Control device and refrigeration cycle device

Abstract

Provided are a control device and a refrigeration cycle device capable of expanding a control range of a refrigeration cycle circuit while suppressing disproportionation reactions. The control device (3) controls a compressor (4) of a refrigeration cycle circuit in which a working medium (20) containing an ethylene-based fluoroolefin as a refrigerant component circulates, in accordance with a result of comparison between a measurement value indicating at least one of an internal temperature and the internal pressure of the compressor (4) and at least one of a plurality of threshold values. The plurality of threshold values include a first threshold value and a second threshold value smaller than the first threshold value. The control device (3) stops the compressor (4) when the measurement value exceeds the first threshold value, operates the compressor (4) such that the drive frequency changes at a first frequency change rate while the measured value is the second threshold value or lower, and operates the compressor (4) such that the drive frequency changes at a second frequency change rate different from the first frequency change rate in at least one case among a case where the drive frequency is increased and a case where the drive frequency is decreased when the measurement value exceeds the second threshold value.

Description

Control device, refrigeration cycle device

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

[0002] Conventionally, R410A has been widely used as a working fluid (heat medium, refrigerant) for refrigeration cycle devices. However, R410A has a high global warming potential (GWP) of 2090. Therefore, from the perspective of preventing global warming, research and development has been conducted on working fluids with lower GWP. Patent Document 1 discloses 1,1,2-trifluoroethylene (HFO1123) as a working fluid with a lower GWP than R410A. Patent Document 2 discloses 1,2-difluoroethylene (HFO1132) as a working fluid with a lower GWP than R410A.

[0003] HFO1123 and HFO1132 have a smaller GWP than R410A, but this makes them less stable than R410A. For example, the generation of radicals can cause disproportionation reactions of HFO1123 or HFO1132, which can change HFO1123 and HFO1132 into other compounds.

[0004] Patent Document 3 discloses a refrigeration system having a refrigerant circuit configured by connecting a compressor, a condenser, a throttling device, and an evaporator with refrigerant piping, and using 1,1,2-trifluoroethylene as the refrigerant circulating through the refrigerant circuit. The refrigeration system disclosed in Patent Document 3 includes a first refrigerant sensor provided on the discharge side of the compressor for detecting the temperature and pressure of the refrigerant, and a control unit for controlling the compressor based on the detection results of the first refrigerant sensor. The control unit includes a disproportionation reaction determination means for determining whether the detection results of the first refrigerant sensor satisfy preset conditions before a disproportionation reaction of the refrigerant occurs, and a compressor rotation speed control means for suppressing the rotation speed of the compressor when the disproportionation reaction determination means determines that the preset conditions are satisfied.

[0005] International Publication No. WO 2012 / 157764 International Publication No. WO 2012 / 157765 International Publication No. WO 2015 / 140882

[0006] The refrigeration system disclosed in Patent Document 3 stops the compressor when it determines that the refrigerant temperature and pressure are equal to or higher than a first temperature and a first pressure before the disproportionation reaction occurs. However, to stop the compressor to prevent the disproportionation reaction from occurring, it is possible to set the first temperature and the first pressure sufficiently lower than the temperature and pressure at which the disproportionation reaction occurs, thereby accelerating the timing of stopping the compressor. However, the lower the first temperature and the first pressure are set below the temperature and pressure at which the disproportionation reaction occurs, the narrower the range of refrigerant temperature and pressure at which the refrigeration system (refrigeration cycle system) can perform normal operation, i.e., the narrower the control range of the refrigeration cycle system. This reduces the marketability of the refrigeration cycle system.

[0007] The present disclosure provides a control device and a refrigeration cycle device that enable the control range of a refrigeration cycle circuit to be expanded while enabling the suppression of disproportionation reactions.

[0008] A control device according to one aspect of the present disclosure controls a compressor of a refrigeration cycle circuit in which a working fluid containing an ethylene-based fluoroolefin as a refrigerant component circulates, the working fluid containing an ethylene-based fluoroolefin. The control device includes: a measurement circuit that outputs a measurement value indicating at least one of an internal temperature or an internal pressure of the compressor; and a control circuit that compares the measurement value from the measurement circuit with at least one of a plurality of thresholds and controls the compressor in accordance with the comparison result. The plurality of thresholds include a first threshold and a second threshold that is smaller than the first threshold. The control circuit stops the compressor when the measurement value exceeds the first threshold, operates the compressor so that the compressor's drive frequency changes at a first frequency change rate while the measurement value is equal to or less than the second threshold, and operates the compressor so that the drive frequency changes at a second frequency change rate different from the first frequency change rate in at least one of increasing the drive frequency and decreasing the drive frequency when the measurement value exceeds the second threshold.

[0009] A control device according to one aspect of the present disclosure controls a compressor and an expansion valve of a refrigeration cycle circuit through which a working fluid circulates, the working fluid including an ethylene-based fluoroolefin as a refrigerant component. The control device includes: a measurement circuit that outputs a measurement value indicating at least one of an internal temperature or an internal pressure of the compressor; and a control circuit that compares the measurement value from the measurement circuit with at least one of a plurality of thresholds and controls the compressor and the expansion valve according to the comparison result. The plurality of thresholds include a first threshold and a second threshold that is smaller than the first threshold. The control circuit stops the compressor when the measurement value exceeds the first threshold, operates the expansion valve of the refrigeration cycle circuit so that its aperture changes at a first aperture change rate while the measurement value is equal to or less than the second threshold, and operates the expansion valve to increase or decrease its aperture at a second aperture change rate different from the first aperture change rate when the measurement value exceeds the second threshold.

[0010] A refrigeration cycle device according to one aspect of the present disclosure includes any one of the control devices described above and a refrigeration cycle circuit.

[0011] The aspects of the present disclosure enable the suppression of disproportionation reactions while expanding the control range of the refrigeration cycle circuit.

[0012] FIG. 1 is a block diagram of a refrigeration cycle device according to a first embodiment; FIG. 2 is a schematic diagram of a compressor and a control device of the refrigeration cycle device according to the first embodiment; FIG. 3 is an explanatory diagram of control of a compressor by a control circuit of a control device according to the first embodiment; FIG. 4 is a block diagram of a refrigeration cycle device according to a second embodiment; FIG. 5 is an explanatory diagram of control of a compressor and an expansion valve by a control circuit of a control device according to the second embodiment; FIG. 6 is an explanatory diagram of control of a compressor by a control circuit of a control device according to a modified example; FIG. 7 is an explanatory diagram of control of a compressor by a control circuit of a control device according to a modified example;

[0013] [1. Embodiments] Hereinafter, embodiments of the present disclosure will be described, with reference to the drawings where appropriate. However, the following embodiments are merely examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following content (e.g., the shape, dimensions, and arrangement of each component). Positional relationships, such as up, down, left, and right, are based on the positional relationships shown in the drawings unless otherwise specified. Each figure described in the following embodiments is a schematic diagram, and the ratios of the size and thickness of each component in each figure do not necessarily reflect the actual dimensional ratios. Furthermore, the dimensional ratios of each element are not limited to the ratios shown in the drawings.

[0014] In the following description, when it is necessary to distinguish between multiple components, prefixes such as "first" and "second" are added to the names of the components. However, when the components can be distinguished from each other by the symbols attached to them, the prefixes such as "first" and "second" may be omitted in consideration of readability of the text.

[0015] In the following description, when it is necessary to distinguish between multiple components, suffixes such as "-1" and "-2" are added to the symbols of the components. However, when it is not necessary to distinguish between multiple components, the suffixes "-1" and "-2" may be omitted to improve readability.

[0016] 1 is a block diagram of a refrigeration cycle apparatus 1 according to this embodiment. The refrigeration cycle apparatus 1 constitutes, for example, an air conditioner capable of cooling and heating operations. The refrigeration cycle apparatus 1 includes a refrigeration cycle circuit 2 and a control device 3.

[0017] The refrigeration cycle circuit 2 constitutes a flow path through which a working medium 20 (see FIG. 2) circulates. In this embodiment, the working medium 20 contains an ethylene-based fluoroolefin as a refrigerant component. The ethylene-based fluoroolefin is preferably an ethylene-based fluoroolefin that undergoes a disproportionation reaction. Examples of ethylene-based fluoroolefins that undergo a disproportionation reaction include 1,1,2-trifluoroethylene (HFO1123), trans-1,2-difluoroethylene (HFO1132(E)), cis-1,2-difluoroethylene (HFO-1132(Z)), 1,1-difluoroethylene (HFO-1132a), and tetrafluoroethylene (CF ２ =CF ２ , FO1114), and monofluoroethylene (HFO-1141).

[0018] The working fluid 20 may contain multiple types of refrigerant components. The working fluid 20 may contain an ethylene-based fluoroolefin as a main refrigerant component and a compound other than an ethylene-based fluoroolefin as a secondary refrigerant component. Examples of the secondary refrigerant component include hydrofluorocarbons (HFCs), hydrofluoroolefins (HFOs), saturated hydrocarbons, carbon dioxide, etc. Examples of hydrofluorocarbons (HFCs) include difluoromethane, difluoroethane, trifluoroethane, tetrafluoroethane, pentafluoroethane, pentafluorobutane, heptafluorocyclopentane, etc. Examples of hydrofluoroolefins (HFOs) include monofluoropropene, trifluoropropene, tetrafluoropropene, pentafluoropropene, hexafluorobutene, etc. Examples of saturated hydrocarbons include ethane, n-propane, cyclopropane, n-butane, cyclobutane, isobutane (2-methylpropane), methylcyclopropane, n-pentane, isopentane (2-methylbutane), neopentane (2,2-dimethylpropane), methylcyclobutane, and the like.

[0019] The working fluid 20 may further contain a disproportionation inhibitor that suppresses the disproportionation reaction of the ethylene-based fluoroolefin. Examples of disproportionation inhibitors include saturated hydrocarbons or haloalkanes. Examples of saturated hydrocarbons include ethane, n-propane, cyclopropane, n-butane, cyclobutane, isobutane (2-methylpropane), methylcyclopropane, n-pentane, isopentane (2-methylbutane), neopentane (2,2-dimethylpropane), methylcyclobutane, and the like. Of the above examples, n-propane is preferred. Examples of haloalkanes include haloalkanes having one or two carbon atoms. Examples of haloalkanes having one carbon atom (i.e., halomethanes) include (mono)iodomethane (CH ３ I), diiodomethane (CH ２ I ２ ), dibromomethane (CH ２ Br ２ ), bromomethane (CH ３ Br), dichloromethane (CH ２ Cl ２ ), chloroiodomethane (CH ２ ClI), dibromochloromethane (CHBr ２ Cl), tetraiodomethane (Cl ４ ), carbon tetrabromide (CBr ４ ), bromotrichloromethane (CBrCl ３ ), dibromodichloromethane (CBr ２ Cl ２ ), tribromofluoromethane (CBr ３ F), fluorodiiodomethane (CHFI ２ ), difluorodiiodomethane (CF ２ I ２ ), dibromodifluoromethane (CBr ２ F ２ ), trifluoroiodomethane (CF ３ Examples of haloalkanes having two carbon atoms (i.e., haloethanes) include 1,1,1-trifluoro-2-iodoethane (CF ３ CH ２ I), monoiodoethane (CH ３ CH ２I), monobromoethane (CH ３ CH ２ Br), 1,1,1-triiodoethane (CH ３ CI ３ The working fluid 20 may contain one or more types of haloalkanes having 1 or 2 carbon atoms. That is, only one type of haloalkane having 1 or 2 carbon atoms may be used, or two or more types may be used in appropriate combination.

[0020] The refrigeration cycle circuit 2 includes a compressor 4 , a first heat exchanger 5 , an expansion valve 6 , a second heat exchanger 7 , and a four-way valve 8 .

[0021] The refrigeration cycle apparatus 1 includes an outdoor unit 1a and an indoor unit 1b. The outdoor unit 1a includes a control device 3, a compressor 4, a first heat exchanger 5, an expansion valve 6, and a four-way valve 8. The outdoor unit 1a further includes a first blower 5a for promoting heat exchange in the first heat exchanger 5. The indoor unit 1b includes a second heat exchanger 7. The indoor unit 1b further includes a second blower 7a for promoting heat exchange in the second heat exchanger 7.

[0022] In the refrigeration cycle circuit 2, the compressor 4 compresses the working medium 20 to increase the pressure of the working medium 20. The compressor 4 will be described in detail later. The first heat exchanger 5 and the second heat exchanger 7 exchange heat between the working medium 20 circulating through the refrigeration cycle circuit 2 and external air (e.g., outside air or room air). The expansion valve 6 adjusts the pressure (evaporation pressure) of the working medium 20 and the flow rate of the working medium 20. The four-way valve 8 switches the direction of the working medium 20 circulating through the refrigeration cycle circuit 2 between a first direction corresponding to cooling operation and a second direction corresponding to heating operation.

[0023] In this embodiment, the first direction is the direction in which the working medium 20 circulates through the refrigeration cycle circuit 2 in the order of the compressor 4, the first heat exchanger 5, the expansion valve 6, and the second heat exchanger 7, as shown by the solid arrow A1 in Figure 1.

[0024] In cooling operation, the compressor 4 compresses and discharges the gaseous working medium 20, which is then sent to the first heat exchanger 5 via the four-way valve 8. The first heat exchanger 5 exchanges heat between the outside air and the gaseous working medium 20, causing the gaseous working medium 20 to condense and liquefy. The liquid working medium 20 is decompressed by the expansion valve 6 and sent to the second heat exchanger 7. In the second heat exchanger 7, heat exchange occurs between the liquid working medium 20 and the room air, causing the liquid working medium 20 to evaporate and become the gaseous working medium 20. The gaseous working medium 20 returns to the compressor 4 via the four-way valve 8. In cooling operation, the first heat exchanger 5 functions as a condenser, and the second heat exchanger 7 functions as an evaporator. Therefore, during cooling, the indoor unit 1b blows air cooled by heat exchange in the second heat exchanger 7 into the room.

[0025] In this embodiment, the second direction is the direction in which the working medium 20 circulates through the refrigeration cycle circuit 2 in the order of the compressor 4, the second heat exchanger 7, the expansion valve 6, and the first heat exchanger 5, as shown by the dashed arrow A2 in Figure 1.

[0026] In heating operation, the compressor 4 compresses and discharges the gaseous working medium 20, which is then sent to the second heat exchanger 7 via the four-way valve 8. The second heat exchanger 7 exchanges heat between the room air and the gaseous working medium 20, causing the gaseous working medium 20 to condense and liquefy. The liquid working medium 20 is decompressed by the expansion valve 6 and sent to the first heat exchanger 5. In the first heat exchanger 5, heat exchange occurs between the liquid working medium 20 and outside air, causing the liquid working medium 20 to evaporate and become the gaseous working medium 20. The gaseous working medium 20 returns to the compressor 4 via the four-way valve 8. In heating operation, the first heat exchanger 5 functions as an evaporator, and the second heat exchanger 7 functions as a condenser. Therefore, during heating, the indoor unit 1b blows air heated by heat exchange in the second heat exchanger 7 into the room.

[0027] The control device 3 controls the compressor 4 , the first blower 5 a , the expansion valve 6 , and the second blower 7 a of the refrigeration cycle circuit 2 .

[0028] FIG. 2 is a schematic diagram of the compressor 4 and the control device 3.

[0029] The compressor 4 is, for example, a hermetic compressor. The compressor 4 may be a rotary type, a scroll type, or any other known type. The compressor 4 includes a hermetic container 40, a compression mechanism 41, and an electric motor 42.

[0030] The sealed container 40 forms a flow path for the working medium 20. The sealed container 40 has a suction pipe 401 and a discharge pipe 402. The working medium 20 is sucked into the sealed container 40 from the suction pipe 401, compressed by the compression mechanism 41, and then discharged from the discharge pipe 402 to the outside of the sealed container 40. The inside of the sealed container 40 is filled with the high-temperature and high-pressure working medium 20 and lubricating oil. The bottom of the sealed container 40 forms an oil reservoir that stores a mixture of the working medium 20 and lubricating oil.

[0031] The compression mechanism 41 is located inside the sealed container 40 and compresses the working medium 20. The compression mechanism 41 may have a conventionally known configuration. The compression mechanism 41 has, for example, a cylinder that forms a compression chamber, a rolling piston that is disposed in the compression chamber inside the cylinder, and a crankshaft that is coupled to the rolling piston.

[0032] The electric motor 42 is located inside the sealed container 40 and drives the compression mechanism 41. The electric motor 42 is, for example, a brushless motor (three-phase brushless motor). The electric motor 42 includes, for example, a rotor fixed to the crankshaft of the compression mechanism 41 and a stator disposed around the rotor. The stator is configured, for example, by concentrating or dispersing a stator winding (magnet wire, etc.) around a stator core (electromagnetic steel plate, etc.) with an insulating material such as insulating paper interposed therebetween. The stator winding is covered with an insulating material. Examples of insulating materials include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), aramid polymer, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), etc.

[0033] The compressor 4 may include an accumulator to prevent liquid compression in the compression chamber of the compression mechanism 41. The accumulator separates the working medium 20 into a gaseous working medium 20 and a liquid working medium 20, and introduces only the gaseous working medium 20 from the suction pipe 401 into the inside of the sealed container 40.

[0034] The control device 3 includes a drive circuit 31 , a measurement circuit 32 , and a control circuit 33 .

[0035] The drive circuit 31 drives the electric motor 42 of the compressor 4. The drive circuit 31 supplies drive power to the electric motor 42 based on power from the power source 10. In this embodiment, the power source 10 is an AC power source. The drive circuit 31 supplies drive power to the electric motor 42 based on the AC power from the power source 10. In particular, the drive circuit 31 supplies three-phase AC power as drive power to the electric motor 42. The frequency of the three-phase AC power corresponds to the drive frequency of the compressor 4. The drive frequency of the compressor 4 corresponds to the rotation speed of the compressor 4.

[0036] The drive circuit 31 includes a converter circuit 311 and an inverter circuit 312 .

[0037] The converter circuit 311 converts AC power from the power supply 10 into DC power. The converter circuit 311 includes a rectifier circuit 311a and a smoothing circuit 311b. The rectifier circuit 311a is a diode bridge composed of multiple diodes D1 to D4. The power supply 10 is connected between the input terminals of the rectifier circuit 311a (the connection point between diodes D1 and D2 and the connection point between diodes D3 and D4), and the smoothing circuit 311b is connected between the output terminals of the rectifier circuit 311a (the connection point between diodes D1 and D3 and the connection point between diodes D2 and D4). The smoothing circuit 311b includes a series circuit of an inductor L1 and a capacitor C1, smoothes the voltage between the output terminals of the rectifier circuit 311a, and outputs the voltage across the capacitor C1. The configurations of the rectifier circuit 311a and the smoothing circuit 311b in FIG. 2 are well known, so detailed description thereof will be omitted.

[0038] The inverter circuit 312 supplies three-phase AC power to the motor 42 based on the DC power from the converter circuit 311. The inverter circuit 312 includes a plurality of arms U1, U2, V1, V2, W1, and W2. Each of the arms U1, U2, V1, V2, W1, and W2 is configured with a semiconductor switching element such as a transistor. The series circuit of the arms U1 and U2 is connected in parallel to the capacitor C1 of the converter circuit 311 and forms a U-phase leg. The series circuit of the arms V1 and V2 is connected in parallel to the capacitor C1 of the converter circuit 311 and forms a V-phase leg. The series circuit of the arms W1 and W2 is connected in parallel to the capacitor C1 of the converter circuit 311 and forms a W-phase leg. The configuration of the inverter circuit 312 in FIG. 2 is well known, so a detailed description thereof will be omitted.

[0039] The measurement circuit 32 outputs a measurement value indicating at least one of the internal temperature and the internal pressure of the compressor 4. In the present embodiment, the measurement circuit 32 measures the internal temperature of the compressor 4 and outputs the measurement value indicating the internal temperature of the compressor 4 to the control circuit 33. The measurement circuit 32 includes, for example, a temperature sensor. The temperature sensor is arranged so as to be able to measure, for example, the temperature of the working medium 20 in the sealed container 40 of the compressor 4 or the temperature of the working medium 20 discharged from the discharge pipe 402 of the compressor 4. The position of the temperature sensor is not particularly limited, and it is sufficient that the measurement circuit 32 can directly or indirectly measure the internal temperature of the compressor 4.

[0040] The control circuit 33 can be realized, for example, by a computer system including at least one processor (microprocessor) and one or more memories.

[0041] The control circuit 33 controls the drive circuit 31 to control the compressor 4. More specifically, the control circuit 33 controls the switching of the multiple arms U1, U2, V1, V2, W1, and W2 of the inverter circuit 312 of the drive circuit 31 so that the inverter circuit 312 supplies three-phase AC power to the electric motor 42 based on the DC power from the smoothing circuit 311b. The switching frequency of the inverter circuit 312 is, for example, 1000 Hz to 5000 Hz. The control circuit 33 controls the frequency of the three-phase AC power to control the drive frequency of the compressor 4, i.e., the rotation speed of the compressor 4.

[0042] The control circuit 33 executes processing to suppress the disproportionation reaction of the working medium 20 circulating through the refrigeration cycle circuit 2 based on the measurement value from the measurement circuit 32 (in this embodiment, the internal temperature of the compressor 4).

[0043] It is believed that heat and radicals are factors that cause the disproportionation reaction of the working fluid 20. For example, it is believed that the disproportionation reaction of the working fluid 20 progresses when radicals are generated under high temperature and high pressure. From this perspective, the control circuit 33 controls the compressor 4 based on the measurement value from the measurement circuit 32.

[0044] Fig. 3 is an explanatory diagram of control by the control circuit 33. In this embodiment, the measurement value from the measurement circuit 32 indicates the internal temperature of the compressor 4. Fig. 3 shows the relationship between the internal temperature of the compressor 4 and the control of the compressor 4.

[0045] The control circuit 33 compares the measurement value (internal temperature of the compressor 4) from the measurement circuit 32 with at least one of a plurality of threshold values ​​T11 to T15, and controls the compressor 4 according to the comparison result. In this embodiment, the relationship of the magnitudes of the plurality of threshold values ​​T11 to T15 is threshold value T11 > threshold value T12 > threshold value T13 > threshold value T14 > threshold value T15.

[0046] When the internal temperature of the compressor 4 exceeds a threshold value T11, the control circuit 33 stops the compressor 4. The threshold value T11 is set based on the temperature at which a disproportionation reaction may occur.

[0047] While the internal temperature of the compressor 4 is equal to or lower than a threshold value T15 that is lower than the threshold value T11, the control circuit 33 operates the compressor 4 so that the drive frequency of the compressor 4 changes at a first frequency change rate. The control circuit 33 increases or decreases the drive frequency of the compressor 4 at the first frequency change rate so that the drive frequency of the compressor 4 becomes a target drive frequency. The first frequency change rate is, for example, 0.3 to 1.0 Hz / s, and is, for example, 0.5 Hz / s.

[0048] The threshold T15 is set based on the temperature at which the treatment for suppressing the disproportionation reaction is started. In this embodiment, the threshold T15 is defined by an upper threshold T15a and a lower threshold T15b that is smaller than the upper threshold T15a. The upper threshold T15a is used when the internal temperature is increasing. The lower threshold T15b is used when the internal temperature is decreasing. In other words, when the internal temperature exceeds the threshold T15, it means that the internal temperature exceeds the upper threshold T15a, and when the internal temperature is equal to or lower than the threshold T15, it means that the internal temperature is equal to or lower than the lower threshold T15b.

[0049] When the internal temperature exceeds the threshold value T15, the control circuit 33 operates the compressor 4 so that the drive frequency changes at a second frequency change rate different from the first frequency change rate in at least one of increasing the drive frequency and decreasing the drive frequency.

[0050] The control circuit 33 increases or decreases the drive frequency of the compressor 4 at the second frequency change rate so that the drive frequency of the compressor 4 becomes the target drive frequency.

[0051] In this embodiment, when increasing the drive frequency, the control circuit 33 sets the second frequency change rate to be smaller than the first frequency change rate. In FIG. 3 , "second frequency change rate (small)" means a second frequency change rate smaller than the first frequency change rate. As an example, the second frequency change rate is 3.0 Hz / 15 s (= 0.2 Hz / s). In other words, when the internal temperature exceeds the threshold T15, the drive frequency is increased more slowly than when the internal temperature is equal to or lower than the threshold T15. Therefore, the drive frequency can be increased so that the internal temperature does not exceed the threshold T11. This allows the control range of the refrigeration cycle circuit 2 to be expanded while suppressing the disproportionation reaction.

[0052] When the control circuit 33 reduces the drive frequency, it makes the second frequency change rate greater than the first frequency change rate. In FIG. 3, "Second Frequency Change Rate (Large)" indicates a second frequency change rate greater than the first frequency change rate. As an example, the second frequency change rate is 1.0 Hz / s. That is, when the internal temperature exceeds the threshold T15, the drive frequency is reduced more significantly than when the internal temperature is equal to or lower than the threshold T15. Therefore, the drive frequency can be reduced quickly so that the internal temperature does not exceed the threshold T11. This allows for further suppression of the disproportionation reaction.

[0053] When the internal temperature exceeds threshold T14, which is greater than threshold T15 but less than threshold T11, control circuit 33 prohibits an increase in the drive frequency. In other words, even if it is necessary to increase the drive frequency of compressor 4 to set the drive frequency of compressor 4 to the target drive frequency, control circuit 33 does not increase the drive frequency. On the other hand, a decrease in the drive frequency is permitted. In this case, control circuit 33 decreases the drive frequency at a second frequency change rate. In this embodiment, the second frequency change rate is set to be greater than the first frequency change rate.

[0054] When the internal temperature exceeds a threshold T13 that is greater than threshold T14 but less than threshold T11, the control circuit 33 operates the compressor 4 so that the drive frequency is reduced at a fourth frequency change rate. More specifically, when reducing the drive frequency of the compressor 4 to a target drive frequency, the control circuit 33 reduces the drive frequency at the fourth frequency change rate. The fourth frequency change rate is not particularly limited. As an example, the fourth frequency change rate is 1.0 Hz / 15 s (= 0.07 Hz / s).

[0055] When the internal temperature exceeds a threshold T12 that is greater than threshold T13 but less than threshold T11, the control circuit 33 operates the compressor 4 so that the drive frequency is reduced at a third frequency change rate. More specifically, when the control circuit 33 reduces the drive frequency of the compressor 4 to a target drive frequency, the control circuit 33 reduces the drive frequency at the third frequency change rate. The third frequency change rate is not particularly limited. As an example, the third frequency change rate is 5.0 Hz / 15 s (= 0.33 Hz / s). This allows for a rapid reduction in the drive frequency. This further suppresses an increase in the internal temperature or internal pressure of the compressor 4, thereby enabling further suppression of the disproportionation reaction.

[0056] As an example, under normal load conditions (e.g., when the outdoor temperature is 43° C. or lower), the threshold T11 may be 62° C., the threshold T12 may be 60° C., the threshold T13 may be 58° C., the threshold T14 may be 56° C., the upper threshold T15a of the threshold T15 may be 54° C., and the lower threshold T15b of the threshold T15 may be 53° C. Under high load conditions (e.g., when the outdoor temperature exceeds 43° C.), the threshold T11 may be 65° C., the threshold T12 may be 64° C., the threshold T13 may be 63° C., the threshold T14 may be 62° C., the upper threshold T15a of the threshold T15 may be 53° C., and the lower threshold T15b of the threshold T15 may be 52° C.

[0057] [1.1.2 Effects, etc.] The control device 3 described above controls the compressor 4 of the refrigeration cycle circuit 2 through which the working medium 20 circulates. The working medium 20 contains an ethylene-based fluoroolefin as a refrigerant component. The control device 3 includes a measurement circuit 32 that outputs a measurement value indicating at least one of the internal temperature and internal pressure of the compressor 4, and a control circuit 33 that compares the measurement value from the measurement circuit 32 with at least one of a plurality of thresholds T11 to T15 and controls the compressor 4 based on the comparison result. The plurality of thresholds T11 to T15 includes a threshold T11 (first threshold) and a threshold T15 (second threshold) that is smaller than the threshold T11. The control circuit 33 stops the compressor 4 when the measurement value exceeds the threshold T11 (first threshold). The control circuit 33 operates the compressor 4 so that the drive frequency of the compressor 4 changes at a first frequency change rate while the measurement value is equal to or less than the threshold T15 (second threshold). When the measured value exceeds the threshold value T15, the control circuit 33 operates the compressor 4 so that the drive frequency is increased or decreased at least one time, and the drive frequency is changed at a second frequency change rate different from the first frequency change rate. This configuration makes it possible to expand the control range of the refrigeration cycle circuit 2 while suppressing the disproportionation reaction.

[0058] In the control device 3, the control circuit 33 makes the second frequency change rate smaller than the first frequency change rate when increasing the drive frequency. This configuration makes it possible to expand the control range of the refrigeration cycle circuit 2 while suppressing the disproportionation reaction.

[0059] In the control device 3, the control circuit 33 makes the second frequency change rate greater than the first frequency change rate when the drive frequency is reduced. This configuration enables further suppression of the disproportionation reaction.

[0060] In the control device 3, the multiple thresholds T11 to T15 include a fourth threshold (threshold T12) that is greater than the second threshold (threshold T15) and less than the first threshold (threshold T11). When the measurement value exceeds threshold T12, the control circuit 33 operates the compressor 4 so that the drive frequency decreases at a third frequency change rate. This configuration enables further suppression of the disproportionation reaction.

[0061] In the control device 3, at least one threshold T15 of the multiple thresholds T11 to T15 is defined by an upper threshold T15a and a lower threshold T15b that is smaller than the upper threshold T15a. When a measurement value exceeds at least one threshold T15, it means that the measurement value exceeds the upper threshold T15a of at least one threshold T15. When a measurement value is equal to or smaller than at least one threshold T15, it means that the measurement value is equal to or smaller than the lower threshold T15b of at least one threshold T15. This configuration can reduce the possibility of frequent control switching due to fluctuations in the measurement value.

[0062] The refrigeration cycle apparatus 1 described above includes the control device 3 and the refrigeration cycle circuit 2. This configuration makes it possible to expand the control range of the refrigeration cycle circuit 2 while suppressing the disproportionation reaction.

[0063] In the refrigeration cycle device 1, the ethylene-based fluoroolefin includes an ethylene-based fluoroolefin that undergoes a disproportionation reaction. This configuration makes it possible to further suppress the disproportionation reaction.

[0064] In the refrigeration cycle device 1, the ethylene-based fluoroolefin is 1,1,2-trifluoroethylene, trans-1,2-difluoroethylene, cis-1,2-difluoroethylene, 1,1-difluoroethylene, tetrafluoroethylene, or monofluoroethylene. This configuration enables further suppression of the disproportionation reaction.

[0065] In the refrigeration cycle apparatus 1, the working fluid 20 further contains difluoromethane as a refrigerant component. This configuration makes it possible to further suppress the disproportionation reaction.

[0066] In the refrigeration cycle apparatus 1, the working medium 20 further contains saturated hydrocarbons. This configuration enables further suppression of the disproportionation reaction.

[0067] In the refrigeration cycle device 1, the working fluid 20 contains a haloalkane having 1 or 2 carbon atoms as a disproportionation inhibitor that suppresses the disproportionation reaction of the ethylene-based fluoroolefin. This configuration enables further suppression of the disproportionation reaction.

[0068] In the refrigeration cycle device 1, the saturated hydrocarbons include n-propane. This configuration enables further suppression of the disproportionation reaction.

[0069] [1.2 Second Embodiment] [1.2.1 Configuration] Fig. 4 is a block diagram of a refrigeration cycle apparatus 1A according to this embodiment. The refrigeration cycle apparatus 1A constitutes, for example, an air conditioner capable of cooling operation and heating operation. The refrigeration cycle apparatus 1A includes a refrigeration cycle circuit 2 and a control device 3A.

[0070] The control device 3A controls the compressor 4 and the expansion valve 6 of the refrigeration cycle circuit 2. The control device 3A includes a drive circuit 31, a measurement circuit 32, and a control circuit 33, similar to the control device 3 of the first embodiment, but the operation of the control circuit 33 differs from that of the control device 3.

[0071] The control circuit 33 controls the expansion valve 6 in addition to the compressor 4. More specifically, the control circuit 33 increases or decreases the opening degree of the expansion valve 6. The opening degree of the expansion valve 6 is an indicator of the degree of opening of the expansion valve 6; the larger the opening degree, the closer the expansion valve 6 is to being fully open, and the smaller the opening degree, the closer the expansion valve 6 is to being fully closed. For example, the opening degree of the expansion valve 6 can be changed in increments of 1 pls. 1 pls corresponds to a value obtained by dividing the range of change in the opening degree of the expansion valve 6 (for example, the difference between the fully open and fully closed opening degrees of the expansion valve 6) by a predetermined number (for example, 480).

[0072] In this embodiment as well, the control circuit 33 executes a process for suppressing the disproportionation reaction of the working medium 20 circulating through the refrigeration cycle circuit 2 based on the measurement value from the measurement circuit 32 (in this embodiment, the internal temperature of the compressor 4). The control circuit 33 executes control of the compressor 4 and the expansion valve 6 based on the measurement value from the measurement circuit 32.

[0073] Fig. 5 is an explanatory diagram of the control of the compressor 4 and the expansion valve 6 by the control circuit 33. In this embodiment, the measurement value from the measurement circuit 32 indicates the internal temperature of the compressor 4. Fig. 4 shows the relationship between the internal temperature of the compressor 4 and the control of the expansion valve 6.

[0074] The control circuit 33 compares the measurement value (internal temperature of the compressor 4) from the measurement circuit 32 with at least one of a plurality of threshold values ​​T21 to T25, and controls the compressor 4 and the expansion valve 6 according to the comparison result. In this embodiment, the relationship in magnitude among the plurality of threshold values ​​T21 to T25 is threshold value T21 > threshold value T22 > threshold value T23 > threshold value T24 > threshold value T25.

[0075] When the internal temperature of the compressor 4 exceeds a threshold value T21, the control circuit 33 stops the compressor 4. The threshold value T21 is set based on the temperature at which a disproportionation reaction may occur.

[0076] The control circuit 33 operates the expansion valve 6 so that the aperture of the expansion valve 6 changes at a first aperture change rate while the internal temperature of the compressor 4 is equal to or lower than a threshold T25 that is lower than the threshold T21. For example, the control circuit 33 increases or decreases the aperture of the expansion valve 6 at the first aperture change rate so that the discharge temperature of the refrigerant discharged from the compressor 4 becomes a target temperature. The internal temperature of the compressor 4 indicated by the measurement value from the measurement circuit 32 can be used as the discharge temperature of the refrigerant. The first aperture change rate is, for example, d × 1 ps / 60 s, where d is the difference between the discharge temperature and the target temperature.

[0077] The threshold T25 is set based on the temperature at which the treatment for suppressing the disproportionation reaction is started. In this embodiment, the threshold T25 is defined by an upper threshold T25a and a lower threshold T25b that is smaller than the upper threshold T25a. The upper threshold T25a is used when the internal temperature is increasing. The lower threshold T25b is used when the internal temperature is decreasing. In other words, when the internal temperature exceeds the threshold T25, it means that the internal temperature exceeds the upper threshold T25a, and when the internal temperature is equal to or lower than the threshold T25, it means that the internal temperature is equal to or lower than the lower threshold T25b.

[0078] When the internal temperature exceeds the threshold value T25, the control circuit 33 operates the expansion valve 6 so that the opening changes at a second opening change rate different from the first opening change rate in at least one of increasing the opening rate and decreasing the opening rate.

[0079] In this embodiment, when decreasing the opening, the control circuit 33 operates the expansion valve 6 so that the opening changes at a second rate of change of opening that is different from the first rate of change of opening. On the other hand, when increasing the opening, the control circuit 33 operates the expansion valve 6 so that the opening changes at the first rate of change of opening.

[0080] As described above, in this embodiment, the opening change rate is different when increasing and decreasing the opening. The opening change rate when increasing the opening is set to the first opening change rate, and the opening change rate when decreasing the opening is set to the second opening change rate. This is because an increase in the opening leads to a decrease in the internal temperature of the compressor 4, while a decrease in the opening leads to an increase in the internal temperature of the compressor 4. In other words, the control circuit 33 decreases the opening of the expansion valve 6 at the second opening change rate or increases the opening of the expansion valve 6 at the first opening change rate so that the discharge temperature of the refrigerant discharged from the compressor 4 becomes the target temperature.

[0081] In this embodiment, when the control circuit 33 decreases the opening, it sets the second opening change rate to be smaller than the first opening change rate. As an example, the second opening change rate is 1 to 5 pls / 60 s. In other words, when the internal temperature exceeds the threshold T25, the opening is decreased more gradually than when the internal temperature is equal to or lower than the threshold T25. Therefore, the opening can be decreased so that the internal temperature does not exceed the threshold T21. This allows the control range of the refrigeration cycle circuit 2 to be expanded while suppressing the disproportionation reaction.

[0082] When the internal temperature exceeds a threshold T24 that is greater than threshold T25 but less than threshold T21, the control circuit 33 operates the expansion valve 6 to decrease the opening at a fourth opening change rate that is smaller than the second opening change rate. For example, the fourth opening change rate is 1 pls / 180 s (= 0.3 pls / 60 s). That is, when the internal temperature exceeds threshold T24, the opening is decreased more gradually than when the internal temperature is equal to or less than threshold T25. Therefore, the opening can be decreased so that the internal temperature does not exceed threshold T21. This allows the control range of the refrigeration cycle circuit 2 to be expanded while suppressing the disproportionation reaction. On the other hand, when the control circuit 33 increases the opening, the control circuit 33 operates the expansion valve 6 to change the opening at a first opening change rate.

[0083] When the internal temperature exceeds a threshold T23 that is greater than threshold T24 but less than threshold T21, the control circuit 33 operates the expansion valve 6 to increase the opening at a third opening change rate. More specifically, when the control circuit 33 increases the opening of the expansion valve 6 to adjust the discharge temperature of the refrigerant discharged from the compressor 4 to a target temperature, the control circuit 33 increases the opening at a third opening change rate. The third opening change rate is not particularly limited. As an example, the third opening change rate is 2 pls / 60 s. On the other hand, when the opening is being decreased, the control circuit 33 prohibits the decrease in the opening. In other words, even if the decrease in the opening of the expansion valve 6 is necessary to adjust the discharge temperature of the refrigerant discharged from the compressor 4 to the target temperature, the control circuit 33 does not decrease the opening. This further suppresses an increase in the internal temperature or internal pressure of the compressor 4. This enables further suppression of the disproportionation reaction.

[0084] When the internal temperature exceeds a threshold T22 that is greater than threshold T23 but less than threshold T21, the control circuit 33 operates the expansion valve 6 to increase the opening at a fifth opening change rate that is greater than the third opening change rate. In this embodiment, the control circuit 33 forcibly increases the opening at the fifth opening change rate. As an example, the fifth opening change rate is 30 pls / 30 s (= 60 pls / 60 s). This allows for a forced, rapid increase in the opening. This further suppresses an increase in the internal temperature or internal pressure of the compressor 4. This therefore enables further suppression of the disproportionation reaction.

[0085] As an example, under normal load conditions (e.g., when the outdoor temperature is 43° C. or lower), the threshold T21 may be 62° C., the threshold T22 may be 60° C., the threshold T23 may be 58° C., the threshold T24 may be 56° C., the upper threshold T25a of the threshold T25 may be 54° C., and the lower threshold T25b of the threshold T25 may be 53° C. Under high load conditions (e.g., when the outdoor temperature exceeds 43° C.), the threshold T21 may be 65° C., the threshold T22 may be 64° C., the threshold T23 may be 63° C., the threshold T24 may be 62° C., the upper threshold T25a of the threshold T25 may be 53° C., and the lower threshold T25b of the threshold T25 may be 52° C.

[0086] [1.2.2 Effects, etc.] The control device 3A described above controls the compressor 4 and expansion valve 6 of the refrigeration cycle circuit 2 through which the working medium 20 circulates. The working medium 20 contains an ethylene-based fluoroolefin as a refrigerant component. The control device 3 includes a measurement circuit 32 that outputs a measurement value indicating at least one of the internal temperature and internal pressure of the compressor 4, and a control circuit 33 that compares the measurement value from the measurement circuit 32 with at least one of a plurality of thresholds T21 to T25 and controls the compressor 4 and the expansion valve 6 based on the comparison result. The plurality of thresholds T21 to T25 includes a threshold T21 (first threshold) and a threshold T25 (second threshold) that is smaller than the first threshold. The control circuit 33 stops the compressor 4 when the measurement value exceeds the threshold T21 (first threshold). The control circuit 33 operates the expansion valve 6 so that the opening of the expansion valve 6 changes at a first opening change rate while the measurement value is equal to or less than the threshold T25 (second threshold). When the measurement value exceeds the threshold value T25, the control circuit 33 operates the expansion valve 6 so that the opening is increased or decreased at least one time at a second rate of change in opening that is different from the first rate of change in opening. This configuration makes it possible to expand the control range of the refrigeration cycle circuit 2 while suppressing the disproportionation reaction.

[0087] In the control device 3A, the control circuit 33 reduces the second rate of change of the opening degree to be smaller than the first rate of change of the opening degree. This configuration makes it possible to expand the control range of the refrigeration cycle circuit 2 while suppressing the disproportionation reaction.

[0088] In the control device 3A, the multiple thresholds T21 to T25 include a third threshold (threshold T23) that is greater than the second threshold (threshold T25) and less than the first threshold (threshold T21). When the measured value exceeds threshold T23, the control circuit 33 operates the expansion valve 6 so that the opening increases at a third opening change rate. This configuration enables further suppression of the disproportionation reaction.

[0089] In the control device 3A, at least one threshold T25 (second threshold) of the multiple thresholds T21 to T25 is defined by an upper threshold T25a and a lower threshold T25b that is smaller than the upper threshold T25a. When a measurement value exceeds at least one threshold T25, it means that the measurement value exceeds the upper threshold T25a of at least one threshold T25. When a measurement value is equal to or smaller than at least one threshold T25, it means that the measurement value is equal to or smaller than the lower threshold T25b of at least one threshold T25. This configuration can reduce the possibility of frequent control switching due to fluctuations in the measurement value.

[0090] [2. Modifications] The embodiments of the present disclosure are not limited to the above-described embodiments. The above-described embodiments can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Modifications of the above-described embodiments are listed below. The modifications described below can be applied in appropriate combinations.

[0091] In the following, reference will be made to the symbols used in embodiment 1, even though they are applicable to both embodiment 1 and embodiment 2. However, this is merely to simplify the description and is not intended to exclude application to embodiment 2.

[0092] In one modified example, the control circuit 33 may be configured to execute both the control shown in FIG. 3 and the control shown in FIG. 5 . That is, the control circuit 33 stops the compressor 4 when the measurement value exceeds a threshold T11 (first threshold). The control circuit 33 operates the compressor 4 so that the drive frequency of the compressor 4 changes at a first frequency change rate while the measurement value is equal to or less than a threshold T15 (second threshold) that is smaller than the threshold T11. The control circuit 33 may operate the compressor 4 so that the drive frequency changes at a second frequency change rate different from the first frequency change rate in at least one of increasing and decreasing the drive frequency when the measurement value exceeds the threshold T15. Furthermore, the control circuit 33 may operate the expansion valve 6 so that the opening of the expansion valve 6 changes at a first opening change rate while the measurement value is equal to or less than a threshold T23 (third threshold) that is smaller than the threshold T11 (first threshold). The control circuit 33 may operate the expansion valve 6 so that when the measurement value exceeds the threshold value T23, the opening degree is increased or decreased at least in one case, and the opening degree is changed at a second opening degree change rate different from the first opening degree change rate. In this case, the threshold values ​​T11 and T21 are set to be the same. On the other hand, the threshold values ​​T12, T13, T14, and T15 do not necessarily have to be set to be the same as the threshold values ​​T22, T23, T24, and T25.

[0093] In one modified example, thresholds other than threshold T15 among the multiple thresholds T11 to T15 may also be defined by upper and lower thresholds. In particular, it is preferable to define thresholds included in a range where the fluctuations of the measurement values ​​from the measurement circuit 32 are large by defining upper and lower thresholds. FIG. 6 is an explanatory diagram of control of the compressor 4 by the control circuit 33 of the control device 3 according to one modified example. In FIG. 6, three thresholds T12, T13, and T15 among the multiple thresholds T11 to T15 are defined by upper thresholds T12a, T13a, and T15a, respectively, and lower thresholds T12b, T13b, and T15b that are smaller than the upper thresholds T12a, T13a, and T15a. When the internal temperature exceeds the threshold value T12, T13, or T15, it means that the internal temperature exceeds the upper threshold value T12a, T13a, or T15a, and when the internal temperature is equal to or lower than the threshold value T12, T13, or T15, it means that the internal temperature is equal to or lower than the lower threshold value T12b, T13b, or T15b. This configuration reduces the possibility of frequent control switching due to fluctuations in the measurement value. The differences between the upper threshold value T12a, T13a, or T15a and the lower threshold value T12b, T13b, or T15b are not particularly limited, but may be set to 1°C, for example. However, it is not necessarily necessary to define the threshold value as an upper threshold value and a lower threshold value.

[0094] In one modified example, the thresholds for controlling the compressor 4 are not limited to the example shown in FIG. 3 . FIG. 7 is an explanatory diagram of control of the compressor 4 by the control circuit 33 of the control device 3 according to one modified example. Unlike FIG. 3 , thresholds T13 and T14 are not set in FIG. 7 . In FIG. 7 , when the internal temperature exceeds threshold T15, the control circuit 33 operates the compressor 4 so that the drive frequency changes at a second frequency change rate different from the first frequency change rate. When the internal temperature exceeds threshold T12, which is greater than threshold T15 but less than threshold T11, the control circuit 33 operates the compressor 4 so that the drive frequency decreases at a third frequency change rate. Furthermore, threshold T12 is not essential. The control circuit 33 may operate the compressor 4 so that the drive frequency changes at the second frequency change rate different from the first frequency change rate while the internal temperature exceeds threshold T15 but is equal to or less than threshold T11.

[0095] In one modified example, the control circuit 33 does not necessarily operate the compressor 4 so that the drive frequency changes at the second frequency change rate different from the first frequency change rate both when the drive frequency is increased and when the drive frequency is decreased. The control circuit 33 only needs to operate the compressor 4 so that the drive frequency changes at the second frequency change rate different from the first frequency change rate at least when the drive frequency is increased or when the drive frequency is decreased.

[0096] In one modified example, the thresholds for controlling the compressor 4 and the expansion valve 6 are not limited to the example shown in FIG. 5 . FIG. 8 is an explanatory diagram of control of the compressor 4 and the expansion valve 6 by the control circuit 33 of the control device 3 according to one modified example. Unlike FIG. 5 , thresholds T22 and T24 are not set in FIG. 8 . In FIG. 8 , when the internal temperature exceeds threshold T25, the control circuit 33 operates the expansion valve 6 to decrease the opening at a second opening change rate different from the first opening change rate. When the internal temperature exceeds threshold T23, which is greater than threshold T25 but less than threshold T21, the control circuit 33 operates the expansion valve 6 to increase the opening at a third opening change rate. Furthermore, threshold T23 is not essential. The control circuit 33 may operate the expansion valve 6 to change the opening at a second opening change rate smaller than the first opening change rate while the internal temperature exceeds threshold T25 but is equal to or less than threshold T21.

[0097] FIG. 9 is an explanatory diagram of control of the compressor 4 and the expansion valve 6 by the control circuit 33 of the control device 3 according to one modification. The control circuit 33 may operate the expansion valve 6 so that the opening changes at a second opening change rate different from the first opening change rate both when increasing the opening and when decreasing the opening. Here, the control circuit 33 may make the second opening change rate smaller than the first opening change rate when decreasing the opening, and may make the second opening change rate larger than the first opening change rate when increasing the opening. In FIG. 9 , the "second opening change rate (small)" refers to a second opening change rate smaller than the first opening change rate, and the "second opening change rate (large)" refers to a second opening change rate larger than the first opening change rate. In FIG. 9 , when the internal temperature exceeds the threshold T25, the opening is increased significantly compared to when the internal temperature is equal to or lower than the threshold T25. Therefore, the opening can be increased quickly so that the internal temperature does not exceed the threshold T21. This enables further suppression of the disproportionation reaction.

[0098] In one modified example, the control circuit 33 does not necessarily operate the expansion valve 6 so that the opening changes at a second rate of change of opening that is different from the first rate of change of opening both when the opening is increased and when the opening is decreased. The control circuit 33 only needs to operate the expansion valve 6 so that the opening changes at a second rate of change of opening that is different from the first rate of change of opening both when the opening is increased and when the opening is decreased.

[0099] In one modification, the control circuit 33 may further control the first blower 5a in the process for suppressing the disproportionation reaction. That is, the refrigeration cycle circuit 2 includes a first heat exchanger 5 of the outdoor unit 1a and a first blower 5a for promoting heat exchange in the first heat exchanger 5. The multiple thresholds may include a fifth threshold lower than the first threshold, and the control circuit 33 may increase the rotation speed of the first blower 5a when the measurement value exceeds the fifth threshold when the first heat exchanger 5 is functioning as a condenser (i.e., when operating in cooling mode). This allows the temperature of the working medium 20 to be further reduced in the first heat exchanger 5, thereby enabling further suppression of the disproportionation reaction. In the example of FIG. 3 , the threshold T11 may be the first threshold, and any of the thresholds T12 to T15 may be used as the fifth threshold. In the example of FIG. 5 , the threshold T21 may be the first threshold, and any of the thresholds T22 to T25 may be used as the fifth threshold. The fifth threshold may be set separately from the thresholds T12 to T15 and T22 to T25.

[0100] In one modification, the control circuit 33 may further control the second fan 7a in the process for suppressing the disproportionation reaction. That is, the refrigeration cycle circuit 2 includes the second heat exchanger 7 of the indoor unit 1b and a second fan 7a for promoting heat exchange in the second heat exchanger 7. The multiple thresholds may include a sixth threshold lower than the first threshold. The control circuit 33 may reduce the rotation speed of the second fan 7a when the measurement value exceeds the sixth threshold when the second heat exchanger 7 functions as an evaporator (i.e., when operating in cooling mode). When the control circuit 33 executes the process for suppressing the disproportionation reaction, the cooling capacity of the refrigeration cycle apparatus 1 tends to decrease. Therefore, by reducing the rotation speed of the second fan 7a from its current value, the evaporation temperature, low-pressure temperature, and temperature of the first heat exchanger 5 can be reduced. In the example of FIG. 3 , threshold T11 may be the first threshold, and any of thresholds T12 to T15 may be used as the sixth threshold. 5, the threshold value T21 is the first threshold value, and any one of the threshold values ​​T22 to T25 may be used as the sixth threshold value. The sixth threshold value may be set separately from the threshold values ​​T12 to T15 and T22 to T25.

[0101] In one modification, the third frequency change rate may be greater than the first frequency change rate. This allows for a rapid reduction in the drive frequency. This further suppresses an increase in the internal temperature or internal pressure of the compressor 4. This allows for further suppression of the disproportionation reaction. Referring to FIG. 7 , when the control circuit 33 reduces the drive frequency when the measurement value is decreasing, the control circuit 33 may set the second frequency change rate to be greater than the first frequency change rate and smaller than the third frequency change rate. "The measurement value is decreasing" includes when the measurement value decreases and becomes equal to or less than threshold T12 (fourth threshold). "The measurement value decreases and becomes equal to or less than threshold" may mean that the previous measurement value exceeded the threshold but the current measurement value becomes equal to or less than the threshold. In this way, when the control circuit 33 reduces the drive frequency when the measurement value is decreasing, the control circuit 33 may set the second frequency change rate to be greater than the first frequency change rate. This allows for a rapid reduction in the drive frequency. This further suppresses an increase in the internal temperature or internal pressure of the compressor 4. This allows for further suppression of the disproportionation reaction.

[0102] In one modification, the third rate of change of opening may be greater than the first rate of change of opening. This allows for a rapid increase in the opening. This further suppresses an increase in the internal temperature or internal pressure of the compressor 4. This allows for further suppression of the disproportionation reaction. Referring to FIG. 9 , when increasing the opening when the measurement value is on a decreasing trend, the control circuit 33 may set the second rate of change of opening to be greater than the first rate of change of opening and smaller than the third rate of change of opening. "The measurement value is on a decreasing trend" includes when the measurement value decreases and becomes equal to or less than threshold T23 (third threshold). In this way, when increasing the opening when the measurement value is on a decreasing trend, the control circuit 33 may set the second rate of change of opening to be greater than the first rate of change of opening. This allows for a rapid increase in the opening. This further suppresses an increase in the internal temperature or internal pressure of the compressor 4. This allows for further suppression of the disproportionation reaction.

[0103] In one modified example, the measurement circuit 32 may output a measurement value indicating the internal pressure of the compressor 4 instead of the internal temperature of the compressor 4. In this case, the descriptions regarding the control by the control circuit 33 shown in FIGS. 3 and 5 can be applied by replacing temperature with pressure. The measurement circuit 32 may output a measurement value indicating the internal temperature of the compressor 4 and a measurement value indicating the internal pressure of the compressor 4 to the control circuit 33 as the measurement values. The control circuit 33 may switch control depending on whether one or both of the internal temperature and the internal pressure of the compressor 4 exceed their respective thresholds. For example, the control circuit 33 may stop the compressor 4 when the internal temperature of the compressor 4 exceeds a first temperature threshold and the internal pressure of the compressor 4 exceeds a first pressure threshold, or the control circuit 33 may stop the compressor 4 when the internal temperature of the compressor 4 exceeds the first temperature threshold or the internal pressure of the compressor 4 exceeds the first pressure threshold.

[0104] In one modification, the drive circuit 31 is not limited to the above configuration, but may be a multilevel inverter such as a three-level inverter.

[0105] In one modified example, the refrigeration cycle apparatus 1 is not limited to an air conditioner (so-called room air conditioner (RAC)) configured with one indoor unit connected to one outdoor unit. The refrigeration cycle apparatus 1 may also be an air conditioner (so-called package air conditioner (PAC) or building multi-air conditioner (VRF)) configured with multiple indoor units connected to one or multiple outdoor units. Alternatively, the refrigeration cycle apparatus 1 is not limited to an air conditioner, and may also be a freezing or refrigeration device such as a refrigerator or a freezer.

[0106] [3. Aspects] As is clear from the above-described embodiment and modifications, the present disclosure includes the following aspects.

[0107] [Aspect 1] A control device that controls a compressor of a refrigeration cycle circuit through which a working medium circulates, wherein the working medium contains an ethylene-based fluoroolefin as a refrigerant component, the control device comprising: a measurement circuit that outputs a measurement value indicating at least one of an internal temperature or an internal pressure of the compressor; and a control circuit that compares the measurement value from the measurement circuit with at least one of a plurality of thresholds and controls the compressor in accordance with a comparison result, the plurality of thresholds including a first threshold and a second threshold that is smaller than the first threshold, the control circuit stopping the compressor when the measurement value exceeds the first threshold, operating the compressor such that a drive frequency of the compressor changes at a first frequency change rate while the measurement value is equal to or less than the second threshold, and operating the compressor such that the drive frequency changes at a second frequency change rate in at least one of cases where the drive frequency is increased and where the drive frequency is decreased when the measurement value exceeds the second threshold.

[0108] [Aspect 2] The control device according to aspect 1, wherein the control circuit, when increasing the drive frequency, makes the second rate of change of frequency smaller than the first rate of change of frequency.

[0109] [Aspect 3] The control device according to aspect 1 or 2, wherein the control circuit, when decreasing the drive frequency, makes the second rate of change of frequency greater than the first rate of change of frequency.

[0110] [Aspect 4] The control device of any one of Aspects 1 to 3, wherein the plurality of threshold values ​​further includes a third threshold value that is smaller than the first threshold value, and wherein the control circuit operates the expansion valve so that the opening of the expansion valve of the refrigeration cycle circuit changes at a first opening change rate while the measurement value is equal to or less than the third threshold value, and operates the expansion valve so that the opening changes at a second opening change rate different from the first opening change rate in at least one of increasing the opening and decreasing the opening when the measurement value exceeds the third threshold value.

[0111] [Aspect 5] The control device according to Aspect 4, wherein the control circuit, when increasing the opening, makes the second rate of change of opening greater than the first rate of change of opening.

[0112] [Aspect 6] The control device according to Aspect 4 or 5, wherein the control circuit, when decreasing the opening, makes the second rate of change of opening smaller than the first rate of change of opening.

[0113] [Aspect 7] The control device of any one of Aspects 1 to 6, wherein the plurality of thresholds includes a fourth threshold that is greater than the second threshold and less than the first threshold, and the control circuit operates the compressor such that the drive frequency decreases at a third frequency change rate when the measurement value exceeds the fourth threshold.

[0114] [Aspect 8] The control device of Aspect 7, wherein the third rate of change of frequency is greater than the first rate of change of frequency, and when the measurement value decreases to be equal to or less than the fourth threshold, the control circuit, in a case of decreasing the drive frequency, makes the second rate of change of frequency greater than the first rate of change of frequency and smaller than the third rate of change of frequency.

[0115] [Aspect 9] The control device of any one of Aspects 1 to 8, wherein at least one of the plurality of thresholds is defined by an upper threshold and a lower threshold that is smaller than the upper threshold, the measurement value exceeding the at least one threshold means that the measurement value exceeds an upper threshold of the at least one threshold, and the measurement value being equal to or smaller than the at least one threshold means that the measurement value is equal to or smaller than a lower threshold of the at least one threshold.

[0116] [Aspect 10] The control device of any one of Aspects 1 to 9, wherein the refrigeration cycle circuit includes a heat exchanger of an indoor unit and a blower for promoting heat exchange in the heat exchanger, the plurality of threshold values ​​includes a fifth threshold value that is smaller than the first threshold value, and the control circuit increases the rotation speed of the blower when the measurement value exceeds the fifth threshold value when the heat exchanger is functioning as a condenser.

[0117] [Aspect 11] The control device of any one of Aspects 1 to 10, wherein the refrigeration cycle circuit includes a heat exchanger of an outdoor unit and a blower for promoting heat exchange in the heat exchanger, the plurality of threshold values ​​includes a sixth threshold value that is smaller than the first threshold value, and the control circuit reduces the rotation speed of the blower when the measurement value exceeds the sixth threshold value when the heat exchanger is functioning as an evaporator.

[0118] [Aspect 12] A control device that controls a compressor and an expansion valve of a refrigeration cycle circuit through which a working medium circulates, wherein the working medium contains an ethylene-based fluoroolefin as a refrigerant component, the control device comprising: a measurement circuit that outputs a measurement value indicating at least one of an internal temperature or an internal pressure of the compressor; and a control circuit that compares the measurement value from the measurement circuit with at least one of a plurality of thresholds and controls the compressor and the expansion valve according to a comparison result, the plurality of thresholds including a first threshold and a second threshold that is smaller than the first threshold, the control circuit stopping the compressor when the measurement value exceeds the first threshold, operating the expansion valve so that the aperture of the expansion valve changes at a first aperture change rate while the measurement value is equal to or smaller than the second threshold, and operating the expansion valve so that the aperture changes at a second aperture change rate different from the first aperture change rate when the measurement value exceeds the second threshold.

[0119] [Aspect 13] The control device according to aspect 12, wherein the control circuit, when increasing the opening, makes the second rate of change of opening larger than the first rate of change of opening.

[0120] [Aspect 14] The control device according to aspect 12 or 13, wherein the control circuit, when decreasing the opening, makes the second rate of change of opening smaller than the first rate of change of opening.

[0121] [Aspect 15] The control device according to any one of Aspects 12 to 14, wherein the plurality of threshold values ​​includes a third threshold value that is greater than the second threshold value and less than the first threshold value, and the control circuit operates the expansion valve so that the opening increases at a third opening change rate when the measurement value exceeds the third threshold value.

[0122] [Aspect 16] The control device of Aspect 15, wherein the third rate of change of opening is greater than the first rate of change of opening, and when the measurement value decreases to be equal to or less than the third threshold, the control circuit, in a case of increasing the opening, makes the second rate of change of opening greater than the first rate of change of opening and smaller than the third rate of change of opening.

[0123] [Aspect 17] The control device of any one of Aspects 12 to 16, wherein at least one of the plurality of thresholds is defined by an upper threshold and a lower threshold that is smaller than the upper threshold, the measurement value exceeding the at least one threshold means that the measurement value exceeds an upper threshold of the at least one threshold, and the measurement value being equal to or less than the at least one threshold means that the measurement value is equal to or less than a lower threshold of the at least one threshold.

[0124] [Aspect 18] A refrigeration cycle device comprising: the control device according to any one of aspects 1 to 17; and the refrigeration cycle circuit.

[0125] [Aspect 19] The refrigeration cycle device of Aspect 18, wherein the ethylene-based fluoroolefin includes an ethylene-based fluoroolefin that undergoes a disproportionation reaction.

[0126] [Aspect 20] The refrigeration cycle device of Aspect 18 or 19, wherein the ethylene-based fluoroolefin is 1,1,2-trifluoroethylene, trans-1,2-difluoroethylene, cis-1,2-difluoroethylene, 1,1-difluoroethylene, tetrafluoroethylene, or monofluoroethylene.

[0127] [Aspect 21] The refrigeration cycle device according to any one of Aspects 18 to 20, wherein the working fluid further contains difluoromethane as the refrigerant component.

[0128] [Aspect 22] The refrigeration cycle device according to any one of Aspects 18 to 21, wherein the working medium further contains a saturated hydrocarbon.

[0129] [Aspect 23] The refrigeration cycle apparatus according to any one of Aspects 18 to 22, wherein the working fluid contains a haloalkane having 1 or 2 carbon atoms as a disproportionation inhibitor that suppresses the disproportionation reaction of the ethylenic fluoroolefin.

[0130] [Aspect 24] The refrigeration cycle device of Aspect 22, wherein the saturated hydrocarbon includes n-propane.

[0131] Aspects 2 to 11, 13 to 17, and 19 to 24 are optional elements and are not essential.

[0132] The present disclosure is applicable to a control device and a refrigeration cycle device. Specifically, the present disclosure is applicable to a control device for a refrigeration cycle circuit in which a working fluid contains an ethylene-based fluoroolefin as a refrigerant component, and a refrigeration cycle device including the refrigeration cycle circuit and the control device.

[0133] REFRIGERATION CYCLE DEVICE 1, 1A 2 REFRIGERATION CYCLE CIRCUIT 3, 3A 32 MEASUREMENT CIRCUIT 33 CONTROL CIRCUIT 4 COMPRESSOR 6 EXPANSION VALVE 7 SECOND HEAT EXCHANGER (Heat Exchanger) 7a SECOND BLOWER (BLOWER)

Claims

1. A control device for controlling a compressor of a refrigeration cycle circuit in which a working medium containing an ethylene-based fluoroolefin as a refrigerant component circulates, the working medium containing an ethylene-based fluoroolefin as a refrigerant component, the control device comprising: a measurement circuit that outputs a measurement value indicating at least one of an internal temperature or an internal pressure of the compressor; and a control circuit that compares the measurement value from the measurement circuit with at least one of a plurality of threshold values ​​and controls the compressor in accordance with a comparison result, the plurality of threshold values ​​including a first threshold value and a second threshold value that is smaller than the first threshold value, the control circuit stopping the compressor when the measurement value exceeds the first threshold value, operating the compressor such that a drive frequency of the compressor changes at a first frequency change rate while the measurement value is equal to or less than the second threshold value, and operating the compressor such that the drive frequency changes at a second frequency change rate different from the first frequency change rate in at least one of cases where the drive frequency is increased and where the drive frequency is decreased when the measurement value exceeds the second threshold value.

2. The control device according to claim 1, wherein said control circuit, when increasing said drive frequency, makes said second rate of change of frequency smaller than said first rate of change of frequency.

3. The control device according to claim 1, wherein said control circuit, when decreasing said drive frequency, makes said second rate of change of frequency greater than said first rate of change of frequency.

4. The control device of claim 1, wherein the plurality of threshold values ​​further includes a third threshold value smaller than the first threshold value, and the control circuit operates the expansion valve so that the opening of the expansion valve of the refrigeration cycle circuit changes at a first opening change rate while the measurement value is equal to or less than the third threshold value, and operates the expansion valve so that the opening changes at a second opening change rate different from the first opening change rate in at least one of increasing the opening and decreasing the opening when the measurement value exceeds the third threshold value.

5. The control device according to claim 4, wherein said control circuit, when increasing said opening, makes said second rate of change of opening larger than said first rate of change of opening.

6. The control device according to claim 4, wherein said control circuit, when decreasing said opening, makes said second rate of change of opening smaller than said first rate of change of opening.

7. The control device of claim 1, wherein the plurality of threshold values ​​includes a fourth threshold value that is greater than the second threshold value and less than the first threshold value, and the control circuit operates the compressor such that the drive frequency is reduced at a third frequency change rate when the measurement value exceeds the fourth threshold value.

8. The control device of claim 7, wherein the third rate of frequency change is greater than the first rate of frequency change, and when the measurement value decreases to below the fourth threshold, the control circuit, in decreasing the drive frequency, makes the second rate of frequency change greater than the first rate of frequency change and smaller than the third rate of frequency change.

9. The control device of claim 1, wherein at least one of the multiple thresholds is defined by an upper threshold and a lower threshold that is smaller than the upper threshold, and the measurement value exceeding the at least one threshold means that the measurement value exceeds an upper threshold of the at least one threshold, and the measurement value becoming equal to or lower than the at least one threshold means that the measurement value becomes equal to or lower than a lower threshold of the at least one threshold.

10. The control device of claim 1, wherein the refrigeration cycle circuit comprises a heat exchanger in an outdoor unit and a blower for promoting heat exchange in the heat exchanger, the plurality of threshold values ​​includes a fifth threshold value smaller than the first threshold value, and the control circuit increases the rotation speed of the blower when the measurement value exceeds the fifth threshold value when the heat exchanger is functioning as a condenser.

11. The control device of claim 1, wherein the refrigeration cycle circuit comprises a heat exchanger in an indoor unit and a blower for promoting heat exchange in the heat exchanger, the plurality of threshold values ​​includes a sixth threshold value smaller than the first threshold value, and the control circuit reduces the rotation speed of the blower when the measurement value exceeds the sixth threshold value when the heat exchanger is functioning as an evaporator.

12. A control device for controlling a compressor and an expansion valve of a refrigeration cycle circuit through which a working medium circulates, wherein the working medium contains an ethylene-based fluoroolefin as a refrigerant component, the control device comprising: a measurement circuit that outputs a measurement value indicating at least one of an internal temperature or an internal pressure of the compressor; and a control circuit that compares the measurement value from the measurement circuit with at least one of a plurality of thresholds and controls the compressor and the expansion valve depending on a result of the comparison, the plurality of thresholds including a first threshold and a second threshold smaller than the first threshold, the control circuit stopping the compressor when the measurement value exceeds the first threshold, operating the expansion valve such that the opening of the expansion valve changes at a first opening change rate while the measurement value is equal to or less than the second threshold, and operating the expansion valve such that the opening changes at a second opening change rate different from the first opening change rate in at least one of cases where the opening is increased and where the opening is decreased when the measurement value exceeds the second threshold.

13. A refrigeration cycle device comprising: the control device according to claim 1 or 12; and the refrigeration cycle circuit.

14. The refrigeration cycle device according to claim 13, wherein the ethylene-based fluoroolefin includes an ethylene-based fluoroolefin that undergoes a disproportionation reaction.

15. The refrigeration cycle device according to claim 13, wherein the ethylene-based fluoroolefin is 1,1,2-trifluoroethylene, trans-1,2-difluoroethylene, cis-1,2-difluoroethylene, 1,1-difluoroethylene, tetrafluoroethylene, or monofluoroethylene.

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