Air conditioning apparatus

Abstract

The present disclosure provides an air conditioning apparatus capable of driving a motor-driven compressor while maintaining a state lower than a lower limit at which a refrigerant undergoes a self-decomposition reaction and thereby inhibiting the refrigerant from undergoing a self-decomposition reaction. The air conditioning apparatus according to the present disclosure, in which an engine-driven compressor 12 that uses a gas engine 11 as a drive source and a motor-driven compressor 14 that uses an electric motor 13 as a drive source are connected to each other in parallel, performs air conditioning by circulating a refrigerant comprising HFO-1123. The air conditioning apparatus is operable in an operation mode in which only the engine-driven compressor 12 is driven, an operation mode in which only the motor-driven compressor 14 is driven, and an operation mode in which the engine-driven compressor 12 and the motor-driven compressor 14 are driven. The air conditioning apparatus includes a controller 40 configured to stop at least the motor-driven compressor 14 in the operation modes in which the motor-driven compressor 14 is driven, if a temperature of the refrigerant discharged from the motor-driven compressor 14 reaches a first set value.

Description

[Technical Field]

[0001] The present disclosure relates to an air conditioning apparatus.[Background Art]

[0002] Patent Literature 1 discloses an air conditioning apparatus in which a compressor having a large volume is driven by a gas engine and a compressor having a small volume is driven by an electric motor, where the compressors are driven individually or in combination according to the magnitude of a load required.[Citation List][Patent Literature]

[0003] [Patent Literature 1] Japanese Patent Laid-Open No. 2003-056931[Summary of Invention][Technical Problem]

[0004] The present disclosure provides an air conditioning apparatus capable of driving a motor-driven compressor while maintaining a temperature of a refrigerant lower than a lower limit at which the refrigerant undergoes a self-decomposition reaction and thereby inhibiting the refrigerant from undergoing a self-decomposition reaction.[Solution to Problem]

[0005] An air conditioning apparatus in the present disclosure, in which an engine-driven compressor that uses a gas engine as a drive source and a motor-driven compressor that uses an electric motor as a drive source are connected to each other in parallel, performs air conditioning by circulating a refrigerant including HFO-1123, wherein the air conditioning apparatus is operable in an operation mode in which only the engine-driven compressor is driven, an operation mode in which only the motor-driven compressor is driven, and an operation mode in which the engine-driven compressor and the motor-driven compressor are driven, and the air conditioning apparatus includes a controller configured to stop at least the motor-driven compressor in the operation modes in which the motor-driven compressor is driven, if a temperature of the refrigerant discharged from the motor-driven compressor reaches a first set value.

[0006] The contents of Japanese Patent Application No. 2023-006771 filed on January 19, 2023 are incorporated herein in its entirety.[Advantageous Effect of Invention]

[0007] The air conditioning apparatus in the present disclosure is capable of performing control to stop a motor-driven compressor in a state in which the temperature of a refrigerant discharged from the motor-driven compressor is above a first set value and thereby inhibiting the refrigerant from undergoing a self-decomposition reaction.[Brief Description of Drawings]

[0008] [FIG. 1] FIG. 1 is a refrigeration cycle diagram showing an air conditioning apparatus in a first embodiment. [FIG. 2] FIG. 2 is a block diagram showing a control configuration in the first embodiment. [FIG. 3] FIG. 3 is a diagram showing an example of operation mode switching control with respect to an air conditioning load in the first embodiment. [FIG. 4] FIG. 4 is a refrigeration cycle diagram showing an air conditioning apparatus in a second embodiment. [Description of Embodiments](Knowledge and the like underlying the present disclosure)

[0009] As of the inventors' conception of the present disclosure, there has been an air conditioning apparatus that combines an electric compressor and an engine-driven compressor having different displacement volumes. This air conditioning apparatus achieves efficient operation by operating the electric compressor and the engine-driven compressor individually or in combination depending on the load to thereby maintain the rotation speeds of the compressors and the rotation speeds of the motor and the engine within a high-efficiency range.

[0010] However, the inventors have found issues with this conventional configuration. When a refrigerant including HFO-1123 is used as the refrigerant in this air conditioning apparatus, and if voltage is applied to magnet coils for the electric-motor-driven compressor while their electrical insulation is degraded and the discharge temperature of the refrigerant is equal to or greater than a certain value, the refrigerant may undergo a self-decomposition reaction, resulting in a sharp increase in the refrigerant pressure. To solve these issues, the inventors have come up with a configuration of the subject matter of the present disclosure.

[0011] The present disclosure provides an air conditioning apparatus capable of driving a motor-driven compressor while maintaining a temperature of a refrigerant lower than a lower limit at which the refrigerant undergoes a self-decomposition reaction and thereby inhibiting the refrigerant from undergoing a self-decomposition reaction.

[0012] Some embodiments are described in detail below with reference to the drawings. However, an unnecessarily detailed description may be omitted. For example, detailed descriptions of matters that have been already well known, or redundant descriptions of substantially identical constituent elements may be omitted. This is to avoid making the descriptions below unnecessarily lengthy and to facilitate understanding of the description for those skilled in the art.

[0013] Note that the accompanying drawings and the following descriptions are provided for those skilled in the art to sufficiently understand the present disclosure and are not intended to limit the subject matter recited in the claims.(First embodiment)

[0014] A first embodiment is described below with reference to the drawings.[1-1. Configuration][1-1-1. Configuration of refrigeration cycle]

[0015] FIG. 1 is a refrigeration cycle diagram showing an air conditioning apparatus in the first embodiment.

[0016] As shown in FIG. 1, an air conditioning apparatus 1 according to the present embodiment includes an outdoor unit 10 and an indoor unit 30. Although only one indoor unit 30 is shown in FIG. 1, a plurality of parallel indoor units may be installed with respect to the outdoor unit 10.

[0017] The outdoor unit 10 includes: a gas engine 11 that uses gas as its drive source; an engine-driven compressor 12 that obtains a driving force from the gas engine 11 to compress a refrigerant: and a motor-driven compressor 14 that uses an electric motor 13 as its drive source. In the present embodiment, the engine-driven compressor 12 has a higher capacity than that of the motor-driven compressor 14.

[0018] Refrigerant outlets from the engine-driven compressor 12 and the motor-driven compressor 14 are joined together where an oil separator 15 is provided. The oil separator 15 separates oil from a refrigerant gas discharged from the engine-driven compressor 12 and the motor-driven compressor 14.

[0019] An outdoor heat exchanger 17 is connected to a downstream side from the oil separator 15 via a four-way valve 16. The four-way valve 16 is provided to switch the refrigeration cycle between cooling and heating. In FIG. 1, during a heating operation, the refrigerant flows as shown with a solid line in the figure, and during a cooling operation, the refrigerant flows as shown with a dashed line in the figure.

[0020] A radiator 18 for cooling a coolant of the gas engine 11 is located on the leeward side of the outdoor heat exchanger 17. An outdoor fan 19 for passing outside air through the outdoor heat exchanger 17 and the radiator 18 is also located near the radiator 18.

[0021] An outdoor expansion valve 20 is located on one side of the outdoor heat exchanger 17. The outdoor expansion valve 20 is coupled to the indoor unit 30 through a refrigerant pipe 35.

[0022] The indoor unit 30 includes an indoor heat exchanger 31, an indoor fan 32, and an indoor expansion valve 33. the refrigerant pipe 35 is coupled to one end of the indoor heat exchanger 31 via the indoor expansion valve 33.

[0023] The other end of the indoor heat exchanger 31 is coupled to intake pipes 36 for the engine-driven compressor 12 and the motor-driven compressor 14 via the four-way valve 16 and an accumulator 21.

[0024] The refrigerant pipe 35 couples the outdoor heat exchanger 17 and the indoor heat exchanger 31, and a bypass pipe 22 is coupled to the refrigerant pipe 35 at an intermediate location of the refrigerant pipe 35. The bypass pipe 22 is coupled to an intake side of the engine-driven compressor 12 and the motor-driven compressor 14. The bypass pipe 22 is provided with a heat-recovering depressurizer 23 and a heat-recovering heat exchanger 24.

[0025] One end of an oil return pipe 25 is coupled to a lower portion of the oil separator 15, and the other end of the oil return pipe 25 is coupled to the intake pipes 36 for the engine-driven compressor 12 and the motor-driven compressor 14.

[0026] A refrigerant temperature sensor 26 for detecting a temperature of the discharged refrigerant is located on a discharge side of each of the engine-driven compressor 12 and the motor-driven compressor 14.[1-1-2. Control configuration]

[0027] A control configuration in the present embodiment is described below.

[0028] FIG. 2 is a block diagram showing a control configuration of the air conditioning apparatus in the present embodiment.

[0029] As shown in FIG. 2, the air conditioning apparatus 1 includes a controller 40.

[0030] The controller 40 includes a processor, such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), which is provided with a memory 41 and operates based on a program having been stored in advance in the memory 41. The controller 40 may be configured using a single processor or a plurality of processors. A DSP (digital signal processor) or the like may be used as the controller 40. A control circuit, such as an LSI (large scale integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programming Gate Array), or the like may be used as the controller 40.

[0031] The controller 40 performs control for components of the air conditioning apparatus 1, such as the engine-driven compressor 12, the motor-driven compressor 14, the outdoor fan 19, the outdoor expansion valve 20, the indoor fan 32, and the indoor expansion valve 33.

[0032] The controller 40 is connected to the refrigerant temperature sensors 26.

[0033] In the present embodiment, the controller 40 performs operation control in an operation mode in which only the engine-driven compressor 12 is driven, an operation mode in which only the motor-driven compressor 14 is driven, and an operation mode in which the engine-driven compressor 12 and the motor-driven compressor 14 are each driven.

[0034] FIG. 3 is a diagram showing an example of operation mode switching control with respect to an air conditioning load.

[0035] As shown in FIG. 3, generally, when the air conditioning load is low, the air conditioning apparatus is operated using only the motor-driven compressor 14, and when the air conditioning load increases, the air conditioning apparatus is operated using only the engine-driven compressor 12, with the motor-driven compressor 14 stopped. When the air conditioning load further increases, the air conditioning apparatus is operated by driving both the engine-driven compressor 12 and the motor-driven compressor 14.

[0036] While the air conditioning apparatus is operated in the mode in which only the motor-driven compressor 14 is driven, the controller 40 performs control to stop the motor-driven compressor 14 if the controller 40 judges that a temperature of a refrigerant discharged from the motor-driven compressor 14 reaches a first set value. That is, the timing at which the operation mode in which only the motor-driven compressor 14 is driven is switched to the operation mode in which only the engine-driven compressor 12 is driven is determined based on the temperature of the refrigerant discharged from the motor-driven compressor 14.

[0037] If the motor-driven compressor 14 is operated in a state in which the temperature of the refrigerant discharged from the motor-driven compressor 14 is above the first set value, the refrigerant may undergo a self-decomposition reaction due to a layer short occurred in the electric motor 13. Thus, the control to stop the motor-driven compressor 14 can inhibit a self-decomposition reaction of the refrigerant.

[0038] Furthermore, if, while the motor-driven compressor 14 is stopped, the temperature of the refrigerant discharged from the engine-driven compressor 12 has reached the first set value, or has not yet reached the first set value but is predicted to reach the first set value, at a timing for starting the operation of the motor-driven compressor 14, the controller 40 performs control to inhibit the operation of the motor-driven compressor 14.

[0039] Whether the temperature of the discharged refrigerant reaches the first set value is judged based on the temperature of the discharged refrigerant, an outside air temperature, and the air conditioning load. For example, a large load may be present under conditions such as if the outside air temperature is high during the cooling operation, or if the outside air temperature is low during the heating operation; thus, in such cases, it is judged that the temperature of the discharged refrigerant is likely to reach the first set value.

[0040] In the manner described above, if, while the engine-driven compressor 12 is operated, the temperature of the refrigerant discharged from the engine-driven compressor 12 is predicted to reach the first set value, the motor-driven compressor 14 is not driven; thus, the refrigerant can be inhibited from undergoing a self-decomposition reaction.

[0041] Furthermore, if, while the air conditioning apparatus is operated in the mode in which only the motor-driven compressor 14 is driven, the controller 40 judges that the temperature of the discharged refrigerant has reached a second set value that is equal to or less than the first set value, the controller 40 may perform control to inhibit the rotation speed of the motor-driven compressor 14 from increasing further.

[0042] Performing control as described above can inhibit a temperature of the electric motor 13 for the motor-driven compressor 14 from increasing.

[0043] The first set value and the second set value are determined as described below.

[0044] A first temperature T1 and a second temperature T2 as used herein are determined according to, for example, the thermal resistance of electrical insulating paper located between a magnet wire for generating a magnetic field when electric current flows through it and a magnetic steel sheet in a stator of the electric motor 13 provided for the motor-driven compressor 14.

[0045] For example, if the electrical insulating paper is classified as heat resistance class B as specified by JIS C 4003, the heat resistance temperature of the electrical insulating paper is 130°C. If the electrical insulating paper is subjected to a temperature condition that is higher than this heat resistance temperature, the electrical insulation between the magnet wire and the magnetic steel sheet is damaged, thereby increasing the likelihood of an electrical discharge occurring, which may cause a disproportionation reaction. Since the electrical insulating paper is under substantially the same temperature condition as that for a discharge temperature T of the refrigerant discharged from the motor-driven compressor 14, the air conditioning apparatus 1 operates to limit the air conditioning operation by using the first set value T1 and the second set value T2 as criteria for the discharge temperature T.

[0046] In the present embodiment, electrical insulating paper having heat resistance class E as specified by JIS C 4003 is used, and its heat resistance temperature is 120°C.

[0047] The first set value T1 is 115°C, which is derived from this heat resistance temperature and includes a safety margin of about 5K. The second temperature T2 is 105°C, which adds a further safety margin of about 10K to the first set value T1.

[0048] If the temperature of the refrigerant becomes equal to or greater than 150°C, the risk of a disproportionation reaction occurring increases regardless of the heat resistance temperature of the electrical insulating paper. Thus, even if the electrical insulating paper in use has the heat resistance temperature of 150°C or greater, the first set value T1 and the second set value T2 are set to temperatures that include a safety margin relative to 150°C. In other words, the first set value T1 and the second set value T2 are respectively set with reference to the lower of a temperature at which the risk of electrical discharge increases and a temperature at which the risk of a disproportionation reaction caused by heat increases.

[0049] While the first set value and the second set value are set based on the discharge temperature of a refrigerant in the first embodiment, this is not a limitation in the present disclosure. For example, the first set value and the second set value may be set based on a discharge pressure of the refrigerant, or they may be set based on both the discharge temperature and discharge pressure of the refrigerant.[1-1-3. Working medium]

[0050] The refrigerant for use in the air conditioning apparatus 1 is a working medium that includes an ethylene-based fluoroolefin. The working medium includes any one or more ethylene-based fluoroolefins, for example, 1,1,2-trifluoroethylene (HFO-1123), trans-1,2-difluoroethylene (HFO-1132(E)), cis-1,2-difluoroethylene (HFO-1132(Z)), 1,1-difluoroethylene (HFO-1132a), tetrafluoroethylene (CF 2 =CF 2 , HFO-1114), and monofluoroethylene (HFO-1141).

[0051] The working medium may include two or more refrigerant components. In other words, the working medium may include an ethylene-based fluoroolefin selected from the examples listed above (for example, 1,1,2-trifluoroethylene) and a second refrigerant component. The second refrigerant component includes one or more refrigerants selected from hydrofluorocarbons (HFCs), hydrofluoroolefins (HFOs), saturated hydrocarbons, carbon dioxide, or other refrigerants. The hydrofluorocarbons include, for example, difluoromethane, difluoroethane, trifluoroethane, tetrafluoroethane, pentafluoroethane, pentafluoropropane, hexafluoropropane, heptafluoropropane, pentafluorobutane, and heptafluorocyclopentane. The hydrofluoroolefins include, for example, monofluoropropene, trifluoropropene, tetrafluoropropene, pentafluoropropene, and hexafluorobutene. The saturated hydrocarbons include, for example, ethane, n-propane, cyclopropane, n-butane, cyclobutane, isobutane (2-methylpropane), methylcyclopropane, n-pentane, isopentane (2-methylbutane), neopentane (2,2-dimethylpropane), and methylcyclobutane, but other hydrocarbons may be used. The second refrigerant component may include a plurality of components. In other words, the second refrigerant component may include two or more refrigerant components selected from hydrofluorocarbons, hydrofluoroolefins, saturated hydrocarbons, carbon dioxide, and other refrigerants.

[0052] The working medium for use as the refrigerant in the air conditioning apparatus 1 may include a disproportionation inhibitor in addition to the refrigerant component(s). The disproportionation inhibitor is, for example, a saturated hydrocarbon. The working medium may include a disproportionation inhibitor that includes one or more components. The saturated hydrocarbons used as the disproportionation inhibitor include ethane, n-propane, cyclopropane, n-butane, cyclobutane, isobutane (2-methylpropane), methylcyclopropane, n-pentane, isopentane (2-methylbutane), neopentane (2,2-dimethylpropane), and methylcyclobutane, but other saturated hydrocarbons may be used. A particularly preferable disproportionation inhibitor may be n-propane.

[0053] The disproportionation inhibitor may be, for example, a haloalkane with a carbon number of 1 or 2. Haloalkanes with a carbon number of 1, which are halomethanes, for use as the disproportionation inhibitor include, for example, 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), fluoro-diiodomethane (CHFI 2 ), difluoroiodomethane (CHF 2 I), difluorodiiodomethane (CF 2 I 2 ), dibromodifluoromethane (CBr 2 F 2 ), and trifluoroiodomethane (CF 3 I), but other halomethanes may be used. Haloalkanes with a carbon number of 2, which are haloethanes, for use as the disproportionation inhibitor include, for example, 1,1,1-trifluoro-2-iodoethane (CF 3 CH 2 I), iodoethane (CH 3 CH 2 I), bromoethane (CH 3 CH 2 Br), and 1,1,1-triiodoethane (C 2 H 3 I 3 ).

[0054] The working medium may include a plurality of disproportionation inhibitors selected from the saturated hydrocarbons listed above and the haloalkanes listed above. The working medium may include one type of saturated hydrocarbon or two or more types of saturated hydrocarbon. The working medium may include one type of haloalkane or two or more types of haloalkane.

[0055] Preferable examples of the working medium include a mixture including 1,1,2-trifluoroethylene and n-propane. This working medium may include the second refrigerant component described above and may include other components.

[0056] Each working medium described above can include unavoidable impurities. Such unavoidable impurities include various additives, including a stabilizer added for the purpose of stabilization during transportation or storage, a residual raw material or byproduct from synthesis of a refrigerant component, and a substance introduced through other reasons.

[0057] A mass ratio between 1,1,2-trifluoroethylene and n-propane included in the working medium can be changed as appropriate.[1-2. Operation and the like]

[0058] An operation of the air conditioning apparatus in the first embodiment is described below.(Cooling operation)

[0059] During the cooling operation, the motor-driven compressor 14 using the electric motor 13 as the drive source, and the engine-driven compressor 12 using the gas engine 11 as the drive source are driven according to a load. The four-way valve 16 is set to allow a refrigerant to flow as shown with the dashed line in FIG. 1.

[0060] The refrigerant is compressed by the engine-driven compressor 12 and the motor-driven compressor 14 to have a high temperature and a high pressure and flows into the oil separator 15. A gas refrigerant having a high purity resulting from oil removal at the oil separator 15 passes through the four-way valve 16 and enters the outdoor heat exchanger 17. At the outdoor heat exchanger 17, the gas refrigerant exchanges heat with outside air to dissipate heat and then condenses into a high-pressure liquid refrigerant. The high-pressure liquid refrigerant flows through the outdoor expansion valve 20 and then into the indoor unit 30.

[0061] In the indoor unit 30, the high-pressure liquid refrigerant is depressurized at the indoor expansion valve 33 and flows into the indoor heat exchanger 31 in a gas-liquid two-phase state. At the indoor heat exchanger 31, the refrigerant in the gas-liquid two-phase state exchanges heat with air in an air-conditioned space to absorb heat and then evaporates into a gas refrigerant. The gas refrigerant exits the indoor unit 30.

[0062] The gas refrigerant that has exited the indoor unit 30 is routed to the outdoor unit 10 again. In the outdoor unit 10, the gas refrigerant passes through the four-way valve 16 and the accumulator 21 and returns to the engine-driven compressor 12 and the motor-driven compressor 14 to repeat the process described above.(Heating operation)

[0063] Dring the heating operation, the engine-driven compressor 12 using the gas engine 11 as the drive source, and the motor-driven compressor 14 using the electric motor 13 as the drive source are driven according to a load. The four-way valve 16 is set to allow the refrigerant to flow as shown with the solid line in FIG. 1.

[0064] The refrigerant is compressed by the engine-driven compressor 12 and the motor-driven compressor 14 to have a high temperature and a high pressure and flows into the oil separator 15. A gas refrigerant having a high purity resulting from oil removal at the oil separator 15 passes through the four-way valve 16 and is routed to the indoor unit 30.

[0065] The high-temperature, high-pressure gas refrigerant in the indoor unit 30 flows into the indoor heat exchanger 31. At the indoor heat exchanger 31, the gas refrigerant exchanges heat with air in the air-conditioned space to dissipate heat and then condenses into a liquid refrigerant. The liquid refrigerant passes through the indoor expansion valve 33 and exits the indoor unit 30.

[0066] The liquid refrigerant that has exited the indoor unit 30 is routed to the outdoor unit 10 again. In the outdoor unit 10, the liquid refrigerant is depressurized at the outdoor expansion valve 20 and flows into the outdoor heat exchanger 17 in a gas-liquid two-phase state. At the outdoor heat exchanger 17, the refrigerant in the gas-liquid two-phase state exchanges heat with outside air to absorb heat and then evaporates into a gas refrigerant. The gas refrigerant passes through the four-way valve 16 and the accumulator 21 and returns to the engine-driven compressor 12 and the motor-driven compressor 14 to repeat the process described above.

[0067] In this case, if the air conditioning apparatus is operated in the mode in which only the motor-driven compressor 14 is driven, the controller 40 judges whether the temperature of the refrigerant discharged from the motor-driven compressor 14 reaches the first set value on the basis of a detected value from the refrigerant temperature sensors 26. If the controller 40 judges that the temperature of the refrigerant reaches the first set value, the controller 40 stops driving the motor-driven compressor 14.

[0068] Operating the motor-driven compressor 14 in a state in which the temperature of the refrigerant discharged from the motor-driven compressor 14 is above the first set value is likely to cause the refrigerant to undergo a self-decomposition reaction due to a layer short in the electric motor 13; however, performing control to stop the motor-driven compressor 14 can inhibit the refrigerant from undergoing a self-decomposition reaction.[1-3. Effects and the like]

[0069] As described above, in the present embodiment, the air conditioning apparatus, in which the engine-driven compressor 12 that uses the gas engine 11 as its drive source and the motor-driven compressor 14 that uses the electric motor 13 as its drive source are connected to each other in parallel, performs air conditioning by circulating a refrigerant comprising HFO-1123. The air conditioning apparatus is operable in the operation mode in which only the engine-driven compressor 12 is driven, the operation mode in which only the motor-driven compressor 14 is driven, and the operation mode in which the engine-driven compressor 12 and the motor-driven compressor 14 are driven. The air conditioning apparatus includes a controller 40 that stops at least the motor-driven compressor 14 in the operation modes in which the motor-driven compressor 14 is driven, if the temperature of the refrigerant discharged from the motor-driven compressor 14 reaches the first set value.

[0070] In this way, performing control to stop the motor-driven compressor 14 in a state in which the temperature of the refrigerant discharged from the motor-driven compressor 14 is above the first set value can inhibit the refrigerant from undergoing a self-decomposition reaction.

[0071] Furthermore, in the present embodiment, if, while at least the motor-driven compressor 14 is stopped, the temperature of the refrigerant discharged from the engine-driven compressor 12 has reached the first set value, or has not yet reached the first set value but is predicted to reach the first set value, at the timing for starting the operation of the motor-driven compressor 14, the controller 40 performs control to inhibit the operation of the motor-driven compressor 14.

[0072] In this way, if, while the engine-driven compressor 12 is operated, the temperature of the discharged refrigerant is predicted to reach the first set value, the motor-driven compressor 14 is not driven; thus, the refrigerant can be inhibited from undergoing a self-decomposition reaction.

[0073] Furthermore, in the present embodiment, if the temperature of the refrigerant discharged from the motor-driven compressor 14 has reached the second set value that is equal to or less than the first set value during the operation modes in which the motor-driven compressor 14 is driven, the controller 40 performs control to inhibit the rotation speed of the motor-driven compressor 14 from exceeding the current rotation speed of the motor-driven compressor 14.

[0074] In this way, the temperature of the electric motor 13 for the motor-driven compressor 14 can be inhibited from increasing.(Second embodiment)

[0075] A second embodiment of the present disclosure is described below.[2-1. Configuration]

[0076] FIG. 4 is a refrigeration cycle diagram showing an air conditioning apparatus in the second embodiment.

[0077] As shown in FIG. 4, in the present embodiment, a subcooling heat exchanger 50 is located on a cooling-operation downstream side of the outdoor heat exchanger 17.

[0078] A subcooling pipe 51 branched from the refrigerant pipe 35 is located on a cooling-operation upstream side of the subcooling heat exchanger 50. The subcooling pipe 51 extends via an expansion valve 52 into the subcooling heat exchanger 50 and is coupled to the intake side of the motor-driven compressor 14.

[0079] In the present embodiment, the refrigerant pipe 35 couples the subcooling heat exchanger 50 and the indoor heat exchanger 31, and the heat-recovering pipe 53 is coupled to the refrigerant pipe 35 at an intermediate location of the refrigerant pipe 35. The heat-recovering pipe 53 is coupled to the intake side of the motor-driven compressor 14. The heat-recovering pipe 53 is provided with the heat-recovering depressurizer 23 and the heat-recovering heat exchanger 24. An expansion valve 54 is located at an intermediate location of the heat-recovering pipe 53.

[0080] The other constituent elements are similar to those in the first embodiment shown in FIG. 1; thus, like reference signs denote like elements and their descriptions are omitted.[2-2. Operation]

[0081] An operation of the second embodiment is described below.

[0082] In the present embodiment, the expansion valve 52 of the subcooling pipe 51 is opened to a predefined degree and the expansion valve 54 of the heat-recovering pipe 53 is closed during the cooling operation.

[0083] The engine-driven compressor 12 and the motor-driven compressor 14 are driven to deliver the refrigerant to the outdoor heat exchanger 17. The refrigerant exchanges heat with outside air at the outdoor heat exchanger 17 and then is routed toward the subcooling heat exchanger 50.

[0084] A portion of the refrigerant from the outdoor heat exchanger 17 is routed through the subcooling pipe 51 and the expansion valve 52 into the subcooling heat exchanger 50 where the portion of the refrigerant exchanges heat with the refrigerant from the outdoor heat exchanger 17.

[0085] The portion of the refrigerant, which has exchanged heat at the subcooling heat exchanger 50, evaporates at a temperature higher than that at the indoor heat exchanger 31 and is directed to the motor-driven compressor 14. Thus, the temperature of the refrigerant discharged from the motor-driven compressor 14 can be lowered.

[0086] Additionally, the motor-driven compressor 14 has a discharge pressure that is substantially the same as that of the engine-driven compressor 12, resulting in a smaller compression ratio; thus, the discharge temperature of the motor-driven compressor 14 is lower than that of the engine-driven compressor 12.

[0087] The refrigerant routed from the outdoor heat exchanger 17 exchanges heat with the portion of the refrigerant, which has been expanded by the expansion valve 52 and is flowing through the subcooling pipe 51, in the subcooling heat exchanger 50 to be cooled, thereby being able to improve the cooling efficiency at the indoor heat exchanger 31.

[0088] During the heating operation, the expansion valve 54 of the heat-recovering pipe 53 is opened to a predefined degree, and the expansion valve 52 of the subcooling pipe 51 is closed.

[0089] In this state, the engine-driven compressor 12 and the motor-driven compressor 14 are each driven to deliver the refrigerant to the indoor heat exchanger 31. The refrigerant exchanges heat with indoor air at the indoor heat exchanger 31 and then is routed though the subcooling heat exchanger 50 to the outdoor heat exchanger 17.

[0090] A portion of the refrigerant that has exited the subcooling heat exchanger 50 is routed to the heat-recovering heat exchanger 24 through the heat-recovering pipe 53.

[0091] The portion of the refrigerant exchanges heat with outside air at the heat-recovering heat exchanger 24, evaporating at a temperature higher than that at the outdoor heat exchanger 17 and is directed to the motor-driven compressor 14. Thus, the temperature of the refrigerant discharged from the motor-driven compressor 14 can be lowered.

[0092] Additionally, the motor-driven compressor 14 has a discharge pressure that is substantially the same as that of the engine-driven compressor 12, resulting in a smaller compression ratio; thus, the discharge temperature of the motor-driven compressor 14 is lower than that of the engine-driven compressor 12.[2-3. Effects]

[0093] As described above, in the present embodiment, the air conditioning apparatus includes the subcooling heat exchanger 50 that exchanges heat between the refrigerant discharged from the outdoor heat exchanger 17 and the refrigerant branched from the discharge side from the outdoor heat exchanger 17 and allows heat to be exchanged between, and the air conditioning apparatus drives the engine-driven compressor 12 and the motor-driven compressor 14 simultaneously in the cooling operation and routes the refrigerant that has undergone heat exchange at the subcooling heat exchanger 50 and has evaporated at a temperature higher than a temperature at the indoor heat exchanger 31 to the intake side of the motor-driven compressor 14.

[0094] In this way, the temperature of the refrigerant discharged from the motor-driven compressor 14 can be lowered. Therefore, it is possible to inhibit the temperature of the refrigerant discharged from the motor-driven compressor 14 from increasing and thus to inhibit the refrigerant from undergoing a self-decomposition reaction.

[0095] Furthermore, in the present embodiment, the air conditioning apparatus includes: the heat-recovering pipe 53 branched from the heating-operation intake side of the outdoor heat exchanger 17 and coupled to the intake side of the motor-driven compressor 14; and the heat-recovering heat exchanger 24 located at an intermediate location of the heat-recovering pipe 53, and the air conditioning apparatus drives the engine-driven compressor 12 and the motor-driven compressor 14 simultaneously in the heating operation and routes the refrigerant that has undergone heat exchange at the heat-recovering heat exchanger 24 and has evaporated at a temperature higher than a temperature at the outdoor heat exchanger 17 to the intake side of the motor-driven compressor 14.

[0096] In this way, the temperature of the refrigerant discharged from the motor-driven compressor 14 can be lowered. Therefore, it is possible to inhibit the temperature of the refrigerant discharged from the motor-driven compressor 14 from increasing and thus to inhibit the refrigerant from undergoing a self-decomposition reaction.(Other embodiments)

[0097] The first embodiment and the second embodiment have been described as examples of the technologies disclosed in the present application. However, this is not a limitation on the technologies in the present disclosure, and the technologies in the present disclosure are applicable to any embodiments that include modifications, permutations, additions, omissions, or the like.(Supplements)

[0098] The descriptions of the foregoing embodiments disclose the following technologies.

[0099] (First technology) An air conditioning apparatus, in which an engine-driven compressor that uses a gas engine as a drive source and a motor-driven compressor that uses an electric motor as a drive source are connected to each other in parallel, to perform air conditioning by circulating a refrigerant including HFO-1123, wherein the air conditioning apparatus is operable in an operation mode in which only the engine-driven compressor is driven, an operation mode in which only the motor-driven compressor is driven, and an operation mode in which the engine-driven compressor and the motor-driven compressor are driven, and the air conditioning apparatus includes a controller configured to stop at least the motor-driven compressor in the operation modes in which the motor-driven compressor is driven, if a temperature of the refrigerant discharged from the motor-driven compressor reaches a first set value.

[0100] In accordance with this configuration, performing control to stop the motor-driven compressor in a state in which the temperature of the refrigerant discharged from the motor-driven compressor is above the first set value can inhibit the refrigerant from undergoing a self-decomposition reaction.

[0101] (Second technology) The air conditioning apparatus according to the first technology, wherein if, while at least the motor-driven compressor is stopped, a temperature of the refrigerant discharged from the engine-driven compressor has reached the first set value, or has not yet reached the first set value but is predicted to reach the first set value, at a timing for starting an operation of the motor-driven compressor, the controller performs control to inhibit the operation of the motor-driven compressor.

[0102] In accordance with this configuration, if, while the engine-driven compressor is operated, the temperature of the discharged refrigerant is predicted to reach the first set value, the motor-driven compressor is not driven; thus, the refrigerant can be inhibited from undergoing a self-decomposition reaction.

[0103] (Third technology) The air conditioning apparatus according to the second technology, wherein, if the temperature of the refrigerant discharged from the motor-driven compressor has reached a second set value that is equal to or less than the first set value during the operation modes in which the motor-driven compressor is driven, the controller performs control to inhibit a rotation speed of the motor-driven compressor from exceeding a current rotation speed of the motor-driven compressor.

[0104] In accordance with this configuration, the temperature of the electric motor for the motor-driven compressor can be inhibited from increasing.

[0105] (Fourth technology) An air conditioning apparatus, in which an engine-driven compressor that uses a gas engine as a drive source and a motor-driven compressor that uses an electric motor as a drive source are connected to each other in parallel, to perform air conditioning by circulating a refrigerant including HFO-1123, wherein the air conditioning apparatus includes a subcooling heat exchanger that exchanges heat between the refrigerant discharged from an outdoor heat exchanger and the refrigerant branched from a discharge side from the outdoor heat exchanger, and the air conditioning apparatus drives the engine-driven compressor and the motor-driven compressor simultaneously in a cooling operation and routes the refrigerant that has undergone heat exchange at the subcooling heat exchanger and has evaporated at a temperature higher than a temperature at an indoor heat exchanger to an intake side of the motor-driven compressor.

[0106] In accordance with this configuration, the temperature of the refrigerant discharged from the motor-driven compressor can be lowered. Therefore, it is possible to inhibit the temperature of the refrigerant discharged from the motor-driven compressor from increasing and thereby to inhibit the refrigerant from undergoing a self-decomposition reaction.

[0107] (Fifth technology) An air conditioning apparatus, in which an engine-driven compressor that uses a gas engine as a drive source and a motor-driven compressor that uses an electric motor as a drive source are connected to each other in parallel, to perform air conditioning by circulating a refrigerant including HFO-1123, wherein the air conditioning apparatus includes: a heat-recovering pipe branched from a heating-operation intake side of an outdoor heat exchanger and coupled to an intake side of the motor-driven compressor; and a heat-recovering heat exchanger located at an intermediate location of the heat-recovering pipe, and the air conditioning apparatus drives the engine-driven compressor and the motor-driven compressor simultaneously in the heating operation and routes the refrigerant that has undergone heat exchange at the heat-recovering heat exchanger and has evaporated at a temperature higher than a temperature at the outdoor heat exchanger to the intake side of the motor-driven compressor.

[0108] In accordance with this configuration, the temperature of the refrigerant discharged from the motor-driven compressor can be lowered. Therefore, it is possible to inhibit the temperature of the refrigerant discharged from the motor-driven compressor from increasing and thus to inhibit the refrigerant from undergoing a self-decomposition reaction.[Industrial Applicability]

[0109] As described above, the air conditioning apparatus according to the present disclosure can be suitably applied to provide an air conditioning apparatus capable of driving the motor-driven compressor while maintaining a refrigerant temperature lower than a lower limit at which the refrigerant undergoes a self-decomposition reaction and thereby inhibiting the refrigerant from undergoing a self-decomposition reaction.[Reference Signs List]

[0110] 1air conditioning apparatus 10outdoor unit 11gas engine 12engine-driven compressor 13electric motor 14motor-driven compressor 15oil separator 16four-way valve 17outdoor heat exchanger 18radiator 19outdoor fan 20outdoor expansion valve 21accumulator 22bypass pipe 23heat-recovering depressurizer 24heat-recovering heat exchanger 25oil return pipe 26refrigerant temperature sensor 30indoor unit 31indoor heat exchanger 32indoor fan 33indoor expansion valve 35refrigerant pipe 36intake pipe 40controller 41memory 50subcooling heat exchanger 51subcooling pipe 52expansion valve 53heat-recovering pipe 54expansion valve

Claims

1. An air conditioning apparatus, in which an engine-driven compressor that uses a gas engine as a drive source and a motor-driven compressor that uses an electric motor as a drive source are connected to each other in parallel, to perform air conditioning by circulating a refrigerant comprising HFO-1123, characterized in that the air conditioning apparatus is operable in an operation mode in which only the engine-driven compressor is driven, an operation mode in which only the motor-driven compressor is driven, and an operation mode in which the engine-driven compressor and the motor-driven compressor are driven, and the air conditioning apparatus comprises a controller configured to stop at least the motor-driven compressor in the operation modes in which the motor-driven compressor is driven, if a temperature of the refrigerant discharged from the motor-driven compressor reaches a first set value.

2. The air conditioning apparatus according to claim 1, wherein if, while at least the motor-driven compressor is stopped, a temperature of the refrigerant discharged from the engine-driven compressor has reached the first set value, or has not yet reached the first set value but is predicted to reach the first set value, at a timing for starting an operation of the motor-driven compressor, the controller performs control to inhibit the operation of the motor-driven compressor.

3. The air conditioning apparatus according to claim 2, wherein, if the temperature of the refrigerant discharged from the motor-driven compressor has reached a second set value that is equal to or less than the first set value during the operation modes in which the motor-driven compressor is driven, the controller performs control to inhibit a rotation speed of the motor-driven compressor from exceeding a current rotation speed of the motor-driven compressor.

4. An air conditioning apparatus, in which an engine-driven compressor that uses a gas engine as a drive source and a motor-driven compressor that uses an electric motor as a drive source are connected to each other in parallel, to perform air conditioning by circulating a refrigerant comprising HFO-1123, characterized in that the air conditioning apparatus comprises a subcooling heat exchanger that exchanges heat between the refrigerant discharged from an outdoor heat exchanger and the refrigerant branched from a discharge side from the outdoor heat exchanger, and the air conditioning apparatus drives the engine-driven compressor and the motor-driven compressor simultaneously in a cooling operation and routes the refrigerant that has undergone heat exchange at the subcooling heat exchanger and has evaporated at a temperature higher than a temperature at an indoor heat exchanger to an intake side of the motor-driven compressor.

5. An air conditioning apparatus, in which an engine-driven compressor that uses a gas engine as a drive source and a motor-driven compressor that uses an electric motor as a drive source are connected to each other in parallel, to perform air conditioning by circulating a refrigerant comprising HFO-1123, characterized in that the air conditioning apparatus comprises: a heat-recovering pipe branched from a heating-operation intake side of an outdoor heat exchanger and coupled to an intake side of the motor-driven compressor; and a heat-recovering heat exchanger located at an intermediate location of the heat-recovering pipe, and the air conditioning apparatus drives the engine-driven compressor and the motor-driven compressor simultaneously in the heating operation and routes the refrigerant that has undergone heat exchange at the heat-recovering heat exchanger and has evaporated at a temperature higher than a temperature at the outdoor heat exchanger to the intake side of the motor-driven compressor.

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