Vehicle air conditioning device

Abstract

[Problem] To provide a vehicle air conditioning device capable of executing a hot gas heating operation mode (FF control and FB control) without impairing the reliability of components on a low pressure side and the comfort of occupants, even when the hot gas heating operation mode is started in an extremely low temperature environment. [Solution] In this vehicle air conditioning device, a pressure reduction unit has a first pressure reduction unit provided on the downstream side of an indoor heat exchange unit, and a second pressure reduction unit provided in a hot gas bypass. A control device can execute a hot gas heating operation mode in which a part of a refrigerant compressed by a compressor is made to flow to the indoor heat exchange unit and the remainder is made to flow to the hot gas bypass. If it is determined that a refrigerant pressure on a suction side of the compressor is a negative pressure when starting the hot gas heating operation mode, the control device executes a pressure adjustment mode for increasing the refrigerant pressure on the suction side of the compressor by controlling opening degrees of the first pressure reduction unit and the second pressure reduction unit to predetermined opening degrees or more.

Description

Vehicle air conditioning system

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

[0002] Air conditioners (vehicle air conditioners) for electric vehicles (EVs) that do not have a combustion-based heat source such as an engine or that have a low heat output from a combustion-based heat source generally use a heat pump as a heat source. In normal heating operation, these vehicle air conditioners absorb heat from outside air using an exterior heat exchanger that functions as a heat absorber, and heat the air to be blown into the vehicle cabin using a heat exchanger in an air conditioning unit (vehicle interior air conditioner) that functions as a heat radiator. Therefore, during 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 high-temperature, high-pressure refrigerant discharged from the heat pump compressor flows through the heat exchange section of the air conditioning unit, and then decompresses and is drawn into the compressor without passing through the outdoor heat exchange section, enabling heating operation in extremely low-temperature outdoor air environments where heat absorption by the outdoor heat exchange section is difficult. In this hot gas heating operation mode, a bypass refrigerant flow path (hot gas bypass) is provided in the refrigerant circuit, which 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. By flowing a portion of the refrigerant compressed by the compressor through the heat exchange section of the air conditioning unit and flowing the remainder through the hot gas bypass, it is possible to adjust the amount of heat input and heat release during operation (see Patent Document 1 below).

[0004] Japanese Patent Application Laid-Open No. 2023-46604

[0005] However, in conventional vehicle air conditioning systems, when the refrigerant temperature is low (e.g., −30°C or below) or in an extremely low-temperature environment where the outside air temperature is, for example, −40°C or below, the saturation pressure of the refrigerant is likely to become negative. When the hot gas heating operation mode is activated in such a state, the refrigerant suction pressure (low-pressure side refrigerant pressure) drawn into the compressor remains negative for a long time. This can potentially impair the reliability of low-pressure side components (e.g., the compressor). Furthermore, in such an extremely low-temperature environment (e.g., −40°C or below), the time required to reach the target outlet temperature is shortened, preventing immediate warmth, potentially compromising passenger comfort.

[0006] The present invention has been proposed in light 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 compromising the reliability of low-pressure side components (such as the compressor) or passenger comfort, even when the hot gas heating operation mode is activated in an extremely low-temperature environment (for example, −40° C. or below).

[0007] In order to solve the above problems, the present invention provides a vehicle air conditioning system including a refrigerant circuit including a compressor, an indoor heat exchanger, an external heat exchanger, a decompression unit, and a hot gas bypass that decompresses at least a portion of the refrigerant compressed by the compressor and returns it to the compressor without passing through the indoor heat exchanger and the external heat exchanger, and a control device that controls the refrigerant circuit, the decompression unit having a first decompression unit provided downstream of the indoor heat exchanger and a second decompression unit provided in the hot gas bypass, the control device being 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 exchanger and the remainder flows through the hot gas bypass, and the control device being configured to execute a pressure adjustment mode in which, when starting the hot gas heating operation mode, the control device determines that the refrigerant pressure on the suction side of the compressor is negative, by controlling the apertures of the first decompression unit and the second decompression unit to be equal to or greater than a predetermined aperture, thereby increasing the refrigerant pressure on the suction side of the compressor.

[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 (for example, below -40°C), the hot gas heating operation mode (FF control and FB control) can be executed without compromising the reliability of low-pressure side components (compressor, etc.) or the comfort of the occupants.

[0009] Fig. 1 is an explanatory diagram showing an example of the configuration of a vehicle air conditioner according to an embodiment of the present invention; Fig. 2 is an explanatory diagram showing a control device for a vehicle air conditioner; Fig. 3 is an explanatory diagram showing the hardware configuration of a control device for a vehicle air conditioner mounted on an electric vehicle (EV); Fig. 4 is an explanatory diagram showing the operation of a refrigerant circuit in a hot gas heating operation mode in a vehicle air conditioner according to an embodiment of the present invention; Fig. 5 is an explanatory diagram (flowchart) showing the processing contents of a hot gas heating operation mode start-up control process; Fig. 6 is an explanatory diagram (flowchart) showing the processing contents of a pressure adjustment mode; 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 intake 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) [°C] 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 the pressure adjustment mode.

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

[0011] 1 shows an example of the configuration of a vehicle air conditioner 1 according to this embodiment. The configuration shown here is merely an example, and the present invention is not 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 decompresses the refrigerant discharged from a 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 refrigerant and air flowing inside the air conditioning unit 20, and the outdoor heat exchanger 11 is provided for heat exchange between the refrigerant and outside air outside the vehicle cabin. For example, the indoor heat exchanger 21 is used to heat the air, and the indoor heat exchanger 22 is used to cool the air. Downstream of the indoor heat exchange section 21 in the refrigerant flow path, there 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 an appropriately selected refrigerant flow path, for example, 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), or a fourth pressure reduction section V4, which are expansion valves. The refrigerant circuit 10 is provided with flow path switching valves 12 and 13 for switching the refrigerant flow path and check valves 14 and 15 for 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 the 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 and 22. Air introduced from inside or outside the room by the blower 23 passes through the indoor heat exchangers 21 and 22 to adjust the temperature and is then blown into the room. The air conditioning unit 20 is also 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 and 22 and is then blown into the room.

[0015] Furthermore, when the air damper 24 is fully closed, it blocks the inlet side of the indoor heat exchanger 21, and air introduced by the blower 23 passes only through the indoor heat exchanger 22 before being blown 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 an air inlet 25A connected to the outdoors or an air inlet 25B connected to the indoors, allowing air to be introduced from either one. Furthermore, by placing the air damper 25 in an intermediate position, air can be introduced from both the air inlet 25A and the air inlet 25B.

[0016] Although the above-described examples of direct heat exchange between the refrigerant and air have been described for the outdoor heat exchange unit (external heat exchange unit) 11 and the indoor heat exchange units 21 and 22, the refrigerant and air may exchange heat indirectly via a heat medium that has exchanged heat with the refrigerant. That is, the refrigerant may absorb heat from the air via the heat medium, or the refrigerant may release heat to the air via the heat medium.

[0017] As shown in FIG. 1 , the vehicle air conditioner 1 includes a heat medium circuit 30 for controlling the temperature of on-board equipment. The heat medium circuit 30 circulates a heat medium using a circulation pump 31, heats the heat medium using a heater (ECH: Electric Coolant Heater) 32, and recovers waste heat from on-board equipment (temperature control target) such as a battery using a temperature control target heat exchanger 33. The refrigerant circuit 10 and the heat medium circuit 30 are provided with a refrigerant-heat medium heat exchanger 34, which 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 controlling the temperature of the on-board equipment. Such a heat medium circuit 30 is provided as needed.

[0018] 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, as 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 the sensor unit 40, and also controls the heat medium circuit 30 as necessary.

[0019] The sensor section 40 that inputs detection signals to the control device 100 includes, for example, an outside air sensor 41 that detects outside air conditions such as outside air temperature and outside air humidity, a compressor current sensor 42 that detects the power consumption (energy consumption) of the compressor 2, a refrigerant temperature sensor 43 and a refrigerant pressure sensor 44 that detect the state of the refrigerant, and a blower temperature sensor 45 that detects the blower temperature of the air conditioning unit 20.

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

[0021] The control devices controlled by 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 control device 100 can switch 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 high-temperature refrigerant compressed by the compressor 2 is dissipated in the indoor heat exchange section 21 to heat the vehicle cabin without outside air absorbing heat in the outside heat exchange section 11.

[0022] [Configuration of Control Device in Electric Vehicle (EV)] As shown in Fig. 3 , the control device (air conditioning ECU) 100 provided in the vehicle air conditioner 1 is configured as a single ECU connected to various ECUs (Electronic Control Units) that control the electric vehicle (EV) via an in-vehicle network L. The control device 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, an input / output I / F (Interface) 104, an in-vehicle communication I / F (Interface) 105, etc., and each piece of hardware is connected to one another via a bus 106.

[0023] The CPU 101 controls the control device 100 by executing various programs stored in the ROM 102. The ROM 102 is a non-volatile memory. For example, the ROM 102 stores programs executed by the CPU 101, data necessary for the CPU 101 to execute the programs, etc. The RAM 103 is a main storage device such as a dynamic random access memory (DRAM) or a static random access memory (SRAM).

[0024] For example, RAM 103 functions as a work area used by CPU 101 when executing a program. Input / output I / F 104 is connected to various sensors and monitors installed in the EV, and inputs data to CPU 101 and outputs data processed by CPU 101. In-vehicle communication I / F 105 is connected to an in-vehicle network L, and controls data transmission and reception with other ECUs set in the EV.

[0025] The control device 100 controls the above-mentioned vehicle air conditioning device 1 by a program executed by the CPU 101 when data regarding surrounding environmental information or data regarding 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 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. Meanwhile, 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, high-temperature, high-pressure refrigerant discharged from the compressor 2 passes through the indoor heat exchanger 21 in the air conditioning unit 20 and is depressurized in the first depressurization section V1. The low-pressure refrigerant passes through the outdoor heat exchanger 11 and passes through the flow path switching valve 13, the check valve 14, and the accumulator 16 before being returned to the compressor 2. At this time, the high-pressure refrigerant discharged from the compressor 2 condenses and releases heat in the indoor heat exchanger 21, is depressurized in the first depressurization section V1 to become low-pressure refrigerant, absorbs heat and evaporates in the outdoor heat exchanger 11, and returns to the compressor 2, completing a cycle. In the air conditioning unit 20, air introduced by the blower 23 is heated by the heat released in the indoor heat exchanger 21 and is blown into the vehicle cabin.

[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 outdoor heat exchanger 11, and some or all of the refrigerant compressed by the compressor 2 is caused to release heat in the indoor heat exchanger 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 Figure 4. In the illustrated refrigerant circuit 10, bold 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, dashed lines in the refrigerant circuit 10 indicate refrigerant flow paths through which refrigerant does not flow, and dashed lines in the heat medium circuit 30 indicate that the flow of the heat medium is stopped.

[0030] 4 , a portion 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 decompressed in the third pressure reduction section V3 (first pressure reduction section) 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, the refrigerant circuit 10 fully closes the first pressure reduction section V1 so that the refrigerant does not flow to the outdoor 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.

[0031] The refrigerant circuit 10 has a hot gas bypass 10V that decompresses and returns at least a portion of the refrigerant compressed by the compressor 2 to the compressor 2 without passing through the indoor heat exchange unit 21 and the outdoor heat exchange unit 11, and is equipped with a refrigerant flow path that can execute a hot gas heating operation mode. In the hot gas bypass 10V, a portion of the high-temperature, high-pressure refrigerant is branched at a branch point P1 immediately downstream of the compressor 2, decompressed at a second decompression unit V2 (second decompression unit), and merged with the low-pressure refrigerant decompressed at a third decompression unit 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 that can be returned to the compressor 2. Furthermore, by increasing the flow rate of refrigerant 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 flow rate of refrigerant flowing through the hot gas bypass 10V by opening or 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 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 becomes high-pressure refrigerant upstream and low-pressure refrigerant downstream. In this case, it is important to maintain heating capacity that heat exchange does not occur in the refrigerant-heat medium heat exchanger 34 in the low-pressure flow path. In the air conditioning unit 20, air introduced by the blower 23 is heated by heat dissipated in the indoor heat exchanger 21 and then blown into the vehicle cabin.

[0034] [Hot Gas Heating Operation Mode Start Control Process] 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 automotive air conditioner 1, if the intake refrigerant pressure Ps is negative when the hot gas heating operation mode is started, the 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 activated, the vehicle air conditioner 1 performs a hot gas heating operation mode activation control process shown in Fig. 5 using the control device 100. When the hot gas heating operation mode is activated, the control device 100 starts the 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 does not execute the pressure adjustment mode (FIG. 6) in step S2, but executes the hot gas heating operation mode (FF control and FB control) in the following step S3. 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 details 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 execution of 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 any rotation speed that is 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, such as 80 to 90% of the maximum rotation speed.

[0038] When the hot gas heating operation mode is started while the intake refrigerant pressure Ps is negative, if the opening degrees of the second pressure reducing section V2 and the third pressure reducing section V3 are reduced from the start of startup, as in conventional automotive air conditioners, the intake refrigerant pressure Ps remains negative for a long time. In such automotive air conditioners, the reliability of low-pressure components (such as the compressor) may be impaired, and passenger comfort may be impaired due to a lack of immediate heating. Therefore, in the automotive air conditioner 1, the control device 100 controls the opening degrees of the second pressure reducing section V2 (second pressure reducing section) and the third pressure reducing section V3 (first pressure reducing section) in step S22 after step S21 so that both the opening degrees 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 high opening degree.

[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 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 predetermined 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] Furthermore, for example, in step S22, when the control device 100 controls the second pressure reduction unit V2 and the third pressure reduction unit V3 to be at or above a predetermined high opening, the control device 100 may control the second pressure reduction unit V2 and the third pressure reduction unit V3 so that the opening of the third pressure reduction unit V3 is equal to or greater than the opening of the second pressure reduction unit 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 (e.g., −40°C or below), the refrigerant can be warmed by flowing refrigerant throughout the refrigerant flow path, thereby preventing excessive decreases in the low-temperature side refrigerant temperature and low-temperature side refrigerant pressure. In other words, in this case, the suction refrigerant pressure Ps can be efficiently increased, thereby improving 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 higher). If 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 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 a pressure value (hereinafter referred to as the "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 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 intake 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 FF control and FB control to be performed stably.

[0045] In step S24 after step S23, because the suction refrigerant pressure Ps is positive, the control device 100 controls both the second pressure reduction section V2 (second pressure reduction section) and the third pressure reduction section V3 (first pressure reduction section) to low openings. Here, the "low openings" refer to openings that are (significantly) smaller than the current "predetermined openings or greater" of the second pressure reduction section V2 (second pressure reduction section) and the third pressure reduction section V3 (first pressure reduction section). For example, the "low openings" may be 3% to 10% of the maximum openings of the second pressure reduction section V2 and the third pressure reduction section V3, respectively, but are not limited thereto and may be other openings.

[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 created 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 greater 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 greater than the threshold value Tm (YES in step S25), the process proceeds to step S26.

[0048] On the other hand, if 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 aforementioned determination process using the outlet refrigerant temperature Tci. This 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 determine whether the outlet refrigerant pressure (high-pressure side refrigerant pressure) Pci from the indoor heat exchange unit 21 detected by the refrigerant pressure sensor 44B is equal to or greater than a first pressure threshold Pm1, and if it determines that the outlet refrigerant pressure Pci is equal to or greater than the first threshold Pm1 (YES in step S25), it may proceed to step S26, but if it determines that the outlet refrigerant pressure Pci is not equal to or greater than the first threshold Pm1 (NO in step S25), it may perform the processing of step S25 again.

[0051] Alternatively, in step S25, instead of using the outlet refrigerant temperature Tci, the control device 100 may use 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 (on the discharge side) of the compressor 2. In this case, in step S25, the control device 100 determines whether the discharge refrigerant pressure Pd is equal to or greater than a second threshold pressure Pm2. If the control device 100 determines that the discharge refrigerant pressure Pd is equal to or greater than the second threshold pressure Pm2 (YES in step S25), the control device 100 proceeds to step S26. If the control device 100 determines that the discharge refrigerant pressure Pd is not equal to or greater than the second threshold pressure Pm2 (NO in step S25), the control device 100 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 airflow rate. Operating the blower 23 can suppress excessive increases in the high-pressure side refrigerant pressure and the high-pressure side refrigerant temperature, and setting the airflow rate at the minimum can also suppress excessive decreases in the high-pressure side refrigerant pressure and the high-pressure side refrigerant temperature. From this perspective, the temperature threshold Tm (or the first pressure threshold Pm1 or the second pressure threshold Pm2) in step S25 described above is not particularly limited as long as it is an appropriate value for the high-pressure side refrigerant temperature (or the high-pressure side refrigerant pressure) when the blower 23 is operated at the minimum airflow rate in step S26.

[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, if 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 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 determines whether the suction refrigerant pressure (low-pressure side refrigerant pressure) Ps detected by the refrigerant pressure sensor 44A is equal to the target value PSO for the low-pressure side refrigerant pressure. If the control device 100 determines that the suction refrigerant pressure (low-pressure side refrigerant pressure) Ps is equal to the target value PSO (YES in step S29), the control device 100 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 equal to the target value PSO" here refers not only to the case where the suction refrigerant pressure Ps is exactly equal to the target value PSO but also to 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), the control device 100 increases the airflow rate of the blower 23 in the subsequent step S30, and then returns to the process of step S27 to control the second pressure reducing section V2 to increase its opening again. That is, the control device 100 repeats the processes of steps S27 to S30 until the suction refrigerant pressure Ps reaches the target value PSO.

[0058] In this way, when the control device 100 increases the aperture of the second pressure reducing section V2 so that the suction refrigerant pressure (low-pressure side refrigerant pressure) Ps increases by a predetermined amount ΔP but has not yet reached the target value PSO for the low-pressure side refrigerant pressure, the control device 100 increases the airflow rate of the blower 23 (step S30) to increase the amount of heat dissipated by the indoor heat exchanger 21, and further increases the aperture of the second pressure reducing section V2 (step S27). In this way, the control device 100 controls the suction refrigerant pressure Ps to reach the target value PSO while balancing the amount of heat dissipated by the refrigerant circuit 10 and the amount of heat input to the compressor 2.

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

[0060] 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 unit 21. Graph f (solid line) represents the outlet refrigerant temperature Tci (ICND Outlet Temp) [°C] from the indoor heat exchange unit 21, graph g (solid line) represents the air flow rate (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 , because the suction refrigerant pressure Ps [bar] (graph d) is less than atmospheric pressure (1.2 bar abs), the control device 100 determines that the suction refrigerant pressure Ps is negative (YES in step S1 described above). The control device 100 then starts the pressure adjustment mode (step S2 described above). At the start of the pressure adjustment mode (start of period A), the control device 100 sets the compressor 2 speed [rpm / 100] (graph a) to the maximum speed (i.e., a maximum rotation speed of 10,000 rpm) and starts the compressor 2 at this maximum speed. Thereafter, the control device 100 controls the compressor 2 to operate at a constant maximum speed throughout the pressure adjustment mode (periods A to E) (step S21 described above).

[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 (graph c) of the third pressure reduction section V3 (EXV_chi) [%] to the maximum opening degree (100%), which is an example of "above a specified opening degree" during period A (step S22 described 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 positive (YES in step S23 described above) and performs the processes from period B onward as preprocessing for stable execution of 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%, an example of a low opening, and controls the opening degree (EXV_chi) [%] (graph c) of the third pressure reducing section V3 to 3.2%, an example of a low opening (step S24 described above). Note that the opening degree (EXV_chi) [%] (graph c) of the third pressure reducing section V3 is consistently controlled to 3.2% thereafter (periods B to E).

[0064] Due to 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] 7 , when the outlet refrigerant temperature Tci (ICND Outlet Temp) [°C] (graph f) of the indoor heat exchanger 21 increases during period B and reaches the temperature threshold Tm (YES in step S25), the control device 100 sets the airflow rate (Air Flow / 10) [kg / h] (graph g) of the blower 23 to the minimum airflow rate during period C and controls the blower 23 to operate at the minimum airflow rate (step S26). By operating the blower 23 at the minimum airflow rate during period C (graph g), excessive increases in the outlet refrigerant pressure Pci [bar] (high-pressure side refrigerant pressure) (graph e) and the outlet refrigerant temperature Tci [°C] (high-pressure side refrigerant temperature) (graph f) are suppressed and excessive decreases are also suppressed.

[0066] During this period C, a necessary pressure difference is generated 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 rate (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 as the opening rate (EXV_bps) [%] (graph b) of the second pressure reducing section V2 increases.

[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) but has not yet reached the target value PSO of the low-pressure side refrigerant pressure (NO in step S29), and therefore further increases the air flow rate (Air Flow / 10) [bar] (graph g) of the blower 23 at the start of period E (step S30). Note that in the example of FIG. 7, as the air flow rate (Air Flow / 10) [kg / h] (graph g) of the blower 23 increases, the heating capacity (Heat Capacity) [kW] (graph h) of the automotive air conditioner 1 also increases.

[0068] As can be seen from the example of FIG. 7 , the automotive air conditioner 1, under the control of the control device 100, can improve the negative pressure state of the intake refrigerant pressure Ps [bar] (graph d) in the pressure adjustment mode, thereby shortening the time during which the intake refrigerant pressure Ps remains negative. Therefore, even if the hot gas heating operation mode is activated in an extremely low-temperature environment (e.g., −40°C or below), the automotive air conditioner 1 can execute the hot gas heating operation mode (FF control and FB control) without compromising the reliability of low-pressure components (e.g., the compressor) or the comfort of the occupants based on the quick heating feature. Furthermore, the automotive air conditioner 1 can stably execute the hot gas heating operation mode (FF control and FB control) by performing preprocessing after period B of the pressure adjustment mode under the control of the control device 100.

[0069] The embodiments (present embodiments) of the present invention have been described in detail above with reference to the drawings, but the specific configurations are not limited to these embodiments, and the present invention also includes design changes and the like that do not deviate from the gist of the present invention.

[0070] [Modifications] Modifications of the present embodiment will be described below. In the configuration of the above-described embodiment, the vehicle air conditioning system 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), any heater, etc.

[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 components (compressor, etc.) at the time of start-up, and can further improve passenger comfort based on the quick heating capability.

[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 content of the pressure adjustment mode (step S2) is 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, the control device 100 executes steps S21 to S24 in the pressure adjustment mode, then ends the processing of the pressure adjustment mode, and proceeds to 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 startup of the hot gas heating operation mode.

[0074] 1: Vehicle air conditioning device, 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-controlled heat exchange unit, 34: Refrigerant / heat medium heat exchange unit, 34A: Flow path, 34B: Flow path, 40: Sensor unit, 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: Air supply temperature sensor, 60: Input signal, 100: Control device (air conditioning ECU), 106: Bus

Claims

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, wherein 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, and 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, and 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, the vehicle air conditioning system executes a pressure adjustment mode in which the opening of the first pressure reduction unit and the second pressure reduction unit is controlled to a predetermined opening level or above to increase the refrigerant pressure on the suction side of the compressor.

2. An air conditioning system for a vehicle as described in claim 1, wherein the control device, in the pressure adjustment mode, controls the first pressure reduction section and the second pressure reduction section so that the opening degree of the first pressure reduction section is equal to or greater than the opening degree of the second pressure reduction section.

3. The vehicle air conditioning system of claim 1, characterized in that, 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 degree of the first pressure reduction section and the second pressure reduction section from the current opening degree.

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

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