Air conditioner for vehicle

Abstract

To stably and effectively continue hot gas heating operation, and improve durability of a compressor.SOLUTION: An air conditioner for a vehicle includes a refrigerant circuit including a compressor, an indoor heat exchange part, an external heat exchange part, and a hot gas bypass for decompressing at least a part of a refrigerant compressed by the compressor without through the indoor heat exchange part and the external heat exchange part, and returning the decompressed refrigerant to the compressor, and a control device for controlling the refrigerant circuit, and being capable of executing a hot gas heating mode of flowing the part of the refrigerant compressed by the compressor to the indoor heat exchange part and flowing the remaining refrigerant to the hot gas bypass, wherein the control device calculates each of first target rotating speed based on a suction refrigerant pressure and second target rotating speed based on a suction refrigerant temperature with respect to the compressor, during execution of the hot gas heating mode, and controls the compressor so that any smaller one of the first target rotating speed and the second target rotating speed is set as the target rotating speed, when the suction refrigerant pressure exceeds a first threshold pressure or when the suction refrigerant temperature exceeds a first threshold temperature.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

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

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

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

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

[0006] In the above-mentioned vehicle air conditioner, in order to continue stable and effective operation not only in endothermic heating operation in which heat is absorbed from outside air, but also in the above-mentioned hot gas heating operation, each component of the refrigerant circuit is controlled so that the pressure and temperature on the suction side and discharge side of the compressor are within a predetermined range including a target value. In particular, when the suction refrigerant pressure decreases, the compression ratio increases and the discharge refrigerant temperature increases, resulting in a decrease in volumetric efficiency. Therefore, in the endothermic heating operation, each component is controlled so that the suction refrigerant pressure does not fall below a predetermined lower limit.

[0007] On the other hand, in hot gas heating operation, a part of the high-temperature, high-pressure refrigerant discharged from the compressor is returned to the compressor through a bypass passage, so that the suction refrigerant pressure to the compressor tends to be higher than that in endothermic heating operation, and the suction refrigerant pressure may exceed a predetermined upper limit. In such a case, the vehicle air conditioner adjusts the suction refrigerant pressure by controlling each component of the refrigerant circuit, for example, by controlling the opening of the expansion valve or the amount of heat dissipated in the indoor heat exchanger, but even with such adjustments, the suction refrigerant pressure may exceed the upper limit. If the suction refrigerant pressure exceeds the upper limit, problems such as difficulty in continuing stable hot gas operation and reduced durability of the compressor may occur.

[0008] The present invention has been made in consideration of the above circumstances, and has as its objective to continue hot gas heating operation stably and effectively while improving the durability of the compressor. [Means for solving the problem]

[0009] The present invention provides an air conditioning system for a vehicle comprising: a refrigerant circuit including a compressor, an indoor heat exchange unit, an external heat exchange unit, and 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 device that controls the refrigerant circuit and is capable of executing a hot gas heating mode in which a portion of the refrigerant compressed by the compressor flows through the indoor heat exchange unit and the remainder flows through the hot gas bypass. When the hot gas heating mode is executed, the control device calculates, for the compressor, a first target rotation speed based on an intake refrigerant pressure and a second target rotation speed based on an intake refrigerant temperature, and controls the compressor with the smaller of the first target rotation speed or the second target rotation speed as the target rotation speed when the intake refrigerant pressure exceeds a first threshold pressure or when the intake refrigerant temperature exceeds the first threshold temperature. Effect of the Invention

[0010] According to the present invention, it is possible to continue hot gas heating operation stably and effectively, and to improve the durability of the compressor. [Brief description of the drawings]

[0011] [Figure 1] 1 is an explanatory diagram showing an example of a system configuration of a vehicle air conditioner according to an embodiment of the present invention; [Diagram 2] 1 is an explanatory diagram showing a control device for a vehicle air conditioner according to an embodiment of the present invention; [Diagram 3] 1 is a diagram showing the configuration of a control device and the like in an electric vehicle (EV) according to an embodiment of the present invention. [Figure 4] FIG. 4 is an explanatory diagram showing the operation of the refrigerant circuit during hot gas heating operation in the vehicle air conditioner according to the embodiment of the present invention. [Diagram 5] 2 is a control block diagram of a compressor by a control device of a vehicle air conditioner according to the embodiment of the present invention. FIG. [Figure 6] 5 is a flowchart showing a flow of control of a compressor by a control device for hot gas heating operation in the vehicle air conditioner according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same reference numerals in different drawings indicate parts with the same functions, and duplicated descriptions in each drawing will be omitted as appropriate. In the drawings, the thick black lines in the refrigerant circuit 10 indicate refrigerant flow paths through which high-pressure refrigerant flows, and the outline lines indicate refrigerant flow paths through which refrigerant flows after decompression. In addition, the dashed lines in the refrigerant circuit 10 indicate refrigerant flow paths through which refrigerant does not flow.

[0013] [Refrigerant circuit configuration, etc.] 1 shows a configuration example of a vehicle air conditioner 1 according to an embodiment of the present invention. The configuration example shown here is just one example, and the present invention is not particularly limited to a specific configuration.

[0014] The vehicle air conditioner 1 includes a refrigerant circuit 10 and an air conditioning unit 20. The refrigerant circuit 10 includes a compressor 2, indoor heat exchangers 21 and 22 provided inside the air conditioning unit 20, and an external heat exchanger 11 provided outside the vehicle cabin, which are arranged along a refrigerant flow path. The indoor heat exchangers 21 and 22 are provided for heat exchange between the air flowing through the air conditioning unit 20 and the refrigerant, and the external heat exchanger 11 is provided for heat exchange between the outside air and the refrigerant outside the vehicle cabin. The indoor heat exchanger 21 is for heating the air, and the indoor heat exchanger 22 is for cooling the air. A refrigerant pressure sensor 44B for detecting an outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) and a refrigerant temperature sensor 43B for detecting an outlet refrigerant temperature Tc (high-pressure side refrigerant temperature) from the indoor heat exchanger 21 are provided immediately downstream of the indoor heat exchanger 21.

[0015] 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 through a refrigerant flow path appropriately selected, for example, through a first pressure reduction section V1, a second pressure reduction section V2, a third pressure reduction section V3, and 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 regulating the flow direction of the refrigerant. An accumulator 16 is provided immediately upstream of the compressor 2 in the refrigerant circuit 10 to recover liquid refrigerant and separate the refrigerant into gas and liquid. A refrigerant pressure sensor 44A for detecting a suction refrigerant pressure Ps (low-pressure side refrigerant pressure) sucked into the compressor 2 and a refrigerant temperature sensor 43A for detecting a suction refrigerant temperature Ts (low-pressure side refrigerant temperature) are provided between the accumulator 16 and the compressor 2.

[0016] As described above, the air conditioning unit 20 includes the indoor heat exchangers 21, 22 therein, and air introduced from the room or the outside by the blower 23 passes through the indoor heat exchangers 21, 22 and is blown into the room. The air conditioning unit 20 is provided with an air damper 24. When the air damper 24 shown in FIG. 1 is fully open, the air introduced by the blower 23 passes through both the indoor heat exchangers 21, 22 and is blown into the room.

[0017] When the air damper 24 is fully closed, it blocks the inlet side of the indoor heat exchanger 21, and the air introduced by the blower 23 passes only through the indoor heat exchanger 22 before being blown into the room. Another air damper 25 provided in the air conditioning unit 20 switches the air introduced into the blower 23 between indoor and outdoor. The air damper 25 can selectively close air inlet 25A connected to the outdoors and air inlet 25B connected to the indoors to take in air from either one of them. Also, by placing the air damper 25 in an intermediate position, it is possible to take in air from both air inlet 25A and air inlet 25B.

[0018] Although the above-mentioned external heat exchanger 11 and indoor heat exchangers 21, 22 are described as examples in which the refrigerant and air directly exchange heat, the refrigerant and air may indirectly exchange heat via a heat medium that has exchanged heat with the refrigerant. That is, the refrigerant may absorb heat from the air via the heat medium, or the refrigerant may dissipate heat to the air via the heat medium.

[0019] As shown in Fig. 1, the vehicle air conditioner 1 includes a heat medium circuit 30. The heat medium circuit 30 circulates the heat medium using a circulation pump 31, heats the heat medium using a heater (ECH: Electric Coolant Heater) 32, and recovers waste heat from a temperature control object such as a battery using a temperature control object heat exchanger 33. The refrigerant circuit 10 and the heat medium circuit 30 are provided with a refrigerant-heat medium heat exchanger 34 that exchanges heat between the refrigerant and the heat medium in a flow path 34A through which the refrigerant flows and a flow path 34B through which the heat medium flows. The heat medium circuit 30 is provided as necessary.

[0020] [Control device] The vehicle air conditioner 1 includes a control device 100 shown in Fig. 2. The control device 100 controls the refrigerant circuit 10, the air conditioning unit 20, and the heat medium circuit 30 described above, based on various input signals (such as an air conditioning instruction signal and a charger connection signal) and detection signals from a sensor section 40.

[0021] The sensor section 40, which inputs detection signals to the control device 100, includes, for example, an outside air sensor 41 which detects outside air conditions such as outside air temperature and outside air humidity, a compressor current sensor 42 for detecting the power consumption (energy consumption) of the compressor 2, a refrigerant temperature sensor 43 and a refrigerant pressure sensor 44 which detect the state of the refrigerant, an occupant sensor 45 which detects the presence or absence of an occupant in the vehicle cabin, and a blower temperature sensor 46 which detects the blower temperature of the air conditioning unit 20.

[0022] In particular, the refrigerant temperature sensor 43 includes a refrigerant temperature sensor 43A that detects the intake refrigerant temperature Ts (low-pressure side refrigerant temperature) sucked into the compressor 2, and a refrigerant temperature sensor 43B that detects the outlet refrigerant temperature Tc (high-pressure side refrigerant temperature) of the indoor heat exchanger 21 (see Figure 1).

[0023] The refrigerant pressure sensor 44 also includes a refrigerant pressure sensor 44A that detects a suction refrigerant pressure Ps (low-pressure side refrigerant pressure) sucked into the compressor 2, and a refrigerant pressure sensor 44B that detects an outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) of the indoor heat exchanger 21 (see FIG. 1). These sensors are merely examples, and various sensors that detect information required when the control device 100 performs various controls are provided as the sensor unit 40.

[0024] The control targets of the control device 100 are the compressor 2, the first pressure reducing section V1, the second pressure reducing section V2, the third pressure reducing section V3, the fourth pressure reducing section V4, and the flow path switching valves 12 and 13 in the refrigerant circuit 10, the blower 23, the air dampers 24 and 25 in the air conditioning unit 20, and the circulation pump 31 in the heat medium circuit 30. The control device 100 also controls the vehicle air conditioner 1 according to the processing results of the control device 100. In the vehicle air conditioner 1, the control device 100 can switch between an endothermic heating operation in which the refrigerant is caused to absorb heat in the external heat exchanger 11, and a hot gas heating operation in which the refrigerant compressed by the compressor 2 is caused to release heat in the indoor heat exchanger 21 without the refrigerant absorbing heat in the external heat exchanger 11, thereby heating the vehicle interior.

[0025] [Configuration of control device in electric vehicle (EV)] 3, the control device 100 provided in the vehicle air conditioner 1 is configured as one ECU connected to various ECUs (Electronic Control Units) that control the electric vehicle EV via an in-vehicle network L. The control device 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, an I / F (Interface) 104 for input / output, an I / F (Interface) 105 for in-vehicle communication, and the like, and each piece of hardware is connected to each other via a bus 106.

[0026] The CPU 101 executes various programs stored in the ROM 102 to control the control device 100. The ROM 102 is a non-volatile memory. For example, the ROM 102 stores programs executed by the CPU 101, data necessary for the CPU 101 to execute the programs, etc. The RAM 103 is a main storage device such as a DRAM (Dynamic Random Access Memory) or an SRAM (Static Random Access Memory).

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

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

[0029] The EV is equipped with a battery B. The battery B is charged by connecting a charger plug PS to a battery plug BP, and power is supplied to the vehicle air conditioner 1 via the battery B. The state in which the plug PS is connected to the battery plug BP is transmitted to the control device 100 via the in-vehicle network L as a charger connection signal.

[0030] [Hot gas heating operation] At extremely low temperatures, hot gas heating is used because it is difficult for the external heat exchanger 11 to absorb heat. In hot gas heating operation, the refrigerant compressed by the compressor 2 is not allowed to absorb heat in the external heat exchanger 11, but some or all of the refrigerant is caused to dissipate heat in the indoor heat exchanger 21 to heat the vehicle interior.

[0031] The operation of the refrigerant circuit 10 in hot gas heating operation will be described with reference to Fig. 4. In this operation, part of the high-temperature, high-pressure refrigerant discharged from the compressor 2 passes through the indoor heat exchanger 21 and the flow path switching valve 12, is depressurized in the third pressure reduction section V3 to become a low-pressure refrigerant, passes through the refrigerant heat medium heat exchanger 34, is separated into gas and liquid in the accumulator 16, and returns to the compressor 2. At this time, in the refrigerant circuit 10, the first pressure reduction section V1 is fully closed, so that the refrigerant does not flow to the external heat exchanger 11. Also, the fourth pressure reduction section V4 is fully closed, so that the refrigerant does not flow to the indoor heat exchanger 22.

[0032] The refrigerant circuit 10 has a hot gas bypass 10V that reduces the pressure of at least a portion of the refrigerant compressed by the compressor 2 and returns it to the compressor 2 without passing through the indoor heat exchanger 21 and the external heat exchanger 11. In the hot gas bypass 10V, a portion of the high-temperature, high-pressure refrigerant is branched off at a branch point P1 immediately downstream of the compressor 2, reduced in pressure at a second pressure reduction section V2, and merged with the low-pressure refrigerant reduced in pressure at a third pressure reduction section V3 at a junction point P2 immediately upstream of the accumulator 16.

[0033] By providing such a hot gas bypass 10V, the liquid refrigerant condensed by heat radiation in the indoor heat exchanger 21 can be mixed with the gas refrigerant that has passed through the hot gas bypass 10V to produce a gas-rich refrigerant, which can then be returned to the compressor 2. In addition, by increasing the flow rate of the refrigerant flowing through the hot gas bypass 10V, the amount of heat radiation in the indoor heat exchanger 21 can be suppressed, and by opening and closing the second pressure reduction section V2 to adjust the flow rate of the refrigerant flowing through the hot gas bypass 10V, the balance between the amount of heat radiation from the refrigerant circuit 10 and the amount of heat input to the compressor 2 can be maintained. In other words, the second pressure reduction section V2 functions as a flow rate adjustment section that adjusts the flow rate of the refrigerant flowing through the hot gas bypass 10V.

[0034] During hot gas heating operation, the refrigerant flow in the flow path passing through the indoor heat exchanger 21 is decompressed in the third decompression section V3, so that the refrigerant upstream of that becomes high pressure refrigerant and the refrigerant downstream of that becomes low pressure refrigerant. At this time, it is important in order to maintain the heating capacity that heat exchange is not performed in the refrigerant heat medium heat exchanger 34 in the low pressure side flow path. In the air conditioning unit 20, the air introduced by the blower 23 is heated by heat radiation in the indoor heat exchanger 21 and is blown out into the vehicle cabin.

[0035] Although the flow of refrigerant in the refrigerant circuit 10 during endothermic heating operation is not shown in the drawings, in the refrigerant circuit 10 during endothermic heating operation, the second pressure reduction section V2, the third pressure reduction section V3, the fourth pressure reduction section V4, and the flow path switching valve 12 are fully closed. On the other hand, the flow path switching valve 13 is fully open, and the first pressure reduction section V1 is open.

[0036] In the endothermic heating operation, the high-temperature, high-pressure refrigerant discharged from the compressor 2 passes through the indoor heat exchanger 21 in the air conditioning unit 20 and is depressurized in the first depressurization section V1, and the low-pressure refrigerant passes through the external heat exchanger 11 and is returned to the compressor 2 via the flow path switching valve 13, the check valve 14, and the accumulator 16. At this time, the high-pressure refrigerant discharged from the compressor 2 condenses and releases heat in the indoor heat exchanger 21, is depressurized in the first depressurization section V1 to become a low-pressure refrigerant, absorbs heat and evaporates in the external heat exchanger 11, and returns to the compressor 2. In the air conditioning unit 20, the air introduced by the blower 23 is heated by the heat released in the indoor heat exchanger 21 and is blown into the vehicle cabin.

[0037] [Control of compressor by control device] The control of the compressor in the vehicle air conditioner according to this embodiment will be described below. The control device 100 acquires, at a predetermined period, the outlet refrigerant pressure Pci leaving 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, and controls the compressor 2 based on these.

[0038] That is, in the control device 100, the restriction judgment unit 200 judges whether the target rotation speed of the compressor 2 needs to be restricted based on the outlet refrigerant pressure Pci, the suction refrigerant pressure Ps, and the suction refrigerant temperature Ts (lower part of Figure 5), and the protection judgment unit 300 judges whether protection of the compressor 2 is needed (upper part of Figure 5).

[0039] The results of the judgments made by the limit judgment unit 200 and the protection judgment unit 300 are input to a selector 400, and the compressor 2 is controlled according to the output from the selector 400. The limit judgment unit 200, the protection judgment unit 300, and the selector 400 are realized by a CPU 101 provided in the control device 100 reading a program stored in a ROM 102 into a RAM 103 and executing the program.

[0040] The restriction determination unit 200 includes a Pci restriction determination unit 201, a Ps restriction determination unit 202, a Psu restriction determination unit 203, a Ts restriction determination unit 204, and a minimum value selection unit 205. The current target rotation 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 restriction determination unit 200, and based on these, it is determined whether or not the target rotation speed of the compressor 2 needs to be restricted, and the target rotation speed TGNC is calculated.

[0041] When the input outlet refrigerant pressure Pci exceeds a predetermined upper limit, the Pci restriction determination unit 201 outputs a target rotation speed TGNC_LPci calculated based on the outlet refrigerant pressure Pci to a minimum value selection unit 205. When the outlet refrigerant pressure Pci does not exceed the predetermined upper limit, the Pci restriction determination unit 201 outputs the current target rotation speed TGNC_BASE of the compressor 2 to the minimum value selection unit 205 as the target rotation speed TGNC_LPci.

[0042] When the input suction refrigerant pressure Ps falls below a predetermined lower limit, the Ps limit determination unit 202 outputs a target rotation speed TGNC_LPs calculated based on the suction refrigerant pressure Ps to a minimum value selection unit 205. When the suction refrigerant pressure Ps does not fall below the predetermined value, the Ps limit determination unit 202 outputs the current target rotation speed TGNC_BASE of the compressor 2 to the minimum value selection unit 205 as the target rotation speed TGNC_LPs.

[0043] When the input suction refrigerant pressure Ps exceeds a predetermined upper limit, the Psu restriction determination unit 203 outputs a target rotation speed TGNC_LPsu calculated based on the suction refrigerant pressure Ps to a minimum value selection unit 205. When the suction refrigerant pressure Ps does not exceed the predetermined upper limit, the Psu restriction determination unit 203 outputs the current target rotation speed TGNC_BASE of the compressor 2 to the minimum value selection unit 205 as the target rotation speed TGNC_LPsu.

[0044] Similarly, when the input suction refrigerant temperature Ts exceeds a predetermined upper limit, the Ts limit determination unit 204 outputs the target rotation speed TGNC_LTs calculated based on the suction refrigerant temperature Ts to the minimum value selection unit 205. When the suction refrigerant temperature Ts does not exceed the predetermined upper limit, the Ts limit determination unit 204 outputs the current target rotation speed TGNC_BASE of the compressor 2 to the minimum value selection unit 205 as the target rotation speed TGNC_LTs.

[0045] The current target rotation speeds TGNC_BASE, TGNC_LPci, TGNC_LPs, TGNC_LPsu, and TGNC_LTs of the compressor 2 are input to the minimum value selection unit 205, and the minimum value among these is output as the target rotation speed TGNC.

[0046] 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 based on these, it is determined whether or not protection of the compressor 2 is required.

[0047] In the Pci protection determination unit 301, when the input outlet refrigerant pressure Pci is greater than the above-mentioned upper limit value and exceeds a predetermined protection value for protecting the compressor 2, a protection signal is output to the OR circuit 305. When the outlet refrigerant pressure Pci does not exceed the protection value, no signal is output to the OR circuit 305.

[0048] In the Ps protection determination unit 302, when the input suction refrigerant pressure Ps is smaller than the above-mentioned lower limit value and falls below a predetermined protection value for protecting the compressor 2, a protection signal is output to the OR circuit 305. When the suction refrigerant pressure Ps does not fall below the protection value, no signal is output to the OR circuit 305.

[0049] In the Psu protection determination unit 303, when the input suction refrigerant pressure Ps is greater than the above-mentioned upper limit value and exceeds a predetermined protection value for protecting the compressor 2, a protection signal is output to the OR circuit 305. When the suction refrigerant pressure Ps does not exceed the protection value, no signal is output to the OR circuit 305.

[0050] Similarly, in the Ts limit determination unit 204, when the input suction refrigerant temperature Ts is greater than the above-mentioned upper limit value and exceeds a predetermined protection value for protecting the compressor 2, a protection signal is output to the OR circuit 305. When the suction refrigerant temperature Ts does not exceed the protection value, no signal is output to the OR circuit 305.

[0051] The OR circuit 305 receives protection signals from the PCI protection determination unit 301, the Ps protection determination unit 302, the Psu protection determination unit 303, and the Ts protection determination unit 304, and when one or more protection signals are input, determines that protection of the compressor 2 is required, and outputs a protection signal to the selector 400. When no protection signal is input from any of the PCI protection determination unit 301, the Ps protection determination unit 302, the Psu protection determination unit 303, and the Ts protection determination unit 304, the OR circuit 305 determines that protection of the compressor 2 is not required, and does not output a protection signal to the selector 400.

[0052] The selector 400 receives an input of the target rotation speed from the limit determination unit 200, and also receives a protection signal only when the protection determination unit 300 requires protection of the compressor 2. When a protection signal is not received from the protection determination unit 300, the selector 400 controls the compressor 2 in accordance with the target rotation speed TGNC calculated by the limit determination unit 200, and when a protection signal for the compressor 2 is output by the protection determination unit 300, the selector 400 protects the compressor 2, i.e., stops driving the compressor 2.

[0053] During heating operation of the vehicle air conditioner 1, when the suction refrigerant pressure Ps of the refrigerant circuit 10 decreases, the compression ratio increases and the discharge refrigerant temperature rises, resulting in a decrease in volumetric efficiency. Therefore, normally, the control device 100 controls each component device including the compressor 2 so that the suction refrigerant pressure does not fall below a predetermined lower limit value.

[0054] Therefore, during heating operation of the vehicle air conditioner 1, particularly during endothermic heating operation, the Pci restriction judgment unit 201 and the Ps restriction judgment unit 202 mainly calculate whether or not restriction of the compressor 2 is necessary and the target rotation speed TGNC at the time of restriction, and the Pci protection judgment unit 301 and the Ps protection judgment unit 302 judge whether or not protection of the compressor 2 is necessary.

[0055] On the other hand, as described above, in hot gas heating operation, a portion of the high-temperature, high-pressure refrigerant discharged from the compressor 2 returns to the compressor 2 via the hot gas bypass 10V, so the suction refrigerant pressure to the compressor 2 tends to be higher than in endothermic heating operation. If the suction refrigerant pressure exceeds an upper limit (a threshold pressure, described later), problems such as difficulty in stably and effectively continuing the hot gas heating operation and a decrease in the durability of the compressor 2 may occur.

[0056] Therefore, during hot gas heating operation, the control device 100 mainly calculates whether compressor restriction is necessary and the target rotation speed TGNC at the time of restriction using the Psu restriction judgment unit 203 and the Ts restriction judgment unit 204, and judges whether protection of the compressor 2 is necessary using the Psu protection judgment unit 303 and the Ts protection judgment unit 304.

[0057] In other words, during hot gas heating operation, when the input suction refrigerant pressure Ps exceeds the first threshold pressure Ps_th1, which is a predetermined upper limit value, the Psu limitation judgment unit 203 outputs the target rotation speed TGNC_LPsu calculated based on the suction refrigerant pressure Ps to the minimum value selection unit 205.

[0058] In addition, when the input suction refrigerant temperature Ts exceeds a first threshold temperature Ts_th1, which is a predetermined upper limit value, the Ts limit determination unit 204 outputs the target rotation speed TGNC_LTs calculated based on the suction refrigerant temperature Ts to the minimum value selection unit 205.

[0059] The current target rotation speeds TGNC_BASE, TGNC_LPci, TGNC_LPs, TGNC_LPsu, and TGNC_LTs of the compressor 2 are input to a minimum value selection unit 205, and the minimum value among these is output as the target rotation speed TGNC.

[0060] Here, the first threshold pressure Ps_th1 can be determined, for example, by the following formula (1) based on the maximum suction refrigerant pressure UL_Psu determined by the specifications of the compressor 2 and a value LON_Psu determined based on the outside air temperature. Ps_th1=UL_Psu-LON_Psu...(1)

[0061] Then, in the Psu restriction judgment unit 203, when the suction refrigerant pressure Ps exceeds the first threshold pressure Ps_th1, the target rotation speed TGNC_LPsu is calculated based on the current target rotation speed TGNC_BASE of the compressor 2, the first threshold pressure Ps_th1, the suction refrigerant pressure Ps, and the gain for the compressor 2, that is, according to the following equation (2).

[0062] TGNC_LPsu=TGNC_BASE+ ((UL_Psu-LON_Psu)-Ps)*GUL_Psu (2)

[0063] In addition, in the Psu restriction determination unit 203, when the suction refrigerant pressure Ps does not exceed the first threshold pressure Ps_th1, the target rotation speed TGNC_LPsu is set to the current target rotation speed TGNC_BASE of the compressor 2.

[0064] Similarly, the first threshold temperature Ts_th1 can be determined, for example, by the following formula (3) based on the maximum suction refrigerant temperature UL_Ts determined by the specifications of the compressor 2 and a value LON_Tsu determined based on the outside air temperature. Ts_th1 = UL_Ts - LON_Ts (3)

[0065] In other words, the first threshold pressure Ps_th1 and the first threshold temperature Ts_th1 can be changed based on the outside air temperature, and it is preferable to lower the first threshold pressure Ps_th1 and the first threshold temperature Ts_th1 as the outside air temperature decreases, and to increase the first threshold pressure Ps_th1 and the first threshold temperature Ts_th1 as the outside air temperature increases.

[0066] As the outside air temperature fluctuates, the amount of heat dissipated in the indoor heat exchanger 21 fluctuates, and the intake refrigerant pressure Ps also fluctuates. However, by changing the first threshold pressure Ps_th1 and the first threshold temperature Ts_th1 based on the outside air temperature, it is possible to determine more appropriate first threshold pressure Ps_th1 and first threshold temperature Ts_th1 that correspond to the fluctuations in the intake refrigerant pressure Ps caused by fluctuations in the outside air temperature.

[0067] Then, in the Ts limit judgment unit 204, when the suction refrigerant temperature Ts exceeds the first threshold temperature Ts_th1, the target rotation speed TGNC_LTs is calculated based on the current target rotation speed TGNC_BASE of the compressor 2, the first threshold temperature Ts_th1, the suction refrigerant temperature Ts, and the gain for the compressor 2, that is, according to the following equation (4).

[0068] TGNC_LTs=TGNC_BASE+ ((UL_Ts-LON_Ts)-Ts)*GUL_Ts (4)

[0069] In addition, the Ts limit determination unit 204 sets the target rotation speed TGNC_LTs to the current target rotation speed TGNC_BASE of the compressor 2 when the suction refrigerant temperature Ts does not exceed the first threshold temperature Ts_th1.

[0070] On the other hand, when the input suction refrigerant pressure Ps exceeds a second threshold pressure Ps_th2 that is higher than the first threshold pressure Ps_th1, the Psu protection determination unit 303 outputs a protection signal to the OR circuit 305. Similarly, when the input suction refrigerant temperature Ts exceeds a second threshold temperature Ts_th2 that is higher than the first threshold temperature Ts_th1, the Ts protection determination unit 304 outputs a protection signal to the OR circuit 305.

[0071] The OR circuit 305 receives protection signals from the Psu protection judgment unit 303 and the Ts protection judgment unit 304, and determines that protection of the compressor 2 is required if a protection signal is input from either one of them, and determines that protection of the compressor 2 is not required if a protection signal is not input from either the Psu protection judgment unit 303 or the Ts protection judgment unit 304.

[0072] Here, the second threshold pressure Ps_th2 is a value greater than the first threshold pressure Ps_th1 and is a predetermined protection value to protect the compressor 2, and can be determined, for example, by the following equation (5) based on the maximum suction refrigerant pressure UL_Psu determined by the specifications of the compressor 2 and a value HYS_Psu that takes hysteresis into account. Ps_th2=UL_Psu-HYS_Psu (5)

[0073] Similarly, the second threshold temperature Ts_th2 is a value greater than the first threshold temperature Ts_th1 and is a predetermined protection value to protect the compressor 2, and can be determined, for example, by the following equation (6) based on the maximum suction refrigerant temperature UL_Ts determined by the specifications of the compressor 2 and a value HYS_Ts that takes hysteresis into account. Ts_th2 = UL_Ts - HYS_Ts (6)

[0074] The control of the compressor 2 by the control device 100 during hot gas heating operation in the vehicle air conditioner configured as above will be described with reference to the flowchart of FIG.

[0075] As shown in FIG. 6, when hot gas heating operation is performed in the vehicle air conditioner 1 (step S11), the control device 100 acquires the suction refrigerant pressure Ps from the refrigerant pressure sensor 44A provided on the suction side of the compressor 2, and acquires the suction refrigerant temperature Ts from the refrigerant temperature sensor 43A at a predetermined period (step S12).

[0076] In the control device 100, when the input suction refrigerant pressure Ps is equal to or lower than the first threshold pressure Ps_th1 (No in step S13) and the suction refrigerant temperature Ts is also equal to or lower than the first threshold temperature Ts_th1 (No in step S14), the compressor 2 is controlled based on the current target rotation speed TGNC_BASE (step S15).

[0077] On the other hand, if the suction refrigerant pressure Ps is equal to or lower than the first threshold pressure Ps_th1 (No in step S13) but the suction refrigerant temperature Ts is greater than the first threshold temperature Ts_th1 (Yes in step S14), proceed to step S17 and determine whether to limit the target rotation speed of compressor 2 (proceed to step S18) or to protect compressor 2 (proceed to step S21) based on the suction refrigerant temperature Ts.

[0078] This is because even if the suction refrigerant pressure Ps is below the first threshold pressure Ps_th1 (No in step S13), the suction refrigerant temperature Ts may become overheated and rise above the saturation temperature, and therefore, in order to ensure safety, it is preferable to control the compressor 2 taking into consideration the relationship between the suction refrigerant temperature Ts and the first threshold temperature Ts_th1 and the second threshold temperature Ts_th2.

[0079] Furthermore, if the suction refrigerant pressure Ps is greater than the first threshold pressure Ps_th1 (Yes in step S13) and is equal to or less than the second threshold pressure Ps_th2 (No in step S16), the process proceeds to step S17, and a decision is made based on the suction refrigerant temperature Ts as to whether to limit the target rotation speed of compressor 2 (proceed to step S18) or to protect compressor 2 (proceed to step S21).

[0080] In step S17, if the suction refrigerant temperature Ts is greater than the first threshold temperature Ts_th1 (Yes in step S14) and is less than or equal to the second threshold temperature Ts_th2 (No in step S17), the target rotation speed TGNC_LPsu and the target rotation speed TGNC_LTs are obtained (steps S18 and S19), and the smaller of the two is set as the target rotation speed TGNC to control the compressor 2 (step S20).

[0081] If the suction refrigerant pressure Ps exceeds the second threshold pressure Ps_th2 (Yes in step S16) and if the suction refrigerant temperature Ts exceeds the second threshold temperature Ts_th2 (Yes in step S17), the compressor 2 is protected, i.e., the operation of the compressor 2 is stopped (step S21).

[0082] After stopping the compressor 2, the control device 100 monitors whether the suction refrigerant pressure Ps falls below the second threshold pressure Ps_th2 (step S22) and whether the suction refrigerant temperature Ts falls below the second threshold temperature Ts_th2 (step S23). When the suction refrigerant pressure Ps and the suction refrigerant temperature Ts fall below the second threshold pressure Ps_th2 (Yes in step S22) and also fall below 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).

[0083] In this way, in the vehicle air conditioner 1 according to this embodiment, during hot gas heating operation, a first target rotation speed TGNC_LPsu based on the suction refrigerant pressure Ps and a second target rotation speed TGNC_LTs based on the suction refrigerant temperature are calculated for the compressor 2. Then, when the suction refrigerant pressure Ps exceeds the first threshold pressure Ps_th1 or when the suction refrigerant temperature Ts exceeds the first threshold temperature Ts_th1, the compressor 2 is controlled with the smaller of the first target rotation speed TGNC_LPsu or the second target rotation speed TGNC_LTs as the target rotation speed TGNC.

[0084] Furthermore, in the control device 100, the first threshold pressure Ps_th1 and the first threshold temperature Ts_th1 are changed in response to fluctuations in the outside air temperature, so that the first threshold pressure Ps_th1 and the first threshold temperature Ts_th1 can be determined in accordance with fluctuations in the suction refrigerant pressure Ps caused by fluctuations in the outside air temperature, and the compressor 2 can be controlled at the optimal target rotation speed TGNC regardless of fluctuations in the outside air temperature.

[0085] In particular, as the outside air temperature drops, the suction refrigerant pressure Ps also drops. By lowering the first threshold pressure Ps_th1 and the first threshold temperature Ts_th1 accordingly, the compressor 2 can be controlled at the optimal target rotation speed TGNC according to the outside air temperature, and operation can be continued more stably and effectively even in the harsh environment of extremely low temperatures where hot gas heating operation is used.

[0086] In this way, by controlling the suction refrigerant pressure Ps and the suction refrigerant temperature Ts to fall within a predetermined range including their target values, hot gas heating operation can be continued stably and effectively while improving the durability of the compressor.

[0087] Furthermore, even when the control device 100 performs the control described above, if the suction refrigerant pressure Ps exceeds the second threshold pressure Ps_th2 that is greater than the first threshold pressure Ps_th1, or if the suction refrigerant temperature Ts exceeds the second threshold temperature Ts_th2 that is greater than the first threshold temperature Ts_th1, the operation of the compressor 2 is stopped, thereby ensuring the durability of the compressor 2 and guaranteeing safety.

[0088] Thereafter, when the suction refrigerant pressure Ps falls below the second threshold pressure Ps_th2 and the suction refrigerant temperature Ts falls below the second threshold temperature Ts_th2, the control device 100 drives the compressor 2 again, thereby ensuring the durability of the compressor 2 and enabling the interrupted hot gas heating operation to be resumed under conditions that allow it to be continued stably and effectively.

[0089] As described above, according to this embodiment, in the hot gas heating operation, the hot gas heating operation can be continued stably and effectively, and the durability of the compressor can be improved.

[0090] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention also includes design changes and the like that do not deviate from the gist of the present invention. [Explanation of symbols]

[0091] 1: vehicle air conditioning system, 2: compressor, 10: refrigerant circuit, 10V: hot gas bypass 11: external heat exchanger, 12, 13: flow path switching valve, 14, 15: check valve 16: accumulator, 20: air conditioning unit, 21, 22: indoor heat exchanger 23: blower, 24, 25: air damper, 25A, 25B: air inlet 30: Heat medium circuit, 31: Circulation pump, 33: Heat exchanger to be temperature-controlled 34: refrigerant / heat medium heat exchanger, 34A, 34B: flow path, 40: sensor unit 41: outdoor air sensor, 42: compressor current sensor, 43, 43A: refrigerant temperature sensor 44, 44A, 44B: refrigerant pressure sensor, 45: occupant sensor, 46: blowing air temperature sensor 100: Control device

Claims

1. a refrigerant circuit including a compressor, an indoor heat exchange unit, an external heat exchange unit, and 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; a control device capable of executing a hot gas heating mode in which the refrigerant circuit is controlled to flow a part of the refrigerant compressed by the compressor into the indoor heat exchange section and the remainder into the hot gas bypass, When the hot gas heating mode is executed, the control device calculating a first target rotation speed of the compressor based on a suction refrigerant pressure and a second target rotation speed of the compressor based on a suction refrigerant temperature; A vehicle air conditioning system that controls the compressor to set the target rotation speed to the smaller of a first target rotation speed or a second target rotation speed when a suction refrigerant pressure exceeds a first threshold pressure or when a suction refrigerant temperature exceeds a first threshold temperature.

2. 2. The vehicle air conditioning system according to claim 1, wherein the control device is capable of changing the first threshold pressure and the first threshold temperature based on an outside air temperature, and adjusts the first threshold pressure and the first threshold temperature so as to decrease as the outside air temperature decreases.

3. 3. The vehicle air conditioning system of claim 1, wherein the control device stops driving the compressor when a suction refrigerant pressure exceeds a second threshold pressure that is greater than the first threshold pressure, or when a suction refrigerant temperature exceeds a second threshold temperature that is greater than the first threshold temperature.

4. 4. The vehicle air conditioner according to claim 3, wherein the control device drives the compressor again when a suction refrigerant pressure falls below the second threshold pressure and a suction refrigerant temperature falls below the second threshold temperature.

Images