Air conditioning device for vehicle

Abstract

The purpose of the present invention is to improve the durability of a compressor while stably and efficiently continuing hot-gas heating operation. Provided is an air conditioner for a vehicle, comprising: a refrigerant circuit having a compressor, an indoor heat exchange unit, an external heat exchange unit, and a hot gas bypass, a hot gas bypass that decompresses at least a portion of the refrigerant compressed by the compressor and returns the refrigerant to the compressor without passing through the indoor heat exchange unit and the external heat exchange unit; and a control device that controls the refrigerant circuit and is capable of executing a hot-air heating mode in which a portion of the refrigerant compressed by the compressor flows through the indoor heat exchange unit and the remainder flows through the hot-air bypass, the control device controlling the refrigerant circuit to heat the refrigerant in the hot-air heating mode when executing the hot-air heating mode, and the control device controlling the refrigerant circuit to heat the refrigerant in the hot-air bypass when executing the hot-air heating mode. A first target rotational speed based on the suction refrigerant pressure and a second target rotational speed based on the suction refrigerant temperature are calculated, respectively, and when the suction refrigerant pressure exceeds the first threshold pressure or the suction refrigerant temperature exceeds the first threshold temperature, the first target rotational speed is calculated. The compressor is controlled using the smaller one of the first target rotational speed and the second target rotational speed as a target rotational speed.

Description

Technical Field

[0001] This invention relates to an air conditioning device for vehicles. Background Technology

[0002] In recent years, hybrid vehicles and electric vehicles, which use electricity supplied from a battery installed in the vehicle to drive an electric motor, have become increasingly popular. As an air conditioning system installed in such vehicles, a device that uses a heat pump (refrigerant circuit) as a heat source is known.

[0003] In automotive air conditioning systems using heat pumps, the external heat exchanger functions as a heat absorber during heating operation, drawing heat from the external atmosphere. Therefore, when the external atmosphere temperature is extremely low, it becomes difficult to absorb heat from it, significantly reducing heating capacity. In contrast, for effective heating in extremely low-temperature environments, a method is known that utilizes the hot gas from the high-temperature, high-pressure refrigerant discharged from the compressor, rather than absorbing heat from external gases.

[0004] For example, in the automotive air conditioning system of Patent Document 1, the refrigerant is circulated in the heat pump to perform hot air heating operation in the following manner: In the heat pump, a portion of the high-temperature, high-pressure refrigerant discharged from the compressor is returned to the compressor after flowing through a bypass path and being depressurized, while the remaining portion is depressurized after exchanging heat with the air supplied to the vehicle interior in the indoor heat exchanger, and then returned to the compressor without passing through an external heat exchanger.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2023-46604 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] In the automotive air conditioning system described above, not to mention the heat absorption heating operation from external gas, even in the aforementioned hot gas heating operation, to ensure continuous, stable, and efficient operation, it is necessary to control each component of the refrigerant circuit to keep the pressure and temperature on the compressor's suction and discharge sides within a specified range that includes target values. In particular, when the suction refrigerant pressure decreases, the compression ratio increases and the discharge refrigerant temperature rises, leading to a decrease in volumetric efficiency. Therefore, in heat absorption heating operation, each component is controlled to ensure that the suction refrigerant pressure does not fall below a preset lower limit.

[0010] On the other hand, during hot-gas heating operation, because a portion of the high-temperature, high-pressure refrigerant discharged from the compressor flows through a bypass path and returns to the compressor, the pressure of the refrigerant drawn towards the compressor is more likely to become high compared to heat absorption heating operation. The pressure of the refrigerant drawn into the compressor can sometimes exceed the specified upper limit. In this situation, automotive air conditioning systems regulate the intake refrigerant pressure by controlling various components of the refrigerant circuit, such as the opening of the expansion valve or the heat dissipation of the interior heat exchanger. However, even with such regulation, the intake refrigerant pressure sometimes still exceeds the upper limit. When the intake refrigerant pressure exceeds the upper limit, it becomes difficult to generate a continuous and stable hot-gas operation, and the compressor's durability decreases, among other adverse effects.

[0011] The present invention was made in view of the above circumstances, and its technical problem is to achieve stable and efficient continuous hot gas heating operation and improve the durability of the compressor.

[0012] Technical solutions adopted to solve technical problems

[0013] This invention provides an automotive air conditioning device, comprising: a refrigerant circuit having a compressor, an indoor heat exchange section, an external heat exchange section, and a hot gas bypass, wherein the hot gas bypass allows at least a portion of the refrigerant compressed in the compressor to be depressurized and returned to the compressor without passing through the indoor and external heat exchange sections; and a control device that controls the refrigerant circuit and is capable of executing a hot gas heating mode, wherein a portion of the refrigerant compressed in the compressor flows through the indoor heat exchange section while the remaining portion flows through the hot gas bypass, wherein when executing the hot gas heating mode, the control device calculates a first target speed based on the intake refrigerant pressure and a second target speed based on the intake refrigerant temperature for the compressor, and controls the compressor to use the smaller of the first and second target speeds as the target speed when the intake refrigerant pressure exceeds a first threshold pressure or the intake refrigerant temperature exceeds a first threshold temperature.

[0014] Invention Effects

[0015] According to the present invention, it is possible to operate continuously and stably with high efficiency for hot gas heating, and to improve the durability of the compressor. Attached Figure Description

[0016] Figure 1 This is an explanatory diagram illustrating an example of the system structure of an automotive air conditioning device according to an embodiment of the present invention.

[0017] Figure 2 This is an explanatory diagram showing the control device of an automotive air conditioning system according to an embodiment of the present invention.

[0018] Figure 3 A diagram showing the structure of a control device and other components in an electric vehicle (EV) according to an embodiment of the invention.

[0019] Figure 4 This is an explanatory diagram showing the operation of the refrigerant circuit during hot air heating operation of an automotive air conditioning device according to an embodiment of the present invention.

[0020] Figure 5 This is a control block diagram showing how the compressor is controlled by the control device of the vehicle air conditioning system according to an embodiment of the present invention.

[0021] Figure 6 This is a flowchart illustrating the process of controlling the compressor using a control device that operates by heating hot air in an automotive air conditioning system according to an embodiment of the present invention. Detailed Implementation

[0022] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same symbols in different figures indicate parts with the same function, and repeated descriptions in each figure are omitted as appropriate. In addition, the thick black lines in the refrigerant circuit 10 in the figures indicate the refrigerant flow path for high-pressure refrigerant, and the blank lines indicate the refrigerant flow path for refrigerant after pressure reduction. In addition, the dashed lines in the refrigerant circuit 10 indicate the refrigerant flow path where refrigerant does not flow.

[0023] [Structure of refrigerant circuit, etc.]

[0024] Figure 1 An example of the structure of an automotive air conditioning device 1 according to an embodiment of the present invention is shown. The example shown here is an example and is not particularly limited to a specific structure.

[0025] The vehicle air conditioning unit 1 includes a refrigerant circuit 10 and an air conditioning unit 20. The refrigerant circuit 10 includes a compressor 2; indoor heat exchangers 21 and 22 disposed inside the air conditioning unit 20; and an outdoor heat exchanger 11 disposed outside the vehicle, arranged along the refrigerant flow path. The indoor heat exchangers 21 and 22 are configured for heat exchange between the air flowing within the air conditioning unit 20 and the refrigerant, while the outdoor heat exchanger 11 is configured for heat exchange between external gas and the refrigerant outside the vehicle. The indoor heat exchanger 21 is used to heat the air, and the indoor heat exchanger 22 is used to cool the air. Immediately downstream of the indoor heat exchanger 21, a refrigerant pressure sensor 44B is provided for detecting the outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) flowing from the indoor heat exchanger 21, and a refrigerant temperature sensor 43B is provided for detecting the outlet refrigerant temperature Tc (high-pressure side refrigerant temperature).

[0026] Compressor 2 compresses the refrigerant and circulates it within refrigerant circuit 10. The refrigerant, after compression in compressor 2, is reduced to the required pressure via a suitably selected refrigerant flow path, for example, through a first pressure-reducing section V1, a second pressure-reducing section V2, a third pressure-reducing section V3, and a fourth pressure-reducing section V4, which function as expansion valves. Flow path switching valves 12 and 13 for switching the refrigerant flow path and check valves 14 and 15 for restricting the direction of refrigerant flow are provided in refrigerant circuit 10. A storage tank 16 for recovering liquid refrigerant and separating refrigerant gas and liquid is provided immediately upstream of compressor 2 in refrigerant circuit 10. A refrigerant pressure sensor 44A for detecting the suction refrigerant pressure Ps (low-pressure side refrigerant pressure) drawn into compressor 2 and a refrigerant temperature sensor 43A for detecting the suction refrigerant temperature Ts (low-pressure side refrigerant temperature) are provided between storage tank 16 and compressor 2.

[0027] As described above, the air conditioning unit 20 includes indoor heat exchangers 21 and 22. Air drawn in from indoors or outdoors is passed through the indoor heat exchangers 21 and 22 and then blown out into the room by the blower 23. An air baffle 24 is provided in the air conditioning unit 20. Figure 1 As shown, when the air baffle 24 is fully open, the air introduced by the blower 23 passes through the indoor heat exchangers 21 and 22 and is blown out into the room.

[0028] Furthermore, when the air baffle 24 is fully closed, the inflow side of the indoor heat exchanger 21 is blocked, and the air introduced by the blower 23 only passes through the indoor heat exchanger 22 and is blown out into the room. Another air baffle 25 provided in the air conditioning unit 20 switches the air introduced into the blower 23 between the indoor and outdoor environments. The air baffle 25 can selectively close the air inlet 25A connected to the outside and the air inlet 25B connected to the inside, and draw in air from one of them. Alternatively, by placing the air baffle 25 in an intermediate position, air can be drawn in from both the air inlet 25A and the air inlet 25B.

[0029] Furthermore, although the example of direct heat exchange between the refrigerant and air in the external heat exchanger 11 and the indoor heat exchangers 21 and 22 described above has been explained, indirect heat exchange between the refrigerant and air can also be achieved via a heat carrier after heat exchange with the refrigerant. That is, it can also be configured such that the refrigerant absorbs heat from the air via the heat carrier, or that the refrigerant dissipates heat to the air via the heat carrier.

[0030] like Figure 1As shown, the vehicle air conditioning unit 1 includes a heat carrier circuit 30. The heat carrier circuit 30 circulates the heat carrier via a circulation pump 31, and heats the heat carrier in a heater (ECH: Electric Coolant Heater) 32, or recovers waste heat from temperature-controlled objects such as batteries in a temperature-controlled heat exchanger 33. Furthermore, a refrigerant heat carrier heat exchanger 34 is provided in both the refrigerant circuit 10 and the heat carrier circuit 30, where heat exchange between the refrigerant and the heat carrier occurs in a flow path 34A for refrigerant flow and a flow path 34B for heat carrier flow. The heat carrier circuit 30 is configured as needed.

[0031] [Control Device]

[0032] Vehicle air conditioning unit 1 includes Figure 2 The control device 100 shown controls the refrigerant circuit 10, the air conditioning unit 20, and the heat transfer circuit 30 based on various input signals (air conditioning indicator signals, charger connection signals, etc.) and detection signals from the sensor unit 40.

[0033] The sensor unit 40 that inputs detection signals to the control device 100 includes, for example, an external gas sensor 41 that detects the external gas state such as external gas temperature and external gas humidity; a compressor current sensor 42 that detects the power consumption (energy consumption) of the compressor 2; a refrigerant temperature sensor 43 and a refrigerant pressure sensor 44 that detect the state of the refrigerant; an occupant sensor 45 that detects whether there are occupants in the vehicle interior; and an air supply temperature sensor 46 that detects the air supply temperature of the air conditioning unit 20, etc.

[0034] Specifically, the refrigerant temperature sensor 43 includes: a refrigerant temperature sensor 43A, which detects the suction refrigerant temperature Ts (low-pressure side refrigerant temperature) drawn into the compressor 2; and a refrigerant temperature sensor 43B, which detects the outlet refrigerant temperature Tc (high-pressure side refrigerant temperature) of the indoor heat exchanger 21 (see reference). Figure 1 ).

[0035] Additionally, the refrigerant pressure sensor 44 includes: a refrigerant pressure sensor 44A, which detects the suction refrigerant pressure Ps (low-pressure side refrigerant pressure) drawn into the compressor 2; and a refrigerant pressure sensor 44B, which detects the outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) of the indoor heat exchanger 21 (see reference). Figure 1 These sensors are just one example; the sensor unit 40 also includes various sensors that detect information required by the control device 100 when performing various controls.

[0036] The controlled objects of the control device 100 are, in the refrigerant circuit 10, compressor 2, first pressure reducing unit V1, second pressure reducing unit V2, third pressure reducing unit V3, fourth pressure reducing unit V4, flow path switching valves 12 and 13, etc.; in the air conditioning unit 20, blower 23, air baffles 24 and 25, etc.; and in the heat transfer circuit 30, circulation pump 31, etc. Furthermore, the control device 100 controls the vehicle air conditioning unit 1 based on the processing results of the control device 100. In the vehicle air conditioning unit 1, the control device 100 can switch between heat absorption heating operation and hot air heating operation. In the heat absorption heating operation, the refrigerant absorbs heat in the external heat exchanger 11. In the hot air heating operation, instead of heat absorption in the external heat exchanger 11, the refrigerant compressed in the compressor 2 dissipates heat in the indoor heat exchanger 21 to heat the vehicle interior.

[0037] [Structure of the control unit in an electric vehicle (EV)]

[0038] like Figure 3 As shown, the control device 100 included in the vehicle air conditioning system 1 is configured as an ECU connected to various ECUs (Electronic Control Units) that control the electric vehicle EV via the vehicle network L. The control device 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, an I / F (Interface) for input / output 104, an I / F (Interface) for in-vehicle communication 105, etc., and all hardware is interconnected via a bus 106.

[0039] CPU 101 executes various programs stored in ROM 102 to control the control device 100. ROM 102 is non-volatile memory. For example, ROM 102 stores programs executed by CPU 101, data required by CPU 101 to execute programs, etc. RAM 103 is a main storage device such as DRAM (Dynamic Random Access Memory) or SRAM (Static Random Access Memory).

[0040] For example, RAM 103 functions as a working area used when the CPU 101 executes a program. Input / output (I / F) 104 connects to various sensors and displays located in the EV to input data to the CPU 101 and outputs data processed by the CPU 101. In-vehicle communication (I / F) 105 connects to the vehicle network L to control data transmission and reception between other ECUs located in the EV.

[0041] The control device 100 receives data related to the surrounding environment or the operating status of the EV via an I / F 104 for input / output or an I / F 105 common to vehicles, and executes the control of the vehicle air conditioning device 1 by the program executed by the CPU 101.

[0042] A battery B is installed in the EV. The battery B is charged by connecting the charger plug PS to the battery plug BP, and the battery B supplies power to the vehicle air conditioning unit 1. When the battery plug BP and plug PS are connected, a charger connection signal is sent to the control device 100 via the vehicle network L.

[0043] [Hot gas heating operation]

[0044] Since it is difficult to absorb heat through the external heat exchanger 11 at extremely low temperatures, hot gas is used for heating. In hot gas heating operation, the refrigerant does not absorb heat in the external heat exchanger 11, but instead, part or all of the refrigerant compressed in the compressor 2 dissipates heat in the indoor heat exchanger 21 to heat the vehicle interior.

[0045] exist Figure 4 The operation of the refrigerant circuit 10 during hot gas heating operation will be explained. In this operation, 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 depressurized in the third pressure reducing section V3 to become low-pressure refrigerant, passes through the refrigerant heat carrier heat exchanger 34, undergoes gas-liquid separation in the storage tank 16, and returns to the compressor 2. At this time, in the refrigerant circuit 10, by setting the first pressure reducing section V1 to be fully closed, the refrigerant does not flow into the external heat exchanger 11. Furthermore, by setting the fourth pressure reducing section V4 to be fully closed, the refrigerant does not flow into the indoor heat exchanger 22.

[0046] The refrigerant circuit 10 has a hot gas bypass 10V, which allows at least a portion of the refrigerant compressed in the compressor 2 to be depressurized and returned to the compressor 2 without passing through the indoor heat exchanger 21 and the external heat exchanger 11. In the hot gas bypass 10V, a portion of the high-temperature, high-pressure refrigerant branches off at a bifurcation point P1 immediately downstream of the compressor 2, is depressurized in the second depressurization section V2, and merges with the low-pressure refrigerant depressurized in the third depressurization section V3 at a confluence point P2 immediately upstream of the storage tank 16.

[0047] By setting up such a hot gas bypass 10V, the gaseous refrigerant passing through the hot gas bypass 10V can be mixed with the liquid refrigerant condensed by heat dissipation in the indoor heat exchanger 21, and then returned to the compressor 2 after becoming a gas-rich refrigerant. Furthermore, by increasing the refrigerant flow rate in the hot gas bypass 10V, the heat dissipation in the indoor heat exchanger 21 can be suppressed. The refrigerant flow rate in the hot gas bypass 10V is regulated by opening and closing the second pressure reducing unit V2, thus maintaining a balance between the heat dissipation of the refrigerant circuit 10 and the heat input to the compressor 2. In other words, the second pressure reducing unit V2 functions as a flow regulating unit that adjusts the flow rate of the refrigerant flowing in the hot gas bypass 10V.

[0048] During hot air heating operation, the refrigerant flow is depressurized in the third pressure reducing section V3 in the flow path via the indoor heat exchanger 21. Therefore, its upstream side becomes high-pressure refrigerant, and its downstream side becomes low-pressure refrigerant. At this time, it is important that no heat exchange occurs in the refrigerant heat carrier heat exchanger 34 in the low-pressure side flow path to maintain heating capacity. Moreover, in the air conditioning unit 20, the air introduced by the blower 23 is heated by heat dissipation in the indoor heat exchanger 21 and blown into the vehicle interior.

[0049] Furthermore, the refrigerant flow diagram for the refrigerant circuit 10 during heat absorption and heating operation is omitted. However, in the refrigerant circuit 10 during heat absorption and heating operation, the second pressure reducing unit V2, the third pressure reducing unit V3, the fourth pressure reducing unit V4, and the flow path switching valve 12 are all closed. On the other hand, the flow path switching valve 13 is fully open, and the first pressure reducing unit V1 is open.

[0050] Furthermore, during heat absorption and heating operation, the high-temperature, high-pressure refrigerant discharged from the compressor 2 passes through the indoor heat exchanger 21 within the air conditioning unit 20, where it is depressurized in the first pressure reduction section V1. The low-pressure refrigerant then passes through the external heat exchanger 11, and via the flow path switching valve 13, check valve 14, and storage tank 16, before returning to the compressor 2. Meanwhile, the high-pressure refrigerant from the compressor 2 condenses and dissipates heat in the indoor heat exchanger 21, is depressurized to low pressure in the first pressure reduction section V1, absorbs heat and evaporates in the external heat exchanger 11, and then returns to the compressor 2. Additionally, within the air conditioning unit 20, the air introduced by the blower 23 is heated by heat dissipation in the indoor heat exchanger 21 and then blown into the vehicle interior.

[0051] [Control device's control over the compressor]

[0052] The following describes the control of the compressor in the vehicle air conditioning system of this embodiment. Figure 5 This is a control block diagram of the control device 100 controlling the compressor 2. In the control device 100, the outlet refrigerant pressure Pci flowing out of the indoor heat exchanger 21 as the high-pressure side refrigerant pressure, the suction refrigerant pressure Ps of the compressor 2 as the low-pressure side refrigerant pressure, and the suction refrigerant temperature Ts of the compressor 2 are acquired at predetermined intervals, and the compressor 2 is controlled based on these.

[0053] That is, in the control device 100, based on the outlet refrigerant pressure Pci, the suction refrigerant pressure Ps, and the suction refrigerant temperature Ts, the limit determination unit 200 determines whether it is necessary to limit the target speed of the compressor 2. Figure 5 (the next section), and the protection judgment unit 300 determines whether protection for compressor 2 is required. Figure 5 of the upper paragraph).

[0054] The judgment results of the limitation judgment unit 200 and the protection judgment unit 300 are input to the selector 400, and the compressor 2 is controlled according to the output from the selector 400. In addition, the limitation judgment unit 200, the protection judgment unit 300 and the selector 400 are implemented by the CPU 101 included in the control device 100 reading the program stored in the ROM 102 into the RAM 103 and executing it.

[0055] The limitation determination unit 200 includes a Pci limitation determination unit 201, a Ps limitation determination unit 202, a Psu limitation determination unit 203, a Ts limitation determination unit 204, and a minimum value selection unit 205. The current target speed TGNC_BASE of the compressor 2, the outlet refrigerant pressure Pci, the suction refrigerant pressure Ps, and the suction refrigerant temperature Ts are input to the limitation determination unit 200, and based on these, a determination is made as to whether the target speed of the compressor 2 needs to be limited, and the target speed TGNC is calculated.

[0056] In the Pci limit determination unit 201, if the input outlet refrigerant pressure Pci exceeds a predetermined upper limit, the target speed TGNC_LPci calculated based on the outlet refrigerant pressure Pci is output to the minimum value selection unit 205. If the outlet refrigerant pressure Pci does not exceed the predetermined upper limit, the current target speed TGNC_BASE of the compressor 2 is used as the target speed TGNC_LPci and output to the minimum value selection unit 205.

[0057] In the Ps limit determination unit 202, if the input suction refrigerant pressure Ps is lower than a predetermined lower limit, the target speed TGNC_LPs calculated based on the suction refrigerant pressure Ps is output to the minimum value selection unit 205. If the suction refrigerant pressure Ps is not lower than the predetermined lower limit, the current target speed TGNC_BASE of the compressor 2 is used as the target speed TGNC_LPs and output to the minimum value selection unit 205.

[0058] In the Psu limit determination unit 203, if the input suction refrigerant pressure Ps exceeds a predetermined upper limit, the target speed TGNC_LPsu calculated based on the suction refrigerant pressure Ps is output to the minimum value selection unit 205. If the suction refrigerant pressure Ps does not exceed the predetermined upper limit, the current target speed TGNC_BASE of the compressor 2 is used as the target speed TGNC_LPsu and output to the minimum value selection unit 205.

[0059] Similarly, in the Ts limit determination unit 204, if the input intake refrigerant temperature Ts exceeds a predetermined upper limit, the target speed TGNC_LTs calculated based on the intake refrigerant temperature Ts is output to the minimum value selection unit 205. If the intake refrigerant temperature Ts does not exceed the predetermined upper limit, the current target speed TGNC_BASE of the compressor 2 is used as the target speed TGNC_LTs and output to the minimum value selection unit 205.

[0060] The minimum value selection unit 205 inputs the current target speed TGNC_BASE, target speed TGNC_LPci, target speed TGNC_LPs, target speed TGNC_LPsu and target speed TGNC_LTs of compressor 2, and outputs the minimum value among them as the target speed TGNC.

[0061] The protection determination unit 300 includes a Pci protection determination unit 301, a Ps protection determination unit 302, a Psu protection determination unit 303, a Ts protection determination unit 304, and an OR circuit 305. The outlet refrigerant pressure Pci, the suction refrigerant pressure Ps, and the suction refrigerant temperature Ts are input to the protection determination unit 300, and the compressor 2 is determined based on these values.

[0062] In the Pci protection judgment unit 301, if the input outlet refrigerant pressure Pci is greater than the aforementioned upper limit value and exceeds the protection value predetermined for protecting the compressor 2, a protection signal is output to the OR circuit 305. If the outlet refrigerant pressure Pci does not exceed the protection value, no signal is output to the OR circuit 305.

[0063] In the Ps protection judgment unit 302, if the input suction refrigerant pressure Ps is lower than the aforementioned lower limit value and below the protection value predetermined for protecting the compressor 2, a protection signal is output to the OR circuit 305. If the suction refrigerant pressure Ps is not lower than the protection value, no signal is output to the OR circuit 305.

[0064] In the Psu protection judgment unit 303, if the input suction refrigerant pressure Ps is greater than the aforementioned upper limit and exceeds the protection value predetermined for protecting the compressor 2, a protection signal is output to the OR circuit 305. If the suction refrigerant pressure Ps does not exceed the protection value, no signal is output to the OR circuit 305.

[0065] Similarly, in the Ts limit determination unit 204, if the input intake refrigerant temperature Ts is greater than the aforementioned upper limit value and exceeds a protection value predetermined for protecting the compressor 2, a protection signal is output to the OR circuit 305. If the intake refrigerant temperature Ts does not exceed the protection value, no signal is output to the OR circuit 305.

[0066] The OR circuit 305 receives protection signals from the Pci protection judgment unit 301, Ps protection judgment unit 302, Psu protection judgment unit 303, and Ts protection judgment unit 304. If any one or more protection signals are input, it determines that protection for the compressor 2 is required and outputs a protection signal to the selector 400. Conversely, if no protection signal is input from any of the Pci protection judgment unit 301, Ps protection judgment unit 302, Psu protection judgment unit 303, or Ts protection judgment unit 304, the OR circuit 305 determines that protection for the compressor 2 is not required and does not output a protection signal to the selector 400.

[0067] The limit determination unit 200 inputs the target speed to the selector 400, and inputs a protection signal only when the protection determination unit 300 requires protection for the compressor 2. If no protection signal is received from the protection determination unit 300, the compressor 2 is controlled according to the target speed TGNC calculated by the limit determination unit 200. If the protection determination unit 300 outputs a protection signal for the compressor 2, the compressor 2 is protected, that is, the drive of the compressor 2 is stopped.

[0068] During the heating operation of the vehicle air conditioning unit 1, if the intake refrigerant pressure Ps of the refrigerant circuit 10 decreases in the control device 100, the compression ratio increases, the discharge refrigerant temperature rises, and the volumetric efficiency decreases. Therefore, the various components including the compressor 2 are usually controlled in such a way that the intake refrigerant pressure is not lower than a predetermined lower limit.

[0069] Therefore, during the heating operation of the vehicle air conditioning unit 1, especially during the heat absorption and heating operation, the Pci limit judgment unit 201 and the Ps limit judgment unit 202 are mainly used to calculate whether the compressor 2 needs to be limited and the target speed TGNC when limited, and the Pci protection judgment unit 301 and the Ps protection judgment unit 302 are used to determine whether the compressor 2 needs protection.

[0070] On the other hand, as mentioned above, during hot gas heating operation, a portion of the high-temperature, high-pressure refrigerant discharged from compressor 2 returns to compressor 2 via the hot gas bypass 10V. Therefore, the suction refrigerant pressure towards compressor 2 is more likely to become high compared to heat absorption heating operation. If the suction refrigerant pressure exceeds the upper limit (the threshold pressure described later), it may lead to adverse conditions such as difficulty in maintaining stable and efficient hot gas heating operation and reduced durability of compressor 2.

[0071] Therefore, during hot gas heating operation, the control device 100 mainly calculates whether the compressor needs to be limited and the target speed TGNC during the limitation by using the Psu limitation judgment unit 203 and the Ts limitation judgment unit 204, and determines whether the compressor 2 needs protection by using the Psu protection judgment unit 303 and the Ts protection judgment unit 304.

[0072] That is, during hot gas heating operation, if the input intake refrigerant pressure Ps exceeds the first threshold pressure Ps_th1 which is a predetermined upper limit value, the Psu limit determination unit 203 outputs the target speed TGNC_LPsu calculated based on the intake refrigerant pressure Ps to the minimum value selection unit 205.

[0073] Furthermore, if the input intake refrigerant temperature Ts exceeds the first threshold temperature Ts_th1, which is a predetermined upper limit value, the Ts limit determination unit 204 outputs the target rotational speed TGNC_LTs calculated based on the intake refrigerant temperature Ts to the minimum value selection unit 205.

[0074] In the minimum value selection unit 205, the current target speed TGNC_BASE, target speed TGNC_LPci, target speed TGNC_LPs, target speed TGNC_LPsu and target speed TGNC_LTs of compressor 2 are input, and the minimum value among them is output as the target speed TGNC.

[0075] Here, the first threshold pressure Ps_th1 can be determined, for example, based on the maximum suction refrigerant pressure UL_Psu determined by the specifications of the compressor 2 and the value LON_Psu determined based on the external gas temperature, by the following equation (1).

[0076] Ps_th1 = UL_Psu - LON_Psu (1)

[0077] Furthermore, in the Psu limit determination unit 203, when the intake refrigerant pressure Ps exceeds the first threshold pressure Ps_th1, the target speed TGNC_LPsu is calculated based on the current target speed TGNC_BASE of the compressor 2, the first threshold pressure Ps_th1, the intake refrigerant pressure Ps, and the gain relative to the compressor 2, i.e., according to the following formula (2).

[0078] TGNC_LPsu=TGNC_BASE+((UL_Psu-LON_Psu)-Ps) GUL_Psu (2)

[0079] In addition, in the Psu limit determination unit 203, if the intake refrigerant pressure Ps does not exceed the first threshold pressure Ps_th1, the target speed TGNC_LPsu is set to the current target speed TGNC_BASE of the compressor 2.

[0080] Similarly, the first threshold temperature Ts_th1 can be determined, for example, based on the maximum intake refrigerant temperature UL_Ts determined by the specifications of the compressor 2 and the value LON_Tsu determined based on the external gas temperature, by the following equation (3).

[0081] Ts_th1 = UL_Ts - LON_Ts (3)

[0082] That is, preferably, the first threshold pressure Ps_th1 and the first threshold temperature Ts_th1 can be changed based on the external gas temperature. The lower the external gas temperature, the lower the first threshold pressure Ps_th1 and the first threshold temperature Ts_th1. The higher the external gas temperature, the higher the first threshold pressure Ps_th1 and the first threshold temperature Ts_th1.

[0083] The heat dissipation in the indoor heat exchanger 21 varies with the change in the external gas temperature, and the intake refrigerant pressure Ps also varies. However, by changing the first threshold pressure Ps_th1 and the first threshold temperature Ts_th1 based on the external gas temperature, a more appropriate first threshold pressure Ps_th1 and first threshold temperature Ts_th1 corresponding to the change in intake refrigerant pressure Ps caused by the change in the external gas temperature can be determined.

[0084] Furthermore, in the Ts limit determination unit 204, when the intake refrigerant temperature Ts exceeds the first threshold temperature Ts_th1, the target speed TGNC_LTs is calculated based on the current target speed TGNC_BASE of the compressor 2, the first threshold temperature Ts_th1, the intake refrigerant temperature Ts, and the gain relative to the compressor 2, i.e., according to the following formula (4).

[0085] TGNC_LTs=TGNC_BASE+((UL_Ts-LON_Ts)-Ts)*GUL_Ts (4)

[0086] In addition, in the Ts limit determination unit 204, if the intake refrigerant temperature Ts does not exceed the first threshold temperature Ts_th1, the target speed TGNC_LTs is set to the current target speed TGNC_BASE of the compressor 2.

[0087] On the other hand, the Psu protection determination unit 303 outputs a protection signal to the OR circuit 305 when the input intake refrigerant pressure Ps exceeds a second threshold pressure Ps_th2, which is greater than the first threshold pressure Ps_th1. Similarly, in the Ts protection determination unit 304, when the input intake refrigerant temperature Ts exceeds a second threshold temperature Ts_th2, which is greater than the first threshold temperature Ts_th1, a protection signal is output to the OR circuit 305.

[0088] The OR circuit 305 receives protection signals from the Psu protection judgment unit 303 and the Ts protection judgment unit 304. If a protection signal is input from either the Psu protection judgment unit 303 or the Ts protection judgment unit 304, it determines that protection for the compressor 2 is required. If no protection signal is input from either the Psu protection judgment unit 303 or the Ts protection judgment unit 304, it determines that protection for the compressor 2 is not required.

[0089] Here, the second threshold pressure Ps_th2 is a value larger than the first threshold pressure Ps_th1, and is a protection value predetermined to protect the compressor 2. For example, it can be determined by the following equation (5) based on the maximum suction refrigerant pressure UL_Psu determined by the specifications of the compressor 2 and the value HYS_Psu that takes into account hysteresis.

[0090] Ps_th2 = UL_Psu - HYS_Psu (5)

[0091] Similarly, the second threshold temperature Ts_th2 is a larger value than the first threshold temperature Ts_th1, and is a protection value predetermined to protect the compressor 2. For example, it can be determined by the following equation (6) based on the maximum suction refrigerant temperature UL_Ts determined by the specifications of the compressor 2 and the value HYS_Ys that takes into account hysteresis.

[0092] Ts_th2=UL_Ts-HYS_Ts (6)

[0093] according to Figure 6 The flowchart illustrates the control device 100's control of the compressor 2 in the hot air heating operation of the vehicle air conditioning unit configured in this way.

[0094] like Figure 6 As shown, when the vehicle air conditioning unit 1 is in hot air heating operation (step S11), the control device 100 obtains the intake refrigerant pressure Ps from the refrigerant pressure sensor 44A installed on the intake side of the compressor 2, and obtains the intake refrigerant temperature Ts from the refrigerant temperature sensor 43A at a predetermined cycle (step S12).

[0095] In the control device 100, when the input intake refrigerant pressure Ps is below the first threshold pressure Ps_th1 (No in step S13) and the intake refrigerant temperature Ts is also below the first threshold temperature Ts_th1 (No in step S14), the compressor 2 is controlled based on the current target speed TGNC_BASE (step S15).

[0096] On the other hand, even if the intake refrigerant pressure Ps is below the first threshold pressure Ps_th1 (No in step S13) and the intake refrigerant temperature Ts is still greater than the first threshold temperature Ts_th1 (Yes in step S14), proceed to step S17, and determine whether to limit the target speed of compressor 2 (proceed to step S18) or protect compressor 2 based on the intake refrigerant temperature Ts (proceed to step S21).

[0097] This is because even if the intake refrigerant pressure Ps is below the first threshold pressure Ps_th1 (No in step S13), there is still a situation where the intake refrigerant temperature Ts becomes an overheated state that rises compared to the saturation temperature. Therefore, in order to ensure safety, it is preferable to consider the relationship between the intake refrigerant temperature Ts and the first threshold temperature Ts_th1 and the second threshold temperature Ts_th2 to control the compressor 2.

[0098] In addition, if the intake refrigerant pressure Ps is greater than the first threshold pressure Ps_th1 ("Yes" in step S13) and less than the second threshold pressure Ps_th2 ("No" in step S16), proceed to step S17, and determine whether to limit the target speed of compressor 2 (proceed to step S18) or protect compressor 2 (proceed to step S21) by using the intake refrigerant temperature Ts.

[0099] In step S17, if the refrigerant intake temperature Ts is greater than the first threshold temperature Ts_th1 ("Yes" in step S14) and less than the second threshold temperature Ts_th2 ("No" in step S17), the target speed TGNC_LPsu and the target speed TGNC_LTs are obtained (steps S18 and S19), and the compressor 2 is controlled by using the smaller one as the target speed TGNC (step S20).

[0100] If the intake refrigerant pressure Ps exceeds the second threshold pressure Ps_th2 ("Yes" in step S16) and the intake refrigerant temperature Ts exceeds the second threshold temperature Ts_th2 ("Yes" in step S17), the compressor 2 is protected, that is, the operation of the compressor 2 is stopped (step S21).

[0101] After stopping the compressor 2, the control device 100 monitors whether the suction refrigerant pressure Ps is lower than the second threshold pressure Ps_th2 (step S22) and whether the suction refrigerant temperature Ts is lower than the second threshold temperature Ts_th2 (step S23). If the suction refrigerant pressure Ps is lower than the second threshold pressure Ps_th2 ("Yes" in step S22) and the suction refrigerant temperature Ts is lower than the second threshold temperature Ts_th2 ("Yes" in step S23), the control device 100 restarts the compressor 2 (step S24), and repeats the above process until the hot gas heating operation ends (step S25).

[0102] Thus, in the vehicle air conditioning unit 1 of this embodiment, during hot air heating operation, a first target speed TGNC_LPsu based on the intake refrigerant pressure Ps and a second target speed TGNC_LTs based on the intake refrigerant temperature are calculated for the compressor 2. Then, if the intake refrigerant pressure Ps exceeds a first threshold pressure Ps_th1, or if the intake refrigerant temperature Ts exceeds a first threshold temperature Ts_th1, the compressor 2 is controlled using the smaller of the first target speed TGNC_LPsu and the second target speed TGNC_LTs as the target speed TGNC.

[0103] Furthermore, in the control device 100, since the first threshold pressure Ps_th1 and the first threshold temperature Ts_th1 are changed in accordance with the change of the external gas temperature, the first threshold pressure Ps_th1 and the first threshold temperature Ts_th1 corresponding to the change of the intake refrigerant pressure Ps caused by the change of the external gas temperature can be determined, and the compressor 2 can be controlled at the optimal target speed TGNC regardless of the change of the external gas temperature.

[0104] In particular, when the external gas temperature decreases, the intake refrigerant pressure Ps also decreases. However, by reducing the first threshold pressure Ps_th1 and the first threshold temperature Ts_th1, the compressor 2 can be controlled at the optimal target speed TGNC corresponding to the external gas temperature, which can be more stable and efficient even in harsh environments at ultra-low temperatures where hot gas is used for heating.

[0105] In this way, by controlling the intake refrigerant pressure Ps and intake refrigerant temperature Ts to converge within a specified range that includes their target values, stable and efficient continuous hot gas heating operation can be achieved, and the durability of the compressor can be improved.

[0106] Furthermore, in the control device 100, even when the control described above is performed, if the intake refrigerant pressure Ps exceeds the second threshold pressure Ps_th2 which is greater than the first threshold pressure Ps_th1, or if the intake refrigerant temperature Ts exceeds the second threshold temperature Ts_th2 which is greater than the first threshold temperature Ts_th1, the drive of the compressor 2 is stopped. Therefore, the durability of the compressor 2 can be ensured, and safety can be guaranteed.

[0107] Subsequently, when the intake refrigerant pressure Ps is lower than the second threshold pressure Ps_th2 and the intake refrigerant temperature Ts is lower than the second threshold temperature Ts_th2, the control device 100 restarts the compressor 2. Therefore, the durability of the compressor 2 can be ensured, and the interrupted hot gas heating operation can be restarted under stable and efficient continuous conditions.

[0108] As described above, according to this embodiment, during hot gas heating operation, stable and efficient continuous hot gas heating operation can be achieved, and the durability of the compressor can be improved.

[0109] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the specific structure is not limited to these embodiments. Even design changes that do not depart from the scope of the present invention are included in the present invention.

[0110] Symbol Explanation

[0111] 1: Vehicle air conditioning unit; 2: Compressor; 10: Refrigerant circuit; 10V: Hot gas bypass.

[0112] 11: External heat exchanger; 12, 13: Flow path switching valve; 14, 15: Check valve.

[0113] 16: Storage tank; 20: Air conditioning unit; 21, 22: Indoor heat exchanger

[0114] 23: Blower; 24, 25: Air baffle; 25A, 25B: Air inlet

[0115] 30: Heat transfer circuit; 31: Circulating pump; 33: Temperature-regulating heat exchanger

[0116] 34: Refrigerant heat transfer medium heat exchanger; 34A, 34B: Flow path; 40: Sensor section

[0117] 41: External gas sensor; 42: Compressor current sensor; 43, 43A: Refrigerant temperature sensor

[0118] 44, 44A, 44B: Refrigerant pressure sensor; 45: Occupant sensor; 46: Supply air temperature sensor

[0119] 100: Control device.

Claims

1. A vehicle air conditioning unit, comprising: A refrigerant circuit having a compressor, an indoor heat exchange section, an external heat exchange section, and a hot gas bypass, wherein the hot gas bypass allows at least a portion of the refrigerant compressed in the compressor to be depressurized and returned to the compressor without passing through the indoor heat exchange section and the external heat exchange section; as well as A control device controls the refrigerant circuit and is capable of executing a hot gas heating mode, which allows a portion of the refrigerant compressed in the compressor to flow through the indoor heat exchange section while the remaining portion flows through the hot gas bypass. When the control device executes the hot gas heating mode... For the compressor, a first target speed based on the suction refrigerant pressure and a second target speed based on the suction refrigerant temperature are calculated respectively. When the intake refrigerant pressure exceeds the first threshold pressure, or when the intake refrigerant temperature exceeds the first threshold temperature, the compressor is controlled by using the smaller of the first target speed and the second target speed as the target speed.

2. The vehicle air conditioning device as described in claim 1, characterized in that, The control device can change the first threshold pressure and the first threshold temperature based on the external gas temperature, and adjust them in such a way that the lower the external gas temperature, the lower the first threshold pressure and the first threshold temperature.

3. The vehicle air conditioning device as described in claim 1 or 2, characterized in that, If the intake refrigerant pressure exceeds a second threshold pressure greater than the first threshold pressure, or if the intake refrigerant temperature exceeds a second threshold temperature greater than the first threshold temperature, the control device stops the compressor drive.

4. The vehicle air conditioning device as described in claim 3, characterized in that, When the intake refrigerant pressure is lower than the second threshold pressure and the intake refrigerant temperature is lower than the second threshold temperature, the control device restarts the compressor.

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