Vehicle Air Conditioning System

Abstract

To provide an on-vehicle air conditioning system which can effectively prevent liquid compression by a compressor.SOLUTION: An on-vehicle air conditioning system 10 comprises: a heat pump circuit 20 having a first channel 22 in which an air conditioning refrigerant flows, a compressor 24 for compressing the air conditioning refrigerant, a capacitor 28, a heating expansion valve 26 provided between the compressor 24 and the capacitor 28 and an accumulator 36 provided between the capacitor 28 and the compressor 24; and an air-conditioning controller 12. The air-conditioning controller 12 causes the compressor 24 to be driven in a rotation frequency equal to or less than a predetermined stand-by rotation frequency until a predetermined start condition is satisfied when the start of heating using a heat pump is necessary. The start condition includes at least such a condition that an opening degree Av of the heating expansion valve 26 becomes equal to or greater than a predetermined reference opening degree Avref.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This specification discloses an in-vehicle air conditioning system that uses heat generated by a heat pump as one of the heating heat sources. [Background technology]

[0002] Conventionally, vehicle air conditioning systems having a heat pump device have been known (for example, Patent Document 1, etc.). A heat pump device is a device that compresses and expands a refrigerant to raise and lower the temperature of the refrigerant and transfer heat. Such a heat pump device has, for example, a flow path through which the refrigerant flows, a compressor that compresses the refrigerant, a condenser that exchanges heat between the refrigerant and outside air, a heating expansion valve provided between the compressor and the condenser, and an accumulator that separates the refrigerant into gas and liquid on the upstream side of the compressor. In the heat pump device, the refrigerant is separated into gas and liquid in the accumulator, and then only the gaseous refrigerant, i.e., the refrigerant gas, is sent to the compressor. The compressor compresses this refrigerant gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-151127 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when the heat pump device starts operating, liquid refrigerant may remain in the compressor. For example, when the heat pump device is stopped in a low-temperature environment, the refrigerant gas remaining in the compressor condenses as the temperature drops and turns into liquid refrigerant. If the compressor is driven while there is liquid refrigerant in the compressor, the liquid refrigerant is compressed, which is called "liquid compression."

[0005] Because liquid refrigerant is incompressible, when liquid compression occurs, extremely large pressure is generated, causing a "liquid hammer" that produces intense shock noises and vibrations. In some cases, liquid compression can also damage the compressor valves and cylinders.

[0006] Therefore, this specification discloses an in-vehicle air conditioning system that can effectively prevent liquid compression by the compressor. [Means for solving the problem]

[0007] The vehicle air conditioning system disclosed in this specification comprises a heat pump circuit having a first flow path through which an air conditioning refrigerant flows, a compressor that compresses the air conditioning refrigerant, a condenser that exchanges heat between the air conditioning refrigerant and outside air, a heating expansion valve provided between the compressor and the condenser to reduce the pressure of the air conditioning refrigerant, and an accumulator provided between the condenser and the compressor to separate the air conditioning refrigerant into gas and liquid forms, and an air conditioning controller, wherein when it becomes necessary to start heating using the heat pump, the air conditioning controller operates the compressor at a rotation speed equal to or lower than a specified standby rotation speed until specified start-up conditions are met, and the start-up conditions include at least an opening degree of the heating expansion valve being equal to or higher than a predetermined reference opening degree.

[0008] By operating the compressor at or below the standby rotation speed until the heating expansion valve is sufficiently opened, in other words, until the air-conditioning refrigerant in the compressor is sent to the accumulator, liquid compression, in which the compressor compresses the liquid refrigerant in the compressor, can be effectively prevented.

[0009] In this case, the standby rotation speed is smaller than a target rotation speed required to exert heating capacity, and the reference opening is larger than the target opening required to exert heating capacity, and the air conditioning controller may drive the compressor at the target rotation speed and narrow the heating expansion valve to the target opening after the start-up condition is met.

[0010] By setting the standby rotation speed lower than the target rotation speed and the reference opening higher than the target opening, it is possible to effectively prevent liquid compression, which compresses the liquid refrigerant in the compressor. In addition, by increasing the compressor rotation speed and throttling the heating expansion valve after the start-up conditions are met, the air-conditioning refrigerant can be appropriately compressed and decompressed, ensuring the required heating capacity.

[0011] The vehicle may further include a heating circuit having a second flow path through which coolant flows, a water-cooled condenser for heat exchange between the air conditioning refrigerant and the coolant, a water pump for pumping the coolant, and a heater core heated by the coolant, and the start-up condition may further include that the water flow rate of the water pump is equal to or greater than a specified standard water flow rate.

[0012] When the start-up condition includes the water flow rate of the water pump being equal to or greater than the reference water flow rate, the start-up condition is established, and the air gap in the cooling water flow path of the water-cooled condenser is eliminated when the compressor starts compressing the air-conditioning refrigerant. As a result, it is possible to prevent an excessive pressure rise in the air-conditioning refrigerant caused by the air gap, and it is possible to prevent vibrations and abnormal noise caused by the pressure rise. In addition, if the air gap remains, the efficiency of heat exchange between the air-conditioning refrigerant and the cooling water decreases, making it difficult to increase the temperature of the cooling water. As a result, if the air gap remains, the compressor rotates excessively in order to increase the temperature of the cooling water, which increases power consumption and ultimately reduces the driving range of the electric vehicle. However, according to the above configuration, the air gap is eliminated when the compressor starts compressing the air-conditioning refrigerant, so that an increase in power consumption can also be prevented.

[0013] The start-up condition may further include that the air-conditioning refrigerant output from the compressor is in a gas phase. In this case, the air-conditioning controller may determine that the air-conditioning refrigerant output from the compressor is in a gas phase when at least one of the following is satisfied: a water temperature of cooling water output from a water-cooled condenser that exchanges heat with the air-conditioning refrigerant is equal to or higher than a specified reference water temperature, a temperature of the air-conditioning refrigerant output from the compressor is equal to or higher than a specified reference refrigerant temperature, and a pressure of the air-conditioning refrigerant output from the compressor is equal to or higher than a specified reference refrigerant pressure.

[0014] With this configuration, it is possible to more reliably prevent liquid compression, in which the compressor compresses the liquid air-conditioning refrigerant. Effect of the Invention

[0015] According to the vehicle air conditioning system disclosed in this specification, liquid compression by the compressor can be effectively prevented. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram showing a configuration of an in-vehicle air conditioning system. [Diagram 2] FIG. 11 is a diagram showing the relationship between a target rotation speed and a standby rotation speed. [Diagram 3] FIG. 4 is a diagram showing the relationship between a target opening degree and a reference opening degree. [Figure 4] FIG. 4 is a diagram showing an example of a reference water temperature. [Diagram 5] 4 is a flowchart showing a process flow of the vehicle air conditioning system. [Figure 6] 10 is a flowchart showing another flow of the process of the vehicle air conditioning system. [Figure 7] FIG. 13 is a diagram showing the configuration of another example of an in-vehicle air conditioning system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The configuration of the vehicle-mounted air conditioning system 10 will be described below with reference to the drawings. The vehicle in which the vehicle-mounted air conditioning system 10 is mounted is a vehicle in which engine exhaust heat cannot be used as a heating heat source, or the timing when engine exhaust heat can be used is limited. Therefore, the vehicle-mounted air conditioning system 10 is mounted on an electric vehicle having a motor as a driving power source, such as an electric vehicle, a fuel cell vehicle, a plug-in hybrid vehicle, or a hybrid vehicle.

[0018] As shown in Fig. 1, the vehicle air conditioning system 10 includes a heat pump circuit 20, a heating circuit 50, a blowing mechanism 70, and an air conditioning controller 12 that controls the driving of these components. The heat pump circuit 20 is a circuit that generates heat and latent heat by compressing, expanding, condensing, and evaporating an air conditioning refrigerant, which is a first refrigerant, in the process of circulating the air conditioning refrigerant. The heat generated by the heat pump circuit 20 is used for heating, and the latent heat is used for cooling.

[0019] More specifically, the heat pump circuit 20 has a first flow path 22 through which the air-conditioning refrigerant flows. The first flow path 22 is provided with a compressor 24, a heating expansion valve 26, a condenser 28, a cooling expansion valve 32, an evaporator 34, and an accumulator 36.

[0020] The compressor 24 is an air compressor that compresses a gaseous air-conditioning refrigerant, that is, a refrigerant gas. A water-cooled condenser 56 is provided downstream of the compressor 24, and the high-temperature, high-pressure refrigerant gas exchanges heat with cooling water, which will be described later. The heating expansion valve 26 is an electromagnetic valve that is throttled during heating operation and fully opened during cooling operation. When the heating expansion valve 26 is throttled, the air-conditioning refrigerant is rapidly depressurized when passing through the heating expansion valve 26. The heating expansion valve 26 is an electronic expansion valve whose opening Av can be electrically controlled. The condenser 28 is a heat exchanger that exchanges heat between the air-conditioning refrigerant and outside air. The condenser 28 functions as an evaporator during heating operation and as a condenser during cooling operation. A condenser fan 30 is disposed behind the condenser 28 to efficiently take in outside air.

[0021] The cooling expansion valve 32 is an electromagnetic valve that is throttled during cooling operation and completely closed during heating operation. When the cooling expansion valve 32 is throttled, the air-conditioning refrigerant is rapidly depressurized when passing through the cooling expansion valve 32. The evaporator 34 is an evaporator that evaporates the liquid air-conditioning refrigerant, and is disposed in the air-conditioning air flow path provided in the blowing mechanism 70. The air around the evaporator 34 is cooled by the latent heat generated during this evaporation. The accumulator 36 separates the air-conditioning refrigerant into gas and liquid, and sends only the refrigerant gas to the compressor 24.

[0022] 1, several solenoid valves for switching the flow direction of the air-conditioning refrigerant are provided in the first flow path 22. Furthermore, a first temperature sensor 40 and a pressure sensor 42 for detecting the temperature and pressure of the air-conditioning refrigerant output from the compressor 24 are also provided in the first flow path 22.

[0023] The heating circuit 50 is a circuit that is mainly used during heating operation, and is a circuit that conveys heat from a heating heat source to a heater core 58 disposed in a blowing mechanism 70. More specifically, the heating circuit 50 has a second flow path 52 through which coolant, which is a second refrigerant, flows. The second flow path 52 is provided with a water pump 54, a water-cooled condenser 56, and a heater core 58. The water pump 54 is a pump that pumps the coolant. The water-cooled condenser 56 is a heat exchanger that exchanges heat between the air-conditioning refrigerant and the coolant. The heater core 58 is disposed in the blowing mechanism 70, and exchanges heat between the air-conditioning air sent to the vehicle interior and the coolant. In addition, a three-way valve 60 is provided in the second flow path 52, and the second flow path 52 can be connected to a coolant flow path of an engine 57 as necessary.

[0024] The blowing mechanism 70 is a mechanism that cools or heats air taken in from outside or inside the vehicle and blows it into the vehicle. The blowing mechanism 70 has a housing 72 and a blower 74. A plurality of blowing outlets 78 that guide the conditioned air into the vehicle are formed at the downstream end of the housing 72. An adjustment door 80 is disposed in each blowing outlet 78 for adjusting the blowing amount of the conditioned air. The evaporator 34 and the heater core 58 are also disposed in the housing 72. During cooling operation, the evaporator 34 cools the air sent from the blower 74 by the latent heat generated when the air-conditioning refrigerant evaporates. The cooled conditioned air is output into the vehicle to cool the vehicle interior.

[0025] The heater core 58 is heated by the heated coolant. A mix door 76 is disposed upstream of the heater core 58. The mix door 76 adjusts the amount of air passing through the heater core 58. During heating operation, the mix door 76 moves to a position where it does not block the heater core 58 (the position indicated by the dashed line in FIG. 1). This allows air sent from the blower 74 to pass through the heater core 58 and be heated. The heated air-conditioned air is output into the vehicle interior, heating the vehicle cabin.

[0026] The air conditioning controller 12 controls the operation of the vehicle-mounted air conditioning system 10 in response to an instruction from a passenger. The air conditioning controller 12 is physically a computer having a processor 12a and a memory 12b. The "computer" also includes a microcontroller in which a computer system is incorporated into a single integrated circuit. The processor 12a may be a single component, or may be composed of multiple components located mechanically apart. Similarly, the memory 12b may be a single component, or may be composed of multiple components located mechanically apart. The memory 12b may include at least one of a semiconductor memory (e.g., RAM, ROM, solid state drive, etc.) and a magnetic disk (e.g., hard disk drive, etc.). The air conditioning controller 12 may be a computer provided exclusively for the vehicle-mounted air conditioning system 10, or a controller used in another device may be used as the air conditioning controller 12.

[0027] Next, the operation of the vehicle air conditioning system 10 during heating operation and cooling operation will be briefly described. During heating operation, the air conditioning refrigerant is compressed by the compressor 24 to become a high-temperature, high-pressure refrigerant gas. This refrigerant gas exchanges heat with the cooling water in the water-cooled condenser 56. This heat exchange heats the cooling water. The cooling water is sent to the heater core 58 by the water pump 54 and exchanges heat with the heater core 58. This causes the heater core 58 to become hot, and the conditioned air is heated by this high-temperature heater core 58. The heated conditioned air is then sent into the vehicle interior to heat the vehicle interior.

[0028] Meanwhile, the air-conditioning refrigerant is condensed in the water-cooled condenser 56 and reduced in pressure by the throttling-controlled heating expansion valve 26. As a result, the air-conditioning refrigerant is sent to the condenser 28 as a low-temperature, low-pressure liquid refrigerant or gas-liquid mixed refrigerant. In the condenser 28, the air-conditioning refrigerant is vaporized by the heat of the outside air and enters a gas-liquid mixed state or a gas state. The air-conditioning refrigerant output from the condenser 28 is sent to the accumulator 36 without proceeding to the cooling expansion valve 32, where it is separated into gas and liquid. Thereafter, only the gaseous refrigerant gas is sent to the compressor 24. Thereafter, the same flow is repeated cyclically.

[0029] During cooling operation, the air conditioning refrigerant is compressed by the compressor 24 to become a high-temperature, high-pressure refrigerant gas. The refrigerant gas then passes through the water-cooled condenser 56 and the heating expansion valve 26. However, during cooling operation, the water pump 54 is stopped and the heating expansion valve 26 is fully open. Therefore, the refrigerant gas is sent to the condenser 28 in a high-temperature, high-pressure gaseous state without being condensed or reduced in pressure. In the condenser 28, the refrigerant gas is cooled by the outside air to become a high-pressure liquid refrigerant. This liquid refrigerant is reduced in pressure by the throttling-controlled air conditioning expansion valve 32. Then, the reduced-pressure air conditioning refrigerant evaporates in the evaporator 34, generating latent heat, which cools the air conditioning air around the evaporator 34. The cooled air conditioning air is sent to the vehicle interior by the blower 74 to cool the vehicle interior. The air conditioning refrigerant that has passed through the evaporator 34 is separated into gas and liquid in the accumulator 36, and only the gaseous refrigerant gas is sent to the compressor 24. Thereafter, the same process is repeated cyclically.

[0030] In either the heating operation or the cooling operation, the rotation speed N of the compressor 24 and the opening degree of the expansion valves 26, 32 are adjusted by the air conditioning controller 12 according to the required heating capacity or cooling capacity. For example, the air conditioning controller 12 determines the target rotation speed N* of the compressor 24 based on the outside air temperature To, the target blowing temperature TAO, etc., so that the target rotation speed N* of the compressor 24 becomes higher as the required heating capacity or cooling capacity increases. Similarly, the opening degree of the expansion valves 26, 32 is also determined by the air conditioning controller 12 based on the coolant temperature Tw, etc.

[0031] As described above, the compressor 24 is an air compressor that compresses gas. Liquid refrigerant is not normally supplied to the compressor 24. However, in a low-temperature environment where a heating operation is performed, the compressor 24 may be driven with liquid air-conditioning refrigerant remaining in the compressor 24. For example, assume that the heating operation is stopped in a low-temperature environment. In this case, as time passes and the temperature inside the compressor 24 drops, the refrigerant gas remaining inside the compressor 24 liquefies. If the heating operation is started again with the liquefied air-conditioning refrigerant remaining, "liquid compression" occurs in which the compressor 24 pressurizes the liquid air-conditioning refrigerant. Since the liquid refrigerant is an incompressible fluid, when liquid compression occurs, an extremely large pressure is generated, and a "liquid hammer" occurs, which causes intense shock noises and vibrations. In addition, when liquid compression occurs, the valves and cylinders of the compressor 24 may be damaged in some cases. Furthermore, if the compressor 24 is driven in a state where liquid refrigerant is produced, the air-conditioning refrigerant cannot be sufficiently compressed, and sufficient heating capacity cannot be obtained. In this case, in order to ensure the necessary heating capacity, the air-conditioning controller 12 rotates the compressor 24 excessively when liquid refrigerant remains compared to when no liquid refrigerant remains. As a result, the power required for air conditioning increases, and the driving range of the electric vehicle decreases.

[0032] Therefore, in this example, when it becomes necessary to start heating using the heat pump in order to prevent liquid compression by the compressor, a non-compression operation is performed in which the air-conditioning refrigerant in the compressor 24 is sent to the accumulator 36 without placing an excessive load on the compressor 24 until the start-up conditions described below are met. After that, when the start-up conditions are met, the heat pump circuit 20 and the heating circuit 50 are driven so that the required heating capacity can be achieved. Hereinafter, the operation for achieving this required heating capacity is referred to as "standard operation."

[0033] When performing non-compression operation, the air conditioning controller 12 operates the compressor 24 at or below a standby rotation speed Nw, which is lower than the rotation speed during normal operation. The standby rotation speed Nw is a rotation speed at which the air-conditioning refrigerant in the compressor 24 can be sent downstream without placing a load on the compressor 24, and is a rotation speed lower than the target rotation speed N* that is set to achieve the desired heating capacity.

[0034] FIG. 2 is a diagram showing the relationship between the target rotation speed N* and the standby rotation speed Nw. In FIG. 2, the horizontal axis is the desired heating capacity, and the vertical axis is the rotation speed of the compressor 24. As shown in FIG. 2, the target rotation speed N* is clipped at a lower limit value Nmin and an upper limit value Nmax, but in principle, the higher the desired heating capacity, the higher the target rotation speed N*. The desired heating capacity is calculated based on the outside air temperature To, the target indoor temperature, the target blowing temperature TAO, the cooling water temperature Tw, and the like. On the other hand, the standby rotation speed Nw is set to a value that is sufficiently lower than the target rotation speed N* and hardly compresses the air-conditioning refrigerant. During standby operation, by driving the compressor 24 at the standby rotation speed Nw, the liquid refrigerant in the compressor 24 can be sent downstream while preventing liquid compression that compresses the liquid refrigerant in the compressor 24.

[0035] In addition, in the case of non-compression operation, the air conditioning controller 12 instructs the heating expansion valve 26 to open to a predetermined reference opening Avref. As will be described in detail later, the reference opening Avref is a value larger than the target opening Av* required to achieve a desired heating capacity, and is a value that allows the air-conditioning refrigerant to pass smoothly without being substantially decompressed.

[0036] FIG. 3 is a diagram showing the relationship between the target opening Av* and the reference opening Avref. In FIG. 3, the horizontal axis is the required heating capacity, and the vertical axis is the opening Av of the heating expansion valve 26. As shown in FIG. 3, the target opening Av* of the heating expansion valve 26 is clipped at the lower limit Avmin and the upper limit Avmax, but in principle, the higher the required heating capacity, the smaller the opening Av* becomes. By executing a throttling control to adjust the opening Av of the heating expansion valve 26 between Avmin and Avmax, the air conditioning refrigerant is decompressed, and the heating capacity can be exerted. The reference opening Avref is higher than the target opening Av* set to exert the heating capacity, and a value is set that allows the air conditioning refrigerant to pass through with almost no decompression. Therefore, for example, the reference opening Avref is 100% (i.e., fully open).

[0037] During non-compression operation, the heating expansion valve 26 is opened to the reference opening Avref, so that the air-conditioning refrigerant output from the compressor 24 can be smoothly sent to the downstream side, and ultimately to the accumulator 36. This allows the liquid refrigerant to be smoothly removed from the compressor 24.

[0038] Furthermore, in the non-compression operation, the air conditioning controller 12 also eliminates the air gap in the cooling water flow path of the water-cooled condenser 56. This is to prevent abnormal noise and the like caused by a pressure rise in the first flow path 22 when switching to standard operation.

[0039] That is, when the water pump 54 is started, an air gap may be generated in the cooling water flow path of the compressor 24. If this air gap remains when the operation shifts to standard operation, that is, when the compressor 24 starts compressing the air-conditioning refrigerant and the heating expansion valve 26 starts throttling control, the heat of the air-conditioning refrigerant is not sufficiently transferred to the cooling water, and the air-conditioning refrigerant flows toward the heating expansion valve 26 while remaining at high temperature and high pressure. At this time, because the heating expansion valve 26 is throttling controlled, the pressure of the air-conditioning refrigerant may rise excessively between the compressor 24 and the heating expansion valve 26, causing vibrations and abnormal noises due to the vibrations.

[0040] In order to prevent such an excessive pressure rise of the air-conditioning refrigerant, in this example, during non-compression operation, the air-conditioning controller 12 instructs the water pump 54 to pump the cooling water at a predetermined reference water flow rate Qwref. This reference water flow rate Qwref is not particularly limited as long as it can remove air accumulation in the cooling water flow path of the water-cooled condenser 56, but in this example, the reference water flow rate Qwref is set to the same value as the target water flow rate Qw* set during standard operation. The target water flow rate Qw* may be changed according to the required heating capacity, but in this example, it is always constant regardless of the required heating capacity. During non-compression operation, the water pump 54 is driven at the reference water flow rate Qwref to eliminate an air gap in the water flow path of the water-cooled condenser 56. This allows the air-conditioning refrigerant and the cooling water to be appropriately heat-exchanged during standard operation, preventing an excessive pressure rise of the air-conditioning refrigerant and, ultimately, the generation of abnormal noise.

[0041] As described above, the non-compression operation is performed until a predetermined start condition is satisfied. The start condition includes that the opening Av of the heating expansion valve 26 is the reference opening Avref. That is, at the start of the non-compression operation, the air conditioning controller 12 instructs the heating expansion valve 26 to open to the reference opening Avref, but it actually takes some time for the heating expansion valve 26 to reach the reference opening Avref. Therefore, the air conditioning controller 12 continues the non-compression operation during the period in which the heating expansion valve 26 does not reach the reference opening Avref.

[0042] The start-up condition also includes that the air-conditioning refrigerant output from the compressor 24 is in a gas phase. Here, the phase state of the air-conditioning refrigerant output from the compressor 24 may be determined based on at least one of the water temperature Tw of the cooling water output from the water-cooled condenser 56, the temperature (refrigerant temperature Tc) of the air-conditioning refrigerant output from the compressor 24, and the pressure (refrigerant pressure Pc) of the air-conditioning refrigerant output from the compressor 24. For example, the air-conditioning controller 12 may determine that the air-conditioning refrigerant is in a gas phase when at least one of the water temperature Tw is equal to or higher than a specified reference water temperature Twref, the refrigerant temperature Tc is equal to or higher than a specified reference refrigerant temperature, and the refrigerant pressure Pc is equal to or higher than a specified reference refrigerant pressure Pcref. The refrigerant temperature Tc is detected by the first temperature sensor 40, the refrigerant pressure Pc is detected by the pressure sensor 42, and the water temperature Tw is detected by the second temperature sensor 62. In this example, the start-up condition includes that the water temperature Tw is equal to or higher than a predetermined reference water temperature Twref.

[0043] Here, the reference water temperature Twref may be a fixed value or a variable value that varies depending on various parameters. In this example, the reference water temperature Twref is a variable value that varies depending on the outside air temperature To. FIG. 4 is a diagram showing an example of the reference water temperature Twref. In FIG. 4, the horizontal axis is the outside air temperature To, and the vertical axis is the reference water temperature Twref. As shown in FIG. 4, the reference water temperature Twref is a constant value T1+α at temperatures below T1, and is a constant value T2+α at temperatures above T2, but is the outside air temperature To+α in the range from temperature T1 to T2, and varies depending on the outside air temperature To.

[0044] The start-up condition further includes that the water flow rate Qw of the water pump 54 is equal to or greater than a predetermined reference water flow rate Qwref. That is, similar to the heating expansion valve 26, at the start of the non-compression operation, the air conditioning controller 12 instructs the water pump 54 to operate at the reference water flow rate Qwref, but it actually takes some time for the water flow rate Qw of the water pump 54 to reach the designated reference water flow rate Qwref. Therefore, the air conditioning controller 12 continues the non-compression operation during the period in which the water flow rate Qw of the water pump 54 does not reach the reference water flow rate Qwref.

[0045] Then, when the above-mentioned start conditions, i.e., Av≧Avref, Tw≧Twref, and Qw≧Qwref, are satisfied, the air conditioning controller 12 stops the non-compression operation and starts the standard operation. At the start of this standard operation, the liquid refrigerant is discharged from the compressor 24 and the air gap in the cooling water flow path of the water-cooled condenser 56 is eliminated, so that liquid compression and excessive pressure increase can be effectively prevented. As a result, vibrations and abnormal noise can be prevented, and further, power consumption can be suppressed, thereby improving the driving distance of the electric vehicle.

[0046] Next, the process flow of the vehicle air conditioning system 10 will be described with reference to Fig. 5. As shown in Fig. 5, the air conditioning controller 12 waits until heating using a heat pump is required (S10). When heating using a heat pump is required (Yes in S10), the air conditioning controller 12 starts non-compression operation (S12). That is, it instructs the compressor 24 to operate at the standby rotation speed Nw, instructs the heating expansion valve 26 to open to the reference opening Avref, and instructs the water pump 54 to operate at the reference water flow rate Qwref.

[0047] Next, the air conditioning controller 12 checks whether the start-up conditions are met (S14 to S18). Specifically, the air conditioning controller 12 compares the coolant temperature Tw with the reference water temperature Twref (S14). If the comparison result shows that the water temperature Tw is less than the reference water temperature Twref (No in S14), the air conditioning controller 12 continues the non-compression operation because it is highly likely that the air-conditioning refrigerant output from the compressor 24 is not in gas phase.

[0048] On the other hand, if Tw≧Twref (Yes in S14), the air conditioning controller 12 compares the water flow rate Qw of the water pump 54 with the reference water flow rate Qwref (S16). If the comparison result shows that the water flow rate Qw is less than the reference water flow rate Qwref (No in S16), the air gap in the water-cooled condenser 56 may not have been eliminated, so the air conditioning controller 12 continues the non-compression operation.

[0049] On the other hand, if Qw≧Qwref (Yes in S16), the air conditioning controller 12 compares the opening Av of the heating expansion valve 26 with the reference opening Avref (S18). If the comparison shows that the opening Av is less than the reference opening Avref (No in S18), there is a possibility that liquid refrigerant has not been removed from the compressor 24, so the air conditioning controller 12 continues the non-compression operation.

[0050] On the other hand, if Av≧Avref (Yes in S18), the start-up condition is met. In this case, the air conditioning controller 12 transitions to standard operation (S20). That is, the air conditioning controller 12 operates the compressor 24 at the target rotation speed N* corresponding to the required heating capacity, and throttles the heating expansion valve 26 to the target opening Av* corresponding to the required heating capacity. In addition, the air conditioning controller 12 continues to operate the water pump 54. Then, standard operation continues until the heating is turned off (Yes in S22).

[0051] As is clear from the above description, in this example, the non-compression operation is performed in which the compressor 24 is operated at low speed until the start-up conditions, including the heating expansion valve 26 reaching the target opening Av*, are met. This allows the liquid refrigerant in the compressor 24 to be guided to the accumulator without placing an excessive load on the compressor 24. In addition, during the non-compression operation, the water pump 54 is operated at the reference water flow rate Qwref, so the air gap in the water-cooled condenser 56 can also be eliminated. As a result, when switching to standard operation, liquid compression and an excessive rise in refrigerant pressure can be effectively prevented. As a result, abnormal noise can be prevented and power consumption can be reduced.

[0052] The above description is merely an example, and other configurations may be changed as long as the compressor 24 is operated at a rotation speed equal to or lower than the standby rotation speed Nw until the specified start-up condition is met, and the start-up condition includes at least that the opening Av of the heating expansion valve 26 is equal to or higher than the reference opening Avref. For example, in the above description, the start-up conditions include three conditions Av≧Avref, Tw≧Twref, and Qw≧Qwref, but at least one of Tw≧Twref and Qw≧Qwref may be excluded from the start-up conditions. Therefore, for example, as shown in FIG. 6, the air conditioning controller 12 may monitor only the opening Av of the heating expansion valve 26, and may directly switch to standard operation if Av≧Avref is met.

[0053] In addition, in the above description, the vehicle air conditioning system 10 has the heat pump circuit 20 and the heating circuit 50, but the heating circuit 50 may be omitted. That is, as shown in Fig. 7, the heat pump circuit 20 may further have an interior condenser 38 arranged in the flow path of the air conditioning air, and the air conditioning air may be heated in this interior condenser 38. [Explanation of symbols]

[0054] 10 vehicle air conditioning system, 12 air conditioning controller, 20 heat pump circuit, 22 first flow path, 24 compressor, 26 heating expansion valve, 28 condenser, 30 condenser fan, 32 cooling expansion valve, 34 evaporator, 36 accumulator, 38 interior condenser, 40 first temperature sensor, 42 pressure sensor, 50 heating circuit, 52 second flow path, 54 water pump, 56 water-cooled condenser, 57 engine, 58 heater core, 60 three-way valve, 62 second temperature sensor, 70 blowing mechanism, 72 housing, 74 blower, 76 mix door, 78 blowing outlet, 80 adjustment door.

Claims

1. a heat pump circuit including: a first flow path through which an air-conditioning refrigerant flows; a compressor that compresses the air-conditioning refrigerant; a condenser that exchanges heat between the air-conditioning refrigerant and outside air; a heating expansion valve that is provided between the compressor and the condenser and that reduces the pressure of the air-conditioning refrigerant; and an accumulator that is provided between the condenser and the compressor and that separates the air-conditioning refrigerant into gas and liquid phases; An air conditioning controller; When it becomes necessary to start heating using a heat pump, the air conditioning controller operates the compressor at a rotation speed equal to or lower than a specified standby rotation speed until a specified start condition is satisfied; The start-up condition includes at least that the opening degree of the heating expansion valve is equal to or greater than a predetermined reference opening degree, The standby rotation speed is lower than a target rotation speed required to exert a heating capacity, The reference opening degree is greater than a target opening degree necessary to achieve heating capacity, After the start-up condition is satisfied, the air conditioning controller drives the compressor at a target rotation speed and throttles the heating expansion valve to the target opening degree. The vehicle air conditioning system is characterized by the above.

2. A heat pump circuit having a first flow path through which an air-conditioning refrigerant flows, a compressor that compresses the air-conditioning refrigerant, a condenser that exchanges heat between the air-conditioning refrigerant and outside air, a heating expansion valve provided between the compressor and the condenser and reducing the pressure of the air-conditioning refrigerant, and an accumulator provided between the condenser and the compressor and separating the air-conditioning refrigerant into gas and liquid phases; An air conditioning controller; When it becomes necessary to start heating using a heat pump, the air conditioning controller operates the compressor at a rotation speed equal to or lower than a specified standby rotation speed until a specified start condition is satisfied; The start-up condition includes at least that the opening degree of the heating expansion valve is equal to or greater than a predetermined reference opening degree, and further includes a heating circuit including a second flow path through which the cooling water flows, a water-cooled condenser for heat exchange between the air-conditioning refrigerant and the cooling water, a water pump for pumping the cooling water, and a heater core heated by the cooling water; The vehicle air conditioning system according to claim 1, wherein the start-up condition further includes a water flow rate of the water pump being equal to or greater than a specified reference water flow rate.

3. A heat pump circuit having a first flow path through which an air-conditioning refrigerant flows, a compressor that compresses the air-conditioning refrigerant, a condenser that exchanges heat between the air-conditioning refrigerant and outside air, a heating expansion valve provided between the compressor and the condenser and reducing the pressure of the air-conditioning refrigerant, and an accumulator provided between the condenser and the compressor and separating the air-conditioning refrigerant into gas and liquid phases; An air conditioning controller; When it becomes necessary to start heating using a heat pump, the air conditioning controller operates the compressor at a rotation speed equal to or lower than a specified standby rotation speed until a specified start condition is satisfied; The start-up condition includes at least that the opening degree of the heating expansion valve is equal to or greater than a predetermined reference opening degree, The vehicle air conditioning system according to claim 1, wherein the start-up condition further includes the air conditioning refrigerant output from the compressor being in a gas phase.

4. 4. The vehicle air conditioning system according to claim 3, The vehicle air conditioning system is characterized in that the air conditioning controller determines that the air conditioning refrigerant output from the compressor is in a gas phase when at least one of the following is satisfied: the temperature of the cooling water output from a water-cooled condenser that exchanges heat with the air conditioning refrigerant is equal to or higher than a specified reference water temperature, the temperature of the air conditioning refrigerant output from the compressor is equal to or higher than a specified reference refrigerant temperature, and the pressure of the air conditioning refrigerant output from the compressor is equal to or higher than a specified reference refrigerant pressure.

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