Vehicle air conditioning device

Abstract

[Problem] To improve comfort of an occupant by seamlessly performing transition between a hot gas heating mode and an endothermic heating mode. [Solution] This vehicle air conditioning device comprises a refrigerant circuit and a control device that controls the refrigerant circuit. The air conditioning device can execute: an endothermic heating mode in which a refrigerant absorbs heat from a heat-absorption target, such as outside air, in an external heat exchanger; and a hot gas heating mode in which a portion of the refrigerant compressed by a compressor is caused to perform bypass and return to the compressor, and the remainder heats the inside of a compartment by heat radiation of the refrigerant, and, when having determined that the heating capacity does not satisfy a target heating capacity during the execution of the endothermic heating mode, transitions to the hot gas heating mode after executing a first transition mode for performing, in order, a first step for performing control so as to open a second decompression part for decompressing the refrigerant flowing through a hot gas bypass, and a second step for performing control so as to close a first decompression part for decompressing the refrigerant flowing into an external heat exchange part, and to open a third decompression part for decompressing the refrigerant suctioned into the compressor.

Description

Vehicle air conditioning system

[0001] The present invention relates to an air conditioning system for a vehicle.

[0002] In recent years, vehicles such as hybrid vehicles and electric vehicles, which have a traction motor powered by power supplied from a battery, have become widespread. A known vehicle air conditioner installed in such vehicles uses a heat pump (refrigerant circuit) as a heat source.

[0003] In a vehicle air conditioning system using a heat pump, an external heat exchanger, such as an exterior heat exchanger, located outside the vehicle cabin functions as a heat absorber during heating operation to obtain a heating heat source from outside air or the like (endothermic heating mode). Therefore, when the outside air temperature becomes extremely low (e.g., −20°C), it becomes difficult to absorb heat from outside air or the like, and heating capacity is significantly reduced. In contrast, hot gas heating, which does not absorb heat from outside air or the like, but instead uses high-temperature, high-pressure refrigerant discharged from a compressor, is known as an effective heating method in extremely low-temperature environments (hot gas heating mode).

[0004] For example, in the vehicle air conditioning system of Patent Document 1, a hot gas heating mode is executed in which a portion of the high-temperature, high-pressure refrigerant discharged from the compressor is passed through a bypass flow path to be decompressed and then returned to the compressor, while the remainder is heat exchanged with the air blown into the vehicle cabin in an indoor heat exchanger, then decompressed and returned to the compressor without passing through an external heat exchanger.

[0005] Japanese Patent Application Laid-Open No. 2023-46604

[0006] In some cases, the above-described vehicle air conditioner is controlled to, for example, execute the hot gas heating mode at startup to raise the temperature in the vehicle cabin as quickly as possible, and then transition to endothermic heating after the desired temperature is reached. Furthermore, in some cases, if heating capacity becomes insufficient while executing the endothermic heating mode, the system is controlled to transition to the hot gas heating mode.

[0007] The hot gas heating mode and the endothermic heating mode require different refrigerant pressure ranges for stable operation in each heating mode. For this reason, automotive air conditioning systems control components of the refrigerant circuit, such as the compressor and flow selector valves (including pressure reducing valves), according to the heating mode so that the pressures on the suction and discharge sides of the compressor fall within the appropriate pressure ranges for each heating mode. However, because the hot gas heating mode and the endothermic heating mode require different refrigerant flow paths in the refrigerant circuit, switching control of multiple flow selector valves is required when transitioning between the heating modes.

[0008] However, if all the flow path switching valves are switched immediately while the compressor is running during the transition between the heating modes, the sudden change in the flow path may cause large fluctuations in the refrigerant pressure, which may deviate from the pressure range suitable for each heating mode and cause the operation of the automotive air conditioner 1 to stop. In other words, it is difficult to seamlessly transition between the hot gas heating mode and the endothermic heating mode while continuing to operate the automotive air conditioner stably, which may result in a loss of comfort for the occupants.

[0009] The present invention was made in consideration of these circumstances, and its objective is to seamlessly transition between hot gas heating mode and endothermic heating mode, thereby improving passenger comfort.

[0010] The present invention provides a vehicle air conditioning system including a refrigerant circuit including a compressor, an indoor heat exchange unit, an external heat exchange unit, and a hot gas bypass that depressurizes at least a portion of the refrigerant compressed by the compressor without passing through the indoor heat exchange unit and the external heat exchange unit, and returns the refrigerant to the compressor, and a control device that controls the refrigerant circuit. The refrigerant circuit includes a first decompression unit that depressurizes the refrigerant flowing into the external heat exchange unit, a second decompression unit that depressurizes the refrigerant flowing through the hot gas bypass, and a third decompression unit that depressurizes the refrigerant to be drawn into the compressor, and the control device controls the external heat exchange unit. The present invention provides an air conditioning system for a vehicle that is capable of executing an endothermic heating mode in which a refrigerant is caused to absorb heat in an exchange unit, and a hot gas heating mode in which a portion of the refrigerant compressed by the compressor is caused to flow through the hot gas bypass and the remainder is caused to flow through the indoor heat exchange unit, and that, if it is determined during execution of the endothermic heating mode that the heating capacity does not satisfy a target heating capacity, executes a first transition mode in which a first stage is performed in which the second pressure reduction unit is controlled to open, and a second stage is performed in which the first pressure reduction unit is controlled to close and the third pressure reduction unit is controlled to open, and then transitions to the hot gas heating mode.

[0011] According to the present invention, a seamless transition between the hot gas heating mode and the endothermic heating mode can be performed, improving passenger comfort.

[0012] 1 is an explanatory diagram showing an example of a system configuration of a vehicle air conditioner according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing a control device of the vehicle air conditioner according to an embodiment of the present invention. FIG. 3 is a diagram showing the configuration of a control device, etc., in an electric vehicle (EV) according to an embodiment of the present invention. FIG. 4 is an explanatory diagram showing operation of a refrigerant circuit in an endothermic heating mode in a vehicle air conditioner according to an embodiment of the present invention. FIG. 5 is an explanatory diagram showing operation of a refrigerant circuit in a hot gas heating mode in a vehicle air conditioner according to an embodiment of the present invention. FIG. 6 is a flowchart showing processing by a control device to determine whether an operation mode is to be selected and whether a transition is necessary, in a vehicle air conditioner according to an embodiment of the present invention. FIG. 7 is a flowchart showing processing by a control device in a first transition mode (transition processing from endothermic heating mode to hot gas heating mode) in a vehicle air conditioner according to an embodiment of the present invention. FIG. 8 is a flowchart showing operation of a refrigerant circuit in the first transition mode by a control device in a vehicle air conditioner according to an embodiment of the present invention. FIG. 9 is a flowchart showing processing by a control device in a second transition mode (transition processing from hot gas heating mode to endothermic heating mode) in a vehicle air conditioner according to an embodiment of the present invention. FIG. 10 is an explanatory diagram showing operation of a refrigerant circuit in the second transition mode by a control device in a vehicle air conditioner according to an embodiment of the present invention. FIG. 6 is an explanatory diagram showing the operation of the refrigerant circuit in a second transition mode by the control device in the vehicle air conditioner according to the embodiment of the present invention.

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same reference numerals in different drawings indicate parts with the same function, and duplicated explanations in each drawing will be omitted as appropriate. In the drawings, bold black lines in the refrigerant circuit 10 indicate refrigerant flow paths through which high-pressure refrigerant flows, and double lines indicate refrigerant flow paths through which low-pressure refrigerant flows after decompression. In addition, triple lines in the heat medium circuit 30 indicate heat medium flow paths through which the heat medium flows. Furthermore, dashed lines in the refrigerant circuit 10 indicate refrigerant flow paths through which no refrigerant flows.

[0014] 1 shows an example of the configuration of a vehicle air conditioner 1 according to an embodiment of the present invention. The configuration shown here is merely an example, and the present invention is not limited to a specific configuration.

[0015] The vehicle air conditioner 1 includes a refrigerant circuit 10 and an air conditioning unit 20. The refrigerant circuit 10 includes a compressor 2, indoor heat exchangers 21 and 22 provided inside the air conditioning unit 20, and an external heat exchanger 11 provided outside the vehicle compartment, which are arranged along a refrigerant flow path. The indoor heat exchangers 21 and 22 are provided to exchange heat between the refrigerant and air flowing inside the air conditioning unit 20 and guided into the vehicle compartment, and the external heat exchanger 11 is provided to exchange heat between the refrigerant and outside air outside the vehicle compartment.

[0016] The external heat exchanger 11 is used to obtain a heat source for heating by having the refrigerant absorb heat from outside air in an endothermic heating mode, which will be described later. Immediately downstream of the external heat exchanger 11, a refrigerant pressure sensor 44C that detects the refrigerant pressure PXO (low-pressure side refrigerant pressure) and a refrigerant temperature sensor 43C that detects the refrigerant temperature TXO (low-pressure side refrigerant temperature) discharged from the external heat exchanger 11 are provided.

[0017] The indoor heat exchanger 21 is used to heat air, and the indoor heat exchanger 22 is used to cool air. A refrigerant pressure sensor 44B that detects an outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) from the indoor heat exchanger 21 and a refrigerant temperature sensor 43B that detects an outlet refrigerant temperature Tc (high-pressure side refrigerant temperature) are provided immediately downstream of the indoor heat exchanger 21 in the refrigerant circuit 10.

[0018] The compressor 2 compresses the refrigerant and circulates it within the refrigerant circuit 10. The refrigerant compressed by the compressor 2 is decompressed by passing through an appropriately selected refrigerant flow path, for example, a first pressure reduction section V1, a second pressure reduction section V2, a third pressure reduction section V3, and a fourth pressure reduction section V4, which are expansion valves. The refrigerant circuit 10 is provided with flow path switching valves 12 and 13 for switching the refrigerant flow path, and check valves 14 and 15 for regulating the flow direction of the refrigerant.

[0019] An accumulator 16 that recovers liquid refrigerant and separates the refrigerant into gas and liquid is provided immediately upstream of the compressor 2 in the refrigerant circuit 10. A refrigerant pressure sensor 44A that detects a suction refrigerant pressure Ps (low-pressure side refrigerant pressure) that is suctioned into the compressor 2 and a refrigerant temperature sensor 43A that detects a suction refrigerant temperature Ts (low-pressure side refrigerant temperature) are provided between the accumulator 16 and the compressor 2.

[0020] As described above, the air conditioning unit 20 includes the indoor heat exchangers 21, 22 therein, a blower 23 that introduces air into the unit from inside or outside the vehicle cabin, and an air damper 24 that adjusts the proportion of the air introduced by the blower 23 that passes through the indoor heat exchanger 21. The air conditioning unit 20 also includes an air damper 25 that is provided upstream of the blower 23 in the air inflow direction and that switches the air introduced into the blower 23 between indoor air and outdoor air.

[0021] In the air conditioning unit 20, air introduced by the blower 23 passes through the indoor heat exchangers 21 and 22 before being blown into the vehicle cabin. When the air damper 24 shown in Fig. 1 is fully open, the air introduced by the blower 23 passes through the indoor heat exchanger 22 and then the indoor heat exchanger 21 before being blown into the vehicle cabin. When the air damper 24 is fully closed, the inlet side of the indoor heat exchanger 21 is closed, and the air introduced by the blower 23 passes only through the indoor heat exchanger 22 before being blown into the vehicle cabin.

[0022] In the air conditioning unit 20, air can be taken in from either the air inlet 25A connected to the outside of the vehicle or the air inlet 25B connected to the inside of the vehicle by selectively closing the air inlet 25A or the air inlet 25B using the air damper 25. In addition, in the air conditioning unit 20, the air from outside the vehicle cabin or the air from outside the vehicle cabin can be taken in at a desired ratio from both the air inlet 25A and the air inlet 25B by, for example, positioning the air damper 25 at a desired position between the air inlet 25A and the air inlet 25B.

[0023] Although the above-described external heat exchanger 11 and indoor heat exchangers 21, 22 have been described as examples in which the refrigerant directly exchanges heat with the air, the refrigerant may indirectly exchange heat with the air via a heat medium that has exchanged heat with the refrigerant. That is, the refrigerant may absorb heat from the air via the heat medium, or the refrigerant may release heat to the air via the heat medium.

[0024] As shown in Fig. 1, the vehicle air conditioner 1 includes a heat medium circuit 30. The heat medium circuit 30 circulates a heat medium using a circulation pump 31, heats the heat medium using a heater (ECH: Electric Coolant Heater) 32, and recovers waste heat from a temperature-controlled object such as a battery using a temperature-controlled object heat exchanger 33. The refrigerant circuit 10 and the heat medium circuit 30 are provided with a refrigerant-heat medium heat exchanger 34 that exchanges heat between the refrigerant and the heat medium via a flow path 34A through which the refrigerant flows and a flow path 34B through which the heat medium flows. The heat medium circuit 30 is provided as needed.

[0025] The vehicle air conditioner 1 includes a control device 100 shown in Fig. 2. The control device 100 controls the refrigerant circuit 10, the air conditioning unit 20, and the heat medium circuit 30 based on various input signals 60 (such as an air conditioning instruction signal and a charger connection signal) and detection signals from the sensor unit 40.

[0026] The sensor section 40 that inputs detection signals to the control device 100 includes, for example, an outside air sensor 41 that detects outside air conditions such as outside air temperature and outside air humidity, a compressor current sensor 42 that detects the power consumption (energy consumption) of the compressor 2, a refrigerant temperature sensor 43 and a refrigerant pressure sensor 44 that detect the state of the refrigerant, an occupant sensor 45 that detects the presence or absence of an occupant in the vehicle cabin, an air outlet temperature sensor 46 that detects the air outlet temperature of the air conditioning unit 20, and an inside air sensor 47 that detects the state of the vehicle cabin such as inside air temperature and inside air humidity.

[0027] In particular, the refrigerant temperature sensor 43 includes a refrigerant temperature sensor 43A that detects the intake refrigerant temperature Ts (low-pressure side refrigerant temperature) sucked into the compressor 2, a refrigerant temperature sensor 43B that detects the outlet refrigerant temperature Tc (high-pressure side refrigerant temperature) of the indoor heat exchanger 21, and a refrigerant temperature sensor 43C that detects the refrigerant temperature TXO (low-pressure side refrigerant temperature) exiting the external heat exchanger 11 (see Figure 1).

[0028] The refrigerant pressure sensors 44 include a refrigerant pressure sensor 44A that detects a suction refrigerant pressure Ps (low-pressure side refrigerant pressure) sucked into the compressor 2, a refrigerant pressure sensor 44B that detects an outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) of the indoor heat exchanger 21, and a refrigerant pressure sensor 44C that detects a refrigerant pressure PXO (low-pressure side refrigerant pressure) exiting the external heat exchanger 11 (see FIG. 1). These sensors are merely examples, and the sensor unit 40 is provided with various sensors that detect information required for the control device 100 to perform various controls.

[0029] The control devices of the control device 100 are the compressor 2, the first pressure reduction section V1, the second pressure reduction section V2, the third pressure reduction section V3, the fourth pressure reduction section V4, and the flow path switching valves 12 and 13 in the refrigerant circuit 10, the blower 23, the air dampers 24 and 25 in the air conditioning unit 20, and the circulation pump 31 in the heat medium circuit 30. The control device 100 also controls the vehicle air conditioner 1 according to the processing results of the control device 100. The vehicle air conditioner 1 can execute various operating modes using the control device 100, including an endothermic heating mode in which the refrigerant is caused to absorb heat in the external heat exchanger 11, and a hot gas heating mode in which the refrigerant compressed by the compressor 2 is caused to release heat in the indoor heat exchanger 21 without the refrigerant absorbing heat in the external heat exchanger 11, thereby heating the vehicle cabin.

[0030] [Configuration of Control Device in Electric Vehicle (EV)] As shown in Fig. 3 , the control device 100 provided in the vehicle air conditioner 1 is configured as a single ECU connected to various ECUs (Electronic Control Units) that control the electric vehicle EV via an in-vehicle network L. The control device 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, an I / F (Interface) 104 for input / output, an I / F (Interface) 105 for in-vehicle communication, and the like, and each piece of hardware is connected to one another via a bus 106.

[0031] The CPU 101 controls the control device 100 by executing various programs stored in the ROM 102. The ROM 102 is a non-volatile memory. For example, the ROM 102 stores programs executed by the CPU 101, data necessary for the CPU 101 to execute the programs, etc. The RAM 103 is a main storage device such as a dynamic random access memory (DRAM) or a static random access memory (SRAM).

[0032] For example, RAM 103 functions as a work area used by CPU 101 when executing a program. Input / output I / F 104 is connected to various sensors and monitors installed in the EV, and inputs data to CPU 101 and outputs data processed by CPU 101. In-vehicle communication I / F 105 is connected to an in-vehicle network L, and controls data transmission and reception with other ECUs set in the EV.

[0033] The control device 100 controls the above-mentioned vehicle air conditioning device 1 by a program executed by the CPU 101 when data related to the surrounding environment or data related to the driving status of the EV is input via the input / output I / F 104 and the in-vehicle communication I / F 105.

[0034] The EV is equipped with a battery B. The battery B is charged by connecting a charger plug PS to a battery plug BP, and power is supplied to the vehicle air conditioner 1 via the battery B. The state in which the plug PS is connected to the battery plug BP is transmitted to the control device 100 via the in-vehicle network L as a charger connection signal.

[0035] [Endothermic Heating Mode] The operation of the refrigerant circuit 10 in the endothermic heating mode will be described below with reference to Fig. 4. In the endothermic heating mode, the refrigerant circuit 10 of the vehicle air conditioner 1 obtains a heat source for heating by causing the refrigerant to flow through the external heat exchanger 11 as follows.

[0036] As shown in Figure 4, in the endothermic heating mode, the control device 100 controls the refrigerant circuit 10 so that the second pressure reduction section V2, the third pressure reduction section V3, the fourth pressure reduction section V4, and the flow path switching valve 12 are fully closed, and the flow path switching valve 13 and the first pressure reduction section V1 are opened.

[0037] In the endothermic heating mode, the high-temperature, high-pressure refrigerant discharged from the compressor 2 passes through the indoor heat exchanger 21 in the air conditioning unit 20 and is depressurized in the first depressurization section V1. The low-pressure refrigerant passes through the external heat exchanger 11 and is returned to the compressor 2 via the flow path switching valve 13, the check valve 14, and the accumulator 16. At this time, the high-pressure refrigerant discharged from the compressor 2 condenses and releases heat in the indoor heat exchanger 21, is depressurized in the first depressurization section V1 to become low-pressure refrigerant, absorbs heat and evaporates in the external heat exchanger 11, and returns to the compressor 2. Then, in the air conditioning unit 20, air introduced by the blower 23 is heated by the heat released in the indoor heat exchanger 21 and is blown into the vehicle cabin.

[0038] In the endothermic heating mode, the control device 100 controls the compressor 2 so that the outlet refrigerant pressure Pci of the indoor heat exchanger 21 (the high-pressure side refrigerant pressure of the refrigerant circuit 10) becomes the target outlet refrigerant pressure PCO. The control device 100 also controls the opening degree of the first pressure reducing section V1 so that the degree of subcooling at the outlet of the indoor heat exchanger 21 becomes the target degree of subcooling, and controls the blower 23 so that the heating capacity Qhp in the endothermic heating mode satisfies the target heating capacity TGQh. The target heating capacity TGQh is determined based on heating requirements, such as the set temperature Tset set by the occupant, and requirements from the vehicle (vehicle requirements).

[0039] [Hot gas heating mode] At extremely low temperatures, it is difficult for the external heat exchanger 11 to absorb heat, so the hot gas heating mode is used. The hot gas heating mode is an operating mode in which the refrigerant compressed by the compressor 2 is not allowed to absorb heat in the external heat exchanger 11, but rather some or all of the refrigerant is dissipated in the indoor heat exchanger 21 to heat the vehicle interior.

[0040] The refrigerant circuit 10 of the vehicle air conditioner 1 according to this embodiment has a hot gas bypass 10V that reduces the pressure of at least a portion of the refrigerant compressed by the compressor 2 and returns it to the compressor 2 without passing through the interior heat exchanger 21 and the external heat exchanger 11. The hot gas bypass 10V is provided with a second pressure reduction section V2, and in the hot gas heating mode, the second pressure reduction section V2 is opened to utilize the hot gas bypass 10V to heat the vehicle cabin.

[0041] The operation of the refrigerant circuit 10 in the hot gas heating mode will be described below with reference to Fig. 5. As shown in Fig. 5, in the hot gas heating mode, the control device 100 controls the first pressure reduction unit V1, the fourth pressure reduction unit V4, and the flow path switching valve 13 to be fully closed, and the flow path switching valve 12, the second pressure reduction unit V2, and the third pressure reduction unit V3 to be open.

[0042] In the hot gas heating mode, the second pressure reduction section V2 is open in the refrigerant circuit 10, and the high-temperature, high-pressure refrigerant discharged from the compressor 2 is branched at a branch point P1 immediately downstream of the compressor 2, with a portion flowing to the hot gas bypass 10V side and the remainder flowing to the indoor heat exchanger 21 side. The refrigerant flowing to the hot gas bypass 10V side is depressurized at the second pressure reduction section V2 and merges with the low-pressure refrigerant depressurized at the third pressure reduction section V3 at a junction P2 immediately upstream of the accumulator 16.

[0043] Meanwhile, the refrigerant branched at branch point P1 toward the indoor heat exchanger 21 passes through the indoor heat exchanger 21 and the flow switching valve 12, is decompressed in the third pressure reduction section V3 to become a low-pressure refrigerant, passes through the refrigerant heat medium heat exchanger 34, and merges with the refrigerant decompressed in the second pressure reduction section V2 at junction P2. The refrigerant merged at junction P2 undergoes gas-liquid separation in the accumulator 16 and returns to the compressor 2. At this time, in the refrigerant circuit 10, because the first pressure reduction section V1 is fully closed, no refrigerant flows to the external heat exchanger 11, and heat is not absorbed from the outside air. Furthermore, because the fourth pressure reduction section V4 is fully closed, no refrigerant flows to the indoor heat exchanger 22 either.

[0044] By providing the hot gas bypass 10V as described above, the liquid refrigerant condensed by heat radiation in the indoor heat exchanger 21 is mixed with the gas refrigerant that has passed through the hot gas bypass 10V to produce a gas-rich refrigerant, which can then be returned to the compressor 2. Furthermore, by increasing the flow rate of the refrigerant flowing through the hot gas bypass 10V, the amount of heat radiation in the indoor heat exchanger 21 can be suppressed, and by controlling the second pressure reduction section V2 to adjust the flow rate of the refrigerant flowing through the hot gas bypass 10V, it is possible to maintain a balance between the amount of heat radiation from the refrigerant circuit 10 and the amount of heat input to the compressor 2. In other words, the second pressure reduction section V2 functions as a flow rate adjustment section that adjusts the flow rate of the refrigerant flowing through the hot gas bypass 10V.

[0045] In the hot gas heating mode, the refrigerant flowing through the refrigerant circuit 10, including the refrigerant flowing through the indoor heat exchanger 21, is decompressed by the third decompression section V3, resulting in a high-pressure refrigerant upstream of the third decompression section V3 and a low-pressure refrigerant downstream of the third decompression section V3. In this case, it is important to maintain heating capacity that heat exchange does not occur in the refrigerant / heat medium heat exchanger 34 in the low-pressure refrigerant flow path. In the air conditioning unit 20, air introduced by the blower 23 is heated by heat dissipated in the indoor heat exchanger 21 and then blown into the vehicle cabin.

[0046] In the hot gas heating mode, the control device 100 controls the compressor 2 so that the outlet refrigerant pressure Pci (the high-pressure side refrigerant pressure of the refrigerant circuit 10) of the indoor heat exchanger 21 becomes the target outlet refrigerant pressure PCO. The control device 100 also controls the openings of the second pressure reducing section V2 and the third pressure reducing section V3 so that the suction refrigerant pressure Ps (the low-pressure side refrigerant pressure of the refrigerant circuit 10) of the compressor 2 of the refrigerant circuit 10 becomes the target suction refrigerant pressure PSO, and controls the blower 23 so that the heating capacity Qhg in the hot gas heating mode satisfies the target heating capacity TGQh.

[0047] As described above, the hot gas heating mode has a higher achievable heating capacity than the endothermic heating mode, allowing for effective heating even at extremely low temperatures. On the other hand, as will be described later, there are cases where the same target heating capacity TGQh can be achieved in both the hot gas heating mode and the endothermic heating mode. In such cases, the hot gas heating mode has lower operating efficiency than the endothermic heating mode, resulting in a higher rotation speed of the compressor 2 and increased power consumption.

[0048] That is, as described above, in the hot gas heating mode, a portion of the refrigerant compressed in the compressor 2 flows through the hot gas bypass 10V and is returned to the compressor 2, thereby increasing the suction refrigerant pressure Ps of the compressor 2 and thereby increasing the discharge pressure of the compressor 2. Meanwhile, the flow rate of the refrigerant flowing to the indoor heat exchanger 21 is reduced by the amount of refrigerant flowing through the hot gas bypass 10V. For this reason, in the hot gas heating mode, the rotation speed of the compressor 2 is made higher than in the endothermic heating mode to ensure the amount of heat dissipated in the indoor heat exchanger 21 and achieve the same target heating capacity TGQh as in the endothermic heating mode. Therefore, power consumption in the hot gas heating mode is greater than in the endothermic heating mode.

[0049] [Operation Mode Transition Control by Control Device] Hereinafter, a description will be given of operation mode transition control by the control device 100 when the vehicle cabin is heated by the vehicle air conditioner 1 according to this embodiment. When the vehicle cabin is heated by the vehicle air conditioner 1, the control device 100 executes either the endothermic heating mode or the hot gas heating mode depending on the external environment such as the outside air temperature Tam, the set temperature Tset, the target heating capacity TGQh, etc.

[0050] The control device 100 normally controls the system to execute an endothermic heating mode to reduce power consumption when the outside air temperature Tam is at or above a predetermined temperature (e.g., -10°C), and to execute a hot gas heating mode to ensure heating capacity when the outside air temperature Tam is in an extremely low temperature environment below the predetermined temperature.

[0051] On the other hand, if the vehicle interior temperature reaches the set temperature Tset and is stable during hot gas heating mode, the target heating capacity TGQh may be satisfied by the heating capacity Qhp in the endothermic heating mode. Conversely, if the heating capacity Qhp decreases due to a change in the external environment, such as a decrease in the outside air temperature Tam or the formation of frost on the external heat exchanger 11 during endothermic heating mode, the heating capacity Qhp in the endothermic heating mode may not satisfy the target heating capacity TGQh.

[0052] Therefore, when the endothermic heating mode is executed, the control device 100 determines whether the target heating capacity TGQh can be satisfied with the heating capacity Qhp that can be realized in the external environment, and based on this determination result, decides whether to execute the endothermic heating mode or the hot gas heating mode.

[0053] That is, the control device 100 executes the endothermic heating mode when the heating capacity Qhp in the endothermic heating mode can satisfy the target heating capacity TGQh, and executes the hot gas heating mode when the heating capacity Qhp cannot. The control device 100 also determines whether or not a transition from the current operating mode is necessary, and heats the vehicle cabin by appropriately switching between the endothermic heating mode and the hot gas heating mode as needed. By controlling in this manner, the vehicle air conditioner 1 can perform heating operation while satisfying the target heating capacity TGQh and suppressing power consumption.

[0054] As described above, the refrigerant flow path in the refrigerant circuit 10 is significantly different between the endothermic heating mode (see FIG. 4) and the hot gas heating mode (see FIG. 5). Specifically, the open / close states of the first pressure reduction section V1, the second pressure reduction section V2, the third pressure reduction section V3, and the flow path switching valves 12 and 13 in the refrigerant circuit 10 are opposite between the endothermic heating mode and the hot gas heating mode. Furthermore, the ranges of achievable heating capacity are different between the hot gas heating mode and the endothermic heating mode, and the refrigerant pressure ranges (pressure bands) suitable for stable continuous operation are significantly different between the two modes.

[0055] For this reason, if the opening and closing states of all of the above-mentioned first pressure reduction section V1 to third pressure reduction section V3 and flow path switching valves 12, 13 are controlled to be switched simultaneously when transitioning between hot gas heating mode and endothermic heating mode, the refrigerant flow path will change suddenly, and as a result, the refrigerant pressure will fluctuate greatly, and there is a risk that it will deviate from the pressure range suitable for each heating mode.

[0056] Therefore, when transitioning from endothermic heating mode to hot gas heating mode, the control device 100 executes the first transition mode before transitioning to the hot gas heating mode. Similarly, when transitioning from hot gas heating mode to endothermic heating mode, the control device 100 executes the second transition mode before transitioning to the endothermic heating mode.

[0057] Below, we will explain (1) the operation mode transition processing (including determining the operation mode, determining whether or not a transition is necessary, and a series of processes for the transition), (2) the processing in the first transition mode (transition processing from endothermic heating mode to hot gas heating mode), and (3) the processing in the second transition mode (transition processing from hot gas heating mode to endothermic heating mode) in the control device 100 of the vehicle air conditioning system 1 according to this embodiment.

[0058] (1) Operation Mode Transition Process Fig. 6 is a flowchart related to the control process of the control device 100 during heating operation of the automotive air conditioner 1. As described above, the control device 100 heats the vehicle cabin by appropriately switching between the endothermic heating mode and the hot gas heating mode as needed. The series of processes from "START" to "END" in the flowchart of Fig. 6 are repeatedly performed at predetermined time intervals while the automotive air conditioner 1 is performing heating operation.

[0059] The control device 100 acquires environmental information at a predetermined cycle during heating operation (step S11). The environmental information includes external environmental information about the vehicle, such as the outside air temperature Tam detected by the outside air sensor 41, as well as vehicle interior temperature, set temperature Tset, and the frost state of the external heat exchanger 11. Here, the frost state of the external heat exchanger 11 can be acquired, for example, based on the difference between the refrigerant temperature TXO obtained by the refrigerant temperature sensor 43C provided on the outlet side of the external heat exchanger 11 and the outside air temperature Tam obtained by the outside air sensor 41.

[0060] Next, the control device 100 estimates the heating capacity Qhp that can be achieved in the endothermic heating mode (step S12). In the endothermic heating mode, the achievable heating capacity Qhp varies depending on the outside air temperature Tam, so the control device 100 needs to grasp the heating capacity Qhp based on the outside air temperature Tam. In addition, in the endothermic heating mode, the heat source is obtained by having the refrigerant absorb heat from the outside air in the external heat exchanger 11. Therefore, the amount of heat absorbed changes depending on whether or not the external heat exchanger 11 is frosted and its state, and the achievable heating capacity Qhp varies accordingly.

[0061] Therefore, in this embodiment, for example, based on the environmental information acquired in step S11, the heating capacity Qhp_map corresponding to the outside air temperature Tam is read from a map stored in the ROM 102 of the control device 100, and the actually achievable heating capacity Qhp is estimated while taking into account the frost state of the external heat exchanger 11, etc. (step S12).

[0062] The map, for example, associates the outside air temperature Tam with the heating capacity Qhp_map in the endothermic heating mode that can be achieved depending on the outside air temperature Tam, and is stored in advance in ROM 102. Alternatively, an arithmetic formula that can calculate the heating capacity Qhp from the outside air temperature Tam may be stored in advance in ROM 102 or the like, and the calculation may be performed each time based on the acquired outside air temperature Tam.

[0063] The control device 100 calculates the target heating capacity TGQh (step S13) and determines whether the heating capacity Qhp achievable in the endothermic heating mode estimated in step S12 satisfies the target heating capacity TGQh (step S14). If the heating capacity Qhp satisfies the target heating capacity TGQh (YES in step S14), the control device 100 determines to execute the endothermic heating mode (referred to as "HP Mode" in the figure) (step S15). If the current operating mode is the endothermic heating mode and no transition is required (NO in step S16), the control device 100 ends the above process. On the other hand, if the current operating mode is the hot gas heating mode and a transition is required (YES in step S16), the control device 100 executes the second transition mode (step S17). The second transition mode will be described later.

[0064] If the control device 100 determines in step S14 that the heating capacity Qhp does not satisfy the target heating capacity TGQh (NO in step S14), it determines to execute the hot gas heating mode (referred to as "HG Mode" in the figure) (step S18). If the current operating mode is the hot gas heating mode and no transition is required (NO in step S19), the control device 100 ends the above process. On the other hand, if the current operating mode is the endothermic heating mode and a transition is required (YES in step S19), the control device 100 executes the first transition mode (step S20). The first transition mode will be described later.

[0065] (2) Processing in the First Transition Mode FIG. 7 is a flowchart showing the transition process from endothermic heating mode to hot gas heating mode (HP → HG). When the control device 100 determines that a transition from endothermic heating mode to hot gas heating mode is necessary, it executes the first transition mode to transition to the hot gas heating mode. As described above, the first pressure reduction unit V1, the second pressure reduction unit V2, the third pressure reduction unit V3, and the flow path switching valves 12 and 13 in the refrigerant circuit 10 are in different open / closed states in the endothermic heating mode and the hot gas heating mode. By executing the first transition mode, the control device 100 controls these open / closed states in a stepwise manner to gradually change the refrigerant flow path, thereby suppressing sudden fluctuations in refrigerant pressure and achieving a seamless transition from the endothermic heating mode to the hot gas heating mode.

[0066] When the first transition mode is started, the control device 100 first controls the refrigerant circuit 10 to open to a predetermined opening degree (step S31) as shown in Fig. 8 from the operating state of the refrigerant circuit 10 in the endothermic heating mode shown in Fig. 4. In this way, by first opening the second pressure reducing section V2 and flowing the high-temperature, high-pressure refrigerant compressed by the compressor 2 into the hot gas bypass 10V, the suction refrigerant pressure Ps can be increased.

[0067] By setting the predetermined opening degree of the second pressure reducing section V2 to the minimum opening degree defined in the specifications of the second pressure reducing section V2, the suction refrigerant pressure Ps can be increased gradually. The predetermined opening degree of the second pressure reducing section V2 is also set so that the refrigerant pressure downstream of the second pressure reducing section V2 is lower than the refrigerant pressure downstream of the first pressure reducing section V1. This allows the check valve 14 provided downstream of the external heat exchanger 11 to open, preventing refrigerant from accumulating in the external heat exchanger 11.

[0068] Note that flowing refrigerant through the hot gas bypass 10V in step S31 reduces the flow rate of refrigerant to the indoor heat exchanger 21, which may further increase the sense of insufficiency relative to the target heating capacity TGQh and reduce passenger comfort. Therefore, the control device 100 controls the blower 23 and air dampers 24, 25 in the air conditioning unit 20 as necessary to adjust the air flow rate, the heat dissipation rate of the indoor heat exchanger 21, the ratio of inside air to outside air, etc. In this way, it is possible to reduce the sense of insufficiency relative to the target heating capacity TGQh when the first transition mode is executed, thereby reducing passenger discomfort.

[0069] After the second pressure reducing unit V2 has opened to the predetermined opening degree, the control device 100 controls the first pressure reducing unit V1 to close (step S32), and simultaneously controls the third pressure reducing unit V3 to open from the closed state to the predetermined opening degree (step S33).In addition, the flow path switching valve 12 is opened.

[0070] At this time, the control device 100 controls the timing (time) at which the opening degree of the first pressure reduction section V1 becomes 0 (fully closed) to coincide with the timing (time) at which the third pressure reduction section V3 becomes a predetermined opening degree. As described above, the refrigerant pressure ranges suitable for stable operation in the endothermic heating mode and the hot gas heating mode are different, so if the opening and closing timings of the first pressure reduction section V1 and the third pressure reduction section V3 are not synchronized, the following problems may occur.

[0071] That is, if the opening and closing timings of the first pressure reduction section V1 and the third pressure reduction section V3 do not match, particularly if both sections are closed, the outlet refrigerant pressure Pci and the suction refrigerant pressure Ps of the compressor 2 increase, which may cause the compressor 2 to stop due to abnormal high pressure. Furthermore, for example, if the third pressure reduction section V3 opens to a predetermined opening degree before the first pressure reduction section V1 is fully closed, the pressure difference between the refrigerant flowing from the first pressure reduction section V1 and the refrigerant flowing from the third pressure reduction section V3 may cause refrigerant to stagnate in the external heat exchanger 11. Therefore, by using the control device 100 to match the opening and closing timings of the first pressure reduction section V1 and the third pressure reduction section V3, complex adjustment of the opening degrees of the first pressure reduction section V1 to the third pressure reduction section V3 is not required. This simplifies the control of the first pressure reduction section V1 to the third pressure reduction section V3 and prevents the above-mentioned problems.

[0072] The control device 100 controls the first pressure reducing unit V1 to close at a constant speed, and similarly controls the third pressure reducing unit V3 to open at a constant speed. In this case, the opening degree of the first pressure reducing unit V1 before closing and the predetermined opening degree of the third pressure reducing unit V3 are not necessarily the same, and therefore the drive speed of the first pressure reducing unit V1 and the drive speed of the third pressure reducing unit V3 do not necessarily match.

[0073] Alternatively, the control device 100 may shift the timing at which the first pressure reduction section V1 begins to close and the timing at which the third pressure reduction section V3 begins to open, so that the timing at which the opening degree of the first pressure reduction section V1 becomes 0 (fully closed) and the timing at which the third pressure reduction section V3 becomes a predetermined opening degree coincide with each other.

[0074] The predetermined opening degree of the third pressure reducing section V3 may be, for example, a minimum opening degree within the pressure range in which the hot gas heating mode is established, which is obtained through experiments or simulations. Alternatively, the control device 100 may determine the predetermined opening degree of the third pressure reducing section V3 based on the target suction refrigerant pressure PSO that can achieve the target outlet refrigerant pressure PCO calculated from the set temperature Tset.

[0075] When the above process is completed, the hot gas heating mode is executed as the heating operation in the automotive air conditioner 1. That is, the control device 100 controls the openings of the second pressure reducing unit V2 and the third pressure reducing unit V3 of the compressor 2 so that the outlet refrigerant pressure Pci of the indoor heat exchanger 21 becomes the target outlet refrigerant pressure PCO and the suction refrigerant pressure Ps becomes the target suction refrigerant pressure PSO, and controls the blower 23 and the like so that the heating capacity Qhg in the hot gas heating mode satisfies the target heating capacity TGQh.

[0076] (3) Processing in the Second Transition Mode FIG. 9 is a flowchart showing the transition process from hot gas heating mode to endothermic heating mode (HG → HP). When the control device 100 determines that a transition from hot gas heating mode to endothermic heating mode is necessary, it executes the second transition mode to transition to endothermic heating mode. As described above, in the endothermic heating mode and the hot gas heating mode, the first pressure reduction unit V1, the second pressure reduction unit V2, the third pressure reduction unit V3, and the flow path switching valves 12 and 13 in the refrigerant circuit 10 are in different open / closed states. By executing the second transition mode, the control device 100 controls these open / closed states in a stepwise manner to gradually change the refrigerant flow path, thereby suppressing sudden fluctuations in refrigerant pressure and achieving a seamless transition from hot gas heating mode to endothermic heating mode.

[0077] In the hot gas heating mode, the suction refrigerant pressure Ps and the outlet refrigerant pressure Pci are both higher than in the endothermic heating mode, so they need to be made as close as possible to values ​​suitable for the endothermic heating mode. Therefore, in the second transition mode, the heat medium in the refrigerant heat medium heat exchanger 34 is temporarily heated using excess heat from the refrigerant in the hot gas heating mode (hereinafter referred to as excess heat), and the refrigerant absorbs heat from the heated heat medium, adjusting the refrigerant pressure range to a pressure range suitable for the endothermic heating mode.

[0078] When the second transition mode is started, the control device 100 drives the circulation pump 31 (step S41) as shown in Fig. 10 from the operating state of the refrigerant circuit 10 in the hot gas heating mode shown in Fig. 5. This causes the heat medium to circulate through the heat medium circuit 30, causing heat exchange between the heat medium and the refrigerant in the refrigerant-heat medium heat exchanger 34. That is, the refrigerant circuit 10 performs heating operation in the hot gas heating mode while simultaneously dissipating heat in the refrigerant-heat medium heat exchanger 34. This causes excess heat in the hot gas heating mode to be dissipated to the heat medium in the heat medium circuit 30, thereby reducing the suction refrigerant pressure Ps.

[0079] It is preferable that, prior to driving the circulation pump 31, the compressor 2 and the blower 23 are controlled by setting the target suction refrigerant pressure PSO and the target outlet refrigerant pressure PCO to the lowest values ​​at which the hot gas heating mode can be operated, and then the excess heat in the hot gas heating mode is dissipated to the heat medium in the heat medium circuit 30. In this way, the transition from the hot gas heating mode to the endothermic heating mode can be made more seamless.

[0080] This operation causes the refrigerant to radiate heat not only from the indoor heat exchanger 21 but also from the refrigerant-heat medium heat exchanger 34, which may lower the outlet temperature and impair passenger comfort. In this case, the control device 100 controls the blower 23 and air dampers 24, 25 in the air conditioning unit 20 as necessary to adjust the airflow rate, the amount of heat radiated by the indoor heat exchanger 21, the ratio of inside air to outside air, etc.

[0081] The control device 100 performs heating operation in the hot gas heating mode with the refrigerant circuit 10 in a state where the refrigerant / heat medium heat exchanger 34 dissipates heat, dissipating excess heat in the hot gas heating mode to the heat medium circulating through the heat medium circuit 30. The control device 100 then monitors whether the excess heat has been sufficiently dissipated to the heat medium, i.e., whether heat dissipation is complete (step S42). In this way, by dissipating as much excess heat as possible in the hot gas heating mode to the heat medium, a sudden change in the suction refrigerant pressure Ps that occurs when the second pressure reduction section V2 is closed in the next step S43 is suppressed.

[0082] In step S42, for example, if the heat medium temperature Wt is approximately equal to the refrigerant saturation temperature (first temperature Wt1), which is a pressure close to the intake refrigerant pressure Ps in the hot gas heating mode, this is one indicator that the excess heat has been sufficiently dissipated and that heat dissipation is complete.

[0083] The control device 100 can also determine that the dissipation of excess heat is complete in the following cases: That is, the control device 100 can determine that the dissipation of excess heat is complete when it has confirmed that the difference between the refrigerant temperature and the heat medium temperature at the outlet of the refrigerant-heat medium heat exchanger 34 is within a certain temperature range (for example, within 2°C), or when it has confirmed that the difference between the heat medium temperatures at the inlet and outlet of the refrigerant-heat medium heat exchanger 34 is within a certain range (for example, within 5°C).

[0084] When the dissipation of the excess heat is completed (YES in step S42), the control device 100 controls the second pressure reducing section V2 to close (step S43), as shown in Fig. 11. This causes the refrigerant to absorb the heat of the heat medium in the refrigerant-heat medium heat exchanger 34 (this is referred to as "heat recovery").

[0085] In addition, the control device 100 controls the third pressure reducing section V3 so that the degree of subcooling of the refrigerant at the outlet of the indoor heat exchanger 21 becomes a target degree of subcooling (SC (subcool) control) (step S44). Note that because heat recovery, i.e., the refrigerant absorbing heat from the heat medium, is only temporary, excess heat from the hot gas heating mode and waste heat recovered from the object to be temperature controlled are stored in the heat medium and then absorbed by the refrigerant.

[0086] If the outlet refrigerant pressure Pci drops together with the suction refrigerant pressure Ps when the second pressure reducing section V2 is closed, the control device 100 controls the blower 23 and air dampers 24, 25 to temporarily adjust the volume of air passing through the indoor heat exchanger 21, thereby adjusting the amount of heat released from the indoor heat exchanger 21. In this way, the balance between heat input and heat release in the hot gas heating mode is maintained, allowing stable operation to continue and the above-mentioned heat recovery to be performed smoothly.

[0087] After the second pressure reduction unit V2 is fully closed and the transition to heat recovery is complete, the control device 100 immediately controls the first pressure reduction unit V1 to open (step S45). At the same time, the flow path switching valve 13 is opened. This causes both the external heat exchanger 11 and the refrigerant-to-heat medium heat exchanger 34 to function as evaporators, and the refrigerant absorbs heat from both the outside air and the heat medium ( FIG. 12 ). At this time, the first pressure reduction unit V1 is set to the minimum opening degree determined by its specifications. As shown in FIG. 12 , when the first pressure reduction unit V1 is opened, the third pressure reduction unit V3 is open and the system is under subcooling control. Therefore, it is preferable to keep the first pressure reduction unit V1 at a predetermined fixed opening degree at this stage.

[0088] Next, the control device 100 determines whether frost has formed on the external heat exchanger 11 (step S46). As described above, the control device 100 determines the frost state on the external heat exchanger 11 based on, for example, the refrigerant temperature TXO obtained by the refrigerant temperature sensor 43C provided on the outlet side of the external heat exchanger 11. If the control device 100 determines that frost has not formed (NO in step S46), the control device 100 proceeds with the transition to the endothermic heating mode. That is, the control device 100 closes the third pressure reducing unit V3 (step S47), controls the first pressure reducing unit V1 so that the degree of subcooling (subcooling) of the refrigerant at the outlet of the indoor heat exchanger 21 becomes a target degree of subcooling (SC (subcooling) control) (step S48), and stops the circulation pump 31 (step S49).

[0089] When the above process is completed, the endothermic heating mode is executed as the heating operation in the vehicle air conditioner 1. That is, the control device 100 controls the compressor 2 so that the outlet refrigerant pressure Pci of the indoor heat exchanger 21 becomes the target outlet refrigerant pressure Pco. The control device 100 also controls the aperture of the first pressure reducing section V1 so that the degree of subcooling at the outlet of the indoor heat exchanger 21 becomes the target degree of subcooling, and controls the blower 23 so that the heating capacity Qhp in the endothermic heating mode satisfies the target heating capacity TGQh.

[0090] On the other hand, if it is determined that frost has formed on the external heat exchanger 11 (YES in step S46), the control device 100 causes the refrigerant to absorb heat from the heat medium and monitors the heat medium temperature Wt in the heat medium circuit 30 until it becomes equal to or lower than a second temperature Wt2 (step S50). If the heat medium temperature Wt becomes equal to or lower than the second temperature Wt2 (YES in step S50), the transition process to the endothermic heating mode is stopped (step S51) and the system returns to the hot gas heating mode (step S52). The second temperature Wt2 is the heat medium temperature at which the target heating capacity TGQh cannot be met during heat recovery.

[0091] When returning to the hot gas heating mode in step S52, the control device 100 opens the second pressure reduction unit V2 to its minimum opening, and when the suction refrigerant pressure Ps reaches the desired pressure, stops the circulation pump 31, controls the third pressure reduction unit V3 to its opening in the hot gas heating mode, and closes the first pressure reduction unit V1. Also, in the example described above, step S50 monitors the heat medium temperature Wt until it becomes equal to or lower than the second temperature Wt2, but it is also possible to proceed to step S51 when a predetermined time has elapsed.

[0092] When the above process is completed, the hot gas heating mode is executed as the heating operation in the automotive air conditioner 1. That is, the control device 100 controls the openings of the second pressure reducing unit V2 and the third pressure reducing unit V3 of the compressor 2 so that the outlet refrigerant pressure Pci of the indoor heat exchanger 21 becomes the target outlet refrigerant pressure PCO and the suction refrigerant pressure Ps becomes the target suction refrigerant pressure PSO, and controls the blower 23 and the like so that the heating capacity Qhg in the hot gas heating mode satisfies the target heating capacity TGQh.

[0093] In this way, the vehicle air conditioning system 1 according to this embodiment compares the achievable heating capacity in the endothermic heating mode or the hot gas heating mode with the target heating capacity to execute the optimal heating mode, so that the required heating capacity can always be secured while operating in a way that minimizes power consumption, thereby improving passenger comfort while minimizing power consumption.

[0094] In addition, when transitioning from endothermic heating mode to hot gas heating mode, the control device 100 executes a first transition mode before transitioning to hot gas heating mode, and similarly, when transitioning from hot gas heating mode to endothermic heating mode, the control device 100 executes a second transition mode before transitioning to endothermic heating mode.

[0095] By executing the first transition mode or the second transition mode, the refrigerant flow path in the refrigerant circuit 10 is changed in stages during the transition between the endothermic heating mode and the hot gas heating mode, and the refrigerant pressure is gradually increased or decreased. This allows the refrigerant pressure to be adjusted to a pressure appropriate for the heating mode after the transition, allowing a seamless transition while the compressor is running, improving passenger comfort.

[0096] That is, in the first transition mode, the first, second, and third pressure reduction units are controlled to open and close in a stepwise manner to gradually increase the suction refrigerant pressure Ps, thereby gradually closing the difference in pressure band between the endothermic heating mode and the hot gas heating mode. This allows a seamless transition from the endothermic heating mode to the hot gas heating mode while the compressor 2 is still operating. Furthermore, during the transition, the air conditioning unit 20 is controlled as needed, so that a perceived lack of heating capacity can be compensated for by adjusting the air volume, etc. Thus, by executing the first transition mode during the transition from the endothermic heating mode to the hot gas heating mode, passenger comfort is improved.

[0097] Furthermore, when transitioning from the hot gas heating mode to the endothermic heating mode in the second transition mode, the heat medium in the heat medium circuit 30 absorbs excess heat accumulated in the refrigerant in the hot gas heating mode, gradually lowering the suction refrigerant pressure Ps, thereby gradually filling the difference in pressure band between the endothermic heating mode and the hot gas heating mode. This allows a seamless transition from the hot gas heating mode to the endothermic heating mode while the compressor 2 is still operating, improving passenger comfort.

[0098] As described above, according to this embodiment, the transition between the hot gas heating mode and the endothermic heating mode can be performed seamlessly, thereby improving the comfort of the passengers.

[0099] The embodiments of the present invention have been described above in detail with reference to the drawings, but the specific configurations are 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.

[0100] 1: Vehicle air conditioning device, 2: Compressor, 10: Refrigerant circuit, 10V: Hot gas bypass, 11: External heat exchanger, 12, 13: Flow path switching valve, 14, 15: Check valve, 16: Accumulator, 20: Air conditioning unit, 21, 22: Indoor heat exchanger, 23: Blower, 24, 25: Air damper, 25A, 25B: Air inlet, 30: Heat medium circuit, 31: Circulation pump, 33: Temperature-controlled heat exchanger, 34: Refrigerant heat medium heat exchanger, 34A, 34B: Flow path, 40: Sensor unit, 41: Outside air sensor, 42: Compressor current sensor, 43, 43A, 43B, 43C: Refrigerant temperature sensor, 44, 44A, 44B, 44C: Refrigerant pressure sensor, 45: Occupant sensor, 46: Outlet air temperature sensor, 47: Inside air sensor, 60: Input signal, 100: Control device

Claims

1. A vehicle air conditioning system comprising a refrigerant circuit including a compressor, an indoor heat exchange unit, an external heat exchange unit, and a hot gas bypass for decompressing at least a portion of the refrigerant compressed by the compressor and returning it to the compressor without passing through the indoor heat exchange unit and the external heat exchange unit, and a control unit for controlling the refrigerant circuit, wherein the refrigerant circuit includes a first decompression unit for decompressing the refrigerant flowing into the external heat exchange unit, a second decompression unit for decompressing the refrigerant flowing through the hot gas bypass, and a third decompression unit for decompressing the refrigerant drawn into the compressor, the control unit being capable of executing an endothermic heating mode in which the refrigerant is caused to absorb heat in the external heat exchange unit, and a hot gas heating mode in which a portion of the refrigerant compressed by the compressor is caused to flow through the hot gas bypass and the remainder is caused to flow through the indoor heat exchange unit, and a first stage of controlling to open the second decompression unit when it is determined that the heating capacity does not satisfy a target heating capacity during execution of the endothermic heating mode; a second stage of controlling the first pressure reduction section to be closed and the third pressure reduction section to be opened, and then a first transition mode is executed, and then the vehicle air conditioning system transitions to the hot gas heating mode.

2. A vehicle air conditioning system as described in claim 1, wherein the control device adjusts the opening degree of the second pressure reduction section so that the pressure of the refrigerant downstream of the second pressure reduction section is lower than the pressure of the refrigerant downstream of the first pressure reduction section.

3. The vehicle air conditioning system according to claim 1, wherein the control device controls the timing at which the first pressure reducing section is fully closed to coincide with the timing at which the third pressure reducing section is opened to a predetermined degree.

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