Refrigeration cycle device and control method

Abstract

The present invention provides a device and a method capable of suppressing a disproportionation reaction. The device is a refrigeration cycle device in which a non-azeotropic refrigerant mixture circulates as a refrigerant in a refrigerant circuit in which a compressor 10, a condenser 11, a first expansion valve 12, and an evaporator 13 have been connected by piping in the given order, said refrigeration cycle device comprising: a low-pressure sensor 16 for detecting the pressure on the intake side of the compressor 10; a branch path 18 that branches from piping connecting the condenser 11 and the first expansion valve 12 and is connected to piping connecting the evaporator 13 and the compressor 10; a second expansion valve 20 provided on the branch path 18; a heat exchanger 19 for performing heat exchange between the refrigerant flowing from the condenser 11 to the first expansion valve 12 and the refrigerant expanded by the second expansion valve 20; and a second solenoid valve 21 that is provided on the branch path 18 downstream of the heat exchanger 19, and opens / closes according to a detection result from the low-pressure sensor 16.

Description

Refrigeration cycle device and control method

[0001] The present invention relates to a refrigeration cycle device and a method for controlling the operation of the refrigeration cycle device.

[0002] In a refrigeration cycle device such as a refrigerator or air conditioner, a compressor, a condenser, an expansion valve, and an evaporator are connected by pipes to form a refrigerant circuit, and the refrigerant circuit is filled with refrigerant. The refrigeration cycle device is controlled so that when the pressure on the suction side of the compressor falls below a first threshold, the compressor stops operating and the flow of refrigerant to the evaporator (use-side heat exchanger) stops, and when the pressure on the suction side rises to or above a second threshold while the compressor is stopped, the compressor restarts and the refrigerant starts flowing to the evaporator.

[0003] When the refrigeration / freezing load is small or when the outside air temperature is high and the refrigerant pressure in the refrigerant circuit is likely to rise, the compressor will restart immediately after being stopped, causing the suction side pressure to drop quickly and the compressor to stop operating again, resulting in the compressor repeatedly starting and stopping.

[0004] Therefore, a technology has been proposed that, when the compressor is restarted and then stops (and the heater is turned off) after a predetermined time, extends the stop time from when the compressor stops until it is restarted, thereby controlling the operation of the refrigerator to stabilize it (see, for example, Patent Document 1).

[0005] Patent No. 347263

[0006] In recent years, there has been a demand for a shift to refrigerants with lower global warming potential (GWP) values ​​in order to prevent global warming. For example, R1234yf (2,3,3,3-tetrafluoropropene), R1132(E) (trans-1,2-difluoroethylene), R1123 (1,1,2-trifluoroethylene), and the like have been proposed as next-generation low-GWP refrigerants.

[0007] When two or more of the above low-GWP refrigerants are mixed, a non-azeotropic refrigerant mixture with different boiling points is formed, which can cause a disproportionation reaction, resulting in a large heat release and a pressure increase, posing a challenge to ensuring the reliability of the compressor and refrigeration cycle. Disproportionation reactions are reactions in which one type of refrigerant is converted into two or more different substances.

[0008] It is known that disproportionation reactions occur when high energy is applied under an excessively high temperature and pressure in a refrigerant atmosphere. Disproportionation reactions are more likely to occur when the concentration of refrigerants that exhibit disproportionation reactions increases. In non-azeotropic refrigerant mixtures, the refrigerant composition changes within the refrigeration cycle, and at certain points in the refrigeration cycle, the concentration of refrigerants that exhibit disproportionation reactions increases, making disproportionation reactions more likely to occur.

[0009] In the above-described conventional technology, the shutdown time between shutdown and restart is extended. During this time, however, the refrigerant with a high boiling point dissolves in the oil that lubricates the sliding parts inside the compressor, increasing the concentration of the refrigerant with a low boiling point, which increases the likelihood of a disproportionation reaction occurring.

[0010] In view of the above problems, the present invention provides a refrigeration cycle device in which a non-azeotropic refrigerant mixture circulates as a refrigerant in a refrigerant circuit in which a compressor, a condenser, a first expansion means, and an evaporator are connected in sequence by piping, the refrigeration cycle device including: a detection means for detecting the pressure on the suction side of the compressor; a branch path branching from the piping connecting the condenser and the expansion means and leading to the piping connecting the evaporator and the compressor; a second expansion means provided in the branch path; a heat exchanger that exchanges heat between the refrigerant flowing from the condenser to the first expansion means and the refrigerant expanded by the second expansion means; and an opening / closing means provided in the branch path after passing through the heat exchanger, which opens and closes in accordance with the detection result of the detection means.

[0011] According to the present invention, the occurrence of disproportionation reactions can be suppressed.

[0012] A diagram showing a first configuration example of a refrigeration cycle apparatus. A diagram showing a second configuration example of a refrigeration cycle apparatus. A diagram showing a third configuration example of a refrigeration cycle apparatus. A flowchart showing a first example of operation control of a refrigeration cycle apparatus. A flowchart showing a second example of operation control of a refrigeration cycle apparatus. A diagram showing a fourth configuration example of a refrigeration cycle apparatus. A flowchart showing a third example of operation control of a refrigeration cycle apparatus. A diagram showing a fifth configuration example of a refrigeration cycle apparatus. A flowchart showing a fourth example of operation control of a refrigeration cycle apparatus.

[0013] A refrigeration cycle device is a device in which a refrigerant circulates in a refrigerant circuit in which a compressor, a condenser, an expansion means, and an evaporator are connected in sequence by piping, and the circulating refrigerant exchanges heat with a fluid such as water or air to provide a cooled or heated fluid. The refrigeration cycle device may be any device, such as a refrigerator, chiller, or air conditioner, as long as it has a refrigerant circuit.

[0014] The refrigerant filled in the refrigerant circuit of a refrigeration cycle device may be R410A, which is the mainstream refrigeration system for refrigerators, freezers, and commercial air conditioners, but because it has a high GWP value of 2090, it is necessary to change to R1234yt, R1132(E), R1123, etc., which have a lower GWP value of approximately 1, in order to prevent global warming. R410A is an azeotropic refrigerant mixture containing 50% by mass each of R32 (difluoromethane) and R125 (pentafluoroethane).

[0015] R1234yt is used as a refrigerant in car air conditioners, vending machines, etc., but because it is an expensive refrigerant, in large refrigeration cycle devices that require a large amount of filling in the refrigerant circuit, it is desirable to use a non-azeotropic refrigerant mixture of R1234yt and R1132(E) or a non-azeotropic refrigerant mixture of R1234yt and R1123. However, when R1132(E) or R1123 is used as a component of a mixed refrigerant, there is a problem that a disproportionation reaction occurs.

[0016] Therefore, it is desired to provide a refrigeration cycle device that can suppress the occurrence of disproportionation reactions even when a non-azeotropic refrigerant mixture is used as the refrigerant.

[0017] 1 is a diagram showing a first configuration example of a refrigeration cycle apparatus. The refrigeration cycle apparatus includes a compressor 10, a condenser 11, a first expansion valve 12 as a first expansion means, an evaporator 13, and an accumulator 14, which are sequentially connected by piping to form a refrigerant circuit. The refrigeration cycle apparatus includes a control means for controlling the operation of the refrigeration cycle apparatus by starting and stopping the compressor 10, changing the operating frequency of the compressor 10, adjusting the opening degree of the first expansion valve 12, etc. The control means can be implemented as a control panel or the like.

[0018] The refrigerant circuit is filled with a non-azeotropic refrigerant mixture (hereinafter simply referred to as the refrigerant), and the refrigerant circulates through the refrigerant circuit when the compressor 10 is started. The compressor 10 sucks in the refrigerant, increases its pressure to a predetermined level, and discharges it toward the condenser 11.

[0019] The condenser 11 has heat transfer tubes and exchanges heat between a high-temperature gaseous refrigerant (also called refrigerant gas or gas refrigerant) flowing inside the heat transfer tubes and air taken in by a fan 15 and flowing outside the heat transfer tubes. The refrigerant gas entering the condenser 11 is condensed by the condenser 11 and discharged as a liquid refrigerant (also called liquid refrigerant). The first expansion valve 12 controls the flow rate of the liquid refrigerant leaving the condenser 11 and expands the liquid refrigerant, partially vaporizing it. As a result, the refrigerant flows into the evaporator 13 in a two-phase flow state, with a mixture of liquid and gas.

[0020] The evaporator 13 has heat transfer tubes and exchanges heat between the refrigerant in a two-phase flow state flowing through the heat transfer tubes and a fluid to be cooled, such as water or air. The refrigerant evaporates at a certain temperature (saturation temperature) corresponding to the pressure inside the evaporator 13, and is discharged from the evaporator 13 at or above the saturation temperature. When the refrigerant is discharged at a temperature about Δt higher than the saturation temperature, Δt indicates the temperature rise from the saturation temperature and is called the degree of superheat.

[0021] The refrigerant that leaves the evaporator 13 is sent to the accumulator 14. The accumulator 14 separates the liquid that was not completely evaporated in the evaporator 13, and sucks only the gas into the compressor 10. Furthermore, if the amount of refrigerant present on the condenser 11 side and the evaporator 13 side changes, the accumulator 14 absorbs the change, allowing the device to operate smoothly.

[0022] The refrigeration cycle device is provided with a low-pressure sensor 16 as a detection means for detecting the pressure of the refrigerant on the suction side of the compressor 10, in a pipe connecting the evaporator 13 and the accumulator 14. The refrigeration cycle device also has a first solenoid valve 17 between the condenser 11 and the first expansion valve 12, which separates the condenser 11 side and the evaporator 13 side of the refrigerant circuit and blocks the flow of refrigerant.

[0023] When the temperature of the fluid to be cooled reaches a set temperature and further cooling is no longer necessary, the refrigeration cycle device switches the first solenoid valve 17 from open to closed to stop the supply of refrigerant to the evaporator 13. Since the compressor 10 continues to operate even when the first solenoid valve 17 is closed, the refrigeration cycle device stops the compressor 10 when the pressure on the evaporator 13 side drops and the low pressure sensor 16 detects that the refrigerant pressure is equal to or lower than the first threshold value.

[0024] When the temperature of the fluid changes by more than a predetermined temperature from the set temperature, the refrigeration cycle device determines that cooling is necessary and switches the first solenoid valve 17 from closed to open. This causes the refrigerant on the condenser 11 side to flow into the evaporator 13 side, increasing the pressure on the evaporator 13 side. When the low pressure sensor 16 detects that the refrigerant pressure is equal to or greater than a second threshold value that is greater than the first threshold value, the refrigeration cycle device starts the compressor 10.

[0025] In this way, the refrigeration cycle device can operate (thermo on) or stop operating (thermo off) based on the refrigerant pressure (the refrigerant pressure on the suction side of compressor 10) corresponding to the refrigeration / freezing load.

[0026] When the refrigeration / freezing load is small, the time required to switch between thermo-on and thermo-off is short, causing the compressor 10 to start and stop repeatedly, resulting in unstable operation of the refrigeration cycle device and a shortened lifespan of the compressor 10. The same is true when the outside temperature is high: even if the device stops due to thermo-off, if the pressure on the suction side of the compressor 10 increases due to the outside air, the compressor 10 will start, but because the first solenoid valve 17 remains closed, the pressure on the suction side will immediately drop, causing the compressor 10 to stop again and start and stop repeatedly.

[0027] Therefore, as in the above-described conventional technology, the stop time from stopping to restarting can be controlled to be longer, thereby preventing the compressor 10 from repeatedly starting and stopping, and stabilizing the operation of the refrigeration cycle device.

[0028] When a non-azeotropic refrigerant mixture is used as the refrigerant filled in the refrigerant circuit, a disproportionation reaction is more likely to occur as the concentration of the refrigerant that exhibits the disproportionation reaction increases. Hereinafter, the non-azeotropic refrigerant mixture will be described as a mixture of R1234yt and R1132(E), but the non-azeotropic refrigerant mixture is not limited to a mixture of these refrigerants.

[0029] In a mixed refrigerant of R1234yt and R1132(E), R1132(E) has a lower boiling point and exhibits disproportionation reaction, and R1234yt dissolves more strongly in oil. For this reason, it is known that the concentration of R1132(E) in the refrigerant gas increases when the refrigeration cycle device is stopped for a long period of time.

[0030] In the conventional technology described above, the compressor 10 is restarted based on the suction-side pressure. Therefore, if the suction-side pressure does not increase, the compressor may not restart and may be shut down for a long time. For example, this occurs when the load is small and the suction-side pressure does not exceed the second threshold, or when the outside air temperature is low and the suction-side piping is cooled. If the compressor 10 is shut down for a long time, the concentration of R1132(E) in the refrigerant gas increases, raising concerns that disproportionation reactions may become more likely to occur.

[0031] Therefore, the refrigeration cycle device includes a branch path 18 that branches off from the pipe connecting the condenser 11 and the first expansion valve 12 (more specifically, the pipe connecting the condenser 11 and the first solenoid valve 17) and leads to the pipe connecting the compressor 10 and the evaporator 13 (more specifically, the pipe connecting the accumulator 14 and the evaporator 13). The refrigeration cycle device also includes a heat exchanger 19, a second expansion valve 20 provided in the branch path 18, and a second solenoid valve 21 as opening / closing means.

[0032] The heat exchanger 19 is also called a subcooler or an economizer, and exchanges heat between the refrigerant flowing from the condenser 11 to the first expansion valve 12 and the refrigerant branched to the branch path 18 and expanded by the second expansion valve 20. The refrigerant expanded by the second expansion valve 20 loses pressure, is partially gasified, and its temperature drops. In the heat exchanger 19, the refrigerant expanded by the second expansion valve 20 absorbs heat from the refrigerant flowing from the condenser 11 to the first expansion valve 12, and its temperature rises and it gasifies.

[0033] Because the refrigerant gas leaving the heat exchanger 19 may be partially condensed while flowing through the branch line 18, it is desirable to provide the branch line 18 so as to connect to the upstream side of the accumulator 14 between the accumulator 14 and the evaporator 13, rather than the downstream side of the accumulator 14 between the accumulator 14 and the compressor 10. Furthermore, when switching from normal operation in which the refrigerant circulates through the refrigerant circuit to operation in which the refrigerant circulates through the branch line, the pressure on the suction side of the compressor 10 drops significantly, preventing the compressor 10 from stopping. To prevent this, it is desirable to connect the branch line 18 upstream of the accumulator 14 to prevent a sudden change in the pressure on the suction side.

[0034] When the first solenoid valve 17 is closed and the compressor 10 remains activated, the pressure detected by the low pressure sensor 16 decreases. When the pressure detected by the low pressure sensor 16 falls below the first threshold, the second solenoid valve 21 is switched from closed to open, forming a bypass circuit so that the refrigerant circulates via the branch path 18, thereby allowing the compressor 10 to continue operating.

[0035] While the compressor 10 is operating, the R1234yt and R1132(E) are mixed and flow, and the refrigerant mixture composition remains almost constant. Therefore, the concentration of R1132(E), which indicates a disproportionation reaction, does not increase. Therefore, by providing the branch path 18 as described above and continuing to operate the compressor 10, the refrigerant does not stagnate, and the disproportionation reaction can be suppressed.

[0036] When the fluid to be cooled needs to be cooled and the first solenoid valve 17 is switched from closed to open, the refrigerant begins to flow through the evaporator 13, causing the pressure detected by the low pressure sensor 16 to rise. When the pressure detected by the low pressure sensor 16 reaches or exceeds a second threshold value that is higher than the first threshold value, the second solenoid valve 21 is switched from open to closed. This returns the system to normal operation in which the refrigerant circulates within the refrigerant circuit.

[0037] The opening and closing of the first solenoid valve 17, the valve opening degree of the second expansion valve 20, and the opening and closing of the second solenoid valve 21 are controlled by the control means described above.

[0038] Here, the refrigeration cycle device is described as a device that cools a fluid by exchanging heat with a refrigerant, but it may also be used as a device that not only cools but also heats (warms) a fluid by providing a four-way valve in the refrigerant circuit and switching the direction in which the refrigerant flows.

[0039] Fig. 2 is a diagram showing a second configuration example of a refrigeration cycle apparatus. In the configuration example shown in Fig. 1, a branch path 18 is provided after the refrigerant leaves the heat exchanger 19, but in the configuration example shown in Fig. 2, a branch path 18 is provided before the refrigerant enters the heat exchanger 19. Therefore, the heat exchanger 19 is configured to perform heat exchange between the refrigerant flowing from the condenser 11 to the first expansion valve 12 and the refrigerant branched to the branch path 18 and expanded by the second expansion valve 20. Note that the functions of the other units such as the compressor 10 have already been described, and therefore will not be described here.

[0040] Fig. 3 is a diagram showing a third configuration example of the refrigeration cycle apparatus. The configuration example shown in Fig. 3 is substantially the same as the configuration example shown in Fig. 1, but includes a second branch path 22 that branches off from the branch path 18 midway and is connected to the injection port of the compressor 10. In addition, a check valve 23 is provided in the second branch path 22 to prevent the refrigerant from flowing back.

[0041] In this example, the second branch line 22 is provided separately, but the branch line 18 may be connected to the injection port of the compressor 10, and the second branch line 22 may branch off from the piping connecting the heat exchanger 19 and the check valve 23 and be connected to the piping connecting the evaporator 13 and the accumulator 14.

[0042] The refrigerant gas returned to the injection port of the compressor 10 is a low temperature gas and is used to reduce the temperature of the refrigerant in the compressor 10, whose operating range may be limited by the temperature of the refrigerant.

[0043] 4 is a flowchart showing a first example of operation control of the refrigeration cycle apparatus. Operation control of the refrigeration cycle apparatus is started by the control means from step 100 when the operation of the refrigeration cycle apparatus is started and power is applied to the control means. In step 101, it is determined whether the pressure detected by the low-pressure sensor 16 is equal to or lower than a first threshold value. The process of step 101 is repeated until the pressure detected by the low-pressure sensor 16 becomes equal to or lower than the first threshold value.

[0044] If it is determined in step 101 that the pressure detected by low pressure sensor 16 is equal to or lower than the first threshold, the process proceeds to step 102, where second solenoid valve 21 provided in branch path 18 is switched from closed to open. In step 103, it is determined whether the pressure detected by low pressure sensor 16 is equal to or higher than the second threshold. If it is determined that the pressure detected by low pressure sensor 16 is equal to or higher than the second threshold, the process returns to step 101. If it is determined that the pressure is not equal to or higher than the second threshold, the process of step 103 is repeated.

[0045] The operation control by the control means ends when the operation of the refrigeration cycle device ends and the power supply to the control means is cut off. The operation control also ends when the power supply to the control means is cut off due to a power outage, etc.

[0046] The compressor 10 may be a capacity control type compressor capable of adjusting the discharge amount, and when the suction pressure falls below the first threshold, the second solenoid valve 21 is opened to circulate the refrigerant through the branch path 18. At this time, the compressor 10 can continue to operate at a minimum operating frequency, which is the lower limit of the operating frequency. Here, the minimum operating frequency includes, for example, not only the minimum operating frequency but also an operating frequency in the vicinity of the minimum operating frequency up to an operating frequency determined with a certain margin above the minimum operating frequency.

[0047] 5 is a flowchart showing a second example of operation control of the refrigeration cycle apparatus. Operation control of the refrigeration cycle apparatus is started by the control means from step 200 when the operation of the refrigeration cycle apparatus is started and power is supplied to the control means. Steps 201, 202, and 204 are the same processes as steps 101 to 103 shown in FIG. 4, and therefore, description thereof will be omitted here.

[0048] In step 203, the operating frequency of the compressor 10 is set to the minimum operating frequency, and the compressor 10 is controlled to operate at the minimum operating frequency.

[0049] Fig. 6 is a diagram showing a fourth configuration example of the refrigeration cycle device. The configuration example shown in Fig. 6 is almost the same as the configuration example shown in Fig. 3, and includes a measuring means 30 for measuring the stop time.

[0050] The control means has operation modes including a normal operation mode in which the first solenoid valve 17 is opened, the compressor 10 is started, and the refrigerant is circulated via the evaporator 13, and an idling operation mode in which the first solenoid valve 17 is closed, the refrigerant is circulated via the branch path 18, and the compressor 10 continues to operate. The normal operation mode is a mode in which the refrigerant circulates through the refrigerant circuit, and the idling operation mode is a mode in which the refrigerant circulates via the branch path 18 and the second solenoid valve 21. In the example shown in Fig. 3, in both the normal operation mode and the idling operation mode, the refrigerant is sent to the injection port of the compressor 10 via the branch path 18 and the check valve 23.

[0051] The control means closes the first solenoid valve 17, and when the pressure detected by the low pressure sensor 16 is equal to or lower than the first threshold value, stops the compressor 10 and stops operation of the refrigeration cycle device, unlike the control shown in Figures 4 and 5.

[0052] The measuring means 30 measures the time that has elapsed since the compressor 10 was stopped. The measuring means 30 then determines whether a predetermined stop time has elapsed, and if the predetermined stop time has elapsed, instructs the control means to transition to an idling operation mode. The predetermined stop time is the time it takes for the concentration of the refrigerant that causes a disproportionation reaction to reach a predetermined concentration (composition ratio), and can be, for example, 1 to 12 hours. Note that the measuring means 30 may simply measure the time and notify the control means of the measured time, and the control means may then determine whether the predetermined stop time has elapsed and switch from the normal operation mode to the idling operation mode.

[0053] 7 is a flowchart showing a third example of operation control of the refrigeration cycle apparatus. As with the operation control shown in FIGS. 4 and 5, when power is applied to the control means, the control means starts from step 300. In step 301, it is determined whether the pressure detected by the low-pressure sensor 16 is equal to or lower than the first threshold. If it is determined that the pressure is not equal to or lower than the first threshold, the process of step 301 is repeated. If it is determined that the pressure is equal to or lower than the first threshold, the process proceeds to step 302, where the compressor 10 is stopped.

[0054] In step 303, the measurement means 30 measures the time during which the compressor 10 is stopped. That is, it measures the time that has elapsed since the compressor 10 stopped operating. In step 304, it is determined whether the measured time has reached a predetermined stop time. The processes of steps 303 and 304 are repeated until it is determined that the predetermined stop time has been reached. If it is determined that the predetermined stop time has been reached, the process proceeds to step 305, where the operation mode is switched to idling operation mode. The measurement means 30 resets the measured time and waits for the next measurement.

[0055] When the operation mode is switched to the idling operation mode, in step 306, the second solenoid valve 21 is opened, the compressor 10 is started, and the refrigerant is circulated through the branch path 18. In step 307, it is determined whether the pressure detected by the low pressure sensor 16 is equal to or greater than the second threshold. If it is determined that the pressure detected by the low pressure sensor 16 is equal to or greater than the second threshold, the process returns to step 301. If it is determined that the pressure detected by the low pressure sensor 16 is not equal to or greater than the second threshold, the process proceeds to step 308, where the operation of the compressor 10 continues and the circulation of the refrigerant through the branch path 18 continues. Then, the process returns to step 307.

[0056] The operation control by the control means ends when the operation of the refrigeration cycle device ends and the power supply to the control means is cut off. The operation control also ends when the power supply to the control means is cut off due to a power outage, etc.

[0057] Fig. 8 is a diagram showing a fifth configuration example of the refrigeration cycle apparatus. The configuration example shown in Fig. 8 is substantially the same as the configuration example shown in Fig. 3, but includes a thermistor 40 as second detection means for detecting the temperature of oil stored in the compressor 10. The oil is a lubricating oil that lubricates sliding parts where members slide against each other, such as between a rotating shaft (shaft) and a bearing provided in the compressor 10.

[0058] R1234yt, which constitutes the non-azeotropic refrigerant mixture, has a higher boiling point than R1132(E) and dissolves easily in oil. The lower the oil temperature, the more easily R1234yt dissolves. When the oil temperature drops and more R1234yt dissolves in the oil, the concentration of R1234yt in the refrigerant gas decreases, while the concentration of R1132(E), which induces a disproportionation reaction, increases, making the disproportionation reaction more likely to occur.

[0059] Therefore, by detecting the oil temperature with the thermistor 40 and controlling the engine to switch to idling operation mode when the oil temperature drops below a predetermined oil temperature, the concentration of R1132(E) can be prevented from increasing any further and the occurrence of disproportionation reactions can be suppressed. The thermistor 40 is a sensor that brings a resistor, whose electrical resistance value changes with temperature changes, into contact with the oil, detects the resulting change in electrical resistance, and measures the temperature from that change.

[0060] 9 is a flowchart showing a fourth example of operation control of the refrigeration cycle apparatus. As with the operation control shown in FIGS. 4, 5, and 7, when power is applied to the control means, the control means starts from step 400. In step 401, it is determined whether the pressure detected by the low-pressure sensor 16 is equal to or lower than the first threshold. If it is determined that the pressure is not equal to or lower than the first threshold, the process of step 401 is repeated. If it is determined that the pressure is equal to or lower than the first threshold, the process proceeds to step 402, where the compressor 10 is stopped.

[0061] In step 403, the thermistor 40 detects the oil temperature. In step 404, it is determined whether the detected oil temperature is equal to or lower than a predetermined oil temperature. Until it is determined that the oil temperature is equal to or lower than the predetermined oil temperature, the oil temperature detection and determination of whether the oil temperature is equal to or lower than the predetermined oil temperature in steps 403 and 404 are repeated. If it is determined that the oil temperature is equal to or lower than the predetermined oil temperature, the process proceeds to step 405, where the engine shifts to the idling operation mode.

[0062] When the operation mode is switched to the idling operation mode, in step 406, the second solenoid valve 21 is opened, the compressor 10 is started, and the refrigerant is circulated through the branch path 18. In step 407, it is determined whether the pressure detected by the low pressure sensor 16 is equal to or greater than the second threshold. If it is determined that the pressure detected by the low pressure sensor 16 is equal to or greater than the second threshold, the process returns to step 401. If it is determined that the pressure detected by the low pressure sensor 16 is not equal to or greater than the second threshold, the process proceeds to step 408, where the operation of the compressor 10 continues and the circulation of the refrigerant through the branch path 18 continues. Then, the process returns to step 407.

[0063] The operation control by the control means ends when the operation of the refrigeration cycle device ends and the power supply to the control means is cut off. The operation control also ends when the power supply to the control means is cut off due to a power outage, etc.

[0064] As described above, by providing the refrigeration cycle apparatus and control method of the present invention, it is possible to suppress the occurrence of disproportionation reactions. Furthermore, since it is not necessary to stop the compressor 10, starting and stopping of the compressor 10 is suppressed, thereby reducing power consumption loss during startup. By transitioning to the idling operation mode, the refrigerant does not accumulate before the first solenoid valve 17, thereby preventing damage to the first expansion valve 12 due to liquid hammer. Furthermore, by transitioning to the idling operation mode, the oil temperature can be maintained at a constant temperature, thereby suppressing the dissolution of the refrigerant into the oil.

[0065] The refrigeration cycle device and control method of the present invention have been described in detail using the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments and can be modified within the scope of what a person skilled in the art can imagine, such as other embodiments, additions, modifications, deletions, etc., and any aspect is included in the scope of the present invention as long as it achieves the functions and effects of the present invention.

[0066] REFERENCE SIGNS LIST 10 compressor 11 condenser 12 first expansion valve 13 evaporator 14 accumulator 15 fan 16 low pressure sensor 17 first solenoid valve 18 branch path 19 heat exchanger 20 second expansion valve 21 second solenoid valve 22 second branch path 23 check valve 30 measuring means 40 thermistor

Claims

A refrigeration cycle device in which a non-azeotropic refrigerant mixture circulates as a refrigerant in a refrigerant circuit in which a compressor, a condenser, a first expansion means, and an evaporator are connected in sequence by piping, a detection means for detecting the pressure on the suction side of the compressor; a branch path branching from a pipe connecting the condenser and the first expansion means and leading to a pipe connecting the evaporator and the compressor; a second expansion means provided in the branch passage; a heat exchanger that performs heat exchange between the refrigerant flowing from the condenser to the first expansion means and the refrigerant expanded by the second expansion means; an opening / closing means that is provided in the branch path after passing through the heat exchanger and that opens and closes in response to the detection result of the detection means; A refrigeration cycle device comprising:

2. The refrigeration cycle apparatus according to claim 1, wherein the opening / closing means switches from closed to open when the pressure detected by the detection means becomes equal to or lower than a first threshold value.

3. The refrigeration cycle apparatus according to claim 2, wherein the opening / closing means switches from open to closed when the pressure detected by the detection means becomes equal to or greater than a second threshold value that is greater than the first threshold value.

3. The refrigeration cycle apparatus according to claim 2, wherein the compressor is capacity-controllable, and operates at a minimum operating frequency when the pressure detected by the detection means reaches the first threshold value. 　 The compressor stops operating when the pressure detected by the detection means becomes equal to or lower than a first threshold value, the refrigeration cycle device includes a measuring means for measuring a time during which the compressor is stopped, 2. The refrigeration cycle apparatus according to claim 1, wherein the opening / closing means switches from closed to open when the time measured by the measuring means reaches a predetermined stop time. 　 a second detection means for detecting a temperature of oil supplied to a sliding part of the compressor; 2. The refrigeration cycle device according to claim 1, wherein the opening / closing means switches from closed to open when the temperature detected by the second detection means becomes equal to or lower than a predetermined oil temperature. 　 an accumulator on the intake side of the compressor for separating the refrigerant into a liquid phase and a gas phase; The refrigeration cycle apparatus according to any one of claims 1 to 6, wherein the branch passage is connected to a pipe that connects the evaporator and the accumulator. 　 A control method for controlling a refrigeration cycle device in which a non-azeotropic refrigerant mixture circulates as a refrigerant in a refrigerant circuit in which a compressor, a condenser, a first expansion means, and an evaporator are sequentially connected by piping, comprising: The refrigeration cycle device includes: a branch path branching from a pipe connecting the condenser and the first expansion means and leading to a pipe connecting the evaporator and the compressor; a second expansion means provided in the branch passage; a heat exchanger that performs heat exchange between the refrigerant flowing from the condenser to the first expansion means and the refrigerant expanded by the second expansion means; an opening / closing means provided in the branch path after passing through the heat exchanger; Including, The control method includes: detecting a pressure on the suction side of the compressor by a detection means; opening and closing the opening / closing means in accordance with the detection result of the detection means; A control method comprising:

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