Refrigeration cycle device

Abstract

To suppress a lubricant becoming hard to return to a compressor when a refrigerant amount decreases.SOLUTION: A refrigeration cycle device includes: a compressor 11 for absorbing and compressing a refrigerant and discharging it; radiators 16, 12 for allowing the refrigerant discharged from the compressor to radiate heat; expansion valves 14b, 14a for decompressing and expanding the refrigerant which radiated heat in the radiator; evaporators 18, 16 for evaporating the refrigerant decompressed and expanded in the expansion valve; and a control part 60 for controlling the opening of the expansion valve. In the case where overheat degrees SHe, SHa of the refrigerant which has flowed out from the evaporator are equal to or lower than predetermined overheat degrees αC, αH, the control part determines opening increase / decrease amounts ΔEVC, ΔEVH of the expansion valve to be first opening increase / decrease amounts ΔEVC1, ΔEVH1, and in the case where the overheat degree of the refrigerant which has flowed out from the evaporator surpasses the predetermined overheat degree, the control part determines the opening increase / decrease amount to be a second opening increase / decrease amounts ΔEVC2, ΔEVH2 which can further suppress the increase of the overheat degree of the refrigerant which has flowed out from the evaporator than the first opening increase / decrease amounts.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a refrigeration cycle device equipped with an electric expansion valve. [Background technology]

[0002] Patent Document 1 describes a conventional refrigeration cycle device that detects a shortage of refrigerant. In this conventional technology, if a pressure difference due to fluctuations in the pressure of the refrigerant compressed by the compressor after a predetermined time has elapsed since the compressor started is less than an abnormality determination value, it is determined that there is a shortage of refrigerant. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-206096 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned conventional technology, during the transitional period from when the refrigerant amount starts to decrease until it is determined that a refrigerant shortage has occurred, the degree of superheat of the refrigerant flowing out of the evaporator gradually increases as the refrigerant amount decreases, so the amount of refrigerant dissolved in the lubricating oil decreases, making it difficult for the lubricating oil to return to the compressor, which may cause problems with the lubrication of the compressor.

[0005] In view of the above, an object of the present invention is to prevent lubricating oil from being difficult to return to a compressor when the amount of refrigerant decreases. [Means for solving the problem]

[0006] In order to achieve the above object, the refrigeration cycle device according to claim 1 comprises: a compressor (11) that draws in, compresses, and discharges a refrigerant; a radiator (16, 12) for radiating heat from the refrigerant discharged from the compressor; an expansion valve (14b, 14a) for reducing the pressure and expanding the refrigerant whose heat has been radiated by the radiator; an evaporator (18, 16) for evaporating the refrigerant decompressed and expanded by the expansion valve; a control unit (60) that controls the opening degree of the expansion valve; The control unit When the degree of superheat (SHe, SHa) of the refrigerant flowing out from the evaporator is equal to or lower than a predetermined degree of superheat (αC, αH), the opening increment / decrement (ΔEVC, ΔEVH) of the expansion valve is determined to be a first opening increment / decrement (ΔEVC1, ΔEVH1); When the degree of superheat of the refrigerant flowing out of the evaporator exceeds a predetermined degree of superheat, the opening increase / decrease amount is determined to be a second opening increase / decrease amount (ΔEVC2, ΔEVH2) that can suppress the increase in the degree of superheat of the refrigerant flowing out of the evaporator more than the first opening increase / decrease amount.

[0007] This prevents the degree of superheat of the refrigerant from further increasing when the amount of refrigerant decreases, thereby preventing the amount of refrigerant dissolved in the lubricating oil from decreasing, making it difficult for the lubricating oil to return to the compressor.

[0008] The symbols in parentheses for each means described in this section and in the claims indicate the correspondence with the specific means described in the embodiments to be described later. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an overall configuration diagram of a vehicle air conditioner according to a first embodiment. [Figure 2] 2 is a block diagram showing an electric control unit of the vehicle air conditioner of the first embodiment. FIG. [Figure 3] 4 is a flowchart showing a control process in a cooling mode in the first embodiment. [Figure 4] 5 is a flowchart showing a subroutine of a cooling mode in the first embodiment. [Figure 5] 4 is a flowchart showing a control process in a heating mode in the first embodiment. [Figure 6] 5 is a flowchart showing a subroutine of a heating mode in the first embodiment. [Figure 7] FIG. 4 is a control characteristic diagram for the amount of refrigerant in a cooling mode in the first embodiment. [Figure 8] FIG. 10 is an overall configuration diagram of a vehicle air conditioner according to a second embodiment. [Figure 9] 10 is a flowchart showing a control process in a cooling mode in a second embodiment. [Figure 10] FIG. 10 is a control characteristic diagram for the amount of refrigerant in a cooling mode in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (First embodiment) In this embodiment, the refrigeration cycle device 10 is applied to a vehicle air conditioner 1. Therefore, the object to be cooled in the refrigeration cycle device 10 of this embodiment is air blown into the vehicle compartment.

[0011] As shown in the overall configuration diagram of FIG. 1, the vehicle air conditioner 1 includes a refrigeration cycle device 10, an interior air conditioning unit 30, a high-temperature side heat medium circuit 40, and the like.

[0012] The refrigeration cycle device 10 performs the functions of cooling the air blown into the vehicle compartment and heating the high-temperature side heat medium circulating in the high-temperature side heat medium circuit 40 in order to perform air conditioning inside the vehicle compartment.

[0013] The refrigeration cycle device 10 is configured to be able to switch between refrigerant circuits for various operation modes to condition the air inside the vehicle cabin, such as a refrigerant circuit for a cooling mode, a refrigerant circuit for a dehumidifying and heating mode, and a refrigerant circuit for a heating mode.

[0014] The refrigeration cycle device 10 uses an HFO refrigerant (specifically, R1234yf) as a refrigerant, and configures a vapor compression subcritical refrigeration cycle in which the pressure of the refrigerant discharged from the compressor 11 does not exceed the critical pressure of the refrigerant. Furthermore, refrigeration oil is mixed into the refrigerant to lubricate the compressor 11. A portion of the refrigeration oil circulates through the cycle together with the refrigerant.

[0015] Among the components of the refrigeration cycle apparatus 10, the compressor 11 draws in, compresses, and discharges the refrigerant in the refrigeration cycle apparatus 10. The compressor 11 is disposed in a drive unit compartment located at the front of the vehicle interior and accommodating an electric motor and the like. The compressor 11 is an electric compressor that uses an electric motor to rotate a fixed displacement compression mechanism with 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 60, which will be described later.

[0016] The discharge port of the compressor 11 is connected to the inlet side of the refrigerant passage of the water-refrigerant heat exchanger 12. The water-refrigerant heat exchanger 12 has a refrigerant passage through which the high-pressure refrigerant discharged from the compressor 11 flows, and a water passage through which the high-temperature side heat medium circulating in the high-temperature side heat medium circuit 40 flows. The water-refrigerant heat exchanger 12 is a heating heat exchanger that heats the high-temperature side heat medium by exchanging heat between the high-pressure refrigerant flowing through the refrigerant passage and the high-temperature side heat medium flowing through the water passage.

[0017] The inlet side of a heating expansion valve 14a is connected to the outlet of the refrigerant passage of the water-refrigerant heat exchanger 12. The heating expansion valve 14a is a heating pressure reducing unit that reduces the pressure of the high-pressure refrigerant flowing out from the refrigerant passage of the water-refrigerant heat exchanger 12 and adjusts the flow rate (mass flow rate) of the refrigerant flowing downstream at least in an operation mode in which the vehicle cabin is heated. The heating expansion valve 14a is an electric variable throttle mechanism that includes a valve element configured to change the throttle opening and an electric actuator that changes the opening of the valve element.

[0018] The refrigeration cycle device 10 includes a cooling expansion valve 14b. The cooling expansion valve 14b and the cooling expansion valve 14c have the same basic configuration as the heating expansion valve 14a.

[0019] The heating expansion valve 14a and the cooling expansion valve 14b have a fully open function that functions as a simple refrigerant passage with almost no flow rate adjustment or refrigerant pressure reduction effect when the valve is fully opened, and a fully closed function that blocks the refrigerant passage when the valve is fully closed.

[0020] The heating expansion valve 14a and the cooling expansion valve 14b can switch the refrigerant circuit for each operation mode by using a full-open function and a full-close function.

[0021] Therefore, the heating expansion valve 14a and the cooling expansion valve 14b of this embodiment also function as a refrigerant circuit switching unit. The operation of the heating expansion valve 14a and the cooling expansion valve 14b is controlled by a control signal (control pulse) output from the control device 60.

[0022] The outlet of the heating expansion valve 14a is connected to the refrigerant inlet side of an exterior heat exchanger 16. The exterior heat exchanger 16 is a heat exchanger that exchanges heat between the refrigerant flowing out of the heating expansion valve 14a and outside air blown by a cooling fan (not shown). The exterior heat exchanger 16 is disposed at the front side of the drivetrain compartment. Therefore, when the vehicle is traveling, traveling air can be applied to the exterior heat exchanger 16.

[0023] The inlet side of a third three-way joint 13c, which has three inlet and outlet ports that communicate with each other, is connected to the refrigerant outlet of the outdoor heat exchanger 16. Such a three-way joint can be formed by joining multiple pipes or by providing multiple refrigerant passages in a metal block or a resin block.

[0024] One outlet of the third three-way joint 13c is connected to one inlet of a fourth three-way joint 13d via a heating passage 22b. The basic configuration of the fourth three-way joint 13d is similar to that of the third three-way joint 13c. A heating on-off valve 15b is disposed in the heating passage 22b. The heating on-off valve 15b is an electromagnetic valve that opens and closes the heating passage 22b.

[0025] The heating on-off valve 15b can switch the refrigerant circuit for each operation mode by opening and closing the refrigerant passage. Therefore, the heating on-off valve 15b is a refrigerant circuit switching unit that switches the refrigerant circuit of the cycle. The operation of the heating on-off valve 15b is controlled by a control voltage output from the control device 60.

[0026] The other outlet of the third three-way joint 13c is connected to the inlet side of the cooling expansion valve 14b. The cooling expansion valve 14b is a cooling pressure reducing part that reduces the pressure of the refrigerant flowing out from the exterior heat exchanger 16 and adjusts the flow rate of the refrigerant flowing downstream at least during an operation mode in which the vehicle cabin is cooled.

[0027] The outlet of the cooling expansion valve 14b is connected to the refrigerant inlet side of the indoor evaporator 18. The indoor evaporator 18 is disposed in the air conditioning case 31 of the indoor air conditioning unit 30. The indoor evaporator 18 is a cooling heat exchanger that exchanges heat between the low-pressure refrigerant decompressed by the cooling expansion valve 14b and the air blown from the blower 32 to evaporate the low-pressure refrigerant and cool the air by causing the low-pressure refrigerant to endothermically act. The refrigerant outlet of the indoor evaporator 18 is connected to the other inlet side of the fourth three-way joint 13d. The outlet of the fourth three-way joint 13d is connected to the inlet side of the accumulator 21. The accumulator 21 is a gas-liquid separator that separates the refrigerant that flows into it into gas and liquid phases and stores excess liquid-phase refrigerant in the cycle. The gas-phase refrigerant outlet of the accumulator 21 is connected to the suction side of the compressor 11.

[0028] The refrigeration cycle device 10 configures an accumulator cycle having an accumulator 21.

[0029] Next, the high-temperature side heat medium circuit 40 will be described. The high-temperature side heat medium circuit 40 is a heat medium circulation circuit that circulates a high-temperature side heat medium. As the high-temperature side heat medium, ethylene glycol, dimethylpolysiloxane, a solution containing nanofluid, antifreeze, etc. can be used. The high-temperature side heat medium circuit 40 includes a water passage of the water-refrigerant heat exchanger 12, a high-temperature side heat medium pump 41, a heater core 42, etc.

[0030] The high-temperature side heat medium pump 41 is a water pump that pumps the high-temperature side heat medium to the inlet side of the water passage of the water-refrigerant heat exchanger 12. The high-temperature side heat medium pump 41 is an electric pump whose rotation speed (i.e., pumping capacity) is controlled by a control voltage output from the control device 60.

[0031] The outlet of the water passage of the water-refrigerant heat exchanger 12 is connected to the heat medium inlet side of a heater core 42. The heater core 42 is a heat exchanger that heats the air by exchanging heat between the high-temperature side heat medium heated in the water-refrigerant heat exchanger 12 and the air that has passed through the indoor evaporator 18. The heater core 42 is disposed in the air conditioning case 31 of the indoor air conditioning unit 30. The heat medium outlet of the heater core 42 is connected to the suction port side of the high-temperature side heat medium pump 41.

[0032] Therefore, in the high-temperature side heat medium circuit 40, the high-temperature side heat medium pump 41 adjusts the flow rate of the high-temperature side heat medium flowing into the heater core 42, thereby adjusting the amount of heat dissipated by the high-temperature side heat medium to the air in the heater core 42, i.e., the amount of heat that is applied to the air in the heater core 42.

[0033] That is, in this embodiment, the water-refrigerant heat exchanger 12 and the components of the high-temperature side heat medium circuit 40 form a heating unit that heats air using the refrigerant discharged from the compressor 11 as a heat source.

[0034] Next, we will explain the interior air conditioning unit 30. The interior air conditioning unit 30 is used to blow air whose temperature has been adjusted by the refrigeration cycle device 10 into the vehicle interior. The interior air conditioning unit 30 is disposed inside the instrument panel at the front end of the vehicle interior.

[0035] As shown in FIG. 1, the indoor air conditioning unit 30 houses a blower 32, an indoor evaporator 18, a heater core 42, etc. in an air passage formed in an air conditioning case 31 that forms the outer shell of the unit.

[0036] The air conditioning case 31 forms an air passage for air to be blown into the vehicle interior. The air conditioning case 31 is molded from a resin (for example, polypropylene) that has a certain degree of elasticity and is also excellent in strength.

[0037] An inside / outside air switching device 33 is disposed on the most upstream side of the air flow of the air conditioning case 31. The inside / outside air switching device 33 switches between introducing inside air (air inside the vehicle cabin) and outside air (air outside the vehicle cabin) into the air conditioning case 31.

[0038] The inside / outside air switching device 33 continuously adjusts the opening areas of the inside air inlet, which introduces inside air, and the outside air inlet, which introduces outside air, into the air-conditioning case 31 using an inside / outside air switching door, thereby changing 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 60.

[0039] A blower 32 is disposed downstream of the inside / outside air switching device 33 in the air flow direction. The blower 32 blows the air drawn in through the inside / outside air switching device 33 toward the vehicle interior. The blower 32 is an electric blower that drives a centrifugal multi-blade fan with an electric motor. The rotation speed (i.e., the blowing capacity) of the blower 32 is controlled by a control voltage output from the control device 60.

[0040] The interior evaporator 18 and the heater core 42 are arranged in this order with respect to the air flow downstream of the blower 32. In other words, the interior evaporator 18 is arranged upstream of the heater core 42 with respect to the air flow.

[0041] A cool air bypass passage 35 is provided in the air conditioning case 31, which allows the air that has passed through the interior evaporator 18 to bypass the heater core 42. An air mix door 34 is disposed in the air conditioning case 31 downstream of the interior evaporator 18 in the air flow direction and upstream of the heater core 42.

[0042] The air mix door 34 is an air volume ratio adjustment unit that adjusts the ratio of the volume of air passing through the heater core 42 side to the volume of air passing through the cool air bypass passage 35 after passing through the interior evaporator 18. The air mix door 34 is driven by an electric actuator for the air mix door. The operation of this electric actuator is controlled by a control signal output from the control device 60.

[0043] A mixing space is disposed downstream of the air flow of the heater core 42 and the cool air bypass passage 35 inside the air conditioning case 31. The mixing space is a space where air heated by the heater core 42 and air that has passed through the cool air bypass passage 35 and has not been heated are mixed.

[0044] Furthermore, at the downstream air flow portion of the air conditioning case 31, an opening hole is arranged for blowing the air mixed in the mixing space (that is, the conditioned air) into the vehicle interior, which is the space to be air-conditioned.

[0045] The openings include a face opening, a foot opening, and a defroster opening (none of which are shown). The face opening is an opening for blowing conditioned air toward the upper bodies of occupants in the vehicle cabin. The foot opening is an opening for blowing conditioned air toward the feet of occupants. The defroster opening is an opening for blowing conditioned air toward the inside surface of the vehicle front windshield.

[0046] These face opening holes, foot opening holes, and defroster opening holes are connected to face air outlets, foot air outlets, and defroster air outlets (none of which are shown) provided in the vehicle cabin via ducts that form air passages, respectively.

[0047] Therefore, the temperature of the conditioned air mixed in the mixing space is adjusted by the air mix door 34 adjusting the ratio of the air volume passing through the heater core 42 to the air volume passing through the cool air bypass passage 35. This adjusts the temperature of the air (conditioned air) blown into the vehicle interior from each air outlet.

[0048] Additionally, a face door, a foot door, and a defroster door (all not shown) are disposed upstream of the face opening, foot opening, and defroster opening, respectively. The face door adjusts the opening area of ​​the face opening. The foot door adjusts the opening area of ​​the foot opening. The defroster door adjusts the opening area of ​​the froster opening.

[0049] The face door, foot door, and defroster door constitute an air outlet mode switching device that switches the air outlet mode. These doors are connected to an electric actuator for driving the air outlet mode doors via a link mechanism or the like, and are rotated in conjunction with each other. The operation of this electric actuator is also controlled by a control signal output from the control device 60.

[0050] Specific examples of the air outlet modes that can be switched by the air outlet mode switching device include a face mode, a bi-level mode, and a foot mode.

[0051] The face mode is an outlet mode in which the face outlet is fully opened and air is blown from the face outlet toward the upper bodies of the vehicle occupants. The bi-level mode is an outlet mode in which both the face outlet and the foot outlet are opened and air is blown toward the upper bodies and feet of the vehicle occupants. The foot mode is an outlet mode in which the foot outlet is fully opened and the defroster outlet is only slightly opened and air is mainly blown from the foot outlet.

[0052] Furthermore, the occupant can manually switch to the defroster mode by operating the air outlet mode selector switch provided on the operation panel 70. The defroster mode is an air outlet mode in which the defroster air outlet is fully opened and air is blown out from the defroster air outlet onto the inner surface of the windshield.

[0053] Next, an overview of the electrical control unit of this embodiment will be described. The control device 60 is composed of a well-known microcomputer including a CPU, ROM, RAM, etc., and its peripheral circuits. It performs various calculations and processes based on an air conditioning control program stored in the ROM, and controls the operation of various control target devices 11, 14a, 14b, 15b, 32, 41, etc. connected to its output side.

[0054] 2, an inside air temperature sensor 61, an outside air temperature sensor 62, a solar radiation sensor 63, first to fifth refrigerant temperature sensors 64a to 64e, an evaporator temperature sensor 64f, first and second refrigerant pressure sensors 65a to 65b, a high-temperature side heat medium temperature sensor 66a, an air conditioning air temperature sensor 69, etc. are connected to the input side of the control device 60. Detection signals from these sensors are input to the control device 60.

[0055] The inside air temperature sensor 61 is an inside air temperature detector that detects the temperature inside the vehicle cabin (inside air temperature) Tr. The outside air temperature sensor 62 is an outside air temperature detector that detects the temperature outside the vehicle cabin (outside air temperature) Tam. The solar radiation sensor 63 is an solar radiation amount detector that detects the amount of solar radiation Ts irradiating the vehicle cabin.

[0056] The first refrigerant temperature sensor 64a is a discharge refrigerant temperature detector that detects the temperature T1 of the refrigerant discharged from the compressor 11. The second refrigerant temperature sensor 64b is a second refrigerant temperature detector that detects the temperature T2 of the refrigerant flowing out from the refrigerant passage of the water-refrigerant heat exchanger 12. The third refrigerant temperature sensor 64c is a third refrigerant temperature detector that detects the temperature T3 of the refrigerant flowing out from the outdoor heat exchanger 16.

[0057] The fourth refrigerant temperature sensor 64d is a fourth refrigerant temperature detection unit that detects a temperature T4 of the refrigerant flowing out from the indoor evaporator 18. The fifth refrigerant temperature sensor 64e is a fifth refrigerant temperature detection unit that detects a temperature T5 of the refrigerant flowing out from the accumulator 21.

[0058] The evaporator temperature sensor 64f is an evaporator temperature detection unit that detects the refrigerant evaporation temperature (evaporator temperature) Tefin in the interior evaporator 18. Specifically, the evaporator temperature sensor 64f of the present embodiment detects the heat exchange fin temperature of the interior evaporator 18.

[0059] The first refrigerant pressure sensor 65a is a first refrigerant pressure detection unit that detects the pressure P1 of the refrigerant flowing out from the refrigerant passage of the water-refrigerant heat exchanger 12. The second refrigerant pressure sensor 65b is a second refrigerant pressure detection unit that detects the pressure P2 of the refrigerant flowing out from the accumulator 21.

[0060] The fifth refrigerant temperature sensor 64e and the second refrigerant pressure sensor 65b are refrigerant state detection units that detect the temperature T5 and pressure P2 of the refrigerant downstream of the accumulator 21 and on the suction side of the compressor 11 in order to calculate the degree of superheat of the refrigerant downstream of the accumulator 21 and on the suction side of the compressor 11.

[0061] The high-temperature side heat medium temperature sensor 66 a is a high-temperature side heat medium temperature detection unit that detects the high-temperature side heat medium temperature TWH, which is the temperature of the high-temperature side heat medium flowing out from the water passage of the water-refrigerant heat exchanger 12 .

[0062] The air conditioning air temperature sensor 69 is an air conditioning air temperature detection unit that detects the temperature TAV of the air blown from the mixing space into the vehicle interior.

[0063] As shown in FIG. 2, an operation panel 70 located near the instrument panel at the front of the vehicle interior is connected to the input side of the control device 60, and operation signals are input from various operation switches provided on this operation panel 70.

[0064] The various operation switches provided on the operation panel 70 include, specifically, an auto switch for setting or canceling the automatic control operation of the vehicle air conditioning system, an air conditioner switch for requesting air cooling by the interior evaporator 18, an air volume setting switch for manually setting the air volume of the blower 32, a temperature setting switch for setting the target temperature Tset inside the vehicle cabin, and a blowing mode changeover switch for manually setting the blowing mode.

[0065] In addition, the control device 60 of this embodiment is configured as an integrated unit that controls various controlled devices connected to its output side, and the configuration (hardware and software) that controls the operation of each controlled device constitutes the control unit that controls the operation of each controlled device.

[0066] For example, in the control device 60, the configuration that controls the refrigerant discharge capacity of the compressor 11 (specifically, the rotation speed of the compressor 11) constitutes a compressor control unit 60a. The configuration that controls the operation of the heating expansion valve 14a and the cooling expansion valve 14b constitutes an expansion valve control unit 60b. The configuration that controls the operation of the heating on-off valve 15b constitutes a refrigerant circuit switching control unit 60c. The configuration that controls the pumping capacity of the high-temperature side heat medium of the high-temperature side heat medium pump 41 constitutes a high-temperature side heat medium pump control unit 60d.

[0067] Next, the operation of the present embodiment with the above configuration will be described. The refrigeration cycle device 10 can be operated in multiple operation modes by switching the refrigerant circuit. For example, the multiple operation modes can be a cooling mode and a heating mode.

[0068] The cooling mode is an operating mode in which the vehicle interior is cooled by blowing cooled air into the vehicle interior, while the heating mode is an operating mode in which the vehicle interior is heated by blowing heated air into the vehicle interior.

[0069] These operating modes are switched by executing an air conditioning control program, which is executed when the occupant turns on the auto switch on the operation panel 70 and sets automatic control of the vehicle interior.

[0070] The air conditioning control program first reads the detection signals from the above-mentioned sensors and the operation signals from the operation panel 70. Next, based on the read detection signals and operation signals, a target outlet temperature TAO, which is the target temperature of the air blown into the vehicle cabin, is determined. Specifically, the target outlet temperature TAO is calculated using the following formula F1. TAO=Kset×Tset-Kr×Tr-Kam×Tam-Ks×Ts+C…(F1) Tset is the cabin temperature set by the temperature setting switch. Tr is the cabin temperature detected by the inside air sensor. Tam is the outside cabin temperature detected by the outside air sensor. Ts is the amount of solar radiation detected by the solar radiation sensor. Kset, Kr, Kam, and Ks are control gains, and C is a correction constant.

[0071] Next, it is determined whether the air conditioner switch is ON (turned on). When the air conditioner switch is ON, it means that the occupant is requesting cooling or dehumidification of the vehicle interior. In other words, when the air conditioner switch is ON, it means that the interior evaporator 18 is requested to cool the air.

[0072] If it is determined that the air conditioner switch is ON, the cooling mode is selected as the operation mode, and if it is determined that the air conditioner switch is not ON, the heating mode is selected as the operation mode.

[0073] As described above, the air conditioning control program of this embodiment switches the operation mode of the refrigeration cycle apparatus 10. Furthermore, the air conditioning control program controls not only the operation of each component of the refrigeration cycle apparatus 10 but also the operation of the high-temperature side heat medium pump 41 of the high-temperature side heat medium circuit 40.

[0074] Specifically, the control device 60 controls the operation of the high-temperature side heat medium pump 41 so as to exhibit a predetermined reference pumping capacity for each operation mode, regardless of the operation mode of the refrigeration cycle device 10 described above.

[0075] Therefore, in the high-temperature side heat medium circuit 40, when the high-temperature side heat medium is heated in the water passage of the water-refrigerant heat exchanger 12, the heated high-temperature side heat medium is pumped to the heater core 42. The high-temperature side heat medium that flows into the heater core 42 exchanges heat with the air, thereby heating the air. The high-temperature side heat medium that flows out of the heater core 42 is sucked into the high-temperature side heat medium pump 41 and pumped to the water-refrigerant heat exchanger 12.

[0076] The detailed operation of the vehicle air conditioner 1 in each operation mode will be described below. The control maps referred to in each operation mode in the following description are stored in advance in the control device 60 for each operation mode. The control maps corresponding to each operation mode may be the same or different from each other.

[0077] (1) Cooling mode In the cooling mode, the control device 60 executes the control flow of the cooling mode shown in Fig. 3. First, in step S600, a target evaporator temperature TEO is determined. The target evaporator temperature TEO is determined based on the target outlet temperature TAO by referring to a control map stored in the control device 60. In the control map of this embodiment, the target evaporator temperature TEO is determined so as to increase with an increase in the target outlet temperature TAO.

[0078] In step S610, an increase / decrease amount ΔIVO of the rotation speed of the compressor 11 is determined. The increase / decrease amount ΔIVO is determined by a feedback control method based on the deviation between the target evaporator temperature TEO and the evaporator temperature Tefin detected by the evaporator temperature sensor 64f so that the evaporator temperature Tefin approaches the target evaporator temperature TEO.

[0079] In the next step S630, a subroutine shown in FIG. 4 is executed to determine the increase / decrease amount ΔEVC of the throttle opening of the cooling expansion valve 14b.

[0080] First, in step S1000, a target degree of subcooling SCOa of the refrigerant flowing out from the outdoor heat exchanger 16 is determined. The target degree of subcooling SCOa is determined by referring to a control map based on, for example, the outdoor air temperature Tam. In the control map of this embodiment, the target degree of subcooling SCOa is determined so that the coefficient of performance (COP) of the cycle approaches a local maximum value.

[0081] In step S1010, a first tentative increase / decrease ΔEVC1 in the throttle opening of the cooling expansion valve 14b is determined. The first tentative increase / decrease ΔEVC1 is determined by a feedback control method based on the deviation between the target degree of subcooling SCOa and the degree of subcooling SCa of the refrigerant on the outlet side of the outdoor heat exchanger 16 so that the degree of subcooling SCa of the refrigerant on the outlet side of the outdoor heat exchanger 16 approaches the target degree of subcooling SCOa. The first tentative increase / decrease ΔEVC1 is the increase / decrease in the throttle opening of the cooling expansion valve 14b during normal control (in other words, the first increase / decrease in the opening).

[0082] The degree of subcooling SCa of the refrigerant on the outlet side of the outdoor heat exchanger 16 is calculated based on the temperature T3 detected by the third refrigerant temperature sensor 64c and the pressure P1 detected by the first refrigerant pressure sensor 65a.

[0083] In step S1020, it is determined whether the degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 exceeds a predetermined degree of superheat αC. The degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 is calculated based on the temperature T5 detected by the fifth refrigerant temperature sensor 64e and the pressure P2 detected by the second refrigerant pressure sensor 65b.

[0084] The predetermined superheat degree αC is a fixed value stored in advance in the control device 60. Even if the amount of refrigerant sealed in the refrigeration cycle device 10 decreases, by controlling the superheat degree SHe to a value smaller than the predetermined superheat degree αC, it is possible to prevent the lubricating oil from being difficult to return to the compressor 11.

[0085] If it is determined in step S1020 that the superheat degree SHe of the refrigerant flowing out from the indoor evaporator 18 does not exceed the predetermined superheat degree αC, the process proceeds to step S1030, where the value of the increase / decrease amount ΔEVC of the throttle opening of the air conditioning expansion valve 14b is set to the same value as the first temporary increase / decrease amount ΔEVC1, and the subroutine shown in FIG. 4 is terminated.

[0086] The increase / decrease amount ΔEVC of the throttle opening of the cooling expansion valve 14b determined in step S1030 is the increase / decrease amount of the throttle opening of the cooling expansion valve 14b during normal control (in other words, the first increase / decrease amount of opening).

[0087] If it is determined in step S1020 that the degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 exceeds the predetermined degree of superheat αC, the process proceeds to step S1040, where a target degree of superheat SHOe of the refrigerant flowing out from the indoor evaporator 18 is determined. The target degree of superheat SHOe is determined to be the same value as the predetermined degree of superheat αC used in step S1020, for example.

[0088] In step S1050, a second temporary increase / decrease amount ΔEVC2 of the throttle opening of the cooling expansion valve 14b is determined. The second temporary increase / decrease amount ΔEVC2 is determined by a feedback control method based on the deviation between the target superheat degree SHOe and the superheat degree SHe of the refrigerant on the outlet side of the indoor evaporator 18 so that the superheat degree SHe of the refrigerant on the outlet side of the indoor evaporator 18 approaches the target superheat degree SHOe.

[0089] The second temporary increase / decrease amount ΔEVC2 is an increase / decrease amount of the throttle opening of the cooling expansion valve 14b that can suppress an increase in the superheat degree SHe of the refrigerant on the outlet side of the indoor evaporator 18 (in other words, a second increase / decrease amount of the opening).

[0090] In step S1060, the value of the increase / decrease ΔEVC in the throttle opening of the cooling expansion valve 14b is determined to be the larger value of the first tentative increase / decrease ΔEVC1 and the second tentative increase / decrease ΔEVC2.

[0091] The increase / decrease in the throttle opening of the air conditioning expansion valve 14b ΔEVC determined in step S1060 is the increase / decrease in the throttle opening of the air conditioning expansion valve 14b (in other words, the second increase / decrease in the throttle opening) that can suppress the increase in the superheat SHe of the refrigerant on the outlet side of the indoor evaporator 18 more than during normal control.

[0092] In step S1070, it is determined whether the throttle opening EXPC of the cooling expansion valve 14b has reached the upper limit opening βC. If it is determined in step S1070 that the throttle opening EXPC of the cooling expansion valve 14b has not reached the upper limit opening βC, the subroutine shown in FIG. 4 is terminated.

[0093] If it is determined in step S1070 that the throttle opening EXPC of the air conditioning expansion valve 14b has reached the upper limit opening βC, the process proceeds to step S1080, where it is determined whether the elapsed time nC since the throttle opening EXPC of the air conditioning expansion valve 14b reached the upper limit opening βC exceeds a predetermined time γC.

[0094] If it is determined in step S1080 that the elapsed time nC since the throttle opening EXPC of the cooling expansion valve 14b reached the upper limit opening βC does not exceed the predetermined time γC, the subroutine shown in FIG. 4 is terminated.

[0095] If it is determined in step S1080 that the elapsed time nC since the throttle opening EXPC of the air conditioning expansion valve 14b reached the upper limit opening βC exceeds the predetermined time γC, the process proceeds to step S1090, where it is determined that there is a shortage of refrigerant (specifically, gas phase refrigerant), the compressor 11 is stopped, and the occupants are notified of the shortage of refrigerant visually or audibly, and the subroutine shown in Figure 4 is terminated.

[0096] In the next step S640, the opening degree SW of the air mix door 34 is calculated using the following formula F2. SW={TAO+(Tefin+C2)} / {TWH+(Tefin+C2)}…(F2) TWH is the high-temperature-side heat medium temperature detected by the high-temperature-side heat medium temperature sensor 66a, and C2 is a control constant.

[0097] In step S650, in order to switch the refrigeration cycle device 10 to a cooling mode refrigerant circuit, the heating expansion valve 14a is fully opened, the cooling expansion valve 14b is throttled to exert a refrigerant decompression effect, and the heating on-off valve 15b is closed. Furthermore, a control signal or a control voltage is output to each controlled device so that the control state determined in steps S610, S630, and S640 is obtained.

[0098] Therefore, in the refrigeration cycle device 10 in cooling mode, a vapor compression refrigeration cycle is formed in which the refrigerant circulates through the compressor 11, water-refrigerant heat exchanger 12, heating expansion valve 14a, outdoor heat exchanger 16, cooling expansion valve 14b, indoor evaporator 18, accumulator 21, and compressor 11 in that order.

[0099] In other words, in the refrigeration cycle device 10 in the cooling mode, the water-refrigerant heat exchanger 12 and the outdoor heat exchanger 16 function as radiators that radiate heat from the refrigerant discharged from the compressor 11, the cooling expansion valve 14b functions as a pressure reducing section that reduces the pressure of the refrigerant, and the indoor evaporator 18 functions as an evaporator, thereby forming a vapor compression refrigeration cycle.

[0100] According to this, the indoor evaporator 18 can cool the air, and the water-refrigerant heat exchanger 12 can heat the high-temperature side heat medium.

[0101] Therefore, in the vehicle air conditioning system 1 in cooling mode, by adjusting the opening of the air mix door 34, a portion of the air cooled in the interior evaporator 18 is reheated in the heater core 42, and the air whose temperature has been adjusted to approach the target outlet temperature TAO is blown into the vehicle cabin, thereby cooling the vehicle cabin.

[0102] (2) Heating mode In the heating mode, the control device 60 executes the heating mode control flow shown in Fig. 5. First, in step S900, a target high-temperature-side heat medium temperature TWHO of the high-temperature-side heat medium is determined so that the heater core 42 can heat the blown air. The target high-temperature-side heat medium temperature TWHO is determined with reference to a control map based on the target blown-out temperature TAO and the efficiency of the heater core 42. In the control map of this embodiment, the target high-temperature-side heat medium temperature TWHO is determined so that it increases as the target blown-out temperature TAO increases.

[0103] In step S910, an increase or decrease ΔIVO in the rotation speed of the compressor 11 is determined. The increase or decrease ΔIVO is determined based on the deviation between the target high-temperature side heat medium temperature TWHO and the high-temperature side heat medium temperature TWH by a feedback control method so that the high-temperature side heat medium temperature TWH approaches the target high-temperature side heat medium temperature TWHO.

[0104] In step S930, a subroutine shown in FIG. 6 is executed to determine the increase / decrease amount ΔEVH of the throttle opening of the heating expansion valve 14a.

[0105] First, in step S2000, a target degree of subcooling SCOc is determined for the refrigerant flowing out of the refrigerant passage of the water-refrigerant heat exchanger 12. The target degree of subcooling SCOc is determined by referring to a control map based on the intake temperature of the air flowing into the water-refrigerant heat exchanger 12 or the outside air temperature Tam. In this embodiment, the control map determines the target degree of subcooling SCOc so that the coefficient of performance (COP) of the cycle approaches a local maximum value.

[0106] In step S2010, a first temporary increase / decrease amount ΔEVH1 of the throttle opening of the heating expansion valve 14a is determined. The first temporary increase / decrease amount ΔEVH1 is determined by a feedback control method based on the deviation between the target degree of subcooling SCOc and the degree of subcooling SCc of the refrigerant on the outlet side of the water-refrigerant heat exchanger 12 so that the degree of subcooling SCc of the refrigerant on the outlet side of the water-refrigerant heat exchanger 12 approaches the target degree of subcooling SCOc.

[0107] The first temporary increase / decrease amount ΔEVH1 is an increase / decrease amount of the throttle opening of the heating expansion valve 14a during normal control (in other words, a first increase / decrease amount of the opening).

[0108] The degree of subcooling SCc of the refrigerant on the outlet side of the water-refrigerant heat exchanger 12 is calculated based on the temperature T2 detected by the second refrigerant temperature sensor 64b and the pressure P1 detected by the first refrigerant pressure sensor 65a.

[0109] In step S2020, it is determined whether the degree of superheat SHa of the refrigerant flowing out from the outdoor heat exchanger 16 exceeds a predetermined degree of superheat αH. The degree of superheat SHa of the refrigerant flowing out from the outdoor heat exchanger 16 is calculated based on the temperature T5 detected by the fifth refrigerant temperature sensor 64e and the pressure P2 detected by the second refrigerant pressure sensor 65b.

[0110] If it is determined in step S2020 that the degree of superheat SHa of the refrigerant flowing out from the outdoor heat exchanger 16 does not exceed the predetermined degree of superheat αH, the process proceeds to step S2030, where the value of the increase / decrease amount ΔEVH of the throttling opening of the heating expansion valve 14a is set to the same value as the first temporary increase / decrease amount ΔEVH1, and the subroutine shown in FIG. 6 is terminated.

[0111] The increase / decrease amount ΔEVH of the throttle opening of the heating expansion valve 14a determined in step S2030 is the increase / decrease amount of the throttle opening of the heating expansion valve 14a during normal control (in other words, the first opening increase / decrease amount).

[0112] If it is determined in step S2020 that the degree of superheat SHa of the refrigerant flowing out from the outdoor heat exchanger 16 exceeds the predetermined degree of superheat αH, the process proceeds to step S2040, where a target degree of superheat SHOa of the refrigerant flowing out from the outdoor heat exchanger 16 is determined. The target degree of superheat SHOa is determined to be the same value as the predetermined degree of superheat αH used in step S2020, for example.

[0113] In step S2050, a second temporary increase / decrease amount ΔEVH2 of the throttle opening of the heating expansion valve 14a is determined. The second temporary increase / decrease amount ΔEVH2 is determined by a feedback control method based on the deviation between the target degree of superheat SHOa and the degree of superheat SHa of the refrigerant on the outlet side of the outdoor heat exchanger 16 so that the degree of superheat SHa of the refrigerant on the outlet side of the outdoor heat exchanger 16 approaches the target degree of superheat SHOa.

[0114] The second temporary increase / decrease amount ΔEVH2 is an increase / decrease amount of the throttle opening of the heating expansion valve 14a that can suppress an increase in the superheat degree SHa of the outlet side refrigerant of the outdoor heat exchanger 16 (in other words, a second increase / decrease amount of the opening).

[0115] In step S2060, the value of the increase / decrease amount ΔEVH of the throttle opening of the heating expansion valve 14a is determined to be the larger value of the first tentative increase / decrease amount ΔEVH1 and the second tentative increase / decrease amount ΔEVH2.

[0116] The increase / decrease in the throttle opening of the heating expansion valve 14a ΔEVH determined in step S2060 is the increase / decrease in the throttle opening of the heating expansion valve 14a (in other words, the second increase / decrease in the throttle opening) that can suppress the increase in the superheat SHa of the refrigerant on the outlet side of the outdoor heat exchanger 16 more than during normal control.

[0117] In step S2070, it is determined whether the throttle opening EXPH of the heating expansion valve 14a has reached the upper limit opening βH. If it is determined in step S2070 that the throttle opening EXPH of the heating expansion valve 14a has not reached the upper limit opening βH, the subroutine shown in FIG. 6 is terminated.

[0118] If it is determined in step S2070 that the throttle opening EXPH of the heating expansion valve 14a has reached the upper limit opening βH, the process proceeds to step S2080, where it is determined whether the elapsed time nH since the throttle opening EXPH of the heating expansion valve 14a reached the upper limit opening βH exceeds a predetermined time γH.

[0119] If it is determined in step S2080 that the elapsed time nH since the throttle opening EXPH of the heating expansion valve 14a reached the upper limit opening βH does not exceed the predetermined time γH, the subroutine shown in FIG. 6 is terminated.

[0120] If it is determined in step S2080 that the elapsed time nH since the throttle opening EXPH of the heating expansion valve 14a reached the upper limit opening βH exceeds the predetermined time γH, the process proceeds to step S2090, where it is determined that there is a refrigerant shortage, the compressor 11 is stopped, and the occupant is notified of the refrigerant shortage visually or audibly, and the subroutine shown in FIG. 6 is terminated.

[0121] In the next step S940, the opening degree SW of the air mix door 34 is calculated, as in the cooling mode. Here, in the heating mode, the target outlet temperature TAO is higher than in the cooling mode, so the opening degree SW of the air mix door 34 approaches 100%. Therefore, in the heating mode, the opening degree of the air mix door 34 is determined so that almost the entire flow rate of the air after passing through the indoor evaporator 18 passes through the heater core 42.

[0122] In step S950, in order to switch the refrigeration cycle apparatus 10 to a heating mode refrigerant circuit, the heating expansion valve 14a is throttled, the cooling expansion valve 14b is fully closed, and the heating on-off valve 15b is opened. Furthermore, a control signal or a control voltage is output to each controlled device so that the control state determined in steps S910, S930, and S940 is obtained.

[0123] Therefore, in the refrigeration cycle device 10 in heating mode, a vapor compression refrigeration cycle is formed in which the refrigerant circulates through the compressor 11, the water-refrigerant heat exchanger 12, the heating expansion valve 14a, the outdoor heat exchanger 16, the heating passage 22b, the accumulator 21, and the compressor 11 in that order.

[0124] In other words, in the refrigeration cycle device 10 in the heating mode, the water-refrigerant heat exchanger 12 functions as a radiator that dissipates heat from the refrigerant discharged from the compressor 11, the heating expansion valve 14a functions as a pressure reducing section, and the outdoor heat exchanger 16 functions as an evaporator, forming a refrigeration cycle.

[0125] This allows the high-temperature side heat medium to be heated in the water-refrigerant heat exchanger 12. Therefore, in the heating mode, the vehicle air conditioning device 1 can heat the vehicle interior by blowing air heated by the heater core 42 into the vehicle interior.

[0126] As described above, the refrigeration cycle device 10 of this embodiment can switch between various operation modes, thereby enabling the vehicle air conditioner 1 to achieve comfortable air conditioning in the vehicle cabin.

[0127] Figure 7 shows the control characteristics for the refrigerant amount in the cooling mode of this embodiment. The control example in the heating mode of this embodiment is the same as the control example in the cooling mode. Therefore, the symbols corresponding to the heating mode are given in parentheses in Figure 7, and the description of the control example in the heating mode will be omitted.

[0128] When the amount of refrigerant sealed in the refrigeration cycle apparatus 10 is equal to or greater than the required amount of refrigerant, normal control is performed. That is, the throttle opening of the cooling expansion valve 14b is controlled so that the degree of subcooling SCa of the refrigerant on the outlet side of the outdoor heat exchanger 16 approaches the target degree of subcooling SCOa. Specifically, as described in step S1030, the increase / decrease amount ΔEVC of the throttle opening of the cooling expansion valve 14b is determined to be the first increase / decrease amount of opening.

[0129] As the amount of refrigerant sealed in the refrigeration cycle apparatus 10 decreases, the degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 increases. When the degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 exceeds a predetermined degree of superheat αC, the throttle opening EXPC of the cooling expansion valve 14b is made larger than the value for normal control so that the degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 does not exceed the target degree of superheat SHOe. Specifically, as described in step S1060, the increase / decrease amount ΔEVC of the throttle opening of the cooling expansion valve 14b is determined to be the second increase / decrease amount of opening.

[0130] This prevents the degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 from increasing significantly, thereby preventing the amount of refrigerant dissolved in the lubricating oil from decreasing and preventing the lubricating oil from being difficult to return to the compressor 11.

[0131] If the amount of refrigerant sealed in the refrigeration cycle device 10 further decreases and the throttle opening EXPC of the air conditioning expansion valve 14b reaches the upper limit opening βC, the superheat SHe of the refrigerant flowing out from the indoor evaporator 18 will increase significantly, making it difficult for the lubricating oil to return to the compressor 11.

[0132] Therefore, as explained in steps S1080 to S1090, when the elapsed time nC after the throttle opening EXPC of the cooling expansion valve 14b reaches the upper limit opening βC exceeds the predetermined time γC, it is determined that a refrigerant shortage has occurred, and the compressor 11 is stopped. This makes it possible to protect the compressor 11 from the situation where it is difficult for lubricating oil to return to the compressor 11.

[0133] It is not determined that a refrigerant shortage has occurred immediately when the throttle opening EXPC of the cooling expansion valve 14b reaches the upper limit opening βC, but rather that a refrigerant shortage has occurred when the elapsed time nC since the throttle opening EXPC of the cooling expansion valve 14b reached the upper limit opening βC exceeds a predetermined time γC, so it is possible to prevent a determination that a refrigerant shortage has occurred when the superheat degree SHe rises transiently due to a load fluctuation, etc. Therefore, it is possible to suppress erroneous determination of a refrigerant shortage.

[0134] In the cooling mode of this embodiment, as described in step S630, when the superheat SHe of the refrigerant flowing out from the indoor evaporator 18 is equal to or lower than the predetermined superheat αC, the control device 60 determines the opening increase / decrease ΔEVC of the cooling expansion valve 14b to be the first opening increase / decrease ΔEVC1, and when the superheat SHe of the refrigerant flowing out from the indoor evaporator 18 is higher than the predetermined superheat αC, the control device 60 determines the opening increase / decrease ΔEVC of the cooling expansion valve 14b to be the second opening increase / decrease ΔEVC2 that can suppress the increase in the superheat SHe more than the first opening increase / decrease ΔEVC1.

[0135] This prevents a further increase in the refrigerant superheat SHe when the amount of refrigerant decreases and the refrigerant superheat SHe increases, thereby preventing the amount of refrigerant dissolved in the lubricating oil from decreasing, making it difficult for the lubricating oil to return to the compressor 11.

[0136] In the cooling mode of this embodiment, the first opening increase / decrease amount ΔEVC1 of the cooling expansion valve 14b is a value determined so as to bring the degree of supercooling SCa of the refrigerant whose heat has been dissipated in the outdoor heat exchanger 16 closer to the target degree of supercooling SCOa, and the second opening increase / decrease amount ΔEVC2 of the cooling expansion valve 14b is a value determined so as to bring the degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 closer to the target degree of superheat SHOe.

[0137] According to this, in the cooling mode of the accumulator cycle equipped with the accumulator 21, when the amount of refrigerant is not decreasing, the accumulator cycle can be appropriately controlled by appropriately controlling the degree of subcooling SCa of the refrigerant, and when the amount of refrigerant decreases, it is possible to prevent the lubricating oil from being difficult to return to the compressor 11.

[0138] In the cooling mode of this embodiment, the control device 60 determines that the refrigerant is insufficient when the opening degree EXPC of the cooling expansion valve 14b reaches the upper limit opening degree βC.

[0139] According to this, a refrigerant shortage is determined when the increase in the opening degree EXPC of the air conditioning expansion valve 14b due to a decrease in the amount of refrigerant reaches its limit, so that a refrigerant shortage can be determined more accurately than when a refrigerant shortage is determined based on the refrigerant pressure.

[0140] In the cooling mode of this embodiment, the control device 60 determines that there is a shortage of refrigerant when the opening degree EXPC of the cooling expansion valve 14b reaches the upper limit opening degree βC and the elapsed time nC since the opening degree EXPC of the cooling expansion valve 14b reached the upper limit opening degree βC exceeds a predetermined time γC.

[0141] This makes it possible to prevent a determination that there is a shortage of refrigerant when the degree of superheat SHe rises transiently due to a load fluctuation, etc. Therefore, it is possible to suppress erroneous determination of a shortage of refrigerant.

[0142] In the cooling mode of this embodiment, when it is determined that the refrigerant is insufficient, the control device 60 stops the compressor 11. This makes it possible to protect the compressor 11 when the refrigerant is insufficient.

[0143] In the cooling mode of this embodiment, the fifth refrigerant temperature sensor 64e and the second refrigerant pressure sensor 65b detect the temperature T5 and pressure P2 of the refrigerant downstream of the accumulator 21 and on the suction side of the compressor 11, and the control device 60 calculates the degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 using the refrigerant temperature and pressure detected by the fifth refrigerant temperature sensor 64e and the second refrigerant pressure sensor 65b.

[0144] This allows the degree of superheat SHe of the refrigerant flowing out from the interior evaporator 18 to be detected with high accuracy, so that a shortage of refrigerant can be determined with high accuracy.

[0145] In the heating mode of this embodiment, as described in step S930, when the superheat SHa of the refrigerant flowing out from the outdoor heat exchanger 16 is equal to or lower than the predetermined superheat αH, the control device 60 determines the opening increase / decrease ΔEVH of the heating expansion valve 14a to be the first opening increase / decrease ΔEVH1, and when the superheat SHa of the refrigerant flowing out from the outdoor heat exchanger 16 is higher than the predetermined superheat αH, the control device 60 determines the opening increase / decrease ΔEVH of the heating expansion valve 14a to be the second opening increase / decrease ΔEVH2, which is more capable of suppressing the increase in superheat SHa than the first opening increase / decrease ΔEVH1.

[0146] This prevents a further increase in the degree of superheat SHa of the refrigerant when the amount of refrigerant decreases and the degree of superheat SHa of the refrigerant increases, thereby preventing a decrease in the amount of refrigerant dissolved in the lubricating oil, which makes it difficult for the lubricating oil to return to the compressor 11.

[0147] In the heating mode of this embodiment, the first opening increase / decrease amount ΔEVH1 of the heating expansion valve 14a is a value determined so as to bring the degree of supercooling SCc of the refrigerant dissipated in the water-refrigerant heat exchanger 12 closer to the target degree of supercooling SCOc, and the second opening increase / decrease amount ΔEVH2 of the heating expansion valve 14a is a value determined so as to bring the degree of superheat SHa of the refrigerant flowing out from the outdoor heat exchanger 16 closer to the target degree of superheat SHOa.

[0148] According to this, in the heating mode of the accumulator cycle equipped with the accumulator 21, when the amount of refrigerant is not decreasing, the accumulator cycle can be appropriately controlled by appropriately controlling the degree of subcooling SCc of the refrigerant, and when the amount of refrigerant decreases, it is possible to prevent the lubricating oil from being difficult to return to the compressor 11.

[0149] In the heating mode of this embodiment, the control device 60 determines that the refrigerant is insufficient when the opening degree EXPH of the heating expansion valve 14a reaches the upper limit opening degree βH.

[0150] According to this, a refrigerant shortage is determined when the increase in the opening degree EXPH of the heating expansion valve 14a due to a decrease in the amount of refrigerant reaches its limit, so that a refrigerant shortage can be determined more accurately than when a refrigerant shortage is determined based on the refrigerant pressure.

[0151] In the heating mode of this embodiment, the control device 60 determines that there is a shortage of refrigerant when the opening degree EXPH of the heating expansion valve 14a reaches the upper limit opening degree βH and the elapsed time nH since the opening degree EXPH of the heating expansion valve 14a reached the upper limit opening degree βH exceeds a predetermined time γH.

[0152] This makes it possible to prevent a determination that there is a shortage of refrigerant when the degree of superheat SHa rises transiently due to a load fluctuation, etc. Therefore, it is possible to suppress erroneous determination of a shortage of refrigerant.

[0153] In the heating mode of this embodiment, when it is determined that the refrigerant is insufficient, the control device 60 stops the compressor 11. This makes it possible to protect the compressor 11 when the refrigerant is insufficient.

[0154] In the heating mode of this embodiment, the fifth refrigerant temperature sensor 64e and the second refrigerant pressure sensor 65b detect the temperature T5 and pressure P2 of the refrigerant downstream of the accumulator 21 and on the suction side of the compressor 11, and the control device 60 calculates the degree of superheat SHa of the refrigerant flowing out of the outdoor heat exchanger 16 using the refrigerant temperature and pressure detected by the fifth refrigerant temperature sensor 64e and the second refrigerant pressure sensor 65b.

[0155] According to this, the degree of superheat SHa of the refrigerant flowing out from the outdoor heat exchanger 16 can be detected with high accuracy, and therefore, a shortage of refrigerant can be determined with high accuracy.

[0156] (Second embodiment) In the first embodiment, the refrigeration cycle apparatus 10 configures an accumulator cycle having an accumulator 21. In the present embodiment, the refrigeration cycle apparatus 10 configures a receiver cycle having a receiver 25, as shown in FIG.

[0157] The receiver 25 is a gas-liquid separator that separates the refrigerant that flows into it into gas and liquid phases and stores a portion of the separated liquid-phase refrigerant as excess liquid-phase refrigerant in the cycle. The inlet side of the receiver 25 is connected to the refrigerant outlet side of the outdoor heat exchanger 16. The liquid-phase refrigerant outlet of the receiver 25 is connected to the refrigerant inlet side of the cooling expansion valve 14b.

[0158] The refrigeration cycle apparatus 10 of the present embodiment is provided with an electric heater 26 instead of the water-refrigerant heat exchanger 12 of the first embodiment. The electric heater 26 is a heating unit that generates heat when supplied with electric power and heats the high-temperature side heat medium.

[0159] The vehicle air conditioner 1 of this embodiment can be operated in a cooling mode. The basic operation of the vehicle air conditioner 1 in the cooling mode of this embodiment is the same as that of the first embodiment.

[0160] In this embodiment, in step S630 in the cooling mode, a subroutine shown in FIG. 9 is executed to determine the increase / decrease amount ΔEVC of the throttle opening of the cooling expansion valve 14b.

[0161] First, in step S3000, a first target degree of superheat SHOe1 of the refrigerant flowing out from the indoor evaporator 18 is determined. The first target degree of superheat SHOe1 is determined by referring to a control map based on, for example, the temperature of intake air flowing into the indoor evaporator 18. In the control map of this embodiment, the first target degree of superheat SHOe1 is determined so that the coefficient of performance (COP) of the cycle approaches a local maximum value.

[0162] In step S3010, a first tentative increase / decrease ΔEVC1 in the throttle opening of the cooling expansion valve 14b is determined. The first tentative increase / decrease ΔEVC1 is determined by a feedback control method based on the deviation between the first target superheat degree SHOe1 and the superheat degree SHe of the refrigerant on the outlet side of the indoor evaporator 18 so that the superheat degree SHe of the refrigerant on the outlet side of the indoor evaporator 18 approaches the first target superheat degree SHOe1. The first tentative increase / decrease ΔEVC1 is the increase / decrease in the throttle opening of the cooling expansion valve 14b during normal control (in other words, the first increase / decrease in the opening degree).

[0163] In step S3020, it is determined whether the degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 exceeds a predetermined degree of superheat αC. If it is determined in step S3020 that the degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 does not exceed the predetermined degree of superheat αC, the process proceeds to step S3030, where the value of the increase / decrease amount ΔEVC of the throttle opening of the cooling expansion valve 14b is set to the same value as the first temporary increase / decrease amount ΔEVC1, and the subroutine shown in FIG. 9 is terminated.

[0164] The increase / decrease amount ΔEVC of the throttle opening of the cooling expansion valve 14b determined in step S3030 is the increase / decrease amount of the throttle opening of the cooling expansion valve 14b during normal control (in other words, the first increase / decrease amount of opening).

[0165] If it is determined in step S3020 that the degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 exceeds the predetermined degree of superheat αC, the process proceeds to step S3040, where a second target degree of superheat SHOe2 of the refrigerant flowing out from the indoor evaporator 18 is determined. The second target degree of superheat SHOe2 is determined to be the same value as the predetermined degree of superheat αC used in step S3020, for example.

[0166] In step S3050, a second temporary increase / decrease amount ΔEVC2 of the throttle opening of the cooling expansion valve 14b is determined. The second temporary increase / decrease amount ΔEVC2 is determined by a feedback control method based on the deviation between the second target superheat degree SHOe2 and the superheat degree SHe of the refrigerant on the outlet side of the indoor evaporator 18 so that the superheat degree SHe of the refrigerant on the outlet side of the indoor evaporator 18 approaches the second target superheat degree SHOe2.

[0167] The second temporary increase / decrease amount ΔEVC2 is an increase / decrease amount of the throttle opening of the cooling expansion valve 14b that can suppress an increase in the superheat degree SHe of the refrigerant on the outlet side of the indoor evaporator 18 (in other words, a second increase / decrease amount of the opening).

[0168] In step S3060, the value of the increase / decrease ΔEVC in the throttle opening of the cooling expansion valve 14b is determined to be the larger value of the first tentative increase / decrease ΔEVC1 and the second tentative increase / decrease ΔEVC2.

[0169] The increase / decrease in the throttle opening of the air conditioning expansion valve 14b ΔEVC determined in step S3060 is the increase / decrease in the throttle opening of the air conditioning expansion valve 14b (in other words, the second increase / decrease in the throttle opening) that can suppress the increase in the superheat SHe of the refrigerant on the outlet side of the indoor evaporator 18 more than during normal control.

[0170] In step S3070, it is determined whether the throttle opening EXPC of the cooling expansion valve 14b has reached the upper limit opening βC. If it is determined in step S3070 that the throttle opening EXPC of the cooling expansion valve 14b has not reached the upper limit opening βC, the subroutine shown in FIG. 9 is terminated.

[0171] If it is determined in step S3070 that the throttle opening EXPC of the air conditioning expansion valve 14b has reached the upper limit opening βC, the process proceeds to step S3080, where it is determined whether the elapsed time nC since the throttle opening EXPC of the air conditioning expansion valve 14b reached the upper limit opening βC exceeds a predetermined time γC.

[0172] If it is determined in step S3080 that the elapsed time nC since the throttle opening EXPC of the cooling expansion valve 14b reached the upper limit opening βC does not exceed the predetermined time γC, the subroutine shown in FIG. 9 is terminated.

[0173] If it is determined in step S3080 that the elapsed time nC since the throttle opening EXPC of the air conditioning expansion valve 14b reached the upper limit opening βC exceeds the predetermined time γH, the process proceeds to step S3090, where it is determined that there is a shortage of refrigerant, the compressor 11 is stopped, and the occupants are notified of the shortage of refrigerant visually or audibly, and the subroutine shown in FIG. 9 is terminated.

[0174] 10 shows the control characteristics for the amount of refrigerant in the cooling mode of this embodiment. When the amount of refrigerant sealed in the refrigeration cycle device 10 is equal to or greater than the required amount of refrigerant, normal control is performed. That is, the throttle opening EXPC of the cooling expansion valve 14b is controlled so that the superheat degree SHe of the refrigerant on the outlet side of the indoor evaporator 18 approaches the first target superheat degree SHOe1. Specifically, as described in step S3030, the increase / decrease amount ΔEVC of the throttle opening of the cooling expansion valve 14b is determined to be the first increase / decrease amount.

[0175] As the amount of refrigerant sealed in the refrigeration cycle apparatus 10 decreases, the degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 increases beyond the first target degree of superheat SHOe1. When the degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 exceeds a predetermined degree of superheat αC, the throttle opening EXPC of the cooling expansion valve 14b is made larger than the value for normal control so that the degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 does not exceed the second target degree of superheat SHOe2. Specifically, as described in step S3060, the increase / decrease amount ΔEVC of the throttle opening of the cooling expansion valve 14b is determined to be the second increase / decrease amount of opening.

[0176] This prevents the degree of superheat SHe of the refrigerant flowing out from the indoor evaporator 18 from increasing significantly, thereby preventing the amount of refrigerant dissolved in the lubricating oil from decreasing and preventing the lubricating oil from being difficult to return to the compressor 11.

[0177] If the amount of refrigerant sealed in the refrigeration cycle device 10 further decreases and the throttle opening EXPC of the air conditioning expansion valve 14b reaches the upper limit opening βC, the superheat SHe of the refrigerant flowing out from the indoor evaporator 18 will rise significantly, making it difficult for lubricating oil to return to the compressor 11. Therefore, if the elapsed time nC after the throttle opening EXPC of the air conditioning expansion valve 14b reaches the upper limit opening βC exceeds a predetermined time γC, it is determined that a refrigerant shortage has occurred, and the compressor 11 is stopped. This makes it possible to protect the compressor 11 from the difficulty in returning lubricating oil to the compressor 11.

[0178] It is not determined that a refrigerant shortage has occurred immediately when the throttle opening EXPC of the cooling expansion valve 14b reaches the upper limit opening βC, but rather that a refrigerant shortage has occurred when the elapsed time nC since the throttle opening EXPC of the cooling expansion valve 14b reached the upper limit opening βC exceeds a predetermined time γC, so it is possible to prevent a determination that a refrigerant shortage has occurred when the superheat degree SHe rises transiently due to a load fluctuation, etc. Therefore, it is possible to suppress erroneous determination of a refrigerant shortage.

[0179] In the cooling mode of this embodiment, the first opening increase / decrease amount ΔEVC1 of the cooling expansion valve 14b is a value determined so as to bring the superheat degree SHe of the refrigerant flowing out from the indoor evaporator 18 closer to the first target superheat degree SHOe1, and the second opening increase / decrease amount ΔEVC2 of the cooling expansion valve 14b is a value greater than the first opening increase / decrease amount ΔEVC1.

[0180] According to this, in the cooling mode of the receiver cycle equipped with the receiver 25, when the amount of refrigerant is not decreasing, the receiver cycle can be appropriately controlled by appropriately controlling the degree of superheat SHe of the refrigerant, and when the amount of refrigerant is decreasing, it is possible to prevent the lubricating oil from being difficult to return to the compressor 11.

[0181] (Other embodiments) The present invention is not limited to the above-described embodiments, and various modifications can be made as follows without departing from the spirit of the present invention. Furthermore, the means disclosed in each of the above-described embodiments may be combined as appropriate within the scope of feasibility.

[0182] (1) In the above embodiment, the predetermined superheat degrees αC and αH are fixed values ​​stored in advance in the control device 60, but they do not necessarily have to be fixed values. For example, the predetermined superheat degrees αC and αH may be varied depending on the operating environment, etc.

[0183] In the above embodiment, the target superheat degrees SHOe, SHOa, and SHOe2 are determined to be the same as the predetermined superheat degrees αC and αH, but they do not necessarily have to be determined to be the same values. For example, the target superheat degrees SHOe, SHOa, and SHOe2 may be varied relative to the predetermined superheat degrees αC and αH depending on the operating environment, etc.

[0184] (2) In the above embodiment, the refrigeration cycle apparatus 10 is switchable between a plurality of operation modes. However, the switching of the operation modes of the refrigeration cycle apparatus 10 is not limited to this.

[0185] For example, the mode may be switchable to a dehumidifying and heating mode in which the low-pressure refrigerant is evaporated in both the exterior heat exchanger 16 and the interior evaporator 18 to cause the low-pressure refrigerant to absorb heat.

[0186] (3) The configuration of the heating unit is not limited to that disclosed in the above-described embodiment. For example, a radiator that dissipates excess heat to the outside air may be added to the high-temperature side heat medium circuit 40 described in the first embodiment. Furthermore, in a vehicle equipped with an internal combustion engine (engine), such as a hybrid vehicle, engine coolant may be circulated through the high-temperature side heat medium circuit 40.

[0187] (4) In the refrigeration cycle device 10, a battery cooling heat exchanger for cooling the battery may be arranged in parallel with the interior evaporator 18.

[0188] Furthermore, the refrigeration cycle device 10 may be provided with a chiller for cooling the low-temperature heat medium, and the low-temperature heat medium cooled by the chiller may be used to cool objects to be cooled, such as a battery, an inverter, or a motor generator.

[0189] (5) In each of the above-described embodiments, the refrigeration cycle device 10 according to the present invention is applied to a vehicle air conditioner 1, but the application of the refrigeration cycle device 10 is not limited to this. For example, the refrigeration cycle device 10 may be applied to an air conditioner with a server cooling function that appropriately adjusts the temperature of a computer server while also providing indoor air conditioning.

[0190] The refrigeration cycle device disclosed in this specification has the following features. (Item 1) a compressor (11) that draws in, compresses, and discharges a refrigerant; a radiator (16, 12) that radiates heat from the refrigerant discharged from the compressor; an expansion valve (14b, 14a) for reducing the pressure and expanding the refrigerant whose heat has been radiated by the radiator; an evaporator (18, 16) that evaporates the refrigerant that has been decompressed and expanded by the expansion valve; a control unit (60) that controls the opening degree of the expansion valve; The control unit When the degree of superheat (SHe, SHa) of the refrigerant flowing out from the evaporator is equal to or lower than a predetermined degree of superheat (αC, αH), the opening increment / decrement (ΔEVC, ΔEVH) of the expansion valve is determined to be a first opening increment / decrement (ΔEVC1, ΔEVH1); a refrigeration cycle device that, when the superheat of the refrigerant flowing out of the evaporator exceeds the predetermined superheat, determines the opening increase / decrease to a second opening increase / decrease (ΔEVC2, ΔEVH2) that can suppress the increase in superheat of the refrigerant flowing out of the evaporator more than the first opening increase / decrease. (Item 2) an accumulator (21) for separating the refrigerant evaporated in the evaporator into gas and liquid, the first opening increase / decrease amount is a value determined so as to bring the degree of supercooling (SCa, SCc) of the refrigerant radiated by the radiator closer to a target degree of supercooling (SCOa, SCOc), Item 1. The refrigeration cycle device according to item 1, wherein the second opening increase / decrease amount is a value determined so as to bring the degree of superheat (SHe, SHa) of the refrigerant flowing out from the evaporator closer to a target degree of superheat (SHOe, SHOa). (Item 3) a receiver (25) for separating the refrigerant, which has been heat-dissipated by the radiator, into gas and liquid; the first opening increase / decrease amount is a value determined so as to bring the degree of superheat (SHe) of the refrigerant flowing out from the evaporator closer to a target degree of superheat (SHOe1), Item 2. The refrigeration cycle device according to item 1, wherein the second opening increase / decrease amount is a value greater than the first opening increase / decrease amount. (Item 4) The refrigeration cycle device according to any one of items 1 to 3, wherein the control unit determines that the refrigerant is insufficient when the opening degree (EXPC, EXPH) of the expansion valve reaches an upper limit opening degree (βC, βH). (Item 5) The refrigeration cycle device according to any one of items 1 to 3, wherein the control unit determines that the refrigerant is insufficient when the opening of the expansion valve (EXPC, EXPH) reaches an upper limit opening (βC, βH) and the elapsed time (nC, nH) since the opening of the expansion valve reached the upper limit opening exceeds a predetermined time (γC, γH). (Item 6) 6. The refrigeration cycle apparatus according to item 4 or 5, wherein the control unit stops the compressor when it is determined that the refrigerant is insufficient. (Item 7) an accumulator (21) for separating the refrigerant evaporated in the evaporator into gas and liquid; a refrigerant state detection unit (64e, 65b) that detects the temperature (T5) and pressure (P2) of the refrigerant downstream of the accumulator and on the suction side of the compressor, Item 1. The refrigeration cycle device according to item 1, wherein the control unit calculates a degree of superheat (SHe, SHa) of the refrigerant flowing out from the evaporator using the temperature (T5) and pressure (P2) of the refrigerant detected by the refrigerant state detection unit. [Explanation of symbols]

[0191] 11 Compressor 12 Water refrigerant heat exchanger (radiator) 14a Heating expansion valve (expansion valve) 14b Cooling expansion valve (expansion valve) 16 Outdoor heat exchanger (evaporator, radiator) 18 Indoor evaporator (evaporator) 21 Accumulator 60 Control device (control unit) 64e Fifth refrigerant temperature sensor (refrigerant state detection unit) 65b Second refrigerant pressure sensor (refrigerant state detection unit)

Claims

1. a compressor (11) that draws in, compresses, and discharges a refrigerant; a radiator (16, 12) that radiates heat from the refrigerant discharged from the compressor; an expansion valve (14b, 14a) for reducing the pressure and expanding the refrigerant whose heat has been radiated by the radiator; an evaporator (18, 16) that evaporates the refrigerant that has been decompressed and expanded by the expansion valve; a control unit (60) that controls the opening degree of the expansion valve, The control unit When the degree of superheat (SHe, SHa) of the refrigerant flowing out from the evaporator is equal to or lower than a predetermined degree of superheat (αC, αH), the opening degree increase / decrease (ΔEVC, ΔEVH) of the expansion valve is determined to be a first opening increase / decrease (ΔEVC1, ΔEVH1), When the superheat of the refrigerant flowing out of the evaporator exceeds the predetermined superheat, the opening increase / decrease amount is determined to be a second opening increase / decrease amount (ΔEVC2, ΔEVH2) that can suppress the increase in superheat of the refrigerant flowing out of the evaporator more than the first opening increase / decrease amount.

2. an accumulator (21) for separating the refrigerant evaporated in the evaporator into gas and liquid, the first opening increase / decrease amount is a value determined so as to bring the degree of supercooling (SCa, SCc) of the refrigerant radiated by the radiator closer to a target degree of supercooling (SCOa, SCOc), 2. The refrigeration cycle device according to claim 1, wherein the second opening increase / decrease amount is a value determined so as to bring the degree of superheat (SHe, SHa) of the refrigerant flowing out of the evaporator closer to a target degree of superheat (SHOe, SHOa).

3. a receiver (25) for separating the refrigerant from gas and liquid after heat dissipation in the radiator; the first opening increase / decrease amount is a value determined so as to bring the degree of superheat (SHe) of the refrigerant flowing out of the evaporator closer to a target degree of superheat (SHOe1), The refrigeration cycle apparatus according to claim 1 , wherein the second opening increase / decrease amount is greater than the first opening increase / decrease amount.

4. 2. The refrigeration cycle device according to claim 1, wherein the control unit determines that the refrigerant is insufficient when the openings (EXPC, EXPH) of the expansion valves reach upper limit openings (βC, βH).

5. 2. The refrigeration cycle device according to claim 1, wherein the control unit determines that the refrigerant is insufficient when the opening degree (EXPC, EXPH) of the expansion valve reaches an upper limit opening degree (βC, βH) and the elapsed time (nC, nH) since the opening degree of the expansion valve reached the upper limit opening degree exceeds a predetermined time (γC, γH).

6. The refrigeration cycle apparatus according to claim 4 or 5, wherein the control unit stops the compressor when it is determined that the refrigerant is insufficient.

7. an accumulator (21) for separating the refrigerant evaporated in the evaporator into gas and liquid; a refrigerant state detection unit (64e, 65b) that detects the temperature (T5) and pressure (P2) of the refrigerant downstream of the accumulator and on the suction side of the compressor, 2. The refrigeration cycle device according to claim 1, wherein the control unit calculates a degree of superheat (SHe, SHa) of the refrigerant flowing out of the evaporator using the temperature (T5) and pressure (P2) of the refrigerant detected by the refrigerant state detection unit.

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