Control device and refrigeration cycle device

Abstract

Provided are a control device and a refrigeration cycle device that enable expansion of a control range of a refrigeration cycle circuit while enabling suppression of a disproportionation reaction. A control device (3) performs control of a compressor (4) of a refrigeration cycle circuit allowing circulation of a working medium (20) containing ethylene-based fluoroolefin as a refrigerant component, based on a result of comparison of a measured value indicating at least one of an internal temperature or an internal pressure of the compressor (4) with at least one of a plurality of threshold values. The plurality of threshold values include a first threshold value, and a second threshold value less than the first threshold value. The control circuit (3) stops the compressor (4) when the measured value exceeds the first threshold value, operates the compressor (4) to allow a drive frequency to change at a first frequency change rate while the measured value is equal to or less than the second threshold value, and operates the compressor (4) to allow the drive frequency to change at a second frequency change rate different from the first frequency change rate in at least one of a case of increasing the drive frequency and a case of decreasing the drive frequency, when the measured value exceeds the second threshold value.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to control devices, and refrigeration cycle devices.BACKGROUND ART

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

[0003] HFO1123 and HFO1132 have a smaller GWP than R410A, but are therefore less stable than R410A. For example, the generation of radicals may cause a disproportionation reaction of HFO1123 or HFO1132, resulting in the conversion of HFO1123 and HFO1132 to other compounds.

[0004] Patent Document 3 discloses a refrigeration apparatus including a refrigerant circuit configured such that a compressor, a condenser, a throttling device, and an evaporator are connected by refrigerant piping, and using 1,1,2-trifluoroethylene as a refrigerant circulating in the refrigerant circuit. The refrigeration apparatus disclosed in Patent Document 3 includes a first refrigerant sensor provided on a discharge side of the compressor and configured to detect a temperature and a pressure of the refrigerant, and a control unit configured to control the compressor based on detection results of the first refrigerant sensor. The control unit includes a disproportionation reaction determination unit configured to determine whether the detection results of the first refrigerant sensor satisfy predetermined conditions before occurrence of a disproportionation reaction of the refrigerant, and a compressor rotational speed control unit configured to suppress a rotational speed of the compressor when the disproportionation reaction determination unit determines that the predetermined conditions are satisfied.PRIOR ART DOCUMENTSPATENT DOCUMENTS

[0005] Patent Document 1: WO 2012 / 157764 A1 Patent Document 2: WO 2012 / 157765 A1 Patent Document 3: WO 2015 / 140882 A1 SUMMARY OF THE INVENTIONPROBLEMS TO BE SOLVED BY THE INVENTION

[0006] In the refrigeration apparatus disclosed in Patent Document 3, when it is determined that the refrigerant temperature and the refrigerant pressure are equal to or higher than a first temperature and a first pressure before a disproportionation reaction occurs, the compressor is stopped. However, in order to stop the compressor so that a disproportionation reaction does not occur, it may be considered to set the first temperature and the first pressure sufficiently lower than the temperature and pressure at which the disproportionation reaction occurs, thereby advancing the timing at which the compressor is stopped. However, the lower the first temperature and the first pressure are set relative to the temperature and pressure at which the disproportionation reaction occurs, the narrower the range of refrigerant temperature and refrigerant pressure within which the refrigeration apparatus (refrigeration cycle device) can perform normal operation, that is, the narrower the control range of the refrigeration cycle device becomes. This leads to a reduction in the commercial value of the refrigeration cycle device.

[0007] The present disclosure provides control devices and refrigeration cycle devices that enable expansion of a control range of a refrigeration cycle circuit while enabling suppression of a disproportionation reaction.SOLUTIONS TO THE PROBLEMS

[0008] A control device according to an aspect of the present disclosure is a control device for controlling a compressor of a refrigeration cycle circuit allowing circulation of a working medium containing ethylene-based fluoroolefin as a refrigerant component. The control device includes: a measurement circuit configured to output a measured value indicating at least one of an internal temperature or an internal pressure of the compressor; and a control circuit configured to compare the measured value from the measurement circuit with at least one of a plurality of threshold values and to perform control of the compressor in accordance with a result of comparison. The plurality of threshold values include a first threshold value, and a second threshold value less than the first threshold value. The control circuit is configured to: stop the compressor when the measured value exceeds the first threshold value; operate the compressor to allow a drive frequency of the compressor to change at a first frequency change rate while the measured value is equal to or less than the second threshold value; and operate the compressor to allow the drive frequency to change at a second frequency change rate different from the first frequency change rate in at least one of a case of increasing the drive frequency and a case of decreasing the drive frequency, when the measured value exceeds the second threshold value.

[0009] A control device according to an aspect of the present disclosure is a control device for controlling a compressor and an expansion valve of a refrigeration cycle circuit allowing circulation of a working medium. The working medium contains ethylene-based fluoroolefin as a refrigerant component. The control device includes: a measurement circuit configured to output a measured value indicating at least one of an internal temperature or an internal pressure of the compressor; and a control circuit configured to compare the measured value from the measurement circuit with at least one of a plurality of threshold values and to perform control of the compressor and the expansion valve in accordance with a result of comparison. The plurality of threshold values include a first threshold value, and a second threshold value less than the first threshold value. The control circuit is configured to: stop the compressor when the measured value exceeds the first threshold value; operate the expansion valve to allow an opening degree of the expansion valve to change at a first opening degree change rate while the measured value is equal to or less than the second threshold value; and operate the expansion valve to allow the opening degree to change at a second opening degree change rate different from the first opening degree change rate in at least one of a case of increasing the opening degree and a case of decreasing the opening degree, when the measured value exceeds the second threshold value.

[0010] A refrigeration cycle device according to an aspect of the present disclosure includes: any of the above control devices; and the refrigeration cycle circuit.EFFECTS OF THE INVENTION

[0011] Aspects of the present disclosure enable expansion of a control range of a refrigeration cycle circuit while enabling suppression of a disproportionation reaction.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Fig. 1 is a block diagram of a refrigeration cycle device according to embodiment 1. Fig. 2 is a schematic view of a compressor and a control device, of the refrigeration cycle device according to embodiment 1. Fig. 3 is an explanatory diagram for control of the compressor by a control circuit of the control device according to embodiment 1. Fig. 4 is a block diagram of a refrigeration cycle device according to embodiment 2. Fig. 5 is an explanatory diagram for control of a compressor and an expansion valve by a control circuit of a control device according to embodiment 2. Fig. 6 is an explanatory diagram for control of a compressor by a control circuit of a control device according to one variation. Fig. 7 is an explanatory diagram for control of a compressor by a control circuit of a control device according to one variation. Fig. 8 is an explanatory diagram for control of a compressor and an expansion valve by a control circuit of a control device according to one variation. Fig. 9 is an explanatory diagram for control of a compressor and an expansion valve by a control circuit of a control device according to one variation. DETAILED DESCRIPTION[1. EMBODIMENTS]

[0013] 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., shapes, dimensions, arrangement and the like, of components). 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 size and thickness of each component in each figure do not necessarily reflect the actual dimensional ratios. Furthermore, the dimensional ratios of each element are not limited to the ratios shown in the drawings.

[0014] In the following description, if it is necessary to distinguish a plurality of components from each other, prefixes, such as, "first", "second", or the like are attached to names of such components. However, if these components can be distinguished from each other by reference signs attached to those components, such prefixes, such as, "first", "second", or the like, may be omitted in consideration of readability of texts.

[0015] Note that, in the following description, if it is necessary to distinguish a plurality of components from each other, suffixes, such as, "-1", "-2", or the like are attached to reference signs of such components. if there is no need to distinguish such components from each other, such suffixes, such as, "-1", "-2", or the like, may be omitted in consideration of readability of texts.[1.1 EMBODIMENT 1][1.1.1 CONFIGURATIONS]

[0016] Fig. 1 is a block diagram of a refrigeration cycle device 1 according to the present embodiment. The refrigeration cycle device 1 constitutes an air conditioner enabling a cooling operation and a heating operation, for example. The refrigeration cycle device 1 includes a refrigeration cycle circuit 2 and a control device 3.

[0017] The refrigeration cycle circuit 2 constitutes a fluidic pathway where a working medium 20 (see Fig. 2) circulates. In the present embodiment, the working medium 20 contains ethylene-based fluoroolefin as a refrigerant component. The ethylene-based fluoroolefin may be ethylene-based fluoroolefin likely to undergo a disproportionation reaction. Examples of the ethylene-based fluoroolefin likely to undergo a disproportionation reaction may include 1,1,2-trifluoroethylene (HFO1123), trans-1,2-difluoroethylene (HFO1132(E)), cis-1,2-difluoroethylene (HFO-1132(Z)), 1,1-difluoroethylene (HFO-1132a), tetrafluoroethylene (CF 2 =CF 2 , FO1114), or monofluoroethylene (HFO-1141).

[0018] The working medium 20 may include a plurality of types of refrigerant components. The working medium 20 may contain ethylene-based fluoroolefin as a main refrigerant component, and additionally contain one or more chemical compounds other than ethylene-based fluoroolefin as one or more auxiliary refrigerant components. Examples of the auxiliary refrigerant components may include hydrofluorocarbons (HFC), hydrofluoroolefins (HFO), saturated hydrocarbons, and carbon dioxide. Examples of hydrofluorocarbons (HFC) may include difluoromethane, difluoroethane, trifluoroethane, tetrafluoroethane, pentafluoroethane, pentafluorobutane, and heptafluorocyclopentane. Examples of hydrofluoroolefins (HFO) may include monofluoropropene, trifluoropropene, tetrafluoropropene, pentafluoropropene, and hexafluorobutene. Examples of saturated hydrocarbons may include ethane, n-propane, cyclopropane, n-butane, cyclobutane, isobutane (2-methylpropane), methylcyclopropane, n-pentane, isopentane (2-methylbutane), neopentane (2,2-dimethylpropane), and methylcyclobutane.

[0019] The working medium 20 may further contain a disproportionation inhibitor for suppressing a disproportionation reaction of the ethylene-based fluoroolefin. Examples of the disproportionation inhibitor may include a saturated hydrocarbon or a haloalkane. Examples of saturated hydrocarbons may include ethane, n-propane, cyclopropane, n-butane, cyclobutane, isobutane (2-methylpropane), methylcyclopropane, n-pentane, isopentane (2-methylbutane), neopentane (2,2-dimethylpropane), and methylcyclobutane. In the above examples, n-propane is preferred. Examples of haloalkanes may include haloalkanes having one or two carbon atoms. Examples of haloalkanes having one carbon atom (i.e., halomethanes) may 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 (CI 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 I), and difluoroiodomethane (CHF 2 I). Examples of haloalkanes with two carbon atoms (i.e. haloethanes) may include 1,1,1-trifluoro-2-iodoethane (CF 3 CH 2 I), monoiodoethane (CH 3 CH 2 I), monobromoethane (CH 3 CH 2 Br), and 1,1,1-triiodoethane (CH 3 CI 3 ). The working medium 20 may contain one or more types of haloalkanes having 1 or 2 carbon atoms. In other words, the haloalkanes having 1 or 2 carbon atoms may be used alone or in combination of two or more types.

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

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

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

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

[0024] In the cooling operation, the compressor 4 compresses and discharges the gaseous working medium 20, and thus the gaseous working medium 20 is sent to the first heat exchanger 5 through the four-way valve 8. The first heat exchanger 5 conducts heat exchange between the outdoor air and the gaseous working medium 20 and then the gaseous working medium 20 is condensed to be liquefied. The liquid working medium 20 is decompressed by the expansion valve 6 and is sent to the second heat exchanger 7. The second heat exchanger 7 conducts heat exchange between the liquid working medium 20 and the indoor air, and then the liquid working medium 20 evaporates to become the gaseous working medium 20. The gaseous working medium 20 returns to the compressor 4 through the four-way valve 8. In the cooling operation, the first heat exchanger 5 functions as a condenser, and the second heat exchanger 7 functions as an evaporator. Thus, the indoor unit 1b sends air cooled via heat exchange at the second heat exchanger 7 to an interior during cooling.

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

[0026] In the heating operation, the compressor 4 compresses and discharges the gaseous working medium 20, and thus the gaseous working medium 20 is sent to the second heat exchanger 7 through the four-way valve 8. The second heat exchanger 7 conducts heat exchange between the indoor air and the gaseous working medium 20 and then the gaseous working medium 20 is condensed to be liquefied. The liquid working medium 20 is decompressed by the expansion valve 6 and is sent to the first heat exchanger 5. The first heat exchanger 5 conducts heat exchange between the liquid working medium 20 and the outdoor air, and then the liquid working medium 20 evaporates to become the gaseous working medium 20. The gaseous working medium 20 returns to the compressor 4 through the four-way valve 8. In the heating operation, the first heat exchanger 5 functions as an evaporator, and the second heat exchanger 7 functions as a condenser. Thus, the indoor unit 1b sends air warmed via heat exchange at the second heat exchanger 7 to an interior during the heating.

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

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

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

[0030] The sealed container 40 constitutes a fluidic pathway for the working medium 20. The sealed container 40 includes a suction pipe 401 and a discharge pipe 402. The working medium 20 is suctioned into the sealed container 40 via the suction pipe 401 and then is compressed by the compression mechanism 41 and thereafter is discharged to an exterior of the sealed container 40 via the discharge pipe 402. The inside of the sealed container 40 is filled with the working medium 20 with a high temperature and a high pressure together with a lubricating oil. The sealed container 40 has a bottom portion which constitutes an oil reservoir for storing a mixed liquid of the working medium 20 and the lubricating oil.

[0031] The compression mechanism 41 is positioned inside the sealed container 40 to compress the working medium 20. The compression mechanism 41 may have a conventional configuration. For example, the compression mechanism 41 may include a cylinder forming a compression chamber, a rolling piston disposed in the compression chamber inside the cylinder, and a crank shaft coupled to the rolling piston.

[0032] The electric motor 42 is positioned inside the sealed container 40 to operate the compression mechanism 41. The electric motor 42 is a brushless motor (three-phase brushless motor). The electric motor 42 includes a rotator fixed to the crank shaft of the compression mechanism 41 and a stator provided in a vicinity of the rotator, for example. The stator is configured by concentrated or distributed winding of the stator windings (magnet wires) around a stator core (electrical or magnetic steel sheet or the like) with an insulation paper in-between. The stator windings are covered with insulating material. Examples of the insulating material may include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), aramid polymer, polyphenylene sulfide (PPS), and polytetrafluoroethylene (PTFE).

[0033] The compressor 4 may include an accumulator for preventing liquid compression in the compression chamber of the compression mechanism 41. The accumulator separates the working medium 20 into the gaseous working medium 20 and the liquid working medium 20 and directs only the gaseous working medium 20 to the sealed container 40 via the suction pipe 401.

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

[0035] The drive circuit 31 is configured to drive the electric motor 42 of the compressor 4. The drive circuit 31 is configured to supply driving power to the electric motor 42 based on electric power from a power supply 10. In the present embodiment, the power supply 10 is an alternating current power supply. The drive circuit 31 supplies driving power to the electric motor 42 based on AC power from the power supply 10. In particular, the drive circuit 31 supplies three-phase AC power to the electric motor 42 as the driving power. A frequency of the three-phase AC power corresponds to a driving frequency of the compressor 4. The driving frequency of the compressor 4 corresponds to a rotational speed of the compressor 4.

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

[0037] The converter circuit 311 is configured to convert the AC power from the power supply 10 into DC power. The converter circuit 311 includes a rectification circuit 311a and a smoothing circuit 311b. The rectification circuit 311a is a diode bridge constituted by a plurality of diodes D1 to D4. The power supply 10 is connected between input terminals (a connecting point between the diodes D1, D2 and a connecting point between the diodes D3, D4) of the rectification circuit 311a and the smoothing circuit 311b is connected between output terminals (a connecting point between the diodes D1, D3 and a connecting point between the diodes D2, D4) of the rectification circuit 311a. The smoothing circuit 311b includes a series circuit of an inductor L1 and a capacitor C1, and smooths a voltage between the output terminals of the rectification circuit 311a to output it as a voltage across the capacitor C1. Configurations of the rectification circuit 311a and the smoothing circuit 311b of Fig. 2 are well-known and therefore detailed explanation thereof is deemed unnecessary.

[0038] The inverter circuit 312 outputs three-phase AC power to the electric motor 42 based on the DC power from the converter circuit 311. The inverter circuit 312 includes a plurality of arms U1, U2, V1, V2, W1, and W2. Each of the plurality of arms U1, U2, V1, V2, W1, and W2 is constituted by one or more semiconductor switching elements such as transistors or the like. A series circuit of the arms U1, U2 is connected in parallel to the capacitor C1 of the converter circuit 311 and constitutes a U-phase leg. A series circuit of the arms V1, V2 is connected in parallel to the capacitor C1 of the converter circuit 311 and constitutes a V-phase leg. A series circuit of the arms W1, W2 is connected in parallel to the capacitor C1 of the converter circuit 311 and constitutes a W-phase leg. A configuration of the inverter circuit 312 of Fig. 2 is well-known and therefore detailed explanation thereof is deemed unnecessary.

[0039] The measurement circuit 32 is configured to output a measured value indicating at least one of an internal temperature or an internal pressure of the compressor 4. In the present embodiment, the measurement circuit 32 measures the internal temperature of the compressor 4 and outputs the measured value indicating the internal temperature of the compressor 4 to the control circuit 33. The measurement circuit 32 includes, for example, one or more temperature sensors. The one or more temperature sensors may be placed to be allowed to measure a temperature of the working medium 20 inside the sealed container 40 of the compressor 4 or a temperature of the working medium 20 discharged from the discharge pipe 402 of the compressor 4, for example. The positions of the one or more temperature sensors are not particularly limited, and the measurement circuit 32 only needs to be capable of directly or indirectly measuring the internal temperature of the compressor 4.

[0040] The control circuit 33 may be implemented by a computer system including at least one processor (microprocessor) and at least one memory.

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

[0042] The control circuit 33 performs processing for suppressing a disproportionation reaction of the working medium 20 circulating in the refrigeration cycle circuit 2, based on the measured value from the measurement circuit 32 (in the present embodiment, the internal temperature of the compressor 4).

[0043] It is considered that factors of the disproportionation reaction of the working medium 20 are heat and radicals. For example, it is considered that the disproportionation reaction of the working medium 20 proceeds when radicals are generated under high temperature and high pressure. From such a viewpoint, the control circuit 33 performs control of the compressor 4 based on the measured value from the measurement circuit 32.

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

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

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

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

[0048] The threshold value T15 is set based on a temperature at which processing for suppressing the disproportionation reaction is started. In the present embodiment, the threshold value T15 is defined by an upper threshold value T15a and a lower threshold value T15b smaller than the upper threshold value T15a. The upper threshold value T15a is used when the internal temperature increases. The lower threshold value T15b is used when the internal temperature decreases. That is, the internal temperature exceeding the threshold value T15 means that the internal temperature exceeds the upper threshold value T15a, and the internal temperature becoming equal to or lower than the threshold value T15 means that the internal temperature becomes equal to or lower than the lower threshold value T15b.

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

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

[0051] In the present embodiment, in the case of increasing the driving frequency, the control circuit 33 makes the second frequency change rate less than the first frequency change rate. In Fig. 3, "Second Frequency Change Rate (Small)" means a second frequency change rate smaller than the first frequency change rate. As one example, the second frequency change rate is 3.0 Hz / 15 s (=0.2 Hz / s). That is, when the internal temperature exceeds the threshold value T15, the driving frequency is increased more gradually than when the internal temperature is equal to or lower than the threshold value T15. Accordingly, the driving frequency can be increased while preventing the internal temperature from exceeding the threshold value T11. This enables suppression of the disproportionation reaction while allowing expansion of a control range of the refrigeration cycle circuit 2.

[0052] In the case of decreasing the driving frequency, the control circuit 33 makes the second frequency change rate larger than the first frequency change rate. In Fig. 3, "Second Frequency Change Rate (Large)" indicates a second frequency change rate larger than the first frequency change rate. As one example, the second frequency change rate is 1.0 Hz / s. That is, when the internal temperature exceeds the threshold value T15, the driving frequency is decreased more greatly than when the internal temperature is equal to or lower than the threshold value T15. Accordingly, the driving frequency can be rapidly decreased so as to prevent the internal temperature from exceeding the threshold value T11. This enables further suppression of the disproportionation reaction.

[0053] When the internal temperature exceeds the threshold value T14, which is greater than the threshold value T15 and smaller than the threshold value T11, the control circuit 33 prohibits an increase in the driving frequency. That is, even when it is necessary to increase the driving frequency of the compressor 4 to make the driving frequency of the compressor 4 equal to the target driving frequency, the control circuit 33 does not perform an increase in the driving frequency. On the other hand, a decrease in the driving frequency is permitted. In this case, the control circuit 33 decreases the driving frequency at the second frequency change rate. In the present embodiment, the second frequency change rate is set to be larger than the first frequency change rate.

[0054] When the internal temperature exceeds the threshold value T13, which is greater than the threshold value T14 and smaller than the threshold value T11, the control circuit 33 operates the compressor 4 to allow the driving frequency to decrease at a fourth frequency change rate. More specifically, in the case of decreasing the driving frequency of the compressor 4 to make the driving frequency of the compressor 4 equal to the target driving frequency, the control circuit 33 decreases the driving frequency at the fourth frequency change rate. The fourth frequency change rate is not particularly limited. As one example, the fourth frequency change rate is 1.0 Hz / 15 s (=0.07 Hz / s).

[0055] When the internal temperature exceeds the threshold value T12, which is greater than the threshold value T13 and smaller than the threshold value T11, the control circuit 33 operates the compressor 4 to allow the driving frequency to decreases at a third frequency change rate. More specifically, in the case of decreasing the driving frequency of the compressor 4 to make the driving frequency of the compressor 4 equal to the target driving frequency, the control circuit 33 decreases the driving frequency at the third frequency change rate. The third frequency change rate is not particularly limited. As one example, the third frequency change rate is 5.0 Hz / 15 s (=0.33 Hz / s). This enables rapid reduction of the driving frequency. As a result, an increase in the internal temperature or internal pressure of the compressor 4 can be further suppressed, thereby enabling further suppression of the disproportionation reaction.

[0056] As one example, under a normal load (for example, when the outdoor temperature is 43°C or lower), the threshold value T11 may be 62°C, the threshold value T12 may be 60°C, the threshold value T13 may be 58°C, the threshold value T14 may be 56°C, the upper threshold value T15a of the threshold value T15 may be 54°C, and the lower threshold value T15b of the threshold value T15 may be 53°C. Under a high load (for example, when the outdoor temperature exceeds 43°C), the threshold value T11 may be 65°C, the threshold value T12 may be 64°C, the threshold value T13 may be 63°C, the threshold value T14 may be 62°C, the upper threshold value T15a of the threshold value T15 may be 53°C, and the lower threshold value T15b of the threshold T15 may be 52°C.[1.1.2 ADVANTAGEOUS EFFECTS]

[0057] The aforementioned control device 3 controls a compressor 4 of a refrigeration cycle circuit 2 allowing circulation of a working medium 20 containing ethylene-based fluoroolefin as a refrigerant component. The control device 3 includes: a measurement circuit 32 configured to output a measured value indicating at least one of an internal temperature or an internal pressure of the compressor 4; and a control circuit 33 configured to compare the measured value from the measurement circuit 32 with at least one of a plurality of threshold values T11 to T15 and to perform control of the compressor in accordance with a result of comparison. The plurality of threshold values T11 to T15 include a threshold value T11 (first threshold value), and a threshold value T15 (second threshold value) less than the threshold value T11. The control circuit 33 is configured to: stop the compressor 4 when the measured value exceeds the threshold value T11 (first threshold value); operate the compressor 4 to allow a drive frequency of the compressor 4 to change at a first frequency change rate while the measured value is equal to or less than the threshold value T15 (second threshold value); and operate the compressor 4 to allow the drive frequency to change at a second frequency change rate different from the first frequency change rate in at least one of a case of increasing the drive frequency and a case of decreasing the drive frequency, when the measured value exceeds the threshold value T15 (second threshold value). This configuration enables expansion of the control range of the refrigeration cycle circuit 2 while enabling suppression of a disproportionation reaction.

[0058] In the control device 3, the control circuit 33 is configured to make the second frequency change rate less than the first frequency change rate in the case of increasing the drive frequency. This configuration enables expansion of the control range of the refrigeration cycle circuit 2 while enabling suppression of a disproportionation reaction.

[0059] In the control device 3, the control circuit 33 is configured to make the second frequency change rate larger than the first frequency change rate in the case of decreasing the drive frequency. This configuration enables further suppression of a disproportionation reaction.

[0060] In the control device 3, the plurality of threshold values T11 to T15 include a fourth threshold value (threshold value T12) that is larger than the second threshold value (threshold value T15) and is smaller than the first threshold value (threshold value T11). The control circuit 33 is configured to operate the compressor 4 to allow the drive frequency to decrease at a third frequency change rate when the measured value exceeds the threshold value T12. This configuration enables further suppression of a disproportionation reaction.

[0061] In the control device 3, at least one threshold value T15 of the plurality of threshold values T11 to T15 is defined by an upper threshold value T15a and a lower threshold value T15b smaller than the upper threshold value T15a. The measured value exceeding the at least one threshold value T15 means the measured value exceeding the upper threshold value T15a of the at least one threshold value T15. The measured value becoming equal to or less than the at least one threshold value T15 means the measured value becoming equal to or less than the lower threshold value T15b of the at least one threshold value T15. This configuration can reduce the possibility that switching of control occurs frequently due to fluctuation of the measured value.

[0062] The aforementioned refrigeration cycle device 1 includes the control device 3 and the refrigeration cycle circuit 2. This configuration enables expansion of the control range of the refrigeration cycle circuit 2 while enabling suppression of a disproportionation reaction.

[0063] In the refrigeration cycle device 1, the ethylene-based fluoroolefin includes ethylene-based fluoroolefin capable of undergoing a disproportionation reaction. This configuration enables further suppression of a disproportionation reaction.

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

[0065] In the refrigeration cycle device 1, the working medium 20 contains difluoromethane as the refrigerant component. This configuration enables further suppression of a disproportionation reaction.

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

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

[0068] In the refrigeration cycle device 1, the saturated hydrocarbon contains n-propane. This configuration enables further suppression of a disproportionation reaction.[1.2. EMBODIMENT 2][1.2.1 CONFIGURATIONS]

[0069] Fig. 4 is a block diagram of a refrigeration cycle device 1A according to the present embodiment. The refrigeration cycle device 1A constitutes an air conditioner enabling a cooling operation and a heating operation, for example. The refrigeration cycle device 1A includes the refrigeration cycle circuit 2 and a control device 3A.

[0070] The control device 3A controls the compressor 4 and the expansion valve 6 of the refrigeration cycle circuit 2. The control device 3A includes the drive circuit 31, the measurement circuit 32, and the control circuit 33, similarly to the control device 3 of Embodiment 1, but differs from the control device 3 in operation of the control circuit 33.

[0071] The control circuit 33 controls the expansion valve 6 in addition to the compressor 4. More specifically, the control circuit 33 increases or decreases an opening degree of the expansion valve 6. The opening degree of the expansion valve 6 is an index of how far the expansion valve 6 is opened, and as the opening degree increases, the expansion valve 6 approaches a fully-open state, whereas as the opening degree decreases, the expansion valve 6 approaches a fully-closed state. For example, the opening degree of the expansion valve 6 can be changed in increments of 1 pls. One pls corresponds to a value obtained by dividing a range of the opening degree of the expansion valve 6 (for example, a difference between a fully-open opening degree and a fully-closed opening degree of the expansion valve 6) by a predetermined number (for example, 480).

[0072] Also in the present embodiment, the control circuit 33 performs processing for suppressing a disproportionation reaction of the working medium 20 circulating in the refrigeration cycle circuit 2, based on a measured value from the measurement circuit 32 (in the present embodiment, an internal temperature of the compressor 4). The control circuit 33 performs control of the compressor 4 and the expansion valve 6 based on the measured value from the measurement circuit 32.

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

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

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

[0076] While the internal temperature of the compressor 4 is equal to or lower than the threshold value T25, which is smaller than the threshold value T21, the control circuit 33 operates the expansion valve 6 to allow the opening degree of the expansion valve 6 to change at a first opening degree change rate. For example, the control circuit 33 increases or decreases the opening degree of the expansion valve 6 at the first opening degree change rate such that a discharge temperature of the refrigerant discharged from the compressor 4 becomes a target temperature. As the discharge temperature of the refrigerant, the internal temperature of the compressor 4 indicated by the measured value from the measurement circuit 32 can be employed. The first opening degree change rate is, for example, d×1 pls / 60 s where d is a difference between the discharge temperature and the target temperature.

[0077] The threshold value T25 is set based on a temperature at which processing for suppressing the disproportionation reaction is started. In the present embodiment, the threshold value T25 is defined by an upper threshold value T25a and a lower threshold value T25b smaller than the upper threshold value T25a. The upper threshold value T25a is used when the internal temperature increases. The lower threshold value T25b is used when the internal temperature decreases. That is, the internal temperature exceeding the threshold value T25 means the internal temperature exceeding the upper threshold value T25a, and the internal temperature becoming equal to or lower than the threshold value T25 means the internal temperature becoming equal to or lower than the lower threshold value T25b.

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

[0079] In the present embodiment, in a case of decreasing the opening degree, the control circuit 33 operates the expansion valve 6 to allow the opening degree to change at the second opening degree change rate different from the first opening degree change rate. On the other hand, in a case of increasing the opening degree, the control circuit 33 operates the expansion valve 6 to allow the opening degree to change at the first opening degree change rate.

[0080] As described above, in the present embodiment, the opening degree change rate differs between a case where the opening degree is increased and a case where the opening degree is decreased. The opening degree change rate when increasing the opening degree is set to the first opening degree change rate, and the opening degree change rate when decreasing the opening degree is set to the second opening degree change rate. This is because an increase in the opening degree leads to a decrease in the internal temperature of the compressor 4, whereas a decrease in the opening degree leads to an increase in the internal temperature of the compressor 4. That is, the control circuit 33 decreases the opening degree of the expansion valve 6 at the second opening degree change rate or increases the opening degree of the expansion valve 6 at the first opening degree change rate such that the discharge temperature of the refrigerant discharged from the compressor 4 becomes the target temperature.

[0081] In the present embodiment, when decreasing the opening degree, the control circuit 33 makes the second opening degree change rate smaller than the first opening degree change rate. As one example, the second opening degree change rate is 1 to 5 pls / 60 s. That is, when the internal temperature exceeds the threshold value T25, the opening degree is decreased more gradually than when the internal temperature is equal to or lower than the threshold value T25. Accordingly, the opening degree can be decreased while preventing the internal temperature from exceeding the threshold value T21. This enables suppression of the disproportionation reaction while allowing expansion of the control range of the refrigeration cycle circuit 2.

[0082] When the internal temperature exceeds the threshold value T24 that is greater than the threshold value T25 and smaller than the threshold value T21, the control circuit 33 operates the expansion valve 6 to allow the opening degree to decrease at a fourth opening degree change rate smaller than the second opening degree change rate, in a case of decreasing the opening degree. As one example, the fourth opening degree change rate is 1 pls / 180 s (= 0.3 pls / 60 s). That is, when the internal temperature exceeds the threshold value T24, the opening degree is decreased even more gradually than when the internal temperature is equal to or lower than the threshold value T25. Accordingly, the opening degree can be decreased while preventing the internal temperature from exceeding the threshold value T21. This enables suppression of the disproportionation reaction while allowing expansion of the control range of the refrigeration cycle circuit 2. On the other hand, when increasing the opening degree, the control circuit 33 operates the expansion valve 6 to allow the opening degree to change at the first opening degree change rate.

[0083] When the internal temperature exceeds the threshold value T23 that is greater than the threshold value T24 and smaller than the threshold value T21, the control circuit 33 operates the expansion valve 6 to allow the opening degree to increase at a third opening degree change rate. More specifically, when increasing the opening degree of the expansion valve 6 in order to set the discharge temperature of the refrigerant discharged from the compressor 4 to the target temperature, the control circuit 33 increases the opening degree at the third opening degree change rate. The third opening degree change rate is not particularly limited. As one example, the third opening degree change rate is 2 pls / 60 s. On the other hand, when the opening degree is being decreased, the control circuit 33 prohibits a decrease in the opening degree. That is, even when it is necessary to decrease the opening degree of the expansion valve 6 in order to set the discharge temperature of the refrigerant discharged from the compressor 4 to the target temperature, the control circuit 33 does not perform a decrease in the opening degree. Accordingly, an increase in the internal temperature or internal pressure of the compressor 4 can be further suppressed, thereby enabling further suppression of the disproportionation reaction.

[0084] When the internal temperature exceeds the threshold value T22 that is greater than the threshold value T23 and smaller than the threshold value T21, the control circuit 33 operates the expansion valve 6 to allow the opening degree to increase at a fifth opening degree change rate larger than the third opening degree change rate. In the present embodiment, the control circuit 33 forcibly increases the opening degree at the fifth opening degree change rate. As one example, the fifth opening degree change rate is 30 pls / 30 s (= 60 pls / 60 s). This enables a forced, rapid increase in the opening degree. Accordingly, an increase in the internal temperature or internal pressure of the compressor 4 can be further suppressed, thereby enabling further suppression of the disproportionation reaction.

[0085] As one example, under a normal load (for example, when the outdoor temperature is 43°C or lower), the threshold value T21 may be 62°C, the threshold value T22 may be 60°C, the threshold value T23 may be 58°C, the threshold value T24 may be 56°C, the upper threshold value T25a of the threshold value T25 may be 54°C, and the lower threshold value T25b of the threshold value T25 may be 53°C. Under a high load (for example, when the outdoor temperature exceeds 43°C), the threshold value T21 may be 65°C, the threshold value T22 may be 64°C, the threshold value T23 may be 63°C, the threshold value T24 may be 62°C, the upper threshold value T25a of the threshold value T25 may be 53°C, and the lower threshold value T25b of the threshold value T25 may be 52°C.[1.2.2 ADVANTAGEOUS EFFECTS]

[0086] The aforementioned control device 3A controls a compressor 4 and an expansion valve 6 of a refrigeration cycle circuit 2 allowing circulation of a working medium 20. The working medium 20 contains ethylene-based fluoroolefin as a refrigerant component. The control device 3 includes: a measurement circuit 32 configured to output a measured value indicating at least one of an internal temperature or an internal pressure of the compressor 4; and a control circuit 33 configured to compare the measured value from the measurement circuit 32 with at least one of a plurality of threshold values T21 to T25 and to perform control of the compressor 4 and the expansion valve 6 in accordance with a result of comparison. The plurality of threshold values T21 to T25 include a threshold value T21 (first threshold value), and a threshold value T25 (second threshold value) less than the first threshold value. The control circuit 33 is configured to: stop the compressor 4 when the measured value exceeds the threshold value T21 (first threshold value); operate the expansion valve 6 to allow an opening degree of the expansion valve 6 to change at a first opening degree change rate while the measured value is equal to or less than the threshold value T25 (second threshold value); and operate the expansion valve 6 to allow the opening degree to change at a second opening degree change rate different from the first opening degree change rate in at least one of a case of increasing the opening degree and a case of decreasing the opening degree, when the measured value exceeds the threshold value T25. This configuration enables expansion of the control range of the refrigeration cycle circuit 2 while enabling suppression of a disproportionation reaction.

[0087] In the control device 3A, the control circuit 33 is configured to make the second opening degree change rate smaller than the first opening degree change rate in a case of decreasing the opening degree. This configuration enables expansion of the control range of the refrigeration cycle circuit 2 while enabling suppression of a disproportionation reaction.

[0088] In the control device 3A, the plurality of threshold values T21 to T25 include a third threshold value (threshold value T23) that is larger than the second threshold value (threshold value T25) and is smaller than the first threshold value (threshold value T21). The control circuit 33 is configured to operate the expansion valve 6 to allow the opening degree to increase at a third opening degree change rate when the measured value exceeds the threshold value T23. This configuration enables further suppression of a disproportionation reaction.

[0089] In the control device 3A, at least one threshold value T25 (second threshold value) of the plurality of threshold values T21 to T25 is defined by an upper threshold value T25a and a lower threshold value T25b smaller than the upper threshold value T25a. The measured value exceeding the at least one threshold value T25 means the measured value exceeding the upper threshold value T25a of the at least one threshold value T25. The measured value becoming equal to or less than the at least one threshold value T25 means the measured value becoming equal to or less than the lower threshold value T25b of the at least one threshold value T25. This configuration can reduce the possibility that switching of control occurs frequently due to fluctuation of the measured value.[2. VARIATIONS]

[0090] Embodiments of the present disclosure are not limited to the embodiments described above. The above embodiments may be variously modified in accordance with design and other factors, provided that the objects of the present disclosure can be achieved. Hereinafter, variations of the above embodiments will be enumerated. The variations described below may be applied in appropriate combinations.

[0091] It is noted that, in the following description, reference will be made to the reference signs used in Embodiment 1, even though the following variations may be applicable to any of Embodiments 1 and 2. This is merely for the purpose of simplifying the description and is not intended to exclude application to Embodiment 2.

[0092] In one variation, the control circuit 33 may be configured to perform both the control shown in Fig. 3 and the control shown in Fig. 5. That is, when the measured value exceeds the threshold value T11 (first threshold value), the control circuit 33 stops the compressor 4. While the measured value is equal to or lower than the threshold value T15 (second threshold value) smaller than the threshold value T11, the control circuit 33 operates the compressor 4 to allow the driving frequency of the compressor 4 to change at the first frequency change rate. When the measured value exceeds the threshold T15, the control circuit 33 may operate the compressor 4 to allow the driving frequency to change at the second frequency change rate different from the first frequency change rate, in at least one of a case of increasing the driving frequency and a case of decreasing the driving frequency. Furthermore, while the measured value is equal to or lower than the threshold value T23 (third threshold value) smaller than the threshold value T11 (first threshold value), the control circuit 33 may operate the expansion valve 6 to allow the opening degree of the expansion valve 6 to change at the first opening degree change rate. When the measured value exceeds the threshold T23, the control circuit 33 may operate the expansion valve 6 to allow the opening degree to change at the second opening degree change rate different from the first opening degree change rate in at least one of a case of increasing the opening degree and a case of decreasing the opening degree. In this case, the threshold value T11 and the threshold value T21 are set to the same value. On the other hand, the threshold values T12, T13, T14, and T15 and the threshold values T22, T23, T24, and T25 do not necessarily need to be set to the same values.

[0093] In one variation, among the plurality of threshold values T11 to T15, one or more threshold values other than the threshold value T15 may also be defined by an upper threshold value and a lower threshold value. In particular, it is preferable to define, by an upper threshold value and a lower threshold value, a threshold value that is included in a range in which fluctuation of the measured value from the measurement circuit 32 is large. Fig. 6 is an explanatory diagram of control of the compressor 4 by the control circuit 33 of the control device 3 according to one variation. In Fig. 6, the three threshold values T12, T13, and T15 among the plurality of threshold values T11 to T15 are respectively defined by upper threshold values T12a, T13a, and T15a and lower threshold values T12b, T13b, and T15b smaller than the upper threshold values T12a, T13a, and T15a. The internal temperature exceeding the threshold values T12, T13, and T15 means the internal temperature exceeding the upper threshold values T12a, T13a, and T15a, and the internal temperature becoming equal to or lower than the threshold values T12, T13, and T15 means the internal temperature becoming equal to or lower than the lower threshold values T12b, T13b, and T15b. With this configuration, it is possible to reduce the possibility that switching of control occurs frequently due to fluctuation of the measured value. Although respective differences between the upper threshold values T12a, T13a, and T15a and the lower threshold values T12b, T13b, and T15b are not particularly limited, they may be set to, for example, 1°C. However, it is not necessarily required to define threshold values by an upper threshold value and a lower threshold value.

[0094] In one variation, threshold values for controlling the compressor 4 are not limited to the example of Fig. 3. Fig. 7 is an explanatory diagram of control of the compressor 4 by the control circuit 33 of the control device 3 according to one variation. In Fig. 7, the threshold values T13 and T14 are not set as compared with Fig. 3. In Fig. 7, when the internal temperature exceeds the threshold T15, the control circuit 33 operates the compressor 4 to allow the driving frequency to change at the second frequency change rate different from the first frequency change rate. When the internal temperature exceeds the threshold value T12 greater than the threshold value T15 and smaller than the threshold value T11, the control circuit 33 operates the compressor 4 to allow the driving frequency to decrease at the third frequency change rate. Further, the threshold value T12 is not essential, and while the internal temperature exceeds the threshold T15 and is equal to or lower than the threshold T11, the control circuit 33 may operate the compressor 4 to allow the driving frequency to change at the second frequency change rate different from the first frequency change rate.

[0095] In one variation, the control circuit 33 does not necessarily need to operate the compressor 4 to allow the driving frequency to change at the second frequency change rate different from the first frequency change rate in both a case of increasing the driving frequency and a case of decreasing the driving frequency. The control circuit 33 only needs to operate the compressor 4 to allow the driving frequency to change at the second frequency change rate different from the first frequency change rate, in at least one of a case of increasing the driving frequency and a case of decreasing the driving frequency.

[0096] In one variation, threshold values for controlling the compressor 4 and the expansion valve 6 are not limited to the example of Fig. 5. Fig. 8 is an explanatory diagram of control of the compressor 4 and the expansion valve 6 by the control circuit 33 of the control device 3 according to one variation. In Fig. 8, the threshold values T22 and T24 are not set as compared with Fig. 5. In Fig. 8, when the internal temperature exceeds the threshold T25, the control circuit 33 operates the expansion to allow the opening degree to decrease at the second opening degree change rate different from the first opening degree change rate in a case of decreasing the opening degree. When the internal temperature exceeds the threshold value T23 that is greater than the threshold value T25 and smaller than the threshold value T21, the control circuit 33 operates the expansion valve 6 to allow the opening degree to increase at the third opening degree change rate. Further, the threshold value T23 is not essential, and while the internal temperature exceeds the threshold T25 and is equal to or lower than the threshold T21, the control circuit 33 may operate the expansion valve 6 to allow the opening degree to change at the second opening degree change rate smaller than the first opening degree change rate.

[0097] Fig. 9 is an explanatory diagram of control of the compressor 4 and the expansion valve 6 by the control circuit 33 of the control device 3 according to one variation. The control circuit 33 may operate the expansion valve 6 to allow the opening degree to change at the second opening degree change rate different from the first opening degree change rate in both a case of increasing the opening degree and a case of decreasing the opening degree. Here, the control circuit 33 may make the second opening degree change rate be smaller than the first opening degree change rate when decreasing the opening degree, and may make the second opening degree change rate be larger than the first opening degree change rate when increasing the opening degree. In Fig. 9, "Second Opening Degree Change Rate (small)" means a second opening degree change rate smaller than the first opening degree change rate, and "Second Opening Degree Change Rate (large)" means a second opening degree change rate larger than the first opening degree change rate. In Fig. 9, when the internal temperature exceeds the threshold value T25, the opening degree is increased more greatly than when the internal temperature is equal to or lower than the threshold value T25. Accordingly, the opening degree can be rapidly increased so as to prevent the internal temperature from exceeding the threshold value T21. This enables further suppression of the disproportionation reaction.

[0098] In one variation, the control circuit 33 does not necessarily need to operate the expansion valve 6 to allow the opening degree to change at the second opening degree change rate different from the first opening degree change rate in both a case of increasing the opening degree and a case of decreasing the opening degree. The control circuit 33 only needs to operate the expansion valve 6 to allow the opening degree to change at the second opening degree change rate different from the first opening degree change rate, in at least one of a case of increasing the opening degree and a case of decreasing the opening degree.

[0099] In one variation, in processing for suppressing the disproportionation reaction, the control circuit 33 may further control the first air blower 5a. That is, the refrigeration cycle circuit 2 includes the first heat exchanger 5 of the outdoor unit 1a and the first air blower 5a for facilitating heat exchange at the first heat exchanger 5. The plurality of threshold values include a fifth threshold value smaller than the first threshold value, and the control circuit 33 may increase a rotational speed of the first air blower 5a when the measured value exceeds the fifth threshold value in a case where the first heat exchanger 5 functions as a condenser (that is, in a cooling operation). Accordingly, the temperature of the working medium 20 can be further decreased at the first heat exchanger 5, thereby enabling further suppression of the disproportionation reaction. In the example of Fig. 3, the threshold value T11 is the first threshold value, and any of the threshold values T12 to T15 may be used as the fifth threshold value. In the example of Fig. 5, the threshold value T21 is the first threshold value, and any of the threshold values T22 to T25 may be used as the fifth threshold value. The fifth threshold value may be set separately from the threshold values T12 to T15 and T22 to T25.

[0100] In one variation, in processing for suppressing the disproportionation reaction, the control circuit 33 may further control the second air blower 7a. That is, the refrigeration cycle circuit 2 includes the second heat exchanger 7 of the indoor unit 1b and the second air blower 7a for facilitating heat exchange at the second heat exchanger 7. The plurality of threshold values include a sixth threshold value smaller than the first threshold value, and the control circuit 33 may decrease a rotational speed of the second air blower 7a when the measured value exceeds the sixth threshold value in a case where the second heat exchanger 7 functions as an evaporator (that is, in a cooling operation). When the control circuit 33 performs processing for suppressing the disproportionation reaction, cooling capacity of the refrigeration cycle device 1 tends to decrease. Therefore, by decreasing the rotational speed of the second air blower 7a from a current value, it is possible to decrease an evaporation temperature, a low-pressure temperature, and a temperature of the first heat exchanger 5. In the example of Fig. 3, the threshold value T11 is the first threshold value, and any of the threshold values T12 to T15 may be used as the sixth threshold value. In the example of Fig. 5, the threshold value T21 is the first threshold value, and any of the threshold values T22 to T25 may be used as the sixth threshold value. The sixth threshold value may be set separately from the threshold values T12 to T15 and T22 to T25.

[0101] In one variation, the third frequency change rate may be larger than the first frequency change rate. This enables rapid reduction of the driving frequency. Accordingly, an increase in the internal temperature or internal pressure of the compressor 4 can be further suppressed, thereby enabling further suppression of the disproportionation reaction. Referring to Fig. 7, when decreasing the driving frequency while the measured value tends to decrease, the control circuit 33 may set the second frequency change rate to be larger than the first frequency change rate and smaller than the third frequency change rate. "The measured value tends to decrease" includes that the measured value decreases to become equal to or lower than the threshold value T12 (fourth threshold value). "The measured value decreases to become equal to or lower than a threshold value" may mean that a previous measured value exceeds the threshold value but a current measured value becomes equal to or lower than the threshold value. In this way, when the measured value tends to decrease, the control circuit 33 may set the second frequency change rate to be larger than the first frequency change rate when decreasing the driving frequency. This enables rapid reduction of the driving frequency. Accordingly, an increase in the internal temperature or internal pressure of the compressor 4 can be further suppressed, thereby enabling further suppression of the disproportionation reaction.

[0102] In one variation, the third opening degree change rate may be larger than the first opening degree change rate. This enables rapid increase of the opening degree. Accordingly, an increase in the internal temperature or internal pressure of the compressor 4 can be further suppressed, thereby enabling further suppression of the disproportionation reaction. Referring to Fig. 9, when increasing the opening degree while the measured value tends to decrease, the control circuit 33 may set the second opening degree change rate to be larger than the first opening degree change rate and smaller than the third opening degree change rate. "The measured value tends to decrease" includes that the measured value decreases to become equal to or lower than the threshold value T23 (third threshold value). In this way, when the measured value tends to decrease, the control circuit 33 may set the second opening degree change rate to be larger than the first opening degree change rate when increasing the opening degree. This enables rapid increase of the opening degree. Accordingly, an increase in the internal temperature or internal pressure of the compressor 4 can be further suppressed, thereby enabling further suppression of the disproportionation reaction.

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

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

[0105] In one variation, the refrigeration cycle device 1 is not limited to an air conditioner having a configuration in which one indoor unit is connected to one outdoor unit (so-called room air conditioner (RAC)). The refrigeration cycle device 1 may be an air conditioner having a configuration in which a plurality of indoor units are connected to one or more outdoor units (so-called package air conditioner (PAC) or variable refrigerant flow (VRF) air conditioner). Alternatively, the refrigeration cycle device 1 is not limited to an air conditioner and may be a refrigeration or freezing apparatus such as a refrigerator or a freezer.[3. ASPECTS]

[0106] As apparent from the above embodiments and variations, the present disclosure includes the following aspects.[ASPECT 1]

[0107] A control device for controlling a compressor of a refrigeration cycle circuit allowing circulation of a working medium containing ethylene-based fluoroolefin as a refrigerant component, comprising: a measurement circuit configured to output a measured value indicating at least one of an internal temperature or an internal pressure of the compressor; and a control circuit configured to compare the measured value from the measurement circuit with at least one of a plurality of threshold values and to perform control of the compressor in accordance with a result of comparison, the plurality of threshold values including a first threshold value, and a second threshold value less than the first threshold value, and the control circuit being configured to: stop the compressor when the measured value exceeds the first threshold value; operate the compressor to allow a drive frequency of the compressor to change at a first frequency change rate while the measured value is equal to or less than the second threshold value; and operate the compressor to allow the drive frequency to change at a second frequency change rate different from the first frequency change rate in at least one of a case of increasing the drive frequency and a case of decreasing the drive frequency, when the measured value exceeds the second threshold value. [ASPECT 2]

[0108] The control device of aspect 1, wherein the control circuit is configured to make the second frequency change rate less than the first frequency change rate in a case of increasing the drive frequency.[ASPECT 3]

[0109] The control device of aspect 1 or 2, wherein the control circuit is configured to make the second opening degree change rate larger than the first opening degree change rate in a case of decreasing the opening degree.[ASPECT 4]

[0110] The control device of any one of aspects 1 to 3, wherein: the plurality of threshold values further include a third threshold value less than the first threshold value; and the control circuit is configured to: operate an expansion valve of the refrigeration cycle circuit to allow an opening degree of the expansion valve to change at a first opening degree change rate while the measured value is equal to or less than the third threshold value; and operate the expansion valve to allow the opening degree to change at a second opening degree change rate different from the first opening degree change rate in at least one of a case of increasing the opening degree and a case of decreasing the opening degree, when the measured value exceeds the third threshold value. [ASPECT 5]

[0111] The control device of aspect 4, wherein the control circuit is configured to make the second opening degree change rate larger than the first opening degree change rate in a case of increasing the opening degree.[ASPECT 6]

[0112] The control device of aspect 4 or 5, wherein the control circuit is configured to make the second opening degree change rate smaller than the first opening degree change rate in a case of decreasing the opening degree.[ASPECT 7]

[0113] The control device of any one of aspects 1 to 6, wherein: the plurality of threshold values include a fourth threshold value that is larger than the second threshold value and is smaller than the first threshold value; and the control circuit is configured to operate the compressor to allow the drive frequency to decrease at a third frequency change rate when the measured value exceeds the fourth threshold value. [ASPECT 8]

[0114] The control device of aspect 7, wherein: the third frequency change rate is larger than the first frequency change rate; and the control circuit is configured to make the second frequency change rate larger than the first frequency change rate and smaller than the third frequency change rate in a case of decreasing the drive frequency after the measured value decreases to the fourth threshold value or less. [ASPECT 9]

[0115] The control device of any one of aspects 1 to 8, wherein: at least one threshold value of the plurality of threshold values is defined by an upper threshold value and a lower threshold value smaller than the upper threshold value; the measured value exceeding the at least one threshold value means the measured value exceeding the upper threshold value of the at least one threshold value; and the measured value becoming equal to or less than the at least one threshold value means the measured value becoming equal to or less than the lower threshold value of the at least one threshold value. [ASPECT 10]

[0116] The control device of any one of aspects 1 to 9, wherein: the refrigeration cycle circuit includes a heat exchanger of an outdoor unit and an air blower for facilitating heat exchange at the heat exchanger; the plurality of threshold values include a fifth threshold value smaller than the first threshold value; and the control circuit is configured to increase a rotational speed of the air blower when the measured value exceeds the fifth threshold value in a case where the heat exchanger functions as a condenser. [ASPECT 11]

[0117] The control device of any one of aspects 1 to 10, wherein: the refrigeration cycle circuit includes a heat exchanger of an indoor unit and an air blower for facilitating heat exchange at the heat exchanger; the plurality of threshold values include a sixth threshold value smaller than the first threshold value; and the control circuit is configured to decrease a rotational speed of the air blower when the measured value exceeds the sixth threshold value in a case where the heat exchanger functions as an evaporator. [ASPECT 12]

[0118] A control device for controlling a compressor and an expansion valve of a refrigeration cycle circuit allowing circulation of a working medium, the working medium containing ethylene-based fluoroolefin as a refrigerant component, the control device comprising: a measurement circuit configured to output a measured value indicating at least one of an internal temperature or an internal pressure of the compressor; and a control circuit configured to compare the measured value from the measurement circuit with at least one of a plurality of threshold values and to perform control of the compressor and the expansion valve in accordance with a result of comparison, the plurality of threshold values including a first threshold value, and a second threshold value less than the first threshold value, and the control circuit being configured to: stop the compressor when the measured value exceeds the first threshold value; operate the expansion valve to allow an opening degree of the expansion valve to change at a first opening degree change rate while the measured value is equal to or less than the second threshold value; and operate the expansion valve to allow the opening degree to change at a second opening degree change rate different from the first opening degree change rate in at least one of a case of increasing the opening degree and a case of decreasing the opening degree, when the measured value exceeds the second threshold value. [ASPECT 13]

[0119] The control device of aspect 12, wherein the control circuit is configured to make the second opening degree change rate less than the first opening degree change rate in a case of increasing the opening degree.[ASPECT 14]

[0120] The control device of aspect 12 or 13, wherein the control circuit is configured to make the second opening degree change rate smaller than the first opening degree change rate in a case of decreasing the opening degree.[ASPECT 15]

[0121] The control device of any one of aspects 12 to 14, wherein: the plurality of threshold values include a third threshold value that is larger than the second threshold value and is smaller than the first threshold value; and the control circuit is configured to operate the expansion valve to allow the opening degree to increase at a third opening degree change rate when the measured value exceeds the third threshold value. [ASPECT 16]

[0122] The control device of aspect 15, wherein: the third opening degree change rate is larger than the first opening degree change rate; and the control circuit is configured to make the second opening degree change rate larger than the first opening degree change rate and smaller than the third opening degree change rate in a case of decreasing the opening degree after the measured value decreases to the third threshold value or less. [ASPECT 17]

[0123] The control device of any one of aspects 12 to 16, wherein: at least one threshold value of the plurality of threshold values is defined by an upper threshold value and a lower threshold value smaller than the upper threshold value; the measured value exceeding the at least one threshold value means the measured value exceeding the upper threshold value of the at least one threshold value; and the measured value becoming equal to or less than the at least one threshold value means the measured value becoming equal to or less than the lower threshold value of the at least one threshold value. [ASPECT 18]

[0124] A refrigeration cycle device comprising: the control device of any one of aspects 1 to 17; and the refrigeration cycle circuit. [ASPECT 19]

[0125] The refrigeration cycle device of aspect 18, wherein the ethylene-based fluoroolefin includes ethylene-based fluoroolefin capable of undergoing a disproportionation reaction.[ASPECT 20]

[0126] The refrigeration cycle device of aspect 18 or 19, wherein the ethylene-based fluoroolefin is 1,1,2-trifluoroethylene, trans-1,2-difluoroethylene, cis-1,2-difluoroethylene, 1,1-difluoroethylene, tetrafluoroethylene, or monofluoroethylene.[ASPECT 21]

[0127] The refrigeration cycle device of any one of aspects 18 to 20, wherein the working medium contains difluoromethane as the refrigerant component.[ASPECT 22]

[0128] The refrigeration cycle device of any one of aspects 18 to 21, wherein the working medium further contains a saturated hydrocarbon.[ASPECT 23]

[0129] The refrigeration cycle device of any one of aspects 18 to 22, wherein the working medium contains a haloalkane with 1 or 2 carbon atoms as a disproportionation inhibitor for suppressing a disproportionation reaction of the ethylene-based fluoroolefin.[ASPECT 24]

[0130] The refrigeration cycle device of aspect 22, wherein the saturated hydrocarbon contains n-propane.

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

[0132] The present disclosure can be applied to control devices and refrigeration cycle devices. In particular, the present disclosure is applicable to a control device for a refrigeration cycle circuit with a working medium containing ethylene-based fluoroolefin as a refrigerant component as well as a refrigeration cycle device including the refrigeration cycle circuit and a control device.REFERENCE SIGNS LIST

[0133] 1, 1ARefrigeration Cycle Device 2Refrigeration Cycle Circuit 3, 3AControl Device 32Measurement Circuit 33Control Circuit 4Compressor 6Expansion Valve 7Second Heat Exchanger (Heat Exchanger) 7aSecond Air Blower (Air Blower)

Claims

1. A control device for controlling a compressor of a refrigeration cycle circuit allowing circulation of a working medium containing ethylene-based fluoroolefin as a refrigerant component, comprising: a measurement circuit configured to output a measured value indicating at least one of an internal temperature or an internal pressure of the compressor; and a control circuit configured to compare the measured value from the measurement circuit with at least one of a plurality of threshold values and to perform control of the compressor in accordance with a result of comparison, the plurality of threshold values including a first threshold value, and a second threshold value less than the first threshold value, and the control circuit being configured to: stop the compressor when the measured value exceeds the first threshold value; operate the compressor to allow a drive frequency of the compressor to change at a first frequency change rate while the measured value is equal to or less than the second threshold value; and operate the compressor to allow the drive frequency to change at a second frequency change rate different from the first frequency change rate in at least one of a case of increasing the drive frequency and a case of decreasing the drive frequency, when the measured value exceeds the second threshold value.

2. The control device of claim 1, wherein the control circuit is configured to make the second frequency change rate less than the first frequency change rate in a case of increasing the drive frequency.

3. The control device of claim 1, wherein the control circuit is configured to make the second frequency change rate larger than the first frequency change rate in a case of decreasing the drive frequency.

4. The control device of claim 1, wherein: the plurality of threshold values further include a third threshold value less than the first threshold value; and the control circuit is configured to: operate an expansion valve of the refrigeration cycle circuit to allow an opening degree of the expansion valve to change at a first opening degree change rate while the measured value is equal to or less than the third threshold value; and operate the expansion valve to allow the opening degree to change at a second opening degree change rate different from the first opening degree change rate in at least one of a case of increasing the opening degree and a case of decreasing the opening degree, when the measured value exceeds the third threshold value.

5. The control device of claim 4, wherein the control circuit is configured to make the second opening degree change rate larger than the first opening degree change rate in a case of increasing the opening degree.

6. The control device of claim 4, wherein the control circuit is configured to make the second opening degree change rate smaller than the first opening degree change rate in a case of decreasing the opening degree.

7. The control device of claim 1, wherein: the plurality of threshold values include a fourth threshold value that is larger than the second threshold value and is smaller than the first threshold value; and the control circuit is configured to operate the compressor to allow the drive frequency to decrease at a third frequency change rate when the measured value exceeds the fourth threshold value.

8. The control device of claim 7, wherein: the third frequency change rate is larger than the first frequency change rate; and the control circuit is configured to make the second frequency change rate larger than the first frequency change rate and smaller than the third frequency change rate in a case of decreasing the drive frequency after the measured value decreases to the fourth threshold value or less.

9. The control device of claim 1, wherein: at least one threshold value of the plurality of threshold values is defined by an upper threshold value and a lower threshold value smaller than the upper threshold value; the measured value exceeding the at least one threshold value means the measured value exceeding the upper threshold value of the at least one threshold value; and the measured value becoming equal to or less than the at least one threshold value means the measured value becoming equal to or less than the lower threshold value of the at least one threshold value.

10. The control device of claim 1, wherein: the refrigeration cycle circuit includes a heat exchanger of an outdoor unit and an air blower for facilitating heat exchange at the heat exchanger; the plurality of threshold values include a fifth threshold value smaller than the first threshold value; and the control circuit is configured to increase a rotational speed of the air blower when the measured value exceeds the fifth threshold value in a case where the heat exchanger functions as a condenser.

11. The control device of claim 1, wherein: the refrigeration cycle circuit includes a heat exchanger of an indoor unit and an air blower for facilitating heat exchange at the heat exchanger; the plurality of threshold values include a sixth threshold value smaller than the first threshold value; and the control circuit is configured to decrease a rotational speed of the air blower when the measured value exceeds the sixth threshold value in a case where the heat exchanger functions as an evaporator.

12. A control device for controlling a compressor and an expansion valve of a refrigeration cycle circuit allowing circulation of a working medium, the working medium containing ethylene-based fluoroolefin as a refrigerant component, the control device comprising: a measurement circuit configured to output a measured value indicating at least one of an internal temperature or an internal pressure of the compressor; and a control circuit configured to compare the measured value from the measurement circuit with at least one of a plurality of threshold values and to perform control of the compressor and the expansion valve in accordance with a result of comparison, the plurality of threshold values including a first threshold value, and a second threshold value less than the first threshold value, and the control circuit being configured to: stop the compressor when the measured value exceeds the first threshold value; operate the expansion valve to allow an opening degree of the expansion valve to change at a first opening degree change rate while the measured value is equal to or less than the second threshold value; and operate the expansion valve to allow the opening degree to change at a second opening degree change rate different from the first opening degree change rate in at least one of a case of increasing the opening degree and a case of decreasing the opening degree, when the measured value exceeds the second threshold value.

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

14. The refrigeration cycle device of claim 13, wherein the ethylene-based fluoroolefin includes ethylene-based fluoroolefin capable of undergoing a disproportionation reaction.

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

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