Vehicle air conditioning device

Abstract

[Problem] To make occupants more comfortable by causing a hot gas heating mode to continue stably and suppressing any variation in blowout temperature during transition from hot-gas air warming to heat absorption air warming. [Solution] A vehicle air conditioner comprising a refrigerant circuit, an air conditioning unit, and a control device for controlling the refrigerant circuit and the air conditioning unit, wherein it is possible to execute a heat-absorption air warming mode in which refrigerant radiated due to air-warming in the cabin is caused to absorb heat from a heat absorption target such as outside air in an external heat exchanger, and a hot gas air-warming mode in which some of the refrigerant compressed by a compressor is returned to the compressor via a bypass route and the remainder is heated in the cabin by heat radiation from the refrigerant. When, during a transition from the hot gas air-warming mode to the heat absorption air-warming mode, the difference between the current air-warming capacity in the hot gas air-warming mode and the air-warming capacity in the heat absorption air-warming mode estimated on the basis of the temperature of the heat absorption target is equal to or greater than a predetermined value, an air damper is driven to lower the current air-warming capacity in the hot gas air-warming mode.

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 an onboard battery, have become widespread. A known vehicle air conditioner for 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, etc. (endothermic heating). Therefore, when the outside temperature becomes extremely low, it becomes difficult to absorb heat from outside air, etc., and heating capacity is significantly reduced. In contrast, hot gas heating, which does not absorb heat from outside air, etc., but uses a high-temperature, high-pressure refrigerant discharged from a compressor, is known as an effective heating method in extremely low-temperature environments.

[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 passenger compartment 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] When heating the passenger compartment in a vehicle air conditioner such as the one described above, the system may be controlled to, for example, operate in hot gas heating mode at startup to raise the passenger compartment temperature as quickly as possible, and then transition to endothermic heating mode after the passenger compartment reaches a desired temperature. In this case, because there is a large difference in heating capacity between the hot gas heating mode and the endothermic heating mode under the same environment, the outlet temperature may fluctuate significantly when transitioning from the hot gas heating mode to the endothermic heating mode, which may impair passenger comfort.

[0007] On the other hand, in order to suppress fluctuations in the discharge temperature during the transition, it is possible to lower the discharge temperature in the hot gas heating mode before transitioning to the endothermic heating mode. If the high-pressure side refrigerant pressure of the refrigerant circuit is reduced, i.e., the compressor speed is reduced, to lower the discharge temperature. However, because there is a lower limit to the compressor speed at which stable operation can be maintained in the hot gas heating mode, the discharge temperature cannot necessarily be lowered to the desired temperature. If the compressor is driven at a speed below the lower limit in the hot gas heating mode, the balance between the heat input and heat release in the refrigerant circuit cannot be maintained, resulting in unstable operation and the risk of the vehicle air conditioning system shutting down.

[0008] The present invention was made in consideration of these circumstances, and its objective is to stably continue the hot gas heating mode while suppressing fluctuations in the blown air temperature when transitioning from the hot gas heating mode to the endothermic heating mode, thereby improving the comfort of occupants.

[0009] The present invention provides an air conditioning unit having a refrigerant circuit including a compressor, an indoor heat exchanger, an external heat exchanger, and a hot gas bypass that decompresses and returns at least a portion of the refrigerant compressed by the compressor without passing through the indoor heat exchanger and the external heat exchanger, and an air conditioning unit in which the indoor heat exchanger is disposed and an air damper that adjusts the proportion of air blown by the air blower to the indoor heat exchanger; an endothermic heating mode that controls the refrigerant circuit and the air conditioning unit, and causes the refrigerant compressed by the compressor to release heat in the indoor heat exchanger and then absorb heat in the external heat exchanger; and a control device capable of executing a hot gas heating mode in which a portion of the refrigerant that has been absorbed is passed through the hot gas bypass and returned to the compressor, while the remainder is dissipated in the indoor heat exchanger. When transitioning from the hot gas heating mode to the endothermic heating mode, the control device controls the air damper to drive the air damper to reduce the current heating capacity in the hot gas heating mode if the difference between the current heating capacity in the hot gas heating mode and the heating capacity in the endothermic heating mode estimated based on the temperature of the heat absorption target by the external heat exchanger is equal to or greater than a predetermined value.

[0010] According to the present invention, the hot gas heating mode can be stably continued, and fluctuations in the blown air temperature during the transition from the hot gas heating mode to the endothermic heating mode can be suppressed, thereby improving the comfort of the occupants.

[0011] 1 is an explanatory diagram showing an example of the system configuration of a vehicle air conditioner according to an embodiment of the present invention; 2 is an explanatory diagram showing a control device of a vehicle air conditioner according to an embodiment of the present invention; 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; 4 is an explanatory diagram showing the operation of a refrigerant circuit in a hot gas heating mode in a vehicle air conditioner according to an embodiment of the present invention; 5 is a flowchart showing the processing flow of a first embodiment regarding a transition from hot gas heating mode to endothermic heating mode by a control device in a vehicle air conditioner according to an embodiment of the present invention; 6 is a flowchart showing the processing flow of a second embodiment regarding a transition from hot gas heating mode to endothermic heating mode by a control device in a vehicle air conditioner according to an embodiment of the present invention;

[0012] 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 hollow lines indicate refrigerant flow paths through which decompressed refrigerant flows. In addition, dashed lines in the refrigerant circuit 10 indicate refrigerant flow paths through which refrigerant does not flow.

[0013] 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.

[0014] 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 cabin, 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 through the air conditioning unit 20, and the external heat exchanger 11 is provided to exchange heat between the refrigerant and outside air outside the vehicle cabin. The indoor heat exchanger 21 is used to heat the air, and the indoor heat exchanger 22 is used to cool the air. A refrigerant pressure sensor 44B and a refrigerant temperature sensor 43B are provided immediately downstream of the indoor heat exchanger 21 to detect an outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) and an outlet refrigerant temperature Tc (high-pressure side refrigerant temperature), respectively, of the indoor heat exchanger 21.

[0015] The compressor 2 compresses the refrigerant and circulates it within the refrigerant circuit 10. The refrigerant compressed by the compressor 2 is reduced to a required pressure 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.

[0016] 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.

[0017] As described above, the air conditioning unit 20 includes the indoor heat exchangers 21 and 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 by the blower 23 to either the air inside the vehicle cabin or the air outside the vehicle cabin.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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, and a refrigerant temperature sensor 43B that detects the outlet refrigerant temperature Tc (high-pressure side refrigerant temperature) of the indoor heat exchanger 21 (see Figure 1).

[0025] The refrigerant pressure sensor 44 also includes a refrigerant pressure sensor 44A that detects a suction refrigerant pressure Ps (low-pressure side refrigerant pressure) sucked into the compressor 2, and a refrigerant pressure sensor 44B that detects an outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) of the indoor heat exchanger 21 (see FIG. 1). These sensors are just examples, and the sensor unit 40 is provided with various sensors that detect information required for the control device 100 to perform various controls.

[0026] 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.

[0027] [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.

[0028] 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).

[0029] 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.

[0030] 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 I / F 105.

[0031] 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.

[0032] [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.

[0033] The operation of the refrigerant circuit 10 in the hot gas heating mode will be described with reference to Figure 4. In this operation, part of the high-temperature, high-pressure refrigerant discharged from the compressor 2 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, is separated into gas and liquid in the accumulator 16, and returns to the compressor 2. At this time, in the refrigerant circuit 10, the first pressure reduction section V1 is fully closed, so that refrigerant does not flow to the external heat exchanger 11. In addition, the fourth pressure reduction section V4 is fully closed, so that refrigerant does not flow to the indoor heat exchanger 22.

[0034] The refrigerant circuit 10 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 indoor heat exchanger 21 and the external heat exchanger 11. In the hot gas bypass 10V, a portion of the high-temperature, high-pressure refrigerant is branched off at a branch point P1 immediately downstream of the compressor 2, reduced in pressure at a second pressure reduction section V2, and merged with the low-pressure refrigerant reduced in pressure at a third pressure reduction section V3 at a junction point P2 immediately upstream of the accumulator 16.

[0035] By providing such a hot gas bypass 10V, 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 that can 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 opening and closing 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.

[0036] In the hot gas heating mode, the refrigerant flowing through the refrigerant circuit 10 is decompressed in the third decompression section V3 in the flow path that passes through the indoor heat exchanger 21, so that the refrigerant becomes high-pressure refrigerant upstream and low-pressure refrigerant downstream. 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 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.

[0037] [Endothermic heating mode] In the endothermic heating mode, the refrigerant circuit 10 obtains a heat source for heating by causing the refrigerant to absorb heat from the outside air, which is the heat absorption target, by flowing the refrigerant through the external heat exchanger 11 as follows: The flow of refrigerant through the refrigerant circuit 10 in the endothermic heating mode is not shown in the drawings.

[0038] In the endothermic heating mode, the second pressure reducing section V2, the third pressure reducing section V3, the fourth pressure reducing section V4, and the flow path switching valve 12 are fully closed in the refrigerant circuit 10. Meanwhile, the flow path switching valve 13 is fully open, and the first pressure reducing section V1 is open.

[0039] 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 passes through the flow path switching valve 13, the check valve 14, and the accumulator 16 before being returned to the compressor 2. 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. 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.

[0040] [Operation Mode Switching Control by Control Device] Hereinafter, the operation mode switching control by the control device 100 when the vehicle air conditioner 1 according to this embodiment heats the vehicle cabin will be described. When the vehicle air conditioner 1 heats the vehicle cabin, 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, etc. Because the hot gas heating mode has a higher heating capacity than the endothermic heating mode, the control device 100 normally executes the endothermic heating mode when the outside air temperature Tam is equal to or higher than a predetermined temperature (for example, −10° C.), and executes the hot gas heating mode when the outside air temperature Tam is an extremely low temperature environment below the predetermined temperature.

[0041] On the other hand, for example, when the vehicle air conditioner 1 is started in an external environment where the outside air temperature Tam is within a predetermined temperature range including the above-mentioned predetermined temperature and both the endothermic heating mode and the hot gas heating mode are executable, the control device 100 can control the vehicle air conditioner 1 to execute the hot gas heating mode at startup and then transition to the endothermic heating mode. By controlling in this manner, the temperature inside the vehicle cabin can be raised as quickly as possible in the hot gas heating mode to ensure quick heating, and then, when the temperature inside the vehicle cabin reaches a target temperature (e.g., a set temperature Tset described below), the control device 100 can transition to the endothermic heating mode, thereby reducing power consumption.

[0042] However, since there is a difference in heating capacity between the hot gas heating mode and the endothermic heating mode as described above, there is a risk that the temperature of the air blown into the vehicle cabin will change significantly when transitioning from the hot gas heating mode to the endothermic heating mode. Therefore, when transitioning from the hot gas heating mode to the endothermic heating mode, the control device 100 controls the mode to reduce the difference in heating capacity between the two modes, thereby suppressing fluctuations in the air blown into the vehicle cabin due to the difference in heating capacity.

[0043] The process of transitioning from the hot gas heating mode to the endothermic heating mode by the control device 100 of the vehicle air conditioner 1 according to this embodiment will be described below with reference to the flowcharts of Figures 5 and 6. In the following description, to reduce the difference in heating capacity, in the example shown in Figure 5, the control device 100 mainly controls the air damper 24 (Example 1), and in the example shown in Figure 6, the control device 100 mainly controls the compressor 2 and the air damper 24 (Example 2).

[0044] 5 , when the vehicle air conditioner 1 starts heating the vehicle cabin, the hot gas heating mode is executed (step S11). The control device 100 fully closes the first pressure reduction unit V1 and the fourth pressure reduction unit V4 and opens the second pressure reduction unit V2 and the third pressure reduction unit V3 in the refrigerant circuit 10. In this state, the control device 100 drives the compressor 2, causing a portion of the high-temperature, high-pressure refrigerant discharged from the compressor 2 to flow through the indoor heat exchanger 21 to exchange heat with air to be supplied into the vehicle cabin and then return the refrigerant to the compressor 2, and causing the remainder of the high-temperature, high-pressure refrigerant discharged from the compressor 2 to flow through the hot gas bypass 10V and return to the compressor 2.

[0045] At this time, in order to stabilize the operating state of the hot gas heating mode, it is desirable to use the air damper 25 to set the ratio of inside and outside air to a fixed ratio (for example, a ratio of 20% outside air and 80% inside air to suppress an increase in carbon dioxide concentration and take into account the possibility of clear windows).

[0046] During the hot gas heating mode, the control device 100 compares the set temperature Tset with the interior temperature Tin, which is the temperature inside the vehicle cabin acquired at a predetermined interval from the inside air sensor 47, and monitors whether the interior temperature is equal to the set temperature Tset (step S12). In the processing of step S12, the control device 100 defines a predetermined temperature range including the set temperature Tset as an allowable temperature range, and can regard the interior temperature Tin as being equal to the set temperature Tset if it is within the allowable temperature range.

[0047] If the indoor temperature Tin is not within the allowable temperature range including the set temperature Tset (NO in step S12), the control device 100 continues the hot gas heating mode. On the other hand, if the indoor temperature Tin is within the allowable temperature range including the set temperature Tset (YES in step S12), the control device 100 proceeds to step S13.

[0048] In step S13, the control device 100 determines whether it is desirable to transition from the hot gas heating mode to the endothermic heating mode (step S13). In this determination, the control device 100 determines whether it is desirable to transition the operating mode to reduce the power consumption of the automotive air conditioner 1, taking into account the outside air temperature Tam, the interior temperature Tin, the operating state in the hot gas heating mode, the current heating capacity, etc. If the control device 100 does not transition the operating mode (NO in step S13), it continues the hot gas heating mode and monitors whether the interior temperature is equal to the set temperature Tset (step S12).

[0049] If the control device 100 determines that the hot gas heating mode should be switched to the endothermic heating mode (YES in step S13), the control device 100 proceeds to step S14. When the control device 100 determines that the hot gas heating mode should be switched to the endothermic heating mode, the control device 100 preferably controls the air damper 25 so that the ratio of inside air is higher than the ratio of inside / outside air in step S11. By increasing the ratio of inside air, the heating load can be reduced.

[0050] In step S14, the controller 100 obtains the current heating capacity in the hot gas heating mode and the heating capacity in the endothermic heating mode estimated based on the outside air temperature Tam, which is the heat absorption target of the external heat exchanger 11, calculates the difference between these heating capacities (hereinafter referred to as the difference value ΔQ) and determines whether the difference value ΔQ is equal to or greater than a predetermined value Qth. If the difference value ΔQ is equal to or greater than the predetermined value Qth (YES in step S14), the controller 100 drives the air damper 24 to reduce the difference value ΔQ, i.e., to reduce the heating capacity in the hot gas heating mode (step S15). If the difference value ΔQ is less than the predetermined value Qth (NO in step S14), the controller 100 transitions to the endothermic heating mode (step S17).

[0051] When the range of heating capacity obtained by controlling the compressor 2 is compared between the hot gas heating mode and the endothermic heating mode, the minimum heating capacity in the hot gas heating mode and the maximum heating capacity in the endothermic heating mode do not overlap, and the minimum heating capacity in the hot gas heating mode is higher than the maximum heating capacity in the endothermic heating mode. Therefore, in step S15, the control device 100 controls the air damper 24 to reduce the proportion of air sent to the indoor heat exchanger 21, thereby reducing the heating capacity in the hot gas heating mode and reducing the difference value ΔQ.

[0052] By controlling the air damper 24 in this manner, the proportion of air blown to the flow path that bypasses the indoor heat exchanger 21 increases, thereby lowering the temperature of air blown into the vehicle cabin. Therefore, by controlling the air damper 24, the difference value ΔQ is reduced and the temperature of air blown in the hot gas heating mode is lowered, thereby suppressing large fluctuations when the operation mode is changed.

[0053] The control device 100 monitors the difference value ΔQ while driving the air damper 24 (step S16) and drives the air damper 24 until the difference value ΔQ becomes less than the predetermined value Qth (NO in step S16). When the difference value ΔQ becomes less than the predetermined value Qth (YES in step S16), the control device 100 transitions from the hot gas heating mode to the endothermic heating mode (step S17).

[0054] In this way, in the vehicle air conditioner 1 according to this embodiment, when transitioning from the hot gas heating mode to the endothermic heating mode, the control device 100 controls the air conditioner 1 so as to reduce the difference in heating capacity between the hot gas heating mode and the endothermic heating mode. This reduces large fluctuations in the outlet temperature due to the difference in heating capacity, thereby improving passenger comfort. In particular, because the control device 100 controls the air damper 24 to reduce the difference in heating capacity, the operating state of the hot gas heating mode does not fluctuate significantly, and the hot gas heating mode can be stably maintained while smoothly transitioning to the endothermic heating mode.

[0055] 6 , when the vehicle air conditioner 1 starts heating the vehicle cabin, the hot gas heating mode is executed (step S21). The control device 100 fully closes the first pressure reduction unit V1 and the fourth pressure reduction unit V4 and opens the second pressure reduction unit V2 and the third pressure reduction unit V3 in the refrigerant circuit 10. In this state, the control device 100 drives the compressor 2, causing a portion of the high-temperature, high-pressure refrigerant discharged from the compressor 2 to flow through the indoor heat exchanger 21 to exchange heat with air to be supplied into the vehicle cabin and then return the refrigerant to the compressor 2, and causing the remainder of the high-temperature, high-pressure refrigerant discharged from the compressor 2 to flow through the hot gas bypass 10V and return it to the compressor 2.

[0056] At this time, in order to stabilize the operating state of the hot gas heating mode, it is desirable to use the air damper 25 to set the ratio of inside and outside air to a fixed ratio (for example, a ratio of 20% outside air and 80% inside air to suppress an increase in carbon dioxide concentration and take into account the possibility of clear windows).

[0057] During the hot gas heating mode, the control device 100 compares the set temperature Tset with the interior temperature Tin, which is the temperature inside the vehicle cabin acquired at a predetermined interval from the inside air sensor 47, and monitors whether the interior temperature is equal to the set temperature Tset (step S22). In the processing of step S22, the control device 100 defines a predetermined temperature range including the set temperature Tset as an allowable temperature range, and can regard the interior temperature Tin as being equal to the set temperature Tset if it is within the allowable temperature range.

[0058] If the indoor temperature Tin is not within the allowable temperature range including the set temperature Tset (NO in step S22), the control device 100 continues the hot gas heating mode. On the other hand, if the indoor temperature Tin is within the allowable temperature range including the set temperature Tset (YES in step S22), the control device 100 proceeds to step S23. In step S23, the control device 100 gradually or stepwise reduces the rotation speed TGNC of the compressor 2 to reduce the current heating capacity in the hot gas heating mode.

[0059] The hot gas heating mode can continue stable operation by maintaining a balance between the amount of heat input and the amount of heat released in the refrigerant circuit 10, and there is a lower limit to the rotation speed TGNC of the compressor 2 that is required to maintain this balance. The control device 100 calculates the minimum rotation speed TGNC_LL, which is the lower limit of the rotation speed TGNC of the compressor 2 that can continue to operate stably in the hot gas heating mode, or stores this in advance in, for example, the ROM 102.

[0060] Therefore, the control device 100 monitors whether the rotation speed TGNC of the compressor 2 has reached the minimum rotation speed TGNC_LL so that the rotation speed TGNC does not fall below the minimum rotation speed TGNC_LL (step S24). The control device 100 reduces the rotation speed TGNC of the compressor 2 until it reaches the minimum rotation speed TGNC_LL (NO in step S24), and proceeds to step S25 when the rotation speed TGNC reaches the minimum rotation speed TGNC_LL (YES in step S24). In this way, the heating capacity in the hot gas heating mode can be reduced as much as possible by controlling the compressor 2, while the operating state in the hot gas heating mode can be stably continued.

[0061] In step S25, the control device 100 determines whether it is desirable to transition from the hot gas heating mode to the endothermic heating mode (step S25). That is, in this determination, the control device 100 determines whether it is desirable to transition the operating mode to reduce the power consumption of the automotive air conditioner 1, taking into account, in particular, the outside air temperature Tam, the interior temperature Tin, the operating state in the hot gas heating mode, the current heating capacity, etc. If the control device 100 does not wish to transition the operating mode (NO in step S25), it continues the hot gas heating mode (step S22).

[0062] If the control device 100 determines in step S25 that the mode should be transitioned from the hot gas heating mode to the endothermic heating mode (YES in step S25), the control device 100 proceeds to step S26. When the control device 100 determines that the mode should be transitioned from the hot gas heating mode to the endothermic heating mode, the control device 100 preferably controls the air damper 25 so that the ratio of inside air is higher than the ratio of inside / outside air in step S21 described above. By increasing the ratio of inside air, the heating load can be reduced.

[0063] In step S26, the current heating capacity in the hot gas heating mode and the heating capacity in the endothermic heating mode estimated based on the outside air temperature Tam, which is the target of heat absorption by the external heat exchanger 11, are obtained, the difference between these heating capacities (hereinafter referred to as the difference value ΔQ) is calculated, and it is determined whether the difference value ΔQ is greater than or equal to a predetermined value Qth.

[0064] In this embodiment, because the rotation speed TGNC of the compressor 2 is reduced to the minimum rotation speed TGNC_LL in the hot gas heating mode, the current heating capacity in the hot gas heating mode obtained in step S26 is the lowest heating capacity that can be achieved by controlling the rotation speed TGNC of the compressor 2. When transitioning from this state to the endothermic heating mode, if the difference value ΔQ is equal to or greater than the predetermined value Qth (YES in step S26), the control device 100 controls the air damper 24 to reduce the difference value ΔQ, that is, to reduce the heating capacity in the hot gas heating mode (step S27). Note that if the difference value ΔQ is less than the predetermined value Qth (NO in step S26), the mode is transitioned to the endothermic heating mode (step S29).

[0065] As mentioned above, when comparing the range of heating capacity obtained by controlling compressor 2 in hot gas heating mode and endothermic heating mode, the minimum heating capacity in hot gas heating mode and the maximum heating capacity in endothermic heating mode do not overlap, and the minimum heating capacity in hot gas heating mode is higher than the maximum heating capacity in endothermic heating mode.

[0066] In this embodiment, the rotation speed TGNC of the compressor 2 is reduced to the minimum rotation speed TGNC_LL, so that in step S27 the control device 100 controls the air damper 24 so that the proportion of air blown to the indoor heat exchanger 21 is reduced, thereby further reducing the heating capacity of the hot gas heating mode and reducing the difference value ΔQ.

[0067] By controlling the air damper 24 in this manner, the proportion of air blown to the flow path that bypasses the indoor heat exchanger 21 increases, thereby lowering the temperature of air blown into the vehicle cabin. Therefore, by controlling the air damper 24, the difference value ΔQ is reduced and the temperature of air blown in the hot gas heating mode is lowered, thereby suppressing large fluctuations when the operation mode is changed.

[0068] The control device 100 monitors the difference value ΔQ while driving the air damper 24 (step S28) and drives the air damper 24 until the difference value ΔQ becomes less than the predetermined value Qth (NO in step S28). When the difference value ΔQ becomes less than the predetermined value Qth (YES in step S28), the control device 100 transitions from the hot gas heating mode to the endothermic heating mode (step S29).

[0069] In this way, in the vehicle air conditioner 1 according to this embodiment, when the mode is switched from the hot gas heating mode to the endothermic heating mode, the control device 100 controls the difference between the heating capacity in the hot gas heating mode and the heating capacity in the endothermic heating mode so as to reduce the difference in heating capacity between the hot gas heating mode and the endothermic heating mode. This reduces large fluctuations in the outlet temperature due to the difference in heating capacity, thereby improving passenger comfort.

[0070] The control device 100 reduces the heating capacity as much as possible by controlling the rotation speed TGNC of the compressor 2, and further controls the air damper 24 to reduce the difference in heating capacity. As a result, the operating state of the hot gas heating mode does not fluctuate significantly, and the hot gas heating mode can be stably continued while smoothly transitioning to the endothermic heating mode, thereby improving passenger comfort.

[0071] As described above, according to this embodiment, the hot gas heating mode is stably continued, and fluctuations in the blown air temperature during the transition from the hot gas heating mode to the endothermic heating mode are suppressed, thereby improving the comfort of the occupants.

[0072] 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.

[0073] 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: Refrigerant temperature sensor, 44, 44A, 44B: 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 conditioner comprising: a refrigerant circuit including a compressor, an indoor heat exchange unit, an external heat exchange unit, and a hot gas bypass that reduces the pressure of 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; an air conditioning unit in which the indoor heat exchange unit is disposed, and which has a blower and an air damper that adjusts the proportion of air blown by the blower to the indoor heat exchange unit; and a control device that controls the refrigerant circuit and the air conditioning unit, and is capable of executing an endothermic heating mode in which the refrigerant compressed by the compressor dissipates heat in the indoor heat exchange unit and then absorbs heat in the external heat exchange unit, and a hot gas heating mode in which a portion of the refrigerant compressed by the compressor flows through the hot gas bypass and is returned to the compressor, and the remainder dissipates heat in the indoor heat exchange unit, wherein the control device, when transitioning from the hot gas heating mode to the endothermic heating mode, When a difference between a current heating capacity in the hot gas heating mode and a heating capacity in the heat absorption heating mode estimated based on a temperature of a heat absorption target by the external heat exchanger is equal to or greater than a predetermined value, the air damper is driven to reduce the current heating capacity in the hot gas heating mode.

2. The vehicle air conditioning system of claim 1, wherein, when transitioning from hot gas heating mode to endothermic heating mode, if a difference between the heating capacity when driving the compressor at a preset minimum rotation speed in the hot gas heating mode and the heating capacity in the endothermic heating mode estimated based on the temperature of the heat absorption target by the external heat exchanger is equal to or greater than a predetermined value, the control device controls the compressor to be driven at the minimum rotation speed and drives the air damper to reduce the current heating capacity in the hot gas heating mode.

3. The vehicle air conditioning system according to claim 1 or 2, wherein the control device controls the air damper so as to reduce the proportion of air blown to the indoor heat exchanger.

4. A vehicle air conditioning system as claimed in claim 1 or claim 2, wherein the air conditioning unit has an inside / outside air switching damper that controls the ratio of air introduced into the vehicle cabin and air introduced outside the vehicle cabin, and the control device increases the ratio of air introduced into the vehicle cabin by using the inside / outside air switching damper when transitioning from the hot gas heating mode to the endothermic heating mode.

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