Vehicle air conditioning system

Abstract

To surely and evenly defrost in accordance with a situation of a vehicle.SOLUTION: Provided is an air conditioner for vehicle that comprises: a refrigerant circuit including a compressor for compressing a refrigerant, an outdoor heat exchanger for exchanging heat between the refrigerant and the outside air, and a heat exchanger for heat absorption for absorbing heat from a heat absorbed object; and a control device for controlling the refrigerant circuit. The control device can selectively execute a plurality of defrosting modes including a hot gas defrosting mode to defrost the outdoor heat exchanger with the refrigerant compressed by the compressor and a heat absorbing defrosting mode to defrost the outdoor heat exchanger with the refrigerant that absorbs heat at the heat absorbed object and is compressed by the compressor. Hot gas defrosting priority conditions to select the hot gas defrosting mode have been set in the air conditioner for vehicle.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vehicle air conditioner that is applied to a vehicle, and more particularly to a vehicle air conditioner that defrosts an exterior heat exchanger. [Background technology]

[0002] Conventionally, air conditioning systems applied to vehicles include a compressor, an indoor heat exchanger (an evaporator for cooling and a condenser for heating), an outdoor heat exchanger (a condenser for cooling and an evaporator for heating), and a refrigerant circuit to which an expansion valve is connected, and air that has exchanged heat with the refrigerant in the indoor heat exchanger is supplied to the vehicle cabin to condition the interior of the vehicle.

[0003] In such a vehicle air conditioner, the exterior heat exchanger functions as a heat absorber during heating operation, and therefore when the exterior temperature is low, condensed water may freeze on the surface of the exterior heat exchanger, causing frost to form. When frost forms, the heat transfer coefficient decreases, resulting in insufficient heat absorption and insufficient heating of the vehicle interior, making it necessary to perform a defrosting operation. Therefore, for example, when frost forms on the outdoor heat exchanger, a vehicle air conditioner is known that performs defrosting operation with an appropriate capacity depending on the situation by switching between a strong defrosting operation mode in which the refrigerant discharged from the compressor flows through the indoor heat exchanger and then circulates it through the outdoor heat exchanger, and a weak defrosting operation mode in which the outdoor heat exchanger is bypassed (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-196018 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the vehicle air conditioner of the above-mentioned Patent Document 1, when the outside air temperature is extremely low during defrosting operation in the strong defrosting operation mode, the heat loss in the piping and the amount of heat dissipated during the outdoor heat exchange are large, and the amount of heat required for defrosting is not sufficient from the heat amount from the compressor alone, so there is a risk that defrosting cannot be performed sufficiently and evenly. On the other hand, the weak defrosting operation mode is an operation mode selected to melt frost on the outdoor heat exchanger when frost forms on the outdoor heat exchanger during heating when the outside air temperature is relatively high (higher than 0°C), and since it does not circulate refrigerant through the outdoor heat exchanger, it does not actively defrost the outdoor heat exchanger, and there is a risk of uneven defrosting.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to perform reliable and uniform defrosting according to the condition of the vehicle. [Means for solving the problem]

[0007] One aspect of the present invention provides a vehicle air conditioning system including a refrigerant circuit including a compressor that compresses a refrigerant, an exterior heat exchanger that performs heat exchange between the refrigerant and outside air, and a heat absorption heat exchanger that absorbs heat from a heat absorption target, and a control device that controls the refrigerant circuit, wherein the control device is capable of selectively executing a plurality of defrosting modes including a hot gas defrosting mode in which the exterior heat exchanger is defrosted by the refrigerant compressed by the compressor, and an endothermic defrosting mode in which the exterior heat exchanger is defrosted by the refrigerant that absorbs heat in the heat absorption target and is compressed by the compressor, and a hot gas defrosting priority condition is set to preferentially select the hot gas defrosting mode. Effect of the Invention

[0008] According to the present invention, it is possible to perform reliable and uniform defrosting according to the condition of the vehicle. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing a schematic configuration of a refrigerant circuit of a vehicle air conditioner according to an embodiment of the present invention; [Diagram 2] 2 is a block diagram showing a schematic configuration of a heat pump ECU as a control device for a vehicle air conditioner according to the embodiment of the present invention. FIG. [Diagram 3] 5 is a diagram showing a flow of refrigerant when defrosting an exterior heat exchanger in a hot gas defrosting mode in the vehicle air conditioning device according to the embodiment of the present invention. FIG. [Figure 4] 5 is a diagram showing a flow of refrigerant when defrosting an exterior heat exchanger in a chiller defrosting mode in the vehicle air conditioning device according to the embodiment of the present invention. FIG. [Diagram 5] 5 is a diagram showing a flow of refrigerant when defrosting an exterior heat exchanger in a cooling cycle defrosting mode in the vehicle air conditioning system according to the embodiment of the present invention. FIG. [Figure 6] 1 is a table showing the relationship between the compression capacity, the opening area of ​​the outdoor heat exchanger, and the outdoor air temperature (threshold value). [Figure 7] 1 shows a graph showing the relationship between the outside air temperature and the defrosting index P. [Figure 8] 1 is a flowchart showing the flow of a defrost mode selection / switching process in a vehicle air conditioner according to an embodiment of the present invention, in which chiller defrosting is selected as endothermic defrosting. [Figure 9] 4 is a flowchart showing the flow of a selection and switching process of a defrost mode in the vehicle air conditioner according to the embodiment of the present invention, in which cooling cycle defrosting is selected as endothermic defrosting. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same reference numerals denote parts having the same functions, and duplicated descriptions in each drawing will be omitted as appropriate.

[0011] 1 shows a schematic configuration of a vehicle air conditioner 1 according to an embodiment of the present invention. The vehicle air conditioner 1 can be applied to vehicles such as electric vehicles (EVs) that are not equipped with an engine (internal combustion engine) and so-called hybrid vehicles that use both an engine and an electric motor for driving. Such vehicles are equipped with a battery (e.g., a lithium battery) and are driven and run by supplying power charged in the battery from an external power source to a motor unit including a motor for driving. The vehicle air conditioner 1 is also driven by power supplied from the battery.

[0012] The vehicle air conditioner 1 according to this embodiment includes a refrigerant circuit R, and performs air conditioning (heating, cooling, dehumidification, and defrosting) in the vehicle cabin by performing heat pump operation using the refrigerant circuit R. In addition, the vehicle air conditioner 1 performs cooling and warming of electrical equipment such as a battery and a motor using a heat medium circuit connected to the refrigerant circuit R. In the following description, the refrigerant is a circulating medium in the refrigerant circuit that undergoes state changes in the heat pump (compression, condensation, expansion, evaporation), and the heat medium is a medium that absorbs and releases heat without undergoing such state changes.

[0013] The refrigerant circuit R is composed of an electric compressor 2 that compresses the refrigerant, an indoor condenser (heat radiator) 4 that is provided in an air flow passage 3 of an HVAC unit 10 through which air in the vehicle cabin is circulated and serves as an indoor heat exchanger that radiates heat from the high-temperature, high-pressure refrigerant discharged from the compressor 2 to heat the air to be supplied to the vehicle cabin, an outdoor expansion valve 6 that reduces the pressure and expands the refrigerant during heating, an outdoor heat exchanger 7 that exchanges heat between the refrigerant and the outside air to function as a radiator (condenser) that radiates heat from the refrigerant during cooling and as an evaporator that absorbs heat from the refrigerant (absorbs heat into the refrigerant) during heating, an indoor expansion valve 8 that reduces the pressure and expands the refrigerant, a heat absorber 9 (heat absorption heat exchanger) that is provided in the air flow passage 3 and serves as an indoor heat exchanger that causes the refrigerant to absorb heat from inside and outside the vehicle cabin during cooling and dehumidification to cool the air to be supplied to the vehicle cabin, and an accumulator 12, all of which are connected by refrigerant piping 13A to 13H.

[0014] The outdoor expansion valve 6 and the indoor expansion valve 8 are both electronic expansion valves driven by a pulse motor (not shown), and the opening degree is appropriately controlled between fully closed and fully open depending on the number of pulses applied to the pulse motor. The outdoor expansion valve 6 reduces the pressure and expands the refrigerant that flows out of the indoor condenser 4 and flows into the outdoor heat exchanger 7. In addition, the opening degree of the outdoor expansion valve 6 is controlled by a heat pump ECU 11 (described later) so that the SC (subcool) value, which is an index of the degree of supercooling achieved at the refrigerant outlet of the indoor condenser 4, becomes a predetermined target value during heating operation using the outdoor heat exchanger 7 (SC control). The indoor expansion valve 8 reduces the pressure and expands the refrigerant that flows into the heat absorber 9, and adjusts the degree of superheat of the refrigerant in the heat absorber 9.

[0015] An exterior blower (not shown) is provided in the exterior heat exchanger 7. The exterior blower forcibly blows outside air through the exterior heat exchanger 7, thereby exchanging heat between the outside air and the refrigerant, so that the outside air is blown through the exterior heat exchanger 7 even when the vehicle is stopped.

[0016] The outdoor heat exchanger 7 is provided with a receiver-drier section 14 and a subcooling section 16 on the refrigerant downstream side. The refrigerant outlet side of the outdoor heat exchanger 7 and the receiver-drier section 14 are connected via a refrigerant pipe 13A and a refrigerant pipe 13B branching off from the refrigerant pipe 13A. The refrigerant pipe 13B is provided with a solenoid valve 17 (for cooling) that serves as an on-off valve that is opened when the refrigerant is caused to flow into the heat absorber 9.

[0017] The outlet side of the supercooling unit 16 and the refrigerant inlet side of the heat absorber 9 are connected via a refrigerant pipe 13C. In the refrigerant pipe 13C, a check valve 18, an indoor expansion valve 8, and a solenoid valve 32 serving as an indoor heat exchanger valve device (on-off valve) are provided in this order from the outdoor heat exchanger 7 side. The check valve 18 is provided in the refrigerant pipe 13C so that the direction toward the heat absorber 9 is the forward direction.

[0018] Further, a solenoid valve 21 (for heating) serving as an opening / closing valve that is opened during heating, an accumulator 12, and a compressor 2 are connected in this order to a refrigerant pipe 13A extending from the outdoor heat exchanger . The refrigerant pipe 13A branches into a refrigerant pipe 13D between the outlet side of the solenoid valve 21 and the inlet side of the accumulator 12, and the refrigerant pipe 13D is connected to the refrigerant outlet side of the heat absorber 9 in communication.

[0019] A refrigerant outlet of the compressor 2 and a refrigerant inlet of the indoor condenser 4 are connected by a refrigerant pipe 13E. One end of a refrigerant pipe 13F is connected to the refrigerant outlet of the indoor condenser 4, and the other end of the refrigerant pipe 13F branches into a refrigerant pipe 13G and a refrigerant pipe 13H just before the outdoor expansion valve 6 (on the upstream side of the refrigerant).

[0020] One of the branched refrigerant pipes, 13H, is connected to the refrigerant inlet side of the outdoor heat exchanger 7 via the outdoor expansion valve 6. The other branched refrigerant pipe, 13G, is connected between the check valve 18 of the refrigerant pipe 13C and the indoor expansion valve 8. A solenoid valve 22 is provided on the refrigerant upstream side of the connection point of the refrigerant pipe 13G with the refrigerant pipe 13C.

[0021] As a result, the refrigerant pipe 13G is connected in parallel to the series circuit of the outdoor expansion valve 6, the outdoor heat exchanger 7, and the check valve 18, and forms a circuit that bypasses the outdoor expansion valve 6, the outdoor heat exchanger 7, and the check valve 18.

[0022] An outside air inlet and an inside air inlet are formed in the air flow passage 3 on the air upstream side of the heat absorber 9 (representatively shown as an inlet 25 in FIG. 1). An inlet switching damper 26 is provided in the inlet 25. The inlet switching damper 26 appropriately switches between inside air (inside air circulation) which is air inside the vehicle cabin and outside air (outside air introduction) which is air outside the vehicle cabin, and introduces the air into the air flow passage 3 from the inlet 25. An indoor blower (blower fan) 27 is provided on the air downstream side of the inlet switching damper 26 to send the introduced inside air and outside air to the air flow passage 3.

[0023] 1, the auxiliary heater 23 functions as an auxiliary heating device. The auxiliary heater 23 is, for example, a PTC heater (electric heater), and is provided in the air flow passage 3 downstream of the interior condenser 4 with respect to the air flow in the air flow passage 3. The auxiliary heater 23 generates heat when electricity is applied, thereby supplementing the heating of the vehicle interior.

[0024] An air mix damper 28 is provided in the air flow passage 3 on the air upstream side of the indoor condenser 4 to adjust the ratio of air (indoor air or outdoor air) in the air flow passage 3 after it flows into the air flow passage 3 and passes through the heat absorber 9 to be ventilated to the indoor condenser 4 and the auxiliary heater 23.

[0025] As the auxiliary heating means, for example, hot water heated by waste heat from a compressor may be circulated through a heater core disposed in the air flow passage 3 to heat the blown air.

[0026] A refrigerant-heat medium heat exchanger 64 (heat absorbing heat exchanger) is connected to the refrigerant circuit R. The refrigerant-heat medium heat exchanger 64 includes a refrigerant flow path 64A and a heat medium flow path 64B, and constitutes a part of the refrigerant circuit R and at the same time constitutes a part of a heat medium circuit 61 such as an equipment temperature adjustment circuit (not shown).

[0027] Specifically, the refrigerant-heat medium heat exchanger 64 is connected to the refrigerant circuit R as follows. In the refrigerant circuit R, one end of refrigerant piping 72 serving as a branch circuit is connected to the downstream side of the check valve 18 provided in the refrigerant piping 13C and the refrigerant upstream side of the indoor expansion valve 8. The refrigerant piping 72 is provided with a chiller expansion valve 73 and a solenoid valve 74 serving as an opening / closing valve.

[0028] The chiller expansion valve 73 is an electronic expansion valve driven by a pulse motor (not shown), and the opening degree is appropriately controlled between fully closed and fully open depending on the number of pulses applied to the pulse motor. The chiller expansion valve 73 reduces the pressure and expands the refrigerant flowing into the refrigerant flow path 64A of the refrigerant-heat medium heat exchanger 64, and adjusts the degree of superheat of the refrigerant in the refrigerant flow path 64A of the refrigerant-heat medium heat exchanger 64.

[0029] In the refrigerant-heat medium heat exchanger 64, the other end of the refrigerant pipe 72 is connected to the inlet of the refrigerant flow path 64A, and one end of the refrigerant pipe 75 is connected to the outlet of the refrigerant flow path 64A. The other end of the refrigerant pipe 75 is connected to the refrigerant upstream side of the heat absorber 9 of the refrigerant pipe 13D. In this way, the chiller expansion valve 73, the solenoid valve 74, the refrigerant flow path 64A of the refrigerant-heat medium heat exchanger 64, etc. also constitute part of the refrigerant circuit R and at the same time constitute part of the heat medium circuit 61.

[0030] When the chiller expansion valve 73 is open, some or all of the refrigerant that has circulated through the refrigerant circuit R and flowed out from the refrigerant pipe 13G and the outdoor heat exchanger 7 flows into the refrigerant pipe 72, is depressurized by the chiller expansion valve 73, and then flows into the refrigerant flow path of the refrigerant-heat medium heat exchanger 64 and evaporates. The heat medium flows into the heat medium flow path 64B. For example, if the heat medium circuit 61 is an equipment temperature adjustment circuit, the heat medium circulating through an object to be temperature adjusted, such as a battery or a motor unit, flows into the heat medium flow path 64B.

[0031] The refrigerant absorbs heat from the heat medium flowing in the heat medium flow path 64B while flowing through the refrigerant flow path 64A of the refrigerant-heat medium heat exchanger 64. As a result, for example, when the heat medium circuit 61 is an equipment temperature adjustment circuit, heat is exchanged between the heat medium circulating in the object to be temperature adjusted such as a battery or a motor unit and the refrigerant circulating in the refrigerant circuit R, thereby adjusting the temperature of the battery or the motor unit. As the heat medium, for example, water, a refrigerant such as HFO-1234yf, a liquid such as a coolant, or a gas such as air can be used.

[0032] 2 shows a schematic configuration of the heat pump ECU 11 as a control device of the vehicle air conditioner 1. The heat pump ECU 11 is connected to a vehicle controller 35, which controls the overall vehicle including driving, via an in-vehicle network such as a Controller Area Network (CAN) or a Local Interconnect Network (LIN), so that they can communicate with each other and transmit and receive information. Both the heat pump ECU 11 and the vehicle controller 35 can be implemented by a microcomputer, which is an example of a computer equipped with a processor.

[0033] The heat pump ECU 11 is connected to the following sensors and detectors, and receives the outputs of these sensors and detectors. Specifically, the heat pump ECU 11 includes an outside air temperature sensor 33 for detecting the outside air temperature Tam of the vehicle, an HVAC suction temperature sensor 36 for detecting the temperature of air drawn into the air flow passage 3 from the suction port 25, an inside air temperature sensor 37 for detecting the temperature of the air inside the vehicle cabin (inside air temperature inside air Tin), a blow-out temperature sensor 41 for detecting the temperature of the air blown into the vehicle cabin from the outlet 29, a discharge pressure sensor 42 for detecting the discharge refrigerant pressure (discharge pressure Pd) of the compressor 2, a discharge temperature sensor 43 for detecting the discharge refrigerant temperature Td of the compressor 2, a suction temperature sensor 44 for detecting the suction refrigerant temperature Ts of the compressor 2, an indoor condenser temperature sensor 46 for detecting the temperature of the indoor condenser 4 (the temperature of the refrigerant that has passed through the indoor condenser 4 or the temperature of the indoor condenser 4 itself: indoor condenser temperature TCI), and a pressure sensor 47 for detecting the indoor condenser 4. An indoor condenser pressure sensor 47 that detects the refrigerant pressure immediately after leaving the indoor condenser 4: indoor condenser outlet pressure Pci, a heat absorber temperature sensor 48 that detects the temperature of the heat absorber 9 (the temperature of the air that has passed through the heat absorber 9, or the temperature of the heat absorber 9 itself: heat absorber temperature Te), a heat absorber pressure sensor 49 that detects the refrigerant pressure of the heat absorber 9 (the pressure of the refrigerant inside the heat absorber 9 or immediately after leaving the heat absorber 9), an air conditioning operation unit 53 for setting the set temperature and switching of air conditioning operation, an outdoor heat exchanger temperature sensor 54 that detects the temperature of the outdoor heat exchanger 7 (in this embodiment, the discharge refrigerant temperature TXO immediately after being discharged from the outdoor heat exchanger 7), and an outdoor heat exchanger pressure sensor 56 that detects the refrigerant pressure of the outdoor heat exchanger 7 (in this embodiment, the discharge refrigerant pressure PXO immediately after being discharged from the outdoor heat exchanger 7).

[0034] In addition to the above, a heat pump ECU 11 is connected to a heat medium temperature sensor 79 that detects the temperature Tw of the heat medium that leaves the heat medium flow path of the refrigerant-heat medium heat exchanger 64 and circulates through the heat medium circuit (hereinafter referred to as the "chiller water temperature").

[0035] On the other hand, the output of the heat pump ECU 11 is connected to the compressor 2, the outdoor blower (not shown), the indoor blower (blower fan) 27, the suction switch damper 26, the air mix damper 28, the outdoor expansion valve 6, the indoor expansion valve 8, the solenoid valves 17, 21, 22, 35, and 74, the auxiliary heater 23, and the chiller expansion valve 73. The heat pump ECU 11 controls these based on the outputs of the various sensors, settings inputted by the air conditioning operation unit 53, and information from the vehicle controller 35.

[0036] In the vehicle air conditioner 1 configured as above, when the vehicle air conditioner 1 performs heating operation, the refrigerant evaporates in the exterior heat exchanger 7 and absorbs heat from the exterior air, causing the exterior heat exchanger 7 to become cold, causing moisture in the exterior air to form frost and adhere to the surface of the exterior heat exchanger 7. For this reason, the exterior heat exchanger 7 needs to be defrosted, and in this case, the vehicle air conditioner 1 defrosts the exterior heat exchanger 7 by appropriately selecting or switching between a plurality of defrosting operation modes according to the vehicle status.

[0037] Specifically, in the vehicle air conditioning device 1 of this embodiment, a hot gas defrosting mode in which defrosting is performed using so-called hot gas, and a heat absorption defrosting mode in which heat is absorbed in the refrigerant-heat medium heat exchanger 64 or the heat absorber 9 and heat is dissipated in the exterior heat exchanger 7 for the refrigerant circulating in the refrigerant circuit R are appropriately selected and executed.

[0038] The hot gas defrost mode has less unevenness in defrosting and is easy to control, but since the refrigerant temperature regulation relies solely on compressor 2, the defrosting capacity is small and defrosting may not be possible reliably when the outside air temperature is extremely low.

[0039] On the other hand, in the endothermic defrost mode, heat is absorbed into the refrigerant by the refrigerant-heat medium heat exchanger 64 or the heat absorber 9, and the refrigerant is compressed by the compressor 2 to a high temperature and high pressure. In addition, since an auxiliary heat source can be used, the defrosting capacity is high and the system can be used even when the outside air temperature is extremely low.

[0040] For this reason, in the vehicle air conditioning device 1 of this embodiment, defrosting can be performed reliably and evenly by selecting or switching between the hot gas defrost mode and the endothermic defrost mode based on conditions (details will be described later) that are preset according to the vehicle conditions (size of the exterior heat exchanger, capacity of the compressor, outside air temperature, etc.).

[0041] (Hot gas defrost mode) FIG. 3 shows the flow of refrigerant in the refrigerant circuit R when defrosting the outdoor heat exchanger 7 in the hot gas defrosting mode. In the hot gas defrost mode, the heat pump ECU 11 fully opens the outdoor expansion valve 6 while keeping the refrigerant circuit R in the heating operation state, operates the compressor 2, and causes the high-temperature, high-pressure refrigerant discharged from the compressor 2 to flow into the indoor condenser 4. Here, in the hot gas defrost mode, the heat of the refrigerant is used for defrosting, so the refrigerant barely condenses in the indoor condenser 4 and just passes through. The refrigerant that leaves the indoor condenser 4 reaches the refrigerant pipe 13H via the refrigerant pipe 13F, and flows into the outdoor heat exchanger 7 via the outdoor expansion valve 6. The high-temperature, high-pressure refrigerant that flows into the outdoor heat exchanger 7 releases heat in the outdoor heat exchanger 7 and melts the frost. In the outdoor heat exchanger 7, defrosting is performed by the sensible heat and latent heat of the refrigerant. Therefore, in the hot gas defrost mode, the outdoor heat exchanger 7 can be defrosted evenly. During defrosting, the outdoor blower is stopped, and if a grill shutter is provided, it is closed.

[0042] (Endothermic defrost mode) The endothermic defrosting mode includes, for example, a chiller defrosting mode in which the refrigerant-heat medium heat exchanger 64 functions as a heat absorber, and a cooling cycle defrosting mode that uses the heat absorber 9. The chiller defrosting mode and the cooling cycle defrosting mode will be described below.

[0043] (1) Chiller defrosting FIG. 4 shows the flow of refrigerant in the refrigerant circuit R when defrosting the outdoor heat exchanger 7 in the chiller defrost mode. In the chiller defrost mode, the heat pump ECU 11 opens the solenoid valve 17, and causes the refrigerant that has flowed out from the outdoor heat exchanger 7 to flow into the refrigerant pipe 72 via the receiver-drier section 14, the subcooling section 16, and the check valve 18. The heat pump ECU 11 also opens the chiller expansion valve 73 and the solenoid valve 74, and causes the refrigerant to flow into the refrigerant flow path 64A of the refrigerant-heat medium heat exchanger 64. The refrigerant absorbs heat from the heat medium that has circulated through the heat medium circuit 61 in the refrigerant flow path 64A.

[0044] The heat pump ECU 11 closes at least one of the indoor expansion valve 8 and the solenoid valve 32, thereby causing the refrigerant after absorbing heat to flow into the refrigerant pipes 13D and 13A via the refrigerant pipe 75, and operates the compressor 2 with the outdoor expansion valve 6 fully open, causing the refrigerant to flow into the compressor 2. Then, the high-temperature, high-pressure refrigerant compressed and discharged by the compressor 2 flows into the outdoor heat exchanger 7 via the indoor condenser 4 and the outdoor expansion valve 6. The high-temperature, high-pressure refrigerant that has flowed into the outdoor heat exchanger 7 releases heat in the outdoor heat exchanger 7 and melts the frost. In the outdoor heat exchanger 7, defrosting is performed by the latent heat of the refrigerant. During defrosting, the outdoor blower is stopped, and if a grill shutter is provided, it is closed.

[0045] In the chiller defrost mode, the defrosting capacity depends not only on the capacity of the compressor 2 but also on the degree of heat absorption by the refrigerant in the refrigerant-heat medium heat exchanger 64. Meanwhile, for example, a water heater (ECH) as an auxiliary heat source provided in the heat medium circuit 61 can be appropriately operated to raise the temperature of the heat medium circulating through the heat medium circuit 61. Therefore, by supplementing the amount of heat absorption from the heat medium to the refrigerant in the refrigerant-heat medium heat exchanger 64 by auxiliary use of the water heater, it is possible to supplement the defrosting capacity in the chiller defrost mode.

[0046] (2) Cooling cycle defrost FIG. 5 shows the flow of refrigerant in the refrigerant circuit R when defrosting the outdoor heat exchanger 7 in the cooling cycle defrost mode. In the cooling cycle defrost mode, the heat pump ECU 11 opens the solenoid valve 17, and causes the refrigerant flowing out from the outdoor heat exchanger 7 to flow into the refrigerant pipe 72 through the receiver-drier section 14, the subcooling section 16, and the check valve 18. The heat pump ECU 11 also opens the indoor expansion valve 8 and the solenoid valve 32 to cause the refrigerant to flow into the heat absorber 9, where it evaporates and absorbs heat. At this time, the indoor blower 27 is operated so that the blown air is ventilated into the heat absorber 9. The heat pump ECU 11 causes the refrigerant that has evaporated and absorbed heat in the heat absorber 9 to flow into the refrigerant pipes 13D and 13A, and operates the compressor 2 with the outdoor expansion valve 6 fully open, causing the refrigerant to flow into the compressor 2. Then, the high-temperature, high-pressure refrigerant compressed and discharged by the compressor 2 flows into the outdoor heat exchanger 7 through the indoor condenser 4 and the outdoor expansion valve 6. The high-temperature refrigerant that flows into the outdoor heat exchanger 7 dissipates heat in the outdoor heat exchanger 7 and melts the frost. In the outdoor heat exchanger 7, defrosting is performed by the latent heat of the refrigerant. During defrosting, the outdoor blower is stopped, and if a grill shutter is provided, it is closed.

[0047] In the cooling cycle defrost mode, the defrosting capacity depends not only on the capacity of the compressor 2 but also on the degree of heat absorption by the refrigerant in the heat absorber 9. Therefore, by appropriately operating the auxiliary heater 23 such as an air heater (PTC) as an auxiliary heat source to complement the heating of the vehicle interior, the amount of heat absorbed by the refrigerant in the heat absorber 9 can also be complemented, and the defrosting capacity in the cooling cycle defrost mode can be supplemented.

[0048] (Selecting the defrost mode or setting the switching conditions) As described above, the selection and switching of the defrosting mode is performed based on the preset conditions. In this embodiment, the heat pump ECU 11 is preset with the conditions for selecting the defrosting mode when defrosting is performed when the need for defrosting arises from a state in which defrosting is not being performed, the conditions for switching from the hot gas defrosting mode to the endothermic defrosting mode, the operating conditions for operating the auxiliary heat source in the endothermic defrosting mode, the defrosting end conditions for ending defrosting, and the like.

[0049] (1) Selection of hot gas defrost mode or endothermic defrost mode As described above, the hot gas defrosting mode is easy to control and enables uniform defrosting, so in a situation where defrosting is possible in the hot gas defrosting mode, it is preferable to perform defrosting in the hot gas defrosting mode as much as possible. However, when the outside air temperature is extremely low or when defrosting in the hot gas defrosting mode is difficult due to the vehicle condition, the heat pump ECU 11 selects the endothermic defrosting mode. Therefore, in the vehicle air conditioner 1, a hot gas defrost priority condition is set in the heat pump ECU 11 as a condition for preferentially selecting the hot gas defrost mode when the need for defrosting arises from a state in which defrosting is not being performed.

[0050] The hot gas defrost priority condition can be set, for example, by the outdoor air temperature, that is, as a threshold value for the outdoor air temperature. In this case, the heat pump ECU 11 preferentially selects the hot gas defrost mode when the outdoor air temperature satisfies the hot gas defrost priority condition, and selects the endothermic defrost mode when the outdoor air temperature does not satisfy the hot gas defrost priority condition.

[0051] Fig. 6 shows the relationship between the compression capacity, the opening area of ​​the outdoor heat exchanger, and the outdoor air temperature (threshold value). Fig. 7 shows a graph showing the relationship between the outdoor air temperature Tam and the defrosting index P. Here, the defrosting index P indicates the opening area of ​​the outdoor heat exchanger / the capacity of the compressor, or the opening area of ​​the outdoor heat exchanger / the maximum heat generation amount (maximum power) of the compressor.

[0052] As shown in Fig. 6, the larger the capacity (volume) of the compressor or the maximum heat generation (maximum power) of the compressor, the higher the defrosting capacity, and the smaller the opening area of ​​the outdoor heat exchanger, the easier the defrosting. Also, the larger the defrosting index P in Fig. 7, the larger the opening area of ​​the outdoor heat exchanger is relative to the heat generation of the compressor, and therefore the greater the amount of heat radiation required for defrosting. Therefore, as shown in Fig. 7, the larger the defrosting index P, the higher the outdoor air temperature Tam at which it is assumed that the endothermic defrosting mode is more suitable than the hot gas defrosting mode.

[0053] In this way, based on the relationship between the capacity of the compressor and the opening area of ​​the outdoor heat exchanger, for example, a threshold value Tx for the outdoor air temperature is set as a hot gas defrost priority condition for preferentially selecting the hot gas defrost mode as shown in Fig. 6. The heat pump ECU 11 preferentially selects the hot gas defrost mode when the outdoor air temperature Tam is higher than the threshold value Tx, and selects the endothermic defrost mode when the outdoor air temperature Tam is lower than the threshold value Tx. The heat pump ECU 11 acquires the outdoor air temperature Tam detected by the outdoor air temperature sensor 33 and compares it with the threshold value Tx set as the hot gas defrost priority condition.

[0054] At this time, it is preferable to provide hysteresis (α1, α2) for the threshold value Tx and determine the hot gas defrost priority condition as follows. That is, Outside air temperature Tam ≧ Threshold Tx+α1 If so, select hot gas defrost mode; Outside air temperature Tam ≦ Threshold Tx-α2 If so, the endothermic defrosting mode is selected.

[0055] (2) Switching from hot gas defrost mode to endothermic defrost mode In addition, when defrosting is being performed in the hot gas defrost mode, if the defrost mode is to be switched to the endothermic defrost mode depending on the vehicle condition, for example, a threshold value Trt1 for the refrigerant temperature or a threshold value Prt1 for the refrigerant pressure is set as the defrost mode switching condition. When defrosting is started in the hot gas defrost mode, if the refrigerant temperature or pressure is lower than a preset threshold (temperature threshold Trt1, pressure Prt1) or if a state in which there is little change continues for a predetermined time TP1, the heat pump ECU 11 switches from the hot gas defrost mode to the endothermic defrost mode.

[0056] The refrigerant temperature is detected and used, for example, as the suction refrigerant temperature Ts of the compressor 2, the discharge refrigerant temperature Td of the compressor 2, and the discharge refrigerant temperature TXO immediately after discharge from the outdoor heat exchanger 7. The refrigerant pressure is detected and used, for example, as the suction refrigerant pressure Ps of the compressor 2, the discharge refrigerant pressure Pd of the compressor 2, and the discharge refrigerant pressure PXO immediately after discharge from the outdoor heat exchanger 7.

[0057] (3) Operation of the auxiliary heat source when defrosting in endothermic defrost mode In addition, the heat pump ECU 11 is set with an operating condition that determines whether to operate the auxiliary heat source and an operation stop condition that stops the operation of the auxiliary heat source when defrosting is performed in the endothermic defrosting mode.

[0058] In the chiller defrost mode, when the chiller water temperature (temperature of the heat medium) Tw is lower than the temperature Twt1 set as the operation condition, the water heater (ECH) is operated as the auxiliary heat source. Also, when the chiller water temperature Tw becomes higher than the temperature Twt2 set as the operation stop condition, the operation of the water heater may be stopped.

[0059] In the cooling cycle defrosting mode, when the temperature Tin in the vehicle cabin is lower than a temperature Tin1 set as an operation condition, the auxiliary heater 23 is operated as an auxiliary heat source. Also, when the temperature Tin in the vehicle cabin becomes higher than a temperature Tin2 set as an operation stop condition, the operation of the auxiliary heater 23 may be stopped.

[0060] (4) Defrosting completed In this embodiment, a threshold value Trt2 for the refrigerant temperature or a threshold value Prt2 for the refrigerant pressure is set as a defrost termination condition for terminating defrosting. The heat pump ECU 11 terminates the execution of the defrost mode when a predetermined time TP2 has elapsed in which the refrigerant temperature or pressure is higher than a preset threshold value (temperature threshold value Trt2, pressure threshold value Prt2).

[0061] (Defrost mode selection / switching process) Hereinafter, the defrost mode selection / switching process in the vehicle air conditioner according to this embodiment will be described with reference to the flowcharts in Figures 8 and 9. In the following explanation, two examples will be described: (1) an example in which the hot gas defrost mode and the chiller defrost mode are applied (Figure 8), and (2) an example in which the hot gas defrost mode and the cooling cycle defrost mode are applied (Figure 9).

[0062] (1) When using hot gas defrost mode and chiller defrost mode When the defrosting operation is selected automatically or manually via the air conditioning operation unit 53, the heat pump ECU 11 determines that there is a defrosting request (step S11) and acquires the outside air temperature Tam detected by the outside air temperature sensor 33. The heat pump ECU 11 compares the outside air temperature Tam with a preset threshold value Tx for the outside air temperature (step S12). In step S12, if the outside air temperature Tam is equal to or higher than the threshold value Tx, the heat pump ECU 11 selects the hot gas defrosting mode (step S13). Note that if the outside air temperature Tam is lower than the threshold value Tx, the heat pump ECU 11 selects the chiller defrosting mode as the endothermic defrosting mode (step S15).

[0063] After starting defrosting of the outdoor heat exchanger 7 in the hot gas defrost mode in step S13, the heat pump ECU 11 acquires the refrigerant temperature (Ts, Td, or TXO) from the intake temperature sensor 44, the discharge temperature sensor 43, or the outdoor heat exchanger temperature sensor 54, and switches from the hot gas defrost mode to the endothermic defrost mode (step S15) if the state in which the refrigerant temperature is lower than the predetermined temperature threshold Trt1 continues for a predetermined time (YES in step S14). If the state in which the refrigerant temperature is lower than the predetermined temperature threshold Trt1 does not continue for the predetermined time, the process proceeds to step S19 without switching the defrost mode. In step S14, the heat pump ECU 11 may monitor the refrigerant pressure instead of the refrigerant temperature. In this case, the heat pump ECU 11 acquires the refrigerant pressure (Ps, Pd, or PXO) from the discharge pressure sensor 42, the outdoor heat exchanger pressure sensor 56, etc., and switches from the hot gas defrost mode to the endothermic defrost mode (step S15) if the refrigerant pressure remains lower than the predetermined pressure threshold Prt1 for a predetermined time (YES in step S14).If the refrigerant pressure does not remain lower than the predetermined pressure threshold Prt1 for a predetermined time, the process proceeds to step S19 without switching the defrost mode (NO in step S14).

[0064] If the outside air temperature Tam is lower than the threshold value Tx in step S12, and if the endothermic defrost mode is selected in step S14 because the refrigerant temperature is lower than the threshold value Trt1 or the refrigerant pressure is lower than the threshold value Prt1, defrosting is performed in the chiller defrost mode, which is the endothermic defrost mode (step S15).

[0065] During defrosting in the chiller defrost mode, the heat pump ECU 11 monitors whether the chiller water temperature Tw is higher than a predetermined temperature Twt1 (step S16). If the chiller water temperature Tw is higher than the predetermined temperature Twt1, the water heating heater is not operated (step S17), and if the chiller water temperature Tw is lower than the predetermined temperature Twt1, the water heating heater is operated (step S18) and the chiller defrost mode is continued. Note that, if the chiller water temperature Tw rises and becomes higher than the predetermined temperature Twt2 after the water heater is operated, the operation of the water heater may be stopped.

[0066] The heat pump ECU 11 continues defrosting until the refrigerant temperature Tr remains higher than a predetermined temperature threshold Trt2 or the refrigerant pressure remains higher than a predetermined pressure threshold Prt2 for a predetermined time TP2 (steps S19 and S20). When the refrigerant temperature Tr remains higher than a predetermined temperature threshold Trt2 or the refrigerant pressure remains higher than a predetermined pressure threshold Prt2 for a predetermined time, the heat pump ECU 11 ends defrosting (step S21).

[0067] (2) When using hot gas defrost mode and cooling cycle defrost mode When the defrosting operation is selected automatically or manually via the air conditioning operation unit 53, the heat pump ECU 11 determines that there is a defrosting request (step S31) and acquires the outside air temperature Tam detected by the outside air temperature sensor 33. The heat pump ECU 11 compares the outside air temperature Tam with a preset threshold value Tx for the outside air temperature (step S32). In step S32, if the outside air temperature Tam is equal to or higher than the threshold value Tx, the heat pump ECU 11 selects the hot gas defrosting mode (step S33). Note that if the outside air temperature Tam is lower than the threshold value Tx, the heat pump ECU 11 selects the cooling cycle defrosting mode as the endothermic defrosting mode (step S35).

[0068] After starting defrosting of the outdoor heat exchanger 7 in the hot gas defrost mode in step S33, the heat pump ECU 11 acquires the refrigerant temperature (any of Ts, Td, and TXO) from any of the intake temperature sensor 44, the discharge temperature sensor 43, and the outdoor heat exchanger temperature sensor 54, and switches from the hot gas defrost mode to the endothermic defrost mode (step S35) if the state in which the refrigerant temperature is lower than the predetermined temperature threshold Trt1 continues for a predetermined time (YES in step S34). If the state in which the refrigerant temperature is lower than the predetermined temperature threshold Trt1 does not continue for the predetermined time, the defrost mode is not switched and the process proceeds to step S39 (NO in step S34). Note that in step S34, the heat pump ECU 11 may monitor the refrigerant pressure instead of the refrigerant temperature. In this case, the heat pump ECU 11 acquires the refrigerant pressure (Ps, Pd, or PXO) from the discharge pressure sensor 42, the outdoor heat exchanger pressure sensor 56, etc., and switches from the hot gas defrost mode to the endothermic defrost mode (step S35) if the refrigerant pressure remains lower than the predetermined pressure threshold Prt1 for a predetermined time (YES in step S34).If the refrigerant pressure does not remain lower than the predetermined pressure threshold Prt1 for a predetermined time, the process proceeds to step S39 without switching the defrost mode (NO in step S34).

[0069] If the outside air temperature Tam is lower than the threshold value Tx in step S32, and if the endothermic defrost mode is selected in step S34 because the refrigerant temperature is lower than the threshold value Trt1 or the refrigerant pressure is lower than the threshold value Prt1, defrosting is performed in the cooling cycle defrost mode as the endothermic defrost mode (step S35).

[0070] During defrosting in the cooling cycle defrost mode, the heat pump ECU 11 monitors whether the vehicle interior temperature Tin is higher than a predetermined temperature Tint1 (step S36). If the vehicle interior temperature Tin is higher than the predetermined temperature Tint1, the auxiliary heater 23 is not operated (step S37), and if the vehicle interior temperature Tin is lower than the predetermined temperature Tint1, the auxiliary heater 23 is operated (step S38) and the cooling cycle defrost mode is continued. It should be noted that, if the vehicle interior temperature Tin rises and becomes higher than the predetermined temperature Tint2 after the auxiliary heater 23 is operated, the operation of the auxiliary heater 23 may be stopped.

[0071] The heat pump ECU 11 continues defrosting until the refrigerant temperature Tr remains higher than a predetermined temperature threshold Trt2 or the refrigerant pressure remains higher than a predetermined pressure threshold Prt2 for a predetermined time (steps S39 and S40). The heat pump ECU 11 ends defrosting when the refrigerant temperature Tr remains higher than a predetermined temperature threshold Trt2 or the refrigerant pressure remains higher than a predetermined pressure threshold Prt2 for a predetermined time (step S41).

[0072] As described above, according to the vehicle air conditioner 1 of this embodiment, the heat pump ECU 11 can execute multiple defrosting modes including a hot gas defrosting mode and an endothermic defrosting mode (chiller defrosting mode or cooling cycle defrosting mode). Then, according to a predetermined hot gas defrosting priority condition, the hot gas defrosting mode, which can achieve uniform defrosting with simple control, is executed preferentially, and the endothermic defrosting mode is executed when defrosting is difficult in the hot gas defrosting mode. This allows reliable and uniform defrosting regardless of the situation.

[0073] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention also includes design changes and the like that do not deviate from the gist of the present invention. [Explanation of symbols]

[0074] 1: Vehicle air conditioner, 2: Compressor, 3: Air flow passage, 4: Indoor condenser, 6: Outdoor expansion valve, 7: Outdoor heat exchanger, 8: Indoor expansion valve, 9: Heat absorber, 11: Heat pump ECU (controller), 64: Refrigerant-heat medium heat exchanger, 73: Chiller expansion valve

Claims

1. A vehicle air conditioner including a refrigerant circuit including a compressor that compresses a refrigerant, an exterior heat exchanger that performs heat exchange between the refrigerant and outside air, and a heat absorption heat exchanger that absorbs heat from a heat absorption target, and a control device that controls the refrigerant circuit, The control device includes: a hot gas defrosting mode in which the outdoor heat exchanger is defrosted by the refrigerant compressed by the compressor; a heat absorption defrosting mode in which heat is absorbed in the heat absorption target and the outdoor heat exchanger is defrosted by the refrigerant compressed by the compressor; A vehicle air conditioner in which a hot gas defrost priority condition is set for preferentially selecting the hot gas defrost mode.

2. The hot gas defrost priority condition is set according to an outside air temperature, 2. The vehicle air conditioning system according to claim 1, wherein the hot gas defrost mode is preferentially selected when the outside air temperature satisfies the hot gas defrost priority condition, and the endothermic defrost mode is selected when the outside air temperature does not satisfy the hot gas defrost priority condition.

3. 3. The vehicle air conditioner according to claim 1, wherein the hot gas defrosting priority condition is an outside air temperature determined based on at least one of an opening area of ​​the exterior heat exchanger and a capacity of the compressor.

4. 4. The vehicle air conditioning system according to claim 1, wherein the control device switches to the endothermic defrosting mode when the temperature of the refrigerant remains lower than a threshold value Trt1 for a predetermined period of time TP1 during execution of the hot gas defrosting mode.

5. 4. The vehicle air conditioning device according to claim 1, wherein the control device switches to the endothermic defrosting mode when a state in which the pressure of the refrigerant is lower than a threshold value Prt1 continues for a predetermined time TP1 during execution of the hot gas defrosting mode.

6. 6. The vehicle air conditioning device according to claim 1, wherein the heat absorption defrosting mode includes a chiller defrosting mode in which the heat absorption heat exchanger is a refrigerant-heat medium heat exchanger that performs heat exchange between the heat medium circulating in a heat medium circuit and the refrigerant.

7. 7. The vehicle air conditioning system according to claim 6, wherein the control device operates an auxiliary heat source provided in the heat medium circuit to heat the heat medium when the temperature of the heat medium is lower than a predetermined temperature Twt1 during execution of the chiller defrost mode.

8. 8. The vehicle air conditioning system according to claim 1, wherein the heat absorption defrosting mode includes a cooling cycle defrosting mode in which the heat absorption heat exchanger is a heat absorber that absorbs heat from air supplied into a passenger compartment into the refrigerant.

9. 9. The vehicle air conditioning system according to claim 8, wherein the control device operates an auxiliary heat source that heats air flowing into the vehicle compartment when the temperature in the vehicle compartment is lower than a predetermined temperature Tint1 during execution of the cooling cycle defrosting mode.

10. 10. The vehicle air conditioning device according to claim 1, wherein the control device terminates execution of the defrost mode when the temperature of the refrigerant is equal to or higher than a predetermined threshold value Trt2 or when the pressure of the refrigerant is equal to or higher than a predetermined threshold value Prt2 for a predetermined period of time TP2.

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