Control device, refrigeration cycle device, control method, and program

Abstract

Provided are a control device, a refrigeration cycle device, a control method, and a program that enable improvement in suppression of a disproportionation reaction of a working medium. The control device controls a refrigeration cycle circuit which comprises a compressor, a condenser, an expansion valve, and an evaporator, and through which the working medium circulates. The control device is provided with: a drive circuit for driving the compressor; a state detection circuit for detecting a state of the compressor and / or the drive circuit; a switching device for switching between a first route for connecting a discharge pipe of the compressor to the condenser and a second route for connecting the discharge pipe of the compressor to a predetermined space for causing the internal pressure of the compressor to decrease to a predetermined pressure or lower; and a control circuit for controlling the drive circuit and the switching device. The control circuit uses the switching device to switch the first route to the second route if the state of the compressor and / or drive circuit detected at the state detection circuit indicates a non-steady state of the refrigeration cycle circuit.

Description

Control device, refrigeration cycle device, control method, and program

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

[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 cycle device that aims to improve the reliability of a refrigeration cycle device that uses a working fluid containing HFO 1123. The refrigeration cycle device disclosed in Patent Document 3 is configured by connecting a compressor equipped with an electric motor, a condenser, an expansion means, and an evaporator in a ring shape to form a refrigeration cycle, and by sealing a working fluid containing an ethylenic fluorohydrocarbon having a double bond in the refrigeration cycle, and is equipped with a protective device that stops the supply of power to the compressor when the current value input to the compressor exceeds a predetermined current value that is set to be three times or more the maximum current value during normal operation other than at startup or two times or more the current value at startup.

[0005] International Publication No. 2012 / 157764 International Publication No. 2012 / 157765 Japanese Patent Application Laid-Open No. 2019-152380

[0006] Patent Document 3 states that "When the current value input to the compressor exceeds a predetermined value, the power supply to the motor is stopped, thereby preventing a layer short circuit due to an overcurrent and effectively suppressing the disproportionation reaction." The discharge energy that influences the reaction propagation of the disproportionation reaction is highly dependent on the internal pressure of the compressor, and if the internal pressure of the compressor is high, the disproportionation reaction may not be sufficiently suppressed.

[0007] The present disclosure provides a control device, a refrigeration cycle device, a control method, and a program that enable improved suppression of disproportionation reactions in a working fluid.

[0008] A control device according to one aspect of the present disclosure controls a refrigeration cycle circuit including a compressor, a condenser, an expansion valve, and an evaporator, through which a working medium circulates. The control device includes: a drive circuit for driving the compressor; a state detection circuit for detecting a state of at least one of the compressor and the drive circuit; a switching device capable of switching between a first path connecting a discharge pipe of the compressor to the condenser and a second path connecting the discharge pipe of the compressor to a predetermined space for reducing the internal pressure of the compressor to a predetermined pressure or lower; and a control circuit for controlling the drive circuit and the switching device. The control circuit switches from the first path to the second path using the switching device when the state of at least one of the compressor and the drive circuit detected by the state detection circuit indicates an unsteady state of the refrigeration cycle circuit.

[0009] A refrigeration cycle device according to an aspect of the present disclosure includes the above-described control device and the above-described refrigeration cycle circuit.

[0010] A control method according to one aspect of the present disclosure is executed by a control device that controls a refrigeration cycle circuit including a compressor, a condenser, an expansion valve, and an evaporator, and through which a working medium circulates. The control device includes a drive circuit that drives the compressor and a control circuit that controls the drive circuit. When a state of at least one of the compressor and the drive circuit indicates an unsteady state of the refrigeration cycle circuit, the control method connects a discharge pipe of the compressor to a predetermined space to reduce the internal pressure of the compressor to or below a predetermined pressure.

[0011] According to one aspect of the present disclosure, there is provided a program executed by a computer system including a control device that controls a refrigeration cycle circuit including a compressor, a condenser, an expansion valve, and an evaporator, and through which a working medium circulates. The control device includes a drive circuit that drives the compressor and a control circuit that controls the drive circuit. The program instructs the computer system to connect a discharge pipe of the compressor to a predetermined space and reduce the internal pressure of the compressor to a predetermined pressure or lower when the state of at least one of the compressor and the drive circuit indicates an unsteady state of the refrigeration cycle circuit.

[0012] Aspects of the present disclosure allow for improved suppression of disproportionation reactions in working fluids.

[0013] 1. Block diagram of a refrigeration cycle device according to a first embodiment. Schematic diagram of a compressor and a control device of the refrigeration cycle device according to the first embodiment. 2. Waveform diagram of a voltage of a smoothing circuit of a drive circuit of the control device according to the first embodiment. 3. Part of a flowchart of the operation of the control device according to the first embodiment. 4. Part of a flowchart of the operation of the control device according to the first embodiment. 5. Part of a flowchart of the operation of the control device according to the first embodiment.

[0014] [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.

[0015] 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.

[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 ２ I), 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] Here, an experiment was conducted to verify the occurrence of a disproportionation reaction using a working fluid 20 containing 1,1,2-trifluoroethylene (HFO1123). In the disproportionation reaction experiment, a pressure sensor (GC61 manufactured by Nagano Keiki Co., Ltd.) for measuring the internal pressure in the pressure-resistant vessel (stainless steel sealed vessel, internal volume 50 mL) was attached, along with a thermocouple (PL Thermocouple Grand PL-18-K-A 4-T manufactured by Conax Technologies) for measuring the internal temperature in the pressure-resistant vessel, and a discharge device for generating a discharge within the pressure-resistant vessel. Furthermore, a gas cylinder of 1,1,2-trifluoroethylene was connected so as to enable pressure adjustment. A mantle heater was installed to heat the entire pressure-resistant vessel, and a ribbon heater (flexible ribbon heater, 1 m, 200 W manufactured by Tokyo Institute of Technology Co., Ltd.) was also installed to heat the piping. Thus, an experimental system for the disproportionation reaction was constructed.

[0021] Table 1 below shows whether or not a disproportionation reaction occurs when 1,1,2-trifluoroethylene is used as the working fluid 20. The temperature [°C] in Table 1 is the internal temperature inside the pressure vessel. The pressure [MPa] in Table 1 is the internal pressure inside the pressure vessel. The stored energy [J] in Table 1 is the electrostatic energy stored in the capacitor section installed inside the discharge device. The number of consecutive discharges is the number of consecutive discharges at regular intervals under the conditions in question. If a disproportionation reaction occurred after that number of discharges, the disproportionation reaction was recorded as "Yes", and if no disproportionation reaction was observed, the disproportionation reaction was recorded as "No".

[0022]

[0023] From Table 1, it can be seen that no disproportionation reaction was observed in Examples 1 and 2, but that a disproportionation reaction was observed in Example 3. Therefore, it was confirmed that the possibility of a disproportionation reaction occurring is extremely low when the internal pressure is low. Table 1 shows that the higher the internal pressure, the higher the possibility of a disproportionation reaction occurring. This indicates that in order to suppress a disproportionation reaction, it is preferable to suppress an increase in internal pressure.

[0024] The refrigeration cycle circuit 2 includes a compressor 4 , a first heat exchanger 5 , an expansion valve 6 , a second heat exchanger 7 , a four-way valve 8 , and an accumulator 9 .

[0025] 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.

[0026] 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.

[0027] 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 four-way valve 8, the first heat exchanger 5, the expansion valve 6, the second heat exchanger 7, the four-way valve 8, and the accumulator 9, as shown by the solid arrow A1 in Figure 1.

[0028] 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 gaseous 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.

[0029] 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 four-way valve 8, the second heat exchanger 7, the expansion valve 6, the first heat exchanger 5, and the accumulator 9, as shown by the dashed arrow A2 in Figure 1.

[0030] 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 become a liquid. 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 gaseous 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.

[0031] FIG. 2 is a schematic diagram of the compressor 4 and the control device 3.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] Accumulator 9 is provided to prevent liquid compression in the compression chambers of compression mechanism 41. Accumulator 9 is located on the suction pipe 401 side of compressor 4. More specifically, accumulator 9 is located between suction pipe 401 of compressor 4 and four-way valve 8. Accumulator 9 separates working medium 20 into gaseous working medium 20 and liquid working medium 20, and introduces only the gaseous working medium 20 from suction pipe 401 into the inside of sealed container 40.

[0037] The control device 3 controls the compressor 4 of the refrigeration cycle circuit 2. The control device 3 includes a drive circuit 31, a state detection circuit 32, a first protection device 33, a second protection device 34, a control circuit 35, and a switching device 36.

[0038] The switching device 36 will be described with reference to FIG. 1 . The switching device 36 constitutes a part of the refrigeration cycle circuit 2. The switching device 36 is capable of switching between a first route R1 and a second route R2. In this embodiment, the switching device 36 is a four-way valve. The switching device 36 is located between the compressor 4 and the four-way valve 8. The switching device 36 is connected to the first heat exchanger 5 during cooling operation and to the second heat exchanger 7 during heating operation by the four-way valve 8. The first heat exchanger 5 during cooling operation and the second heat exchanger 7 during heating operation are both condensers. Therefore, the switching device 36 is located between the compressor 4 and the condenser.

[0039] The first path R1 connects the discharge pipe 402 of the compressor 4 to the first heat exchanger 5 during cooling operation and to the second heat exchanger 7 during heating operation. That is, the first path R1 connects the discharge pipe 402 of the compressor 4 to the condenser. Furthermore, the first path R1 connects the second heat exchanger 7 to the accumulator 9 during cooling operation and the first heat exchanger 5 to the accumulator 9 during heating operation. The second heat exchanger 7 during cooling operation and the first heat exchanger 5 during heating operation are both evaporators. Therefore, the first path R1 connects the evaporator to the accumulator 9. In the first path R1, the path connecting the discharge pipe 402 of the compressor 4 to the condenser and the path connecting the evaporator to the accumulator 9 are independent of each other.

[0040] The second path R2 connects the discharge pipe 402 of the compressor 4 to a predetermined space. The predetermined space is set so that the internal pressure of the compressor 4 can be reduced to or below a predetermined pressure. The predetermined pressure is set to a pressure at which substantially no heat exchange occurs in the first heat exchanger 5 or the second heat exchanger 7 during heating operation. As an example, the predetermined space is a space with a pressure of 0.4 MPa or less. The predetermined pressure is, for example, 3.0 MPa or less. The predetermined space is located inside the refrigeration cycle circuit 2. The predetermined space is the internal space of the accumulator 9. The second path R2 connects the discharge pipe 402 of the compressor 4 to the accumulator 9. As a result, the discharge pipe 402 of the compressor 4 is connected to the suction pipe 401 of the compressor 4 via the accumulator 9. Furthermore, the second path R2 connects the evaporator to the condenser via the four-way valve 8. In the second path R2, the path connecting the discharge pipe 402 of the compressor 4 to the accumulator 9 and the path connecting the evaporator to the condenser are independent of each other.

[0041] In this way, the switching device 36 constitutes a pressure control mechanism that reduces the internal pressure of the compressor 4 below a predetermined value by switching the connection destination of the discharge pipe 402 of the compressor 4 from the condenser to a predetermined space.

[0042] Next, the drive circuit 31, the state detection circuit 32, the first protection device 33, the second protection device 34, and the control circuit 35 will be described with reference to FIG.

[0043] The drive circuit 31 drives the electric motor 42 based on input power from the power supply 10. In this embodiment, the power supply 10 is an AC power supply, and the input power is AC power. The drive circuit 31 includes a converter circuit 311 and an inverter circuit 312.

[0044] The converter circuit 311 outputs DC output power based on the input power from the power supply 10 so that the voltage becomes a first voltage. That is, the converter circuit 311 converts the input power into DC output power so that the voltage of the DC output power becomes the first voltage. The first voltage corresponds to the rated voltage of the drive circuit 31.

[0045] The converter circuit 311 includes a rectifier circuit 311a and a smoothing circuit 311b.

[0046] The rectifier circuit 311a is a diode bridge composed of a plurality of diodes D1 to D4. The power supply 10 is connected between the input terminals of the rectifier circuit 311a (the connection point between the diodes D1 and D2 and the connection point between the diodes D3 and D4), and the smoothing circuit 311b is connected between the output terminals of the rectifier circuit 311a (the connection point between the diodes D1 and D3 and the connection point between the diodes D2 and D4).

[0047] The smoothing circuit 311b smoothes and outputs the voltage between the output terminals of the rectifier circuit 311a. The smoothing circuit 311b sets the voltage of the DC output power to a first voltage. The smoothing circuit 311b includes a series circuit of an inductor L1 and smoothing capacitors C1 and C2. In the smoothing circuit 311b, the connection point between the inductor L1 and the smoothing capacitor C1 is a first output point P1 that outputs a voltage corresponding to the first voltage. In the smoothing circuit 311b, the connection point between the diodes D2 and D4 and the smoothing capacitor C2 is a second output point P2 that outputs a voltage lower than the voltage at the first output point P1. In the smoothing circuit 311b, the connection point between the smoothing capacitor C1 and the smoothing capacitor C2 is a third output point P3 that outputs a voltage between the voltage at the first output point P1 and the voltage at the second output point P2. In the relationship between the first output point P1, the second output point P2, and the third output point P3, the first output point P1 is a high-voltage point, the second output point P2 is a low-voltage point, and the third output point P3 is an intermediate-voltage point. In the smoothing circuit 311b, the smoothing capacitors C1 and C2 have the same capacitance. Therefore, the voltage between the first output point P1 and the third output point P3 is equal to the voltage between the second output point P2 and the third output point P3. If the voltage between the first output point P1 and the second output point P2 (which corresponds to the first voltage) is E, the voltage between the first output point P1 and the third output point P3 is E / 2, and similarly, the voltage between the second output point P2 and the third output point P3 is E / 2. This allows the drive circuit 31 to provide five voltage levels: E, E / 2, 0, −E / 2, and −E.

[0048] The inverter circuit 312 outputs AC output power to the electric motor 42 based on the DC output power from the converter circuit 311. In the present embodiment, the AC output power is three-phase AC power. The inverter circuit 312 includes a plurality of semiconductor switching elements U1 to U4, V1 to V4, and W1 to W4. The semiconductor switching elements U1 to U4, V1 to V4, and W1 to W4 are, for example, transistors.

[0049] The semiconductor switching elements U1 to U4, V1 to V4, and W1 to W4 each form a series circuit and are connected between a first output point P1 and a second output point P2.

[0050] The connection point of the semiconductor switching elements U1 and U2, the connection point of the semiconductor switching elements V1 and V2, and the connection point of the semiconductor switching elements W1 and W2 are connected to a third output point P3 via diodes D5, D7, and D9, respectively.

[0051] The anodes of diodes D5, D7, and D9 are connected to the third output point P3, and the cathodes of diodes D5, D7, and D9 are connected to the connection point of semiconductor switching elements U1 and U2, the connection point of semiconductor switching elements V1 and V2, and the connection point of semiconductor switching elements W1 and W2, respectively.

[0052] The connection point of the semiconductor switching elements U2 and U3 forms a U-phase output terminal Pu connected to a U-phase input terminal of the motor 42. The connection point of the semiconductor switching elements V2 and V3 forms a V-phase output terminal Pv connected to a V-phase input terminal of the motor 42. The connection point of the semiconductor switching elements W2 and W3 forms a W-phase output terminal Pw connected to a W-phase input terminal of the motor 42.

[0053] The connection point of the semiconductor switching elements U3 and U4, the connection point of the semiconductor switching elements V3 and V4, and the connection point of the semiconductor switching elements W3 and W4 are connected to a third output point P3 via diodes D6, D8, and D10, respectively.

[0054] The cathodes of diodes D6, D8, and D10 are connected to the third output point P3, and the anodes of diodes D6, D8, and D10 are connected to the connection point of semiconductor switching elements U3 and U4, the connection point of semiconductor switching elements V3 and V4, and the connection point of semiconductor switching elements W3 and W4, respectively.

[0055] In the inverter circuit 312, the semiconductor switching elements U1, U2, V1, V2, W1, and W2 constitute a first semiconductor switching element group connected between the first output point P1 and the electric motor 42. In particular, the semiconductor switching elements U1 and U2 constitute a U-phase first semiconductor switching element group connected between the first output point P1 and the U-phase input terminal of the electric motor 42. The semiconductor switching elements V1 and V2 constitute a V-phase first semiconductor switching element group connected between the first output point P1 and the V-phase input terminal of the electric motor 42. The semiconductor switching elements W1 and W2 constitute a W-phase first semiconductor switching element group connected between the first output point P1 and the W-phase input terminal of the electric motor 42.

[0056] The semiconductor switching elements U3, U4, V3, V4, W3, and W4 constitute a second semiconductor switching element group connected between the second output point P2 and the motor 42. In particular, the semiconductor switching elements U3 and U4 constitute a U-phase second semiconductor switching element group connected between the second output point P2 and a U-phase input terminal of the motor 42. The semiconductor switching elements V3 and V4 constitute a V-phase second semiconductor switching element group connected between the second output point P2 and a V-phase input terminal of the motor 42. The semiconductor switching elements W3 and W4 constitute a W-phase second semiconductor switching element group connected between the second output point P2 and a W-phase input terminal of the motor 42.

[0057] The semiconductor switching elements U2, U3, V2, V3, W2, and W3 constitute a second semiconductor switching element group connected between the second output point P2 and the motor 42. In particular, the semiconductor switching elements U2 and U3 constitute a U-phase third semiconductor switching element group connected between the third output point P3 and the U-phase input terminal of the motor 42. The semiconductor switching elements V2 and V3 constitute a V-phase third semiconductor switching element group connected between the third output point P3 and the V-phase input terminal of the motor 42. The semiconductor switching elements W2 and W3 constitute a W-phase third semiconductor switching element group connected between the third output point P3 and the W-phase input terminal of the motor 42.

[0058] The converter circuit 311 has a plurality of output points including first to third output points P1 to P3. The inverter circuit 312 has a plurality of semiconductor switching element groups including a first semiconductor switching element group (semiconductor switching elements U1, U2, V1, V2, W1, W2) connected between the first output point P1 and the motor 42, a second semiconductor switching element group (semiconductor switching elements U3, U4, V3, V4, W3, W4) connected between the second output point P2 and the motor 42, and a third semiconductor switching element group (semiconductor switching elements U2, U3, V2, V3, W2, W3) connected between the third output point P3 and the motor 42. The drive circuit 31 is a so-called multilevel inverter, particularly a three-level inverter.

[0059] The state detection circuit 32 detects the state of at least one of the compressor 4 and the drive circuit 31. In this embodiment, the state detection circuit 32 detects the state of the drive circuit 31. The state of the drive circuit 31 is the voltage of the DC output power of the converter circuit 311. In this embodiment, the state detection circuit 32 is a voltage detector that detects the DC output power of the converter circuit 311 and outputs a detection voltage indicating the voltage of the DC output power. In this embodiment, the state detection circuit 32 includes a voltage divider circuit connected between the output terminals of the smoothing circuit 311b of the converter circuit 311, i.e., between the first output point P1 and the second output point P2, and outputs the detection voltage based on the voltage obtained from the voltage divider circuit. Alternatively, the state detection circuit 32 may output the detection voltage based on the output of the voltage divider circuit and a differential amplifier. As an example, the non-inverting input terminal and the inverting input terminal of the differential amplifier are connected to both ends of a resistor in the voltage divider circuit, respectively, and the differential amplifier can output the voltage across the resistor as the detection voltage. The use of a differential amplifier makes it possible to detect the potential difference in the floating state, thereby improving the accuracy of the detected voltage. The position at which the state detection circuit 32 is connected to the drive circuit 31 is not particularly limited as long as it is at a position at which the DC output power of the converter circuit 311 can be detected. The position at which the DC output power of the converter circuit 311 can be detected is not limited to within the converter circuit 311, but may be at a position within the inverter circuit 312 that is circuit-equivalent to each of the first output point P1 and the second output point P2. A conventionally known configuration can be used for the voltage divider circuit, and therefore a detailed description thereof will be omitted.

[0060] The first protection device 33 is provided to stop the output of AC output power. The first protection device 33 includes switches Su, Sv, and Sw interposed between the drive circuit 31 and the electric motor 42. The switches Su, Sv, and Sw are connected between the U-phase, V-phase, and W-phase input terminals of the electric motor 42 and the U-phase output terminals Pu, Pv, and Pw, respectively. The switches Su, Sv, and Sw may be controllable switches such as semiconductor switches or electromagnetic relays. When the switches Su, Sv, and Sw are closed in an ON state, the first protection device 33 allows the output of AC output power from the drive circuit 31 to the electric motor 42. When the switches Su, Sv, and Sw are open in an OFF state, the first protection device 33 stops the output of AC output power from the drive circuit 31 to the electric motor 42.

[0061] The second protection device 34 is provided to stop the input of input power. The second protection device 34 includes switches S1 and S2 interposed between the drive circuit 31 and the power source 10. The switches S1 and S2 are respectively connected between the input terminal of the rectifier circuit 311a and the power source 10. The switches S1 and S2 may be controllable switches such as semiconductor switches or electromagnetic relays. When the switches S1 and S2 are closed in an on state, the second protection device 34 allows the input of input power from the power source 10 to the drive circuit 31, and when the switches S1 and S2 are open in an off state, the second protection device 34 stops the input of input power from the power source 10 to the drive circuit 31.

[0062] The control circuit 35 may be realized, for example, by a computer system including at least one processor (microprocessor) and one or more memories. The computer system may also include one or more A / D converters. For example, the one or more A / D converters are used to convert the detected voltage from the state detection circuit 32 from analog to digital format. The control circuit 35 controls the drive circuit 31, the first protection device 33, the second protection device 34, and the switching device 36. In particular, the control circuit 35 performs PWM control of a group of semiconductor switching elements in the inverter circuit 312 of the drive circuit 31 so that the drive circuit 31 operates the electric motor 42. More specifically, the control circuit 35 controls the switching of the semiconductor switching elements U1 to U4, V1 to V4, and W1 to W4 in the inverter circuit 312 of the drive circuit 31 so that the inverter circuit 312 supplies AC output power (three-phase AC power) to the electric motor 42 based on the DC output power from the smoothing circuit 311b.

[0063] The semiconductor switching elements U1 to U4 have three states: a first state in which the semiconductor switching elements U1 and U2 are on and the semiconductor switching elements U3 and U4 are off, a second state in which the semiconductor switching elements U3 and U4 are on and the semiconductor switching elements U1 and U2 are off, and a third state in which the semiconductor switching elements U2 and U3 are on and the semiconductor switching elements U1 and U4 are off. The voltage at the U-phase output terminal Pu is E / 2 in the first state, −E / 2 in the second state, and 0 in the third state.

[0064] The semiconductor switching elements V1 to V4 have three states: a first state in which the semiconductor switching elements V1 and V2 are on and the semiconductor switching elements V3 and V4 are off, a second state in which the semiconductor switching elements V3 and V4 are on and the semiconductor switching elements V1 and V2 are off, and a third state in which the semiconductor switching elements V2 and V3 are on and the semiconductor switching elements V1 and V4 are off. The voltage at the V-phase output terminal Pv is E / 2 in the first state, −E / 2 in the second state, and 0 in the third state.

[0065] The semiconductor switching elements W1 to W4 have three states: a first state in which the semiconductor switching elements W1 and W2 are on and the semiconductor switching elements W3 and W4 are off, a second state in which the semiconductor switching elements W3 and W4 are on and the semiconductor switching elements W1 and W2 are off, and a third state in which the semiconductor switching elements W2 and W3 are on and the semiconductor switching elements W1 and W4 are off. The voltage at the W-phase output terminal Pw is E / 2 in the first state, −E / 2 in the second state, and 0 in the third state.

[0066] In this way, the drive circuit 31 can provide voltages at five levels: E, E / 2, 0, −E / 2, and −E.

[0067] The control circuit 35 controls the switching of the semiconductor switching elements U1 to U4, V1 to V4, and W1 to W4 of the inverter circuit 312 of the drive circuit 31 based on, for example, U-phase, V-phase, and W-phase output voltage command values ​​corresponding to the sinusoidal AC voltages of the U-phase, V-phase, and W-phase of the three-phase AC, respectively, and on the basis of first and second carrier triangular waves. The value of the first carrier triangular wave is equal to or greater than 0, and the value of the second carrier triangular wave is equal to or less than 0. The drive circuit 31 can apply five voltage levels, E, E / 2, 0, −E / 2, and −E, thereby making the voltage between the U-phase input terminal and the V-phase input terminal of the motor 42, the voltage between the V-phase input terminal and the W-phase input terminal of the motor 42, and the voltage between the W-phase input terminal and the U-phase input terminal of the motor 42 each closer to a sine wave.

[0068] When the state of at least one of the compressor 4 and the drive circuit 31 detected by the state detection circuit 32 indicates an unsteady state of the refrigeration cycle circuit 2, the control circuit 35 executes processing to suppress a disproportionation reaction of the working medium 20 circulating through the refrigeration cycle circuit 2. The unsteady state of the refrigeration cycle circuit 2 may include, for example, an abnormality in at least one of the compressor 4 and the drive circuit 31, a state in which a discharge phenomenon that may cause a disproportionation reaction of the working medium 20 circulating through the refrigeration cycle circuit 2 has occurred or is likely to occur, or a state in which a disproportionation reaction of the working medium 20 circulating through the refrigeration cycle circuit 2 is progressing or is likely to progress.

[0069] In this embodiment, the control circuit 35 further executes a process for suppressing the disproportionation reaction of the working medium 20 circulating through the refrigeration cycle circuit 2 based on the detected voltage from the state detection circuit 32 .

[0070] 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. The radicals may be generated by a discharge phenomenon that may occur when some abnormality occurs in the compressor 4 or the drive circuit 31, for example.

[0071] The inventors discovered that when a discharge occurs in the compressor 4, a sudden change occurs in the voltage of the DC output power of the converter circuit 311, i.e., the voltage of the smoothing circuit 311b of the drive circuit 31. FIG. 3 is a waveform diagram of the voltage of the DC output power of the converter circuit 311. In FIG. 3, the voltage of the DC output current gradually decreases from time t11 to t12, t21 to t22, t31 to t32, t41 to t42, and t51 to t52. This voltage decrease is due to the switching of the semiconductor switching elements U1 to U4, V1 to V4, and W1 to W4 of the inverter circuit 312. If the switching frequency of the inverter circuit 312 is, for example, 1.0 kHz to 5.0 kHz, the time between time t11 and time t21 is approximately 0.2 to 1.0 ms. At time t33, a sudden drop in the voltage of the DC output current is observed, which is believed to be due to the occurrence of a discharge phenomenon.

[0072] From this perspective, the control circuit 35 determines whether a discharge phenomenon has occurred based on the detected voltage from the state detection circuit 32, and if it determines that a discharge phenomenon has occurred, it switches from the first route R1 to the second route R2 using the switching device 36 in order to suppress the disproportionation reaction of the working medium 20 circulating through the refrigeration cycle circuit 2.

[0073] The control device 3 detects a sign of a disproportionation reaction based on a change in the DC output power (voltage of the smoothing circuit 311b) inside the drive circuit 31, rather than a change in the current actually flowing from the drive circuit 31 to the electric motor 42. The time scale of the discharge phenomenon is shorter than the time scale of smoothing (rectification) in the drive circuit 31. For example, the time scale of the discharge phenomenon is on the order of μs. Therefore, whether a discharge phenomenon is occurring can be determined based on the DC output power inside the drive circuit 31. Furthermore, measurement of the DC output power (voltage of the smoothing circuit 311b) inside the drive circuit 31 can be performed in a shorter time and at a shorter cycle than measurement of the current actually flowing from the drive circuit 31 to the electric motor 42. This enables earlier detection of a sign of a disproportionation reaction of the working fluid 20. If a sign of a disproportionation reaction of the working fluid 20 can be detected earlier in this way, the disproportionation reaction can be suppressed earlier, thereby improving the suppression of the disproportionation reaction.

[0074] In this embodiment, the control circuit 35 switches from the first path R1 to the second path R2 using the switching device 36 when the detected voltage falls below a second voltage that is equal to or less than the first voltage. The second voltage is set to determine whether a discharge phenomenon has occurred, which can occur when some abnormality occurs in the compressor 4 or the drive circuit 31. Referring to FIG. 3 , if the normal voltage (first voltage) of the DC output current is E, it has been observed that the voltage of the DC output current falls below 0.8E, or even below 0.3E, due to a discharge phenomenon. From this perspective, the second voltage is preferably between 0.3 and 0.8 times the first voltage. In this embodiment, the second voltage is 0.8 times the first voltage.

[0075] The control circuit 35 reduces the internal pressure of the compressor 4 to a predetermined pressure or lower by switching from the first route R1 to the second route R2 using the switching device 36. The reduction in the internal pressure of the compressor 4 increases the discharge energy required for the disproportionation reaction to proceed, thereby improving the suppression of the disproportionation reaction. In a disproportionation reaction triggered by discharge, there is an induction period between the occurrence of discharge and the rapid reaction propagation. A disproportionation inhibitor can lengthen the induction period, for example, to several seconds. Therefore, when the working fluid 20 contains a disproportionation inhibitor, the possibility of the disproportionation reaction proceeding before the control circuit 35 reduces the internal pressure of the compressor 4 can be reduced. The reduction in the internal pressure of the compressor 4 and the long induction period can more effectively suppress the disproportionation reaction of the working fluid 20.

[0076] When the detected voltage becomes lower than a second voltage that is equal to or lower than the first voltage, the control circuit 35 stops or limits the operation of the drive circuit 31 in addition to switching the switching device 36 from the first path R1 to the second path R2.

[0077] The operation of the drive circuit 31 can be stopped by stopping the output of AC output power, stopping the output of DC output power, or stopping the input of input power. The operation of the drive circuit 31 can be limited by reducing the set value of the amplitude of the AC output power or reducing the set value of the frequency of the AC output power.

[0078] In this embodiment, the control circuit 35 sets the first protection device 33 to the OFF state to electrically isolate the electric motor 42 from the drive circuit 31 and stop the output of AC output power. To resume the output of AC output power, the control circuit 35 sets the first protection device 33 to the ON state to connect the electric motor 42 to the drive circuit 31.

[0079] In this embodiment, control circuit 35 controls drive circuit 31 to reduce the set value of the amplitude of the AC output power. In this embodiment, drive circuit 31 can apply five levels of voltage: E, E / 2, 0, −E / 2, and −E, and therefore changes the set value of the amplitude of the AC output power from E to E / 2. In this case, the rotation speed of motor 42 decreases compared to when the set value of the amplitude of the AC output power is E.

[0080] When the input of input power is stopped, the output of AC output power is stopped as a result. In this embodiment, the control circuit 35 sets the second protection device 34 to the OFF state to electrically isolate the power supply 10 from the drive circuit 31 and stop the output of AC output power. When the input of input power is resumed, the control circuit 35 sets the second protection device 34 to the ON state to connect the power supply 10 to the drive circuit 31.

[0081] The control circuit 35 stops or limits the operation of the drive circuit 31 in different ways depending on the number of times the detected voltage falls below the second voltage. In particular, the control circuit 35 executes processing to suppress the disproportionation reaction to a higher degree as the number of times the detected voltage falls below the second voltage increases. This enables the control device 3 to suppress the disproportionation reaction even when relatively minor discharge phenomena occur consecutively within a short period of time. For example, this prevents the disproportionation reaction from being induced by consecutive low-energy abnormal states (discharges) exceeding a predetermined energy, thereby improving the safety of use of the working fluid 20.

[0082] The control circuit 35 stops or limits the operation of the drive circuit 31 in different ways depending on the time difference between the first time when the detected voltage first becomes less than the second voltage and the second time when the detected voltage next becomes less than the second voltage. In particular, the control circuit 35 executes processing that suppresses the disproportionation reaction to a greater extent the shorter the time difference. This enables the control device 3 to suppress the disproportionation reaction even when relatively minor discharge phenomena occur consecutively within a short period of time. This prevents, for example, the disproportionation reaction from being induced by consecutive low-energy abnormal states (discharges) exceeding a predetermined energy, thereby improving the safety of use of the working fluid 20.

[0083] The process for suppressing the disproportionation reaction includes, for example, first to third processes. The first process is a process of stopping the output of AC output power and resuming the output of AC output power after a standby time has elapsed. The second process is a process of stopping the output of AC output power and operating with a reduced set value for the amplitude of the AC output power after a standby time has elapsed. The third process is a process of stopping the output of AC output power and stopping the input of input power. Among the first to third processes, the degree of suppression of the disproportionation reaction increases in the order of the third process, the second process, and the first process. In the first or second process, the longer the standby time, the higher the degree of suppression of the disproportionation reaction.

[0084] Next, an example of the operation of the control circuit 35 of the control device 3 will be briefly described with reference to Figures 4 to 9. Each of Figures 4 to 9 is a part of a flowchart of the operation of the control circuit 35 of the control device 3, and Figures 4 to 9 are combined to form a complete flowchart.

[0085] Referring to Figure 4, the control circuit 35 causes the drive circuit 31 to output AC output power to the motor 42 based on the input power of the power supply 10, thereby driving the compressor 4. The control circuit 35 sets the number of abnormalities to 0 (S10). The number of abnormalities indicates the number of times the detected voltage has fallen below the second voltage. The number of abnormalities is an indicator of the likelihood of a disproportionation reaction occurring.

[0086] The control circuit 35 acquires the detected voltage from the state detection circuit 32 (S11). The control circuit 35 determines whether the detected voltage is less than the second voltage (S12).

[0087] If the detected voltage is not less than the second voltage (S12: NO), the process returns to step S10. In steps S11 and S12, the control circuit 35 determines whether the detected voltage is less than the second voltage at a predetermined cycle. The predetermined cycle here is preferably shorter than the cycle corresponding to the reference frequency of the inverter circuit 312 (e.g., 1000 to 5000 Hz).

[0088] In step S12, if the detected voltage is less than the second voltage (S12: YES), the control circuit 35 switches from the first route R1 to the second route R2 using the switching device 36 (S13). As a result, the control circuit 35 reduces the internal pressure of the compressor 4 to a predetermined pressure or less. The reduction in the internal pressure of the compressor 4 increases the discharge energy required for the disproportionation reaction to proceed, thereby suppressing the disproportionation reaction. Furthermore, the control circuit 35 increments the number of abnormalities by 1 (S14) and determines whether the number of abnormalities is 1 or less (S15).

[0089] If the number of abnormalities is 1 or less in step S15 (S15: YES), the control circuit 35 sets the first protection device 33 to the OFF state to stop the output of AC output power (S16). The control circuit 35 determines whether a first standby time has elapsed since the output of AC output power was stopped (S17). The first standby time is, for example, 1 second. When the first standby time has elapsed (S17: YES), the control circuit 35 sets the first protection device 33 to the ON state to resume the output of AC output power (S18), switches the switching device 36 from the second route R2 to the first route R1, and resumes operation of the compressor 4 (S19). After that, the process returns to step S11.

[0090] In this way, when the detected voltage becomes less than the second voltage, the control circuit 35 switches from the first path R1 to the second path R2 using the switching device 36, thereby reducing the internal pressure of the compressor 4 to a predetermined pressure or less. Furthermore, the control circuit 35 stops the output of the AC output power. The control circuit 35 resumes the output of the AC output power when the first standby time has elapsed since the output of the AC output power was stopped.

[0091] If the number of abnormalities is not equal to or less than 1 in step S15 (S15: NO), referring to FIG. 5, the control circuit 35 determines whether the time difference between the first time when the detected voltage first fell below the second voltage and the second time when the detected voltage next fell below the second voltage is within a first predetermined time (step S20). A short time difference is an indicator of the likelihood of a disproportionation reaction occurring. The first predetermined time is, for example, approximately 100 times the period corresponding to the reference frequency of the inverter circuit 312, or approximately 20 to 100 ms.

[0092] In step S20, if the time difference is within the first predetermined time (step S20: YES), the control circuit 35 sets the first protection device 33 to the OFF state to stop the output of AC output power (S21). The control circuit 35 sets the second protection device 34 to the OFF state to stop the input of input power (S22). The control circuit 35 outputs a first abnormality notification (S23). The first abnormality notification indicates that an abnormality has occurred in the refrigeration cycle apparatus 1 that is highly likely to cause a disproportionation reaction. The first abnormality notification is output to, for example, the control circuit and remote controller of the indoor unit 1b. Thereafter, the control circuit 35 stops operation of the compressor 4 (S24).

[0093] In this way, if the detected voltage becomes less than the second voltage (S20: YES) before a predetermined time (first predetermined time) has elapsed since the output of AC output power was resumed after the first waiting time had elapsed (S18), the control circuit 35 stops the output of AC output power (S21) and stops the input of input power (S22).

[0094] If the time difference is not within the first predetermined time in step S20 (step S20: NO), referring to Fig. 6, the control circuit 35 determines whether the time difference is within a second predetermined time that is longer than the first predetermined time (step S25). The second predetermined time is, for example, about 1000 times the period corresponding to the reference frequency of the inverter circuit 312, and is about 200 ms to 1 s.

[0095] If the time difference is within the second predetermined time in step S25 (step S25: YES), the control circuit 35 sets the first protection device 33 to the OFF state and stops the output of AC output power (S26). The control circuit 35 changes the switching control of the semiconductor switching elements of the drive circuit 31 so that the set value of the amplitude of the AC output power decreases from E to E / 2 (S27). The control circuit 35 outputs a second abnormality notification (S28). The second abnormality notification indicates that an abnormality that is likely to cause a disproportionation reaction has occurred in the refrigeration cycle apparatus 1. The second abnormality notification is output to, for example, the control circuit and remote controller of the indoor unit 1b.

[0096] The control circuit 35 determines whether a fourth standby time has elapsed since the output of the AC output power was stopped (S29). The fourth standby time is longer than the first standby time. The fourth standby time is, for example, 60 seconds. When the fourth standby time has elapsed (S29: YES), as shown in FIG. 7 , the control circuit 35 sets the first protection device 33 to the ON state to resume the output of the AC output power (S30), switches the switching device 36 from the second path R2 to the first path R1, and resumes operation of the compressor 4 (S31). In this case, the set value of the amplitude of the AC output power remains lowered from E to E / 2.

[0097] In this way, if the detected voltage becomes less than the second voltage before a predetermined time (second predetermined time) has elapsed since the output of the AC output power was resumed after the first standby time (S18), the control circuit 35 stops the output of the AC output power (S26) and reduces the set value of the amplitude of the AC output power (S27).If a fourth standby time longer than the first standby time has elapsed since the output of the AC output power was stopped, the control circuit 35 resumes the output of the AC output power while keeping the set value of the amplitude of the AC output power reduced (S30).

[0098] Thereafter, the control circuit 35 acquires the detected voltage from the state detection circuit 32 (S32), and determines whether the detected voltage is less than the second voltage (S33).

[0099] In step S33, if the detected voltage is lower than the second voltage (S33: YES), the control circuit 35 switches from the first route R1 to the second route R2 using the switching device 36 (S34), and proceeds to step S20 in FIG.

[0100] In step S33, if the detected voltage is not less than the second voltage (S33: NO), the control circuit 35 determines whether the second monitoring time has elapsed since the operation of the compressor 4 was restarted (S35).

[0101] In step S35, if the second monitoring time has elapsed since the operation of the compressor 4 was restarted (S35: YES), the control circuit 35 cancels the reduction in the set value of the amplitude of the AC output power, returns the set value of the amplitude of the AC output power to E (S36), and proceeds to step S11 in FIG. 4.

[0102] In step S35, if the second monitoring time has not elapsed since the operation of the compressor 4 was restarted (S35: NO), the process returns to step S32.

[0103] In steps S32 to S34, if the detected voltage becomes less than the second voltage between the time when the compressor 4 restarts operation and the time when the second monitoring time has elapsed, the process proceeds to step S21 in Figure 5, and if the detected voltage does not become less than the second voltage between the time when the compressor 4 restarts operation and the time when the second monitoring time has elapsed, the process proceeds to step S36.

[0104] In this way, if the detected voltage does not become less than the second voltage during the second monitoring time from when the output of AC output power is resumed after the fourth waiting time has elapsed (S30) (YES at S35), the control circuit 35 cancels the reduction of the set value of the amplitude of the AC output power (S36). If the detected voltage becomes less than the second voltage before the second monitoring time has elapsed from when the output of AC output power is resumed after the fourth waiting time has elapsed (S30) (YES at S33), the control circuit 35 stops the output of AC output power (S21) and stops the input of input power (S22).

[0105] 6, if the time difference is not within the second predetermined time in step S25 (step S25: NO), referring to Fig. 8, the control circuit 35 determines whether the time difference is within a third predetermined time, which is longer than the second predetermined time (step S37). The third predetermined time is, for example, about 10,000 times the period corresponding to the reference frequency of the inverter circuit 312, which is about 2 to 10 seconds.

[0106] In step S37, if the time difference is not within the third predetermined time (step S37: NO), the process returns to step S10, and the control circuit 35 sets the number of abnormalities to 0 (see FIG. 4). In other words, if a sufficient amount of time has passed since the detection of the abnormality, the possibility of the occurrence of a discharge phenomenon is considered low, and therefore the number of abnormalities is reset to 0.

[0107] In step S37, if the time difference is within the third predetermined time (step S37: YES), the control circuit 35 determines whether the number of abnormalities is 2 or less (S38).

[0108] If the number of abnormalities is two or less in step S38 (S38: YES), the control circuit 35 sets the first protection device 33 to the OFF state and stops the output of AC output power (S39). The control circuit 35 outputs a third abnormality notification (S40). The third abnormality notification indicates that an abnormality that may cause a disproportionation reaction has occurred in the refrigeration cycle apparatus 1. The third abnormality notification is output, for example, to the control circuit of the indoor unit 1b and a remote controller. The control circuit 35 determines whether a second standby time has elapsed since the output of AC output power was stopped (S41). The second standby time is longer than the first standby time. The second standby time is, for example, 10 seconds. When the second standby time has elapsed (S41: YES), the control circuit 35 sets the first protection device 33 to the ON state and resumes the output of AC output power (S42), thereby restarting the operation of the compressor 4 (S43). Then, the process returns to step S11.

[0109] In this way, if the detected voltage becomes less than the second voltage before the predetermined time (third predetermined time) has elapsed since the output of AC output power was resumed after the first standby time (S18), the control circuit 35 switches from the first path R1 to the second path R2 using the switching device 36, thereby reducing the internal pressure of the compressor 4 to below the predetermined pressure. Furthermore, the control circuit 35 stops the output of AC output power. The control circuit 35 resumes the output of AC output power when a second standby time longer than the first standby time has elapsed since the output of AC output power was stopped (S42).

[0110] In step S38, if the number of abnormalities is not two or less (S38: NO), that is, if the number of abnormalities is three or more, the control circuit 35 sets the first protection device 33 to the off state and stops the output of AC output power (S44). The control circuit 35 changes the switching control of the semiconductor switching elements of the drive circuit 31 so that the set value of the amplitude of the AC output power decreases from E to E / 2 (S45). The control circuit 35 outputs a second abnormality notification (S46).

[0111] The control circuit 35 determines whether a third standby time has elapsed since the output of the AC output power was stopped (S47). The third standby time is longer than the second standby time. The third standby time is, for example, 60 seconds. When the third standby time has elapsed (S47: YES), as shown in FIG. 9 , the control circuit 35 sets the first protection device 33 to the ON state to resume the output of the AC output power (S48), switches the switching device 36 from the second path R2 to the first path R1, and resumes operation of the compressor 4 (S49). In this case, the set value of the amplitude of the AC output power remains lowered from E to E / 2.

[0112] In this way, if the detected voltage becomes less than the second voltage before a predetermined time (third predetermined time) has elapsed since the output of the AC output power was resumed after the second standby time (S42), the control circuit 35 switches from the first path R1 to the second path R2 using the switching device 36, thereby reducing the internal pressure of the compressor 4 to below the predetermined pressure. Furthermore, the control circuit 35 stops the output of the AC output power (S44) and reduces the set value of the amplitude of the AC output power (S45). When a third standby time, which is longer than the second standby time, has elapsed since the output of the AC output power was stopped, the control circuit 35 resumes the output of the AC output power while keeping the set value of the amplitude of the AC output power reduced (S48).

[0113] Thereafter, the control circuit 35 acquires the detected voltage from the state detection circuit 32 (S50). The control circuit 35 determines whether the detected voltage is less than the second voltage (S51).

[0114] In step S51, if the detected voltage is lower than the second voltage (S51: YES), the control circuit 35 switches from the first route R1 to the second route R2 using the switching device 36 (S52), and proceeds to step S21 in FIG.

[0115] In step S51, if the detected voltage is not less than the second voltage (S51: NO), the control circuit 35 determines whether the first monitoring time has elapsed since the operation of the compressor 4 was restarted (S53). The first monitoring time may be the same as or different from the second monitoring time in step S35.

[0116] In step S53, if the first monitoring time has elapsed since the operation of the compressor 4 was restarted (S53: YES), the control circuit 35 cancels the reduction in the set value of the amplitude of the AC output power, returns the set value of the amplitude of the AC output power to E (S54), and proceeds to step S11 in FIG. 4.

[0117] In step S53, if the first monitoring time has not elapsed since the operation of the compressor 4 was restarted (S53: NO), the process returns to step S50.

[0118] In steps S50 to S53, if the detected voltage becomes less than the second voltage between the time when the compressor 4 restarts operation and the time when the first monitoring time has elapsed, the process proceeds to step S21 in Figure 5, and if the detected voltage does not become less than the second voltage between the time when the compressor 4 restarts operation and the time when the first monitoring time has elapsed, the process proceeds to step S54.

[0119] In this way, if the detected voltage does not become less than the second voltage during the first monitoring time period from when the output of AC output power is resumed after the third standby time period has elapsed (S48) (YES in S53), the control circuit 35 cancels the reduction in the set value of the amplitude of the AC output power (S54). If the detected voltage becomes less than the second voltage during the first monitoring time period from when the output of AC output power is resumed after the third standby time period has elapsed (S48) (YES in S51), the control circuit 35 switches from the first path R1 to the second path R2 using the switching device 36, thereby reducing the internal pressure of the compressor 4 to a predetermined pressure or lower. Furthermore, the control circuit 35 stops the output of AC output power (S21) and stops the input of input power (S22).

[0120] [1.1.2 Effects, etc.] The control device 3 described above controls the refrigeration cycle circuit 2, which includes the compressor 4, the condenser (first heat exchanger 5, second heat exchanger 7), the expansion valve 6, and the evaporator (first heat exchanger 5, second heat exchanger 7), and through which the working medium 20 circulates. The control device 3 includes: a drive circuit 31 that drives the compressor 4; a state detection circuit 32 that detects a state of at least one of the compressor 4 and the drive circuit 31; a switching device 36 that can switch between a first path R1 that connects the discharge pipe 402 of the compressor 4 to the condenser (first heat exchanger 5, second heat exchanger 7) and a second path R2 that connects the discharge pipe 402 of the compressor 4 to a predetermined space that reduces the internal pressure of the compressor 4 to a predetermined pressure or lower; and a control circuit 35 that controls the drive circuit 31 and the switching device 36. When the state of at least one of the compressor 4 and the drive circuit 31 indicates an unsteady state of the refrigeration cycle circuit 2 (in response to detection of an abnormality in at least one of the compressor 4 and the drive circuit 31), the control circuit 35 switches from the first route R1 to the second route R2 using the switching device 36. This configuration enables improved suppression of the disproportionation reaction of the working medium 20.

[0121] In the control device 3, the predetermined space is a space where the pressure is 0.4 MPa or less. When the pressure in the predetermined space is 0.4 MPa or less, the pressure inside the compressor 4 is 2.0 MPa or less. This configuration enables improved suppression of the disproportionation reaction of the working fluid 20.

[0122] In the control device 3, the predetermined pressure is 3.0 MPa or less. This configuration enables improved suppression of the disproportionation reaction of the working medium 20.

[0123] In the control device 3, the switching device 36 is located between the discharge pipe 402 of the compressor 4 and the condenser. The first route R1 connects the discharge pipe 402 of the compressor 4 to the condenser. The second route R2 connects the discharge pipe 402 of the compressor 4 to a predetermined space. This configuration enables improved suppression of the disproportionation reaction of the working medium 20.

[0124] In the control device 3, the refrigeration cycle circuit 2 includes an accumulator 9 located on the suction pipe 401 side of the compressor 4. The second route R2 connects the discharge pipe 402 of the compressor 4 to the internal space of the accumulator 9. This configuration enables improved suppression of the disproportionation reaction of the working medium 20. Furthermore, since the working medium 20 is not discharged to the outside from the refrigeration cycle circuit 2, switching from the second route R2 to the first route R1 allows the refrigeration cycle circuit 2 to return to normal operation (cooling operation, heating operation).

[0125] In the control device 3, the control circuit 35 stops or limits the operation of the drive circuit 31 when the state of at least one of the compressor 4 and the drive circuit 31 indicates an unsteady state (in response to detection of an abnormality in at least one of the compressor 4 and the drive circuit 31). This configuration enables improved suppression of the disproportionation reaction of the working medium 20.

[0126] In the control device 3, the drive circuit 31 includes a converter circuit 311 that outputs DC output power based on input power from the power source 10 so that the voltage becomes a first voltage, and an inverter circuit 312 that outputs AC output power to the compressor 4 based on the DC output power. The state detection circuit 32 detects the DC output power and outputs a detection voltage indicative of the voltage of the DC output power. The non-steady state (abnormality in at least one of the compressor 4 and the drive circuit 31) includes a state in which the detection voltage is less than a second voltage that is equal to or less than the first voltage. This configuration enables earlier detection of a sign of a disproportionation reaction of the working medium 20 and enables improved suppression of the disproportionation reaction of the working medium 20.

[0127] In the control device 3, the second voltage is 0.3 to 0.8 times the first voltage. This configuration enables improved suppression of the disproportionation reaction of the working medium 20.

[0128] The refrigeration cycle device 1 described above includes the control device 3 and the refrigeration cycle circuit 2. This configuration enables the suppression of the disproportionation reaction of the working fluid 20 to be improved.

[0129] In the refrigeration cycle device 1, the working fluid 20 contains an ethylene-based fluoroolefin. This configuration enables improved suppression of the disproportionation reaction of the working fluid 20.

[0130] 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 improved suppression of the disproportionation reaction of the working fluid 20.

[0131] In the refrigeration cycle apparatus 1, the working fluid 20 further contains difluoromethane. This configuration enables improved suppression of the disproportionation reaction of the working fluid 20.

[0132] In the refrigeration cycle device 1, the working fluid 20 further contains saturated hydrocarbons. This configuration enables the suppression of the disproportionation reaction of the working fluid 20 to be improved.

[0133] In the refrigeration cycle apparatus 1, the working fluid 20 contains a haloalkane having one or two carbon atoms as a disproportionation inhibitor that suppresses the disproportionation reaction of ethylene-based fluoroolefins. This configuration enables improved suppression of the disproportionation reaction of the working fluid 20. In particular, in a disproportionation reaction triggered by discharge, there is an induction period between the occurrence of discharge and the rapid reaction propagation, and the disproportionation inhibitor can prolong this induction period. Therefore, the possibility that the disproportionation reaction will proceed before the control circuit 35 reduces the internal pressure of the compressor 4 can be reduced. The reduction in the internal pressure of the compressor 4 and the long induction period can more effectively suppress the disproportionation reaction of the working fluid 20.

[0134] In the refrigeration cycle device 1, the saturated hydrocarbons include n-propane. This configuration enables improved suppression of the disproportionation reaction of the working medium 20.

[0135] The control device 3 described above can be said to execute the following control method. The control method is executed by the control device 3, which controls the refrigeration cycle circuit 2, which includes the compressor 4, the condenser (first heat exchanger 5, second heat exchanger 7), the expansion valve 6, and the evaporator (first heat exchanger 5, second heat exchanger 7), and through which the working medium 20 circulates. The control device 3 includes a drive circuit 31 that drives the compressor 4 and a control circuit 35 that controls the drive circuit 31. When the state of at least one of the compressor 4 and the drive circuit 31 indicates an unsteady state of the refrigeration cycle circuit 2 (in response to detection of an abnormality in at least one of the compressor 4 and the drive circuit 31), the control method connects the discharge pipe 402 of the compressor 4 to a predetermined space to reduce the internal pressure of the compressor 4 to a predetermined pressure or lower. This configuration enables improved suppression of the disproportionation reaction of the working medium 20.

[0136] The control method executed by the control device 3 can be realized by a computer system executing a program. The program is executed by a computer system included in the control device 3, which controls the refrigeration cycle circuit 2 including the compressor 4, the condenser (first heat exchanger 5, second heat exchanger 7), the expansion valve 6, and the evaporator (first heat exchanger 5, second heat exchanger 7), through which the working medium 20 circulates. The control device 3 includes a drive circuit 31 that drives the compressor 4 and a control circuit 35 that controls the drive circuit 31. The program instructs the computer system to connect the discharge pipe 402 of the compressor 4 to a predetermined space and reduce the internal pressure of the compressor 4 to a predetermined pressure or lower when the state of at least one of the compressor 4 and the drive circuit 31 indicates an unsteady state of the refrigeration cycle circuit 2 (in response to detection of an abnormality in at least one of the compressor 4 and the drive circuit 31). This configuration enables improved suppression of the disproportionation reaction of the working medium 20.

[0137] 1.2. Second Embodiment 1.2.1 Configuration Fig. 10 is a block diagram of a refrigeration cycle apparatus 1A according to this embodiment. The refrigeration cycle apparatus 1A includes a refrigeration cycle circuit 2A and a control device 3A.

[0138] The control device 3A includes a drive circuit 31, a state detection circuit 32, a first protection device 33, a second protection device 34, a control circuit 35, and a switching device 36A.

[0139] The switching device 36A is a four-way valve that switches the direction in which the working medium 20 circulates through the refrigeration cycle circuit 2A between a first direction A1 corresponding to cooling operation and a second direction A2 corresponding to heating operation. The first path R1 corresponds to the second direction and connects the discharge pipe 402 of the compressor 4 to the second heat exchanger 7. The second path R2 corresponds to the first direction and connects the discharge pipe 402 of the compressor 4 to the first heat exchanger 5. The first heat exchanger 5 functions as a condenser during cooling operation and as an evaporator during heating operation. In the refrigeration cycle circuit 2A, the internal pressure of the evaporator is lower than the internal pressure of the condenser. The internal space of the first heat exchanger 5, which functions as an evaporator during heating operation, constitutes a predetermined space. Therefore, the predetermined space is located inside the refrigeration cycle circuit 2A.

[0140] In the third embodiment, the four-way valve 8 of the refrigeration cycle apparatus 1 of the first and second embodiments is used as the switching device 36A. Therefore, in the third embodiment, there is no need to add any components to the refrigeration cycle circuit 2A, and there is no need to change the existing configuration of the refrigeration cycle circuit 2A itself. This allows for cost reduction.

[0141] In this embodiment, when the detected voltage falls below a second voltage that is equal to or lower than the first voltage, the control circuit 35 switches from the first path R1 to the second path R2 using the switching device 36A, thereby increasing the aperture of the expansion valve 6. When the path is switched from the first path R1 to the second path R2, the discharge pipe 402 of the compressor 4 is connected from the second heat exchanger 7, which functions as a condenser during heating operation, to the first heat exchanger 5, which functions as an evaporator during heating operation. Because the internal pressure of the evaporator is lower than the internal pressure of the condenser, the internal pressure of the compressor 4 is reduced to a predetermined pressure or lower. Increasing the aperture of the expansion valve 6 promotes the flow of the working medium 20 from the first heat exchanger 5 to the second heat exchanger 7, thereby efficiently reducing the internal pressure of the compressor 4.

[0142] [1.2.2 Effects, etc.] In the control device 3A described above, the refrigeration cycle circuit 2A includes the first heat exchanger 5 and the second heat exchanger 7. The switching device 36A is a four-way valve that switches the direction in which the working medium 20 circulates through the refrigeration cycle circuit 2A between a first direction A1 corresponding to cooling operation and a second direction A2 corresponding to heating operation. The first path R1 corresponds to the second direction and connects the discharge pipe 402 of the compressor 4 to the second heat exchanger 7. The second path R2 corresponds to the first direction and connects the discharge pipe 402 of the compressor 4 to the first heat exchanger 5. When the state of at least one of the compressor 4 and the drive circuit 31 indicates an unsteady state of the refrigeration cycle circuit 2 (in response to detection of an abnormality in at least one of the compressor 4 and the drive circuit 31), the control circuit 35 switches from the first path R1 to the second path R2 using the switching device 36A and increases the opening degree of the expansion valve 6. This configuration improves the suppression of the disproportionation reaction of the working fluid 20. Furthermore, since there is no need to modify the refrigeration cycle circuit 2A itself, it is possible to reduce costs. Furthermore, since the working fluid 20 is not discharged from the refrigeration cycle circuit 2A to the outside, switching from the second route R2 to the first route R1 allows the refrigeration cycle circuit 2A to return to normal operation (cooling operation or heating operation).

[0143] 11 shows a control device 3B according to embodiment 4. The control device 3B includes a drive circuit 31, a state detection circuit 32, a first protection device 33, a second protection device 34, a control circuit 35B, a switching device 36, and a measurement circuit 37.

[0144] The measurement circuit 37 is provided to measure the internal state of the refrigeration cycle circuit 2. The internal state of the refrigeration cycle circuit 2 may include at least one of the pressure, temperature, and amount of product in the refrigeration cycle circuit 2. Therefore, the measurement circuit 37 detects at least one of the pressure, temperature, and amount of product in the refrigeration cycle circuit 2.

[0145] The pressure in the refrigeration cycle circuit 2 may be, for example, the internal pressure of the compressor 4. The internal pressure of the compressor 4 can be obtained, for example, by a pressure sensor disposed in a refrigerant piping near the discharge pipe 402 of the compressor 4 or in the sealed container 40 of the compressor 4.

[0146] The temperature in the refrigeration cycle circuit 2 may be, for example, the internal temperature of the compressor 4. The internal temperature of the compressor 4 can be obtained, for example, by a temperature sensor disposed in a refrigerant piping near the discharge pipe 402 of the compressor 4 or in the sealed container 40 of the compressor 4.

[0147] The amount of product may be, for example, the amount of product generated from the working fluid 20 by the disproportionation reaction of the working fluid 20. Such products may include intermediate products or final products. The final product refers to a thermodynamically stable chemical species among the chemical species generated in the disproportionation reaction of the working fluid 20. Here, "thermodynamically stable" means that the type and composition of the compound do not change when exposed to a high temperature of 2000 K or higher at 1 atmosphere for a predetermined time (e.g., approximately 10 minutes) and then returned to room temperature and normal pressure. The intermediate product refers to a thermodynamically unstable chemical species among the chemical species generated in the disproportionation reaction of the working fluid 20. "Thermodynamically unstable" means that at least one of the type and composition of the compound changes when exposed to a high temperature of 2000 K or higher at 1 atmosphere. Thermodynamically unstable chemical species also include so-called metastable chemical species. In particular, the intermediate products are chemical species that may exist with a lifetime of 1 ms or more among the chemical species generated in the disproportionation reaction of the working fluid 20, but may decompose at high temperatures (e.g., 2000 K or higher) to generate final products. Naturally, such intermediate products do not include final products. The lifetime here is measured under a measurement environment corresponding to the interior of the refrigeration cycle circuit 2. As an example, the lifetime is measured under conditions of a maximum temperature of 500 K and a maximum pressure of 6 MPa.

[0148] For example, when the working fluid 20 contains an ethylene-based fluoroolefin as a refrigerant component, the intermediate products include carbenes, carbene inserts (compounds produced by the insertion reaction of carbene), tetrafluoroethylene, perfluoroolefins, and fluorobenzene. The final products include soot, hydrogen fluoride, and tetrafluoromethane.

[0149] A variety of techniques can be used to measure the amount of product.

[0150] As a first example, the amount of the product can be measured by utilizing a change in the transmittance of the working fluid 20. This is particularly effective when the product circulates as an insoluble component together with the working fluid 20 within the refrigeration cycle circuit 2. For example, when the working fluid contains an ethylene-based fluoroolefin, soot or hydrogen fluoride (HF) is generated as an insoluble component. When discharge phenomena are repeated, the amount of insoluble components such as soot increases. Such an increase in insoluble components is one factor that reduces the transmittance of the working fluid 20.

[0151] In this case, the measurement circuit 37 may include a photodetection circuit that utilizes transmittance. The photodetection circuit that utilizes transmittance may include, for example, a light source device and a photodetection device. The light source device emits light into the refrigeration cycle circuit 2. The light may be directional light (for example, laser light or parallel light obtained by parallelizing a light-emitting diode (LED) using a lens or a double slit). The color of the light is not particularly limited, and may be white or red with a wavelength of 650 nm to 690 nm. The photodetection device receives the light and outputs the intensity of the received light. The photodetection device can output a photodetection signal indicating the light intensity to the control circuit 35B.

[0152] The location of the working medium 20 in the refrigeration cycle circuit 2 from which the light source device radiates light is not particularly limited, but the light may be radiated to the working medium 20 in the compressor 4 of the refrigeration cycle circuit 2. Because a discharge phenomenon may occur in the electric motor 42 of the compressor 4, it is considered that a decrease in transmittance due to insoluble components such as soot in the working medium 20 in the compressor 4 is easily detected. The light detection circuit may be located within the sealed container 40 of the compressor 4. The light source device may radiate light to the working medium 20 in the region between the electric motor 42 and the suction pipe 401. The working medium 20 may contain bubbles. Bubbles in the working medium 20 scatter light, causing a decrease in the transmittance of the working medium 20 and adversely affecting evaluations using transmittance. Here, it is considered that the amount of bubbles is small in the region between the electric motor 42 and the suction pipe 401. Therefore, it is possible to suppress a decrease in accuracy due to bubbles.

[0153] As a second example, the amount of product can be measured using a fluorescent dye. When a discharge phenomenon occurs, products resulting from a chemical reaction of the working fluid 20 may circulate within the refrigeration cycle circuit 2 along with the working fluid 20. For example, when the working fluid contains an ethylene-based fluoroolefin, hydrogen fluoride (HF) may be an example of a product resulting from a chemical reaction of the working fluid 20 (hereinafter also referred to as product (A)). Such product (A) is an example of a product resulting from a disproportionation reaction of the working fluid 20. Repeated discharge phenomena increase the amount of product (A). An increase in product (A) may also cause an abnormality in the refrigeration cycle circuit 2. The present inventors have discovered that a fluorescent dye can be used to quantitatively evaluate product (A). That is, if a fluorescent dye has the property of changing at least one of the fluorescence wavelength or quantum yield upon reaction with product (A), an increase in product (A) can be observed as a change in the intensity of light at a wavelength corresponding to the fluorescence wavelength of the fluorescent dye. By focusing on the intensity of light at a wavelength corresponding to the fluorescence wavelength of the fluorescent dye, product (A) can be quantitatively evaluated.

[0154] In this case, the measurement circuitry 37 may include a light detection circuit that utilizes phosphors.

[0155] The fluorescent material contains a fluorescent dye and is arranged in the refrigeration cycle circuit 2 so as to be able to come into contact with the working medium 20. For example, the fluorescent material is refrigeration oil in which the fluorescent dye is dissolved. That is, the fluorescent material may be formed by dissolving the fluorescent dye in the refrigeration oil of the compressor 4. The fluorescent material circulates through the refrigeration cycle circuit 2 together with the working medium 20. This increases the possibility that the fluorescent dye of the fluorescent material will come into contact with and react with the product (A).

[0156] The fluorescent dye has the property of changing at least one of the fluorescence wavelength or quantum yield upon reacting with the product (A) produced by the chemical reaction of the working medium 20. Therefore, depending on the type of fluorescent dye, the reaction between the fluorescent dye and the product (A) can cause an increase or decrease in the amount of light of the fluorescent wavelength.

[0157] Examples of fluorescent dyes are shown below: The following examples of fluorescent dyes are particularly preferred when the product (A) is a substance that generates fluoride ions (for example, hydrogen fluoride).

[0158] The fluorescent dye may be a triarylfluorosilane compound. The triarylfluorosilane compound is, for example, SiFR １ R ２ R ３ (See formula (1)). １ , R ２ and R ３ are either anthracene or a derivative thereof, or R １ and R ２ is anthracene or its derivative and R ３ is benzene or its derivatives.

[0159]

[0160] The fluorescent dye may be a compound having a structure in which a donor group and an acceptor group are bonded. The donor group has donor properties in an excited state. The donor group is a chromophore. The acceptor group has high acceptor properties in a free state and low acceptor properties when bonded to product (A) or an ion derived from product (A). The acceptor group is a receptor.

[0161] The acceptor group may be selected from the group consisting of a compound having a structure in which two or more amino groups are bonded via one or two methylene groups (hereinafter also referred to as compound (B)), a compound having a structure in which two or more pyrrole groups or indole groups are bonded via two methylene groups (hereinafter also referred to as compound (C)), benzamide, bis(methylidene)hydrazine, and calixarene.

[0162] Examples of the compound (B) include urea and its derivatives, thiourea and its derivatives, and polyamine macrocycles.

[0163] Examples of compound (C) include 1,2-ethanediyl-bis(pyrrole) and 1,2-ethanediyl-bis(indol).

[0164] The donor group may be selected from the group consisting of anthracene, naphthalimide, pyrene, bodipy, fluorescein, rhodamine, resorufin, coumarin, and cyanine.

[0165] For example, some of the above-mentioned fluorescent dyes change their fluorescence wavelength upon reaction with product (A). As an example, in the case of a triarylfluorosilane compound, the fluorescence wavelength at an excitation wavelength of 366 nm changes from 416 nm to 396 nm. Therefore, the presence of product (A) can be detected by a decrease in the intensity of light with a fluorescence wavelength of 416 nm or an increase in the intensity of light with a fluorescence wavelength of 396 nm.

[0166] The photodetection circuit using a phosphor may include a light source device and a photodetection device. The light source device emits excitation light having a wavelength corresponding to the excitation wavelength of the fluorescent dye into the refrigeration cycle circuit 2. The excitation light may be directional light (e.g., laser light). The wavelength range of the excitation light may include the excitation wavelength of the fluorescent dye. However, it is preferable that the wavelength range of the excitation light does not include the fluorescence wavelength of the fluorescent dye. The light source device may be, for example, a laser diode. The photodetection device receives light having a wavelength corresponding to the fluorescence wavelength of the fluorescent dye and outputs the intensity of the received light. The photodetection device may output a photodetection signal indicating the intensity of the light to the control circuit 35B. The wavelength range to which the photodetection device is sensitive may include the fluorescence wavelength of the fluorescent dye. However, if the fluorescence wavelength of the fluorescent dye changes, it is preferable that the wavelength range to which the photodetection device is sensitive includes only either the fluorescence wavelength before the change or the fluorescence wavelength after the change. It is also preferable that the wavelength range to which the photodetection device is sensitive does not include the excitation wavelength of the fluorescent dye. The photodetection device may include, for example, a photodiode and an optical system (e.g., a lens, etc.).

[0167] The light source device preferably radiates excitation light to a portion between the discharge pipe 402 of the compressor 4 and the condenser (the first heat exchanger 5 during cooling operation and the second heat exchanger 7 during heating operation) of the refrigeration cycle circuit 2. In particular, the light source device preferably radiates excitation light to a portion between the discharge pipe 402 of the compressor 4 and the four-way valve 8. Since the light source device radiates excitation light to a portion closer to the discharge pipe 402 of the compressor 4 than the four-way valve 8, the possibility that the excitation light will hit the fluorescent element can be increased.

[0168] The optical detection device preferably receives light from a portion between the discharge pipe 402 of the compressor 4 and the condenser (the first heat exchanger 5 during cooling operation, and the second heat exchanger 7 during heating operation) of the refrigeration cycle circuit 2. In particular, the optical detection device preferably receives light from a portion between the discharge pipe 402 of the compressor 4 and the four-way valve 8. Since the optical detection device receives light from a portion closer to the discharge pipe 402 of the compressor 4 than the four-way valve 8, the intensity of the light received by the optical detection device can be improved.

[0169] The fluorescent material is not limited to refrigeration oil in which the fluorescent dye is dissolved. The fluorescent material may also be a support carrying the fluorescent dye. The support may be, for example, a porous material. The porous material may be inorganic or organic. Examples of inorganic porous materials include mesoporous silica. Examples of organic porous materials include synthetic resin membranes or paper. Porous materials can ensure a larger surface area, thereby increasing the likelihood of the fluorescent dye coming into contact with the working medium 20. Such a fluorescent material may be fixed at a predetermined location in the refrigeration cycle circuit 2. For example, the fluorescent material may be disposed within the sealed container 40 of the compressor 4, in the region between the motor 42 and the discharge pipe 402. Unlike fluorescent materials with a support, fluorescent materials with a support are located in a predetermined location rather than dispersed throughout the refrigeration cycle circuit 2. This reduces the likelihood of contact with the working medium 20, but ensures reliable application of excitation light.

[0170] As a third example, the amount of the product can be measured using a dye. When a discharge phenomenon occurs, there is a possibility that a product generated by a chemical reaction of the working medium 20 may circulate in the refrigeration cycle circuit 2 together with the working medium 20. For example, when the working medium contains an ethylene-based fluoroolefin, the product generated by the chemical reaction of the working medium 20 (hereinafter also referred to as product (D)) may be tetrafluoroethylene (C ２ F ４ ) or hydrogen fluoride (HF). Such product (D) is an example of a product generated from the working fluid 20 by a disproportionation reaction. Repeated discharge phenomena increase the amount of product (D). An increase in product (D) may cause an abnormality in the refrigeration cycle circuit 2. A dye can be used to quantitatively evaluate product (D). That is, if the dye has the property of changing its absorption maximum wavelength upon reaction with product (D), the increase in product (D) can be observed as a change in the intensity of light in a wavelength band including the absorption wavelength of the dye. It is desirable that the difference between the absorption maximum wavelength of the dye and the absorption maximum wavelength of the dye after reaction with product (D) be large enough to sufficiently distinguish the waveform of the wavelength change in absorbance of the dye from the waveform of the wavelength change in absorbance after reaction with product (D).

[0171] In this way, by focusing on the intensity of light in a wavelength band including the absorption wavelength of the dye, the product (D) can be quantitatively evaluated.

[0172] In this case, the measurement circuit 37 may include a light sensing circuit that utilizes a light absorber.

[0173] The light absorber contains a dye and is arranged in the refrigeration cycle circuit 2 so as to be able to come into contact with the working medium 20. For example, the light absorber is refrigeration oil in which a dye is dissolved. That is, the light absorber is formed by dissolving a dye in the refrigeration oil of the compressor 4. The light absorber circulates through the refrigeration cycle circuit 2 together with the working medium 20. This increases the possibility that the dye in the light absorber will come into contact with and react with the product (D).

[0174] The dye has the property of changing the maximum absorption wavelength upon reaction with the product (D) produced by the chemical reaction of the working medium 20. Therefore, depending on the type of dye, the reaction between the dye and the product (D) can cause an increase or decrease in the amount of light at the absorption wavelength.

[0175] A first example of the dye is shown below. This first example of the dye is preferred when the product (D) is tetrafluoroethylene. The first example of the dye may include a nickel complex. The nickel complex may react with tetrafluoroethylene and change its absorbance. Therefore, the presence of tetrafluoroethylene as the product (D) can be detected by a change in the intensity of light at the wavelength at which the absorbance changes. Examples of nickel complexes include bistriphenylphosphine nickel(0) (see formula (2)), bis(ortho-diphenylphosphanylphenyl)ether nickel(0) (see formula (3)), 2,2'-bis(ortho-diphenylphosphino)trans-stilbene nickel(0) (see formula (4)), 2,2'-bis(diphenylphosphino)biphenyl nickel(0) (see formula (5)), 2,2'-bis(diphenylphosphino)diphenylmethane nickel(0) (see formula (6)), and 2,2'-bis(diphenylphosphino)diphenylpropane nickel (see formula (7)).

[0176]

[0177]

[0178]

[0179]

[0180]

[0181]

[0182] A second example of the dye is shown below. The second example of the dye is preferred when the product (D) is hydrogen fluoride. The second example of the dye may include a boron compound having an aromatic substituent. A boron compound having an aromatic substituent may react with hydrogen fluoride and change its absorbance. Therefore, the presence of hydrogen fluoride as the product (D) can be detected by a change in the intensity of light at a wavelength at which the absorbance changes. An example of a boron compound having an aromatic substituent is diarylnaphthylborane represented by formula (8). Note that R １ and R ２ are each selected from the group consisting of a naphthyl group represented by formula (9) or a mesityl group represented by formula (10).

[0183]

[0184]

[0185]

[0186] The photodetection circuit using a light absorber includes a light source device and a photodetection device. The light source device emits light in a wavelength band including the absorption wavelength of the dye into the refrigeration cycle circuit 2. For example, the light source device may include a first light source and a second light source. The first light source and the second light source can emit first and second lights having different wavelength bands into the refrigeration cycle circuit 2. This means that the first and second lights correspond to different absorption wavelengths of the dye. In this manner, the light source device may emit multiple lights having different wavelength bands. For example, the first and second lights are directional lights (e.g., laser beams). The first and second light sources are, for example, laser diodes. The photodetection device receives the first and second lights from the light source device and outputs the intensities of the received first and second lights. The photodetection device may output a photodetection signal indicating the intensities of the received first and second lights to the control circuit 35B. Using the intensities of multiple lights having different wavelength bands can reduce the influence of the colors of substances other than the dye of the light absorber, such as the influence of a change in the hue of the refrigeration oil. The light detection device may include, for example, a first light detector and a second light detector. The first light detector may be arranged to receive a first light emitted from a first light source, and the second light detector may be arranged to receive a second light emitted from a second light source. Each of the first light detector and the second light detector may include a light detection element and an optical system. The light detection element may include, for example, a photodiode. The optical system may include, for example, a lens (condenser lens).

[0187] The light source device may radiate the first light and the second light to a portion between the discharge pipe 402 of the compressor 4 and the condenser (the first heat exchanger 5 during cooling operation and the second heat exchanger 7 during heating operation) of the refrigeration cycle circuit 2. In particular, the light source device may radiate the first light and the second light to a portion between the discharge pipe 402 of the compressor 4 and the four-way valve 8. By radiating the first light and the second light to a portion closer to the discharge pipe 402 of the compressor 4 than the four-way valve 8, the light source device can increase the possibility that the first light and the second light will hit the dye.

[0188] The optical detection device receives the first light and the second light from a portion between the discharge pipe 402 of the compressor 4 and the condenser (the first heat exchanger 5 during cooling operation, and the second heat exchanger 7 during heating operation) of the refrigeration cycle circuit 2. In particular, the optical detection device may receive the first light and the second light from a portion between the discharge pipe 402 of the compressor 4 and the four-way valve 8. By receiving the first light and the second light from a portion closer to the discharge pipe 402 of the compressor 4 than the four-way valve 8, the intensity of the first light and the second light received by the optical detection device can be improved.

[0189] The light absorber is not limited to refrigeration oil in which a dye is dissolved. The light absorber may also be a support carrying a dye. The support is, for example, a porous body. The porous body may be inorganic or organic. Examples of inorganic porous bodies include mesoporous silica. Examples of organic porous bodies include synthetic resin membranes or paper. Porous bodies can ensure a larger surface area, thereby increasing the likelihood of the dye coming into contact with the working medium 20. Preferably, the porous body has the property of transmitting light without blocking it. The light absorber is fixed at a predetermined location in the refrigeration cycle circuit 2. The light absorber may be disposed in the sealed container 40 of the compressor 4. For example, the light absorber may be located in the region between the electric motor 42 and the discharge pipe 402. Unlike light absorbers with refrigeration oil, light absorbers with a support have the dye located in a predetermined location rather than dispersed throughout the refrigeration cycle circuit 2. This reduces the likelihood of contact with the working medium 20, but ensures that light can be irradiated reliably.

[0190] The control circuit 35B stops the operation of the drive circuit 31 after switching the first path R1 to the second path R2 by the switching device 36. When the control circuit 35B determines that the unsteady state is not continuing based on a time-dependent change in at least one of the pressure, temperature, and amount of product in the refrigeration cycle circuit 2, the control circuit 35B resumes the operation of the drive circuit 31.

[0191] Next, a first example of the operation of the control circuit 35B of the control device 3B will be briefly described with reference to Fig. 12. Fig. 12 is a flowchart of the first example of the operation of the control circuit 35B of the control device 3B.

[0192] The control circuit 35B acquires the detected voltage from the state detection circuit 32 (S60). The control circuit 35B determines whether the detected voltage is less than the second voltage (S61).

[0193] If the detected voltage is not less than the second voltage (S61: NO), the process returns to step S60. In steps S60 and S61, the control circuit 35B determines whether the detected voltage is less than the second voltage at a predetermined cycle. The predetermined cycle is preferably shorter than the cycle corresponding to the reference frequency of the inverter circuit 312 (e.g., 1000 to 5000 Hz).

[0194] In step S61, if the detected voltage is less than the second voltage (S61: YES), the control circuit 35B switches from the first route R1 to the second route R2 using the switching device 36 (S62). As a result, the control circuit 35B reduces the internal pressure of the compressor 4 to a predetermined pressure or less. The reduction in the internal pressure of the compressor 4 increases the discharge energy required for the disproportionation reaction to proceed, thereby suppressing the disproportionation reaction.

[0195] Furthermore, the control circuit 35B stops the operation of the compressor 4 (S63). Here, the control circuit 35B sets the first protection device 33 to the OFF state to stop the output of AC output power.

[0196] Next, the control circuit 35B acquires the internal state from the measurement circuit 37 (S64).

[0197] The control circuit 35B determines whether the unsteady state of the refrigeration cycle circuit 2 continues based on the internal state (S65).

[0198] As described above, the internal state may include at least one of the pressure, temperature, and amount of product in the refrigeration cycle circuit 2. The control circuit 35B determines whether the unsteady state continues based on a change over time in at least one of the pressure, temperature, and amount of product in the refrigeration cycle circuit 2.

[0199] The control circuit 35B may determine that the unsteady state continues when the amount or rate of increase in pressure in the refrigeration cycle circuit 2 in a predetermined time is equal to or greater than a threshold. For example, with respect to pressure, the predetermined time may be 10 seconds, and the threshold may be a 10% increase amount.

[0200] The control circuit 35B may determine that the unsteady state continues when the increase in temperature in the refrigeration cycle circuit 2 over a predetermined time period is equal to or greater than a threshold value. For example, with respect to temperature, the predetermined time period may be 10 seconds, and the threshold value may be 50 K.

[0201] The control circuit 35B may determine that an unsteady state continues when the increase in the amount or volume fraction of the product in the refrigeration cycle circuit 2 over a predetermined time period is equal to or greater than a threshold value. For example, the predetermined time period and the threshold value depend on the type of product. As an example, if the product is hydrogen fluoride, the predetermined time period may be 30 seconds, and the threshold value may be 0.1% in terms of volume fraction. Note that the amount of product may be measured using the amount of light emitted, transmittance, or absorbance.

[0202] In step S65, when it is determined that the unsteady state of the refrigeration cycle circuit 2 is not continuing (S65: NO), the control circuit 35B sets the first protection device 33 to the ON state to resume the output of AC output power, thereby restarting the operation of the compressor 4 (S66). After that, the process returns to step S60.

[0203] If it is determined in step S65 that the unsteady state of the refrigeration cycle circuit 2 continues (S65: YES), the control circuit 35B determines whether a pause time has elapsed since it was determined that the unsteady state of the refrigeration cycle circuit 2 continues (S67). The pause time is, for example, 60 seconds.

[0204] When the pause time has elapsed (S67: YES), the control circuit 35B increments the pause count by 1 and determines whether the pause count has exceeded a predetermined number (S68). The predetermined number is, for example, 5.

[0205] In step S68, if it is determined that the number of pauses exceeds the predetermined number (S68: YES), the control circuit 35B outputs an abnormality notification (S69). The abnormality notification indicates that an abnormality has occurred in the refrigeration cycle apparatus 1 that is highly likely to cause a disproportionation reaction.

[0206] In step S68, if it is determined that the number of pauses does not exceed the predetermined number (S68: NO), the process returns to step S64.

[0207] 12 , the control circuit 35B confirms that the unsteady state of the refrigeration cycle circuit 2 is not continuing when restarting the operation of the compressor 4. Therefore, the operation of the drive circuit 31 can be restarted in a state where the possibility of the disproportionation reaction of the working medium 20 occurring is reduced. Therefore, the continuity of the operation of the refrigeration cycle circuit 2 can be improved while the suppression of the disproportionation reaction of the working medium 20 can be improved.

[0208] Next, a second example of the operation of the control circuit 35B of the control device 3B will be briefly described with reference to Figures 13 and 14. Figures 13 and 14 each show a part of a flowchart of the operation of the control circuit 35B of the control device 3B, and a single flowchart is completed by combining Figures 13 and 14.

[0209] Steps S70 to S75 in FIG. 13 are the same as steps S60 to S65 in FIG. 12, and therefore a description thereof will be omitted.

[0210] If it is determined in step S75 that the unsteady state of the refrigeration cycle circuit 2 is not continuing (S75: NO), the control circuit 35B performs idling operation (S76). Idling operation is performed to stabilize the state of the working medium 20. For example, idling operation circulates the working medium 20 to suppress stagnation of the refrigerant components of the working medium 20. Since this type of idling operation is well known, a detailed description thereof will be omitted. After the idling operation (S76), the control circuit 35B resumes operation of the compressor 4 with its functions restricted (S77). For example, the control circuit 35B changes the switching control of the semiconductor switching elements of the drive circuit 31 so that the set value of the amplitude of the AC output power decreases from E to E / 2, and sets the first protection device 33 to the ON state to resume output of the AC output power.

[0211] Thereafter, the control circuit 35B acquires the detected voltage from the state detection circuit 32 (S78), and determines whether the detected voltage is less than the second voltage (S79).

[0212] If the detected voltage is not less than the second voltage (S79: NO), the control circuit 35 releases the restriction on the function of the compressor 4 and allows the compressor 4 to operate normally (S80). For example, the control circuit 35B releases the reduction in the set value of the amplitude of the AC output power and returns the set value of the amplitude of the AC output power to E. After step S80, the process returns to step S70.

[0213] In step S79, if the detected voltage is less than the second voltage (S79: YES), the process proceeds to step S72.

[0214] In step S75, if it is determined that the unsteady state of the refrigeration cycle circuit 2 continues (S75: YES), the process proceeds to step S81. Steps S81, S82, and S83 are the same as steps S67, S68, and S69 in FIG. 12, and therefore a description thereof will be omitted.

[0215] 13 and 14 , the control circuit 35B confirms that the unsteady state of the refrigeration cycle circuit 2 is not continuing when restarting the operation of the compressor 4. Therefore, the operation of the drive circuit 31 can be restarted in a state where the possibility of the disproportionation reaction of the working medium 20 occurring is reduced. Therefore, the continuity of the operation of the refrigeration cycle circuit 2 can be improved while the suppression of the disproportionation reaction of the working medium 20 can be improved.

[0216] Furthermore, after the operation of the compressor 4 is stopped, the operation of the compressor 4 can be restarted in stages, which makes it possible to further improve the suppression of the disproportionation reaction of the working medium 20.

[0217] [1.3.2 Effects, etc.] In the control device 3B described above, the control circuit 35B stops the operation of the drive circuit 31 after switching the first path R1 to the second path R2 by the switching device 36, and resumes the operation of the drive circuit 31 when it determines that the unsteady state is not continuing based on changes over time in at least one of the pressure, temperature, and amount of product in the refrigeration cycle circuit 2. This configuration allows the operation of the drive circuit 31 to be resumed in a state where the possibility of the disproportionation reaction of the working medium 20 occurring is reduced. Therefore, it is possible to improve the suppression of the disproportionation reaction of the working medium 20 while improving the continuity of the operation of the refrigeration cycle circuit 2.

[0218] [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.

[0219] In the following, reference will be made to the symbols used in embodiment 1, even though they are applicable to both embodiments 1 and 2 above. However, this is merely to simplify the description and is not intended to exclude application to embodiments 2 and 3.

[0220] In one modified example, the configuration of the switching device 36 is not limited to the above embodiment. For example, in the switching device 36B, the second path R2 may connect the discharge pipe 402 of the compressor 4 to a container capable of storing the working medium 20, instead of the discharge port 11. In this way, the working medium 20 is not discharged to the outside of the refrigeration cycle circuit 2, and therefore the refrigeration cycle circuit 2 can return to normal operation (cooling operation or heating operation).

[0221] In one modified example, in the control circuit 35, stopping the operation of the drive circuit 31 may include one or more of stopping the output of AC output power, stopping the output of DC output power, or stopping the input of input power. Restricting the operation of the drive circuit 31 may include one or more of reducing the set value of the amplitude of the AC output power or reducing the set value of the frequency of the AC output power.

[0222] In one modified example, the control circuit 35 may stepwise stop or decelerate the electric motor 42. As an example, the control circuit 35 may stepwise reduce at least one of the amplitude and frequency of the AC output power, thereby stepwise reducing the effective value of the AC output power supplied to the electric motor 42.

[0223] In this modification, the operation of the control circuit 35 is not necessarily limited to the operations shown in the flowcharts of Figures 4 to 9. The flowcharts of Figures 4 to 9 are merely examples.

[0224] For example, the processing of steps S20 to S24, i.e., the processing of stopping the output of AC output power and stopping the input of input power, is not essential in the operation of the control circuit 35. The processing of steps S25 to S29, i.e., the processing of stopping the output of AC output power and reducing the set value of the amplitude of the AC output power after the standby time has elapsed, is not essential in the operation of the control circuit 35. Similarly, the processing of steps S30 to S36, steps S37 to S43, or steps S42 to S51 is not essential in the operation of the control circuit 35.

[0225] In steps S19, S31, S43, and S49, when restarting the operation of the compressor 4, it is preferable to confirm that the internal pressure of the compressor 4 is equal to or lower than the threshold value before switching from the second route R2 to the first route R1 by the switching device 36. In other words, it is preferable to restart the operation of the compressor 4 when the internal pressure of the compressor 4 has dropped and the possibility of the disproportionation reaction occurring is reduced. The internal pressure of the compressor 4 can be obtained, for example, by a pressure sensor disposed in the refrigerant piping near the discharge pipe 402 of the compressor 4 or in the sealed container 40 of the compressor 4. The threshold value can be set based on the internal pressure of the compressor 4 during normal operation of the refrigeration cycle apparatus 1.

[0226] The control circuit 35 does not necessarily have to stop or restrict the operation of the drive circuit 31 in different ways depending on the time difference between the first time when the detected voltage first becomes less than the second voltage and the second time when the detected voltage next becomes less than the second voltage, or the number of times the detected voltage becomes less than the second voltage.

[0227] In one modified example, the first protection device 33 is not limited to a circuit configuration including the switches Su, Sv, and Sw, and may include a circuit configuration that adjusts the magnitude of the AC output power, for example, the magnitude of the voltage, output from the drive circuit 31 to the electric motor 42. The first protection device 33 may be disposed within the drive circuit 31.

[0228] In one modified example, the second protection device 34 is not limited to a circuit configuration including the switches S1 and S2, and may include a circuit configuration that adjusts the magnitude of the input power, for example, the magnitude of the voltage, input from the power source 10 to the drive circuit 31. The second protection device 34 may be disposed within the drive circuit 31.

[0229] In one modified example, the control device 3 does not necessarily include both the first protection device 33 and the second protection device 34, and may include either the first protection device 33 or the second protection device 34, or the first and second protection devices 33, 34 may be omitted if the drive circuit 31 has a function of adjusting the AC output power. For example, the control circuit 35 may stop the output of AC output power to the motor 42 by turning on the semiconductor switching elements V1 to V4 of the inverter circuit 312 and turning off the remaining semiconductor switching elements U1 to U4, W1 to W4. In this case, the first protection device 33 may be omitted.

[0230] FIG. 15 shows a modified control device 3C. In FIG. 15, the control device 3C includes a third protection device 38. The third protection device 38 is provided to stop the output of DC output power. The third protection device 38 includes switches S3, S4, and S5 interposed between the converter circuit 311 and the inverter circuit 312 of the drive circuit 31. The switch S3 is commonly connected between the first output point P1 and the semiconductor switching elements U1, V1, and W1. The switch S4 is commonly connected between the second output point P2 and the semiconductor switching elements U4, V4, and W4. The switch S5 is commonly connected between the third output point P3 and the connection point between diodes D5 and D6, the connection point between diodes D7 and D8, and the connection point between diodes D9 and D10. The switches S3, S4, and S5 may be controllable switches such as semiconductor switches or electromagnetic relays. The third protection device 38 allows the output of DC output power from the converter circuit 311 to the inverter circuit 312 when the switches S3, S4, and S5 are closed in the on state, and stops the output of DC output power from the converter circuit 311 to the inverter circuit 312 when the switches S3, S4, and S5 are open in the off state.

[0231] When stopping the output of power to the compressor 4, the safety level increases in the order of stopping the input of input power, stopping the output of DC output power, and stopping the output of AC output power. Therefore, after the operation of the first protection device 33, the third protection device 38 may be operated before the operation of the second protection device 34. Note that if the third protection device 38 is present, the second protection device 34 may be omitted.

[0232] In one variant, the third protection device 38 is not limited to a circuit configuration including switches S3, S4, and S5, but may include a circuit configuration that adjusts the magnitude of the DC output power, for example, the magnitude of the voltage, output from the converter circuit 311 to the inverter circuit 312.

[0233] In one modified example, the state detection circuit 32 is not limited to a configuration that detects the voltage value of the DC output power of the converter circuit 311. The state detection circuit 32 may be configured to detect the state of at least one of the compressor 4 and the drive circuit 31.

[0234] For example, the state of the drive circuit 31 may be the current value of the current flowing through the connection lines corresponding to the three phases of the AC output power output from the inverter circuit 312 to the compressor 4. In other words, the state detection circuit 32 may detect the AC output power. In this case, the abnormality of the drive circuit 31 may include an abnormality related to leakage current detected between the connection lines corresponding to the three phases of the AC output power. Since methods for detecting abnormalities related to leakage current are well known, detailed description thereof will be omitted. In another example, the state of the drive circuit 31 may be the current value of the current flowing through the drive circuit 31. As an example, the current value of the current flowing through the drive circuit 31 may include at least one of the current values ​​of the output AC current of the U-phase, V-phase, and W-phase legs of the drive circuit 31. In this case, the abnormality of the drive circuit 31 is a current abnormality. The control circuit 35 may detect a current abnormality in response to the current value of the current flowing through the drive circuit 31 detected by the state detection circuit 32 exceeding a predetermined current value. As another example, the current value of the current flowing in the drive circuit 31 may include the current value of the direct current flowing between the converter circuit 311 and the inverter circuit 312 of the drive circuit 31. In this case, the control circuit 35 may determine that a current abnormality has occurred in the drive circuit 31 if the current value of the direct current flowing between the converter circuit 311 and the inverter circuit 312 of the drive circuit 31 exceeds a predetermined current value.

[0235] For example, the state of the compressor 4 may include at least one of the phase current of the compressor 4 and the rotation speed of the motor 42 of the compressor 4. The current value of the phase current of the compressor 4 may include the current values ​​of the U phase, the V phase, and the W phase. In this case, the abnormality of the compressor 4 may include an abnormality related to a layer short of the compressor 4. An abnormality related to a layer short of the compressor 4 may include the layer short of the compressor 4 itself, an abnormality that may cause the layer short of the compressor 4, and an abnormality that may be caused by the layer short of the compressor 4. Specific examples of abnormalities related to a layer short of the compressor 4 include a layer short of the compressor 4, a ground fault of the compressor 4, and open-phase operation of the compressor 4. If an imbalance in the phase current of the compressor 4 occurs, an abnormality related to a layer short of the compressor 4 may have occurred. The control circuit 35 may determine whether an abnormality of the compressor 4 has occurred based on the state of the compressor 4 detected by the state detection circuit 32. For example, if an imbalance in the phase currents of the compressor 4 occurs, the control circuit 35 may determine that an abnormality related to a layer short in the compressor 4 has occurred. Furthermore, if a deviation in the rotation speed of the motor 42 of the compressor 4 occurs, there is a possibility that an abnormality related to a layer short in the compressor 4 has occurred.

[0236] In one variant, the power supply 10 may be any of a variety of AC power sources, particularly a commercial power source. The voltage and frequency of the commercial power source vary depending on the country, and the drive circuit 31 may be configured to be able to drive the motor 42 using any of a variety of commercial power sources.

[0237] In one modified example, the drive circuit 31 may be configured to supply AC output power corresponding to the type of the electric motor 42. The AC output power is not limited to three-phase AC power, but may be single-phase AC power.

[0238] In one variation, the converter circuit 311 may have a plurality of third output points. The plurality of third output points may output different voltages. The inverter circuit 312 may have a plurality of third semiconductor switching element groups connected between the plurality of third output points and the electric motor 42. If the total number of the first output point P1, the second output point P2, and the plurality of third output points P3 is n, the drive circuit 31 can provide voltages at (2×n−1) levels. By increasing n, the voltage waveform applied to the electric motor 42 by the drive circuit 31 can be made closer to a sine wave.

[0239] In one modified example, the circuit configuration of the inverter circuit 312 is not limited to the circuit configuration shown in FIG. 2 . The circuit configuration of the inverter circuit 312 shown in FIG. 2 is a so-called NPC (Neutral-Point-Clamped) type, but may also be an A-NPC (Advanced-NPC) type. The inverter circuit 312 only needs to have multiple semiconductor switching element groups connected between multiple output points with different voltages and the electric motor. The multiple semiconductor switching elements constituting the multiple semiconductor switching element groups may include semiconductor switching elements that are commonly included in two or more semiconductor switching element groups. The inverter circuit 312 does not necessarily have to be a multilevel inverter.

[0240] 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.

[0241] [3. Aspects] As is clear from the above-described embodiment and modifications, the present disclosure includes the following aspects.

[0242] [Aspect 1] A control device that controls a refrigeration cycle circuit including a compressor, a condenser, an expansion valve, and an evaporator, and through which a working medium circulates, the control device comprising: a drive circuit that drives the compressor; a state detection circuit that detects a state of at least one of the compressor and the drive circuit; a switching device that can switch between a first path that connects a discharge pipe of the compressor to the condenser and a second path that connects the discharge pipe of the compressor to a predetermined space that reduces the internal pressure of the compressor to a predetermined pressure or lower; and a control circuit that controls the drive circuit and the switching device, wherein the control circuit switches the first path to the second path using the switching device when the state of at least one of the compressor and the drive circuit detected by the state detection circuit indicates an unsteady state of the refrigeration cycle circuit.

[0243] [Aspect 2] The control device according to Aspect 1, wherein the predetermined space is a space having a pressure of 0.4 MPa or less.

[0244] [Aspect 3] The control device according to aspect 1 or 2, wherein the predetermined pressure is 3.0 MPa or less.

[0245] [Aspect 4] The control device of any one of Aspects 1 to 3, wherein the switching device is located between a discharge pipe of the compressor and the condenser, the first path connects the discharge pipe of the compressor to the condenser, and the second path connects the discharge pipe of the compressor to the predetermined space.

[0246] [Aspect 5] The control device according to Aspect 4, wherein the refrigeration cycle circuit includes an accumulator located on a suction pipe side of the compressor, and the second path connects a discharge pipe of the compressor to an internal space of the accumulator.

[0247] [Aspect 6] The control device of any one of Aspects 1 to 3, wherein the refrigeration cycle circuit includes a first heat exchanger and a second heat exchanger, the switching device is a four-way valve that switches a direction in which the working medium circulates through the refrigeration cycle circuit between a first direction corresponding to a cooling operation and a second direction corresponding to a heating operation, the first path corresponds to the second direction and connects a discharge pipe of the compressor to the second heat exchanger, and the second path corresponds to the first direction and connects a discharge pipe of the compressor to the first heat exchanger, and the control circuit, when a state of at least one of the compressor and the drive circuit detected by the state detection circuit indicates the unsteady state, switches the first path to the second path by the switching device and increases an opening of the expansion valve.

[0248] [Aspect 7] The control device of any one of Aspects 1 to 6, wherein the control circuit stops or limits operation of the drive circuit when the state of at least one of the compressor and the drive circuit detected by the state detection circuit indicates the unsteady state.

[0249] [Aspect 8] The control device of Aspect 7, wherein the drive circuit includes an inverter circuit that outputs AC output power to the compressor, the state detection circuit detects the AC output power, and the unsteady state includes an abnormality related to leakage current detected between connection lines corresponding to three phases of the AC output power.

[0250] [Aspect 9] The control device of Aspect 7, wherein the drive circuit includes: a converter circuit that outputs DC output power based on input power from a power source so that the voltage becomes a first voltage; and an inverter circuit that outputs AC output power to the compressor based on the DC output power; the state detection circuit detects the DC output power and outputs a detection voltage indicating the voltage of the DC output power; and the non-steady state includes a state where the detection voltage is less than a second voltage that is equal to or less than the first voltage.

[0251] [Aspect 10] The control device of Aspect 9, wherein the second voltage is 0.3 to 0.8 times the first voltage.

[0252] [Aspect 11] The control device of any one of Aspects 1 to 10, wherein the control circuit stops operation of the drive circuit after the switching device switches from the first path to the second path, and resumes operation of the drive circuit when it determines that the unsteady state is not continuing based on a time-dependent change in at least one of pressure, temperature, and amount of product in the refrigeration cycle circuit.

[0253] [Aspect 12] A refrigeration cycle device comprising: the control device according to any one of aspects 1 to 11; and the refrigeration cycle circuit.

[0254] [Aspect 13] The refrigeration cycle device of Aspect 12, wherein the working fluid includes an ethylene-based fluoroolefin.

[0255] [Aspect 14] The refrigeration cycle device of Aspect 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.

[0256] [Aspect 15] The refrigeration cycle device of Aspect 12, wherein the working fluid further contains difluoromethane.

[0257] [Aspect 16] The refrigeration cycle device of Aspect 12, wherein the working medium further contains a saturated hydrocarbon.

[0258] [Aspect 17] The refrigeration cycle apparatus of Aspect 13, 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.

[0259] [Aspect 18] The refrigeration cycle device of Aspect 16, wherein the saturated hydrocarbon includes n-propane.

[0260] [Aspect 19] A control method executed by a control device that controls a refrigeration cycle circuit including a compressor, a condenser, an expansion valve, and an evaporator, and through which a working medium circulates, wherein the control device comprises: a drive circuit that drives the compressor; and a control circuit that controls the drive circuit, and the control method comprises, when a state of at least one of the compressor and the drive circuit indicates an unsteady state of the refrigeration cycle circuit, connecting a discharge pipe of the compressor to a predetermined space and reducing an internal pressure of the compressor to a predetermined pressure or less.

[0261] [Aspect 20] A program executed by a computer system equipped with a control device that controls a refrigeration cycle circuit including a compressor, a condenser, an expansion valve, and an evaporator, and through which a working medium circulates, wherein the control device comprises: a drive circuit that drives the compressor; and a control circuit that controls the drive circuit, and the program causes the computer system to connect a discharge pipe of the compressor to a predetermined space and reduce the internal pressure of the compressor to a predetermined pressure or less when a state of at least one of the compressor and the drive circuit indicates an unsteady state of the refrigeration cycle circuit.

[0262] Aspects 2 to 11 and 13 to 18 are optional elements and are not essential. Aspects 2 to 11 and 13 to 18 can be appropriately combined with Aspect 19 or 20.

[0263] The present disclosure is applicable to a control device, a refrigeration cycle device, a control method, and a program. 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, a refrigeration cycle device including the refrigeration cycle circuit and the control device, a control method executed by the control device, and a program (computer program) used in the control device.

[0264] DESCRIPTION OF SYMBOLS 1, 1A, 1B Refrigeration cycle device 2 Refrigeration cycle circuit 3, 3A, 3B, 3C Control device 4 Compressor 401 Suction pipe 402 Discharge pipe 5 First heat exchanger (condenser, evaporator) 6 Expansion valve 7 Second heat exchanger (condenser, evaporator) 9 Accumulator 10 Power source 11 Discharge port 20 Working medium 31 Drive circuit 32 State detection circuit 33 First protection device 34 Second protection device 35 Control circuit 36, 36A, 36B Switching device 311 Converter circuit 312 Inverter circuit

Claims

1. A control device for controlling a refrigeration cycle circuit in which a working medium circulates, including a compressor, condenser, expansion valve, and evaporator, The control device is A drive circuit for driving the compressor, A state detection circuit for detecting the state of at least one of the compressor and the drive circuit, A switching device that can switch between a first path connecting the discharge pipe of the compressor to the condenser and a second path connecting the discharge pipe of the compressor to a predetermined space that reduces the internal pressure of the compressor to a predetermined pressure or lower, The drive circuit and the control circuit that controls the switching device, Equipped with, The control circuit, when the state of at least one of the compressor and the drive circuit detected by the state detection circuit indicates an unsteady state of the refrigeration cycle circuit, switches the first path to the second path using the switching device, and stops or limits the operation of the drive circuit. The aforementioned drive circuit is A converter circuit that outputs DC output power such that the voltage becomes a first voltage based on the input power from the power supply, An inverter circuit that outputs AC output power to the compressor based on the DC output power, Includes, The state detection circuit detects the DC output power and outputs a detection voltage indicating the voltage of the DC output power. The aforementioned transient state includes a state in which the detected voltage is less than or equal to the second voltage, which is less than or equal to the first voltage. Control device.

2. The aforementioned predetermined space is a space with a pressure of 0.4 MPa or less. The control device according to claim 1.

3. The predetermined pressure is 3.0 MPa or less. The control device according to claim 1.

4. The switching device is located between the discharge pipe of the compressor and the condenser. The first path connects the discharge pipe of the compressor to the condenser, The second path connects the discharge pipe of the compressor to the predetermined space. The control device according to claim 1.

5. The refrigeration cycle circuit includes an accumulator located on the suction pipe side of the compressor. The second path connects the discharge pipe of the compressor to the internal space of the accumulator. The control device according to claim 4.

6. The aforementioned refrigeration cycle circuit includes a first heat exchanger and a second heat exchanger. The switching device is a four-way valve that switches the direction in which the working medium circulates in the refrigeration cycle circuit between a first direction corresponding to cooling operation and a second direction corresponding to heating operation. The first path corresponds to the second direction and connects the discharge pipe of the compressor to the second heat exchanger. The second path corresponds to the first direction and connects the discharge pipe of the compressor to the first heat exchanger. The control circuit, when the state of at least one of the compressor and the drive circuit detected by the state detection circuit indicates the transient state, switches the first path to the second path using the switching device and increases the opening degree of the expansion valve. The control device according to claim 1.

7. The second voltage is 0.3 times or more and 0.8 times or less the first voltage. The control device according to claim 1.

8. The aforementioned control circuit is After the switching device switches the first path to the second path, the operation of the drive circuit is stopped. If it is determined that the transient state is not continuing based on the time-dependent changes in pressure, temperature, and amount of products within the refrigeration cycle circuit, the operation of the drive circuit is restarted. The control device according to claim 1.

9. The control device according to claim 1, The aforementioned refrigeration cycle circuit, Equipped with, Refrigeration cycle device.

10. The working medium includes an ethylene-based fluoroolefin. A refrigeration cycle apparatus according to claim 9.

11. A control method performed by a control device that controls a refrigeration cycle circuit in which a working medium circulates, including a compressor, condenser, expansion valve, and evaporator, The control device is A drive circuit for driving the compressor, A control circuit for controlling the aforementioned drive circuit, Equipped with, The control method, when the state of at least one of the compressor and the drive circuit indicates an unsteady state of the refrigeration cycle circuit, connects the discharge pipe of the compressor to a predetermined space to reduce the internal pressure of the compressor to below a predetermined pressure, and stops or limits the operation of the drive circuit. The aforementioned drive circuit is A converter circuit that outputs DC output power such that the voltage becomes a first voltage based on the input power from the power supply, An inverter circuit that outputs AC output power to the compressor based on the DC output power, Includes, The aforementioned transient state includes a state in which the voltage of the DC output power is less than or equal to the second voltage which is less than or equal to the first voltage. Control method.

12. A program executed in a computer system equipped with a control device that controls a refrigeration cycle circuit in which a working medium circulates, including a compressor, condenser, expansion valve, and evaporator, The control device is A drive circuit for driving the compressor, A control circuit for controlling the aforementioned drive circuit, Equipped with, The program instructs the computer system, when the state of at least one of the compressor and the drive circuit indicates an unsteady state of the refrigeration cycle circuit, to connect the discharge pipe of the compressor to a predetermined space, thereby reducing the internal pressure of the compressor to below a predetermined pressure, and stopping or limiting the operation of the drive circuit. The aforementioned drive circuit is A converter circuit that outputs DC output power such that the voltage becomes a first voltage based on the input power from the power supply, An inverter circuit that outputs AC output power to the compressor based on the DC output power, Includes, The aforementioned transient state includes a state in which the voltage of the DC output power is less than or equal to the second voltage which is less than or equal to the first voltage. program.