Refrigeration cycle system

Abstract

In a refrigeration cycle system, a mixed refrigerant is used as a working medium for the refrigeration cycle, and the mixed refrigerant contains a hydrofluoroolefin and a high-solubility refrigerant having a higher solubility in refrigerating machine oil than the hydrofluoroolefin. The control unit controls at least one of the compressor and the expansion valve by setting the upper limit value of the internal pressure to P0 (P0 < P1) and the upper limit value of the exhaust gas temperature to T0 (T0 < T1) during a period from when the compressor is started until a predetermined time t1 has elapsed. After a predetermined time t1 has elapsed, the upper limit value of the internal pressure is changed from P0 to P1, and the upper limit value of the exhaust gas temperature is changed from T0 to T1, thereby controlling at least one of the compressor and the expansion valve. This makes it possible to satisfactorily suppress or alleviate disproportionation reactions even when a refrigerant oil is used together with a working medium for a refrigeration cycle containing a fluoroolefin and another refrigerant.

Description

TECHNICAL FIELD

[0001] The present application relates to a refrigeration cycle system using a working medium for a refrigeration cycle containing a hydrofluoroolefin, and particularly to a refrigeration cycle system capable of well inhibiting disproportionation reaction of a hydrofluoroolefin. BACKGROUND

[0002] As a working medium for a refrigeration cycle (refrigerant or heat medium), a hydrofluoroolefin (HFO) having a smaller global warming potential (GWP) has recently been proposed. As a representative hydrofluoroolefin, 1,1,2-trifluoroethylene (HFO1123) can be cited. Since 1,1,2-trifluoroethylene has a low stability compared with the conventional HFC or the like, it is less likely to remain in the atmosphere, and thus has a small ODP and GWP.

[0003] It is known that such a hydrofluoroolefin is likely to undergo a self-decomposition reaction called disproportionation reaction and a polymerization reaction after the self-decomposition reaction (hereinafter, described as disproportionation reaction) due to its low stability.

[0004] The disproportionation reaction is likely to occur induced by heat generation or the like generated in the use of the working medium for a refrigeration cycle, and the occurrence of the disproportionation reaction is accompanied by a large amount of heat release. Therefore, it is also known that the disproportionation reaction occurs in a chain. As a result, a large amount of carbon deposit can be generated, and the reliability of the refrigeration cycle system or a compressor or the like provided in the system is reduced.

[0005] Further, a compressor provided in the refrigeration cycle system generally stores a refrigeration oil (lubricating oil) for lubrication in the inside. Therefore, it can be said that in the refrigeration cycle system, the working medium for a refrigeration cycle and the refrigeration oil are used in combination. In this case, the working medium containing composition (or working fluid) is considered to be constituted at least by a refrigerant component (working medium for a refrigeration cycle) and a refrigeration oil component.

[0006] As for such a working medium containing composition, a technology for achieving an improvement in performance of a refrigeration cycle system by adjusting a refrigerant solubility viscosity under high temperature and high pressure conditions to a prescribed range is known. For example, in Patent Literature 1, a working fluid (working medium containing composition) constituted by a refrigerant and a refrigeration oil is adjusted to exhibit a refrigerant solubility viscosity of 2 to 4 mm / s under a condition of a temperature of 80°C and an absolute pressure of 3.4 MPa. 2 As a specific refrigerant, a hydrofluoroolefin (HFO) such as fluoroethylene or fluoro-propylene, a fluorine-containing refrigerant such as a hydrofluorocarbon (HFC), or a natural refrigerant such as a hydrocarbon refrigerant, ammonia (R717), carbon dioxide (R744) or the like can be cited.

[0007] According to Patent Literature 1, when the refrigerant solubility viscosity of the working fluid is too low, the refrigeration capacity or cooling capacity of the refrigeration machine (refrigeration cycle system) is reduced due to, for example, a decrease in the sealability of the compressor. In addition, when the refrigerant solubility viscosity of the working fluid is too high, the energy consumption increases due to, for example, an increase in the stirring resistance or resistance at the start of the refrigeration machine, and the refrigeration capacity or cooling capacity is reduced. Thus, by adjusting the refrigerant solubility viscosity to the above range, improvement in the coefficient of performance (COP) of the refrigeration cycle system is achieved.

[0008] Prior Art Documents

[0009] Patent Literature

[0010] Patent Literature 1: Japanese Patent Application Publication No. 2017-141974 SUMMARY

[0011] PROBLEMS TO BE SOLVED BY THE INVENTION

[0012] However, in the refrigeration cycle system disclosed in Patent Literature 1, as described above, the refrigerant is not limited to a hydrofluoroolefin, and the disproportionation reaction of a hydrofluoroolefin is not described. In addition, although a mixed refrigerant in which a plurality of refrigerants are combined is described, as a specific example, only an R410A refrigerant in which difluoromethane (R32) and pentafluoroethane (R125) are mixed at a ratio of 50 / 50 is described, and the relationship between the refrigerant solubility viscosity of the working fluid and the COP of the refrigeration machine is verified.

[0013] Thus, in the refrigeration cycle system disclosed in Patent Literature 1, the working medium for a refrigeration cycle is not at all assumed to be a mixed refrigerant containing a hydrofluoroolefin. Therefore, with the technology described in Patent Literature 1, it is difficult to sufficiently suppress the disproportionation reaction of a hydrofluoroolefin.

[0014] The present application was made in order to solve such a technical problem, and has an object to provide a refrigeration cycle system in which the disproportionation reaction is sufficiently suppressed or mitigated even when a working medium for a refrigeration cycle containing a hydrofluoroolefin and another refrigerant is used together with a refrigeration machine oil.

[0015] MEANS OF SOLVING THE PROBLEM

[0016] To solve the above-described technical problem, the refrigeration cycle system according to the present application is configured as follows. A refrigeration cycle includes a compressor and an expansion valve that internally store refrigeration oil. A control unit controls at least one of the rotation speed of the compressor and the opening degree of the expansion valve using a mixed refrigerant as a working medium for the refrigeration cycle, the mixed refrigerant containing at least one hydrofluoroolefin and at least one high-solubility refrigerant having a higher solubility in the refrigeration oil than the hydrofluoroolefin. When the upper limit of the internal pressure in the compressor is set to P1 and the upper limit of the discharge gas temperature is set to T1, the control unit sets the upper limits of the internal pressure and the discharge gas temperature to P0 (P0 < P1) and T0 (T0 < T1), respectively, which are lower than P1 and T1, respectively, during a period from the start of the compressor to the elapse of a predetermined time t1, and controls at least one of the rotation speed of the compressor and the opening degree of the expansion valve. After the elapse of the predetermined time t1, the control unit changes the upper limits of the internal pressure and the discharge gas temperature from P0 and T0 to P1 and T1, respectively, and controls at least one of the rotation speed of the compressor and the opening degree of the expansion valve.

[0017] When the working medium for the refrigeration cycle is the mixed refrigerant containing the hydrofluoroolefin and the high-solubility refrigerant, the high-solubility refrigerant is relatively more dissolved in the refrigeration oil at the time of the stop of the compressor. Therefore, the concentration of the hydrofluoroolefin in the mixed refrigerant is relatively higher at the time of the start of the compressor, and the conditions (disproportionation conditions) of the internal pressure and the internal temperature (discharge gas temperature) at which the disproportionation reaction occurs are lower than those in the case of the ordinary refrigerant composition.

[0018] According to the above-described configuration, the upper limits of the internal pressure and the discharge gas temperature at which the protection control is triggered are set to P0 and T0, which are lower than the predetermined values P1 and T1, respectively, during the initial period of the operation from the start of the compressor to the elapse of the predetermined time t1. The control unit controls the compressor or the expansion valve or both of them based on the P0 / T0 during the initial period of the operation. After the initial period of the operation ends and the ordinary operation is started, the control unit changes the upper limits of the internal pressure and the discharge gas temperature from P0 / T0 to the predetermined values P1 / T1, and controls at least one of the compressor and the expansion valve.

[0019] Thus, even during the initial period of the operation in which the concentration of the hydrofluoroolefin is relatively higher and the disproportionation reaction is likely to occur, the occurrence probability of the disproportionation reaction can be favorably suppressed. Also, after the initial period of the operation ends and the ordinary operation is started, the occurrence of the disproportionation reaction can be favorably suppressed or mitigated. As a result, the reliability of the refrigeration cycle system can be further improved.

[0020] The above-described objects, other objects, features, and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

[0021] Inventive Effects

[0022] In the present application, the following effects are obtained by the above-described means: a refrigeration cycle system capable of suppressing or mitigating the disproportionation reaction even when a working medium for a refrigeration cycle containing a hydrofluoroolefin and other refrigerant is used together with a refrigerant oil. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 In the present application, the following effects are obtained by the above-described means: a refrigeration cycle system capable of suppressing or mitigating the disproportionation reaction even when a working medium for a refrigeration cycle containing a hydrofluoroolefin and other refrigerant is used together with a refrigerant oil. Figure 1 A is a schematic piping diagram representing a representative structure of an air conditioner, which is an example of a refrigeration cycle system according to an embodiment of the present application, Figure 1 B is a schematic piping diagram representing a representative structure of an air conditioner, Figure 1 A is a main part block diagram representing a representative control structure of the air conditioner shown in A.

[0024] Figure 2 In the present application, the following effects are obtained by the above-described means: a refrigeration cycle system capable of suppressing or mitigating the disproportionation reaction even when a working medium for a refrigeration cycle containing a hydrofluoroolefin and other refrigerant is used together with a refrigerant oil. Figure 2 A is a graph schematically representing a change in conditions of the disproportionation reaction of a hydrofluoroolefin when a predetermined time has elapsed after the start of a compressor, Figure 2 B is a graph representing an example of control of pressure / temperature before a predetermined time in a refrigeration cycle system according to the present application.

[0025] Figure 3 is a flowchart representing an example of a representative control of the air conditioner shown in B. Figure 1 BRIEF DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION

[0026] [Insights and the like that form the basis of the present application]

[0027] According to the in-depth research of the inventor of the present application, it has been clarified that, in the case where a hydrofluoroolefin that will undergo a disproportionation reaction is combined with other refrigerants to be used as a refrigerant component of a working medium for a refrigeration cycle, the difference in solubility of the refrigerant in a refrigerant oil (hereinafter appropriately referred to as "oil solubility") that has not been considered in the existing refrigeration cycle system needs to be considered.

[0028] For example, assume the case where the refrigeration cycle working medium contains only one kind of hydrofluoroolefin as a refrigerant component (the case of a single refrigerant). In this case, in a state where the compressor is stopped, one kind of hydrofluoroolefin is dissolved in the refrigerant oil according to its oil solubility. Therefore, at the time of starting the compressor, it is sufficient to control the pressure and temperature of the compressor only by considering the occurrence conditions of the disproportionation reaction of the hydrofluoroolefin.

[0029] However, in the case of a mixed refrigerant, and when the oil solubility of the other refrigerant is greater than that of the hydrofluoroolefin, the amount of dissolution of the other refrigerant in the refrigerant oil will be greater than that of the hydrofluoroolefin in the refrigerant oil.

[0030] When the compressor is started from a stopped state to enter a running state, the internal pressure and temperature change greatly, and in conjunction therewith, other refrigerant dissolved in the refrigeration oil returns to the mixed refrigerant. That is, when the compressor is stopped or immediately after starting, the other refrigerant is relatively small and the hydrofluoroolefin is relatively large, and when the compressor is in normal operation, the content of the other refrigerant returns to the original level. In other words, the refrigerant composition when the compressor is stopped and immediately after starting is different from the refrigerant composition when the compressor is in normal operation.

[0031] When the compressor starts to operate, the inside of the compressor rapidly changes to a high temperature and high pressure state. However, the change in the amount of dissolution of the hydrofluoroolefin and the other refrigerant, that is, the change in the refrigerant composition, is difficult to rapidly follow the change in the temperature and the pressure inside. This is because the solubility of the refrigerant in the refrigeration oil is basically premised on a state in which the refrigerant and the refrigeration oil coexist quasi-statically. Therefore, the refrigerant composition when the compressor is stopped or immediately after starting is different from the refrigerant composition when the compressor is in normal operation (at a high temperature and a high pressure).

[0032] As described above, the disproportionation reaction of the hydrofluoroolefin easily occurs particularly under high temperature and high pressure conditions. Therefore, for example, in order to suppress the disproportionation reaction, it is assumed that the pressure and the temperature inside the compressor are controlled based on the refrigerant composition at the time of normal operation. However, immediately after the compressor is started, since the refrigerant composition is relatively large in the hydrofluoroolefin, the disproportionation reaction can occur even under conditions of relatively low pressure and low temperature compared to the time of normal operation.

[0033] Furthermore, during a period from the start of operation of the compressor until a prescribed time elapses, that is, in the initial stage of the start of operation, the refrigerant composition at the time of stopping does not change slowly in response to the rapid change in the internal pressure and the internal temperature of the compressor. Therefore, even if the compressor is controlled based on the refrigerant composition at the time of normal operation for the purpose of suppressing the disproportionation reaction, it cannot be well adapted to the demand for suppressing the disproportionation reaction in the initial stage of the start of operation, and as a result, the disproportionation reaction of the hydrofluoroolefin easily occurs in the initial stage of the start of operation.

[0034] Thus, the inventors of the present application further intensively studied and found that, in a general refrigeration cycle system, by setting the upper limit values of the internal pressure and the discharge gas temperature, which are set in advance for the purpose of implementing protection control of the compressor, to a pressure and a temperature that are lower in the initial stage of the start of operation, and controlling the operation of the compressor, and then raising the upper limit values of the internal pressure and the discharge gas temperature to the values set in advance after a prescribed time elapses, the disproportionation reaction can be particularly well suppressed or mitigated in the initial stage of the start of operation, and thus the present application was completed.

[0035] That is, the refrigeration cycle system according to the present application is configured to include: a refrigeration cycle including a compressor and an expansion valve that internally store refrigeration machine oil; and a control unit that uses a mixed refrigerant containing at least one hydrofluoroolefin and at least one high-solubility refrigerant having a higher solubility in the refrigeration machine oil than the hydrofluoroolefin as a working medium for the refrigeration cycle, wherein, when an upper limit value of an internal pressure in the compressor is set to P1 and an upper limit value of a discharge gas temperature is set to T1, the control unit sets the upper limit value of the internal pressure to P0 (P0 < P1) that is lower than P1 and sets the upper limit value of the discharge gas temperature to T0 (T0 < T1) that is lower than T1 during a period from startup of the compressor to elapse of a predetermined time tl, and controls at least one of a rotational speed of the compressor and an opening degree of the expansion valve, and changes the upper limit value of the internal pressure from P0 to P1 and changes the upper limit value of the discharge gas temperature from T0 to T1 after the predetermined time tl elapses, and controls at least one of the rotational speed of the compressor and the opening degree of the expansion valve.

[0036] When the working medium for the refrigeration cycle is the mixed refrigerant containing the hydrofluoroolefin and the high-solubility refrigerant as described above, the high-solubility refrigerant is relatively more dissolved in the refrigeration machine oil at the time of stop of the compressor. Therefore, the hydrofluoroolefin is relatively more in the mixed refrigerant at the time of startup of the compressor, and the conditions (disproportionation conditions) of the internal pressure and the internal temperature (discharge gas temperature) at which the disproportionation reaction occurs are lower than those of the usual refrigerant composition.

[0037] According to the above configuration, therefore, the upper limit values of the internal pressure and the discharge gas temperature at which the protection control is triggered are set to P0 and T0 that are lower than the predetermined values P1 and T1 during the initial period of operation from the startup of the compressor to the elapse of the predetermined time tl. The control unit controls the compressor or the expansion valve or both the compressor and the expansion valve on the basis of the P0 / T0 during the initial period of operation. After the initial period of operation ends and the usual operation is entered, the control unit changes the upper limit values of the internal pressure and the discharge gas temperature from P0 / T0 to the predetermined values P1 / T1, and controls at least one of the compressor and the expansion valve.

[0038] Accordingly, even during the initial period of operation in which the concentration of the hydrofluoroolefin is relatively high and the disproportionation reaction is likely to occur, the occurrence probability of the disproportionation reaction can be favorably suppressed. Also, after the initial period of operation is entered into the usual operation, the occurrence of the disproportionation reaction can be favorably suppressed or mitigated. As a result, the reliability of the refrigeration cycle system can be further improved.

[0039] In the refrigeration cycle system described above, it can also be configured to include a pressure sensor that measures the internal pressure of the compressor, and the control section controls at least one of the rotational speed of the compressor and the opening degree of the expansion valve using the pressure value measured by the pressure sensor.

[0040] In the refrigeration cycle system described above, it can also be configured to include a first temperature sensor that approximately measures the internal pressure of the compressor according to temperature, and the control section controls at least one of the rotational speed of the compressor and the opening degree of the expansion valve using the pressure value indirectly measured by the first temperature sensor.

[0041] In the refrigeration cycle system described above, it can also be configured to include a second temperature sensor that measures the temperature of the discharge gas from the compressor, and the control section controls at least one of the rotational speed of the compressor and the opening degree of the expansion valve using the discharge gas temperature measured by the second temperature sensor.

[0042] In the refrigeration cycle system described above, it can also be configured such that the high solubility refrigerant is a saturated hydrocarbon, and it can also be configured such that the saturated hydrocarbon is propane (R290).

[0043] In the refrigeration cycle system described above, it can also be configured such that the working medium for the refrigeration cycle further contains a disproportionation inhibitor.

[0044] Hereinafter, representative embodiments of the present application will be described with reference to the accompanying drawings. In addition, the same reference numerals are assigned to the same or corresponding elements throughout all the drawings, and repeated description thereof will be omitted.

[0045] [Structure Example of Refrigeration Cycle System]

[0046] First, as a representative example of the refrigeration cycle system to which the present application is applied, an air conditioner 10 schematically shown in Figure 1 A, Figure 1 The air conditioner 10 schematically shown in Figure 1 As shown in the schematic piping diagram of A, the air conditioner 10 to which the present application is applied includes an outdoor unit 11 and an indoor unit 12, and these units 11, 12 are connected by an inter-unit piping 13. The indoor unit 12 is provided in a space (referred to as an object space) that is an air conditioning target, and the outdoor unit 11 is provided outside the object space. The inter-unit piping 13 is provided with a piping connection portion 13a and a piping connection portion 13b.

[0047] The air conditioner 10 circulates refrigerant compressed in the outdoor unit 11 between the outdoor unit 11 and the indoor unit 12, thereby performing air conditioning in a target space in which the indoor unit 12 is provided. The air conditioner 10 is capable of switching operation between a cooling operation mode in which the target space is cooled and a heating operation mode in which the target space is heated.

[0048] The outdoor unit 11 includes a compressor 20, an outdoor heat exchanger 14, an outdoor fan 15, an expansion valve 16, a switching valve 17, and the like. The compressor 20 compresses a working medium for a refrigeration cycle containing refrigerant. In addition, refrigeration oil is stored in the inside of the compressor 20. The outdoor heat exchanger 14 performs heat exchange of refrigerant outside the target space (outdoors). The outdoor fan 15 blows air outdoors to the outdoor heat exchanger 14. The expansion valve 16 depressurizes and expands refrigerant. The switching valve 17 is used to switch to the cooling operation mode or the heating operation mode.

[0049] The indoor unit 12 includes an indoor heat exchanger 18, an indoor fan 19, and the like. The indoor heat exchanger 18 performs heat exchange of refrigerant supplied from the outdoor unit 11 through the inter-unit pipe 13 in the target space. The indoor fan 19 blows air in the target space (indoors) in the target space.

[0050] The outdoor heat exchanger 14 functions as a condenser in the cooling operation mode and functions as an evaporator in the heating operation mode. The indoor heat exchanger 18 functions as an evaporator in the cooling operation mode and functions as a condenser in the heating operation mode. The compressor 20, the outdoor heat exchanger 14 (condenser or evaporator), the indoor heat exchanger 18 (evaporator or condenser), and the expansion valve 16 are connected in a ring shape through the inter-unit pipe 13, thereby constituting a refrigeration cycle (refrigerant circuit).

[0051] The specific kind of refrigeration oil stored in the inside of the compressor 20 is not particularly limited, and it is possible to cite, as a base oil, a lubricating oil known in the field of compressors, and a structure containing a known additive as needed.

[0052] The lubricating oil used as the base oil of the refrigeration oil can cite, for example, hydrocarbon oils such as mineral oil, olefin polymer, naphthalene compound, alkylbenzene, ester oils such as monoester, diester, polyol ester, complex ester, oxygen-containing oils such as polyalkylene glycol, polyvinyl ether, polyphenyl ether, perfluoro ether, and the like, but is not particularly limited. These base oils can be used only one kind, or two or more kinds can be appropriately combined and used.

[0053] The additive contained in the refrigeration oil is also not particularly limited, and it is possible to cite oiliness agent, sliding property improver, extreme pressure additive, antioxidant, acid scavenger, metal deactivator, antifoaming agent, rust preventive, dispersant, and the like.

[0054] In the present embodiment, as the base oil of the refrigerant oil, at least one selected from the group consisting of polyol esters, polyalkylene glycols, and polyvinyl ethers is preferably used as a main component, and more preferably a polyol ester or a polyvinyl ether is used as the main component. The main component herein refers to a component having a content of 50% by mass or more, based on the total amount (100% by mass) of the base oil in the refrigerant oil. Further, the content of the lubricating oil base oil in the refrigerant oil is not particularly limited, and can be 80% by mass or more, 90% by mass or more, or 95% by mass or more, based on the total amount (100% by mass) of the refrigerant oil.

[0055] The air conditioner 10 is as shown in a block diagram of a main part of B. Figure 1 The control unit 21 controls the operation of the compressor 20, the opening degree and / or opening / closing of the expansion valve 16, the switching of the flow path of the switching valve 17, and the operation and / or stop of the outdoor fan 15 and the indoor fan 19. In addition, in the air conditioner 10, the control unit 21 controls the operation of the compressor 20, the opening degree and / or opening / closing of the expansion valve 16, the switching of the flow path of the switching valve 17, and the operation and / or stop of the outdoor fan 15 and the indoor fan 19, based on the operation or setting of the operation unit provided in the air conditioner 10. Figure 1

[0056] Further, the control unit 21 operates the expansion valve 16 and the switching valve 17 to switch between the cooling operation mode and the heating operation mode of the air conditioner 10. Further, the control unit 21 performs control of the operation frequency (rotational speed) of the compressor 20, the operation and / or stop, and the control of the outdoor fan 15 and the indoor fan 19, based on the operation or setting of the operation unit provided in the air conditioner 10, thereby performing air conditioning of the target space in accordance with the target temperature. The rotational speed of the compressor 20 is controlled by changing the operation frequency of the compressor 20.

[0057] The pressure sensor 22 measures the internal pressure of the compressor 20. As such a pressure sensor 22, a type that indirectly measures the internal pressure of the compressor 20, a type that approximately measures the internal pressure from the temperature inside the compressor 20 (temperature sensor), a type that directly measures the internal pressure, and the like can be exemplified. In general, a type that indirectly measures the internal pressure of the compressor 20 by measuring the pressure on the high-pressure side in the refrigeration system, such as the pressure of the discharge pipe provided in the compressor 20 or the outlet of the condenser that constitutes the refrigeration system, can be used. As a specific pressure sensor 22, a type known in the field of refrigeration cycle systems such as the air conditioner 10 can be preferably used, and is not particularly limited.

[0058] ​Temperature sensor 23 measures the temperature (discharge gas temperature) of the high-temperature, high-pressure gas discharged from the discharge pipe of compressor 20. Based on the measured discharge gas temperature, the internal temperature of compressor 20 can be estimated. Here, as described above, pressure sensor 22 can be a temperature sensor that measures the internal pressure by measuring the internal temperature of compressor 20; however, the temperature sensor for measuring internal pressure is different from the temperature sensor for measuring the discharge gas temperature (internal temperature of compressor 20). Therefore, for convenience, in this specification, the temperature sensor used as pressure sensor 22 is referred to as the "first temperature sensor," and the temperature sensor for measuring the discharge gas temperature is referred to as the "second temperature sensor" for distinction. The specific temperature sensor 23 (second temperature sensor) can preferably be a sensor known in the field of refrigeration cycle systems such as air conditioner 10, and is not particularly limited.

[0059] As described below, in the refrigeration cycle system of the present invention, the control unit 21 sets the upper limit values ​​of the internal pressure and discharge gas temperature of the compressor 20 to be lower during the period from the start of the compressor 20 until a predetermined time t1 has elapsed, i.e., the initial stage of operation. Based on this, the control unit 21 controls the compressor 20's rotational speed or the opening degree of the expansion valve 16, or both (at least one of rotational speed and opening degree), and then changes the upper limit values ​​of the internal pressure and discharge gas temperature to predetermined values. In this control, the control unit 21 uses at least the output of the pressure sensor 22 (measured value of internal pressure) and the output of the temperature sensor 23 (measured value of discharge gas temperature).

[0060] Of course, the refrigeration cycle system (air conditioner 10, etc.) involved in this invention may also include sensors or measuring devices other than pressure sensor 22 and temperature sensor 23. Furthermore, the control unit 21 can use the measured or detected values ​​from these sensors or measuring devices other than pressure sensor 22 and temperature sensor 23 to control the compressor 20 and expansion valve 16. Moreover, the control unit 21 can also use the measured or detected values ​​from these sensors or measuring devices to control other structural elements (switching valve 17, outdoor fan 15, indoor fan 19, etc.).

[0061] exist Figure 1 In the example shown in A, block arrows (solid arrows) indicate the refrigerant flow direction in cooling operation mode. In the cooling operation mode of air conditioner 10, the refrigerant (working medium for the cooling cycle) flows in the following sequence: compressor 20, outdoor heat exchanger 14, expansion valve 16, indoor heat exchanger 18, and switching valve 17, and returns to compressor 20 from switching valve 17. Furthermore, the refrigerant flow direction in heating operation mode is the same as... Figure 1The block arrow shown in A is reversed. In the heating operation mode of the air conditioner 10, the refrigerant flows in the order of the compressor 20, the indoor heat exchanger 18, the expansion valve 16, the outdoor heat exchanger 14, and the switching valve 17, and returns to the compressor 20 from the switching valve 17.

[0062] The pipe connection portions 13a and 13b provided in the air conditioner 10 are provided between the outdoor unit 11 and the indoor unit 12 in the annular connection unit inter-pipe 13. As these pipe connection portions 13a and 13b, for example, a two-way valve or a three-way valve is used. Thereby, the outdoor unit 11 and the indoor unit 12 are connected to each other, and the circulation of the refrigerant can be achieved. Further, the opening degree and / or opening / closing of the pipe connection portions 13a and 13b can be controlled by manual or control by the control portion 21.

[0063] Further, the specific structure of the air conditioner 10, the outdoor unit 11, the indoor unit 12, and each structural element (the compressor 20, the outdoor heat exchanger 14, the outdoor fan 15, the expansion valve 16, the switching valve 17, the indoor heat exchanger 18, the indoor fan 19, the unit inter-pipe 13, the pipe connection portions 13a and 13b, and the like) constituting the refrigeration cycle (refrigerant circuit) is not particularly limited, and various known structures can be appropriately adopted. In the present embodiment, since the refrigeration cycle system is the air conditioner 10, the compressor 20 is preferably a rotary compressor, but of course, other types of compressors can be adopted.

[0064] Further, the specific structure of the air conditioner 10 and the refrigeration cycle (refrigerant circuit) is not limited to Figure 1 A, Figure 2 B, and can include other structural elements, and can not include a part of the structural elements. Further, the refrigeration cycle system is not limited to the air conditioner 10, and can be a dehumidifier, a display case, an ice maker, a heat pump water heater, a heat pump laundry dryer, a vending machine, or the like.

[0065] [Refrigerant components]

[0066] In the refrigeration cycle system according to the present application, as the refrigerant, a working medium for a refrigeration cycle containing a hydrofluoroolefin (HFO) that undergoes disproportionation reaction and one or more other refrigerants is used. Further, the other refrigerant is a refrigerant having a high solubility (oil solubility) to refrigeration oil stored inside the compressor 20, as compared with the hydrofluoroolefin.

[0067] Further, for convenience of explanation, the refrigerant having a larger oil solubility than the hydrofluoroolefin is referred to as a "high solubility refrigerant". In the case where the working medium for a refrigeration cycle contains two or more refrigerants other than the hydrofluoroolefin, at least one of the refrigerants is a high solubility refrigerant.

[0068] As the hydrofluoroolefin, specifically, for example, 1,1,2-trifluoroethylene (CF2=CHF, HFO1123), trans-1,2-difluoroethylene (CHF=CHF (E), HFO1132 (E)), cis-1,2-difluoroethylene (CHF=CHF (Z), HFO1132 (Z)), and the like, which are compounds having 2 carbon atoms, can be listed, but there is no particular limitation. These hydrofluoroolefins can be used as the refrigerant component either singly or in combination of two or more.

[0069] These hydrofluoroolefins have an ethylene structure, that is, a double bond between carbon atoms, as a skeleton, and have a chemical structure having the following characteristics: at least one of the two hydrogen atoms bonded to one carbon atom is substituted with a fluorine atom, or at least one of the two hydrogen atoms bonded to each of the two carbon atoms is substituted with a fluorine atom. In addition, in the hydrofluoroolefin, a part of the hydrogen atoms can also be substituted with other atoms or other substituents.

[0070] For example, 1,1,2-trifluoroethylene has the following structure: both of the two hydrogen atoms bonded to one carbon atom (1-position carbon atom) of the ethylene structure are substituted with fluorine atoms, and one of the two hydrogen atoms bonded to the other carbon atom (2-position carbon atom) is substituted with a fluorine atom.

[0071] Alternatively, trans-1,2-difluoroethylene has the following structure: one of the two hydrogen atoms bonded to the 1-position carbon atom of the ethylene structure is substituted with a fluorine atom, and of the two hydrogen atoms bonded to the 2-position carbon atom, only the hydrogen atom at the position opposite to the adjacent position from the 1-position carbon atom across the double bond is substituted with a fluorine atom.

[0072] Such a hydrofluoroolefin, as described above, because it contains an ethylene skeleton, that is, a carbon-carbon double bond, the double bond is easily decomposed. That is, because the ozone in the atmosphere generates hydroxyl radicals (OH radicals) through a photochemical reaction, and the hydroxyl radicals can adduct to the double bond, the hydrofluoroolefin is easily decomposed. Therefore, the hydrofluoroolefin becomes a substance having less influence on the ozone layer destruction and global warming.

[0073] The working medium for a refrigeration cycle used in the present application can contain, in addition to the hydrofluoroolefin, for example, propane (R290) as a refrigerant component. As described above, the refrigerant oil exemplified in the present embodiment uses a base oil having a molecular structure with a hydrocarbon skeleton. Therefore, compared with the hydrofluoroolefin, propane is easily dissolved in the refrigerant oil. Therefore, propane is a high-solubility refrigerant having a larger solubility in the refrigerant oil (oil solubility) than the hydrofluoroolefin.

[0074] Further, in the working medium for refrigeration cycle used in the present application, as the "other refrigerant" which can be contained in addition to the hydrofluoroolefin, there is no particular limitation, and representative examples include hydrofluorocarbons (HFCs), saturated hydrocarbons, carbon dioxide, and the like.

[0075] As the HFC, specifically, for example, fluoromethanes such as difluoromethane (R32), trifluoromethane (R23); fluoroethanes such as fluoroethane (R161), 1,1-difluoroethane (R152a), 1,1,1-trifluoroethane (R143a), 1,1,2,2-tetrafluoroethane (R134), 1,1,1,2-tetrafluoroethane (R134a), pentafluoroethane (R125), difluoroethane, trifluoroethane; fluoropropanes such as 1,1,1,3,3-pentafluoropropane (R245fa), 1,1,1,2,3,3-hexafluoropropane (R236ea), 1,1,1,3,3,3-hexafluoropropane (R236fa), 1,1,1,2,3,3,3-heptafluoropropane (R227ea); fluorobutanes such as 1,1,1,3,3-pentafluorobutane (R365mfc); fluoropentanes such as 1,1,1,2,3,4,4,5,5,5-decafluoropentane (R4310mee), heptafluorocyclopentane (Rc447ef); and the like can be exemplified.

[0076] As the saturated hydrocarbon, specifically, for example, ethane, n-propane, cyclopropane, n-butane, cyclobutane, isobutane (2-methylpropane), methylcyclopropane, n-pentane, isopentane (2-methylbutane), neopentane (2,2-dimethylpropane), methylcyclobutane, and the like can be exemplified.

[0077] These other refrigerants can be used singly or two or more of them can be appropriately combined and used as the refrigerant. Among them, R32 (difluoromethane) is preferably used. In addition, as described later, a kind of the saturated hydrocarbon can be used as the disproportionation inhibitor. Therefore, the saturated hydrocarbon can be used as both the other refrigerant and the disproportionation inhibitor.

[0078] These other refrigerants are all known as substances having little influence on the ozone layer and global warming, and therefore can be used as the refrigerant component together with the hydrofluoroolefin, or together with the hydrofluoroolefin and difluoromethane. The above other refrigerant component can be used singly or two or more of them can be appropriately combined and used. Further, among these other refrigerants, there is a high-solubility refrigerant. For example, the saturated hydrocarbon is as easily soluble in the refrigeration machine oil as propane, and therefore can be appropriately used as the high-solubility refrigerant.

[0079] The content (concentration) of the hydrofluoroolefin and other refrigerants (including a high solubility refrigerant) in the working medium for a refrigeration cycle is not particularly limited. For example, the hydrofluoroolefin and other refrigerants are collectively referred to as "mixed refrigerant", and the content of the hydrofluoroolefin can be 50% by mass or more, can be 60% by mass or more, can be 70% by mass or more, or can be 80% by mass or more, based on 100% by mass of the total amount of the mixed refrigerant. In addition, the content of the other refrigerant can be less than 50% by mass, can be 40% by mass or less, can be 30% by mass or less, or can be 20% by mass or less, based on 100% by mass of the total amount of the mixed refrigerant.

[0080] If the content of the hydrofluoroolefin is less than 50% by mass of the total amount of the mixed refrigerant, the content of the hydrofluoroolefin in the mixed refrigerant is too low, resulting in a large amount of other refrigerants. Therefore, in the working medium for a refrigeration cycle, the advantages of using a hydrofluoroolefin having a small GWP cannot be sufficiently obtained.

[0081] In addition, for example, if the other refrigerant is propane or a saturated hydrocarbon described above, the influence of the flammability of propane can increase in the mixed refrigerant, that is, the working medium for a refrigeration cycle containing the mixed refrigerant. In this case, in the working medium for a refrigeration cycle, the advantages of achieving good operational convenience while having a small GWP cannot be sufficiently obtained.

[0082] [Other components that can be used]

[0083] As described above, the working medium for a refrigeration cycle used in the present application can be used in combination with refrigerant oil (lubricating oil) stored inside the compressor 20 provided in the refrigeration cycle system. The working medium for a refrigeration cycle used in the present application, as described above, can be a mixed refrigerant consisting essentially of a hydrofluoroolefin and at least one high solubility refrigerant. Further, in the case where the working medium for a refrigeration cycle is used in combination with refrigerant oil, the working medium containing composition can be considered to be composed of the mixed refrigerant and the refrigerant oil and other components.

[0084] The refrigerant oil (lubricating oil) contained in the working medium containing composition (used in combination with the working medium for a refrigeration cycle) can be appropriately used various refrigerant oils (lubricating oils) known in the refrigeration cycle system. As specific refrigerant oils, ester-based lubricating oils, ether-based lubricating oils, glycol-based lubricating oils, alkylbenzene-based lubricating oils, fluorine-based lubricating oils, mineral oils, hydrocarbon-based synthetic oils, and the like can be exemplified, but are not particularly limited. These refrigerant oils can be used alone or two or more can be appropriately combined and used.

[0085] Further, the working medium containing composition can also add various additives known per se. As specific additives, there can be mentioned antioxidants, moisture catchers, metal deactivators, anti-wear agents, antifoaming agents, and the like, but there is no particular limitation. The antioxidants serve to improve the thermal stability, oxidation resistance, chemical stability, and the like of the mixed refrigerant or the refrigerant oil. The moisture catchers serve to remove moisture in the event of moisture intrusion into the refrigeration cycle system, and in particular to suppress changes in the properties of the refrigerant oil. The metal deactivators serve to suppress or prevent chemical reactions induced by the catalytic action of metal components. The anti-wear agents serve to reduce wear of sliding portions in the compressor, particularly at the time of high-pressure operation. The antifoaming agents serve to suppress the generation of bubbles in the refrigerant oil, among other things.

[0086] The specific kinds of these additives are not particularly limited, and known compounds and the like can be used as appropriate in accordance with various conditions. Further, as these additives, one compound or the like can be used alone, or two or more compounds or the like can be used in appropriate combination. Further, the amounts of these additives to be added are not particularly limited, and can be added within a known range, provided that the properties of the working medium for a refrigeration cycle or the working medium containing composition containing the same used in the present application are not impaired.

[0087] Here, in the working medium for a refrigeration cycle used in the present application, as described above, a disproportionation inhibitor that is a gas or a liquid at normal temperature and normal pressure can also be added in advance. Specifically, for example, as the disproportionation inhibitor, there can be mentioned at least one of saturated hydrocarbons having 2 to 5 carbon atoms, halogenated alkanes in which the halogen atoms are not all fluorine except for those having 1 or 2 carbon atoms, and fluorinated alkanes having 1 to 3 carbon atoms having a boiling point of 0°C or lower (excluding difluoromethane), among others. These disproportionation inhibitors can be used alone or two or more can be used in appropriate combination.

[0088] As specific disproportionation inhibitors, for example, as saturated hydrocarbons, there can be mentioned ethane, n-propane, cyclopropane, n-butane, cyclobutane, isobutane (2-methylpropane), methylcyclopropane, n-pentane, isopentane (2-methylbutane), neopentane (2,2-dimethylpropane), methylcyclobutane, and the like, but there is no particular limitation. Of these, n-propane is particularly preferred.

[0089] In addition, as the halogenated alkane having 1 carbon atom, i.e., halogenated methane, for example, there can be mentioned (i) methyl iodide (CH3I), diiodomethane (CH2I2), dibromomethane (CH2Br2), bromomethane (CH3Br), dichloromethane (CH2Cl2), chloroiodomethane (CH2ClI), dibromochloromethane (CHBr2Cl), tetraiodomethane (CI4), carbon tetrabromide (CBr4), bromotrichloromethane (CBrCl3), dibromodichloromethane (CBr2Cl2), tribromofluoromethane (CBr3F), fluorodiiodomethane (CHFI2), difluorodiiodomethane (CF2I2), dibromodifluoromethane (CBr2F2), trifluoroiodomethane (CF3I), difluoroiodomethane (CHF2I), and the like, but there is no particular limitation. Among them, dibromomethane (CH2Br2), bromomethane (CH3Br), dibromodichloromethane (CBr2Cl2), or trifluoroiodomethane (CF3I), and the like are preferable, and trifluoroiodomethane (CF3I) is more preferable.

[0090] In addition, as the halogenated alkane having 2 carbon atoms, i.e., halogenated ethane, for example, there can be mentioned 1,1,1-trifluoro-2-iodoethane (CF3CH2I), monoiodoethane (CH3CH2I), monobromoethane (CH3CH2Br), 1,1,1-triiodoethane (CH3CI3), and the like. Among them, if the availability, the value of ODP, the handling easiness, and the like are taken into consideration, 1,1,1-trifluoro-2-iodoethane (CF3CH2I) can be particularly preferable.

[0091] In addition, as the fluoroalkane having 1 to 3 carbon atoms, for example, there can be mentioned fluoromethane (boiling point -78.2°C), difluoromethane (boiling point -51.6°C), trifluoromethane (boiling point -84.4°C), tetrafluoromethane (boiling point -127.8°C), and the like, fluoromethane; fluoroethane (boiling point -37.1°C), 1,1-difluoroethane (boiling point -24.7°C), 1,1,1-trifluoroethane (boiling point -47.2°C), 1,1,1,2-tetrafluoroethane (boiling point -26.3°C), 1,1,1,2,2-pentafluoroethane (boiling point -48.5°C), and the like, fluoroethane; 1-fluoropropane (boiling point -2.5°C), 2-fluoropropane (boiling point -10.0°C), 2,2-difluoropropane (boiling point -1.0°C), 1,1,1-trifluoropropane (boiling point -12.0°C), 1,1,2,2-tetrafluoropropane (boiling point -0.8°C), 1,1,1,3,3,3-hexafluoropropane (boiling point -1.4°C), and the like, fluoropropane; and the like.

[0092] The addition amount of the disproportionation inhibitor is not particularly limited, and the upper limit of the addition amount (content) of the disproportionation inhibitor can be 10% by mass or less, preferably 5% by mass or less, and more preferably 3% by mass or less, based on 100% by mass of the total amount of the refrigerant-related components (total amount of the mixed refrigerant and the disproportionation inhibitor). If the content of the disproportionation inhibitor exceeds 10% by mass of the total amount of the refrigerant-related components, the content of the disproportionation inhibitor is too large when viewed as a working medium for a refrigeration cycle, and the disproportionation inhibitor can not exhibit good properties as a "refrigerant". Of course, 10% by mass or more of the total amount of the refrigerant-related components can be added, depending on the composition of the working medium for a refrigeration cycle.

[0093] As the disproportionation inhibitor, two or more of the saturated hydrocarbon, the halogenated alkane, and the fluoroalkane can be used in combination, as described above. In this case, the mixing ratio of the saturated hydrocarbon, the halogenated alkane, and the fluoroalkane is not particularly limited. As the preferable content of the total amount of the disproportionation inhibitor, 10% by mass or less can be cited, and therefore two or more of the saturated hydrocarbon, the halogenated alkane, and the fluoroalkane can be used in combination in an appropriate mixing ratio within this range.

[0094] In addition, in the present application, a plurality of compounds can be used in combination as the saturated hydrocarbon, the halogenated alkane, and the fluoroalkane, respectively. Therefore, the use of two or more of the saturated hydrocarbon, the halogenated alkane, and the fluoroalkane described herein means that two or more of one or more compounds classified as a saturated hydrocarbon, one or more compounds classified as a halogenated alkane, and one or more compounds classified as a fluoroalkane can be used in combination.

[0095] Here, the saturated hydrocarbon, the halogenated alkane, and the fluoroalkane can suppress or alleviate the progress of the disproportionation reaction even if each is added in an amount of 10% by mass or less. Further, in the case where two or more of the saturated hydrocarbon, the halogenated alkane, and the fluoroalkane are used in combination as in the present application, the suppression or alleviation of the disproportionation reaction can be achieved in a smaller amount than in the case where only one kind is added. More specifically, the upper limit of the addition amount of the total amount of the disproportionation inhibitor (total amount of two or more of the saturated hydrocarbon, the halogenated alkane, and the fluoroalkane) can be 10% by mass or less, and can be 5% by mass or less, and in the case where the saturated hydrocarbon and the halogenated alkane are combined, 3% by mass or less can be cited as a more preferable upper limit.

[0096] At this time, the mixing ratio of two or more of the saturated hydrocarbon, the halogenated alkane, and the fluoroalkane is not particularly limited. For example, if the saturated hydrocarbon and the halogenated alkane are used in combination, in the case where the additive amount is 3 mass% or less, as a representative example of the mixing ratio of the saturated hydrocarbon and the halogenated alkane, the mass ratio can be exemplified in the range of 1 : 0.5 to 1 : 2. Here, as the combination of the saturated hydrocarbon and the halogenated alkane, three can be exemplified, and thus representative mixing ratios for each combination are as follows: [1] in the combination in which the saturated hydrocarbon, the halogenated ethane, and the halogenated methane are used in combination, the mass ratio can be exemplified in the range of 1 : 0.25 : 0.25 to 1 : 1 : 1, [2] in the combination in which the saturated hydrocarbon and the halogenated ethane are used in combination, the mass ratio can be exemplified in the range of 1 : 0.25 to 1 : 1, and [3] in the combination in which the saturated hydrocarbon and the halogenated methane are used in combination, the mass ratio can be exemplified in the range of 1 : 0.25 to 1 : 1.

[0097] Further, the lower limit value of the additive amount of two or more of the saturated hydrocarbon, the halogenated alkane, and the fluoroalkane is also not particularly limited, but as a representative lower limit value, 1.2 mass% or more of the total amount of the refrigerant-related components can be exemplified. Even if the total amount of two or more of the saturated hydrocarbon, the halogenated alkane, and the fluoroalkane is less than 1.2 mass%, the effects such as the suppression of the disproportionation reaction can be obtained, but if it is 1.2 mass% or more, the effects such as the suppression of the disproportionation reaction can be more appropriately achieved. Thus, in the present application, as a more preferable range of the content of two or more of the saturated hydrocarbon, the halogenated alkane, and the fluoroalkane, the range of 1.2 mass% or more and 3 mass% or less of the total amount of the refrigerant-related components can be exemplified.

[0098] In addition, generally, the impurities contained in the refrigerant used in the refrigeration cycle system are 2 to 3 mass% or less. For example, it is known that the purity of the 1,1,2-trifluoroethylene commercially available is about 97 mass%, and as impurities, less than 3 mass% of the remaining portion of the synthetic raw material or a by-product is contained.

[0099] The disproportionation inhibitor can effectively suppress or alleviate the progress of the disproportionation reaction even if it is added to the hydrofluoroolefin at an impurity level (3 mass% or less). Thus, the additive amount of the saturated hydrocarbon and the halogenated alkane as the disproportionation inhibitor is not necessarily particularly limited, and the upper limit value, the lower limit value, or the additive amount of the disproportionation inhibitor described above is ultimately only a representative preferred example exemplified.

[0100] [Control example of refrigeration cycle system]

[0101] Next, with reference to Figure 2 A, Figure 3 B, and Figure 2 , a control example of the refrigeration cycle system according to the present application will be specifically described.

[0102] Figure 2A is a graph schematically showing how the conditions of the disproportionation reaction of the hydrofluoroolefin change when the compressor 20 is started from a stopped state and passes a certain time to enter a normal operation state. Figure 2 The vertical axis of A is the internal pressure of the compressor 20 (unit: Pa), and the horizontal axis is the discharge gas temperature of the compressor 20 (unit: °C).

[0103] In Figure 2 In A, as the refrigerant contained in the working medium for the refrigeration cycle, 1,1,2-trifluoroethene (HFO1123) is used as the hydrofluoroolefin, and propane (R290) is used as the other refrigerant (high solubility refrigerant). That is, in Figure 2 In A, the mixed refrigerant as the working medium for the refrigeration cycle is composed of 1,1,2-trifluoroethene and propane. In addition, for convenience of explanation, the conditions of the disproportionation reaction of 1,1,2-trifluoroethene are referred to as "disproportionation conditions".

[0104] Figure 2 The circular symbol in A is the disproportionation condition immediately after the start of the compressor 20 from the stopped state. In addition, the diamond symbol is the disproportionation condition after a prescribed time tl, that is, after the compressor 20 enters the normal operation state. In the state where the compressor 20 is stopped, it is considered that the mixed refrigerant is in contact with the refrigeration oil inside the compressor 20 at normal temperature and normal pressure. Therefore, propane, which has a relatively large oil solubility, is relatively much dissolved in the refrigeration oil, and 1,1,2-trifluoroethene, which has a relatively small oil solubility, is less dissolved in the refrigeration oil than propane.

[0105] In this state, the control section 21 starts the compressor 20. At this time, the composition of the mixed refrigerant is different from the refrigerant composition in the stable operation state, and a refrigerant composition in which the content of 1,1,2-trifluoroethene relatively increases while the content of propane relatively decreases due to the dissolution of propane is formed. If this composition is referred to as, for example, "HFO-rich refrigerant composition", then in the HFO-rich composition, the disproportionation reaction occurs at a relatively lower pressure and temperature than in the stable operation state. This is Figure 2 The disproportionation condition immediately after the start shown by the circular symbol in A. In addition, the internal pressure of the compressor 20 in the disproportionation condition immediately after the start is set to Pi Pa, and the discharge gas temperature is set to Ti °C. In addition, the refrigerant composition in the stable operation state is a refrigerant composition that is assumed in the control of the refrigeration cycle system (air conditioner 10) in order to suppress the disproportionation reaction.

[0106] After that, if the start condition of the compressor 20 is satisfied, the control unit 21 increases the operation frequency of the compressor 20 at a predetermined speed. Until the temperature of the object space (room) of the indoor unit 12 set in the refrigeration cycle is brought to the vicinity of the set temperature, the control unit 21 operates the compressor 20 at the maximum frequency. Thus, the internal pressure of the compressor 20 also gradually increases, and the discharge gas temperature also gradually increases. Then, the operation of the compressor 20 stabilizes, and the normal operation state is entered.

[0107] In the normal operation state, the propane dissolved in the refrigerant oil is separated and returned to the mixed refrigerant. Therefore, the refrigerant composition in the normal operation state becomes a state in which 1,1,2-trifluoroethylene is relatively more, compared to the composition immediately after the start, i.e., the HFO-rich composition. The refrigerant composition in the normal operation state is a composition at which the disproportionation reaction occurs at relatively higher temperature and pressure, compared to the disproportionation condition immediately after the start. This is because Figure 2 The disproportionation condition in the normal operation state indicated by the rhombus symbol in A.

[0108] In addition, if the internal pressure of the compressor 20 under the disproportionation condition in the normal operation state is set to Pii Pa, and the discharge gas temperature is set to Tii °C, the internal pressure Pii Pa is greater than the internal pressure Pi Pa immediately after the start (Pii > Pi), and the discharge gas temperature Tii °C is greater than the discharge gas temperature Ti °C immediately after the start (Tii > Ti).

[0109] Therefore, by the control of the control unit 21, when the compressor 20 shifts from the start to the normal operation state, the disproportionation condition of the mixed refrigerant (working medium for the refrigeration cycle) transitions from the relatively low-temperature and low-pressure condition to the high-temperature and high-pressure condition, as indicated by the dotted arrow in the figure.

[0110] In the case where the working medium for the refrigeration cycle contains a hydrofluoroolefin, if it is assumed that the occurrence of the disproportionation reaction is suppressed, the upper limit values of the internal pressure and the internal temperature of the compressor 20 should be set to be lower than the pressure and the temperature of the disproportionation condition in the normal operation state. The upper limit values of the internal pressure and the internal temperature are predetermined values set as the pressure and the temperature at the time of the protection control start of the compressor 20. In addition, the upper limit value of the internal pressure is usually the design pressure of the compressor 20, and the upper limit value of the internal temperature is usually the specification temperature of the compressor 20.

[0111] In the present embodiment, for example, the upper limit value of the internal pressure described above is set to "pressure upper limit value P1", and the upper limit value of the discharge gas temperature corresponding to the upper limit value of the internal pressure described above is set to "temperature upper limit value T1", as Figure 2The upper limit value P1 of the pressure and the upper limit value T1 of the temperature are each set to a value smaller than the internal pressure Pii Pa and the discharge gas temperature Tii °C as the disassociation condition in the normal operation state.

[0112] On the contrary, in the case where the working medium for the refrigeration cycle contains a high solubility refrigerant having a higher oil solubility than the hydrogen fluorinated olefin, as Figure 2 As shown in A, the disassociation condition immediately after the start-up is a relatively low pressure and temperature compared to the disassociation condition in the normal operation state. Therefore, the internal pressure Pi Pa and the discharge gas temperature Ti °C of the disassociation condition immediately after the start-up can be smaller than the upper limit value P1 of the pressure and the upper limit value T1 of the temperature.

[0113] Therefore, in the refrigeration cycle system according to the present application, as Figure 2 As shown in B, when the refrigerant composition is HFO-rich immediately after the start-up of the compressor 20, an "initial upper limit value P0 of the pressure" (P0 < P1) lower than the upper limit value P1 of the pressure and an "initial upper limit value T0 of the temperature" (T0 < T1) lower than the upper limit value T1 of the temperature are set. When the compressor 20 is continuously operated, the mixed refrigerant in the refrigeration cycle is sufficiently circulated, and the refrigerant composition is restored from the HFO-rich composition to the predetermined composition, the initial upper limit value P0 of the pressure is restored to the original upper limit value P1 of the pressure, the initial upper limit value T0 of the temperature is restored to the original upper limit value T1 of the temperature, and the operation control of the compressor 20 is continued.

[0114] Thus, during the period from immediately after the start-up of the compressor 20 to the HFO-rich refrigerant composition, the probability of the hydrogen fluorinated olefin undergoing the disassociation reaction can be well suppressed. As a result, the reliability of the refrigeration cycle system (for example, the air conditioner 10) can be further improved.

[0115] Referring to Figure 2 B, the control of such a refrigeration cycle system will be described in more detail. Figure 2 B is a graph showing an example of the control of the control unit 21 on the upper limit values of the internal pressure and the internal temperature of the compressor 20. Figure 2 The vertical axis of B is the ratio of the internal pressure to the discharge gas temperature of the compressor 20, and the horizontal axis is time. Further, Figure 2 The circular symbol and the diamond symbol in B respectively correspond to Figure 2 A, which are the disassociation condition immediately after the start-up and the disassociation condition in the normal operation state.

[0116] In Figure 3In B, time = 0 corresponds to the time when the compressor 20 is started. If the compressor 20 satisfies the start condition, the control section 21 raises the operation frequency of the compressor 20 at a predetermined speed. Thereafter, until the control section 21 causes the compressor 20 to operate at the maximum frequency, before the mixed refrigerant in the refrigeration cycle is sufficiently circulated and the refrigerant composition returns to the original refrigerant composition (i.e., the refrigerant composition in the normal operation state) from the HFO-enriched refrigerant composition, the control section 21 causes the compressor 20 to operate at the maximum frequency.

[0117] At this time, the control section 21 sets the upper limit values of the internal pressure and the internal temperature to the initial pressure upper limit value P0 and the initial temperature upper limit value T0. In Figure 1 In B, it is written as P0 / T0. The upper limit value of this P0 / T0 is lower than the value of the disproportionation condition Pi / Ti immediately after the start shown by the circular symbol in the figure. At the disproportionation condition Pi / Ti immediately after the start, the mixed refrigerant is the HFO-enriched refrigerant composition.

[0118] Thereafter, when the compressor 20 continues to operate at the maximum frequency, the high-solubility refrigerant that has been dissolved gradually separates from the refrigeration oil inside the compressor 20, and the concentration of the high-solubility refrigerant in the mixed refrigerant gradually increases, and the concentration of the hydrofluoroolefin gradually decreases. Eventually, at the time of reaching Figure 2 In B, at the time of time = tf, the concentration of the high-solubility refrigerant becomes a predetermined value, and the refrigerant composition returns to the refrigerant composition that is assumed in advance. At this time, the disproportionation condition becomes the disproportionation condition Pii / Tii of the normal operation state shown by the diamond symbol in the figure.

[0119] The control section 21 changes the upper limit values of the internal pressure and the internal temperature from the initial pressure upper limit value P0 / initial temperature upper limit value T0 to the pressure upper limit value P1 / temperature upper limit value T1 (P1 / T1) at the time of reaching time = tl with a margin from the time tf. Thus, even when the mixed refrigerant is the HFO-enriched refrigerant composition at the time of starting the compressor 20, it is possible to effectively suppress the probability of occurrence of the disproportionation reaction. In addition, the period from the time immediately after starting the compressor 20 (time = 0) to the time of reaching time = tl is the initial period of the operation of the compressor 20.

[0120] With regard to the control of the refrigeration cycle system by such a control section 21, refer to Figure 2 (And Figure 2 B) for a more specific control example.

[0121] First, the control section 21, when starting the operation of the compressor 20, performs normal control on the compressor 20 and the expansion valve 16 (step S01). The operation of the compressor 20 is controlled by the operation frequency as described above. At this time, the upper limit values of the internal pressure and the internal temperature in the control of the compressor 20 are the initial pressure upper limit value P0 and the initial temperature upper limit value T0 as described above (refer to​ B). The opening degree of the expansion valve 16 is controlled in accordance with the discharge gas temperature (or the superheat degree on the suction side of the compressor 20).

[0122] Next, the control section 21 measures the internal pressure of the compressor 20 by the pressure sensor 22 and the discharge gas temperature by the temperature sensor 23 (step S02). Thereafter, the control section 21 determines whether or not the time = tl has elapsed since the start of the operation of the compressor 20 (refer to FIG. 2) (step S03). If tl has not elapsed (No in step S03), it is determined whether or not the measured pressure value exceeds the initial pressure upper limit value P0 (step S04). If the pressure value does not exceed P0 (No in step S04), it is determined whether or not the measured discharge gas temperature exceeds the initial temperature upper limit value T0 (step S05). If the discharge gas temperature does not exceed T0 (No in step S05), the normal control of step S01 is repeated. ​ B) (step S03). If tl has not elapsed (No in step S03), it is determined whether or not the measured pressure value exceeds the initial pressure upper limit value P0 (step S04). If the pressure value does not exceed P0 (No in step S04), it is determined whether or not the measured discharge gas temperature exceeds the initial temperature upper limit value T0 (step S05). If the discharge gas temperature does not exceed T0 (No in step S05), the normal control of step S01 is repeated.

[0123] On the other hand, when the measured pressure value exceeds P0 (Yes in step S04) or the measured discharge gas temperature exceeds T0 (Yes in step S05), the control section 21 lowers the operation frequency of the compressor 20 and raises the opening degree of the expansion valve 16 (step S06). Thereafter, when a certain time elapses (step S07), the measurement of the internal pressure of the compressor 20 and the discharge gas temperature is again returned to step S02.

[0124] That is, when the measured value of the internal pressure reaches a predetermined pressure (the initial pressure upper limit value P0) (Yes in step S04) while the compressor 20 is operating, a protection control operates which lowers the operation frequency of the compressor 20 or raises the opening degree of the expansion valve 16, or performs both of the lowering of the operation frequency and the raising of the opening degree of the expansion valve 16 (step S06). This protection control continues for a certain time, and if the internal pressure of the compressor 20 decreases (step S07), the compressor 20 returns to the normal control, and the operation frequency also returns to the normal frequency. Thereafter, the measurement of the internal pressure is again repeated (step S02).

[0125] The control of the expansion valve 16 is also the same, and when the measured value of the discharge gas temperature reaches a predetermined temperature (the initial temperature upper limit value T0) (Yes in step S05), a protection control operates which raises the opening degree of the expansion valve 16, or lowers the operation frequency of the compressor 20, or performs both of the opening degree control of the expansion valve 16 and the operation frequency control (step S06). This protection control continues for a certain time, and if the discharge gas temperature of the compressor 20 decreases (step S07), the expansion valve 16 returns to the normal control, and the opening degree of the expansion valve 16 also returns to the normal opening degree. Thereafter, the measurement of the discharge gas temperature is again repeated (step S02).

[0126] Here, if the elapsed time from the start of the operation of the compressor 20 = tl (YES in step S03), the control unit 21 changes the set value of the internal pressure from the initial pressure upper limit value P0 to the pressure upper limit value Pl, and changes the set value of the discharge gas temperature from the initial temperature upper limit value T0 to the temperature upper limit value Tl (refer to FIG. 2B). Thus, the control unit 21 determines whether the measured pressure value exceeds the pressure upper limit value Pl (step S08), and if the pressure value does not exceed Pl (NO in step S08), determines whether the measured discharge gas temperature exceeds the temperature upper limit value Tl (step S09). ​ B). Thus, the control unit 21 determines whether the measured pressure value exceeds the pressure upper limit value Pl (step S08), and if the pressure value does not exceed Pl (NO in step S08), determines whether the measured discharge gas temperature exceeds the temperature upper limit value Tl (step S09).

[0127] If the discharge gas temperature does not exceed Tl (NO in step S09), the control returns to the normal control of step S01, and when the measured pressure value exceeds Pl (YES in step S08) or the measured discharge gas temperature exceeds Tl (YES in step S09), the control unit 21 lowers the operation frequency of the compressor 20 and raises the opening degree of the expansion valve 16 (step S06). The control returns again to step S02 to measure the internal pressure and the discharge gas temperature of the compressor 20.

[0128] The control in the case where the set values of the internal pressure and the internal temperature are changed from P0 / T0 to Pl / Tl is also the same as the control in the case of P0 / T0 described above. That is, in the case where the measured value of the internal pressure reaches the set pressure (the pressure upper limit value Pl) (YES in step S08), the protection control works (step S06), and if the internal pressure of the compressor 20 is lowered (step S07), the compressor 20 returns to the normal control and the measurement of the internal pressure is repeated again (step S02). Further, in the case where the measured value of the discharge gas temperature reaches the set temperature (the temperature upper limit value Tl) (YES in step S09), the protection control works (step S06). If the discharge gas temperature of the compressor 20 is lowered (step S07), the expansion valve 16 returns to the normal control and the measurement of the discharge gas temperature is repeated again (step S02).

[0129] Here, the specific structure of the control unit 21 that performs the control of the refrigeration cycle system described above is not particularly limited. For example, the control unit 21 described in the present embodiment can be configured by an arithmetic device and a storage device of a microcomputer or a microcontroller.

[0130] The storage device that configures the control unit 21 can be configured as an internal memory of a microcomputer or a microcontroller, or as an independent memory or a storage device. Further, the storage device is not necessarily a single structure, and can be configured as a plurality of storage devices (for example, an internal memory and an external hard disk drive or an SSD, etc.).

[0131] The arithmetic device constituting the control unit 21 can adopt a configuration in which a general-purpose processor, a dedicated processor, an integrated circuit, an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), a GPU, or the like is used alone or in combination of two or more, and operates in a manner to realize the function of the control unit according to a program stored in the storage device.

[0132] The processor as the arithmetic device is a circuit (or processing circuit) as hardware because it includes a circuit constituted by a large number of transistors, memories, and the like. The integrated circuit or the ASIC also includes a processor such as a CPU or a processing module, and is also a circuit as hardware. The FPGA is a circuit as hardware because it includes a large number of logic circuits (function modules) integrated. The GPU is a circuit as hardware because it includes a large number of arithmetic circuits (computing cores) loaded in parallel. The software such as a program stored in the storage device is used to construct a circuit as hardware (processor, integrated circuit, FPGA, ASIC, GPU, and the like). Alternatively, the arithmetic device can be configured as a logic circuit or the like realized by a known switching element, subtracter, comparator, and the like.

[0133] As such, the refrigeration cycle system according to the present application uses a mixed refrigerant as a working medium for a refrigeration cycle, the mixed refrigerant containing at least one hydrofluoroolefin and at least one high-solubility refrigerant having a solubility in the above-mentioned refrigeration machine oil higher than that of the hydrofluoroolefin. Further, when an upper limit value of the internal pressure preset in the compressor 20 is set as a pressure upper limit value P1 and an upper limit value of the discharge gas temperature is set as a temperature upper limit value T1, the control unit 21 sets the upper limit value of the internal pressure to an initial pressure upper limit value P0 (P0 < P1) and sets the upper limit value of the discharge gas temperature to an initial temperature upper limit value T0 (T0 < T1) to control at least one of the rotation speed of the compressor 20 and the opening degree of the expansion valve 16 from the start of the compressor 20 until a prescribed time tl elapses. Further, after the prescribed time tl elapses, the upper limit value of the internal pressure is changed from the initial pressure upper limit value P0 to the pressure upper limit value P1, and the upper limit value of the discharge gas temperature is changed from the initial temperature upper limit value T0 to the temperature upper limit value T1 to control at least one of the rotation speed of the compressor 20 and the opening degree of the expansion valve 16.

[0134] When the working medium for the refrigeration cycle is the mixed refrigerant containing the hydrofluoroolefin and the high-solubility refrigerant as described above, the high-solubility refrigerant is relatively much dissolved in the refrigerant oil at the time when the compressor 20 is stopped. Therefore, at the time when the compressor 20 is started, the hydrofluoroolefin is relatively much in the mixed refrigerant, and the conditions (disproportionation conditions) of the internal pressure and the internal temperature (discharge gas temperature) at which the disproportionation reaction occurs are lower than those of the usual refrigerant composition.

[0135] Therefore, in the refrigeration cycle system according to the present application, the upper limit values of the internal pressure and the discharge gas temperature at which the protection control is triggered are set to P0 and T0 which are lower than the predetermined values P1 and T1 at the operation start initial stage from the time when the compressor 20 is started until the elapse of the prescribed time t1. The control section 21 controls the compressor 20 and the expansion valve 16 based on the P0 / T0 at the operation start initial stage. After the operation start initial stage ends and the usual operation is entered, the control section 21 changes the upper limit values of the internal pressure and the discharge gas temperature from the P0 / T0 to the P1 / T1 of the predetermined values, to control the compressor 20 and the expansion valve 16.

[0136] Thus, even at the operation start initial stage at which the concentration of the hydrofluoroolefin is relatively high and the disproportionation reaction easily occurs, the occurrence probability of the disproportionation reaction can be favorably suppressed. Further, after the usual operation is entered from the operation start initial stage, the occurrence of the disproportionation reaction can be favorably suppressed or mitigated. As a result, the reliability of the refrigeration cycle system can be further improved.

[0137] In addition, the present application is not limited to the description of the above-described embodiments, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining the technical means respectively disclosed in different embodiments or modified examples are also included in the technical scope of the present application.

[0138] Further, many modifications and other embodiments of the application will come to mind to one skilled in the art to which the application pertains having the benefit of the teachings presented in the foregoing descriptions. Therefore, it is to be understood that the application is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions have been described in the context of particular embodiments, it should be appreciated that particular embodiments include not only the exemplary constructions falling within the scope of the appended claims, but also equivalents and modifications of the exemplary constructions.

[0139] (Postscript)

[0140] By the description of the above embodiments, the following technical contents are disclosed in the present specification.

[0141] (Technique 1) A refrigeration cycle system including: a refrigeration cycle including a compressor and an expansion valve that internally store refrigeration oil; and a control section that uses a mixed refrigerant as a working medium for the refrigeration cycle, the mixed refrigerant containing at least one hydrofluoroolefin and at least one high solubility refrigerant having a higher solubility to the refrigeration oil than the hydrofluoroolefin, when an upper limit value of an internal pressure in the compressor is set to P1 and an upper limit value of a discharge gas temperature is set to T1, the control section controls at least one of a rotational speed of the compressor and an opening degree of the expansion valve during a period from when the compressor is started to when a prescribed time tl elapses, by setting the upper limit value of the internal pressure to PO (PO < P1) that is smaller than P1 and setting the upper limit value of the discharge gas temperature to TO (TO < T1) that is smaller than T1, and after the prescribed time tl elapses, controls at least one of the rotational speed of the compressor and the opening degree of the expansion valve by changing the upper limit value of the internal pressure from PO to P1 and changing the upper limit value of the discharge gas temperature from TO to T1.

[0142] (Technique 2) The refrigeration cycle system according to Technique 1, including a pressure sensor that measures the internal pressure of the compressor, and the control section controls at least one of the rotational speed of the compressor and the opening degree of the expansion valve using a pressure value measured by the pressure sensor.

[0143] (Technique 3) The refrigeration cycle system according to Technique 1, including a first temperature sensor that measures the internal pressure of the compressor approximately according to temperature, and the control section controls at least one of the rotational speed of the compressor and the opening degree of the expansion valve using a pressure value indirectly measured by the first temperature sensor.

[0144] (Technique 4) The refrigeration cycle system according to any one of Techniques 1 to 3, including a second temperature sensor that measures a temperature of a discharge gas from the compressor, and the control section controls at least one of the rotational speed of the compressor and the opening degree of the expansion valve using the discharge gas temperature measured by the second temperature sensor.

[0145] (Technique 5) The refrigeration cycle system according to any one of Techniques 1 to 4, wherein the high solubility refrigerant is a saturated hydrocarbon.

[0146] (Technique 6) The refrigeration cycle system according to Technique 5, wherein the saturated hydrocarbon is propane (R290).

[0147] (Technique 7) The refrigeration cycle system according to any one of Techniques 1 to 6, wherein the working medium for the refrigeration cycle further contains a disproportionation inhibitor.

[0148] Industrial applicability

[0149] The present application can be widely applied to the field of refrigeration cycle systems using a working medium for a refrigeration cycle using a hydrogen fluoride olefin (HFO) and other refrigerants as a refrigerant component, such as air conditioning devices (air conditioners), refrigerators (household, commercial), dehumidifiers, display cases, ice makers, heat pump water heaters, heat pump laundry dryers, vending machines, and the like.

[0150] BRIEF DESCRIPTION OF DRAWINGS

[0151] 10: Air conditioner (refrigeration cycle system)

[0152] 11: Outdoor unit

[0153] 12: Indoor unit

[0154] 13: Inter-unit piping

[0155] 13a: Piping connection portion

[0156] 13b: Piping connection portion

[0157] 14: Outdoor heat exchanger

[0158] 15: Outdoor fan

[0159] 16: Expansion valve

[0160] 17: Switching valve

[0161] 18: Indoor heat exchanger

[0162] 19: Indoor fan

[0163] 20: Compressor

[0164] 21: Control portion

[0165] 22: Pressure sensor

[0166] 23: Temperature sensor

Claims

1. A refrigeration cycle system, characterized in that, include: The refrigeration cycle includes a compressor and an expansion valve that internally store refrigeration oil; and Control Department A mixed refrigerant is used as the working medium for the refrigeration cycle, wherein the mixed refrigerant contains at least one hydrofluoroolefin and at least one refrigerant with higher solubility in the refrigeration oil than the hydrofluoroolefin. Let the upper limit of the internal pressure in the compressor be P1, and the upper limit of the discharge gas temperature be T1. The control unit sets the upper limit of the internal pressure to P0 (P0 < P1), which is less than P1, and the upper limit of the discharge gas temperature to T0 (T0 < T1), which is less than T1, during a predetermined time t1, in order to control at least one of the compressor speed and the opening degree of the expansion valve. After the specified time t1, the upper limit of the internal pressure is changed from P0 to P1, and the upper limit of the exhaust gas temperature is changed from T0 to T1, so as to control at least one of the compressor speed and the opening degree of the expansion valve.

2. The refrigeration cycle system as described in claim 1, characterized in that: Includes a pressure sensor that measures the internal pressure of the compressor. The control unit uses the pressure value measured by the pressure sensor to control at least one of the compressor speed and the opening degree of the expansion valve.

3. The refrigeration cycle system as described in claim 1, characterized in that: This includes a first temperature sensor that approximates the internal pressure of the compressor based on temperature. The control unit uses the pressure value indirectly measured by the first temperature sensor to control at least one of the compressor speed and the opening degree of the expansion valve.

4. The refrigeration cycle system as described in claim 1, characterized in that: Includes a second temperature sensor that measures the temperature of the exhaust gas from the compressor. The control unit uses the exhaust gas temperature measured by the second temperature sensor to control at least one of the compressor speed and the opening degree of the expansion valve.

5. The refrigeration cycle system according to any one of claims 1 to 4, characterized in that: The highly soluble refrigerant is a saturated hydrocarbon.

6. The refrigeration cycle system as described in claim 5, characterized in that: The saturated hydrocarbon is propane (R290).

7. The refrigeration cycle system according to any one of claims 1 to 4, characterized in that: The working medium for the refrigeration cycle also contains a disproportionation inhibitor.

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