Refrigeration Cycle Equipment

Abstract

To provide a refrigeration cycle device having a plurality of evaporators, which can suppress the accumulation of refrigeration oil in an evaporator, and liquid back to a compressor, and can effectively use the plurality of evaporators.SOLUTION: A refrigeration cycle device 10 has a compressor 11, a heat medium / refrigerant heat exchanger 12, a branch portion 13a, a first expansion valve 14a, an indoor evaporator 15, an evaporation pressure adjusting valve 17, a second expansion valve 14b, a chiller 16, a merging portion 13b, and a control device 70. A determining portion 70b circulates a refrigerant to the indoor evaporator 15 and the chiller 16, and determines whether or not a liquid back condition is satisfied in an operation mode in which a flow rate of the refrigerant circulating in the indoor evaporator 15 is a reference flow rate or more for suppressing the accumulation of the refrigeration oil. A decompression control portion 70c controls the second expansion valve 14b so as to reduce refrigerant pressure at an outflow port of the chiller 16 until the refrigerant discharged from the compressor 11 has the degree of overheat, when it is determined to satisfy the liquid back condition.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a refrigeration cycle device. [Background technology]

[0002] Conventionally, in a refrigeration cycle device, in order to protect the compressor, the refrigeration oil contained in the refrigerant is prevented from accumulating inside the heat exchanger. If the refrigeration oil accumulates in the heat exchanger, the amount of refrigeration oil that actually circulates through the cycle decreases, and it is considered that the compressor may burn out. In this regard, in Patent Document 1, the flow rate of the refrigerant flowing through the evaporator that exchanges heat with a specific object is ensured to be at least to an extent that the accumulation of the refrigeration oil can be suppressed, thereby protecting the compressor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-129087 A Summary of the Invention

[0004] Here, in Patent Document 1, if a condition is added to the refrigerant flow rate flowing through the heat exchanger as in Patent Document 1, it is assumed that the cooling load and the refrigerant flow rate in the evaporator will not be balanced, and the refrigerant flow rate will be excessive for the cooling load. In this case, liquid backflow will occur in which the liquid phase refrigerant that has not been completely evaporated in the evaporator flows into the compressor, which is thought to be a cause of compressor failure such as liquid compression. In view of this, it is also conceivable to control the operation, such as intermittent operation of the compressor, in order to adjust the refrigerant flow rate as a time average so as to correspond to the cooling load of the evaporator.

[0005] On the other hand, there exists a configuration having a plurality of evaporators as a refrigeration cycle device. Here, we consider a case where the operation of a compressor is controlled as a method for suppressing the accumulation of refrigeration oil in one of the plurality of evaporators and the liquid backflow from one evaporator to the compressor. In this case, if the operation of the compressor is controlled to suppress the accumulation of refrigeration oil in one evaporator, the refrigerant flow rate to the other evaporator also changes, which affects the cooling performance of the other evaporator.

[0006] In view of the above, the present disclosure relates to a refrigeration cycle device having multiple evaporators, and aims to provide a refrigeration cycle device that can effectively utilize the multiple evaporators while suppressing refrigeration oil retention in the evaporators and liquid backflow to the compressor. [Means for solving the problem]

[0007] To achieve the above object, a refrigeration cycle apparatus according to a first aspect of the present disclosure includes a compressor (11), a condenser (12), a branch section (13a), a first pressure reduction section (14a), and a first evaporator (15). The refrigeration cycle apparatus further includes a second pressure reduction section (14b), a second evaporator (16), a junction section (13b), and a control section (70).

[0008] The compressor compresses and discharges a refrigerant containing refrigeration oil. The condenser condenses the refrigerant discharged from the compressor. The branching section branches the refrigerant flowing out from the condenser. The first pressure reduction section reduces the pressure of the refrigerant flowing out from one of the outlets in the branching section. The first evaporator evaporates the refrigerant flowing out from the first pressure reduction section.

[0009] The second pressure reducing section reduces the pressure of the refrigerant flowing out from the other outlet of the branch section. The second evaporator evaporates the refrigerant flowing out from the second pressure reducing section. The confluence section combines the refrigerant flowing out from the first evaporator and the refrigerant flowing out from the second evaporator and guides the combined refrigerant to the compressor. The control section controls the operation of the first pressure reducing section and the second pressure reducing section.

[0010] The control unit has a determination unit (70b) and a pressure reduction control unit (70c). The determination unit determines whether or not a liquid backflow condition is satisfied in an operation mode in which refrigerant is circulated through the first evaporator and the second evaporator and the refrigerant flow rate through the first evaporator is equal to or higher than a reference flow rate for suppressing accumulation of refrigeration oil. The liquid backflow condition is a condition related to liquid backflow in which liquid phase refrigerant flows into the compressor. When the determination unit determines that the liquid backflow condition is satisfied, the pressure reduction control unit controls the operation of the second pressure reduction unit to reduce the refrigerant pressure at the outlet of the second evaporator until the refrigerant discharged from the compressor has a degree of superheat.

[0011] When the determining unit determines that the liquid back condition is satisfied, the refrigeration cycle device reduces the refrigerant pressure at the outlet of the second evaporator until the refrigerant discharged from the compressor has a degree of superheat. As a result, the refrigeration cycle device circulates the refrigerant through the first evaporator and the second evaporator, and sets the refrigerant flow rate through the first evaporator to a reference flow rate or more, thereby suppressing retention of refrigeration oil in the first evaporator.

[0012] At the same time, the refrigeration cycle device can increase the dryness of the refrigerant at the junction by lowering the refrigerant pressure at the outlet of the second evaporator. Therefore, the refrigeration cycle device can make the state of the refrigerant sucked into the compressor closer to the gas phase, thereby suppressing the occurrence of liquid backflow into the compressor.

[0013] In the Mollier diagram, the slope of the isentropic line is smaller as the pressure is lower. Therefore, the refrigeration cycle device can discharge the gas phase refrigerant from the compressor by lowering the refrigerant pressure at the junction, so that the refrigerant discharged from the compressor has a degree of superheat, and can prevent failures caused by liquid backflow, such as liquid compression in the compressor.

[0014] As a result, in a refrigeration cycle device configured with a first evaporator and a second evaporator, it is possible to suppress failures caused by refrigeration oil stagnation in the first evaporator and liquid backflow to the compressor, and to make full use of the first and second evaporators.

[0015] A refrigeration cycle apparatus according to a second aspect of the present disclosure includes a compressor (11), a condenser (12), a branch section (13a), a first pressure reduction section (14a), and a first evaporator (15). The refrigeration cycle apparatus further includes a second pressure reduction section (14b), a second evaporator (16), a junction section (13b), and a control section (70).

[0016] The compressor compresses and discharges a refrigerant containing refrigeration oil. The condenser condenses the refrigerant discharged from the compressor. The branching section branches the refrigerant flowing out from the condenser. The first pressure reduction section reduces the pressure of the refrigerant flowing out from one of the outlets in the branching section. The first evaporator evaporates the refrigerant flowing out from the first pressure reduction section.

[0017] The second pressure reducing section reduces the pressure of the refrigerant flowing out from the other of the outlets in the branch section. The second evaporator evaporates the refrigerant flowing out from the second pressure reducing section. The confluence section combines the refrigerant flowing out from the first evaporator and the refrigerant flowing out from the second evaporator, and guides the combined refrigerant to the compressor. The control section controls the operation of the compressor.

[0018] The control unit has a determination unit (70b) and a discharge capacity control unit (70d). The determination unit determines whether or not a liquid backflow condition is satisfied in an operation mode in which refrigerant is circulated through the first evaporator and the second evaporator and the refrigerant flow rate through the first evaporator is equal to or higher than a reference flow rate for suppressing accumulation of refrigeration oil. The liquid backflow condition is a condition related to liquid backflow in which liquid phase refrigerant flows into the compressor. When the determination unit determines that the liquid backflow condition is satisfied, the discharge capacity control unit controls the operation of the compressor to reduce the refrigerant pressure at the outlet of the second evaporator until the refrigerant discharged from the compressor has a degree of superheat.

[0019] When the determining unit determines that the liquid back condition is satisfied, the refrigeration cycle device controls the operation of the compressor to reduce the refrigerant pressure at the outlet of the second evaporator until the refrigerant discharged from the compressor has a degree of superheat. As a result, the refrigeration cycle device circulates the refrigerant to the first evaporator and the second evaporator, and sets the refrigerant flow rate flowing through the first evaporator to a reference flow rate or more, thereby suppressing stagnation of refrigeration oil in the first evaporator.

[0020] At the same time, the refrigeration cycle device can increase the dryness of the refrigerant at the junction by lowering the refrigerant pressure at the outlet of the second evaporator. Therefore, the refrigeration cycle device can make the state of the refrigerant sucked into the compressor closer to the gas phase, thereby suppressing the occurrence of liquid backflow into the compressor.

[0021] In the Mollier diagram, the slope of the isentropic line is smaller as the pressure is lower. Therefore, the refrigeration cycle device can discharge the gas phase refrigerant from the compressor by lowering the refrigerant pressure at the junction, so that the refrigerant discharged from the compressor has a degree of superheat, and can prevent failures caused by liquid backflow, such as liquid compression in the compressor.

[0022] As a result, in a refrigeration cycle device configured with a first evaporator and a second evaporator, it is possible to suppress failures caused by refrigeration oil stagnation in the first evaporator and liquid backflow to the compressor, and to make full use of the first and second evaporators.

[0023] In addition, the reference numerals in parentheses for each means described in this section and in the claims indicate the correspondence with the specific means described in the embodiments described later. [Brief description of the drawings]

[0024] [Figure 1] 1 is a configuration diagram of a vehicle air conditioner including a refrigeration cycle device according to a first embodiment. [Diagram 2] FIG. 1 is a configuration diagram of an indoor air conditioning unit according to a first embodiment. [Diagram 3] 1 is a block diagram showing a control system of a vehicle air conditioner according to a first embodiment. [Figure 4] 5 is a flowchart of a control process for suppressing liquid backflow according to the first embodiment. [Diagram 5] FIG. 4 is an explanatory diagram showing an example of a control table for determining whether or not a liquid return condition is satisfied in the first embodiment. [Figure 6] FIG. 11 is an explanatory diagram relating to an example of a criterion for determining whether or not a liquid back condition is satisfied. [Figure 7] 1 is an example of a Mollier diagram when a liquid back condition is satisfied. [Figure 8] 11 is an example of a Mollier diagram when liquid backflow suppression control is being executed. [Figure 9] FIG. 4 is an explanatory diagram showing an example of a control table for determining a target low pressure of the liquid backflow suppression control in the first embodiment. [Figure 10] FIG. 11 is an explanatory diagram showing an example of a control table for determining a target degree of superheat in liquid backflow suppression control in the second embodiment. [Figure 11] FIG. 13 is an explanatory diagram showing an example of a control table for determining the minimum rotation speed of the compressor in the liquid backflow prevention control in the third embodiment. [Figure 12] 1 shows a first modified example of the configuration of the refrigeration cycle device. [Figure 13] 13 is a second modified example relating to the configuration of the refrigeration cycle device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, a number of embodiments for carrying out the present disclosure will be described with reference to the drawings. In each embodiment, the same reference numerals may be used to designate parts corresponding to matters described in the preceding embodiment, and duplicated descriptions may be omitted. In each embodiment, when only a part of the configuration is described, other embodiments described previously may be applied to the other parts of the configuration. In addition to combinations of parts that are specifically indicated as being possible in each embodiment, it is also possible to partially combine embodiments even if not indicated, as long as there is no particular problem with the combination.

[0026] (First embodiment) First, a first embodiment of the present disclosure will be described with reference to Figs. 1 to 3. In the first embodiment, a vehicle air conditioner 1 according to the present disclosure is applied to an electric vehicle that obtains driving force for running the vehicle from a running electric motor. The vehicle air conditioner 1 performs air conditioning of the vehicle cabin, which is the space to be air-conditioned, and temperature adjustment of equipment including a battery 42 and the like in the electric vehicle. The vehicle air conditioner 1 can switch between a cooling mode, a heating mode, and a dehumidifying and heating mode as operation modes for air conditioning the vehicle cabin.

[0027] The refrigeration cycle device 10 in the vehicle air conditioner 1 employs an HFC refrigerant (specifically, R134a) as the refrigerant, and constitutes a subcritical refrigeration cycle in which the high-pressure side refrigerant pressure does not exceed the critical pressure of the refrigerant. It is also possible to employ R1234yf or the like as the refrigerant. The refrigerant is mixed with refrigeration oil for lubricating the compressor 11. As the refrigeration oil, PAG oil (polyalkylene glycol oil) that is compatible with liquid phase refrigerants is employed. A portion of the refrigeration oil circulates through the cycle together with the refrigerant.

[0028] Next, a specific configuration of the vehicle air conditioner 1 according to the first embodiment will be described with reference to Fig. 1. The vehicle air conditioner 1 has a refrigeration cycle device 10, a high-temperature side heat medium circuit 20, a low-temperature side heat medium circuit 40, an equipment heat medium circuit 50, an interior air conditioning unit 60, and a control device 70.

[0029] First, a configuration of a refrigeration cycle device 10 in the vehicle air conditioner 1 will be described. The refrigeration cycle device 10 is a vapor compression type refrigeration cycle device. In the refrigeration cycle device 10, a compressor 11 draws in a refrigerant, compresses it, and discharges it. The compressor 11 is disposed inside the vehicle bonnet.

[0030] The compressor 11 is an electric compressor that uses an electric motor to rotate a fixed displacement compression mechanism having a fixed discharge capacity. The rotation speed (i.e., refrigerant discharge capacity) of the compressor 11 is controlled by a control signal output from a control device 70, which will be described later.

[0031] The discharge port of the compressor 11 is connected to an inlet side of a refrigerant passage of a heat medium refrigerant heat exchanger 12. The heat medium refrigerant heat exchanger 12 is a heat exchanger that transfers heat contained in the high-pressure refrigerant discharged from the compressor 11 to the heat medium of the high-temperature side heat medium circuit 20 for heating.

[0032] The heat medium refrigerant heat exchanger 12 is configured by a so-called subcooling type condenser, and has a condensing section 12a, a receiver section 12b, and a supercooling section 12c. The condensing section 12a is a heat exchange section that condenses the refrigerant by heat exchange between the high-pressure refrigerant and the heat medium of the high-temperature side heat medium circuit 20. The receiver section 12b is a liquid-receiving section that stores the liquid-phase refrigerant that flows out from the condensing section 12a. The supercooling section 12c is a heat exchange section that supercools the liquid-phase refrigerant by heat exchange between the liquid-phase refrigerant that flows out from the receiver section 12b and the heat medium of the high-temperature side heat medium circuit 20.

[0033] This allows the so-called receiver cycle to be configured, and the high-pressure liquid-phase refrigerant condensed in the condenser 12a can be stored in the receiver 12b as surplus refrigerant of the cycle. Therefore, the refrigerant flowing out of the indoor evaporator 15 can be evaporated until it becomes a gas-phase refrigerant having a degree of superheat. Furthermore, by supercooling the refrigerant in the supercooling section 12c, the enthalpy difference between the enthalpy of the refrigerant on the outlet side of the indoor evaporator 15 and the enthalpy of the refrigerant on the inlet side can be increased.

[0034] The heat medium refrigerant heat exchanger 12 corresponds to an example of a condenser. As the heat medium in the high temperature side heat medium circuit 20, a solution containing ethylene glycol, an antifreeze solution, or the like can be used.

[0035] The refrigerant inlet side of the branching section 13a is connected to the outlet of the refrigerant passage of the heat medium refrigerant heat exchanger 12. The branching section 13a branches the flow of the liquid phase refrigerant flowing out from the heat medium refrigerant heat exchanger 12. The branching section 13a is formed to have a three-way joint structure having three refrigerant inlet and outlets that are connected to each other. In the branching section 13a, one of the three inlet and outlets is a refrigerant inlet, and the remaining two are refrigerant outlets.

[0036] One refrigerant outlet of the branch portion 13a is connected to the refrigerant inlet side of the indoor evaporator 15 via a first expansion valve 14a. The other refrigerant outlet of the branch portion 13a is connected to the refrigerant inlet side of the chiller 16 via a second expansion valve 14b.

[0037] The first expansion valve 14a is a pressure reducing section that reduces the pressure of the refrigerant flowing out from one of the refrigerant outlets of the branch section 13a at least in the cooling mode, and corresponds to an example of a first pressure reducing section. The first expansion valve 14a is an electric variable throttle mechanism and has a valve body and an electric actuator. That is, the first expansion valve 14a is configured as a so-called electric expansion valve.

[0038] The valve element of the first expansion valve 14a is configured to be able to change the passage opening degree (in other words, the throttle opening degree) of the refrigerant passage. The electric actuator has a stepping motor that changes the throttle opening degree of the valve element. The operation of the first expansion valve 14a is controlled by a control signal output from the control device 70.

[0039] The first expansion valve 14a is configured as a variable throttle mechanism having a full opening function that fully opens the refrigerant passage when the throttle opening is fully opened, and a full closing function that closes the refrigerant passage when the throttle opening is fully closed. In other words, the first expansion valve 14a can prevent the refrigerant from decompressing by fully opening the refrigerant passage.

[0040] The first expansion valve 14a can block the inflow of refrigerant to the indoor evaporator 15 by closing the refrigerant passage. That is, the first expansion valve 14a has both a function as a decompression unit that decompresses the refrigerant and a function as a refrigerant circuit switching unit that switches the refrigerant circuit.

[0041] The outlet of the first expansion valve 14a is connected to the refrigerant inlet side of the indoor evaporator 15. The indoor evaporator 15 is an evaporator that, at least in the cooling mode, exchanges heat between the low-pressure refrigerant decompressed by the first expansion valve 14a and the blown air W to evaporate the low-pressure refrigerant and cool the blown air W. The indoor evaporator 15 corresponds to an example of a first evaporator. As shown in Figs. 1 and 2, the indoor evaporator 15 is disposed in a casing 61 of the indoor air-conditioning unit 60.

[0042] 1, a second expansion valve 14b is connected to the other refrigerant outlet of the branch portion 13a. The second expansion valve 14b is a pressure reducing part that reduces the pressure of the refrigerant flowing out from the other refrigerant outlet of the branch portion 13a at least in the heating mode, and corresponds to an example of a second pressure reducing part.

[0043] The second expansion valve 14b is an electric variable throttle mechanism, similar to the first expansion valve 14a, and includes a valve body and an electric actuator. That is, the second expansion valve 14b is a so-called electric expansion valve, and has a full-open function and a full-close function.

[0044] That is, the second expansion valve 14b can prevent the refrigerant from being depressurized by fully opening the refrigerant passage. Also, the second expansion valve 14b can block the inflow of refrigerant to the chiller 16 by closing the refrigerant passage. That is, the second expansion valve 14b has both a function as a decompression unit that depressurizes the refrigerant and a function as a refrigerant circuit switching unit that switches the refrigerant circuit.

[0045] The outlet of the second expansion valve 14b is connected to the refrigerant inlet side of the chiller 16. The chiller 16 is a heat exchanger that exchanges heat between the low-pressure refrigerant decompressed by the second expansion valve 14b and the heat medium circulating through the low-temperature side heat medium circuit 40. The chiller 16 corresponds to an example of a second evaporator.

[0046] The chiller 16 has a refrigerant passage through which the low-pressure refrigerant decompressed by the second expansion valve 14b flows, and a heat medium passage through which the heat medium circulating in the low-temperature side heat medium circuit 40 flows. Therefore, the chiller 16 is a heat absorber that evaporates the low-pressure refrigerant and absorbs heat from the heat medium by heat exchange between the low-pressure refrigerant flowing through the refrigerant passage and the heat medium flowing through the heat medium passage.

[0047] The inlet side of an evaporation pressure regulating valve 17 is connected to the refrigerant outlet of the indoor evaporator 15. The evaporation pressure regulating valve 17 is an evaporation pressure adjusting section that maintains the refrigerant evaporation pressure in the indoor evaporator 15 at or above a predetermined reference pressure. The evaporation pressure regulating valve 17 is configured with a mechanical variable throttle mechanism that increases the valve opening degree as the refrigerant pressure on the outlet side of the indoor evaporator 15 increases.

[0048] The evaporation pressure regulating valve 17 is configured to maintain the refrigerant evaporation temperature in the indoor evaporator 15 at a reference temperature (1° C. in this embodiment) at which frost formation on the indoor evaporator 15 can be suppressed or higher.

[0049] The other refrigerant inlet side of the junction 13b is connected to the outlet of the evaporation pressure regulating valve 17. As shown in Fig. 1, one of the refrigerant inlets of the junction 13b is connected to the refrigerant outlet side of the chiller 16.

[0050] The junction 13b has a three-way joint structure similar to the branching section 13a, and two of the three inlet / outlet ports are refrigerant inlets and the remaining one is a refrigerant outlet. The junction 13b merges the refrigerant flow out from the evaporation pressure regulating valve 17 and the refrigerant flow out from the chiller 16. The refrigerant outlet of the junction 13b is connected to the suction port side of the compressor 11.

[0051] Next, a description will be given of the configuration of the high-temperature side heat medium circuit 20 in the vehicle air conditioner 1. The high-temperature side heat medium circuit 20 is a heat medium circuit that circulates a heat medium. As the heat medium in the high-temperature side heat medium circuit 20, a solution containing ethylene glycol, an antifreeze solution, or the like can be used.

[0052] The high-temperature side heat medium circuit 20 includes a heat medium passage of the heat medium refrigerant heat exchanger 12, a radiator 21, a heater core 22, an electric heater 26, a high-temperature side pump 27, a first reserve tank 28, a second reserve tank 29, a circuit switching unit 30, and the like.

[0053] The radiator 21 is a heat exchanger that exchanges heat between a heat medium heated in the heat medium-refrigerant heat exchanger 12 or the like and outside air OA blown by an outside air fan (not shown), thereby dissipating heat contained in the heat medium to the outside air OA.

[0054] The radiator 21 is disposed at the front side inside the vehicle bonnet. As the above-mentioned outside air fan is operated, the outside air OA flows from the front side of the vehicle to the rear and passes through the heat exchange portion of the radiator 21. When the vehicle is traveling, the traveling wind can be applied to the radiator 21 from the front side of the vehicle to the rear.

[0055] The heater core 22 is a heat exchanger that exchanges heat between the heat medium heated in the heat medium-refrigerant heat exchanger 12 or the like and the blown air W that has passed through the indoor evaporator 15 to heat the blown air W. As shown in Figs. 1 and 2, the heater core 22 is disposed in a casing 61 of the indoor air-conditioning unit 60.

[0056] 1, in the high-temperature side heat medium circuit 20, the radiator 21 and the heater core 22 are connected in parallel with respect to the flow of the heat medium in the high-temperature side heat medium circuit 20. That is, the high-temperature side heat medium circuit 20 has a common flow path 23 through which both the heat medium circulating through the radiator 21 and the heat medium circulating through the heater core 22 flow in common.

[0057] The common flow path 23 is configured to include a heat medium passage of the heat medium refrigerant heat exchanger 12. A heat medium branching section 24 is disposed on one end side of the common flow path 23. The heat medium branching section 24 is formed to have a three-way joint structure having three inlet and outlets that communicate with each other. In the heat medium branching section 24, one of the three inlet and outlets is used as an inlet, and the remaining two are used as outlets.

[0058] One end of the common flow path 23 is connected to the heat medium inlet side of the heat medium branching portion 24. The inlet side of the radiator 21 is connected to one outlet side of the heat medium branching portion 24 via a first solenoid valve 30a and a second reserve tank 29.

[0059] The other outlet side of the heat medium branching section 24 is connected to the inlet side of the heater core 22 via the second solenoid valve 30b. That is, the heat medium branching section 24 branches the flow of the heat medium at the end of the common flow path 23 into a flow toward the radiator 21 side and a flow toward the heater core 22 side.

[0060] A heat medium junction 25 is disposed on the other end side of the common flow path 23. The heat medium junction 25 is configured to have a three-way joint structure similar to the heat medium branching section 24, with one of the three inlet / outlet ports being an outlet port and the remaining two being inlets.

[0061] An outlet side of the radiator 21 is connected to one inlet side of the heat medium junction 25. An outlet side of the heater core 22 is connected to the other inlet side of the heat medium junction 25. An other end of the common flow path 23 is connected to the outlet side of the heat medium junction 25.

[0062] Therefore, in the high temperature side heat medium circuit 20, the common flow path 23 is connected so that the heat medium flowing out from the radiator 21 and the heat medium flowing out from the heater core 22 can flow in. In the common flow path 23, the heat medium junction 25 is located at the most upstream side of the heat medium flow. And the heat medium branching portion 24 is located at the most downstream side of the heat medium flow in the common flow path 23.

[0063] 1, in addition to the heat medium-refrigerant heat exchanger 12, an electric heater 26, a high-temperature side pump 27, and a first reserve tank 28 are arranged in the common flow path 23. The electric heater 26 is a heating device that generates heat when power is supplied to heat the heat medium flowing through the common flow path 23.

[0064] For example, a PTC heater having a PTC element (i.e., a positive temperature coefficient thermistor) can be used as the electric heater 26. The electric heater 26 can arbitrarily adjust the amount of heat for heating the heat medium by a control voltage output from the control device 70.

[0065] The electric heater 26 is disposed upstream of the heat medium branching section 24 with respect to the flow of the heat medium in the common flow path 23. Specifically, the inlet of the heat medium passage in the electric heater 26 is connected to the outlet side of the heat medium passage in the heat medium-refrigerant heat exchanger 12. The outlet side of the heat medium passage in the electric heater 26 is connected to the inlet side of the heat medium branching section 24. In other words, the electric heater 26 is disposed between the heat medium-refrigerant heat exchanger 12 and the heat medium branching section 24 in the common flow path 23.

[0066] The high-temperature side pump 27 is a heat medium pump that pumps the heat medium to circulate it in the high-temperature side heat medium circuit 20. The high-temperature side pump 27 is an electric pump whose rotation speed (i.e., pumping capacity) is controlled by a control voltage output from the control device 70.

[0067] 1, the suction port of the high-temperature side pump 27 is connected to the outlet side of the heat medium junction 25 via a first reserve tank 28. The discharge port of the high-temperature side pump 27 is connected to the inlet side of the heat medium passage in the heat medium-refrigerant heat exchanger 12. Therefore, the high-temperature side pump 27 is disposed in the common flow path 23 upstream of the heat medium-refrigerant heat exchanger 12 with respect to the flow of the heat medium.

[0068] The first reserve tank 28 is a heat medium storage section that stores excess heat medium. By storing excess heat medium in the first reserve tank 28, it is possible to suppress a decrease in the amount of heat medium circulating in the heat medium circuit. In addition, the first reserve tank 28 functions as a heat medium supply port for supplying the heat medium when the amount of heat medium in the heat medium circuit is insufficient.

[0069] In this manner, in the common flow path 23 of the high-temperature side heat medium circuit 20, the heat medium junction 25, the first reserve tank 28, the high-temperature side pump 27, the heat medium-refrigerant heat exchanger 12, the electric heater 26, and the heat medium branching section 24 are arranged in this order according to the flow of the heat medium.

[0070] The second reserve tank 29 is a heat medium storage section that stores excess heat medium, and is disposed on the inlet side of the radiator 21. The second reserve tank 29 also functions as a heat medium supply port for supplying the heat medium when the amount of heat medium in the heat medium circuit becomes insufficient.

[0071] 1, the high temperature side heat medium circuit 20 has a circuit switching unit 30 for controlling the flow rate of the heat medium flowing to the radiator 21 side and the flow rate of the heat medium flowing to the heater core 22 side at the heat medium branching section 24. Specifically, the circuit switching unit 30 is composed of a first solenoid valve 30a and a second solenoid valve 30b.

[0072] The first solenoid valve 30a is a solenoid valve configured to be able to adjust the opening degree of the heat medium flow path, and is connected to one of the outlets of the heat medium branching portion 24. The first solenoid valve 30a has a fully closing function and a fully opening function.

[0073] The second solenoid valve 30b, like the first solenoid valve 30a, is a solenoid valve configured to be able to adjust the opening degree of the heat medium flow path, and is disposed at the other outlet of the heat medium branching section 24. The second solenoid valve 30b has a full-close function and a full-close function.

[0074] Therefore, when the second solenoid valve 30b is fully closed, the circuit switching unit 30 can cause the heat medium that has passed through the heat medium branching unit 24 to flow into the radiator 21. When the first solenoid valve 30a is fully closed, the circuit switching unit 30 can cause the heat medium that has passed through the heat medium branching unit 24 to flow into the heater core 22. In other words, the circuit switching unit 30 can switch the circuit configuration of the high temperature side heat medium circuit 20.

[0075] In the vehicle air conditioner 1, a shutter device 31 is disposed in front of the radiator 21. The shutter device 31 is configured by rotatably arranging a plurality of blades in an opening of a frame. The plurality of blades rotate in conjunction with each other by the operation of an electric actuator (not shown) to adjust the opening area of ​​the opening of the frame. In this way, the shutter device 31 can adjust the flow rate of the outside air OA passing through the heat exchange section of the radiator 21, and therefore the heat exchange capacity of the radiator 21 can be adjusted.

[0076] The high-temperature side heat medium circuit 20 configured in this manner can switch the flow of the heat medium by controlling the circuit switching unit 30. When the second solenoid valve 30b is fully closed, the heat medium circulates in the order of the heat medium junction 25, the first reserve tank 28, the high-temperature side pump 27, the heat medium-refrigerant heat exchanger 12, the electric heater 26, the first solenoid valve 30a, the second reserve tank 29, the radiator 21, and the heat medium junction 25. In this case, it is possible to dissipate heat of the heat medium in the high-temperature side heat medium circuit 20 to the outside air OA, and to defrost the radiator 21 that has become frosted by the heat of the heat medium.

[0077] On the other hand, when the first solenoid valve 30a is fully closed, the heat medium circulates in the order of the heat medium junction 25, the first reserve tank 28, the high temperature side pump 27, the heat medium-refrigerant heat exchanger 12, the electric heater 26, the second solenoid valve 30b, the heater core 22, and the heat medium junction 25. In this case, the heat of the heat medium in the high temperature side heat medium circuit 20 can be used to heat the blown air W in the heater core 22, thereby realizing heating of the vehicle interior.

[0078] Next, a description will be given of the configuration of the low-temperature side heat medium circuit 40 in the vehicle air conditioner 1. The low-temperature side heat medium circuit 40 is a heat medium circuit that circulates a heat medium. As the heat medium in the low-temperature side heat medium circuit 40, the same fluid as that in the high-temperature side heat medium circuit 20 can be used.

[0079] The low-temperature side heat medium circuit 40 includes a heat medium passage of the chiller 16, a low-temperature side pump 41, a battery 42, a charger 43, a low-temperature side three-way valve 44, etc. The discharge port side of the low-temperature side pump 41 is connected to the inlet of the heat medium passage in the chiller 16. The low-temperature side pump 41 is a heat medium pump that pumps the heat medium in the low-temperature side heat medium circuit 40 to the inlet side of the heat medium passage of the chiller 16. The basic configuration of the low-temperature side pump 41 is the same as that of the high-temperature side pump 27.

[0080] One of the inlet and outlet of the low-temperature side three-way valve 44 is connected to the outlet of the heat medium passage in the chiller 16. The low-temperature side three-way valve 44 is configured by an electric three-way flow control valve having three inlet and outlets.

[0081] Another inlet / outlet of the low-temperature side three-way valve 44 is connected to the inlet side of the heat medium passage in the battery 42. The battery 42 supplies power to various electric devices of the vehicle, and is, for example, a chargeable and dischargeable secondary battery (in this embodiment, a lithium ion battery). The heat medium passage of the battery 42 is formed in a cover of the battery 42, and by passing a heat medium through it, the temperature of the battery 42 can be adjusted and the temperature of the battery 42 can be maintained within a predetermined temperature range.

[0082] The outlet side of the heat medium passage of the battery 42 is connected to the inlet side of the heat medium passage of the charger 43. The charger 43 is a charger that charges the battery 42 with power. The charger 43 generates heat when charging the battery 42, and therefore the charger 43 can be cooled by the heat medium of the low-temperature side heat medium circuit 40.

[0083] An outlet side of the heat medium passage in the charger 43 is connected to the suction port of the low-temperature side pump 41. Therefore, the low-temperature side heat medium circuit 40 can circulate the heat medium by the low-temperature side pump 41.

[0084] 1, yet another inlet / outlet of the low-temperature side three-way valve 44 is connected to a heat medium pipe that connects the outlet of the radiator 21 and the heat medium junction 25. In addition, the outlet of the heat medium passage in the charger 43 is connected to a heat medium pipe that connects the outlet of the first solenoid valve 30a and the inlet of the second reserve tank 29. That is, the low-temperature side heat medium circuit 40 according to the first embodiment connects the battery 42 and the charger 43 to the radiator 21 and the second reserve tank 29 in parallel.

[0085] Therefore, the low-temperature side heat medium circuit 40 can switch the flow of the heat medium in the low-temperature side heat medium circuit 40 by controlling the operation of the low-temperature side three-way valve 44. For example, the low-temperature side three-way valve 44 can communicate the inlet / outlet on the chiller 16 side with the inlet / outlet on the battery 42 side, and close the remaining inlet / outlet.

[0086] In this case, the heat medium in the low-temperature side heat medium circuit 40 flows in the order of the low-temperature side pump 41, the chiller 16, the low-temperature side three-way valve 44, the battery 42, the charger 43, and the low-temperature side pump 41, and circulates through the low-temperature side heat medium circuit 40. According to this embodiment, the heat medium cooled by the chiller 16 can be supplied to the battery 42 and the charger 43, so that the battery 42 and the charger 43 can be cooled.

[0087] Furthermore, the low-temperature side three-way valve 44 can interconnect the three inlet and outlet ports. According to this embodiment, the heat medium in the low-temperature side heat medium circuit 40 flows through the low-temperature side pump 41, chiller 16, and low-temperature side three-way valve 44 in this order, and then branches at the low-temperature side three-way valve 44. One direction of the heat medium flow passes through the low-temperature side three-way valve 44, battery 42, and charger 43 in this order, and the other direction passes through the low-temperature side three-way valve 44, radiator 21, and second reserve tank 29 in this order.

[0088] Then, the heat medium flowing out from the charger 43 and the heat medium flowing out from the second reserve tank 29 join together and reach the suction port of the low-temperature side pump 41. In this case, the low-temperature side heat medium circuit 40 can simultaneously cool the battery 42 and the charger 43 and exchange heat with the outside air OA in the radiator 21.

[0089] The vehicle air conditioner 1 can cool and adjust the temperature of the battery 42 and the charger 43 by utilizing the low-temperature side heat medium circuit 40. In addition, the vehicle air conditioner 1 can use the outside air OA as a heat source and dissipate heat to the outside air OA by utilizing the radiator 21.

[0090] Next, a description will be given of the configuration of the equipment heat medium circuit 50 in the vehicle air conditioner 1. The equipment heat medium circuit 50 is a heat medium circuit that circulates a heat medium. As the heat medium for the equipment heat medium circuit 50, the same fluid as that for the high temperature side heat medium circuit 20 described above can be used.

[0091] The heat medium circuit 50 for equipment includes a heat medium passage for an on-vehicle device 51, an equipment pump 52, an equipment three-way valve 53, etc. The on-vehicle device 51 is mounted on an electric vehicle and is composed of devices that generate heat when in operation. The on-vehicle device 51 includes, for example, an inverter, a motor generator, a transaxle device, etc.

[0092] The inverter is a power conversion unit that converts direct current into alternating current. The motor generator receives power to output driving force for running, and generates regenerative power during deceleration. The transaxle device is a device that integrates a transmission with a final gear and a differential gear (diff gear). The heat medium passages in the on-vehicle equipment 51 are formed so that each equipment can be cooled by circulating the heat medium in the equipment heat medium circuit 50.

[0093] An outlet of an equipment pump 52 is connected to the inlet side of the heat medium passage in the on-vehicle equipment 51. The equipment pump 52 is a heat medium pump that pumps the heat medium in the equipment heat medium circuit 50 to the inlet side of the heat medium passage in the on-vehicle equipment 51. The basic configuration of the equipment pump 52 is similar to that of the high-temperature side pump 27 and the like.

[0094] 1, the suction port of the equipment pump 52 is connected to a heat medium piping that connects the outlet of the first solenoid valve 30a and the inlet of the second reserve tank 29. More specifically, the heat medium piping extending from the equipment pump 52 is connected between the connection portion with the heat medium piping extending from the suction port of the low-temperature side pump 41 and the inlet of the second reserve tank 29.

[0095] One of the inlet / outlet ports of the equipment three-way valve 53 is connected to the outlet side of the heat medium passage in the vehicle-mounted equipment 51. The equipment three-way valve 53 is configured by an electric three-way flow control valve having three inlet / outlets.

[0096] Another inlet / outlet of the equipment three-way valve 53 is connected to a heat medium piping that connects the outlet of the radiator 21 and the heat medium junction 25. More specifically, the heat medium piping extending from the equipment three-way valve 53 is connected between the outlet of the radiator 21 and a connection portion with the heat medium piping extending from the low-temperature side three-way valve 44.

[0097] Therefore, according to the equipment heat medium circuit 50, the heat medium that has passed through the in-vehicle equipment 51 can be supplied to the radiator 21, and the heat absorbed from the in-vehicle equipment 51 can also be dissipated to the outside air OA via the heat medium.

[0098] Here, a bypass flow passage 54 is connected to yet another inlet / outlet of the equipment three-way valve 53. The bypass flow passage 54 is a heat medium flow passage for causing the flow of the heat medium to bypass the radiator 21 and the second reserve tank 29. The other end of the bypass flow passage 54 is connected to the suction port side of the equipment pump 52.

[0099] Therefore, the equipment heat medium circuit 50 can switch the flow of the heat medium in the equipment heat medium circuit 50 by controlling the operation of the equipment three-way valve 53. For example, the equipment three-way valve 53 can communicate the inlet / outlet on the in-vehicle equipment 51 side with the inlet / outlet on the bypass flow path 54 side, and close the remaining inlet / outlet. In this case, the heat medium in the equipment heat medium circuit 50 circulates by flowing through the equipment pump 52, the in-vehicle equipment 51, the equipment three-way valve 53, the bypass flow path 54, and the equipment pump 52 in this order.

[0100] Moreover, the equipment three-way valve 53 can close the inlet / outlet on the bypass flow path 54 side and communicate the remaining two inlet / outlets. In this case, the heat medium in the equipment heat medium circuit 50 circulates by flowing through the equipment pump 52, the in-vehicle equipment 51, the equipment three-way valve 53, the radiator 21, the second reserve tank 29, and the equipment pump 52 in that order.

[0101] According to this embodiment, the heat medium that absorbs heat from the in-vehicle equipment 51 can be supplied to the radiator 21, so that the heat generated in the in-vehicle equipment 51 can be dissipated to the outside air OA. In other words, the vehicle air conditioner 1 can cool and adjust the temperature of the in-vehicle equipment 51 by using the equipment heat medium circuit 50.

[0102] Next, the interior air conditioning unit 60 constituting the vehicle air conditioner 1 will be described with reference to Fig. 2. The interior air conditioning unit 60 is a unit for blowing out the blown air W, the temperature of which has been adjusted by the refrigeration cycle device 10, to an appropriate location in the vehicle cabin in the vehicle air conditioner 1. The interior air conditioning unit 60 is disposed inside the instrument panel (i.e., the instrument panel) at the frontmost part of the vehicle cabin.

[0103] The interior air conditioning unit 60 accommodates a blower 62, the interior evaporator 15, the heater core 22, etc. in an air passage formed inside a casing 61 that forms the outer shell of the unit. The casing 61 forms an air passage for blown air W into the vehicle cabin. The casing 61 is molded from a resin (specifically, polypropylene) that has a certain degree of elasticity and excellent strength.

[0104] 2, an inside / outside air switching device 63 is disposed on the most upstream side of the blown air flow of the casing 61. The inside / outside air switching device 63 switches between introducing inside air (air inside the vehicle cabin) and outside air (air outside the vehicle cabin) into the casing 61.

[0105] The inside / outside air switching device 63 continuously adjusts the opening area of ​​the inside air inlet for introducing inside air into the casing 61 and the outside air inlet for introducing outside air into the casing 61 using an inside / outside air switching door to change the ratio of the amount of inside air introduced to the amount of outside air introduced. The inside / outside air switching door is driven by an electric actuator for the inside / outside air switching door. The operation of this electric actuator is controlled by a control signal output from the control device 70.

[0106] A blower 62 is disposed downstream of the inside / outside air switching device 63 in the flow of blown air. The blower 62 is configured by an electric blower that drives a centrifugal multi-blade fan by an electric motor. The blower 62 blows the air drawn in through the inside / outside air switching device 63 toward the vehicle interior. The rotation speed (i.e., blowing capacity) of the blower 62 is controlled by a control voltage output from the control device 70.

[0107] The indoor evaporator 15 and the heater core 22 are disposed in this order with respect to the flow of the blown air downstream of the blower 62. That is, the indoor evaporator 15 is disposed upstream of the heater core 22 with respect to the flow of the blown air.

[0108] Further, a cold air bypass passage 65 is formed inside the casing 61. The cold air bypass passage 65 is an air passage that causes the blown air W that has passed through the indoor evaporator 15 to bypass the heater core 22 and flow downstream.

[0109] An air mix door 64 is disposed downstream of the indoor evaporator 15 and upstream of the heater core 22. The air mix door 64 adjusts the ratio of the amount of air passing through the heater core 22 and the amount of air passing through the cold air bypass passage 65 of the air W that has passed through the indoor evaporator 15.

[0110] The air mix door 64 is driven by an electric actuator for driving the air mix door. The operation of this electric actuator is controlled by a control signal output from the control device 70.

[0111] A mixing space 66 is provided downstream of the heater core 22 in the flow of the blown air. In the mixing space 66, the blown air W heated by the heater core 22 and the blown air W that has passed through the cold air bypass passage 65 and has not been heated by the heater core 22 are mixed.

[0112] Furthermore, at the most downstream portion of the blown air flow of the casing 61, openings for blowing out the blown air (conditioned air) mixed in the mixing space 66 into the vehicle compartment are arranged. As these openings, a face opening, a foot opening, and a defroster opening (none of which are shown) are provided.

[0113] The face opening is an opening for blowing conditioned air toward the upper body of the occupant in the vehicle cabin, the foot opening is an opening for blowing conditioned air toward the feet of the occupant, and the defroster opening is an opening for blowing conditioned air toward the inside surface of the vehicle front windshield.

[0114] These face opening holes, foot opening holes, and defroster opening holes are each connected to a face air outlet, a foot air outlet, and a defroster air outlet (none of which are shown) provided in the vehicle cabin via ducts that form air passages.

[0115] Therefore, the air mix door 64 adjusts the ratio of the air volume passing through the heater core 22 and the air volume passing through the cold air bypass passage 65, thereby adjusting the temperature of the conditioned air mixed in the mixing space 66. This also adjusts the temperature of the blown air (conditioned air) blown into the vehicle compartment from each air outlet.

[0116] A face door, a foot door, and a defroster door (none of which are shown) are disposed upstream of the face opening hole, the foot opening hole, and the defroster opening hole in the flow of blown air, respectively. The face door adjusts the opening area of ​​the face opening hole. The foot door adjusts the opening area of ​​the foot opening hole. The defroster door adjusts the opening area of ​​the defroster opening hole.

[0117] The face door, foot door, and defroster door constitute a blowing mode switching device that switches the blowing outlet from which the conditioned air is blown out. The face door, foot door, and defroster door are connected to an electric actuator for driving the blowing outlet mode door via a link mechanism or the like, and are rotated in conjunction with each other. The operation of this electric actuator is controlled by a control signal output from the control device 70.

[0118] Next, a control system of the vehicle air conditioner 1 according to the first embodiment will be described with reference to Fig. 3. The control device 70 is composed of a well-known microcomputer including a CPU, ROM, RAM, etc., and its peripheral circuits.

[0119] The control device 70 performs various calculations and processes based on the control programs stored in the ROM, and controls the operation of various control target devices connected to the output side of the control device 70. The control device 70 corresponds to an example of a control unit.

[0120] The controlled devices include the compressor 11, the first expansion valve 14a, the second expansion valve 14b, the electric heater 26, the high-temperature side pump 27, the first solenoid valve 30a, the second solenoid valve 30b, and the shutter device 31. Furthermore, the controlled devices include the low-temperature side pump 41, the low-temperature side three-way valve 44, the device pump 52, the device three-way valve 53, the blower 62, and the like.

[0121] As shown in Fig. 3, a group of sensors for controlling air conditioning is connected to the input side of the control device 70. The group of sensors for controlling air conditioning includes an inside air temperature sensor 72a, an outside air temperature sensor 72b, a solar radiation sensor 72c, a high pressure sensor 72d, a chiller side pressure sensor 72e, an evaporator temperature sensor 72f, a junction temperature sensor 72g, an air conditioning air temperature sensor 72h, and a battery temperature sensor 72i. Detection signals of the group of sensors for controlling air conditioning are input to the control device 70.

[0122] The inside air temperature sensor 72a is an inside air temperature detector that detects the temperature inside the vehicle cabin (inside air temperature) Tr. The outside air temperature sensor 72b is an outside air temperature detector that detects the temperature outside the vehicle cabin (outside air temperature) Tam. The solar radiation sensor 72c is an solar radiation amount detector that detects the amount of solar radiation As irradiated into the vehicle cabin.

[0123] The high-pressure sensor 72d is a refrigerant temperature detection unit that detects the high-pressure refrigerant temperature in the refrigerant flow path from the discharge port side of the compressor 11 to the inlet side of the first expansion valve 14a or the second expansion valve 14b. The high-pressure sensor 72d is disposed on the outlet side of the refrigerant passage of the heat medium refrigerant heat exchanger 12, and detects the temperature of the refrigerant flowing out from the refrigerant passage of the heat medium refrigerant heat exchanger 12. The high-pressure sensor 72d corresponds to an example of a high-pressure side temperature detection unit. The chiller side pressure sensor 72e is a refrigerant pressure detection unit that detects the refrigerant pressure on the outlet side of the refrigerant flow path of the chiller 16. The chiller side pressure sensor 72e corresponds to an example of a refrigerant pressure detection unit.

[0124] The evaporator temperature sensor 72f is an evaporator temperature detector that detects the refrigerant evaporation temperature (evaporator temperature) Tefin in the interior evaporator 15. The junction temperature sensor 72g is a refrigerant temperature detector that detects the refrigerant temperature at the junction 13b of the refrigeration cycle device 10. The air conditioning air temperature sensor 72h is an air conditioning air temperature detector that detects the temperature TAV of the air blown into the vehicle cabin.

[0125] The battery temperature sensor 72i is a battery temperature detection unit that detects the battery temperature TB (i.e., the temperature of the battery 42). The battery temperature sensor 72i has multiple temperature sensors and detects the temperatures of multiple locations of the battery 42. Therefore, the control device 70 can also detect the temperature difference between each portion of the battery 42. The average value of the detection values ​​of the multiple temperature sensors is used as the battery temperature TB.

[0126] A plurality of heat medium temperature sensors are connected to the input side of the control device 70 in order to detect the temperature of the heat medium in each of the high-temperature side heat medium circuit 20, the low-temperature side heat medium circuit 40, and the equipment heat medium circuit 50. The plurality of heat medium temperature sensors include a first heat medium temperature sensor 73a to a fifth heat medium temperature sensor 73e.

[0127] The first heat medium temperature sensor 73a is disposed at the inlet of the heat medium branching section 24 to which the common flow path 23 is connected, and detects the temperature of the heat medium flowing out from the common flow path 23. The second heat medium temperature sensor 73b is disposed at the inlet of the radiator 21, and detects the temperature of the heat medium passing through the radiator 21. The third heat medium temperature sensor 73c is disposed at the inlet of the heater core 22, and detects the temperature of the heat medium passing through the heater core 22.

[0128] The fourth heat medium temperature sensor 73d is disposed at the outlet of the heat medium passage in the chiller 16, and detects the temperature of the heat medium flowing out from the chiller 16. The fifth heat medium temperature sensor 73e is disposed at the outlet of the heat medium passage in the in-vehicle device 51, and detects the temperature of the heat medium flowing out from the heat medium passage of the in-vehicle device 51.

[0129] The vehicle air conditioner 1 refers to the detection results of the first heat medium temperature sensor 73a to the fifth heat medium temperature sensor 73e and switches the flow of the heat medium in the high temperature side heat medium circuit 20, the low temperature side heat medium circuit 40, and the equipment heat medium circuit 50. This allows the vehicle air conditioner 1 to manage heat in the vehicle using the heat medium.

[0130] Furthermore, an operation panel 71 arranged near the instrument panel at the front of the vehicle interior is connected to the input side of the control device 70. A plurality of operation switches are arranged on the operation panel 71. Therefore, operation signals from the plurality of operation switches are input to the control device 70. The various operation switches on the operation panel 71 include an auto switch, a cooling switch, an air volume setting switch, a temperature setting switch, etc.

[0131] The auto switch is operated to set or cancel the automatic control operation of the vehicle air conditioner 1. The cooling switch is operated to request cooling of the vehicle interior. The air volume setting switch is operated to manually set the air volume of the blower 62. And the temperature setting switch is operated to set a target temperature Tset for the vehicle interior.

[0132] In the control device 70, a control unit that controls various controlled devices connected to the output side is integrally configured, and the configuration (hardware and software) that controls the operation of each controlled device configures the control unit that controls the operation of each controlled device. For example, in the control device 70, when an operation mode (e.g., air conditioning cooling mode) in which the refrigerant is circulated through the indoor evaporator 15 and the chiller 16 is performed, the configuration that controls the operation to suppress the retention of refrigeration oil is the retention suppression control unit 70a.

[0133] In the control device 70, a configuration for making a determination regarding liquid backflow of refrigerant to the compressor 11 in an operation mode in which the refrigerant is circulated through the indoor evaporator 15 and the chiller 16 is the determination unit 70b. In the control device 70, a configuration for controlling the operation of the second expansion valve 14b in order to suppress liquid backflow of refrigerant to the compressor 11 is the pressure reduction control unit 70c. In the control device 70, a configuration for controlling the refrigerant discharge capacity (i.e., rotation speed) of the compressor 11 in order to suppress liquid backflow of refrigerant to the compressor 11 is the discharge capacity control unit 70d.

[0134] Next, the operation of the vehicle air conditioner 1 in the first embodiment will be described. As described above, the vehicle air conditioner 1 in the first embodiment can switch between a plurality of operation modes as appropriate. The switching between these operation modes is performed by executing a control program stored in advance in the control device 70.

[0135] More specifically, the control program calculates a target blowing temperature TAO of the air to be blown into the vehicle cabin based on detection signals detected by the group of air conditioning control sensors and operation signals output from the operation panel 71. Then, based on the target blowing temperature TAO and the detection signals, the operation mode related to the vehicle cabin air conditioning is switched.

[0136] Moreover, based on detection signals from the heat medium temperature sensor group and the battery temperature TB, an operation mode for adjusting the temperature of the battery 42 and the in-vehicle device 51 is determined. Whether or not to cool the battery 42 is determined based on, for example, whether or not the battery temperature TB exceeds a threshold value. When the battery temperature TB exceeds the threshold value, the operation mode is switched to one for cooling the battery 42.

[0137] Therefore, the multiple operation modes of the vehicle air conditioner 1 are configured by combinations of operation modes related to the air conditioning of the vehicle interior and operation modes related to cooling the battery 42. The multiple operation modes include a heating mode, a cooling mode, a dehumidifying heating mode, a heating / cooling mode, a cooling / cooling mode, and a dehumidifying heating / cooling mode.

[0138] The heating mode is an operation mode in which the blown air to be blown into the vehicle cabin is heated by the heater core 22 and supplied to the vehicle cabin without cooling the battery 42. The cooling mode is an operation mode in which the blown air is cooled by the interior evaporator 15 and supplied to the vehicle cabin without cooling the battery 42. The dehumidification heating mode is an operation mode in which the blown air dehumidified by the interior evaporator 15 is heated by the heater core 22 and supplied to the vehicle cabin without cooling the battery 42.

[0139] Furthermore, the heating / cooling mode is an operation mode in which the battery 42 is cooled, and the blown air is heated by the heater core 22 and supplied to the vehicle interior. The cooling / cooling mode is an operation mode in which the battery 42 is cooled, and the blown air is cooled by the interior evaporator 15 and supplied to the vehicle interior. And the dehumidifying heating / cooling mode is an operation mode in which the battery 42 is cooled, and the blown air dehumidified by the interior evaporator 15 is heated by the heater core 22 and supplied to the vehicle interior.

[0140] Among the multiple operation modes in the first embodiment, there are a cooling / cooling mode and a dehumidifying / heating / cooling mode as operation modes in which refrigerant flows through both the indoor evaporator 15 and the chiller 16. In the following description, the operation of the cooling / cooling mode will be described in detail as a specific example of the operation mode in which refrigerant flows through both the indoor evaporator 15 and the chiller 16.

[0141] In the cooling / cooling mode, the control device 70 opens the first expansion valve 14a and the second expansion valve 14b to a predetermined throttle opening. Therefore, in the refrigeration cycle device 10 in the cooling / cooling mode, the refrigerant first flows through the compressor 11, the heat medium refrigerant heat exchanger 12, and the branch portion 13a.

[0142] Then, the refrigerant flowing out from one side of the branching portion 13a flows to the first expansion valve 14a, the indoor evaporator 15, and the evaporation pressure regulating valve 17, and the refrigerant flowing out from the other side of the branching portion 13a flows to the second expansion valve 14b and the chiller 16. The refrigerant flowing out from the evaporation pressure regulating valve 17 and the refrigerant flowing out from the chiller 16 join at the joining portion 13b, and then flow and circulate in this order to the compressor 11.

[0143] In other words, in the air-conditioning cooling mode, the refrigerant is caused to flow into the indoor evaporator 15 to cool the blown air W, and the refrigerant is caused to flow into the chiller 16 to cool the heat medium in the low-temperature side heat medium circuit 40.

[0144] In this cycle configuration, the control device 70 controls the operation of various control target devices connected to the output side. For example, the control device 70 controls the operation of the compressor 11 so that the refrigerant evaporation temperature Tefin detected by the evaporator temperature sensor 72f becomes the target evaporation temperature TEO. The target evaporation temperature TEO is determined based on the target blowing temperature TAO by referring to a control map for the cooling mode stored in advance in the control device 70.

[0145] Specifically, in this control map, the target evaporation temperature TEO is increased with an increase in the target outlet temperature TAO so that the blown air temperature TAV detected by the air conditioning air temperature sensor 72h approaches the target outlet temperature TAO. Furthermore, the target evaporation temperature TEO is determined to a value within a range (specifically, 1° C. or higher) that can suppress frost formation on the indoor evaporator 15.

[0146] Then, the control device 70 determines the control voltage (blowing capacity) of the blower 62 by referring to a control map stored in advance in the control device 70 based on the target blowing temperature TAO. Specifically, in this control map, the blowing amount of the blower 62 is maximized in the extremely low temperature range (maximum cooling range) and the extremely high temperature range (maximum heating range) of the target blowing temperature TAO, and the blowing amount is reduced as the temperature approaches the intermediate temperature range. In addition, the control device 70 controls the operation of the air mix door 64 so that the cool air bypass passage 65 is fully opened and the ventilation passage on the heater core 22 side is closed.

[0147] For the high-temperature side heat medium circuit 20, the control device 70 controls the operation of the high-temperature side pump 27 so as to exert a predetermined water pumping capacity in the air-conditioning cooling mode. The control device 70 also controls the circuit switching unit 30 so as to fully open the first solenoid valve 30a and fully close the second solenoid valve 30b.

[0148] As a result, the heat medium in the high-temperature side heat medium circuit 20 circulates through the high-temperature side pump 27, heat medium-refrigerant heat exchanger 12, electric heater 26, heat medium branching section 24, first solenoid valve 30a, second reserve tank 29, radiator 21, heat medium junction 25, and high-temperature side pump 27 in that order.

[0149] With regard to the low-temperature side heat medium circuit 40, the controller 70 controls the operation of the low-temperature side pump 41 so as to exert the water pumping capacity in the air-conditioning cooling mode. The controller 70 also controls the operation of the low-temperature side three-way valve 44 to communicate the inlet / outlet on the chiller 16 side with the inlet / outlet on the battery 42 side, and closes the remaining inlet / outlet. As a result, the heat medium in the low-temperature side heat medium circuit 40 circulates in the order of the low-temperature side pump 41, chiller 16, low-temperature side three-way valve 44, battery 42, charger 43, and low-temperature side pump 41.

[0150] In the equipment heat medium circuit 50, the control device 70 controls the operation of the equipment pump 52 so as to exert a predetermined water pumping capacity in the air-conditioning cooling mode. The control device 70 also controls the operation of the equipment three-way valve 53 to communicate the inlet / outlet on the vehicle-mounted equipment 51 side with the inlet / outlet on the bypass flow path 54 side, and closes the remaining inlet / outlet. As a result, the heat medium in the equipment heat medium circuit 50 circulates in the order of the equipment pump 52, the vehicle-mounted equipment 51, the equipment three-way valve 53, the bypass flow path 54, and the equipment pump 52.

[0151] In this way, in the refrigeration cycle apparatus 10 in the cooling / cooling mode, the high-pressure refrigerant discharged from the compressor 11 flows into the heat medium refrigerant heat exchanger 12. In the heat medium refrigerant heat exchanger 12, since the high-temperature side pump 27 is operating, the high-pressure refrigerant and the heat medium in the high-temperature side heat medium circuit 20 exchange heat, so that the high-pressure refrigerant is cooled and condensed, and the heat medium is heated.

[0152] In the high-temperature side heat medium circuit 20, the heat medium heated in the heat medium-refrigerant heat exchanger 12 flows into the radiator 21 via the heat medium branching section 24 and the first solenoid valve 30a. The heat medium that flows into the radiator 21 exchanges heat with the outside air OA and dissipates heat. This cools the heat medium in the high-temperature side heat medium circuit 20. The heat medium cooled in the radiator 21 is sucked into the high-temperature side pump 27 and pumped back to the heat medium passage of the heat medium-refrigerant heat exchanger 12.

[0153] On the other hand, the high-pressure refrigerant cooled in the refrigerant passage of the heat medium refrigerant heat exchanger 12 flows into the first expansion valve 14a via the branching portion 13a and is reduced in pressure. The throttle opening of the first expansion valve 14a is basically adjusted so that the degree of superheat of the refrigerant on the outlet side of the indoor evaporator 15 is approximately 3°C.

[0154] However, the minimum value of the throttle opening of the first expansion valve 14a is limited in order to suppress the accumulation of refrigeration oil in the indoor evaporator 15 by the low-pressure refrigerant decompressed by the first expansion valve 14a. By limiting the minimum value of the throttle opening of the first expansion valve 14a, the flow rate of the refrigerant flowing through the indoor evaporator 15 is ensured to be equal to or higher than a reference flow rate capable of suppressing the accumulation of refrigeration oil.

[0155] The low-pressure refrigerant decompressed by the first expansion valve 14a flows into the indoor evaporator 15. The refrigerant that flows into the indoor evaporator 15 absorbs heat from the blown air W blown by the blower 62 and evaporates, cooling the blown air W. The refrigerant that flows out of the indoor evaporator 15 is appropriately decompressed by the evaporation pressure regulating valve 17, and is sucked into the compressor 11 via the junction 13b and compressed again.

[0156] Therefore, in the air-cooling mode, the ventilation air W cooled by the interior evaporator 15 is blown into the vehicle compartment, thereby cooling the vehicle compartment.

[0157] The high-pressure refrigerant flowing out from the other side of the branch portion 13a flows into the second expansion valve 14b and is reduced in pressure. The throttle opening of the second expansion valve 14b is usually determined so that the superheat degree of the refrigerant on the outlet side of the refrigerant passage of the chiller 16 approaches a target superheat degree.

[0158] The low-pressure refrigerant decompressed by the second expansion valve 14b flows into the chiller 16 and evaporates by absorbing heat from the heat medium flowing through the heat medium passage of the chiller 16. This cools the heat medium in the low-temperature side heat medium circuit 40. The low-pressure refrigerant flowing out of the chiller 16 is drawn into the compressor 11 via the junction 13b and compressed again.

[0159] Here, in the low-temperature side heat medium circuit 40, the heat medium cooled in the chiller 16 flows into the battery 42 and the charger 43 through the low-temperature side three-way valve 44. In the heat medium passages of the battery 42 and the charger 43, the heat medium absorbs heat from the battery 42 and the charger 43, thereby cooling the battery 42 and the charger 43. The heat medium flowing out of the charger 43 is sucked into the low-temperature side pump 41 and pumped back to the heat medium passage of the chiller 16.

[0160] In other words, according to the vehicle air conditioning device 1, the heat absorbed when cooling the blown air W and the heat absorbed when cooling the battery 42 and the charger 43 can be absorbed by the chiller 16 from the heat medium in the low-temperature side heat medium circuit 40 to the low-pressure refrigerant.

[0161] In the vehicle air conditioner 1, the refrigeration cycle device 10 pumps up heat absorbed in the chiller 16 and the indoor evaporator 15, and dissipates the heat to the heat medium in the high-temperature side heat medium circuit 20 in the heat medium refrigerant heat exchanger 12, thereby heating the heat medium. The vehicle air conditioner 1 can dissipate the heat of the heat medium in the high-temperature side heat medium circuit 20 to the outside air OA in the radiator 21.

[0162] In this air conditioning / cooling mode, the high-temperature side heat medium circuit 20 is configured to dissipate the heat contained in the heat medium to the outside air OA. However, by changing the circuit configuration of the high-temperature side heat medium circuit 20, a circuit configuration for the dehumidification / heating / cooling mode can be realized.

[0163] Specifically, in the circuit configuration in the dehumidifying, heating and cooling mode, the circuit configurations of the refrigeration cycle device 10, the low-temperature side heat medium circuit 40 and the equipment heat medium circuit 50 are the same as those in the cooling and cooling mode. For the high-temperature side heat medium circuit 20 in the dehumidifying, heating and cooling mode, the control device 70 controls the circuit switching unit 30 to fully open the second solenoid valve 30b and fully close the first solenoid valve 30a.

[0164] As a result, the heat medium in the high-temperature side heat medium circuit 20 circulates in the order of the high-temperature side pump 27, the heat medium refrigerant heat exchanger 12, the electric heater 26, the heat medium branching section 24, the second solenoid valve 30b, the heater core 22, the heat medium junction 25, and the high-temperature side pump 27. In other words, in the dehumidification, heating, and cooling mode, the blown air W dehumidified by the interior evaporator 15 can be heated by the heater core 22 using the heat of the heat medium as a heat source, and supplied to the vehicle interior. It goes without saying that in the dehumidification, heating, and cooling mode, the electric heater 26 may be operated as necessary.

[0165] In this way, the lower limit of the throttle opening of the first expansion valve 14a is limited to suppress accumulation of refrigeration oil in the air-conditioning mode of the vehicle air-conditioning device 1. In other words, there is a limit to the minimum value of the refrigerant flow rate circulating through the indoor evaporator 15 that can be adjusted by the first expansion valve 14a.

[0166] On the other hand, the cooling load in the indoor evaporator 15 is determined by the temperature of the blown air W to be cooled and the air volume of the blown air W passing through the indoor evaporator 15. For this reason, the cooling load in the indoor evaporator 15 may be too low compared to the refrigerant flow rate circulating through the indoor evaporator 15. In this case, the refrigerant that has flowed into the indoor evaporator 15 may not be completely evaporated, and liquid backflow may occur, in which the refrigerant remains in the liquid phase and flows into the intake port of the compressor 11. When liquid backflow occurs, it is expected that the compression mechanism in the compressor 11 may break down due to liquid compression.

[0167] In the vehicle air conditioning system 1 according to the first embodiment, a control program is executed during an air conditioning mode or the like to suppress both accumulation of refrigeration oil in the interior evaporator 15 and failure of the compressor 11 due to liquid backflow.

[0168] The control program shown in Fig. 4 is executed when the minimum value of the throttle opening of the first expansion valve 14a is restricted in an operation mode (e.g., air-conditioning mode, dehumidifying heating and cooling mode) in which the refrigerant circulates through the indoor evaporator 15 and the chiller 16. That is, the control device 70 executes the control program shown in Fig. 4 when the refrigerant flow rate to the indoor evaporator 15 is sufficient to suppress stagnation of refrigeration oil in an operation mode in which the refrigerant circulates through the indoor evaporator 15 and the chiller 16.

[0169] First, in step S10, it is determined whether or not a liquid backflow condition is satisfied, which indicates a state in which there is a high possibility of a breakdown of the compressor 11 due to liquid backflow. In the first embodiment, with reference to the control map shown in Fig. 5, it is determined whether or not the liquid backflow condition is satisfied by comparing the cooling load in the indoor evaporator 15 with a reference value defined in the control map.

[0170] Specifically, the process in step S10 will be described. In step S10, first, the cooling load in the indoor evaporator 15 is determined using the volume of the air passing through the indoor evaporator 15 and the temperature of the air passing through the indoor evaporator 15.

[0171] The volume of the air passing through the indoor evaporator 15 can be determined, for example, from the control voltage for the blower 62. The temperature of the air passing through the indoor evaporator 15 can be determined, for example, from the detection results of the indoor air temperature sensor 72a and the outdoor air temperature sensor 72b, and a control signal input to the electric actuator for the indoor / outdoor air switching door in the indoor / outdoor air switching device 63.

[0172] The control map shown in FIG. 5 is read out from the ROM of the control device 70, and the cooling load of the interior evaporator 15 is compared with the reference line KL defined in the control map to determine whether or not the liquid back condition is satisfied.

[0173] Specifically, when the cooling load of the indoor evaporator 15 is smaller than the reference line KL defined in the control map, it is determined that the liquid backflow condition is met since there is a high possibility that the compressor 11 will fail due to liquid backflow. On the other hand, when the cooling load of the indoor evaporator 15 is equal to or greater than the reference line KL defined in the control map, it is determined that there is a low possibility that the compressor 11 will fail due to liquid backflow and it is determined that the liquid backflow condition is not met. The control device 70 when executing step S10 corresponds to the determination unit 70b.

[0174] 5 is determined so as to indicate a state in which the refrigerant circulating in the refrigeration cycle apparatus 10 is likely to cause a breakdown in the compressor 11 due to liquid backflow. Specifically, the reference line KL is determined so that the relationship between the dryness of the refrigerant discharged from the compressor 11 and the amount of refrigeration oil remaining inside the compressor 11 (i.e., the remaining oil amount) is a predetermined relationship. The remaining oil amount is calculated from the amount of refrigeration oil adhering to the back surface of the scroll arranged inside the compressor 11.

[0175] As shown in FIG. 6, there is a relationship between the dryness fraction of the discharged refrigerant and the amount of remaining oil such that the amount of remaining oil inside the compressor 11 increases as the dryness fraction of the refrigerant discharged from the compressor 11 increases.

[0176] Here, the minimum oil amount Vol at which the compressor 11 is likely to break down due to liquid back is experimentally determined for the compressor 11 based on the specifications of the configuration of the compression mechanism in the compressor 11. Therefore, from the relationship between the dryness of the discharged refrigerant and the amount of remaining oil shown in Fig. 6, a reference value Kp can be obtained as the dryness of the discharged refrigerant required to ensure the minimum oil amount Vol.

[0177] In other words, the reference line KL in the first embodiment shows the relationship between the suction air volume to the indoor evaporator 15 and the temperature of the suction air to the indoor evaporator 15, assuming that the dryness of the discharged refrigerant is the reference value Kp.

[0178] Next, the Mollier diagram of the refrigeration cycle apparatus 10 when the liquid back condition is satisfied will be described with reference to the drawings. In the Mollier diagram shown in Fig. 7, point a indicates the state of the refrigerant discharged from the compressor 11, and is located to the left of the saturated vapor line. Therefore, point a indicates the state in which the refrigerant discharged from the compressor 11 contains liquid phase refrigerant.

[0179] Between points a and b, the high-pressure refrigerant discharged from the compressor 11 is condensed in the heat medium-refrigerant heat exchanger 12 by dissipating heat to the heat medium in the high-temperature side heat medium circuit 20. Point b indicates the state of the refrigerant from the outlet side to the branching point 13a in the refrigerant flow path of the heat medium-refrigerant heat exchanger 12, and it can be seen that the refrigerant has a predetermined degree of subcooling.

[0180] Between points b and c, the refrigerant flowing out from one side of branch portion 13a is depressurized by first expansion valve 14a. Meanwhile, between points b and e, the refrigerant flowing out from the other side of branch portion 13a is depressurized by second expansion valve 14b.

[0181] Here, in the refrigeration cycle apparatus 10 when the control program is being executed, the lower limit of the throttle opening of the first expansion valve 14a is limited to a refrigerant flow rate that can suppress refrigeration oil retention. On the other hand, the throttle opening of the second expansion valve 14b is determined so that the superheat degree of the refrigerant on the outlet side of the refrigerant passage of the chiller 16 approaches a target superheat degree. For this reason, the amount of pressure reduction in the first expansion valve 14a is smaller than the amount of pressure reduction in the second expansion valve 14b.

[0182] Between point c and point d, the refrigerant flowing out of the first expansion valve 14a evaporates in the indoor evaporator 15 by exchanging heat with the blown air W. At this time, since the cooling load in the indoor evaporator 15 is low compared to the flow rate of the refrigerant circulating through the indoor evaporator 15, the refrigerant at point d is in a gas-liquid two-phase state.

[0183] On the other hand, between point e and point f, the refrigerant flowing out of the second expansion valve 14b absorbs heat from the heat medium in the low-temperature side heat medium circuit 40 and evaporates in the chiller 16. The refrigerant flowing out of the chiller 16 is guided to the suction port of the compressor 11 via the junction 13b.

[0184] Between point d and point f, the refrigerant flowing out from the indoor evaporator 15 flows into the evaporation pressure regulating valve 17 and is reduced in pressure. The refrigerant reduced in pressure by the evaporation pressure regulating valve 17 merges with the refrigerant flowing out from the chiller 16 at the junction 13b, and is then guided to the suction port of the compressor 11. Point f indicates the state of the refrigerant from the junction 13b to the suction port of the compressor 11, and is in a two-phase gas-liquid state.

[0185] 7, the compressor 11 draws in refrigerant in a two-phase gas-liquid state as indicated by point f, and discharges it as refrigerant in a two-phase gas-liquid state as indicated by point a. In other words, because the compressor draws in and compresses liquid-phase refrigerant, and discharges it in the liquid state, it is expected that the compression mechanism of the compressor 11 will break down due to liquid compression of the refrigerant.

[0186] In other words, in step S10, it is determined whether or not points a and f in the Mollier diagram of FIG. 7 are in a gas-liquid two-phase state, using the cooling load in the interior evaporator 15.

[0187] When the process proceeds to step S20, since it has been determined that the liquid backflow condition is met and there is a possibility of the compressor 11 failing due to liquid backflow, liquid backflow suppression control is executed. The liquid backflow suppression control is a control for adjusting the throttle opening of the second expansion valve 14b in order to suppress failure of the compressor 11 due to liquid backflow (for example, failure of the compression mechanism due to liquid compression). The control device 70 that executes step S20 is the pressure reduction control unit 70c.

[0188] Specifically, in the liquid backflow suppression control in step S20, the controller 70 first controls the throttle opening of the second expansion valve 14b in a manner different from that in the normal case (step S30 described later). More specifically, the controller 70 reduces the throttle opening of the second expansion valve 14b until the refrigerant on the discharge port side of the compressor 11 has a degree of superheat. This increases the amount of pressure reduction in the second expansion valve 14b, making it possible to reduce the pressure of the refrigerant flowing through the chiller 16.

[0189] Here, the state of the refrigerant when the liquid backflow suppression control is being executed will be described with reference to Fig. 8. Note that points a to f in Fig. 8 indicate the same states as points a to f in the Mollier diagram shown in Fig. 7 described above (i.e., states that satisfy the liquid backflow condition).

[0190] As described above, in the liquid backflow suppression control in step S20, the throttle opening of the second expansion valve 14b is reduced to reduce the pressure of the refrigerant flowing through the chiller 16. For this reason, point e1 indicating the state of the refrigerant on the refrigerant outlet side of the second expansion valve 14b indicates a lower pressure than point e indicating the state of the refrigerant on the refrigerant outlet side of the second expansion valve 14b when the liquid backflow condition is determined.

[0191] As a result, point f1, which indicates the state of the refrigerant at the outlet side of the refrigerant flow path of chiller 16, indicates a lower pressure than point f, which indicates the state of the refrigerant at the refrigerant outlet side of chiller 16 when the liquid backflow condition is determined. In addition, when the throttle opening of second expansion valve 14b is adjusted by liquid backflow suppression control, the amount of pressure reduction in evaporation pressure regulating valve 17 increases.

[0192] Point f1 in Fig. 8 indicates the state of the refrigerant from the junction 13b to the suction port of the compressor 11 when liquid backflow suppression control is being executed. Here, the saturated vapor line in the Mollier diagram shown in Fig. 7 and Fig. 8 is inclined so that the specific enthalpy becomes smaller as the pressure becomes lower in the low pressure region.

[0193] For this reason, by lowering the refrigerant pressure on the outlet side of the chiller 16 through the liquid backflow prevention control, the dryness of the refrigerant at point f1 can be made greater than the dryness of the refrigerant at point f. In other words, by lowering the refrigerant pressure on the outlet side of the chiller 16 through the adjustment of the throttle opening of the second expansion valve 14b through the liquid backflow prevention control, the state of the refrigerant sucked into the compressor 11 can be made closer to the gas phase.

[0194] 7 and 8, the gradient of the isentropic line decreases as the pressure decreases. Therefore, in the liquid backflow suppression control, the specific enthalpy of the refrigerant discharged from the compressor 11 can be increased by decreasing the throttle opening of the second expansion valve 14b, thereby creating a state in which the refrigerant has a degree of superheat.

[0195] In other words, by executing the liquid backflow suppression control, the state of the refrigerant discharged from the compressor 11 can be changed from point a to point a1 in the Mollier diagram shown in Fig. 8, and the refrigerant discharged from the compressor 11 can be adjusted to a superheated vapor state. Since the refrigerant at the discharge port of the compressor 11 is in a superheated vapor state, the possibility of liquid compression occurring in the compressor 11 can be reduced.

[0196] In other words, by adjusting the refrigerant discharged from the compressor 11 to be in a superheated vapor state through the liquid backflow suppression control, it is possible to suppress a breakdown of the compressor 11 caused by liquid backflow.

[0197] In addition, in the liquid backflow suppression control in step S20, the throttling opening of the second expansion valve 14b is adjusted using the difference between the target low pressure Plo determined according to the cooling load of the indoor evaporator 15 and the detection result detected by the chiller side pressure sensor 72e.

[0198] Specifically, the control device 70 determines a target low pressure Plo as a target value of the refrigerant pressure at the outlet side of the refrigerant flow path of the chiller 16 according to the cooling load in the indoor evaporator 15. The target low pressure Plo corresponds to an example of a target pressure. The cooling load in the indoor evaporator 15 is specified using the air volume of the blown air passing through the indoor evaporator 15 and the temperature of the blown air passing through the indoor evaporator 15, similar to when determining the liquid backflow condition.

[0199] When determining the target low pressure Plo, the target low pressure Plo is determined using the cooling load of the specified indoor evaporator 15 and a control table for determining the target low pressure Plo. As shown in Fig. 9, in the control table for determining the target low pressure Plo, a plurality of types of target low pressures Plo are associated with the cooling load of the indoor evaporator 15.

[0200] The target low pressure Plo associated with the control table is of three types, Ploa, Plob, and Ploc, with Ploa indicating the smallest value. Ploc indicating the largest value, and Plob indicating a value larger than Ploa and smaller than Ploc. In the control table shown in FIG. 9, the target low pressure Plo is associated with a larger value as the cooling load on the indoor evaporator 15 increases.

[0201] The control device 70 adjusts the throttle opening of the second expansion valve 14b by feedback control using the difference between the detection result of the chiller-side pressure sensor 72e and the target low pressure Plo determined using the control table shown in Fig. 9. At this time, the throttle opening of the second expansion valve 14b is adjusted so that the value of the refrigerant pressure detected by the chiller-side pressure sensor 72e approaches the target low pressure Plo.

[0202] As a result, according to the liquid backflow suppression control of step S20, the throttle opening of the second expansion valve 14b is adjusted according to the cooling load of the indoor evaporator 15, so that liquid compression of the compressor 11 caused by liquid backflow can be suppressed, and breakdown of the compressor 11 can be prevented.

[0203] On the other hand, if it is determined in step S10 that the liquid back condition is not satisfied, the control device 70 executes normal control in step S30. In normal control, the control device 70 adjusts the degree of superheat of the refrigerant on the outlet side of the refrigerant passage of the chiller 16 so that it approaches a target value. A predetermined constant (for example, 5°C) can be used as the target value.

[0204] As described above, in the air-conditioning cooling mode according to the first embodiment, the refrigeration cycle apparatus 10 ensures that the refrigerant flow rate to the indoor evaporator 15 is a flow rate that can suppress accumulation of refrigeration oil by limiting the minimum value of the throttle opening of the first expansion valve 14a. This allows the refrigeration cycle apparatus 10 to suppress accumulation of refrigeration oil in the indoor evaporator 15.

[0205] 4, the refrigeration cycle apparatus 10 executes the liquid backflow suppression control in step S20 to adjust the throttle opening of the second expansion valve 14b and reduce the pressure of the refrigerant flowing through the chiller 16. This makes it possible to increase the dryness of the refrigerant between the junction 13b located downstream of the chiller 16 and the suction port of the compressor 11, thereby making it possible to suppress liquid backflow to the compressor 11.

[0206] Then, in the liquid backflow suppression control of step S20, the refrigeration cycle apparatus 10 controls the throttle opening of the second expansion valve 14b so that the refrigerant at the discharge port of the compressor 11 has a degree of superheat when lowering the pressure of the refrigerant flowing through the chiller 16. As a result, the refrigerant discharged from the compressor 11 is in a superheated vapor state, so that the refrigeration cycle apparatus 10 can prevent liquid compression in the compressor 11 and suppress breakdown of the compressor 11 due to liquid backflow.

[0207] As a result, according to the refrigeration cycle device 10 of the first embodiment, by executing the liquid backflow suppression control of step S20, it is possible to suppress the accumulation of refrigeration oil in the indoor evaporator 15 and prevent failure of the compressor 11 due to liquid backflow.

[0208] Then, in step S10, the refrigeration cycle device 10 according to the first embodiment determines whether or not the liquid-back condition is satisfied by comparing the cooling load of the indoor evaporator 15 with a standard defined in the control table.

[0209] As a result, in step S10, the degree of the possibility of a breakdown in the compressor 11 due to liquid back can be accurately estimated from the cooling load of the indoor evaporator 15, thereby improving the accuracy of the determination.

[0210] Furthermore, during the liquid backflow suppression control in step S20, the refrigeration cycle apparatus 10 according to the first embodiment performs feedback control using the difference between a target low pressure Plo determined according to the cooling load in the indoor evaporator 15 and the detection value of the chiller-side pressure sensor 72e. Specifically, the control device 70 controls the throttle opening of the second expansion valve 14b according to the difference between the target low pressure Plo and the detection value of the chiller-side pressure sensor 72e so that the refrigerant pressure detected by the chiller-side pressure sensor 72e approaches the target low pressure Plo.

[0211] As a result, the liquid backflow suppression control in step S20 prevents refrigeration oil from stagnating in the indoor evaporator 15 and malfunction of the compressor 11 caused by liquid backflow, while at the same time allowing the indoor evaporator 15 and chiller 16 to properly demonstrate their cooling performance.

[0212] Second embodiment Next, a second embodiment different from the first embodiment will be described with reference to Fig. 10. In the second embodiment, the processing contents of steps S10 and S20 in the control program shown in Fig. 4 are different from those of the first embodiment. The basic configurations of the vehicle air conditioner 1, the refrigeration cycle device 10, the high-temperature side heat medium circuit 20, the low-temperature side heat medium circuit 40, the equipment heat medium circuit 50, and the interior air conditioning unit 60 are the same as those of the first embodiment, so repeated explanations will be omitted.

[0213] In step S10 in the second embodiment, it is determined whether or not the liquid back condition is satisfied, as in the first embodiment. In the first embodiment, the determination of whether or not the liquid back condition is satisfied is made by comparing the cooling load of the indoor evaporator 15 with a standard set in a control map, but in the second embodiment, the determination is made using the refrigerant temperature on the discharge port side of the compressor 11 detected by the high pressure sensor 72d.

[0214] Specifically, in the second embodiment, the control device 70 uses the detection value of the high pressure sensor 72d to determine whether the refrigerant on the discharge side of the compressor 11 has a degree of superheat, thereby determining whether the liquid back condition is satisfied.

[0215] When the refrigerant on the discharge side of the compressor 11 has a degree of superheat, the discharged refrigerant is in a superheated vapor state, so it is considered that there is a low possibility that the compressor 11 will malfunction due to liquid compression. For this reason, when the refrigerant discharged from the compressor 11 has a degree of superheat, it is determined that the liquid back condition is not satisfied.

[0216] On the other hand, when the refrigerant on the discharge port side of the compressor 11 does not have a degree of superheat, the discharged refrigerant is in a gas-liquid two-phase state and contains liquid-phase refrigerant. Since the refrigerant discharged from the compression mechanism contains liquid-phase refrigerant, it is considered that there is a possibility that the compressor 11 may malfunction due to liquid compression. For this reason, when the refrigerant discharged from the compressor 11 does not have a degree of superheat, it is determined that the liquid back condition is satisfied.

[0217] In the second embodiment, the actual measurement value detected by the high pressure sensor 72d is used to determine whether or not the liquid backflow condition is met, so that failure of the compressor 11 due to liquid backflow can be reliably suppressed.

[0218] Next, the liquid backflow suppression control in step S20 according to the second embodiment will be described. In the liquid backflow suppression control in the second embodiment, the control device 70 reduces the throttle opening of the second expansion valve 14b until the refrigerant at the discharge port side of the compressor 11 has a degree of superheat, as in the first embodiment. This is the same as in the first embodiment, so a repeated description will be omitted.

[0219] Here, in the liquid backflow suppression control of the first embodiment, the throttle opening of the second expansion valve 14b is adjusted using the difference between the target low pressure Plo determined according to the cooling load of the indoor evaporator 15 and the detection result detected by the chiller side pressure sensor 72e.

[0220] On the other hand, in the liquid backflow suppression control of the second embodiment, the throttle opening of the second expansion valve 14b is adjusted using the difference between the target superheat degree determined according to the cooling load of the indoor evaporator 15 and the refrigerant temperature on the discharge side of the compressor 11 detected by the high pressure sensor 72d.

[0221] Specifically, the control device 70 determines the target degree of superheat Sho as a target value of the refrigerant temperature on the discharge port side of the compressor 11 in accordance with the cooling load in the indoor evaporator 15. The cooling load in the indoor evaporator 15 is specified by the same method as in the first embodiment described above.

[0222] When determining the target degree of superheat Sho, the target degree of superheat Sho is determined using the identified cooling load of the indoor evaporator 15 and a control table for determining the target degree of superheat Sho. As shown in Fig. 10, in the control table for determining the target degree of superheat Sho, a plurality of types of target degrees of superheat Sho are associated with the cooling load of the indoor evaporator 15.

[0223] The target superheat degree Sho associated with the control table is of three types, Shoa, Shob, and Shoc, with Shoa indicating the smallest value. Shoc indicating the largest value, and Shob indicating a value larger than Shoa and smaller than Shoc. In the control table shown in FIG. 10, the target superheat degree Sho is associated with a larger value as the cooling load on the indoor evaporator 15 increases.

[0224] The control device 70 adjusts the throttle opening of the second expansion valve 14b by feedback control using the difference between the detection result of the high pressure sensor 72d and the target superheat degree Sho determined using the control table shown in Fig. 10. At this time, the throttle opening of the second expansion valve 14b is adjusted so that the value of the superheat degree of the refrigerant discharged from the compressor 11 detected by the high pressure sensor 72d approaches the target superheat degree Sho.

[0225] In the second embodiment, feedback control is performed on the throttle opening of the second expansion valve 14b so as to approach the target superheat degree Sho determined using the actual measurement value detected by the high pressure sensor 72d. Therefore, the refrigeration cycle apparatus 10 can appropriately adjust the cooling capacities of the indoor evaporator 15 and the chiller 16 according to the current situation.

[0226] As described above, according to the refrigeration cycle device 10 of the second embodiment, even if the control mode is changed to one using the refrigerant superheat on the discharge port side of the compressor 11, the action and effect achieved from the configuration and operation common to the first embodiment described above can be obtained in the same manner as in the first embodiment.

[0227] In the second embodiment, the liquid backflow condition is determined and the throttle opening of the second expansion valve 14b is controlled using the result of actually detecting the state of the refrigerant discharged from the compressor 11. Therefore, when a breakdown of the compressor 11 due to liquid backflow is likely to occur, the breakdown of the compressor 11 can be reliably suppressed.

[0228] Third embodiment Next, a third embodiment different from the above-mentioned embodiment will be described with reference to Fig. 11. In the third embodiment, the processing contents of steps S10 and S20 in the control program shown in Fig. 4 are different from those of the above-mentioned embodiment. The basic configurations of the vehicle air conditioner 1, the refrigeration cycle device 10, the high-temperature side heat medium circuit 20, the low-temperature side heat medium circuit 40, the equipment heat medium circuit 50, and the interior air conditioning unit 60 are the same as those of the above-mentioned embodiment, so repeated explanations will be omitted.

[0229] In the third embodiment as well, the control device 70 executes the control program shown in Fig. 4 in an operation mode in which the refrigerant circulates through the indoor evaporator 15 and the chiller 16. In step S10 of the third embodiment, the control device 70 determines, as a liquid return condition, whether the required refrigerant flow rate in the indoor evaporator 15 is equal to or less than a reference flow rate for suppressing accumulation of refrigeration oil.

[0230] The required refrigerant flow rate means the refrigerant flow rate required for the indoor evaporator 15 to dehumidify the blown air, and can be estimated using the inside air temperature sensor 72a, the outside air temperature sensor 72b, the evaporator temperature sensor 72f, the operation state of the inside / outside air switching device 63, the blowing volume of the blower 62, etc. The reference flow rate is defined as the refrigerant flow rate required to ensure that the remaining oil volume in the compressor 11 is the minimum oil volume Vol.

[0231] If the required refrigerant flow rate is equal to or less than the reference flow rate, it is determined that the amount of refrigerant liquid-backed to the compressor 11 is excessive, and the process proceeds to step S20. On the other hand, if the required refrigerant flow rate is greater than the reference flow rate, the process proceeds to step S30. The process content of step S30 is the same as in the above-described embodiment, and therefore will not be described again.

[0232] In step S20 according to the third embodiment, control is performed to adjust the lower limit of the refrigerant discharge capacity of the compressor 11 (i.e., the minimum rotation speed) as liquid backflow suppression control to suppress failure of the compressor 11 due to liquid backflow (for example, failure of the compression mechanism due to liquid compression). The control device 70 that executes step S20 constitutes a discharge capacity control unit 70d according to the third embodiment.

[0233] Incidentally, setting the minimum rotation speed of the compressor 11 means that the rotation speed will not be lower than the minimum rotation speed in controlling the refrigerant discharge capacity of the compressor 11. In other words, in controlling the refrigerant discharge capacity of the compressor 11, as long as the refrigerant discharge capacity is greater than the minimum rotation speed, it can be appropriately changed according to the required cooling capacity, etc.

[0234] Specifically, in the liquid backflow prevention control in step S20, the control device 70 sets the minimum rotation speed of the compressor 11 using the lower of the refrigerant pressure on the outlet side of the indoor evaporator 15 and the refrigerant pressure on the outlet side of the chiller 16.

[0235] Here, in the refrigeration cycle device 10 of the vehicle air conditioner 1, the interior evaporator 15 and the chiller 16 are connected in parallel to the flow of refrigerant flowing out from the heat medium refrigerant heat exchanger 12. Also, an evaporation pressure regulating valve 17 is arranged on the refrigerant outlet side of the interior evaporator 15. Therefore, in the third embodiment, the lower refrigerant pressure of the refrigerant pressure on the outlet side of the interior evaporator 15 and the refrigerant pressure on the outlet side of the chiller 16 becomes the refrigerant pressure on the outlet side of the chiller 16, and can be detected by the chiller-side pressure sensor 72e.

[0236] Therefore, in step S20 according to the third embodiment, the control device 70 determines the minimum rotation speed of the compressor 11 by referring to the refrigerant pressure on the outlet side of the chiller 16 detected by the chiller-side pressure sensor 72e and the control map shown in Fig. 11. In the control map shown in Fig. 11, the minimum rotation speed of the compressor 11 is determined so that the dryness of the refrigerant discharged from the compressor 11 becomes equal to or higher than a reference value Kp, and there is a tendency that the higher the refrigerant pressure on the outlet side of the chiller 16, the smaller the minimum rotation speed of the compressor 11 becomes.

[0237] In the liquid backflow suppression control according to the third embodiment, the lower the refrigerant pressure at the outlet side of the chiller 16 detected by the chiller-side pressure sensor 72e, the higher the minimum rotation speed of the compressor 11 is set. As a result, the refrigerant discharge capacity of the compressor 11 becomes higher overall.

[0238] The operating mode at this time is an operating mode in which the refrigerant circulates through the indoor evaporator 15 and chiller 16, and an evaporation pressure regulating valve 17 is disposed on the outlet side of the indoor evaporator 15. For this reason, when the refrigerant discharge capacity is increased by setting the minimum rotation speed of the compressor 11, the refrigerant flow rate on the indoor evaporator 15 side hardly changes, and the refrigerant flow rate on the chiller 16 side increases.

[0239] Here, the enthalpy of the refrigerant sucked into the compressor 11 can be expressed using the enthalpy of the refrigerant flowing out from the indoor evaporator 15 and the enthalpy of the refrigerant flowing out from the chiller 16. As described above, when the refrigerant discharge capacity of the compressor 11 increases due to the liquid backflow suppression control, the refrigerant flow rate on the indoor evaporator 15 side hardly changes, and the refrigerant flow rate on the chiller 16 side increases. Therefore, the enthalpy of the refrigerant sucked into the compressor 11 approaches the enthalpy of the refrigerant flowing out from the chiller 16, and the enthalpy of the refrigerant discharged from the compressor 11 increases.

[0240] It is known that in a pressure-enthalpy diagram, the lower the pressure, the smaller the inclination of the isentropic line for enthalpy. As a result, in the liquid backflow suppression control according to the third embodiment, the minimum rotation speed of the compressor 11 can be adjusted according to the refrigerant pressure on the outlet side of the chiller 16, so that the refrigerant discharged from the compressor 11 can be made to have a degree of superheat, thereby suppressing liquid backflow into the compressor 11.

[0241] As described above, according to the refrigeration cycle device 10 of the third embodiment, even if the control mode is changed to one using the minimum rotation speed of the compressor 11, the effects achieved by the configuration and operation common to the above-mentioned embodiments can be obtained in the same manner as in the above-mentioned embodiments.

[0242] In step S10 in the third embodiment, the liquid return condition is determined by determining whether the required refrigerant flow rate in the indoor evaporator 15 is equal to or less than the reference flow rate for suppressing accumulation of refrigeration oil, but the present invention is not limited to this. The liquid return condition may be the same as that in the above-mentioned embodiment.

[0243] (Other embodiments) Although the present invention has been described based on the embodiments, the present invention is not limited to the above-mentioned embodiments. In other words, various improvements and modifications are possible within the scope of the present invention. For example, the above-mentioned embodiments may be appropriately combined, and the above-mentioned embodiments may be modified in various ways.

[0244] (1) In the above-described embodiment, the refrigeration cycle apparatus 10 is configured to include two evaporators, namely, the first evaporator and the second evaporator, but is not limited to this. As the multiple evaporators arranged in the refrigeration cycle apparatus 10, for example, a configuration in which three or more evaporators are connected in parallel can also be adopted.

[0245] As a configuration in which an auxiliary evaporator 18 is disposed in addition to the indoor evaporator 15 and the chiller 16, a configuration in which the auxiliary evaporator 18 is connected in parallel to the indoor evaporator 15 as shown in Fig. 12 can be adopted. In this case, it is desirable that the refrigerant inlet side of the auxiliary evaporator 18 is connected so as to branch off from the outlet of the first expansion valve 14a, and the refrigerant outlet side of the auxiliary evaporator 18 is connected so as to merge with the flow of the outflowing refrigerant of the indoor evaporator 15 and then flow into the refrigerant inlet side of the evaporation pressure regulating valve 17.

[0246] 13, it is also possible to adopt a configuration in which an auxiliary evaporator 18 is connected in parallel to the chiller 16. In this case, it is desirable that the refrigerant inlet side of the auxiliary evaporator 18 is connected so as to branch off from the outlet of the second expansion valve 14b, and the refrigerant outlet side of the auxiliary evaporator 18 is connected so as to merge with the flow of refrigerant outflowing from the chiller 16 upstream of the merging portion 13b.

[0247] (2) In the above-described embodiment, the present invention is applied to the vehicle air conditioner 1 including the refrigeration cycle device 10, the high-temperature side heat medium circuit 20, the low-temperature side heat medium circuit 40, and the equipment heat medium circuit 50, but is not limited to this embodiment. The present invention can be applied to various configurations as long as the configuration includes at least the refrigeration cycle device 10 and the control device 70.

[0248] (3) In the above embodiment, the cooling / cooling mode is given as a specific example of an operation mode to which the present invention is applied, but the present invention is not limited to this mode. As long as the refrigerant is circulated through the indoor evaporator 15 and the chiller 16 and the refrigerant flow rate to the indoor evaporator 15 is sufficient to prevent refrigeration oil from accumulating, various modes can be adopted, and the present invention can also be applied to the dehumidifying heating / cooling mode.

[0249] (4) In the above-described embodiment, the indoor evaporator 15 is used as an example of the first evaporator, and the chiller 16 is used as an example of the second evaporator, but the present invention is not limited to this embodiment. As long as the refrigeration cycle device 10 is configured to include a first evaporator and a second evaporator, the present invention can be applied to various embodiments. For example, the object to be cooled by the first evaporator and the second evaporator can be different from the blown air and the heat medium in the above-described embodiment.

[0250] It is also possible to adopt a configuration in which the first evaporator and the second evaporator are arranged at significantly different positions, for example, the first evaporator may be arranged for air conditioning the front side of the vehicle, and the second evaporator may be arranged for air conditioning the rear side of the vehicle.

[0251] (5) In the above embodiment, the heat medium refrigerant heat exchanger 12 is used as the condenser, but the present invention is not limited to this. The condenser may be any device capable of dissipating heat from the high-pressure refrigerant to condense the refrigerant, and may be, for example, an indoor condenser that dissipates heat from the high-pressure refrigerant to the blown air to condense the refrigerant. [Explanation of symbols]

[0252] 1. Vehicle air conditioning system 11 Compressor 14a First expansion valve 14b Second expansion valve 15 Indoor evaporator 16 Chiller 17 Evaporation pressure control valve 70 Control device 70b Judgment part 70c Pressure reduction control section

Claims

1. A compressor (11) that compresses and discharges a refrigerant including refrigeration oil; a condenser (12) for condensing the refrigerant discharged from the compressor; A branching portion (13a) for branching the refrigerant flowing out from the condenser; a first pressure reducing section (14a) for reducing the pressure of the refrigerant flowing out from one of the outlets of the branch section; a first evaporator (15) for evaporating the refrigerant flowing out from the first pressure reduction section; a second pressure reducing section (14b) for reducing the pressure of the refrigerant flowing out from the other of the outlets in the branch section; a second evaporator (16) for evaporating the refrigerant flowing out from the second pressure reduction section; a confluence section (13b) that confluences the refrigerant flowing out of the first evaporator and the refrigerant flowing out of the second evaporator and guides the refrigerant to the compressor; A control unit (70) that controls the operation of the first pressure reducing unit and the second pressure reducing unit, The control unit is a determination unit (70b) that determines whether or not a liquid backflow condition related to liquid backflow in which a liquid-phase refrigerant flows into the compressor is satisfied in an operation mode in which a refrigerant is circulated through the first evaporator and the second evaporator and a refrigerant flow rate through the first evaporator is equal to or higher than a reference flow rate for suppressing accumulation of the refrigeration oil; a pressure reduction control unit (70c) that controls operation of the second pressure reduction unit so as to reduce the refrigerant pressure at the outlet of the second evaporator until the refrigerant discharged from the compressor has a degree of superheat when the determination unit determines that the liquid back condition is satisfied.

2. 2. The refrigeration cycle apparatus according to claim 1, further comprising: an evaporation pressure regulating valve (17) disposed between the outlet of the first evaporator and the junction, the evaporation pressure regulating valve (17) reducing the pressure of the refrigerant flowing out from the first evaporator to adjust the refrigerant evaporation pressure in the first evaporator.

3. 3. The refrigeration cycle apparatus according to claim 1, wherein the determination unit (70b) determines that the liquid-back condition is satisfied when a cooling load in the first evaporator (15) is smaller than a reference (KL).

4. a refrigerant pressure detection unit (72e) for detecting a refrigerant pressure at an outlet side of the second evaporator (16); 4. The refrigeration cycle device according to claim 1, wherein when the determination unit (70b) determines that the liquid back condition is satisfied, the pressure reduction control unit (70c) controls an opening degree of the second pressure reduction unit (14b) in accordance with a difference between a target pressure determined from a cooling load in the first evaporator (15) and the refrigerant pressure detected by the refrigerant pressure detection unit so that the refrigerant pressure approaches the target pressure.

5. A high-pressure side temperature detection unit (72d) for detecting the temperature of the refrigerant discharged from the compressor, The refrigeration cycle apparatus according to claim 1 or 2, wherein the judgment unit (70b) judges that the liquid back condition is satisfied when the detection result of the high-pressure side temperature detection unit indicates that the refrigerant discharged from the compressor does not have a degree of superheat.

6. 6. The refrigeration cycle apparatus according to claim 5, wherein, when the determination unit (70b) determines that the liquid back condition is satisfied, the pressure reduction control unit (70c) controls an opening degree of the second pressure reduction unit (14b) in accordance with a difference between a target superheat degree determined from a cooling load in the first evaporator (15) and the superheat degree of the refrigerant detected by the high-pressure side temperature detection unit so that the superheat degree of the refrigerant approaches the target superheat degree.

7. A compressor (11) that compresses and discharges a refrigerant including refrigeration oil; a condenser (12) for condensing the refrigerant discharged from the compressor; A branching portion (13a) for branching the refrigerant flowing out from the condenser; a first pressure reducing section (14a) for reducing the pressure of the refrigerant flowing out from one of the outlets of the branch section; a first evaporator (15) for evaporating the refrigerant flowing out from the first pressure reduction section; a second pressure reducing section (14b) for reducing the pressure of the refrigerant flowing out from the other of the outlets in the branch section; a second evaporator (16) for evaporating the refrigerant flowing out from the second pressure reduction section; a confluence section (13b) that confluences the refrigerant flowing out of the first evaporator and the refrigerant flowing out of the second evaporator and guides the refrigerant to the compressor; A control unit (70) that controls the operation of the compressor, The control unit is a determination unit (70b) that determines whether or not a liquid backflow condition related to liquid backflow in which a liquid-phase refrigerant flows into the compressor is satisfied in an operation mode in which a refrigerant is circulated through the first evaporator and the second evaporator and a refrigerant flow rate through the first evaporator is equal to or higher than a reference flow rate for suppressing accumulation of the refrigeration oil; a discharge capacity control unit (70d) that controls operation of the compressor so as to reduce the refrigerant pressure at the outlet of the second evaporator until the refrigerant discharged from the compressor has a degree of superheat when the determination unit determines that the liquid back condition is satisfied.

8. 8. The refrigeration cycle apparatus according to claim 7, further comprising: an evaporation pressure regulating valve (17) disposed between the outlet of the first evaporator and the junction, the evaporation pressure regulating valve reducing the pressure of the refrigerant flowing out from the first evaporator to adjust the evaporation pressure of the refrigerant in the first evaporator.

9. 9. The refrigeration cycle apparatus according to claim 7, wherein the determination unit (70b) determines that the liquid back condition is satisfied when a cooling load in the first evaporator (15) is smaller than a reference (KL).

10. The refrigeration cycle device according to any one of claims 7 to 9, wherein when the judgment unit (70b) judges that the liquid back condition is satisfied, the discharge capacity control unit (70d) controls the refrigerant discharge capacity of the compressor in accordance with the lower of the refrigerant pressures of the refrigerant pressure at the outlet side of the first evaporator (15) and the refrigerant pressure at the outlet side of the second evaporator (16), so that the refrigerant discharged from the compressor has a degree of superheat.

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