrigeration cycle device stops.

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