Vehicular air conditioner

Abstract

To provide a vehicular air conditioner configured so that a compressor can be prevented from being driven in a state where pressure of a suctioned refrigerant is high to improve durability of the compressor.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 a portion of a refrigerant compressed by the compressor and returns the refrigerant 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 refrigerant flowing through the hot gas bypass. The control device can execute a hot gas heating mode in which the portion of the refrigerant compressed by the compressor is flown to the indoor heat exchange part and the other is flown to the hot gas bypass, which when determining that pressure of the refrigerant suctioned in the compressor overshoots, in the hot gas heating mode, controls an aperture of the flow volume adjusting part so that the aperture becomes a preset first aperture that is smaller than a current aperture.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 hot gas heating operation of the vehicle air conditioner described above, the heat input to the compressor can be adjusted by adjusting the flow rate of the refrigerant flowing through the bypass passage. Therefore, in the hot gas heating operation, the opening of the flow rate control valve provided in the bypass passage is controlled by feedforward control (hereinafter, FF control) and feedback control (hereinafter, FB control) so that the suction refrigerant pressure of the refrigerant sucked into the compressor approaches the target suction refrigerant pressure.

[0007] When controlling the suction refrigerant pressure by adjusting the opening of the flow control valve, if the suction refrigerant pressure rises, the flow control valve is controlled in the closing direction. However, if the suction refrigerant pressure suddenly rises due to, for example, an external disturbance, the control of the flow control valve may not be able to keep up, and the suction refrigerant pressure may overshoot.

[0008] When the suction refrigerant pressure overshoots, the outlet refrigerant pressure of the indoor heat exchanger also rises and may overshoot. When the suction refrigerant pressure reaches a high pressure equal to or higher than a predetermined value, a protection device stops the compressor to protect the compressor. When the compressor stops, even if the operation is restarted, it takes time for the operation to stabilize after the operation is restarted, so the temperature of the air blown into the vehicle cabin drops, reducing the comfort of the user. Even if the compressor does not stop, if hot gas heating is operated for a long time with a high suction refrigerant pressure, the durability of the compressor decreases and may lead to a breakdown.

[0009] The present invention has been made in consideration of the above circumstances, and has as its objective to prevent the compressor from being driven when the suction refrigerant pressure is high and to improve the durability of the compressor. [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, wherein the refrigerant circuit has a hot gas bypass that reduces the pressure of at least a portion of the refrigerant compressed by the compressor and returns it 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, and the control unit is 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 it is determined that the suction refrigerant pressure of the compressor will overshoot, the control unit controls the opening degree of the flow rate adjustment unit to a preset first opening degree that is smaller than the current opening degree. Effect of the Invention

[0011] According to the present invention, it is possible to prevent the compressor from being driven when the suction refrigerant pressure is high, and to improve the durability of the compressor. [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] 6 is a 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 rotation speed of the compressor, and the opening degree of the second pressure reducing section during hot gas heating operation using a control method according to a reference example. [Figure 7] FIG. 4 is a control mode transition diagram of the second pressure reducing unit during hot gas heating operation in the vehicle air conditioning system according to the embodiment of the present invention. [Figure 8] 5 is a flowchart showing a control flow of a second pressure reducing section during hot gas heating operation in the vehicle air conditioner according to the embodiment of the present invention. [Figure 9] 6 is a graph showing an example of behavior of the outlet refrigerant pressure of the indoor heat exchanger, the suction refrigerant pressure of the compressor, the rotation speed of the compressor, and the opening degree of the second pressure reducing section during hot gas heating operation by the control method according to the first embodiment. [Figure 10] 10 is a graph showing an example of behavior of the outlet refrigerant pressure of the indoor heat exchanger, the suction refrigerant pressure of the compressor, the rotation speed of the compressor, and the opening degree of the second pressure reducing section during hot gas heating operation according to Example 2. 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 of the second pressure reducing section V2 (flow rate adjusting section) during hot gas heating operation] In the vehicle air conditioner 1, during hot gas heating operation, the opening degree of the second pressure reduction section V2 provided in the hot gas bypass 10V is controlled so that the suction refrigerant pressure Ps of the compressor 2 of the refrigerant circuit 10 becomes the target suction refrigerant pressure PSO. Hereinafter, a control method for the second pressure reducing section V2 in the vehicle air conditioner 1 will be described while comparing with a reference example.

[0038] (Control method according to the reference example) 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, and the target opening TGECCVdis of the second pressure reduction section V2 when the second pressure reduction section V2 is controlled by a control method according to a reference example during hot gas heating operation. Note that the graph in Fig. 6 shows the change in the pressure value of the high-pressure side refrigerant as the behavior of the outlet refrigerant pressure Pci, and the change in the pressure value of the low-pressure side refrigerant as the behavior of the suction refrigerant pressure Ps.

[0039] The control device 100 can selectively execute the "open direction mode" and the "FF / FB mode" during hot gas heating operation, and controls the second pressure reduction unit V2 by switching between these two control modes. The open direction mode is a mode in which refrigerant starts to flow to the hot gas bypass 10V at the start of hot gas heating operation, and the FF / FB mode is a mode in which the opening degree of the second pressure reduction unit V2 is adjusted by FF control and FB control so that the suction refrigerant pressure Ps becomes the target suction refrigerant pressure PSO.

[0040] As shown in Fig. 6, when the hot gas heating operation starts, the control device 100 executes the opening direction mode to operate the second pressure reducing section V2 in the opening direction and circulates the refrigerant through the hot gas bypass 10V (period A in Fig. 6). When the suction refrigerant pressure Ps reaches a target pressure region including the target suction refrigerant pressure PSO (a range from PSO-α, which is lower than the target suction refrigerant pressure PSO by a predetermined value α, to PSO+α, which is higher than the target suction refrigerant pressure PSO by a predetermined value α, see Fig. 6), the control device 100 transitions to the FF / FB mode and adjusts the opening degree of the second pressure reducing section V2. In Fig. 6, the control device 100 executes the FF / FB mode from period B to period E.

[0041] 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.

[0042] In the FF / FB mode, the opening degree of the second pressure reducing section V2 is calculated while monitoring the suction refrigerant pressure Ps at a predetermined control cycle, and the second pressure reducing section V2 is controlled based on the calculated result. 6, the suction refrigerant pressure Ps is approximately equal to the target suction refrigerant pressure PSO, and the outlet refrigerant pressure Pci is approximately equal to the target outlet refrigerant pressure PCO. The rotation speed of the compressor 2 and the opening degree of the second pressure reducing section V2 are constant, and the vehicle air conditioner 1 continues the hot gas heating operation in a stable state.

[0043] Thereafter, when an external disturbance is input between periods B and C in Figure 6 and the suction refrigerant pressure Ps rises sharply, the control device 100 controls the second pressure reduction section V2 in the closing direction in FF / FB mode to bring the suction refrigerant pressure Ps closer to the target suction refrigerant pressure PSO.

[0044] However, in the case of a sudden rise in the suction refrigerant pressure Ps due to disturbances or the like, the control of the second pressure reducing section V2 in the FF / FB mode cannot keep up, and the suction refrigerant pressure Ps overshoots (exceeding the target pressure region of the target suction refrigerant pressure PSO in FIG. 6, i.e., exceeding PSO+α), and the overshooting state may continue for a long time. In addition, when the suction refrigerant pressure Ps overshoots, the outlet refrigerant pressure Pci also rises accordingly, resulting in an overshoot (periods C and D in FIG. 6).

[0045] External disturbances that can cause the intake refrigerant pressure Ps to suddenly rise include, for example, a sudden decrease in the amount of air blown by the blower 23, a change from inside air mode to outside air mode by the air damper 25, a change in the opening degree of the air damper 24 reducing the amount of air blown to the indoor heat exchanger 21, a change in the speed of the vehicle in which the vehicle air conditioning device 1 is installed from high to low, etc.

[0046] When both the suction refrigerant pressure Ps and the outlet refrigerant pressure Pci overshoot and the suction refrigerant pressure Ps becomes higher than a predetermined value (period D in FIG. 6), a protection device provided in the compressor 2 is activated and the compressor 2 is stopped (between periods D and E in FIG. 6). With the compressor 2 stopped, the compressor speed TGNC is turned OFF, and the suction refrigerant pressure Ps drops and continues to drop even if it falls below the target suction refrigerant pressure PSO. Similarly, the outlet refrigerant pressure Pci also drops and continues to drop even if it falls below the target suction refrigerant pressure PSO (period E in FIG. 6).

[0047] When this happens, it is necessary to restart the compressor 2, but since it takes time for the operation to stabilize after restart, the temperature of the air blown into the vehicle cabin drops, reducing user comfort. On the other hand, if hot gas heating operation continues for a long period of time with the suction refrigerant pressure Ps high, as in periods C and D in Figure 6, the durability of the compressor 2 will decrease, which may lead to a breakdown.

[0048] (Control method according to this embodiment) Therefore, the control device 100 is capable of executing a plurality of control modes for the second pressure reducing section V2, and during hot gas heating operation, switches between these plurality of control modes for control. Specifically, in hot gas heating operation of the vehicle air conditioning system 1 of this embodiment, the control device 100 can selectively execute "Lo mode" and "OFF mode" for the second pressure reduction section V2 in addition to "open direction mode" and "FF / FB mode", and appropriately switches between these four control modes based on the suction refrigerant pressure Ps.

[0049] The open direction mode is executed at the start of hot gas heating operation and starts the flow of refrigerant to the hot gas bypass 10V. The FF / FB mode is a mode that adjusts the opening of the second pressure reduction section V2 by feedforward control and feedback control so that the suction refrigerant pressure Ps becomes the target suction refrigerant pressure PSO. The Lo mode is a mode that maintains the second pressure reduction section V2 at a predetermined first opening OD1, and the OFF mode is a mode that fully closes the second pressure reduction section V2.

[0050] Fig. 7 shows a control mode transition diagram for the second pressure reduction part V2 during hot gas heating operation. As shown in Fig. 7, when the hot gas heating operation starts in the vehicle air conditioner 1, the control device 100 executes the opening direction mode and controls the second pressure reduction part V2 to gradually operate in the opening direction from the fully closed state.

[0051] During execution of the opening direction mode, when the suction refrigerant pressure Ps reaches a target pressure region of the target suction refrigerant pressure PSO (a range from PSO-α, which is lower than the target suction refrigerant pressure PSO by a predetermined value α, to PSO+α, which is higher than the target suction refrigerant pressure PSO by a predetermined value α; see Figs. 9 and 10), the control device 100 switches from the opening direction mode to the FF / FB mode to control the second pressure reducing section V2 ("1" in Fig. 7). Note that the control device 100 may switch from the opening direction mode to the FF / FB mode when the suction refrigerant pressure Ps reaches the target pressure region of the target suction refrigerant pressure PSO, or when the second pressure reducing section V2 reaches a preset maximum opening degree and a predetermined time has elapsed.

[0052] When the control device 100 determines that the suction refrigerant pressure Ps will overshoot (exceed the upper limit value PSO+α of the target pressure region of the target suction refrigerant pressure PSO) while the open direction mode or FF / FB mode is being executed, it switches from the open direction mode or FF / FB mode to the Lo mode and controls the second pressure reduction section V2 ("2" in Figure 7).

[0053] Here, when the change per unit time of the control amount for the second pressure reducing section V2 is equal to or greater than a certain amount, it is assumed that a disturbance has occurred in the vehicle air conditioner 1, and it is highly likely that the suction refrigerant pressure Ps will rise sharply and overshoot due to this. On the other hand, when the change per unit time of the control amount for the second pressure reducing section V2 is small, the probability of a disturbance or a sudden rise in the suction refrigerant pressure Ps due to the disturbance is low. Therefore, the control device 100 may determine whether the suction refrigerant pressure Ps exceeds the target suction refrigerant pressure PSO when the change per unit time of the control amount for the second pressure reducing section V2 is equal to or greater than a certain amount.

[0054] In the Lo mode, the control device 100 controls the second pressure reducing section V2 to a first opening OD1 that is smaller than the opening during the open direction mode or the FF / FB mode and is preset in the Lo mode. Note that a plurality of openings can be preset for the second pressure reducing section V2, and the first opening OD1 can be set to the smallest opening among the openings that can be set for the second pressure reducing section V2.

[0055] The control device 100 sets the second pressure reduction section V2 to the first opening degree OD1 in Lo mode, and if the suction refrigerant pressure Ps continues to overshoot even after a predetermined period of time has elapsed since the second pressure reduction section V2 was maintained at the first opening degree OD1, the control device 100 switches from Lo mode to OFF mode to control the second pressure reduction section V2 ("3" in Figure 7).

[0056] In the OFF mode, the control device 100 controls the second pressure reducing unit V2 to be fully closed. When the suction refrigerant pressure Ps falls below the target suction refrigerant pressure PSO and below a predetermined threshold pressure (for example, a lower limit value PSO-α of a target pressure region of the target suction refrigerant pressure PSO) with the second pressure reducing unit V2 fully closed, the control device 100 transitions again to the Lo mode and controls the second pressure reducing unit V2 to the first opening degree OD1 ("4" in FIG. 7).

[0057] When the suction refrigerant pressure Ps is below the target suction refrigerant pressure PSO and remains below a predetermined threshold pressure (for example, the lower limit value PSO-α of the target pressure region of the target suction refrigerant pressure PSO) for a predetermined period of time during execution of the Lo mode, the control device 100 can determine that there is room to execute FF / FB mode, and therefore switches from the Lo mode to the FF / FB mode and controls the second pressure reduction section V2 ("5" in Figure 7).

[0058] Next, the control mode switching process by the control device 100 in the hot gas heating operation of the vehicle air conditioner 1 according to this embodiment will be described with reference to the flowchart of FIG.

[0059] As shown in FIG. 8, when the hot gas heating operation starts in the vehicle air conditioner 1, the control device 100 executes the opening mode and controls the second pressure reducing section V2 to gradually operate in the opening direction from the fully closed state (step S10).

[0060] The control device 100 monitors the suction refrigerant pressure Ps while operating the second pressure reducing section V2 in the opening direction (step S11), and continues the opening direction mode if the suction refrigerant pressure Ps does not reach the target pressure region of the target suction refrigerant pressure PSO, i.e., if it does not reach the lower limit value PSO-α of the target pressure region (NO in step S11).If the suction refrigerant pressure Ps reaches the target pressure region of the target suction refrigerant pressure PSO, i.e., if it exceeds the lower limit value PSO-α of the target pressure region (YES in step S11), the control device 100 switches from the opening direction mode to the FF / FB mode (step S12).

[0061] The control device 100 executes the FF / FB mode to control the second pressure reducing section V2 by the FF control and the FB control (step S12), and monitors whether the suction refrigerant pressure Ps overshoots (step S13). If the suction refrigerant pressure Ps does not overshoot and is maintained within the target pressure region of the target suction refrigerant pressure PSO, the FF / FB mode is continued (NO in step S13). If it is determined that the suction refrigerant pressure Ps overshoots (YES in step S13), the control device 100 switches to the Lo mode (step S14).

[0062] The control device 100 controls the opening degree of the second pressure reducing unit V2 in the Lo mode so as to be fixed to a predetermined first opening degree OD1 (step S14). The first opening degree OD1 is smaller than the opening degree of the second pressure reducing unit V2 in the open direction mode or the FF / FB mode.

[0063] The control device 100 monitors the suction refrigerant pressure Ps (step S15) while maintaining the second pressure reducing section V2 at the first opening degree OD1 in the Lo mode, and if the suction refrigerant pressure Ps continues to overshoot for a predetermined period of time (YES in step S15), switches from the Lo mode to the OFF mode (step S16). On the other hand, if the suction refrigerant pressure Ps does not continue to overshoot for the predetermined period of time (NO in step S15), switches to the FF / FB mode (step S20).

[0064] In the OFF mode, the control device 100 controls the second pressure reducing unit V2 to be fully closed (step S16), and monitors the suction refrigerant pressure Ps with the second pressure reducing unit V2 fully closed (step S17). When the suction refrigerant pressure Ps is in the target pressure region of the target suction refrigerant pressure PSO, the control device 100 continues the OFF mode (NO in step S17), and when the suction refrigerant pressure Ps falls below the lower limit value PSO-α of the target pressure region of the target suction refrigerant pressure PSO (YES in step S17), the control device 100 switches back to the Lo mode (step S18).

[0065] The control device 100 executes the Lo mode and monitors the suction refrigerant pressure Ps while maintaining the opening of the second pressure reducing unit V2 at the first opening OD1 (step S19). If the suction refrigerant pressure Ps is in the target pressure region of the target suction refrigerant pressure PSO (NO in step S19), the control device 100 continues to execute the Lo mode, and if the state where the suction refrigerant pressure Ps is below the lower limit value PSO-α continues for a predetermined period of time (YES in step S19), the control device 100 switches to the FF / FB mode and controls the second pressure reducing unit V2 by FF control and FB control (step S20).

[0066] 9 and 10 show graphs showing an example of 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, and the target opening TGECCVdis of the second pressure reducing section V2 during hot gas heating operation by the control method (mode switching process) according to Examples 1 and 2. Note that the graphs in Figures 9 and 10 show the change in the pressure value of the high-pressure side refrigerant as the behavior of the outlet refrigerant pressure Pci, and the change in the pressure value of the low-pressure side refrigerant as the behavior of the suction refrigerant pressure Ps.

[0067] During hot gas heating operation, the control device 100 can selectively execute four modes: "open direction mode," "FF / FB mode," "Lo mode," and "OFF mode," and controls the second pressure reduction section V2 by appropriately switching between these four control modes based on the suction refrigerant pressure Ps.

[0068] Example 1 FIG. 9 shows an example in which the second pressure reducing section V2 is controlled by switching between three control modes without executing control in the OFF mode, with the open direction mode being executed in period A, the FF / FB mode being executed in periods B and C, the Lo mode being executed in period D, and the FF / FB mode being executed in periods E and F.

[0069] As shown in Fig. 9, when the hot gas heating operation starts, the control device 100 executes the open direction mode to operate the second pressure reduction section V2 in the open direction and circulates the refrigerant through the hot gas bypass 10V (period A in Fig. 9). When the suction refrigerant pressure Ps reaches the target pressure region of the target suction refrigerant pressure PSO, the control device 100 transitions to the FF / FB mode and adjusts the opening degree of the second pressure reduction section V2 (periods B and C in Fig. 9).

[0070] In the FF / FB mode, the opening degree of the second pressure reducing section V2 is calculated while monitoring the suction refrigerant pressure Ps at a predetermined control cycle, and the second pressure reducing section V2 is controlled based on the calculated result. 9, the suction refrigerant pressure Ps is approximately equal to the target suction refrigerant pressure PSO, and the outlet refrigerant pressure Pci is approximately equal to the target outlet refrigerant pressure PCO. The compressor 2 is driven at a constant rotation speed, the opening degree of the second pressure reducing section V2 is constant, and the vehicle air conditioner 1 continues the hot gas heating operation in a stable state.

[0071] If a disturbance is input between periods B and C in Figure 9 while the FF / FB mode is being executed, causing the suction refrigerant pressure Ps to suddenly rise and overshoot, i.e., exceed the upper limit value PSO+α of the target pressure region of the target suction refrigerant pressure PSO (period C in Figure 9), the control device 100 transitions to Lo mode and controls the second pressure reduction section V2 to the first opening degree OD1 (period D in Figure 9).

[0072] The first opening OD1 is smaller than the opening of the second pressure reduction unit V2 during periods B and C when the FF / FB mode was being executed, and by maintaining the second pressure reduction unit V2 at the first opening OD1 in the Lo mode, the compressor 2 is driven at a lower rotation speed than in periods B and C, and both the suction refrigerant pressure Ps and the outlet refrigerant pressure Pci decrease. When the state in which the suction refrigerant pressure Ps overshoots is resolved, the control device 100 switches from the Lo mode to the FF / FB mode to control the second pressure reduction unit V2 (periods E and F in FIG. 9).

[0073] In the control device 100, by switching from the Lo mode to the FF / FB mode, the suction refrigerant pressure Ps is acquired at a predetermined control cycle, the opening degree of the second pressure reduction section V2 is calculated based on the acquired suction refrigerant pressure Ps, and the second pressure reduction section V2 is controlled to the calculated opening degree. As a result, in the period E of Fig. 9, the second pressure reduction section V2 operates in the opening direction, and accordingly, the rotation speed of the compressor 2 increases, and the suction refrigerant pressure Ps and the outlet refrigerant pressure Pci increase. When the suction refrigerant pressure Ps and the outlet refrigerant pressure Pci both reach the target suction refrigerant pressure PSO and the target outlet refrigerant pressure PCO, the compressor 2 is driven at a substantially constant rotation speed, the second pressure reduction section V2 is maintained at a substantially constant opening degree, and the hot gas heating operation continues in a stable state (period F of Fig. 9).

[0074] In the example of Figure 9, after the second pressure reduction section V2 is maintained at the first opening during period D, the suction refrigerant pressure Ps falls below the target suction refrigerant pressure PSO, so the mode transitions to FF / FB mode without transitioning to OFF mode.

[0075] Example 2 When the suction refrigerant pressure Ps does not decrease and overshoots even after a predetermined period of time has elapsed since the second pressure reduction section V2 was set to the first opening degree, the control device 100 transitions from the Lo mode to the OFF mode and controls the second pressure reduction section V2 to be fully closed (see FIG. 7). In this case, the behavior of the outlet refrigerant pressure Pci of the indoor heat exchanger 21, the suction refrigerant pressure Ps of the compressor 2, the target rotation speed TGNC of the compressor 2, and the target opening TGECCVdis of the second pressure reduction section V2 becomes, for example, as shown in the graph of FIG.

[0076] FIG. 10 shows an example of controlling the second pressure reducing section V2 by switching between four control modes, with the open direction mode being executed in period A, the FF / FB mode being executed in periods B and C, the Lo mode being executed in period D, the OFF mode being executed in period E, the Lo mode being executed in period F, and the FF / FB mode being executed in periods G and H.

[0077] As shown in Fig. 10, when the hot gas heating operation starts, the control device 100 executes the open direction mode to operate the second pressure reduction section V2 in the open direction and circulates the refrigerant through the hot gas bypass 10V (period A in Fig. 10). When the suction refrigerant pressure Ps reaches the target pressure region including the target suction refrigerant pressure PSO, the control device 100 transitions to the FF / FB mode and adjusts the opening degree of the second pressure reduction section V2 (periods B and C in Fig. 10).

[0078] In the FF / FB mode, the opening degree of the second pressure reducing section V2 is calculated while monitoring the suction refrigerant pressure Ps at a predetermined control cycle, and the second pressure reducing section V2 is controlled based on the calculated result. 10, the suction refrigerant pressure Ps is approximately equal to the target suction refrigerant pressure PSO, and the outlet refrigerant pressure Pci is approximately equal to the target outlet refrigerant pressure PCO. The compressor 2 is driven at a constant rotation speed, the opening degree of the second pressure reducing section V2 is constant, and the vehicle air conditioner 1 continues the hot gas heating operation in a stable state.

[0079] If an external disturbance is input between periods B and C in Figure 10 while the FF / FB mode is being executed, causing the suction refrigerant pressure Ps to suddenly rise and overshoot, that is, exceed the target pressure region of the target suction refrigerant pressure PSO, that is, exceed PSO+α (period C in Figure 10), the control device 100 transitions to Lo mode and controls the second pressure reduction section V2 to the first opening degree OD1 (period D in Figure 10).

[0080] The first opening OD1 is smaller than the opening of the second pressure reduction section V2 during periods B and C when FF / FB mode was executed. By maintaining the second pressure reduction section V2 at the first opening OD1 in Lo mode, the compressor 2 operates at a lower rotation speed than in periods B and C, and the suction refrigerant pressure Ps and the outlet refrigerant pressure Pci gradually decrease (period D in Figure 10).

[0081] The control device 100 transitions from Lo mode to OFF mode (between periods D and E in FIG. 10) because the suction refrigerant pressure Ps is in an overshoot state even after a predetermined time has elapsed with the opening of the second pressure reducing section V2 set to the first opening OD1 in the Lo mode. In the OFF mode, the control device 100 controls the second pressure reducing section V2 to be fully closed (period E in FIG. 10), and when the suction refrigerant pressure Ps falls below the lower limit value PSO-α of the target pressure region, transitions again to Lo mode and controls the second pressure reducing section V2 to be the first opening OD1 (period F in FIG. 10).

[0082] The control device 100 monitors the suction refrigerant pressure Ps while maintaining the second pressure reduction section V2 at the first opening OD1 in Lo mode, and when the suction refrigerant pressure Ps remains at the lower limit value PSO-α of the target pressure region for a predetermined period of time (period F in Figure 10), it switches from Lo mode to FF / FB mode and controls the second pressure reduction section V2 (periods G and H in Figure 10).

[0083] In the control device 100, by switching from the Lo mode to the FF / FB mode, the suction refrigerant pressure Ps is acquired at a predetermined control cycle, the opening degree of the second pressure reduction section V2 is calculated based on the acquired suction refrigerant pressure Ps, and the second pressure reduction section V2 is controlled to the calculated opening degree. As a result, in the period G in Fig. 10, the second pressure reduction section V2 operates in the opening direction, and accordingly, the rotation speed of the compressor 2 increases, and the suction refrigerant pressure Ps and the outlet refrigerant pressure Pci increase. When the suction refrigerant pressure Ps and the outlet refrigerant pressure Pci both reach the target suction refrigerant pressure PSO and the target outlet refrigerant pressure PCO, the compressor 2 is driven at a substantially constant rotation speed, the second pressure reduction section V2 is maintained at a substantially constant opening degree, and the hot gas heating operation continues in a stable state (period H in Fig. 10).

[0084] In this way, in the vehicle air conditioner 1 according to this embodiment, when the suction refrigerant pressure Ps overshoots, the control device 100 immediately transitions the control mode from the FF / FB mode to the Lo mode. That is, when the control device 100 determines that the suction refrigerant pressure Ps will overshoot, it controls the opening degree of the second pressure reducing section V2 to be smaller than the current opening degree and to the preset first opening degree OD1.

[0085] Therefore, compared to controlling the second pressure reduction unit V2 in the closing direction in the FF / FB mode, the second pressure reduction unit V2 immediately operates to the first opening degree OD1, so that the suction refrigerant pressure Ps can be reduced in response to the operation of the second pressure reduction unit V2. Furthermore, if the suction refrigerant pressure Ps is still in an overshoot state even after a predetermined period of time has elapsed while maintaining the second pressure reduction unit V2 at the first opening degree OD1 in the Lo mode, the control device 100 transitions to the OFF mode and fully closes the second pressure reduction unit V2 to reduce the suction refrigerant pressure Ps.

[0086] Therefore, according to this embodiment, it is possible to prevent the compressor from continuing to operate in a high-pressure state, such as when the suction refrigerant pressure Ps overshoots, thereby improving the durability of the compressor. In addition, since it is possible to prevent the compressor from stopping due to high-pressure protection caused by overshooting, it is also possible to prevent fluctuations in the blown air temperature caused by stopping and restarting the compressor, thereby improving user comfort.

[0087] As described above, according to this embodiment, it is possible to prevent the compressor from being driven when the suction refrigerant pressure is high, thereby improving the durability of the compressor.

[0088] 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]

[0089] 1: vehicle air conditioning system, 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: Heat exchanger to be temperature-controlled 34: refrigerant / heat medium heat exchanger, 34A, 34B: flow path, 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 it is determined that the suction refrigerant pressure of the compressor will overshoot, the opening degree of the flow control unit is controlled to a predetermined first opening degree that is smaller than the current opening degree.

2. 2. The vehicle air conditioner according to claim 1, wherein the first opening degree is a minimum opening degree among preset opening degrees.

3. 2. The vehicle air conditioning system according to claim 1, wherein the control device controls the flow rate adjustment unit to be fully closed when a suction refrigerant pressure is still overshooting even after a predetermined time has elapsed after controlling the flow rate adjustment unit to be at the first opening degree.

4. 4. The vehicle air conditioning system according to claim 3, wherein the control device controls the flow rate adjustment unit to be fully closed, and then controls the flow rate adjustment unit to be opened when a suction refrigerant pressure is equal to or lower than a target suction refrigerant pressure and falls below a predetermined threshold pressure.

5. 2. The vehicle air conditioning system according to claim 1, wherein the control device determines whether or not the suction refrigerant pressure exceeds a target suction refrigerant pressure when a change per unit time in a control amount for the flow rate adjustment unit is equal to or greater than a certain amount in a hot gas heating mode.

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