Vehicular air conditioner

Abstract

To suppress variation in temperature in blowoff, while securing fast-heating performance to improve comfort of a user, in hot gas heating operation.SOLUTION: A vehicular air conditioner is provided with a refrigerant circuit including a compressor, an indoor heat exchange part and an external heat exchange part, and a control device that controls the refrigerant circuit. The refrigerant circuit has a hot gas bypass that decompresses at least some of refrigerants compressed by the compressor and returns the refrigerants to the compressor, without going through the indoor heat exchange part and the external heat exchange part, and a flow volume adjusting part that adjusts flow volumes of the refrigerant flowing through the hot gas bypass. The control device drives the compressor at predetermined fixed rotation speed at the time of starting the compressor, and then executes an FF / FB mode in which the rotation speed of the compressor is controlled by FF control and FB control, and also sets a predetermined initial value on an integral term of the FB control when the mode is switched to the FF / FB mode, in a hot gas heating mode in which some of the refrigerants compressed by the compressor are flown to the indoor heat exchange part and the remainder is flown to the hot gas bypass.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

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

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

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

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

[0006] In the above-mentioned vehicle air conditioner, the compressor is usually controlled so as to operate at a target rotation speed calculated at a predetermined cycle by feedforward control (hereinafter, FF control) and feedback control (hereinafter, FB control) from the start of hot gas heating operation. In this case, for example, when hot gas heating is started, it takes time for the compressor to operate at the maximum rotation speed from a stopped state, which may result in a lack of quick heating and a loss of comfort for the user.

[0007] On the other hand, if the compressor is driven at a high fixed speed from the start of hot gas heating operation in order to ensure fast heating and this state continues for a certain period of time, NVH (Noise Vibration Harshness) will occur and the durability of the compressor will decrease. In addition, if the compressor is driven at a fixed speed, there is a problem that the refrigerant pressure cannot be adjusted when an external disturbance is input.

[0008] Therefore, it is possible to drive the compressor at a fixed rotation speed when hot gas heating operation starts, and then, for example, when the outlet temperature or outlet refrigerant pressure of the indoor heat exchanger reaches a target value, switch to FF control and FB control to control the compressor.

[0009] However, when switching to FF control and FB control, the integral term of FB control is small because the execution time of FB control up to that point is almost nonexistent or short, and the calculated target rotation speed is a value smaller than the fixed rotation speed up to that point. Therefore, when switching to FF control and FB control, the rotation speed of the compressor temporarily decreases, which causes the blown air temperature to fluctuate, and this may impair user comfort.

[0010] The present invention has been made in consideration of these circumstances, and has as its objective to suppress fluctuations in blowing temperature during hot gas heating operation while ensuring rapid heating, thereby improving user comfort. [Means for solving the problem]

[0011] The present invention provides a vehicle air conditioner including a refrigerant circuit including a compressor, an indoor heat exchange unit, and an external heat exchange unit, and a control unit that controls the refrigerant circuit, the refrigerant circuit having a hot gas bypass that reduces the pressure of at least a portion of the refrigerant compressed by the compressor and returns it to the compressor without passing through the indoor heat exchange unit and the external heat exchange unit, and a flow rate adjustment unit that adjusts the flow rate of the refrigerant flowing through the hot gas bypass, the control unit being capable of executing a hot gas heating mode in which a portion of the refrigerant compressed by the compressor flows through the indoor heat exchange unit and the remainder flows through the hot gas bypass, and in the hot gas heating mode, after executing a fixed mode in which the compressor is driven at a predetermined fixed rotation speed at the start of the hot gas heating mode, an FF / FB mode in which the rotation speed of the compressor is controlled by feedforward control and feedback control is executed, and a predetermined initial value is set for the integral term of the feedback control when switching from the fixed mode to the FF / FB mode. Effect of the Invention

[0012] According to the present invention, in hot gas heating operation, it is possible to suppress fluctuations in the blown air temperature while ensuring rapid heating, thereby improving user comfort. [Brief description of the drawings]

[0013] [Figure 1] 1 is an explanatory diagram showing an example of a system configuration of a vehicle air conditioner according to an embodiment of the present invention; [Diagram 2] 1 is an explanatory diagram showing a control device for a vehicle air conditioner according to an embodiment of the present invention; [Diagram 3] 1 is a diagram showing the configuration of a control device and the like in an electric vehicle (EV) according to an embodiment of the present invention. [Figure 4] FIG. 4 is an explanatory diagram showing the operation of the refrigerant circuit during endothermic heating operation in the vehicle air conditioner according to the embodiment of the present invention. [Diagram 5] FIG. 4 is an explanatory diagram showing the operation of the refrigerant circuit during hot gas heating operation in the vehicle air conditioner according to the embodiment of the present invention. [Figure 6]6 is a graph showing an example of behavior of the outlet refrigerant pressure of the indoor heat exchanger, the compressor rotation speed, and the blowing temperature during hot gas heating operation using a control method according to a reference example. [Figure 7] 6 is a graph showing an example of the behavior of the outlet refrigerant pressure of the indoor heat exchanger, the compressor rotation speed, and the blowing temperature during hot gas heating operation using the control method according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 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.

[0015] [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.

[0016] The vehicle air conditioner 1 includes a refrigerant circuit 10 and an air conditioning unit 20. The refrigerant circuit 10 includes a compressor 2, indoor heat exchangers 21 and 22 provided inside the air conditioning unit 20, and an external heat exchanger 11 provided outside the vehicle cabin, which are arranged along a refrigerant flow path. The indoor heat exchangers 21 and 22 are provided for heat exchange between the air flowing through the air conditioning unit 20 and the refrigerant, and the external heat exchanger 11 is provided for heat exchange between the outside air and the refrigerant outside the vehicle cabin. The indoor heat exchanger 21 is for heating the air, and the indoor heat exchanger 22 is for cooling the air. A refrigerant pressure sensor 44B is provided immediately downstream of the indoor heat exchanger 21 to detect an outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) from the indoor heat exchanger 21.

[0017] The compressor 2 compresses the refrigerant and circulates it through the refrigerant circuit 10. The refrigerant compressed by the compressor 2 is reduced in pressure to a required level by passing through a first pressure reducing section V1, a second pressure reducing section V2, a third pressure reducing section V3, and a fourth pressure reducing section V4, which are, for example, expansion valves, in an appropriately selected refrigerant flow path. The refrigerant circuit 10 is provided with flow path switching valves 12 and 13 for switching the refrigerant flow path, and check valves 14 and 15 for regulating the flow direction of the refrigerant. An accumulator 16 is provided immediately upstream of the compressor 2 in the refrigerant circuit 10 to recover liquid refrigerant and separate the refrigerant into gas and liquid. A refrigerant pressure sensor 44A is provided between the accumulator 16 and the compressor 2 to detect a suction refrigerant pressure Ps (low-pressure side refrigerant pressure) sucked into the compressor 2.

[0018] 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.

[0019] When the air damper 24 is fully closed, it blocks the intake side of the indoor heat exchanger 21, and the air introduced by the blower 23 passes only through the indoor heat exchanger 22 before being blown out into the room. Another air damper 25 provided in the air conditioning unit 20 switches the air introduced into the blower 23 between indoor and outdoor. The air damper 25 can selectively close air inlet 25A connected to the outdoors and air inlet 25B connected to the indoors to take in air from either one of them. Also, by placing the air damper 25 in an intermediate position, it is possible to take in air from both air inlet 25A and air inlet 25B.

[0020] 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.

[0021] 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.

[0022] [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.

[0023] 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.

[0024] In particular, the refrigerant pressure sensor 44 includes a refrigerant pressure sensor 44A that detects a suction refrigerant pressure Ps (low-pressure side refrigerant pressure) sucked into the compressor 2, and a refrigerant pressure sensor 44B that detects an outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) of the indoor heat exchanger 21 (see FIG. 1). These sensors are merely examples, and various sensors that detect information required when the control device 100 performs various controls are provided as the sensor unit 40.

[0025] The control targets of the control device 100 are the compressor 2, the first pressure reducing section V1, the second pressure reducing section V2, the third pressure reducing section V3, the fourth pressure reducing section V4, and the flow path switching valves 12 and 13 in the refrigerant circuit 10, the blower 23, the air dampers 24 and 25 in the air conditioning unit 20, and the circulation pump 31 in the heat medium circuit 30. The control device 100 also controls the vehicle air conditioner 1 according to the processing results of the control device 100. In the vehicle air conditioner 1, the control device 100 can switch between an endothermic heating operation in which the refrigerant absorbs heat in the external heat exchanger 11, and a hot gas heating operation in which the refrigerant compressed by the compressor 2 is allowed to dissipate heat in the indoor heat exchanger 21 without absorbing heat in the refrigerant in the external heat exchanger 11 to heat the vehicle interior.

[0026] [Configuration of control device in electric vehicle (EV)] 3, the control device 100 provided in the vehicle air conditioner 1 is configured as one ECU connected to various ECUs (Electronic Control Units) that control the electric vehicle (EV) via an in-vehicle network L. The control device 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, an input / output I / F (Interface) 104, an in-vehicle communication I / F (Interface) 105, and the like, and each piece of hardware is connected to each other via a bus 106.

[0027] 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).

[0028] For example, the RAM 103 functions as a working area used by the CPU 101 when executing a program. The input / output I / F 104 is connected to various sensors and monitors installed in the EV, and inputs data to the CPU 101 and outputs data processed by the CPU 101. The in-vehicle communication I / F 105 is connected to an in-vehicle network L to control data transmission and reception with other ECUs set in the EV.

[0029] The control device 100 controls the above-mentioned vehicle air conditioner 1 by a program executed by the CPU 101 when data related to surrounding environmental information or data related to the driving status of the EV is input via the input / output I / F 104 or the in-vehicle communication I / F 105.

[0030] 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.

[0031] [Endothermic heating operation] The operation of the refrigerant circuit 10 in endothermic heating operation will be described with reference to Fig. 4. In the refrigerant circuit 10 in endothermic heating operation, the second pressure reduction section V2, the third pressure reduction section V3, the fourth pressure reduction section V4, and the flow path switching valve 12 are fully closed. On the other hand, the flow path switching valve 13 is fully open, and the first pressure reduction section V1 is open.

[0032] In the endothermic heating operation, the high-temperature, high-pressure refrigerant discharged from the compressor 2 passes through the indoor heat exchanger 21 in the air conditioning unit 20 and is depressurized in the first depressurization section V1, and the low-pressure refrigerant passes through the external heat exchanger 11 and is returned to the compressor 2 via the flow path switching valve 13, the check valve 14, and the accumulator 16. At this time, the high-pressure refrigerant discharged from the compressor 2 condenses and releases heat in the indoor heat exchanger 21, is depressurized in the first depressurization section V1 to become a low-pressure refrigerant, absorbs heat and evaporates in the external heat exchanger 11, and returns to the compressor 2. Then, in the air conditioning unit 20, the air introduced by the blower 23 is heated by the heat released in the indoor heat exchanger 21 and is blown into the vehicle cabin.

[0033] [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.

[0034] The operation of the refrigerant circuit 10 in hot gas heating operation will be described with reference to Fig. 5. In this operation, part of the high-temperature, high-pressure refrigerant discharged from the compressor 2 passes through the indoor heat exchanger 21 and the flow path switching valve 12, is depressurized in the third pressure reduction section V3 to become a low-pressure refrigerant, passes through the refrigerant heat medium heat exchanger 34, is separated into gas and liquid in the accumulator 16, and returns to the compressor 2. At this time, in the refrigerant circuit 10, the first pressure reduction section V1 is fully closed, so that the refrigerant does not flow to the external heat exchanger 11. Also, the fourth pressure reduction section V4 is fully closed, so that the refrigerant does not flow to the indoor heat exchanger 22.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] [Compressor control during hot gas heating operation] During hot gas heating operation of the vehicle air conditioner 1, the control device 100 controls the compressor 2 in a fixed mode and a FF / FB mode. That is, when hot gas heating is started, the control device 100 executes the fixed mode and controls the compressor 2 to be driven at a predetermined fixed rotation speed, and then executes the FF / FB mode to control the compressor 2 by FF control and FB control so that the high-pressure side refrigerant pressure of the refrigerant circuit 10 (in this embodiment, the outlet refrigerant pressure Pci of the indoor heat exchanger 21) becomes a target pressure (target outlet refrigerant pressure Pco).

[0039] Hereinafter, the control of the compressor 2 in the vehicle air conditioner 1 during hot gas heating operation will be described while comparing with a reference example.

[0040] (Control method according to the reference example) Fig. 6 shows a graph illustrating an example of the behavior of the outlet refrigerant pressure Pci (high pressure side refrigerant pressure) of the indoor heat exchanger 21, the target rotation speed TGNC of the compressor 2, and the blowing temperature Tv during hot gas heating operation using the control method according to the reference example. Note that in the example of Fig. 6, the fixed mode is executed in the period indicated by "Mode1", and the FF / FB mode is executed in the period indicated by "Mode2". In the following description, the target rotation speed TGNC of the compressor 2 is defined as a fixed rotation speed TGNCf of the compressor 2 in the fixed mode, and the target rotation speed TGNCz calculated by the control device 100 in the FF / FB mode.

[0041] 6, the control device 100 drives the compressor 2 with the target rotation speed TGNC set to a fixed rotation speed TGNCf in the fixed mode, and accordingly, both the outlet refrigerant pressure Pci and the blowing temperature Tv rise. When the control device 100 detects that the blowing temperature Tv has risen to a predetermined threshold or higher, it switches from the fixed mode to the FF / FB mode and controls the compressor 2 by the FF control and the FB control.

[0042] In the FF / FB mode, the control device 100 uses FF control and FB control to control the rotation speed of the compressor 2. That is, the control device 100 calculates a target rotation speed TGNCz of the compressor 2 for each predetermined control period based on the difference between the target outlet refrigerant pressure PCO and the outlet refrigerant pressure Pci, and drives the compressor 2 according to the calculated target rotation speed TGNCz.

[0043] Specifically, the control device 100 calculates an FF term TGNCh_FF as an FF manipulated variable of the target rotation speed TGNCz based on the outlet refrigerant pressure Pci and the target outlet refrigerant pressure PCO. Similarly, the control device 100 calculates an FB manipulated variable TGNCh_FB of the target rotation speed TGNCz by PID (proportional integral differential) calculation or PI (proportional integral) calculation based on the outlet refrigerant pressure Pci and the target outlet refrigerant pressure PCO.

[0044] The control device 100 adds the FF term TGNCh_FF as the FF manipulated variable and the FB manipulated variable TGNCh_FB to calculate the target rotation speed TGNCz of the compressor 2. That is, the target rotation speed TGNCz of the compressor 2 is expressed by the following formula (1). TGNCz=TGNCh_FF+TGNCh_FB ··· (1)

[0045] Here, the FB manipulated variable TGNCh_FB includes a ratio term TGNCh_FB_P, an integral term TGNCh_FB_I, and a previous value of the integral term TGNCh_FB_Iz. However, when switching to the FF / FB mode, since there has not been an execution period of the FF / FB mode up to that point, the integral term TGNCh_FB_I and the previous value of the integral term TGNCh_FB_Iz of the FB manipulated variable TGNCh_FB become 0.

[0046] Due to this effect, since the target rotation speed TGNCz calculated by the control device 100 is smaller than the fixed rotation speed TGNCf, the target rotation speed TGNC of the compressor 2 temporarily drops when switching from the fixed mode to the FF / FB mode, and the outlet refrigerant pressure Pci drops accordingly, so that the blowing temperature Tv also drops. After that, an integral term is added as the FF / FB mode is executed, and the target rotation speed TGNCz is adjusted based on the outlet refrigerant pressure Pci, but it takes time for the outlet refrigerant pressure Pci to reach the target outlet refrigerant pressure PCO, and it takes time for the blowing temperature Tv to stabilize (see FIG. 6).

[0047] In this way, when switching from the fixed mode to the FF / FB mode, the target rotation speed TGNC of the compressor 2 fluctuates, such as temporarily decreasing, and the blown temperature Tv also fluctuates accordingly, resulting in a loss of comfort for the user.

[0048] (Control method according to this embodiment) Therefore, in this embodiment, when switching from fixed mode to FF / FB mode during hot gas heating operation, the control device 100 suppresses fluctuations in the target rotation speed TGNC of the compressor 2 during hot gas heating operation by calculating the target rotation speed TGNCz of the compressor 2 in FF / FB mode as follows.

[0049] 7 shows a graph illustrating an example of the behavior of the outlet refrigerant pressure Pci (high-pressure side refrigerant pressure) of the indoor heat exchanger 21, the target rotation speed TGNC of the compressor 2, and the blowing temperature Tv. The control device 100 controls the rotation speed of the compressor 2 in a fixed mode and a FF / FB mode, and in the example of FIG. 7, the fixed mode is executed in the period indicated by "Mode1", and the FF / FB mode is executed in the period indicated by "Mode2". In the explanation of FIG. 7 as well, of the target rotation speed TGNC of the compressor 2, the fixed rotation speed TGNCf of the compressor 2 in the fixed mode is defined as the target rotation speed TGNCz calculated by the control device 100 in the FF / FB mode.

[0050] During the period of Mode 1 shown in Fig. 7, the control device 100 applies a fixed rotation speed TGNCf as the target rotation speed TGNC of the compressor 2. The control device 100 sets the fixed rotation speed TGNCf to the larger of the target rotation speed calculated based on the outside air temperature and the target rotation speed calculated based on the user setting. Since the hot gas heating operation is performed when the outside air temperature is extremely low, both the target rotation speed calculated based on the outside air temperature and the target rotation speed calculated based on the user setting are in the high rotation speed range within the range of rotation speeds at which the compressor 2 can be driven.

[0051] In the fixed mode, the compressor 2 is driven at a relatively high fixed rotation speed, so that both the outlet refrigerant pressure Pci and the blowing temperature Tv rise relatively quickly, ensuring fast heating. In the fixed mode, when the outlet refrigerant pressure Pci exceeds a predetermined threshold, the control device 100 drives the blower 23 to start blowing air into the vehicle cabin. As a result, in the indoor heat exchanger 21, heat is exchanged between the high-temperature, high-pressure refrigerant and the air passing through the indoor heat exchanger 21, and the outlet refrigerant pressure Pci drops slightly and then rises again.

[0052] Thereafter, when the control device 100 detects that the blowing temperature Tv has increased to a predetermined threshold value or higher, it switches from the fixed mode to the FF / FB mode and controls the rotation speed of the compressor 2 by FF control and FB control. In the FF / FB mode, the control device 100 drives the compressor 2 at a target rotation speed TGNCz calculated at a predetermined control cycle. The control device 100 calculates the target rotation speed TGNCz by adding together the FF manipulated variable TGNCh_FF and the FB manipulated variable TGNCh_FB, which are calculated based on the outlet refrigerant pressure Pci and the target outlet refrigerant pressure PCO (the above-mentioned formula (1)).

[0053] If there is no change in the target rotation speed TGNC of the compressor 2 when switching from the fixed mode to the FF / FB mode, that is, if the target rotation speed TGNCz when switching to the FF / FB mode calculated by the control device 100 is approximately equal to the fixed rotation speed TGNCf in the fixed mode, fluctuations in the target rotation speed TGNC of the compressor 2, and therefore fluctuations in the outlet refrigerant pressure Pci and the blowing temperature Tv, can be suppressed.

[0054] As described above, when switching to the FF / FB mode, the integral term in the FB manipulated variable TGNCh_FB becomes 0, which affects the target rotation speed, so the control device 100 sets a predetermined initial value D to the integral term in the FB manipulated variable TGNCh_FB to compensate for this. Specifically, the control device 100 sets, for the integral term in the FB manipulated variable TGNCh_FB, an initial value D obtained by the fixed rotation speed TGNCf, the FF term TGNCh_FF, and the ratio term TGNCh_FB_P as shown in the following equation (2). D=TGNCf-TGNCh_FF-TGNCh_FB_P ··· (2)

[0055] In addition, the control device 100 may use, as the initial value, a value calculated, for example, by simulation and stored in advance in ROM 102, etc., as long as the value is such that the target rotation speed TGNCz at the time of switching to the FF / FB mode is approximately equal to the fixed rotation speed TGNCf in the fixed mode.

[0056] When switching between the FF / FB modes, the control device 100 sets the target rotation speed TGNCz obtained by adding the FB manipulated variable TGNCh_FB and the FF manipulated variable TGNCh_FF, for which the initial value D is set, to a value that is substantially equal to the fixed rotation speed TGNCf. Therefore, when switching from the fixed mode to the FF / FB mode, fluctuations in the rotation speed of the compressor 2 are suppressed, and fluctuations in the outlet refrigerant pressure Pci and the blowing temperature Tv are also suppressed.

[0057] Thus, according to this embodiment, the control device 100 drives the compressor 2 at a relatively high fixed rotation speed in the fixed mode at the start of hot gas heating operation, thereby increasing the outlet refrigerant pressure Pci at an early stage and ensuring fast heating. Furthermore, when the control device 100 detects that the blowing temperature Tv has exceeded a predetermined threshold while the fixed mode is being executed, it switches to the FF / FB mode, thereby ensuring responsiveness to disturbances.

[0058] Furthermore, when switching from the fixed mode to the FF / FB mode, a predetermined initial value D is set for the integral term of the FB manipulated variable TGNCh_FB to calculate a target rotation speed TGNCz that is substantially equal to the fixed rotation speed TGNCf in the fixed mode, and the compressor 2 is driven by the calculated target rotation speed TGNCz. As a result, when switching from the fixed mode to the FF / FB mode, i.e., when the target rotation speed TGNC of the compressor 2 switches from the fixed rotation speed TGNCf to the target rotation speed TGNCz, fluctuations in the rotation speed of the compressor 2 are suppressed, and therefore fluctuations in the outlet refrigerant pressure Pci and the blowing temperature Tv are also suppressed.

[0059] As described above, according to this embodiment, in hot gas heating operation, it is possible to suppress fluctuations in the blown air temperature while ensuring rapid heating, thereby improving user comfort.

[0060] 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]

[0061] 1: vehicle air conditioning system, 2: compressor, 10: refrigerant circuit, 10V: hot gas bypass 11: external heat exchanger, 12, 13: flow path switching valve, 14, 15: check valve 16: accumulator, 20: air conditioning unit, 21, 22: indoor heat exchanger 23: blower, 24, 25: air damper, 25A, 25B: air inlet 30: Heat medium circuit, 31: Circulation pump, 33: Heat exchanger to be temperature-controlled 34: refrigerant / heat medium heat exchanger, 34A, 34B: flow path, 40: sensor unit 41: Outside air sensor, 42: Compressor current sensor, 43: Refrigerant temperature sensor 44, 44A, 44B: refrigerant pressure sensor, 45: occupant sensor, 46: blowing air temperature sensor 100: Control device

Claims

1. A vehicle air conditioner including a refrigerant circuit including a compressor, an interior heat exchanger, and an exterior heat exchanger, and a control device that controls the refrigerant circuit, The refrigerant circuit includes: a hot gas bypass that reduces the pressure of at least a portion of the refrigerant compressed by the compressor and returns the refrigerant to the compressor without passing through the indoor heat exchange unit and the external heat exchange unit; a flow rate adjusting unit that adjusts the flow rate of the refrigerant flowing through the hot gas bypass, The control device includes: A hot gas heating mode can be executed in which a part of the refrigerant compressed by the compressor flows into the indoor heat exchange section and the remainder flows into the hot gas bypass. In the hot gas heating mode, a fixed mode is executed in which the compressor is driven at a predetermined fixed rotation speed when the hot gas heating mode is started, and then an FF / FB mode is executed in which the rotation speed of the compressor is controlled by feedforward control and feedback control, and a predetermined initial value is set for the integral term of the feedback control when switching from the fixed mode to the FF / FB mode.

2. The initial value is 2. The vehicle air conditioner according to claim 1, wherein the fixed rotation speed is a value calculated based on a feedforward term and a ratio term of the target rotation speed calculated in the FF / FB mode.

3. The control device includes:

2. The vehicle air conditioning system according to claim 1, wherein the fixed mode is executed by setting the larger of a target rotation speed of the compressor calculated based on an outside air temperature and a target rotation speed calculated based on a user setting as the fixed rotation speed.

4. The control device includes:

2. The vehicle air conditioner according to claim 1, wherein the fixed mode is switched to the FF / FB mode when a temperature of the air blown into the passenger compartment is equal to or higher than a predetermined threshold value.

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