Vehicular air conditioner

Abstract

To suppress mutual interference in driving states of objects to be controlled to improve comfort of a user.SOLUTION: A vehicular air conditioner is provided with a refrigerant circuit including a compressor, an indoor heat exchange part and an external heat exchange part, and a control device that controls the refrigerant circuit. The refrigerant circuit has a hot gas bypass that decompresses at least some of refrigerants compressed by the compressor and returns the refrigerants to the compressor, without going through the indoor heat exchange part and the external heat exchange part, and a flow volume adjusting part that adjusts flow volumes of the refrigerants flowing through the hot gas bypass. The control device can execute a hot gas heating mode in which some of the refrigerants compressed by the compressor are flown to the indoor heat exchange part and the remainder is flown to the hot gas bypass. In the hot gas heating mode, when pressure of the refrigerant at a high pressure-side in the refrigerant circuit becomes equal to a predetermined threshold or lower, control of either or both of an air blower that blows air to the indoor heat exchange part and the flow volume adjusting part is restricted.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an air conditioner for a vehicle. [Background technology]

[0002] In recent years, vehicles such as hybrid cars and electric cars that drive a driving motor with power supplied from a battery mounted on the vehicle have become widespread. As a vehicle air conditioner mounted on such vehicles, one that uses a heat pump (refrigerant circuit) as a heat source is known.

[0003] In a vehicle air conditioner using a heat pump, an external heat exchanger functions as a heat absorber during heating operation to obtain a heating heat source from outside air. Therefore, when the outside air temperature becomes extremely low, it becomes difficult to absorb heat from the outside air, and the heating capacity is significantly reduced. In response to this, hot gas heating is known as an effective heating method in an extremely low temperature environment, which does not absorb heat from the outside air, but uses a high-temperature, high-pressure refrigerant discharged from a compressor in a refrigerant circuit.

[0004] For example, in the vehicle air conditioner of Patent Document 1, the heat pump circulates the refrigerant to perform hot gas heating operation as follows: In other words, in the heat pump, part of the high-temperature, high-pressure refrigerant discharged from the compressor flows through a bypass flow path to be decompressed and then returned to the compressor, and the remainder is heat exchanged with air to be blown into the vehicle cabin in an indoor heat exchanger, after which it is decompressed and returned to the compressor without passing through an external heat exchanger. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2023-46604 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the vehicle air conditioning system as described above, during hot gas heating operation, the compressor is controlled so that the outlet refrigerant pressure of the indoor heat exchanger becomes the target outlet refrigerant pressure, the flow control valve of the bypass flow path is controlled so that the suction refrigerant pressure of the refrigerant sucked into the compressor becomes the target suction refrigerant pressure, and the blower is controlled so that the actual heating capacity becomes the target heating capacity.

[0007] However, since the compressor, the flow control valve, and the blower, which are the objects of control, are each controlled independently, they may interfere with each other depending on their driving state. For example, when the compressor is driven at the maximum rotation speed to set the outlet refrigerant pressure to the target outlet refrigerant pressure, if the flow control valve is simultaneously controlled in the opening direction to make the suction refrigerant pressure reach the target suction refrigerant pressure, the flow rate of the refrigerant to the indoor heat exchanger decreases, the outlet refrigerant pressure decreases, and the blowing temperature of the air blown into the passenger compartment decreases.

[0008] Similarly, when the compressor is operated at the maximum rotation speed to set the outlet refrigerant pressure to the target outlet refrigerant pressure, if the blower is controlled to increase the air volume to set the heating capacity to the target heating capacity at the same time, the blown air volume is large compared to the amount of heat dissipated by the refrigerant in the indoor heat exchanger, and the blown temperature drops. In this way, if the blown temperature fluctuates due to the mutual interference of the drive states of the control objects, the comfort of the user will be impaired.

[0009] The present invention has been made in consideration of the above circumstances, and has as its object to suppress mutual interference between the driving states of each controlled object and improve user comfort. [Means for solving the problem]

[0010] The present invention provides a vehicle air conditioning system including a refrigerant circuit including a compressor, an indoor heat exchange unit, and an external heat exchange unit, and a control unit that controls the refrigerant circuit, the refrigerant circuit having a hot gas bypass that decompresses and returns at least a portion of the refrigerant compressed by the compressor to the compressor without passing through the indoor heat exchange unit and the external heat exchange unit, and a flow rate adjustment unit that adjusts the flow rate of the refrigerant flowing through the hot gas bypass, the control unit being capable of executing a hot gas heating mode in which a portion of the refrigerant compressed by the compressor flows through the indoor heat exchange unit and the remainder flows through the hot gas bypass, and in the hot gas heating mode, when the high-pressure side refrigerant pressure of the refrigerant circuit falls below a predetermined threshold, the control unit limits control of either or both of a blower that blows air to the indoor heat exchange unit and the flow rate adjustment unit. Effect of the Invention

[0011] According to the present invention, it is possible to suppress mutual interference between the drive states of each controlled object, and improve comfort for the user. [Brief description of the drawings]

[0012] [Figure 1] 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; [Diagram 2] 1 is an explanatory diagram showing a control device for a vehicle air conditioner according to an embodiment of the present invention; [Diagram 3] 1 is a diagram showing the configuration of a control device and the like in an electric vehicle (EV) according to an embodiment of the present invention. [Figure 4] FIG. 4 is an explanatory diagram showing the operation of the refrigerant circuit during endothermic heating operation in the vehicle air conditioner according to the embodiment of the present invention. [Diagram 5] FIG. 4 is an explanatory diagram showing the operation of the refrigerant circuit during hot gas heating operation in the vehicle air conditioner according to the embodiment of the present invention. [Figure 6] Graph showing an example of the behavior of the outlet refrigerant pressure of the indoor heat exchanger, the suction refrigerant pressure of the compressor, the compressor rotation speed, the opening degree of the second pressure reduction section, and the blowing temperature during hot gas heating operation using a control method according to a reference example. [Figure 7] Graphs showing an example of the outlet refrigerant pressure of the indoor heat exchanger, the suction refrigerant pressure of the compressor, the compressor rotation speed, the opening degree of the second pressure reduction section, and the blowing temperature during hot gas heating operation using the control method of an embodiment of the present invention. [Figure 8] Graphs showing an example of the behavior of the outlet refrigerant pressure of the indoor heat exchanger, the suction refrigerant pressure of the compressor, the compressor rotation speed, the blower air volume, and the blowing temperature during hot gas heating operation using a control method according to a reference example. [Figure 9] Graphs showing an example of the outlet refrigerant pressure of the indoor heat exchanger, the suction refrigerant pressure of the compressor, the compressor rotation speed, the blower air volume, and the blowing temperature during hot gas heating operation using the control method of an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 functions, and duplicated descriptions in each drawing will be omitted as appropriate. In the drawings, the thick black lines in the refrigerant circuit 10 indicate refrigerant flow paths through which high-pressure refrigerant flows, and the outline lines indicate refrigerant flow paths through which refrigerant flows after decompression. In addition, the dashed lines in the refrigerant circuit 10 indicate refrigerant flow paths through which refrigerant does not flow.

[0014] [Refrigerant circuit configuration, etc.] 1 shows a configuration example of a vehicle air conditioner 1 according to an embodiment of the present invention. The configuration example shown here is just one example, and the present invention is not particularly 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 cabin, which are arranged along a refrigerant flow path. The indoor heat exchangers 21 and 22 are provided for heat exchange between the air flowing through the air conditioning unit 20 and the refrigerant, and the external heat exchanger 11 is provided for heat exchange between the outside air and the refrigerant outside the vehicle cabin. The indoor heat exchanger 21 is for heating the air, and the indoor heat exchanger 22 is for cooling the air. A refrigerant pressure sensor 44B is provided immediately downstream of the indoor heat exchanger 21 to detect an outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) from the indoor heat exchanger 21.

[0016] The compressor 2 compresses the refrigerant and circulates it through the refrigerant circuit 10. The refrigerant compressed by the compressor 2 is reduced in pressure to a required level by passing through a first pressure reducing section V1, a second pressure reducing section V2, a third pressure reducing section V3, and a fourth pressure reducing section V4, which are, for example, expansion valves, in an appropriately selected refrigerant flow path. 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. An accumulator 16 is provided immediately upstream of the compressor 2 in the refrigerant circuit 10 to recover liquid refrigerant and separate the refrigerant into gas and liquid. A refrigerant pressure sensor 44A is provided between the accumulator 16 and the compressor 2 to detect a suction refrigerant pressure Ps (low-pressure side refrigerant pressure) sucked into the compressor 2.

[0017] As described above, the air conditioning unit 20 includes the indoor heat exchangers 21, 22 therein, and air introduced from the room or the outside by the blower 23 passes through the indoor heat exchangers 21, 22 and is blown into the room. The air conditioning unit 20 is provided with an air damper 24. When the air damper 24 shown in FIG. 1 is fully open, the air introduced by the blower 23 passes through both the indoor heat exchangers 21, 22 and is blown into the room.

[0018] When the air damper 24 is fully closed, it blocks the intake side of the indoor heat exchanger 21, and the air introduced by the blower 23 passes only through the indoor heat exchanger 22 before being blown out into the room. Another air damper 25 provided in the air conditioning unit 20 switches the air introduced into the blower 23 between indoor and outdoor. The air damper 25 can selectively close air inlet 25A connected to the outdoors and air inlet 25B connected to the indoors to take in air from either one of them. Also, by placing the air damper 25 in an intermediate position, it is possible to take in air from both air inlet 25A and air inlet 25B.

[0019] Although the above-mentioned external heat exchanger 11 and indoor heat exchangers 21, 22 are described as examples in which the refrigerant and air directly exchange heat, the refrigerant and air may indirectly exchange heat 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 dissipate heat to the air via the heat medium.

[0020] As shown in Fig. 1, the vehicle air conditioner 1 includes a heat medium circuit 30. The heat medium circuit 30 circulates the 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 control object such as a battery using a temperature control 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 in 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 necessary.

[0021] [Control device] 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 described above, based on various input signals (such as an air conditioning instruction signal and a charger connection signal) and detection signals from a sensor section 40.

[0022] The sensor section 40, which inputs detection signals to the control device 100, includes, for example, an outside air sensor 41 which detects outside air conditions such as outside air temperature and outside air humidity, a compressor current sensor 42 for detecting the power consumption (energy consumption) of the compressor 2, a refrigerant temperature sensor 43 and a refrigerant pressure sensor 44 which detect the state of the refrigerant, an occupant sensor 45 which detects the presence or absence of an occupant in the vehicle cabin, and a blower temperature sensor 46 which detects the blower temperature of the air conditioning unit 20.

[0023] In particular, the refrigerant pressure sensor 44 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 merely examples, and various sensors that detect information required when the control device 100 performs various controls are provided as the sensor unit 40.

[0024] The control targets of the control device 100 are the compressor 2, the first pressure reducing section V1, the second pressure reducing section V2, the third pressure reducing section V3, the fourth pressure reducing 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. In the vehicle air conditioner 1, the control device 100 can switch between an endothermic heating operation in which the refrigerant absorbs heat in the external heat exchanger 11, and a hot gas heating operation in which the refrigerant compressed by the compressor 2 is allowed to dissipate heat in the indoor heat exchanger 21 without absorbing heat in the refrigerant in the external heat exchanger 11 to heat the vehicle interior.

[0025] [Configuration of control device in electric vehicle (EV)] 3, the control device 100 provided in the vehicle air conditioner 1 is configured as one 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 input / output I / F (Interface) 104, an in-vehicle communication I / F (Interface) 105, and the like, and each piece of hardware is connected to each other via a bus 106.

[0026] The CPU 101 executes various programs stored in the ROM 102 to control the control device 100. 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 DRAM (Dynamic Random Access Memory) or an SRAM (Static Random Access Memory).

[0027] For example, the RAM 103 functions as a working area used by the CPU 101 when executing a program. The input / output I / F 104 is connected to various sensors and monitors installed in the EV, and inputs data to the CPU 101 and outputs data processed by the CPU 101. The in-vehicle communication I / F 105 is connected to an in-vehicle network L to control data transmission and reception with other ECUs set in the EV.

[0028] The control device 100 controls the above-mentioned vehicle air conditioner 1 by a program executed by the CPU 101 when data related to surrounding environmental information or data related to the driving status of the EV is input via the input / output I / F 104 or the in-vehicle communication I / F 105.

[0029] 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.

[0030] [Endothermic heating operation] The operation of the refrigerant circuit 10 in endothermic heating operation will be described with reference to Fig. 4. In the refrigerant circuit 10 in endothermic heating operation, 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. On the other hand, the flow path switching valve 13 is fully open, and the first pressure reduction section V1 is open.

[0031] In the endothermic heating operation, 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, and 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 a 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, the 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.

[0032] [Hot gas heating operation] At extremely low temperatures, hot gas heating is used because it is difficult for the external heat exchanger 11 to absorb heat. In hot gas heating operation, the refrigerant compressed by the compressor 2 is not allowed to absorb heat in the external heat exchanger 11, but some or all of the refrigerant is caused to dissipate heat in the indoor heat exchanger 21 to heat the vehicle interior.

[0033] The operation of the refrigerant circuit 10 in hot gas heating operation will be described with reference to Fig. 5. 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 path switching valve 12, is depressurized 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 the refrigerant does not flow to the external heat exchanger 11. Also, the fourth pressure reduction section V4 is fully closed, so that the 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 can be 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. In addition, 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, the balance between the amount of heat radiation from the refrigerant circuit 10 and the amount of heat input to the compressor 2 can be maintained. 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] During hot gas heating operation, the refrigerant flow in the flow path passing through the indoor heat exchanger 21 is decompressed in the third decompression section V3, so that the refrigerant upstream of that becomes high pressure refrigerant and the refrigerant downstream of that becomes low pressure refrigerant. At this time, it is important in order to maintain the heating capacity that heat exchange is not performed in the refrigerant heat medium heat exchanger 34 in the low pressure side flow path. In the air conditioning unit 20, the air introduced by the blower 23 is heated by heat radiation in the indoor heat exchanger 21 and is blown out into the vehicle cabin.

[0037] [Control during hot gas heating operation] In the vehicle air conditioner 1, during hot gas heating operation, the compressor 2 is controlled so that the high-pressure side refrigerant pressure of the refrigerant circuit 10 (such as the outlet refrigerant pressure Pci of the indoor heat exchanger 21 and the discharge refrigerant pressure of the compressor 2) becomes a target pressure, the second pressure reduction section V2 provided in the hot gas bypass 10V is controlled so that the low-pressure side refrigerant pressure of the refrigerant circuit (such as the suction refrigerant pressure Ps of the compressor 2) becomes a target pressure, and the blower 23 is controlled so that the actual heating capacity Qhp of the vehicle air conditioner 1 becomes the target heating capacity TGQh.

[0038] That is, the control device 100 independently controls the compressor 2, the second decompression section V2, and the blower 23, which are the objects to be controlled. Here, the actual heating capacity Qhp is calculated from the high-pressure side refrigerant pressure and the air blowing volume Af, and the target heating capacity TGQh is calculated from the target pressure of the high-pressure side refrigerant pressure and the air blowing volume Af. Hereinafter, the control of the compressor 2, the second pressure reducing section V2, and the blower 23 in the vehicle air conditioner 1 will be described while comparing with a reference example.

[0039] (Control method according to reference example 1) Fig. 6 shows a graph illustrating an example of the behavior of the outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) of the indoor heat exchanger 21, the suction refrigerant pressure Ps (low-pressure side refrigerant pressure) of the compressor 2, the target rotation speed TGNC of the compressor 2, the target opening TGECCVdis of the second pressure reducing section V2, and the blowing temperature Tv during hot gas heating operation using the control method according to Reference Example 1. In the example of Fig. 6, the air flow rate Af of the blower 23 is constant from period A to period D, so the behavior is not shown.

[0040] During period A of the graph shown in Figure 6, the control device 100 controls the compressor 2 to operate at the maximum rotational speed and controls the second pressure reduction section V2 to be at a substantially constant target opening degree TGECCVdis (hereinafter simply referred to as "opening degree"). In response to this, both the outlet refrigerant pressure Pci and the suction refrigerant pressure Ps increase.

[0041] During period B, since the outlet refrigerant pressure Pci does not reach the target pressure region of the target outlet refrigerant pressure PCO (the range from PCO-α, which is lower than the target outlet refrigerant pressure PCO by a predetermined value α, to PCO+α, which is higher than the target outlet refrigerant pressure PCO by a predetermined value α; see Figure 6), the control device 100 controls the compressor 2 to continue operating at the maximum rotation speed.

[0042] The target pressure region of the target outlet refrigerant pressure PCO is a predetermined allowable range of pressure values ​​for the target outlet refrigerant pressure PCO, and although it does not completely match the target outlet refrigerant pressure PCO, it is a region that includes the lower limit value to the upper limit value of the pressure value that can tolerate deviation from the target outlet refrigerant pressure PCO.

[0043] Since the suction refrigerant pressure Ps has not yet reached the target pressure region of the target suction refrigerant pressure PSO (the range from PSO-α, which is a predetermined value α lower than the target suction refrigerant pressure PSO, to PSO+α, which is a predetermined value α higher than the target suction refrigerant pressure PSO; see Figure 6), and the suction refrigerant pressure Ps is increasing slowly, the control device 100 controls the second pressure reduction section V2 to be driven in the opening direction in order to make the suction refrigerant pressure Ps reach the target suction refrigerant pressure PSO more quickly. As a result, the amount of refrigerant flowing to the indoor heat exchanger 21 decreases, so that even though the compressor 2 is driven at the maximum rotation speed, the outlet refrigerant pressure Pci tends to decrease, and the blowing temperature Tv also tends to decrease.

[0044] The target pressure region of the target suction refrigerant pressure PSO is a predetermined allowable range of pressure values ​​for the target suction refrigerant pressure PSO, and although it does not completely match the target suction refrigerant pressure PSO, it is a region that includes the lower limit value to the upper limit value of the pressure value that can tolerate deviation from the target suction refrigerant pressure PSO.

[0045] Thereafter, in Periods C and D, the compressor 2 continues to be driven at the maximum rotation speed, and the second pressure reducing section V2 is maintained at a larger opening than in Period A, but the outlet refrigerant pressure Pci and the suction refrigerant pressure Ps continue to decrease, and the blown temperature Tv also continues to decrease. Then, in Period D, the amount of decrease in the blown temperature Tv becomes large (arrow d in FIG. 6), and the user's comfort is impaired.

[0046] (Control method according to reference example 2) Fig. 7 shows a graph illustrating an example of the behavior of the outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) of the indoor heat exchanger 21, the suction refrigerant pressure Ps (low-pressure side refrigerant pressure) of the compressor 2, the target rotation speed TGNC of the compressor 2, the blower air volume Af of the blower 23, and the blowing temperature Tv during hot gas heating operation using the control method according to Reference Example 2. In the example of Fig. 7, the target opening TGECCVdis of the second pressure reducing section V2 is constant from Period A to Period D, so the behavior is not shown.

[0047] During period A of the graph shown in Figure 7, the control device 100 controls the compressor 2 to operate at the maximum rotation speed and controls the air blowing volume Af of the blower 23 to be approximately constant, and accordingly, both the outlet refrigerant pressure Pci and the suction refrigerant pressure Ps increase.

[0048] During period B, since the outlet refrigerant pressure Pci does not reach the target pressure region of the target outlet refrigerant pressure PCO (the range from the target outlet refrigerant pressure PCO-α to the target outlet refrigerant pressure PCO+α in Figure 7), the control device 100 controls the compressor 2 to continue operating at the maximum rotation speed.

[0049] Because the outlet refrigerant pressure Pci has not reached the target pressure region of the target outlet refrigerant pressure PCO, it can be determined that the actual heating capacity Qhp has not reached the target heating capacity TGQh, but because the compressor 2 is driven at the maximum rotation speed, the actual heating capacity Qhp cannot be increased by controlling the driving state of the compressor 2. Therefore, in order to make the actual heating capacity Qhp reach the target heating capacity TGQh more quickly, the control device 100 controls the blower 23 to increase the air flow rate Af when transitioning from Period A to Period B.

[0050] As a result, during period B, the amount of air passing through the indoor heat exchanger 21 increases and the actual heating capacity Qhp increases. However, since the amount of air passing through the indoor heat exchanger 21 Af is greater than the amount of refrigerant flowing through the indoor heat exchanger 21, even though the compressor 2 is driven at the maximum rotation speed, the outlet refrigerant pressure Pci tends to decrease and the blowing temperature Tv also tends to decrease.

[0051] Thereafter, in periods C and D, the compressor 2 continues to be driven at the maximum rotation speed, and the airflow rate Af of the blower 23 is maintained constant at a level greater than that in period A, but the outlet refrigerant pressure Pci and suction refrigerant pressure Ps continue to decrease, and the blown temperature Tv also continues to decrease. Then, in period D, the amount of decrease in the blown temperature Tv becomes large (arrow d in FIG. 7), causing a loss of comfort for the user.

[0052] In this way, the compressor 2, the second pressure reducing section V2, and the blower 23, which are the objects of control, are controlled independently of each other, and therefore may interfere with each other depending on the driving state of each object of control. In particular, if the high-pressure side refrigerant pressure of the refrigerant circuit 10 cannot reach the target pressure, or if the high-pressure side refrigerant pressure starts to decrease, the blowing temperature Tv from the air conditioning unit 20 also decreases, which reduces the comfort of the user.

[0053] (Control method according to this embodiment) Therefore, in this embodiment, the control device 100 prioritizes control so that the high-pressure side refrigerant pressure of the refrigerant circuit 10 becomes a target pressure during hot gas heating operation, and restricts control of the second pressure reduction unit V2 and the blower 23 if the control would cause the high-pressure side refrigerant pressure of the refrigerant circuit 10 to move away from the target pressure. That is, the control device 100 restricts control of either or both of the second pressure reduction unit V2 and the blower 23 when the high-pressure side refrigerant pressure of the refrigerant circuit 10 is equal to or lower than a predetermined threshold during hot gas heating operation.

[0054] (1) Example 1 Fig. 8 shows a graph illustrating an example of the behavior of the outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) of the indoor heat exchanger 21, the suction refrigerant pressure Ps (low-pressure side refrigerant pressure) of the compressor 2, the target rotation speed TGNC of the compressor 2, the target opening TGECCVdis of the second pressure reducing section V2, and the blowing temperature Tv during hot gas heating operation by the control method according to Example 1. In the example of Fig. 8, the air flow rate Af of the blower 23 is constant from period A to period D, so the behavior is not shown.

[0055] During period A of the graph shown in Figure 8, the control device 100 controls the compressor 2 to operate at the maximum rotational speed and controls the second pressure reduction section V2 to have a substantially constant opening degree, and accordingly, both the outlet refrigerant pressure Pci and the suction refrigerant pressure Ps increase.

[0056] During period A, the outlet refrigerant pressure Pci has not reached the target pressure region of the target outlet refrigerant pressure PCO (the range from the target outlet refrigerant pressure PCO-α to the target outlet refrigerant pressure PCO+α in Figure 8), and the suction refrigerant pressure Ps has not reached the target pressure region of the target suction refrigerant pressure PSO (the range from the suction refrigerant pressure PSO-α to the suction refrigerant pressure PSO+α in Figure 8).

[0057] When transitioning from Period A to Period B, the control device 100 controls the upper limit value of the opening degree of the second pressure reduction unit V2 in Period B to the current opening degree (the opening degree of the second pressure reduction unit V2 in Period A) because the outlet refrigerant pressure Pci in Period A did not reach the target pressure region of the target outlet refrigerant pressure PCO, i.e., was equal to or lower than a predetermined threshold value. In other words, the control device 100 prohibits control of the second pressure reduction unit V2 in the opening direction.

[0058] As a result, during period B, the suction refrigerant pressure Ps does not reach the target pressure region of the target suction refrigerant pressure PSO and remains approximately constant while not meeting the target pressure region of the target suction refrigerant pressure PSO, but the decrease in the outlet refrigerant pressure Pci caused by the control of the second pressure reduction section V2 can be suppressed.

[0059] In the example of Figure 8, during period B, the control device 100 controls the compressor 2 to continue operating at the maximum rotational speed, which causes the outlet refrigerant pressure Pci to rise gradually and reach the target pressure region of the target outlet refrigerant pressure PCO between periods B and C. As a result, the blown air temperature Tv during periods A and B in FIG. 8 hardly changes, so that the comfort of the user can be improved.

[0060] Since the outlet refrigerant pressure Pci reaches the target pressure region of the target outlet refrigerant pressure PCO between Period B and Period C, the control device 100 controls the second pressure reducing unit V2 to be driven in the direction of opening more than the current opening in Period C. As a result, the suction refrigerant pressure Ps rises, and the outlet refrigerant pressure Pci also rises accordingly, and between Period C and Period D, the outlet refrigerant pressure Pci reaches the target outlet refrigerant pressure PCO and the suction refrigerant pressure Ps also reaches the target suction refrigerant pressure PSO. At this time, the compressor 2 continues to be driven at the maximum rotation speed, the second pressure reducing unit V2 is maintained constant at a larger opening than in Period B, the hot gas heating operation is stably performed, and the fluctuation of the blowing temperature Tv is reduced.

[0061] (2) Example 2 Fig. 9 shows a graph illustrating an example of the behavior of the outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) of the indoor heat exchanger 21, the suction refrigerant pressure Ps (low-pressure side refrigerant pressure) of the compressor 2, the target rotation speed TGNC of the compressor 2, the blower air volume Af of the blower 23, and the blowing temperature Tv during hot gas heating operation using the control method according to Example 2. In the example of Fig. 9, the target opening TGECCVdis of the second pressure reducing section V2 is constant from period A to period D, so the behavior is not shown.

[0062] During period A of the graph shown in Figure 9, the control device 100 controls the compressor 2 to operate at the maximum rotational speed and controls the air flow rate Af of the blower 23 to be approximately constant, and accordingly, both the outlet refrigerant pressure Pci and the suction refrigerant pressure Ps increase.

[0063] During period A, the outlet refrigerant pressure Pci has not reached the target pressure region of the target outlet refrigerant pressure PCO (the range from the target outlet refrigerant pressure PCO-α to the target outlet refrigerant pressure PCO+α in Figure 8), and the suction refrigerant pressure Ps has not reached the target pressure region of the target suction refrigerant pressure PSO (the range from the suction refrigerant pressure PSO-α to the suction refrigerant pressure PSO+α in Figure 8).

[0064] When transitioning from Period A to Period B, since the outlet refrigerant pressure Pci in Period A did not reach the target pressure region of the target outlet refrigerant pressure Pco, i.e., was equal to or lower than a predetermined threshold, the control device 100 controls the upper limit value of the air flow rate Af by the blower 23 in Period B to the current air flow rate Af (air flow rate Af of the blower 23 in Period A). In other words, the control device 100 controls the air flow rate Af by the blower 23 not to increase.

[0065] As a result, during period B, the suction refrigerant pressure Ps does not reach the target pressure region of the target suction refrigerant pressure PSO and remains approximately constant while not meeting the target pressure region of the target suction refrigerant pressure PSO, but the decrease in the outlet refrigerant pressure Pci caused by the control of the blower 23 can be suppressed.

[0066] In the example of Figure 8, during period B, the control device 100 controls the compressor 2 to continue operating at the maximum rotational speed, which causes the outlet refrigerant pressure Pci to rise gradually and reach the target pressure region of the target outlet refrigerant pressure PCO between periods B and C. As a result, the blown air temperature Tv during periods A and B in FIG. 8 hardly changes, so that the comfort of the user can be improved.

[0067] Since the outlet refrigerant pressure Pci reaches the target pressure region of the target outlet refrigerant pressure Pco between Period B and Period C, the control device 100 controls the blower 23 to increase the air flow rate Af from the current air flow rate Af in Period C. This increases the actual heating capacity Qhp, and therefore the blowing temperature Tv, the suction refrigerant pressure Ps, and the outlet refrigerant pressure Pci increase.

[0068] Between Period C and Period D, the outlet refrigerant pressure Pci reaches the target outlet refrigerant pressure PCO, and the suction refrigerant pressure Ps reaches the target suction refrigerant pressure PSO. At this time, the compressor 2 continues to operate at the maximum rotation speed, and the blower 23 is controlled to maintain a blowing volume Af larger than in Periods A and B. The hot gas heating operation is performed stably, and the fluctuation of the blowing temperature Tv becomes small.

[0069] In the above-mentioned first and second embodiments, examples have been described in which the control of the second pressure reduction unit V2 or the blower 23 is limited when the high-pressure side refrigerant pressure of the refrigerant circuit 10 is equal to or lower than a predetermined threshold value, but the control of the second pressure reduction unit V2 and the blower 23 can also be limited simultaneously. Furthermore, when the high-pressure side refrigerant pressure of the refrigerant circuit 10 is equal to or lower than a predetermined threshold value, the control device 100 can also perform control to prohibit driving in the opening direction of the third pressure reduction unit V3, which reduces the pressure of the refrigerant that has flowed through the indoor heat exchanger 21. The control device 100 can also limit the control of the third pressure reduction unit V3 together with the second pressure reduction unit V2.

[0070] Thus, according to this embodiment, during hot gas heating operation, priority is given to controlling the high-pressure side refrigerant pressure of the refrigerant circuit 10 to a target pressure, and if control of the second pressure reduction section V2 and the blower 23 would cause the outlet refrigerant pressure Pci, i.e., the high-pressure side refrigerant pressure of the refrigerant circuit 10, to move away from the target pressure, such control is restricted.

[0071] In other words, during hot gas heating operation, when the high-pressure side refrigerant pressure of the refrigerant circuit 10 is below a predetermined threshold, the control device 100 limits control of either or both of the second pressure reduction section V2 and the blower 23, thereby suppressing mutual interference between the driving states of each controlled object and suppressing a decrease in the high-pressure side refrigerant pressure of the refrigerant circuit 10, thereby suppressing fluctuations in the blowing temperature Tv, thereby improving user comfort.

[0072] As described above, according to this embodiment, it is possible to suppress mutual interference between the drive states of the respective control targets, thereby improving user comfort.

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

[0074] 1: vehicle air conditioner, 2: compressor, 4: indoor heat exchanger, 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: heat exchanger to be temperature-controlled, 34: refrigerant / heat medium heat exchanger, 34A, 34B: flow paths 40: sensor unit, 41: outside air sensor, 42: compressor current sensor, 43: refrigerant temperature sensor 44, 44A, 44B: refrigerant pressure sensor, 45: occupant sensor, 46: blowing air temperature sensor 100: Control device

Claims

1. A vehicle air conditioner including a refrigerant circuit including a compressor, an interior heat exchanger, and an exterior heat exchanger, and a control device that controls the refrigerant circuit, The refrigerant circuit includes: a hot gas bypass that reduces the pressure of at least a portion of the refrigerant compressed by the compressor and returns the refrigerant to the compressor without passing through the indoor heat exchange unit and the external heat exchange unit; a flow rate adjusting unit that adjusts the flow rate of the refrigerant flowing through the hot gas bypass, The control device includes: A hot gas heating mode can be executed in which a part of the refrigerant compressed by the compressor flows into the indoor heat exchange section and the remainder flows into the hot gas bypass. In the hot gas heating mode, when the high-pressure side refrigerant pressure of the refrigerant circuit is below a predetermined threshold, control of either or both of a blower that blows air to the indoor heat exchange section and the flow rate adjustment section is limited.

2. 2. The vehicle air conditioning system according to claim 1, wherein the control device, in the hot gas heating mode, sets an upper limit value of the opening degree of the flow rate adjustment unit to a current opening degree when a refrigerant pressure on a high-pressure side of the refrigerant circuit is equal to or lower than a predetermined threshold value.

3. 2. The vehicle air conditioning system according to claim 1, wherein, in the hot gas heating mode, when a high-pressure side refrigerant pressure of the refrigerant circuit is equal to or lower than a predetermined threshold, the control device sets an upper limit value of the air blown by the blower to a current air blowing amount.

4. 2. The vehicle air conditioning system according to claim 1, wherein, in the hot gas heating mode, when a high-pressure side refrigerant pressure of the refrigerant circuit is equal to or lower than a predetermined threshold, the control device prohibits driving of a pressure reduction section in an opening direction, which reduces the pressure of the refrigerant that has flowed through the indoor heat exchange section.

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