Cooling system

Abstract

To accurately and efficiently cool a battery by a refrigerant in a cooling system for circulating the refrigerant including CO2 to cool the inside of a car.SOLUTION: The cooling system 100 includes the compressor 1 that compresses refrigerant, the heat exchangers 5a and 6a that use refrigerant cooled by the heat exchangers 2, the refrigerant line 17 that supplies refrigerant from the heat exchangers 5a and 6a to the battery 6, the refrigerant line 14 that supplies refrigerant cooled by the heat exchangers 2 to the refrigerant line 17 without passing through the heat exchangers 5a and 6a, the expansion valves E2 provided in the refrigerant line 17, and the flow control valves V3 provided in the refrigerant line 14. The control device 80 increases the opening degree of the flow control valve V3 when the specific entropy of the refrigerant supplied to the battery 6 exceeds a predetermined range, and decreases the opening degree of the flow control valve V3 when the specific entropy falls below the predetermined range.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a cooling system that circulates a refrigerant containing CO2 to cool the interior of a vehicle. [Background technology]

[0002] Conventionally, systems that circulate a refrigerant through a compressor, a heat exchanger, etc. have been used in refrigeration cycles used in air conditioners. In recent years, such refrigerant circulating systems have also been used to cool components inside vehicles, such as the batteries of electric vehicles and hybrid vehicles. In one example, Patent Document 1 describes a system that cools or heats battery cells by connecting a compressor, a first heat exchanger, and a second heat exchanger through a refrigerant flow path and performing heat exchange between the refrigerant and the battery cells using the second heat exchanger. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-180455 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the demand for battery cooling has increased with the rapid charging and higher output of batteries. To address this, battery cooling technologies using insulating coolants that can directly cool the inside of the battery have been developed. While such battery cooling technologies using coolants offer high cooling capacity, they suffer from pressure loss due to the viscosity of the oil. In response, the present inventors have devised a method for efficiently cooling batteries while reducing pressure loss by using an insulating, low-viscosity refrigerant containing CO2 (hereinafter referred to as a "CO2 refrigerant"). Because such CO2 refrigerants are so-called natural refrigerants, they are also environmentally friendly and considerate of the impact on the human body.

[0005] When a CO2 refrigerant is used to cool a battery, it is typically considered that the CO2 refrigerant is pressurized by a compressor, then decompressed by an expansion valve and supplied to the battery. This is because it may not be desirable to supply high-pressure CO2 refrigerant directly to the battery. For example, it is not desirable to supply high-pressure CO2 refrigerant to multiple cells in a battery.

[0006] However, when the CO2 refrigerant supplied to the battery is decompressed using an expansion valve as described above, if the CO2 refrigerant is in a relatively low enthalpy state, the decompression may cause the CO2 refrigerant to transition to a dry ice state. This dry ice-state CO2 refrigerant has low fluidity, making it difficult to cool the battery evenly, and its extremely low temperature can cause localized low temperatures, resulting in reduced battery performance and degradation.

[0007] Therefore, it is possible to heat the CO2 refrigerant supplied to the battery by heat exchange to make it in a relatively high enthalpy state before decompressing it. This prevents the CO2 refrigerant from transforming into a dry ice state when decompressed. However, if the enthalpy of the CO2 refrigerant is made too high, the temperature of the CO2 refrigerant will rise (specifically, the temperature of the CO2 refrigerant will approach the temperature of the battery), and the CO2 refrigerant will not be able to provide sufficient cooling capacity for the battery.

[0008] The present invention has been made to solve the problems of the conventional technology described above, and aims to accurately and efficiently cool a battery using a refrigerant in a cooling system that circulates a refrigerant containing CO2 to cool the interior of a vehicle. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a cooling system for cooling the interior of a vehicle by circulating a refrigerant containing CO2, the system comprising: a compressor for compressing the refrigerant; a first heat exchanger for cooling the refrigerant compressed by the compressor; a second heat exchanger for cooling a predetermined cooling target within the vehicle with the refrigerant cooled by the first heat exchanger; a first refrigerant passage for supplying the refrigerant to a battery in the vehicle after being used for cooling in the second heat exchanger in order to further cool the battery; and a second refrigerant passage for supplying the refrigerant cooled by the first heat exchanger to the first cooling target without passing through the second heat exchanger. the control device is configured to calculate the enthalpy of the refrigerant supplied to the battery from the first refrigerant passage, and to increase the opening of the flow rate control valve when the enthalpy exceeds a predetermined range, while decreasing the opening of the flow rate control valve when the enthalpy is below the predetermined range.

[0010] According to the present invention configured as described above, the refrigerant in a relatively low enthalpy state from the first heat exchanger is converted to a relatively high enthalpy state by heat exchange in the second heat exchanger and then supplied to the battery. This prevents the refrigerant from becoming dry ice-like. In other words, the expansion (decompression) of the expansion valve provided in the first refrigerant passage prevents the refrigerant supplied to the battery from becoming dry ice-like. Furthermore, in the present invention, not only the refrigerant in a relatively high enthalpy state from the second heat exchanger but also the refrigerant in a relatively low enthalpy state from the first heat exchanger that does not pass through the second heat exchanger is supplied to the battery. In particular, in the present invention, the opening degree of the flow control valve in the second refrigerant passage is controlled to adjust the amount of the refrigerant in a relatively low enthalpy state from the first heat exchanger that is mixed with the refrigerant in a relatively high enthalpy state from the second heat exchanger, thereby maintaining the enthalpy of the refrigerant supplied to the battery within a predetermined range. This allows a relatively low-temperature refrigerant to be supplied to the battery, thereby effectively cooling the battery. As described above, according to the present invention, it is possible to improve the cooling capacity of the battery by the refrigerant while preventing the refrigerant from being supplied in a dry ice state to the battery.

[0011] In the present invention, preferably, the cooling system further includes a battery heat exchanger for causing the refrigerant from the first refrigerant passage to flow around the plurality of cells in the battery to directly cool the plurality of cells with the refrigerant, and the battery heat exchanger is supplied with refrigerant whose pressure has been reduced by an expansion valve. According to the present invention configured as described above, the battery heat exchanger directly cools the multiple cells with the refrigerant, thereby effectively cooling the multiple cells. In this case, since the pressure resistance of the battery pack and the like is relatively low, it is not desirable to supply the high-pressure refrigerant from the compressor directly to the battery heat exchanger. Therefore, in the present invention, the refrigerant from the compressor is decompressed by an expansion valve before being supplied to the battery heat exchanger. This effectively protects the inside of the battery (multiple cells, etc.).

[0012] In the present invention, preferably, when the flow control valve is a first flow control valve, the cooling system further has a second flow control valve for adjusting the flow rate of the refrigerant supplied to the second heat exchanger, and the control device is configured to control the second flow control valve to increase its opening when the first flow control valve is fully open when the enthalpy exceeds a predetermined range, and to control the second flow control valve to decrease its opening when the first flow control valve is fully closed when the enthalpy is below the predetermined range. According to the present invention configured in this manner, when the first flow control valve is already in a fully open state, the refrigerant flow rate is insufficient for the cooling demands of the cooling system, so the opening of the second flow control valve can be increased to increase the refrigerant flow rate; on the other hand, when the first flow control valve is already in a fully closed state, the refrigerant flow rate is excessive for the cooling demands of the cooling system, so the opening of the second flow control valve can be decreased to decrease the refrigerant flow rate.

[0013] In the present invention, the predetermined range is preferably set to a range higher than the enthalpy at which the refrigerant containing CO2 becomes in a dry ice state. According to the present invention configured as described above, it is possible to reliably prevent refrigerant in a dry ice state from being supplied to the battery.

[0014] In the present invention, the predetermined range is preferably set based on the enthalpy at which the degree of superheat, as defined by the saturated vapor line of the refrigerant, is less than a predetermined value. According to the present invention configured in this manner, a refrigerant with a relatively small degree of superheat (i.e., a relatively low temperature refrigerant that is not in a dry ice state) can be supplied to the battery, thereby making it possible to effectively improve the cooling capacity of the battery by the refrigerant.

[0015] In the present invention, preferably, the cooling system further includes a refrigerant pressure sensor that detects the pressure of the refrigerant from the first heat exchanger, and a refrigerant temperature sensor that detects the temperature of the refrigerant in the first refrigerant passage, and the control device calculates the enthalpy from the pressure and temperature detected by the refrigerant pressure sensor and the refrigerant temperature sensor, respectively. According to the present invention configured as described above, the enthalpy of the refrigerant can be determined with high accuracy by using the pressure and temperature of the refrigerant detected by the sensor.

[0016] In the present invention, the second heat exchanger preferably includes an air conditioning heat exchanger for air conditioning the vehicle, and / or a battery heat exchanger for supplying refrigerant to the outside of a battery pack including a plurality of cells in a battery, thereby indirectly cooling the plurality of cells with the refrigerant. According to the present invention configured as described above, a single system (cooling system) that circulates a refrigerant can adequately achieve vehicle air conditioning and battery cooling. In particular, by using a battery heat exchanger that supplies refrigerant to the outside of the battery pack, the battery can be adequately cooled and a relatively large amount of heat can be exchanged between the battery and the refrigerant.

[0017] In the present invention, the first heat exchanger is preferably configured as a cascade heat exchanger that exchanges heat between a first heat cycle circuit that includes at least a compressor, a second heat exchanger, first and second refrigerant passages, an expansion valve, and a flow control valve, and a second heat cycle circuit that is separate from the first heat cycle circuit and includes an outside air heat exchanger that exchanges heat with outside air. According to the present invention configured in this manner, by performing heat exchange (cascade heat exchange) between the first heat cycle circuit and the second heat cycle circuit, which performs heat exchange with outside air, the efficiency of the entire system of the first heat cycle circuit can be improved, in other words, the work of the compressor in the first heat cycle circuit can be reduced.

[0018] In the present invention, the cooling system is preferably configured to further cool a motor that drives the vehicle using electric power from the battery, with the refrigerant cooled by the first heat exchanger. According to the present invention configured in this manner, it is possible to appropriately cool various components within a vehicle, such as the motor, using a single system (cooling system) that circulates a refrigerant. [Effects of the Invention]

[0019] According to the present invention, in a cooling system that circulates a refrigerant containing CO2 to cool the interior of a vehicle, the battery can be cooled accurately and efficiently by the refrigerant. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic configuration diagram of a vehicle to which a cooling system according to an embodiment of the present invention is applied; [Figure 2] 1 is a schematic configuration diagram of a cooling system according to an embodiment of the present invention. [Figure 3] 3(a) and 3(b) are schematic configuration diagrams of a first battery heat exchanger and a second battery heat exchanger according to an embodiment of the present invention, respectively. [Figure 4] FIG. 2 is a block diagram showing the electrical configuration of the cooling system according to the embodiment of the present invention. [Figure 5] FIG. 1 is an explanatory diagram illustrating a basic concept of control according to an embodiment of the present invention. [Figure 6] 4 is a flowchart illustrating a control according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, a cooling system according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0022] [Overall configuration] First, the overall configuration of the cooling system according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram of a vehicle to which the cooling system according to this embodiment is applied.

[0023] 1, vehicle 200 is, for example, an electric vehicle, and has a cooling system 100 that circulates a refrigerant in a refrigeration cycle. This cooling system 100 mainly has a compressor 1 for compressing the refrigerant, a heat exchanger 2 for cooling the refrigerant compressed by compressor 1, a motor 4 for generating power to drive vehicle 200, an air conditioner 5 for conditioning the interior of vehicle 200, and a battery 6 for supplying power to drive motor 4.

[0024] The cooling system 100 circulates a CO2 refrigerant (hereinafter sometimes simply referred to as "refrigerant") as a natural refrigerant. Typically, CO2 refrigerant is a refrigerant containing refrigeration oil (oil) such as PAG and additives. To use this CO2 refrigerant, the compressor 1 is configured to compress the refrigerant to extremely high pressures. The motor 4 uses the refrigerant (liquid (typically supercritical) refrigerant) compressed by the compressor 1 to cool its rotor and stator. In addition, the motor 4 is configured to use the refrigerant to lubricate the sliding bearings that support the rotating shaft. The refrigerant compressed by the compressor 1 is used for air conditioning in the air conditioner 5 and for cooling the battery 6. For example, in the cooling system 100, a high-temperature, high-pressure gas refrigerant is supplied from the compressor 1 to the heat exchanger 2, a low-temperature, high-pressure liquid refrigerant is supplied from the heat exchanger 2 to the motor 4, and a room-temperature, low-pressure gas refrigerant is supplied from the motor 4 to the compressor 1.

[0025] [Cooling system configuration] Next, the cooling system 100 according to this embodiment will be specifically described with reference to Fig. 2. Fig. 2 is a schematic configuration diagram of the cooling system 100 according to this embodiment.

[0026] As shown in Fig. 2, the cooling system 100 includes a first heat cycle circuit (low-temperature circuit) 100a that circulates the CO2 refrigerant described above, and a second heat cycle circuit (high-temperature circuit) 100b that includes an outside-air heat exchanger 30 that exchanges heat with outside air and circulates a refrigerant such as propane or a fluorine-based refrigerant, and is configured to realize a cascade refrigeration cycle. Specifically, the first heat cycle circuit 100a and the second heat cycle circuit 100b perform cascade heat exchange in a heat exchanger 2 (hereinafter, the heat exchanger 2 will be referred to as the "cascade heat exchanger 2" as appropriate). This cascade heat exchanger 2 corresponds to the "first heat exchanger" in this invention.

[0027] The first heat cycle circuit 100a of the cooling system 100 mainly includes, in addition to the compressor 1 and motor 4 described above, an air conditioning heat exchanger 5a (specifically, an evaporator that generates cool air to be supplied to the vehicle interior) for performing heat exchange in the air conditioner 5, a first battery heat exchanger 6a and a second battery heat exchanger 6b for performing heat exchange to cool the battery 6, refrigerant passages 11 to 20 through which the refrigerant flows, a compressor 23 that compresses the refrigerant, flow control valves V1, V2, and V3 that adjust the flow rate of the refrigerant, and expansion valves E1, E2, and E3 that expand the refrigerant to reduce its pressure.

[0028] In this embodiment, the compressor 1 has a first compressor 1a on the upstream side and a second compressor 1b on the downstream side, and is configured to compress the refrigerant in two stages. The first compressor 1a increases the refrigerant pressure P3 to pressure P2 (pressure P2 > pressure P3), and the second compressor 1b increases the refrigerant pressure P2 to pressure P1 (pressure P1 > pressure P2). In one example, pressure P1 is about 3 MPa, pressure P2 is about 1.5 MPa, and pressure P3 is about 0.1 MPa.

[0029] In this embodiment, the battery 6 is configured to be cooled by two heat exchangers: a first battery heat exchanger 6a and a second battery heat exchanger 6b. The configurations of the first battery heat exchanger 6a and the second battery heat exchanger 6b will be described with reference to FIGS. 3(a) and 3(b). FIGS. 3(a) and 3(b) schematically show examples of the first battery heat exchanger 6a and the second battery heat exchanger 6b, respectively. More specifically, FIG. 3(a) shows a plan view of a battery pack 61 of the battery 6 as seen from the outside, and FIG. 3(b) shows a plan view of the battery pack 61 seen through.

[0030] As shown in FIG. 3(a), the first battery heat exchanger 6a is configured to supply a refrigerant to the outside (typically, the surface of the case) of a battery pack 61 including a plurality of cells 62 in the battery 6, and more specifically, to flow the refrigerant through a meandering flow path 63, thereby indirectly cooling the plurality of cells 62 in the battery 6 with the refrigerant. Note that the configuration for indirectly cooling the cells 62 in the battery 6 with the refrigerant is not limited to the configuration shown in FIG. 3(a), and various known configurations are applicable. In contrast, as shown in FIG. 3(b), the second battery heat exchanger 6b is configured to flow the refrigerant around the plurality of cells 62 in the battery 6, that is, to flow the refrigerant inside the battery pack 61, thereby directly cooling the plurality of cells 62 with the refrigerant. Note that the first battery heat exchanger 6a and the above-described air-conditioning heat exchanger 5a correspond to the "second heat exchanger" in the present invention. In this case, the air conditioning heat exchanger 5a cools the evaporator (object to be cooled) of the air conditioner 5 with the refrigerant, and the first battery heat exchanger 6a cools the battery 6 (object to be cooled) with the refrigerant.

[0031] Returning to FIG. 2 , the flow of refrigerant within the first heat cycle circuit 100a will be specifically described. Refrigerant compressed by compressor 1 is supplied to cascade heat exchanger 2 through refrigerant passage 11, and the refrigerant cooled by cascade heat exchanger 2 is supplied to air conditioning heat exchanger 5a, first battery heat exchanger 6a, and motor 4 through refrigerant passages 12, 13, and 15 connected to refrigerant passage 11. Refrigerant passages 12 and 13 join at a junction C1 and are connected to refrigerant passage 16, whereby the refrigerant that has exchanged heat in air conditioning heat exchanger 5a and first battery heat exchanger 6a is supplied to refrigerant passage 16. Refrigerant cooled by cascade heat exchanger 2 is supplied directly to refrigerant passage 16 through refrigerant passage 14 connected to refrigerant passage 11 without passing through air conditioning heat exchanger 5a and first battery heat exchanger 6a (i.e., bypassing refrigerant passages 12, 13, and 15). In this case, refrigerant passage 14 and refrigerant passage 16 merge at junction C2 downstream of junction C1. Refrigerant passages 12, 13, and 14 are provided with flow control valves V1, V2, and V3, respectively, for adjusting the flow rate of the refrigerant flowing through each passage, and refrigerant passage 15 is provided with expansion valve E1 for expanding the refrigerant supplied to motor 4. Expansion valve E1 functions to reduce the pressure of the refrigerant from pressure P1 to pressure P2. Flow control valve V3 corresponds to the "first flow control valve" in this invention, and flow control valves V1 and V2 correspond to the "second flow control valve" in this invention.

[0032] A refrigerant passage 17 is connected to the refrigerant passage 16, and the refrigerant in the refrigerant passage 16 is supplied from the refrigerant passage 17 to the second battery heat exchanger 6b. An expansion valve E2 for expanding the refrigerant is provided in the refrigerant passage 17 upstream of the second battery heat exchanger 6b, and the refrigerant decompressed by the expansion valve E2 is supplied to the second battery heat exchanger 6b. The expansion valve E2 functions to decompress the refrigerant from pressure P1 to pressure P3. An internal heat exchanger (IHX) 6c having a known double-pipe structure is provided downstream of the second battery heat exchanger 6b in the refrigerant passage 17, and its downstream side is connected to the first compressor 1a of the compressor 1. The refrigerant decompressed to pressure P3 by the expansion valve E2 is supplied to the first compressor 1a. The refrigerant passage 17 corresponds to the "first refrigerant passage" in this invention, and the refrigerant passage 14 corresponds to the "second refrigerant passage" in this invention.

[0033] Furthermore, refrigerant passage 16 branches into refrigerant passages 18 and 20 downstream of the connection point with refrigerant passage 17. Refrigerant passage 18 is provided with an expansion valve E3 for expanding the refrigerant. The expansion valve E3 functions to reduce the pressure of the refrigerant from pressure P1 to pressure P2. Refrigerant passage 18 also merges with refrigerant passage 15, which includes the motor 4, at a junction C3 downstream of the expansion valve E3, and these refrigerant passages 15 and 18 are connected to refrigerant passage 19. Refrigerant passage 19 is connected between the first compressor 1a and the second compressor 1b of compressor 1, and supplies the refrigerant at pressure P2 reduced by the expansion valve E1 and the expansion valve E3 to the second compressor 1b. Meanwhile, refrigerant passage 20 is connected to refrigerant passage 11 between compressor 1 and cascade heat exchanger 2 at a junction C4 downstream of refrigerant passage 20. The refrigerant passage 20 is provided with a compressor 23 and an internal heat exchanger (IHX) 24 having a known double-pipe structure. Such refrigerant passage 20 allows the refrigerant from the refrigerant passage 16 to be supplied to the cascade heat exchanger 2 by the compressor 23 without passing through the compressor 1 (i.e., by bypassing the compressor 1).

[0034] Next, the second heat cycle circuit 100b of the cooling system 100 is a high-temperature circuit that circulates a refrigerant such as propane or a fluorine-based refrigerant, as described above, and includes an outside air heat exchanger 30 that exchanges heat with outside air, a refrigerant passage 31 through which the refrigerant flows, a compressor 32 that compresses and feeds the refrigerant, and an expansion valve 33 that expands the refrigerant. In the cooling system 100 according to this embodiment, the second heat cycle circuit 100b is provided separately from the first heat cycle circuit 100a, thereby improving the efficiency of the entire system of the first heat cycle circuit 100a, in other words, reducing the work of the compressor 1.

[0035] Next, the electrical configuration of the cooling system 100 according to this embodiment will be described with reference to Fig. 4 in addition to Fig. 2. Fig. 4 is a block diagram showing the electrical configuration of the cooling system 100 according to this embodiment.

[0036] 4, the cooling system 100 has a control device 80 configured to perform various controls in the system. The control device 80 is configured by a computer including one or more processors 80a (typically a CPU) and memory 80b such as a ROM or RAM that stores various programs interpreted and executed on the processor 80a (including basic control programs such as an OS and application programs that are started on the OS and realize specific functions) and various data.

[0037] The cooling system 100 also includes refrigerant temperature sensors 41, 42, 43, and 44 that detect the temperature of the refrigerant and refrigerant pressure sensors 51, 52, and 53 that detect the pressure of the refrigerant (see FIG. 2), a vehicle interior temperature sensor 71 that detects the temperature of the vehicle interior (cabin), a battery temperature sensor 72 that detects the temperature of the battery 6, and a motor temperature sensor 73 that detects the temperature of the motor 4. Specifically, as shown in FIG. 2, the refrigerant temperature sensor 41 is provided in the refrigerant passage 11 between the compressor 1 and the cascade heat exchanger 2 (more specifically, upstream of a junction C4 of the refrigerant passage 11 and the refrigerant passage 20), the refrigerant temperature sensor 42 is provided at a junction C2 of the refrigerant passage 14 and the refrigerant passage 16, the refrigerant temperature sensor 43 is provided at a junction C3 of the refrigerant passage 15 and the refrigerant passage 18, and the refrigerant temperature sensor 44 is provided in the refrigerant passage 17 downstream of the second battery heat exchanger 6b and the IHX 6c. In addition, the refrigerant pressure sensor 51 is provided on the refrigerant passage 11 downstream of the cascade heat exchanger 2, the refrigerant pressure sensor 52 is provided on the refrigerant passage 15 downstream of the motor 4, and the refrigerant pressure sensor 53 is provided on the refrigerant passage 17 downstream of the second battery heat exchanger 6b and the IHX 6c.

[0038] The control device 80 controls the compressor 1, the flow rate adjustment valves V1, V2, V3, and the expansion valves E1, E2, E3 by supplying control signals thereto based on the detection signals from the sensors 41 to 44, 51 to 53, 71 to 73. In particular, in this embodiment, the control device 80 controls the openings of the flow rate adjustment valves V1, V2, V3 and the discharge rate of the compressor 1 so that the battery 6 is cooled accurately and efficiently by the refrigerant in the second battery heat exchanger 6b (details will be described later).

[0039] [Control method] Next, the control performed by the control device 80 in this embodiment will be described. First, the basic concept of control according to this embodiment will be described with reference to FIG. 5. In FIG. 5, the horizontal axis represents the specific enthalpy (enthalpy per unit mass) of the CO2 refrigerant, and the vertical axis represents the pressure of the CO2 refrigerant. Specifically, FIG. 5 shows a portion of a Mollier diagram (ph diagram) realized by the first heat cycle circuit 100a of the cooling system 100. Note that the specific enthalpy illustrated in FIG. 5 is defined based on the liquid side of the saturated vapor pressure line at 0°C (200 kJ / kg).

[0040] As described above, in this embodiment, in the second battery heat exchanger 6b, the refrigerant flows around the multiple cells 62 in the battery pack 61 to directly cool the multiple cells 62 (FIG. 3(b)). In this case, however, because the pressure resistance of the battery pack 61 is relatively low, it is not desirable to directly supply the refrigerant compressed by the compressor 1 to the second battery heat exchanger 6b. Therefore, in this embodiment, the refrigerant compressed by the compressor 1 is decompressed (pressure P1 → pressure P3) by the expansion valve E2 provided upstream of the second battery heat exchanger 6b in the refrigerant passage 17, and then supplied to the second battery heat exchanger 6b (FIG. 2).

[0041] However, as shown in FIG. 5, if the refrigerant in a relatively low enthalpy state (point X1) is decompressed (arrow A11) and supplied to the second battery heat exchanger 6b (arrow A12), the refrigerant (CO2 refrigerant) will become dry ice. For example, the refrigerant will become dry ice at a specific enthalpy of 440 kJ / kg or less. Because the refrigerant in the dry ice state has low fluidity, it may not be able to uniformly cool the gaps between the cells 62 in the battery 6. Furthermore, because the refrigerant is extremely cold, localized low-temperature areas may occur, resulting in performance degradation or deterioration of the battery 6. Therefore, it is undesirable to use the refrigerant in the dry ice state (arrow B1) for cooling in the second battery heat exchanger 6b.

[0042] Therefore, in this embodiment, the refrigerant in a relatively low enthalpy state cooled in the cascade heat exchanger 2 is heated by heat exchange in the air-conditioning heat exchanger 5a and the first-battery heat exchanger 6a. This refrigerant is then supplied to the second-battery heat exchanger 6b via refrigerant passages 12, 13, 16, and 17 (FIG. 2). The refrigerant, whose specific enthalpy has been increased before being decompressed by the expansion valve E2 (arrow A2, point X2 in FIG. 5), is then supplied to the second-battery heat exchanger 6b. However, when a refrigerant with an excessively high specific enthalpy, specifically a refrigerant in a highly superheated state (e.g., approximately 500 kJ / kg), is decompressed by the expansion valve E2 (arrow A3), the refrigerant temperature approaches the temperature of the battery 6 (point X3), although it does not become dry ice. Refrigerant in this state (arrow B2) does not provide sufficient cooling capacity for the second-battery heat exchanger 6b.

[0043] Therefore, in this embodiment, in addition to supplying the refrigerant that has passed through the air-conditioning heat exchanger 5a and the first-battery heat exchanger 6a to the second-battery heat exchanger 6b as described above, the refrigerant that has not passed through the air-conditioning heat exchanger 5a and the first-battery heat exchanger 6a, specifically the refrigerant that has been cooled in the cascade heat exchanger 2 and is in a relatively low-enthalpy state, is supplied directly to the second-battery heat exchanger 6b through a refrigerant passage 14 that bypasses the refrigerant passages 12 and 13 (FIG. 2). As a result, the refrigerant in a relatively low-enthalpy state from the cascade heat exchanger 2 is mixed with the refrigerant that has become relatively high-enthalpy in the air-conditioning heat exchanger 5a and the first-battery heat exchanger 6a (arrows A41 and A42 in FIG. 5), and the refrigerant with an appropriate specific enthalpy is supplied to the second-battery heat exchanger 6b (point X4). As a result, when the refrigerant is decompressed by the expansion valve E2, the refrigerant can be prevented from becoming dry ice (arrow A51), and the temperature difference between the refrigerant and the battery 6 can be maintained (arrow A52), thereby improving the cooling capacity of the refrigerant in the second battery heat exchanger 6b.

[0044] More specifically, in this embodiment, the control device 80 calculates the specific enthalpy of the refrigerant supplied to the second battery heat exchanger 6b, and in particular the current specific enthalpy of the refrigerant at the confluence C2 of the refrigerant passage 14 and the refrigerant passage 16 (hereinafter referred to as the "C2 actual enthalpy"), and if the C2 actual enthalpy exceeds a predetermined range, the control device 80 increases the opening of the flow rate adjustment valve V3 provided on the refrigerant passage 14 that bypasses the refrigerant passages 12 and 13 in order to increase the flow rate of the refrigerant in a relatively low enthalpy state. On the other hand, if the C2 actual enthalpy is below the predetermined range, the control device 80 reduces the opening of the flow rate adjustment valve V3 in order to reduce the flow rate of the refrigerant in a relatively low enthalpy state. In this way, the control device 80 controls the opening of the flow control valve V3 on the refrigerant passage 14 to adjust the amount of refrigerant in a relatively low enthalpy state from the cascade heat exchanger 2 to be mixed with the refrigerant that has become in a relatively high enthalpy state in the air conditioning heat exchanger 5a and the first battery heat exchanger 6a, thereby ensuring that the C2 actual enthalpy is within a predetermined range.

[0045] This prevents the refrigerant in a dry ice state from being supplied to the second battery heat exchanger 6b, while improving the cooling capacity of the refrigerant in the second battery heat exchanger 6b. From this perspective, the predetermined range applied to the C2 actual enthalpy used in the above control is set to a range higher than the specific enthalpy at which the refrigerant becomes in a dry ice state, and is set based on the specific enthalpy (e.g., 440 kJ / kg) at which the degree of superheat defined by the saturated vapor line of the refrigerant becomes less than a predetermined value (preferably close to 0).

[0046] In this embodiment, when the C2 actual enthalpy exceeds a predetermined range and the flow rate control valve V3 is fully open, the control device 80 increases the apertures of the flow rate control valves V1 and V2 provided on the refrigerant passages 12 and 13 including the air conditioning heat exchanger 5a and the first battery heat exchanger 6a. In this case, the refrigerant flow rate is insufficient relative to the cooling demands of the air conditioner 5 and the battery 6, so the control device 80 increases the apertures of the flow rate control valves V1 and V2 to increase the refrigerant flow rates of the air conditioning heat exchanger 5a and the first battery heat exchanger 6a. In contrast, when the C2 actual enthalpy falls below the predetermined range and the flow rate control valve V1 is fully closed, the control device 80 decreases the apertures of the flow rate control valves V1 and V2. In this case, the refrigerant flow rate is excessive relative to the cooling demands of the air conditioner 5 and the battery 6, so the control device 80 decreases the apertures of the flow rate control valves V1 and V2 to decrease the refrigerant flow rates of the air conditioning heat exchanger 5a and the first battery heat exchanger 6a.

[0047] Furthermore, in this embodiment, when the C2 actual enthalpy exceeds a predetermined range and the flow control valves V1, V2, and V3 are all fully open, the control device 80 increases the discharge rate of the compressor 1. In this case, the cooling capacity is improved by increasing the overall flow rate of the cooling system 100 (particularly the first heat cycle circuit 100a).

[0048] Next, a flowchart showing specific control according to this embodiment will be described with reference to Fig. 6. This flow is repeatedly executed at a predetermined cycle by the control device 80. In detail, the processor 80a in the control device 80 reads a program stored in the memory 80b and executes the program, thereby realizing the control related to this flow.

[0049] First, in step S10, the control device 80 acquires various information such as the detection values ​​detected by the above-mentioned sensors 41 to 44, 51 to 53, 71 to 73 (FIG. 4).

[0050] Next, in step S11, the control device 80 determines the opening degrees (hereinafter referred to as "V1 opening degree" and "V2 opening degree" as appropriate) of the flow control valves V1 and V2 provided on the refrigerant passages 12 and 13 including the air conditioning heat exchanger 5a and the first battery heat exchanger 6a, respectively, in accordance with the respective cooling requirements of the air conditioner 5 and the battery 6. In this case, the control device 80 determines these V1 opening degree and V2 opening degree based on the current temperature of the vehicle compartment detected by the vehicle compartment temperature sensor 71 and the current temperature of the battery 6 detected by the battery temperature sensor 72, in addition to the cooling requirements.

[0051] Next, in step S12, the control device 80 determines the specific enthalpy of the refrigerant at the confluence C1 of the refrigerant passages 12, 13, and 16 based on the V1 opening, V2 opening, etc. determined in step S11 (hereinafter referred to as the "C1 estimated enthalpy" where appropriate. The C1 estimated enthalpy corresponds to the specific enthalpy at point X2 in FIG. 5). For example, the control device 80 determines the C1 estimated enthalpy using a predefined map or equation based on the V1 opening, V2 opening (or the flow rates of the refrigerant passages 12, 13 according to the V1 opening, V2 opening), etc.

[0052] Next, in step S13, the control device 80 determines the aperture of the flow control valve V3 (hereinafter referred to as "V3 aperture") provided on the refrigerant passage 14 that bypasses the refrigerant passages 12 and 13, to set the specific enthalpy of the refrigerant at the confluence C2 of the refrigerant passages 14 and 16 within the above-mentioned predetermined range based on the C1 estimated enthalpy calculated in step S12. For example, the control device 80 calculates the flow rate from the refrigerant passage 14 necessary to set the specific enthalpy at the confluence C2 within the predetermined range based on the C1 estimated enthalpy at the confluence C1, and determines the V3 aperture to achieve this flow rate.

[0053] Next, in step S14, the control device 80 calculates the specific enthalpy of the refrigerant at the junction C2 based on the V3 opening determined in step S13 (hereinafter referred to as the "C2 estimated enthalpy" where appropriate. The C2 estimated enthalpy corresponds to the estimated value of the specific enthalpy at point X4 in FIG. 5). That is, the control device 80 calculates the specific enthalpy at the junction C2 (C2 estimated enthalpy), which is achieved by setting the flow control valve V3 to the V3 opening determined in step S13, using a predefined map, calculation formula, or the like.

[0054] Next, in step S15, the control device 80 calculates the C2 actual enthalpy (corresponding to the measured value of the specific enthalpy at point X4 in FIG. 5) based on the pressure (corresponding to P1) detected by the refrigerant pressure sensor 51 provided in the refrigerant passage 11 downstream of the cascade heat exchanger 2 and the temperature (the temperature of the refrigerant supplied to the second battery heat exchanger 6b of the battery 6) detected by the refrigerant temperature sensor 42 provided at the confluence C2. Usually, the specific enthalpy can be calculated from the pressure and temperature based on a predetermined Mollier diagram.

[0055] Next, in step S16, the control device 80 determines whether the difference between the C2 estimated enthalpy calculated in step S14 and the C2 actual enthalpy calculated in step S15 (hereinafter referred to as the "enthalpy error") is equal to or greater than a predetermined value. If the control device 80 determines that the enthalpy error is equal to or greater than the predetermined value (step S16: Yes), the control device 80 proceeds to step S17, corrects the V3 opening based on the enthalpy error, and returns to step S13. In step S13, the control device 80 determines the V3 opening corrected in step S17 as the opening to be applied. On the other hand, if the control device 80 does not determine that the enthalpy error is equal to or greater than the predetermined value (step S16: No), that is, if the enthalpy error is less than the predetermined value, the control device 80 proceeds to step S18 without performing the processing of step S17 as described above.

[0056] Next, in step S18, the control device 80 determines whether the C2 actual enthalpy calculated in step S15 exceeds a predetermined range, that is, whether the C2 actual enthalpy is equal to or greater than the upper limit of the predetermined range. As a result, if the control device 80 determines that the C2 actual enthalpy is equal to or greater than the upper limit (step S18: Yes), the control device 80 proceeds to step S19 and performs control (expansion control) to increase the V3 opening of the flow rate adjustment valve V3 in order to increase the refrigerant in a relatively low enthalpy state supplied from the refrigerant passage 14.

[0057] Then, the control device 80 proceeds to step S20, where it determines whether the V3 opening is fully open, that is, whether the V3 opening is already fully open due to the expansion control of the flow rate adjustment valve V3. As a result, if it is determined that the V3 opening is fully open (step S20: Yes), the control device 80 proceeds to step S21, where it performs control (expansion control) to increase the V1 and V2 openings of the flow rate adjustment valves V1 and V2. In this case, the refrigerant flow rate is insufficient to meet the cooling demands of the air conditioner 5 and the battery 6, so the refrigerant flow rates of the air conditioning heat exchanger 5a and the first battery heat exchanger 6a are increased.

[0058] The control device 80 then proceeds to step S22 to determine whether the V1 and V2 valves are fully open, i.e., whether the V1 and V2 valves are already fully open due to the expansion control of the flow control valves V1 and V2. If the control device 80 determines that the V1 and V2 valves are fully open (step S22: Yes), the control device 80 proceeds to step S23 to control the compressor 1 to increase its discharge rate. In this case, the control device 80 increases the discharge rate of the compressor 1 to increase the flow rate of the entire system of the first heat cycle circuit 100a, thereby improving the cooling capacity. After this, the control device 80 returns to step S18 and performs the processes from step S18 onwards again. Note that the control device 80 may re-calculate the C2 actual enthalpy using the same procedure as step S15 before determining the C2 actual enthalpy in step S18 (the same applies hereinafter).

[0059] On the other hand, if the control device 80 determines in step S18 that the C2 actual enthalpy is not equal to or greater than the upper limit (step S18: No), that is, if the C2 actual enthalpy is less than the upper limit, it proceeds to step S24. Also, if the control device 80 determines in step S20 that the V3 opening is not fully open (step S20: No), or if the control device 80 determines in step S22 that the V1 and V2 openings are not fully open (step S22: No), it returns to step S18.

[0060] Next, in step S24, the control device 80 determines whether the C2 actual enthalpy is below a predetermined range, that is, whether the C2 actual enthalpy is below the lower limit of the predetermined range. As a result, if the control device 80 determines that the C2 actual enthalpy is below the lower limit (step S24: Yes), the control device 80 proceeds to step S25 and performs control to reduce the V3 opening of the flow rate adjustment valve V3 (reduction control) in order to reduce the refrigerant in a relatively low enthalpy state supplied from the refrigerant passage 14.

[0061] The control device 80 then proceeds to step S26, where it determines whether the V3 opening is fully closed, that is, whether the V3 opening has already been fully closed due to the reduction control of the flow rate adjustment valve V3. As a result, if it is determined that the V3 opening is fully closed (step S26: Yes), the control device 80 proceeds to step S27, where it performs control to reduce the V1 and V2 openings of the flow rate adjustment valves V1 and V2 (reduction control). In this case, the refrigerant flow rate is excessive relative to the cooling requirements of the air conditioner 5 and the battery 6, so the refrigerant flow rates of the air conditioning heat exchanger 5a and the first battery heat exchanger 6a are reduced. After this, the control device 80 returns to step S18.

[0062] On the other hand, if the control device 80 does not determine in step S24 that the C2 actual enthalpy is less than the lower limit (step S24: No), in this case the C2 actual enthalpy is within the predetermined range, and therefore ends the processing shown in the flow of Fig. 6. Also, if the control device 80 does not determine in step S26 that the V3 opening is fully closed (step S26: No), the control device 80 returns to step S18.

[0063] In the above-described flow, processing was performed using specific enthalpy, but instead of this specific enthalpy, processing of the above flow may also be performed using the degree of superheat defined from the specific enthalpy and the saturated vapor line.

[0064] [Action and effect] Next, the operation and effect of the cooling system 100 according to this embodiment will be described. In this embodiment, the cooling system 100, which circulates a refrigerant containing CO2 (CO2 refrigerant) to cool the interior of the vehicle 200, includes a compressor 1 that compresses the refrigerant, a cascade heat exchanger 2 that cools the refrigerant compressed by the compressor 1, an air conditioning heat exchanger 5a and a first battery heat exchanger 6a that use the refrigerant cooled by the cascade heat exchanger 2, a refrigerant passage 17 that supplies the refrigerant to the battery 6 after being used for cooling in the air conditioning heat exchanger 5a and the first battery heat exchanger 6a to further cool the battery 6, and a refrigerant passage 18 that supplies the refrigerant cooled by the cascade heat exchanger 2 to the air conditioning heat exchanger 5a and the first battery heat exchanger 6a. The battery 6 includes a refrigerant passage 14 for supplying the refrigerant to the refrigerant passage 17 without passing through the exchanger 6a, an expansion valve E2 provided on the refrigerant passage 17 for expanding the refrigerant, a flow control valve V3 provided on the refrigerant passage 14 for adjusting the flow rate of the refrigerant, and a control device 80 configured to control at least the flow control valve V3, wherein the control device 80 calculates the specific enthalpy (actual enthalpy C2) of the refrigerant supplied from the refrigerant passage 17 to the battery 6, and when the specific enthalpy exceeds a predetermined range, controls the flow control valve V3 to increase the opening degree, while when the specific enthalpy is below the predetermined range, controls the flow control valve V3 to decrease the opening degree.

[0065] According to this embodiment, the refrigerant in a relatively low enthalpy state from the cascade heat exchanger 2 is converted to a relatively high enthalpy state by heat exchange in the air conditioning heat exchanger 5a and the first battery heat exchanger 6a, and this refrigerant is supplied to the battery 6, thereby preventing refrigerant in a dry ice state from being supplied to the battery 6. In other words, the refrigerant supplied to the battery 6 is prevented from becoming dry ice due to expansion (decompression) of the expansion valve E2 provided in the refrigerant passage 17. Furthermore, in this embodiment, not only the refrigerant in a relatively high enthalpy state from the air conditioning heat exchanger 5a and the first battery heat exchanger 6a, but also the refrigerant in a relatively low enthalpy state from the cascade heat exchanger 2 that does not pass through the air conditioning heat exchanger 5a and the first battery heat exchanger 6a is supplied to the battery 6. In particular, in this embodiment, the opening of the flow rate adjustment valve V3 in the refrigerant passage 14 is controlled to adjust the amount of relatively low-enthalpy refrigerant from the cascade heat exchanger 2 that is mixed with the relatively high-enthalpy refrigerant from the air conditioning heat exchanger 5a and the first battery heat exchanger 6a, thereby maintaining the specific enthalpy of the refrigerant supplied to the battery 6 within a predetermined range. This allows a relatively low-temperature refrigerant to be supplied to the battery 6, making it possible to effectively cool the battery 6 with the refrigerant. As described above, according to this embodiment, the cooling capacity of the refrigerant for the battery 6 can be improved while preventing the refrigerant from being supplied in a dry ice state to the battery 6.

[0066] According to this embodiment, the cooling system 100 further includes a second battery heat exchanger 6b for circulating the refrigerant from the refrigerant passage 17 around the cells 62 in the battery 6 to directly cool the cells 62 with the refrigerant. The second battery heat exchanger 6b is supplied with refrigerant decompressed by an expansion valve E2. According to this embodiment, the cells 62 of the battery 6 are directly cooled with the refrigerant in the second battery heat exchanger 6b, so the cells 62 can be effectively cooled. In this case, since the pressure resistance of the battery pack 61 and the like is relatively low, it is undesirable to directly supply the high-pressure refrigerant from the compressor 1 to the second battery heat exchanger 6b. Therefore, in this embodiment, the refrigerant from the compressor 1 is decompressed by the expansion valve E2 and then supplied to the second battery heat exchanger 6b. This allows the interior of the battery 6 (such as the cells 62) to be adequately protected.

[0067] According to the present embodiment, the cooling system 100 further includes flow control valves V1 and V2 for adjusting the flow rates of the refrigerant supplied to the air conditioning heat exchanger 5a and the first battery heat exchanger 6a. When the specific enthalpy of the refrigerant exceeds a predetermined range and the flow control valve V3 is fully open, the control device 80 increases the apertures of the flow control valves V1 and V2. When the specific enthalpy of the refrigerant is below the predetermined range and the flow control valve V3 is fully closed, the control device 80 decreases the apertures of the flow control valves V1 and V2. As a result, when the flow control valve V3 is already fully open, the refrigerant flow rate is insufficient for the cooling demand in the cooling system 100, so the apertures of the flow control valves V1 and V2 can be increased to increase the refrigerant flow rate. When the flow control valve V3 is already fully closed, the refrigerant flow rate is excessive for the cooling demand in the cooling system 100, so the apertures of the flow control valves V1 and V2 can be decreased to decrease the refrigerant flow rate.

[0068] Furthermore, according to this embodiment, the above-mentioned predetermined range is set to a range higher than the specific enthalpy at which the refrigerant containing CO2 becomes a dry ice state. By controlling the flow rate adjustment valve V3 using such a predetermined range, it is possible to reliably prevent the refrigerant in a dry ice state from being supplied to the battery 6.

[0069] According to this embodiment, the predetermined range is set based on the specific enthalpy at which the degree of superheat defined by the saturated vapor line of the refrigerant is less than a predetermined value. This allows a refrigerant with a relatively low degree of superheat (i.e., a refrigerant at a relatively low temperature that is not in a dry ice state) to be supplied to the battery 6, thereby effectively improving the cooling capacity of the refrigerant for the battery 6.

[0070] Furthermore, according to this embodiment, the cooling system 100 further includes a refrigerant pressure sensor 51 that detects the pressure of the refrigerant from the cascade heat exchanger 2 and a refrigerant temperature sensor 42 that detects the temperature of the refrigerant in the refrigerant passage 17, and the control device 80 calculates the specific enthalpy from the pressure and temperature detected by the refrigerant pressure sensor 51 and the refrigerant temperature sensor 42. By using the pressure and temperature of the refrigerant detected by the sensors in this manner, the specific enthalpy of the refrigerant can be calculated with high accuracy.

[0071] Furthermore, according to this embodiment, the heat exchangers using the refrigerant cooled by the cascade heat exchanger 2 include an air conditioning heat exchanger 5a for air conditioning the vehicle 200, and a first battery heat exchanger 6a that supplies refrigerant to the outside of a battery pack 61 including a plurality of cells 62 in the battery 6 to indirectly cool the plurality of cells 62 with the refrigerant. According to this embodiment, both the air conditioning of the vehicle 200 and the cooling of the battery 6 can be appropriately achieved using the refrigerant circulated in the cooling system 100. In particular, by using the first battery heat exchanger 6a that supplies refrigerant to the outside of the battery pack 61 to indirectly cool the plurality of cells 62, a relatively large amount of heat exchange can be achieved with the refrigerant.

[0072] Furthermore, according to this embodiment, the cascade heat exchanger 2 is configured to exchange heat between a first heat cycle circuit 100a including the compressor 1, the air conditioning heat exchanger 5a, the first battery heat exchanger 6a, etc., and a second heat cycle circuit 100b including an outside air heat exchanger 30 that exchanges heat with outside air, separate from the first heat cycle circuit 100a. This allows the first heat cycle circuit 100a to exchange heat (cascade heat exchange) with the second heat cycle circuit 100b that exchanges heat with outside air, thereby improving the efficiency of the entire system of the first heat cycle circuit 100a; in other words, reducing the work of the compressor 1.

[0073] Furthermore, according to this embodiment, the cooling system 100 further cools the motor 4, which drives the vehicle 200 using power from the battery 6, with the refrigerant cooled by the cascade heat exchanger 2. This makes it possible to appropriately cool various components in the vehicle 200, such as the motor 4, using the refrigerant circulated in the cooling system 100.

[0074] [Variations] In the above-described embodiment, the cooling system 100 is configured with the first heat cycle circuit 100a and the second heat cycle circuit 100b. However, in other examples, the cooling system 100 may be configured with only the first heat cycle circuit 100a. In this case, the cascade heat exchanger 2 may be configured as an outside air heat exchanger. Note that, when the cooling system 100 is configured with the first heat cycle circuit 100a and the second heat cycle circuit 100b, the system efficiency is increased (i.e., the work of the compressor 1 can be reduced), but the configuration becomes more complex. Therefore, when prioritizing a simple configuration over system efficiency, it is preferable to configure the cooling system 100 with only the first heat cycle circuit 100a.

[0075] Furthermore, in the above-described embodiment, the temperature of the battery 6 is detected by the battery temperature sensor 72, but in other examples, the temperature of the battery 6 may be estimated based on the current value, voltage value, output requirement of the battery 6, or charging speed requirement of the battery 6. In still another example, the temperature of the battery 6 may be estimated based on the temperature of the refrigerant detected by a refrigerant temperature sensor 44 provided in the refrigerant passage 17 downstream of the second battery heat exchanger 6b. [Explanation of symbols]

[0076] 1 Compressor 1a First compressor 1b Second compressor 2 Heat exchanger (cascade heat exchanger) 4 motors 5. Air Conditioning 5a air conditioning heat exchanger 6 Battery 6a First battery heat exchanger 6b Second battery heat exchanger 11~20 Refrigerant passage 41, 42, 43, 44 Refrigerant temperature sensors 51, 52, 53 Refrigerant pressure sensors 61 Battery pack 62 cells 80 Control device 100 Cooling System 100a First thermal cycle circuit 100b Second thermal cycle circuit 200 vehicles E1, E2, E3 expansion valves V1, V2, V3 flow adjustment valve

Claims

1. CO 2 A cooling system for cooling a vehicle interior by circulating a refrigerant containing a compressor that compresses the refrigerant; a first heat exchanger for cooling the refrigerant compressed by the compressor; a second heat exchanger for cooling a predetermined cooling target within the vehicle by the refrigerant cooled by the first heat exchanger; a first refrigerant passage for supplying the refrigerant to the battery in the vehicle so that the refrigerant after being used for cooling in the second heat exchanger can further cool the battery; a second refrigerant passage for supplying the refrigerant cooled by the first heat exchanger to the first refrigerant passage without passing through the second heat exchanger; an expansion valve provided on the first refrigerant passage for expanding the refrigerant; a flow rate adjusting valve provided on the second refrigerant passage for adjusting a flow rate of the refrigerant; a control device configured to control at least the flow regulating valve; and The control device is configured to calculate an enthalpy of the refrigerant supplied from the first refrigerant passage to the battery, and when the enthalpy exceeds a predetermined range, to control the flow rate adjustment valve to increase an opening degree, and when the enthalpy is below the predetermined range, to control the flow rate adjustment valve to decrease an opening degree. A cooling system characterized by:

2. the cooling system further includes a battery heat exchanger for causing the refrigerant from the first refrigerant passage to flow around a plurality of cells in the battery to directly cool the plurality of cells with the refrigerant; The refrigerant decompressed by the expansion valve is supplied to the battery heat exchanger. The cooling system of claim 1 .

3. When the flow rate adjustment valve is a first flow rate adjustment valve, the cooling system further includes a second flow rate adjustment valve for adjusting a flow rate of the refrigerant supplied to the second heat exchanger, The control device is configured to control the second flow rate adjustment valve to increase its opening degree when the enthalpy exceeds the predetermined range and the first flow rate adjustment valve is fully open, and to control the second flow rate adjustment valve to decrease its opening degree when the enthalpy falls below the predetermined range and the first flow rate adjustment valve is fully closed.

3. The cooling system according to claim 1 or 2.

4. The predetermined range is CO 2 The cooling system according to claim 1 or 2, wherein the enthalpy of the refrigerant is set to a range higher than that at which the refrigerant becomes in a dry ice state.

5. 3. The cooling system according to claim 1, wherein the predetermined range is set based on an enthalpy at which a degree of superheat defined by a saturated vapor line of the refrigerant becomes less than a predetermined value.

6. the cooling system further includes a refrigerant pressure sensor that detects a pressure of the refrigerant from the first heat exchanger, and a refrigerant temperature sensor that detects a temperature of the refrigerant in the first refrigerant passage; the control device determines the enthalpy from the pressure and temperature detected by the refrigerant pressure sensor and the refrigerant temperature sensor, respectively.

3. The cooling system according to claim 1 or 2.

7. 3. The cooling system according to claim 1, wherein the second heat exchanger includes an air conditioning heat exchanger for air conditioning the vehicle, and / or a battery heat exchanger for supplying the refrigerant to the outside of a battery pack including a plurality of cells in the battery, thereby indirectly cooling the plurality of cells with the refrigerant.

8. 3. The cooling system according to claim 1, wherein the first heat exchanger is configured as a cascade heat exchanger that exchanges heat between a first heat cycle circuit including at least the compressor, the second heat exchanger, the first and second refrigerant passages, the expansion valve, and the flow control valve, and a second heat cycle circuit that is separate from the first heat cycle circuit and includes an outside air heat exchanger that exchanges heat with outside air.

9. 3. The cooling system according to claim 1, wherein the cooling system is configured to further cool a motor that drives the vehicle using power from the battery with the refrigerant cooled by the first heat exchanger.

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