Air conditioner for vehicle

Abstract

To provide an air conditioner for a vehicle capable of executing a hot-gas heating operation mode (FF control and FB control) without spoiling reliability of a low-pressure side component and comfort of an occupant even when the hot-gas heating operation mode is started up under an extremely low temperature environment.SOLUTION: In an air conditioner for a vehicle, a decompression unit has a first decompression unit provided on the downstream side of an indoor heat exchange unit and a second decompression unit provided on a hot-gas bypass. A controller can execute a hot-gas heating operation mode for flowing a part of a refrigerant compressed by a compressor to the indoor heat exchange unit, and flowing the rest to the hot-gas bypass. When starting up the hot-gas heating operation mode, if a refrigerant pressure on the suction side of the compressor is determined to be a negative pressure, the controller executes a pressure adjustment mode for controlling openings of the first decompression unit and the second decompression unit to a predetermined opening or more to raise the refrigerant pressure on the suction side of the compressor.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] Air conditioners using a heat pump as a heat source are generally used in electric vehicles (EVs) that do not have a combustion-based heat source such as an engine, or in vehicles (vehicle air conditioners) that have a low heat output from a combustion-based heat source. In normal heating operation, this vehicle air conditioner absorbs heat from outside air in an exterior heat exchanger that functions as a heat absorber, and heats the air to be blown into the vehicle cabin in a heat exchanger of an air conditioning unit (vehicle interior air conditioner) that functions as a heat radiator. For this reason, in normal heating operation, when the outside air temperature becomes extremely low, it becomes difficult to absorb heat from the outside air, resulting in a decrease in heating capacity.

[0003] In contrast, the hot gas heating operation mode executes a cycle in which the high-temperature, high-pressure refrigerant discharged from the compressor of the heat pump flows through the heat exchange section of the air conditioning unit, and then the refrigerant is decompressed and sucked into the compressor without passing through the outdoor heat exchange section, enabling heating operation in extremely low-temperature outdoor air environments where it is difficult to absorb heat in the outdoor heat exchange section. This hot gas heating operation mode provides a bypass refrigerant flow path (hot gas bypass) in the refrigerant circuit that decompresses and returns a portion of the high-temperature, high-pressure refrigerant discharged from the compressor to the compressor without passing through the heat exchanger of the air conditioning unit, and allows a portion of the refrigerant compressed by the compressor to flow through the heat exchange section of the air conditioning unit and the remainder to flow through the hot gas bypass, making it possible to adjust the amount of heat input and release during operation (see Patent Document 1 below). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2023-46604 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in a conventional vehicle air conditioner, when the refrigerant temperature is low (e.g., -30°C or lower) or in an extremely low temperature environment where the outside air temperature is, for example, -40°C or lower, the saturation pressure of the refrigerant is likely to become negative, and when the hot gas heating operation mode is started in this state, the time during which the refrigerant pressure (low-pressure side refrigerant pressure) sucked into the compressor becomes negative increases. This may result in a loss of reliability of the low-pressure side components (compressor, etc.). In addition, in such an extremely low temperature environment (e.g., -40°C or lower), the time until the target blowing temperature is reached is not long, and immediate warmth cannot be obtained, which may result in a loss of comfort for the occupants.

[0006] The present invention has been proposed in view of the above circumstances. That is, an object of the present invention is to provide a vehicle air conditioner that can execute the hot gas heating operation mode (feedforward control (FF control) and feedback control (FB control)) without impairing the reliability of low-pressure side parts (compressor, etc.) and the comfort of passengers, even when the hot gas heating operation mode is started in an extremely low temperature environment (for example, -40°C or lower). [Means for solving the problem]

[0007] In order to solve such problems, the present invention has the following configuration. 1. A vehicle air conditioning system comprising: a compressor, an indoor heat exchange unit, an external heat exchange unit, a pressure reduction unit, and a refrigerant circuit including 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 control unit that controls the refrigerant circuit. The pressure reduction unit has a first pressure reduction unit provided downstream of the indoor heat exchange unit and a second pressure reduction unit provided in the hot gas bypass. The control unit is capable of executing a hot gas heating operation 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. When the control unit determines that the refrigerant pressure on the suction side of the compressor is negative pressure when starting the hot gas heating operation mode, the control unit executes a pressure adjustment mode in which the openings of the first pressure reduction unit and the second pressure reduction unit are controlled to a predetermined opening or more to increase the refrigerant pressure on the suction side of the compressor. Effect of the Invention

[0008] According to the vehicle air conditioning system of the present invention having such characteristics, even when the hot gas heating operation mode is activated in an extremely low temperature environment (e.g., below -40°C), the hot gas heating operation mode (FF control and FB control) can be executed without compromising the reliability of the low-pressure side components (compressor, etc.) or the comfort of the occupants. [Brief description of the drawings]

[0009] [Figure 1] 1 is an explanatory diagram illustrating an example of the configuration of a vehicle air conditioning device according to an embodiment of the present invention; [Diagram 2] FIG. 2 is an explanatory diagram showing a control device of a vehicle air conditioner. [Diagram 3] FIG. 2 is an explanatory diagram showing the hardware configuration of a control device for a vehicle air conditioner mounted on an electric vehicle (EV). [Figure 4] FIG. 4 is an explanatory diagram showing a refrigerant circuit operation in a hot gas heating operation mode in the vehicle air conditioning system according to the embodiment of the present invention. [Diagram 5] FIG. 4 is an explanatory diagram (flowchart) showing the processing contents of hot gas heating operation mode startup control processing. [Figure 6] FIG. 11 is an explanatory diagram (flowchart) showing the processing content of a pressure adjustment mode. [Figure 7] FIG. 1 is an explanatory diagram (graph) showing an example of the behavior of the compressor speed (Compressor Speed) [rpm / 100] (NC / 100 [rpm]) (graph a), the opening of the second pressure reduction section (EXV_bps) [%] (EXC [%]) (graph b), the opening of the third pressure reduction section (EXV_chi) [%] (EXC [%]) (graph c), the suction refrigerant pressure Ps [bar] drawn into the compressor (graph d), the outlet refrigerant pressure Pci [bar] leaving the indoor heat exchange section (graph e), the outlet refrigerant temperature Tci (ICND Outlet Temp) [℃] leaving the indoor heat exchange section (graph f), the air flow rate of the blower (Air Flow / 10) [kg / h] (graph g), and the heating capacity (Heat Capacity) [KW] (graph h) in pressure adjustment mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention (the present embodiment) will be described with reference to the drawings. In the following description, the same reference numerals in different drawings indicate parts having the same function, and duplicated descriptions in each drawing will be omitted as appropriate.

[0011] [Configuration of refrigerant circuit, etc. in vehicle air conditioning system] 1 shows a configuration example of a vehicle air conditioner 1 according to this embodiment. The configuration example shown here is just one example, and the present invention is not particularly limited to a specific configuration.

[0012] The vehicle air conditioner 1 includes a refrigerant circuit 10 and an air conditioning unit (vehicle interior air conditioner) 20. The refrigerant circuit 10 has a refrigerant flow path that reduces the pressure of the refrigerant discharged from the compressor 2 and returns it to the compressor 2. The compressor 2, indoor heat exchangers 21 and 22 provided inside the air conditioning unit 20, and an outdoor heat exchanger (external heat exchanger) 11 provided outside the vehicle cabin are arranged along the refrigerant flow path. The indoor heat exchangers 21 and 22 are provided for heat exchange between the air flowing inside the air conditioning unit 20 and the refrigerant, and the outdoor heat exchanger 11 is provided for heat exchange between the outside air and the refrigerant outside the vehicle cabin. For example, the indoor heat exchanger 21 is for heating the air, and the indoor heat exchanger 22 is for cooling the air. Downstream of the indoor heat exchange section 21 in the refrigerant flow path is a refrigerant temperature sensor 43A that detects the outlet refrigerant temperature (high-pressure side refrigerant temperature) Tci leaving the indoor heat exchange section 21, and a refrigerant pressure sensor 44B that detects the outlet refrigerant pressure (high-pressure side refrigerant pressure) Pci leaving the indoor heat exchange section 21.

[0013] The compressor 2 compresses the refrigerant and circulates it through the refrigerant circuit 10. The refrigerant compressed by the compressor 2 is decompressed to a required pressure by selectively passing through a first pressure reduction section V1, a second pressure reduction section V2 (second pressure reduction section), a third pressure reduction section V3 (first pressure reduction section), and a fourth pressure reduction 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 restricting the flow direction of the refrigerant. An accumulator 16 is provided 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 (low-pressure side refrigerant pressure) Ps sucked into the compressor 2.

[0014] As described above, the air conditioning unit 20 includes the indoor heat exchangers 21, 22, and air introduced from the room or the outside by the blower 23 passes through the indoor heat exchangers 21, 22 to be temperature-adjusted and then 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.

[0015] When the air damper 24 is fully closed, it blocks the inlet side of the indoor heat exchange section 21, and the air introduced by the blower 23 passes only through the indoor heat exchange section 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 also possible to take in air from both air inlet 25A and air inlet 25B.

[0016] Although the above-mentioned examples of the outdoor heat exchange section (external heat exchange section) 11 and the indoor heat exchange sections 21 and 22 have been described in which the refrigerant and the air directly exchange heat, the refrigerant and the 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.

[0017] As shown in Fig. 1, the vehicle air conditioner 1 includes a heat medium circuit 30 for adjusting the temperature of an in-vehicle device. 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 an in-vehicle device (temperature adjustment target) such as a battery using a temperature adjustment target 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, as a heat exchanger for adjusting the temperature of the in-vehicle device. Such a heat medium circuit 30 is provided as necessary.

[0018] [Control device] The vehicle air conditioner 1 includes a control device (air conditioning ECU) 100 shown in Fig. 2. The control device 100 controls the refrigerant circuit 10 and the air conditioning unit 20 described above based on various input signals 60 (such as an air conditioning instruction signal and a charger connection signal) including user setting information and information from the vehicle, and detection signals from a sensor unit 40, and also controls the heat medium circuit 30 as necessary.

[0019] The sensor section 40, which inputs detection signals to the control device 100, includes, for example, an outside air sensor 41 for detecting 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 for detecting the state of the refrigerant, and a blower temperature sensor 45 for detecting the blower temperature of the air conditioning unit 20.

[0020] The refrigerant temperature sensor 43 includes a refrigerant temperature sensor 43A that detects an outlet refrigerant temperature (high-pressure side refrigerant temperature) Tci exiting the indoor heat exchange section 21 (see FIG. 1). The refrigerant pressure sensor 44 includes a refrigerant pressure sensor 44A that detects a suction refrigerant pressure (low-pressure side refrigerant pressure) Ps sucked into the compressor 2, and a refrigerant pressure sensor 44B that detects an outlet refrigerant pressure (high-pressure side refrigerant pressure) Pci of the indoor heat exchange section 21 (see FIG. 1). The refrigerant pressure sensor 44 may also include a refrigerant pressure sensor (not shown) that detects a discharge refrigerant pressure (high-pressure side refrigerant pressure) Pd discharged from the compressor 2. These sensors are merely examples, and the sensor section 40 is provided with various sensors that detect information required when the control device 100 performs various controls.

[0021] The control targets of the control device 100 are the compressor 2, the first pressure reduction section V1, the second pressure reduction section V2 (second pressure reduction section), the third pressure reduction section V3 (first pressure reduction section), the fourth pressure reduction section V4, and the flow path switching valves 12 and 13 in the refrigerant circuit 10, the blower 23, the air dampers 24 and 25 in the air conditioning unit 20, and the circulation pump 31 in the heat medium circuit 30. The vehicle air conditioner 1 can be switched by the control device 100 between an outside air heat absorption heating operation mode in which outside air is absorbed by the outside heat exchange section 11, and a hot gas heating operation mode in which the high-temperature refrigerant compressed by the compressor 2 is dissipated by the indoor heat exchange section 21 without the outside air absorbing heat in the outside heat exchange section 11 to heat the vehicle cabin.

[0022] [Configuration of control device in electric vehicle (EV)] 3, the control device (air conditioning ECU) 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, etc., and each piece of hardware is connected to each other via a bus 106.

[0023] 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).

[0024] 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.

[0025] 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.

[0026] 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.

[0027] [Outdoor air heat absorption heating operation mode] In the outdoor air heat absorption heating operation mode, 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 in the refrigerant circuit 10 shown in Fig. 1. On the other hand, the flow path switching valve 13 is open, and the first pressure reduction section V1 is open.

[0028] In the outdoor air heat absorption heating operation mode, the high-temperature, high-pressure refrigerant discharged from the compressor 2 passes through the indoor heat exchange section 21 in the air conditioning unit 20 and is depressurized in the first depressurization section V1, and the low-pressure refrigerant passes through the outdoor heat exchange section 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 exchange section 21, is depressurized in the first depressurization section V1 to become a low-pressure refrigerant, absorbs heat and evaporates in the outdoor heat exchange section 11, and returns to the compressor 2, completing a cycle. In the air conditioning unit 20, the air introduced by the blower 23 is heated by the heat released in the indoor heat exchange section 21 and is blown out into the vehicle cabin.

[0029] [Refrigerant circuit operation in hot gas heating operation mode] In the hot gas heating operation mode, the refrigerant is not allowed to absorb heat in the exterior heat exchange section 11, and some or all of the refrigerant compressed by the compressor 2 is caused to dissipate heat in the interior heat exchange section 21 to heat the vehicle cabin. The operation of the refrigerant circuit 10 in the hot gas heating operation mode will be described with reference to Fig. 4. In the illustrated refrigerant circuit 10, thick black lines indicate refrigerant flow paths through which high-pressure refrigerant flows, and hollow lines indicate refrigerant flow paths through which decompressed refrigerant flows. Furthermore, the dashed lines in the refrigerant circuit 10 indicate refrigerant flow paths through which refrigerant does not flow, and the dashed lines in the heat medium circuit 30 indicate that the flow of the heat medium has stopped.

[0030] 4, a portion of the high-temperature, high-pressure refrigerant discharged from the compressor 2 passes through the indoor heat exchange section 21 and the flow path switching valve 12, is depressurized in the third pressure reduction section V3 (first pressure reduction section) to become a low-pressure refrigerant, passes through the refrigerant heat medium heat exchange section 34, is separated into gas and liquid in the accumulator 16, and returns to the compressor 2. At this time, the refrigerant circuit 10 does not allow the refrigerant to flow to the outdoor heat exchange section 11 by fully closing the first pressure reduction section V1. Also, the fourth pressure reduction section V4 is fully closed to prevent the refrigerant from flowing to the indoor heat exchange section 22.

[0031] 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 exchange section 21 and the outdoor heat exchange section 11, and is provided with a refrigerant flow path capable of executing a hot gas heating operation mode. 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 (second pressure reduction section), 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.

[0032] By providing such a hot gas bypass 10V, in the hot gas heating operation mode, the liquid refrigerant condensed by heat radiation in the indoor heat exchanger 21 is mixed with the gas refrigerant that has passed through the hot gas bypass 10V to produce a gas-rich refrigerant, which is then returned to the compressor 2. In addition, by increasing the refrigerant flow rate flowing through the hot gas bypass 10V, the amount of heat radiation in the indoor heat exchanger 21 can be suppressed, and by adjusting the refrigerant flow rate flowing through the hot gas bypass 10V by opening and closing the second pressure reduction section V2, 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.

[0033] In the hot gas heating operation mode, 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.

[0034] [Hot gas heating operation mode start control process] Incidentally, when the hot gas heating operation mode is started in an extremely low temperature environment (for example, -40°C or lower), the intake refrigerant pressure Ps is likely to become a negative pressure (for example, less than 1.2 bar abs) lower than atmospheric pressure. Therefore, in the vehicle air conditioner 1, if the intake refrigerant pressure Ps is negative when the hot gas heating operation mode is started, a pressure adjustment mode (FIG. 6) is executed to improve the negative pressure state, and then the hot gas heating operation mode is executed.

[0035] Specifically, when the hot gas heating operation mode is started, the vehicle air conditioner 1 performs a hot gas heating operation mode start control process shown in Fig. 5 by the control device 100. When the hot gas heating operation mode is started, the control device 100 starts a series of processes shown in Fig. 5 and determines in step S1 whether the suction refrigerant pressure (low pressure side refrigerant pressure) Ps detected by the refrigerant pressure sensor 44A is a negative pressure lower than atmospheric pressure.

[0036] When the control device 100 determines that the suction refrigerant pressure Ps is negative pressure (YES in step S1), it executes the pressure adjustment mode (FIG. 6) in the following step S2, and then executes the hot gas heating operation mode (feedforward control (FF control) and feedback control (FB control)) in step S3. On the other hand, when the control device 100 determines that the suction refrigerant pressure Ps is not negative pressure (i.e., positive pressure) (NO in step S1), it executes the hot gas heating operation mode (FF control and FB control) in the following step S3 without executing the pressure adjustment mode (FIG. 6) in step S2. After executing the hot gas heating operation mode (FF control and FB control) in step S3, the control device 100 ends the series of processes shown in FIG. 5.

[0037] Here, the processing contents of the pressure adjustment mode in step S2 by the control device 100 will be described with reference to Fig. 6. When the control device 100 starts executing the pressure adjustment mode, in step S21, the control device 100 sets the rotation speed of the compressor 2 to a high rotation speed, and controls the compressor 2 to start at this high rotation speed (i.e., high speed). This high rotation speed may be a rotation speed sufficient to increase the suction refrigerant pressure (low pressure side refrigerant pressure) Ps sucked into the compressor 2, and may be, for example, the maximum rotation speed (i.e., maximum speed) of the compressor 2, but may also be another rotation speed, for example, a rotation speed that is 80 to 90% of the maximum rotation speed.

[0038] When the hot gas heating operation mode is started with the intake refrigerant pressure Ps at negative pressure, if the openings of the second pressure reducing section V2 and the third pressure reducing section V3 are reduced from the start of the operation as in the conventional vehicle air conditioner, the time during which the intake refrigerant pressure Ps is at negative pressure becomes longer. In such a vehicle air conditioner, there is a risk of impairing the reliability of the low-pressure side components (compressor, etc.), and there is a risk of impairing the comfort of the occupants because immediate heating cannot be obtained. Therefore, in the vehicle air conditioner 1, in step S22 after step S21, the control device 100 controls the second pressure reducing section V2 (second pressure reducing section) and the third pressure reducing section V3 (first pressure reducing section) so that both the openings of the second pressure reducing section V2 (second pressure reducing section) and the third pressure reducing section V3 (first pressure reducing section) are equal to or greater than a predetermined opening, which is a high opening.

[0039] In this way, by controlling the control device 100, the compressor 2 is started at a high rotation speed (i.e., high speed) and the opening degree of the second pressure reduction section V2 and the third pressure reduction section V3 is set to a predetermined opening degree or more, thereby increasing the suction refrigerant pressure Ps and shortening the time during which the suction refrigerant pressure Ps is negative pressure.

[0040] Here, "above a specified opening degree" may mean, for example, a high opening degree such as 80% or more of the maximum opening degree in each of the second pressure reduction section V2 and the third pressure reduction section V3, and as a more specific example, it may be the maximum opening degree (100%) in each of the second pressure reduction section V2 and the third pressure reduction section V3.

[0041] Also, for example, in step S22, when the control device 100 controls the second pressure reducing section V2 and the third pressure reducing section V3 to a predetermined opening degree or more, which is a high opening degree, the control device 100 may control the second pressure reducing section V2 and the third pressure reducing section V3 so that the opening degree of the third pressure reducing section V3 is equal to or greater than the opening degree of the second pressure reducing section V2. In this case, even if the refrigerant flow path (piping) used in the hot gas heating operation mode is excessively cooled in an extremely low temperature environment (for example, below -40°C), the refrigerant flow path can be warmed by flowing the refrigerant throughout the refrigerant flow path, so that excessive drops in the low-temperature side refrigerant temperature and the low-temperature side refrigerant pressure can be prevented. That is, in this case, the suction refrigerant pressure Ps can be efficiently increased to improve the negative pressure state of the suction refrigerant pressure Ps.

[0042] In step S23 after step S22, the control device 100 determines whether the suction refrigerant pressure (low pressure side refrigerant pressure) Ps detected by the refrigerant pressure sensor 44A is a positive pressure (e.g., 1.2 bar abs or more). When the control device 100 determines that the suction refrigerant pressure Ps is a positive pressure (YES in step S23), the control device 100 proceeds to step S24. Note that here, the control device 100 may determine that "the suction refrigerant pressure Ps is a positive pressure (YES in step S23)" when the suction refrigerant pressure Ps reaches any pressure value (hereinafter referred to as "specific pressure") within a specific range including the lower limit of the positive pressure.

[0043] On the other hand, if the control device 100 determines that the suction refrigerant pressure Ps detected by the refrigerant pressure sensor 44A is not a positive pressure (NO in step S23), the control device 100 repeats the process of step S23. That is, the control device 100 repeats the process of step S23 until it determines that the suction refrigerant pressure Ps is a positive pressure.

[0044] In the vehicle air conditioning system 1, the control device 100 performs a process (negative pressure improvement process) to improve the negative pressure state of the suction refrigerant pressure Ps in the pressure adjustment mode, and then performs the processes of steps S24 to S30 as pre-processing for the hot gas heating operation mode (FF control and FB control), thereby enabling the FF control and FB control to be performed stably.

[0045] In step S24 after step S23, since the suction refrigerant pressure Ps is a positive pressure, the control device 100 controls both the opening degree of the second pressure reduction section V2 (second pressure reduction section) and the opening degree of the third pressure reduction section V3 (first pressure reduction section) to a low opening degree. Here, the "low opening degree" is an opening degree (significantly) smaller than the current "predetermined opening degree or more" opening degree of the second pressure reduction section V2 (second pressure reduction section) and the third pressure reduction section V3 (first pressure reduction section), and may be, for example, 3% to 10% of the maximum opening degree of each of the second pressure reduction section V2 and the third pressure reduction section V3, but is not limited thereto and may be another opening degree.

[0046] In this way, by using the control device 100 to control the opening degree of the second pressure reduction section V2 and the third pressure reduction section V3 to a low opening degree, a pressure difference is generated between the high pressure side refrigerant pressure and the low pressure side refrigerant pressure in the refrigerant circuit 10, and excessive increases in the high pressure side refrigerant pressure and the high pressure side refrigerant temperature can also be suppressed.

[0047] In step S25 after step S24, the control device 100 determines whether the outlet refrigerant temperature (high-pressure side refrigerant temperature) Tci from the indoor heat exchanger 21 detected by the refrigerant temperature sensor 43A is equal to or higher than the temperature threshold value Tm. If the control device 100 determines that the outlet refrigerant temperature (high-pressure side refrigerant temperature) Tci is equal to or higher than the threshold value Tm (YES in step S25), the process proceeds to step S26.

[0048] On the other hand, when the control device 100 determines that the outlet refrigerant temperature Tci from the indoor heat exchange unit 21 detected by the refrigerant temperature sensor 43A is not equal to or higher than the threshold value Tm (i.e., is lower than the threshold value Tm) (NO in step S25), the control device 100 performs the process of step S25 again. That is, the control device 100 repeats the process of step S25 until it determines that the outlet refrigerant temperature Tci has become equal to or higher than the threshold value Tm.

[0049] In step S25, the control device 100 may perform a determination process using another value instead of the above-mentioned determination process using the outlet refrigerant temperature Tci. The other value may be any value detected for the high-pressure side refrigerant.

[0050] For example, in this step S25, instead of the judgment process using the aforementioned outlet refrigerant temperature Tci, the control device 100 may judge whether the outlet refrigerant pressure (high pressure side refrigerant pressure) Pci from the indoor heat exchange section 21 detected by the refrigerant pressure sensor 44B is greater than or equal to a first pressure threshold Pm1, and if it is determined that the outlet refrigerant pressure Pci is greater than or equal to the first threshold Pm1 (YES in step S25), it may proceed to processing in step S26, and if it is determined that the outlet refrigerant pressure Pci is not greater than or equal to the first threshold Pm1 (NO in step S25), it may perform the processing of step S25 again.

[0051] Also, for example, in step S25, the control device 100 may perform a determination process using a discharge refrigerant pressure (high-pressure side refrigerant pressure) Pd discharged from the compressor 2, which is detected by a refrigerant pressure sensor (not shown) provided immediately downstream (discharge side) of the compressor 2, instead of the determination process using the outlet refrigerant temperature Tci described above. In this case, in step S25, the control device 100 determines whether the discharge refrigerant pressure Pd is equal to or higher than a second threshold pressure Pm2, and if it determines that the discharge refrigerant pressure Pd is equal to or higher than the second threshold pressure Pm2 (YES in step S25), it proceeds to step S26, and if it determines that the discharge refrigerant pressure Pd is not equal to or higher than the second threshold pressure Pm2 (NO in step S25), it performs the process of step S25 again.

[0052] In step S26 following step S25, the control device 100 controls the blower 23 to operate at its minimum air volume. Operating the blower 23 can suppress an excessive increase in the high-pressure side refrigerant pressure and the high-pressure side refrigerant temperature, and setting the air volume at that time to the minimum air volume can also suppress an excessive decrease in the high-pressure side refrigerant pressure and the high-pressure side refrigerant temperature. From this point of view, the temperature threshold Tm (or the first pressure threshold Pm1 or the second pressure threshold Pm2) in the above-mentioned step S25 may be an appropriate value as the high-pressure side refrigerant temperature (or the high-pressure side refrigerant pressure) when the blower 23 is operated at the minimum air volume in this step S26, and is not particularly limited.

[0053] In step S27 following step S26, the control device 100 increases the opening degree of the second pressure reducing section V2, thereby increasing the suction refrigerant pressure Ps.

[0054] In step S28 after step S27, the control device 100 determines whether the suction refrigerant pressure (low pressure side refrigerant pressure) Ps detected by the refrigerant pressure sensor 44A has increased by a predetermined amount ΔP (any value). If the control device 100 determines that the suction refrigerant pressure Ps has increased by the predetermined amount ΔP (YES in step S28), the process proceeds to step S29.

[0055] On the other hand, when the control device 100 determines that the suction refrigerant pressure Ps detected by the refrigerant pressure sensor 44A has not increased by the predetermined amount ΔP (NO in step S28), the control device 100 performs the process of step S28 again. That is, the control device 100 repeats the process of step S28 until the suction refrigerant pressure Ps increases by the predetermined amount ΔP.

[0056] In step S29 after step S28, the control device 100 judges whether the suction refrigerant pressure (low-pressure side refrigerant pressure) Ps detected by the refrigerant pressure sensor 44A is the target value PSO of the low-pressure side refrigerant pressure. When the control device 100 judges that the suction refrigerant pressure (low-pressure side refrigerant pressure) Ps is the target value PSO (YES in step S29), it ends the series of processes in the pressure adjustment mode shown in Fig. 6 and proceeds to step S3 (hot gas heating operation mode) in Fig. 5. Note that "the suction refrigerant pressure Ps is the target value PSO" here includes not only the case where the suction refrigerant pressure Ps is completely equal to the target value PSO, but also the case where the suction refrigerant pressure Ps is close to the target value PSO.

[0057] On the other hand, if the control device 100 determines that the suction refrigerant pressure (low-pressure side refrigerant pressure) Ps has not reached the target value PSO (NO in step S29), it increases the airflow rate of the blower 23 in the following step S30, and then returns to the process of step S27 to control the opening of the second pressure reducing section V2 to be increased again. That is, the processes of steps S27 to S30 by the control device 100 are repeated until the suction refrigerant pressure Ps reaches the target value PSO.

[0058] In this way, by increasing the opening degree of the second pressure reducing section V2, the control device 100 increases the suction refrigerant pressure (low-pressure side refrigerant pressure) Ps by a predetermined amount ΔP, but in a state where the target value PSO of the low-pressure side refrigerant pressure has not been reached, the control device 100 increases the air volume of the blower 23 (step S30) and increases the amount of heat dissipated in the indoor heat exchange section 21, while further increasing the opening degree of the second pressure reducing section V2 (step S27). In this way, the control device 100 controls the suction refrigerant pressure Ps to become the target value PSO, while balancing the amount of heat dissipated in the refrigerant circuit 10 and the amount of heat input to the compressor 2.

[0059] An example of the behavior of each value in the pressure adjustment mode is shown in Fig. 7. That is, in the example of Fig. 7, graph a (solid line) is the speed of the compressor 2 (Compressor Speed) [rpm / 100] (NC / 100 [rpm]), graph b (short dashed line) is the opening degree (EXV_bps) [%] (EXC [%]) of the second pressure reduction section V2, and graph c (long dashed line) is the opening degree (EXV_chi) [%] (EXC [%]) of the third pressure reduction section V3.

[0060] Moreover, graph d (solid line) represents the suction refrigerant pressure Ps [bar] sucked into the compressor 2, and graph e (solid line) represents the outlet refrigerant pressure Pci [bar] from the indoor heat exchange section 21. Moreover, graph f (solid line) represents the outlet refrigerant temperature Tci (ICND Outlet Temp) [°C] from the indoor heat exchange section 21, graph g (solid line) represents the air flow (Air Flow / 10) [kg / h] of the blower 23, and graph h (solid line) represents the heating capacity (Heat Capacity) [KW].

[0061] In the example of FIG. 7, since the suction refrigerant pressure Ps [bar] (graph d) is less than the atmospheric pressure (1.2 bar abs), the control device 100 determines that the suction refrigerant pressure Ps is a negative pressure (YES in the above-mentioned step S1). Then, the control device 100 starts executing the pressure adjustment mode (the above-mentioned step S2). At the start of the mode (at the start of period A), the control device 100 sets the speed [rpm / 100] (graph a) of the compressor 2 to the maximum speed (i.e., the maximum rotation speed of 10,000 rpm) and controls the compressor 2 to start at this maximum speed, and thereafter controls the compressor 2 to operate at a constant maximum speed throughout the pressure adjustment mode (periods A to E) (the above-mentioned step S21).

[0062] At the same time, the control device 100 consistently controls the opening degree (EXV_bps) [%] (graph b) of the second pressure reduction section V2 and the opening degree (EXV_chi) [%] (graph c) of the third pressure reduction section V3 to the maximum opening degree (100%), which is an example of "above a specified opening degree" during period A (step S22 mentioned above).

[0063] Then, when the suction refrigerant pressure Ps [bar] (graph d) rises and reaches atmospheric pressure (1.2 bar abs), the control device 100 determines that the suction refrigerant pressure Ps is a positive pressure (YES in step S23 described above), and performs processing from period B onward as preprocessing for stably executing the subsequent hot gas heating operation mode (FF control and FB control). At the start of period B, the control device 100 controls the opening degree (EXV_bps) [%] (graph b) of the second pressure reducing section V2 to 5.4%, which is an example of a low opening degree, and controls the opening degree (EXV_chi) [%] (graph c) of the third pressure reducing section V3 to 3.2%, which is an example of a low opening degree (step S24 described above). Note that the opening degree (EXV_chi) [%] (graph c) of the third pressure reducing section V3 is consistently controlled to this 3.2% from this point onwards (periods B to E).

[0064] By such control by the control device 100, a pressure difference occurs between the suction refrigerant pressure (low pressure side refrigerant pressure) Ps (graph d) and the outlet refrigerant pressure Pci [bar] (graph e) of the indoor heat exchange unit 21 during period B. At the same time, excessive increases in the outlet refrigerant pressure Pci [bar] (graph e) of the indoor heat exchange unit 21 and the outlet temperature Tci [°C] (graph f) of the indoor heat exchange unit 21 are also suppressed.

[0065] In the example of Fig. 7, when the outlet refrigerant temperature Tci (ICND Outlet Temp) [°C] (graph f) from the indoor heat exchanger 21 rises during period B and reaches the temperature threshold Tm (YES in step S25 above), the control device 100 sets the airflow (Air Flow / 10) [kg / h] (graph g) of the blower 23 to the minimum airflow during period C, and controls the blower 23 to operate at the minimum airflow (step S26 above). During this period C, by operating the blower 23 at the minimum airflow (graph g), excessive increases in the outlet refrigerant pressure Pci [bar] (high-pressure side refrigerant pressure) in graph e and the outlet refrigerant temperature Tci [°C] (high-pressure side refrigerant temperature) in graph f are suppressed, and excessive decreases are also suppressed.

[0066] During this period C, a necessary pressure difference occurs between the high pressure side and the low pressure side of the refrigerant circuit 10, between the outlet refrigerant pressure Pci [bar] (graph e) and the suction refrigerant pressure Ps [bar] (graph d). In this state, during the following period D, the control device 100 increases the opening degree (EXV_bps) [%] (graph b) of the second pressure reducing section V2 (step S27 described above). As a result, during period D, the suction refrigerant pressure Ps [bar] (graph d) also increases with the increase in the opening degree (EXV_bps) [%] (graph b) of the second pressure reducing section V2.

[0067] 7, the control device 100 determines that the suction refrigerant pressure Ps [bar] (graph d) has increased by a predetermined amount ΔP (YES in step S28 described above) but has not yet reached the target value PSO of the low-pressure side refrigerant pressure (NO in step S29 described above), and thus further increases the airflow (Air Flow / 10) [bar] (graph g) of the blower 23 at the start of period E (step S30 described above). Note that in the example of FIG. 7, as the airflow (Air Flow / 10) [kg / h] (graph g) of the blower 23 increases, the heating capacity (Heat Capacity) [KW] (graph h) of the vehicle air conditioner 1 also increases.

[0068] As can be seen from the example of FIG. 7, the vehicle air conditioner 1 can improve the negative pressure state of the intake refrigerant pressure Ps [bar] (graph d) in the pressure regulation mode under the control of the control device 100, thereby shortening the time during which the intake refrigerant pressure Ps is at negative pressure. Therefore, even if the hot gas heating operation mode is started in an extremely low temperature environment (for example, below -40°C), the vehicle air conditioner 1 can execute the hot gas heating operation mode (FF control and FB control) without impairing the reliability of the low-pressure side parts (compressor, etc.) and without impairing the comfort of the occupants based on the quick heating property. In addition, the vehicle air conditioner 1 can stably execute the hot gas heating operation mode (FF control and FB control) by performing pre-processing after the period B of the pressure regulation mode under the control of the control device 100.

[0069] The above describes in detail the embodiment (present embodiment) of the present invention with reference to the drawings. However, 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.

[0070] [Variations] A modified example of this embodiment will be described below. In the configuration of the above-described embodiment, the vehicle air conditioner 1 may further include a heat insulating material (not shown) on the outer surface of the accumulator 16. The heat insulating material is not particularly limited, and may be, for example, any heat insulating material (not shown) or any heater.

[0071] In this way, in the vehicle air conditioner 1, by providing a heat insulating material on the outer surface of the accumulator 16, the low-pressure side refrigerant temperature can be maintained at a certain value or higher. As a result, even if the hot gas heating operation mode is started in an extremely low temperature environment (for example, -40°C or lower), the vehicle air conditioner 1 can further improve the reliability of the low-pressure side parts (compressor, etc.) at the time of start-up, and can further improve the comfort of the occupants based on the quick heating property.

[0072] In the above embodiment, the control device 100 performs a series of processes shown in steps S21 to S30 in Fig. 6 as the pressure adjustment mode of step S2 in Fig. 5, but the process contents of the pressure adjustment mode (step S2) are not limited to this example. For example, the control device 100 may perform only steps S21 to S24 shown in Fig. 6 in the pressure adjustment mode (step S2).

[0073] In this case, after executing steps S21 to S24 in the pressure adjustment mode, the control device 100 ends the processing of the pressure adjustment mode and proceeds to the processing of the hot gas heating operation mode (FF control and FB control) in step S3 shown in Fig. 5. In this case, the vehicle air conditioner 1 can further simplify the processing at the start of the hot gas heating operation mode. [Explanation of symbols]

[0074] 1: vehicle air conditioner, 2: compressor, 10: refrigerant circuit, 10V: hot gas bypass, 11: outdoor heat exchange section (external heat exchange section), 12, 13: flow path switching valve, 14, 15: check valve, 16: accumulator, 20: air conditioning unit, 21, 22: indoor heat exchange section, 23: blower, 24, 25: air damper, 25A, 25B: air inlet, 30: heat medium circuit, 31: circulation pump, 32: heater (ECH: Electric Coolant Heater), 33: temperature control target heat exchange section, 34: refrigerant heat medium heat exchange section, 34A: flow path, 34B: flow path, 40: sensor section, 41: outside air sensor, 42: compressor current sensor, 43, 43A: refrigerant temperature sensor, 44: refrigerant pressure sensor, 44A: refrigerant pressure sensor, 44B: refrigerant pressure sensor, 45: blower temperature sensor, 60: input signal, 100: control device (air conditioning ECU), 106: bus

Claims

1. A refrigerant circuit including a compressor, an indoor heat exchange unit, an external heat exchange unit, a decompression unit, and a hot gas bypass that decompresses and returns at least a portion of a refrigerant compressed by the compressor to the compressor without passing through the indoor heat exchange unit and the external heat exchange unit, and a control device that controls the refrigerant circuit, The pressure reducing section includes a first pressure reducing section provided downstream of the indoor heat exchange section and a second pressure reducing section provided in the hot gas bypass, The control device includes: A hot gas heating operation 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. This vehicle air conditioning system, when starting the hot gas heating operation mode, if it is determined that the refrigerant pressure on the suction side of the compressor is negative pressure, executes a pressure adjustment mode in which the opening degree of the first pressure reduction section and the second pressure reduction section is controlled to a predetermined opening degree or greater to increase the refrigerant pressure on the suction side of the compressor.

2. 2. The vehicle air conditioning system according to claim 1, wherein the control device, in the pressure adjustment mode, controls the first pressure reduction unit and the second pressure reduction unit so that an opening degree of the first pressure reduction unit is equal to or greater than an opening degree of the second pressure reduction unit.

3. 2. The vehicle air conditioning system according to claim 1, wherein, in the pressure adjustment mode, when the refrigerant pressure on the suction side of the compressor reaches a specific pressure, the control device reduces the opening degrees of the first pressure reduction section and the second pressure reduction section from their current opening degrees.

4. 2. The vehicle air conditioner according to claim 1, wherein the control device controls the opening degrees of the first pressure reducing section and the second pressure reducing section to maximum opening degrees in the pressure adjustment mode.

Images